Dynamic Current Sharing Mechanism Analysis of Paralleled SiC MOSFETs Considering Parasitic Mutual Inductances Based on an Improved Model

The dynamic current imbalance between paralleled SiC
mosfet
s can cause unbalanced switching losses and limit the current capacity. It is essential to investigate the influences of the circuit parameters. However, the influences of the unbalanced parasitic mutual inductances and the influences of the common values between the paralleled parameters are unclear. To address these issues, an improved current sharing model is established considering all the parasitic mutual inductances. Based on this model, it is found that the influence degrees of the unbalanced power-drive source mutual inductance (Δ
M
_pk
), the unbalanced drain-source mutual inductance (Δ
M
_ds
) and the unbalanced power-source inductance (Δ
L
_s
), the unbalanced power-gate mutual inductance (Δ
M
_pg
), and the unbalanced threshold voltages (Δ
V
_th
) increase in order. The influence mechanisms of the unbalanced parasitic mutual inductances are also analyzed. Moreover, the effects of the common values between the paralleled parameters (
M
_gk
,
R
_gin
,
M
_pg
,
M
_pk
,
M
_ds
, and
L
_s
) are also investigated. Increasing
M
_pg
,
M
_ds
, and
L
_s
or decreasing
M
_pk
and
M
_gk
can help reduce the current imbalance. Increasing
R
_gin
can also decrease the unbalanced currents if Δ
V
_th
is small. All conclusions are well verified by experiments, and their contributions to the design of circuit layouts and current sharing methods are discussed.