Abstract
Gallium nitride high electron mobility transistor (GaN HEMT) is liable to gate false turn-on problem when the gate crosstalk voltage exceeds its threshold voltage in the widely adopted phase-leg topology due to its low threshold voltage and high switching speed. Without considering the gate loop stray inductance, gate internal resistance, nonlinearity of parasitic capacitances and power loop stray parameters, traditional false turn-on analytical method is insufficient to support accurate analysis. And it has been found that GaN HEMT gate-source parasitic capacitance C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gs</sub> previously assumed constant is otherwise highly nonlinear and has strong impacts on the gate crosstalk voltage. This paper has measured C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gs</sub> by vector network analyzer and constructed an accurate nonlinear model of C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gs</sub> , based on which an accurate GaN HEMT behavior model is further fulfilled. The accuracy of the proposed behavior model has been verified by large amounts of experiment results. The proposed GaN HEMT model is used to accurately calculate gate crosstalk voltage and switching losses. Besides, false turn-on induced extra loss has been calculated and is adopted as a criterion to evaluate the severity of false turn-on and optimal design method for false turn-on suppression has been detailed further.
Highlights
Gallium nitride high electron mobility transistor (GaN HEMT) with the merits of high switching speed, low switching and conduction loss and small package size is becoming more and more prevalent in recent years [1], [2]
Some methods have been proposed to address false turn-on problems, and they can be classified into three types
The first type is trying to eliminate the intensity of exciting source that induces gate crosstalk voltage, among which the simplest way is to slow down the turn-on speed of GaN HEMT with large turn-on resistance, but it will increase the overlap loss during the turn-on transient [4]–[7]
Summary
Gallium nitride high electron mobility transistor (GaN HEMT) with the merits of high switching speed, low switching and conduction loss and small package size is becoming more and more prevalent in recent years [1], [2]. Traditional analytical methods addressing false turn-on problem are mostly applicable to silicon power devices without taken the gate loop inductance and nonlinearity of device parasitic capacitances into account as in [14]–[16]. They are not accurate enough for the analysis of GaN HEMT. The nonlinearity of device gate-source capacitance has not been taken into consideration and modeling false turn-on excitation signal with a simple ramp function is not accurate enough Aiming at these issues, this paper has constructed an accurate behavior model of GaN HEMT with the modeling accuracy of gate-source capacitance enhanced, based on which a precise false turn-on analysis model is constructed further. Once the induced gate-source crosstalk voltage surpasses the intrinsic low threshold voltage of GaN, false turn-on will be triggered
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