Re: undervoltage lockout for flyback powersupply input

Jamie Morken wrote:


Hi,

I have a flyback powersupply that operates from about 20V to 450V+ (AC or DC input) and I would like to reduce the operation to 75V to 450V,
what is a possible circuit to use on its input to keep it from starting
up until this threshold is reached?

cheers,
Jamie

For simplicity reasons, Get your self a DIAC rated around 75 volts
connect one end to the cathode of D34 and the other end will be
the V+ supply for R5 instead of connecting R5 directly to V+.

Using a comparator circuit would also be fine how ever, you would need
to use a voltage divider and protection zener to make sure you don't over do the input. The output could then simply control the base of
that transistor switch you have.


--
"I'd rather have a bottle in front of me than a frontal lobotomy"
http://webpages.charter.net/jamie_5

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