Development Of A Dc To Dc Buck Converter For Photovoltaic Application .
VOL. 14, NO. 7, APRIL 2019ISSN 1819-6608ARPN Journal of Engineering and Applied Sciences 2006-2019 Asian Research Publishing Network (ARPN). All rights reserved.www.arpnjournals.comDEVELOPMENT OF A DC TO DC BUCK CONVERTER FORPHOTOVOLTAIC APPLICATION UTILIZING PERIPHERAL INTERFACECONTROLLERZ. A. Ghani1, K. Kamit2, M. Y. Zeain1, Z. Zakaria1, F. A. Azidin1, N. A. A. Hadi 3, A. S. M. Isira1,H. Othman4 and H. Lago51Advanced Sensors and Embedded Control Systems (ASECs), Center for Telecommunication Research and Innovation (CeTRI), Facultyof Electronic and Computer Engineering, Universiti Teknikal Malaysia Melaka, Hang Tuah Jaya, Durian Tunggal, Melaka, Malaysia2Department of Electrical Engineering, Politeknik Ibrahim Sultan, Masai, Johor, Malaysia3Faculty of Electrical and Electronic Engineering Technology, Universiti Teknikal Malaysia Melaka, Hang Tuah Jaya, Durian Tunggal,Melaka, Malaysia4Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, Bangi, Selangor, Malaysia5Faculty of Engineering, Universiti Malaysia Sabah, Kota Kinabalu, Sabah, MalaysiaE-Mail: zamre@utem.edu.myABSTRACTNowadays, renewable energy has become one of the important energy resources in our daily lives. One of theimportant and promising renewable energy resource today is the photovoltaic (PV). However, weather changes contributeto the PV output power fluctuations. Thus, for a PV-related system, a closed-loop control system is necessary for ensuringthe system produces a regulated dc output voltage. This paper presents the development of PIC16F877A microcontrollerbased dc to dc buck converter. This converter steps down a dc voltage source to a specific voltage which suitable for otherspecific applications. For the PV output voltage fluctuating from 18V to 12V, the microcontroller generates a pulse-widthmodulation (PWM) signal accordingly to control the converter switching device MOSFET IRF540, thus regulating theconverter output voltage to 12V. The system simulation was carried out in the PROTEUS ISIS Professional software tool.Due to the unavailability of the PV device in this simulation software, a dc voltage source is utilized. This voltage source isvaried to emulate the PV output variations. The simulation results show that the controller managed to step-down thevoltage source and regulated at 11.98Vdc. The prototype was built and tested in a laboratory for validation. Due to theconstrains and limitations of the PV module, an adjustable power supply was used to provide variation of input voltagelevels for the buck converter. The experiment results also show that the output voltage is managed to be regulated at 12V.The results signify the efficacy of developed converter control system algorithm.Keywords: renewable energy, photovoltaic (PV), dc to dc, buck converter, pulse-width modulation (PWM), PIC16F877Amicrocontroller.1. INTRODUCTIONPresently, with the advancement of technology,there is a need to look for alternative energy resources aspart of the world future energy sustainability. Renewableenergy resources are one of the latest technologies for thealternative energy that being used nowadays [1-2]. Someof the energy resources are sun, wind, water, etc. Theworld has a highly significant need for a new energysources to replace the existing fuel. In countries where thesun shines throughout the year, solar energy is veryeffective and convenient to use. The use of photovoltaic(PV) modules to convert sunlight directly into electricity isvery practical. PV is known as a method for generatingelectric power by using solar cells to convert energy fromthe sun into a flow of electrons.In order to utilize the PV for delivering power tospecific loads, the output needs voltage conversion. A dcto dc conversion technology is a major subject area in thefield of power electronic, power engineering and drives.This conversion technique is widely adopted in industrialapplication and computer hardware circuits, where thesimplest dc to dc conversion technology is a voltagedivider, potentiometer and more. Based on the knowledgein the field of electrical engineering there are threemethods that can be used to change or reduce the value ofthe dc voltage to a lower dc voltage value.Firstly, is a voltage divider; secondly are a linearvoltage regulator technique and lastly a buck convertercircuit [3]. The buck converter acquires the highestefficiency among other dc conversion techniques. In PVsystems, power electronics circuits are utilized as a part ofa PV charge controller to achieve a good productivity,accessibility and dependability The utilization of powerelectronics circuits such as dc to dc converters topologieslike buck converter, boost converter, buck-boost converterand other topologies as power molding hardware to supplycurrent needed to charge battery successfully [4-7]. Theconverter control system in PV is capable of storingelectrical energy through the battery charging process,thus, supplying energy to electrical loads such as dcmotors and other home appliances.However, the voltage produced by PV fluctuatesdue to the weather inconsistency and this issue needs to beaddressed in the design of PV systems [8-10]. Thus, for aPV-related system, a closed-loop control system is vitalfor ensuring the system produces a constant dc outputvoltage even in the presence of PV output fluctuations [9].In this regard, a dc to dc buck converter is integrated into1317
VOL. 14, NO. 7, APRIL 2019ISSN 1819-6608ARPN Journal of Engineering and Applied Sciences 2006-2019 Asian Research Publishing Network (ARPN). All rights reserved.www.arpnjournals.comthis PV system. The converter converts the output voltagegenerated by the PV to the desired output voltage.The essence of the developed converter controlalgorithm in regulating the desired output voltage is that itspecifies only a specific input voltage ranges, e.g. 18Vdown to 12V. Instead of using the converter output as afeedback parameter, the controller uses the input voltageas the feedback parameter. For the PV output voltagevalues lower than the minimum level or out of the range,no energy conversion is performed, thus conserving thesystem operating energy.2. SYSTEM CONFIGURATIONThe general configuration of PV system for a dcto dc buck converter is shown in Figure-1.Buck converterDc inputLoadPWMGate driverVoltage sensorPWMinputControllerFigure-1. Configuration of PV dc to dc buck converter.It consists of a PV module, buck converter,controller, transistor gate driver circuit, voltage sensorcircuit and load. The PV module provides a dc voltagesource to the buck converter which then steps it down to aspecific voltage lower than the input voltage. Dependingon the weather conditions, the PV exhibits the outputvoltage fluctuations. This voltage is measured by thevoltage sensor and fed to the controller for the purpose ofvoltage generation and regulation.Considering the controller input voltage levelrequirement which is normally 5V, the output of thevoltage sensor must not exceed 5V. Based on the voltagelevel, the controller generates an appropriate PWM signalfor the switching device such as metal oxidesemiconductor field-effect transistor (MOSFET), thusgenerating the desired output voltage at the converteroutput terminal. A PWM is a switching method where theduty ratio, D of the transistor is varied [11]. A duty ratiowhich represented by equation 1 is defined as the ratio ofthe ‘on’ duration, ton to the switching time period, Ts [11].𝑡𝑜𝑛𝑡𝑜𝑛 𝑡𝑜𝑓𝑓 𝑡𝑜𝑛𝑇𝑠3. SYSTEM DESIGN AND SIMULATIONIn this section, the design of the system and itssimulation are presented.A. SYSTEM DESIGNThe design of the buck converter system involvesboth hardware and software aspects.a) Buck converter circuit designThe dc input voltage source and desired outputvoltage are taken into consideration in designing the buckconverter circuit. The parameters are illustrated in Table-1.Table-1. Buck converter parameters.PV module𝐷 Depending on the type of switching device, MOSFET forinstance, a gate driver circuit is required. It converts thePWM signal voltage level to suit the device triggeringlevel requirement(1)It is usually expressed in the form of percentage,ranging from 0 to 98%. The transistor duty ratio is variedaccording to the variations of the input voltage in order toproduce a constant output voltage [10-11].ParameterSpecificationOutput voltage, Vodc12VInput voltage, Vi18V 12VLoad current, Iodc1AOutput power, Po12WInductor current ripple, ΔiL1.6AOutput voltage ripple, ΔVout2%Switching frequency, fsw50 kHz.The design of the dc to dc buck converter circuitconsiders the continuous current operation mode (CCM).The dc to dc buck converter is a converter that functions tostep-down the dc input voltage supply to a desired dcvoltage. Figure-2 shows the buck converter circuit whichuses a dc input source, Vi. For this purpose, a component,Q which represents a transistor acts effectively as a switchmust be used.Figure-2. Buck converter with transistor in aswitched off mode.Depending on the power capacity of the circuit,semiconductor switching devices such as MOSFET,insulated-gate bipolar transistor (IGBT) and bipolarjunction transistor (BJT) are suitable to carry out this task.The dc input voltage is transferred to the inductor whenthe transistor Q is switched on. The input current rises andflows through the inductor L and capacitor C, and loadresistor, RL and has resulted an output voltage across the1318
VOL. 14, NO. 7, APRIL 2019ISSN 1819-6608ARPN Journal of Engineering and Applied Sciences 2006-2019 Asian Research Publishing Network (ARPN). All rights reserved.www.arpnjournals.comcapacitor, Vo. The capacitance must be large enough sothat the output voltage ripple is small.The inductance should be of high value as toensure the inductor current is maintained positive and inthe CCM mode during the switching period. Thecombination of the capacitor and inductor forms a lowpass filter to reduce the output voltage fluctuations. Theinductor stores energy and this energy can be used in timesof need. The factors taken into account for the selection ofthe inductance are the peak current, current ripple, andmaximum operating frequency. The detail of theseselections is described in [12].𝑉𝑜 𝐷𝑉𝑖𝑛(2)where Vo and Vin are the dc output voltage and inputvoltage respectively.b) Voltage sensor and gate driverConsidering the need for a stable power supplyfor the operation of the peripheral interface controller(PIC), a 5V voltage regulator circuit is designed as shownin Figure-3. The 220µF capacitors act as a stabilizer to theinput and output of the regulator U1 78L05.D11N4007U178L05IN V19VOUTCOMC1220uFC2220uFFigure-3. Voltage Regulator Circuit.In order to measure the input voltage source, avoltage divider circuit which acts as the voltage sensor isemployed. Based on the microcontroller input/output (I/O)port voltage level requirement, this circuit ensures that theinput voltage must not exceeding 5V.The microcontrollergenerates an appropriate PWM switching signal for theMOSFET according to the input voltage level. In general,MOSFET is a voltage-controlled device and requires agate voltage of 15V to switch on. Considering thisrequirement, a gate driver circuit utilizing the driverdevice U1 (IR2110) is designed as shown in Figure-4.This device receives a 5V level-PWM signal at pin 10 andgenerates a 15V level-PWM at pin 7.c) Software designThe PIC microcontroller is programmed in Clanguage and compiled using CCS compiler and thenlinked to the buck converter system in PROTEUS ISISProfessional. One of the most important part of the codingis the generation of the PWM signal. The followingsection explains the process of the PWM signalgeneration. The coding needs to configure the PIC I/O portpin 17 (RC2/CCP1) as an output port where the PWMsignal is generated.The generation of the PWM signal involves theI/O port module called Capture/Compare/PWM (CCP).The control register (CCP1CON) and data register(CCPR1) are often associated with the generation ofPWM. The CCP1CON controls the operation of CCP1(pin 17). This module contains a 16-bit register which canoperates as a PWM Duty Cycle register. It is comprised oftwo 8-bit control registers which are CCPR1L (low byte)and CCPR1H (high byte). For configuring the CCP1 inPWM mode, the Timer2 type of timer resource is required.The time base (period) and duty cycle of thePWM output need to be set. The CCP1 pin in PWMproduces 10-bit resolution PWM output. The PWM periodis specified by writing to the PR2 register. The period iscalculated using equation 3 [13]. The frequency of thePWM is the inverse of the period.𝑇𝑃𝑊𝑀 [(𝑃𝑅2) 1] 4 𝑇𝑂𝑆𝐶 (𝑇𝑀𝑅(3)The following steps should be taken whendesigning the CCP1 module for PWM operation:a)Set the PWM period by writing to the PR2 register.b) Set the PWM duty cycle by writing to the CCPR1Lregister and CP1CON 5:4 bits.c)Make the CCP1 pin an output by clearing theappropriate TRISC 2 bit.d) Set the TMR2 prescale value, then enable Timer2 bywriting to T2CON.e)Configure the CCP1 module for PWM operation.When TMR2 is equal to PR2, the following threeevents occur on the next addition cycle:a)TMR2 is cleared.b) The CCP1 pin is set (exception: if PWM dutycycle 0%, the CCP1 pin will not be set).c)Figure-4. Gate driver circuit.The PWM duty cycle is latched from CCPR1L intoCCPR1H.The PWM duty cycle is specified by writing tothe CCPR1L register and to the CCP1CON 5:4 bits.TheCCPR1L contains the eight most significant bits (MSbs)1319
VOL. 14, NO. 7, APRIL 2019ISSN 1819-6608ARPN Journal of Engineering and Applied Sciences 2006-2019 Asian Research Publishing Network (ARPN). All rights reserved.www.arpnjournals.comAnd CCP1CON 5:4 bits contain the two least significantbits (LSbs). This 10-bit value is represented by CCPR1L:CCPxCON 5:4 . Equation 4 is used to calculate thePWM duty cycle in time [13]:PWM Duty cycle (CCPR1L: CCp1CON 5:4) Tosc (TMR2Prescale Value)The in-lab experimental setups are shown in Figure-6 andFigure-7. Some of equipment used are oscilloscope, powersupply and digital voltmeter panel.(4)B. SYSTEM SIMULATIONFor the purpose of observing the systemperformance and the integration of buck converter and thePIC embedded control algorithm, the simulation isconducted in PROTEUS ISIS Professional environment asshown in Figure-5.Figure-6. In-lab experimental setup showing buckconverter, power source, oscilloscope and PICmicrocontroller.Figure-5. Simulation of buck converter inPROTEUS ISIS.It consists of four sections which are buckconverter, PIC16F877A microcontroller, voltage sensor,and gate driver. Considering the unavailability of the PVdevice in this simulation software, the input voltage sourceis set to nominal voltage of 15V. Then, this input voltageis varied to simulate the PV output voltage variations.The microcontroller which has been loaded withthe control algorithm receives and measures the dc inputvoltage from the voltage sensor circuit through pin 2(RA0/AN0). Pin 2 and pin 17 (RC2/CCP1) are configuredas the input and output port, respectively. By determiningthe level of the input voltage together with the controlstrategy as explained earlier, a PWM signal is generated atpin 17. For generating this switching signal, the algorithmutilizes the microcontroller PWM built-in function calledCapture/Compare/PWM (CCP). The important element inthe buck converter is Q1, the MOSFET model IRF540Nwhich capable of handling high currents and high speedswitching.Finally, the converter generated output voltageis connected to the resistive load.4. EXPERIMENTAL SET-UPDue to the constrain and limitation of the PV, anadjustable power source was used to provide variation ofinput voltage levels to the buck converter.For validating the system simulation, the buckconverter prototype was built and tested in a laboratory.Figure-7. In-lab experimental setup showing the buckconverter, resistive load box and digital voltmeter panel.5. RESULTS AND DISCUSSIONSIn order to justify the effectiveness of the designand algorithm of the buck converter overall systemoperation, the simulation and experimental results arepresented. In the simulation and in-lab experimental setup,the dc input voltage is varied from 17V to 12V foremulating the PV behavior and then the correspondingoutput responses of the system are measured.A. Simulation resultsThe generated PWM switching signals for theMOSFET are depicted in Figure-8. Channel A shows thePWM waveform generated by the PIC microcontroller atpin 17 (RC2/CCP1). It is observed that, it has a peak-topeak voltage of 5V and period of 20 microseconds. Theswitching frequency is calculated to be 50 kHz. The outputof the gate driver is shown by Channel B.It also has a frequency of 50 kHz and peak-topeak voltage of 22V which suitable for triggering theMOSFET.1320
VOL. 14, NO. 7, APRIL 2019ISSN 1819-6608ARPN Journal of Engineering and Applied Sciences 2006-2019 Asian Research Publishing Network (ARPN). All rights reserved.www.arpnjournals.comPeriod 20 µsChannel A1.05AChannel BFigure-8. PWM switching waveforms observed at pin 17of PIC and pin 7 of gate driver.Figure-9 shows the buck converter simulationload voltage waveform for the input voltage of 15V.Initially, the waveform exhibits an overshoot at time ofapproximately 0.1 millisecond and gradually reachessteady state at approximately 11.98V as anticipated.Figure-11. Output load current waveform.The power dissipated by the load resistor is 12Was shown in Figure-12.Figure-12. Power dissipated by the load.Figure-9. Simulation load voltage.Figure-10 shows the inductor current waveform,IL. Since the current is always positive ( 0), the buckoperates in the CCM mode as expected. The triangularwaveform is the result of the MOSFET switching processfor a frequency of 50 kHz. As seen in the Figure, thecurrent acquires an approximate peak of 1.75A andminimum of 0.17A. Thus, the current ripple, ΔIL iscalculated to be 1.58A as anticipated.Figure-13 shows the buck converter simulationload voltage waveform for the input voltage of 17V.Initially, the waveform exhibits an overshoot at time ofapproximately 0.1 millisecond and gradually reachessteady state at slightly above 12V. This shows that thesystem manages to regulate the output at 12.4V in spites ofthe changes in the input voltage.12.4VFigure-13. Load output voltage waveform.Figure-10. Current across the inductor (iL).Figure-14 shows the load output currentwaveform. Initially, it has a slight overshoot atapproximately 0.15 milliseconds and reaches steady stateat 1.07A.Figure-11 shows the simulation load currentwaveform. It exhibits an overshoot at time ofapproximately 0.1 millisecond and gradually reachessteady state at approximately 1.05A.1321
VOL. 14, NO. 7, APRIL 2019ISSN 1819-6608ARPN Journal of Engineering and Applied Sciences 2006-2019 Asian Research Publishing Network (ARPN). All rights reserved.www.arpnjournals.comTable-2. Comparison result between calculation andsimulation for input voltage of 15V.1.07AFigure-14. Output load current waveform for inputvoltage of 17V.Figure-15 shows the inductor current waveform,IL. The current shows that the system is in the CCM mode.It has the peak current of 2.2A and minimum current iscloser to zero. The current ripple for the waveform, ΔIL is2.2A.2.2AParameterOutputvoltageLoad currentInductorripple currentOutput powerDesignSimulation % 2.4W3.33%Table-3. Comparison result between calculation andsimulation for input voltage of 17V.ParameterOutputvoltageLoad currentInductorripple currentOutput powerDesignSimulation % .8W6.7%It is observed that both design and simulationresults are considered in good agreement except theinductor ripple current which shows slightly higher.Figure-15. Inductor current waveform showing the currentripple.Figure-16 shows the power dissipated by the loadresistor, RL which is 12.8W.B. Experimental resultsDue to some constraints in the power capacity ofthe PV, the experiment was carried out with the utilizationof a dc power source to replace the PV.The dc input voltage is varied manually and theparameters such as load voltage and the PWM duty cycleare recorded accordingly. Figure-17, Figure-18 andFigure-19 depict the few selected snapshots of the dc inputvoltage and the corresponding microcontroller PWM dutycycle. Table-4 presents the values obtained from theexperiment.12.8 WFigure-16. Power dissipated by the load resistor.Comparisons between the design specificationsand the simulation results for two different input voltagesare conducted in order to observe the system performance.They are shown in Table-2 and Table-3.Figure-17. DC input voltage showing 11.8V andcorresponding PWM waveform duty cycle (99%).1322
VOL. 14, NO. 7, APRIL 2019ISSN 1819-6608ARPN Journal of Engineering and Applied Sciences 2006-2019 Asian Research Publishing Network (ARPN). All rights reserved.www.arpnjournals.comThese parameters values are plotted to observethe response the buck converter dc output voltageregulation as shown in Figure-20.Figure-18. DC input voltage showing 12.9V andcorresponding PWM waveform duty cycle (91%).Figure-20. DC output voltage regulation.It is observed that the output voltage is wellregulated at 12V for the input voltage range of 17V to12V. This essence of the developed buck converter controlalgorithm which functions to step-down the input voltageand regulated the output simultaneously. As purposelydesigned, any voltage level drops beyond the input voltageof 12V causes the abrupt drop of the output and graduallyshut down the system as shown in the figure.Figure-19. DC input voltage showing 14.3V andcorresponding PWM waveform duty cycle (82%).Table-4. Parameters obtained from experiment.InputLoad voltage, Duty cyclevoltage (V)VRL(%)17.012.171% 11.811.5994.1611.611.4995.0CONCLUSIONSThe development of the dc to dc buck converterfor PV application utilizing the PIC16F877Amicrocontroller was presented in this paper. Both theconverter circuit and its embedded control algorithm wasdeveloped and simulated in the PROTEUS ISISProfessional software environment. For justification, thebuck converter prototype was built and tested in thelaboratory. Due to the power capability constraint, the PVwas replaced with a dc power supply.Both the simulation and prototype test resultsshowed that the developed control algorithm managed tostep-down the input voltage to 12V as well as regulated iteffectively. The controller managed to generate theappropriate PWM switching signal in accordance to theincoming dc input voltage. These results have shown theefficacy of the buck converter control algorithm ingenerating and stabilizing the desired output voltage.REFERENCES[1] O.C. Ruppel and B. Althusmann. 2016. Perspectiveson Energy Security and Renewable Energies in SubSaharan Africa, Practical Opportunities andRegulatory Challenges, Second Revised andExpanded Edition.[2] S. Romero-Hernandez and O. Romero-Hernandez.2013. Renewable Energy in Mexico: Policy andTechnologies for a Sustainable Future.1323
VOL. 14, NO. 7, APRIL 2019ISSN 1819-6608ARPN Journal of Engineering and Applied Sciences 2006-2019 Asian Research Publishing Network (ARPN). All rights reserved.www.arpnjournals.com[3] E. Fiorucci, G. Bucci, F. Ciancetta, D. Gallo, C. Landiand M. Luiso. 2013. Variable Speed DriveCharacterization: Review of Measurement Techniquesand Future Trends. Advances in Power Electronics. p.14.[13] 2018. PIC micro Mid-range MCU family- Section 14.Compare/Capture/PWM (CCP) DeviceDoc/31014a, accessed on 31 July 2018.[4] Z.A. Ghani, W.K. Wong, S. Saat, Mohd Fauzi AbdRahman, F.A. Azidin, N.R. Mohamad. 2015.Peripheral Interface Controller-Based nication, Electronic and ComputerEngineering (JTEC). 7(2): 13-127.[5] Z.M. Abdullah, O.T. Mahmood and A.M.T. IbraheemAl-Naib. 2014. Photovoltaic battery charging systembased on PIC16F877A microcontroller. InternationalJournal of Engineering and Advanced Technology.3(4): 27-31.[6] R.I. Putri, M. Rifa’i, M. Pujiantara, A. Priyadi, andM.H. Purnomo. 2017. Fuzzy MPPT controller forsmall scale stand-alone PMSG wind turbine. 2017.ARPN Journal of Engineering and Applied Sciences.12(1): 188-193.[7] G. Senthil Kumar and S. Indira. 2014. Embeddedboost converter using voltage feedback technique.International Journal of Research in Engineering andTechnology. 2(2): 207-212.[8] Z.A. Ghani, M.A. Hannan, and A. Mohamed. 2013.Simulation model linked PV inverter implementationutilizing dSPACE DS1104 controller. Energy andBuildings. 57: 65-73.[9] G. C. Sowparnika. 2015. Design and Implementationof Sliding Mode Control for Boost Converter usingPV Cell. 1(10): 75-78.[10] P. Sathya and R. Natarajan. 2013. Design andimplementation of 12V/24V closed loop boostconverter for solar powered LED lighting system.International Journal of Engineering and Technology.5(1): 254-264.[11] N. Mohan, T. Undeland and M. Robbins. 2003. PowerElectronics: Converters, Applications, and Design.Third Edition, John Wiley & Sons, Inc., New Jersey.[12] M.H. Rashid. 2007. Power Electronics Circuits,Devices and Applications. Third Edition, PrenticeHall of India Private Limited, New Delhi.1324
The design of the dc to dc buck converter circuit considers the continuous current operation mode (CCM). The dc to dc buck converter is a converter that functions to step-down the dc input voltage supply to a desired dc voltage. Figure-2 shows the buck converter circuit which uses a dc input source, V i. For this purpose, a component,
work/products (Beading, Candles, Carving, Food Products, Soap, Weaving, etc.) ⃝I understand that if my work contains Indigenous visual representation that it is a reflection of the Indigenous culture of my native region. ⃝To the best of my knowledge, my work/products fall within Craft Council standards and expectations with respect to
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Collectively make tawbah to Allāh S so that you may acquire falāḥ [of this world and the Hereafter]. (24:31) The one who repents also becomes the beloved of Allāh S, Âَْ Èِﺑاﻮَّﺘﻟاَّﺐُّ ßُِ çﻪَّٰﻠﻟانَّاِ Verily, Allāh S loves those who are most repenting. (2:22
iii 1 Basic Concepts and Methods 1 2 Theories of Development 20 3 Prenatal Development and Birth 42 4 Physical, Sensory, and Perceptual Development in Infancy 67 5 Cognitive Development in Infancy 87 6 Social and Personality Development in Infancy 107 7 Physical and Cognitive Development in Early Childhood 127 8 Social and Personality Development in
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roles, marriage, and family infl uences a person’s development. General Characteristics of Development 1. Development is continuous. 2. Development is a process, not a state. 3. Development has order. 4. Development moves from general to specifi c and from simple to more complex. 5. Dev
1.2.7. Economic growth and development 1.2.8. Barriers to economic growth 1.3 Human Development 1.3.1. Human Development: The Concept 1.3.2. Human Development in the United Nations Agenda 1.3.3. Human development Approach vs. the Conventional Development Approach 1.3.4. Indicator
product development process? 5. The product development process - What is a product development process? 3.2 Development of Concepts 3.2.1 Introduction For a long time up to 2003, concepts of product development had been very stable. Both researchers and industry used the same concepts about e.g. products and product development models and .
