Philips 27PS60S321 manual Abbreviation list, AbbreviationDescription

SPMS Page 27 of 32

Protection Events

Several protection events are controlled bythe UOC:

zBC protection , to protect thepicture tube from a too high beam current. The UOC has the capabilityof measuring the normal back level current during the vertical flyback.So if for some reason the CRT circuit is malfunctioning (i.e. highbeam current), the normal black current will be out of the 75 μArange, and the UOC will trigger the power supply to shut down. However,this is a high beam-current situation, the TV screen will be brightwhite before the set is shut down.

zE/Wprotection , two protection mechanisms are built in, over-currentand over-voltage.

„In case ofover-current due to defective parts in the line deflection outputstage, a high current will flow through resistors 3405//3406.If this current is large enough to create a voltage drop of 0.7V across 3405//3406, transistor Q7606 (in A7 diagram) will conduct and pin 80 of the UOC will be pulled down. Thereafter,the UOC will shut down the power supply. In case of further currentincrease, the fused resistor 3411 is built-in for double protection.

„In case of a high voltage appearing across capacitor 2401(dependent of the tube size), which is high enough to trigger zenerdiode 6401 into conduction, transistor Q7606 (in A7 diagram) willconduct and UOC is triggered to shut down the power supply.

zI 2 C protection , to check whetherall I 2 C IC"sare functioning.

In case one of these protections is activated, the setwill go into ‘standby’.

The ‘on’ and ‘standby’ LEDsare controlled via the UOC.

Abbreviation list

AbbreviationDescription

2CS

ACI

2 Carrier (or Channel) Stereo

Automatic Channel Installation: algorithm that installsTV sets directly from cable network by means of a predefined TXTpage

ADC	Analogue to Digital Converter
AFC	Automatic Frequency Control: control signal used totune to
	the correct frequency
AFT	Automatic Fine Tuning
AGC	Automatic Gain Control: algorithm that controls thevideo

7/8/2004