Loop Gain Test Of Switching Converter

In the field of power electronics technology and all kinds of power supply systems,the switching converter technology is in the core position.The loop gain of the switching converter is a way to reflect the "dynamic" characteristics of the system in the frequency domain and also a powerful tool to detect whether the system design is reasonable.Loop gain can often be measured by frequency response analyzer,but frequency response analyzer equipment is very expensive,not easy to carry and the test is complex.Therefore,it is necessary to study a low-cost and convenient way to measure the loop gain of switching converters.An online measurement method for DC-DC converter loop gain based on cross-correlation algorithm is proposed in this thesis.Beside,on this basis,an on-line fault diagnosis function is designed for detecting the failure of the core components on the main circuit.Firstly,the basic concepts and principles of loop gain and cross-correlation algorithms are introduced in this thesis.Based on the introduction of the existing loop gain measurement methods,namely sinusoidal signal perturbation measurement method and pseudo-random sequence perturbation measurement method,the principle and design scheme of the new measurement in this thesis are presented by mathematical theoretical formula.Beside,the basic principle of circuit fault diagnosis is explained.Secondly,buck circuit of DC-DC converter is selected as the basic structure of the test platform.The main device parameters of buck circuit,the compensator of control circuit and the sampling frequency of digital circuit are designed reasonably in this thesis.Then,the simulation model was built in PSIM software.By using sweep module in PSIM software,the sweep simulation of the main circuit is carried out under consideration of noise interference.Using the simulation results by sweep module from PSIM software to compare with the simulation result by using the method in this thesis,the theoretical analysis of the measurement method in this thesis was proved to be correct on the basis of detailed analysis and comparison of theresults.By means of the measurement method in this thesis,the loop gain variation interval under different fault states is measured,and the fault judgment basis of the circuit is established.Finally,the experimental hardware test platform is built,and the design ideas of the hardware components and software components are introduced.Using the frequency response analyzer to measure the gain curve of the experimental platform,as a standard reference for digital test results,analyze the experimental test results and the causes of errors in this thesis,and prove the feasibility of the test method in this thesis.Based on this,the fault state of the circuit is simulated,and the online fault diagnosis function is verified.