Design Of High Switching Frequency Constant On- Time Controlled DC-DC Converter

The popularity of 5G and AI intelligent technologies has promoted the development of smart medical,smart home and smart transportation industries,and further improved the quality of human life.The development of these electronic information industries is inseparable from the development of switching power supplies.With the continuous pursuit of the concept of green and sustainable development,this has also promoted the development of switching power supplies in the direction of high frequency and high efficiency.The dissertation mainly focuses on the high-frequency of Constant On Time?COT?controlled Buck converters.First,the small-signal model of the Phase Locked Loop?PLL?-modulated current-mode COT controlled Buck converter and the Ripple-Based Constant On-Time controlled?RBCOT?Buck converter are analyzed with the description function method.The loop stability is analyzed and the loop compensation scheme is given.Then,the key technologies of Buck's high frequency are analyzed,including ultra-narrow pulse width technology,the influence of loop delay on bandwidth,frequency drift,efficiency optimization,and ringing.Finally,two high frequency COT controlled Buck converters are designed based on the above research.A COT-controlled high-frequency Buck converter with PLL sychronization is designed in this dissertation based on the 0.18?m BCD process.The T_ON of Buck is adjusted by the PLL to maintain constant switching frequency and then the converters supports multi-phase paralleling.System architecture,work and protection logic settings are designed in this dissertation.R3D is used to optimize the wiring resistance of the power MOS,and the power stage isolation scheme is given.The sub-module and the overall circuit were verified by Spectre.Test results show that the converter supports working at switching frequency of 4MHz;the maximum load current is 4A,and the output of a 4-phase paralleling of 16A is supported;when the load current changes from 0A to2.5A,the output voltage undershoot is 27mV and recovery time is 7.8?s;output voltage overshoot is 38mV and recovery time is 6.4?s;load regulation is less than 0.5%under typical 12V input and 1.2V output;linear regulation is less than 0.1%/V when power supply voltage changes from 4V to 16V The peak efficiency is up to 97.5%;the functions of the chip meet the design requirements.A high frequency stability RBCOT control Buck converter based on Single Cycle Output Voltage Prediction?SCOVP?technique is designed based on the 0.18?m BCD process.A one-shot timer?OST?circuit with SCOVP technology is proposed.It predicts the output voltage information through a single-cycle duty cycle,and compensates the T_ONN time based on the predicted output voltage.By predicting the output voltage through single duty cycle,the operational frequency was stabilized.The simulation results show that the maximum load current of the chip is 5A;at a working frequency of 2MHz,when the load current changes from 5A to 1A,the output voltage overshoot is 58mV,the output voltage recovery time is 4?s,and the frequency re-stabilization time is 5?s.The undershoot is 33mV,the output voltage recovery time is 1.46?s,and the frequency re-stabilization time is 3?s.When the load changes from 1A to 5A,the maximum frequency drift?f_SWW is only 13kHz,and the average load frequency change?f _SW/?I_Load is 3.24kHz/A.Meanwhile,the switching frequency accuracy was enhanced from 88%to 99.35%with proposed SCOVP technique.