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长虹2939FD彩电开关电源采用TDA4605集成电路去控制开关调整管V840模式,如图1所示。 1.振荡电路:市电接通后,交流电正半周通过RT802、R802对C819充电,使TDA4605⑥脚(电源供电端)电压上升,当⑥脚电压上升到门限值(约12V)时,TDA4605开始工作并产生内部基准电压。同时,桥式整流输出的+300V电压经R812对C812充电,使②脚(高电平输入截止功能端)电压上升,使其内部的“启动脉冲发生器”产生启动脉冲,送到逻辑电路,由⑤脚输出激励脉冲,去控制开关管V840振荡工作。另
Changhong 2939FD color TV switching power supply using TDA4605 integrated circuit to control the switch to adjust the tube V840 mode, shown in Figure 1. 1. Oscillator circuit: After the mains is connected, the AC power is charged to the C819 for half a week via RT802 and R802, so that the voltage on the TDA4605 pin (power supply terminal) rises. When the voltage on pin ⑥ rises to the threshold (about 12V), the TDA4605 starts Work and produce the internal reference voltage. At the same time, the bridge rectifier output voltage of +300 V by R812 C812 charge, so that ② feet (high-level input cut-off function) voltage rise, so that the internal “start pulse generator” to generate start pulse to the logic circuit, By ⑤ pin output excitation pulse, to control the switch V840 oscillation work. another