Epson LQ-2550, Technical Manual

Page: 82 / 301

REV.-A
Figure 2-28 shows the +35 V supply circuit.
Current flowing in the direction shown by@ is applied to choke coil L4 and smoothing capacitors
and via D 10-1, and then output.
If the output voltage from the secondary side reaches the limit of the current limiting or voltage regulator
circuits in the latter stage of this circuit, transistors TR 1 and of turn off so that no current
flows to coil therefore stops flowing to coil (Refer to Figure 2-27.), VG becomes O V, and
turns off. No current
flows to coil and
the energy accumulated in choke coil L4 is output
rectified by D 10-2, smoothed by C31, and and output.
When the current drops below the limit of the current limiting or voltage regulator circuits (after Q3
has turned off), and turn on again, and this sequence is repeated. Figure 2-29 shows the
waveforms at various points in main switching circuit 2.
In this way, the voltage output from this circuit is kept constant by controlling the ON/OFF time of
which is the different method employed in main switching circuit 1.
See Figure
10
12
0
2-30,
D
10-1
T3
- - - - - - - -
1
L4
7
2 . 5 A
( O - 5 A )
#
D1O-2
,
1
I
10
. 5
R42 G
H
1
‘. - - - - - - - -
- -
—
Figure 2-28. +35 V Supply Circuit
2. T2 5-8
of T2 Current O
of T 3 C u r r e n t
6.
Choke
coil L4 Current
8. Output current
1035
Figure 2-29. Main Switching Circuit 2 Waveforms
2-35