Power Semiconductor Devices
Xi Liu Biomedical Engineering ECE423
Introduction
What are Power Semiconductor Devices (PSD)? They are devices used as switches or rectifiers in power electronic circuits
What is the difference of PSD and low-power semiconductor device? Large voltage in the off state High current capability in the on state
Classification
Fig. 1. The power semiconductor devices family
Important Parameters
Breakdown voltage. On-resistance. Trade-off between breakdown voltage and onresistance. Rise and fall times for switching between on and off states. Safe-operating area.
Power MOSFET: Structure
Power MOSFET has much higher current handling capability in ampere range and drain to source blocking voltage(50-100V) than other MOSFETs.
Fig.2.Repetitive pattern of the cells structure in power MOSFET
Power MOSFET: R-V Characteristics
An important parameter of a power MOSFET is on resistance:
R on R S R C H R D
, where R C H
L W n C ox (V G S VT )
Fig. 3. Typical RDS versus ID characteristics of a MOSFET.
Thyristor: Structure
Thyristor is a general class of a four-layer pnpn
semiconducting device.
Fig.4 (a) The basic four-layer pnpn structure. (b) Two two-transistor equivalent circuit.
Thyristor: I-V Characteristics
Three States: Reverse Blocking Forward Blocking Forward Conducting
Fig.5 The current-voltage characteristics of the pnpn device.
Applications
Power semiconductor devices have widespread applications: Automotive Alternator, Regulator, Ignition, stereo tape Entertainment Power supplies, stereo, radio and television Appliance Drill motors, Blenders, Mixers, Air conditioners and Heaters
Application: Automotive
Table. 1. Power Devices in automotive systems.
Future Developments
For future power conversion applications, new semiconductor devices are needed to be developed. 1.Structure Improvement Insulated Gate Bipolar Transistor (IGBT), static induction transistor (SIT) and MOS-controlled thyristor (MCT) .
Future Developments
2. Material Improvement Silicon carbide (SiC), with a higher field characteristic, is a promising candidate for high power, high temperature and high frequency applications.
High electric breakdown property High carrier drift velocity
High thermal conductivity
The native oxide of SiC is SiO2
Conclusion
The development of power semiconductor devices is very essential for modern electronics. The power devices based on new structures and materials are promising and commercially realistic for future electronic developments.
Thanks!