How does the built-in dimmer work in power supplies of the MEAN WELL LED series

One of the key needs in modern lighting systems is the ability to easily and effectively control brightness, or dimming (from the English dimming – dimming). In LED lighting systems, brightness control can be carried out using a separate dimmer device, which is connected between the power source and the LED lamp itself, but the brightness control function is implemented more efficiently due to the dimming system built into the power supply.

Unlike external third-party dimmers, where the variable parameter is the output voltage level (changed using pulse width modulation PWM), in MEAN WELL power supplies with a built-in dimmer, the variable parameter is the output current! In this case, the efficiency of the power supply remains very high, and the "unnecessary" energy is not dissipated in the form of heat, but it is consumed exactly as much as is required to ensure a given brightness level. That is, the MEAN WELL power supply with a built-in dimmer adjusts to the required load power level. The full schedule of operating modes of power supplies for LED lighting MEAN WELL is shown on the graph (using the example of the ELG-150 series):

Schedule of operating modes and changes in output parameters on the example of the ELG-150 series

By default, the power supply operates in voltage stabilization mode (Constant Voltage area (A) on the graph) with the nominal voltage level of the power supply and the current level determined by the LED strip or lamp. In the case of 90-100% load, the operating point of the output power is located in the italicized area. Brightness control using the built-in dimmer actually "shifts" the boundary of the Constant Current area (B) left–right - from 100% to 0% (or 10% depending on the power supply series) of the output current and vice versa. The output voltage level remains at 100% (for example, 24V for ELG-75-24B), that is, the operating point of the output power moves along a horizontal line Constant Voltage area (A).

If for some reason the load power increases (or it is initially LED with current stabilization, for example, LED modules or individual LEDs), then the power supply switches to CC (constant current) operation mode and the output voltage level can decrease from nominal 100% to 50% at maximum current, that is, the operating the point "moves" vertically along the segment B on the graph. If this reduction (limitation) of the output power is not enough and the load will "demand" more power, then the power supply will go into protection and will periodically turn on and off (with a short period, a few seconds) – this is the Hiccup Protection segment (C). In fact, this is the overload protection mode of the power supply.

Thus, it is possible to formulate a recommendation that the power of the dimmed power supply MEAN WELL should be approximately equal to (have a small margin of 5-10%) the power of an LED lamp or tape – only in this case the dimming will occur in the full range of output power. For example, if a standard 24V LED strip with a power of 14.4W/m and a length of 5m is connected to the HLG-320H-24B with a maximum output current of 13.34A (the load current will be only 14.4W · 5m/24V = 3A), then the brightness adjustment of this tape will only be in the range of 0 – 22% of the output power of the unit. In other words, the tape will shine at full brightness for most of the brightness adjustment, and only at the end of the adjustment it will go out very quickly. And if the load is even less, then the brightness adjustment will become almost invisible, and the dimmer will work simply as a switch from maximum brightness to minimum and back.

Separately, it is worth noting the feature of the built-in dimmer in PWM series power supplies. The power supplies of these series have a separate module for pulse-width modulation of the output current, which, with the help of PWM control, allows you to have a deeper adjustment of the output current level and, accordingly, brightness (for example, the PWM-90 series):

The principle of generating output current in PWM-90 series power supplies

Visually, such output current pulsations due to the selected modulation frequency will not be visible to the human eye, but this feature should be borne in mind when using PWM series power supplies in agriculture and animal housing (farms, animal husbandry, veterinary institutions, etc.) – such pulsations can negatively affect the behavior of animals.

At the same time, the PWM series power supplies achieve the greatest depth of brightness adjustment of an LED lamp or ribbon – the minimum threshold is only 0.15-0.2% (depending on the type of dimmer control), as opposed to 6-10% of the minimum brightness threshold for other series.

Depth adjustment of output current in PWM-60 series power supplies

For comparison, the depth of adjustment of the output current in the examples HLG-320H with a minimum output current level of 10%, and ELG-150 with a minimum output current level of 8% and then a complete shutdown:

Depth of output current adjustment in HLG-320H and ELG-150 series power supplies

For advice or clarification of information on MEAN WELL power supplies, please contact us by e-mail Meanwell@chipdip.ru .