ISSN Vol.04,Issue.10, August-2016, Pages:

Transcription

1 ISSN Vol.04,Issue.10, August-2016, Pages: DC-DC Step-Up Converter using Switched Coupled Inductor P. RADHA RANI 1, J. NAGARAJUNA BABU 2 1 PG Scholar, Dept of EEE (PE & D), Kottam Karunakar Reddy Institute of Technology, Kurnool, AP, India, radha.reddynr@gmil.com. 2 Assistant Professor, Dept of EEE, Kottam Karunakar Reddy Institute of Technology, Kurnool, AP, India, nagmtech307@gmail.com. Abstract: A closed-loop high-gain switched-coupled-inductor switched-capacitor (SCISC) converter is proposed by combining a sawtooth wave generator, pulse-widthmodulation based (PWM based) compensator and nonoverlapping circuit for step-up DC-DC conversion and regulation. The power part between source VS and output V O contains two sub-circuits: (i) a switched-coupled-inductor (SCI) booster circuit, and (ii) a three-stage switched-capacitor (SC) Tripler circuit. With the help of a clamping capacitor and a coupled-inductor with the turn ratio n, this SCI booster can provide the voltage of (2+n-D)/(1-D)V S theoretically, where D means the duty cycle of the MOSFET. And then by using the SC Tripler, the overall step-up gain can reach to 3(2+n-D)/ (1- D) at most. Practically, this SCISC can boost the voltage gain up to 37 when D=0.6, n=4. Further, the PWM technique is adopted not only to enhance the output regulation for the compensation of the dynamic error between the practical and desired outputs, but also to reinforce output robustness against source or loading variation. Finally, the closed-loop SCISC is designed by Or CAD SPICE and simulated for some cases: steady-state and dynamic responses. All results are illustrated to show the efficacy of the proposed scheme. Keywords: Coupled Inductor, High Step-Up Converter, Switched Capacitor, Transformer Less Converter. I. INTRODUCTION Recently, with the rapid development of power electronics, the step-up DC-DC converters are emphasized more widely for the electricity-supply applications, such as photovoltaic system, fuel cell, X-ray systems. General speaking, these power electronics converters are always required for a small volume, a light weight, a high efficacy, and a better regulation capability. The switched-capacitor converter (SCC), possessed of the charge pump structure, is one of solutions to DC-DC power conversion because it has only semiconductor switches and capacitors. Unlike traditional converters, the inductor-less SCC has light weight and small volume. Up to now, many types have been suggested, and some well-known topologies are presented, e.g. Dickson charge pump, Ioinovici SC. In 1976, Dickson charge pump was proposed with a twophase diode-capacitor chain, but it has the drawbacks of fixed gain and large device area. In the 1990s, Ioinovici proposed a SCC with two symmetrical capacitor cells, and presented a current-mode SCC. In 1997, Zhu and Ioinovici performed a comprehensive steady-state analysis of SCC. In 1998, Mak and Ioinovici suggested a high-power-density SC inverter. In 2004, Chang presented a current-mode SC inverter. In 2009, Tan et al. proposed the modeling and design of SCC by variable structure control. In 2011, Chang proposed an integrated step-up/down SCC (SCVM/SCVD). In 2013, Chang proposed a gain/efficiency improved serial-parallel switched-capacitor converter (SPSCC) by combining an adaptive-conversion-ratio (ACR) and pulse-width-modulation (PWM) control. In 2014, Chang proposed a high-gain switched-inductor switched capacitor step-up DC-DC converter (SISCC) is proposed by phase generator and PWM control. In 2015, Wu proposed a non-isolated high step-up DC-DC converter adopting switched-capacitor cell. For a higher voltage gain, it is one of the good ways to utilize the device of coupledinductor. Nevertheless, the stress on transistors and the volume of magnetic device might be considered. In 2011, Berkovich et al. proposed a switched-coupled inductor cell for DC-DC converter with very large conversion ratio. In 2015, Chen et al. proposed a novel switched-coupled- inductor DC- DC step-up converter via adopting a coupled inductor to charge a switched capacitor for making voltage gain effectively increased. Not only lower conduction losses but also higher power conversion efficiency is benefited from a lower part count and lower turn ratio. Based on the above descriptions, for achieving a compromise among volume size, component count, and voltage gain, the closed-loop SCISC is proposed here by combining the ideas of to realize a high-gain conversion as well as enhance the regulation capability. II. LITERATURE REVIEW A conventional boost converter can achieve high voltage gain only with a higher duty ratio. At high duty cycle low conversion efficiency, reverse recovery and EMI problems occur resulting in the deterioration of the performance of the system. Some transformer based converters can achieve high voltage gain by adjusting the turn s ratio of the transformer.however, the leakage inductance of the transformer will cause serious problems such as voltage spikes on the main switch and high power dissipation switched capacitors and voltage lift techniques have been used to achieve high voltage 2016 IJIT. All rights reserved.

2 P. RADHA RANI, J. NAGARAJUNA BABU gain. High charging current through the switches increases conduction losses in these structures. Coupled inductors based converters can achieve high step up voltage gain by adjusting the turn s ratios. However, the energy stored in the leakage inductor causes voltage spikes in the main switches and deteriorates the conversion efficiency. As a solution for this problem coupled inductor with active clamp circuit was presented. However, the conversion ratio was not large enough.as a solution for the above mentioned problems this paper presents a new topology. III. CONFIGURATION OF SCISC Fig1 shows the overall circuit configuration of SCISC step-up converter, and it contains two major parts: power part and control part for achieving the high-gain step-up DC-DC conversion and closed-loop regulation. Fig2 shows the detailed circuit of the control part. A. Power part The power part of SCISC is shown in the upper half of Fig. 1 and it consists of two sub circuits: a switched coupledinductor booster and a three-stage SC doubler, connected in cascade between source V s and output V o. This converter contains one coupled-inductor (L 1, L 2 ) with the turn ratio n=n 2 /N 1, four power switches (S 1 -S 4 ), one clamping capacitor (C 1 ), three pumping capacitors (C 2 -C 4 ), one output capacitor C o and 8 diodes (D 1 -D 8 ), where each capacitor of SC doubler has the same capacitance C (C 2 =C 3 =C 4 =C). Fig. 3 shows the theoretical waveforms of SCISC in a switching cycle T S (T S =1/f S, f S : switch frequency). Each T S contains two phases: Phase I and II. The operations for Phase I and II are described as follows. Fig.2. Detailed circuit of control part. Phase I: While V dt =1 (PWM ON), turn on S 1, S 3, S 4, and turn off S 2. Then, the diodes D 1, D 8 are turned on, and D 2 -D 7 is off. The current-flow path is shown as --- in Fig. 4(a). The inductors L 1, L 2 and capacitor C 1 are charged in parallel by the source V s. At the same time, C 2 -C 4 is discharged in series to transfer the energy to output capacitor C o and load R L. Phase II: While V dt =0 (PWM OFF), turn off S 1, S 3, S 4, and turn on S 2. Then, the diodes D 2 -D 7 are turned on, and D 1, D 8 are off. The current-flow path is shown as --- in Fig. 4(b). The capacitors C 2 -C 4 are charged in parallel by the series voltages of inductors L 1, L 2 and capacitor C 1. Simultaneously, output capacitor C o just stands alone to supply load R L. Fig.1. Closed-loop configuration of SCISC. Based on the scheduled operations of Phase I and II cyclically, the overall step-up gain can reach the value of 3(2+n-D)/ (1-D) theoretically. Extending the capacitor count, the gain can reach up to the value of m (2+n-D)/ (1-D) where m is the number of pumping capacitors.

3 DC-DC Step-Up Converter using Switched Coupled Inductor paper, the closed-loop control will be achieved via the PWMbased compensator to improve the regulation capability of this converter. Fig.4. Topologies for Phase (a) I, and (b) II. TABLE I: Component Parameters of SCISC Fig.3. Theoretical waveforms of SCISC. B. Control part The control part of SCISC is shown in the lower half of Fig1, and its detailed logic circuit is as in Fig. 2. It is composed of sawtooth wave generator, PWM block and nonoverlapping circuit. In the sawtooth wave generator, first, a current mirror is employed for generating a constant current source to charge the capacitor C, and then voltage V rp across this C is linearly increasing like a ramp. Next, V rp is sent and compared with two external voltages V max and V min in the Schmitt trigger in order to keep the V rp moving in the range between V max and V min, just like the waveforms as in Fig. 3. From the controller signal flow, the feedback signal V o is sent into the OP-amp low-pass filter (LPF) for high-frequency noise rejection. The filtered signal V o is compared with the desired output reference V ref to produce the V dt (D: duty cycle of signal V dt ) via the PWM block. And then, this duty-cycle signal is sent to the non overlapping circuit for obtaining a set of non-overlapping phase signals so as to produce the driver signals of S 1 -S 4 for the different topologies as in Fig. 4(a) and (b). The goal of PWM control is to keep V o on following the different desired V ref for better output regulation. In this IV. EXPERIMENTAL RESULTS A 250-W laboratory prototype is made for performance verification. The specification of the proposed converter is shown in Table II. It was tested under an input voltage of 20 V and an output of 220 V/250 W. The parameters of the devices used in the proposed converter are shown in Table III. The turn ratios n of the coupled inductor is three, and its magnetizing inductance is 23 μh, with a leakage inductance of 0.32 μh. The capacitance values of C 1 and C 2 are 100 and 10 μf, respectively. The part number of switch S1 and diodes D 1 and D 2 are IXFK180N15P and IDH05SG60C. The measured waveforms of the voltage and current of active switch S1 and diodes D 1 and D 2 at a full-load condition are shown in Fig. 5. These current and voltage waveforms agreed with the operating principles and the steady-state analysis.

4 P. RADHA RANI, J. NAGARAJUNA BABU Fig. 6 illustrates the proposed converter efficiency curve, which shows that the maximum efficiency is 97.2% at a lightload (10W) operation, and the full-load efficiency is about 93.6%. Fig.6 also shows the duty cycle versus the output load. The output load is set to be larger than 100 W to make the proposed converter operate under the CCM operation with a duty ratio of 60%. Under the DCM operation, the duty ratio will be gradually decreased with the load to keep the output voltage at 220 V. Fig. 7 shows the hardware prototype. TABLE II: Specification of the Proposed Converter TABLE III: Devices of the Proposed Converter Fig.6. Efficiency curve of the proposed converter. Fig.7. Hardware prototype of the proposed converter. V. CONCLUSION A closed-loop high-gain SCISC converter is proposed by combining a sawtooth wave generator, PWM-based compensator and non-overlapping circuit for step-up DC-DC conversion and regulation. The advantages of the proposed scheme are listed as follows. (i) In the SCISC, the large conversion ratio can be achieved with four switches and five capacitors for a step-up gain of 37 or above. (ii) As for the higher step-up gain, it is easily realized through increasing the turn ratio or extending the number of pumping capacitors. (iii) The PWM technique is adopted here not only to enhance output regulation capability for the different desired output, but also to reinforce the output robustness against source/loading/reference variation. At present, the prototype circuit of the proposed converter is implemented in the laboratory as some experimental results will be obtained and measured for the verification of the proposed converter. Fig.5. Current and voltage waveforms of (a) active switch S 1, (b) diode D 1, and (c) output diode D 2. VI. REFERENCES [1] Shih-Ming Chen, Member, IEEE, Man-Long Lao, Yi- Hsun Hsieh, Tsorng-Juu Liang, Senior Member, IEEE, and Kai-Hui Chen, A Novel Switched-Coupled-Inductor DC DC Step-Up Converter and Its Derivatives, IEEE Transactions on Industry Applications, Vol. 51, No. 1, January/February 2015.

5 DC-DC Step-Up Converter using Switched Coupled Inductor [2] B. Axelrod and Y. Berkovich, Switched-coupled inductor cell for DC DC converters with very large conversion ratio, IET Power Electron., vol. 4, no. 3, pp , Mar [3] B. Axelrod, Y. Berkovich, and A. Ioinovici, Switchedcapacitor/switched-inductor structures for getting transformer less hybrid DC DC PWM converters, IEEE Trans. Circuits Syst. I, Reg. Papers, vol. 55, no. 2, pp , Mar [4] D. Li, P. C. Loh, M. Zhu, F. Gao, and F. Blaabjerg, Generalized multi-cell switched-inductor and switchedcapacitor Z-source inverters, IEEE Trans. Power Electron., vol. 28, no. 2, pp , Feb [5] L. S. Yang, T. J. Liang, and J. F. Chen, Transformer less DC DC converters with high step-up voltage gain, IEEE Trans. Ind. Electron., vol. 56, no. 8, pp , Aug [6] C. M. Young, M. H. Chen, T. A. Chang, C. C. Ko, and K. Jen, Cascade Cockcroft Walton voltage multiplier applied to transformer less high step-up DC DC converter, IEEE Trans. Ind. Electron., vol. 60, no. 2, pp , Feb [7] Y. Jiao, F. L. Luo, and B. K. Bose, Voltage-lift splitinductor-type boost converters, IET Power Electron., vol. 4, no. 4, pp , Apr [8] Q. Zhao and F. C. Lee, High-efficiency, high step-up DC DC converters, IEEE Trans. Power Electron., vol. 18, no. 1, pp , Jan [9] W. Li, X. Xiang, C. Li, W. Li, and X. He, Interleaved high step-up ZVT converter with built-in transformer voltage doubler cell for distributed PV generation system, IEEE Trans. Power Electron., vol. 28, no. 1, pp , Jan [10] S.M. Chen, T. J. Liang, L. S. Yang, and J. F. Chen, A cascaded high step up DC DC converter with single switch for micro-source applications, IEEE Trans. Power Electron., vol. 26, no. 4, pp , Apr [11] S. K. Changchien, T. J. Liang, J. F. Chen, and L. S. Yang, Novel high step-up DC DC converter for fuel cell energy conversion system, IEEE Trans. Ind. Electron., vol. 57, no. 6, pp , Jun [12] S. Zhang, J. Xu, and P. Yang, A single-switch high gain quadratic boost converter based on voltage-lift-technique, in Proc. IPEC, 2012, pp