High Step-down Voltage Conversion Research Articles

Fully Soft-Switched Non-Isolated High Step-Down DC–DC Converter With Reduced Voltage Stress and Expanding Capability

In this article, a fully soft-switched expandable high step-down dc–dc converter is presented. In order to achieve a high step-down voltage conversion ratio and low component count, the synchronous buck and Cuk converters are integrated. Lower switches’ voltage stress is realized by splitting the input voltage, which can considerably decrease the switches’ conduction loss. Moreover, switching losses along with the reverse recovery problems are mitigated due to the soft-switching operation of all semiconductor devices. The switch utilized for soft-switching operation is also used to replace the output diode as a synchronous rectifier, which reduces the conduction loss. The mentioned features have considerably contributed to the converter efficiency. Furthermore, the converter shares a common ground between the input and the output, which is desirable in many applications, while the converter output current is continuous without adding current ripple cancellation methods. Finally, the number of converter cells can be expanded or reduced; therefore, the converter can be applied to a wide range of loads. The operating principles and analysis of the proposed converter are presented, and the results from the implemented prototype are provided to verify the converter operation and performance.

Four-Channel Buck-Type LED Driver with Automatic Current Sharing and Soft Switching

A buck-type LED driver together with automatic current sharing and high step-down voltage conversion ratio but without complex control is proposed. The proposed LED driver can not only achieve zero voltage switching (ZVS) turn-on by adding only one resonant coupled inductor, which resonates with parasitic capacitors of active switches, but also can obtain lower voltage gain and better conversion efficiency. In this paper, the operating principles and design considerations of the proposed converter are discussed in detail. In addition, the number of LED strings can be extended to more than four channels. Finally, the theoretical analysis and performance of the proposed LED driver are verified by simulations and experiments using a field-programmable logic gate array (FPGA) named EP3C5E144C8N as a circuit control kernel.

48-V Input DC-DC High Step-Down Converter in GaN-Based Design

This paper presents a novel high step-down DC-DC converter based on a switched-capacitor resonant topology. It is presented in a 48/8 V version, which was verified by simulations and experiments. The most notable features specific to this converter are an almost non-iductive design and relatively low voltage stress across switching devices. The proposed topology allows for zero-current-switching (ZCS) and zero-voltage-switching (ZVS). Experimental tests confirm that ZVS operation brings a significant increase in the efficiency of the proposed device. Taking into account all the advantages of the suggested converter, it can be concluded that this device is suitable for any application where a high step-down voltage conversion is required. In a prospective application, the proposed converter can be utilized as a part of the power supply unit for data centers.

A non‐isolated DC‐DC converter with low voltage stress and high step‐down voltage conversion ratio

This work focuses on a new non-isolated interleaved DC-DC converter with very high step-down voltage conversion ratio. By employing the switched/series capacitor concept, along with the proper component interconnection, the converter features a high step-down voltage conversion ratio where, in the private case of equal duty ratios, it is six times higher than the conventional buck converter. This high step-down voltage conversion ratio is achieved with the lowest number of components compared to other similar topologies of the same conversion ratio. Also, due to the blocking/series capacitors, the voltage stress on the switches is reduced, improving the converter efficiency. One of the key features of the proposed converter is the inherent automatic current sharing between the interleaved phases, which in the case of equal duty ratios, is uniformly distributed. To add on, due to the use of only two interleaved phases, the converter has a wide output voltage range, since the duty cycle can be extended to 0.5. To validate the proposed converter operation, a 250 W wide-input/wide-output experimental prototype was built, achieving a peak efficiency of 94%.

PWM Switched Capacitor Converter With Switched-Capacitor-Inductor Cell for Adjustable High Step-Down Voltage Conversion

High step-down voltage conversion is necessary to bridge the voltage gap between main power converters and low-voltage auxiliary electronics in power conversion systems. Switched capacitor converters (SCCs) are an attractive candidate as a high step-down converter, but their poor voltage regulation capability may limit their applications. Pulsewidth modulation (PWM) SCCs with adjustable high step-down voltage conversion are proposed in this paper. The proposed PWM SCCs can be derived from traditional SCCs by replacing an energy transfer capacitor with a switched-capacitor-inductor (SCL) cell that comprises inductors, capacitors, and diodes to realize PWM-controllable voltage conversion. The voltage step-down ratio of the proposed PWM SCCs is not only PWM controllable but also adjustable with structures of SCCs and SCL cells. Two representative PWM SCCs were taken as examples to perform the operational analysis. The prototypes of both representative PWM SCCs were built and tested to demonstrate the proposed concept.

An Expandable Two-Phase Interleaved Ultrahigh Step-Down Converter With Automatic Current Balance

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.

An Expandable Four-Phase Interleaved High Step-Down Converter With Low Switch Voltage Stress and Automatic Uniform Current Sharing

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.

Comparison between Phase-Shift Full-Bridge Converters with Noncoupled and Coupled Current-Doubler Rectifier

This paper presents comparison between phase-shift full-bridge converters with noncoupled and coupled current-doubler rectifier. In high current capability and high step-down voltage conversion, a phase-shift full-bridge converter with a conventional current-doubler rectifier has the common limitations of extremely low duty ratio and high component stresses. To overcome these limitations, a phase-shift full-bridge converter with a noncoupled current-doubler rectifier (NCDR) or a coupled current-doubler rectifier (CCDR) is, respectively, proposed and implemented. In this study, performance analysis and efficiency obtained from a 500 W phase-shift full-bridge converter with two improved current-doubler rectifiers are presented and compared. From their prototypes, experimental results have verified that the phase-shift full-bridge converter with NCDR has optimal duty ratio, lower component stresses, and output current ripple. In component count and efficiency comparison, CCDR has fewer components and higher efficiency at full load condition. For small size and high efficiency requirements, CCDR is relatively suitable for high step-down voltage and high efficiency applications.