A Power-Switch Thermal Limiting Technique for Current-Mode Monolithic DC-DC Converters

Abstract This paper presents a power-switch thermal limiting technique for peak current-mode DC-DC converters to achieve maximized load current deliverability under a fixed thermal constraint. The inductor current limit of the converter is adaptively set based on the sensed switching duty-cycle to maintain a fixed power consumption limit across a wide input voltage range. The proposed current limiting circuit exhibits a fast-transient response and the chances of power-switch overheating is minimized. Since the temperature rise of the converter chip is also a function of the heat-conduction conditions such as the package type, the PCB layout, and the ambient temperature, the proposed architecture allows the power limit to be adjustable through a single off-chip resistor. Compared with a conventional switching converter which sets the inductor current limit to be constant across the entire input voltage range, the proposed approach achieves a higher available load current, especially with a higher input voltage under the same thermal constraint. In the proposed boost converter with an allowable temperature rise of 40 ° C , the proposed converter achieved 46% more available load current compared with the conventional one at the highest input voltage.