Operation Of Power Supply (Aps-M550) - Toshiba TDP-TW300U Service Manual

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Operation of Power Supply (APS-M550)

The APS-M550 power supply circuit is shown as below. (Fig.1)
Input
AC Input
Line Filter
1)
Input Line Filter
A switching power supply generates a lot of electromagnetic noise. The function of the AC line filter,
which is made up of capacitors (e.g. C103) and inductor choke (e.g. L101), is to attenuate these noise
so that other equipments may not be affected.
SW101 which on/off Input lines, and the surge absorber Z101 which absorbs high voltage surge from
the input lines. These are mounted on the input filter.
Notes:
a) The fuse (F101) becomes open in order to protect other parts, when excessive current flows at
abnormal conditions.
b) CN101 is connected thermo. sensing element (e.g. Thermal protector).
Power Supply is operated by CN101 shorted condition.
2)
Power Factor Control Circuit
This circuit has 4 functions as below.
A) To generate stable voltage
B) To reduce input harmonic currents
C) Over current protection
D) Over voltage protection
E) (Inrush current suppression circuit)
A) Generate stable voltage
This circuit operates as step up to 370Vdc (type) and voltage control.
Actually, Q102 ,Q103 and Q104 are switched by MC101.
Initial voltage setting of 370V output (between pin 1 and pin 3 of CN102) has set at 370V (type.) by
VR101. (Input voltage : 85 Vac , max. load)
(Inrush current
DC/DC
suppression circuit)
Switching
Power Factor
Converter
Control Circuit
Lamp Output
Fig. 1
6-25
Secondary
Rectifier
Circuit
Time Sharing
Feedback
Multi-output
Control
Control circuit
Chapter 6
Output
15V
12 V
6.5 V
0 V
3.4 V
0 V

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