Input Circuits; Logic Power Source Circuit; Power Source Specifications - Epson TM-U675 Service Manual

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Input Circuits

Logic Power Source Circuit

The logic power source circuit generates the power for this printer. The CPU, GA, and most
other circuits do not operate if voltage is not output by the logic power source circuit. The
power source circuit has an input of 24V, and uses a dedicated DC/DC converter IC (U11:
PQ1CZ1) to output 5V
24VB
Table D-13 Power source specifications
Item
Output Voltage (V)
Output Current (A)
Input Voltage (V)
Over-Current
Protection (A)
Over-Voltage
Protection (V)
The output voltage is determined by the potential division of R82 and R85. In other words, the
circuit operates so that the crossover voltage of R82 and R85 is 1.26 V.
The input voltage of 24V for the power supply circuit is supplied to U11 through the R2 fuse
resistor (KOA RF73B2HTE0.51). R3 may burn out in the event of a malfunction in the U11 area.
R3 will also burn out in the event of excessive VCC voltage (approx. 7.5 V or more). This fuse
resistor cannot be replaced. Therefore, the circuit cannot be repaired by replacing the R3 in the
event it has burned out due to a circuit malfunction.
Appendix D-66 Product Overview
±
4%.
C38
C37
R3
CY1
C155
Min. Typ.
4.85 5.04
- -
21.6 24
1.55 2
7.5
L2
D13
U11
1 R82
VIN
2
VOUT
6
3
COM G
4
ADJ
5
ON/OFF
PQ1CZ1
R253
Figure D-63
Max. Remarks
5.24
1.0
26.4
2.6 L2, D13, C35 not provided. The peak current
is detected, and detected voltage is
lowered. Automatic reset.
CY1 goes On after detection, and R3 burns
out. Does not reset.
AVCC
VCC
L1
ZD3
C35
R85
Rev.D