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Simplistic Mosfet HV Shunt Regs
Simplistic Mosfet HV Shunt Regs
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Old 16th October 2019, 07:00 PM   #6001
Tix88 is offline Tix88  Italy
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Originally Posted by Salas View Post
Avoid a peak. For various reasons, not only possible harm. Glitches can activate the choke to radiate an interference field. 220uF standard value for C2 should be enough for your moderate mA.
This is a detail of the simulation 20 seconds after the start of the AC. The initial ripple has been eliminated. So the shunt should filter out the residual ripple? Would I have a good power section like this?
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Old 16th October 2019, 07:30 PM   #6002
Salas is offline Salas  Greece
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Simplistic Mosfet HV Shunt Regs
Yes the CCS and the Vref in this shunt have some PSRR to filter 100Hz ripple enough. Mainly the CCS.
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Old 16th October 2019, 07:36 PM   #6003
Salas is offline Salas  Greece
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Simplistic Mosfet HV Shunt Regs
P.S. Your VC2 or VI1 ripple should also simulate less if for 35mA load you initially mentioned.
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Old 16th October 2019, 07:46 PM   #6004
Tix88 is offline Tix88  Italy
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P.S. Your VC2 or VI1 ripple should also simulate less if for 35mA load you initially mentioned.
The total load is 70mA, 2x15mA for the two preamplifier channels and 2x20mA for the two shunts. Then I will proceed to the construction of the filtering as well as to simulation.
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Old 22nd October 2019, 02:29 AM   #6005
Embehu is offline Embehu  Viet Nam
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Hi, I just replaced with k117 and it works like a charm, more stable than the previous jfet.

With 80VDC and 80mA do I need a big heatsink for irf630? I touched it but didn’t feel any heat come out
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Old 22nd October 2019, 09:42 AM   #6006
Salas is offline Salas  Greece
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Simplistic Mosfet HV Shunt Regs
Dissipation of it is Vout*Ibias where Ibias is the extra current you allow in the CCS setting beyond the load's own consumption. If it is 20mA extra as usually recommended then 80V*20mA is 1.6W. That's roughly because a little of it goes to the other transistors.

So you don't need a really big sink for the shunt MOSFET in your case. You had used a big sink in your picture link so its cool for that but you could also be using less than 20mA extra right now. If so, adjust the CCS setting accordingly.

Don't test the shunt reg unloaded for long when with smaller sink because it will be burning the whole CCS setting of mA at 80V on the shunt MOSFET in such an occasion. 1.6W becomes 6.4W then.
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Old 22nd October 2019, 12:01 PM   #6007
Embehu is offline Embehu  Viet Nam
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Thanks so much. Then I will choose the smaller heatsink for good looking reason
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Old 22nd October 2019, 02:42 PM   #6008
Salas is offline Salas  Greece
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Simplistic Mosfet HV Shunt Regs
By the way, forgot to ask you before, what is the application circuit you want this 80V-90V PSU for? Is it for a low anode voltage tube preamp?
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Old 22nd October 2019, 02:49 PM   #6009
Salas is offline Salas  Greece
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Simplistic Mosfet HV Shunt Regs
Quote:
Originally Posted by Tix88 View Post
The total load is 70mA, 2x15mA for the two preamplifier channels and 2x20mA for the two shunts. Then I will proceed to the construction of the filtering as well as to simulation.
If not satisfied in the end, two RC branches after the CLC (one going to each reg's input), could be easily added to improve ripple filtering while contributing some isolation between them.
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Old 23rd October 2019, 11:00 AM   #6010
bigpandahk is offline bigpandahk  Hong Kong
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Hi Salas

I am building a SSHV2 for my phono amp which has estimated power consumption of 200mA at 250V. With 270V input and a 2K resistor as load, I adjusted R4 with voltage at TP at maximum 1.07V but the output only has 206V.

Which part should I check to diagnose the problem ?
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