Sony KV-E29MF1 color TV switching power supply working principle - Power Circuit - Circuit Diagram

MOS power IC full range

inductance

SMD aluminum electrolytic capacitor

First, a brief description of the working principle

In the figure, IC2601 (STR-81145A) is an automatic voltage switching IC. The automatic switch consists of two-way thyristor between the 2nd and 3rd legs. The on/off determines the sampling voltage between 2 and 5 feet. When the B point of the mains is positive and the point A is negative, the half-wave rectification is performed by B→R2613→C2612→D2601→A, so the sampling voltage is formed at both ends of C2612. When the sampling voltage is less than 159V (corresponding to the mains input voltage is less than 145V), the IC26012 and 3 pins are turned on, and the rectifier circuit becomes the voltage doubler rectification mode: when the mains point A is positive and the B point is negative, the current path is sufficient: A→D2600A→C2617→IC26013 foot→2 feet→B, so DC voltage will be formed at both ends of C2617; when the power supply B point is positive and A point is negative, the current channel is full: B→IC26012 foot→3 feet →C2616→ground→D2603→A.

Obviously, in one cycle, the output voltage after rectification of the power supply is C2617, and the voltage across C2616 is superimposed in series, that is, the so-called double voltage output, but the total voltage does not exceed 300V.

When the IC26012 and 5 pin voltages are greater than 159V (corresponding to the mains input voltage is greater than 145V), the IC2601 internal detection circuit detects the disconnection between pins 3 and 2, and the mains is full-wave rectified by the bridge rectifier circuit composed of D2600A to D2600D. The positive electrode of the filter capacitor C2617 and the negative terminal of the C2616 get about 300V DC voltage (the filter capacitor is equivalent to the equivalent capacitance of the two capacitors in series, the capacity is 500μF).

In addition, the switching power supply has a distinctive delay degaussing control circuit. The principle is: when booting, CPU (CXP85224A-006S or CXP80424A) 24 pin output degaussing high level, through R026, CN1178 end, CN05243 end, control triode Q2600 b pole, and make it conductive, in the foot relay RY2600 work coil The electric, normally open contact is closed, and the 220V voltage is connected to the degaussing coil through the degaussing resistor THP2600 to degauss the picture tube. After a delay of about 3 seconds, the CPU 24 pin outputs a low level, the Q2600 is turned off, and the degaussing ends. This avoids long-term energization of the degaussing resistor, which saves power and extends the life of the degaussing resistor.