The working principle of triac dimming is to cut the input voltage waveform through the conduction angle to produce a tangential output voltage waveform. Using the principle of tangential direction, the effective value of the output voltage can be reduced, thereby reducing the power of the ordinary load (resistive load). The advantages of triac dimming are higher working efficiency and stable performance.

  In fact, not all phase controllers are cut off from the same direction of the AC sine wave. The triac is used for dimming of incandescent lamps and halogen lamps. It starts to cut off from the front phase of the sine wave. At the cut-off point, the input voltage has just crossed zero and the input current has just reversed. Therefore, it is also called a leading-edge triac dimmer, which will generate a current spike when it starts to conduct. This spike current will cause buzzing and increase the pressure on the electronic driver.

  Rear-edge triac dimming can avoid the above problems, because it starts to cut off the dimmer from the second half of the AC sine wave or the back edge. The reverse phase control dimmer turns on when the input current just changes direction, it allows the voltage to gradually rise, and then cuts it off in the next half cycle. Inverting control dimmers are also called electronic low voltage (ELV) dimmers and are used to improve the performance of halogen lamps using electronic transformers.

  So theoretically speaking, the triac dimming power supply is more suitable for LED dimming.