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3.脉冲丢失检测电路脉冲丢失检测电路如图16所示。当行扫描电路或场扫描电路发生故障时,就会无行、场脉冲输出。电容器C通过分压电路或降压电阻接行、场输出端,对行、场输出的脉冲进行监测,正常时不断有行、场脉冲通过C和R1输入到三极管VTl的基极,VTl处于脉冲放大状态,集电极c的电压相对较低;当行、场扫描电路发生故障停止工作时,无脉冲送入VTl的基极,VTl处于截止状态,集电极c的电压升高接近VCC电压。该高电压经隔离电阻R3送入电压翻转电路,致使保护电
3. Pulse Loss Detection Circuit The pulse loss detection circuit is shown in Figure 16. When the line scan circuit or field scan circuit fails, there will be no line, field pulse output. Capacitor C through the voltage divider circuit or step-down resistor row, the field output, the line, field output pulse monitoring, there are constantly normal line, the field pulse input through the C and R1 to the base of the transistor VTl, VTl pulse In the enlarged state, the voltage of the collector c is relatively low; when the line and field scanning circuit stop working, no pulse is sent to the base of VT1, VT1 is in the off state, and the voltage of the collector c is increased close to the VCC voltage. The high voltage into the voltage flip-flop circuit R3, resulting in protection of electricity