Slow fade-in circuit...

[Tabby]

On Monday, 28 September 2020 01:19:11 UTC+1, rhor...@gmail.com wrote:

I did some testing, and the dimmable LED bulb I used did not turn on with 64VDC, although it did pull a couple of milliamps at that voltage. That is as high a voltage as my lab power supply can produce, so I am going to order some parts to build a variable output high voltage supply, but of course they will take a few days to get here.

Meanwhile, pending testing, I am leaning toward a PWM oscillator with a voltage controlled duty cycle fed by a simple voltage integrator, pending the results of the high voltage testing. It is already clear a simple AC or DC voltage ramp is not going to work well. Pity

no such thing is clear, but a current ramp-up works much better.


NT

 

[Tabby]

On Monday, 28 September 2020 04:00:57 UTC+1, whit3rd wrote:

On Sunday, September 27, 2020 at 8:40:17 AM UTC-7, George Herold wrote:

That is fun!
Do NTCs, PTCs have lifetime, number of uses limits?
(I know I could search on DK... but that\'s work. :^)

PTCs definitely do; the motor start circuit in my fridge konked out a few years back,
and (1) GE parts department didn\'t have any stock, (2) it was available on eBay
only after I identified the 120V version (Chinese electricity is 220V, and there\'s
a LOT of 220V motor-start PTC aka \"relay\" available). Before the part came in
the mail, I\'d been tripping over ice chests in the kitchen for almost a week.

PTCs, though, ARE cheap; I got half a dozen spares.

If\'n you want a light to come up slow, resistive can work for you, but not if you want it to dim
gently as well.

drop it in ice

 

[Fred Bloggs]

On Friday, September 25, 2020 at 10:25:53 PM UTC-4, jla...@highlandsniptechnology.com wrote:

On Fri, 25 Sep 2020 17:29:21 -0700 (PDT), \"rhor...@gmail.com\"
rhor...@gmail.com> wrote:

On Friday, September 25, 2020 at 4:56:32 PM UTC-5, John Larkin wrote:

Do you feel like building a circuit? It could be done with 5 discrete
parts, or possibly 3.

Yes, of course! I am having a little trouble imagining only 5 components, let alone 3, but I am game to look at anything.

I did find a nice, small buck converter module that is only 7mm x 4.5mm with up to 450V input and 300ma output. It only requires 13 external components, all of which can be 1206 SMDs except for a small inductor. This makes a trailing edge MOSFET based dimmer using a 555 practical. It\'s $2.24, but I can handle that.
Guess nobody wants to play. As usual.

One of these might work:

https://www.dropbox.com/s/616xu5p4z1bw2yb/LED_Soft-Start.JPG?raw=1

The lower one starts at half brightness, because of the mosfet
substrate diode. Upper one probably doesn\'t need R2 if you use a
protected-gate fet.

I don\'t have time to Spice these, but either should work.

There are some variants, like an RC and a source follower maybe.

https://www.dropbox.com/s/g3kaaaauft986b9/LED_Soft_Follower.JPG?raw=1





--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

According to a summary published in one of the industry mags, the dimmable LEDs contain this circuit or something similar. It has PFC correction as well as an algorithm to decode the RMS input from a conventional TRIAC dimmer to a current drive for the LED.
https://www.ti.com/product/LM3450
The operation of the eval boards makes no sense whatsoever. LIke what good is a 700mA CC on a low wattage bulb.
So working with this idea, you can buy a miniaturized TRIAC dimmer off ebay, replace the slider with an LDR, and control it with a cheap Arduino or something. Any more effort than that isn\'t worth it.

 

[John Larkin]

On Mon, 28 Sep 2020 12:27:46 -0700 (PDT), Fred Bloggs
<bloggs.fredbloggs.fred@gmail.com> wrote:

On Friday, September 25, 2020 at 10:25:53 PM UTC-4, jla...@highlandsniptechnology.com wrote:
On Fri, 25 Sep 2020 17:29:21 -0700 (PDT), \"rhor...@gmail.com\"
rhor...@gmail.com> wrote:

On Friday, September 25, 2020 at 4:56:32 PM UTC-5, John Larkin wrote:

Do you feel like building a circuit? It could be done with 5 discrete
parts, or possibly 3.

Yes, of course! I am having a little trouble imagining only 5 components, let alone 3, but I am game to look at anything.

I did find a nice, small buck converter module that is only 7mm x 4.5mm with up to 450V input and 300ma output. It only requires 13 external components, all of which can be 1206 SMDs except for a small inductor. This makes a trailing edge MOSFET based dimmer using a 555 practical. It\'s $2.24, but I can handle that.
Guess nobody wants to play. As usual.

One of these might work:

https://www.dropbox.com/s/616xu5p4z1bw2yb/LED_Soft-Start.JPG?raw=1

The lower one starts at half brightness, because of the mosfet
substrate diode. Upper one probably doesn\'t need R2 if you use a
protected-gate fet.

I don\'t have time to Spice these, but either should work.

There are some variants, like an RC and a source follower maybe.

https://www.dropbox.com/s/g3kaaaauft986b9/LED_Soft_Follower.JPG?raw=1





--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

According to a summary published in one of the industry mags, the dimmable LEDs contain this circuit or something similar. It has PFC correction as well as an algorithm to decode the RMS input from a conventional TRIAC dimmer to a current drive for the LED.
https://www.ti.com/product/LM3450
The operation of the eval boards makes no sense whatsoever. LIke what good is a 700mA CC on a low wattage bulb.
So working with this idea, you can buy a miniaturized TRIAC dimmer off ebay, replace the slider with an LDR, and control it with a cheap Arduino or something. Any more effort than that isn\'t worth it.

I occasionally rip open an LED bulb. Lately they seem to have no
inductors, just a bridge and a simple linear IC current limiter. All
that other stuff is too complex and too expensive.

 

[Lasse Langwadt Christensen]

mandag den 28. september 2020 kl. 22.41.59 UTC+2 skrev John Larkin:

On Mon, 28 Sep 2020 12:27:46 -0700 (PDT), Fred Bloggs
bloggs.fredbloggs.fred@gmail.com> wrote:

On Friday, September 25, 2020 at 10:25:53 PM UTC-4, jla...@highlandsniptechnology.com wrote:
On Fri, 25 Sep 2020 17:29:21 -0700 (PDT), \"rhor...@gmail.com\"
rhor...@gmail.com> wrote:

On Friday, September 25, 2020 at 4:56:32 PM UTC-5, John Larkin wrote:

Do you feel like building a circuit? It could be done with 5 discrete
parts, or possibly 3.

Yes, of course! I am having a little trouble imagining only 5 components, let alone 3, but I am game to look at anything.

I did find a nice, small buck converter module that is only 7mm x 4.5mm with up to 450V input and 300ma output. It only requires 13 external components, all of which can be 1206 SMDs except for a small inductor. This makes a trailing edge MOSFET based dimmer using a 555 practical. It\'s $2.24, but I can handle that.
Guess nobody wants to play. As usual.

One of these might work:

https://www.dropbox.com/s/616xu5p4z1bw2yb/LED_Soft-Start.JPG?raw=1

The lower one starts at half brightness, because of the mosfet
substrate diode. Upper one probably doesn\'t need R2 if you use a
protected-gate fet.

I don\'t have time to Spice these, but either should work.

There are some variants, like an RC and a source follower maybe.

https://www.dropbox.com/s/g3kaaaauft986b9/LED_Soft_Follower.JPG?raw=1





--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

According to a summary published in one of the industry mags, the dimmable LEDs contain this circuit or something similar. It has PFC correction as well as an algorithm to decode the RMS input from a conventional TRIAC dimmer to a current drive for the LED.
https://www.ti.com/product/LM3450
The operation of the eval boards makes no sense whatsoever. LIke what good is a 700mA CC on a low wattage bulb.
So working with this idea, you can buy a miniaturized TRIAC dimmer off ebay, replace the slider with an LDR, and control it with a cheap Arduino or something. Any more effort than that isn\'t worth it.


I occasionally rip open an LED bulb. Lately they seem to have no
inductors, just a bridge and a simple linear IC current limiter. All
that other stuff is too complex and too expensive.

I assume they have switched to much longer strings of LEDs so they don\'t have
to drop much voltage

 

[Fred Bloggs]

On Monday, September 28, 2020 at 4:41:59 PM UTC-4, John Larkin wrote:

On Mon, 28 Sep 2020 12:27:46 -0700 (PDT), Fred Bloggs
bloggs.fred...@gmail.com> wrote:

On Friday, September 25, 2020 at 10:25:53 PM UTC-4, jla...@highlandsniptechnology.com wrote:
On Fri, 25 Sep 2020 17:29:21 -0700 (PDT), \"rhor...@gmail.com\"
rhor...@gmail.com> wrote:

On Friday, September 25, 2020 at 4:56:32 PM UTC-5, John Larkin wrote:

Do you feel like building a circuit? It could be done with 5 discrete
parts, or possibly 3.

Yes, of course! I am having a little trouble imagining only 5 components, let alone 3, but I am game to look at anything.

I did find a nice, small buck converter module that is only 7mm x 4.5mm with up to 450V input and 300ma output. It only requires 13 external components, all of which can be 1206 SMDs except for a small inductor. This makes a trailing edge MOSFET based dimmer using a 555 practical. It\'s $2.24, but I can handle that.
Guess nobody wants to play. As usual.

One of these might work:

https://www.dropbox.com/s/616xu5p4z1bw2yb/LED_Soft-Start.JPG?raw=1

The lower one starts at half brightness, because of the mosfet
substrate diode. Upper one probably doesn\'t need R2 if you use a
protected-gate fet.

I don\'t have time to Spice these, but either should work.

There are some variants, like an RC and a source follower maybe.

https://www.dropbox.com/s/g3kaaaauft986b9/LED_Soft_Follower.JPG?raw=1





--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

According to a summary published in one of the industry mags, the dimmable LEDs contain this circuit or something similar. It has PFC correction as well as an algorithm to decode the RMS input from a conventional TRIAC dimmer to a current drive for the LED.
https://www.ti.com/product/LM3450
The operation of the eval boards makes no sense whatsoever. LIke what good is a 700mA CC on a low wattage bulb.
So working with this idea, you can buy a miniaturized TRIAC dimmer off ebay, replace the slider with an LDR, and control it with a cheap Arduino or something. Any more effort than that isn\'t worth it.
I occasionally rip open an LED bulb. Lately they seem to have no
inductors, just a bridge and a simple linear IC current limiter. All
that other stuff is too complex and too expensive.

My point was not to use the LM3450, but to justify using this piece of crap:

https://www.homedepot.com/p/Westek-200-Watt-Full-Range-Replacement-Dimmer-Black-6077B/100644824

Get it?

 

[John Larkin]

On Mon, 28 Sep 2020 13:54:32 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

mandag den 28. september 2020 kl. 22.41.59 UTC+2 skrev John Larkin:
On Mon, 28 Sep 2020 12:27:46 -0700 (PDT), Fred Bloggs
bloggs.fredbloggs.fred@gmail.com> wrote:

On Friday, September 25, 2020 at 10:25:53 PM UTC-4, jla...@highlandsniptechnology.com wrote:
On Fri, 25 Sep 2020 17:29:21 -0700 (PDT), \"rhor...@gmail.com\"
rhor...@gmail.com> wrote:

On Friday, September 25, 2020 at 4:56:32 PM UTC-5, John Larkin wrote:

Do you feel like building a circuit? It could be done with 5 discrete
parts, or possibly 3.

Yes, of course! I am having a little trouble imagining only 5 components, let alone 3, but I am game to look at anything.

I did find a nice, small buck converter module that is only 7mm x 4.5mm with up to 450V input and 300ma output. It only requires 13 external components, all of which can be 1206 SMDs except for a small inductor. This makes a trailing edge MOSFET based dimmer using a 555 practical. It\'s $2.24, but I can handle that.
Guess nobody wants to play. As usual.

One of these might work:

https://www.dropbox.com/s/616xu5p4z1bw2yb/LED_Soft-Start.JPG?raw=1

The lower one starts at half brightness, because of the mosfet
substrate diode. Upper one probably doesn\'t need R2 if you use a
protected-gate fet.

I don\'t have time to Spice these, but either should work.

There are some variants, like an RC and a source follower maybe.

https://www.dropbox.com/s/g3kaaaauft986b9/LED_Soft_Follower.JPG?raw=1





--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

According to a summary published in one of the industry mags, the dimmable LEDs contain this circuit or something similar. It has PFC correction as well as an algorithm to decode the RMS input from a conventional TRIAC dimmer to a current drive for the LED.
https://www.ti.com/product/LM3450
The operation of the eval boards makes no sense whatsoever. LIke what good is a 700mA CC on a low wattage bulb.
So working with this idea, you can buy a miniaturized TRIAC dimmer off ebay, replace the slider with an LDR, and control it with a cheap Arduino or something. Any more effort than that isn\'t worth it.


I occasionally rip open an LED bulb. Lately they seem to have no
inductors, just a bridge and a simple linear IC current limiter. All
that other stuff is too complex and too expensive.

I assume they have switched to much longer strings of LEDs so they don\'t have
to drop much voltage

Probably so. The fake Edison lamps have a *lot* of LEDs in series.

There is some common, ultra-cheap current limiter IC. I can\'t recall
the part number.

 

[gray_wolf]

On 28/09/2020 3:41 pm, John Larkin wrote:

On Mon, 28 Sep 2020 12:27:46 -0700 (PDT), Fred Bloggs
bloggs.fredbloggs.fred@gmail.com> wrote:

On Friday, September 25, 2020 at 10:25:53 PM UTC-4, jla...@highlandsniptechnology.com wrote:
On Fri, 25 Sep 2020 17:29:21 -0700 (PDT), \"rhor...@gmail.com\"
rhor...@gmail.com> wrote:

On Friday, September 25, 2020 at 4:56:32 PM UTC-5, John Larkin wrote:

Do you feel like building a circuit? It could be done with 5 discrete
parts, or possibly 3.

Yes, of course! I am having a little trouble imagining only 5 components, let alone 3, but I am game to look at anything.

I did find a nice, small buck converter module that is only 7mm x 4.5mm with up to 450V input and 300ma output. It only requires 13 external components, all of which can be 1206 SMDs except for a small inductor. This makes a trailing edge MOSFET based dimmer using a 555 practical. It\'s $2.24, but I can handle that.
Guess nobody wants to play. As usual.

One of these might work:

https://www.dropbox.com/s/616xu5p4z1bw2yb/LED_Soft-Start.JPG?raw=1

The lower one starts at half brightness, because of the mosfet
substrate diode. Upper one probably doesn\'t need R2 if you use a
protected-gate fet.

I don\'t have time to Spice these, but either should work.

There are some variants, like an RC and a source follower maybe.

https://www.dropbox.com/s/g3kaaaauft986b9/LED_Soft_Follower.JPG?raw=1





--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

According to a summary published in one of the industry mags, the dimmable LEDs contain this circuit or something similar. It has PFC correction as well as an algorithm to decode the RMS input from a conventional TRIAC dimmer to a current drive for the LED.
https://www.ti.com/product/LM3450
The operation of the eval boards makes no sense whatsoever. LIke what good is a 700mA CC on a low wattage bulb.
So working with this idea, you can buy a miniaturized TRIAC dimmer off ebay, replace the slider with an LDR, and control it with a cheap Arduino or something. Any more effort than that isn\'t worth it.


I occasionally rip open an LED bulb. Lately they seem to have no
inductors, just a bridge and a simple linear IC current limiter. All
that other stuff is too complex and too expensive.

I wonder if a soft start circuit would work for this. My 3.5 HP router
has a lovely startup action instead of the big unnerving jerk when you
pull the trigger

 

[bitrex]

On 9/27/2020 1:36 PM, Tabby wrote:

On Sunday, 27 September 2020 02:56:49 UTC+1, bitrex wrote:

I think a thermistor might work with some cheapo LED bulbs but the
good-quality ones have an integrated buck converter that likely has some
undervoltage lock-out on the rectified mains input.

why would anyone design that into an LED lamp? What for?


NT

You mean the lockout, or the converter? You can manufacture a
universal-input bulb for 100-220 VAC for one thing. You can accommodate
(some?) triac dimmers. Here\'s a data sheet:

<https://www.digchip.com/datasheets/parts/datasheet/1019/SSL5251T_1J-pdf.php>

This one doesn\'t lock out exactly but it senses low mains voltage and
enters a power-saving mode, though the context is supposed to be either
near the zero-crossings of the mains, and/or when it\'s being fed a
leading-edge chopped waveform with a relatively high peak but low RMS.

So not sure exactly what would happen if it was fed from just an inline
thermistor.

 

[bitrex]

On 9/27/2020 2:19 PM, jlarkin@highlandsniptechnology.com wrote:

On Sun, 27 Sep 2020 10:36:34 -0700 (PDT), Tabby <tabbypurr@gmail.com
wrote:

On Sunday, 27 September 2020 02:56:49 UTC+1, bitrex wrote:

I think a thermistor might work with some cheapo LED bulbs but the
good-quality ones have an integrated buck converter that likely has some
undervoltage lock-out on the rectified mains input.

why would anyone design that into an LED lamp? What for?


NT

It\'s common for them to have a bridge rectifier and a linear IC
voltage regulator. Or even some passive-part current limiters.

The \"best\" way to do it if a switcher is going to be used is to have
high-voltage LEDs that have a string integrated into a common substrate
and use a boost rather than a buck or buck-boost, and boost the
rectified mains up to say 400 from 270.

Boosts are just simpler and more efficient in this context than bucks or
buck-boosts.

 

[bitrex]

On 9/29/2020 3:05 AM, bitrex wrote:

On 9/27/2020 2:19 PM, jlarkin@highlandsniptechnology.com wrote:
On Sun, 27 Sep 2020 10:36:34 -0700 (PDT), Tabby <tabbypurr@gmail.com
wrote:

On Sunday, 27 September 2020 02:56:49 UTC+1, bitrex  wrote:

I think a thermistor might work with some cheapo LED bulbs but the
good-quality ones have an integrated buck converter that likely has
some
undervoltage lock-out on the rectified mains input.

why would anyone design that into an LED lamp? What for?


NT

It\'s common for them to have a bridge rectifier and a linear IC
voltage regulator. Or even some passive-part current limiters.



The \"best\" way to do it if a switcher is going to be used is to have
high-voltage LEDs that have a string integrated into a common substrate
and use a boost rather than a buck or buck-boost, and boost the
rectified mains up to say 400 from 270.

Boosts are just simpler and more efficient in this context than bucks or
buck-boosts.

And ideally have no electrolytic filter caps in the circuit, or no caps
at all, even. There are research papers to that effect idk if it\'s done
in any commercial products, though.

 

[bitrex]

On 9/28/2020 4:54 PM, Lasse Langwadt Christensen wrote:

mandag den 28. september 2020 kl. 22.41.59 UTC+2 skrev John Larkin:
On Mon, 28 Sep 2020 12:27:46 -0700 (PDT), Fred Bloggs
bloggs.fredbloggs.fred@gmail.com> wrote:

On Friday, September 25, 2020 at 10:25:53 PM UTC-4, jla...@highlandsniptechnology.com wrote:
On Fri, 25 Sep 2020 17:29:21 -0700 (PDT), \"rhor...@gmail.com\"
rhor...@gmail.com> wrote:

On Friday, September 25, 2020 at 4:56:32 PM UTC-5, John Larkin wrote:

Do you feel like building a circuit? It could be done with 5 discrete
parts, or possibly 3.

Yes, of course! I am having a little trouble imagining only 5 components, let alone 3, but I am game to look at anything.

I did find a nice, small buck converter module that is only 7mm x 4.5mm with up to 450V input and 300ma output. It only requires 13 external components, all of which can be 1206 SMDs except for a small inductor. This makes a trailing edge MOSFET based dimmer using a 555 practical. It\'s $2.24, but I can handle that.
Guess nobody wants to play. As usual.

One of these might work:

https://www.dropbox.com/s/616xu5p4z1bw2yb/LED_Soft-Start.JPG?raw=1

The lower one starts at half brightness, because of the mosfet
substrate diode. Upper one probably doesn\'t need R2 if you use a
protected-gate fet.

I don\'t have time to Spice these, but either should work.

There are some variants, like an RC and a source follower maybe.

https://www.dropbox.com/s/g3kaaaauft986b9/LED_Soft_Follower.JPG?raw=1





--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

According to a summary published in one of the industry mags, the dimmable LEDs contain this circuit or something similar. It has PFC correction as well as an algorithm to decode the RMS input from a conventional TRIAC dimmer to a current drive for the LED.
https://www.ti.com/product/LM3450
The operation of the eval boards makes no sense whatsoever. LIke what good is a 700mA CC on a low wattage bulb.
So working with this idea, you can buy a miniaturized TRIAC dimmer off ebay, replace the slider with an LDR, and control it with a cheap Arduino or something. Any more effort than that isn\'t worth it.


I occasionally rip open an LED bulb. Lately they seem to have no
inductors, just a bridge and a simple linear IC current limiter. All
that other stuff is too complex and too expensive.

I assume they have switched to much longer strings of LEDs so they don\'t have
to drop much voltage

This chip drives series-parallel strings with current regulators but
tracks the mains voltage, turning them all on at the peak and less on
the slopes. Decent efficiency with no magnetics and would probably work
OK with a thermistor limiter.

<https://www.microchip.com/wwwproducts/en/CL8800>

 

[rhor...@gmail.com]

*IF* it turns out LED light bulbs can work on 170VDC, then I have cobbled together a circuit I think might work. Please take a look at the link below and see if any of you can find any issues with this.

http://http://siliconventures.net/images/Fader1.PNG

 

[rhor...@gmail.com]

*IF* it turns out LED light bulbs can work on 170VDC, then I have cobbled together a circuit I think might work. Please take a look at the link below and see if any of you can find any issues with this.

<http://siliconventures.net/images/Fader1.PNG >

The 12VDC supply is provided by an MP9488GS-P Buck regulator. U1 integrates the 0V differential signal provided by R1 - R4 with a time constant determined by R5 and C1. C2 provides a delay, keeping the output of U1 high until C2 is charged to 6V by R4 (~2ms). Once C2 is charged, the output of U1 slowly decreases from ~10V to ~2V over a period of 5 seconds. U2 inverts the slope of the signal from U1 and produces a necessary offset. Its output changes from 4.5V to 12V over the same 5 second time period. The 555 timer X1 operates as a short pulse generator, creating pulses a few microseconds wide approximately every 8 milliseconds. Transistor Q1 prevents X1 from generating any pulses until C2 is charged to ~1.4V by R8, allowing time for the 12V buck converter to settle before X1 begins operation. X2 is configured as a variable pulse width monostable timer triggered by Q2 from the short pulses produced by X1. The output of X2 is held high by the internal flip flop until the voltage across C6 rises to be greater than Control voltage, which is the output of U2. Initially, the output of U2 is within 1/2 volt of the Trigger voltage, so the voltage across C6 reaches this value very quickly. As time passes, the Control voltage increases, causing the output of X2 to remain high longer and longer, increasing the duty cycle to near 100%. The output of X2 drives Q3, causing M1 to turn on whenever X2 is high.

 

[John S]

On 9/29/2020 8:37 AM, rhor...@gmail.com wrote:

*IF* it turns out LED light bulbs can work on 170VDC, then I have cobbled together a circuit I think might work. Please take a look at the link below and see if any of you can find any issues with this.

http://http://siliconventures.net/images/Fader1.PNG

\"Hmm. We’re having trouble finding that site.

We can’t connect to the server at http.\"

 

[rhor...@gmail.com]

On Tuesday, September 29, 2020 at 9:34:09 AM UTC-5, John S wrote:

http://http://siliconventures.net/images/Fader1.PNG


\"Hmm. We’re having trouble finding that site.

We can’t connect to the server at http.\"

That was a typo. I deleted the old message and replaced it. Try the new one.

 

[John S]

On 9/29/2020 9:32 AM, rhor...@gmail.com wrote:

*IF* it turns out LED light bulbs can work on 170VDC, then I have cobbled together a circuit I think might work. Please take a look at the link below and see if any of you can find any issues with this.

http://siliconventures.net/images/Fader1.PNG >

The 12VDC supply is provided by an MP9488GS-P Buck regulator. U1 integrates the 0V differential signal provided by R1 - R4 with a time constant determined by R5 and C1. C2 provides a delay, keeping the output of U1 high until C2 is charged to 6V by R4 (~2ms). Once C2 is charged, the output of U1 slowly decreases from ~10V to ~2V over a period of 5 seconds. U2 inverts the slope of the signal from U1 and produces a necessary offset. Its output changes from 4.5V to 12V over the same 5 second time period. The 555 timer X1 operates as a short pulse generator, creating pulses a few microseconds wide approximately every 8 milliseconds. Transistor Q1 prevents X1 from generating any pulses until C2 is charged to ~1.4V by R8, allowing time for the 12V buck converter to settle before X1 begins operation. X2 is configured as a variable pulse width monostable timer triggered by Q2 from the short pulses produced by X1. The output of X2 is held high by the internal flip flop until the voltage across C6 rises to be greater than Control voltage, which is the output of U2. Initially, the output of U2 is within 1/2 volt of the Trigger voltage, so the voltage across C6 reaches this value very quickly. As time passes, the Control voltage increases, causing the output of X2 to remain high longer and longer, increasing the duty cycle to near 100%. The output of X2 drives Q3, causing M1 to turn on whenever X2 is high.

For want of a micro controller the kingdom was lost.

 

[rhor...@gmail.com]

On Tuesday, September 29, 2020 at 9:45:42 AM UTC-5, John S wrote:
> For want of a micro controller the kingdom was lost.
I thought about using a PIC. They take time to boot, though. I could supply power full time, but I am sort of avoiding that.

 

[bitrex]

On 9/29/2020 11:05 AM, rhor...@gmail.com wrote:

On Tuesday, September 29, 2020 at 9:45:42 AM UTC-5, John S wrote:
For want of a micro controller the kingdom was lost.
I thought about using a PIC. They take time to boot, though. I could supply power full time, but I am sort of avoiding that.

Yea they \"boot\" in like half a microsecond.

 

[John S]

On 9/29/2020 10:09 AM, bitrex wrote:

On 9/29/2020 11:05 AM, rhor...@gmail.com wrote:
On Tuesday, September 29, 2020 at 9:45:42 AM UTC-5, John S wrote:
For want of a micro controller the kingdom was lost.
I thought about using a PIC.  They take time to boot, though.  I could
supply power full time, but I am sort of avoiding that.


Yea they \"boot\" in like half a microsecond.

And how long does the buck regulator take to come up?