– 58 –
(2) Lower Arm Drive Circuit
●
Fig. 7-4 shows the lower arm drive circuit.
The circuit configuration is completely the same for phases A, B and C.
●
When pin
y
of the micro computer goes "LO"
[
"HI", a photocoupler between PQ5 pins
1
and
2
turn
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.
●
The operation is the same for V– and W– phases.
●
When the peak current cut off function operates, Q306, PQ2-PQ4 and PQ5-PQ7 turn off and the upper/
lower arm drive circuits stop.
●
Only the lower arm drive circuits turns off when reset.
●
When pin
y
of the micro computer goes "HI"
[
"LO", a photocoupler. between PQ5 pins
1
and
2
turns
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
y
u i
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.
1
2
5
6
1
2
1
8
2
PQ5
PQ6
PQ7
7
5
6
8
7
7
8
5
6
c
R411
R414
R412
R415
R413
R416
R417
C411
CN28
Ew
Bw-
Bv-
Bu-
Power module
U- phase
V- phase
W- phase
Fig. 7-4
D411
D412
d
1
2
5
6
1
2
1
8
2
PQ5
PQ6
PQ7
7
5
6
8
7
7
8
5
6
R411
R414
R412
R415
R413
R416
R417
C411
CN28
Ew
Bw-
Bv-
Bu-
Power module
U- phase
V- phase
W- phase
Fig. 7-5
D411
D412