Tri-State Power Factor Correction Converter Topology And Control Technique

In order to eliminate harmonic pollution in electric power network and improve power factor (PF), the input terminal of electronic equipments need to add active power factor correction (PFC) converter. The PFC converter with constant switch frequency can operate in discontinuous conduction mode (DCM) or continuous conduction mode (CCM). The PFC converter is designed to operate in DCM when load is light, but high current stress of switch restrict it only to apply in small power system. When the load is heavy, the PFC converter is designed to operate in CCM. However, in order to reduce the input current distortion, which caused by the output voltage ripple related to twice of the power frequency, the low pass filter cut-off frequency of the feedback voltage loop should be decreased and that leads to poor dynamic performance of load variation.According to the problems existing in DCM and CCM PFC converter, a novel constant switch frequency PFC technique operating in pseudo continuous conduction mode(PCCM) is proposed in this paper. By utilizing the added power switch to control the power switch time sequence, which makes the inductance current or capacitor voltage of the PFC converter exist three operating modes in each switching cycle. Hence, the proposed PFC converter decouples the control variable of the control loop, which makes the control objective of the output voltage stable can be decoupled with high power factor. Compared with the dual-close-loop control of CCM PFC converter, the voltage control loops of the tri-state PCCM PFC converter is independent of the current control loop, which decreases the difficult of controller design and increase the bandwidth of voltage loop. Dynamic response speed of the tri-state PCCM PFC converter also can be improved. Besides, compared with DCM PFC converter, the tri-state PCCM PFC converter extends the load range and the inductance is not restricted by operating modes.In this paper, the tri-state PCCM Boost PFC converter is systematically studied. By connecting a power switch and a diode in parallel with the inductor of boost converter, which provides an additional inductance current route. Hence, the inductance current of the tri-state PCCM Boost PFC converter has three working modes in each switching cycle.The tri-state PCCM Boost PFC converter also is analyzed, such as the stable-state character, the controller design, input current and PF. Although the tri-state PCCM Boost PFC converter has good steady and transient performance, but the efficiency of the converter is low because of the additional power switch. Hence, the paper further presents the two-switch tri-state PCCM Buck-Boost PFC converter which has two power switches itself and the tri-state PCCM can be realized by controlling sequence of the power switch. Favorable steady and transient performance of the two-switch tri-state PCCM Buck-Boost PFC converter can be obtained. Because of the conduction losses of the diode is larger than that of the power switch, so the efficiency of the two-switch tri-state PCCM Buck-Boost PFC converter can be promoted.In order to expend the application range of the tri-state PCCM PFC technique, the isolated tri-state PCCM Flyback PFC converter is also proposed and studied. Compared with traditional DCM Flyback PFC converter, the tri-state PCCM Flyback PFC converter can reduce the voltage stress of the power switch and extend the load range. Hence, the proposed converter can be used in the isolated and heavy load situation.Based on the duality principle, the non-isolated tri-state PCCM CUK PFC and isolated tri-state PCCM SEPIC PFC converter are proposed and studied. Three operating modes are obtained by connecting a power switch in series with the storage capacitor. By time average equivalent principle, the paper research DC steady state analysis of the tri-state PCCM CUK PFC converter. The results show that the tri-state PCCM CUK PFC converter can be equivalent to cascade Boost converter and Buck converter. So compared with traditional DCM and CCM CUK PFC converter, the output voltage ripple in the twice of the power frequency of the tri-state PCCM CUK PFC converter is very low and gets a fast load dynamic response.In order to verify the correctness of the theoretical analysis, a mass of simulation results are provided, and corresponding prototypes in lab is set up to present experimental results. Simulation and experimental results have a good agreement with the theoretical analysis presented in this dissertation.