Hitachi DV-P303U, Service Manual

Page: 51 / 106

Circuit Descriptions
6-2
•
Advantages and disadvantages of linear power supply
1) Advantages : Little noise because the output
waveform of transformer is sine wave.
2) Disadvantages :
1
Additional margin is required because Vs is chan-
ged (depending on power source). (The regulator
loss is caused by margin design).
2
Greater core size and condensor capacity are ne-
eded, because the transformer works on a single
power frequency.
6-1-1 (b) S.M.P.S. (Pulse width modulation method)
v
Vreg
Vout
0
t
Change by common power
Regulator loss
Fig. 6-5
•
Terms
1) 1st : Common power input to 1st winding.
2) 2nd : Circuit followings output winding of transformer.
3) f (Frequency) : Switching frequency (T : Switching cycle)
4) Duty : (Ton/T) x 100
Transformer
Vout
(Np)
(Vp)
Switch
Vs switch
I switch
Vin
ON/OFF Control
+
–
+
–
+
+
+
–
(Vs)
(Ns)
REGULATOR
Fig. 6-6