| With the depletion of natural resources,the energy issue is receiving more and more attention from all countries.In recent years,the clean energy industry has continued to flourish,promoting the development of industries such as electric vehicles.Fast-growing electric vehicles and handheld electronic devices have raised more and more requirements for convenient and reliable charging methods.Wireless charging has attracted much attention due to its high security,small space,easy maintenance and good compatibility.In the wireless charging chip,because the pre-level output voltage is not suitable for the control of each internal circuit module,a buck converter is needed to modulate the input voltage to generate an appropriate power level so that the internal module of the wireless charging chip can work normally.Based on the above background,aiming at the special requirements of wireless charging chip,the main research goal of this paper is to design a buck converter module which can be integrated in the wireless charging chip and has high conversion efficiency.This paper first analyzes the two basic principles in the DC-DC converter,which are the volt-second balance and the charge balance of capacitor.Based on this,we get the basic relationship in the DC-DC converter.After that,topologies,modulation methods,control methods and source of losses of DC-DC,and the reasons and solutions of subharmonic oscillation are briefly analyzed.Then,the state space averaging method is used to model the converter,and the parasitic effect of capacitance and inductance is taken into account in modeling.Finally,we get the large signal model and small signal model of the DC-DC converter and do the system modeling and simulation by Simulink.Next,we introduce the compensation network commonly used in the DC-DC system,and the compensation network for the current mode DC-DC is designed.In addition,the bandgap reference,error amplifier,PWM comparator,current detection,oscillator,over temperature protection circuit and dead time control circuit in DC-DC converter are designed.The starting circuit is added in the designed bandgap reference circuit,the error amplifier adopts the folded Cascode structure,and the current detection circuit uses the SenseFETS detection method.Meanwhile,Cadence software is used to simulate each functional module.Finally,based on the 0.35μm BCD process,the layout of the DC-DC converter module is designed.Simulink simulation results show that the established model can make a good prediction of DC-DC system behavior.After adding compensation network,the Bert diagram of the system shows that the compensated DC-DC has good phase margin.The circuit simulation results show that the temperature coefficient of the bandgap reference is 17.24 ppm/℃,the power supply rejection ratio is 62.84 dB,and the performance of bandgap reference circuit is good;the DC gain of the error amplifier is 74.7dB,the phase margin is 58 degrees,and it has higher DC gain and better stability.The system simulation results show that the input voltage range of the DC-DC converter module is 8 ~ 20 V,the output voltage is 5V,the operating frequency is 1MHz,the ripple voltage is less than 20 mV,and the conversion efficiency is up to 92%.At the same time,it can also be seen from the system simulation that the designed DC-DC has good linear regulation and load regulation. |
PDF Full Text Request