Dimmer rise time, IGBT

IGBT Dimmers deal with rise time in a different manner than Thyristor phase-control dimmers, which use filter chokes to create rise time.

IGBT dimmers operate in the "linear" region of their power transistor during the transition from off to on (forward phase control) or on to off (reverse phase control--now it's called "fall time"). Thus, an IGBT dimmer simulates the effect of a filter choke in a thyristor phase-control dimmer, by causing the IGBT transistor to not switch instantaneously, but in a controlled rise or fall time. This causes the IGBT to dissipate additional power and causes additional heating. Thus, some IGBT dimmers must reduce their rise or fall time (causing more filament noise) as temperature increases.