Re: Over-voltage protection circuit does not work as expected
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I would not designate the proposed circuit as an overvoltage protection circuit. At most it's something like a "voltage clipper" or "voltage limiter" for excessive input voltage excursions. Let's assume there are any failures within the control circuit, or a defective Power-MOSFet, or even overvoltages, coming from external sources directly to the Load, then you will get in trouble with that circuit.
A true overvoltage protection circuit requires a crowbar arrangement, as well known in the power electronics industry.
Best regards Udo?? Am Mi., 5. Feb. 2025 um 15:40?Uhr schrieb jerzy przezdziecki via <jprzezdziecki= [email protected]>:
Hello, ? I have uploaded circuit that finally works as executed with a good TLV1805 model found online. The problem was the ic. I have used a voltage comparator from the LTSpice library list with an open collector ¨C instead of an original TLV1805 push-pull one. This made a simulation not working properly. So everything was fine with the PMOS. ? Anyway thanks to all for advices. ? Jurek ? Two other suggestions: Keep Vcc at 36V, but add a separate PWL(0 0 1 36) source to the comparator signal input, rather than the R2/R3 divider. THEN(!) swap the + & - inputs. As is, it turns the output FET ON when the test voltage exceeds the Zener. ? Dave ? ? Works a heck of a lot better, with the S pin NOT grpinded¡ As David Schultz suggested, maybe add the bypass cap between B and S,. but don¡¯t ground it ¨C that forces the out out to an open/pulled-up state. ? Dave ? ? Isn't that what it is supposed to do?? 19V is not overvoltage so you would expect the mosfet to conduct.
-- Dipl.Ing.Udo Huhn-Rohrbacher Albert-Kratz-Str.1 D-75180 Pforzheim phone: +497231-352339 fax: +497231-140338 mobile: +491523-3612096 E-mail: u.huhn.rohrbacher@...
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