hello,i am acually constructing a SEPIC converter for photovoltaic application ...i would like to know if 555 timer is suitable to use to drive the pulse width modulation or its better to use PIC microcontroller..thanks

 

You might use a 555 timer, but your parts count will be higher than with a PIC.

Have a look at a PIC12F683 uC. It's an 8-pin DIP uC with built-in PWM, ADC and comparator with 2k flash program memory.

 

doest the 555 timer support up 50khz frequency ...

 

another thing i hv want 2 get constant 9v output with 6v-12v input.i dont know how to design the pwm circuit as well

 

Many 555's can operate much higher than 50kHz.

Well, you mentioned SEPIC topology. Have you research that at all?

You need a buck-boost converter. You say you want a constant 9v output, but at what current?

 

1A current....