Greetings,

I have incorporated an AVR microcontroller to act as a feedback system (Voltage Sample -> PWM) in a SMPS boost converter to get a regulated boosted voltage. Trying it out on a very low power scale, it worked great.

Once I decided to go up in power, I quickly hit a ceiling (~100mA output).

My circuit is just the simple model for a boost converter you can find on wikipedia or anywhere. The inductor is rated for 2.2A continuous, the power MOSFET rated for 20A continuous, with a switching frequency way past my PWM frequency and drain to source voltage higher than what I need, diode rated for 5 amps continuous. The voltage sampling divider used large resistor values that shouldn't significantly effect the load. Everything SOUNDED fine to get at least a third amp out of the system.

The boost ratio I wanted was large, but still seeming plausible: 9V in, 50V out. So 50V * 0.3A = 15W. 15W/9V = 1.66A.

My suspicion was that my feedback algorithm was going screwy, so I just did an open-loop, pot adjustable PWM signal, but I still had no luck.

So here I am, asking for some advice. Is there some inductor property I misinterpreted for switching? Is there an optimal PWM frequency I should be hitting? Does the transistor need to be rated much higher than the desired output to handle inductor spikes?

Any help would be appreciated, and please spare me the "you're going to die" speech, because I haven't yet!