Epson LX-86TM Especificações descarregar pdf (Página 39)

REV.-A

2.3.2.2 +24 V Supply Circuit

The +24 V supply circuit is a chopper type switching regulator circuit. Figure 2-8 shows the block

diagram of the +24 V supply circuit based on Figure 2-6.

Q25

125V

R67

o.47/3w

LP401 -02SD

3.1

C3747

+24VDC

DB1

R50

D3SB1

2 4/0 5

R49

AC1

C22

330

6800

/-f

C26

50V

R47

2200jL\35V

(3A)

3.3K

AC1

494

ZBF503

R46

-01 TA

330

OGP

—

Fig. 2-8. +24 V Supply Circuit

AC 1

input from the ROC filter unit is full-wave rectified by DB 1 and is smoothed by C22. The voltage

across

C22 becomes 32.3 VDC. Transistors Q23, Q24, and

Q25,

which are used as Darlington

amplifiers, D7, L2 and

C26 in Figure 2-8 are equivalent to switching transistor St, flywheel diode D,

choke coil L, and smoothing capacitor C in Figure 2-6. Switching is controlled by the 494

(IC3A),

and

pin 9 of the 494 is the emitter of the internal switching transistor. Therefore, switching is performed

as follows:

494 internal transistor: ON

Q23: ON

Q24: ON

Q25: ON

494 internal transistor: OFF

Q23: OFF

Q24: OFF

Q25: OFF

Figure 2-9 shows a block diagram of

494.

+323V

~. ---,

+24VDC

1/6w

GND

?!”5

Oscdat.r

W,v.-fonll

Ptn9

1,,

”s!s,.,

W... -from

1,11

Q25

Ern,tw

W.v.-fom

(

[

(

[

( (

Fig. 2-9.

IC494

Block Diagram and Switching Wava-form

2-7

1 2 ... 34 35 36 37 38 39 40 41 42 43 44 ... 141 142

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