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EETE MAY 2015

Motor control Designing a temperature ruggedized gate driver By Pierre Delatte There is a growing demand for integrated circuits (ICs) able to operate in higher temperature environments without compromising on reliability and lifetime. For years, the Oil & Gas Drilling industry has been pushing the limits of semiconductor components by developing electronic systems able to operate in the harshest environments in terms of temperature, in excess of 200°C, pressure, shocks or vibrations. Automotive electronic components have been progressively pushed towards operating temperatures approa-ching 175°C, but with carefully selected mission profiles to their reliability during the vehicle lifetime. Specialized semiconductor processes, e.g. based on Silicon-on-Insulator (SOI) technology, can help with the development of ICs able to operate reliably at extreme temperatures. However, selecting the appropriate semiconductor manufacturing process is not the only answer. Device modelling, circuit design techniques, IC packaging, characterization and reliability testing are other key expertise’s required to build reliable IC’s for these highly demanding applications. Also, choosing the right trade-off between operating temperature, reliability, Fig. 1: (a) Efficiency of a 1.5KW DC-DC Converter using SiC JFET driven by HADES® Gate Driver (b) turn-Off waveforms. lifetime, cost and production volumes is essential. This is why part of CISSOID components targeting industrial and automotive applications are rated from -55°C up to 175°C, while we address markets requiring extreme temperatures or ultimate lifetime such as Oil & Gas Drilling or Aerospace with products rated from -55°C up to 225°C. With the advent of fast switching Silicon Carbide (SiC) and Gallium Nitride (GaN) transistors and the race for high power Fig. 2: HADES® v2 Isolated Gate Driver Board rated at 175°C. density, a new market is emerging for high temperature electronics. Indeed, these new devices can operate at higher temperatures, reducing cooling requirements, and have very low switching energy, enabling higher switching frequency while dramatically reducing the size of filters and transformers. Reduced cooling and higher switching frequencies mean higher temperatures for the power switches but also the proximity gate drivers. In 2009, CISSOID started the development of gate drivers for the first generation of SiC transistors. In 2011, HADES® isolated gate driver was the first high temperature driver dedicated to SiC power switches. Since then, HADES® has been used in first SiC power converters for Oil & Gas Drilling, Aerospace and Railways applications, as well as for EV battery charger prototypes. High temperature operation, dedicated protection functions and robustness to high dV/dt were crucial to support the design of reliable and efficient power converters – see figure 1. Based on first generation users’ feedback, a new chipset has been developed and was released in March 2015. This second generation (HADES® v2) is more powerful, with output drive current up to 12A, and offers higher level of integration. For systems requiring extended lifetime and where the junction temperature doesn’t exceed 175°C, one primary side (HADES2P) and two secondary side (HADES2S) ICs, both packaged in a plastic QFP44, are required to build a power leg. For extreme temperatures up to 225°C, these chips are assembled in a hermetic ceramic QFP32 package. A gate driver board has been developed to demonstrate a half bridge built on the HADES® v2 gate driver chipset. The 60x55mm board has been designed for operation at 175°C, with short excursions possible up to 225°C. It also includes two CISSOID “NEPTUNE’s” 10A/1200V SiC MOSFET’s. For SiC MOSFET’s, the gate is typically driven between -5V and +20V. These voltages can easily be adapted to drive SiC JFET’s, Si MOSFET’s, Si IGBT’s or GaN transistors by modifying the power transformer. The primary side IC – see figure 3 - embeds a currentmode fly-back DC-DC controller together with an integrated 0.8Ohm/80V switch, providing all the active functions to Pierre Delatte is CTO of CISSOID – www.cissoid.com 40 Electronic Engineering Times Europe May 2015 www.electronics-eetimes.com


EETE MAY 2015
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