– 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.