Here is one although it only supplies 350V max.
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18 years ago
Here is one although it only supplies 350V max.
And
The LR8 is an elegant part, even though it can't handle 500V as the O.P. requested. But it's low cost and is readily available from Mouser in several package types.
The simple regulator circuit in the second link may be suitable for retrofitting an old tube set, etc., where the wiring is well-controlled and the likelihood of a mishap such as a short is small, but without any current limiting, it's not suited for use as a lab-bench power supply, in my opinion. The circuit in Terry's link uses a 500V Vactrol to provide current limiting, which is an improvement (they're rather hard to get), but it lacks a foldback current-limit capability.
Both designs specify a TIP50 BJT-type pass transistor. Although these are rated at 500V, they are SOA-disabled like all BJTs, as I detailed before, and will be quickly destroyed if they dissipate much power at full voltage, such as happens under a short circuit. If you look at old commercial high-voltage linear power-supply designs using BJTs, you will see they stack them in series cascode as a solution to the severe SOA problem. Hence, neither design is well suited as it stands for use as a lab bench supply.
One small additional comment. Supertex LR8's are floating regulators powered from the Vin-Vout difference. This type of regulator always requires a brute-force compensation capacitor on its output. The LR8 datasheet specifies 1uF minimum, which both circuits fail to include. The 20uF capacitor after the emitter-follower has some effect, but if the TIP50's beta is 100, it looks like only 0.2uF to the regulator IC, and isn't a good substitute. After adding a capacitor, one should also add some TIP50 base resistance.
-- Thanks, - Win
What about using the HV regulator shown on page 369 in the 2nd edition of AOE as a strating point? Maybe add a 2nd pass transistor with drain resistors and use mosfets in a TO247 pkg.
Mike
Fairchild's 240W FQA10N80C mosfet is one candidate, from Mouser at $3.82 each,
-- Thanks, - Win
Here's another good candidate, STW8NB100, on eBay at $2 each.
-- Thanks, - Win
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