Epson LQ-2550 Technical Manual page 81

2.2.6 Main Switching Circuit 2 (+35 V Supply Circuit)
Figure 2-27
shows main switching circuit 2.
2
Main switching circuit
turns on after
mainly by regulator IC TL594 (IC2) at the secondary side. The circuit configuration of main switching
circuit 2 is a general forward converter system, which is a separately-excited system. This circuit is
turned on after the + 5 V line turns on, -+ 12 V is applied to pin 12 of IC2,
One end of coil T2s-z is connected to the + 5 V line and the other end is connected to the collectors
(pin 8 pin 1 1) of the output transistors TR1 and TR2 of IC2 (Refer to
started switching when it received the + 12 V, transistors TR 1 and TR2 are on. Therefore, current flows
through coil T2s-z of T2 in the direction shown by Q. Gate current IG, then flows through coil T2s.e in
the direction shown by @, potential VG is generated across R 10, and Q3 turns on. Input voltage V3iN
is applied to coil T3 10.12 on the primary side of T3 and voltage
side.
the + 5 V line is turned on. The +35 V supPly circuit is controlled
9
D5
10
R6
I —
IL2
12
D
Figure 2-27. Main Switching Circuit 2
T 3
T2
I
(Refer to Figure 2-30.)
induced in coil T3z.s on the secondary
2 - 3 4
and
Figure 2-30.). Since
. ;,&,