Microcomputer
STANDBY output
RESET
6. Peripheral circuits of microcomputer
Fig. 6-1 shows the microcomputer and its peripheral circuits, Table 6-1 shows the basic operation of
each circuit block, and Fig. 6-2 shows the system configuration.
IPM (Intelligent Power Module)
Detection resistor
DC current
DC voltage
Fig. 6-1 Peripheral circuits of microcomputer
Table 6-1
Circuit block
Peak current cutoff circuit
Detects DC current flowing into power module and, when over-current
(instantaneous value) flows, stops lower arm drive circuit and creates
Ip signal to stop microcomputer at the same time.
Overload control circuit
Protects compressor by judging overload status based on input current,
DC current and DC voltage.
Reset circuit
Creates reset voltage.
Basic operation
◯
◯
◯
◯
◯
◯
◯
◯
◯
◯
◯
5V, 12V
◯
◯
◯
◯
◯
◯
〜
approx.
DC 235 V
Reset circuit
Dividing resistor
Current amplifier
circuit
Detailed description for the operation of each circuit is given here.
DC voltage
Chopper
signal
Ip signal
Drive circuit
Drive signal
DC current
DC current
Detection
resistor
Fig. 6-2
Fig. 6-3
DC current
Detection resistor
Compressor
motor
Inverter section
Peak current
cutoff circuit
Input current
DC current
Outdoor microcomputer
Reset voltage
Current
transformer
DC current Id
25A
0.6V
R
2
41
R
9
0
5
0V
0V
0V
11
5
5
C
21
0
0V
F
0
I
P
A
B
IPM
5V
R906
C
91
9
R001
2
2
2
26
6
6
6
2
2
2
24
4
4
4
1111
2
2
2
N
Rectifier circuit
6-1. Peak current cutoff circuit
Fig. 6-3 shows the peak current cutoff circuit and waveforms at each section.
Voltage at point
Voltage at point
(Main P.W.B.)
HIC
Outdoor
microcomputer
Ip cut circuit detects instantaneous large current and operates to protect various parts, such as IPM,
by stopping inverter.
When current exceeding 25A flows as shown in the diagram, voltage at point
◯
◯
, detected by
detection resistor, is divided by R906 and R905, and then input to IPM pin
◯
◯
.
◯
◯
Since this exceeds
threshold value, IMP pin
◯
◯
is set to Lo (voltage at point
◯
◯
). When Lo signal is input to pin
◯
◯
of
microcomputer, microcomputer will stop drive output, and self-diagnosis lamp will enter a 2-time
blinking mode. When peak current is detected, IPM holds lower arm output off status for a fixed
period (approx. 4 msec.), and then enters drive signal standby mode. Microcomputer outputs drive
signal 3 minutes later to restart operation.
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