Table of Contents
Advertisement
C.1.2 Rectifier Diode Selection
Voltage rating
For the bridge rectifier configuration shown, the peak inverse
voltage (PIV) equals 1.414 times the secondary rms voltage. For
example, a 40 Vrms secondary will develop 1.414 * 40 = 56.6
PIV across the rectifier diodes. To allow for line variation and
spiking, allow at least a 50% safety factor in the diode rating.
Therefore, the PIV rating of the rectifier diodes should be at
least twice the rated secondary rms voltage.
Current Rating
Since each diode conducts only on alternate cycles, the average
diode current will be half the supply's average DC current load
on the supply. When power is first applied, there is a surge of
current to charge the capacitor(s) which must be less than the
diode's peak one cycle surge current (I
diodes are chosen with an average current rating of at least twice
the average current load of the supply. It is often advisable to
select diodes with an even greater average current rating because
they have lower thermal resistance between junction and case and
hence ease heat sinking requirements. It is good design practice
to limit the maximum junction temperature to 125
should be done to insure the power-on surge current is within the
diode's I
6415 Installation & Hardware Reference Manual - Rev E
rating.
FSM
) rating. Typically,
FSM
o
C. Testing
C - 5
Advertisement
Table of Contents
