Semiconductor Device Output Capacitance Dynamics for EMI Reduction

The patent applies dynamics by making the output capacitance variable rather than fixed. A floating doping region is introduced that changes the effective capacitance during switching transitions. The capacitance dynamically adjusts based on the depletion zone position, providing low capacitance during steady state for low losses, and increasing capacitance during transitions to reduce ringing and EMI.

The patent changes the electrical parameter of output capacitance from a constant value to a variable value. By controlling the depletion zone position through the floating doping region, the effective capacitance parameter is changed during operation. This allows optimization of both switching losses and ringing/EMI performance by having different capacitance values at different operating points.

The patent uses dynamics to adjust the capacitance based on the switching state. During rapid transitions, the floating doping region modifies the depletion zone position to increase effective capacitance, which dampens the extreme edges and reduces ringing while still allowing fast switching. During steady state, the capacitance is minimized to maintain high switching speed capability.

The floating doping region acts as a feedback mechanism where the depletion zone position automatically adjusts the capacitance based on the instantaneous voltage conditions. This self-regulating feedback provides increased capacitance when switching edges become too extreme, thereby reducing ringing and EMI without requiring external control circuits.

The patent resolves this contradiction by making capacitance dynamic rather than static. The floating doping region ensures that high capacitance is only present transiently during switching events when needed for reducing ringing and EMI, while low capacitance is maintained during steady state to minimize switching losses. This temporal separation of capacitance values eliminates the need to continuously maintain high capacitance.

The patent implements periodic action by having the capacitance vary cyclically with each switching cycle. During each switching event, the capacitance temporarily increases to suppress ringing and EMI, then returns to a low value for the majority of the cycle. This periodic modulation of capacitance allows reduction of harmful effects without the continuous energy penalty of high static capacitance.