Analog dimming is the adjustment of the average continuous LED current. This method of dimming typically has the lowest dimming ratio among standard dimming techniques. The dimming ratio can vary from 10 to 1 to up to 250 to one. The performance of the dimming ratio varies based off of the control topology of the LED driver, as well as how you implement analog dimming. For dimming ratios in the thousands to one range, typically you need to use a pulse width modulation dimming method or a combination of analog and pulse width modulation.

Some customers prefer to stay in the linear dimming range, primarily because of the simplicity of having a linear relationship between the output current and light, and linear dimming can also be more efficient.

Analog dimming is typically the simplest dimming method to implement. To implement the dimming, simply adjust the analog voltage on the current adjust pin on an LED driver, which is used as a reference to adjust the output LED current. Depending upon the specific LED driver, you can adjust the analog voltage through the pin or using a resistor divider or even using a signal from a microcontroller that is converted PWM signal through a filter into analog voltage.

Figure 2-1 DIM Duty Cycle vs FB Voltage in Analog Dimming