Technology of Q 2500 colour TV set

Technology of Q 2500 colour TV setOn the secondary side, BUZ 71 A V-MOStransistors are used to stabilise U3.3, U5 andU12 in order to keep power dissipation to aminimum.The converter transformer, which also providesthe standard VDE power distribution,has a primary working winding and a secondarywinding to supply voltage to the IC and togenerate a control voltage.Secondary windings also generate the followingvoltages:UBto supply the line output stageU 25 to supply the line driver stage2.2.1 Primary sideThe mains voltage flows through the mainspower switch, the working contact of thestandby relay and the mains RFI suppressionfilter to the degaussing coil, and via the startupcurrent limiter R 613 to the bridge rectifierD613.A voltage of approx. 310 V very rapidly buildsup at charging capacitor C 620. This is appliedto the drain terminal on the switching transistorvia the working winding in the convertertransformer.Since the gate BUZ 91 is not driven at thistime, there is no load on the operating voltage.U 3.3, U 5 and U 12predominantly to supply an operatingvoltage to the digital controlU9U8for the interface switching ICsfor the video ICsUNF+ and UNFusedto supply a floating voltage to theVF output stages, approx. + 18 VDocument Q 2500 14 © Loewe ProCollege