Circuit Operating Descriptions
13-2
Samsung Electronics
◆
Advantages and disadvantages of linear power supply
1) Advantages : Little noise because the output waveform
of transformer is sine wave.
2) Disadvantages :
Œ
Additional margin is required because Vs is chan-
ged (depending on power source). (The regulator
loss is caused by margin design).
´
Greater core size and condensor capacity are ne-
eded, because the transformer works on a single
power frequency.
13-1-1 (b) S.M.P.S. (Pulse Width Modulation)
v
Vreg
Vout
0
t
Change by common power
Regulator loss
Fig. 13-5
◆
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
Vin
(Np)
(Vp)
PICF1
CTL IC
Vin
PWM CTL + MOS Fet
+
—
+
—
—
+
+
(Vs)
(Ns)
REGULATOR
Vout
+
Fig. 13-6
