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In this paper, a nonisolated two-phase interleaved LED driver with capacitive current sharing is presented. In the proposed LED driver, the current sharing capacitor can be used to balance the input inductor currents and the LED currents. Furthermore, only one grounded LED string current is sensed and controlled. Moreover, under the interleaved control, the input current ripple can be reduced. Finally, the operating principles, analyses, and experimental results are provided to verify the effectiveness of the proposed LED driver. [ABSTRACT FROM PUBLISHER]

In the high step-down voltage applications, the dc–dc converter with a high step-down voltage conversion ratio is usually used. Recently, a high step-down converter, named ultrahigh step-down converter, has been presented. As compared with the nonisolated tapped-inductor buck converter, the ultrahigh step-down converter has not only a higher voltage step-down gain but also a lower voltage spike. On the other hand, in the high-current applications, a multiple phase structure is preferable. Therefore, in this paper, a novel expandable two-phase interleaved ultrahigh step-down converter with automatic current balance is presented, which is derived from the existing single-phase ultrahigh step-down converter. There are four main advantages of the proposed converter. First, the step-down voltage gain is improved. Therefore, the turns ratio of each phase can be decreased. Second, due to the charge balance of the energy-transferring capacitor, the proposed two-phase ultrahigh step-down converter possesses an automatic current balance. Third, as compared with a single-phase ultrahigh step-down converter, the output current ripple can be reduced. Fourth, the phase number of the proposed converter can be expanded. Finally, the basic operating principle of the proposed converter is analyzed, and a prototype is constructed to verify its effectiveness by some experimental results. [ABSTRACT FROM PUBLISHER]

In this paper, a single-switch coupled-inductor-based two-channel light-emitting diode (LED) driver with a passive regenerative snubber is presented. In the proposed LED driver, the energy-transferring capacitor is not only used to step up the voltage gain but also to achieve the current balance among LED strings. Moreover, a passive regenerative snubber is added not only to recycle the leakage inductance energy but also to improve the voltage gain. As compared with the prior work, only one switch is required. Thus, the configuration of the proposed LED driver is simpler. Since the proposed LED driver has a higher voltage gain than the prior work, the turns ratio of the proposed LED driver can be lower. Thus, the magnetic core size can be reduced. In addition, both LED drivers have the same component count. Finally, the operating principle, analysis, and experimental results are provided to verify the effectiveness of the proposed LED driver. [ABSTRACT FROM AUTHOR]

In this paper, a nonisolated two-channel light-emitting diode (LED) driver with automatic current balance and zero-voltage switching (ZVS) is presented. In this LED driver, a dc-blocking capacitor is connected with one side of the coupled inductor. Therefore, based on the ampere–second balance, a current source is generated with the average value of the positive current identical to the absolute average value of the negative current. Accordingly, the LED currents can be balanced naturally without extra active components or current sharing transformer. Consequently, the circuit components can keep at a low count. In addition, the proposed LED driver can achieve ZVS turn-on. Thus, the switching loss can be decreased. Above all, the proposed two-channel LED driver can be extended to a multichannel LED driver. In this paper, detailed theoretical analyses and experimental results are provided to verify the feasibility and effectiveness of the proposed LED driver. [ABSTRACT FROM AUTHOR]

In this paper, a novel four-phase interleaved high step-down converter is presented. The proposed converter can provide an extremely high step-down voltage conversion ratio within a moderate duty cycle. There are four main advantages of the proposed converter. First, the blocking capacitors can store energy as usual. Therefore, they are used as voltage sources to reduce the input voltage as well as to reduce the switch voltage stresses. Second, due to the charge balance of the dc blocking capacitors, the converter possesses an automatic uniform current sharing characteristic of the interleaved phases without adopting any extra circuitry. Third, due to the phase shift between the interleaved phases, the architecture provides a low output current ripple. Fourth, the number of phases can be expanded or reduced to any even phases; therefore, the converter has a wide range of applications. Finally, the operating principles and analysis of this architecture are given, and an experimental prototype is also provided to verify the effectiveness of the proposed converter. [ABSTRACT FROM PUBLISHER]

A nonisolated coupled-inductor-based high step-down converter with zero dc magnetizing inductance current and nonpulsating output current is presented. Since the dc magnetizing inductance current is zero, the magnetizing current can be positive and negative. Therefore, the entire core B–H loop can be used, ranging from the first quadrant to the third quadrant. That is, the utilization of the coupled inductor can be improved and, hence, the core loss can also be reduced. Moreover, due to a discrete output inductor, the proposed converter also features a nonpulsating output current, which makes the output current ripple smaller. In this paper, detailed theoretical analyses and experimental results are provided to verify the feasibility and effectiveness of the proposed converter. [ABSTRACT FROM AUTHOR]

In this paper, an ultrahigh step-down converter is presented, which combines one coupled inductor and one energytransferring capacitor. The corresponding voltage conversion ratio is much lower than that of the traditional synchronously rectified (SR) buck converter, and the proposed converter can achieve extremely low output voltage with an appropriate duty ratio. Moreover, there are three major merits in the proposed converter. One merit is that the voltage conversion ratio of the proposed converter is linear, thereby making control quite easy. Another merit is that if one of the switches fails or is abnormally controlled, a high voltage does not appear in the output terminal, so the output load can be protected. The other merit is that the proposed converter can be driven using the existing SR buck pulse-width modulation control integrated circuit. In this study, brief theoretical deductions and some experimental results are given to verify the feasibility and effectiveness of the proposed converter. [ABSTRACT FROM AUTHOR]

As generally acknowledged, the high step-up dc-dc converter is widely used in the sustainable energy system as the front-end stage of the dc-ac converter. Therefore, a high step-up converter combining one coupling inductor and two bootstrap capacitors, together with the active voltage-clamping circuit which pumps portion of the leakage inductance energy to the output, is presented herein. By doing so, the efficiency at light load can be upgraded greatly, and hence tends to be flat between the minimum load and the rated load. In this letter, the basic operating principles of this converter are first illustrated in detail, and second some experimental results are provided to demonstrate the effectiveness of the proposed high step-up converter topology. [ABSTRACT FROM AUTHOR]

In this paper, novel high voltage-boosting converters are presented. By changing the connection position of the anode of the diode and by using different pulse-width-modulation control strategies, different voltage conversion ratios can be obtained. These converters are constructed based on bootstrap capacitors and boost inductors. Above all, two boost inductors with different values, connected in series, can still make the proposed converters work appropriately. Furthermore, although there are three switches in each converter, only one half-bridge gate driver and one low-side gate driver are needed, but no isolated gate driver would be needed. After some mathematical deductions, some experimental results are provided to verify the effectiveness of the proposed converters. [ABSTRACT FROM PUBLISHER]

In this letter, a buck-boost converter, i.e., 2D converter with a positive output voltage, is presented, which combines the KY converter and the traditional synchronously rectified (SR) buck converter. By doing so, the problem in voltage bucking of the KY converter can be solved, thereby increasing the application capability of the KY converter. Since such a converter operates in continuous conduction mode inherently, it possesses the nonpulsating output current, thereby not only decreasing the current stress on the output capacitor but also reducing the output voltage ripple. Above all, both the KY converter and the SR buck converter, combined into a buck-boost converter with no right-half plane zero, use the same power switches, thereby causing the required circuit to be compact and the corresponding cost to be down. Furthermore, during the magnetization period, the input voltage of the KY converter comes from the input voltage source, whereas during the demagnetization period, the input voltage of the KY converter comes from the output voltage of the SR buck converter. [ABSTRACT FROM AUTHOR]

In this paper, a novel step-up converter is presented, where the charge pump concept, combined with the traditional boost converter structure, is utilized. Although two inductors are used in such a converter, the difference in value between the two inductors affects the regulation performance of this converter slightly. Furthermore, the behavior of this converter is similar to the traditional boost converter, and hence, the control of this converter can be realized easily. Above all, the energy stored in the two inductors, connected in series with the energy stored in the charge pump capacitor and the input voltage, is released to the load during the demagnetization period. In this paper, the basic operating principles of the proposed converter are presented along with some experimental results to demonstrate the effectiveness of this converter. [ABSTRACT FROM AUTHOR]

In this paper, a resonant voltage divider (RVD) is presented with the fixed switching frequency and used as a bus converter. The proposed RVD without any control loop embedded can reach very high efficiency from the light load to the rated load, especially for the light load. In addition, the bidirectional operation of the RVD is taken into consideration, so the RVD not only can transfer energy to the voltage-regulated module (VRM) but also can reversely transfer the energy to the dc bus during the download transient period of the VRM. However, the RVD has a serious drawback that a large surge current at startup causes components to be saturated or destroyed. Consequently, how to reduce such a current based on the proposed variable switching frequency at startup is also taken into account. In this paper, the bidirectional operation of the RVD and how to suppress the startup surge current are illustrated in detail, along with some simulated and experimental results to demonstrate its effectiveness. [ABSTRACT FROM AUTHOR]

A multifunction circuit is presented herein and applied to a synchronously rectified flyback converter, with the circuit not only playing the role of an LC snubber but also detecting the zero crossing of the current to reduce switching loss and feeding the peripheral circuit. Hence, such a converter has high efficiency all over the operating range and, together with one front-end power-factor-correction ac–dc converter, is applied to feeding a LED streetlight. In this paper, the basic operating principles of the proposed topology are first illustrated in detail, and second, some simulated and experimental results are provided to demonstrate the effectiveness of the proposed topology. [ABSTRACT FROM AUTHOR]

In this paper, a simple dimming control is presented and applied to a cold cathode fluorescent lamp (CCFL). Traditionally, the digital dimming takes back-and-fro start and cutoff of the CCFL, thereby causing current spike and hence reducing the life of the CCFL. Consequently, to overcome these problems, a dimming strategy is presented according to the frequency shift. Moreover, a full-bridge phase-shift resonant inverter is utilized to power the CCFL. Some experimental results are provided to demonstrate the effectiveness of the proposed scheme. [ABSTRACT FROM PUBLISHER]

In this letter, a KY boost converter is presented, which is the KY converter combined with the traditional synchronously rectified (SR) boost converter. Such a converter has continuous input and output inductor currents, different from the traditional SR boost converter, and has a larger voltage conversion ratio than the traditional SR boost converter does, and hence, this converter is very suitable for low-ripple applications. A detailed description of the proposed converter is presented herein along with a mathematical deduction and some experimental results. [ABSTRACT FROM PUBLISHER]

A LED dimming circuit, together with the KY converter, is presented, which is controlled based on a field-programmable gate array. Via the proposed feedback control strategy, the voltage across the linear current regulator is reduced so as to upgrade the efficiency of the overall system, with the proposed maximum error selection based on a suitable voltage turning on the diode. Aside from this, each LED string takes direct dimming, and is powered by the KY converter, which has an output inductor and hence upgrades the life of the output capacitor. Experimental results show that the efficiency based on the proposed control method is higher than that based on the traditional control one, particularly at light load. [ABSTRACT FROM AUTHOR]

To overcome the traditional buck converter, which is difficult to achieve a high step-down gain with an appropriate duty cycle, a coupled-inductor-based step-down converter, named ultrahigh step-down converter, is proposed by Hwu et al. [11]. 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, the ultrahigh step-down converter is designed at a fixed input voltage of 48 V. In the telecommunication applications, the high dc bus voltage varies in a wide range, not kept at a fixed nominal voltage of 48 V. The experimental results show that as the input voltage increases, the efficiency of the ultrahigh step-down converter decreases. Therefore, in this paper, an improved ultrahigh step-down converter with a wide input voltage range is presented. According to the topology exchange, the voltage gain can be changed to a suitable one when the input voltage changes. By doing so, as compared with the ultrahigh step-down converter [11], the duty cycle of the proposed converter can be extended, and hence the efficiencies of the proposed converter can be improved. The proposed converter is verified by a wide input voltage (18–54 V), with an output voltage of 1.2 V and a rated output current of 10 A. [ABSTRACT FROM AUTHOR]

In this paper, a high step-down bidirectional converter, utilizing one coupled inductor and two energy-transferring capacitors, is presented. In the step-down mode, the capacitor is connected between input voltage and coupled inductor, which plays a role to step down the input voltage. Therefore, the corresponding voltage conversion ratio is much lower than that of the traditional buck converter and also can be lower than that of the tapped-inductor buck converter. Moreover, the output voltage varies with the duty cycle linearly, making control easier. In the step-up mode, one capacitor is first charged by the coupled inductor, and then releases the energy along with the coupled inductor and the other capacitor connected in series. Therefore, a higher voltage gain can be obtained. Furthermore, the leakage inductance energy can be recycled. Therefore, the switching losses can be reduced and the efficiency can be improved. In this study, the operating principles and experimental results are provided to verify the effectiveness and performance of the proposed converter. [ABSTRACT FROM AUTHOR]