PWM(Pulse Width Modulation)

PWM(Pulse Width Modulation)

How the dimming feature on an Optodrive module works

In light application we need to consider this method as the only method to dim the LED down to a lower level. The LED are so called bin coded at a certain mA to have a prefect light according to the black body curve. Depending on the stability on the LED this is the fixed maximum driving current of the LED if the professional aspect is involved. To dim the LED down in intensity we take away some Dute but the LED is still running on the same currant (mA) but in less time during the duty cycle. This light will be stable and keep the same colour temperature in Kelvin as well as the same CRI.

The human eyes perceive an object in motion when it is moving more than 16 times a second. This useful principal has been used in theatre film. Although a film is constantly showing24 different images in a second, the human brain recognizes it as a single moving image. This phenomenon is called persistence of vision.

Pulse Width Modulation of LED is a LED driving method, using this persistence of vision of human eyes. In PWM operation, input current doesn’t flow through LED continuously. Instead, input current is provided during fixed time for a certain period of time and not provided the rest of time for a certain period, so called Duty. The time that current flows through LED depends on its applications and user’s objectives. When LED is driven in PWM, we are able to save unnecessary power supplied to LED, and reduce heat emitting from the devices. But less current means less luminous flux. So PWM must be reconsidered when user needs much luminous flux. For the reason, driving method should be properly adopted according to the applications.