A NEW ZVT SNUBBER CELL FOR PWM-PFCBOOST CONVERTER
Abstract
In this paper, a new Zero Voltage Transition (ZVT) snubber cell is developed for Pulse Width Modulated(PWM) and Power Factor Corrected (PFC) boostconverters operating in Continuous Conduction Mode(CCM). A new family of PFC boost converter implementedwith this new ZVT snubber cell is proposed. In this newPFC boost converter, the main switch is turned-onperfectly with ZVT and turned-off under Zero VoltageSwitching (ZVS). Besides, the auxiliary switch is turned-onunder Zero Current Switching (ZCS) and turned-off underZVS. The main and all auxiliary diodes are operating underSoft Switching (SS). During ZVT operation, the switchingenergies on the snubber inductance are transferred to theoutput by a transformer, and so the current stresses of theinductance and the auxiliary switch are significantlydecreased. Also, this transformer ensures the usage ofsufficient capacitors for ZVS turning off of the main andauxiliary switches. The main switch and main diode arenot subjected to any additional voltage and currentstresses. In this study, a detailed steady state analysis ofthe proposed new ZVT-PWM-PFC boost converter ispresented and this theoretical analysis is verified by aprototype with 100 kHz, 2 kW.
EXISTING SYSTEM:
Basically PFC means reducing reactive power andharmonics to zero. In the PFC circuits, as the frequencyincreases, the wave shape of the current drawn from the sourceapproaches to sinusoidal wave, thus Total HarmonicDistortion (THD) of the current is reduced. In power factorcorrected AC-DC converters, boost converters are used widelybecause of simple structure, ease of control and high-powerdensity. Continuous Current Mode (CCM) operation ispreferred in high-power applications. In this case, the reverserecovery of main diode causes turning off loss on this diodeand turning on loss on main switch, Electro MagneticInterference (EMI), and so a decrease in efficiency. Whenfrequency is increased for a more quality PFC, the problemsmentioned above increase. These problems can be solved byusing soft switching (SS) techniques instead of hard switching(HS) techniques. SS techniques can be classified as zerovoltage switching (ZVS), zero current switching (ZCS), zerovoltage transition (ZVT) and zero current transition (ZCT). In order to solve the problems of the boost converteroperating in CCM, a lot of papers have been proposed in theliterature .Although these studies are successful and provide most of thedesired properties, they still have some drawbacks. WhenMOSFET is used as a power switch, discharge loss of theparasitic capacitor becomes important. In basic ZVTtechnique providing the recovery of parasitic capacitor energy, an anti-parallel diode to the main switch, an auxiliaryswitch and an inductor are used for the aim of activesuppression. In this circuit, main switch is turned-on perfectlywith ZVT and main diode is turned off with ZCS. A parallelcapacitor can be added to the main switch for ZVS turn off ofthe main switch and ZVS turn on of the main diode. However,the auxiliary switch turns off hard and the current stress of thisswitch is high in the circuit. Also, the capacitor added to themain switch increases these problems further. In order to solvethese problems in the conventional ZVT converter, a lot ofpapers have been proposed in the literature.
PROPOSED SYSTEM:
In the paper , a ZVT circuit is proposed inorder to reduce the current stress of the auxiliary switch. Inthis circuit, ZVT turn on and ZVS turn off of the main switchand reducing of current stress of the auxiliary switch areachieved. However, in this circuit a transformer with amagnetizing inductance of high value is required and theauxiliary switch is turned off partially hard under themagnetizing current. A capacitor with high value and aresistance are used to reset magnetizing energy. Also, theauxiliary switch and the auxiliary diode are subjected to anadditional voltage stress. Consequently, a perfect PFC system can be achieved byusing a suitable AC-DC converter and with the application ofa convenient SS technique. In recent years, many papers havebeen published about this topic. These studies focus onproviding SS operation for all semiconductor devices at allload conditions and wide line range. In this study, a new ZVT-PWM-CCM-PFC boost converter,which ensures most of the desired features and does not havemost of the drawbacks listed above, is proposed. In the PFCboost converter equipped with new ZVT snubber cell, SSoperation of all main and auxiliary semiconductor devices isprovided. The switching energies are transferred to the outputby using a transformer during ZVT operation, thus the currentstresses of the auxiliary semiconductor devices aresignificantly reduced, and so the usage of sufficient capacitorsfor ZVS turning off of the main and auxiliary switches isensured. The main switch and the main diode are not subjectedto any additional voltage and current stresses. There is noadditional voltage stress on the auxiliary switch. Moreover,this new converter can operate successfully at all rectified linevoltage values and under all load conditions. The proposedconverter has a quite simple structure, low cost and ease ofcontrol. In this study, a detailed steady state analysis of theproposed new ZVT-PWM-CCM-PFC boost converter ispresented and this theoretical analysis is verified by aprototype with 100 kHz, 2 kW
CONCLUSION
In this paper, a new ZVT-PWM-PFC boost converter ispresented for PFC applications. In the proposed newconverter, the main switch is turned-on perfectly with ZVTand turned-off under ZVS. The auxiliary switch is turned-onunder ZCS and turned-off with ZVS. All diodes are operatingunder SS. By using a transformer, during ZVT operation theswitching energies are transferred to the output, and so thecurrent stresses of the auxiliary components are significantlydecreased. Also, this transformer ensures the usage ofsufficient capacitors for ZVS turning off of the main andauxiliary switches. The main switch and the main diode arenot subjected to any additional voltage and current stresses.The auxiliary switch is not subjected to any additional voltagestress. Furthermore, the proposed converter can operate successfully at all input voltage and output current values. Thenew converter has a quite simple structure, ease of control andlow cost. In this study, a detailed steady state analysis of thenew converter has been done and this theoretical analysis hasbeen verified by a prototype with 100 kHz, 2 kW.
REFERENCES
[1] O. Garcia, J. A. Cobos, R. Prieto, P. Alou, J. Uceda, “Single PhasePower Factor Correction: A Survey,” IEEE Trans. Power Electron., vol.18, no. 3, pp. 749-755, May. 2003.
[2] Q C. Qiao, K. M. Smedley, “A topology survey of single-stage powerfactor corrector with a boost type input-current-shaper,” IEEE Trans.Power Electron., vol. 16, no. 3, pp. 360-368, May. 2001.
[3] Liu, H.F., Chang, L.K., (2008). “Flexible and low cost design for aflyback AC/DC converter with harmonic current correction,” IEEETrans. Power Electron., vol. 20, no. 1, pp. 17-24, Jan. 2005.
[4] S. Luo, W. Qiu, W. Wu, I. Batarseh, “Flyboost power factor correctioncell and a new family of single-stage AC/DC converters,” IEEE Trans.Power Electron., vol. 20, no. 1, pp. 25-34, Jan. 2005.
[5] A. Lazaro, A. Barrado, M. Sanz, V. Salas, E. Olias, “New Power FactorCorrection AC-DC Converter With Reduced Storage CapacitorVoltage,” IEEE Trans. Ind. Electron., vol. 54, no. 1, pp. 384-397, Feb.2007.
[6] D.D.C. Lu, H. Iu, V. Pjevalica, “A Single-Stage AC/DC Converter WithHigh Power Factor, Regulated Bus Voltage, and Output Voltage,” IEEETrans. Power Electron., vol. 23, no. 1, pp. 218-228, Jan. 2008.
[7] J.-J. Lee, J.-M. Kwon, E.-H. Kim, W.-Y. Choi, B.-H. Kwon, “SingleStageSingle-Switch PFC Flyback Converter Using a SynchronousRectifier,” IEEE Trans. Ind. Electron., vol. 55, no. 3, pp. 1352-1365,Mar. 2008.
[8] E. H. Ismail, A. J. Sabzali, M. A. Al-Saffar, “Buck–Boost-Type UnityPower Factor Rectifier With Extended Voltage Conversion Ratio,” IEEETrans. Ind. Electron., vol. 55, no. 3, pp. 1123-1132, Mar. 2008.
[9] J. M. Alonso, M. A. D. Costa, C. Ordiz, “Integrated Buck-FlybackConverter as a High-Power-Factor Off-Line Power Supply,” IEEETrans. Ind. Electron., vol. 55, no. 3, pp. 1090-1100, Mar. 2008.
[10] L. Huber, Y. Jang, M. M. Jovanovic, “Performance Evaluation ofBridgeless PFC Boost Rectifiers,” IEEE Trans. Power Electron., vol. 23,no. 3, pp. 1381-1390, May. 2008