25-01-2013, 03:03 PM
Introduction to Power Electronics
[attachment=48485]
Introduction to Power Electronics
• Power electronics relates to the control and flow of
electrical energy
• Control is done using electronic switches, capacitors,
magnetics, and control systems
• Scope of power electronics: milliWatts ⇒ gigaWatts
• Power electronics is a growing field due to the
improvement in switching technologies and the need for
more and more efficient switching circuits
Summary
• History/scope of power electronics
• Some interesting PE-related projects
• Circuit concepts important to power electronics
• Some tools for approximate analysis of power
electronics systems
• DC/DC converters --- first-cut analysis
• Key design challenges in DC/DC converter design
• Basic system concepts
Some Power Electronics-Related Projects
Worked on at TCI (Harvard Labs)
• High speed lens actuator
• Laser diode pulsers
• Levitated flywheel
• Maglev
• Permanent magnet brakes
• Switching power supplies
• Magnetic analysis
• Laser driver pulsers
• 50 kW inverter switch
• Transcutaneous (through-skin) non-contact power supply
Selected History of Power Switching Devices
• 1960s - switching speed of BJTs allow DC/DC converters
possible in 10-20 kHz range
• 1960 - Metal Oxide Semiconductor Field-Effect Transistor
(MOSFET) for integrated circuits
• 1976 - power MOSFET becomes commercially available,
allows > 100 kHz operation
Power Factor
• With pure sine wave and resistive load, PF = 1
• With pure sine wave and purely reactive load, PF = 0
• Whenever PF < 1 the circuit carries currents or voltages
that do not perform useful work
• The more “spikey” a waveform is the worse is its PF
– Diode rectifiers have poor power factor
• Power factor can be helped by “power factor correction”
Power Factor Correction
• Typical toaster can draw 1400W from a 120VAC/15A line
• Typical offline switching converter can draw <1000W
because it has poor power factor
• High power factor results in:
– Reduced electric utility bills
– Increased system capacity
– Improved voltage
– Reduced heat losses
• Methods of power factor correction
– Passive
• Add capacitors across an inductive load to resonate
• Add inductance in a capacitor circuit
– Active
[attachment=48485]
Introduction to Power Electronics
• Power electronics relates to the control and flow of
electrical energy
• Control is done using electronic switches, capacitors,
magnetics, and control systems
• Scope of power electronics: milliWatts ⇒ gigaWatts
• Power electronics is a growing field due to the
improvement in switching technologies and the need for
more and more efficient switching circuits
Summary
• History/scope of power electronics
• Some interesting PE-related projects
• Circuit concepts important to power electronics
• Some tools for approximate analysis of power
electronics systems
• DC/DC converters --- first-cut analysis
• Key design challenges in DC/DC converter design
• Basic system concepts
Some Power Electronics-Related Projects
Worked on at TCI (Harvard Labs)
• High speed lens actuator
• Laser diode pulsers
• Levitated flywheel
• Maglev
• Permanent magnet brakes
• Switching power supplies
• Magnetic analysis
• Laser driver pulsers
• 50 kW inverter switch
• Transcutaneous (through-skin) non-contact power supply
Selected History of Power Switching Devices
• 1960s - switching speed of BJTs allow DC/DC converters
possible in 10-20 kHz range
• 1960 - Metal Oxide Semiconductor Field-Effect Transistor
(MOSFET) for integrated circuits
• 1976 - power MOSFET becomes commercially available,
allows > 100 kHz operation
Power Factor
• With pure sine wave and resistive load, PF = 1
• With pure sine wave and purely reactive load, PF = 0
• Whenever PF < 1 the circuit carries currents or voltages
that do not perform useful work
• The more “spikey” a waveform is the worse is its PF
– Diode rectifiers have poor power factor
• Power factor can be helped by “power factor correction”
Power Factor Correction
• Typical toaster can draw 1400W from a 120VAC/15A line
• Typical offline switching converter can draw <1000W
because it has poor power factor
• High power factor results in:
– Reduced electric utility bills
– Increased system capacity
– Improved voltage
– Reduced heat losses
• Methods of power factor correction
– Passive
• Add capacitors across an inductive load to resonate
• Add inductance in a capacitor circuit
– Active