Switching Power Supplies A - Z

Chapter 5

In most vendors’ datasheets, we can usually find Ciss, Coss, and Crss under the section

“typical performance curves.” We will then see that these parasitic capacitances are a

function of voltage. Clearly, that can significantly complicate any analysis. So as an

approximation, we are going to assume that the interelectrode capacitances are all constants.

We will consult the typical performance curves of the mosfet, and then pick the value of the

capacitance corresponding to the voltage that appears across the mosfet when it is OFF (in

our given application). Later, we will show how to minimize this error, by the use of a

certain “scaling factor ...