DPA425是美国POWER Integrations公司生产的脉宽调制器，采用P、G、R三种不同的封装形式，各引脚功能如下：C脚为误差放大器和反馈电流的输入端，外部通过光电耦合器的下拉电流来调节占空比；L脚为电压检测端，为用户提供过压OV、过压UV、同步控制，在该脚引入同步脉冲，电路工作在外同步模式，但同步信号要高于振荡器频率；X脚为极限电流设置端，在该脚与源极之间接入不同参数的电阻，可设置DPA425的限流点；S脚为源极端，初级控制电路的公共点和参考点，内部连接功率。MOSFET的源极；D脚为漏极端。输入电压范围1～75VDC，在启动时可通过内部高压电流源为控制电路提供偏置电流。(DPA425 is American POWER Integrations company's pulse width modulator, P, G, R three different forms of packaging, each pin function is as follows: C foot as the input of error amplifier and feedback current, external through photoelectric coupler drop-down current to adjust the duty ratio; L feet for voltage detection, to provide users with overpressure OV, overvoltage UV, synchronous control, synchronous pulse, introduced in the foot, working circuit synchronous mode, but the synchronous signal than the oscillator frequency; The X foot is the limit current setting end, and the resistance of the different parameters is connected to the source and the limit of the DPA425 can be set. The s-foot is the source extreme, the primary control circuit common point and reference point, internal connection power. The source of MOSFET; D foot is the drain. The input voltage range is 1 ~ 75VDC, and the offset current can be provided by the internal high voltage current source at startup.)