Research And Design Of CMOS High Temperature DC-DC Converter

With the rapid development of science and technology,especially in some special fields,the requirements for the temperature range of circuit operation are getting higher and higher.Many applications such as the automotive industry,avionics and oil and gas exploration require electronics capable of operating over a wide temperature range of-55°C to 200°C.In view of the current domestic research on high-temperature CMOS DC-DC chips is relatively small,based on previous research on high-temperature CMOS integrated circuit design,this paper studies the mobility and PN junction of silicon MOS devices based on the carrier concentration.For parameters that are seriously affected by temperature,such as leakage current and threshold voltage,a leakage current compensation method and zero temperature coefficient bias point theory are used to design a model that can work stably in the range of-50～200℃,with overcurrent and overvoltage,Over-temperature protection function,wide-range input and constant voltage output DC-DC converter,mainly completed the following work:(1)The structure,modulation mode,control mode,working mode,and small-signal model of Buck-type DC-DC converter are studied,focusing on the voltage-based PWM modulation mode,and the small-signal model and Its transfer function,and designed a loop compensation circuit according to this model,which improves the stability of the circuit and its dynamic response,and reduces the output voltage ripple.(2)The reasons for the instability of CMOS integrated circuits at high temperatures are studied,and the characteristics of MOS transistors at high temperatures are analyzed.The design method of high temperature CMOS integrated circuit is calculated,analyzed and verified by simulation.The zero temperature coefficient bias point theory is applied to deal with each key point in the circuit,so that the circuit can maintain stable performance at high temperature.(3)Based on SMIC 0.18 um BCD process,a high temperature CMOS DC-DC converter is researched and designed.A linear voltage regulator circuit is integrated in the converter to provide a stable low voltage,which ensures the stability of error amplifier,oscillator and reference module in the control loop.The performance indicators of the system are simulated and verified by Cadence Spectre.The simulation results show that the output voltage can be stabilized at 5V within the input voltage range of 20V～35V,the maximum load current is 5A,and the linear adjustment rate is 0.1356%/V.The load regulation rate is 0.616%/A,the output voltage ripple is 17 m V.