555 color TV switching power supply circuit

Published:2011/6/15 22:31:00 Author:TaoXi | Keyword: 555, color TV, switching, power supply | From:SeekIC

As the figure 14-12 shows, the color TV switching power supply uses the pulse width modulation mode, the pulse width adjustment range is wide, and the voltage stabilizing effect is good, when the input voltage is in the range of 12 to 280V, the output DC voltage is +110V+/-1V. The double-base port transistor relaxation oscillator is composed of the VT2 and R3, R5, C9, it is used as the time base pulse source, and it is amplified by the VT3 that can be used as the trigger pulse of IC1(555). The controllable monostable trigger circuit is composed of the 555 and the R8, C10. The temporary stability time depends not only on the R8 and the charging time constant of C10, but also the sampling voltage VCT. By changing the duty ratio of the 555's output pulse, you can change the voltage. The output square wave of 555 adds to the power amplifier tube VT1 to encourage the switching power supply of the collector load.



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