Research And Design Of A Fast Response COT Controlled Buck Converter

With the continuous upgrading of industries and intelligent manufacturing,various forms of electronic equipment continue to decrease.The essence behind it is the increasing hardware processing capabilities and equipment manufacturing capabilities.Among them,the power management integrated circuit is an important type of hardware equipment,which centrally and uniformly supplies power to each hardware system.The COT controlled Buck converter is a step-down converter with excellent transient response capability,especially suitable for complex application environments with large voltage drop and variable load.In this paper,basic performance and dynamic analysis of typical Buck converters are studied in depth to study the performance indicators and dynamic response processes.By studying the transient response of large signal loads in the COT mode,a variety of fast response technologies are designed.These technologies are implemented on Buck chips.The final simulation and test results show that the designed Buck chips have excellent dynamic and fast response capabilities.This paper proposes a variety of fast response schemes for Buck converters suitable for COT control.The fast response T_on and T_offmin technology is to increase the transient T_on value and reduce the instantaneous T_offmin value when the load step occurs to achieve a larger switching duty cycle,which can effectively improve the response speed of the Buck system from light load to heavy load.Meanwhile,this paper proposes body diode freewheeling technology suitable for low voltage output and FCCM fast response technology suitable for high voltage output,and designs high and low voltage fast response mode switching circuit which allows the system to achieve fast response over a wide output range.The body diode freewheeling technology reduces transient voltage overshoot by increasing the speed of the inductor current drop,while the FCCM mode improves the recovery speed of the transient overshoot by accelerating discharging.The design of the Buck system in this paper is implemented on the 0.18?m BCD process.The input voltage is 6V-15V and output voltage is 1.2V-3.3V.The switching frequency is 1MHz,and the max load current is 2A.In the circuit design,the power stage parameters are determined through the analysis of the steady-state switching ripple and efficiency.The loop compensation strategy is given through the stability analysis of the COT control loop.The current sampling and driving circuit are designed and simulated.In the end,the overall simulation,tape-out verification and test analysis of the designed Buck chip are performed in this paper.The final test results show that the Buck chip designed in this paper can achieve transient voltage undershoot of 63mV and overshoot of 168mV,and the recovery time is4.39?s and 17.2?s,respectively.This is greatly improved compared to the ordinary COT-controlled Buck converter,which improves the response speed of the chip under complex load environments.