Half-Wave Rectifier Question?

Hello Everyone,

Well, I built a half-wave rectifier using a diode and a resistor, but it doesn't seem to be working as I want. I'm thinking of adding a capacitor to help smooth out the wave, but my whole purpose was to produce a pulse of energy at 60Hz. Basically, to just chop off the lower half of the sine wave. For my diode I used a 1N5406 rated at 600V and 3 amps. The resistors are rated at 20 watts and the whole thing just plugs into the electric outlet. It seems to work ok, but when I take this rectified output and put it into a transformer to step it up to around 1000V thats when I have a problem. After its stepped up its supposed to charge a small capacitor from which the electricity (when built up) will jump across a small spark gap. The spark gap is adjusted correctly, but he capacitor doesn't seem to like to charge on this wave. Its rated 2KV so voltage isn't the problem. The problem is that it will fire once, but not repeat the cycle. 
(The transformer shouldn't be the problem because I'm pulsing the dc)

Any Ideas?


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Do you have a diode between the stepped up AC voltage and the capacitor?

What you are describing sounds like you are trying to make a charge pump.

If you just have the small capacitor across the transformer high voltage winding, you basically have a short across that winding because the capacitor's impedence to AC will be very low.

 If you have a diode in series with the capacitor then the capacitor will charge up.

In fact if I understand what you are trying to do, you don't have to rectify the input to the transformer. You should move the diode to the other side (high voltage winding).

transistorguy (author)  Doug Paradis6 years ago
Your more accurate here. I did move the diode and resistor to the other side of the transformer, but when I tried it.... the transformer exploded. This was why I originally wanted all of that on the other side of the transformer... to protect it from th brunt of the power coming in. Now that I'm getting a new transformer anyway, do you have any suggestions on what to do so it doesn't burn out again?

Sorry to hear about your transformer. What type of transformer was it? You do not want to use a audio, or impedance matching, or pulse, or unknown rated transformer across the mains.

 Is your capacitor and/or diode shorted?

Does your project have a schematic and is it available on the web?
transistorguy (author)  Doug Paradis6 years ago
Here is my schematic. It is of my own design. This is the latest version I have been working on.

The transformer is just a 12V to 120V that I flipped around (I have done this before and it has worked fine) to give me 1200V when I put 120V into it. This is my latest design. Take a look and if you see any problems please tell me about them.
You can not expect more then 600V out of the diode at the capacitor. In fact you may be damaging the diode by over voltage in the reverse direction! If you want to withstand 1200V, use 3 diodes in series and hope they share equally. Or get a single diode that is rated 2000V. Good luck.
This site has a circuit for a disposable camera flash about half way down the page. If you think of the transformer that is part of the transistor  oscilator as your AC source, the diode and capacitor on the other winding is similar to what you want to do.