A Low-EMI Buck Converter Using a Binary Comparator based Asynchronous Pulse Width Modulator for Wide Adjustable Switching Frequency Application

This paper proposes a low spurious noise and wide-range adjustable switching frequency buck converters utilizing a binary comparator-based asynchronous pulse width modulation (BAPWM) controller. The modulation frequencies of both first- and second-order BAPWM are investigated through time domain analysis, revealing that the second-order BAPWM achieves a broader adjustable range of modulation frequencies. A linearized model of the BAPWM scheme is analyzed, revealing its frequency response to be similar to that of conventional pulse width modulation (PWM), thereby facilitating the direct replacement of PWM without altering the existing compensation network in the converter. Furthermore, the inherent spread spectrum characteristic of BAPWM effectively suppresses electromagnetic interference (EMI). Experimental results demonstrate that the proposed BAPWM-based buck converter reduces EMI while maintaining a wide adjustable switching frequency range and stability compared to traditional PWM-based converters.