Transformerless DC–DC Converters With High Step-Up Voltage Gain
TL;DR: This paper proposes transformerless dc-dc converters to achieve high step-up voltage gain without an extremely high duty ratio and develops a prototype circuit to verify the performance.
Abstract: Conventional dc-dc boost converters are unable to provide high step-up voltage gains due to the effect of power switches, rectifier diodes, and the equivalent series resistance of inductors and capacitors. This paper proposes transformerless dc-dc converters to achieve high step-up voltage gain without an extremely high duty ratio. In the proposed converters, two inductors with the same level of inductance are charged in parallel during the switch-on period and are discharged in series during the switch-off period. The structures of the proposed converters are very simple. Only one power stage is used. Moreover, the steady-state analyses of voltage gains and boundary operating conditions are discussed in detail. Finally, a prototype circuit is implemented in the laboratory to verify the performance.
Citations
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TL;DR: In this paper, the authors comprehensively review and classify various step-up dc-dc converters based on their characteristics and voltage-boosting techniques, and discuss the advantages and disadvantages of these voltage boosting techniques and associated converters.
Abstract: DC–DC converters with voltage boost capability are widely used in a large number of power conversion applications, from fraction-of-volt to tens of thousands of volts at power levels from milliwatts to megawatts. The literature has reported on various voltage-boosting techniques, in which fundamental energy storing elements (inductors and capacitors) and/or transformers in conjunction with switch(es) and diode(s) are utilized in the circuit. These techniques include switched capacitor (charge pump), voltage multiplier, switched inductor/voltage lift, magnetic coupling, and multistage/-level, and each has its own merits and demerits depending on application, in terms of cost, complexity, power density, reliability, and efficiency. To meet the growing demand for such applications, new power converter topologies that use the above voltage-boosting techniques, as well as some active and passive components, are continuously being proposed. The permutations and combinations of the various voltage-boosting techniques with additional components in a circuit allow for numerous new topologies and configurations, which are often confusing and difficult to follow. Therefore, to present a clear picture on the general law and framework of the development of next-generation step-up dc–dc converters, this paper aims to comprehensively review and classify various step-up dc–dc converters based on their characteristics and voltage-boosting techniques. In addition, the advantages and disadvantages of these voltage-boosting techniques and associated converters are discussed in detail. Finally, broad applications of dc–dc converters are presented and summarized with comparative study of different voltage-boosting techniques.
1,230 citations
Cites background from "Transformerless DC–DC Converters Wi..."
...An active switched inductor (A-SL) based converter was presented in [91]....
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TL;DR: In this article, the authors proposed a new high step-up dc-dc converter designed especially for regulating the dc interface between various microsources and a dc-ac inverter to electricity grid.
Abstract: This paper proposes a new high step-up dc-dc converter designed especially for regulating the dc interface between various microsources and a dc-ac inverter to electricity grid. The figuration of the proposed converter is a quadratic boost converter with the coupled inductor in the second boost converter. The converter achieves high step-up voltage gain with appropriate duty ratio and low voltage stress on the power switch. Additionally, the energy stored in the leakage inductor of the coupled inductor can be recycled to the output capacitor. The operating principles and steady-state analyses of continuous-conduction mode and boundary-conduction mode are discussed in detail. To verify the performance of the proposed converter, a 280-W prototype sample is implemented with an input voltage range of 20-40 V and an output voltage of up to 400 V. The upmost efficiency of 93.3% is reached with high-line input; on the other hand, the full-load efficiency remains at 89.3% during low-line input.
377 citations
Cites background from "Transformerless DC–DC Converters Wi..."
...Previous research on various converters for high step-up applications has included analyses of the switched-inductor and switched-capacitor types [5, 6, 24, 25], the boost type integrating with the switchedcapacitor technique [7, 25], the voltage-lift type [8, 9] the capacitor-diode voltage multiplier type [10], and the transformerless DC-DC converters [11, 23]....
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TL;DR: In this paper, a novel high step-up dc/dc converter is presented for renewable energy applications, which consists of a coupled inductor and two voltage multiplier cells, in order to obtain high step up voltage gain.
Abstract: In this paper, a novel high step-up dc/dc converter is presented for renewable energy applications. The suggested structure consists of a coupled inductor and two voltage multiplier cells, in order to obtain high step-up voltage gain. In addition, two capacitors are charged during the switch-off period, using the energy stored in the coupled inductor which increases the voltage transfer gain. The energy stored in the leakage inductance is recycled with the use of a passive clamp circuit. The voltage stress on the main power switch is also reduced in the proposed topology. Therefore, a main power switch with low resistance $R_{{\rm DS} ({\rm ON})}$ can be used to reduce the conduction losses. The operation principle and the steady-state analyses are discussed thoroughly. To verify the performance of the presented converter, a 300-W laboratory prototype circuit is implemented. The results validate the theoretical analyses and the practicability of the presented high step-up converter.
327 citations
Cites background from "Transformerless DC–DC Converters Wi..."
...Theoretically, conventional boost converters can achieve high-voltage gain with an extremely high duty ratio [11]....
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TL;DR: The topological derivation of H-SLCs is deduced by combining the passive and active switched-inductor unit and the operation modes of the proposed asymmetrical and symmetrical converters are illustrated.
Abstract: In applications where the high voltage gain is required, such as photovoltaic grid-connected system, fuel-cell and high-intensity discharge lamps for automobile, high step-up dc-dc converters have been introduced to boost the low voltage to a high bus voltage. The voltage gain of traditional boost converter is limited, considering the issues such as the system efficiency and current ripple. This paper proposes a class of hybrid switched-inductor converters (H-SLCs) for high step-up voltage gain conversion. First, the topological derivation of H-SLCs is deduced by combining the passive and active switched-inductor unit; second, this paper illustrates the operation modes of the proposed asymmetrical and symmetrical converters; third, the performance of the proposed converters is analyzed in detail and compared with existing converters; finally, a prototype is established in the laboratory, and the experimental results are given to verify the correctness of the analysis.
320 citations
Cites background from "Transformerless DC–DC Converters Wi..."
...The noncoupled inductor type can achieve high voltage gain with minimized magnetic components [25]–[28]....
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...[28] presents a novel transformerless converter with high step-up voltage gain, the...
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...Transformerless high-gain converters with passive switchedinductor (P-SL) unit and active switched-inductor (A-SL) unit have been presented in [29] and [28], respectively, as shown in Fig....
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...Although the two switches in the cascade boost converter can be integrated into one switch to reduce circuit complexity, the switch voltage and current stress are still high [26]– [28]....
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TL;DR: A novel high step-up dc-dc converter with coupled-inductor and switched-capacitor techniques is proposed, which can achieve highstep-up voltage gain with appropriate duty ratio and reduce the conduction loss.
Abstract: A novel high step-up dc-dc converter with coupled-inductor and switched-capacitor techniques is proposed in this paper. The capacitors are charged in parallel and are discharged in series by the coupled inductor, stacking on the output capacitor. Thus, the proposed converter can achieve high step-up voltage gain with appropriate duty ratio. Besides, the voltage spike on the main switch can be clamped. Therefore, low on-state resistance RDS(ON) of the main switch can be adopted to reduce the conduction loss. The efficiency can be improved. The operating principle and steady-state analyses are discussed in detail. Finally, a prototype circuit with 24-V input voltage, 400-V output voltage, and 200-W output power is implemented in the laboratory. Experiment results confirm the analysis and advantages of the proposed converter.
291 citations
References
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TL;DR: The superiority of the new, hybrid converters is mainly based on less energy in the magnetic field, leading to saving in the size and cost of the inductors, and less current stresses in the switching elements, lead to smaller conduction losses.
Abstract: A few simple switching structures, formed by either two capacitors and two-three diodes (C-switching), or two inductors and two-three diodes (L-switching) are proposed. These structures can be of two types: ldquostep-downrdquo and ldquostep-up.rdquo These blocks are inserted in classical converters: buck, boost, buck-boost, Cuk, Zeta, Sepic. The ldquostep-downrdquo C- or L-switching structures can be combined with the buck, buck-boost, Cuk, Zeta, Sepic converters in order to get a step-down function. When the active switch of the converter is on, the inductors in the L-switching blocks are charged in series or the capacitors in the C-switching blocks are discharged in parallel. When the active switch is off, the inductors in the L-switching blocks are discharged in parallel or the capacitors in the C-switching blocks are charged in series. The ldquostep-uprdquo C- or L-switching structures are combined with the boost, buck-boost, Cuk, Zeta, Sepic converters, to get a step-up function. The steady-state analysis of the new hybrid converters allows for determing their DC line-to-output voltage ratio. The gain formula shows that the hybrid converters are able to reduce/increase the line voltage more times than the original, classical converters. The proposed hybrid converters contain the same number of elements as the quadratic converters. Their performances (DC gain, voltage and current stresses on the active switch and diodes, currents through the inductors) are compared to those of the available quadratic converters. The superiority of the new, hybrid converters is mainly based on less energy in the magnetic field, leading to saving in the size and cost of the inductors, and less current stresses in the switching elements, leading to smaller conduction losses. Experimental results confirm the theoretical analysis.
1,186 citations
TL;DR: In this article, a family of high-efficiency, high step-up DC-DC converters with simple topologies is proposed, which use diodes and coupled windings instead of active switches to realize functions similar to those of active clamps.
Abstract: Many applications call for high step-up DC-DC converters that do not require isolation. Some DC-DC converters can provide high step-up voltage gain, but with the penalty of either an extreme duty ratio or a large amount of circulating energy. DC-DC converters with coupled inductors can provide high voltage gain, but their efficiency is degraded by the losses associated with leakage inductors. Converters with active clamps recycle the leakage energy at the price of increasing topology complexity. A family of high-efficiency, high step-up DC-DC converters with simple topologies is proposed in this paper. The proposed converters, which use diodes and coupled windings instead of active switches to realize functions similar to those of active clamps, perform better than their active-clamp counterparts. High efficiency is achieved because the leakage energy is recycled and the output rectifier reverse-recovery problem is alleviated.
974 citations
01 Mar 2004
TL;DR: In this paper, a high-efficiency high step-up converter with low voltage stress on power switch, power diodes and output capacitors is proposed, which consists of an energy clamp circuit and a voltage boost cell.
Abstract: As a result of the equivalent series resistor of the boost inductor, conventional boost converters are not able to provide high voltage gain. A high-efficiency high step-up converter is proposed, with low voltage stress on power switch, power diodes and output capacitors. The circuit topology of the proposed converter consists of an energy clamp circuit and a voltage boost cell. The boost converter functions as an active clamp circuit to suppress the voltage spike on power switch during the turn-off transient period. The boost converter output terminal and flyback converter output terminal are serially connected to increase the output voltage gain with the coupled inductor. By serially connecting the secondary windings of the boost inductor, a high voltage gain is achieved with less voltage stress on the power devices, such as power MOSFET and power diodes. The operational principle and steady-state analysis are described. A 35 W converter with simulation and experimental results is presented to demonstrate the performance. It shows that the efficiency of the proposed converter is very high (nearly 93%) with four times the voltage output.
458 citations
TL;DR: In this paper, a switch-capacitor (SC) circuit is integrated within a boost converter for a steep step-up of the line voltage, allowing for a boost of the input voltage to high values.
Abstract: A new circuit is proposed for a steep step-up of the line voltage. It integrates a switched-capacitor (SC) circuit within a boost converter. An SC circuit can achieve any voltage ratio, allowing for a boost of the input voltage to high values. It is unregulated to allow for a very high efficiency. The boost stage has a regulation purpose. It can operate at a relatively low duty cycle, thus avoiding diode-reverse recovery problems. The new circuit is not a cascade interconnection of the two power stages; their operation is integrated. The simplicity and robustness of the solution, the possibility of getting higher voltage ratios than cascading boost converters, without using transformers with all their problems, and the good overall efficiency are the benefits of the proposed converter.
439 citations
TL;DR: An improved boost converter with coupled inductors and buck-boost type of active-clamp feature, PWM control and zero-voltage switching in both main and auxiliary switches, and efficiency can be improved significantly.
Abstract: This paper proposes a boost converter with coupled inductors and a buck-boost type of active clamp. In the converter, the active-clamp circuit is used to eliminate the voltage spike that is induced by the trapped energy in the leakage inductor of the coupled inductors. The active switch in the converter can still sustain a proper duty ratio even under high step-up applications, reducing voltage and current stresses significantly. Moreover, since both main and auxiliary switches can be turned on with zero-voltage switching, switching loss can be reduced, and conversion efficiency therefore can be improved significantly. A 200 W prototype of the proposed boost converter was built, from which experiment results have shown that efficiency can reach as high as 92% and surge can be suppressed effectively. It is relatively feasible for low-input-voltage applications, such as fuel cell and battery power conversion.
387 citations