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The starting sequence is described below.
2.
3.
4.
5.
6.
7.
8.
When the printer power is turned on, DC input voltage V
IN
is input to this circuit.
Drive current Is flows to the base of switching transistor
via starting resistor R4, and
turns
on.
At the same time as step 2, V
IN
is
applied to coil T1
at the primary side of pulse transformer
Tl, voltage VIA is induced in coil T1
of
at the primary side, and positive bias current flows.
Therefore,
turns on quickly.
Since the
of current is constant as shown in the expression below, current applied to
T1
increases continuously in proportion to time.
+
R5 + R2
+
where,
Voltage drop across D2
Voltage drop between the base and emitter of Q 1
At this time, voltages
V1O+12, and V1O-12 are induced in coils
3-4, and
at the
secondary side. Since the current flows in the reverse direction to diodes
and D9, no voltage
is output to the circuits at the secondary side.
increases as time passes. When
x = however,
saturates, so that the value of is limited.
Therefore, voltage V across coil T110.E drops. At the same time, a reverse voltage is applied to
coil
7-6, the value of lowers, and current flows in the reverse direction via R 1 and D 1. Since the
potential at point
becomes higher than that at point@, speed-up capacitor C 11 absorbs current
which flows from point
to
Therefore, Q turns off quickly.
When Q 1 turns off, the energy induced in coils
3.5,
3-4,
and
at the secondary side in step
4 is released in the reverse direction and the forward current flows to diodes
and D9 at the
secondary side. In this way, voltage is applied to the secondary side of the circuit.
The energy being released decreases linearly with time. When the energy release is completed, the
voltage at each coil of
reaches zero momentarily, but switching current flows in the forward
direction again due to R5, and
switches on again. The potential at point@ becomes higher than
that at point
and the energy accumulated in C 11 is released to keep flowing to
The operating sequence then returns to step 3. The circuit continues switching by repeating this
sequence.
The above described sequence is generally known as a self-excited ringing choke converter (R. C. C.)
system.
When
turns off in step 5, reverse voltage is induced at point
momentarily, but D4, R7, and C 13
(snubber circuit) act as a limiter.
2-29
Содержание LQ-2550
Страница 1: ...L Q 2 5 5 0 TECHNICAL MANUAL EPSON ...
Страница 215: ...REV A EEEl n R O M A B O A R D m CJ P R I N T E R MECHAN SM Figure 5 2 Extension Cable Connections 5 3 ...
Страница 240: ...REV A P r cl Figure 6 3 LQ 2550 Lubrication and Adhesive Application Points Diagram 2 6 3 ...
Страница 241: ...REV A 7 i_ Figure 6 4 LQ 2550 Lubrication and Adhesive Application Points Diagram 3 6 4 ...
Страница 252: ...REV A I 1 I 7 v m o m x b Figure A 6 PPD781OHG Block Diagram A 7 ...
Страница 294: ...REV A I A 3 D r a w i n g s UNIT Y4S620200000 FI 6 3A 2SV rJl 1 T T 1 T I n b 0 e l ml Component Layout A 49 ...
Страница 296: ...REV A A h 0s am 1 I I I I 1 I I 1 1 It m I I r u n 1 1 5 Q Lo O 6xm Figure A 49 ROPS Board A 5 1 Circuit Diagram ...
Страница 297: ...REV A 1 L I Irl N I i t 1 I I x Figure A 50 ROPSE Board Circuit Diagram A 52 ...
Страница 301: ...Figure A 57 Model 5560 Exploded Diagram 2 2 Figure A 58 Model 5560 Push Tractor Unit Exploded Diagram REV A A 59 ...