Hitachi RAS-25CNH2 Service Manual page 53

7. Drive Circuit
(1) Upper Arm Drive Circuit
Fig. 7-1 shows the upper arm drive circuit.
G
The circuit configuration is completely the same for phases A, B and C.
a
8
1
PQ2
2
7
b
8
1
PQ3
2
7
8
1
PQ4
2
7
Forward
current
O
A
e
When pin of the micro computer goes "HI" [ "LO", a photocoupler between PQ2 pins 1 and 2 turns
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on and current flows to terminal A [ R401 [ PQ2 [ R404 [ power module's Bu + terminals [ Eu +
terminals [ D402 [ D401 [ terminal B and drives the upper arm transistors. (Fig.7-2)
As described in the rotor magnetic pole position detecting circuit, the upper arm drive circuit supplies
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current to the bases of the transistors on the power module's positive e side which turn on or off according
to the position detection signals. The signals according to the position detection detection signals are
output from pins
R401
5
R404
6
D401 D402
R402
5
R405
6
D403 D404
R403
5
R406
6
D405 D406
Current at point
Fig. 7-2 Forward Current Waveform at Point
e r t
, and of the micro computer and are input to pins 2 of photocouplers PQ2 - PQ4.
A
R407
C404
+
C401
–
R408
C405
+
C402
–
R409
C406
+
C403
–
Fig. 7-1
A
– 56 –
Power module
Bu +
1
U + phase
Eu +
2
Bv +
5
V + phase
Ev +
6
Bw +
9
W + phase
Ew +
10
CN27
A