switching frequency will be decided in PWM buck converter...

[bharatsmile2007]

hi all,

how switching frequency will be decided in PWM buck converter?If we see data sheets some company's have 500KHZ,200KHZ...etc...

Thanks

 

[cdh7]

Re: switching frequency will be decided in PWM buck converte

Hi,

It's a trade off between inductor size and switching loss. Faster switching speeds mean a smaller inductor can be used, making the power supply relatively small. However, when the transistor switching time becomes significant with respect to the period of the switching signal, switching loss makes the design too inefficient. So basically the companies selling the controllers try to make the clock speed as fast as possible while maintaining moderate gate drive requirements.

Regards,
Chris

 

[dick_freebird]

There are several practicalities to respect in the power
train, and others at board / system level.

With discrete power FETs (10A or higher) switching losses
will eat you alive at more than a few hundred kHz using
power MOSFETs, worse with IGBTs. But low switching puts
you on a fat ol' ferrite and huge capacitors and makes
you have a slow loop.

Older bipolar PWMs can't switch past about 1MHz, themselves,
let alone smack a power FET around at that rate.

RF systems care a lot about exactly where the switching
note sits. Preferably right on top of some dirty-but-known
system clock, where you're already prepared to trap
and process out, or the umptyieth and umptyoneth odd
harmonic both sit comfortably out-of-band.

 

[bharatsmile2007]

Re: switching frequency will be decided in PWM buck converte

Thanks..for the information...

do u have any document,explaining how to decide switching frequency?pls upload...