Power semiconductors

Why are power devices required to be 'normally off', with no current flowing at 0 V gate voltage?

  1. ATo slow down switching
  2. BTo avoid the danger of current flowing unintentionally when, for example, the drive circuit fails
  3. CTo make the device cheaper
Show answer and explanation

Answer: B. To avoid the danger of current flowing unintentionally when, for example, the drive circuit fails

With a normally-on device, if the gate drive power is lost or the drive circuit fails, the device turns on and a large current may flow. For safety, power supply circuits generally require normally-off devices. GaN HEMTs use specially designed structures to achieve normally-off operation.

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More Power semiconductors questions

  1. What is the main advantage of using SiC Schottky barrier diodes as freewheeling diodes in inverters and similar circuits?
  2. Which is a characteristic of a thyristor?
  3. In high-power modules, what is the main purpose of the insulating substrate (such as a ceramic substrate) placed under the power chips?
  4. When SiC or GaN power devices switch at high speed, which problem particularly needs countermeasures?
  5. If the current in a wire with a parasitic inductance of 10 nH changes by 10 A in 10 ns, approximately what voltage is induced?