固定关断时间控制Buck变换器斜坡补偿技术及其机理研究

Ramp Compensation Technique and Its Mechanism Investigation of Fixed Off-time Controlled Buck Converters

当输出电容等效串联电阻(equivalent series resistance,ESR)较小时,固定关断时间控制(fixed off-time,FOT)控制Buck变换器可能工作在不稳定的混沌状态。提出FOT控制Buck变换器的斜坡补偿技术,通过采样电感电流信息对输出电容电压进行电压斜坡补偿,实现了低ESR输出电容FOT控制Buck变换器的稳定工作。分析斜坡补偿的作用机理,给出确保变换器稳定工作时斜坡补偿电压斜率的临界值。建立斜坡补偿FOT控制Buck变换器的离散映射模型,研究斜坡补偿电压斜率作为分岔参数时斜坡补偿FOT控制Buck变换器的动力学行为。研究结果表明,斜坡补偿有效拓宽了变换器输出电容ESR的稳定工作范围,通过斜坡补偿技术,输出电容ESR较小时FOT控制Buck变换器也能稳定正常工作。实验结果验证了理论分析的正确性。

The fixed off-time（FOT） controlled buck converter often operates in an unstable and chaotic state when the output capacitor has a low equivalent series resistance（ESR）. By sensing inductor current information of main circuits for compensating the slope of output capacitor voltage, a ramp compensation technique of FOT controlled buck converter is proposed, which realizes that the converter is in stable and normal operation when a low ESR output capacitor is used. The action mechanism of the ramp compensation technique is analyzed, and the critical slope of compensation ramp voltage to ensure the converter stable operation is achieved quantitatively. The discrete-time map model of FOT controlled buck converter with ramp compensation is established, upon which the dynamical behaviors of the converter are investigated by taking the slope of compensation ramp voltage as the bifurcation parameter. The results indicate that the ramp compensation effectively extends the stable operating range of the output capacitor ESR of the converter, and the ramp compensation technique makes that FOT controlled buck converter with the low ESR output capacitor can also be in stable and normal operation. The experimental results verify the validity of the theoretical analysis.