INTERNATIONAL CONFERENCE ON RENEWABLE AND SUSTAINABLE ENERGY (ICRSE-13) Jose. J. and Jayanand B., Vol. 2, Special Issue, pp. 72-76, 2014 Simulation and Implementation of Superlift Luo Converter Josily Jose* and Jayanand B. Department of Electrical and Electronics, Government Engineering College, Idukki, Kerala,India *Corresponding author: jose.josily@gmail.com Abstract—Voltage lift technique is a popular method widely used in electronic circuit design. However the voltage increases stage by stage along arithmetic progression. But with a super-lift converter, the output increases stage by stage along a geometric progression. Thus it effectively enhances the transfer gain in power series. This paper presents the development of PI control capable of providing good static and dynamic performance. MATLAB software is used to study the dynamic characteristics and analyze the closed loop performances of these converters with resistive load under supply and load disturbances.DAC card is used for the hardware implementation of positive output elementary super lift Luo converter and its PI control. The simulation and experimental results closely match with each other and highlight the feasibility and validity of the developed control scheme. Index Terms–DC-DC Converter, PI control, DAC card I. INTRODUCTION DC to DC converters are important in portable electronic devices such as cellular phones and laptop computers, which are supplied with power from batteries. Such electronic devices often contain several subcircuits which each require unique voltage levels different than supplied by the battery (sometimes higher or lower than the battery voltage, or even negative voltage). Additionally, the battery voltage declines as its stored power is drained. DC to DC converters offer a method of generating multiple controlled voltages from a single variable battery voltage, thereby saving space instead of using multiple batteries to supply different parts of the device. Luo converters are DC-DC Switching Mode Boost converters. A boost converter (step-upconverter) is a power converter with an output dc voltage greater than its input dc voltage. Luo converters are a class of converters providing a high gain with relatively lesser number of components. Although Luo converters provide a high gain, when cascaded, the gain increases stage by stage only in Arithmetic progression i.e. these converters uses the voltage lift (VL) technique. In order to solve this discrepancy in the Classical Luo Converters, another class of converters called Super-lift Luo Converters were developed. While the positive aspects of the Classical Luo Converters are retained in Super-lift converters, Super-lift converters also have the advantage that the gain in this converter increases in geometric progression, stage by stage. II. POSITIVE OUTPUT SUPERLIFT LUO CONVERTERS The positive output elementary super lift Luo converter is a new series of DC-DC converters possessing high-voltage transfer gain, high power density; high efficiency, reduced ripple voltage and current . These converters are widely used in computer peripheral equipment, industrial applications and switch mode power supply, especially for high voltagevoltage projects. The positive output elementary super lift Luo converter performs the voltage conversion from positive source voltage to positive load voltage. The gain in this converter increases in geometric progression, stage by stage. It effectively enhances the voltage transfer gain in power series. Each circuit has one switch, n inductors, 2n capacitors, and (3n-1) diodes. The conduction duty ratio is d, switching frequency is f (period T = 1/ f ) the load is resistive load R . The input voltage and current are Vin and Iin, output voltage and current are VO and IO . Assume no power losses during the conversion process, Vin × Iin = VO × IO . The voltage transfer gain is G. G = VO/ Vin. The first three stages of positive output super-lift converters are shown. For convenience to explain, we call them as a) Elementary circuit (n = 1) b) Relift circuit (n = 2) c) Triple-lift circuit (n = 3) respectively. The positive output elementary super lift Luo converter is shown. in Fig. 1. It includes dc supply voltage Vin, capacitors C1 and C2 , inductor L1, power switch (n-channel MOSFET) S, freewheeling diodes D1 and D2 and load resistance R. 72 INTERNATIONAL CONFERENCE ON RENEWABLE AND SUSTAINABLE ENERGY (ICRSE-13) Jose. J. and Jayanand B., Vol. 2, Special Issue, pp. 72-76, 2014 i L1 Vo Vin V 2Vin dT o dT L1 L1 (1) 2d Vin 1 d (2) The voltage transfer gain is G Figure 1. Positive Output Elementary Superlift Luo converter In the description of the converter operation, it is assumed that all the components are ideal and also the positive output elementary super lift Luo converter operates in a continuous conduction mode. Figs. 2 and 3 shows the modes of operation of the converter. Vo 2d Vin 1 d (3) The input current iin is equal to (iL1 + iC1) during switching on and only equal to iL1 during switching-off. Capacitor current iC1 is equal to iL1 during switching-off. In steady state, the average charges across capacitor C1 should not change. We have the following relations: iin-off iL1off iC1off (4) iinon iL1on iCion (5) dTiC1on (1 d )TiC1off (6) If inductance L1 is large enough, iL1 is nearly equal to its average current iL1. Therefore iinoff iC1off I L1 Figure 2. Mode I operation In Fig. 2 when the switch S is closed, voltage across capacitor C1 is charged to Vin . The current iL1 flowing through inductor L1 increases with voltage Vin. iinon I L1 iC1on (7) I 1 d I L1 L1 d d (8) 1 d I L1 d (9) and average input current Iin diinon (1 d )iinoff I L1 (1 d )I L1 (2 d )I L1 (10) Considering T = 1/ f and Vin 1 d Vo 1 d R Iin 2 d I o 2 d 2 Fig.ure 3. Mode II operation In Fig. 3 when the switch S is opened, the inductor current iL1 decreases with voltage (Vo - 2 Vin). Therefore, the ripple of the inductor current iL1 2 (11) The variation ratio of inductor current iL1 is 73 INTERNATIONAL CONFERENCE ON RENEWABLE AND SUSTAINABLE ENERGY (ICRSE-13) Jose. J. and Jayanand B., Vol. 2, Special Issue, pp. 72-76, 2014 1 iL1 / 2 d (2 d )TVin d (1 d ) 2 R I L1 2 L1 I in 2(2 d ) fL1 (12) The ripple voltage of output voltage Vo is Vo Q I o (1 d )T 1 d Vo C2 C2 fC 2 R (13) Therefore, the variation ratio of output voltage Vo is Vo / 2 1 d Vo 2 fRC 2 (14) The static and dynamic performance of PI control for the positive output elementary super lift Luo converter is evaluated in Matlab/Simulink. The Matlab/Simulink simulation model is depicted in Fig.4. It can be seen that error in output voltage of the power switch (n – MOSFET) of PI control input is obtained by the difference between feedback output voltage and feedback reference output voltage, and output of PI control, change in duty cycle of the power switch ( n - channel MOSFET). III. PI CONTROL OF POSITIVE OUTPUT ELEMENTARY SUPERLIFT LUO CONVERTERS For the purpose of optimize the stability of positive output elementary super lift Luo converter dynamics, while ensuring correct operation in any working condition, a PI control is a more feasible approach. The PI control has been presented as a good alternative to the control of switching power converters. The main advantage PI control schemes is its insusceptibility to plant/system parameter variations that leads to invariant dynamics and static response in the ideal case. The PI control is designed to ensure the specifying desired nominal operating point for POESLLC, then regulating POESLLC, so that it stays very closer to the nominal operating point in the case of sudden disturbances, set point variations, noise, modeling errors and components variations. The PI regulator is: U ( s) K KP I E ( s) s (15) IV. Figure 4. Simulation model of PI control of positive output elementary luo converter SIMULATION V. Simulations have been performed on the positive output elementary super lift Luo converter circuit with parameters as in the table 1. SIMULATION RESULTS Output volage vs time 40 35 Parameter’s name Symbol Value Input voltage Vin 12 V Output voltage Vo 36 V Inductor L1 100µH Capacitors C1,C2 30µF Nominal switching frequency Load resistance Fs 100KHz R 100 Duty cycle d 0.5 output voltage(volt) 30 Table 1. Circuit parameters 25 20 15 10 5 0 0 0.1 0.2 0.3 0.4 0.5 time(sec) 0.6 0.7 0.8 0.9 1 Figure 5. Output voltage of positive output superlift luo converter when input is 12 V 74 INTERNATIONAL CONFERENCE ON RENEWABLE AND SUSTAINABLE ENERGY (ICRSE-13) Jose. J. and Jayanand B., Vol. 2, Special Issue, pp. 72-76, 2014 50 45 40 output voltage(v) 35 30 25 20 15 10 5 0 0 0.1 0.2 0.3 0.4 0.5 time(s) 0.6 0.7 0.8 0.9 1 Figure 6. Output voltage of positive output superlift luo converter when input takes a step change from 12 V to 15 V Figure 9. Input voltage=12 V 40 35 output voltage(v) 30 25 20 15 10 5 0 0 0.1 0.2 0.3 0.4 0.5 time(s) 0.6 0.7 0.8 0.9 1 Figure 7. Output voltage of positive output superlift luo converter when input takes a step change from 12 V to 9 V VI. HARDWARE IMPLEMENTATION Figure 10.Pulse from the real time card The hardware implementation of positive output elementary superlift luo converter was done.IRF540n was used as the switch. The PWM signal from the data acquisition card PCI1711L is not capable of driving MOSFET. In order to strengthen the triggering pulses, IR2111 driver is used.. Input to the converter was 12 V. For d = 0.5 , an output voltage of 36 V is obtained. Figure 11. Output of IR2111 Figure 8. Experimental set up 75 INTERNATIONAL CONFERENCE ON RENEWABLE AND SUSTAINABLE ENERGY (ICRSE-13) Jose. J. and Jayanand B., Vol. 2, Special Issue, pp. 72-76, 2014 Figure 12. Output voltage = 36 V, for d = 0.5 VII. [3] F.L.Luo and H.Ye, “Positive outputsuper lift converters,” IEEE Transaction on power electronics,Vol.18, No. 1, pp. 105-113, January 2003. [4]Luo, F. L.: ‘Re-Lift Converter: Design, Test, Simulation and Stability Analysis’, IEE Proceedings on EPA, Vol. 45, No. 4, July 2003, pp. 315-325. [5]F.L.Luo and H.Ye, “Negative outputsuper lift converters,” IEEE Transaction on power electronics,Vol.18, No. 5, pp. 1113-1121, September 2003 [6]F. L. Luo, H. Ye, and M. H. Rashid, “Four-quadrant operating Luo converters,” in Proc. IEEE Int. PESC’00 Conf., Galway, Ireland, June 18–23, 2000, pp. 1047–1052. [7]Power Electronics Handbook by M.H.Rashid [8]Power Electronics by Umanand (Inductor design) CONCLUSION A series of dc/dc converters—positive output super-lift converters has been successfully created. It largely increases the voltage transfer gain in power-law. Very high output voltage is easily obtained. Simulation and experimental results verified the design and calculations. The effect of the parasitic elements of DC-DC converters limits their output voltage and power transfer efficiency .This work introduced the advanced voltage lift techniques to be successfully applied in the DC-DC converter design and feedback with PI controller. They overcome the effect of parasitic elements and greatly increase the output voltage of the DC-DC converters, introducing the characteristic of high efficiency, high power density, cheap topology in simple structure and near-zero output voltage and current ripples. These establish the validity of the proposed PI controller that effectively rejects changes in DC supply voltage and load resistance which achieving fast tracking of the converter output voltage. ACKNOWLEDGMENT The authors would like to thank the head of the department of Electrical Engineering, Government College of Engineering, Idukki, Kerala for providing the facilities to conduct Research in Power Electronics lab. The research was conducted during 2012-2013. 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