The light-emitting principle of LEDs is different from that of traditional lighting. LED light sources with the same power have different current and voltage parameters because of different chips, so the internal wiring structure and circuit distribution are also different.
As a result, the manufacturers’ light sources have different dimming drive requirements. Therefore, the mismatch between the control system and the light source electrical appliances has also become a common problem in the industry.
Meanwhile, the diversification of LEDs also poses higher challenges to the control system. If the control system is not compatible with the lighting equipment, the lamps may turn off or flicker, and damages may be caused to the LED drive circuit and light source.
There are 5 common dimming methods on the market:
- DALI dimming
- TRIAC dimming
- PWM dimming
- 0/1-10V dimming
- DMX dimming
I: DALI dimming
The DALI standard has defined a DALI network, including up to 64 units (with independent addresses), 16 groups and 16 scenes. In order to be able to deal with many different occasions, each lighting unit can be grouped arbitrarily.
Generally, the conventional DALI system has 40-50 lamps, and the final grouping can be 16 groups. At the same time, it can process some controls/scenes in parallel.
The advantage of DALI is that it has a special protocol, which enhances the product interoperability between different brands. Moreover, each DALI device has a unique address code, which can truly achieve the control of a single lamp. The two-way communication makes it easier to check and learn about the equipment status and information.
II: TRIAC dimming
The dimming method of incandescent lamps long ago was the use of thyristor dimming. It is also the most widely used dimming method for LEDs at present.
TRIAC dimming is a kind of dimming with physical properties. Starting from AC phase 0, the input voltage is chopped into segments and there is only voltage input until the thyristor is turned on.
It works by generating a voltage waveform, which is also a tangential output from the cut. With the application of the tangential principle, reducing the power of the ordinary load.
Now the TRIAC dimmer is basically used by the majority, because it has many advantages, such as: high adjustment accuracy, operation and ease of operation, etc.
III: PWM dimming
Through the control of the on and off of the inverter circuit switching device, the Pulse Width Modulation (PWM) technology realizes the analog circuit control. The output waveform of the PWM technology is a series of pulses with equal amplitude for the replacement of the desired waveform.
Taking the sine wave as an example, that is, to make the equivalent voltage of this series of pulses a sine wave, and the output pulse is as smooth as possible with less low-order harmonics. The width of each pulse can be adjusted accordingly on the basis of different needs to change the output voltage or output frequency, thereby achieving the control of the analog circuit.
The duty cycle of the square wave is modulated to the level of the analog signal, a process that can be achieved by having a high counter, but is required to belong to the high resolution.
Since the full-amplitude DC power supply is either fully on or completely off at any given moment, the PWM signal is still digital. Repeated pulse trains are added to the simulated load, When the power is on, it is the time when the DC power supply is added to the load, and when the power is off, it is the time when the power supply is disconnected.
The human eye to see the LED is a continuous bright, or intermittent flashing based on whether the frequency is greater than 100Hz. Within a PWM cycle, since the brightness perceived by the human eyes to flicker within 100Hz is a cumulative process, that is, the longer the bright time in the entire cycle, the brighter the human eyes feel, PWM adjusts the brightness by adjusting the percentage of the time the lamps are on/off.
IV: 0/1-10V dimming
There are two independent circuits in the 0/1-10V dimmer, with one being an ordinary voltage circuit used to connect or disconnect the power supply to the lighting equipment, and the other being a low-voltage circuit that provides a reference voltage to tell the dimming level of the lighting equipment.
The 0/1-10V dimming controller was often used for the dimming control of fluorescent lamps before. Presently, as the LED driver module has a power supply and a special control circuit, the 0-10V dimmer can also support lots of LED lamps.
As for 1-10V, only the dimmer is 1-10V. When the resistance dimmer is adjusted to the minimum 1V, the output current is 10% (not a fixed value). If the output current is 10.