Simplistic Mosfet HV Shunt Regs - Page 339 - diyAudio
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Old 21st October 2012, 09:34 PM   #3381
roger57 is offline roger57  Canada
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Quote:
Originally Posted by Salas View Post
OK drop 55V on an RC cell, and no worries.
cutoff for RC filter at what frequency?
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Old 21st October 2012, 09:52 PM   #3382
Salas is offline Salas  Greece
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Use PSUDII, depict your transformer, rectification & capacitor filter components there, simulate the reg draw as 50mA CCS load at the end of the chain to ground. 50mA is good for 32mA load. Then insert a resistive element either between bridge and cap or between caps if you got two, tweak value until it will give you 395VDC with smooth rise curve. Take care that the physical resistor will be 10W.
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Old 21st October 2012, 09:59 PM   #3383
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Quote:
Originally Posted by Salas View Post
Use PSUDII, depict your transformer, rectification & capacitor filter components there, simulate the reg draw as 50mA CCS load at the end of the chain to ground. 50mA is good for 32mA load. Then insert a resistive element either between bridge and cap or between caps if you got two, tweak value until it will give you 395VDC with smooth rise curve. Take care that the physical resistor will be 10W.
OK, I see what you mean. I've already got a well-filtered DC supply coming in, so I just need a resistor to drop the voltage, not an RC filter. Ok, thanks. Will run that in LT Spice just to make sure. I guess and additional filter cap wouldn't hurt, though.

Gary
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Old 21st October 2012, 10:08 PM   #3384
roger57 is offline roger57  Canada
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Quote:
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OK, I see what you mean. I've already got a well-filtered DC supply coming in, so I just need a resistor to drop the voltage, not an RC filter. Ok, thanks. Will run that in LT Spice just to make sure. I guess and additional filter cap wouldn't hurt, though.

Gary
Isn't there any "overhead" from the rest of the circuit though? Or is it fairly trivial?
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Old 21st October 2012, 11:11 PM   #3385
Salas is offline Salas  Greece
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32mA your load + 20mA for the reg is what you should set. ~50mA.
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Old 24th October 2012, 09:14 PM   #3386
RollE2k is offline RollE2k  Sweden
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Update regarding my regulator - changed all transistors except the CCS ones.
The CCS works fine when i run them as CCS with 12V input. When i test with 230v input and my line-stage as load R1 burns. DN2540's damaged also?!
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Old 24th October 2012, 09:32 PM   #3387
Salas is offline Salas  Greece
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R1 spans the Vds imposed on the lower DMOS as upper one's Vgs. Burning means some over current to the gate. I suggest you exchange that upper DMOS to see. Maybe the lower one just works so its showing OK in lower voltage test.
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Old 27th October 2012, 04:33 AM   #3388
roger57 is offline roger57  Canada
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Default Regulator "Latching" ?

Salas,

I've got a 12K load on the output. 400V input, with 375V out. R4 set to measure 500mV across test points. I'm using a variac to bring the voltage up to 400V in.
However, when I switch the power supply on from 0, the regulator seems to latch up. The voltage is around 10V, with current still showing around 50mA as set.

I have a similar setup for the 350V out, 75mA load and it's behaving the same.

Any suggestions as to what might cause this?
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Old 27th October 2012, 05:10 AM   #3389
Salas is offline Salas  Greece
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Never brought it up with a variac. Just straight with a switch. Maybe the Vref protection Zener latches something when you start from 0? Don't know.
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Old 27th October 2012, 05:54 AM   #3390
roger57 is offline roger57  Canada
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Quote:
Originally Posted by Salas View Post
Never brought it up with a variac. Just straight with a switch. Maybe the Vref protection Zener latches something when you start from 0? Don't know.
After building any HV board, I always use a variac for initial testing; this one was no different. After doing all the adjustments, I then bypass the variac and just plug in directly. It wasn't until then I noticed this was happening.

I have another question - what should the drain to source voltage across Q2 be, with 400V in?
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