摘要
UC3842是高性能电流控制型脉宽调制(PWM)芯片,以其为核心的开关电源电路成本低廉,结构简单.但反激变换器在电流连续模式(CCM)下运行,占空比大于50%时,系统会在有扰动时发散或双闭环调节时产生分谐波振荡,使这类电源产品存在安全隐患.分析了系统控制不稳的原因,研制出能使扰动得以收敛的斜率补偿电路,电源能在小于0.1%的电压调整率,低于3%的负荷调整率的状态下,稳定运行.
The UC3842 has are specifically designed in performance fixed frequency and current mode PWM controller. They switching power supplies curcuits, with low cost by using minimal external components. But flybackconverters run in continuous current mode witha duly cycle greater than50%, then the system will disperse if disturbed or exhibit subharmonic oscillations when in the two-closed-loop regulation, forming inevitable risks in this kind of power supply. The paper analyses the causes of instability in the system control, develops a slope compensation circuit to enable the disturbance to converge, and the power can be in stable condition with less than 0.1% voltage regulation, or lower than 3% load-adjustment.
基金
安徽省高校自然科学研究重点基金资助项目(kj2007a047)
关键词
开关电源
UC3842
斜波补偿
switching power supplies
UC3842 chip
slope compensation
