Here are two waveforms of a TRIAC dimmer controlling a traditional 40 W incandescent bulb. As per the legend at the bottom of the slide: green is the line current, black is the line current without a dimmer and is just there for reference, and blue is the line voltage. The figure on the left shows the dimmer at its maximum conduction angle, or maximum light output. There are a couple of points to note here. The first is that even at full light output, there is still some phase cutting; it may be small, but it is always present. The second point is that this phase cutting produces a sharp edge in the waveform. The figure on the right shows the dimmer at its minimum brightness. There are a couple of points to note here as well. First, notice that this dimmer, like most others, does not dim all the way to zero; there is still some AC passing through, even at the minimum setting. The second point is that there can be some asymmetry in the waveform related to the point where the TRIAC starts conducting. Now that a mental picture of how TRIAC dimmers work has been established, this presentation will now discuss how the TPS92070 manages this.