EE 442 POWER ELECTRONICS I DIODE CIRCUITS Dr

EE 442 POWER ELECTRONICS I DIODE CIRCUITS Dr. Said A. Deraz Assistant Professor Electrical Engineering Department Faculty of Engineering, King Abdulaziz University sderaz@kau. edu. sa saidderaz@yahoo. com

Desired Characteristics of a Power Electronic Device • On-State Low forward voltage drop Von Low resistance Ron (low power loss) High switching frequency fsw High withstanding forward voltage VBF • Off-State High withstanding reverse voltage (PIV) Low leakage current IOFF High resistance ROFF (low power loss) Transition between On and Off Low delay time, rise time, and fall time to operate at high frequency Low gate drive voltage, current and power for turn-on and off Controllable turn-on and turn-off times High withstanding dv/dt and di/dt. Low price 2

Uncontrollable Devices Power Electronic Devices Power Diode General purpose diode Fast recovery diode Schottky diode Thyristor SCR, TRIAC, GTO, BCT, Fast switching SCR, LASCR, RCT, FET-CTH, MTO, ETO, IGCT, MCT, SITH Controllable Devices BJT Power Transistor MOSFET IGBT COOLMOS, SIT Classification of Power Electronic Devices 3

Power Diode Power diode is a PN junction, that allow the current to flow in one direction. V-I Characteristics 4

Diode with RC Load When Vco=0 5

Diode with RL Load 6

Ex#1 For the following circuit, R= 44Ω and C=0. 1 µF. The capacitor has an initial voltage of V 0=220 V. If the switch is closed at t=0, draw the current and voltage waveforms and determine a) the peak diode current, b) the energy dissipated in the resistor R, c) the capacitor voltage at t= 2 µs. 7

Ex#2 For the following circuit, L= 80 µH and C=0. 1 µF. The capacitor has an initial voltage of V 0=220 V. If the switch is closed at t=0, draw the current and voltage waveforms and determine a) the peak current through the diode, b) conduction time of the diode, c) the steady state capacitor voltage. 8