01-02-2013, 04:26 PM
NEXT-GENERATION POWER ELECTRONICS
[attachment=49286]
ABSTRACT:
With government green-energy programmers’ and CO2 reduction plans reaching as far forward as 2050, the power semiconductor industry is expected to contribute by enabling significant improvements in energy efficiency. The article discusses the options to improve efficiency for power semiconductors.
AREAS FOR IMPROVEMENT:
Power Transistor Technologies:
As far as power transistors are concerned – either as discrete devices or within power modules - bipolar transistors are presently preferred for voltages above 1kV, while MOSFETs are superior for voltages below 1kV, especially for frequencies above 10-100 kHz. IGBTs are chosen for high-current applications over 1000V and up to 10kVA, and above 1MVA when combined in power modules.
Wide-Band gap Materials:
While all types of silicon-based transistors continue to improve, it is clear that significant further advances will become constrained in the coming decade by the limitations of the material. To overcome this, wide-band gap materials such as GaN, SiC and diamond are expected to grow over the coming decade. These can offer dramatically better tradeoff between on-state resistance (RDS (ON)) and breakdown voltage (VBD), as well as lower switching losses and better thermal properties. The main challenges in power-switch development centre around minimizing internal losses at increasing switching frequencies, by reducing conduction losses due to RDS (ON), reducing internal capacitances and improving reverse-recovery performance. Increasing breakdown robustness, through higher VBD and UIS, and proper thermal management are also important goals.
Low-Voltage (<40V) MOSFETs:
Traditionally, the evolution of low-voltage power FETs has sought to minimize die area, and hence reduce cost, for a given RDS (ON): the main Figure-Of-Merit has been the specific RDS (ON) (RDS (ON) spec) expressed in mΩ x mm2. Since in low-voltage FETs, the channel resistance is a main contributor to RDS (ON) spec, the main effort was into packing as many as possible FET channels per mm2. This has resulted in moving from planar channels to vertical 'trench gate' channels, and using small-lithography tools to shrink surface dimensions.
POWER SEMICONDUCTOR MODULES:
The first power modules arrived in the mid 1970s, combining multiple thyristors /rectifiers in one package to achieve higher power rating. Tremendous advances followed and, today, there are two main types of modules. Intelligent Power Modules (IPMs) are typically 1kW-30kW devices comprising several power transistors/rectifiers, pre-drivers and sometimes a controller chip. On the other hand, Power Integrated Modules (PIMs), achieve very high power ratings in the range 10kW-1MW by parallelizing several IGBT/rectifiers in a single package. Technological progress mainly focuses on substrate technologies such as direct-bonded copper (DBC) to improve electrical performance, combined with ceramic substrates such as Al2O3 and AlN to simultaneously increase cooling efficiency.
CONCLUSION:
In summary, this overview of major technology trends among power semiconductors highlights the need for innovations in all system aspects to help improve energy management globally and so meet the world's long-term environmental needs.
[attachment=49286]
ABSTRACT:
With government green-energy programmers’ and CO2 reduction plans reaching as far forward as 2050, the power semiconductor industry is expected to contribute by enabling significant improvements in energy efficiency. The article discusses the options to improve efficiency for power semiconductors.
AREAS FOR IMPROVEMENT:
Power Transistor Technologies:
As far as power transistors are concerned – either as discrete devices or within power modules - bipolar transistors are presently preferred for voltages above 1kV, while MOSFETs are superior for voltages below 1kV, especially for frequencies above 10-100 kHz. IGBTs are chosen for high-current applications over 1000V and up to 10kVA, and above 1MVA when combined in power modules.
Wide-Band gap Materials:
While all types of silicon-based transistors continue to improve, it is clear that significant further advances will become constrained in the coming decade by the limitations of the material. To overcome this, wide-band gap materials such as GaN, SiC and diamond are expected to grow over the coming decade. These can offer dramatically better tradeoff between on-state resistance (RDS (ON)) and breakdown voltage (VBD), as well as lower switching losses and better thermal properties. The main challenges in power-switch development centre around minimizing internal losses at increasing switching frequencies, by reducing conduction losses due to RDS (ON), reducing internal capacitances and improving reverse-recovery performance. Increasing breakdown robustness, through higher VBD and UIS, and proper thermal management are also important goals.
Low-Voltage (<40V) MOSFETs:
Traditionally, the evolution of low-voltage power FETs has sought to minimize die area, and hence reduce cost, for a given RDS (ON): the main Figure-Of-Merit has been the specific RDS (ON) (RDS (ON) spec) expressed in mΩ x mm2. Since in low-voltage FETs, the channel resistance is a main contributor to RDS (ON) spec, the main effort was into packing as many as possible FET channels per mm2. This has resulted in moving from planar channels to vertical 'trench gate' channels, and using small-lithography tools to shrink surface dimensions.
POWER SEMICONDUCTOR MODULES:
The first power modules arrived in the mid 1970s, combining multiple thyristors /rectifiers in one package to achieve higher power rating. Tremendous advances followed and, today, there are two main types of modules. Intelligent Power Modules (IPMs) are typically 1kW-30kW devices comprising several power transistors/rectifiers, pre-drivers and sometimes a controller chip. On the other hand, Power Integrated Modules (PIMs), achieve very high power ratings in the range 10kW-1MW by parallelizing several IGBT/rectifiers in a single package. Technological progress mainly focuses on substrate technologies such as direct-bonded copper (DBC) to improve electrical performance, combined with ceramic substrates such as Al2O3 and AlN to simultaneously increase cooling efficiency.
CONCLUSION:
In summary, this overview of major technology trends among power semiconductors highlights the need for innovations in all system aspects to help improve energy management globally and so meet the world's long-term environmental needs.