Fast robust gate-drivers with easily adjustable voltage ranges for driving normally-on wide-bandgap power transistors

Abstract

Wide-bandgap (WBG) semiconductors, such as gallium nitride (GaN), are more and more being used in switching power devices. An AlGaN/GaN/AlGaN Double Heterojunction Field Effect transistor (DHFET) was developed in previous work and needed to be tested. The used test circuit was a buck converter. This type of converter, in addition with the normally-on switching behaviour of the GaN-based transistors, requires dedicated gate drive circuitry, resulting in the development of three types of gatedrivers. This paper presents the topology and performance of these drivers. Because of the type of converter, the drivers need to be galvanically isolated. Furthermore, because the experimental GaN transistors are normally-on, the drivers need to be robust so that they apply a negative gate-to-source voltage to switch off the transistor in case an error occurs in the driver. A third requirement for the drivers is that it has to be easy to adjust the voltage levels, in order to test the devices at different gate-to-source voltage conditions. A final requirement is that it has to be possible to construct the drivers with readily available electronic components. Because the drivers are galvanically isolated, there is a parasitic isolation capacitance in the DC-DC-converter of the drivers. This gives rise to a common-mode current which possibly can disturb the operation of the driver. The article also discusses this common-mode problem.

Gallium-Nitride Semiconductor Technology and Its Practical Design Challenges in Power Electronics Applications: An Overview

“…Since its creation, many gate driver circuits have been proposed to overcome the issue with the voltage level. Some of these driver circuits are adjustable [37], depending on the threshold and full turn-on/-off voltages of the devices. Resonant drivers [38] are also reported in the literature.…”

Gallium Nitride Electrical Characteristics Extraction and Uniformity Sorting

“…Moreover, GaN FETs and the design of their gate drivers are relatively new. When using GaN FET power transistors in circuit applications, their unique electrical properties must be considered: (1) no intrinsic body diode [8][9][10], (2) low gateto-source voltage limits [9,10], (3) full-conduction voltage of the gate and uncommon power supply voltage (e.g., 7 V, 8 V) [11][12][13], and (4) low threshold voltage [9,10,12,13]. The following properties are applicable to bridge-leg architecture power transistors: (1) floating source of the high-side power switch [14,15] and (2) faulty turn-on [9,15].…”

Accurately modelling of parasitics in power electronics circuits using an easy RLC-extraction method

“…As an example, a so-called reversed buck converter is used. It has almost the same operating principle as an ordinary buck, or step-down, converter, but in the reversed buck topology, the source of the switching transistor is connected with the ground line, thus facilitating the gate-driver, which does not have to be isolated as explained in [7]. The topology is depicted in Fig.…”