How to choose the PWM frequency

Hi! I am making a 12V 2200mAh battery charger, and am trying to develop it's charge controller by the use of PIC16F1503, how should I choose the right PWM for my design?

Hi,

There is no general answer.

* lower frequency is (maybe) easier to handle, easier PCB layout design
* lower frequency means lower switching loss

* higher frequency means smaller devices (L, C)
* higher frequency has benefits in regulation of transient loads

In either case you need careful design and device value calculations.

Klaus

Assuming you really want to learn how to do this
with a microcontroller and "whatever" power train,
I'd stick with 100kHz - 1MHz. Above this you don't
find so many good components (capacitors of
low enough ESR/ESL). Down at the tens of kHz
the inductor becomes real chubby.

Have you given any thought at all to the power
switches you will use, how you're going to drive
them, and the sense and feedback functions? The
switching hardware (conduction vs switching loss
trades) often has a big say in picking fSW. Here
you aren't talking a real "agile" load so transient
response and loop bandwidth probably don't matter
much and slow only costs you inductor size / weight.
You have to define these trades for yourself.

Of course you could just buy the IC that's on the
shelf for whatever the battery chemistry and size
is. At a 1/10C charging rate it's only about 200mA
which is well within many charge control ICs'
current capability. But you'd miss all the programming
fun.