An over-temperature protection circuit for smart power switch

An over-temperature protection circuit with low temperature protection and power limiting circuit was designed on the basis of high-temperature over-temperature protection circuit. In the smart power switch chip, it prevented the junction temperature of the power transistor and the temperature gradient in the chip from exceeding the safe range, which could damage the chip to varying degrees and affect the reliability of the chip. The negative temperature coefficient voltage was used to detect the chip temperature in real time, and the logic turnover point was obtained by comparing it with reference voltage of the band gap reference circuit, after processing by hysteresis logic circuit the hysteresis logic signals are outputted to control the working state of the chip. The circuit was fabricated with a 40V 0.35 µm BCD process. The simulation results show that when the temperature is lower than -40°C, the low temperature protection circuit is turned on; when the temperature is higher than 175°C, the high temperature protection is turned on, and the hysteresis temperature is 14°C;When the temperature gradient exceeds 60°C, the power limiting is turned on, and the hysteresis temperature is 14°C. It can be applied to smart power switch chips in harsh working environments.