Samsung DVD-P380, Service Manual, Page: 71 / 82

Schematic Diagrams
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7-2 Power
7-2-1 About S.M.P.S (Ringing Choke Converter Method)
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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
7-2-2 Circuit description [FLY-Back RCC(Ringing Choke Converter)] Control
(a) AC Power Rectification/Smoothing Terminal
1) PDS01, PDS02, PDS03, PDS04 : Convert AC power to DC(Full wave rectification).
2) PEF10 : Smooth the voltage converted to DC.
3) PCD01, PCD02, PBS01 : Noise removal at power input/output.
4) PVA1 : SMPS protection at power surge input.
Fig. 7-1
Fig. 7-2
(b) SNUBBER Circuit :
PDS11, PCD12, PRS13, PCD11, PPS12
1) Prevent residual high voltage at the terminals of
switch during switch off/Suppress noise.
High inverted power occurs at switch (PQR11) off,
because of the 1st winding of transformer :
(V=-L1 xdi/dt. L1 : Leakage Induction)
A very high residual voltage exist on both terminals
of PICF1 4, 5~8pin because dt is a very short.
2) SNUBBER circuit protects PQR11 from damage
through leakage voltage suppression by RC,
(Charges the leakage voltage to PDS11, PER13,
PCD12 and discharges to PRS11, PRS12).
(c) Driving circuit
When Vin supplied, driving current Ig occurs throuhg the PICF1. By this I1 (=Hfe x Ig)
occurs throug the PICF1 and the Vb is inducted to base winding coil NB.
By inducted Vb, Ib start flow and the VCC voltage of PQR11 is sustained stable.
Ib is constant and I1 increases in Proportion to time. After constant time passed Ib
become to shortage and PICF1 is cut OFF (S/W OFF).