High Voltage Cap charger

[f4cepl4nt]

Hey guys, just doing some research into converting voltages, and I was just thinking: Would it be possible to say hook up a 9v battery to a IC555 timer, and connect the output of that timer to the primary winding of a transformer and connect the secondary winding to a high voltage capacitor?

Just a thought...I've seen so many complicated charge circuits which I couldn't possibly hope to understand  ;D

Just let me know if my idea is completely idiotic or not. Hahahah

Thanks

 

[audioguru2]

Hi F4,
An IC555 timer's output is rated at 200mA of current, and a little 9V battery can supply that much for a while. So you could make the IC555 oscillate and connect its output to the low voltage wires of a 230VAC to 3V/200mA power transformer. The resulting 690VAC could be rectified and used to charge a capacitor to 975VDC. Since 9V x 200mA= 1.8W went into the transformer then a little less will exit the transformer and will be rectified which is 1.8W/975V= only 1.8mA which is very small.

 

[f4cepl4nt]

So the idea is plausible then =) Great.

A small current of 1.8mA doesn't worry me, I have all the time in the world to charge a cap

 

[audioguru2]

A small current of 1.8mA doesn't worry me, I have all the time in the world to charge a cap

The little 9V battery might run down before the capacitor is charged enough.

You also said the ~690VAC output (rectified) would be able to charge the capacitor to ~975V, but doesn't a capacitor's voltage only approach the supply voltage? Wouldn't it only charge to ~690V? I suppose I'm missing some part where rectifying an AC signal increases the voltage?

You are absolutely correct and I was wrong! ;D :-[
The peak voltage of a sine wave is 1.414 times higher. This project has a square-wave so its output voltage will be 690AC and 690VDC.

Actually, the DC voltage will probably be near 500V because the IC555 isn't perfect and has some voltage loss at its max output current of 200mA. Then the voltage will get less as the battery runs down.

 

[f4cepl4nt]

Hahahah its ok Audio, you've helped me enough over time that it compensates for that minor error

thanks again ;D

Oh yeah just one more thing: The output of the rectifier will still be pulsating rather than constant voltage, will that affect the charging of the capacitor? Is there any way to change that pulsating signal (From 0-~690V) to a constant voltage?


Last question! Promise!  ;D

 

[audioguru2]

The output of the rectifier will still be pulsating rather than constant voltage, will that affect the charging of the capacitor? Is there any way to change that pulsating signal (From 0-~690V) to a constant voltage?

Make the oscillator run at a frequency high enough that the capacitor's charge pulses occur very frequently.
Use a high value capacitor so it won't discharge much into its load.
Use a more powerful (higher current rating) transformer that has less resistance so it can charge the capacitor quicker.

 

[steven2]

use the transformer in reverse if useing the timer circuit for higher ac voltage output , if useing a voltage multiplier for high output dc dont ever use the 10uf electros with the 1n4148 diodes for it , you can use the 1n4007 types and bigger value  electros  just follow my high voltage photo flash caps topic it chargers non photo flash  caps to , it uses a timer circuit  to but it uses a mosfet in one version and a 2n3055 transister in another  version so if you want to use a transformer instead of ignition coil  and flyback transformer, you can use the mosfet version cap charger that allso drives a transformer in reverse mode and use the same circuitry as i did at the section near output of the igntition coil version hv cap charger as i did for the ignition coil version hv cap charger  and with a bit of tweeking you may be able to get a cap charger useing the transformer

 

[cjk2]

You may want to look into using a "boost converter".  That way you only need an inductor and dont have to make a 900v transformer.

 

[steven2]

just grab any car ignition coil and use, it and even flyback transformers without the biult in high voltage trippler , will do  as for inductors which type are you refering to , i made a circuit i found on net, it uses inducter and it was suposed to make high voltage but it dident work ,  and the circuit had a lousy 10uh inducter, i think it was uselless