
– 64 –
9. Trip Signal Synthesis Circuit
●
Fig. 9-1 shows the trip signal synthesis circuit.
This circuit uses the upper and lower arm transistor drive signals to modulate the chopper signal or stops
the drive signal, according to the presence or absence of the Ip cut signal and reset signal.
●
Table 9-1 shows the circuits to which the modulated signals are transferred.
For example, the chopper signal is transferred only to the upper arm transistor drive circuit, and the reset
signal is transferred to the microcomputer and upper and lower arm transistor drive circuits.
●
Pins
e i
of the micro computer change from "Lo" to "Hi" alternately and supply signals to PQ2-PQ7.
●
The chopper signal from the micro computer is inverted by Q307, and turns on or off PQ2-PQ4, to which
voltage is supplied, with high frequencies, to let current flow to them to transfer the upper arm drive signal.
●
When the reset voltage is "Lo", the current operating PQ5-P07 is stopped, and the lower arm transistor
drive signal is turned off.
●
The peak current cut off (Ip cut off) signal fixes the voltage at upper and lower arm drive circuits to "Lo"
via D301 and D304, and turns off the drive signal in the same way as when the reset signal is "Lo".
23
71
I
5
PQ2
24
6
PQ3
25
7
PQ4
Upper
arm
drive
26
8
PQ5
27
9
PQ6
0V
0V
0V
R7
28
10
11
12
PQ7
Lower
arm
drive
5V
D304
D301
D305
Q306
5V
Q307
Ip
Chopper
5V
0V
R315
Q304
5V
Reset circuit
Q1
8J-HIC
Fig. 9-1 Trip Signal Synthesis Circuit
Modulated signals
Circuit
Chopper signal
Start current limit signal
Peak current cut off signal
Reset signal
––––
––––
Microcomputer
Upper arm transistor
drive circuit
Lower arm transistor
drive circuit
––––
––––
Table 9-1 Circuits to which trip signals are transferred