Abstract
GaN devices are developed rapidly in recent years, which makes it possible to produce power electronic converters with higher efficiency and higher power density. However, with the circuit parasitic parameters, large di/dt and dv/dt caused by the GaN devices' extremely fast switching can easily lead to voltage and current oscillations. This problem affects circuit stabilities and increases the difficulty of application with GaN devices. In this paper, oscillation problems will be explained by oscillator theory and an oscillation suppression method will be introduced. All the researches here are based on Cascode GaN devices. Considering all circuit parasitic parameters, negative conductance models of the GaN devices in the switching-on and switching-off process have been established according to oscillation mechanism analysis. And stability criteria of the GaN-based circuit have been derived which can well predict that whether the oscillations will happen and how will the oscillations last. Besides, the suppression method that placing a ferrite bead in power loop in series has been introduced based on the established model. Selection method is provided quantitively and suppression effect can be calculated. All the achievements of this research have been verified by simulations and experiments.
Highlights
In recent years, the wide bandgap semiconductor devices such as Gallium Nitride (GaN) HEMT and Silicon Carbide (SiC) MOSFET are booming
Based on Cascode GaN devices, switching oscillation problems and circuit stability have been studied in this paper
High operating frequency of GaN devices leads to large dv/dt and di/dt during switching process
Summary
The wide bandgap semiconductor devices such as Gallium Nitride (GaN) HEMT and Silicon Carbide (SiC) MOSFET are booming. The studied oscillation is during the active device’s switching-on process and the model is based on Cascode GaN devices. The oscillation problem of Cascode GaN-based circuit will be analyzed with negative resistance oscillator theory. Part III establishes the negative conductance oscillation model of Cascode GaN devices in the switching-on and switching-off process. With the feedback oscillation theory, a full recalculation is required if the circuit changes In this part, the application method of the negative resistance theory in GaN devices’ oscillation analysis is introduced. The application method of the negative resistance theory in GaN devices’ oscillation analysis is introduced To use this theory, the switching stages to be analyzed should be selected first, which determines the equivalent circuit diagram. NEGATIVE CONDUCTANCE MODELING In this part, the negative conductance modeling method for the DPT circuit with Cascode GaN devices are introduced in details
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