AN1857 Freescale Semiconductor / Motorola, AN1857 Datasheet - Page 23

• Manufacturer Part Number: AN1857
• Description: A 3-Phase ac Induction Motor Control System Based on the MC68HC908MR32
• Manufacturer: Freescale Semiconductor / Motorola

dc Bus
Overcurrent
Detection
AN1857
MOTOROLA
CAUTION:
Excessive dc bus current can destroy the power transistors on the power
stage. Including overcurrent protection circuitry in a design is a wise
choice, if not an absolute necessity.
bus overcurrent detection circuit. The input signal to this circuit is a
0.075- resistor, placed in series with the dc bus and amplified by the
same type circuit as shown in
in
Whenever the overall bus current exceeds 2.82 amperes, the
IR2112S’s outputs are disabled.
Excessive dc bus current can destroy the power transistors on the power
stage.
Figure 14
Freescale Semiconductor, Inc.
For More Information On This Product,
I_sense_A2
I_sense_DCB
I_sense_A1
Figure 14. dc Bus Overcurrent Detection Circuit
+3.3V_A
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drives the shut down input to the IR2112S’s IGBT drivers.
100 nF
+3.3V_A
Figure 13. Bus Current Sensing Circuit
OVERCURRENT
THRESHOLD=
3.23 Vdc
1.2 k
GNDA
10.0 k
10.0 k
680 pF
220
+
3.3 F
GNDA
1.2 k
390
10 k
LM285M
Figure
GNDA
+15V_D
1.65 V
Figure 14
680 k
GND
+
-
13. The output of this circuit shown
LM393
100 k
75.0 k
33.2 k
is the schematic of the dc
75.0 k
-
+
MC33502D
Shut_Down_Open_C.
Application Note
Power Stage
I_sense_A
23