Research And Design Of The Push-Pull Pulse Width Modulator

The DC-DC converter is an important device that provides stable power for various electronic products.With the diversification of the electronic information industry,the application scenarios of DC-DC converters are becoming more abundant,and the performance requirements for switching power supply chips are getting higher and higher.Switching power supply chips are now moving toward fast transient response,high efficiency and low power consumption,small integration,digital control,and system intelligence.Based on the basic principles of the DC-DC converter,the key technology of slope compensation and the research of the key technology of fast transient,this paper designs a high-voltage wide input,high efficiency,fast transient push-pull pulse width modulator chip,and a push-pull DC-DC converter can be directly built using this chip to power electronic devices.The main research contents and results are as follows:1.An adaptive slope compensation circuit is designed to eliminate sub-harmonic oscillation.By using the secondary slope instead of the traditional linear slope,it can follow the duty cycle change and highly fit the ideal compensation slope of the system,which significantly improves the problem of over-compensation in traditional slope compensation,effectively suppresses sub-harmonic oscillation,and improves System performance.2.A fast transient control is proposed to improve the transient response of the system.Improve the transient response speed by designing a limiting error amplifier,transient detection and transient control circuits.When the load change is detected and the error signal change is directly controlled,the error signal is set to the maximum or minimum voltage during the load transient,and the duty cycle rapidly increases or decreases to the lowest or highest level that the system can reach,effectively accelerates the transient Responding to and reduces the output overshoot/undershoot voltage,can obtain better output performance.3.A high-voltage LDO is designed to meet the requirements of a wide input voltage range of the system.By designing a high-voltage LDO,the input voltage is converted into a stable low-voltage power supply voltage to provide power for the internal circuit modules of the chip.It mainly includes pre-regulator circuit,operational amplifier,power tube,protection circuit and under-voltage lockout.The stability design of the high-voltage LDO is carried out to ensure the stable operation of the circuit.4.The PWM comparator and drive output circuit are designed and optimized.Optimizing the structure of the traditional comparator improves the flipping speed of the comparator,and can achieve the minimum identification duty cycle requirements;Analyzing the working process of the power MOSFET to obtain the design requirements of the drive output circuit.Through the optimized design of the drive output circuit,the output drive capability is effectively enhanced,and the drive control of the switch tube is realized.Based on the above research work,using 0.18 um 100V BCD technology,and by using Cadence software to complete the circuit design,simulation verification and layout design.The simulation results show that the stable output voltage is 3.3V,the load transient response requires stabilization time within 158 ?s,the output overshoot/undershoot voltage when the load jumps is 54 m V,and the conversion efficiency Up to 88%,the function of the push-pull pulse width modulator is normal,and the various parameters meet the design requirements.