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Reset voitage
Chopper signal
DC current
12v (SC
sReset circuit
"Reset signal
@
Peak current cut off
a>
Trp signal synthesis
ae
circuit
circuit
J
Chopper signal
5
a
E
8
DC260V
Ip signal
§
Power
-360V
E
module
g
|
(e)
Compressor]
motor
Photocoupler
ce
Drive
signal
OC current level
Voltage amp. creut,
{7
DC current
'
Detection
Oise" _|
RSO3
Fig.8-2
@
The following describes the operations of each circuit in detail.
(1) Peak current cut off circuit
Fig. 8-3 shows the peak current cut off circuit and the waveforms at each section.
8L-HIC
OC current Id
28A
¢
'
1
Voltage at point @)|
'
1
'
1.4V-
Power Module
drive circult
Micro computer
1
Voltage at pin
I
ist
@ !
resaior
Voltage at point ©}
1
Hi
Fig.8-3 Peak Current Cut off Circuit and Waveforms at Each Section
@
The Ip cut off circuit detects an instantaneous high-level current and stops the inverter to protect
components including the power module.
e@
Ifa current exceeding 28A flows as shown in the diagram, the voltage at point © detected by the
detecation resistor is input to the positive @ terminal of COM (2), and when it exceeds the voltage at the
negative © terminal which is the set value, the output pin voltage (at point ®) of COM (2) goes "LO" >
HI". This turns. Q303 on and stops the power module circuit via D4 and D2; also the voltage at point ©
goes "Hi" -> "LO" and the Ip signal is supplied to pin @ of the micro computer which stops the inverter.
@
On the other hand, since the voltage at the positive @ terminal is pulled up by R318, it is higher than
the voltage at the negative © terminal even after the DC current becomes OA and the voltage at point @
returns to OV, therefore the output is temporarily kept at "Hi" (memory function).
@
The micro computer sets pin @9 from "Hi" to "Lo" after the drive signal stops to release the memory
function of COM (2) and return it to the initial state.
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