Peak Current Mode Bifrequency Control Technique for Switching DC–DC Converters in DCM With Fast Transient Response and Low EMI

Abstract

Peak current mode bifrequency (PCM-BF) control, a novel control technique for switching dc-dc converters in the discontinuous conduction mode (DCM), is proposed in this paper. It realizes output voltage regulation by employing high- and low-frequency control pulses with preset switching frequencies. At the beginning of each control pulse cycle, the output voltage is sampled and compared with reference voltage to determine whether high- or low-frequency control pulse should be generated as control pulse. Compared with conventional pulse-width-modulation-based PCM control (hereafter called PCM-PWM), which realizes output voltage regulation by adjusting the duty ratio of the control pulse cycle by cycle, the PCM-BF control is simple, cost effective, and enjoys fast transient response. Moreover, more low-frequency control pulses are generated for light load, which improve the power conversion efficiency at light load. Besides, high- and low-frequency control pulses with different switching frequencies spread the spectrum over discrete frequencies, resulting in low electromagnetic interference. A buck converter operating in the DCM is taken as an example to illustrate the applications and benefits of the PCM-BF control technique. Simulation and experimental results are presented to verify the analytical results.