Power semiconductors

Among soft-switching techniques for power converters, which correctly describes ZVS (zero-voltage switching)?

  1. AKeeping the switch on all the time
  2. BTurning the switch on when the voltage across it is nearly zero, reducing switching loss
  3. CMaking the output voltage zero
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Answer: B. Turning the switch on when the voltage across it is nearly zero, reducing switching loss

In ZVS, resonance or similar is used to bring the voltage across the switch down to near zero before turning it on. Because there is almost no period when voltage and current are both large, turn-on switching loss and noise are reduced. It is widely used in high-frequency power supplies.

  • A. A switch that is always on cannot convert power.
  • B. Correct. Turning on at zero voltage reduces loss.
  • C. It is not a method of making the output voltage zero.
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More Power semiconductors questions

  1. When a power MOSFET's gate is charged with a constant current, why does the gate voltage stay flat for a while (the Miller plateau)?
  2. Why is a negative gate voltage (for example, −3 to −5 V) sometimes applied to SiC MOSFETs or IGBTs in the off state?
  3. What maximum junction temperature (Tj max) is commonly specified for typical silicon power devices?
  4. When choosing power devices, why are devices with a voltage rating higher than the actual operating voltage used (derating)?
  5. When does the avalanche ruggedness of a power MOSFET become important?