Peak Current Mode Control With Emulated Ramp For Buck Converter

Switched-mode converters are widely used in power supply applications,such as communications,servers,electric vehicles and aerospace,thank for their high efficiency,small size,light weight,good performance and so on.As a popular control method for switched-mode converters,peak current control has the advantages of current limiting capacity,better dynamic performance and better current sharing capacity for paralleled modules.However,it has poor anti-interference ability.This thesis studies the peak current control method based on emulated current ramp,where the current signal is constructed by adding the valley value of the inductor current and the ramp generated by an additional circuit consisting of a resistor and a capacitor.Thus,the case that the PWM comparator turn off mistakenly caused by leading edge spikes of the switch current signal is avoided.In this thesis,the principle of peak current control is analyzed firstly,and it is pointed out that the anti-interference ability is insufficient.Then,the principle of peak current mode control with emulated current ramp is introduced and studied.After that,the models of the the power stage and the control loop of the buck converter based on the emulated current mode control are built,and the small-signal model of converter system and the closed-loop transfer function are derived.According to the derived model,the closed-loop parameters design of current loop and voltage loop of the converter is given.The performance of system-level design is verified by using MATLAB,and the emulated current control and peak current control are compared and the simulation of Saber verifies that the emulated current control can effectively avoid the false turn-off problem caused by the leading edge spikes.The steady state performance and dynamic performance of the emulated current control are also simulated and verified.Finally,a prototype is developed,and the theoretical analysis is verified by experiments.