i suppose that there is a big time difference. my responses are late too
It's probably just as well. I keep finding improvements. The latest is to change R9 to 100 Ω. This increases the current limint to about 4 ma.
yes, i will use seperate unregulated supply for each regulator. this is only for try out, at the final i will use rectifier. 12-bit R-2R DAC with current-voltage converter at the output will be the programming voltage. and 10.24V precise voltage referance for the DAC, so 1 LSB change at the DAC input corresponds 0.1V change at the output. every regulator will have it's own DAC. i'm planning a PIC that controls all of the DACs with an optocoupler for isolation. at the software side, i will use matlab for commanding PIC via RS-232. a have a figure of merit acquired from the system. so, i can optimize it by changing regulator outputs.
Okay, sounds like we are good.
it may be neccesary that a complementary bipolar regulator outputs. can i use a resistor divider for obtaining complementary outputs from an unipolar one? for example, two ±200V outputs from a 400V unipolar?
Let me think about this.
what kind of transistors, resistors and capacitors should i use? are 2W %1 thin film resistors and 450V grade ceramic capacitors work? and worried about the pass element, which power transistor best suits the design?
There is nothing special. let me check wattage. I think we can make the 75K larger to reduce the power needed. and the 560K should be 1/2 watt. What will be the voltage range on your DAC? We may need to resize the feedback resistors to match. I just used 0 to 5 volts. You say the input will be 420 volts. What is the maximum required output?
I think the MJE18002 transistors will work but let me look at some others. Same with the op amp.
is there a mininmum current requirement and what happens when short the output?
There is no minimum because the voltage divider on the output supplies some load. When the current goes above 4 ma or so Q1 turns on and turns off the pass transistor. During a short there will still be a short pulse of high current, but I think the pass transistor may survive