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‫بسم هللا الرحمن الرحيم‬
The Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
POWER ELECTRONICS
EELE 5450 — Summer 2012
Instructor: Eng. Jalal Al Roumy
Lecture 4
Chapter Two
Series and Parallel operation
In many applications, the power handling capability of a
single power diode is not sufficient. (HVDC applications).
Chapter Two
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.
Chapter Two
Series operation of diodes
Series-Connected Diodes
Chapter Two
Series operation of diodes
Series-Connected Diodes with Voltage Sharing
Chapter Two
Series operation of diodes
Is=Is1+IR1=Is2+IR2, IR1=VD1/R1, IR2=VD2/R2
Chapter Two
Series operation of diodes
More than two diodes
Chapter Two
Series operation of diodes
Series-Connected Diodes with Dynamic Voltage Sharing
Chapter Two
Example:
Find the diode voltages if R1 = R2 =R = 100 k
Find the voltage sharing resistances R1 and R2 for equal diode voltages
VS  5kV
I S1  30mA I S 2  35mA
Chapter Two
Example:
 Find the diode voltages if R1 = R2 =R = 100 k
1) Vd1=2750V
2) Vd2=2250V
 Find the voltage sharing resistancesR1 and R2 for equal diode voltages
1) Let R1=100k
2) R2= 125K
Chapter Two
Parallel-Connected Diodes
End of Lecture