wide range supply...

[server]

Given that I have 24 vdc, I want a supply adjustable from +1V to +100.
Stable, quiet, current limited. Roughly 10 watts out. I might want
several of these on a board, with independently programmable voltage.
Multi-channel pulse generator.

There are boost-buck chips around, but not to 100v, probably not very
quiet. This might be demanding for a sepic, too.

I was thinking that I could put a boost converter ahead of a linear
regulator. The boost output wouldn\'t go below 24ish, but that\'s ok...
the linear can work from that. I guess the boost output would always
stay 10 volts or so ahead of what the linear needs, kind of like the
trick of bootstrapping an LM317.





--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[Phil Hobbs]

On 2020-08-21 17:56, jlarkin@highlandsniptechnology.com wrote:

Given that I have 24 vdc, I want a supply adjustable from +1V to +100.
Stable, quiet, current limited. Roughly 10 watts out. I might want
several of these on a board, with independently programmable voltage.
Multi-channel pulse generator.

There are boost-buck chips around, but not to 100v, probably not very
quiet. This might be demanding for a sepic, too.

I was thinking that I could put a boost converter ahead of a linear
regulator. The boost output wouldn\'t go below 24ish, but that\'s ok...
the linear can work from that. I guess the boost output would always
stay 10 volts or so ahead of what the linear needs, kind of like the
trick of bootstrapping an LM317.

Could get a bit toasty providing +1V at 100 mA. (I assume that \"10
watts\" doesn\'t include 1V @ 10A.)

You could maybe put a buck before the boost, and at low voltage, let the
current pass through the boost inductor with the converter turned off.

A PFET in parallel with the buck would let you avoid loss of efficiency
at higher voltages, and right near +24, you could run both to avoid any
holes in the adjustment range due to the wall wart sagging a bit, for
instance.

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, 21 Aug 2020 18:33:44 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-08-21 17:56, jlarkin@highlandsniptechnology.com wrote:
Given that I have 24 vdc, I want a supply adjustable from +1V to +100.
Stable, quiet, current limited. Roughly 10 watts out. I might want
several of these on a board, with independently programmable voltage.
Multi-channel pulse generator.

There are boost-buck chips around, but not to 100v, probably not very
quiet. This might be demanding for a sepic, too.

I was thinking that I could put a boost converter ahead of a linear
regulator. The boost output wouldn\'t go below 24ish, but that\'s ok...
the linear can work from that. I guess the boost output would always
stay 10 volts or so ahead of what the linear needs, kind of like the
trick of bootstrapping an LM317.

Could get a bit toasty providing +1V at 100 mA. (I assume that \"10
watts\" doesn\'t include 1V @ 10A.)

If the pulse generator drives an external 50 ohm load, 1 volt is only
20 mA! It\'s at higher output voltages that I\'ll really need a power
limit. I\'d probably have a uP so we could do all sorts of presumably
intelligent DAC-programmed limits.

At 20 volts into the output stage, my 50 ohms and the customer\'s 50
ohms is 100, so my internal dissipation is only 2 watts. But 100 volts
into a customer short is different. They could drive a bar laser stack
or something with low drop too.

(On my cute new all-analog pulse generator, the intelligence comes
from a thermistor!)

You could maybe put a buck before the boost, and at low voltage, let the
current pass through the boost inductor with the converter turned off.

A PFET in parallel with the buck would let you avoid loss of efficiency
at higher voltages, and right near +24, you could run both to avoid any
holes in the adjustment range due to the wall wart sagging a bit, for
instance.

Cheers

Phil Hobbs

--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[Lasse Langwadt Christensen]

fredag den 21. august 2020 kl. 23.57.05 UTC+2 skrev jla...@highlandsniptechnology.com:

Given that I have 24 vdc, I want a supply adjustable from +1V to +100.
Stable, quiet, current limited. Roughly 10 watts out. I might want
several of these on a board, with independently programmable voltage.
Multi-channel pulse generator.

There are boost-buck chips around, but not to 100v, probably not very
quiet. This might be demanding for a sepic, too.

I was thinking that I could put a boost converter ahead of a linear
regulator. The boost output wouldn\'t go below 24ish, but that\'s ok...
the linear can work from that. I guess the boost output would always
stay 10 volts or so ahead of what the linear needs, kind of like the
trick of bootstrapping an LM317.

buck-boost,boost or sepic set for 100V output, pfet with source-gate across
linear regulator(maybe with a divider to increase voltage) shunting the upper set resistor on the switcher

 

[dagmargoodboat@yahoo.com]

On Friday, August 21, 2020 at 5:57:05 PM UTC-4, jla...@highlandsniptechnology.com wrote:

Given that I have 24 vdc, I want a supply adjustable from +1V to +100.
Stable, quiet, current limited. Roughly 10 watts out. I might want
several of these on a board, with independently programmable voltage.
Multi-channel pulse generator.

There are boost-buck chips around, but not to 100v, probably not very
quiet. This might be demanding for a sepic, too.

I was thinking that I could put a boost converter ahead of a linear
regulator. The boost output wouldn\'t go below 24ish, but that\'s ok...
the linear can work from that. I guess the boost output would always
stay 10 volts or so ahead of what the linear needs, kind of like the
trick of bootstrapping an LM317.

Phil\'s buck-into-a-boost is attractive. Here\'s a nuttier idea--you
could convert a buck into a boost with external switches when
needed, or revert to buck mode when that\'s appropriate.

(conceptual boost-mode operation)
Synchronous
Buck L1
.----. .-.-.-. D1
+24V >---| |--+--\' \' \' \'---+--->|---+---> +24..100V
| | | | |
| | | Q1 ||-\' ---
| | | ||<-. --- C1
\'----\' \'---------\'|--+ |
| | GND
GND GND

For buck mode, turn off Q1 and short D1 with a P-FET.

Cheers,
James Arthur

 

[Phil Hobbs]

On 2020-08-21 21:01, dagmargoodboat@yahoo.com wrote:

On Friday, August 21, 2020 at 5:57:05 PM UTC-4, jla...@highlandsniptechnology.com wrote:
Given that I have 24 vdc, I want a supply adjustable from +1V to +100.
Stable, quiet, current limited. Roughly 10 watts out. I might want
several of these on a board, with independently programmable voltage.
Multi-channel pulse generator.

There are boost-buck chips around, but not to 100v, probably not very
quiet. This might be demanding for a sepic, too.

I was thinking that I could put a boost converter ahead of a linear
regulator. The boost output wouldn\'t go below 24ish, but that\'s ok...
the linear can work from that. I guess the boost output would always
stay 10 volts or so ahead of what the linear needs, kind of like the
trick of bootstrapping an LM317.

Phil\'s buck-into-a-boost is attractive. Here\'s a nuttier idea--you
could convert a buck into a boost with external switches when
needed, or revert to buck mode when that\'s appropriate.

(conceptual boost-mode operation)
Synchronous
Buck L1
.----. .-.-.-. D1
+24V >---| |--+--\' \' \' \'---+--->|---+---> +24..100V
| | | | |
| | | Q1 ||-\' ---
| | | ||<-. --- C1
\'----\' \'---------\'|--+ |
| | GND
GND GND

For buck mode, turn off Q1 and short D1 with a P-FET.

Cheers,
James Arthur

Fun!

I wonder if there are any sync bucks simple enough that that would work
stably. The feedback would have to be really slow to avoid the unstable
zero in CCM boost mode. ISTM it makes the volt-second problem a bit
worse, since in boost operation the left end of the inductor is at
ground instead of +24V.

We really need a fast synchronous version of the uA78S40 or MC34060 to
play these sorts of games with. I bet the inventor of the buck
regulator didn\'t think of the trick of grounding the output and letting
it pump its ground pin negative.

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, 21 Aug 2020 22:19:19 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-08-21 21:01, dagmargoodboat@yahoo.com wrote:
On Friday, August 21, 2020 at 5:57:05 PM UTC-4, jla...@highlandsniptechnology.com wrote:
Given that I have 24 vdc, I want a supply adjustable from +1V to +100.
Stable, quiet, current limited. Roughly 10 watts out. I might want
several of these on a board, with independently programmable voltage.
Multi-channel pulse generator.

There are boost-buck chips around, but not to 100v, probably not very
quiet. This might be demanding for a sepic, too.

I was thinking that I could put a boost converter ahead of a linear
regulator. The boost output wouldn\'t go below 24ish, but that\'s ok...
the linear can work from that. I guess the boost output would always
stay 10 volts or so ahead of what the linear needs, kind of like the
trick of bootstrapping an LM317.

Phil\'s buck-into-a-boost is attractive. Here\'s a nuttier idea--you
could convert a buck into a boost with external switches when
needed, or revert to buck mode when that\'s appropriate.

(conceptual boost-mode operation)
Synchronous
Buck L1
.----. .-.-.-. D1
+24V >---| |--+--\' \' \' \'---+--->|---+---> +24..100V
| | | | |
| | | Q1 ||-\' ---
| | | ||<-. --- C1
\'----\' \'---------\'|--+ |
| | GND
GND GND

For buck mode, turn off Q1 and short D1 with a P-FET.

Cheers,
James Arthur


Fun!

I wonder if there are any sync bucks simple enough that that would work
stably. The feedback would have to be really slow to avoid the unstable
zero in CCM boost mode. ISTM it makes the volt-second problem a bit
worse, since in boost operation the left end of the inductor is at
ground instead of +24V.

We really need a fast synchronous version of the uA78S40 or MC34060 to
play these sorts of games with. I bet the inventor of the buck
regulator didn\'t think of the trick of grounding the output and letting
it pump its ground pin negative.

The cheap potted LM78xx replacements will do that. They are really
slick, for a few dollars.

Cheers

Phil Hobbs

I have persuaded the LTM8078 dual synchronous switcher brick to make
+24 into -2.5 and -5, or to make +5 and -5.

My original problem here seems to be non-trivial, especially if I want
to put maybe 5 on a board.

Sepics maybe? Over a 100:1 output range?

These things are fun to design, but you never know if anybody would
want to buy them. It\'s not enough that *I* think it\'s cool.




--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[Bill Sloman]

On Saturday, August 22, 2020 at 7:57:05 AM UTC+10, jla...@highlandsniptechnology.com wrote:

Given that I have 24 vdc, I want a supply adjustable from +1V to +100.
Stable, quiet, current limited. Roughly 10 watts out.

Curious specification. You want 10A at 1v and 100mA at 100V?

I might want
several of these on a board, with independently programmable voltage.
Multi-channel pulse generator.

The different channels need to deliver bigger current pulses into lower output voltages?

<snipped ideas about parts to use for the ill-specified job>

--
Bill Sloman, Sydney

 

[Klaus Kragelund]

On Saturday, August 22, 2020 at 12:33:58 AM UTC+2, Phil Hobbs wrote:

On 2020-08-21 17:56, jlarkin@highlandsniptechnology.com wrote:
Given that I have 24 vdc, I want a supply adjustable from +1V to +100.
Stable, quiet, current limited. Roughly 10 watts out. I might want
several of these on a board, with independently programmable voltage.
Multi-channel pulse generator.

There are boost-buck chips around, but not to 100v, probably not very
quiet. This might be demanding for a sepic, too.

I was thinking that I could put a boost converter ahead of a linear
regulator. The boost output wouldn\'t go below 24ish, but that\'s ok...
the linear can work from that. I guess the boost output would always
stay 10 volts or so ahead of what the linear needs, kind of like the
trick of bootstrapping an LM317.

Could get a bit toasty providing +1V at 100 mA. (I assume that \"10
watts\" doesn\'t include 1V @ 10A.)

You could maybe put a buck before the boost, and at low voltage, let the
current pass through the boost inductor with the converter turned off.

A PFET in parallel with the buck would let you avoid loss of efficiency
at higher voltages, and right near +24, you could run both to avoid any
holes in the adjustment range due to the wall wart sagging a bit, for
instance.

I would do it with a boost first, then a buck

Boost has higher efficiency at high output voltage
Buck is easier to stabilize, so you can turn down the crossover for the boost

 

[server]

On Friday, August 21, 2020 at 5:57:05 PM UTC-4, jla...@highlandsniptechnology.com wrote:

Given that I have 24 vdc, I want a supply adjustable from +1V to +100.
Stable, quiet, current limited. Roughly 10 watts out. I might want
several of these on a board, with independently programmable voltage.
Multi-channel pulse generator.

There are boost-buck chips around, but not to 100v, probably not very
quiet. This might be demanding for a sepic, too.

I was thinking that I could put a boost converter ahead of a linear
regulator. The boost output wouldn\'t go below 24ish, but that\'s ok...
the linear can work from that. I guess the boost output would always
stay 10 volts or so ahead of what the linear needs, kind of like the
trick of bootstrapping an LM317.





--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

If you start off the AC lines and move down?

In the lab supplies I use I hear clicking sounds when certain voltage points are crossed. They must have more than one internal configuration

 

[Jan Panteltje]

On a sunny day (Fri, 21 Aug 2020 14:56:56 -0700) it happened
jlarkin@highlandsniptechnology.com wrote in
<guf0kfd3ip0c7fthrunnhck9hm9k7lc5gr@4ax.com>:

Given that I have 24 vdc, I want a supply adjustable from +1V to +100.
Stable, quiet, current limited. Roughly 10 watts out. I might want
several of these on a board, with independently programmable voltage.
Multi-channel pulse generator.

There are boost-buck chips around, but not to 100v, probably not very
quiet. This might be demanding for a sepic, too.

I was thinking that I could put a boost converter ahead of a linear
regulator. The boost output wouldn\'t go below 24ish, but that\'s ok...
the linear can work from that. I guess the boost output would always
stay 10 volts or so ahead of what the linear needs, kind of like the
trick of bootstrapping an LM317.

When I need higher voltage AC 60Hz I use my audio amp and a mains
transformer in reverse.. PC as signal generator, 50 Hz mains here.
(to drive cryo cooler for example)
Depending on the step up transformer you could go to several kHz
my smaller amp is about 60 W, the bigger 300W.. both are linear,
not much RFI.
Simple rectifier filter at kHz,
use a current sensor to pull volume down (JFET or something).
Volume control is output voltage adjustment.
There must be some 24 DC audio amp modules around,
else a few transistors, classic.
Efficiency? important at 10W?

 

[server]

On Sat, 22 Aug 2020 04:04:01 -0700 (PDT), blocher@columbus.rr.com
wrote:

On Friday, August 21, 2020 at 5:57:05 PM UTC-4, jla...@highlandsniptechnology.com wrote:
Given that I have 24 vdc, I want a supply adjustable from +1V to +100.
Stable, quiet, current limited. Roughly 10 watts out. I might want
several of these on a board, with independently programmable voltage.
Multi-channel pulse generator.

There are boost-buck chips around, but not to 100v, probably not very
quiet. This might be demanding for a sepic, too.

I was thinking that I could put a boost converter ahead of a linear
regulator. The boost output wouldn\'t go below 24ish, but that\'s ok...
the linear can work from that. I guess the boost output would always
stay 10 volts or so ahead of what the linear needs, kind of like the
trick of bootstrapping an LM317.





--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

If you start off the AC lines and move down?

We very rarely connect to the AC lines. Most of our stuff runs off
24VDC from a wall-wart. The better warts are cheap and work really
well and are plastered with compliance stickers, presumably real. It\'s
easier to write up a CE conformance report if you use a wart.

Our new rackmount AC source uses a MeanWell 48V, 1KW metal-box supply.
I hope no customer asks for a CE sticker on that one! That would take
some creative writing.

My new tiny pulse generator uses a 48V wart. The wart accepts
worldwide line voltages and comes with a set of international plug
adapters. I just linear regulate down from 48, to get +44 to +1, but
that\'s inefficient and won\'t scale for voltage or more channels.

The abstract problem is, what\'s a good way to get quiet 1 to 100 volts
DC in a couple of square inches of PCB area?

In the lab supplies I use I hear clicking sounds when certain voltage points are crossed. They must have more than one internal configuration

Some of ours do that. They are the heavy ones that probably have a
line-frequency power transformer, and they are switching taps with
relays.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[server]

On Sat, 22 Aug 2020 12:37:38 GMT, Jan Panteltje
<pNaOnStPeAlMtje@yahoo.com> wrote:

On a sunny day (Fri, 21 Aug 2020 14:56:56 -0700) it happened
jlarkin@highlandsniptechnology.com wrote in
guf0kfd3ip0c7fthrunnhck9hm9k7lc5gr@4ax.com>:

Given that I have 24 vdc, I want a supply adjustable from +1V to +100.
Stable, quiet, current limited. Roughly 10 watts out. I might want
several of these on a board, with independently programmable voltage.
Multi-channel pulse generator.

There are boost-buck chips around, but not to 100v, probably not very
quiet. This might be demanding for a sepic, too.

I was thinking that I could put a boost converter ahead of a linear
regulator. The boost output wouldn\'t go below 24ish, but that\'s ok...
the linear can work from that. I guess the boost output would always
stay 10 volts or so ahead of what the linear needs, kind of like the
trick of bootstrapping an LM317.

When I need higher voltage AC 60Hz I use my audio amp and a mains
transformer in reverse.. PC as signal generator, 50 Hz mains here.
(to drive cryo cooler for example)
Depending on the step up transformer you could go to several kHz
my smaller amp is about 60 W, the bigger 300W.. both are linear,
not much RFI.
Simple rectifier filter at kHz,
use a current sensor to pull volume down (JFET or something).
Volume control is output voltage adjustment.
There must be some 24 DC audio amp modules around,
else a few transistors, classic.
Efficiency? important at 10W?

I used to make electric meters, and we did that to test them. I got a
gigantic PA amp from a music store (Peavey, 800 watt stereo) and ran a
big power transformer backwards for voltage, and used a 190-amp
filament transformer to make current.

Ordinary power transformers seem to work fine over the audio range, or
more.




--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[Phil Hobbs]

On 2020-08-22 06:23, Klaus Kragelund wrote:

On Saturday, August 22, 2020 at 12:33:58 AM UTC+2, Phil Hobbs wrote:
On 2020-08-21 17:56, jlarkin@highlandsniptechnology.com wrote:
Given that I have 24 vdc, I want a supply adjustable from +1V to +100.
Stable, quiet, current limited. Roughly 10 watts out. I might want
several of these on a board, with independently programmable voltage.
Multi-channel pulse generator.

There are boost-buck chips around, but not to 100v, probably not very
quiet. This might be demanding for a sepic, too.

I was thinking that I could put a boost converter ahead of a linear
regulator. The boost output wouldn\'t go below 24ish, but that\'s ok...
the linear can work from that. I guess the boost output would always
stay 10 volts or so ahead of what the linear needs, kind of like the
trick of bootstrapping an LM317.

Could get a bit toasty providing +1V at 100 mA. (I assume that \"10
watts\" doesn\'t include 1V @ 10A.)

You could maybe put a buck before the boost, and at low voltage, let the
current pass through the boost inductor with the converter turned off.

A PFET in parallel with the buck would let you avoid loss of efficiency
at higher voltages, and right near +24, you could run both to avoid any
holes in the adjustment range due to the wall wart sagging a bit, for
instance.

I would do it with a boost first, then a buck

Boost has higher efficiency at high output voltage
Buck is easier to stabilize, so you can turn down the crossover for the boost

Do you have any fave bucks that will survive 100V on the supply pin, or
even half that?

I\'m frequently in need of a decent buck that\'ll run at 500 kHz or more
and handle >40V on the input, generally on account of wanting to make
-18 or so from +24. I usually buck down to ~+13, then invert from
there. (It\'s also an OK rail to make logic supplies from--mine usually
don\'t take a lot of current.)

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 2020-08-22 00:53, jlarkin@highlandsniptechnology.com wrote:

On Fri, 21 Aug 2020 22:19:19 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-08-21 21:01, dagmargoodboat@yahoo.com wrote:
On Friday, August 21, 2020 at 5:57:05 PM UTC-4, jla...@highlandsniptechnology.com wrote:
Given that I have 24 vdc, I want a supply adjustable from +1V to +100.
Stable, quiet, current limited. Roughly 10 watts out. I might want
several of these on a board, with independently programmable voltage.
Multi-channel pulse generator.

There are boost-buck chips around, but not to 100v, probably not very
quiet. This might be demanding for a sepic, too.

I was thinking that I could put a boost converter ahead of a linear
regulator. The boost output wouldn\'t go below 24ish, but that\'s ok...
the linear can work from that. I guess the boost output would always
stay 10 volts or so ahead of what the linear needs, kind of like the
trick of bootstrapping an LM317.

Phil\'s buck-into-a-boost is attractive. Here\'s a nuttier idea--you
could convert a buck into a boost with external switches when
needed, or revert to buck mode when that\'s appropriate.

(conceptual boost-mode operation)
Synchronous
Buck L1
.----. .-.-.-. D1
+24V >---| |--+--\' \' \' \'---+--->|---+---> +24..100V
| | | | |
| | | Q1 ||-\' ---
| | | ||<-. --- C1
\'----\' \'---------\'|--+ |
| | GND
GND GND

For buck mode, turn off Q1 and short D1 with a P-FET.

Cheers,
James Arthur


Fun!

I wonder if there are any sync bucks simple enough that that would work
stably. The feedback would have to be really slow to avoid the unstable
zero in CCM boost mode. ISTM it makes the volt-second problem a bit
worse, since in boost operation the left end of the inductor is at
ground instead of +24V.

We really need a fast synchronous version of the uA78S40 or MC34060 to
play these sorts of games with. I bet the inventor of the buck
regulator didn\'t think of the trick of grounding the output and letting
it pump its ground pin negative.

The cheap potted LM78xx replacements will do that. They are really
slick, for a few dollars.

Their only problem for that use is that the input reservoir cap gets
returned to the negative output instead of ground, so you have to put in
an outboard reservoir.

I have persuaded the LTM8078 dual synchronous switcher brick to make
+24 into -2.5 and -5, or to make +5 and -5.

Nice.

My original problem here seems to be non-trivial, especially if I want
to put maybe 5 on a board.

Sepics maybe? Over a 100:1 output range?

Dunno. Never done any SMPSes fancier than a flybuck or an auxiliary HV
output based on the free AC at the switch node.

These things are fun to design, but you never know if anybody would
want to buy them. It\'s not enough that *I* think it\'s cool.

Customers are so annoying. Fortunately if you ignore them, they go away.

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 Sat, 22 Aug 2020 12:08:18 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-08-22 00:53, jlarkin@highlandsniptechnology.com wrote:
On Fri, 21 Aug 2020 22:19:19 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-08-21 21:01, dagmargoodboat@yahoo.com wrote:
On Friday, August 21, 2020 at 5:57:05 PM UTC-4, jla...@highlandsniptechnology.com wrote:
Given that I have 24 vdc, I want a supply adjustable from +1V to +100.
Stable, quiet, current limited. Roughly 10 watts out. I might want
several of these on a board, with independently programmable voltage.
Multi-channel pulse generator.

There are boost-buck chips around, but not to 100v, probably not very
quiet. This might be demanding for a sepic, too.

I was thinking that I could put a boost converter ahead of a linear
regulator. The boost output wouldn\'t go below 24ish, but that\'s ok...
the linear can work from that. I guess the boost output would always
stay 10 volts or so ahead of what the linear needs, kind of like the
trick of bootstrapping an LM317.

Phil\'s buck-into-a-boost is attractive. Here\'s a nuttier idea--you
could convert a buck into a boost with external switches when
needed, or revert to buck mode when that\'s appropriate.

(conceptual boost-mode operation)
Synchronous
Buck L1
.----. .-.-.-. D1
+24V >---| |--+--\' \' \' \'---+--->|---+---> +24..100V
| | | | |
| | | Q1 ||-\' ---
| | | ||<-. --- C1
\'----\' \'---------\'|--+ |
| | GND
GND GND

For buck mode, turn off Q1 and short D1 with a P-FET.

Cheers,
James Arthur


Fun!

I wonder if there are any sync bucks simple enough that that would work
stably. The feedback would have to be really slow to avoid the unstable
zero in CCM boost mode. ISTM it makes the volt-second problem a bit
worse, since in boost operation the left end of the inductor is at
ground instead of +24V.

We really need a fast synchronous version of the uA78S40 or MC34060 to
play these sorts of games with. I bet the inventor of the buck
regulator didn\'t think of the trick of grounding the output and letting
it pump its ground pin negative.

The cheap potted LM78xx replacements will do that. They are really
slick, for a few dollars.

Their only problem for that use is that the input reservoir cap gets
returned to the negative output instead of ground, so you have to put in
an outboard reservoir.


I have persuaded the LTM8078 dual synchronous switcher brick to make
+24 into -2.5 and -5, or to make +5 and -5.

Nice.


My original problem here seems to be non-trivial, especially if I want
to put maybe 5 on a board.

Sepics maybe? Over a 100:1 output range?

Dunno. Never done any SMPSes fancier than a flybuck or an auxiliary HV
output based on the free AC at the switch node.

We\'ve done some SEPICs with the cheap dual inductors. They are a nice
boost-buck thing at small additional expense.

These things are fun to design, but you never know if anybody would
want to buy them. It\'s not enough that *I* think it\'s cool.

Customers are so annoying. Fortunately if you ignore them, they go away.

Cheers

Phil Hobbs

--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[Phil Hobbs]

On 2020-08-22 00:53, jlarkin@highlandsniptechnology.com wrote:

On Fri, 21 Aug 2020 22:19:19 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-08-21 21:01, dagmargoodboat@yahoo.com wrote:
On Friday, August 21, 2020 at 5:57:05 PM UTC-4, jla...@highlandsniptechnology.com wrote:
Given that I have 24 vdc, I want a supply adjustable from +1V to +100.
Stable, quiet, current limited. Roughly 10 watts out. I might want
several of these on a board, with independently programmable voltage.
Multi-channel pulse generator.

There are boost-buck chips around, but not to 100v, probably not very
quiet. This might be demanding for a sepic, too.

I was thinking that I could put a boost converter ahead of a linear
regulator. The boost output wouldn\'t go below 24ish, but that\'s ok...
the linear can work from that. I guess the boost output would always
stay 10 volts or so ahead of what the linear needs, kind of like the
trick of bootstrapping an LM317.

Phil\'s buck-into-a-boost is attractive. Here\'s a nuttier idea--you
could convert a buck into a boost with external switches when
needed, or revert to buck mode when that\'s appropriate.

(conceptual boost-mode operation)
Synchronous
Buck L1
.----. .-.-.-. D1
+24V >---| |--+--\' \' \' \'---+--->|---+---> +24..100V
| | | | |
| | | Q1 ||-\' ---
| | | ||<-. --- C1
\'----\' \'---------\'|--+ |
| | GND
GND GND

For buck mode, turn off Q1 and short D1 with a P-FET.

Cheers,
James Arthur


Fun!

I wonder if there are any sync bucks simple enough that that would work
stably. The feedback would have to be really slow to avoid the unstable
zero in CCM boost mode. ISTM it makes the volt-second problem a bit
worse, since in boost operation the left end of the inductor is at
ground instead of +24V.

We really need a fast synchronous version of the uA78S40 or MC34060 to
play these sorts of games with. I bet the inventor of the buck
regulator didn\'t think of the trick of grounding the output and letting
it pump its ground pin negative.

The cheap potted LM78xx replacements will do that. They are really
slick, for a few dollars.

I have persuaded the LTM8078 dual synchronous switcher brick to make
+24 into -2.5 and -5, or to make +5 and -5.

My original problem here seems to be non-trivial, especially if I want
to put maybe 5 on a board.

For a miniature laser driver board, I\'ve used AOZ1282CI-2 (400 mA, 1
MHz, SOT23) for an inverting buck to make -14 from +5, LMR23630 (2 MHz,
3A) for the class-H TEC driver, and TPS61175 (2 MHz, 3A) to make +15.
That boost won\'t take 24V input, but the whole works fit inside a 1\" x
1.5\" x 1/4\" board-level shield can (Leader Tech SMS-205 series).

The board is credit-card sized, stuffed both sides, and cooled via a 5
W/m/K gap pad.

With all those volt-seconds to deal with, your gizmo will probably need
a larger-volume inductor for the boost, and to make +100V I expect
you\'ll need a controller chip plus outboard FET, but on the plus side
you only need two supplies rather than three.

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 Sat, 22 Aug 2020 12:03:59 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-08-22 06:23, Klaus Kragelund wrote:
On Saturday, August 22, 2020 at 12:33:58 AM UTC+2, Phil Hobbs wrote:
On 2020-08-21 17:56, jlarkin@highlandsniptechnology.com wrote:
Given that I have 24 vdc, I want a supply adjustable from +1V to +100.
Stable, quiet, current limited. Roughly 10 watts out. I might want
several of these on a board, with independently programmable voltage.
Multi-channel pulse generator.

There are boost-buck chips around, but not to 100v, probably not very
quiet. This might be demanding for a sepic, too.

I was thinking that I could put a boost converter ahead of a linear
regulator. The boost output wouldn\'t go below 24ish, but that\'s ok...
the linear can work from that. I guess the boost output would always
stay 10 volts or so ahead of what the linear needs, kind of like the
trick of bootstrapping an LM317.

Could get a bit toasty providing +1V at 100 mA. (I assume that \"10
watts\" doesn\'t include 1V @ 10A.)

You could maybe put a buck before the boost, and at low voltage, let the
current pass through the boost inductor with the converter turned off.

A PFET in parallel with the buck would let you avoid loss of efficiency
at higher voltages, and right near +24, you could run both to avoid any
holes in the adjustment range due to the wall wart sagging a bit, for
instance.

I would do it with a boost first, then a buck

Boost has higher efficiency at high output voltage
Buck is easier to stabilize, so you can turn down the crossover for the boost


Do you have any fave bucks that will survive 100V on the supply pin, or
even half that?

I\'m frequently in need of a decent buck that\'ll run at 500 kHz or more
and handle >40V on the input, generally on account of wanting to make
-18 or so from +24. I usually buck down to ~+13, then invert from
there. (It\'s also an OK rail to make logic supplies from--mine usually
don\'t take a lot of current.)

Cheers

Phil Hobbs

Rather than battling the high voltage multiple times, I just go down
to 12 and split off from there. A couple of people make the little
3-pin things that will work from 72 volts.






--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[Phil Hobbs]

On 2020-08-22 12:31, jlarkin@highlandsniptechnology.com wrote:

On Sat, 22 Aug 2020 12:03:59 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-08-22 06:23, Klaus Kragelund wrote:
On Saturday, August 22, 2020 at 12:33:58 AM UTC+2, Phil Hobbs wrote:
On 2020-08-21 17:56, jlarkin@highlandsniptechnology.com wrote:
Given that I have 24 vdc, I want a supply adjustable from +1V to +100.
Stable, quiet, current limited. Roughly 10 watts out. I might want
several of these on a board, with independently programmable voltage.
Multi-channel pulse generator.

There are boost-buck chips around, but not to 100v, probably not very
quiet. This might be demanding for a sepic, too.

I was thinking that I could put a boost converter ahead of a linear
regulator. The boost output wouldn\'t go below 24ish, but that\'s ok...
the linear can work from that. I guess the boost output would always
stay 10 volts or so ahead of what the linear needs, kind of like the
trick of bootstrapping an LM317.

Could get a bit toasty providing +1V at 100 mA. (I assume that \"10
watts\" doesn\'t include 1V @ 10A.)

You could maybe put a buck before the boost, and at low voltage, let the
current pass through the boost inductor with the converter turned off.

A PFET in parallel with the buck would let you avoid loss of efficiency
at higher voltages, and right near +24, you could run both to avoid any
holes in the adjustment range due to the wall wart sagging a bit, for
instance.

I would do it with a boost first, then a buck

Boost has higher efficiency at high output voltage
Buck is easier to stabilize, so you can turn down the crossover for the boost


Do you have any fave bucks that will survive 100V on the supply pin, or
even half that?

I\'m frequently in need of a decent buck that\'ll run at 500 kHz or more
and handle >40V on the input, generally on account of wanting to make
-18 or so from +24. I usually buck down to ~+13, then invert from
there. (It\'s also an OK rail to make logic supplies from--mine usually
don\'t take a lot of current.)

Cheers

Phil Hobbs

Rather than battling the high voltage multiple times, I just go down
to 12 and split off from there. A couple of people make the little
3-pin things that will work from 72 volts.

Yeah, I\'ve come to the same conclusion. Those LMR23630s are pretty good
medicine if you don\'t mind the 650-ps edges. (I always put them in a
Faraday cage, so I don\'t care very much.)

I have this little discrete Schmitt trigger circuit for startup
purposes--it runs the +3.3 linear supply for the MCU off +24 until the
low-voltage rail comes up. One dual NPN, one BSS84, a diode, and four
resistors. That way I can just have the micro deal with the supply
sequencing as it likes. (Since Simon has got so good at it, we put
Cortex M0+ or M4F/M0+ micros in lots of things that would have been
all-analogue previously.)

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

 

[Lasse Langwadt Christensen]

lørdag den 22. august 2020 kl. 18.04.13 UTC+2 skrev Phil Hobbs:

On 2020-08-22 06:23, Klaus Kragelund wrote:
On Saturday, August 22, 2020 at 12:33:58 AM UTC+2, Phil Hobbs wrote:
On 2020-08-21 17:56, jlarkin@highlandsniptechnology.com wrote:
Given that I have 24 vdc, I want a supply adjustable from +1V to +100..
Stable, quiet, current limited. Roughly 10 watts out. I might want
several of these on a board, with independently programmable voltage.
Multi-channel pulse generator.

There are boost-buck chips around, but not to 100v, probably not very
quiet. This might be demanding for a sepic, too.

I was thinking that I could put a boost converter ahead of a linear
regulator. The boost output wouldn\'t go below 24ish, but that\'s ok...
the linear can work from that. I guess the boost output would always
stay 10 volts or so ahead of what the linear needs, kind of like the
trick of bootstrapping an LM317.

Could get a bit toasty providing +1V at 100 mA. (I assume that \"10
watts\" doesn\'t include 1V @ 10A.)

You could maybe put a buck before the boost, and at low voltage, let the
current pass through the boost inductor with the converter turned off.

A PFET in parallel with the buck would let you avoid loss of efficiency
at higher voltages, and right near +24, you could run both to avoid any
holes in the adjustment range due to the wall wart sagging a bit, for
instance.

I would do it with a boost first, then a buck

Boost has higher efficiency at high output voltage
Buck is easier to stabilize, so you can turn down the crossover for the boost


Do you have any fave bucks that will survive 100V on the supply pin, or
even half that?

LM5164 ?