2.2.2 Power Supply Circuit Operation
The power supply circuit is composed of an RCC (ringing choke converter) system and the power switch
circuit in the secondary circuitry. The power supply circuit has several protection and control circuits. This
section describes these circuits.
1. Power Switch Circuit
The power switch circuit is in the secondary circuitry. It is shown in the illustration below.
When printer power is off, the PSC line is connected to a ground line and the current is loaded from
C55 to PC1. Consequently, Q32 and Q31 are turned on, and the switching FET is shut off.
(2) +35 V/+5 VDC Line Over Voltage Protection Circuit
This circuit is shown below.
The +35 VDC over voltage protection circuit operates when voltage exceeds 42.42 V between ZD52 and
ZD87 and shuts off the switching FET (Q1: K1692 or K1531). The +5 VDC over voltage protection circuit
operates when voltage exceeds 7.5 V between ZD53, and shuts off the switching FET (Q1: K1692 or
K1531). When either of these protection circuits operate, the protection cannot be removed without turning
power off and on again.
D 8 5
D 8 4
R 6 8
R 6 9
3
4
6
5
Q 3 1
Ope r a ti o n SW
(Power SW )
PSC line
O F F
+35 V Li n e
C 5 5
R 9 1
D 5 2
8
7
P C 1
Figure 2-23 Power Switch Circuit
ZD52
ZD87
+35V Line
R90
C82
Q81
Q55
D82
R89
ZD86
ZD53
+5V Line
GND
Q31
FET
PC1
3
4
6
5
Figure 2-24 Over Voltage Protection Circuit
Operating Principles
LQ-2170 Service Manual
2-18
Rev.A
Содержание LQ-2170
Страница 1: ...EPSON TERMINAL PRINTER LQ 2170 SERVICE MANUAL EPSON 4005735 ...
Страница 5: ...REVISION SHEET Revision Issued Date Revision Page Rev A December 5 1995 1st issued ...
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Страница 159: ...Figure A 3 C165 PSB Board Assembly Circuit Diagram LQ 2170 Service Manual Appendix Rev A A 13 ...
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