Changing the brightness (dimming) of LEDs

There are two main ways to dim an LED.

The simplest method is analog control, where the current flowing through the LED is controlled directly: lower current results in lower brightness. Unfortunately, this method has two significant drawbacks. First, the LED brightness is not fully proportional to the current, and second, the wavelength (and therefore the color) of the emitted light shifts as the LED current changes relative to the nominal value. Both of these phenomena should be avoided in most cases.

A slightly more complex control method uses a constant current source designed to deliver the nominal operating current to the LED. Additional circuitry can easily turn the LED on and off at a specified duty cycle, thus reducing the emission. This is perceived as a decrease in brightness. By adjusting the duty cycle, the perceived brightness of the LED can be easily adjusted. This method is known as pulse width modulation (or PWM)

There is also a software method of simulating PWM, which changes the fill factor of the LEDs by alternating the intervals of switching the LEDs on and off with a certain sequence. This method is called BAM (Binary angular measurement). It is relevant if the system components or microprocessors do not support standard PWM and is actually its software analogue.

It is on this principle that dimmers for adjusting the brightness of LEDs are designed. Therefore, adjusting the brightness of LED products is possible only with the use of special dimmers; the use of conventional dimmers for incandescent lamps is unacceptable.

Please note that there are a certain number of LED strips or lamps of the cheap segment of Asian manufacturers that are of low quality and are not able to provide a change in brightness. Attempts to dim such LEDs usually result in flickering when trying to reduce the brightness. Such LEDs can only operate at 100% duty cycle and cannot change brightness, especially when it comes to modern advanced dimmers with high pulse width modulation frequencies. Please pay attention to dimming support when choosing light sources.