The Novel Control Techniques Of Switching Converters Based On Multi Pulse Train Modulation

With the rapid development of power electronics and information techniques, the electrical equipments require switching supplies with high performances, including fast transient response, low output voltage ripple, accurate output voltage regulation and great stability. In order to address the challenges above and improve the performances of switching converters, the novel control techniques based on multi pulse train (MPT) modulation for switching converters are proposed and studied in this dissertation. The main contents and conclusions of this dissertation are depicted as follow.Ⅰ. The characteristic and implementation of voltage mode/current mode pulse train (PT) control techniques are studied. The steady state performance and start-up state performance of voltage mode/current mode PT controlled Buck converter operating in discontinuous conduction mode (DCM) are analyzed. The study results indicate that when the load increases, both voltage mode PT controller and current mode PT controller will generated more Ph control pulses. When the input voltage increases, voltage mode PT controller will generated more PL control pulses, and current mode PT controller will generated more PH control pulses. Current mode PT controlled converter enjoys smooth start-up process. The large difference of the energy delivered in PH control pulse cycle and in PL control pulse cycle causes large output voltage ripple.Ⅱ. The novel multi pulse train (MPT) modulation method, and MPT based voltage mode/current mode control techniques are proposed. The principle and implementation of voltage mode/current mode MPT control techniques are introduced. The output voltage variation and the control pulse proportion of voltage mode/current mode MPT controlled DCM Buck converter are analyzed. The design process of the control parameters are provided. The output voltage ripple of the converter in steady state is calculated. The light load mode of MPT technique is proposed and studied. The theoretical foundation that causes the great performance of MPT technique is illuminated. The simulation and experimental analysis of voltage mode/current mode MPT control techniques are performed. The study results indicate that MPT based control techniques are simple and practicable, they also enjoy great transient performance. Compared with PT technique, the novel MPT technique can reduce the output voltage ripple of the converter effectively.Ⅲ. Current referenced pulse train (CRPT) control technique for switching converters is proposed. The principle and implementation of CRPT are introduced. For CRPT control method, the design process of control parameters, the output voltage variation, the proportion and combination of control pulses, the voltage ripple, the light load mode are studied respectively. The small signal model of CRPT controlled DCM Buck converter is set up. CRPT controlled Boost converter and Buck-Boost converter are analyzed briefly. The universal equation for CRPT controlled basic converters is given. The control theories of PT, MPT and CRPT techniques are compared with each other. The simulation and experimental analysis of CRPT control technique are performed. The study results indicate that CRPT control technique is simple and practicable, and it also enjoys great transient performance. Compared with PT technique, CRPT technique can reduce the output voltage ripple obviously. Compared with MPT technique, CRPT technique can improve the output voltage accuracy effectively.IV. For the switching converters, the recurrence relations of energy transfer are studied. The energy recurrence models of voltage mode MPT controlled and CRPT controlled Buck converter are set up. By the energy track and the recurrence relation of output voltage, the performance and physical phenomenon are illustrated. The study results indicate that the physical meaning of the energy recurrence model is clear. By observing the energy track, the variation of the energy stored in the capacitor, the control pulse combination and the transient process of the converter can be obtained. For MPT converter, the energy track will encircle several different energy reference values, and for CRPT converter, the energy track will encircle single energy reference value. Compared with PT converter, the energy and output voltage variations of MPT converter and CRPT converter are much smaller. The output voltage of CRPT converter is accurate. The repetition state of multi switching cycles will not affect the operation of the converter. There are bifurcations and no chaos existed in MPT converter and CRPT converter. The parasitic parameter will not affect the stability of converter.