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  • DC to AC Converters
    • How to Get AC Output From DC Input Supply?
    • What If The Load Is Not Resistive?
    • General Structure of Voltage Source Inverters
    • Need For Isolated Gate-Control Signals For The Switches
    • Classification of Voltage Source Inverters
    • Harmonic Analysis of The Load Voltage And Load Current Waveforms
    • Time Domain Analysis
    • Frequency Domain Analysis
    • Analysis Of The Single-Phase Full Bridge Inverter
    • Voltage And Current Ratings Of Inverter Switches & Applications Of Square Wave Inverter
    • Three-phase square wave VSI
    • Determination Of Load Phase-Voltages
    • Uses & Limitation of 3-Phase Square Wave Inverter
    • Nature Of Pole Voltage Waveforms Output By PWM Inverters
    • Harmonic Analysis Of Pole Voltage Waveform
    • Trade Off Between Low Order And High Order Harmonics
    • Brief Description Of Some Popular PWM Techniques
    • Two-Level Versus Three-Level PWM Inverters
    • Considerations On Switch Voltage And Current Ratings
    • Introduction to sine PWM
    • Analysis Of The Pole Voltage Waveform With A Dc Modulating Signal
    • Pole Voltage Waveform With Sinusoidal Modulating Signal
    • Modulation Index & Over-Modulation
    • A 1-Phase Sine-PWM Inverter Of H-Bridge Topology
    • Generation Of 3-Phase Sine-PWM Waveform
    • A Typical Circuit For Generation Of PWM Waveforms
    • More Output Voltage From The Same DC Bus Voltage
    • Sine + 3rd Harmonic PWM Technique
    • Space Vector PWM (SV-PWM) Technique
    • Smoothly Rotating Space Voltage Vector From Inverter
    • Algorithm For Producing Sinusoidal Output Voltages Using SV-PWM
    • Some Other Popular PWM Techniques
    • Single-phase Current Source Inverter
    • Mode I operation of Single-phase Current Source Inverter
    • Mode II operation of Single-phase Current Source Inverter
    • Three-phase Current Source Inverter
    • Commutation phases of Three Phase CSI
    • Advantages and Disadvantages of CSI
    • Load-Commutated CSI
    • Equivalent circuit of Load commutated CSI
    • Characteristics of Load commutated CSI and Output

  • Power Semiconductor Devices
    • Introduction to Power Electronics
    • Difference between Power Electronics and Linear Electronics
    • Varieties of Power semiconductor Devices
    • Classification of Power Diodes
    • Silicon Controlled Rectifier (SCR)
    • Introduction to MOSFET
    • Introduction to the IGBT
    • Base/Gate drive circuit
    • Introduction to the GTO
    • Power converter Topologies
    • Protection of Power devices and converters
    • Introduction to power semiconductor devices
    • Review of P-N diode characteristics
    • Volt-Ampere ( i-v ) characteristics of a p-n junction diode
    • Construction and characteristics of Power Diodes
    • Power Diode under Reverse Bias conditions
    • Power Diode under Forward Bias Conditions
    • Specifications related to forward bias operation of power diodes
    • Switching characteristics of Power diodes
    • Parameters defining the turn off characteristics of a Power diode
    • Introduction to power BJT
    • Basic Operating Principle of a Bipolar Junction Transistor
    • Input and Output characteristics of NPN transistor
    • Constructional Features of a Power BJT
    • Output I-V characteristics of a Power Transistor
    • Safe operating areas of a Power Transistor
    • Switching characteristics of a Power Transistor
    • Turn On characteristics of a Power Transistor
    • Turn Off Characteristics of a Power Transistor
    • Switching Trajectory and Switching Losses in a Power Transistor
    • Base Drive Design of power transistor
    • Power Darlington Transistor
    • Introduction to Thyristors and Triacs
    • Constructional Features of a Thyristor
    • Basic operating principle of a thyristor
    • Static output i-v characteristics of a thyristor
    • Thyristor Gate Characteristics
    • Thyristor ratings & Voltage ratings of a thyristor
    • Current ratings of a thyristor
    • Gate Specifications of a thyristor
    • Switching Characteristics of a Thyristor
    • Turn on Switching Characteristics of thyristor
    • Turn off Switching Characteristics of Thyristor
    • Introduction to The Triac
    • Construction and operating principle of Triac
    • Steady State Output Characteristics and Ratings of a Triac
    • Triac Switching and gate trigger circuit
    • Features of GTO
    • Constructional Features of GTO
    • Operating principle of GTO
    • Steady state output and gate characteristics of a GTO
    • Dynamic characteristics of a GTO
    • GTO gate drive circuit
    • GTO Ratings - Steady state voltage and current rating
    • GTO Ratings - Gate specification & Specifications related to the switching performance
    • Features of MOSFET
    • Constructional Features of a Power MOSFET
    • Operating principle of a MOSFET
    • Steady state output i-v characteristics of a MOSFET
    • Safe operating area of a MOSFET
    • Circuit models of a MOSFET cell
    • Switching waveforms of MOSFET
    • MOSFET Gate Drive
    • MOSFET Ratings
    • Features of IGBT
    • Constructional Features of an IGBT
    • Operating principle of an IGBT
    • Steady state characteristics of an IGBT
    • Switching characteristics of IGBT
    • Gate Drive Circuit of an IGBT
    • IGBT ratings and safe operating area
    • Soft and Hard Switching & Losses of semiconductors
    • Conduction,Blocking & Switching Losses of Semiconductors
    • Diode as semiconductor device
    • Soft switching of diode

  • AC to DC Converters
    • Introduction to Rectifiers
    • Terminologies used in Single Phase Uncontrolled Rectifier
    • Single phase uncontrolled half wave rectifier with resistive Load - Circuit Diagram & Waveforms
    • Single phase uncontrolled half wave rectifier with inductive load- Circuit Diagram & Waveforms
    • Single phase uncontrolled half wave rectifier with capacitive Load - Circuit Diagram & Wave forms
    • Split supply Single Phase Uncontrolled Full wave rectifier supplying R-L Load - Circuit Diagram & Waveforms
    • Split supply Single phase uncontrolled full wave rectifier supplying a Capacitive Load- Circuit Diagram &Waveforms
    • Single phase uncontrolled full bridge rectifier supplying R-L-E Load - circuit diagram &Waveforms
    • Single phase uncontrolled full bridge rectifier supplying R-L-E Load -Input Current waveform
    • Continuous Conduction Mode and Discontinuous conduction mode
    • Single phase fully controlled halfwave rectifier with resistive Load -Circuit Diagram & Waveforms
    • Single phase fully controlled halfwave rectifier with R-L Load - circuit Diagram & waveforms
    • Single phase fully controlled bridge converter supplying an R-L-E load- Circuit Diagram & Conduction Table
    • Operation of single phase fully controlled bridge converter in the continuous conduction mode
    • Input current and its fundamental component of a fully controlled bridge rectifier
    • Operation of a single phase fully controlled bridge rectifier in DCM
    • Inverter Mode of operation in single phase fully controlled converter
    • Operating principle of a single phase half controlled bridge converter
    • Single phase half controlled converter in the continuous conduction mode
    • Variation of average output voltageas a functionof firing angle
    • Input current waveform of half controlled converters
    • Single phase half controlled converter in the discontinuous conduction mode
    • Introduction to Three Phase Uncontrolled rectifier
    • Operating principle of three phase half wave uncontrolled rectifier
    • Operation of a 3 phase full wave uncontrolled bridge rectifier supplying an RLE load Waveforms
    • Operation of a 3 phase full wave uncontrolled bridge rectifier supplying an RLE load Circuit diagram & conduction table
    • Operation of a three phase uncontrolled bridge rectifier supplying a capacitive load Circuit diagram & Waveforms
    • Introduction to Three Phase controlled bridge converter
    • Operating principle of 3 phase fully controlled bridge converter
    • Analysis of the 3 phase fully controlled bridge converter in the rectifier mode
    • Analysis of the 3 phase fully controlled bridge converter in the inverting mode
    • Higher pulse number converters
    • Dual converters
    • Gate Drive circuit for three phase fully controlled converter
    • Operating principle of three phase half controlled converter
    • Analysis of three phase half controlled converters
    • Operation of single phase fully controlled converter with source inductance- circuit diagram & waveforms
    • Three Phase Fully Controlled Converter With Source Inductance
    • Power Factor Improvement & Extinction Angle Control
    • Symmetrical Angle Control & Pulse Width Modulation Control
    • Sinusoidal Pulse Width Modulation (SPWM) Control
    • Filters
    • Low pass (L-C) filter & Two stage Filter
    • Harmonic Reductin,Low pass (L-C) filter circuit on ac side & Active Shaping of Input (line) Current

  • DC to DC Converters
    • DC-DC Converters
    • Buck Converters (dc-dc)
    • Boost Converters (dc-dc)
    • Buck-Boost Converters (dc-dc)
    • Control Strategies of DC-DC conversion
    • Two mode operation of chopper ( Buck Converter DC-DC)
    • Maximum and Minimum Values of the Load Current
    • The Duty Ratio (k) for the Limit of Continuous Conduction & The Average Value of the Output Current
    • Classification of forced commutation methods
    • Class A, Self commutated by resonating the load & Class B, Self commutated by an L-C circuit
    • Class C, C or L-C switched by another load–carrying SCR & Class D, L-C or C switched by an auxiliary SCR
    • Class E - External pulse source for commutation & Class F, AC line commutated
    • Rate of rise of forward voltage, dv/dt
    • Three phase phase angle converter & Commutation in PAC
    • Input voltage waveform distortion & Three-phase converters
    • Commutation in DC - DC choppers
    • Introduction to regulated dc power supplies
    • Linear regulated power supply
    • SMPS versus linear power supply
    • Types of Power Supplies
    • Power supply specifications & some common types of SMPS circuits
    • Basic Topology of Fly-Back Converter
    • Principle of Operation of fly back converter
    • Circuit Equations Under Continuous-Flux Operation
    • Circuit Equations Under Discontinuous-Flux Mode & comparison
    • A Practical Fly-Back Converter
    • Introduction to Forward Type Switched Mode Power Supply
    • Principle of Operation of Forward converters
    • Modes of Circuit Operation - Forward Type Switched Mode Power Supply
    • Relation Between Input and Output Voltage of FTSMPS
    • Practical Topology of A Forward Converter Circuit
    • Selection of Transformer Turns Ratio, Filter Circuit Inductor and Capacitor
    • Analysis of CuK converter
    • Expression for average output voltage and inductor currents
    • Current ripple and voltage ripple calculations
    • The SEPIC Converter
    • Introduction to transformers in switched mode
    • Governing Equations for Utility Transformer
    • Transformer with Square-Wave Voltage and Bipolar Flux
    • Transformer with Unipolar Flux
    • Design of Inductor-Transformer

  • AC to AC Voltage Converter
    • Operation of an AC-AC converter with resistive load
    • Power Factor of an AC-AC converter with resistive load
    • Operation of an AC-AC converter with inductive load
    • PAC as a static switch & AC Chopper
    • Three-phase, Three-wire AC Regulator with Balanced Resistive Load
    • Three-phase Delta-connected AC Regulator with Balanced Resistive Load
    • Comparison of the Different Circuits used for Three-phase AC Regulators
    • Rating of the Parameters used in Three-phase AC Regulators
    • Phase Angle Controller Circuit for Triac-based Single-phase AC Regulator
    • TRIAC as PAC
    • DIAC as PAC
    • Basic Principle of Operation of cyclo-converters
    • Single-phase to Single-phase Cyclo-converter Resistive (R) Load
    • Discontinuous load current of single phase to single phase cyclo converter Inductive Load
    • Continuous load current of single phase to single phase cyclo converter Inductive Load
    • Advantages & Disadvantages of Cyclo-converter
    • DC Link Converter
    • Three-phase to Single-phase Cyclo-converter
    • Mode of Operation of a Three phase to Single Phase Cycloconverter
    • Cyclo-converter, using two three-phase half-wave converters
    • Three-phase to Three-phase Cyclo-converter
    • Analysis of the Cyclo-converter Output Waveform
    • Control Circuit & Synchronising Circuit for Cyclo-converters
    • Reference Voltage Sources
    • Logic and Triggering Circuit
    • Circuit for Converter Group Selection

Branch : Electrical and Electronics Engineering
Subject : Power Electronics
Unit : Power Semiconductor Devices

Safe operating areas of a Power Transistor


Safe operating areas of a Power Transistor:

Fig: Safe operating areas of a Power Transistor.(a) FBSOA; (b) RBSOA

 

  • In the hard saturation region base current loses control over the collector current which is determined entirely by the collector load and the biasing voltage VCC. This behavior is similar to what happens in a signal transistor except that the drift region of a power transistor continues to offer a small resistance even when it is completely shorted out (by excess carrier injection from the base).
  • For larger collector currents the collector-emitter voltage drop is almost proportional to the collector current. Manufacturers usually provide the plots of the variation of VCE (sat) vs. iC for different values of base current and junction temperature. Curves showing the variation of VCE (sat) with iB for different values of iC and junction temperature are also provided by certain manufacturers.
  • Applicable operating limits on a power transistor are compactly represented in two diagrams called the Forward Bias Safe Operating Area (FBSOA) and the Reverse Bias Safe Operating Area. (RBSOA) applicable to iB > 0 and iB ≤ 0 conditions respectively.
  • The horizontal upper limit of the FBSOA is determined by the maximum allowable collector current (ICM) that should not be exceeded even as a pulse. Exceeding this current limit may cause bonding wire or metallization of the wafer to vaporize or otherwise fail. Since a power transistor does not have any appreciable reverse voltage blocking capacity they are usually not used in ac circuits. However, if the collector current, for some reason is not dc or a pulse, the rms value of the collector current waveform should not exceed this limit.
  • The next applicable limit in the FBSOA (green lines) corresponds to the restriction on the maximum allowable power dissipation and maximum junction temperature. Since FBSOA is shown on a log-log scale constant Power dissipation (Pd = VCE iC) limits appear as straight lines. This limit is different for dc and pulsed operation due to the thermal time constant of the device. The “DC” limit is applicable to the average power loss if the transistor remains continuously in the conduction state (active, quasi saturation or saturation).
  • The third limit of the FBSOA (red line) arises due to the “second break down” failure mode of a Power transistor. It shows the limiting combinations of collector voltage and current so that second break down does not occur. On the log –log scale of the FBSOA this limit also appears as a straight limit. Like the maximum power dissipation limit, the second break down limit is also different for “DC” and “Pulsed” operation of different pulse durations. The interpretation of the pulse duration corresponding to a particular limit is also same.
  • The final limit of the FBSOA corresponds to the forward biased avalanche break down voltage (VSUS) of the transistor and appears as a vertical line in the FBSOA at VCE = VSuS .The FBSOA of a Power transistor is given at a specified case temperature. Both the maximum power dissipation limit and the second break down limits are to be derated as per the derating characteristics provided by the manufacturers when the case temperature exceeds the specified value.
  • The RBSOA is plotted on a linear scale and has a more rectangular shape. RBSOA is a switching SOA since a transistor cannot conduct current for any appreciable duration under reverse biased condition. It shows the limiting permissible combinations of VCE & iC with base emitter junction reverse biased. The upper horizontal limit corresponds to the maximum allowable collector current (ICM) and is same as that in the FBSOA.
  • The right hand side vertical limit correspond the avalanche break down voltage of the transistor with reverse bias. If a negative voltage is applied across the BE junction the right hand side limit of the RBSOA increases somewhat to the value VCBO at low value of the collector current.

Questions of this topic


  • In the \\\"Cut off\\\" region collector current of a Power Transistor is _____________.

    Answer this
  • In the __________________ region of a Power Transistor the dc current gain remains fairly constant.

    Answer this
  • Saturation region of a Power Transistor can be divided into _______________ region and ______________________ region

    Answer this
  • Active region operation of a Power BJT is limited mostly by _______________ consideration.

    Answer this
  • “Second breakdown” in a Power BJT occurs due to ________________ of the collector current distribution.

    Answer this
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