Switching Regulator Circuit; Activation; Voltage Regulator Circuit - Epson LQ-1050 Technical Manual

REV.-A
2.2.5 +5

Switching Regulator Circuit

Figure 2-17 shows the +5
regulator STR20005
capacitor at the external output section.
L _

2.2.5.1 Activation

When the +35
the positive terminal of comparator
at this time, the
collector, and the + 5 V line turns on.

2.2.5.2 Voltage Regulator Circuit

Resistors R4 and R5 in
circuit and prevent noise and abnormal oscillation. The output voltage is fed back from 2 pin of
and is delivered to R4 and R5 and then input to the negative side of
The voltage input to the negative side regulates the output voltage by controlling the on-time of
It is compared with the reference voltage, and if it is larger than +5 V, it switches on the
so as to turn on
Figure 2-18 shows the
switching regulator. This circuit employs a hybrid type switching
which consists of a voltage
S T R 2 0 0 0 5
R 2
-
- <
I "
CIRCUIT
I
I
I
L
Fig. 2-17. +5
rises, the start circuit of
output goes high, Tr 1 is turned on so that current flows from the emitter to the
regulate the +5 V output voltage.
This operation is called Pulse Width Modulation
sequence.
(xc 20)
I
-
- 1
R3
R 4
Y
I
– Reference - ,
C
R5
Voltage
I
Switching Regulator Circuit
is activated, and a reference voltage is applied to
in Since the negative side of
2-18
circuit along with coil
3
, . 2
/
( I 'C25
23
B20
and compose a differentiation
control.
and
+5 v
still remains at O V
output