Simplistic Mosfet HV Shunt Regs - Page 278

Salas · 21st February 2012, 12:29 AM

Quote:

Originally Posted by alphaigor

OK, I have burned IRF840.It was near cold on heat sink.The magic SSHV sound is here again.Obviously I was to fast during ON/OFF/ON, it haven't had chance to start normally. Thanks for ingenious regulator ,Salas.

All well then. What type is it? SSHV1? Post some picture with your (SRPP?) phono.

Salas · 21st February 2012, 12:31 AM

Quote:

Originally Posted by bigpandahk

I tried to but the SSHV 1 but upto now, having burnt more than twenty semicon (FET, LED, MOSFET, ZENER), still can't get it work. Can anyone suggest a step by step safe way to test the circuit? Thanks

Variac test, to bring it up slowly. What are your target settings and what is your raw dc source?

roger57 · 21st February 2012, 12:54 AM

Quote:

Originally Posted by bigpandahk

I tried to built the SSHV 1 but upto now, having burnt more than twenty semicon (FET, LED, MOSFET, ZENER), still can't get it work. Can anyone suggest a step by step safe way to test the circuit? Thanks

I think Salas and other knowledgeable folks have posted some pretty good steps in safe testing. Personally, I never test any high voltage circuit without using a voltage variac, I put a couple of DMM's on the key circuit points and bring the voltage up slowly and observe the meters. Sometimes that doesn't even work if there's a serious issue and something can burn before switching off the AC!
I've built the first revision of the Salas SSHV and made a PCB for it, it works just fine. Are you using a PCB already made? Or are you using point-to-point wiring? If FETs are blowing, sounds like the gate voltage is being exceeded; or a FET backwards? Do you have a zener across the drain to source? I had this issue when I first built it, and found that the Vds was exceeded during the charge up of the capacitor. Another thing is to make sure the load is adequate for the desired output current.
Perhaps you know someone that could go through the board with you before powering up?
Hope that helps...it can be frustrating to figure these things out!

Gary

bigpandahk · 21st February 2012, 04:18 AM

Thanks Salas and Roger57 's prompt reply. My target setting is 300V 75mA and the raw DC is 400V CLC. I changed the 56ohm to 22ohm for higher current. Last night I tested my latest built, connected a 5.6k 20W resistor as load, the output voltage go up to about only 25V, after a few second, the 22ohm on fire and the 9610 gone.

Will built a simple CRC connect to variac for testing again.

Salas · 21st February 2012, 07:24 AM

Your raw DC is high for the 9610 at such CCS before it settles especially if there is a charging peak in an underdamped CLC pre-filter. Also much heat will be developed with 75mA and 100V drop over the reg. Burn some before. As you are, delete R10, C1, damp the input with 100 Ohm series, stick a 47uf/450V input to ground, a 12V Zener from top of the 1uf Vref capacitor C2 to Vo rail with cathode up and have a go. I suppose you already use clamping zeners on gates before the 220R stoppers to sources on both Mosfets. If not, look at the link from post#1 for SSHV1 again. Your R3 should be 82K/5W with such Vin. If all fails maybe a SSHV2 on a PCB would be better for you, but we can't be sure of any possible other difficulties in your case.

bigpandahk · 12:07 PM

Thanks Salas, The input voltage is 300V and output is 250V 75mA. Sorry for my mistake. I will check the wiring again and use the calculator for the resistors. I've GB the SSHV2 and it may be better for me to wait for the kit

Salas · 21st February 2012, 12:09 PM

Do those things above anyway only don't put the 82k.

bigpandahk · 21st February 2012, 12:26 PM

Quote:

Originally Posted by Salas

Do those things above anyway only don't put the 82k.

Yes sir

buzzforb · 22nd February 2012, 11:38 PM

I have a peculiar problem. On one channel of sshv2, i have no voltage drop across zener, LED is not lighting up, and i just replaced jfet. Ccs is set and working at 45mA, but i only have 100mV at output.

Salas · 22nd February 2012, 11:40 PM

Was working OK before, yes? In that case measure the semis. BJTs should have 0.6V between b,e IRF840 ~4V g,s. Maybe one of those is shot.

21st February 2012, 11:52 AM	#2776
bigpandahk diyAudio Member Join Date: Jul 2009	Thanks Salas, The input voltage is 300V and output is 250V 75mA. Sorry for my mistake. I will check the wiring again and use the calculator for the resistors. I've GB the SSHV2 and it may be better for me to wait for the kit Last edited by bigpandahk; 21st February 2012 at 12:07 PM.

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21st February 2012, 04:18 AM	#2774
bigpandahk diyAudio Member Join Date: Jul 2009	Thanks Salas and Roger57 's prompt reply. My target setting is 300V 75mA and the raw DC is 400V CLC. I changed the 56ohm to 22ohm for higher current. Last night I tested my latest built, connected a 5.6k 20W resistor as load, the output voltage go up to about only 25V, after a few second, the 22ohm on fire and the 9610 gone. Will built a simple CRC connect to variac for testing again.

21st February 2012, 07:24 AM	#2775
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Your raw DC is high for the 9610 at such CCS before it settles especially if there is a charging peak in an underdamped CLC pre-filter. Also much heat will be developed with 75mA and 100V drop over the reg. Burn some before. As you are, delete R10, C1, damp the input with 100 Ohm series, stick a 47uf/450V input to ground, a 12V Zener from top of the 1uf Vref capacitor C2 to Vo rail with cathode up and have a go. I suppose you already use clamping zeners on gates before the 220R stoppers to sources on both Mosfets. If not, look at the link from post#1 for SSHV1 again. Your R3 should be 82K/5W with such Vin. If all fails maybe a SSHV2 on a PCB would be better for you, but we can't be sure of any possible other difficulties in your case.

21st February 2012, 12:09 PM	#2777
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Do those things above anyway only don't put the 82k.

22nd February 2012, 11:38 PM	#2779
buzzforb diyAudio Member Join Date: Oct 2010 Location: Burlington, NC	I have a peculiar problem. On one channel of sshv2, i have no voltage drop across zener, LED is not lighting up, and i just replaced jfet. Ccs is set and working at 45mA, but i only have 100mV at output.

22nd February 2012, 11:40 PM	#2780
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Was working OK before, yes? In that case measure the semis. BJTs should have 0.6V between b,e IRF840 ~4V g,s. Maybe one of those is shot.