Inductor & Capacitor Operation in DC Circuits
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What does the conversion ratio M(D, K) in DC-DC converters primarily represent?

  • The relationship between output voltage and duty cycle
  • The relationship between duty cycle and efficiency
  • The relationship between transformer turns ratio and input voltage
  • The relationship between output voltage and input voltage (correct)

    • In a buck converter, the output voltage is inversely proportional to the duty cycle.

    False

    What is the equation for the conversion ratio of a boost converter?

    M(D) = 1 / (1 - D)

    The buck-boost converter can produce a __________ output voltage.

    <p>negative</p> Signup and view all the answers

    How does increasing the transformer turns ratio K in a flyback converter affect the output voltage?

    <p>It modifies the output voltage</p> Signup and view all the answers

    What is the formula for the conversion ratio of a buck-boost converter?

    <p>M(D) = -D / (1 - D)</p> Signup and view all the answers

    Match the following DC-DC converters with their respective conversion ratio formulas:

    <p>Buck Converter = M(D) = D Boost Converter = M(D) = 1 / (1 - D) Buck-Boost Converter = M(D) = -D / (1 - D) Flyback Converter = M(D, K) = (D / (1 - D))(K)</p> Signup and view all the answers

    Which of the following switches is commonly used in lighting control and power distribution systems?

    <p>T r i a c s</p> Signup and view all the answers

    The duty cycle D is defined as the fraction of the switching period when the power switch is off.

    <p>False</p> Signup and view all the answers

    Power MOSFETs are typically used for AC applications.

    <p>False</p> Signup and view all the answers

    Name one application of high-frequency switches.

    <p>RF amplifiers</p> Signup and view all the answers

    Soft switches minimize switching losses through techniques such as __________ and __________.

    <p>zero-voltage switching, zero-current switching</p> Signup and view all the answers

    Match the type of switch with its application:

    <p>IGBTs = Motor drives Triacs = Lighting control GaN transistors = RF circuits Soft switches = High-efficiency power supplies</p> Signup and view all the answers

    Which type of switch is designed for applications requiring fast switching and low losses?

    <p>High-frequency switches</p> Signup and view all the answers

    Solid-state switches have lower maintenance requirements compared to electromechanical relays.

    <p>True</p> Signup and view all the answers

    What is the primary function of DC switches?

    <p>Power flow management and overcurrent protection</p> Signup and view all the answers

    Which of the following components can be classified as switching elements in power electronics?

    <p>Transistors</p> Signup and view all the answers

    Switch realization improves the efficiency of electric power circuits.

    <p>True</p> Signup and view all the answers

    Name two common applications of switch elements in power electronics.

    <p>Power supplies and motor drives</p> Signup and view all the answers

    The primary goal of switch realization is to efficiently convert power by turning on and off the __________ devices.

    <p>semiconductor</p> Signup and view all the answers

    Which type of switches manage alternating current circuits?

    <p>AC switches</p> Signup and view all the answers

    Thyristors can be used in power electronic circuits for controlling energy flow.

    <p>True</p> Signup and view all the answers

    What is the role of switches in energy transfer within power circuits?

    <p>To control the flow and conversion of electrical energy.</p> Signup and view all the answers

    Match the switching elements to their characteristics:

    <p>SCR = Used for controlled rectification MOSFET = Ideal for fast switching applications IGBT = Combines the best features of MOSFET and bipolar junction transistors Triac = Allows current flow in both directions</p> Signup and view all the answers

    What does the dc component of a converter waveform represent?

    <p>The average value of the waveform</p> Signup and view all the answers

    In a well-designed converter, the ripple can be significant compared to the dc components.

    <p>False</p> Signup and view all the answers

    What does the principle of inductor volt-second balance allow?

    <p>It allows the determination of dc voltage components in any switching converter.</p> Signup and view all the answers

    The average current applied to a _______ must be zero in steady-state conditions.

    <p>capacitor</p> Signup and view all the answers

    Match the principles to their functions:

    <p>Inductor volt-second balance = Determines dc voltage components Capacitor charge balance = Determines dc current components Small-ripple approximation = Simplifies the analysis Refined model = Accounts for loss elements</p> Signup and view all the answers

    Which type of converter is used to increase voltage?

    <p>Boost converter</p> Signup and view all the answers

    The dc transformer model assumes 100% efficiency in ideal conditions.

    <p>True</p> Signup and view all the answers

    What is the main purpose of the dc transformer model in converters?

    <p>To transform dc voltage and current levels.</p> Signup and view all the answers

    Which semiconductor device is used for blocking voltage in the OFF state?

    <p>Power diodes</p> Signup and view all the answers

    During the turn-on transient of a diode, the stored charge does not contribute to conductivity modulation.

    <p>False</p> Signup and view all the answers

    What happens to the current during transient conditions in a diode?

    <p>The current deviates from the equilibrium i-v curve.</p> Signup and view all the answers

    The term used to describe the blocking behavior of a diode when it is reverse-biased is __________.

    <p>depletion region</p> Signup and view all the answers

    Match the following power semiconductor devices to their functions:

    <p>Power diodes = Rectification Bipolar Junction Transistors (BJTs) = Amplification Thyristors = Control of high power Power MOSFETs = Switching applications</p> Signup and view all the answers

    Which factor is primarily associated with the reduction in the on-resistance of a diode during forward-biased conditions?

    <p>Stored minority charge</p> Signup and view all the answers

    Thyristors can also be referred to as Insulated Gate Bipolar Transistors.

    <p>False</p> Signup and view all the answers

    What is the role of the depletion region in a reverse-biased diode?

    <p>It blocks the applied reverse voltage.</p> Signup and view all the answers

    What is one essential difference between two SPST switches and one SPDT switch?

    <p>Both SPST switches can be simultaneously ON or OFF.</p> Signup and view all the answers

    Two SPST switches are equivalent to one SPDT switch.

    <p>False</p> Signup and view all the answers

    What are the two states of operation for an SPST switch?

    <p>ON-state and OFF-state</p> Signup and view all the answers

    An SPST switch can operate in a __________ quadrant mode.

    <p>single</p> Signup and view all the answers

    In the ON-state for a single-quadrant switch, what condition must be met?

    <p>i &gt; 0</p> Signup and view all the answers

    The conducting state of an SPST switch can depend on the applied voltage or current.

    <p>True</p> Signup and view all the answers

    Match the following switch types with their characteristics:

    <p>Single quadrant switch = Operates in one direction Bidirectional switch = Permits current flow in both directions Two-quadrant switch = Allows current in two directions with limitations Four-quadrant switch = Operates with full flexibility in all directions</p> Signup and view all the answers

    The ________ switch will not conduct in both forward and reverse directions.

    <p>single quadrant</p> Signup and view all the answers

    What type of switch allows for bidirectional current flow?

    <p>Bidirectional switch</p> Signup and view all the answers

    In a two-quadrant switch, current can flow in both directions, but with restrictions.

    <p>True</p> Signup and view all the answers

    Study Notes

    Inductor Operation in DC Circuits

    • In a DC circuit, an inductor acts like a short circuit when the current is constant
    • The current flows through the inductor without any voltage drop
    • The inductor offers no resistance to the DC current once it's stabilized
    • Inductor's inductance opposes any changes in current

    Capacitor Operation in DC Circuits

    • In a DC circuit, a capacitor acts like an open circuit when fully charged or discharged
    • No current flows through a fully charged or discharged capacitor
    • DC current stops flowing through the capacitor after being fully charged
    • The capacitor's electrode plates are separated by an insulator
    • A capacitor blocks DC current unless the insulator disintegrates

    Boost Converter DPST Method

    • Alternates between two states
    • When the switch is closed, the inductor stores energy from the input voltage.
    • When the switch opens, the inductor releases energy through a diode.
    • Output voltage is boosted.
    • This process is continuous, stepping up the input voltage to a higher output voltage.
    • Pulse-width modulation (PWM) controls the duration the switch stays closed vs open

    Bipolar Junction Transistor (BJT)

    • A current-controlled device
    • Has three regions: emitter, base, collector.
    • Operates in different modes: active, saturation, and cutoff.
    • Made of p-n-p or n-p-n semiconductor layers

    Field Effect Transistor (FET)

    • A voltage-controlled device
    • High input impedance and fast switching times
    • Has three terminals: source, drain, gate
    • Types: JFET and MOSFET

    Insulated Gate Bipolar Transistor (IGBT)

    • Combines MOSFET's high input impedance with BJT's low saturation voltage.
    • Ideal for high-voltage/current applications

    DC Switches

    • Control direct current circuits
    • Perform functions such as power flow management and overcurrent protection
    • Common types: MOSFETs, IGBTs, BJTs, FET-based switches

    High-Frequency Switches

    • Designed for fast switching, low losses, high reliability
    • Used in switching power supplies and RF circuits
    • Examples: GaN transistors, SiC MOSFETs, high-frequency IGBTs, and RF FET switches

    Soft Switches

    • Minimize switching losses and electromagnetic interference in power circuits
    • Uses techniques like zero-voltage switching (ZVS) and zero-current switching (ZCS)
    • Examples: resonant, quasi-resonant, and multi-resonant switches
    • Used in high-efficiency power supplies and renewable energy systems

    Discontinuous Conduction Mode (DCM)

    • Occurs when inductor current drops to zero during part of the switching period
    • Typically happens at low output currents or low inductance
    • The transition point between CCM and DCM is affected by load resistance, inductance, switching frequency, and duty cycle

    Conversion Ratio, M(D,K)

    • Represents the relationship between output and input voltage in DC-DC converters
    • Influenced by duty cycle (D) and transformer turns ratio (K)
    • K is a factor that accounts for transformer effect in isolated converters like the flyback converter

    Non-idealities Affecting Conversion Ratio

    • Switching losses
    • Inductor resistance
    • Capacitor ESR
    • Transformer losses

    Chapter 4: Switch Realization

    • Switch realization refers to the process of implementing and designing switching elements within power electronic circuits using transistors, thyristors, or diodes.
    • It's used for things like controlling electrical energy flow and conversion.
    • Switch applications involve converters, inverters, and rectifiers.
    • Power switches have many roles in managing electrical power and increasing efficiency.

    SPST (Single-Pole Single-Throw) Switches

    • Basic switching elements
    • One input-output connection
    • Used in all power semiconductor devices

    SPDT (Single-Pole Double-Throw) Switches

    • Switches have two connections for input, which is connected to one output
    • A power switch having two output connections from one input

    Single-Quadrant Switches

    • Control current in one direction only
    • Examples: diodes, certain types of transistors or other semiconductor devices

    Current-Bidirectional Two-Quadrant Switches

    • Can conduct current in both directions
    • Example: power MOSFET with anti-parallel diode

    MOSFET Body Diode

    • A device present in power MOSFETs, used to conduct current in specific situations.
    • Using external diodes is beneficial for high-current/voltage applications

    Simple Inverter

    • A circuit used to convert direct current (DC) to alternating current (AC)
    • Components include transistors, diodes, inductors, and capacitors
    • Generates AC output from DC input.

    Inverter: Sinusoidal Modulation of D

    • Sinusoidal modulation adjusts duty cycle (D) to produce sinusoidal AC output
    • The resulting inductor current variation is also sinusoidal

    The dc-3øac Voltage Source Inverter (VSI)

    • Specific circuit converts direct current (DC) to three-phase alternating current (AC).
    • Component switches control current flow & voltage in various sequences

    Bidirectional Battery Charger/Discharger

    • A circuit capable of charging or discharging a battery.
    • Allows controlling and converting power flow
    • Two-quadrant, voltage-directional switches are needed to control this type of converter

    Voltage-Bidirectional Two-Quadrant Switches

    • Control voltage and current flow in both directions
    • Includes transistors and diodes

    Four-Quadrant Switches

    • Can conduct positive & negative currents and block positive & negative voltages.
    • Examples in various ways of implementing this type of switch

    Power Diode

    • A passive switch
    • Typically used for single-quadrant current situations
    • Carries current only when forward biased

    Bipolar Junction Transistor (BJT)

    • Active/Controlled switch
    • Typically used for high-power/low-frequency applications
    • Has three terminals (emitter, base, collector)

    Insulated Gate Bipolar Transistor (IGBT)

    • Active/Controlled switch
    • High voltage & high current capability
    • Generally used in high-voltage power switching applications

    Silicon Controlled Rectifier (SCR)

    • Active/Controlled switch
    • Cannot actively turn itself off
    • Used in applications where high voltage/current are important

    Gate Turn-Off Thyristor (GTO)

    • Active/Controlled switch
    • Able to turn itself off
    • Offers performance in high voltage/current applications

    Thyristor Family

    • Features variable levels of voltage and current
    • Vary in turning off mechanisms and general functionality
    • Includes SCRs, GTOs, MCTs

    Synchronous Rectifiers

    • Use a MOSFET to replace the diode in a rectifier circuit
    • Reduces conduction loss

    Summary of Chapter 4

    • Summarizes the information provided about switching applications/elements.
    • Explains how SPST switch realization methods work
    • Explains different types of switches - how they are used, and their capabilities
    • Discusses various reasons for power loss during switching transitions

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    BSEE 3-1 Past Paper PDF

    Description

    Test your understanding of how inductors and capacitors operate in DC circuits. This quiz covers key concepts such as inductance behavior under steady current and capacitor functionality when charged. Additionally, explore the working principles of a boost converter using the DPST method.

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