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(3)如图3所示是NCPl377内部电路框图。其引脚功能如表2所示。①启动电路当接通电源时,从PFC(功率因素校正)电路输出的高压HV从NCPl377的⑧脚引入,芯片内部电流源(典型值4 mA)向NCPl377的⑥脚外接电容器C34充电,当电压Vcc达到12.5 V时,电流源关断。这一过程还会激活l ms软启动功能,使启动变得较缓慢。NCPl377启动后,内部电路开始工作,并从⑤脚输出开关脉冲,加到大功率MOS开关管Q5的G极,使Q5
(3) As shown in Figure 3 is the NCPl377 internal circuit block diagram. The pin functions shown in Table 2. ① start-up circuit When the power is turned on, the high-voltage HV output from the PFC (power factor correction) circuit is introduced from pin 8 of the NCP1377 and the internal current source (4 mA typ.) Charges the external capacitor C34 of NCP1377. When the voltage When Vcc reaches 12.5 V, the current source is turned off. This process also activates the lms soft-start feature, making startup slower. NCPl377 start, the internal circuit to work, and from the ⑤ pin output switching pulse, added to the G power MOS transistor Q5, Q5