– 57 –
● When pin
e
of the micro computer then goes "Lo" [ "Hi", a photocoupler between PQ2 pins 1 and 2
turns off and the reverse bias current flows to C401 [ power module’s Eu
+
terminals [ Bu
+
terminals
[ R404 [ PQ2 to cut off the upper arm transistors. (Fig.7-3)
5
6
1
8
2
PQ2
7
b
a
1
Bu
+
Eu
+
Power module
U
+
phase
+
–
A
2
R401
R404
D401 D402
C401
R407
A
Current at point
Reverse
bias
current
O
A
Fig. 7-3 Waveform of Transistor Base Current (Reverse Current at Point )
A
● R407 is used to charge C401 initally.
● The operation is the same for V
+
and W
+
phases.
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