Re: Linear regulated 150V supply

From: Winfield Hill (hill_a_at_t_rowland-dotties-harvard-dot.s-edu)
Date: 11/22/04 

Date: 22 Nov 2004 03:34:26 -0800

Spehro Pefhany wrote...
>
> Robert Baer wrote:
>
>> John Fields wrote:
>>>
>>> Rene Tschaggelar wrote:
>>>
>>>> Is the LM723 still the regulator of choice for a regulated
>>>> 150V supply driven by a line transformer? The current to
>>>> be supplied is moderate, say up too 200mA. Or are there
>>>> any alternatives with an external pass transistor / FET ?
>>>
>>> How about something like this?
>>>
>>> 4W
>>> ////////
>>> +170>--+------+------D S--------+----------+---->+150
>>> | | G | |
>>> | [R] | [R] [R]
>>> | | | | |
>>> | +--------+ +---+-----+ |
>>> | | | | | |
>>> |+ | | [R] | |
>>> [BFC] | | | +| |
>>> | D /-|--+ [C] |
>>> | G--+--[R]---< | | | |
>>> | S | \+|--|-----|----+
>>> | | | | |+ | |
>>> | | [C] | [REF] | [R]
>>> | | | | | | |
>>> GND>---+------+----+----------+---+-----+----+---->GND
>>
>> Oh, my! No consideration for all that extra gain (and
>> likely oscillation)!

 Likely? Guaranteed. Three poles in the feedback loop, no zeros.

> It'll stop when the gate punctures on the pass transistor.
 
. 20W
. ///////
. +170>--+---+---+--+-R1--+--S D----+-----+----+---->+150
. | | | | | G | | |
. | | | E R2 | | | |
. + | | R4 B---+----|--R3--' | _|_+
. BFC | | C | | --- C3
. | R10 +--+----------' | | large
. | | | ,-----+ |
. gnd +---|-----------, C2 | | gnd
. | | ,--R6--|-||-, R7 R8
. Z1 | | |_ | | |
. | C | / -|--+---|-----+
. gnd B--+----< | | |
. E \_+|------+ R9
. | | |+ |
. R5 | REF gnd
. | gnd |
. gnd gnd

 Startup opamp voltage regulator. Pole-zero loop compensation.
 Level shift with gate-voltage limit. Fold-back current limit.
 P-channel pass element, medium-large output capacitor.

 Opamp HV regulator designs are a bit awkward. A design based
 on a TL431 with cascode transistor or a zener plus transistor
 is more straightforward, as we've shown with several drawings
 within the last few years here on s.e.d. 

-- 
 Thanks,
    - Win