Power Electronics

Power Semiconductor Devices
  • Silicon Atom Structure:
    • Layer 1: 2 electrons
    • Layer 2: 8 electrons
    • Layer 3: 4 electrons
Operating Principles of Power Semiconductor Devices

  • Diodes:

    • Forward Biased:
    • The external voltage attracts electrons to enter the junction, overcoming the electric field (E).
    • Reverse Biased:
    • Both E and reverse voltage (Ve) act to prevent electrons from entering the junction.

  • BJT (Bipolar Junction Transistor):

    1. Apply forward bias to the base-emitter (BE) junction.
    2. Electrons enter the base, which is thin and lightly doped, allowing them to pass to the collector.
    3. If $V_{CE} = 0$, electrons accumulate at the collector.
    4. If $V_{CE} > 0$, electrons flow out of the collector.

  • JFET (Junction Field Effect Transistor):

    1. Electrons flow from source to drain, passing through depletion layers.
    2. If $V{GS} = 0$, $I{D} = I{P{max}}$ (Normally ON).
    3. When $V_{GS} < 0$, the depletion layer expands and narrows the conducting channel.

  • MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor):

    • Depletion Mode: Negative $V_{GS}$ pushes away electrons and attracts holes.
    • Enhanced Mode: Positive $V_{GS}$ pushes away holes, attracting electrons and forming an n-type inversion layer.

  • IGBT (Insulated Gate Bipolar Transistor):

    1. When $U{GE} = 0$, $i{c} = 0$.
    2. When $V{GE} o V{GECO}$, electrons diffuse from heavily doped to lightly doped regions.
    3. If $V{i} o 0$, $i{c} = Bi^s$, $ie - ie = (B + 1)in$.

  • Thyristors:

    1. As $is$ increases, $in$ also increases ($ic = Bi b z$).
    2. If $is$ increases, $ib i = (2)$.
    3. Current $ic$ increases ($ic = B_i b$).
Classification of Power Semiconductor Devices by Controllability
  • Uncontrollable: Diode
  • Semicontrollable: Thyristor
  • Fully Controllable: BJT, MOSFET, IGBT
DC-DC Converters
  • Types: Buck, Boost, Buck-Boost
  • Output Voltage Relationships:
    • Buck: $Vo = Vi D$
    • Boost: $Vo = rac{Vi}{1 - D}$
    • Buck-Boost: $Vo = rac{Vi D}{1 - D}$
Current Waveforms
  • Current waveforms for inductor, switch, and diode:
    • Buck: Simplified current relationships and switching behaviors.
    • Boost: Similar but consider current dynamics during charging and discharging of inductor.
    • Buck-Boost: Composite behavior corresponding to switching actions.
AC-DC Converters
  • Types: Half-Wave, Full-Wave, Full-Bridge Rectifiers.
  • Half-Wave: Current flows during positive cycle.
  • Full-Wave: Both halves of the AC signal are used, yielding higher output.
  • Full-Bridge: Achieves more efficient rectification by utilizing all four switching elements.
  • Output Voltage Calculations:
    • Half-Wave: $V{o{avg}} = rac{V_{m}}{
      ho ext{ for the given cycle}}$
    • Full-Wave: $V{o{avg}} = 0.9 V_{rms}$ for perfect conditions.
Inverters
  • Half-Bridge, Push-Pull, Full-Bridge Inverter Circuits:
    • Conduction Modes:
    • 180° conduction (Half-Bridge)
    • 120° conduction modes (Full-Bridge)
  • SPWM (Sinusoidal Pulse Width Modulation):
    • Types: Unipolar/Bipolar, Double Frequency SPWM.
    • Advantages: Low THD (Total Harmonic Distortion), reduced switching loss.
    • Disadvantages: Complexity in implementation, requires multiple comparators.
Advanced Modulation Techniques
  • Bipolar SPWM:
    • Advantages: Simple implementation, fundamental frequency strong.
    • Disadvantages: High harmonic distortion, difficult EMI management.
AC-AC Converters
  • Phase Angle Control: Amplitude modulation through adjusting phase angle.
  • Adjustment Outcomes:
    • Adjustments typically reduce total harmonic distortion and improve waveform quality but may increase switching losses.
Control Techniques
  1. ON-OFF Control:
    • Low harmonic distortion but slow response times.
    • Ratio determining power delivered influenced by ON/OFF cycles.
  2. Zero Voltage PWM Control:
    • Uses high-frequency switching for modulation, reducing harmonic issues.
  3. Resonant Converters:
    • Advantages: Smaller sizes of components, better waveform quality.
    • Disadvantages: Increased switching losses and thermal stress.
Resonant Circuits
  • Describe relationships and dynamics across various configurations:
    • Series and Parallel behaviors: Current and voltage profiles exhibit sine and cosine relationships across elements.