Analysis And Circuit Design Of Over-Temperature Protection In Smart Power Integrated Circuit

Compared with the traditional intelligent power module, smart power integrated circuit (SPIC) has many advantages such as small volume and low power dissipation. With the increasingly improved demand of compact motor and motor reliability and the implementation of energy conservation and environment protection policy, the demand of SPIC is rapidly improving. However, the rigorous application environment and unique interior structure of SPIC make the chip temperature rises easily, and cause reliability problem. Therefore a high precision and good stability built-in over-temperature protection (OTP) circuit is vital to the reliability of SPIC and its application environment.This thesis first gives an introduction to the working principle and basic structure of OTP circuit, and analyzes the on-chip temperature sensing technology and the problem of traditional OTP circuit in SPIC. Then deeply analyzes the over-temperature protection of SPIC according to the actual conditions, and design a high reliable over-temperature strategy. Finally focuses on the linearity, sensitivity and power supply characteristics of the temperature sensor based on bipolar junction transistor (BJT) and proposes an optimized temperature sensing method for OTP circuit, designs a high-precision, low power consumption OTP circuit of SPIC, and simulates with Cadence Spectre. The designed OTP circuit utilizes the base-emitter voltage difference △VBE of BJT to sense chip temperature, thereby improving the temperature sensing linearity and reducing the influence of power supply and process variation. Adopting the proposed optimized temperature sensing method with low temperature sensing sensitivity in low temperature zone and high temperature sensing sensitivity in high temperature zone to reduce the output voltage of temperature sensing circuit based on △VBE, thus reducing the power supply voltage and power consumption. Increasing a regenerative comparator with internal positive feedback to improve the conversion rate of the designed OTP circuit, thereby reducing the comparator delay and improving the precision of the OTP circuit.Based on the CSMC 0.5μm 600V SOI BCD process, the OTP circuit designed in this thesis is taped out and tested. Tested results show that the average temperature sensing sensitivity is greater than 11mV/℃ and the temperature sensing non-linearity error is less than 5%when temperature changes from 50 ℃ to 150℃. When power supply voltage changes from 3 V to 6V, the deviations of both shutdown temperature and restart temperature are all less than 2%. When the power supply voltage is 5V, the overall power consumption of the designed over-temperature protection circuit is 0.65mW, all the above indexes meet the design requirements.