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 on-resistance.

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 CharacteristicsAn important parameter of a power MOSFET is on resistance:

, whereon S CH DR R R R ( )CH

n ox GS T

LR

W C V V

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.

Three States: Reverse Blocking Forward Blocking Forward Conducting

Thyristor: I-V Characteristics

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: AutomotiveTable. 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!