12v 220v Dc-Dc

[gevv]

used pc atx power transformer








Orjinal



easy circuit

[huanfai]

I was like you... I've also made a same one but I blew my transistor because my heatsink is too small......... 
I belive that your transistor is very hot when you operate it.....
You can improve your circuit by using a pwm controller to make the output being regulated so that can save a lot of power and protect your transistor being fried....
That is a pwm controller IC that is a free sample from Texas Instrument that match your need: MC33063A   

[picavr]

hi gevv ,can you give me more information about transformer fouund in atx power supply,because i have a project about an high voltage generator (variable) ,in the atx box there are generally 2 transformers,;what is the methode   

[tAhm1D]

Hi,
The above placed circuit by gevv is simple but it is good for only testing purpose. Simplicity is not always good in smps. The circuit is uncontrolled and risky as flyback circuit requires lot of transient suppression because in this circuit, peak current is 5.5 times than the nominal current and since no suppressor is used in this circuit, one should be very careful in testing this circuit.

For Picavr,
Yes, in normal ATX Power Supply, there are 2 transformers. One is main transformer, may be EI33 or ERL35 and another is Pulse Transformer, small in size, used to drive the gate of Mosfets or base of Transistors.

[ajmain]

gevv,
You can improve this circuit by adding a mosfet driver before the mosfet maybe by using a totem-pole stage or any ready-made IC. You should also add a snubber across the transformer primary and if possible from drain to ground. Plus, you should rectify the high frequency to dc before the lamp.

[Jagi]

Hi,
The above placed circuit by gevv is simple but it is good for only testing purpose. Simplicity is not always good in smps. The circuit is uncontrolled and risky as flyback circuit requires lot of transient suppression because in this circuit, peak current is 5.5 times than the nominal current and since no suppressor is used in this circuit, one should be very careful in testing this circuit.

tAhm1D I agree with your observation. The above circuit and the associated diagram is very good for someone who is learning about SMPS and how it operates. In the real world you'll need more than just a 555 IC.

@ gevv, how fast is the output switching? Remember the faster the output is switching the more the energy that is dissipated in the MOSFET driver. Additionally, one also needs to keep in mind the saturation of the core, which results in decreased efficiency of the SMPS as drive frequency increases.