Roger, Yes. Looks like the common dielectrics (X7T, X7R) available in the 250v 1-3uf range suffer from a 30-80% reduction in capacitance at 180v. I hadn't realized it was that high. Thank you, I'll look at the polymer caps. It's my last remaining electrolytic on my board and if possible I would like to use a solid one instead.
Regards, -Moses On Wednesday, May 18, 2022 at 7:54:10 PM UTC-7 Roger Brinkman wrote: > Hi Moses, > > What David writes below about the capacitance reduction of ceramic > capacitors is correct. > I have experienced success using polymer aluminium electrolytics (solid > electrolyte) to replace conventional low-ESR electrolytic capacitors that > regularly fail in similar applications. > You might like to experiment with these. > > Best regards > Roger Brinkman. > > On 19 May 2022, at 12:42 pm, David Forbes <[email protected]> wrote: > > > > I haven't tried it, but I can make some observations. The MAX1771 isn't > connected directly to the output circuit, so it's not likely to suffer from > a problem. The current flows through the inductor which will accommodate a > momentary short circuit caused by the capacitor. > In short, it shouldn't be a problem. > Bear in mind that the effective capacitance of a modern ceramic capacitor > is much lower with a DC bias near its rated voltage, so you would need to > use either capacitors rated for 5x the output voltage, or about 5x the > desired capacitance. > Some capacitor data sheets publish this reduction in capacitance as a > function of bias voltage, most don't. Look for it. > > > On Wed, May 18, 2022, 6:49 PM Moses <[email protected]> wrote: > >> Before I let the magic smoke out of half a dozen MAX1771 ICs.. has anyone >> ever tried using ceramic output capacitors? It wants a low ESR capacitor, >> so ceramics may work well. >> >> The datasheet doesn't mention ceramics on the output side.. but then >> again it was written a few decades ago when the required >> voltage/capacitance probably was not readily available. >> >> Regards, >> -Moses >> >> -- >> You received this message because you are subscribed to the Google Groups >> "neonixie-l" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To view this discussion on the web, visit >> https://groups.google.com/d/msgid/neonixie-l/7ae38dca-64ca-459d-a1e5-283a062f8f9en%40googlegroups.com >> >> <https://groups.google.com/d/msgid/neonixie-l/7ae38dca-64ca-459d-a1e5-283a062f8f9en%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > -- > You received this message because you are subscribed to the Google Groups > "neonixie-l" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > > To view this discussion on the web, visit > https://groups.google.com/d/msgid/neonixie-l/CAPbqtvcg0ak%2BLMH_7JJ01eFnYjFzu38v2N59k8ZfoFxrRY3J_g%40mail.gmail.com > > <https://groups.google.com/d/msgid/neonixie-l/CAPbqtvcg0ak%2BLMH_7JJ01eFnYjFzu38v2N59k8ZfoFxrRY3J_g%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > > -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/9b6cbb33-9ecb-40e0-9628-e7a09e784661n%40googlegroups.com.
