恒流源负载固定导通时间V^2控制Buck变换器研究

Research on Constant On-time V^2 Controlled Buck Converter with Constant Current Source Load

V^2控制是基于输出电压纹波的双环电压型控制方法,具有对负载变化的超快响应速度,通常应用于对输出响应要求较高的开关变换器中。但在输出电容等效串联电阻(ESR)较小时,V^2控制Buck变换器会工作在不稳定状态,往往出现开关频率变化、输出电压纹波偏大等现象。为改善这些缺点,提出固定导通时间V^2控制技术,用导通定时器取代原先的时钟脉冲信号,使得开关变换器保留了V^2控制的优点,同时可以应用恒定导通时间控制方法来计算合适的输出电容参数,降低了V^2控制Buck变换器输出电容参数的计算难度,也避免了需要增加斜坡补偿来消除时钟脉冲占空比大于50%时的开环不稳定和次谐波振荡这一措施。PSIM电路仿真验证了分析的正确性。

V^2 control is a double voltage control method based on output voltage ripple; it has a fast transient response speed, so it is suitable for various applications which require fast transient response. However, when equivalent series resistance （ESR） of output capacitor is small, the V^2 controlled buck converter works in instability state, which will cause variable-frequency and high output ripple. In order to avoid the disadvantages, constant on-time V^2 control method was proposed by adding an on-timer to replace the clock signal, so the V^2 controlled ad- vantages were retained, and constant on-time control method could be used to calculate the proper capacitance parameter. In this case, the dif- ficulties of calculating capacitance parameter for V^2 controlled buck converter were reduced, and it was also avoided slope compensation should be added to eliminate the open loop instability and sub-harmonic oscillation when clock signal＇ s duty exceeded 50%. PSIM simulation results have proved the analysis conclusion.