One of the key challenges in driving multiple light-emitting-diode (LED) strings for a liquid-crystal-display (LCD) backlight system is to ensure uniform current control. Unequal current sharing between the strings is due to manufacturing spread and temperature variations. In this paper, a novel current-balancing circuit for LED backlights is proposed. A smart combination of an inherent symmetry of circuit and capacitive balancing mechanism enables an efficient and cost-effective current balancing. The operating principle of the proposed method is analyzed, and an appealing generalization is made. The feasibility of the proposed scheme is verified by developing a hardware prototype with a dimming feature to drive a 100-W edge-type backlight system, having six LED strings for a large-scale LCD panel.

This paper proposes and analyzes a new bridgeless flyback power factor correction rectifier for ac-dc power conversion. By eliminating four bridge diodes and adding a few circuit elements, the proposed rectifier reduces the primary side conduction loss and improves efficiency. The addition of the new elements has minimal effect on the circuit simplicity because it does not need any additional gate driver and magnetic elements. The losses in the semiconductor devices of the proposed circuit are analyzed and compared with that of the conventional one, followed by transformer design guideline. Experimental results with the practically implemented prototype prove its higher efficiency than its conventional counterparts.

The I–V curve serves as an effective representation of the inherent nonlinear characteristics describing typical photovoltaic (PV) panels, which are essential for achieving sustainable energy systems. Over the years, several PV models have been proposed in the literature to achieve the simplified and accurate reconstruction of PV characteristic curves as specified in the manufacturer’s datasheets. Based on their derivation, PV models can be classified into three distinct categories: circuit-based, analytical-based, and empirical-based models. However, an extensive analysis of the accuracy of the reconstructed curves for different PV models at the maximum power point (MPP) has not been conducted at the time of writing this paper. The IEC EN 50530 standard stipulates that the absolute errors within the vicinity of MPP should always be less than or equal to 1%. Therefore, this review paper conducts an in-depth analysis of the accuracy of PV models in reconstructing characteristic curves for different PV panels. The limitations of existing PV models were identified based on simulation results obtained using MATLAB and performance indices. Additionally, this paper also provides suggestions for future research directions.

In series battery strings, cell-inconsistency is caused by the state-of-charge (SOC) mismatch, nonidentical battery impedance, or different self-discharging rates, and this leads to overcharge and overdischarge. Practically, switched-capacitor equalizers are the most promising means to eliminate the cell inconsistency by virtue of automatic equalization, but the performance is heavily dependent on the initial cell voltage distribution and the number of series connections due to inefficient switch utilization. This article proposes a direct cell-to-cell equalizer for a series-connected battery using a switch-matrix single-capacitor converter to further improve the switched-capacitor equalizer in term of performance consistency and Coulomb efficiency. By adopting one extra current sensor and an optimal pairing algorithm, energy is transferred directly between the highest-SOC cell and the lowest-SOC cell to eliminate the impact of battery-impedance difference and false voltage measurement in battery monitoring integrated circuit caused by polarization effect. The experimental results verify the feasibility of the proposed scheme. Real-time tests are also implemented to fairly compare the proposed with the conventional methods. It is found that the performance of the proposed method is independent from initial voltage distribution in a series string, where the performance indices are consistent regardless of initial conditions. Besides, the energy loss of the proposed equalizer is further reduced and its overall efficiency is high in all test scenarios.

An investigation of a high-power piezoelectric transformer (PT) as a potential component for a fluorescent lamp (FL) ballast with power factor correction (PFC) is discussed. The attractiveness of the PT is primarily the simplicity of the resulting circuit, and it is easy to be produced in mass with a low cost. A single-stage charge-pump PFC ballast using a PT is proposed. The proposed ballast circuit improved the drawbacks of the conventional voltage-source charge-pump PFC (VS-CPPFC) scheme. Empirical PT modeling based on power level excitation is performed to design the proposed circuit, and the experimental and simulation results are provided to verify theoretical analysis.

This study proposes the shaft voltage mitigation method according to change in parasitic capacitances of a permanent magnet synchronous motor. To consider the shaft voltage reduction in the initial motor design process without any filter, the parasitic capacitances affecting the shaft voltage are calculated using the motor geometry parameters. Then, the shaft voltage is analyzed according to change in parasitic capacitances using the equivalent circuit model and the torque characteristic is also analyzed to effectively mitigate the shaft voltage. As a result, the rotor-to-winding is determined as an appropriate parameter to mitigate the shaft voltage among the parasitic capacitances, because it affects the shaft voltage and does not affect the output torque. Finally, the shaft voltage mitigation method according to variation of rotor-to-winding capacitance is verified by experiment.