PC928
Fig. 24 Overcurrent Detecting Voltage
vs. Supply Voltage
25
Overcurrent Detecting Voltage -
Supply Voltage Characteristics Test Circuit
Anode
V
CC
Overcurrent detecting voltage V
CTH
(V)
Cathode
O
2
R
G
10
0.5k
Ω
1k
Ω
V
C
R
C
V
O2
5
1.5k
Ω
0
15
18
21
24
27
30
C
P
FS
GND
C
G
V
V
C
Supply voltage V
cc
(V)
Application Circuit (IGBT Drive for Inverter)
Anode
Anode
Cathode
O
1
+
R
G
R
C
C
FS
GND
+
V
CC2
=
12V
CP
V
CC1
=
12V
IGBT
(
+
)
V
CC
PC928
TTL, microcomputer, etc.
U
V
W
(
-
)
Feedback to primary side
s
Operations of Shortcircuit Protector Circuit
PC928
14 GND
V
13
CC
O
1
12
11
O
2
R
G
R
C
9
8
10
C
FS
GND
V
EE
Feedback to primary side
C
P
IGBT
V
CC
Anode
Light emitting diode
1
3
Anode
2
Cathode
TTL, microcomputer, etc.
Photodiode
Constant voltage circuit
Amp.
Interface
IGBT protector circuit
1. Detection of increase in V
CE(sat)
of IGBT due to overcurrent by means of C-terminal (
9
terminal)
2. Reduction of the IGBT gate voltage, and suppression of the collector current
3. Simultaneous issue of signals to indicate the shortcircuit condition (FS signal) from FS terminal to the microcomputer
In the case of instantaneous shortcircuit, run continues.
4. Judgement and processing by the microcomputer
At fault, input to the photocoupler is cut off, and IGBT is turned OFF.
Power supply
O
2
Added resistance
Ta = 25˚C
I
F
= 10mA
V
CC
= 24V
20 R
G
= 47Ω
C
G
= 3 000pF
R
C
= 1k
Ω
FS = OPEN
15 C = 1 000pF
P
Added resistance=0
Ω
I
F
O
1
V
CC
PC928
SHARP [ SHARP ELECTRIONIC COMPONENTS ]
