Hi Guys,
I have been working on two HV regulator circuits in the past year where
I
needed +375 volts at up to 100 ma. In the first case I had 600 volts to
start with, so I used a tube circuit. In the second case, all I had was
about +430 which dips to about 390 at maximum output, and reduced AC line
voltage, so I went solid state.
My two circuits are here:
Tube version:
http://pages.prodigy.net/jcandela/CentralElectronics20AModifications/CE_20A_
QRO_Power_Supply.jpg
Solid State version:
http://pages.prodigy.net/jcandela/Sherwood_S8000/HV_REG/SS_HV_VOLTAGE_REGULA
TOR.jpg
The first circuit shows my complete power supply in my Central
Electronics
20A QRO #2 rig. I used a pair of 7591's in the RF final to make up to 12.5
watts AM output, or about 55 watts PEP SSB output. I ended up with a 6W6 in
the series regulator as it had more emission than a 5V6, even though the 6W6
only had 5 1/2 volts on the filament. This regulator is always at +374, hot,
cold, month after month. The ripple from it is unmeasurable (with my
equipment), and dynamic load response is excellent, although I cannot
remember exactly what the results were, as that was last winter. The rest of
my 20a info on the web is at:
http://pages.prodigy.net/jcandela/CentralElectronics20AModifications/
The second regulator circuit is much simpler, and cheaper to build, and
the
performance is similar with one big exception. The regulator only needs a 15
volt delta input to output, whereas a 6W6 at zero bias triode connected
needs closer to 100 volts (and that is saturated, i.e. no regulation)to pass
100 ma. The main drawback is that the solid state circuit is not adjustable.
You have to get a string of zeners to add up to the desired output voltage.
This is no big deal though. You can buy from Mouser (www.mouser.com) the 1
watt zeners series (1n47xx) for about 15 cents each in packs of 10, and they
carry them up to 200 volts, although I prefer to go no more than 100 volts
per zener for power dissipation reasons. For folk with higher input
voltages, there are higher voltage fets that can pass 900 volts or more, so
that isn't a big problem. The one I use is rated at 500 volts, and can be
had for about one dollar. To keep the power dissipation down, add as much
series "R" into the regulator input so that you have slightly greater than
15 volts across the regulator circuit shown at maximum load current, and
minimum ac (brownout) voltage. The opto coupler in this circuit has a
Darlington transistor, and the CTR (current transfer ratio) is very high,
hence the excellent closed loop regulation. Reduction of power line ripple
is > 40 db. With only 1 ma through the zeners, the zener warm-up drift is
about 1-2 volts rise. Keep in mind that this solid state regulator is still
a work in progress, and still populates a proto-board on top of my Sherwood
30+30watt stereo amplifier with 4 X 7868 output tubes. I designed the
circuit to be short circuit proof with the intention that if the output were
shorted, the Sherwood fuse would pop before anything fried too bad. I have
been way "too-chicken" to try this feature out. Maybe one of you brave souls
can perform this test using components bought from your very own checking
account!
These circuits can find there way into all sorts of AM equipment...I
hope
that somebody tries one of these circuits and then asks me "why didn't you
do this _____ instead"
Regards,
Jim Candela
WD5JKO
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