Switching Energy per Event: Repetition Frequency Converts It to Average Loss

Preserve the energy test conditions

Infineon gives average switching loss as (Eon +Eoff) times switching frequency. The energy values belong to their device and operating conditions. Primary reference: switching losses, equation 11.

An energy measured for one current, voltage and gate path should not silently be transferred to another condition. First identify what one cycle contains, then distinguish an energy in joules from the repeated average power in watts.

A fictional repetition comparison

Suppose invented applicable energies are 15 µJ at turn-on and 10 µJ at turn-off. With one of each event per cycle at 20 kHz, the modeled loss is 25 µJ×20,000/s =0.50 W. Holding both energies fixed while increasing repetition to 40 kHz gives 1.0 W.

A real frequency change may also alter device conditions or the applicable energies, so the fixed-energy comparison is explicitly conditional. It adds no conduction loss, driver loss or other circuit contribution. None of the values is an HM converter result or a selected semiconductor rating.

Keep the calculation traceable

Make fields for each event energy, test conditions, events per cycle, switching frequency and the resulting power term. Check whether a quoted energy already combines multiple events.

Ask for evidence that supports using the energies at the actual application conditions. This avoids multiplying an unexplained switching-energy label by frequency and presenting the resulting number as a complete thermal budget.

Customer Questions

Primary References

These references support the technical principles discussed in this guide. The worked examples and review questions are educational.

• Primary reference: switching losses, equation 11