400V digital potentiometer

[lordsandman]

hi everyone,
i want to design a digital power supply with 400V, max 2mA output and 0.1V resolution(12-bit). i know its hard to control 400V with MCU but output current so tiny. is it possible to divide 400V by digital pots? any specific high voltage IC or a method for transforming high voltages appropriate to digital ICs?
just an idea, it may be absurd

 

[IanP]

How about constructing a ladder consisting of 12 resistors connected in parallel with 12 reed relays that can be driven directly by a microcontroller?

:wink:
IanP

 

[lordsandman]

hey Ian,
thats a solution but i need 10 independent outputs. it means 120 relays, and will a huge circuit, not practical in my case.
can i amplify a 10V DAC output to 400V(with 40 gain and regulated)?

 

[FvM]

Of course, you can use HV OPs, e.g. from APEX Apex Precision Power
Or design your own amplifier using discrete devices for the HV part.

 

[lordsandman]

from the apex link, PA15 is what i need but 200$ unit price. 10x200=2000$
guess i have to design my specific amplifier. what type of amplifier serve to my purpose? can you lead about this?

 

[FvM]

I would think of an complementary class AB or B output stage with HV transistors as used in an audio amplifier with an OP gain stage. You need at least two output transistors, a sriver transistor and a current source transistor, two npn and two pnp HV transistors.