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Old 13th May 2014, 10:31 PM   #1
Pyramid is offline Pyramid  United States
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Default ESL High Voltage supply

I've built a HV supply for my DIY hybrid ESLs based on a CCFL xfmr and capacitive multiplier. Runs from a 12V wall wart and produces ~3KV (adjustable). Also has a music sense circuit which can be left unpopluated and bypassed (always on or on with external switch). There is a SMT LED on the PCB to show when the circuit is active and a connector for an off board LED for same.

The PCB is 2.50" x 4.00" double sided; mixed SMT and thru hole.

If anyone is interested in building this, I can make the gerber files and BOM available. I'm not familiar with how to do a group buy, but if someone else wants to run with it, I'll do what I can to assist.
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File Type: jpg DSCN0778.jpg (254.4 KB, 375 views)
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Old 13th May 2014, 11:07 PM   #2
tyu is offline tyu  United States
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... ...Vary cool setup..... thanks for posting it....just add more diodes an caps an get 5-7k Bias V....if needed....

Drop the 180meg down too................5ea 1/2watt 2meg..........youll get 3-4more db output........ helps the topend i have found in fullrang esl...
ML only set at 60meag....
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Old 13th May 2014, 11:30 PM   #3
Pyramid is offline Pyramid  United States
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I did 5x 18M (90MΩ) on the output so a 10MΩ DVM to ground would form a 10:1 voltage divider. If you read 315VDC on the meter, it means 3150 VDC on the output.

I didn't notice any difference in sound with different values. Of course, you are free to popluate with any values you see appropriate.

The PCB is also missing the HV connections. I've used 4-40 " alum standoffs press fitted into the PCB. The HV wires have ring connectors crimped on and are then connected with 4-40 SS screws.

It might be hard to tell from the pics, but the ground pour is restricted around the HV section to prevent arcing.
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Old 24th May 2014, 08:37 PM   #4
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Quote:
Originally Posted by Pyramid View Post
I did 5x 18M (90MΩ) on the output so a 10MΩ DVM to ground would form a 10:1 voltage divider. If you read 315VDC on the meter, it means 3150 VDC on the output.
Good thinking

Overall a nicely thought out design. I did have 2 questions/ 2 comments:
Q1) Was there a reason you chose such high value capacitors? With oscillator frequency > 20kHz you could easily get by with values 100x smaller without affecting DC output voltage or ripple.

Q2) Was there a reason you have the IN terminal of the LM78L08 hooked up on the oscillator side of the C-L-C filter rather than to the IN or OUT of the LM317? As drawn, the HF noise generated by the oscillator current would be fed into the LM780L8, potentially false triggering the signal sense circuit. Perhaps it is not a concern since currents are minimal after oscillator start-up.

C1) For good common mode noise rejection in the signal sense circuit, the input capacitor pairs(C13-C18, C14-C19) need to be as tight a tolerance as the resistors.

C2) The input fuse is an excellent idea. Without it, an accidental short somewhere in the oscillator circuit could easily take out both transistors, the transformer and filter inductor.

Quote:
I didn't notice any difference in sound with different values. Of course, you are free to populate with any values you see appropriate.
My experience agrees with yours. If your panels are well built with minimal leakage and high resistance diaphragm coating, changing the bias resistance has no impact on the sound. In fact after diaphragm charging is complete, you should be able to completely disconnect/reconnect the supply without a listener noticing.
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Old 26th May 2014, 03:07 AM   #5
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I agree, Nice design.

If you wanted to, it would be very easy to add a feedback circuit for regulation as well as I have done with only just a few more parts here,

how can test the stator insulation and mylar coating?

Does anyone have schematics of a varible HV power supply

More parts (another dual opamp), but regulation is good?!!!!

This post shows the HV regulation recovery under an arcing condition at 4.23Kv,

http://www.esldiy.com/index.php?topic=5.msg69#msg69


Cheers !!!

jer

Last edited by geraldfryjr; 26th May 2014 at 03:17 AM.
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Old 3rd June 2014, 03:43 AM   #6
Pyramid is offline Pyramid  United States
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Quote:
Originally Posted by bolserst View Post
Good thinking

Overall a nicely thought out design. I did have 2 questions/ 2 comments:
Q1) Was there a reason you chose such high value capacitors? With oscillator frequency > 20kHz you could easily get by with values 100x smaller without affecting DC output voltage or ripple.

Q2) Was there a reason you have the IN terminal of the LM78L08 hooked up on the oscillator side of the C-L-C filter rather than to the IN or OUT of the LM317? As drawn, the HF noise generated by the oscillator current would be fed into the LM780L8, potentially false triggering the signal sense circuit. Perhaps it is not a concern since currents are minimal after oscillator start-up.

C1) For good common mode noise rejection in the signal sense circuit, the input capacitor pairs(C13-C18, C14-C19) need to be as tight a tolerance as the resistors.

C2) The input fuse is an excellent idea. Without it, an accidental short somewhere in the oscillator circuit could easily take out both transistors, the transformer and filter inductor.


My experience agrees with yours. If your panels are well built with minimal leakage and high resistance diaphragm coating, changing the bias resistance has no impact on the sound. In fact after diaphragm charging is complete, you should be able to completely disconnect/reconnect the supply without a listener noticing.
Q1: I did the original design on this ~8 years ago. I may have picked the values somewhat arbitrarily.

Q2: Ditto. It may have been layout related, easier to go to the output side of the filter rather than input side, I'd have to look at the PCB plots again.

These are both good points, and could easily be changed before a GB was done. I'd welcome any other input/optimization of the circuit....

Regarding the music sense circuit: I ended up defeating the sense input on mine; the delay for the power supply to start was minimal (<1 sec) but the delay to charge the panels adequately was 10-15 secs which was quite annoying. I'd have to start the track over to hear it from the beginning. Really wasn't a big deal to flip a couple of switches when I want to listen to something.
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Old 10th September 2014, 10:00 PM   #7
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Would these be a good alternative to Russ Knotts B3 Bias Supply? If so, I need Five of them.
I've been using two B3from Russ of justrealmusic, with the Mains from a Final Sound Surround, since he determined that the Central unit was Bad. Attempting to get three more Bias Supplies; but Russ seems quite difficult to reach...

Help, Please & Thanks
Ken
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Old 2nd December 2014, 03:50 PM   #8
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I also would be interested in getting a few of these. My own PCB stator ESL project is moving along nicely and I would like to use adjustable supplies. I have considered using a variac in front of a simple supply like Jazzman's but the cost for the variacs alone would be about $115 each.
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Old 2nd December 2014, 04:21 PM   #9
AndrewT is offline AndrewT  Scotland
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Could you "write up" how each section works?
__________________
regards Andrew T.
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Old 2nd December 2014, 10:41 PM   #10
WrineX is offline WrineX  Netherlands
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They look really profesional! i like the music sence part. i usually get a power suplly for a ccf tubed, the inverters kind of like the ones you see in TFT screens. and feed them wit a regulated dc and add some capacitors on the end. 3 euro for the inverterd (with tube ) and few euros for the caps. and ofc a transformer to regulate the end result.


what would boards like this coast with some more caps with lower values at the end?
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