Hitachi RAS-25CNH2 Service Manual page 55

(2) Lower Arm Drive Circuit
Fig. 7-4 shows the lower arm drive circuit.
G
The circuit configuration is completely the same for phases A, B and C.
y
When pin of the micro computer goes "HI" [ "LO", a photocoupler. between PQ5 pins 1 and 2 turns
G
on and current flows to terminal C [ R411 [ PQ5 [ R414 [ power module's BU – terminals [ Ew –
terminals [ D412 [ D411 [ terminal D and drives the lower arm transistors. (Fig. 7-4)
The signals which turn on or off according to the position detection signals are output from pins
G
of the micro computer in the same way as in the upper arm drive circuit and are input to pins 2 of
photocouplers PQ5-PQ7.
No chopper signal is input to the lower arm drive circuit.
G
y
When pin of the micro computer goes "LO" [ "HI", a photocoupler between PQ5 pins 1 and 2 turn
G
off and reverse bias current flows to C411 [ power module's Ew – terminals [ Bu – terminals [ R414
[ PQ5 to cut off the lower arm transistors. (Fig. 7-5)
R417 is used to charge C411 initally.
G
The operation is the same for V – and W – phases.
G
When the peak current cut off function operates, Q306, PQ2-PQ4 and PQ5-PQ7 turn off and the upper/
G
lower arm drive circuits stop.
Only the lower arm drive circuits turns off when reset.
G
c
R411
8
1 5
PQ5 R414
2 6
7
R412
8
1 5
R415
PQ6
2 6
7
R413
8
1 5
R416
PQ7
2 6
7
d
D411 D412
C411
R411
8
1 5
PQ5 R414
2 6
7
R412
8
1 5
R415
PQ6
2 6
7
R413
8
1 5
R416
PQ7
2 6
7
D411 D412
C411
R417
CN28
Fig. 7-4
R417
CN28
Fig. 7-5
– 58 –
Power module
Bu -
U - phase
Bv -
V - phase
Bw -
W - phase
Ew
Power module
Bu -
U - phase
Bv -
V - phase
Bw -
W - phase
Ew
y u i