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本刊94年8期曹虎成文《维修稿件撰写杂谈》中提出:某维修文章说一台采用STR5412的彩电开关电源,故障现象为输出电压升高,甚至“输入100V交流电压时,输出电压已升至120V”,曹文认为这是不可能的。然而就笔者的分析及维修经验来看,此种情况是可能出现的。STR5412为彩电开关电源厚膜块,其内部电路如附图所示。BG_3为开关管,BG_2为脉宽调制管,BG_1为取样放大管。市电整流后的直流电压加至BG_3集电极,②脚输入的正反馈
The issue of 94 years 8 Cao Hu Cheng Wen “maintenance manuscript writing Zan Tan” put forward: a repair article that a color TV using STR5412 switching power supply, the fault phenomenon is the output voltage increases, and even “input 100Vac voltage, the output voltage has Rose to 120V ”, Cao Wen think it is impossible. However, the author’s analysis and maintenance experience point of view, this situation is likely to occur. STR5412 color TV switching power supply thick film block, the internal circuit as shown in the figure. BG_3 for the switch, BG_2 for the pulse width modulation tube, BG_1 sampling amplifier. Mains rectified DC voltage added to BG_3 collector, ② feet input positive feedback