1. Lab For the following simple switch mode power supply:
Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
For the following simple switch mode power supply:
The switch (1-2) is closed at t = 0 S.
When the switch is open, a freewheeling current IF = 20 A flows through the load (RL), freewheeling diode (DF), and the large load circuit inductance (LL).
The diode reverse recovery current is 20 A and it then decays to zero at the rate of 10 𝐴 𝜇𝑠 . The load is rated at 10Ω and the forward on-state voltage drop is neglected.
(a) Draw the current waveform during the reverse recovery
(Irr ) and find its time (trr ).
(b) Calculate the maximum voltage across the diode
during this process (Irr ).
Lab
Introduction to Power Electronics , Dr. Moayed Almobaied
Lecture 4

2. Series and Parallel operation
Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
Series and Parallel operation
Series and parallel combination of diodes are essentially for handling the high voltage and high current necessary in such applications.
Steady-state and transient voltages must be equally shared when diodes are connected in series.
When diodes are connected in parallel, each diode must share the total load current equally, both under transient and under steady state conditions.
Introduction to Power Electronics , Dr. Moayed Almobaied
Lecture 4

3. Series operation of diodes Series-Connected Diodes
Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
Series operation of diodes
Series-Connected Diodes
Introduction to Power Electronics , Dr. Moayed Almobaied
Lecture 4

4. Series operation of diodes
Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
Series operation of diodes
Series-Connected Diodes with Voltage Sharing
Introduction to Power Electronics , Dr. Moayed Almobaied
Lecture 4

5. Series operation of diodes Is=Is1+IR1=Is2+IR2,IR1=VD1/R1,IR2=VD2/R2
Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
Series operation of diodes
Is=Is1+IR1=Is2+IR2,IR1=VD1/R1,IR2=VD2/R2
Introduction to Power Electronics , Dr. Moayed Almobaied
Lecture 4

6. Example: Find the diode voltages if R1 = R2 =R = 100 k
Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
Example:
Find the diode voltages if R1 = R2 =R = 100 k
Find the voltage sharing resistancesR1 and R2 for equal diode voltages
Introduction to Power Electronics , Dr. Moayed Almobaied
Lecture 4

7. Example: Find the diode voltages if R1 = R2 =R = 100 k Vd1=2750V
Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
Example:
Find the diode voltages if R1 = R2 =R = 100 k
Vd1=2750V
Vd2=2250V
Find the voltage sharing resistancesR1 and R2 for equal diode voltages
Let R1=100k
R2= 125K
Introduction to Power Electronics , Dr. Moayed Almobaied
Lecture 4

8. Series operation of diodes
Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
Series operation of diodes
More than two diodes
Introduction to Power Electronics , Dr. Moayed Almobaied
Lecture 4

9. Series operation of diodes
Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
Series operation of diodes
Series-Connected Diodes with Dynamic Voltage Sharing
Introduction to Power Electronics , Dr. Moayed Almobaied
Lecture 4

10. Parallel-Connected Diodes
Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
Parallel-Connected Diodes
Introduction to Power Electronics , Dr. Moayed Almobaied
Lecture 4