Design Of Buck Converter With Wide Input Range Based On ACOT Control

With the development of science and technology,a variety of electronic products play a vital role in all aspects of social life,changing people’s production and lifestyle and making it more convenient and faster.Whether the power management chip can supply high-quality and stable power to electronic equipment is crucial to the efficient and reliable operation of the equipment,which is the core of electronic equipment.DC-DC converters represented by switching power supplies are widely used in the industry due to their high power density,high efficiency,high reliability,and low cost.Buck converters,as representatives of switching power supplies,are continuously moving towards a wide input range,high power density,low EMI,and Trends such as new power devices continue to evolve.This article designs a wide input voltage range Buck converter with adaptive constant on-time(ACOT)control.First,the Buck converter architecture and principle are introduced,the ACOT control strategy is analyzed,Describe the small signal modeling using the description function method to guide the loop compensation design and propose an on-chip compensation scheme for adaptively setting the switching frequency.For the traditional ACOT controlled Buck converter,the sampling input and output voltage information determines the on-time of the upper tube TON.In order to realize that the switching frequency is consistent with the set reference frequency and the phase is consistent over a wide range of input voltage,output voltage and load current,a dual phase-locked loop architecture is introduced.In TON,the setting switching frequency and the frequency difference and phase difference information between the switching action and the reference clock are introduced to realize the frequency-locking and phase-locking function.Clock synchronization phase-locked loop can perform out-of-phase processing on the external input clock or generate a clock according to the frequency modulation resistor and output the clock backward.Phase synchronization Phase-locked loop fine-tunes the TON determined according to the input and output voltage and reference frequency information according to the frequency difference and phase difference information between the switching action and the reference clock to implement the frequency-locked phase-lock function.Introducing the set switching frequency information in TON can reduce the maximum adjustment range of the phase-locked loop to reduce the frequency jitter.Adjusting TON enables the switching action to be achieved under a wide range of input and output voltage and load current.Frequency-locked and phase-locked,providing basic conditions for multi-chip on-chip or module integration.In the load current step,the equivalent duty cycle will be increased under the adjustment of the phase-locked loop.In order to further improve the transient response speed,an adaptive compensation scheme of the phase synchronous phase-locked loop is proposed.Based on the systemlevel design,the key sub-modules such as clock synchronization phase-locked loop,Phase-locked loop modulation adaptive constant on-time generating circuit,wide input voltage range LDO,and adaptive zero-crossing detector are mainly designed.Based on the 0.18 μm BCD process,a wide input range Buck converter controlled by ACOT is designed in this paper.The input voltage is 6V-32 V,the output voltage is 1.2V-28 V,and the maximum load capacity is 2A.Using simulation software for simulation verification,The simulation results are normal,and the overall layout design,COB packaging,schematic and PCB design,and chip testing are performed,the chip test results show that it works normally under various input and output voltages and CCM and DCM modes.The switching action and reference clock can achieve frequencylocking and phase-locking,and the load current changes from 0.5A to 1.5A The recovery time is 7.25 μs.