Device Screening Strategy for Suppressing Current Imbalance in Parallel-Connected SiC MOSFETs

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 (
$V_{\mathrm{ th*}}$
) that characterize the transfer curve are obtained through cubic fitting. A screening method based on g and
$V_{\mathrm{ th*}}$
for suppressing dynamic current imbalance is proposed. Moreover, the relationship curve between the on-state resistance (
$R_{\mathrm{ ds}}$
) and the drain current (
$I_{\mathrm{ d}}$
) is linearly fitted to obtain the minimum on-state resistance (
$R_{\mathrm{ dsmin}}$
) and the maximum on-state resistance (
$R_{\mathrm{ dsmax}}$
) to characterize the on-state resistance under different current levels. A screening method based on
$R_{\mathrm{ dsmin}}$
and
$R_{\mathrm{ dsmax}}$
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.