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1.去掉驱动电阻R11 自举电容的充电路径 [img]https:  [/img] 上电稳定以后,使用万用表测得输出电压是2.719V,电感两端电压是0.008V,自举电容两端电压是7.95V,二极管D1两端电压是0.673V,电阻R1两端电压是12.05V, 电源输入端电压24V,D11电压0.604V,C10电压是23.39V 2.719V+0.008V+7.95V+0.673V+12.05V=23.4V [img]https:  [/img] 上电稳定以后,使用万用表测得R12的电压是2.908V(可知Q2的BE电流是2.908V/2K=1.454mA),ZD2电压是4.314V,Q2的BE电压0.725V,Q2的CE电压0.029V,自举电容两端电压7.95V 2.908V+4.314V+0.725V=7.947V 下次记得测量R10压降,ZD1压降,Q7的BE压降,推测此时Q7是微导通状态,BE电流很小 [img]https:  [/img] 示波器探头夹持的照片 [img]https:  [/img] 示波器测出的黄线是比较器2脚,红线是比较器5脚
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[img]https:  [/img] 通道3和通道4重合,通道3是Q2的C极,通道4是自举电容正极 [img]https:  [/img] [img]https:  [/img] [img]https:  [/img] 如上图,自举电容从0V充到15.53V的时间是334ms [img]https:  [/img] [img]https:  [/img] [img]https:  [/img] [img]https:  [/img] Q2的C极电压和自举电容电压几乎重合 [img]https:  [/img] [img]https:  [/img] [img]https:  [/img] 第三通道改成隔离探头,测量输出电压 [img]https:  [/img] [img]https:  [/img] 蓝色改为测量上面的PWM电压,绿色测量输出电压 [img]https:  [/img] [img]https:  [/img] 此时PWM成为三角波 更换了一块新板,去掉驱动电阻R11 [img]https:  [/img] 测量上图3点的波形 [img]https:  [/img] [img]https:  [/img] [img]https:  [/img] [img]https:  [/img] 测量上面3点的电压 [img]https:  [/img] C3改成470nF,再次测量 [img]https:  [/img] [img]https:  [/img] 将C2改成1uF,再次测量 [img]https:  [/img] [img]https:  [/img] [img]https:  [/img] [img]https:  [/img] [img]https:  [/img] [img]https:  [/img] [img]https:  [/img] 装回驱动电阻R11,R11用10R电阻 黄线是MOS管GS波形,红线DS波形 [img]https:  [/img] [img]https:  [/img] [img]https:  [/img] [img]https:  [/img] 不同的示波器暂停时刻,会出现下面的几种波形,这是什么原因?
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