Filter
Top Products
5. +35 V Line Over Current Protection Circuit
The +35 V line over current control circuit is illustrated below.
When the +35 V line becomes less than 27 V, Q82 and Q54 turn on, and PC1 turns on. Consequently, Q32
and Q31 turn off, and then switching FET Q1 shuts off. When the protection circuit operates, this protection
can only be removed by turning the power off and on again.
6. +5 V Line Over Current Protect Circuit
+5 V line over current control circuit is shown below.
Port 2 of IC51 (TL494CN) monitors the +5 V line, and this protection circuit operates when the +5 V line
goes below 4.75 V. When this circuit operates, port 8 signal output of the PWM pulse stops, and Q51 stops its
switching operation. Consequently, the +5 V line stops generating.
+35V Line
GND
Q53
R70
R71
R72
R73
Q54
Q82
C57
R74
R75
R54
R68
3
4
6
5
D85
Q31
PSC
Figure 2-27 +35 V Line Over Current Protection Circuit
+5v Line
GND
R53
R88
R64
R65
-
+
-
+
R67
IC51
TL494CN
2
1
D51
L51
8
R51
+35V Line
R61
Q51
Figure 2-28 +5 V Line Over Current Protection Circuit
Operating Principles FX-2170 Service Manual
2-20 Rev.A