Device Screening Strategy for Suppressing Current Imbalance in Parallel-Connected SiC MOSFETs
Bin Zhao, Qiuping Yu, Peng Sun, Yumeng Cai, Zhibin Zhao
Abstract
Device parameter mismatch generates current imbalance between parallel devices. In severe cases, the device that withstands excessive current may incur overcurrent failure, which poses challenges to the safety of the parallel system. To suppress the current imbalance, it is necessary to screen parallel devices to obtain approximate device parameters. This paper addresses the influence of parameter spread on the dynamic and static current distributions in parallel SiC metal- oxide- semiconductor field-effect transistors (MOSFETs) and proposes a device screening method to suppress current imbalance. First, the dispersity of device parameters that affect the dynamic and static current distributions are statistically analyzed. Then, the parameter transconductance coefficient (g) and fitting threshold voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\mathrm{ th*}}$ </tex-math></inline-formula> ) that characterize the transfer curve are obtained through cubic fitting. A screening method based on g and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\mathrm{ th*}}$ </tex-math></inline-formula> for suppressing dynamic current imbalance is proposed. Moreover, the relationship curve between the on-state resistance ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R_{\mathrm{ ds}}$ </tex-math></inline-formula> ) and the drain current ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{\mathrm{ d}}$ </tex-math></inline-formula> ) is linearly fitted to obtain the minimum on-state resistance ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R_{\mathrm{ dsmin}}$ </tex-math></inline-formula> ) and the maximum on-state resistance ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R_{\mathrm{ dsmax}}$ </tex-math></inline-formula> ) to characterize the on-state resistance under different current levels. A screening method based on <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R_{\mathrm{ dsmin}}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R_{\mathrm{ dsmax}}$ </tex-math></inline-formula> is proposed to suppress static current imbalance. Finally, a test bench with a symmetrical layout is designed to experimentally verify the performance of the device screening methods. The experimental results validate the effectiveness of the proposed device screening method for suppressing dynamic and static current imbalances. In addition, a comprehensive control method of suppressing the current imbalance based on device parameters and circuit parameters is proposed.