Power semiconductors

When choosing power devices, why are devices with a voltage rating higher than the actual operating voltage used (derating)?

  1. ATo ensure reliability against switching surge voltages and failures caused by cosmic rays
  2. BTo lower the component price
  3. CTo lower the on-resistance
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Answer: A. To ensure reliability against switching surge voltages and failures caused by cosmic rays

In real circuits, surge voltages from parasitic inductance appear during switching, and prolonged operation at high voltage raises the probability of sudden failures caused by cosmic rays (neutrons). Devices with voltage ratings comfortably above the operating voltage are therefore chosen to ensure reliability.

  • A. Correct. Margin is kept for surges and cosmic-ray failures.
  • B. Higher-rated devices are generally more expensive.
  • C. Higher-rated devices generally have higher on-resistance.
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More Power semiconductors questions

  1. When does the avalanche ruggedness of a power MOSFET become important?
  2. What is a typical failure seen in power cycling tests, which repeatedly heat and cool power modules?
  3. In packages for fast-switching power devices, what is the purpose of a dedicated source terminal for the gate-drive return (Kelvin source)?
  4. Which circuit uses a diode and capacitor to create a gate voltage above the supply to drive the upper (high-side) n-channel MOSFET of a half bridge?
  5. In Baliga's figure of merit, used to compare materials for unipolar power devices, which material property has a particularly strong effect?