The document provides an introduction to DC-DC conversion and discusses different types of DC-DC converters including linear regulators and switching mode power supplies. Linear regulators such as series and shunt regulators are described as well as concepts such as voltage regulation, line regulation, and load regulation. Examples are provided to illustrate how to design both series and shunt linear regulators. The advantages of linear regulators include low cost and simplicity while disadvantages include low efficiency and inability to boost voltage. Applications that are well-suited for linear regulators are also outlined.
Lecture Outline
Introduction to subject
Application Areas
Power Electronic Devices
Power Converters
What is power electronics?
1) Definition
Power Electronics: is the electronics applied to conversion and control of electric power.
Prerequisites
Power electronics incorporates concepts from the fields of
Analog circuits
Electronic devices
Control systems
Power systems
Magnetics
Electric machines
Numerical simulation
Scope
It is not possible to build practical computers, cell phones, personal data devices, cars, airplanes, industrial processes, and other everyday products without power electronics.
Alternative energy systems such as wind generators, solar power, fuel cells, and others require power electronics to function.
Technology advances such as electric and hybrid vehicles, laptop computers, microwave ovens, flat-panel displays, LED lighting, and hundreds of other innovations were not possible until advances in power electronics enabled their implementation.
Although no one can predict the future, it is certain that power electronics will be at the heart of fundamental energy innovations.
Applications: Electric VehicleTesla Model S
Functions of the power electronics:
1. Convert the DC battery voltage to the variable AC required to drive the AC motor
240 V battery
Variable-frequency, variable-voltage AC drives the motor
AC motor propels the rear axle
Up to 330 kW (acceleration)
Up to 60 kW regenerative braking
2. Control charging of the battery
Interface to 240 V 60 Hz 1φ 100 A circuit in garage.
Control AC current waveform to be sinusoidal, unity power factor.
Control charging of battery to maximize life.
Applications: Hybrid VehiclesPrius
Power Electronics Module:
Convert the DC battery voltage to the variable AC required to drive the AC motor.
Includes dc-dc boost converter and dc-3φ ac inverter
Control system can operate in all-electric mode or in hybrid gas+electric mode
Partial-power electronics
A Schering Bridge is a bridge circuit used for measuring an unknown electrical capacitance and its dissipation factor. The dissipation factor of a capacitor is the the ratio of its resistance to its capacitive reactance. The Schering Bridge is basically a four-arm alternating-current (AC) bridge circuit whose measurement depends on balancing the loads on its arms .
Lecture Outline
Introduction to subject
Application Areas
Power Electronic Devices
Power Converters
What is power electronics?
1) Definition
Power Electronics: is the electronics applied to conversion and control of electric power.
Prerequisites
Power electronics incorporates concepts from the fields of
Analog circuits
Electronic devices
Control systems
Power systems
Magnetics
Electric machines
Numerical simulation
Scope
It is not possible to build practical computers, cell phones, personal data devices, cars, airplanes, industrial processes, and other everyday products without power electronics.
Alternative energy systems such as wind generators, solar power, fuel cells, and others require power electronics to function.
Technology advances such as electric and hybrid vehicles, laptop computers, microwave ovens, flat-panel displays, LED lighting, and hundreds of other innovations were not possible until advances in power electronics enabled their implementation.
Although no one can predict the future, it is certain that power electronics will be at the heart of fundamental energy innovations.
Applications: Electric VehicleTesla Model S
Functions of the power electronics:
1. Convert the DC battery voltage to the variable AC required to drive the AC motor
240 V battery
Variable-frequency, variable-voltage AC drives the motor
AC motor propels the rear axle
Up to 330 kW (acceleration)
Up to 60 kW regenerative braking
2. Control charging of the battery
Interface to 240 V 60 Hz 1φ 100 A circuit in garage.
Control AC current waveform to be sinusoidal, unity power factor.
Control charging of battery to maximize life.
Applications: Hybrid VehiclesPrius
Power Electronics Module:
Convert the DC battery voltage to the variable AC required to drive the AC motor.
Includes dc-dc boost converter and dc-3φ ac inverter
Control system can operate in all-electric mode or in hybrid gas+electric mode
Partial-power electronics
A Schering Bridge is a bridge circuit used for measuring an unknown electrical capacitance and its dissipation factor. The dissipation factor of a capacitor is the the ratio of its resistance to its capacitive reactance. The Schering Bridge is basically a four-arm alternating-current (AC) bridge circuit whose measurement depends on balancing the loads on its arms .
Includes Introduction, Derivation of power flow through transmission line, Single line diagram of three phase transmission, methods of finding the performance of transmission line. 1.Analytical Method 2.Graphical method (circle diagram)., circle diagram of receiving end side and sending end side.
A Maxwell bridge is a modification to a Wheatstone bridge used to measure an unknown inductance (usually of low Q value) in terms of calibrated resistance and inductance or resistance and capacitance. When the calibrated components are a parallel resistor and capacitor, the bridge is known as a Maxwell-Wien bridge. It is named for James C. Maxwell, who first described it in 1873.
It uses the principle that the positive phase angle of an inductive impedance can be compensated by the negative phase angle of a capacitive impedance when put in the opposite arm and the circuit is at resonance; i.e., no potential difference across the detector (an AC voltmeter or ammeter)) and hence no current flowing through it. The unknown inductance then becomes known in terms of this capacitance.
Different Types of Voltage Regulators with Working Principleelprocus
A voltage regulator is designed to automatically maintain a constant voltage level. Know more about different types of voltage regulators and their working principle . Learn its Advantages, disadvantages, circuit theory and applications.
Includes Introduction, Derivation of power flow through transmission line, Single line diagram of three phase transmission, methods of finding the performance of transmission line. 1.Analytical Method 2.Graphical method (circle diagram)., circle diagram of receiving end side and sending end side.
A Maxwell bridge is a modification to a Wheatstone bridge used to measure an unknown inductance (usually of low Q value) in terms of calibrated resistance and inductance or resistance and capacitance. When the calibrated components are a parallel resistor and capacitor, the bridge is known as a Maxwell-Wien bridge. It is named for James C. Maxwell, who first described it in 1873.
It uses the principle that the positive phase angle of an inductive impedance can be compensated by the negative phase angle of a capacitive impedance when put in the opposite arm and the circuit is at resonance; i.e., no potential difference across the detector (an AC voltmeter or ammeter)) and hence no current flowing through it. The unknown inductance then becomes known in terms of this capacitance.
Different Types of Voltage Regulators with Working Principleelprocus
A voltage regulator is designed to automatically maintain a constant voltage level. Know more about different types of voltage regulators and their working principle . Learn its Advantages, disadvantages, circuit theory and applications.
Pre Final Year project/ mini project for Electronics and communication engine...Shirshendu Das
Mini project for Electronics and communication engineering (ECE) to build an AC to DC power supply using Full Wave Rectifier having input as 220-240V AC and giving stable filtered output of 5V, -5V & variable 5V DC. Simulation of the circuit was done in Proteus design suite.
The following presentation is a part of the level 5 module -- Electronic Engineering. This resources is a part of the 2009/2010 Engineering (foundation degree, BEng and HN) courses from University of Wales Newport (course codes H101, H691, H620, HH37 and 001H). This resource is a part of the core modules for the full time 1st year undergraduate programme.
The BEng & Foundation Degrees and HNC/D in Engineering are designed to meet the needs of employers by placing the emphasis on the theoretical, practical and vocational aspects of engineering within the workplace and beyond. Engineering is becoming more high profile, and therefore more in demand as a skill set, in today’s high-tech world. This course has been designed to provide you with knowledge, skills and practical experience encountered in everyday engineering environments.
Hierarchical Digital Twin of a Naval Power SystemKerry Sado
A hierarchical digital twin of a Naval DC power system has been developed and experimentally verified. Similar to other state-of-the-art digital twins, this technology creates a digital replica of the physical system executed in real-time or faster, which can modify hardware controls. However, its advantage stems from distributing computational efforts by utilizing a hierarchical structure composed of lower-level digital twin blocks and a higher-level system digital twin. Each digital twin block is associated with a physical subsystem of the hardware and communicates with a singular system digital twin, which creates a system-level response. By extracting information from each level of the hierarchy, power system controls of the hardware were reconfigured autonomously. This hierarchical digital twin development offers several advantages over other digital twins, particularly in the field of naval power systems. The hierarchical structure allows for greater computational efficiency and scalability while the ability to autonomously reconfigure hardware controls offers increased flexibility and responsiveness. The hierarchical decomposition and models utilized were well aligned with the physical twin, as indicated by the maximum deviations between the developed digital twin hierarchy and the hardware.
Cosmetic shop management system project report.pdfKamal Acharya
Buying new cosmetic products is difficult. It can even be scary for those who have sensitive skin and are prone to skin trouble. The information needed to alleviate this problem is on the back of each product, but it's thought to interpret those ingredient lists unless you have a background in chemistry.
Instead of buying and hoping for the best, we can use data science to help us predict which products may be good fits for us. It includes various function programs to do the above mentioned tasks.
Data file handling has been effectively used in the program.
The automated cosmetic shop management system should deal with the automation of general workflow and administration process of the shop. The main processes of the system focus on customer's request where the system is able to search the most appropriate products and deliver it to the customers. It should help the employees to quickly identify the list of cosmetic product that have reached the minimum quantity and also keep a track of expired date for each cosmetic product. It should help the employees to find the rack number in which the product is placed.It is also Faster and more efficient way.
Hybrid optimization of pumped hydro system and solar- Engr. Abdul-Azeez.pdffxintegritypublishin
Advancements in technology unveil a myriad of electrical and electronic breakthroughs geared towards efficiently harnessing limited resources to meet human energy demands. The optimization of hybrid solar PV panels and pumped hydro energy supply systems plays a pivotal role in utilizing natural resources effectively. This initiative not only benefits humanity but also fosters environmental sustainability. The study investigated the design optimization of these hybrid systems, focusing on understanding solar radiation patterns, identifying geographical influences on solar radiation, formulating a mathematical model for system optimization, and determining the optimal configuration of PV panels and pumped hydro storage. Through a comparative analysis approach and eight weeks of data collection, the study addressed key research questions related to solar radiation patterns and optimal system design. The findings highlighted regions with heightened solar radiation levels, showcasing substantial potential for power generation and emphasizing the system's efficiency. Optimizing system design significantly boosted power generation, promoted renewable energy utilization, and enhanced energy storage capacity. The study underscored the benefits of optimizing hybrid solar PV panels and pumped hydro energy supply systems for sustainable energy usage. Optimizing the design of solar PV panels and pumped hydro energy supply systems as examined across diverse climatic conditions in a developing country, not only enhances power generation but also improves the integration of renewable energy sources and boosts energy storage capacities, particularly beneficial for less economically prosperous regions. Additionally, the study provides valuable insights for advancing energy research in economically viable areas. Recommendations included conducting site-specific assessments, utilizing advanced modeling tools, implementing regular maintenance protocols, and enhancing communication among system components.
KuberTENes Birthday Bash Guadalajara - K8sGPT first impressionsVictor Morales
K8sGPT is a tool that analyzes and diagnoses Kubernetes clusters. This presentation was used to share the requirements and dependencies to deploy K8sGPT in a local environment.
Using recycled concrete aggregates (RCA) for pavements is crucial to achieving sustainability. Implementing RCA for new pavement can minimize carbon footprint, conserve natural resources, reduce harmful emissions, and lower life cycle costs. Compared to natural aggregate (NA), RCA pavement has fewer comprehensive studies and sustainability assessments.
Welcome to WIPAC Monthly the magazine brought to you by the LinkedIn Group Water Industry Process Automation & Control.
In this month's edition, along with this month's industry news to celebrate the 13 years since the group was created we have articles including
A case study of the used of Advanced Process Control at the Wastewater Treatment works at Lleida in Spain
A look back on an article on smart wastewater networks in order to see how the industry has measured up in the interim around the adoption of Digital Transformation in the Water Industry.
6th International Conference on Machine Learning & Applications (CMLA 2024)ClaraZara1
6th International Conference on Machine Learning & Applications (CMLA 2024) will provide an excellent international forum for sharing knowledge and results in theory, methodology and applications of on Machine Learning & Applications.
HEAP SORT ILLUSTRATED WITH HEAPIFY, BUILD HEAP FOR DYNAMIC ARRAYS.
Heap sort is a comparison-based sorting technique based on Binary Heap data structure. It is similar to the selection sort where we first find the minimum element and place the minimum element at the beginning. Repeat the same process for the remaining elements.
Forklift Classes Overview by Intella PartsIntella Parts
Discover the different forklift classes and their specific applications. Learn how to choose the right forklift for your needs to ensure safety, efficiency, and compliance in your operations.
For more technical information, visit our website https://intellaparts.com
2. OBJECTIVES
• Introduction of DC-DC Converter
• Voltage Regulation
• Types of DC-DC Converters
• Linear regulator (LR)
• Series regulator
• Shunt regulator.
• Switching mode power supply (SMPS)
• Advantages and Disadvantages
3. • DC to DC Converters convert DC power to another DC power level or
convert voltage/current to another voltage/current
• Batteries are often shown on a schematic diagram as the source of DC
voltage but usually the actual DC voltage source is a power supply.
• DC to DC converters are important portable electronic devices used
whenever we want to change DC electrical power efficiently from one
voltage level to another.
• A power converter generates output voltage and current for the load from
a given input power source.
• Depending on the specific application, either a linear regulator (LR) or a
switching mode power supply (SMPS) solution to be chosen.
Introduction
4. • Car battery 12V must be stepped down to 3-5V DC voltage to run DVD/CD player
• Laptop computers or cellular phone battery voltage must be stepped down to run
several sub-circuts, each with its own voltage level requirement different from
that supplied by the battery.
• Single cell 1.5 V DC must be stepped up to 5V operate an electronic circuitry.
• A 6V or 9V DC must be stepped up to 500V DC or more, to provide an insulation
testing voltage.
• A 12V DC must be stepped up to +/-40V or so, to run a car hifi amplifier circuitry.
• A 12V DC must be stepped up to 650V DC or so, as part of a DC-AC sinewave
inverter.
Typical Application of DC-DC converter
5. Voltage Regulation
1. Line regulation: To maintain constant output voltage when the input voltage varies.
Line regulation is defined as the percentage change in the output voltage for a
given change in the input voltage.
or %/V
2. Load regulation: To maintain constant output voltage when the load varies. Load
regulation is defined as the % change in the output voltage from no-load (VNL) to full-
load (VFL).
%100
FL
FLNL
V
VV
regulationLoad
%100
IN
OUT
V
V
regulationLine
IN
OUTOUT
V
VV
regulationLine
%100/
7. • The linear regulator is a DC-DC converter to provide a constant voltage output without using switching components.
• The linear regulator is very popular in many applications for its low cost, low noise and simple to use.
• It was the basis for the power supply industry until switching mode power supplies became prevalent after the 1960s.
• Power management suppliers have developed many integrated linear regulators.
• The linear regulator has limited efficiency and can not boost voltage to make Vout > Vin.
• Two basic types of linear regulator are the series regulator and the shunt regulator:
• Series regulator: Control element of series regulator is connected in series with load.
• Shunt regulator: Control element of the shunt regulator is connected in parallel with the load.
The Basic Linear Regulator
8. The output voltage will be maintained at a constant value of:
VOUT = (1 + R2/R3) VREF
1. Ideally, VX = VREF Error Amp = 0 VO is constant.
2. When VOUT decreases, VX < VREF The error amplifier
output will be high which turns on Q1 VIN connect to the
output that adjusts the output to desired level.
3. When VOUT increases, VX > VREF The error amplifier
output will be low which turns off Q1 VIN disconnect
from the output that adjusts the output to desired level.
Series Linear Regulator
Example 1: For VIN = 15V, R2 = R3 = 10kΩ , R1=1kΩ
and VZ = 5.1V. Find VOUT, IR1 ,IR2, IR3 and IZ
Solution:
VO = (1 + R1/R2) VREF = (1 + 10kΩ / 10kΩ)5.1 = 10.2V
IR1 = (15 – 5.1) / 1kΩ = 9.9mA = IZ
IR2 = 10.2 / (10kΩ + 10kΩ) = 0.51mA = IR3
IR1 = (Vin – VREF) / R1 = IZ (I+ = 0 = I_ Op-Amp)
R1 = (Vin – VREF)2 / PR1
IR2 = IR3 = VOUT/(R2+R3) (I+ = 0 = I_ Op-Amp)
Example 2: For VIN = 16V, PZ = 500mW, VZ = 2.4V. Design a
series regulator to yield a regulated output VOUT = 8V.
Solution:
Vo = (1 + R2/R3) VREF = (1 + R2/R3) VZ = (1 + R2/R3) 2.4V= 8V
R2/R3 = 2.33 R2 = 2.33R3
Choose R3 = 10 kΩ and R2 = 23.33 kΩ.
IZ = 500 mW / 2.4V = 208.3mA
R1 = (VIN(max) – VZ) / IZ = (16 – 2.4)V / 208.3 mA = 65Ω
Efficiency: η = VOUT/VIN = 8/16 = 50%
VOUT(max) = VIN – VCE = 16V – 0.2V = 15.8V
VX
VZ
9. The output voltage will be maintained at a constant value of:
VOUT = (1 + R3/R4) VREF
1. Ideally, VX = VREF Error Amp = 0 VO is constant.
2. When VOUT increases, VX > VREF The error amplifier
output will be driving Q1 more increase input current
causes higher voltage drop in R1 that adjusts the output to
desired level.
3. When VO decreases, VX < VREF The error amplifier will be
driving Q1 less decrease input current causes lower
voltage drop in R1 that adjusts the output to desired level.
Shunt Linear Regulator
IZ = (VIN – VZ)/R2 = IR2
IZ(max) = (PZ / VZ)
R1 = (VIN – VOUT)/IR1
IR1(max) = (Vin – 0)/RR1 (when VOUT = 0)
IR3 = VOUT/(R3 + R4) = IR4
Example 1: For VIN = 15V, R1=30Ω, R2=1kΩ,
R3 = R4 = 10kΩ. Find power rating for R1
Solution:
Worst case: VOUT = 0V short
PR1 = (VIN – VOUT)2/R1 = (15 – 0)2/22 = 7.5W
Use 10W
Example 2: Vin = 12V, PZ = 500mW, VZ = 2.4V and current limiting
IR1(max) = 50mA. Design a parallel regulator to yield a regulated output
VOUT = 3.3V.
Solution:
VOUT = (1 + R3/R4) VREF = (1 + R3/R4) VZ = (1 + R3/R4) 2.4V = 3.3V
R3/R4 = 0.375 R3 = 0.375R4 Choose R3 = 10 kΩ and R4 = 3.75 kΩ.
IZ = 500mW/2.4V = 208.33mA
R2 = (VIN – VZ) / IZ = (12 – 2.4)V / 208.33mA = 46Ω
R1 = (12 – 0)V / 50mA = 240Ω Required PR1 > 12x0.05 = 0.6W
Efficiency: η = 3.3/12 = 27.5%
10. • For low current power supplies - a simple shunt voltage regulator can be made with a resistor and a Zener diode.
• Zener diodes are rated by their breakdown voltage VZ (1.24 – 200V, ±5-10% ), maximum power PZ (typically
250mW-50W) and minimum IZ (in µA).
Example: For Vin = 12V and the Zerner diode power rating PZ = 1W to produce a regulated output voltage Vout = 5V.
Find load current IL for RL = 50Ω.
Solution: Maximum IZ = PZ / VZ = 1 / 5 = 200mA Minimum RS = (Vin – VZ) / IZ = (12 – 5)V / 200 mA = 35 Ω.
Load current IL = VZ / RL = (5V / 50 Ω) = 100mA IZ at full load IZ = IS – IL = 200 – 100 = 100 mA
Efficiency η = 5/12 = 42%
Zener Diode Shunt Regulator
http://www.electronics-tutorials.ws/diode/diode_7.html
11. A typical integrated linear regulator needs only VIN, VOUT, FB and optional GND pins. Figure below shows a
typical 3-pin linear regulator, it only needs an input capacitor, output capacitor and two feedback resistors to
set the output voltage.
ADJUSTABLE LINEAR REGULATORS
12. LINEAR REGULATORS DRAWBACK
• A major drawback of using linear regulators can be the excessive power dissipation of its series transistor Q1
operating in a linear mode.
• Since all the load current must pass through the series transistor, its power dissipation is PLoss = (VIN – VO) •IO.
• The efficiency of a linear regulator can be estimated by:
13. ₊ Low number of components makes linear power supplies very cost-effectiveness overall and space
savings (unless heat sink is used).
₊ Simplicity and low complexity design makes linear power supplies more reliable.
₊ No switching noise and low output voltage ripple makes linear power supplies best suitable for
applications where noise-sensitivity is essential.
₊ Low output voltage ripple
₊ The linear regulator is free of any switching noise, having ripple rejection capability and its low voltage
noise, which makes the linear regulator of choice in such noise-averse applications as audio-visual,
communication, medical, and measurement devices.
Linear Regulators Advantages
14. • The linear regulator can be very efficient only if VO is close to VIN.
• The linear regulator (LR) has another limitation, which is the minimum voltage difference between VIN and VO. The
transistor in the LR must be operated in its linear mode. So it requires a certain minimum voltage drop across the
collector to emitter of a bipolar transistor or drain to source of a FET. When VO is too close to VIN, the LR may be
unable to regulate output voltage anymore.
• The linear regulators that can work with low headroom (VIN – VO) are called low dropout regulators (LDOs).
• The linear regulator or an LDO can only provide step-down DC/DC conversion.
• Typical design may require a heat sink.
• These disadvantages to linear power supplies include size, high heat loss, and lower efficiency levels when
compared to a switch-mode power supply. The problem with linear power supply units, when used in a high
power application, is that it requires a large transformer and other large components to handle the power. Using
larger components increases the overall size and weight of the power supply and can pose a challenge for weight
distribution within a given application.
Linear Regulators Disadvantages
15. LINEAR REGULATORS APPLICATIONS
There are many applications in which linear regulators provide superior solutions to switching supplies:
1. Simple/low cost solutions. Linear regulator or LDO solutions are simple and easy to use, especially for
low power applications with low output current where thermal stress is not critical. No external power
inductor is required.
2. Low noise/low ripple applications. For noise-sensitive applications, such as communication and radio
devices, minimizing the supply noise is very critical.
3. Fast transient applications. The linear regulator feedback
loop is usually internal, so no external compensation
is required.
4. Low dropout applications. For applications where output voltage is close to the input voltage, LDOs
may be more efficient than an SMPS.
We see that price sensitive applications prefer linear regulators over their sampled-time counterparts.
The design decision is especially clear cut for makers of:
• communications equipment
• small devices
• battery operated systems
• low current devices
• high performance microprocessors with sleep mode (fast transient recovery required)
16. Regulators Linear regulators are less energy efficient than switching regulators. Why do we
continue using them?
Depending upon the application, linear regulators have several redeeming features:
• lower output noise is important for radios and other communications equipment
• faster response to input and output transients
• easier to use because they require only filter capacitors for operation
• generally smaller in size (no magnetics required)
• less expensive (simpler internal circuitry and no magnetics required)
Furthermore, in applications using low input-to-output voltage differentials, the efficiency is not
all that bad! For example, in a 5V to 3.3V microprocessor application, linear regulator efficiency
approaches 66%. And applications with low current subcircuits may not care that regulator
efficiency is less than optimum as the power lost may be negligible overall.
LINEAR REGULATORS VS SWITCHING REGULATORS
17. • The switching-mode power supply is a power supply that provides the power supply function through low loss
components such as capacitors, inductors, and transformers -- and the use of switches that are in one of two states,
on or off.
• It offers high power conversion efficiency and design flexibility.
• It can step down or step up output voltage.
• The term switchmode was widely used for this type of power supply until Motorola, Inc., who used the trademark
SWITCHMODE TM for products aimed at the switching-mode power supply market, started to enforce their
trademark. Switching-mode power supply or switching power supply are used to avoid infringing on the trademark.
• Typical switching frequencies lie in the range 1 kHz to 1 MHz, depending on the speed of the semiconductor
devices.
• Types of SMPS:
• Buck converter: Voltage to voltage converter, step down.
• Boost Converter: Voltage to voltage converter, step up.
• Buck-Boost or FlyBack Converter: Voltage-Voltage, step up and down (negative voltages)
• Cuk Converter: Current-Current converter, step up and down
These converters typically have a full wave rectifier front-end to produce a high DC voltages
SWITCHING MODE POWER SUPPLY (SMPS)
20. • The buck converter is known as voltage step-down converter, current step-up converter,
chopper, direct converter. It is the simplest and most popular switching regulator.
• There are two Mode of Operations:
1. Continuous Conduction Mode (CCM): Inductor current IL does not reach zero, when output current IO is very large.
2. Discontinuous Conduction Mode (DCM): Inductor current IL will reach zero, when output current IO is very small.
Size:30mm(L)*18mm(W)*14(H) mm
The Buck Converter
Continuous Conduction Mode (CCM):
• LC low-pass filter: to pass the DC component while
attenuating the switching components.
• diode is reversed biased during ON period, input
provides energy to the load and to the inductor
• energy is transferred to the load from the inductor
during switch OFF period
• Interchange of energy between inductor and capacitor is
referred as flywheel effect.
• in the steady-state, average inductor voltage is zero
• in the steady-state, average capacitor current is zero
21. When the switch is on (close):
• VL = Vi – VO and VD = Vi
• Inductor current IL will rise at rate of (Vi – VO)/L IL = Iin
• Diode D is reverse biased and does not conduct (open circuit) Idiode = 0.
When the switch is off (open), current must still flow as the inductor works to
keep the same current flowing through inductor and into the load.
• VL = – Vo and VD = 0.7
• Inductor current IL decreases at rate of (– VO)/L Iin = 0.
• Diode D is forward biased and conducts IL = Idiode
The Buck Converter in CCM
23. The Buck Converter in DCM Formula
The discontinuous conduction mode occurs when the output load current IO is reduced below the critical current level
that causes the inductor current IL to be zero for a portion of the switching cycle.
In a buck power stage, if the inductor current attempts to fall below zero, it just stops at zero (due to the unidirectional
current flow in diode) and remains there until the beginning of the next switching cycle.
24.
25. Given an input voltage of Vi=12V. The required average output voltage is VO=5V at R=500Ω and the peak-to-
peak output ripple voltage is 20 mV. The switching frequency is 25 kHz. If the peak-to-peak ripple current of
inductor is limited to 0.8 A, determine (a) the duty cycle D, (b) the filter inductance L, (c) the filter capacitor C,
and (d) the critical values of L and C.
Solution:
a) D = 5/12 = 0.42
b) L = (1 – D)VO / (ΔiL x f) = (1 – 0.42)5 /(0.8 x 25,000) = 145μH
c) C = ΔIL / (8f ΔVC) = 0.8 / (8 x 25000 x 0.02) = 200μF
d) Lcrit = (1 – D)R / 2f = (1 – 0.42) x 500 / (2 x 25000) = 5.83 mH
Ccrit = (1 – D) / (16 x L x f2) = (1 – 0.42) / (16 x 145 x 10-6 x 250002) = 0.4μF
The Buck Converter Example
28. 1) When switch MOSFET conducts (CLOSE) a current Iin flows through
inductor L1 which stores energy in its magnetic field.
2) When the MOSFET is rapidly turned off (OPEN) the sudden drop in
current causes L1 to produce a back e.m.f. in the opposite polarity to the
voltage across L1 during the on period, to keep current flowing. This results
in two voltages, the supply voltage VIN and the back e.m.f.(VL) across L1 in
series with each other.
This higher voltage (VIN +VL) forward biases D1. The resulting current
through D1 charges up C1 to VIN +VL minus the small forward voltage drop
across D1, and also supplies the load.
3) shows the circuit action during MOSFET on periods after the initial start
up. Each time the MOSFET conducts, the cathode of D1 is more positive
than its anode, due to the charge on C1. D1 is therefore turned off so the
output of the circuit is isolated from the input, however the load continues
to be supplied with VIN +VL from the charge on C1. Although the charge C1
drains away through the load during this period, C1 is recharged each time
the MOSFET switches off, so maintaining an almost steady output voltage
across the load.
http://www.learnabout-electronics.org/PSU/psu32.php
THE BOOST CONVERTER
30. A boost regulator has an input voltage of Vi = 5V. The average output voltage Vo = 15V and the average load current
IO = 0.5A. The switching frequency is 25 kHz. If L=150μH and C=220μF, determine
a) The duty cycle D
b) The ripple current of inductor ΔI.
c) The peak-peak current of inductor (Imin and Imax).
d) The ripple voltage of filter capacitor ΔVc
e) The critical values of L and C.
Solution:
a) 15V = 5V/(1 − D) or D = 2/3 = 0.6667 = 66.67%.
b)
c) Ii = 0.5/(1 − 0.667) = 1.5A peak inductor currents: Imax = Ii + ΔI/2 = 1.5 + 0.89/2 = 1.945A
Imin = Ii – ΔI/2 = 1.5 – 0.89/2 = 1.055A
d) The Ripple voltage:
e) R = VO / IO = 15 / 0.5 = 30 Ω
The Boost Converter Examples:
31. Example:
1) If the switching square wave has a period of 10µs, the input voltage is 9V and the ON is half of the periodic time, i.e.
5µs, then the output voltage will be:
VOUT = 9/(1- 0.5) = 9/0.5 = 18V (minus output diode voltage drop)
Because the output voltage is dependent on the duty cycle, it is important that this is accurately controlled. For
example if the duty cycle increased from 0.5 to 0.99 the output voltage produced would be:
VOUT = 9/(1- 0.99) = 9/0.01 = 900V
Before this level of output voltage was reached however, there would of course be some serious damage (and smoke)
caused, so in practice, unless the circuit is specifically designed for very high voltages, the changes in duty cycle are
kept much lower than indicated in this example.
2) A step-up dc-dc converter is to be analyzed. Vi = 14V, Vout = 42V, L = 10 mH, R = 1 Ω and fs=10 kHz
(a) Duty ratio, switch on and off time.
(b) Plot inductor voltage.
Solution:
(a) D = 1 – (Vi / Vout) = 1 – 14/42 = 0.67 0r 67%, T = 1/fs = 100µs tON = 67µs and tOFF = 33µs
The Boost Converter Examples
Vi
Vi – VO
32. Given a buck converter design with fsw = 200 kHz (TS = 5 μsec), VD = 0.7V, I0(min) = 0.5A , I0(nom)= 10A and D = 50% duty
cycle. Find:
a) VO if Vi = 10 V in continuous mode
b) Inductor L
c) VO if Vi = 10 V in discontinuous mode
Solution:
a) Vo = Vi / (1 –D) = 10 / (1 – 0.5) = 20V
b) Inductor L
c)
= (20 – 10 + 0.7) (1 – 0.5) / (0.5 x 200 k) = 54 µH
= 1 + {(10 x 0.52 x5µs)/ (2 x 54 µH x 10)} = 1 + 0.012
Vo = 10.12V
The Boost Converter Examples: