Samsung DVD-P355B/XET, DVD-P355B/XEU, DVD-P355B/XEH, DVD-P355B/XEG d Feedback Control Circuit

Circuit Operating Descriptions

13-1-2 (d) Feedback Control Circuit

PTDI

PDS34

NP

Ig

Ns

I2

Vout

+

Vin	Ig	R		Snubber
		R	D
		+	Ib
		C		VB	VB

VCC		Drain
Softs
POWER-CTL
C	Mos-Fet	R
		FB
GND
		Icease
		R
		C

PICF1

VsPES34

GND

A

K

Fig.13-9

◆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 13-5