how to step up voltage from 9v to 30v

Hi,
i want to step up the voltage from 9v to 30v dc, i require 20mA current at output.what scheme i use, i have heard about PWM,can i use 555 for that purpose? if yes then how? or any other scheme?

You'll want to use a DC-to-DC converter, also called switch-mode power supplies/power converters. National Semiconductor offers a product line called SIMPLE SWITCHERS, and an online design tool called WebBench. Start with WebBench to help you design a circuit.

PWM (Pulse-Width Modulation) is the type of signaling used to drive a switch-mode power supply. The rest of the power supply typically consists of a transformer, diode and switching FET. You need to calculate a lot of things in this design, as well as design the feedback network to control the PWM modulator. 555 timers are very much not what you'd want to use... it's much more complex than that.

For a quick circuit, start with a pre-packaged converter ($$) or use Linear's tools to help you design a simple circuit (cheaper) that you can build yourself, and experiment with.

you can use this chip LM2577 step up regulator