High Voltage Regulator

[mod_evil]

Dear Friends,

For a long time, I'm thinking to regulate the B+ voltage of mine vaccum tube amplifier.

I found many solutions but this is able to 400v ~ 350v in the input. I need a regulator to put on input 500v and in the output 400v.

I passed some time searching for some transistors which can put 800v or more on Vce. But It is very difficult to found.

Anybody have a solution to this?

Best Regards,
Felipe

[eatitdean]

what are you building?

[eatitdean]

most power amps that ive seen dont have a regulated supply, usually thats more of an issue in preamps,

[mod_evil]

eatitdean,

I will build a 6l6 Push-Pull Amp. I have 500v at the B+. But, I need 400v in the amplifer, and I would like to regulate this.

But In another time, I need to regulate this 500v to use in a 300v pre-amp.

Best Regards,
Felipe

[eatitdean]

look inside an old tv, a tube one maybee, ill look through my stock and see what i got. i take apart every peice of electronic equipment i find and save components.

[eatitdean]

the highest value i could find in my stock was 160 volt, try looking in a microwave oven, i know they use high voltages, but i dont know right off if they are regulated. remember to be carefull, discharge those big caps first.

[star882]

Originally posted by eatitdean
the highest value i could find in my stock was 160 volt, try looking in a microwave oven, i know they use high voltages, but i dont know right off if they are regulated. remember to be carefull, discharge those big caps first.

Microwave ovens are not regulated, except the really fancy ones with continuous power control, but those regulate with high frequency PWM on the primary side just like modern power supplies.
High voltage MOSFETs are not very hard to find. Maybe use two along with an opamp circuit for control?

[mod_evil]

Star, eatitdean,

And the Horizontal Deflexion Transistors? Are they allow to High Voltage?

Do you have any idea to make the circuit with the mosfet? I don't know so much about some mosfets, but I can study this.

Best Regards,
Felipe

[star882]

Originally posted by mod_evil
Star, eatitdean,

And the Horizontal Deflexion Transistors? Are they allow to High Voltage?

Do you have any idea to make the circuit with the mosfet? I don't know so much about some mosfets, but I can study this.

Best Regards,
Felipe

A horizontal drive transistor is rated for high voltages, but they're optimized for switching.

Have a resistor from drain to gate to bias the MOSFET on, a zener diode from gate to source to limit bias voltage, then the drain of another MOSFET connects to the gate of the first through a resistor. The second MOSFET is connected to an opamp that compares the voltage from a voltage divider on the output to a reference.

Interestingly enough, a similar circuit was designed by some HVAC engineers in the drive circuit for a piezoelectric expansion valve, which requires a varying bias voltage of up to hundreds of volts, although practically no current. From what I could remember, there was a small high voltage MOSFET, a small high voltage bipolar transistor, along with lots of resistors and a diode or two in the high voltage circuit. There was also a low voltage opamp for closing the loop and it accepts a signal from a DAC to allow digital control of the output voltage.

[mod_evil]

Star,

It can be simple... We needn't DAC. We can make a simple regulator. But the problem with the simple is the High Voltage.

How the Op-Amp can compare high voltages and correct it? Your idea is so good, but I think the Operational Amplifier isn't able to this high voltages.

I'm searching... And I see this schematic.

See this:

http://www.duncanamps.com/technical/mosfet.html

How can I change the ouput voltage in this regulator? Can this regulator able to have in the output 350v or 300v?

Best Regards,
Felipe Navarro