Power semiconductors

What is the conduction loss of a power MOSFET with an on-resistance of 10 mΩ carrying 10 A?

  1. A0.1 W
  2. B1 W
  3. C100 W
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Answer: B. 1 W

Conduction loss is P = I² × R. (10 A)² × 0.01 Ω = 100 × 0.01 = 1 W. Because it is proportional to the square of the current, small differences in on-resistance cause large differences in loss at high currents.

  • A. 0.1 W is I × R, which is not the formula for power.
  • B. Correct. 10² × 0.01 = 1 W.
  • C. 100 W results from mis-converting the resistance unit (mΩ).
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More Power semiconductors questions

  1. What is the main purpose of attaching a heat sink to a power device?
  2. How many switching devices does a typical three-phase inverter for driving a three-phase motor use?
  3. In power circuits and the like, what is the small resistor placed in series in the current path to measure current called?
  4. Why is a switching power supply more efficient than a linear power supply, which operates its transistor linearly?
  5. What is the main advantage of the trench gate structure in power MOSFETs, in which the gate is buried in a groove etched into the silicon?