Simple low‐cost ZVS bidirectional forward converter with phase shift control and voltage matching for low power applications

Abstract

In this study, a new zero‐voltage switching (ZVS) output inductor‐less bidirectional forward (OILBF) converter is presented. The OILBF has two diodes less than the conventional forward converter and is convenient for low‐power bidirectional applications. Moreover, the OILBF converter uses the leakage inductance of transformer as the forward inductor. In the proposed OILBF, two capacitors paralleled with main switches realise ZVS conditions for main switches in both directions without any auxiliary switches. Also, the reset of the converter transformer is done without any additional circuit. The proposed converter structure due to employing simultaneously OILBF topology with the simple auxiliary soft‐switching circuit is simple and low cost. The ZVS soft‐switching range is from light load to full load which enhances the converter efficiency. Phase shift is applied with the proposed converter. The proposed converter is completely analysed and its design approach is considered. Finally, an experimental prototype is implemented to verify theoretical results.

An improved wide ZVS soft‐switching range PWM bidirectional forward converter for low power applications with simple control circuit

“…The efficiency of the proposed converter is measured 97.46% and 96.28 % at the buck and boost directions, respectively. As shown in Figure 11a, the efficiency of the proposed converter is higher than [27], because the circulating current decreases to minimum during the load variations. At the buck direction, at the high voltage side, the channel of the MOSFET S H conducts the main current and at the low voltage side, the body diode of the MOS-FET S L conducts the main current, at the buck direction, this…”

“…Several bidirectional forward converters are presented in [22]- [27]. The proposed converter in [22] employs PWM (Pulse Width Modulation) control and operates in discontinuous conduction mode (DCM).…”

“…However, two auxiliary switches along with their complex control circuits and ZCS technique along with the capacitive turn-on losses are drawbacks of [26]. A bidirectional dc-dc ZVS forward converter with the phase shift voltage matching control approach is proposed in [27] without any auxiliary switches and with constant frequency. However, a constant circulating current along with the voltage matching is employed to provide the wide range ZVS soft switching which increases the conduction losses and degrades the efficiency especially in the low powers.…”

“…However, a constant circulating current along with the voltage matching is employed to provide the wide range ZVS soft switching which increases the conduction losses and degrades the efficiency especially in the low powers. In [27], the voltage matching can easily be destroyed when the input voltage changes slightly which ruins the ZVS soft switching range. Moreover, in practice implementing the phase shift control is more complex in comparison to the conventional PWM control.…”

“…In this paper, a bidirectional ZVS soft switching PWM forward converter is proposed to eradicate the drawbacks of [27]. In the proposed converter, the PWM control approach and the high value of the magnetizing inductance solve the problems related to the circulating current and the phase shift voltage matching control.…”