transistor HELP!!

[wolf08]

i want to make a small transformer, but i have no ac power supplie so i was going to use a transistor to creat pulse dc can you help me find a circuit *I am using a low dc voltage and im trying to step up*

 

[Hero999]

Care to mention the voltages and power requirements?

 

[vne147]

i want to make a small transformer, but i have no ac power supplie so i was going to use a transistor to creat pulse dc can you help me find a circuit *I am using a low dc voltage and im trying to step up*

What is your input voltage and available current and what is your desired output voltage?

 

[Vizier87]

I suppose he meant it to be like this?
**broken link removed**

He'll have to use, er, quite a lot of trannies for that, I suppose?

 

[Hero999]

That circuit is not very good because it has a high voltage loss, the output stage of the 555 plus Vbe of the output transistors which will be a couple of volts.

 

[Vizier87]

but will it be up to 230V? I cannot help wondering....

 

[Hero999]

Sorry, the output won't be 230V.

An emitter follower looses 0.6V without a load, about 1V with a load and the 555's output stage looses between up to 2.5V so the voltage delivered to the primary of the transformer will be a couple of V lower than half the power supply voltage.

The transformer will also have more turns on the lower voltage winding than you'd expect, to make up for the losses. For example measure the secondary voltage from a mains transformer with no load connected and it will be up to 25% higher than the voltage rating, so a 6V transformer might measure 7.5V which means that you'll need 7.5V connected to get the rated primary voltage.

If you use a 12V power supply, you'll need to use a 3V transformer to get anywhere near 240V on the output.

 

[Vizier87]

I'm still sensing this mental blockade that 15V supply can be transformed into an output even above 150V... the output would shock someone, wouldn't it?

 

[Hero999]

Yes, with the input at 15V and a 4.5V transformer, the output would shock but apart from that, the circuit isn't useful for much else and there are far more effective ways to build a shocker from a mains transformer.