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2. 发明授权

US06205037B1 Overload protection for a switch mode power supply 有权
标题翻译：开关电源的过载保护
公开(公告)号：US06205037B1
公开(公告)日：2001-03-20
申请号：US09468667
申请日：1999-12-21
申请人： William Vincent Fitzgerald, Jr.
发明人： William Vincent Fitzgerald, Jr.
IPC分类号： H02M3335
CPC分类号： H02M3/3385 , H02M1/32 , H02M3/33546
摘要： When a main switching transistor of a zero voltage switching power supply is conductive, a voltage is developed in a current sensing resistor coupled in series with the transistor. The voltage in the current sensing resistor is coupled to a first input of a comparator of the control circuit. A second input of the comparator is coupled to a capacitor that develops a voltage that varies in accordance with an output voltage of the power supply. During a given conduction interval of the transistor, the comparator is triggered in accordance with the difference between the current sensing resistor voltage and the capacitor voltage. An output of the comparator is coupled to the base of the transistor for controlling the turn off instant of the transistor on a current pulse-by-current pulse basis. Under overload condition, when the transistor is turned off, a reverse collector current flows through the base-collector junction of the transistor. The reverse collector current produces a voltage in the current sensing resistor that is at opposite polarity with respect to the voltage there, during forward conduction of the transistor. The voltage produced by the sensed reverse current turns on a diode switch and charges the capacitor that is coupled to the comparator of the control circuit in a manner to reduce the peak forward collector current. Thereby, the peak forward current in the transistor decreases relative to a value that would have occurred without the protection.
摘要翻译：当零电压开关电源的主开关晶体管导通时，在与晶体管串联耦合的电流感测电阻器中产生电压。电流感测电阻器中的电压耦合到控制电路的比较器的第一输入端。比较器的第二输入耦合到电容器，其产生根据电源的输出电压而变化的电压。在晶体管的给定导通间隔期间，根据电流感测电阻器电压和电容器电压之间的差异来触发比较器。比较器的输出耦合到晶体管的基极，用于以电流脉冲逐脉冲为基础控制晶体管的截止时刻。在过载条件下，当晶体管截止时，反向集电极电流流过晶体管的基极 - 集电极结。在晶体管的正向导通期间，反向集电极电流在电流感测电阻器中产生相对于其上的电压具有相反极性的电压。由感测的反向电流产生的电压打开二极管开关，并以以减小峰值正向收集器电流的方式对耦合到控制电路的比较器的电容器进行充电。因此，晶体管中的峰值正向电流相对于没有保护而将发生的值减小。

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