How to decrease volts and increase current without a transformer?

Please, I have a transformer with a 10V x 100mA secondary. I plan to power an MCU based project with it, but my problem is: 10V is much more volts than I need, I plan to power my circuit with 3.3V at most. And 100mA of current is too low, I need more.

So I'm wondering: is there a way to reduce the volts to 3.3V, and increase the current capabitity to, say, 300mA? Since the total power would be the same (10V x 0.1A = 1W and 3.3V x 0.3A = 1W), I think it's possible.

I would also need to make this using only electronic components, and not with another transformer, because that would be pointless.

I know it's possible to use an oscillator to build a circuit that will increase voltage and reduce current, but is it possible to use the same approach to do the inverse, reducing voltage and increasing current capability?

Thanks in advance for any help!

Eduardo

it will be a affordable to by a 9volt 500ma transformer rather than using any dc to dc converter use lm317 as a voltage regulator to get 3.3v or simply use a zener

Thanks for the reply!

I know a DC converter would be costly, but just out of curiosity: isn't there any kind of simple circuit that would convert AC power, just after the transformer output? A circuit that would do exactly what a low power transformer would do?