During an ESD event, both D1 and D2 can conduct, but the voltage at VIN exceeds the power-supply-rail voltage by only two forward-biased diode voltage drops.

Using the averaged switch modeling approach, a non-linear large-signal averaged model of non-ideal PWM switch is derived, taking into account all parasitic resistances and threshold voltage of diode.

For example, the typical power diodes and the power transistors have high reverse voltages in hundreds to thousands of volts and microamps to milliamps through them in the off state.