Samsung DVD-905, Service Manual

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Reference Information
2-2 Samsung Electronics
3 Advantages and disadvantages of linear power supply
a. Advantages :
Little noise because the output waveform of transformer is
sine wave.
b. Disadvantages :
È Additional margin is required because Vs is changed
(depending on power source). (The regulator loss is
caused by margin design).
È Greater core size and condensor capacity are needed,
because the transformer works on a single power
frequency.
Fig. 2-5
2-1-1 (B) SMPS(PULSE WIDTH MODULATION METHOD)
Fig. 2-6
3 Terms
- 1st : Common power input to 1st winding.
- 2d : Circuit followings output winding of transformer.
- f(Frequency) : Switching frequency(T : Switching cycle)
- Duty : (Ton/T) x 100
V
Vreg
Vout
0 t
Change by common power
Regulator loss
Transformer Vout
(Np)
(Vp)
Switch
Vs switch
I switch
Vin
ON/OFF Control
+
–
+
–
+
+
+
–
(Vs)
(Ns)
Regulator