Using CAD Pspice to calibrate the output of the Proposed DC-DC Power Converter

Using CAD Pspice to calibrate the output of the Proposed DC-DC Power Converter

Irfan Jamil1, Prof. Jinquan Zhao2, Muhammad Aurangzeb3, Muhammad Fahad Ali4

1 2 3 4Hohai University, College of Energy & Electrical Engineering, Nanjing, China

Rehan Jamil

Project Manager, TBEA, China

Abstract— In this research paper a detailed study of zero current switching buck converters is done and also practically implemented in hardware. The hardware is simulated & layout into two widely using CAD software’s which are PSpice & Protel In this research report, the Buck type circuit structure and working principle are analyzed and a DC-DC buck converter is designed. The designed converter uses ZCS scheme and realized the function that the power form is converted from 12V DC voltages to 5 V DC voltages. The output voltage can be adjusted according to the output resistor. The output voltage is stable and the performance of the designed converter is ensured. Simulation study was carried out and effectiveness of the designed converter is verified by simulation results. Finlay design is implemented in hardware and PCB layout using PSpice & protel software as well.

I. Introduction

Direct current to direct current (DC-DC) converters are power electronics circuits that converts direct current (DC) voltage input from for low power applications to solve the problem of buck converter. The converter uses switching scheme operates the switches such as MOSFET in Cut-off and saturation region to reduce power loss across the transistor or switch. The output voltage level is then regulated by the control circuit and power circuit to desired output voltage level as in the design specification.one level to another. DC-DC converters are also known as switching converters, switching power supplies or switches. DC-DC converters are important in portable device like such as cellular phones and laptops. The main objective of this project is to design a buck converter to convert the input DC voltage to lower DC output voltage level operates the switches such as MOSFET in Cut-off and saturation region to reduce power loss across the transistor or switch. The output voltage level is then regulated by the control circuit and power circuit to desired output voltage level as in the design specification.

II. Hardware design

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Above Block diagram shows that the circuit working stage that how to work this circuit to build control and power stages. Control circuit has main role in the buck converter design as where power circuit is followed by control stage. 555NE chip is controller with MOSFET IRF and variable resistor. In Power circuit the components are worked such as diode, Load resistance, resonant capacitor, load capacitor and resonant inductor as well. Schematic diagram of buck converter 12VDC to 5VDc is drawn first in PSpice software and after the successfully run the simulation, the diagram is schematized by protel software to obtain the PCB documents file. It is final diagram of circuit which is use for PCB layout. The diagram is included two main part of converter Control & power circuits which is shown in fig.1

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Fig.1 schematic diagram of buck converter

Hardware design has first step in simulation design by using PSpice software. So we got Simulation running results are reading and checking circuit and finding no errors. Calculating bias point for transient analysis then starting power supply stepping. When the bias point calculated transient analysis then transient analysis finished at meanwhile simulation complete as we can see in fig.1 simulations. In this simulation we have values from the input power supply 12VDC and from the load resistor Ro + Vdc probe 12.00Vdc and other probe –Vdc 7.053Vdc , Hence we gained two values As we can calculated by simulation result by load resistor probe 12.00Vdc-7.053Vdc= 4.947~ 5.00Vdc. Here in fig. 2 Simulation is done by PSpice

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Fig. 2.Simulation

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Fig.3. Simulation

III. Work & implementation

We have done experiments in lab and got require values according to experimental hardware which proves that the hardware could be possible implemented in condition of PCB layout from the below figures, we got exact value of 5v dc to supply 12vdc from the power supply device. In different section, we have absolutely 5.09vdc, 5.06vdc and so on. These values are relatively near to our require values to test our output. For our circuit the multimeter reading showed that for an input of 12V, output is 5V (when the switch is turned to one side) and the output is 5.01V(when the switch is turned to other side) and the current drawn is 0.13A . The oscilloscope reading, on the other hand, gave us an output value of 5.06V and 5.09V and a current of 0.l3A. A major problem in our circuit was noise. For an output of 5.06V, the noise was found to have amplitude of 531.3mV and frequency of 32 MHz’s. To reduce the noise in the circuit, we increased the load capacitance. As we managed the load capacitor 47UF to control the noise for output voltage.

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Iv. PCB layout project contraction consideration

Using protel software builds up schematic design of buck converter and at the end PCB layout. The PCB is layout with two layers, one is Top layer and other is Bottom layer which give the indication of hardware components connection. The components wired with adjunct in PCB board as shown in the pictures. When the simulation results had been confirmed to be approximately the same with the predictions, the power circuit and control circuit are assembled on the PCB.

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Fig.4. PCB Top Layer

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Fig.5. PCB Bottom Layer

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Fig. 6. Before the layout and Test Circuit Board TCB with DC Components

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Fig.7. After the layout and Printed Circuit Board PCB with DC Components

v. observations of waveforms

By using oscilloscope device to obtain the waveforms from the different Test point of the hardware. The waveforms figures as shown below.

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Fig.8. Output Voltage across Load Ro

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Fig.9. Voltage across Test point

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Fig.10. Voltage across Test

vi. Calculation & Mathematical Analysis of Modes of Operation

We operate from a regulated DC voltage supply and as the capacitor rating is a maximum voltage of 25V we select Vs=12V.Assuming a purely resistive load the approximate current flowing in the load resistance is obtained as: Io = 12/90=0.133A.Resonant inductor = 2mH; Resonant capacitor C3 = 1uF

Mode 1

This mode is valid for 0 < t < t1. Switch S1 is turned on and diode Dm conducts. The inductor current iL which rises linearly is given by IL = (Vs/L)t. This mode ends at time t=t1 when il (t=t1) = 0.133. That is t1 = I0L/Vs = (0.133*2*e-3)/(12)= 2.21xe-5 sec.

Mode 2

This mode is valid for 0 < t < t2. Switch S1 remains on but diode Dm is off. The inductor current iL is given by iL=Im sin ωot + I0 , where Im = Vs√(C/L)= 12(1*e-6/2*e-3) ^0.5=0.268 The capacitor voltage Vc is given by Vc = 12(1 – cosω0t). The peak current which occurs at t = (π/2)√LC is Ip = Im + I0 = 0.133+0.268=0.401A The peak capacitor voltage is given by Vc(pk) = 2Vs =24V. This mode ends at t = t2 when iL(t = t2) = I0 and Vc( t = t2 ) = Vc2 = 2Vs=24V. Therefore t2 = π√LC = 3.14*(2*e-3*1*e-6) ^0.5 =1.40xe-5 sec.

Mode 3

This mode is valid for 0 < t < t3. The inductor current that falls from I0 to zero is given by iL = I0 – Im sinω0t. The capacitor voltage is given by Vc = 10cosω0t. This mode ends at t = t3 when iL (t = t3 ) = 0. And Vc(t = t3) = Vc3. Thus t3 = √LCsin-1(1/x) Where x = Im/I0 = (Vs/I0)√C/L= 1.67xe-5

Mode 4

This mode is valid for 0 < t < t4. The capacitor supplies the load current Io(0.133) and its voltage is given by Vc = Vc3 – (I0/C)t This mode ends at t = t4 when Vc (t = t4) = 0. Thus t4 = Vc3C/I0 ; Vc3=1.6V; t4=1.20xe-5 sec.

Mode 5

This mode is valid for 0 < t < t5. When the capacitor voltage tends to be negative, the diode Dm conducts. The load current Io flows through diode Dm. This mode ends at time t=t5 when the switch S1 is turned on again and the cycle is repeated i.e. t5=T-(t1+t2+t3+t4). For the sake of simplicity we assume t5=0.Therefore Ton = t1+t2+t3= 5.28xe-5 Toff = t4+t5= t4 = 1.20xe-5 T= Ton + Toff = 6.48xe-5 Duty ratio = Ton/T = 81.48% Frequency of operation = 1/T = 15 KHz.

vii. conclusion

An overview on the results obtained and the future development of low power in electronics devices are in the concluding statement. This research concludes this report by suggesting some possible future recommendations to the enhancement of this “ZCS Buck Converter 12vdc to 5vdc”.ZCS buck converter is an efficient step down DC-DC converter used in numerous electronics devices. The same was implemented as a hardware project and an output voltage of 5V was obtained with an input of 12V DC supply. The time analysis of various modes of zcs buck converter was done and tuning of the IC555 was done accordingly. Also the waveforms across capacitors and various test points were obtained, studied and compared with the theoretical waveforms. The waveforms were found to be in precise proximity of theoretical waveforms. And software’s were included from CAD design such as PSpice & Protel in this project as well.

references

[1]. Switching Power supply A to Z Sanjaya Maniktala book 2006, Dc Dc converter design and magnetic.
[2]. Muhammad Saad Rahman, Master thesis in Electronic Devices at Linköping Institute of Technology, Buck Converter Design Issues.
[3]. Fayaz Kadair,s Blog /page Dc-Dc converters , Buck converter
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[7]. Wilson Eberle, Zhiliang Zhang, Yan-Fei Liu and Paresh C. Sen ; IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 24, NO. 3, MARCH 2009, A Practical Switching Loss Model for Buck Voltage Regulators.
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[9]. Power Electronics By M D Singh, K. B. Khanchandani second edition Chapter 8 Chopper Control Strategies
[10]. NE555 Datasheet and Circuit Schematic Overview http://datasheetreference.com/ne555-datasheet.html