Samsung DVD-P360/CDM Service Manual page 84

13-1-2 (d) Feedback Control Circuit

Vin

Softs

C

◆ Operation descriptions

1) Internal OP-Amp '+' base potential of PICS2 is 2.5V and external "-" input potential is connected with PRS33

and PRS34 to maintain Vout of 4.4V.

2) If load of 4.4V terminal increase (or AC inout voltage decrease) and Vout decrease over 4.4V,

Then : PICS2 "R" potential decrease over 2.5V --> PICS2 A-K BASE Current decrease --> PICS2 A-K Current

decrease --> PICS1 DIODE Current decrease --> PICS1 C-E Current decrease --> PICS1 C-E Voltage increase -->

PICS1 F-B Voltage increase --> OUT DUTY increase TRANS Primary Cuttent Increase --> TRANS Primary

Power increase --> Vout increase --> Vout maintain 4.4V

- PRD31, PRD32 : Reduce 4.4V overshoot.

- PRS32, PCS32 : Prevent PICS2 oscillation (for phase correction).

Samsung Electronics

Snubber

Ig

R

D

R

+

Ib

C

VCC

POWER-CTL

Mos-Fet

GND

PICF1

PTDI

NP

Ig

VB

VB

Drain

R

FB

Icease

R

C

A

K

Fig.13-9

Circuit Operating Descriptions

PDS34

Ns

+

I2

PES34

Vs

Vout

GND

13-5