Epson LX-86TM Especificações descarregar pdf (Página 40)

REV.-A

When the printer power is turned on, ZD1 on the +20 VDC line turns on,

Q22

turns on, and Vcc is

applied to

494. Then the oscillator

(OSC)

starts generating an approximately 20 kHz sawtooth

waveform, which is regulated by R40 and C20, and the reference voltage generator outputs the +5

VDC & 10% reference voltage. Internal switching transistor Tr is switched on and off using the output

from error amplifiers 1 and 2.

EA1

and

EA2

limit voltage and current, respectively.

EA1

compares the

voltage obtained by dividing the +24 V applied to pin 1 by R22 and R21

(approx.

4.9

with the + 5

V reference voltage applied to pin 2.

EA2

compares the voltage monitored by R66 with the voltage

obtained by dividing the +24 V applied to pin 16 by R21

(approx.

0.31 V). Therefore, the current is

limited to approximately 3.1 [amps].

2.3.2.3 +5 V Supply Circuit

The +5 V supply circuit is also a chopper type switching regulator, which is the same as the +24 V

supply circuit.

+24V

Q21

~P201

–2R5SD

C3746

470P

Q20

Al O

15(

RI 4

2K SRI

ERB81

R12

78L05A

–004

Vvv

0 –=

330

1 Ov

( )

R13

0.1--

ZBF503

-=01

GND

77)7-

Fig. 2-10. +5 V Supply Circuit

When +24 V is applied to this circuit, current flows via

R12 and

1, and operation of

SR1

is started.

SR1

includes a +5 V reference voltage generator and compares the voltage at terminal O (pin 2) with

the reference voltage. When this voltage is lower than the reference voltage,

1 turns terminal I (pin

1 ) on. If the voltage is higher than the reference voltage,

1 turns the terminal off. This controls the

switching transistors

Q20

and Q21, and the output voltage is kept constant. Actual output voltage is

5.024 V (calculated value) because the

GND

terminal (pin 3) of

1 is raised to 0.024 V using the divider

composed of R 14 and R 13.

2-8

1 2 ... 35 36 37 38 39 40 41 42 43 44 45 ... 141 142

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Epson LX-86TM Especificações Página 40

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