The modernization of modern buildings is getting higher and higher, and the architectural lighting effect occupies a very high importance in the entire architectural design, and is also a large energy consumer. The correct and reasonable design of the intelligent dimming system can greatly improve the ornamental value of the building and the purpose of energy saving and emission reduction.

Lighting dimming is one of the most important system functions in weak current integrators and smart home integration. Doing a good job of dimming can greatly enhance the effect of the project. However, there are many types of lamps on the market, and each type of lamps has different dimming methods. How to do a good job of dimming system solutions is a major problem for most integrators. I have published articles on dimming methods before. Today, I will discuss with you the content and methods of dimming.

The most commonly used dimming methods can be divided into two types: analog dimming and digital dimming, in which analog dimming is achieved by changing the current in the lighting circuit; digital dimming, also known as PWM dimming, is turned on by PWM waves. And turn off the lamp to change the conduction time of the forward current to achieve the effect of brightness adjustment.

Detailed explanation of five LED dimming control methods

The light-emitting principle of LED is different from traditional lighting. It relies on P-N junction to emit light. LED light sources of the same power have different current and voltage parameters due to different chips used, so their internal wiring structure and circuit distribution are also different, resulting in various manufacturers. Different light sources have different requirements for dimming drives, so the mismatch between the control system and the light source electrical appliances has become a common problem in the industry. At the same time, the diversification of LEDs also poses higher challenges to the control system. If the control system and lighting equipment are not matched, it may cause the light to go out or flicker, and may cause damage to the LED drive circuit and light source. There are five control methods of LED lighting equipment on the market

1. Frontier Phase Cut (FPC), SCR dimming

2. Rear edge phase cut (RPC) MOS tube dimming

3, 0/1-10V dimming

4, DALI (Digital Addressable Lighting Interface)

5. DMX512 (or DMX)

1. Frontier Phase Cut (FPC), SCR dimming

Leading edge dimming is to use thyristor circuit, starting from AC phase 0, the input voltage is chopped, and there is no voltage input until the thyristor is turned on. The principle is to adjust the conduction angle of each half-wave of the alternating current to change the sine waveform, thereby changing the effective value of the alternating current, so as to achieve the purpose of dimming.

Leading-edge dimmers have the advantages of high adjustment accuracy, high efficiency, small size, light weight, and easy long-distance manipulation. They are dominant in the market, and most manufacturers' products are this type of dimmer. Leading edge phase control dimmers generally use thyristors as switching devices, so they are also called thyristor dimmers.

The advantages of using FPC dimmers on LED lighting are: low dimming cost, compatibility with existing wiring, and no need for rewiring. The disadvantage is the poor dimming performance of FPC, which usually results in a reduced dimming range and causes the minimum required load to exceed the rated power of a single or small number of LED lamps. Because of the properties of the thyristor semi-controlled switch, it only has the function of turning on the current, but cannot completely turn off the current. Even if it is adjusted to the lowest level, there is still a weak current passing through. After the LED is turned off, the phenomenon of weak light still exists, which has become a difficult problem in the promotion of this wiring-free LED dimming method.

Leading edge phase-cut to PWM

2. Trailing edge phase-cut control dimming

The trailing edge phase-cut control dimmer is made of Field Effect Transistor (FET) or Insulated Gate Bipolar Transistor (IGBT) devices. The trailing edge phase-cut dimmer generally uses MOSFET as the switching device, so it is also called MOSFET dimmer, commonly known as "MOS tube". MOSFET is a fully controlled switch, which can be controlled both on and off, so there is no phenomenon that the thyristor dimmer cannot be completely turned off. In addition, the MOSFET dimming circuit is more suitable for capacitive load dimming than the thyristor, but because of the high cost and the relatively complex dimming circuit, which is not easy to stabilize, the MOS tube dimming method has not been developed. Optical devices still occupy the vast majority of the dimming system market.

Compared with leading edge phase-cut dimmers, trailing edge phase-cut dimmers are used on LED lighting devices, which can achieve better performance on a single lighting device or very small loads because there is no minimum load requirement, however, Since MOS tubes are rarely used in dimming systems, they are generally only made into knob-type single-lamp dimming switches. Such low-power post-cut phase dimmers are not suitable for engineering. And many lighting manufacturers use this dimmer to do dimming tests on their own dimming drivers and lamps. And then push their own dimming products to the engineering market, which often leads to the situation of phase-cut dimming drive after modulation with thyristor dimming system in engineering.

3. 0/1-10V dimming

There are two independent circuits in the 0/1-10V dimming device, one is an ordinary voltage circuit, which is used to turn on or off the power supply to the lighting equipment, and the other is a low-voltage circuit, which provides a reference voltage and tells the lighting equipment to adjust the power supply. Light level, 0-10V dimming controller was commonly used in the dimming control of fluorescent lamps before. Now, because a constant power supply is added to the LED driver module and there is a special control circuit, the 0-10V dimmer is also the same Can support a large number of LED lighting. However, the application disadvantages are also very obvious. The low-voltage control signal requires an additional set of lines, which greatly improves the construction requirements.

4. DALI

The DALI standard has defined a DALI network, including a maximum of 64 units (with independent addresses), 16 groups and 16 scenarios. Different lighting units on the DALI bus can be flexibly grouped to achieve different scene control and management. In practical applications, a typical DALI controller controls as many as 40 to 50 lamps, which can be divided into 16 groups, while being able to process some actions in parallel. In a DALI network, 30 to 40 control instructions can be processed per second. This means that the controller needs to manage 2 dimming commands per second for each lighting group. DALI is not a real point-to-point network, it controls the ballast instead of the 1-10V voltage interface. Compared with the traditional 1-10V dimming, the advantage of DALI is that each node has a unique address code and feedback, and the longer distance dimming will not have signal attenuation like 1-10V, but in engineering practice, this distance is still Should not exceed 200 meters.

Obviously DALI is not suitable for LED lighting control, a DALI network can only control 21 full-color LED lamps. DALI is oriented to traditional lighting control, focusing on the static control and reliability, stability and compatibility of the system. The scale of the LED lighting system is much larger than that of the DALI system. It mainly pursues the artistic effect of lamps and lanterns, and properly takes into account the intelligence of the system. This requires the system to be connected to a larger bus network, with unlimited expansion capabilities and higher scenes. Refresh ability. Therefore, DALI systems are often incorporated into other bus systems as a subsystem in large lighting projects.

The advantages of DALI dimming need not be repeated, the disadvantages are still annoying signal line layout and high price. It is worth mentioning that the current DALI dimming driver still needs standby power consumption when the light is turned off in order to ensure that the microcontroller is in a standby state at any time.

5. DMX512 dimming

The DMX512 protocol was first developed by the USITT (American Society of Theater Technology) as a way to control dimmers from a standard digital interface for consoles.

DMX512 surpasses the analog system, but cannot completely replace the analog system. The simplicity, reliability (if properly installed and used), and flexibility of the DMX512 make it the protocol of choice when money allows.

In practical applications, the control method of DMX512 is generally to design the power supply and the controller together. The DMX512 controller controls the 8-24 lines, and directly drives the RBG line of the LED lamps. However, in the architectural lighting project, due to the large weakening of the DC line, it is required to install a controller at about 12 meters, and the control bus is in parallel mode. , Therefore, the wiring of the controller is very large, and it is even impossible to construct in many occasions. The receiver of DMX512 needs to set the address so that it can receive the dimming command clearly, which is also very inconvenient in practical application. Multiple controllers are interconnected to control complex lighting solutions, and the design of operating software will also be more complex. Therefore, DMX512 is more suitable for occasions where lamps are concentrated together, such as stage lighting. To sum up, the main disadvantage of DMX controller is that it requires special wiring layout and type, and requires certain programming in order to set basic colors and scenes, which is costly for later maintenance.

   In short, with the continuous progress of science and technology, the dimming technology is becoming more and more mature, it is very important to choose a good product. , Green lighting contributes its own strength.