Research And Design Of Boost Converter With Large Load Capability

With the development of integrated circuits and the electronics industry,our lives have long been inseparable from portable electronic devices.The performance of the power supply will determine the performance of the entire electronic system,so the power supply is a very important part of the entire electronic system electronic system.As an important part of electronic equipment,the screen has higher requirements for its resolution,refresh rate and various performances,which requires the load capacity of the power management chip to be higher.Through the research on the topological structure of the boost DC/DC converter,the PWM peak current mode control loop,and the research and analysis of the factors that affect the system’s load capacity,this paper designs a boost converter with a large load capacity.The dualloop control mode combining current loop and voltage loop has significant advantages in DC/DC converter design,but in PWM peak current mode,when the system duty cycle is greater than 50%,the inductor current will generate sub-harmonics oscillation,affecting the stability of the loop.Aiming at the stability of the loop,based on the research on the slope compensation method,this paper designs a high linearity fixed slope slope compensation circuit;for the problem that the introduction of slope compensation will reduce the load capacity of the converter,this paper proposes a The negative DC current inverse slope compensation method related to the system duty cycle is superimposed on the sampled current,so that the peak current of the inductor can be restored to more than 96%,which can effectively eliminate the influence of the traditional slope compensation method on the load capacity;in order to solve the chip off state Under the problem that the output is not completely turned off due to the forward bias of the parasitic body diode of the freewheeling tube,the substrate switching circuit is used,and the digital circuit controls the substrate switching circuit to realize the true turn-off of the chip,so that the output current of the chip in the off state is 28.3pA(less than 1nA under PVT);Aiming at the problem that the excessive current in the startup phase may cause damage to the device,the method of digitally controlling the potential of the positive terminal of the error amplifier is used,and the substrate switching circuit is reused to precharge the output capacitor,which realizes the soft start of the chip and will start The inrush current of the stage is reduced from 2.42A to 513mA.Based on the 0.18μm BCD process,the specific circuit design,layout design and presimulation and post-simulation verification of the boost DC/DC converter designed in this paper are completed.The results show that the converter has a switching frequency of 1.5MHz,an offchip inductance of 10μH,an input capacitor of 30μF and an output capacitor of 20μF.When the input power supply voltage is in the range of 2.9V to 4.5V,It can realize dynamic adjustment of output voltage 4.6V～5.0V,its typical value is 4.6V.The load current jumps under 596.3mA～998μA～596.5mA,and its load regulation rate is-0.11%/A and+0.07%/A.When the input voltage jumps between 2.9V and 4.5V,the linear adjustment rate is 0.02%/V.It can be seen that the slope compensation method with inverse slope compensation technology proposed in this paper can significantly improve the chip load capacity,and provide an effective solution for the design of a boost converter with a large load.