EPotencia

1. Power Semiconductor Devices
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2. A brief survey of power semiconductor devices
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● Power diodes
● Power MOSFETs
● Insulated Gate Bipolar Transistors (IGBTs)
● Thyristors (SCR, GTO)
● On resistance vs. breakdown voltage vs.
switching times
● Minority carrier and majority carrier devices

3. The power diode
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Appearance
Construction Symbol

4. Reverse-biased power diode
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5. Forward-biased power diode
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6. Typical power diode characteristics
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7. Typical diode switching waveforms
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8. Types of power diodes
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Standard recovery
Reverse recovery time not specified, intended for 50/60Hz
Fast recovery and ultra-fast recovery
Reverse recovery time and recovered charge specified
Intended for converter applications
Schottky diode
A majority carrier device
Essentially no recovered charge
Model with equilibrium i-v characteristic, in parallel with
depletion region capacitance
Restricted to low voltage (few devices can block 100V or
more)

9. Characteristics of several commercial power
rectifier diodes
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10. The power MOSFET
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Appearance
Symbol
n-channel p-channel

11. The construction of Power MOSFET
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12. MOSFET: Off state
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13. MOSFET: On state
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14. MOSFET body diode
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15. Typical MOSFET characteristics (1)
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16. Typical MOSFET characteristics (2)
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17. Power MOSFET switching waveform
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18. A simple MOSFET equivalent circuit
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19. Characteristics of several commercial
power MOSFETs
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20. MOSFET: conclusion
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● A majority-carrier device: fast switching speed
● Typical switching frequencies: tens and
hundreds of kHz
● On-resistance increases rapidly with rated
blocking voltage
● Easy to drive
● The device of choice for blocking voltages less than
500V
● 1000V devices are available, but are useful only at low power
levels(100W)
● Part number is selected on the basis of on-resistance rather than
current rating

21. The Insulated Gate Bipolar Transistor (IGBT)
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Appearance Symbol

22. The construction of IGBT
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23. The equivalent circuit of IGBT
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24. Typical IGBT characteristics
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25. IGBT switching waveform
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26. Current tailing in IGBTs
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27. Characteristics of several
commercial devices
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28. Conclusions: IGBT
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● Becoming the device of choice in 500-1700V applications, at
power levels of 1-1000kW
● Positive temperature coefficient at high current —easy to
parallel and construct modules
● Forward voltage drop: diode in series with on-resistance.
2- 4V typical
● Easy to drive —similar to MOSFET
● Slower than MOSFET, but faster than Darlington, GTO, SCR
● Typical switching frequencies: 3-30kHz
● IGBT technology is rapidly advancing —next generation:
2500V

29. The Thyristor (silicon controlled rectifier, SCR)
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Appearance Symbol

30. The equivalent circuit and
construction of thyristor
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31. Typical thyristor characteristics
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32. Thyristor switching waveform
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33. Why the conventional SCR cannot be
turned off via gate control
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34. The Gate Turn-Off Thyristor (GTO)
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35. Summary: Thyristors
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● The thyristor family: double injection yields lowest forward
voltage drop in high voltage devices. More difficult to
parallel than MOSFETs and IGBTs
● The SCR: highest voltage and current ratings, low cost,
passive turn-off transition
● The GTO: intermediate ratings (less than SCR, somewhat
more than IGBT). Slower than IGBT. Slower than MCT.
Difficult to drive.
● The MCT: So far, ratings lower than IGBT. Slower than IGBT.
Easy to drive. Still emerging devices?

36. Summary of power semiconductor
devices
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1. Majority carrier devices, including the MOSFET and Schottky diode, exhibit
very fast switching times, controlled essentially by the charging of the
device capacitances. However, the forward voltage drops of these devices
increases quickly with increasing breakdown voltage.
2. Minority carrier devices, including the BJT, IGBT, and thyristor family, can
exhibit high breakdown voltages with relatively low forward voltage drop.
However, the switching times of these devices are longer, and are
controlled by the times needed to insert or remove stored minority charge.
3. Energy is lost during switching transitions, due to a variety of mechanisms.
The resulting average power loss, or switching loss, is equal to this energy
loss multiplied by the switching frequency. Switching loss imposes an
upper limit on the switching frequencies of practical converters.

37. Two classifications based on carriers
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Classification I Classification II