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(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.
Power module
U- phase
_ W' phase
ID411 — +D412
Te
|
C411
Fig. 7-4
@
When pin @ of the micro computer goes "HI" — "LO", a photocoupler between PQS pins @ and @ turns
on and current flows to terminal © - R411 — PQ5 — R414 — power module's BU~ terminals ~ Ew~
terminals -> D412 — D411 — terminal @ 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 @ @
@8 of the micro computer in the same way as in the upper arm drive circuit and are input to pins @ of
photocouplers PQ5-PQ7..
@
No chopper signal is input to the lower arm drive circuit.
Power module
Bu-
U" phase
I
V' phase
Fig. 7-5
@
When pin @ of the micro computer goeé "LO" - "HI", a photocoupler between PQ5 pins @ and @ turn
off and reverse bias current flows to C411 -> power module's Ew terminals — Bu- terminals ~ R414 —
PQS 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.
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