Abstract
Magnetic components are important parts of the phase shifted full bridge (PSFB) converter. During the dead-time of switches located in the same leg, the converter can achieve zero-voltage-switching (ZVS) by using the energies stored in magnetic components to discharge or charge the output capacitances of switches. Dead-time is usually calculated under a given set of pre-defined load condition which results in that the available energies are insufficient and ZVS capability is lost at light loads. In this paper, the PSFB converter is controlled by variable dead-time method and thus full advantage can be taken of the energies stored in magnetic components. Considering that dead-time has a great effect on ZVS, the relationship between available energies and magnetic component values is formulated by analyzing the equivalent circuits during dead-time intervals. Magnetic component values are chosen based on such relationship. The proposed choice procedure can make the available energies greater than the required energies for ZVS operation over a wide range of load conditions. Moreover, the burst mode control is adopted in order to reduce the standby power loss. Experimental results coincide with the theoretical analysis. The proposed method is a simple and practical solution to extend the ZVS range.
Highlights
By using parasitic circuit elements such as junction capacitances of switches and leakage inductance of transformer, phase-shifted full-bridge (PSFB) converter provides zero-voltage-switching (ZVS) for switches without requiring any additional active devices [1,2]
The light-load efficiency of the converter with the proposed variable dead-time control method can be significantly improved since switching loss is dominant in Cases 2 and 3 operations
By analyzing the equivalent circuits during dead-time intervals in a PSFB converter, a variable dead-time control method and choice procedure of magnetic component values are presented in this paper
Summary
By using parasitic circuit elements such as junction capacitances of switches and leakage inductance of transformer, phase-shifted full-bridge (PSFB) converter provides zero-voltage-switching (ZVS) for switches without requiring any additional active devices [1,2]. These characteristics can reduce switching loss and enable high switching frequency operation. Such advantages make the PSFB converter well suited for high efficiency, high power density and high reliability applications [3,4].
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