Epson LQ-510 - Page 67

REV.-A
PRINCIPLES OF OPERATION
2.2.7 VOLTAGE LIMITING CIRCUIT
Figure 2-32 shows the voltage limiting circuit. In this circuit, switching transistor Q1 goes off if the voltage
on the + 24 V line reaches about + 30 V, or if the voltage on ‘the + 5 V line reaches about + 6 V. Zener
diode ZD22 is used to detect abnormal voltage on the + 24 V line; Zener diode ZD21 is used on the + 5 V line.
- +24VDC
line
a
L ----- --__I
1
PC1
(120 V Version)
Figure 2-32. Voltage Limiting Circuit
LQ-510
2-25