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

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. (c) 2023 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.