Hybrid phase shifted full bridge and LLC half bridge DC–DC converter for low‐voltage and high‐current output applications

The phase-shift modulation (PSM) brings wider voltage-gain range compared with pulse-frequency modulation (PFM) control to the LLC resonant converter in particular occasions such as battery charging converters. Current researches have less discussion about the converter current transfer gain especially at low voltage-gain range. The switching frequency is much increased and high circulating current occurs under low voltage range, which brings large error in the fundamental harmonic approximation analysis. This work has proposed a numerical derivation method to derive the accurate transfer gain for LLC converters with PSM + PFM control. The accurate model and equations for resonant variables are built by the static state-plane analysis. With the help of the iteration algorithm, numerical solutions are got for the resonant variables. The output current gain and the loss estimations are acquired and discussed at each operating point. The results also indicate that there are multiple solutions for the control variables, switching frequency and phase-shift angle, at the same output point. The loss optimisation method is proposed and the losses on the switches are optimised by using lower switching frequency and greater phase angle. The simulation approach and the experiment prototype test have both proved the theoretical calculations and the optimisation results.

Section: Loss Of the Switches Estimations On The Constant Current Linmentioning

confidence: 99%

State variable derivation with numerical approach and efficiency optimisation method for phase‐shift LLC converters under wide voltage‐gain range

Liu

Zhang

2019

“…However, the extra power losses are introduced in these topologies and the circuit efficiency cannot be improved significantly. Soft-switching techniques [12][13][14][15] applied to two-level or three-level converters have researched and developed to diminish switching losses on power devices, increase circuit efficiency and decrease converter size.…”

Section: Introductionmentioning

confidence: 99%

Hybrid full‐bridge converter for DC microgrids: analysis and implementation

Lin

2018

This study presents a soft-switching converter for direct current microgrid applications. The studied converter includes n cells of the hybrid full-bridge converter with primary-series-secondary-parallel connection for high-voltage input and large current output applications. Thus, the voltage stress of power switches and the current stress of rectifier diodes are decreased. Therefore, the low-voltage stress and low conduction resistance of power metal-oxide-semiconductor field-effect transistors are utilised in the studied converter to reduce conduction losses on power switches. The flying capacitors are connected between each circuit cell to prevent voltage unbalance on input split capacitors. On each circuit cell, a full-bridge converter with an additional half-bridge circuit is employed to achieve low circulating current losses, less output inductance and a wide range of zero-voltage switching. Finally, the studied converter with 1800 W rated power is constructed and tested to verify the theoretical analysis.

“…Switching power converters are widely employed for power conversion purposes. Among these converters, DC-DC converters are frequently applied to produce a regulated DC voltage as a boost or buck converter [1][2][3]. Moreover, this type of power converter usually operates as a power supply providing the voltages required by the electronic circuits.…”

Section: Introductionmentioning

confidence: 99%

Soft‐switching DC–DC Cuk converter operating in discontinuous‐capacitor‐voltage mode

Poorali

Adib

Farzanehfard

2017

This paper proposes an improved topology for the conventional DC-DC Cuk converter operating in discontinuouscapacitor-voltage mode which provides soft-switching conditions for all the semiconductor devices. The improved topology has only three passive components in addition to the elements of the conventional counterpart, an extra winding, an auxiliary diode, and an auxiliary inductor. Therefore, without using any extra active switch, the soft-switching operation is attained and the switching losses are reduced. In the proposed converter, the power switch turns on and off under zero-current-switching and zero-voltage-switching conditions, respectively. In addition, the switch current is reduced in comparison with the conventional Cuk converter resulting in lower current stress. Also, the leakage inductance energy is recycled and continuity of the input and output currents are preserved. It is shown that reduction of the switch current and soft-switching operation improves the overall efficiency. Analysis of the proposed converter together with the design guidelines is presented. Moreover, the experimental results of a 100 W prototype producing −24 V from 150 V input voltage are provided and compared with the results obtained from a similar prototype of the conventional Cuk converter.