DC/DC CONVERTERS MADE EASY A Beginner Guide To Power Electronics NORAIN BINTI ZAKARIA ROSMANI BINTI RAMLI SYAHFITRI BIN SAIDIN
DC/DC CONVERTERS MADE EASY A BEGINNER GUIDE TO POWER ELECTRONICS NORAIN BINTI ZAKARIA ROSMANI BINTI RAMLI SYAHFITRI BIN SAIDIN
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The Ebook DC/DC Converters Made Easy: A Beginner Guide To Power Electronics contains a basic knowledge developed specifically for polytechnic students. This book focuses on guiding readers to understand the DC/DC Converters and step by step of the usage MATLAB software to carry out practical work. This guide contains 2 topics related to the DC/DC Converters which is Buck and Boost Chopper. Also at the end of chapter, Exercises are provided to further enhance the understanding of the chapter. Alhamdulillah, praises to Allah SWT, with His grace and mercy, the eBook DC/DC Converters Made Easy: A Beginner Guide To Power Electronics has finally completed. We would like to express our appreciation to the eLearning Politeknik Sultan Abdul Halim Mu’adzam Shah which gave opportunities and inspiration to produce this eBook. Our experience in the teaching and learning process of the previous subject is an advantage that guides us along the way. The editor would like to give highest regards and appreciation to all who have been involved either directly or indirectly in making this project eBook work. Any positive feedback from lecturers and students are mostly welcomed and appreciated. It is hoped that this eBook will be one of the tiny steps that we have made to start the long journey of road to excellent. PREFACE
NORAIN BINTI ZAKARIA ROSMANI BINTI RAMLI SENIOR LECTURER SENIOR LECTURER BACHELOR OF ELECTRICAL AND ELECTRONICS ENGINEERING (POWER) UNIVERSITI PUTRA MALAYSIA BACHELOR OF ELECTRICAL ENGINEERING WITH HONORS UNIVERSITI TUN HUSSEIN ONN MALAYSIA (UTHM) SYAHFITRI BIN SAIDIN SENIOR LECTURER MASTER OF ELECTRICAL ENGINEERING UNIVERSITI TUN HUSSEIN ONN MALAYSIA (UTHM) Meet Our Team Together, we're committed to delivering excellence and making a positive impact
Buck Chopper (Step-Down Converter) Practical Work with DC/DC Converters Comparison 01 02 03 04 TABLE OF CONTENTS Page 01 Page 15 Page 29 Page 34 Function Waveform Circuit Operation Analysis Formula Function Waveform Circuit Operation Analysis Formula Buck Chopper by using MATLAB Software Boost Chopper by using MATLAB Software Boost Chopper (Step-Up Converter) 05 Exercises Page 37
BUCK STEP-DOWN CONVERTER ------------------ CHOPPER Chapter 1 1
The input voltage source is connected to a controllable solid state device which operates as a switch. The solid state device can be a Power MOSFET or IGBT. To maintain a continuous output, the circuit uses the energy stored in the inductor L, during the on periods of the switching transistor, to continue supplying the load during the off periods. Vo < Vin The Buck Converter is used in SMPS circuits where the DC output voltage needs to be lower than the DC input voltage. The DC input can be derived from rectified AC or from any DC supply. A buck chopper is a type of power electronic converter that can reduces the input DC voltage to a specified DC output voltage. Step-down converter Output voltage (Vo) lower than Input Voltage (Vi) 2 THE FUNCTION OF BUCK CHOPPER
THE WAVEFORMS STEP-DOWN CONVERTER 3
MODE 1 Switch is ON Diode is Off (ON STATE) 4 CIRCUIT OPERATION FOR A CLOSED SWITCH STEP-DOWN CONVERTER
The inductor current increases and energy is stored in the inductor L MODE 1 (ON STATE) 5 When switch S is ON (closed) the diode is reverse biased and the input voltage, Vin is connected to the inductor. This results in positive inductor voltage VL Capacitor will charge during this state CIRCUIT OPERATION FOR A CLOSED SWITCH STEP-DOWN CONVERTER
ANALYSIS OF STEP-DOWN CONVERTER MODE 1 (ON STATE) 6 Vin supplies load and charges L and C. ON Switching ON Field Expanding D Reverse Biased OFF C charging Load + + - - +
ANALYSIS OF STEP-DOWN CONVERTER Since the switch is closed for a time Ton = DT we can say that Δt = DT. MODE 1 (ON STATE) 7 Using Kirchoff Voltage Law (KVL).
Switch is OFF Diode is ON 8 MODE 2 (OFF STATE) CIRCUIT OPERATION FOR AN OPEN SWITCH STEP-DOWN CONVERTER
9 When the switch is OFF (open) the diode becomes forward biased The energy stored in the inductor L is released back into the circuit Due to capacitor discharge, there will be an output at load. MODE 2 (OFF STATE) CIRCUIT OPERATION FOR AN OPEN SWITCH STEP-DOWN CONVERTER
ANALYSIS OF STEP-DOWN CONVERTER Switching OFF Field Collapsing D Forward Biased ON C Discharging Load + + MODE 2 (OFF STATE) 10 Vl and Vc supply load via D
ANALYSIS OF STEP-DOWN CONVERTER MODE 2 (OFF STATE) Using Kirchhoff Voltage Law (KVL) Since the switch is open for a time Toff = (1-D) T we can say that Δt = (1-D) T 11
@ r e a l l y g r e a t s i t e It is already established that the net change of the inductor current over any one complete cycle is zero. B U C K C O N V E R T E R ANALYSIS OF STEP-DOWN CONVERTER 01 12
Benjamin Shah Lorem ipsum dolor sit amet, consectetur adipiscing elit. Mauris scelerisque venenatis augue, et tincidunt magna aliquet quis. Morbi pretium ipsum ac sapien tempor porta. Proin semper, turpis id posuere placerat, augue augue rhoncus justo, vitae egestas enim velit vel metus. Quisque neque erat, placerat eget volutpat nec, auctor at nibh. FORMULA B STEP-DOWN CONVERTER U C K C H O P P E R Output Voltage Output Current Duty cycle Output Power 163
Benjamin Shah Lorem ipsum dolor sit amet, consectetur adipiscing elit. Mauris scelerisque venenatis augue, et tincidunt magna aliquet quis. Morbi pretium ipsum ac sapien tempor porta. Proin semper, turpis id posuere placerat, augue augue rhoncus justo, vitae egestas enim velit vel metus. Quisque neque erat, placerat eget volutpat nec, auctor at nibh. FORMULA STEP-DOWN CONVERTER B U C K C H O P P E R Max inductor current Min inductor current Peak to peak inductor current Peak to peak ripple voltage of the capacitor 164
BOOST STEP-UP CONVERTER ------------------ CHOPPER Chapter 2 15
In a boost chopper, the input voltage is applied to an inductor, which stores energy during the "on" time of the switch and releases it during the "off" time. This creates a voltage boost across the output capacitor, resulting in a higher output voltage than the input voltage The boost chopper operates by controlling the duty cycle of a switching device (usually a transistor) that is connected to an inductor and a diode. Vo > Vin A boost chopper is a type of power electronic converter that can increase the output voltage of a DC power source. Step-up converter Output voltage (Vo) higher than Input Voltage (Vi) 16 THE FUNCTION OF BOOST CHOPPER
THE WAVEFORMS STEP-UP CONVERTER 17
MODE 1 Switch is ON Diode is Off (ON STATE) 18 CIRCUIT OPERATION FOR A CLOSED SWITCH STEP-UP CONVERTER
Inductor will start charging and its polarity will make the D reverse bias MODE 1 (ON STATE) 19 During switch ON, TON = DT. No current will pass through D. The energy stored earlier in the capacitor is discharged and supplies the current to load. Vo still exist across the load. CIRCUIT OPERATION FOR A CLOSED SWITCH STEP-UP CONVERTER
ANALYSIS OF STEP-UP CONVERTER Vin charges L Vc supply load MODE 1 (ON STATE) 20 ON Square Wave HIGH L Storing Energy Load + - MOSFET Switch ON - + C Supplies Load
ANALYSIS OF STEP-UP CONVERTER Since the switch is closed for a time Ton = DT we can say that Δt = DT. Using Kirchoff Voltage Law (KVL). MODE 1 (ON STATE) 21
Switch is OFF Diode is ON 22 MODE 2 (OFF STATE) CIRCUIT OPERATION FOR AN OPEN SWITCH STEP-UP CONVERTER
23 During switch OFF, TOFF = (1-D)T Inductor will start discharging and its polarity will make the D1 forward bias. Current now can pass through D and reach the load. The output stage receives energy from the input as well as from the inductor. Hence output is large. MODE 2 (OFF STATE) During this time capacitor will start charging. CIRCUIT OPERATION FOR AN OPEN SWITCH STEP-UP CONVERTER
L Returning energy to circuit Vin and Vl supply load ANALYSIS OF STEP-UP CONVERTER D Forward Biased ON C charges Load - - MODE 2 (OFF STATE) 24 + + MOSFET switch OFF Square wave LOW
ANALYSIS OF STEP-UP CONVERTER MODE 2 (OFF STATE) Using Kirchhoff Voltage Law (KVL) Since the switch is open for a time Toff = (1-D) T we can say that Δt = (1-D) T 25
@ r e a l l y g r e a t s i t e It is already established that the net change of the inductor current over any one complete cycle is zero. B O O S T C O N V E R T E R ANALYSIS OF STEP-UP CONVERTER 26
Benjamin Shah Lorem ipsum dolor sit amet, consectetur adipiscing elit. Mauris scelerisque venenatis augue, et tincidunt magna aliquet quis. Morbi pretium ipsum ac sapien tempor porta. Proin semper, turpis id posuere placerat, augue augue rhoncus justo, vitae egestas enim velit vel metus. Quisque neque erat, placerat eget volutpat nec, auctor at nibh. FORMULA B STEP-UP CONVERTER O O S T C H O P P E R Output Voltage Output Current Duty cycle Output Power 267
Benjamin Shah Lorem ipsum dolor sit amet, consectetur adipiscing elit. Mauris scelerisque venenatis augue, et tincidunt magna aliquet quis. Morbi pretium ipsum ac sapien tempor porta. Proin semper, turpis id posuere placerat, augue augue rhoncus justo, vitae egestas enim velit vel metus. Quisque neque erat, placerat eget volutpat nec, auctor at nibh. FORMULA STEP-UP CONVERTER B O O S T C H O P P E R Max inductor current Min inductor current Peak to peak inductor current Peak to peak ripple voltage of the capacitor 268
Practical Work with DC/DC Converters ------------------ Chapter 3 29 MATLAB SIMULINK
BUCK CONVERTER Buck converter circuit diagram Buck converter circuit diagram using Matlab Simulink 30
BUCK CONVERTER Waveform: Induction Voltage (VL) and Induction Current (IL) using Matlab Simulink Waveform: Input Voltage (VIN) and Output Voltage (VOUT) using Matlab Simulink 31
BOOST CONVERTER Boost converter circuit diagram using Matlab Simulink Boost converter circuit diagram 32
BOOST CONVERTER Waveform: Induction Voltage (VL) and Induction Current (IL) using Matlab Simulink Waveform: Input Voltage (VIN) and Output Voltage (VOUT) using Matlab Simulink 33
COMPARISON ------------------ Chapter 4 34
BUCK CONVERTER (STEP DOWN) BOOST CONVERTER (STEP UP) The average output DC voltage is always less than the input DC voltage The average output DC voltage is always greater than the input DC voltage The switching device is connected in series with load The switching device is connected in parallel with load The average output voltage Vo = DVin where D = duty cycle The average output voltage Vo = Vin 1-D where D = duty cycle It steps down Vo and steps up Io It steps down Io and steps up Vo Input current is discontinues Input current is continues Application: DC Motor speed control Application: Voltage booster/ Battery charging COMPARISON 35
Comparison: On Sate and Off State for Buck and Boost Converter Buck Converter II Boost Converter 36
EXERCISES ------------------ Chapter 5 37
Figure below shows an output waveform of step down converter. Calculate the value of switching frequency and input voltage. EEXXAAMMPPLLEE 1 SOLUTION 38 BUCK CONVERTER
A buck converter operates from 50V source battery with a resistive load of 20Ω. The frequency of the chopper is 200Hz. Determine the average output voltage, Voavg and average output current, Ioavg, if the chopper conduction time is 2ms. EEXXAAMMPPLLEE 22 SOLUTION 39 BUCK CONVERTER
a. Ton and Toff b. The new output voltage if the duty cycle increased to 60%. If the chopper is operated at 50Hz with input voltage is, Vin= 200V and the output voltage is Vout=60V, calculate: EEXXAAMMPPLLEE 3 SOLUTION 40 BUCK CONVERTER
A buck converter is supplied from a 65V battery source. Given L=450µH, C=150µF, R=25Ω, f=20kHz and D=0.5. Calculate: i. Average output voltage,V0 ii Minimum inductor current, IL (min) iii. Maximum inductor current, IL (max) EEXXAAMMPPLLEE 44 SOLUTION 41 BUCK CONVERTER
A step up converter operates at frequency of 25kHz from 12V DC source. Given resistive load=50Ω, inductive load=120µH and the duty cycle is 60%. Calculate the minimum and maximum current and then sketch the inductor current waveform of the converter. EEXXAAMMPPLLEE 5 SOLUTION 42 BOOST CONVERTER
EEXXAAMMPPLLEE 5 43 SOLUTION BOOST CONVERTER
Construct the schematic circuit of Boost converter with RL load and label completely the parameters Vi = 30V, Vo = 75, R = 10Ω, L = 150mH, C = 470µF and F = 10kHz. Based on the circuit, sketch the waveform of input voltage (Vi), switch state (VSW) and inductor voltage (VL). The sketch should include the value of total time, T and conduction time, Ton. EEXXAAMMPPLLEE 6 SOLUTION 44 BOOST CONVERTER