NC—3机芯是四川长虹公司与日本东芝公司共同开发成功的I~2C总线控制大屏幕彩色电视机用机芯。使用该机芯的有:C2919、C2939、C3418等系列机型。该机芯保护功能齐全,设有过压、过流、欠压、负载短路、防开机冲击电流等保护电路。本文以 C2919P型机为例,分析其保护电路及其典型故障的检修。一、保护电路分析 1.过压保护电路:有关电路参见图1所示。开关电源正常工作时,开关变压器T803⑦～⑧绕组的脉冲 NC-3 movement is Sichuan Changhong Company and Japan Toshiba co-developed a successful I ~ 2C bus control large screen color TV movement. The use of the movement are: C2919, C2939, C3418 series models. The movement protection is complete, with overvoltage, overcurrent, undervoltage, load short circuit, anti-boot impact current protection circuit. In this paper, C2919P-type machine, for example, analysis of its protection circuit and its typical fault repair. First, the protection circuit analysis 1 over-voltage protection circuit: the circuit shown in Figure 1. Switching power supply normal work, the switch transformer T803 ⑦ ~ ⑧ winding pulse