how to step up 5VDC to 100-200VDC? (for APD)

I'm guessing the classic "boost" switch mode power supply to convert

Piezo?

Ok its neat but too much for your application.

Stepup transformer is the way to go. If you had more than 5 volts you could use a voltage multiplier.

Cheers

app doesnt show high voltage supply but use with either a small step up transformer or a voltage multiplier, or both.

Colin =^.^=

On a sunny day (Sat, 02 Jun 2007 17:56:06 -0000) it happened Michael wrote in :

Eh, I take small potcore (rip from old PCB or something).

The circuit:

C1 decouples C2 is 'upside down,. the top will become negative. C3 set frequency (sinewave), several kHz, do not use ceramic, too many losses. C4 should be able to handle your volts, and Q= CxU = i x t helps you estimate the ripple. R1 T1 can be any low power si NPN that can handle some 45 V Waveform is close to sinewave (bottom slightly flat). L1 is simply 1 turn per volt. If it does not oscillate reverse the feedback loop connections before the transistor evaporates.

I have used this many times.... even in EPROM programmer. If you know how to wind some turns of wire you can build it in a few minutes,

Beyond about a 10:1 ratio, the classic boost regulator isn't going to be very good. There are several things that start to work against you.

Basically what is happening as the ratio goes up is that the high frequency content of the switching waveform is increasing. This puts extra requirements on all the parts that see the wave form.

The output rectifier has to handle narrow pulses of quite high currents. The power in the diode follows a function between the average and RMS current since the forward voltage on it is not a linear function of current, but you still end up needing a bigger diode. Bigger diode tend to be worse from a high frequency point of view.

The high voltage requirement on the inductor may cause trouble.

If the OP only needs small currents, a voltage multiplier on the output may be the way to go. At higher currents, a transformer is needed.

Have a look at app note 98 from Linear Technology - there is a 0-300V low noise circuit - good stuff!

MJ

It could be worth looking at the disposable flash camera boards. Asking nicely at a photo processor normally gets you several. They use a single AA cell and generate about 300 volts, If your current is only uA or nA just use a divider to get what you need.

You can get some ideas from

Barry