Power semiconductors

When does the avalanche ruggedness of a power MOSFET become important?

  1. AWhen the device is overcooled
  2. BWhen no voltage is applied to the gate
  3. CWhen the current in an inductive load is interrupted and its energy drives the drain voltage up to breakdown
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Answer: C. When the current in an inductive load is interrupted and its energy drives the drain voltage up to breakdown

Suddenly interrupting the current flowing in an inductor makes its stored energy drive the drain voltage up, possibly reaching the breakdown voltage and putting the device into avalanche. Avalanche ruggedness is the amount of energy the device can absorb in this state without failing, evaluated by tests such as UIS.

  • A. Cooling is not directly related to avalanche ruggedness.
  • B. Simply having no gate voltage does not cause avalanche.
  • C. Correct. Interrupting an inductive load can drive the device into avalanche.
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More Power semiconductors questions

  1. What is a typical failure seen in power cycling tests, which repeatedly heat and cool power modules?
  2. In packages for fast-switching power devices, what is the purpose of a dedicated source terminal for the gate-drive return (Kelvin source)?
  3. 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?
  4. In Baliga's figure of merit, used to compare materials for unipolar power devices, which material property has a particularly strong effect?
  5. What is the main reason SiC (silicon carbide) is advantageous over Si for high-voltage power devices?