On the right is a diagram of the traditional TRIAC dimmer most people have in their homes. Basically, the TRIAC works by phase cutting the leading edge of the AC line, reducing the power delivered to the light. Notice that the light is an integral part of the load. For the TRIAC to work properly, it needs to have sufficient current to trigger. This is seen as the current path in red. The RC filter adjusts where on the AC line cycle the phase cutting takes place. Once triggered, the second requirement is to maintain holding current. This is shown in green. When incandescent bulbs are replaced with switch mode power supplies and use traditional dimmers, there are a number of problems which result from trying to maintain the TRIAC in conduction. These challenges, as well as how the TPS92070 addresses them, will be covered in a moment.