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This paper proposes a modified bridge switch-type flux-coupling nonsuperconducting fault current limiter (BSFC-NSFCL) for suppressing the fault current and voltage sag. A flux-coupling reactor and a bidirectional bridge switch are combined to perform the functions of steady-state line current sharing and fault current suppression. The modified BSFC-NSFCL mainly utilizes the magnetic flux cancellation effect to make the limiter behave as a short circuit on the circuit during normal operation. Hence, there is almost no impact on the power system when the limiter is used. When a fault event occurs, the bridge switch turnsoffimmediately, and then, the magnetic flux cancellation effect disappears. Thus, the impedance of primary coil inserts into the circuit to restrict the fault current and voltage sag phenomena. Once the fault is removed, the bridge switch turnsonagain, and the BSFC-NSFCL recovers to the normal operation. The modified NSFCL is more cost-effective and easy to be implemented than the flux-coupling superconducting fault current limiter. Theoretical analysis for the BSFC-NSFCL has been fully developed and proven by MATLAB software. Finally, the analytical, simulated, and experimental results have been carried out to verify the feasibility and performance of the proposed BSFC-NSFCL. [ABSTRACT FROM AUTHOR]

As compared with the buck converter, the ultrahigh step-down converter can achieve a much higher step-down gain, which can be determined by not only the duty cycle, but also the turns ratio of the coupled inductor. However, this converter suffers from some problems, such as pulsating output current and large dc magnetizing inductance current, which will degrade the core utilization. As compared with the ultrahigh step-down converter, the coupled-inductor-based high step-down converter features a nonpulsating output current and a zero dc magnetizing inductance current. Therefore, the output current ripple is lower and the core utilization can be upgraded. Since the core size is proportional to the square of the applied flux-linkages, an improved coupled-inductor-based high step-down converter is presented herein. By employing an auxiliary circuit, consisting of a small capacitor and a mosfet, the flux linkage of the coupled inductor can be decreased, and hence the required core size can be reduced. In addition, due to the auxiliary circuit, the voltage spike across the tapped switch can be reduced. Above all, the step-down gain can be improved. Finally, detailed theoretical analyses and experimental results are provided to verify the feasibility and effectiveness of the proposed converter. [ABSTRACT FROM AUTHOR]

Even though the coupled-inductor-based high-step-down-ratio converters can achieve a higher step-down voltage gain than the traditional buck converter, their output current suffer from a high output current ripple, causing a high output voltage ripple. Therefore, a bulky electrolytic output capacitor is usually used to suppress the output voltage ripple. Moreover, the longevity of the output electrolytic capacitor is highly dependent on the output current ripple. In [6–8], a passive current ripple cancellation circuit was applied to the DC–DC converters to reduce the output current ripple. However, these literatures did not mention and analyze the situations for coupled-inductor converters. Moreover, the same concept, including analysis and design, cannot be directly applied to the coupled-inductor-based converters. Therefore, in this paper, the analysis, design, and experimental results of the current ripple cancellation circuit applied to the coupled-inductor-based high-step-down-ratio converter are given to verify the effectiveness. [ABSTRACT FROM PUBLISHER]

In this study, a voltage superposition concept is used without phase adjustment of the input current command and without enlarging the turn-on period of the switch in the vicinity of the zero input voltage, but only with a few components added to the PFC converter, so as to improve the zero-crossing distortion of the input current, thereby further reducing the total harmonic distortion. Eventually, the mathematical deductions and experimental results are provided to verify the effectiveness of the proposed circuit. [ABSTRACT FROM AUTHOR]

In this paper, an input-current-ripple-free two-channel light-emitting diode (LED) driver is presented. In the proposed LED driver, a current-sharing capacitor is integrated into the boost converter to achieve the current-sharing among the LEDs and to enhance the output voltage gain. Moreover, an input current ripple cancellation circuit is employed to eliminate the input current ripple. Finally, the operating principle, analysis, and experimental results are provided to verify the effectiveness of the proposed LED driver. [ABSTRACT FROM PUBLISHER]

In this paper, an LLC light-emitting diode (LLC LED) driver based on the current-sharing capacitor is presented. In the proposed LED driver, the LLC resonant converter is used to step down the high input voltage, to provide galvanic isolation, to offer a constant current for LEDs. Moreover, the current-sharing capacitor connected to the central-tapped point of the secondary-side winding is used to balance the currents in two LED strings. By doing so, the voltage stress on this capacitor is quite low. Above all, the equivalent forward voltages of the two LED strings are generally influenced by the temperature and the LED current, and this does not affect the current-sharing performance, as will be demonstrated by experiment on the difference in number of LEDs between the two LED strings. In addition, only the current in one LED string is sensed and controlled by negative feedback control, while the current in the other LED string is determined by the current-sharing capacitor. Moreover, this makes the current control so easy. Afterwards, the basic operating principles and analyses are given, particularly for how to derive the effective resistive load from the LED string. Eventually, some experimental results are provided to validate the effectiveness of the proposed LED driver. [ABSTRACT FROM AUTHOR]

A modified step-down converter is presented herein, which is mainly based on one coupled inductor and several energy-transferring capacitors to improve the voltage conversion ratio as well as to reduce the switch voltage stress. In addition, the portion of the leakage inductance energy can be recycled to the input via the active clamp circuit during the turn-off period and the switches have zero-voltage switching (ZVS) during the turn-on transient. In this paper, the basic operating principles of the proposed converter are firstly described and analyzed, and its effectiveness is finally demonstrated by experiment based on a prototype with input voltage of 60 V, output voltage of 3.3 V and rated output power of 33 W. [ABSTRACT FROM AUTHOR]