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Simplistic Mosfet HV Shunt Regs
Simplistic Mosfet HV Shunt Regs
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Old 6th April 2018, 01:57 PM   #5801
mbrennwa is offline mbrennwa  Switzerland
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I am thinking about my next tube project. This will need some 440 VDC for B+ at 60 mA or so. I found an SSHV2 kit in my parts box (2 boards + parts), sooo... but wait! The SSHV2 is rated to 380 VDC max. output, which is too low for my project. Can I modify the SSHV2 to suit my needs? How?
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Old 6th April 2018, 02:18 PM   #5802
Salas is offline Salas  Greece
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Simplistic Mosfet HV Shunt Regs
First you would need a higher voltage rated Q1 like the IXTP01N100D then you should use higher value R9 R10 like 82k. Watch the isolation to main sink be good and better use a sturdy Schottky diode instead of the D3 Zener for faster low threshold clamping.
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Old 6th April 2018, 02:48 PM   #5803
Vernonia1 is offline Vernonia1
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Salas I was thinking of using the SSHV2 as the bias supplies for my 6550/KT88PP driver (-200V, 10mA)and output stage (-100V, 4mA) grid bias. Do you see any issues with this implementation?
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Old 6th April 2018, 03:03 PM   #5804
Salas is offline Salas  Greece
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Simplistic Mosfet HV Shunt Regs
But this is a positive polarity supply unit and you need negative bias voltages
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Old 6th April 2018, 03:13 PM   #5805
Vernonia1 is offline Vernonia1
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OMG.......... I knew that
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Old 6th April 2018, 05:27 PM   #5806
mbrennwa is offline mbrennwa  Switzerland
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Quote:
Originally Posted by Salas View Post
First you would need a higher voltage rated Q1 like the IXTP01N100D then you should use higher value R9 R10 like 82k. Watch the isolation to main sink be good and better use a sturdy Schottky diode instead of the D3 Zener for faster low threshold clamping.
Thanks! I don't quite understand "use a sturdy Schottky diode instead of the D3 Zener for faster low threshold clamping". I actually don't understand what this diode does, or how the error amp works, so... could you recommend a specific part?
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Old 6th April 2018, 06:09 PM   #5807
Salas is offline Salas  Greece
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Simplistic Mosfet HV Shunt Regs
Its a protection measure for Q5 and Q6 while C2 charges and there is voltage difference or for when there is bad handling or some transient. Say an MBR1100. Same orientation as the silkscreen shows for the D3 Zener.
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Old 15th April 2018, 10:26 AM   #5808
merlin el mago is offline merlin el mago
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Salas will be very complicated to mod the schematic to have no NFB?
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Old 15th April 2018, 12:12 PM   #5809
Salas is offline Salas  Greece
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Simplistic Mosfet HV Shunt Regs
NFB is inherent in this, doesn't have an external control loop to break. No NFB would mean no regulator basically but a passively stabilized PSU like the DCSTB for the DCG3 but in HV form.
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Old 15th April 2018, 12:22 PM   #5810
merlin el mago is offline merlin el mago
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Thanks for your explanation.

Salas do you know where to buy in Europe the IXTP08N50D2 or IXTP01N100D?

TIA
Felipe
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