Re: Need "constant voltage-drop device"
- From: Terry Given <my_name@xxxxxxxx>
- Date: Wed, 22 Feb 2006 15:44:26 +1300
jwallacq@xxxxxxxxxxx wrote:
Is there any kind of 2-terminal device, circuit, or "black box"
commercially available that will automatically maintain a constant
voltage drop between a DC power source and its Load over a very wide
range of supply voltages and load resistances??
For my application, I would need something that maintains a voltage
drop of, say, 100 volts while the power supply output fluctuates from
about 150 volts to 1000 volts, and the load current varies from 1 amp
to 20 amps --- sort of a "super-zener-diode."
Actually, a 100 volt, 20 amp zener diode would be ideal, but as far as
I know, there ain't no such animal.
Suggestions, anyone? TIA, john w.
make an "active zener" - I would use a 100A~300A, 1200V IGBT with a suitable zener from C to G, and some gate impedance too (say 10k//100n//12V zener). Voila, a giant zener that can dissipate (with a large heatsink) you 2kW. BTDT for a 300A 750Vdc dynamic brake (in which case the DB resistor was in series with the IGBT collector).
you might want to use a resistor too, and greatly reduce the heatsink size (by letting the resistor get effing hot):
K-----+----------------+
| |
__/ [R] R = 90V/20A = 4R7 or so, rated 2kW
90V /\ |
| |
| / c
+----+-----+---||
| | | \ e
__/ [10k] [100n] |
12V /\ | | |
| | | |
A-----+----+-----+-----+
Cheers
Terry
.
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