A Robust Duty‐Cycle‐Comparison‐Based Overload Detector for DC‐DC Converter

Abstract

A novel duty‐cycle‐sensing overload detector for DC‐DC converter is proposed in this paper. Firstly, the theoretical analysis is conducted to reveal the susceptibility of the conventional overload detectors to temperature variation and the input/output‐voltage change of the DC‐DC converter. Then, the schematic of the novel duty‐cycle‐sensing overload detector is presented and its operation principle is analyzed. Thanks to the time register, the proposed detector generates a theoretically voltage‐and‐temperature‐insensitive threshold duty cycle, compares it with the real‐time duty cycle of the converter's PWM signal, and announces an overload event if the real‐time duty cycle exceeds the threshold. Finally, a prototype of a BUCK DC‐DC converter including the proposed detector and a conventional current‐sensing overload detector is constructed and measured. As the measurement results show, the threshold duty cycle only varies by about 2.4% as the temperature changes from 0 to 90 °C while the threshold voltage of the conventional current‐sensing detector changes by about 4.6%. The proposed detector can keep effective even the temperature rises to 90 °C while the conventional current‐sensing detector can work at a temperature no higher than 85 °C. Without circuitry modification, the proposed detector correctly senses the overload event as the DC‐DC converter's output voltage changes in a range of 2.1–2.9 V while the conventional one loses its effectiveness if the output voltage is set higher than 2.54 V. © 2023 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.