ISSN Vol.03,Issue.07, August-2015, Pages:

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1 ISSN Vol.03,Issue.07, August-2015, Pages: ZCS Phase shift PWM Full-Bridge DC DC Converter with Simple Auxiliary Circuits SURESH KUMAR 1, AMARNATH NAIDU 2 1 PG Scholar, Dept of EEE(PE), G. Pulla Reddy Engineering College, Kurnool, Andhra Pradesh, India. 2 Asst Prof, Dept of EEE, G. Pulla Reddy Engineering College, Kurnool, Andhra Pradesh, India. Abstract: Pulse Width Modulated dc-dc full bridge converters has vast applications in various industries and mostly employed with soft switching to increase power density by increasing power frequency which causes more switching losses if used with hard switching techniques. For low power applications ZVS techniques are employed but for high power applications ZCS techniques with IGBTs are preferred which are having fixed collector-emitter voltage, hence lower conduction losses than MOSFETs. The proposed project presents a new soft-switching pwm full bridge converter with two simple auxiliary circuits, one is active ZCS auxiliary circuit, the other is passive ZVZCS auxiliary circuit. This topology can be implemented with IGBTs for all four main power switches and ZCS turn-off and ZCS turn-on for all switches. This gives lesser conduction losses than conventional. Therefore, the proposed converter overcomes the drawbacks of previous ZCS PWM techniques with auxiliary circuits. Keywords: Bidirectional Converters, DC DC Converters, Efficiency Measurement, Full Bridge, Pulse Width Modulated (PWM) Converters, Zero-Current Switching (ZCS) Converters, Zero-Voltage and Zero-Current Switching (ZVZCS). I. INTRODUCTION Pulse width modulated (PWM) dc dc full-connect converters with delicate exchanging are broadly utilized as a part of industry. For lower force applications, where the converters are for the most part executed with MOSFETs, zero-voltageswitching (ZVS) procedures are utilized to enhance the productivity of the full-connect converter. For higher force applications, where IGBTs are the favored gadgets as they have lower conduction misfortunes than MOSFETs because of their settled collector-emitter voltage drop, zero-current switching (ZCS) procedures are favored. This is since ZCS systems can altogether decrease the tail in the IGBT gadget current that shows up when the gadget is off. Decreasing this present tail helps an IGBT work with less turn-off misfortunes and permits it to work at higher switching frequencies. Already proposed delicate exchanging strategies for higher power dc dc full-connect converters have no less than one of the taking after downsides: 1. They are thunderous systems in which full components for example, capacitors and inductors are utilized to shape the current through a converter switch with the goal that it can fall to zero to permit the change to kill with ZCS. 2. They are ZCS-PWM methods that utilization dynamic assistant circuit comprising of dynamic switches and uninvolved segments to help the primary converter switches kill with ZCS. 3. They are uninvolved snubber systems. In spite of the fact that the utilization of various assistant switches is dodged with these converters, the detached circuits themselves can be truly advanced and the general converter productivity is lower than that of the previously stated converters that utilization various helper switches. 4. They are zero-voltage zero-current-switching (ZVZCS) strategies. These procedures either utilize an auxiliary side assistant switch or an optional side inactive circuit to make a counter voltage in the converter essential. 5. They oblige the putting of converse blocking diodes in arrangement with primary force changes to keep current from coursing through their body diode or oblige that IGBTs with converse blocking capacity be utilized. Fig.1. Proposed ZCS converter. Another ZCS-PWM full-connect converter is proposed in this project. The remarkable component of the new converter is that it permits its fundamental force changes to work with ZCS and with less conduction misfortunes than traditional full-connect converters IJIT. All rights reserved.

2 SURESH KUMAR, AMARNATH NAIDU II. CONVERTER OPERATION The proposed converter is indicated in Fig. 1. It works like a ZVZCS-PWM converter with the exception of that the assistant circuit is initiated at whatever point the fundamental force switches in the main leg to which it is appended speak the truth to kill. It ought to be noticed that in this outline, as in other circuit graph display in this paper, the transformer spillage inductance is not demonstrated as a different component, however is thought to be a piece of the transformer. The converter's methods of operation are as per the following: Mode 1 (t0 t t1): Switches S1 and S2 are on before this mode and the info force is exchanged to the yield through D3 and D4. Toward the start of this mode, assistant switch Sa is turned on and Ca begins to release, resounding with La. This mode closes when the present streaming through Sa achieves zero. From the identical circuit of Mode 1 indicated in Fig. 4(a), the essential streams and voltages can be Communicate Fig. 2. Equivalent circuit for each mode of operation. Fig.3. Ideal waveforms.

3 ZCS Phase shift PWM Full-Bridge DC DC Converter with Simple Auxiliary Circuits Where, Mode 4 (t3 t t4 ): At the start of this mode, S3 is turned on delicately as the ascent in switch current is obliged by the vicinity of La and transformer spillage inductance. Cc is releasing all through this mode. Fig. 4. Equivalent circuit for: (a) Mode 1, (b) Mode 2, and (c) Mode 3. For straightforwardness, the essential current amid this mode is approximated as the reflected essential current nio. Explaining these mathematical statements gives The initial conditions for (15) and (16) are VCa (t3) = 0 and ila (t3) = nio. Solving these equations gives Where, Where Vin is the data voltage and Mode 2 (t1 t t2 ): At the start of this mode, current in Sa begins streaming the other way from its stream in Mode 1, through the anti parallel diode of Sa, i.e., DSa. Sa can be killed delicately while current is streaming in DSa. Mode 3 (t2 t t3 ): At the start of this mode, current in S1 begins streaming in the converse heading through the anti parallel diode of S1, i.e., DS1 ; in this way, S1 can be killed in this mode delicately with ZCS. The voltage crosswise over Ca and the present moving through La can be communicate The initial conditions for (8) (10) are VCa (t2) = nioz1 and ila (t2) = nio. Solving these equations gives Mode 5 (t4 t t5): This mode starts when current in S2 has come to zero. S2 can be killed with ZCS at some point after the begin of this mode. Amid this mode, current keeps on flowing through the body diode of Sa and S3. Cc supplies the heap current and the voltage crosswise over it proceeds to drop. Mode 6 (t5 t t6): Current has halted coursing through the essential of the converter toward the starting of this mode. S3 can be killed with ZCS amid this mode as there is no present streaming in the essential side. Capacitor Cc keeps on releasing. Mode 7 (t6 t t7): This mode starts when Cc has been totally released. DiodesD1 D4 begin leading toward the start of this mode and the heap current freewheels through them. Mode 8 (t7 t t8 ): At the start of this mode, S4 is turned on delicately and the current through it rises bit by bit following the essential current can't change all of a sudden due to the transformer spillage inductance. It ought to be noticed that the proposed converter can be actualized utilizing standard stage shift PWM. III.FEAUTRES OF CONVERTER AND ITS DRAWBACKS: The proposed converter has the accompanying components: 1. The voltage crosswise over auxiliary circuit capacitor Cc is reflected to the converter essential when the converter is in a freewheeling method of operation. 2. The main leg switches kill with ZCS as the primary side helper circuit infuses current into their body diodes before they are killed. 3. Sa can be killed with ZCS (Mode 3) as the Ca La full circuit powers current through the switch to be slowly evacuated then move through its body diode. 4. All converter switches turn on with ZCS on the grounds that they either have an inductor in arrangement with them.

4 SURESH KUMAR, AMARNATH NAIDU 5. Due to the steady ascent and fall of the essential current Where amid any exchanging move, the auxiliary diodes turn off delicately. The proposed converter, in any case, has the accompanying downsides: 1. Since it is a ZCS-PWM converter, it is not a suitable topology on the off chance that a converter is to be executed with MOSFETs it is standard practice to work MOSFETs with ZVS. 2. The present in any given switch in the proposed converter will have a full crest so that the converter's top switch current will be higher than that of a switch in a ZVS-PWM converter. 3. The light load effectiveness of the converter is more terrible when the dynamic helper circuit is executed than when it is definitely not. 4. It ought to be noticed that all the previously stated disadvantages are basic to ZCS-PWM converters by and large. IV. DESIGN PARAMETERS: A method for the configuration of the two assistant circuits for the converter the dynamic circuit at the essential side and the uninvolved circuit at the optional side is displayed in this segment also, is shown with a sample. The accompanying configuration targets ought to be considered: a. The helper circuit is joined to the main converter leg, which is the leg with switches that would typically turn on and off with ZVS in a ZVZCS-PWM full-connect converter. b. It has been resolved from past emphases that an assistant switch crest current that speaks the truth two times the greatest crest switch current permits current to be exchanged far from a fundamental switch at a rate that is not one or the other excessively sudden nor excessively slow. c. A proper "ZCS time window" should be considered in the configuration of the assistant circuit. The ZCS time window is the measure of time amid which a primary switch in the main converter leg can turn on with ZCS. d. It would be best if the voltage crosswise over full capacitor Ca in the assistant circuit does not surpass 400 V so that standard 450 V capacitors can be utilized with some voltage edge. This places a limitation on the impedance of the thunderous circuit in the helper circuit as it must be such that it permits the crest helper circuit current to be adequately high so that the principle power switches in the leg can kill with ZCS. e. The switches in the slacking converter leg kill with ZCS because of the optional side assistant circuit. 2. The configuration of the converter's helper circuit should be possible with the accompanying steps. Step 1:Active Auxiliary Circuit Component Values: In this stride, preparatory estimations of Ca and La are resolved based the voltage crosswise over Ca. The greatest voltage over the resounding capacitor Ca can be ascertained from the accompanying mathematical statement: Mathematical statement (20) is determined utilizing Kirchhoff's present law as a part of Mode 3 by considering the reflected voltage source from the auxiliary side Vo/n and the transformer spillage inductance Step 2:Characteristic Impedance of the Active Helper Circuit: The trademark impedance of the helper circuit, characterize that influences the top current anxiety of the assistant circuit segments also, the window of time inside of the main leg switches can be killed with ZCS. The key comparison that depicts the obligation cycle of the of the dynamic helper circuit (tc) is regularly equal to three times the opposite recuperation time of the helper diode, which can be decided from Where Therefore As a consequence of the helper segment values, the obligation cycle of the assistant circuit is 120 ns or 6% of the obligation cycle in one cycle. C. Step 3: ZCS Range of Leading Leg Switches: With the helper circuit estimations of La and Ca known, the next step is to affirm whether the helper circuit can permit the converter's driving leg changes to work with ZCS and the assistant switch to work with ZCS. D. Step 4: ZCS Turn-Off of Lagging Leg Switches: An extremely straightforward aloof assistant circuit with no extra switch is connected in the auxiliary side of the converter to accomplish ZCS for the slacking leg switches, by resetting the essential current with the vitality put away in Cc. The voltage crosswise over Cc can be communicated agreeing to the accompanying comparisons: Where VCc is the voltage crosswise over capacitor Cc and ICc is the current through it. The starting conditions for (26) and (27) are VCc (t8) = 0 and ILl k (t8) = 0. Explaining these mathematical statements gives

5 ZCS Phase shift PWM Full-Bridge DC DC Converter with Simple Auxiliary Circuits Is3: Where Vs3: Explaining (32) for Cc, the insignificant worth to guarantee the vitality put away in Cc is sufficiently extensive to reset the essential current Bigger estimations of Cc require littler obligation cycle amid light load conditions to verify that the holding capacitor totally releases amid the freewheeling period. Soft switching of lagging leg: Is4: s1,s3: V. SIMULATION RESULTS Vs4: s2,s4: IS-aux: s1,s2: V-sa: For s1: Primary current: Primary Voltage: Is2: Vs2: VI. CONCLUSION Another ZCS-PWM full bridge converter is proposed in this paper. The exceptional element of the new converter is that it permits its principle power changes to work with ZCS and with less conduction misfortunes than routine fullconnect converters. The proposed converter does not have the downsides of beforehand proposed strategies for higher force dc dc full-connect converters with IGBTs, including

6 SURESH KUMAR, AMARNATH NAIDU thunderous procedures, ZCS-PWM methods with dynamic assistant circuits, inactive procedures, ZVZCS methods, and systems that oblige the utilization of opposite blocking diodes. VII. REFERENCES [1] C. Liu, B. Gu, J. Lai, M. Wang, C. Zheng, Y. Ji, and P. Sun, High efficiency hybrid full bridge half-bridge converter with shared ZVS lagging leg and dual outputs in series, IEEE Trans. Power Electron., vol. 28,no. 2, pp , Feb [2] K. Jin, Y. Sun, M. Xu, D. Sterk, and F.C. Lee, Integrated magnetic selfdrive ZVS non isolated full-bridge converter, IEEE Trans. Ind. Electron., vol. 57, no. 5, pp , May [3] X. Zhang, W. Chen, X. Ruan, and K. Yao, A novel ZVS PWM phase shifted full-bridge converter with controlled auxiliary circuit, in Proc.IEEE APEC, Feb. 2009, pp [4] I. Lee and G. Moon, Soft-switching dc/dc converter with a full ZVS range and reduced output filter for high-voltage applications, IEEE Trans.Power Electronics, vol. 28, no. 1, pp , Jan [5] W. Chen, X. Ruan, and J. Ge, A novel full-bridge converter achieving ZVS over wide load range with a passive auxiliary circuit, in Proc. IEEEECCE, Sep. 2010, pp Author s Profile: P R Suresh Kumar, received B. Tech degree in Electrical and Electronics Engineering from Santhiram Engineering college, JNTU, Anantapur in the year He is currently pursuing M.Tech in G. Pulla Reddy Engineering College, JNTUA, Kurnool. His research interests include Electrical Power Converters. B Amarnath Naidu, graduated from St.Johns College of Engineering and Technology, JNTU, Anatapur in the year He received M.Tech degree from G. Pulla Reddy Engineering College, SKUA, Kurnool, India in the year At present he is working as Assistant Professor in the Electrical and Electronics Engineering Department, G. Pulla Reddy Engineering College, Kurnool, India. His areas of interest include Power Converters and Multilevel Inverters