Selecting the Right LED Driver for LED ControlDimming LEDs has benefits in terms of energy savings, ambiance, and increased lifespan. The performance of dimming is primarily determined by the LED source and driver. LED sources can generally be divided into two categories: LED diodes only and LED diodes with a resistor.
Sometimes, LED sources are designed as modules containing DC-DC converters. However, if the LED source or module is composed solely of LED diodes, the standard dimming method is accomplished by adjusting the LED's current amplitude. MEAN WELL HLG family features current adjusting and is controlled by an external dimmer with a signal of DC1-10V or 10V pulse width modulation (PWM) or with a simple resistor.
Another type of LED source is the LED diode with a resistor, also known as an LED strip. Due to the presence of resistors in conjunction with LED diodes, LED strip is widely used because their voltage is relatively constant. Therefore, the user or installer can power the LED strip with any constant voltage source or LED driver. The LED strip can be powered by either 12V or 24V easily. Using a dimmable LED driver with output PWM is the best and simplest method for dimming an LED strip.
LED Dimming Undesirable BehaviorsIf you want a good and smooth dimming performance, you need to think about a few things. If not, bad things could happen that would lower expectations.
|Dead Travel||Adjusting the dimmer without a corresponding change in the light level|
|Flickering||Small changes in light intensity|
|Drop-Out||Lights turning off unexpectedly|
|Popcorn||Different turn-on times for each LED module on a dimmed circuit|
|Flashing||The light source is intermittently on when it should be off|
|Ghosting||The light source is at a low level on state when it should be off|
|Pop-On||Dimmer settings need to be raised above their existing setting in order to get light output|
|Visible Steps||Visible steps in light level while adjusting the dimmer|
In the figure below, a MEAN WELL amplitude current adjusting LED driver HLG-100 is connected to a LED strip at different load (length) conditions:
- (a) full load (length) resulting in the best dimming performance
- (b) 70% load(length) implying a non-perfect dimming experience due to small dead travel
- (c) 30% load(length) implying the worst dimming result due to huge dead travel
Output PWM Resolving Dead TravelPeople might not like that the dead travel problem is gone if the LED driver is always being used at full load in the end application. Also, it doesn't make much sense to pay for a high-wattage driver that isn't used at its full voltage. It is a very simple way of thinking, but it may not be true. Because LED strips are often used in situations where the length can't be predicted exactly. For example, the lights in a bar or restaurant that are used for decoration.
The solution is to use an output PWM LED driver to dim the light instead of changing the amplitude of the current. Depending on the duty cycle of the dimming signal, the amount of light that comes out is cut up. The resolution of the dimming and the output PWM frequency are two important parameters. For 8-bit dimming resolutions to work for most applications, the minimum dimming level should be as low as 0.1%. The table above shows that the output PWM frequency should be as high as possible to avoid flickering. To keep the visual distractions to a minimum, the frequency should be at least 1.25kHz.
The best way to turn down the brightness of an LED strip is to use the output PWM method, which gets rid of the dead travel that is often a problem with dimming. Mean Well's PWM series, which has a range of 40–200Watt and analog 3-in-1 dimming and IP67 protection, is a good driver for LED strip applications.
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