—
28
—
2. Applicable range of input power is 90~220 V ac.
7.5.2 Overview of operation principle of the “green” power supply (refer to fig. 2)
·
The operation principle of this power supply is same as general switching power supply. The
output voltage is controlled through controlling of the conduction period and duty cycle of switching
transistor. Only some new type elements such as controlled thyristorV642 MCR22-6 / Programmable
zenan Diode V640 TL431LP are used in this power supply, besides MC44608 mentioned above.
·
Programmable voltage-regulator TL431LP
Stabilized output voltage V
KA
= - [V
ref
(1+R1/R2)+I
ref
×
R1]
The stabilized voltage is inverse proportion with sampled voltage.
·
Stabilized process (B increasing)
+B
↑→
V640/V
ref
↑→
V
KA
↓→
Current of diode of photo-coupler
↑→
Current of transistor of
photo-coupler
↑→
Voltage of N601/3
↑→
Conduction period of switching transistor of
switching type power supply
↓→
+B
↓
·
STANDBY and normal operation
Normal operation:
CPU N101/42 at high level
→
V604 saturated conduction
→
Thyristor V642G at low level
→
V642 cut-off
→
Power of photo-coupler N604/1 supplied by V614.
STANDBY operation:
CPU N101/42 at low level
→
V642 cut-off
→
Thyristor V642G at high level
→
V642
conducted
→
Power of photo-coupler N604/1 supplied by V642
→
Current of N604 increased
largely
→
+B decreased to 17 V.
Cathode
(K)
Reference
(R)
Anode
(A)
input V
KA
V
ref
I
ref
I
K
R
1
R
2
Summary of Contents for 2168
Page 1: ...ATEC PANDA Type 2188 Type 2168 54 cm Color TV Set Service Manual ...
Page 35: ... 34 10 Waveform Diagrams at Each Point ...
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