Re: Power Supply Design

Brian wrote: 
Hello, I have a need of a 300-350VDC Power Supply. I was wondering what
the cheapest design solution would be.  The power supply will be used
to charge large capacitors.  (I am tired of using a hacked disposable
camera circuit board which takes forever to charge up the caps.)
Winding my own transformer is possible although I dont look forward to
1000s of turns if thats what it will involve.


The camera supplies have one advantage that most AC powered capacitors do not have. They don't mind being essentially short circuited for the long time that the capacitor has low voltage at the early stage of charging. This sort of supply uses the step up transformer as an energy storage device. The transformer is loaded with a certain amount of energy in the form of magnetic field, then that energy is dumped into the output. The lower the output voltage, the longer it takes for the energy to dump. The recharge part of the cycle waits, patiently till this part of the cycle is done before putting more energy into the transformer. This is called a flyback supply.

Most AC powered supplies will try to get the voltage up to normal very quickly by putting out as large a current as they can manage, even if this high current causes some parts like the transformer and rectifier diodes to overheat.

So if you are going to try to scale up camera supplies, I think you should be looking for another current limited approach like another flyback type supply.

And winding transformers is not so bad. It is kind of neat, that with
just a little care and patience (and the right materials), you can produce an excellent device, as good as a commercial unit. Try that with an integrated circuit, or even a diode.
.

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