Waveform Of Transistor Base Current - Hitachi RAS-25CNH1 Service Manual

e
When pin of HIC-1 then goes "Hi" [ "Lo", a photocoupler between PQ2 pins 1 and 2 turns off and
the reverse bias current flows to C501 [ power module's Eu + terminals [ Bu + terminals [ R504 [
PQ501 Switching incomplete to cut off the upper arm transistors. (Fig.7-3)
a
1
2
b
O
A
Reverse
bias
current
Fig. 7-3 Waveform of Transistor Base Current (Reverse Current at Point
R507 is used to charge C501 initally.
The operation is the same for B + and C + phases.
8
R401
5
PQ2
R404
6
7
D401 D402
C401
Current at point
A
R407
1
2
A
– 76 –
Power module
Bu +
A + phase
Eu +
)
A