Design And Implementation Of BUCK Converter With Fast Response

With the coming of semiconductor technology and the wide application of switching power supplies,DC-DC converters are playing an increasingly important role.The DC-DC converter's control method also develops more and more diversified from the earliest voltage mode current mode.The current mode control BUCK converter has advantages such as simple compensation loop and fast transient response,and it is durable.With the rapid development of various control methods,the current mode is still unique and widely used.In this context,this paper presents a BUCK converter based on peak current mode architecture.From the application requirements,design the BUCK converter inductance capacitance value.According to the input voltage range,the power supply selection module is designed for the system internal supply voltage.For the current-mode current sampling problem,this design uses a DCR current sampling method based on the parasitic resistance of the inductor.For loop stability problems,this paper uses the pseudo TYPE III compensation method.For the problem of sub-harmonic oscillation of the current mode,this paper deduces the appropriate slope compensation amount from the Q value of half the switching frequency and guides the design.With high output capacitance,high-bandwidth op amps are designed to improve loop stability and transient response.When the system is working,the soft start is used to power on and the hiccup mode is used to deal with unexpected situations such as over-current and over-temperature.In this paper,several control methods for BUCK converter are analyzed in detail.The stability of each control method is modeled,and the loop stability conditions are introduced.Based on this,a loop compensation scheme suitable for different control modes is given.Based on the Dongbu 0.35?m BCD process,this paper designs the relevant circuit submodules,and guides the design of the peak current mode loop according to the loop modeling results.Use the simplis tool to perform loop stability simulations for both typical and large capacitive loads respectively to verify the design reliability.The cadance tool was used to verify the transient operating characteristics of the two operating conditions,including inductor current ripple,output capacitor ripple,load transient response,and linear transient response.Verify loop transient performance at high duty cycle.Under the situation of light loads,zero-crossing detection circuitry is used to sense the current to improve system efficiency at light loads.In the case of outputting large capacitive loads,high-bandwidth op amps and other passive devices are added to the original loop system,which increases the stability of the system and increases the unit gain bandwidth of the loop,thereby increasing the speed of transient response.Finally,the simulation validated the system efficiency at heavy loads and light loads.