1. Power Semiconductor Devices
Xi Liu
Biomedical Engineering
ECE423

2. 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

3. Fig. 1. The power semiconductor devices family
Classification
Fig. 1. The power semiconductor devices family

4. Important Parameters Breakdown voltage. On-resistance.
Trade-off between breakdown voltage and on-resistance.
Rise and fall times for switching between on and off states.
Safe-operating area.

5. 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

6. Power MOSFET: R-V Characteristics
An important parameter of a power MOSFET is on resistance:
, where
Fig. 3. Typical RDS versus ID characteristics of a MOSFET.

7. 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.

8. Thyristor: I-V Characteristics
Three States:
Reverse Blocking
Forward Blocking
Forward Conducting
Fig.5 The current-voltage characteristics of the pnpn device.

9. 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

10. Application: Automotive
Table. 1. Power Devices in automotive systems.

11. 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) .

12. 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

13. 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.

14. Thanks!