Question about switching frequency of a converter

[contactz]

got some qn on the switching freq of a converter

1) how do i determine the switching freq of a converter?

2)how does the switching frequency in a buck converter affect its efficiency?

3)how does the charge storage at the gate (mosfet) relate to the switching loss? Any formula that i can use?

thax

 

[SkyHigh]

Re: switching frequency

Read chapters on Switching Power Supplies and Pulse-Width Modultion in books, for example by Mohan, "Power Electronics"

For a buck or step-down converter, the average output voltage Vo = Vi.(ton/T), where Vi is input supply voltage, ton is turn on pulse-width or turn on time, and T is the switching period of 1/f where f is the switching frequency.

The higher the switching frequency, the greater the switching loss and lower efficiency.

 

[nandu_r]

Re: switching frequency

you have to make trade of between the ripple in the output, and switching frequency of the convertor for a fixed load capacitor(de-couple capacitor).
If you dont have any constaint on area, you can increase the capacitor size and reduce the switching frequency.

 

[wisepie]

Re: switching frequency

Read chapters on Switching Power Supplies and Pulse-Width Modultion in books, for example by Mohan, "Power Electronics"

For a buck or step-down converter, the average output voltage Vo = Vi.(ton/T), where Vi is input supply voltage, ton is turn on pulse-width or turn on time, and T is the switching period of 1/f where f is the switching frequency.

The higher the switching frequency, the greater the switching loss and lower efficiency.

Can you upload the book here...Mohan, "Power Electronics"