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ISSN 2347 - 3983 Volume 3, No.7, July 2015

Journal ofEmerging Emerging in Engineering Research Nihina AInternational M et al., International Journal of TrendsTrends in Engineering Research, 3(7), July 2015, 50 - 54 Available Online at http://www.warse.org/IJETER/static/pdf/file/ijeter02372015.pdf

Comparative study of zeta converter and a novel zeta converter with coupled inductor Nihina A M(M.Tech student)

Dhivya Haridas(Assistant professor)

Electrical and Electronics Engineering Ilahia College of Engineering and Technology Ernakulam, India nihinaam@gmail.com

Electrical and Electronics Engineering Ilahia College of Engineering and Technology Ernakulam, India dhivyadec25@gmail.com

the coil. That energy is fed to the load during each switching cycle. Now a days, concept of coupled inductor become more prevalence. That is, two separate inductors wound on the same core. This leads to many advantages like low cost,less size etc. In this paper a zeta converter [2],[4],[5] and a novel zeta converter with coupled inductor[1] are compared. The performance of each convereter are analysed.

Abstract-Recently, inductor manufacturers have begun to release off-the-shelf coupled inductors. Consisting of two separate inductors wound on the same core, coupled inductors typically come in a package with the same length and width as that of a single inductor of the same inductance value, only slightly taller. The price of a coupled inductor is also typically much less than the price of two single inductors. The windings of the coupled inductor can be connected in series, in parallel, or as a transformer. In this paper a zeta converter is presented with coupled inductor and a capacitor multiplier in the secondary of coupled inductor to achieve high voltage gain.Open loop simulations of conventional zeta converter and the novel zeta converter has been carried out using MATLAB/SIMULINK and compared the performance of the two converters. Keywords- zetaconverter, coupled inductor, capacitor multiplier .

2.TOPOLOGICAL AND ELECTRICAL PROPERTIES OF THE CONVERTERS. A.zeta converter S

1.INTRODUCTION Electronic switch-mode DC to DC converters convert one DC voltage level to another, by storing the input energy temporarily and then releasing that energy to the output at a different voltage. The storage may be in either magnetic field storage components (inductors, transformers) or electric field storage components (capacitors). This conversion method is more power efficient (often 75% to 98%) than linear voltage regulation (which dissipates unwanted power as heat). This efficiency is beneficial to increasing the running time of battery operated devices. Linear regulators can only output at lower voltages from the input. They are very inefficient when the voltage drop is large and the current is high as they dissipate heat equal to the product of the output current and the voltage drop; consequently they are not normally used for largedrop high-current applications. The inefficiency wastes energy and requires higher-rated and consequently more expensive and larger components. The heat dissipated by high-power supplies is a problem in itself and it must be removed from the circuitry to prevent unacceptable temperature rises.That is why we go for switch mode dc-dc converters. Energy storage method of dc-dc converters have mentioned above. When a current flows through an inductor, energy is stored temporarily in a magnetic field in

Figure 1.Zeta converter circuit

The zeta converter circuit is shown in Figure 1. It consists of IGBT transistor as a switch, Diode, two capacitors and , two inductors and load resistor . In the first mode of operation (switch is ON) the inductors L1 and L2 are in charging state. During the second mode (switch is off)the inductors L1 and L2 are in the discharging state.L1 is discharging its stored energy into the capacitor , and the inductor L2 transform energy to output section. The relation between input and output voltage of the zeta converter is given by, Vo=

B.Novel zeta converter with capacitor multiplier and coupled inductor. 50

Nihina A M et al., International Journal of Emerging Trends in Engineering Research, 3(7), July 2015, 50 - 54 The simplified circuit model of the proposed converter is shown in Figure 2. The coupled inductor T1 includes a magnetizing inductor Lm, and an ideal transformer primary winding N1 and secondary winding N2. To simplify the circuit analysis of the proposed converter, the following assumptions are made.

decreasing. The secondary leakage inductor current iLK2 is declining according to iLm/n. Once the increasing iLk1 equals the decreasing iLm at t = t1, this mode ends. Stage 2 [t1-t2]:

Figure 2.Novel zeta converter with coupled inductor

Figure 4.Mode II of Novel zeta converter with coupled inductor

1) All components are ideal, except for the leakage inductance of coupled inductor T1. The ON-state resistanceRDS(ON) and all parasitic capacitances of the main switch S1 are neglected, as are the forward voltage drops of

During this interval, source energy Vin is series connected with C1, C2, secondary winding N2, and Lk2 to charge output capacitor C3 and load R; meanwhile, magnetizing inductor Lm is also receiving energy from Vin. The current flow path is shown in Figure .3; as illustrated, switch S1 remains on, and only diode D3 is conducting. The iLm, iLk1, and iD3 are increasing because the Vin is crossing Lk1, Lm and primary winding N1; Lm and Lk1 are storing energy from Vin; meanwhile, Vin is also in series with N2 of coupled inductor T1, and capacitors C1 and C2 are discharging their energy to capacitor C3 and load R, which leads to increases in iLm, iLk1, iDS, and iD3. This mode ends when switch S1 is turned off at t = t2.

the diodes D1 ∼ D3. 2) The capacitors C1 ∼ C3 are sufficiently large that the voltages across them are considered to be constant. 3) The ESR of capacitors C1 ∼ C3 and the parasitic resistance of coupled-inductor T1 are neglected. 4) The turns ratio n of the coupled inductor T1 winding is equal to N2/N1. A. Analysis of Operation Stages

Stage 3[t2-t3] : For one switching cycle, the proposed circuit operations can be divided into five stages. Stage 1[t0-t1]:

Figure 3.Mode I of Novel zeta converter with coupled inductor Figure 5.Mode III of Novel zeta converter with coupled inductor

In this transition interval, the secondary leakage inductor Lk2 is continuously releasing its energy to capacitor C2. The current flow path is shown in Figure.2; as shown, switch S1 and diodes D2 are conducting. The current iLm is descending because source voltage Vin is applied on magnetizing inductor Lm and primary leakage inductor Lk1; meanwhile, Lm is also releasing its energy to the secondary winding, as well as charging capacitor C2 along with the decrease in energy, the charging current iD2 and iC2 are also

During this transition interval, secondary leakage inductor Lk2 keeps charging C3 when switch S1 is off. The current flow path is shown in Figure. 4, and only diodes D1 and D3 are conducting. The energy stored in leakage inductor Lk1 flows through diode D1 to charge capacitor C1 instantly when S1 turns off. Meanwhile, the Lk2 keeps the same current direction as in the prior mode and is in series with C2 to charge output capacitor C3 and load R. The 51

Nihina A M et al., International Journal of Emerging Trends in Engineering Research, 3(7), July 2015, 50 - 54 voltage across S1 is the summation of Vin, VLm, and VLk1. Currents iLk1 and iLk2 are rapidly declining, but iLm is increasing because Lm is receiving energy from Lk2. Once current iLk2 drops to zero, this mode ends at t = t3.

3.DESIGN CONSIDERATION A. Duty Ratio and Turns Ratio: 1+ = 1−

Stage 4[t3-t4]: :

Duty ratio and turns ratio can be selected from the above equation.D>70% would result in greater conduction losses.Also ≥ 4 will result in small duty ratio.So selection should be made by compromise between these two.

Figure 6.Mode IV of Novel zeta converter with coupled inductor

During this transition interval, the energy stored in magnetizing inductor Lm releases simultaneously to C1 and C2. The current flow path is shown in Figure. 5. Only diodes D1 and D2 are conducting. Currents iLk1 and iD1 are persistently decreased because leakage energy still flows through diode D1 and continues charging capacitor C1. The Lm is delivering its energy through T1 and D2 to charge capacitor C2. The energy stored in capacitors C3 is constantly discharged to the load R. The voltage across S1 is the same as previous mode. Currents iLk1 and iLm are decreasing, but iD2 is increasing. This mode ends when current iLk1 is zero at t = t4. Stage 5[t4-t5] :

Figure 8.Typical waveforms of the novel converter.

B. Magnetizing Inductor =

−2 + +4 +2

C. Active Switch and Diodes: The general voltage-rating active components obtained as follows

Figure 7.Mode V of Novel zeta converter with coupled inductor

During this interval, magnetizing inductor Lm is constantly transferring energy to C2. The current flow path is shown in Figure. 6, and only diode D2 is conducting. The iLm is decreasing due to the magnetizing inductor energy flowing continuously through the coupled inductor T1 to secondary winding N2 and D2 to charge capacitor C2. The energy stored in capacitors C3 is constantly discharged to the load R. The voltage across S1 is the summation of Vin and VLm. This mode ends when switch S1 is turned on at the beginning of the next switching period.

= =

VD3 =VO

Nihina A M et al., International Journal of Emerging Trends in Engineering Research, 3(7), July 2015, 50 - 54 D. Switched capacitors The energy transfers from the input through switched capacitors C1 and C2 to the output. Calculating the minimum capacitance of the switched capacitors depends on the maximum transferring power, the capacitor’s voltage, and the operating frequency. The voltage of C1 and C2 can be obtained as follows

C1≥ C2≥ Where

From the waveforms,it is seen that input voltage is 25v dc and the output voltage is 50v dc with large amount of ripple.

. . . .

Figure 11.Simulink model novel zeta converter with capacitor multiplier and coupled inductor.

and

= 4.SIMULATION RESULTS AND DISCUSSIONS

Figure 12.Input-output voltage waveform of novel zeta converter with capacitor multiplier and coupled inductor. The Figure. 11 shows the Simulink model for the novel zeta converter configuration. The circuit is built using MATLAB simulation package with an input voltage of 25v, a switching frequency of 50 kHz .From the waveform it is seen that output voltage is 200v dc.The ripple content is less in the output voltage when compared to that of conventional converter.The settling time is reduced by 0.09s. Table I List of components of two converters.

Figure 9.Simulink model of ZETA converter The Figure. 8 shows the Simulink model for the conventional converter configuration. The circuit is built using MATLAB simulation package with an input voltage of 25v, a switching frequency of 50 kHz . .

Figure 10.Input-output voltage waveforms of conventional ZETA converter.

Parameter

Zeta converter

Input voltage,Vi

25 v

Novel zeta converter 25 v

Output voltage,Vo Voltage gain,Vo/Vi Capacitor,C1 Capacitor,C2 Capacitor,C3 Inductor ,L1 Inductor ,L2 Duty ratio,D Switching frequency,fs Output power,P out

50 v 2 150µF 0 600µF 70µH 50mH 50% 50kHz 250W

200v 8 47µF 47µF 10µF 12.5µH 500µH 50% 50kHz 250W

Nihina A M et al., International Journal of Emerging Trends in Engineering Research, 3(7), July 2015, 50 - 54 The parameters of two converters are listed above.It was observed that the novel zeta converter is very much cost effective.The voltage gain of new converter is four times better than the conventional converter. Plot between the voltage gain(Vo/Vi) and duty ratio(D) of the converters are shown below.The voltage gain is 8 for the new converter even at 50% duty cycle, that may help to reduce conduction losses.

Figure 16.Input-output waveform of novel zeta converter with capacitor multiplier and coupled inductor with PI controller. The output voltage is more regulated with PI controller.Smooth changes is observed.

5.CONCLUSION The zeta converter is a fourth order dc-dc converter.To increase the voltage an extra capacitor and a coupled inductor is used.The coupled inductor replaces the two independent inductor,that leads to the reduced size and cost.The mutual induction in the coupled inductor also increase the voltage level.

Figure 13.Voltage gain(Vo/Vi) as a function of duty ratio(D) for the proposed converter(C1) and zeta converter(C2).

REFERENCES [1] Shih-Ming Chen, Tsorng-Juu Liang,Lung-Sheng

Yang and Jiann-Fuh Chen,” A Boost Converter With Capacitor Multiplier and Coupled Inductor for AC Module Applications”, IEEE transactions on Industrial electronics, vol. 60, no. 4, april 2013. [2] D. C. Martins, "Zeta Converter with High Power Factor Operating in Continuous Conduction Mode", Federal University of Catarina, Industrial Electronics, Control, and Instrumentation, IEEE pp. 1802-1807, 1996. [3] O.A.Taha "Cuk Converter Circuit Controller Design and Implemementation "M.Sc Thesis Mosul University, Mosul Iraq, 2007.. [4] J. Falin," Designing DC/DC converters based on ZETA topology", Analog Applications Journal, Texas Instruments Incorporated, pp, 16-20, 2010. [5] Ali H. Ahmad, Nashwan Saleh Sultan,” Design and Implementation of Controlled ZetaConverter Power Supply”, American JournaElectrical and Electronic Engineering, 2014, Vol. 2, No. 3, 121-128.

Figure 14.Simulink model novel zeta converter with capacitor multiplier and coupled inductor with PI controller.

Figure 15.System for generating gate signal