HV dc/dc...

[legg]

On Fri, 17 Jul 2020 14:31:26 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Fri, 17 Jul 2020 22:42:44 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

jlarkin@highlandsniptechnology.com wrote:

I need eight isolated 150 volt DC supplies, low current, under 1 mA
average. Commercial dc/dc converters are crazy expensive:

If each channel needs some degree of control, the ultimate low-cost
solution looks like this thing:

https://www.ti.com/lit/ds/symlink/tpic6c595.pdf

Strobe G, load whatever you want to SER IN. One of my faves; works like
a charm.

If no control is needed, use 8 MOSFETs fed with the same 50% waveform,
then use each of them as the switch driving a forward/flyback
transformer, whatever you like, and burn excessive power in a zener.

Best regards, Piotr

We use a ton of TPIC6595, a simlar part, as our universal relay and
LED driver. But I don\'t need independent control, and there will be no
uP or FPGA or anything. It\'s refreshing to design an all-analog box
once in a while.

I think one big fet can drive all 8 flyback transformers.

With independent flyback transformers, you\'ll get lousy
cross-regulation, and poor output voltage tolerance, due
to Lp differences (that determine energy transfer).

You\'d be better off going for preregulated voltage inverters,
which are (at least) voltage regulated, to begin with.

Or fit all the flyback secondaries on the same core. ($)

RL

 

[server]

On Fri, 17 Jul 2020 19:22:37 -0400, legg <legg@nospam.magma.ca> wrote:

On Fri, 17 Jul 2020 14:31:26 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Fri, 17 Jul 2020 22:42:44 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

jlarkin@highlandsniptechnology.com wrote:

I need eight isolated 150 volt DC supplies, low current, under 1 mA
average. Commercial dc/dc converters are crazy expensive:

If each channel needs some degree of control, the ultimate low-cost
solution looks like this thing:

https://www.ti.com/lit/ds/symlink/tpic6c595.pdf

Strobe G, load whatever you want to SER IN. One of my faves; works like
a charm.

If no control is needed, use 8 MOSFETs fed with the same 50% waveform,
then use each of them as the switch driving a forward/flyback
transformer, whatever you like, and burn excessive power in a zener.

Best regards, Piotr

We use a ton of TPIC6595, a simlar part, as our universal relay and
LED driver. But I don\'t need independent control, and there will be no
uP or FPGA or anything. It\'s refreshing to design an all-analog box
once in a while.

I think one big fet can drive all 8 flyback transformers.

With independent flyback transformers, you\'ll get lousy
cross-regulation, and poor output voltage tolerance, due
to Lp differences (that determine energy transfer).

All 8 transformers will have the same turns ratio. I was thinking
their primaries would be in parallel. Same input, same output.

You\'d be better off going for preregulated voltage inverters,
which are (at least) voltage regulated, to begin with.

Or fit all the flyback secondaries on the same core. ($)

RL

I was planning to regulate in each isolated channel

https://www.dropbox.com/s/5lkbvlwz7b4rb2h/Isol_Pulser_1.jpg?raw=1

so the primary-side flyback regulation doesn\'t need to be very good.
Just good enough to make about 200 volts in each channel.

It doesn\'t need to be flyback. Some h-bridge forward converter would
work, if I can get the right transformer ratios. But the flyback looks
easy and versatile.








--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[server]

On Fri, 17 Jul 2020 19:22:37 -0400, legg <legg@nospam.magma.ca> wrote:

On Fri, 17 Jul 2020 14:31:26 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Fri, 17 Jul 2020 22:42:44 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

jlarkin@highlandsniptechnology.com wrote:

I need eight isolated 150 volt DC supplies, low current, under 1 mA
average. Commercial dc/dc converters are crazy expensive:

If each channel needs some degree of control, the ultimate low-cost
solution looks like this thing:

https://www.ti.com/lit/ds/symlink/tpic6c595.pdf

Strobe G, load whatever you want to SER IN. One of my faves; works like
a charm.

If no control is needed, use 8 MOSFETs fed with the same 50% waveform,
then use each of them as the switch driving a forward/flyback
transformer, whatever you like, and burn excessive power in a zener.

Best regards, Piotr

We use a ton of TPIC6595, a simlar part, as our universal relay and
LED driver. But I don\'t need independent control, and there will be no
uP or FPGA or anything. It\'s refreshing to design an all-analog box
once in a while.

I think one big fet can drive all 8 flyback transformers.

With independent flyback transformers, you\'ll get lousy
cross-regulation, and poor output voltage tolerance, due
to Lp differences (that determine energy transfer).

All 8 transformers will have the same turns ratio. I was thinking
their primaries would be in parallel. Same input, same output.

You\'d be better off going for preregulated voltage inverters,
which are (at least) voltage regulated, to begin with.

Or fit all the flyback secondaries on the same core. ($)

RL

I was planning to regulate in each isolated channel

https://www.dropbox.com/s/5lkbvlwz7b4rb2h/Isol_Pulser_1.jpg?raw=1

so the primary-side flyback regulation doesn\'t need to be very good.
Just good enough to make about 200 volts in each channel.

It doesn\'t need to be flyback. Some h-bridge forward converter would
work, if I can get the right transformer ratios. But the flyback looks
easy and versatile.








--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[sea moss]

On Friday, July 17, 2020 at 5:00:09 PM UTC-7, jla...@highlandsniptechnology..com wrote:

On Fri, 17 Jul 2020 19:22:37 -0400, legg <legg@nospam.magma.ca> wrote:

On Fri, 17 Jul 2020 14:31:26 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Fri, 17 Jul 2020 22:42:44 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

jlarkin@highlandsniptechnology.com wrote:

I need eight isolated 150 volt DC supplies, low current, under 1 mA
average. Commercial dc/dc converters are crazy expensive:

If each channel needs some degree of control, the ultimate low-cost
solution looks like this thing:

https://www.ti.com/lit/ds/symlink/tpic6c595.pdf

Strobe G, load whatever you want to SER IN. One of my faves; works like
a charm.

If no control is needed, use 8 MOSFETs fed with the same 50% waveform,
then use each of them as the switch driving a forward/flyback
transformer, whatever you like, and burn excessive power in a zener.

Best regards, Piotr

We use a ton of TPIC6595, a simlar part, as our universal relay and
LED driver. But I don\'t need independent control, and there will be no
uP or FPGA or anything. It\'s refreshing to design an all-analog box
once in a while.

I think one big fet can drive all 8 flyback transformers.

With independent flyback transformers, you\'ll get lousy
cross-regulation, and poor output voltage tolerance, due
to Lp differences (that determine energy transfer).

All 8 transformers will have the same turns ratio. I was thinking
their primaries would be in parallel. Same input, same output.


You\'d be better off going for preregulated voltage inverters,
which are (at least) voltage regulated, to begin with.

Or fit all the flyback secondaries on the same core. ($)

RL

I was planning to regulate in each isolated channel

https://www.dropbox.com/s/5lkbvlwz7b4rb2h/Isol_Pulser_1.jpg?raw=1

so the primary-side flyback regulation doesn\'t need to be very good.
Just good enough to make about 200 volts in each channel.

It doesn\'t need to be flyback. Some h-bridge forward converter would
work, if I can get the right transformer ratios. But the flyback looks
easy and versatile.








--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

A single flyback with multiple secondaries seems like the cleanest solution.. Since you would need 18 pins on a bobbin, it might be more practical to use two independent flyback converters, each with 4 outputs. There might actually be an off-the-shelf transformer that works for this.

I\'ve never considered driving multiple flyback primaries from one switching FET, but it seems like the outputs could vary by a lot. ... ok you piqued my curiosity, I scribbled out the equations, using V = L dI/dt , and E = 1/2 L I^2, if you vary L by say 20% it looks like the transferred energy will also vary by 20% (if I did that right). So for your idea it might just work. It might be a good idea to add a DC load at the outputs to soak up any energy from the transformers\' leakage inductance.

 

[server]

On Fri, 17 Jul 2020 17:32:44 -0700 (PDT), sea moss
<danluster81@gmail.com> wrote:

On Friday, July 17, 2020 at 5:00:09 PM UTC-7, jla...@highlandsniptechnology.com wrote:
On Fri, 17 Jul 2020 19:22:37 -0400, legg <legg@nospam.magma.ca> wrote:

On Fri, 17 Jul 2020 14:31:26 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Fri, 17 Jul 2020 22:42:44 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

jlarkin@highlandsniptechnology.com wrote:

I need eight isolated 150 volt DC supplies, low current, under 1 mA
average. Commercial dc/dc converters are crazy expensive:

If each channel needs some degree of control, the ultimate low-cost
solution looks like this thing:

https://www.ti.com/lit/ds/symlink/tpic6c595.pdf

Strobe G, load whatever you want to SER IN. One of my faves; works like
a charm.

If no control is needed, use 8 MOSFETs fed with the same 50% waveform,
then use each of them as the switch driving a forward/flyback
transformer, whatever you like, and burn excessive power in a zener.

Best regards, Piotr

We use a ton of TPIC6595, a simlar part, as our universal relay and
LED driver. But I don\'t need independent control, and there will be no
uP or FPGA or anything. It\'s refreshing to design an all-analog box
once in a while.

I think one big fet can drive all 8 flyback transformers.

With independent flyback transformers, you\'ll get lousy
cross-regulation, and poor output voltage tolerance, due
to Lp differences (that determine energy transfer).

All 8 transformers will have the same turns ratio. I was thinking
their primaries would be in parallel. Same input, same output.


You\'d be better off going for preregulated voltage inverters,
which are (at least) voltage regulated, to begin with.

Or fit all the flyback secondaries on the same core. ($)

RL

I was planning to regulate in each isolated channel

https://www.dropbox.com/s/5lkbvlwz7b4rb2h/Isol_Pulser_1.jpg?raw=1

so the primary-side flyback regulation doesn\'t need to be very good.
Just good enough to make about 200 volts in each channel.

It doesn\'t need to be flyback. Some h-bridge forward converter would
work, if I can get the right transformer ratios. But the flyback looks
easy and versatile.








--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

A single flyback with multiple secondaries seems like the cleanest solution. Since you would need 18 pins on a bobbin, it might be more practical to use two independent flyback converters, each with 4 outputs. There might actually be an off-the-shelf transformer that works for this.

I\'ve never considered driving multiple flyback primaries from one switching FET, but it seems like the outputs could vary by a lot. ... ok you piqued my curiosity, I scribbled out the equations, using V = L dI/dt , and E = 1/2 L I^2, if you vary L by say 20% it looks like the transferred energy will also vary by 20% (if I did that right). So for your idea it might just work. It might be a good idea to add a DC load at the outputs to soak up any energy from the transformers\' leakage inductance.

If the transformers primaries are in parallel, and the turns ratios
are identical, the secondary voltages will be the same.

We have the Coilcraft flyback transformers in stock, so there\'s no
incentive to wind a custom transformer with multiple secondaries.





--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[server]

On Fri, 17 Jul 2020 17:32:44 -0700 (PDT), sea moss
<danluster81@gmail.com> wrote:

On Friday, July 17, 2020 at 5:00:09 PM UTC-7, jla...@highlandsniptechnology.com wrote:
On Fri, 17 Jul 2020 19:22:37 -0400, legg <legg@nospam.magma.ca> wrote:

On Fri, 17 Jul 2020 14:31:26 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Fri, 17 Jul 2020 22:42:44 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

jlarkin@highlandsniptechnology.com wrote:

I need eight isolated 150 volt DC supplies, low current, under 1 mA
average. Commercial dc/dc converters are crazy expensive:

If each channel needs some degree of control, the ultimate low-cost
solution looks like this thing:

https://www.ti.com/lit/ds/symlink/tpic6c595.pdf

Strobe G, load whatever you want to SER IN. One of my faves; works like
a charm.

If no control is needed, use 8 MOSFETs fed with the same 50% waveform,
then use each of them as the switch driving a forward/flyback
transformer, whatever you like, and burn excessive power in a zener.

Best regards, Piotr

We use a ton of TPIC6595, a simlar part, as our universal relay and
LED driver. But I don\'t need independent control, and there will be no
uP or FPGA or anything. It\'s refreshing to design an all-analog box
once in a while.

I think one big fet can drive all 8 flyback transformers.

With independent flyback transformers, you\'ll get lousy
cross-regulation, and poor output voltage tolerance, due
to Lp differences (that determine energy transfer).

All 8 transformers will have the same turns ratio. I was thinking
their primaries would be in parallel. Same input, same output.


You\'d be better off going for preregulated voltage inverters,
which are (at least) voltage regulated, to begin with.

Or fit all the flyback secondaries on the same core. ($)

RL

I was planning to regulate in each isolated channel

https://www.dropbox.com/s/5lkbvlwz7b4rb2h/Isol_Pulser_1.jpg?raw=1

so the primary-side flyback regulation doesn\'t need to be very good.
Just good enough to make about 200 volts in each channel.

It doesn\'t need to be flyback. Some h-bridge forward converter would
work, if I can get the right transformer ratios. But the flyback looks
easy and versatile.








--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

A single flyback with multiple secondaries seems like the cleanest solution. Since you would need 18 pins on a bobbin, it might be more practical to use two independent flyback converters, each with 4 outputs. There might actually be an off-the-shelf transformer that works for this.

I\'ve never considered driving multiple flyback primaries from one switching FET, but it seems like the outputs could vary by a lot. ... ok you piqued my curiosity, I scribbled out the equations, using V = L dI/dt , and E = 1/2 L I^2, if you vary L by say 20% it looks like the transferred energy will also vary by 20% (if I did that right). So for your idea it might just work. It might be a good idea to add a DC load at the outputs to soak up any energy from the transformers\' leakage inductance.

If the transformers primaries are in parallel, and the turns ratios
are identical, the secondary voltages will be the same.

We have the Coilcraft flyback transformers in stock, so there\'s no
incentive to wind a custom transformer with multiple secondaries.





--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[sea moss]

On Friday, July 17, 2020 at 5:55:47 PM UTC-7, jla...@highlandsniptechnology..com wrote:

On Fri, 17 Jul 2020 17:32:44 -0700 (PDT), sea moss
spam@spam.com> wrote:

On Friday, July 17, 2020 at 5:00:09 PM UTC-7, jla...@highlandsniptechnology.com wrote:
On Fri, 17 Jul 2020 19:22:37 -0400, legg <legg@nospam.magma.ca> wrote:

On Fri, 17 Jul 2020 14:31:26 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Fri, 17 Jul 2020 22:42:44 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

jlarkin@highlandsniptechnology.com wrote:

I need eight isolated 150 volt DC supplies, low current, under 1 mA
average. Commercial dc/dc converters are crazy expensive:

If each channel needs some degree of control, the ultimate low-cost
solution looks like this thing:

https://www.ti.com/lit/ds/symlink/tpic6c595.pdf

Strobe G, load whatever you want to SER IN. One of my faves; works like
a charm.

If no control is needed, use 8 MOSFETs fed with the same 50% waveform,
then use each of them as the switch driving a forward/flyback
transformer, whatever you like, and burn excessive power in a zener..

Best regards, Piotr

We use a ton of TPIC6595, a simlar part, as our universal relay and
LED driver. But I don\'t need independent control, and there will be no
uP or FPGA or anything. It\'s refreshing to design an all-analog box
once in a while.

I think one big fet can drive all 8 flyback transformers.

With independent flyback transformers, you\'ll get lousy
cross-regulation, and poor output voltage tolerance, due
to Lp differences (that determine energy transfer).

All 8 transformers will have the same turns ratio. I was thinking
their primaries would be in parallel. Same input, same output.


You\'d be better off going for preregulated voltage inverters,
which are (at least) voltage regulated, to begin with.

Or fit all the flyback secondaries on the same core. ($)

RL

I was planning to regulate in each isolated channel

https://www.dropbox.com/s/5lkbvlwz7b4rb2h/Isol_Pulser_1.jpg?raw=1

so the primary-side flyback regulation doesn\'t need to be very good.
Just good enough to make about 200 volts in each channel.

It doesn\'t need to be flyback. Some h-bridge forward converter would
work, if I can get the right transformer ratios. But the flyback looks
easy and versatile.








--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

A single flyback with multiple secondaries seems like the cleanest solution. Since you would need 18 pins on a bobbin, it might be more practical to use two independent flyback converters, each with 4 outputs. There might actually be an off-the-shelf transformer that works for this.

I\'ve never considered driving multiple flyback primaries from one switching FET, but it seems like the outputs could vary by a lot. ... ok you piqued my curiosity, I scribbled out the equations, using V = L dI/dt , and E = 1/2 L I^2, if you vary L by say 20% it looks like the transferred energy will also vary by 20% (if I did that right). So for your idea it might just work. It might be a good idea to add a DC load at the outputs to soak up any energy from the transformers\' leakage inductance.


If the transformers primaries are in parallel, and the turns ratios
are identical, the secondary voltages will be the same.

We have the Coilcraft flyback transformers in stock, so there\'s no
incentive to wind a custom transformer with multiple secondaries.





--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

I understand you\'re trying to use parts in stock, I get that. For a flyback though you have to keep in mind it doesn\'t follow the transformer equation; it transfers energy stored in its magnetizing inductance. E = 1/2 Lmag I^2, and the FET\'s ON time is adjusted so that Energy in = Energy out. For a given lot of flyback inductors, you can expect Lm to vary by maybe 20%. I still think your idea has a good chance of working, especially if you add a DC load to each output.

 

[sea moss]

On Friday, July 17, 2020 at 5:55:47 PM UTC-7, jla...@highlandsniptechnology..com wrote:

On Fri, 17 Jul 2020 17:32:44 -0700 (PDT), sea moss
spam@spam.com> wrote:

On Friday, July 17, 2020 at 5:00:09 PM UTC-7, jla...@highlandsniptechnology.com wrote:
On Fri, 17 Jul 2020 19:22:37 -0400, legg <legg@nospam.magma.ca> wrote:

On Fri, 17 Jul 2020 14:31:26 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Fri, 17 Jul 2020 22:42:44 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

jlarkin@highlandsniptechnology.com wrote:

I need eight isolated 150 volt DC supplies, low current, under 1 mA
average. Commercial dc/dc converters are crazy expensive:

If each channel needs some degree of control, the ultimate low-cost
solution looks like this thing:

https://www.ti.com/lit/ds/symlink/tpic6c595.pdf

Strobe G, load whatever you want to SER IN. One of my faves; works like
a charm.

If no control is needed, use 8 MOSFETs fed with the same 50% waveform,
then use each of them as the switch driving a forward/flyback
transformer, whatever you like, and burn excessive power in a zener..

Best regards, Piotr

We use a ton of TPIC6595, a simlar part, as our universal relay and
LED driver. But I don\'t need independent control, and there will be no
uP or FPGA or anything. It\'s refreshing to design an all-analog box
once in a while.

I think one big fet can drive all 8 flyback transformers.

With independent flyback transformers, you\'ll get lousy
cross-regulation, and poor output voltage tolerance, due
to Lp differences (that determine energy transfer).

All 8 transformers will have the same turns ratio. I was thinking
their primaries would be in parallel. Same input, same output.


You\'d be better off going for preregulated voltage inverters,
which are (at least) voltage regulated, to begin with.

Or fit all the flyback secondaries on the same core. ($)

RL

I was planning to regulate in each isolated channel

https://www.dropbox.com/s/5lkbvlwz7b4rb2h/Isol_Pulser_1.jpg?raw=1

so the primary-side flyback regulation doesn\'t need to be very good.
Just good enough to make about 200 volts in each channel.

It doesn\'t need to be flyback. Some h-bridge forward converter would
work, if I can get the right transformer ratios. But the flyback looks
easy and versatile.








--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

A single flyback with multiple secondaries seems like the cleanest solution. Since you would need 18 pins on a bobbin, it might be more practical to use two independent flyback converters, each with 4 outputs. There might actually be an off-the-shelf transformer that works for this.

I\'ve never considered driving multiple flyback primaries from one switching FET, but it seems like the outputs could vary by a lot. ... ok you piqued my curiosity, I scribbled out the equations, using V = L dI/dt , and E = 1/2 L I^2, if you vary L by say 20% it looks like the transferred energy will also vary by 20% (if I did that right). So for your idea it might just work. It might be a good idea to add a DC load at the outputs to soak up any energy from the transformers\' leakage inductance.


If the transformers primaries are in parallel, and the turns ratios
are identical, the secondary voltages will be the same.

We have the Coilcraft flyback transformers in stock, so there\'s no
incentive to wind a custom transformer with multiple secondaries.





--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

I understand you\'re trying to use parts in stock, I get that. For a flyback though you have to keep in mind it doesn\'t follow the transformer equation; it transfers energy stored in its magnetizing inductance. E = 1/2 Lmag I^2, and the FET\'s ON time is adjusted so that Energy in = Energy out. For a given lot of flyback inductors, you can expect Lm to vary by maybe 20%. I still think your idea has a good chance of working, especially if you add a DC load to each output.

 

[sea moss]

On Friday, July 17, 2020 at 5:55:47 PM UTC-7, jla...@highlandsniptechnology..com wrote:

On Fri, 17 Jul 2020 17:32:44 -0700 (PDT), sea moss
spam@spam.com> wrote:

On Friday, July 17, 2020 at 5:00:09 PM UTC-7, jla...@highlandsniptechnology.com wrote:
On Fri, 17 Jul 2020 19:22:37 -0400, legg <legg@nospam.magma.ca> wrote:

On Fri, 17 Jul 2020 14:31:26 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Fri, 17 Jul 2020 22:42:44 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

jlarkin@highlandsniptechnology.com wrote:

I need eight isolated 150 volt DC supplies, low current, under 1 mA
average. Commercial dc/dc converters are crazy expensive:

If each channel needs some degree of control, the ultimate low-cost
solution looks like this thing:

https://www.ti.com/lit/ds/symlink/tpic6c595.pdf

Strobe G, load whatever you want to SER IN. One of my faves; works like
a charm.

If no control is needed, use 8 MOSFETs fed with the same 50% waveform,
then use each of them as the switch driving a forward/flyback
transformer, whatever you like, and burn excessive power in a zener..

Best regards, Piotr

We use a ton of TPIC6595, a simlar part, as our universal relay and
LED driver. But I don\'t need independent control, and there will be no
uP or FPGA or anything. It\'s refreshing to design an all-analog box
once in a while.

I think one big fet can drive all 8 flyback transformers.

With independent flyback transformers, you\'ll get lousy
cross-regulation, and poor output voltage tolerance, due
to Lp differences (that determine energy transfer).

All 8 transformers will have the same turns ratio. I was thinking
their primaries would be in parallel. Same input, same output.


You\'d be better off going for preregulated voltage inverters,
which are (at least) voltage regulated, to begin with.

Or fit all the flyback secondaries on the same core. ($)

RL

I was planning to regulate in each isolated channel

https://www.dropbox.com/s/5lkbvlwz7b4rb2h/Isol_Pulser_1.jpg?raw=1

so the primary-side flyback regulation doesn\'t need to be very good.
Just good enough to make about 200 volts in each channel.

It doesn\'t need to be flyback. Some h-bridge forward converter would
work, if I can get the right transformer ratios. But the flyback looks
easy and versatile.








--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

A single flyback with multiple secondaries seems like the cleanest solution. Since you would need 18 pins on a bobbin, it might be more practical to use two independent flyback converters, each with 4 outputs. There might actually be an off-the-shelf transformer that works for this.

I\'ve never considered driving multiple flyback primaries from one switching FET, but it seems like the outputs could vary by a lot. ... ok you piqued my curiosity, I scribbled out the equations, using V = L dI/dt , and E = 1/2 L I^2, if you vary L by say 20% it looks like the transferred energy will also vary by 20% (if I did that right). So for your idea it might just work. It might be a good idea to add a DC load at the outputs to soak up any energy from the transformers\' leakage inductance.


If the transformers primaries are in parallel, and the turns ratios
are identical, the secondary voltages will be the same.

We have the Coilcraft flyback transformers in stock, so there\'s no
incentive to wind a custom transformer with multiple secondaries.





--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

I understand you\'re trying to use parts in stock, I get that. For a flyback though you have to keep in mind it doesn\'t follow the transformer equation; it transfers energy stored in its magnetizing inductance. E = 1/2 Lmag I^2, and the FET\'s ON time is adjusted so that Energy in = Energy out. For a given lot of flyback inductors, you can expect Lm to vary by maybe 20%. I still think your idea has a good chance of working, especially if you add a DC load to each output.

 

[Phil Hobbs]

On 2020-07-17 20:55, jlarkin@highlandsniptechnology.com wrote:

On Fri, 17 Jul 2020 17:32:44 -0700 (PDT), sea moss
danluster81@gmail.com> wrote:

On Friday, July 17, 2020 at 5:00:09 PM UTC-7, jla...@highlandsniptechnology.com wrote:
On Fri, 17 Jul 2020 19:22:37 -0400, legg <legg@nospam.magma.ca> wrote:

On Fri, 17 Jul 2020 14:31:26 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Fri, 17 Jul 2020 22:42:44 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

jlarkin@highlandsniptechnology.com wrote:

I need eight isolated 150 volt DC supplies, low current, under 1 mA
average. Commercial dc/dc converters are crazy expensive:

If each channel needs some degree of control, the ultimate low-cost
solution looks like this thing:

https://www.ti.com/lit/ds/symlink/tpic6c595.pdf

Strobe G, load whatever you want to SER IN. One of my faves; works like
a charm.

If no control is needed, use 8 MOSFETs fed with the same 50% waveform,
then use each of them as the switch driving a forward/flyback
transformer, whatever you like, and burn excessive power in a zener.

Best regards, Piotr

We use a ton of TPIC6595, a simlar part, as our universal relay and
LED driver. But I don\'t need independent control, and there will be no
uP or FPGA or anything. It\'s refreshing to design an all-analog box
once in a while.

I think one big fet can drive all 8 flyback transformers.

With independent flyback transformers, you\'ll get lousy
cross-regulation, and poor output voltage tolerance, due
to Lp differences (that determine energy transfer).

All 8 transformers will have the same turns ratio. I was thinking
their primaries would be in parallel. Same input, same output.


You\'d be better off going for preregulated voltage inverters,
which are (at least) voltage regulated, to begin with.

Or fit all the flyback secondaries on the same core. ($)

RL

I was planning to regulate in each isolated channel

https://www.dropbox.com/s/5lkbvlwz7b4rb2h/Isol_Pulser_1.jpg?raw=1

so the primary-side flyback regulation doesn\'t need to be very good.
Just good enough to make about 200 volts in each channel.

It doesn\'t need to be flyback. Some h-bridge forward converter would
work, if I can get the right transformer ratios. But the flyback looks
easy and versatile.








--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

A single flyback with multiple secondaries seems like the cleanest solution. Since you would need 18 pins on a bobbin, it might be more practical to use two independent flyback converters, each with 4 outputs. There might actually be an off-the-shelf transformer that works for this.

I\'ve never considered driving multiple flyback primaries from one switching FET, but it seems like the outputs could vary by a lot. ... ok you piqued my curiosity, I scribbled out the equations, using V = L dI/dt , and E = 1/2 L I^2, if you vary L by say 20% it looks like the transferred energy will also vary by 20% (if I did that right). So for your idea it might just work. It might be a good idea to add a DC load at the outputs to soak up any energy from the transformers\' leakage inductance.


If the transformers primaries are in parallel, and the turns ratios
are identical, the secondary voltages will be the same.

Hmm, interesting. ISTM that only works with sufficiently tight
coupling--in the limit of loose coupling the secondary voltages can be
anything depending on the loading on each one. Might work fine for this
purpose though.

We have the Coilcraft flyback transformers in stock, so there\'s no
incentive to wind a custom transformer with multiple secondaries.

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Phil Hobbs]

On 2020-07-17 20:55, jlarkin@highlandsniptechnology.com wrote:

On Fri, 17 Jul 2020 17:32:44 -0700 (PDT), sea moss
danluster81@gmail.com> wrote:

On Friday, July 17, 2020 at 5:00:09 PM UTC-7, jla...@highlandsniptechnology.com wrote:
On Fri, 17 Jul 2020 19:22:37 -0400, legg <legg@nospam.magma.ca> wrote:

On Fri, 17 Jul 2020 14:31:26 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Fri, 17 Jul 2020 22:42:44 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

jlarkin@highlandsniptechnology.com wrote:

I need eight isolated 150 volt DC supplies, low current, under 1 mA
average. Commercial dc/dc converters are crazy expensive:

If each channel needs some degree of control, the ultimate low-cost
solution looks like this thing:

https://www.ti.com/lit/ds/symlink/tpic6c595.pdf

Strobe G, load whatever you want to SER IN. One of my faves; works like
a charm.

If no control is needed, use 8 MOSFETs fed with the same 50% waveform,
then use each of them as the switch driving a forward/flyback
transformer, whatever you like, and burn excessive power in a zener.

Best regards, Piotr

We use a ton of TPIC6595, a simlar part, as our universal relay and
LED driver. But I don\'t need independent control, and there will be no
uP or FPGA or anything. It\'s refreshing to design an all-analog box
once in a while.

I think one big fet can drive all 8 flyback transformers.

With independent flyback transformers, you\'ll get lousy
cross-regulation, and poor output voltage tolerance, due
to Lp differences (that determine energy transfer).

All 8 transformers will have the same turns ratio. I was thinking
their primaries would be in parallel. Same input, same output.


You\'d be better off going for preregulated voltage inverters,
which are (at least) voltage regulated, to begin with.

Or fit all the flyback secondaries on the same core. ($)

RL

I was planning to regulate in each isolated channel

https://www.dropbox.com/s/5lkbvlwz7b4rb2h/Isol_Pulser_1.jpg?raw=1

so the primary-side flyback regulation doesn\'t need to be very good.
Just good enough to make about 200 volts in each channel.

It doesn\'t need to be flyback. Some h-bridge forward converter would
work, if I can get the right transformer ratios. But the flyback looks
easy and versatile.








--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

A single flyback with multiple secondaries seems like the cleanest solution. Since you would need 18 pins on a bobbin, it might be more practical to use two independent flyback converters, each with 4 outputs. There might actually be an off-the-shelf transformer that works for this.

I\'ve never considered driving multiple flyback primaries from one switching FET, but it seems like the outputs could vary by a lot. ... ok you piqued my curiosity, I scribbled out the equations, using V = L dI/dt , and E = 1/2 L I^2, if you vary L by say 20% it looks like the transferred energy will also vary by 20% (if I did that right). So for your idea it might just work. It might be a good idea to add a DC load at the outputs to soak up any energy from the transformers\' leakage inductance.


If the transformers primaries are in parallel, and the turns ratios
are identical, the secondary voltages will be the same.

Hmm, interesting. ISTM that only works with sufficiently tight
coupling--in the limit of loose coupling the secondary voltages can be
anything depending on the loading on each one. Might work fine for this
purpose though.

We have the Coilcraft flyback transformers in stock, so there\'s no
incentive to wind a custom transformer with multiple secondaries.

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Phil Hobbs]

On 2020-07-17 20:55, jlarkin@highlandsniptechnology.com wrote:

On Fri, 17 Jul 2020 17:32:44 -0700 (PDT), sea moss
danluster81@gmail.com> wrote:

On Friday, July 17, 2020 at 5:00:09 PM UTC-7, jla...@highlandsniptechnology.com wrote:
On Fri, 17 Jul 2020 19:22:37 -0400, legg <legg@nospam.magma.ca> wrote:

On Fri, 17 Jul 2020 14:31:26 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Fri, 17 Jul 2020 22:42:44 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

jlarkin@highlandsniptechnology.com wrote:

I need eight isolated 150 volt DC supplies, low current, under 1 mA
average. Commercial dc/dc converters are crazy expensive:

If each channel needs some degree of control, the ultimate low-cost
solution looks like this thing:

https://www.ti.com/lit/ds/symlink/tpic6c595.pdf

Strobe G, load whatever you want to SER IN. One of my faves; works like
a charm.

If no control is needed, use 8 MOSFETs fed with the same 50% waveform,
then use each of them as the switch driving a forward/flyback
transformer, whatever you like, and burn excessive power in a zener.

Best regards, Piotr

We use a ton of TPIC6595, a simlar part, as our universal relay and
LED driver. But I don\'t need independent control, and there will be no
uP or FPGA or anything. It\'s refreshing to design an all-analog box
once in a while.

I think one big fet can drive all 8 flyback transformers.

With independent flyback transformers, you\'ll get lousy
cross-regulation, and poor output voltage tolerance, due
to Lp differences (that determine energy transfer).

All 8 transformers will have the same turns ratio. I was thinking
their primaries would be in parallel. Same input, same output.


You\'d be better off going for preregulated voltage inverters,
which are (at least) voltage regulated, to begin with.

Or fit all the flyback secondaries on the same core. ($)

RL

I was planning to regulate in each isolated channel

https://www.dropbox.com/s/5lkbvlwz7b4rb2h/Isol_Pulser_1.jpg?raw=1

so the primary-side flyback regulation doesn\'t need to be very good.
Just good enough to make about 200 volts in each channel.

It doesn\'t need to be flyback. Some h-bridge forward converter would
work, if I can get the right transformer ratios. But the flyback looks
easy and versatile.








--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

A single flyback with multiple secondaries seems like the cleanest solution. Since you would need 18 pins on a bobbin, it might be more practical to use two independent flyback converters, each with 4 outputs. There might actually be an off-the-shelf transformer that works for this.

I\'ve never considered driving multiple flyback primaries from one switching FET, but it seems like the outputs could vary by a lot. ... ok you piqued my curiosity, I scribbled out the equations, using V = L dI/dt , and E = 1/2 L I^2, if you vary L by say 20% it looks like the transferred energy will also vary by 20% (if I did that right). So for your idea it might just work. It might be a good idea to add a DC load at the outputs to soak up any energy from the transformers\' leakage inductance.


If the transformers primaries are in parallel, and the turns ratios
are identical, the secondary voltages will be the same.

Hmm, interesting. ISTM that only works with sufficiently tight
coupling--in the limit of loose coupling the secondary voltages can be
anything depending on the loading on each one. Might work fine for this
purpose though.

We have the Coilcraft flyback transformers in stock, so there\'s no
incentive to wind a custom transformer with multiple secondaries.

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[server]

On Fri, 17 Jul 2020 21:22:44 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-07-17 20:55, jlarkin@highlandsniptechnology.com wrote:
On Fri, 17 Jul 2020 17:32:44 -0700 (PDT), sea moss
danluster81@gmail.com> wrote:

On Friday, July 17, 2020 at 5:00:09 PM UTC-7, jla...@highlandsniptechnology.com wrote:
On Fri, 17 Jul 2020 19:22:37 -0400, legg <legg@nospam.magma.ca> wrote:

On Fri, 17 Jul 2020 14:31:26 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Fri, 17 Jul 2020 22:42:44 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

jlarkin@highlandsniptechnology.com wrote:

I need eight isolated 150 volt DC supplies, low current, under 1 mA
average. Commercial dc/dc converters are crazy expensive:

If each channel needs some degree of control, the ultimate low-cost
solution looks like this thing:

https://www.ti.com/lit/ds/symlink/tpic6c595.pdf

Strobe G, load whatever you want to SER IN. One of my faves; works like
a charm.

If no control is needed, use 8 MOSFETs fed with the same 50% waveform,
then use each of them as the switch driving a forward/flyback
transformer, whatever you like, and burn excessive power in a zener.

Best regards, Piotr

We use a ton of TPIC6595, a simlar part, as our universal relay and
LED driver. But I don\'t need independent control, and there will be no
uP or FPGA or anything. It\'s refreshing to design an all-analog box
once in a while.

I think one big fet can drive all 8 flyback transformers.

With independent flyback transformers, you\'ll get lousy
cross-regulation, and poor output voltage tolerance, due
to Lp differences (that determine energy transfer).

All 8 transformers will have the same turns ratio. I was thinking
their primaries would be in parallel. Same input, same output.


You\'d be better off going for preregulated voltage inverters,
which are (at least) voltage regulated, to begin with.

Or fit all the flyback secondaries on the same core. ($)

RL

I was planning to regulate in each isolated channel

https://www.dropbox.com/s/5lkbvlwz7b4rb2h/Isol_Pulser_1.jpg?raw=1

so the primary-side flyback regulation doesn\'t need to be very good.
Just good enough to make about 200 volts in each channel.

It doesn\'t need to be flyback. Some h-bridge forward converter would
work, if I can get the right transformer ratios. But the flyback looks
easy and versatile.








--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

A single flyback with multiple secondaries seems like the cleanest solution. Since you would need 18 pins on a bobbin, it might be more practical to use two independent flyback converters, each with 4 outputs. There might actually be an off-the-shelf transformer that works for this.

I\'ve never considered driving multiple flyback primaries from one switching FET, but it seems like the outputs could vary by a lot. ... ok you piqued my curiosity, I scribbled out the equations, using V = L dI/dt , and E = 1/2 L I^2, if you vary L by say 20% it looks like the transferred energy will also vary by 20% (if I did that right). So for your idea it might just work. It might be a good idea to add a DC load at the outputs to soak up any energy from the transformers\' leakage inductance.


If the transformers primaries are in parallel, and the turns ratios
are identical, the secondary voltages will be the same.

Hmm, interesting. ISTM that only works with sufficiently tight
coupling--in the limit of loose coupling the secondary voltages can be
anything depending on the loading on each one. Might work fine for this
purpose though.

Leakage inductances won\'t affect rectified voltage much, and are a
fraction of magnetizing inductance, and the transformers are
identical.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[server]

On Fri, 17 Jul 2020 21:22:44 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-07-17 20:55, jlarkin@highlandsniptechnology.com wrote:
On Fri, 17 Jul 2020 17:32:44 -0700 (PDT), sea moss
danluster81@gmail.com> wrote:

On Friday, July 17, 2020 at 5:00:09 PM UTC-7, jla...@highlandsniptechnology.com wrote:
On Fri, 17 Jul 2020 19:22:37 -0400, legg <legg@nospam.magma.ca> wrote:

On Fri, 17 Jul 2020 14:31:26 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Fri, 17 Jul 2020 22:42:44 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

jlarkin@highlandsniptechnology.com wrote:

I need eight isolated 150 volt DC supplies, low current, under 1 mA
average. Commercial dc/dc converters are crazy expensive:

If each channel needs some degree of control, the ultimate low-cost
solution looks like this thing:

https://www.ti.com/lit/ds/symlink/tpic6c595.pdf

Strobe G, load whatever you want to SER IN. One of my faves; works like
a charm.

If no control is needed, use 8 MOSFETs fed with the same 50% waveform,
then use each of them as the switch driving a forward/flyback
transformer, whatever you like, and burn excessive power in a zener.

Best regards, Piotr

We use a ton of TPIC6595, a simlar part, as our universal relay and
LED driver. But I don\'t need independent control, and there will be no
uP or FPGA or anything. It\'s refreshing to design an all-analog box
once in a while.

I think one big fet can drive all 8 flyback transformers.

With independent flyback transformers, you\'ll get lousy
cross-regulation, and poor output voltage tolerance, due
to Lp differences (that determine energy transfer).

All 8 transformers will have the same turns ratio. I was thinking
their primaries would be in parallel. Same input, same output.


You\'d be better off going for preregulated voltage inverters,
which are (at least) voltage regulated, to begin with.

Or fit all the flyback secondaries on the same core. ($)

RL

I was planning to regulate in each isolated channel

https://www.dropbox.com/s/5lkbvlwz7b4rb2h/Isol_Pulser_1.jpg?raw=1

so the primary-side flyback regulation doesn\'t need to be very good.
Just good enough to make about 200 volts in each channel.

It doesn\'t need to be flyback. Some h-bridge forward converter would
work, if I can get the right transformer ratios. But the flyback looks
easy and versatile.








--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

A single flyback with multiple secondaries seems like the cleanest solution. Since you would need 18 pins on a bobbin, it might be more practical to use two independent flyback converters, each with 4 outputs. There might actually be an off-the-shelf transformer that works for this.

I\'ve never considered driving multiple flyback primaries from one switching FET, but it seems like the outputs could vary by a lot. ... ok you piqued my curiosity, I scribbled out the equations, using V = L dI/dt , and E = 1/2 L I^2, if you vary L by say 20% it looks like the transferred energy will also vary by 20% (if I did that right). So for your idea it might just work. It might be a good idea to add a DC load at the outputs to soak up any energy from the transformers\' leakage inductance.


If the transformers primaries are in parallel, and the turns ratios
are identical, the secondary voltages will be the same.

Hmm, interesting. ISTM that only works with sufficiently tight
coupling--in the limit of loose coupling the secondary voltages can be
anything depending on the loading on each one. Might work fine for this
purpose though.

Leakage inductances won\'t affect rectified voltage much, and are a
fraction of magnetizing inductance, and the transformers are
identical.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[server]

On Fri, 17 Jul 2020 21:22:44 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-07-17 20:55, jlarkin@highlandsniptechnology.com wrote:
On Fri, 17 Jul 2020 17:32:44 -0700 (PDT), sea moss
danluster81@gmail.com> wrote:

On Friday, July 17, 2020 at 5:00:09 PM UTC-7, jla...@highlandsniptechnology.com wrote:
On Fri, 17 Jul 2020 19:22:37 -0400, legg <legg@nospam.magma.ca> wrote:

On Fri, 17 Jul 2020 14:31:26 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Fri, 17 Jul 2020 22:42:44 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

jlarkin@highlandsniptechnology.com wrote:

I need eight isolated 150 volt DC supplies, low current, under 1 mA
average. Commercial dc/dc converters are crazy expensive:

If each channel needs some degree of control, the ultimate low-cost
solution looks like this thing:

https://www.ti.com/lit/ds/symlink/tpic6c595.pdf

Strobe G, load whatever you want to SER IN. One of my faves; works like
a charm.

If no control is needed, use 8 MOSFETs fed with the same 50% waveform,
then use each of them as the switch driving a forward/flyback
transformer, whatever you like, and burn excessive power in a zener.

Best regards, Piotr

We use a ton of TPIC6595, a simlar part, as our universal relay and
LED driver. But I don\'t need independent control, and there will be no
uP or FPGA or anything. It\'s refreshing to design an all-analog box
once in a while.

I think one big fet can drive all 8 flyback transformers.

With independent flyback transformers, you\'ll get lousy
cross-regulation, and poor output voltage tolerance, due
to Lp differences (that determine energy transfer).

All 8 transformers will have the same turns ratio. I was thinking
their primaries would be in parallel. Same input, same output.


You\'d be better off going for preregulated voltage inverters,
which are (at least) voltage regulated, to begin with.

Or fit all the flyback secondaries on the same core. ($)

RL

I was planning to regulate in each isolated channel

https://www.dropbox.com/s/5lkbvlwz7b4rb2h/Isol_Pulser_1.jpg?raw=1

so the primary-side flyback regulation doesn\'t need to be very good.
Just good enough to make about 200 volts in each channel.

It doesn\'t need to be flyback. Some h-bridge forward converter would
work, if I can get the right transformer ratios. But the flyback looks
easy and versatile.








--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

A single flyback with multiple secondaries seems like the cleanest solution. Since you would need 18 pins on a bobbin, it might be more practical to use two independent flyback converters, each with 4 outputs. There might actually be an off-the-shelf transformer that works for this.

I\'ve never considered driving multiple flyback primaries from one switching FET, but it seems like the outputs could vary by a lot. ... ok you piqued my curiosity, I scribbled out the equations, using V = L dI/dt , and E = 1/2 L I^2, if you vary L by say 20% it looks like the transferred energy will also vary by 20% (if I did that right). So for your idea it might just work. It might be a good idea to add a DC load at the outputs to soak up any energy from the transformers\' leakage inductance.


If the transformers primaries are in parallel, and the turns ratios
are identical, the secondary voltages will be the same.

Hmm, interesting. ISTM that only works with sufficiently tight
coupling--in the limit of loose coupling the secondary voltages can be
anything depending on the loading on each one. Might work fine for this
purpose though.

Leakage inductances won\'t affect rectified voltage much, and are a
fraction of magnetizing inductance, and the transformers are
identical.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[server]

On Fri, 17 Jul 2020 18:14:25 -0700 (PDT), sea moss
<danluster81@gmail.com> wrote:

On Friday, July 17, 2020 at 5:55:47 PM UTC-7, jla...@highlandsniptechnology.com wrote:
On Fri, 17 Jul 2020 17:32:44 -0700 (PDT), sea moss
spam@spam.com> wrote:

On Friday, July 17, 2020 at 5:00:09 PM UTC-7, jla...@highlandsniptechnology.com wrote:
On Fri, 17 Jul 2020 19:22:37 -0400, legg <legg@nospam.magma.ca> wrote:

On Fri, 17 Jul 2020 14:31:26 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Fri, 17 Jul 2020 22:42:44 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

jlarkin@highlandsniptechnology.com wrote:

I need eight isolated 150 volt DC supplies, low current, under 1 mA
average. Commercial dc/dc converters are crazy expensive:

If each channel needs some degree of control, the ultimate low-cost
solution looks like this thing:

https://www.ti.com/lit/ds/symlink/tpic6c595.pdf

Strobe G, load whatever you want to SER IN. One of my faves; works like
a charm.

If no control is needed, use 8 MOSFETs fed with the same 50% waveform,
then use each of them as the switch driving a forward/flyback
transformer, whatever you like, and burn excessive power in a zener.

Best regards, Piotr

We use a ton of TPIC6595, a simlar part, as our universal relay and
LED driver. But I don\'t need independent control, and there will be no
uP or FPGA or anything. It\'s refreshing to design an all-analog box
once in a while.

I think one big fet can drive all 8 flyback transformers.

With independent flyback transformers, you\'ll get lousy
cross-regulation, and poor output voltage tolerance, due
to Lp differences (that determine energy transfer).

All 8 transformers will have the same turns ratio. I was thinking
their primaries would be in parallel. Same input, same output.


You\'d be better off going for preregulated voltage inverters,
which are (at least) voltage regulated, to begin with.

Or fit all the flyback secondaries on the same core. ($)

RL

I was planning to regulate in each isolated channel

https://www.dropbox.com/s/5lkbvlwz7b4rb2h/Isol_Pulser_1.jpg?raw=1

so the primary-side flyback regulation doesn\'t need to be very good.
Just good enough to make about 200 volts in each channel.

It doesn\'t need to be flyback. Some h-bridge forward converter would
work, if I can get the right transformer ratios. But the flyback looks
easy and versatile.








--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

A single flyback with multiple secondaries seems like the cleanest solution. Since you would need 18 pins on a bobbin, it might be more practical to use two independent flyback converters, each with 4 outputs. There might actually be an off-the-shelf transformer that works for this.

I\'ve never considered driving multiple flyback primaries from one switching FET, but it seems like the outputs could vary by a lot. ... ok you piqued my curiosity, I scribbled out the equations, using V = L dI/dt , and E = 1/2 L I^2, if you vary L by say 20% it looks like the transferred energy will also vary by 20% (if I did that right). So for your idea it might just work. It might be a good idea to add a DC load at the outputs to soak up any energy from the transformers\' leakage inductance.


If the transformers primaries are in parallel, and the turns ratios
are identical, the secondary voltages will be the same.

We have the Coilcraft flyback transformers in stock, so there\'s no
incentive to wind a custom transformer with multiple secondaries.





--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

I understand you\'re trying to use parts in stock, I get that. For a flyback though you have to keep in mind it doesn\'t follow the transformer equation; it transfers energy stored in its magnetizing inductance. E = 1/2 Lmag I^2, and the FET\'s ON time is adjusted so that Energy in = Energy out. For a given lot of flyback inductors, you can expect Lm to vary by maybe 20%. I still think your idea has a good chance of working, especially if you add a DC load to each output.

The flyback primary inductance is the inductance of all 8 primary
windings *in parallel*. They are not independent.

I don\'t expect leakage inductances to have much effect on output
voltage differences.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[server]

On Fri, 17 Jul 2020 18:14:25 -0700 (PDT), sea moss
<danluster81@gmail.com> wrote:

On Friday, July 17, 2020 at 5:55:47 PM UTC-7, jla...@highlandsniptechnology.com wrote:
On Fri, 17 Jul 2020 17:32:44 -0700 (PDT), sea moss
spam@spam.com> wrote:

On Friday, July 17, 2020 at 5:00:09 PM UTC-7, jla...@highlandsniptechnology.com wrote:
On Fri, 17 Jul 2020 19:22:37 -0400, legg <legg@nospam.magma.ca> wrote:

On Fri, 17 Jul 2020 14:31:26 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Fri, 17 Jul 2020 22:42:44 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

jlarkin@highlandsniptechnology.com wrote:

I need eight isolated 150 volt DC supplies, low current, under 1 mA
average. Commercial dc/dc converters are crazy expensive:

If each channel needs some degree of control, the ultimate low-cost
solution looks like this thing:

https://www.ti.com/lit/ds/symlink/tpic6c595.pdf

Strobe G, load whatever you want to SER IN. One of my faves; works like
a charm.

If no control is needed, use 8 MOSFETs fed with the same 50% waveform,
then use each of them as the switch driving a forward/flyback
transformer, whatever you like, and burn excessive power in a zener.

Best regards, Piotr

We use a ton of TPIC6595, a simlar part, as our universal relay and
LED driver. But I don\'t need independent control, and there will be no
uP or FPGA or anything. It\'s refreshing to design an all-analog box
once in a while.

I think one big fet can drive all 8 flyback transformers.

With independent flyback transformers, you\'ll get lousy
cross-regulation, and poor output voltage tolerance, due
to Lp differences (that determine energy transfer).

All 8 transformers will have the same turns ratio. I was thinking
their primaries would be in parallel. Same input, same output.


You\'d be better off going for preregulated voltage inverters,
which are (at least) voltage regulated, to begin with.

Or fit all the flyback secondaries on the same core. ($)

RL

I was planning to regulate in each isolated channel

https://www.dropbox.com/s/5lkbvlwz7b4rb2h/Isol_Pulser_1.jpg?raw=1

so the primary-side flyback regulation doesn\'t need to be very good.
Just good enough to make about 200 volts in each channel.

It doesn\'t need to be flyback. Some h-bridge forward converter would
work, if I can get the right transformer ratios. But the flyback looks
easy and versatile.








--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

A single flyback with multiple secondaries seems like the cleanest solution. Since you would need 18 pins on a bobbin, it might be more practical to use two independent flyback converters, each with 4 outputs. There might actually be an off-the-shelf transformer that works for this.

I\'ve never considered driving multiple flyback primaries from one switching FET, but it seems like the outputs could vary by a lot. ... ok you piqued my curiosity, I scribbled out the equations, using V = L dI/dt , and E = 1/2 L I^2, if you vary L by say 20% it looks like the transferred energy will also vary by 20% (if I did that right). So for your idea it might just work. It might be a good idea to add a DC load at the outputs to soak up any energy from the transformers\' leakage inductance.


If the transformers primaries are in parallel, and the turns ratios
are identical, the secondary voltages will be the same.

We have the Coilcraft flyback transformers in stock, so there\'s no
incentive to wind a custom transformer with multiple secondaries.





--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

I understand you\'re trying to use parts in stock, I get that. For a flyback though you have to keep in mind it doesn\'t follow the transformer equation; it transfers energy stored in its magnetizing inductance. E = 1/2 Lmag I^2, and the FET\'s ON time is adjusted so that Energy in = Energy out. For a given lot of flyback inductors, you can expect Lm to vary by maybe 20%. I still think your idea has a good chance of working, especially if you add a DC load to each output.

The flyback primary inductance is the inductance of all 8 primary
windings *in parallel*. They are not independent.

I don\'t expect leakage inductances to have much effect on output
voltage differences.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[Phil Hobbs]

On 2020-07-17 21:41, jlarkin@highlandsniptechnology.com wrote:

On Fri, 17 Jul 2020 21:22:44 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-07-17 20:55, jlarkin@highlandsniptechnology.com wrote:
On Fri, 17 Jul 2020 17:32:44 -0700 (PDT), sea moss
danluster81@gmail.com> wrote:

On Friday, July 17, 2020 at 5:00:09 PM UTC-7, jla...@highlandsniptechnology.com wrote:
On Fri, 17 Jul 2020 19:22:37 -0400, legg <legg@nospam.magma.ca> wrote:

On Fri, 17 Jul 2020 14:31:26 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Fri, 17 Jul 2020 22:42:44 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

jlarkin@highlandsniptechnology.com wrote:

I need eight isolated 150 volt DC supplies, low current, under 1 mA
average. Commercial dc/dc converters are crazy expensive:

If each channel needs some degree of control, the ultimate low-cost
solution looks like this thing:

https://www.ti.com/lit/ds/symlink/tpic6c595.pdf

Strobe G, load whatever you want to SER IN. One of my faves; works like
a charm.

If no control is needed, use 8 MOSFETs fed with the same 50% waveform,
then use each of them as the switch driving a forward/flyback
transformer, whatever you like, and burn excessive power in a zener.

Best regards, Piotr

We use a ton of TPIC6595, a simlar part, as our universal relay and
LED driver. But I don\'t need independent control, and there will be no
uP or FPGA or anything. It\'s refreshing to design an all-analog box
once in a while.

I think one big fet can drive all 8 flyback transformers.

With independent flyback transformers, you\'ll get lousy
cross-regulation, and poor output voltage tolerance, due
to Lp differences (that determine energy transfer).

All 8 transformers will have the same turns ratio. I was thinking
their primaries would be in parallel. Same input, same output.


You\'d be better off going for preregulated voltage inverters,
which are (at least) voltage regulated, to begin with.

Or fit all the flyback secondaries on the same core. ($)

RL

I was planning to regulate in each isolated channel

https://www.dropbox.com/s/5lkbvlwz7b4rb2h/Isol_Pulser_1.jpg?raw=1

so the primary-side flyback regulation doesn\'t need to be very good.
Just good enough to make about 200 volts in each channel.

It doesn\'t need to be flyback. Some h-bridge forward converter would
work, if I can get the right transformer ratios. But the flyback looks
easy and versatile.








--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

A single flyback with multiple secondaries seems like the cleanest solution. Since you would need 18 pins on a bobbin, it might be more practical to use two independent flyback converters, each with 4 outputs. There might actually be an off-the-shelf transformer that works for this.

I\'ve never considered driving multiple flyback primaries from one switching FET, but it seems like the outputs could vary by a lot. ... ok you piqued my curiosity, I scribbled out the equations, using V = L dI/dt , and E = 1/2 L I^2, if you vary L by say 20% it looks like the transferred energy will also vary by 20% (if I did that right). So for your idea it might just work. It might be a good idea to add a DC load at the outputs to soak up any energy from the transformers\' leakage inductance.


If the transformers primaries are in parallel, and the turns ratios
are identical, the secondary voltages will be the same.

Hmm, interesting. ISTM that only works with sufficiently tight
coupling--in the limit of loose coupling the secondary voltages can be
anything depending on the loading on each one. Might work fine for this
purpose though.


Leakage inductances won\'t affect rectified voltage much, and are a
fraction of magnetizing inductance, and the transformers are
identical.

Yeah, but flyback transformers have pretty loose coupling, 0.8 or
thereabouts IIRC. Probably still fine at the +-15% level.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Phil Hobbs]

On 2020-07-17 21:41, jlarkin@highlandsniptechnology.com wrote:

On Fri, 17 Jul 2020 21:22:44 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-07-17 20:55, jlarkin@highlandsniptechnology.com wrote:
On Fri, 17 Jul 2020 17:32:44 -0700 (PDT), sea moss
danluster81@gmail.com> wrote:

On Friday, July 17, 2020 at 5:00:09 PM UTC-7, jla...@highlandsniptechnology.com wrote:
On Fri, 17 Jul 2020 19:22:37 -0400, legg <legg@nospam.magma.ca> wrote:

On Fri, 17 Jul 2020 14:31:26 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Fri, 17 Jul 2020 22:42:44 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

jlarkin@highlandsniptechnology.com wrote:

I need eight isolated 150 volt DC supplies, low current, under 1 mA
average. Commercial dc/dc converters are crazy expensive:

If each channel needs some degree of control, the ultimate low-cost
solution looks like this thing:

https://www.ti.com/lit/ds/symlink/tpic6c595.pdf

Strobe G, load whatever you want to SER IN. One of my faves; works like
a charm.

If no control is needed, use 8 MOSFETs fed with the same 50% waveform,
then use each of them as the switch driving a forward/flyback
transformer, whatever you like, and burn excessive power in a zener.

Best regards, Piotr

We use a ton of TPIC6595, a simlar part, as our universal relay and
LED driver. But I don\'t need independent control, and there will be no
uP or FPGA or anything. It\'s refreshing to design an all-analog box
once in a while.

I think one big fet can drive all 8 flyback transformers.

With independent flyback transformers, you\'ll get lousy
cross-regulation, and poor output voltage tolerance, due
to Lp differences (that determine energy transfer).

All 8 transformers will have the same turns ratio. I was thinking
their primaries would be in parallel. Same input, same output.


You\'d be better off going for preregulated voltage inverters,
which are (at least) voltage regulated, to begin with.

Or fit all the flyback secondaries on the same core. ($)

RL

I was planning to regulate in each isolated channel

https://www.dropbox.com/s/5lkbvlwz7b4rb2h/Isol_Pulser_1.jpg?raw=1

so the primary-side flyback regulation doesn\'t need to be very good.
Just good enough to make about 200 volts in each channel.

It doesn\'t need to be flyback. Some h-bridge forward converter would
work, if I can get the right transformer ratios. But the flyback looks
easy and versatile.








--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

A single flyback with multiple secondaries seems like the cleanest solution. Since you would need 18 pins on a bobbin, it might be more practical to use two independent flyback converters, each with 4 outputs. There might actually be an off-the-shelf transformer that works for this.

I\'ve never considered driving multiple flyback primaries from one switching FET, but it seems like the outputs could vary by a lot. ... ok you piqued my curiosity, I scribbled out the equations, using V = L dI/dt , and E = 1/2 L I^2, if you vary L by say 20% it looks like the transferred energy will also vary by 20% (if I did that right). So for your idea it might just work. It might be a good idea to add a DC load at the outputs to soak up any energy from the transformers\' leakage inductance.


If the transformers primaries are in parallel, and the turns ratios
are identical, the secondary voltages will be the same.

Hmm, interesting. ISTM that only works with sufficiently tight
coupling--in the limit of loose coupling the secondary voltages can be
anything depending on the loading on each one. Might work fine for this
purpose though.


Leakage inductances won\'t affect rectified voltage much, and are a
fraction of magnetizing inductance, and the transformers are
identical.

Yeah, but flyback transformers have pretty loose coupling, 0.8 or
thereabouts IIRC. Probably still fine at the +-15% level.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Phil Hobbs]

On 2020-07-17 21:41, jlarkin@highlandsniptechnology.com wrote:

On Fri, 17 Jul 2020 21:22:44 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-07-17 20:55, jlarkin@highlandsniptechnology.com wrote:
On Fri, 17 Jul 2020 17:32:44 -0700 (PDT), sea moss
danluster81@gmail.com> wrote:

On Friday, July 17, 2020 at 5:00:09 PM UTC-7, jla...@highlandsniptechnology.com wrote:
On Fri, 17 Jul 2020 19:22:37 -0400, legg <legg@nospam.magma.ca> wrote:

On Fri, 17 Jul 2020 14:31:26 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Fri, 17 Jul 2020 22:42:44 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

jlarkin@highlandsniptechnology.com wrote:

I need eight isolated 150 volt DC supplies, low current, under 1 mA
average. Commercial dc/dc converters are crazy expensive:

If each channel needs some degree of control, the ultimate low-cost
solution looks like this thing:

https://www.ti.com/lit/ds/symlink/tpic6c595.pdf

Strobe G, load whatever you want to SER IN. One of my faves; works like
a charm.

If no control is needed, use 8 MOSFETs fed with the same 50% waveform,
then use each of them as the switch driving a forward/flyback
transformer, whatever you like, and burn excessive power in a zener.

Best regards, Piotr

We use a ton of TPIC6595, a simlar part, as our universal relay and
LED driver. But I don\'t need independent control, and there will be no
uP or FPGA or anything. It\'s refreshing to design an all-analog box
once in a while.

I think one big fet can drive all 8 flyback transformers.

With independent flyback transformers, you\'ll get lousy
cross-regulation, and poor output voltage tolerance, due
to Lp differences (that determine energy transfer).

All 8 transformers will have the same turns ratio. I was thinking
their primaries would be in parallel. Same input, same output.


You\'d be better off going for preregulated voltage inverters,
which are (at least) voltage regulated, to begin with.

Or fit all the flyback secondaries on the same core. ($)

RL

I was planning to regulate in each isolated channel

https://www.dropbox.com/s/5lkbvlwz7b4rb2h/Isol_Pulser_1.jpg?raw=1

so the primary-side flyback regulation doesn\'t need to be very good.
Just good enough to make about 200 volts in each channel.

It doesn\'t need to be flyback. Some h-bridge forward converter would
work, if I can get the right transformer ratios. But the flyback looks
easy and versatile.








--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

A single flyback with multiple secondaries seems like the cleanest solution. Since you would need 18 pins on a bobbin, it might be more practical to use two independent flyback converters, each with 4 outputs. There might actually be an off-the-shelf transformer that works for this.

I\'ve never considered driving multiple flyback primaries from one switching FET, but it seems like the outputs could vary by a lot. ... ok you piqued my curiosity, I scribbled out the equations, using V = L dI/dt , and E = 1/2 L I^2, if you vary L by say 20% it looks like the transferred energy will also vary by 20% (if I did that right). So for your idea it might just work. It might be a good idea to add a DC load at the outputs to soak up any energy from the transformers\' leakage inductance.


If the transformers primaries are in parallel, and the turns ratios
are identical, the secondary voltages will be the same.

Hmm, interesting. ISTM that only works with sufficiently tight
coupling--in the limit of loose coupling the secondary voltages can be
anything depending on the loading on each one. Might work fine for this
purpose though.


Leakage inductances won\'t affect rectified voltage much, and are a
fraction of magnetizing inductance, and the transformers are
identical.

Yeah, but flyback transformers have pretty loose coupling, 0.8 or
thereabouts IIRC. Probably still fine at the +-15% level.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com