Study On Voltage Mode Multiple Frequency Controlled Switching Converter

Compared with traditional pulse width modulation (PWM) control, the control circuit of voltage mode multi-frequency control technology for switching converter is not only simple, but also it has fast response. Compared with voltage mode bi-frequency modulation technique, voltage mode multi-frequency control technology has the advantages of small output voltage ripple and fast response. At present, the research on voltage mode multi-frequency control technology for Buck converter is limited to the inductor current discontinuous conduction mode (DCM), which severely limits the output power. The principle and characteristic of voltage mode multi-frequency voltage control for Buck converter which is as an example are studied.The principle of voltage mode multi-frequency control technology is discussed. The voltage mode multi-frequency control for DCM Buck converter is studied. The control pulse combination and stable working range of the Buck converter operating in a steady-state is also analysed. The simulation model is built to verify the correctness of the theoretical analysis by using PSIM software.In order to improve the converter output power, voltage mode multi-frequency control technology for Buck converter which is operated in continuous conduction mode of inductor current (CCM) is studied. When the equivalent series resistance (ESR) in the output capacitor is relatively large, the control pulse combination and the fluctuation of the output voltage in a control pulse cycle is analysed carefully. When the equivalent series resistance in the output capacitor is relatively small, Buck converter will appear low-frequency oscillation phenomenon. The reason of low-frequency oscillation phenomenon is analysed.For low-frequency oscillation phenomenon is appeared in CCM Buck converter, voltage mode Multi-frequency control technology for Buck converter which works in pseudo continuous conduction mode (PCCM) is studied. When PCCM Buck converter works on the stability, the control pulse combination, the stable working range and the output voltage fluctuation in a control pulse cycle are analyzed. Voltage mode multi-frequency control technology for PCCM Buck converter can effectively avoid low-frequency oscillation phenomenon, and simulation model is built to verify the correctness of theoretical analysis by using PSIM software.Each circuit of voltage mode Multi-frequency control technology for Buck converter is designed in this paper at last. The experimental prototype is built to verify the correctness of simulation and theoretical analysis.