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GaN Power Module with High Temperature Gate Driver and Insulated Power Supply
Keywords: GaN HEMT , High temperature, Flyback DC/DC converter
Emerging GaN power switches show advantages for integration in power modules at high temperature and/or high efficiency. These modules are good candidates for embedded power converters in harsh environment such as three phase inverters for Electro-Mechanical Actuators (EMA) in the vicinity of internal combustion engines. The power range is usually within 1 to 5 kW, extending sometimes up to 50 kW, using a HVDC bus voltage that is usually comprised between 200 V and 600V. For aeronautical applications, GaN power switches could challenge SiC transistors for their high switching speed, hence reduced switching losses, therefore lower embarked mass. For automotive applications, it is the relative lower cost per Amp that is pushing this technology up. This is why a project joining GaN device conception, power module development and gate driver optimization using high temperature technologies was set-up. This paper presents the first practical results: a functional GaN power inverter-leg driven by a specific high temperature gate driver with signal and power insulation. This building block requires an auxiliary DC supply with a input voltage of 14 V or 28 V, an external PWM control signal, the HVDC bus voltage is 200 V, the load draws 30 A. This intelligent power module consists of a GaN power section –an inverter leg— controlled by two SoI gate drivers. The control signals are insulated using high temperature coreless transformers and SoI integrated transceivers. The modulation frequency is 24 MHz, the transmission delay is lower than 170 ns, the insulation is better than 3 kV and the parasitic capacitance is lower than 10 pF. The auxiliary DC/DC converter is a flyback structure built around a nano-crystalline core transformer and controlled by a SoI High Temperature High Reliability integrated PWM controller from a European supplier. Input filter capacitors are chosen with a high isolation voltage (NPO series) to withstand the high common mode voltage produced by the floating point of the inverter-leg. The GaN module is composed by two N-channel depletion modes GaN High Electron Mobility Transistors (HEMT) produced by one of the partners in the project. The device’s preliminary specification is: the nominal voltage is 200V, the average current at 25°C is 30A with a channel resistance of 30mΩ. GaN transistors are soldered and packaged using a laboratory high temperature technology. Most of the demonstrator has been prototyped with engineering samples provided by the partners (coreless transformers, ceramic capacitors, cored transformers and integrated circuits. This paper provides an experimental validation and a design review of a High Temperature GaN HEMTs Power System. Full paper includes electrical measurements of key parameters such as dv/dt across power switches, oscilloscope plots of main waveforms, comprehensive bloc diagrams of the experimental setup and zoomed colors photographs of the demonstrator.
Villeurbanne, Rhone Alpes

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