Epson LX-850 Specifications download pdf (Page 51)

REV.-A

Feedback Circuit

A voltage switching circuit is formed by RI 1, R 12, and

R16,

and the potential of the

+24V

output

voltage is fed back to

PPC494C.

The line between R 12 and R 16 feeds back to the positive terminal of EA 1 in the

PPC494C,

where it

is compared against the standard + 5V voltage. The electric potential of the feedback line becomes

the same as the standard potential at

24.3V,

as shown by the equation below. If the voltage exceeds

24.3V,

the EA1 output goes HIGH, the

(3N

time of the switching pulse drops, the switching duty is

lowered, and, as a result, the

+24V

potential drops. This action is repeated in order to maintain a stable

voltage of

+24V.

5V X (Rl 1+R12+R16)

(RI 1 +

R12)

+24V

line

Vref(+

5V)

RI 6

1 9.6K

R12

4.75 K

RI 1

316

Figure 2-17. Voltage Feedback Circuit

2-15

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Epson LX-850 Specifications Page 51