A comparative study of hysteretic voltage-mode buck converters for high switching frequency and high accuracy

We present a comparative study of hysteretic voltagemode buck converters (HVMBC) in achieving high switching frequency and high regulation accuracy. With simple geometrical analysis we show that in order to minimize the switching delay and hence maximize the switching frequency, strategies of single boundary control (SBC) and ramp generation in-phase with the inductor current should be employed in the HVMBC. By using an RC integrator in parallel with the inductor, a power-efficient ramp generation is achieved, while an error-correction path can be introduced to lessen the degradation in regulation accuracy. Various simulation and experimental results are presented to verify the study. An AMS 0.35-μm CMOS prototype HVMBC employing the above strategies measured 9.6-14.3 MHz of switching frequency, 10.9mV/A of load regulation and 6.9mV/V of line regulation, respectively.