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Int. J. Elec&Electr.Eng&Telecoms. 2015 Rashmi B Kananthoor and Bharathi A Rao, 2015

INTERLEAVED BOOST CONVERTER

Rashmi B Kananthoor1* and Bharathi A Rao1

*Corresponding Author: Rashmi B Kananthoor, rashmi.bk90@yahoo.com

Interleaved boost converter is a converter where boost converters are connected in parallel. Inthis paper a IBC for input voltage of 15 V and 60 V is proposed. The topology is used to increasethe efficiency and reliability.

Keywords: Interleaved boost converter, Continuous Conduction Mode (CCM), Total HarmonicDistortion (THD)

INTRODUCTIONThe Interleaved Boost Converter (IBC)consists of two boost converters connected inparallel with a 180° phase delay, and operatingat the same frequency. The IBC has bettercharacteristics when compared to a boostconverter with improved efficiency, reducedsize, greater reliability and lower TotalHarmonic Distortions (THD). The gating pulsesof the two switches in the converter are shiftedby a phase difference of 360/n where n is thenumber of parallel boost converters.

The converter considered is operating inContinuous Conduction Mode (CCM) whichresults in lower input peak current (amplitude)and less conduction losses. It operates atlarger duty cycle say 0.5 due to high outputvoltage and low input voltage. The input currentfor the IBC is the sum of each inductor currents

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Int. J. Elec&Electr.Eng&Telecoms. 2015

1 Department of Electrical and Electronics, St. Joseph Engineering College, Vamanjoor, India.

and as the two devices are phase shifted by180°, the input current ripples are small.

The proposed interleaved boost converteris as shown in Figure 1.

Research Paper

Figure 1: Block Diagram of the ProposedInterleaved Boost Converter

The input is an unregulated DC voltage,which is obtained by rectifying line voltage. DC-DC converters are switched mode DC to DCconverter and are used to convert unregulatedDC input to controlled DC output. The IBC

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Int. J. Elec&Electr.Eng&Telecoms. 2015 Rashmi B Kananthoor and Bharathi A Rao, 2015

consists of two boost converters in parallel witha phase delay of 180° operating in CCM mode.The converter uses two MOSFET switches, twoinductors, two diodes, one capacitor and aresistive load.

PROPOSED TOPOLOGYProposed IBCThe circuit diagram and the ideal waveformsof the currents in the inductors L1 and L2 forinterleaved boost converter operating at CCMare shown in Figures 2 and 3.

inductor L1. When S1 is turned OFF, diodeD1 conducts and the stored energy in theinductor ramps down with a slope based onthe difference between the input and outputvoltage. The inductor starts to discharge andtransfer the current via the diode to the load.After a half switching cycle of S1, S2 is alsoturned ON completing the same cycle ofevents. Since both the power channels arecombined at the output capacitor, the effectiveripple frequency is twice than that of a single-phase boost converter. The amplitude of theinput current ripple is small.

Design ParametersBoost RatioThe boosting ratio of the converter is a functionof the duty ratio. It is same as in conventionalboost converter. It is defined as:

푉표푉푖푛

=1

1 − 퐷

where Vo is the output voltage, Vin is the inputvoltage and D is the duty ratio.

Input Current

The input current can be calculated by the inputpower and the input voltage.

퐼푖푛 =푃푖푛푉푖푛

where Pin is the input power and Vin is theinput voltage.

Inductor Current Ripple Peak-To-Peak Amplitude

∆퐼푙1,푙2 =푉푖푛 ∗ 퐷푓푠 ∗ 퐿

where is the fs switching frequency, D is theduty cycle, Vin is the input voltage and L is theinductance.

Figure 2: Interleaved Boost Converter

Figure 3: Ideal Waveforms of InductorCurrents for IBC in CCM

When the device S1 is turned ON, thecurrent in the inductor iL1 increases linearly.During this period energy is stored in the

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Int. J. Elec&Electr.Eng&Telecoms. 2015 Rashmi B Kananthoor and Bharathi A Rao, 2015

Selection of Inductor andCapacitorThe operation of IBC, the inductor is used totransform the energy from the input voltage tothe inductor current and to convert it back fromthe inductor current to the output voltage. Asper the principle the two inductors are identicalin order to balance the current in the two boostconverters.

The value of the inductor can be found outby the following formula

퐿 =푉푖푛 ∗ 퐷∆퐼푙 ∗ 푓푠

where Vs represents the source voltage andIl represents the inductor current ripple, Drepresents the duty ratio. The value of thecapacitor is given by the formula

퐶 =푉푖푛 ∗ 퐷푅 ∗ ∆푉표

where Vo represents the output voltage (V), Drepresents the duty ratio, R represents theresistance and Vo represents the change inthe output voltage.

Parameters Considered

The value of the parameters considered in thesimlation is shown in Table 1.

SIMULATION AND RESULTSUsing MATLAB/SIMULINK the simulation ofinterleaved boost converter is performed. Thewaveforms of the input voltage, output voltage,inductor currents, and voltage ripple are shown.

Open Loop SimulationFor Vin = 60 V, D = 0.5The open loop simulation circuit is shown inFigure 4, Input voltage Vin = 60 V, Duty cycle =0.5, Inductances L1 and L2 = 1.25 mH,Capacitance Co = 330, Resistance Ro = 120, switching frequency = 100 KHz. Outputvoltage of approximately 120 V is obtained.MOSFET switches are used because of itshigh commutation speed and high efficiencyat low voltages.

Parameter Symbol Value Unit

Input Voltage Vin 60 15 V

Output Voltage Vout 120 30 V

Inductotrs L1, L2 1.25 1.25 m H

Output Capacitor Co 330 30 µF

Resistance Ro 120 60

Switching Freqency fs 100 100 KHz

Duty Cycle D 0.5 0.5 -

Table 1: Parameters Considered

Figure 4: Open Loop Simlation Circuitfor IBC

Figure 5: Waveforms for Output and InputVoltage

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Int. J. Elec&Electr.Eng&Telecoms. 2015 Rashmi B Kananthoor and Bharathi A Rao, 2015

The waveforms for the output voltage andthe input voltage is shown in Figure 5, currentthrough the inductors L1 and L2, capacitorvoltage and input current shown in 6, the output

voltage ripple shown in Figure 7, the pulsesapplied to the switches are shown in Figure 8.

For Vin = 15 V, D = 0.5Input voltage Vin = 15 V, Duty cycle = 0.5,Inductances L1 and L2 = 1.25 mH, CapacitanceCo = 30, Resistance Ro = 60, switchingfrequency = 100 KHz. A output voltage ofapproximately 30 V is obtained.

The waveforms for the output voltage andthe input voltage is shown in Figure 9, currentthrough the inductors L1 and L2, and inputcurrent shown in 10, the output voltage rippleshown in Figure 11.

Figure 6: Waveforms for Two InductorCurrents, Capacitor Voltage and Input

Current

Figure 7: Output Voltage Ripple

Figure 8: Gate Pulses for the IBC

Figure 9: Waveforms for Outputand Input Voltage

Figure 10: Waveforms for Two InductorCurrents, and Input Current

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Int. J. Elec&Electr.Eng&Telecoms. 2015 Rashmi B Kananthoor and Bharathi A Rao, 2015

Closed Loop SimulationThe closed loop simulaion circuit for theconverter is shown in Figure 12 where Vin =15 V, D = 0.5, Co = 30 µF, L1 and L2 = 1.25 mH,fs = 100 KHz, Vo = 30 V. A PI controller is used.

Ac-Dc Interleaved Boost ConverterThe open loop simulation circuit is shown inFigure 13, Vin = 15 V, D = 0.5, L1 and L2 = 1.25mH, Co = 330 µF, Ro = 60 , fs = 100 KHz, Vo =30 V.

Figure 12: Output Voltage Ripple

Duty Cycle Vin = 60 V Vin = 15 V

50% 119.1 V 29.92 V

60% 148.4 V 38.58 V

70% 197.5 V 46.22 V

80% 293.9 V 64.48 V

90% 559.2 V 164.1 V

Table 2: Variation of Output Voltagewith Duty Ratio

Figure 12: Closed Loop Simulation Circuitof IBC

Figure 13: Ac-Dc IBC

Figure 14: Inductor Currents and OutputVoltage

Figure 15: Gate Pulses for the Switches

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Int. J. Elec&Electr.Eng&Telecoms. 2015 Rashmi B Kananthoor and Bharathi A Rao, 2015

The waveforms for the output voltage andcurrent through the inductors L1 and L2 areshown in Figure 14, the gate pulses for theswitches is shown in Figure 15.

CONCLUSIONIn this paper interleaved boost converteroperating at input voltages 60 V and 15 V isproposed. The simulation results are obtainedfor open loop operation for dc-dc IBC and ac-dc IBC.

ACKNOWLEDGMENTWe would like to thank our Head of theDepartment and Principal of St. JosephEngineering College, Mangalore for guidingus and supporting us throughout the work.

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