Abstract
In this paper, a switching method is proposed for power device temperature-balancing in a phase-shift full-bridge (PSFB) converter. PSFB is commonly used for applications that require high efficiency, because a zero-voltage switching (ZVS) operation is possible on the primary-side. In PSFB, the circulation current complicates ZVS under a light-load condition, which generates heat. Meanwhile, the heat generated in PSFB creates a temperature deviation between the lagging leg and the leading leg, which shortens the lifetime of the power device, thereby reducing system reliability and efficiency. To solve this problem, previous studies applied a pulse-width modulation (PWM) switching method for light and medium loads, and a phase-shift switching method for the region where ZVS is possible. Although this method has the advantage of easy control, the maximum temperature of the legs of the PSFB increases with medium loads. In this paper, a temperature-balancing algorithm—a temperature-balance control—is proposed to decrease the leg temperature using switching based on position exchanges of the leading leg and lagging leg along with PWM switching. Temperature-balance control minimizes leg temperature deviation under light load conditions. The proposed control method provides a minimum temperature difference between the two legs and high efficiency.
Highlights
A phase-shift full-bridge (PSFB) converter is a topology for achieving zero-voltage switching (ZVS) in power devices by applying a simple control method
According to the load current, the switching current are provided to the feedback through digital signal processing (DSP), and the control modeprogresses is divided into two types: the conventional pulse-width modulation (PWM) switching control and phase-shift switching by calculating the errors between them and references
Temperature balancing is proposed under a light-load condition in a PSFB converter
Summary
A phase-shift full-bridge (PSFB) converter is a topology for achieving zero-voltage switching (ZVS) in power devices by applying a simple control method. The PWM switching method is used to reduce the initial circulating current to increase efficiency, and from the load condition where ZVS can be achieved, the phase-shift switching method is used to increase efficiency. In the case of the phase-shift switching method, the ZVS region differs between legs [13,14] These regions occur at light loads and result in reduced efficiency. PSFB converter decreases efficiency due to hard switching operation and magnetic core loss under the light-load conditions [17]. To resolve this issue, the PWM control operates in the light-load state.
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