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有些应用场合要求集成电路的输入电压高于其电源引脚的击穿电压。在升压变换器和SEPIC(单端初级电感变换器)中,可以把集成电路的V_(IN)引脚与输入电感器分开,并使用简单的齐纳稳压器来产生集成电路的电源电压。图1示出了一种使用4～28V输入电压、在输出电流为100mA时产生5V输出电压的SEPIC。在这一应用中,因为电源电压超过了IC_1的最大输入电压,所以IC_1的电源电压是由Q_1和Q_2产生的。该电路使用Q_1代替齐纳二极管以节约成本。Q_1的射极-基极击穿电压提供了稳定的6V基准电压。Q_2是一个跟随器,它为集成电路提供电源电压。此电路展示了一种拓宽集成电路输入电压范
Some applications require the integrated circuit input voltage is higher than the breakdown voltage of its power pin. In step-up converters and SEPICs (Single-Ended Primary Inductor Converters), it is possible to separate the IC’s V IN pin from the input inductor and use a simple Zener voltage regulator to create the integrated circuit supply voltage . Figure 1 shows a SEPIC that uses a 4 to 28V input voltage and produces a 5V output voltage at an output current of 100mA. In this application, because the supply voltage exceeds the maximum input voltage of IC_1, the supply voltage of IC_1 is generated by Q_1 and Q_2. This circuit uses Q_1 instead of Zener diodes to save costs. Q_1’s emitter-base breakdown voltage provides a stable 6V reference voltage. Q_2 is a follower that supplies the integrated circuit with the supply voltage. This circuit shows a way to broaden the range of integrated circuit input voltage