Simplistic Mosfet HV Shunt Regs

[adamus]

Originally Posted by merlin el mago

You are right, but I have no idea to calculate the right resistor value without change bias for heater supply, how can calculate?

its a potential divider, use ohms law

Vheaterbias = (Rbottom * Vin) /(Rtop + Rbottom)

50 to 70v should be fine.

[merlin el mago]

Originally Posted by Salas

The MJE's resistor is better at 5K6. If having 180V in its enough for having stable 165Vout. Use the reg's trimmer to adjust. The trimmer has its middle pin connected to its lower pin. Rheostat. Measure drop across 15K. Drop/15K=Running current. Adjust value using Ohm's law for whatever you need.

Originally Posted by adamus

Edit - double post, see next post

Salas - we are talking about different resistors. Instead of the marginal 180v in, by changing the PS we can get a higher V in (there is a large voltage ddropping R in the PS circuit , the 15k)

Cheers

adam.

Thank you guys for kind advice, I will follows Salas advice because don't need to modificate the PSU voltage, I take note for future problems about voltage divider thank you Adam

Cheers

Felipe

[adamus]

Originally Posted by merlin el mago

Thank you guys for kind advice, I will follows Salas advice because don't need to modificate the PSU voltage, I take note for future problems about voltage divider thank you Adam

Cheers

Felipe

No problem. Personally i would drop the 15k resistor a bit, 15v maybe marginal so why risk it.

[Hearinspace]

I built up the first version with BC560C and MPSA92 last week and on the bench with dummy load it took a long time to settle. Twenty minutes after power up and setting it was still dropping 0.1VDC every 15 - 20 seconds. Has anybody else seen this? I don't want to put it in circuit until it is stable on the bench. I'm wondering if I need to learn about temperature compensation or some other wonderful new thing.

Thanks

[Salas]

The BJT reference one with MPSA92 drifts more due to 3 tempcos and TO-92 error amp heating up. I remember it taking 10-15mins to settle. Up R4 to 4K7 so it runs less mW on MPSA92 for starters. Best for drift would be the later Jfet ref one with TO-126 driver. An easy to get J201 can work fine too if having no K170, with the trimmer half way at 500R for Rs will give you circa 0.35mA under Vbe potential. You can extrapolate the voltage reference resistor at its drain needed for your targeted voltage output.

[merlin el mago]

Advice best diodes for rectification 1N4007? manufacturer? other diode?

[Salas]

Soft recovery 600-1000V Peak Inverse Voltage TO-220 high speed. Do your search of what's available easier to you and has a good reputation.

[merlin el mago]

What about these

Digi-Key - APT15DQ100KG-ND (Manufacturer - APT15DQ100KG)

http://es.mouser.com/ProductDetail/F...2bSYrMoRNSM%3d

[Salas]

Fine components IMO. I would choose the 1000V PIV one for use in even higher voltage bridges given the opportunity.

[merlin el mago]

Yes was also mine first election but I have to place an order to Mouser.