IGBTs, FETs Play It Cool At PCIM

paulWhytock168x144Engineers visit the PCIM Show and Conference for one reason: the new technology on display. This year’s event maintained its reputation, with IGBT and FET innovations stealing the thunder at the show. Switching and on-resistance efficiencies lay at the heart of many such breakthroughs. One standout among them was Toshiba Electronics Europe’s (TEE) new generation of superjunction (SJ) technology for power MOSFETs.

This technology is important because SJ MOSFETs offer ultra-low on-resistance below the silicon limit. They also facilitate device miniaturisation, subsequently saving printed circuit board space, without power loss penalties.

As a result, Toshiba’s DTMOS-IV process, which is being deployed in the company’s latest family of high-speed, high-efficiency 600V power MOSFETs, offers up to 40% lower on-resistance ratings versus first-generation DTMOS products for the same die size. This means design engineers can now choose a 600V MOSFET in a TO-220SIS package with an RDS(ON) of 0.065Ω, or a similar device in a TO-3P(N) package with an RDS(ON) down to 0.04Ω.

It's not all about driving down on-resistance, though. DTMOS-IV also helps minimise MOSFET output capacitance (COSS) for optimised SPS operation at light load. In addition, an optimised gate-drain capacitance (CGD) enhances dv/dt switching control, while an optimised RDS(ON)Qg figure of merit supports high-efficiency switching. Finally, by supporting lower dv/dt ratings, DTMOS-IV also reduces the tendency to ringing in high-speed switching circuitry.

At the heart of the DTMOS-IV is a deep-trench filling process. The technology is essential in narrowing the lateral superjunction pitch.

COOL IGBT

The continued development of practical electric vehicles always seems to be at the forefront of the electronics world. PCIM 2012 mirrored that trend with International Rectifier’s introduction of a 600V automotive-grade IGBT platform called “COOLiRIGBT.” Designed for use in fast switching applications for electric (EV) and hybrid electric vehicles (HEV), COOLiRIGBT devices can operate at the same switching speeds as MOSFETs, but they provide enhanced efficiency at high current levels.

The first-generation COOLiRIGBT devices cover a broad current range and offer a minimum short-circuit rating of 5μs, low VCE(ON), and positive VCE(ON) temperature coefficient. Other design features common to the family include square reverse-bias safe operating area (SRBSOA) and maximum junction temperature of 175°C.  Interestingly, the COOLiRIGBTs also give designers the flexibility to select a diode with optimised performance for their application.

The AUIRGC655A1N0 is designed for main electric and hybrid-vehicle inverters and large motor drives. The AUIRGC65A20N0 and AUIRGC65G20N0 target power-supply and high-switching-frequency applications.

Cool JFET

Also playing it cool, Infineon Technologies used PCIM 2012 to unveil its new CoolSiC 1200V SiC JFET family. The  company claims it dramatically lowers switching losses compared to IGBTs.

By implementing the 1200V SiC JFETs, higher switching frequencies are able be used without sacrificing overall system efficiency. Consequently, much smaller passive components can be employed, which predictably results in smaller overall solution size. However, it’s possible to realise a higher output power solution within the same inverter housing.

To ensure that the “normally on” JFET technology is easy to use, Infineon developed a concept called “Direct Drive Technology.” In this scenario, the JFET is combined with an external low-voltage MOSFET and a dedicated driver IC, which ensures safe system startup conditions as well as fast and controlled switching.

Continuing with JFET developments, SemiSouth announced its new 1700V/1400mΩ SiC JFETs, which the company believes simplify fast startup of three-phase power supplies.

According to SemiSouth, traditional solutions go in one of two directions. They will use an HV bleed resistor, resulting in a slow startup at low line voltages and a high quiescent power loss. Or they are MOSFET-based, which necessitates overload protection, leading to potential high power losses in the MOSFET under fault condition (e.g., short circuit).

The SJDT170R1400 will come in a newly developed SMD D2PAK-7L package that simplifies PCB layout and optimises switching performance due to lower inductance. The package will feature a high creepage distance of 6.85mm to support 1700V applications. It measures 16mm by 10mm by 4.4mm.

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