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Gallium Nitride (GaN) HFETS are an enabling technology for high-density converter design. This paper proposes a three-level dc-dc converter with dual outputs based on enhancement-mode GaN devices, intended for use as a battery charger in aircraft applications. The charger can output either 28 V or 270 V, selected with a jumper, which meets the two most common dc bus voltages in airplanes. It operates...
This paper designed the gate driver circuits and optimized the PCB layout in a 7.2kW battery charger using paralleled GaN HEMTs. 650V/60A enhancement mode GaN HEMTs provided by GaN Systems Inc are adopted. To optimize the switching performance of paralleled GaN HEMTs with low loss and high reliability, effects of parasitic inductance and capacitance are modeled and analyzed. Through cancelling the...
In power transistor models, it is very important that device capacitances are modelled accurately so that switching losses, EMI filter requirements and gate timing requirements of the converter can be accurately determined. In this paper, a modelling technique utilizing modified sigmoid functions to describe the device capacitances is applied on a GaN HEMT and a silicon MOSFET to develop their corresponding...
Normally-on high-voltage (HV) power transistors are usually operated in a series connection with low-voltage (LV) MOSFETs to ensure safe operation. In the widely used cascode configuration (CC) the status of the combined switch is controlled via the MOSFET gate, whereas the alternative direct drive (DD) method controls the gate of the HV switch directly and utilizes the LV transistor as a safety switch...
This work presents a high-voltage GaN-based power HEMT with a highly-linear, monolithically-integrated temperature sensor. The principle is shown and compared to other concepts. The sensor is fabricated by using a interconnect metallization without additional process steps. The performance of the sensor as well as of the power device is characterized. The 600 V power device achieves an on-state resistance...
Recently differential-mode inverter has been introduced, which has shown significant promise for low-power applications due to its modularity, symmetry, and reduced component count. Initially a continuous modulation scheme was adopted which has now been superseded using hybrid modulation that introduces discontinuity in modulation or yields topological switching that results in enhanced efficiency,...
The gate drive output transient properties of conventional power semiconductors (Silicon MOSFET, Silicon-Carbide MOSFET, and Silicon IGBT) have been studied for online junction temperature (Tj) sensing. This method utilizes the semiconductor intrinsic Tj-dependent characteristics and the gate drive output dynamics. In this paper, the method is applied to Gallium Nitride (GaN) high electron mobility...
Enhancement-mode GaN HFETs enable efficient high-frequency converter design, but this technology is relatively new and exhibits different characteristics from Si or SiC MOSFETs. GaN performance at elevated temperature is especially unique. Turn-on time increases significantly with temperature, and turn-on losses increase as a result. This phenomenon can be explained based on the relationships between...
In this paper, detailed static characterization of the new 650 V/ 30 A GaN device from GaN Systems is presented. The on-resistance and output capacitance of this device are considerably low making GaN a viable option for high switching frequency (in the range of MHz) medium power applications (> 3 kW). A comprehensive examination of device characteristics and variation of device parasitics depending...
Paralleling devices is an effective way to achieve higher power applications while still having the convenience brought by discrete devices. However, very few papers investigate the challenges of paralleling Gallium Nitride high electron mobility transistors (GaN HEMTs) in cascode configuration, especially the potential failure modes and its related mechanisms. In this paper, a comprehensive study...
Envelope tracking (ET) is an appealing alternative to the widely used Doherty power amplifier (PA) due to its potential to increase efficiency, particularly for high data rate transmissions. In this work, we demonstrate a 28 V, 865 MHz switching speed step-down converter that can be applied to envelope tracking. The converter's ET capability is demonstrated at up to 865 MHz PWM carrier frequency....
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