The demand for dimming is divided into three categories: one is the functional adjustment of the need for light, such as the entrance gate, conference rooms and so on; The second is the embodiment of comfort and life style in our daily life, the light and shade can be adjusted according to the needs of the environment, sometimes dimming plays a role in setting off the atmosphere; The need for environmental protection and energy conservation perhaps is the next most important reason.
At present, there are four main ways of LED dimming on the market: one is triac dimming, the other is 0-10V dimming, the third is Dali dimming ,the last is PWM dimming. Each of the four dimming techniques has its merits and demerits.
1. Triac Dimming
Triac dimming is a widely used dimming method in incandescent and energy-saving fixtures applications. Its working principle is to produce an output voltage waveform of tangential direction after the waveform of the input voltage is passed through the on-angle tangent wave. Applying tangential principle, the effective value of output voltage can be reduced, thus the power of ordinary load (resistance load) can be reduced. The advantages of Triac dimming are high efficiency and stable performance.
2. 0-10V Dimming
0-10V dimming also known as the 0-10V signal dimming, is an analog dimmer that distinguishes itself from the triac power supply by adding two additional 0 -10 V interfaces (+10 V and-10 V) to the 0-10 V power supply. It controls the output current of the power supply by changing the voltage of 0 V to achieve dimming. 10 V is the brightest, and 0 V is turned off. Almost all products from OKT Lighting support 0-10V dimming.
When the resistive dimmer is set to a min of 1V, the output current will be changed to 10%, and if the output current will reach the power output at 10V, the brightness will be 100%, and the output current will also be 100%, and the output current will be 100% at 10V, and the output current will also be 10% when the resistor dimmer is set to a minimum 1V.
1-10V does not have a switch function, and could not adjust the fixtures to the lowest closing effect.
3. DALI Dimming
When more than one fixture needs dimming, we can use DALI dimming instead of 1-10V dimming. DALI dimming is a typical digital control mode.
DALI (Digital Addressable Lighting Interface) is an internationally-recognized lighting control communication protocol with a communication speed of 1200 BPS ± 10%. Mainly used for dimming control of multiple fluorescent lights and LED lighting. DALI can form a network with a maximum of 64 short addresses and 16 group addresses. A host can control one or more computers and communicate in half-duplex mode.
Each of the four letters DALI has meaning:Digital, Addressable, Lighting, Interface. DALI can dimmer each fixture with DALI driver. Different lighting units on DALI bus can be flexibly grouped to achieve different scene control and management. Compared to other dimming methods, the advantages of DALI dimming are:
Digital dimming, dimming accurate, stable and smooth;
Dali can communicate with each other in both directions, and can feedback the lamp to the system;
Dali control is more flexible;
Dali has strong anti-jamming ability.
4. PWM Dimming
PWM dimming technology is currently considered to be the most promising LED dimming technology. An additional pulse width adjustment signal source is required for pulse width PWM dimming. The gate control signal of the LED driver chip to the power FET is modulated by changing the duty ratio of the input pulse signal, thereby achieving the purpose of adjusting the magnitude of the current through the LED. The advantages of this dimming technology are high efficiency and precision, feasibility for application and significant dimming performance.