隔离式双闭环开关电源的系统分析与实验

Analysis and design of isolating double closed loop switching power supply

针对单闭环结构的开关电源受外界干扰时的动态响应速度慢,严重时会造成系统的不稳定问题,采用UC3842电流控制模式控制器,设计了一种基于电流型PWM(PulseWidthModulation)控制技术的单端反激式隔离开关稳压电源。采用连续建模的状态空间平均法,建立了小信号模型,并利用控制理论,对双闭环反馈控制下的反激式变换器进行了补偿和稳定性分析,分析了其频域特性与系统性能指标之间的关系。实验结果表明:该系统具有快速限流特性,使高频变压器功耗和开关管功耗下降,系统动态响应的快速性和稳定性较好。

The single closed loop switching supply has serious disadvantages. The system has slow dynamic response when it is exposed to disturbance. And the disturbance makes the system unstable. Based on the PWM(Pulse Width Modulation) control technique of current mode, an isolating single-ended flyback switching power supply is designed with IC controller UC3842, the small mathematic mode is constructed with the average state method. The compensation and stability analysis is discussed using control theory for this double closed loop flyback converter. The relationship between the system performance and frequency domain characteristic is analyzed. The experimental results show that the advantage of the double closed loop switching power supply lies in rapid current limiting characteristics,low power of the high frequency transformer and power switching transistor,good rapidity and stability of the dynamic response.