Simplistic MosFET HV Shunt Regs

[merlin el mago]

Yes it's very useful. I have only one IRF840 and one DN2540, if gone I have to order more.

 

[merlin el mago]

I will do tomorrow, I want to be fresh.

 

[thuanth43]

I'm a bit late for this, but is it possible to have +-450v with this shunt reg?

 

[Salas]

If you will look some pages back a member used higher voltage spec DMOS and higher value ref resistors and succeeded. Gave some practical account of how he did for low Vout drift at so high Vout also.

 

[thuanth43]

Thanks, Salas, will take a look at it.

 

[merlin el mago]

Salas it's possible to use for Q1 Ixys 10M45S in order to robust the CCS?

 

[Salas]

Sure. Not same low capacitance but not bad. There are IXTP 02N50D (500V 250mA) IXTP 08N50D2 (500V 800mA) and IXTP 01N100D (1000V 100mA) also.

 

[Salas]

Thanks, Salas, will take a look at it.

For making (+)/(-) you can only stack them like batteries using two secondaries and two bridges. Their middle point will be virtual zero. Like we do with SSLV1.1 some times or like they used to do in NAIM NAP 250 etc.

 

[Tubenstein]

Normally the transformer has 225v @0.15A for positive per channel.

Does it mean the negative rail per channel require the secondary winding with 2 x 225v @0.15A?

So I need 4 x 225v 0.15A and 4 x SSHV2 for 2 channels' negative rail 200v dc regulation, right??

 

[merlin el mago]

Salas is working OK. Have a nice Sunday.

 

[Salas]

Normally the transformer has 225v @0.15A for positive per channel.

Does it mean the negative rail per channel require the secondary winding with 2 x 225v @0.15A?

So I need 4 x 225v 0.15A and 4 x SSHV2 for 2 channels' negative rail 200v dc regulation, right??

Right. To make +/0/- from two positive regulators, independent secondary, bridge, and filter are required for each one. In double mono construction that means four secondaries, four bridges, four filters, four regulators.

 

[Salas]

Salas is working OK. Have a nice Sunday.

Nice

 

[merlin el mago]

Is working OK the regulator not you

 

[Salas]

 

[poty]

I want to know whether the outstage has the same B+ as the first and second stages? Is that 179v??

Well, from the schematic provided - yes. (English is not my mother tongue, maybe I haven't caught your question's meaning.)

Do you suggest he put one SSHV2 for the first and second stage and the other SSHV2 for the output stage? I meant per channel.

My opinion - if we copy the original layout - one SSHV per channel for +179V.

Also, one power transformer for first and second stages and the other transformer for the output stage.

One transformer per stage. (Again - only my opinion)

Normally the transformer has 225v @0.15A for positive per channel.
Does it mean the negative rail per channel require the secondary winding with 2 x 225v @0.15A?
So I need 4 x 225v 0.15A and 4 x SSHV2 for 2 channels' negative rail 200v dc regulation, right??

You shouldn't be fooled by the word "balanced". In the positive rail you need +179V? In the negative rail you need -110V? The positive rail powers all four stages (one value for current). The negative rail powers only the first two stages (another value for current). Saying this - why do you want to use secondaries with the same voltage and current values?
Yes, you'll have to use 2 independent secondaries for positive and negative rails. Whether you'll want to use different secondaries/transformers for each channel or not is for your decision.

 

[Tubenstein]

Dear Salas,
Looks like this one?

Thanks!

For making (+)/(-) you can only stack them like batteries using two secondaries and two bridges. Their middle point will be virtual zero. Like we do with SSLV1.1 some times or like they used to do in NAIM NAP 250 etc.

 

[poty]

Looks like this one?

Essentially - yes, but if you are going to build the SSHV on the "official" PCB the "current limiter" part will be in the positive rail for both halves.

 

[Tubenstein]

Well, from the schematic provided - yes. (English is not my mother tongue, maybe I haven't caught your question's meaning.)
My opinion - if we copy the original layout - one SSHV per channel for +179V.
One transformer per stage. (Again - only my opinion)

You shouldn't be fooled by the word "balanced". In the positive rail you need +179V? In the negative rail you need -110V? The positive rail powers all four stages (one value for current). The negative rail powers only the first two stages (another value for current). Saying this - why do you want to use secondaries with the same voltage and current values?
Yes, you'll have to use 2 independent secondaries for positive and negative rails. Whether you'll want to use different secondaries/transformers for each channel or not is for your decision.

Regardless the 110v negative rail, how much current the 179v rail drawing from the positive regulator (let's say SSHV2)?

Thanks!

 

[poty]

Regardless the 110v negative rail, how much current the 179v rail drawing from the positive regulator (let's say SSHV2)?

We can only guess. I hope if you have the schematic you may have some explanations/tuning procedure.
How to guess:
Tubes V1+V3 have (179-[from 40 to 60])/(27.4k/2)=8.7-10.1 mA for each half, 17.4-20.2 mA in total.
V5 has (179-[from 119 to 123])/15k=3.7-4 mA for each half, 7.4-8 mA in total.
V7 is not so obvious, but considering R28, R29 and R19 it should be less than V5, but how much is unknown. I'd use the same values as the top guess, so 14.8-16 mA in total.
Then the whole +179V rail should be something like 39.6-44.2mA (not counting possible biasing current in the power supply if any).

 

[Salas]

How he is gonna get a virtual zero midpoint when the two voltages will be asymmetric? Anything connected at that point will be on a large DC voltage difference then. Isn't it so?