Instability in Half-Bridge Circuits Switched With Wide Band-Gap Transistors

Abstract

Wide band-gap (WBG) field-effect devices are known to provide a system-level performance benefit compared to silicon devices when integrated into power electronics applications. However, the near-ideal features of these switching devices can also introduce unexpected behavior in practical systems due to the presence of parasitic elements. The occurrence of self-sustained oscillation is one such behavior that has not received adequate study in the literature. This paper provides an analytical treatment of this phenomenon by casting the switching circuit as an unintentional negative resistance oscillator. This treatment utilizes an established procedure from the oscillator design literature and applies it to the problem of power circuit oscillation. A simulation study is provided to identify the sensitivity of the model to various parameters, and the predictive value of the model is confirmed by experiment involving two exemplary WBG devices: a SiC vertical-channel JFET and a SiC lateral-channel MOSFET. The results of this study suggest that susceptibility to self-sustained oscillation is correlated to the available power density of the device relative to the parasitic elements in the circuit, for which wide band-gap devices, to include SiC and GaN transistors, are in a class approaching that of the radio frequency domain.

Analysis and Suppression of Unwanted Turn-On and Parasitic Oscillation in SiC JFET-Based Bi-Directional Switches

“…The driver X (X = F or R), which is represented as a transformer in Figure 3, is an isolated driver IC (Integrated Circuit) 1EDI30J12CP for normally on SiC JFETs recommended by Infineon Technologies AG [20]. The voltage across the gate impedance (LG F -RG F ) under such an iG F represents a positive voltage source into the gate loop (A F ) according to (3). This voltage source charges the gate-source interelectrode capacitor CGS F .…”

“…When UTO occurs periodically in a constant cycle, undamped oscillation or even divergent oscillation may occur [3,4]. A limited number of UTO means that damped oscillations will be the result.…”

“…Wide Band-Gap (WBG) power devices, which provide a system-level performance benefit with high-voltage blocking capability, high-temperature operation and high-frequency switching performance, have been employed in various power electronic converter applications [1][2][3][4]. The switching behavior of WBG devices, such as Silicon Carbide (SiC) and Gallium Nitride (GaN) FETs (Field Effect Transistors), has attracted considerable research attention.…”

“…The switching behavior of WBG devices, such as Silicon Carbide (SiC) and Gallium Nitride (GaN) FETs (Field Effect Transistors), has attracted considerable research attention. There are basically three issues concerning WBG device switching behavior currently being considered in research literature [3][4][5][6][7][8][9][10][11][12][13][14].…”

“…The second issue is the Unwanted Turn-On (UTO) of a WBG device during its turn-off transient [3,4,10]. This issue has got less attention compared with the shoot-through issue.…”