Research And Design Of Synchronous Buck DC-DC Switching Power Converter

As the rapid development of power electronics technology,more and more portable electronic products flood into the market,and the demand for power management chip is also increasing,and the quality of power supply plays a crucial role in the performance of electronic equipment.Therefore,the research and design of high-efficiency,miniaturized and high-frequency DC-DC switching power supply chip is of great value.In this paper,a synchronous Buck DC-DC switching power converter with peak current control mode is designed and controlled by PWM modulation.Firstly,the basic theory of DC-DC switching power supply is described in detail,and the working principle,control mode,modulation mode and loop stability of Buck type open power supply circuit are introduced.Then the design principle of key circuit modules in the system is described and verified by simulation,including bandgap circuit,oscillator circuit,error amplifier,ramp compensation and PWM comparator.In addition,a variety of protection circuits are integrated inside the chip,including UVLO,overcurrent and over-temperature protection circuits,to ensure that the chip can work safely and stably for a long time.In addition,based on the theory of switch power supply,combined with the actual circuit design to the traditional peak current control mode is improved in the structure,convert the output error voltage of the error amplifier into the error current,current comparison is performed directly in PWM comparator instead of converting inductance current information into voltage signal.This method avoids multiple switching between different levels in actual circuit design and improves the response speed of the circuit.Besides,based on the consideration of reliability,the traditional switching power supply overcurrent protection circuit is innovated,and a kind of sampling and comparison circuit based on valley current limit is proposed.The circuit structure is simple,and the precision of current limit and response speed are improved.All the circuits were designed using 0.18μm BCD process,and the circuit system was simulated based on Cadence platform Spectre environment.Then the tape-out is carried out after the validation of the layout design.The input voltage range of the chip is 3-6V,the output voltage range is 0.8-3.6V,the maximum output load is 6A,the switching frequency can be adjusted in the range of 200 k Hz～2000k Hz,according to the test results,all indicators meet the design requirements.