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T2517型彩电的开关电源有比较完善的输出过压、过流保护,无论负载电路过流还是开关电源本身故障造成的输出过压,除行扫描电路“X射线”保护电路断开行扫描驱动脉冲之外,开关电源立即呈保护性待机。该电源系分立元件组成,当过压保护动作时一般采用两种检查方法:一是断开电源,用电阻法对取样系统、稳压系统元器件做逐个检测。但此法很难查出故障,对某些元器件的软故障根本无能为力;二是将过压保护电路断开,此法更不可取。虽然负载电路已断开,因为输出过压无疑是PWM系统、取样系统、光电耦合
T2517 color TV switching power supply has a relatively perfect output over-voltage, over-current protection, regardless of the load circuit over-current or switching power supply itself caused by the failure of the output over-voltage, in addition to line scan circuit “X-ray” protection circuit to open the line scan drive pulse In addition, the switching power supply was immediately protective standby. The power system is composed of discrete components, when the over-voltage protection action generally used two kinds of inspection methods: First, disconnect the power supply, the resistance of the sampling system, voltage regulator system components to do one by one test. However, this method is difficult to find fault, the soft failure of some components simply powerless; the second is the over-voltage protection circuit is disconnected, this method is less desirable. Although the load circuit has been disconnected, because the output overvoltage is undoubtedly the PWM system, sampling system, optocoupler