Power Electronics & Semiconductor Devices – Diodes

Diodes are simple device with 2 terminals – It allow current to only flow in 1 direction.

Electron flows from ANODE –> CATHODE direction

The diode characteristics can be placed in 3 regions

  • Forward biased region VAK > V Forward ON (0.7-3 Volts)
  • Reverse biased region VAK < 0 OFF or Blocking
  • Breakdown region VAK <- VZK DAMAGED

Normally there is some Reverse leakage current in practical which we will look into later.

Voltage Rating

Forward voltage Vd
For computing conduction losss and heat sink requirements.
Heat Loss calculation – P (W) = V (voltage) * I (Current)
For semiconductor silicon based – max temperature should not exceed 150C
(semiconductor when faced with extreme heat will short-circuit or go haywire)

Repetitive reverse maximum voltage VRRM
Gives the maxmium continuous blocking voltage. Anything more than this voltage, the diode will give way / blown.

Current Rating

Average vs. Peak AC Voltage

The maximum average forward current If(AV)

The maximum r.m.s forward current If(RMS)
RMS is roots mean square – the RMS is not an “Average” voltage, and its mathematical relationship to peak voltage varies depending on the type of waveform. The RMS value is the square root of the mean (average) value of the squared function of the instantaneous values.

The peak, forward current If(p)
The short burst of current the diode can take without damage

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Yong Han can be found writing about things that matters to him. He is an expert in hazardous zone equipment by day and a IT fanatic by night. Yong Han thinks the world is made better by standards and is actively looking to improve. Yong Han lives in singapore.