Introduction of five kinds of LED dimming control methods

If the control system and lighting equipment are not matched, it may cause the light to go out or flicker, and may damage the LED's drive circuit and light source.

There are five LED lighting control methods on the market:

1. Front edge phase cut (FPC), thyristor dimming

2, trailing edge phase-cut (RPC) MOS tube dimming

3, 1-10VDC

4, DALI (digital addressable lighting interface)

5, DMX512 (or DMX)

1. Front edge phase-cut control dimming

The leading edge dimming is to use a thyristor circuit, starting from the AC phase 0, the input voltage is chopped, and the voltage input is only available when the thyristor is turned on.

The principle is to adjust the conduction angle of each half wave of the alternating current to change the sinusoidal waveform, thereby changing the effective value of the alternating current, thereby achieving the purpose of dimming.

The leading edge dimmer has the advantages of high adjustment precision, high efficiency, small size, light weight and easy remote control. It is dominant in the market, and most manufacturers' products are this type of dimmer.

The leading edge phase control dimmer generally uses a thyristor as a switching device, so it is also called a thyristor dimmer. The advantage of using an FPC dimmer on an LED illuminator is that the dimming cost is low and compatible with existing lines. No need to reroute. The disadvantage is that the FPC dimming performance is poor, usually resulting in a reduced dimming range, and will result in the minimum required load exceeding the single or a small number of LED lighting rated power.

Because of the properties of the thyristor half-control switch, only the function of turning on the current can not completely turn off the current, even if it is adjusted to the lowest, there is still a weak current, and the characteristic of the LED micro-current illuminating makes the thyristor dimming exist in a large amount. After the shutdown, the LED still has a weak luminescence phenomenon, which has become a problem in the current promotion of the wiring-free LED dimming method.

El The leading edge phase-cut LED dimming driver developed by inker Yilian has solved this problem very well. Through the “C-TURNOFF” technology of the drive circuit, it avoids the problems of “continuous” and “stroboscopic bad light”.

Match El Inker's front-phase phase-cut LED dimming driver can be perfectly matched with other thyristor dimming systems, saving users wire and wiring man-hours, solving thyristor LED dimming matching and non-turning off. Chaotic pattern.

Figure: Front edge phase-cut wiring principle and leading edge phase-to-phase PWM

2, trailing edge phase-cut control dimming

The trailing edge phase-cut control dimmer is fabricated using field effect transistor (FET) or insulated gate bipolar transistor (IGBT) devices. The trailing edge phase-cut dimmer generally uses a MOSFET as a switching device, so it is also called a MOSFET dimmer, commonly known as a "MOS tube."

The MOSFET is a fully controlled switch that can be controlled either on or off, so there is no thyristor dimmer that cannot be completely turned off.

Another MOSFET dimming circuit is more suitable for capacitive load dimming than thyristor, but because of the high cost and relatively complicated dimming circuit, it is not easy to be stable, so the MOS tube dimming method has not developed, thyristor tuning Optical devices still occupy the vast majority of the dimming system market.

Compared to leading-edge phase-cut dimmers, trailing-edge phase-cut dimmers are used in LED lighting equipment, and because there is no minimum load requirement, better performance can be achieved in a single lighting device or very small loads, however, Since MOS tubes are rarely used in dimming systems, they are generally only made into knob-type single-lamp dimmer switches. This low-power rear-cut phase dimmer is not suitable for engineering applications.

Many lighting manufacturers use this dimmer to do dimming tests on their own dimming drivers and lamps. Then, the dimming products of their own are pushed to the engineering market, which leads to the situation that the phase-cut dimming drive is modulated by the thyristor dimming system.

This mismatch in dimming mode causes dimming to flicker, which can quickly damage the power supply or dimmer.

Figure: trailing edge phase-cut wiring principle and trailing edge phase-cut PWM

3, 1-10V dimming

There are two independent circuits in the 1-10V dimming device, one is the ordinary voltage circuit for turning on or off the power to the lighting device, and the other is the low voltage circuit, which provides the reference voltage to tell the lighting device the dimming level. 0-10V dimming controller is often used in the dimming control of fluorescent lamps. Now, because a constant power supply is added to the LED driver module and there is a special control circuit, the 0-10V dimmer can also support A large number of LED lights.

However, the application disadvantages are also very obvious. The low-voltage control signal requires an additional set of lines, which greatly increases the requirements for construction.

Figure: 1-10V wiring principle

4, DALI

The DALI standard has defined a DALI network that includes a maximum of 64 units (independent addresses), 16 groups and 16 scenes. Different lighting units on the DALI bus can be flexibly grouped for different scene control and management.

In practical applications, a typical DALI controller controls up to 40 to 50 lamps and 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 instructions per second for each lighting group.

DALI is not a true peer-to-peer network. It is a ballast that replaces the 1 to 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 far-distance dimming does not cause signal attenuation like 1-10V, but this distance in engineering practice is still Not more than 200 meters.

Obviously DALI is not suitable for LED lighting control, a DALI network can only control 21-inch full-color LED lamps. DALI is geared towards traditional lighting control, focusing on the system's static control and reliability, stability and compatibility.

The scale of the LED lighting system is far greater than that of the DALI system. It mainly pursues the expressive effect of the lighting art, and properly considers the intelligence of the system. This requires the system to access a larger bus network, with unlimited expansion capability and high scene. Refresh capability.

Therefore, DALI systems are often incorporated into other bus systems as a subsystem in large lighting projects. El The inker COS system is perfectly compatible with the DALI system. The advantages of DALI dimming need not be described. 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 turning off the lights in order to ensure that the MCU is on standby at any time. Equipped with El Inker's dimmers can be physically powered down when the lights are turned off, avoiding energy loss during standby.

Figure: DALI wiring principle

5, DMX512 dimming

The DMX512 protocol was first developed by USITT (American Theatre Technology Association) to use a standard digital interface from the console to control the dimmer.

The DMX512 goes beyond the analog system, but it does not completely replace the analog system. The simplicity, reliability (if properly installed and used) and flexibility of the DMX512 make it an option for funding.

In practical applications, the control mode of the DMX512 is generally to design the power supply and the controller together.

The DMX512 controller controls the 8 to 24 lines and directly drives the RBG line of the LED lamps. However, in the architectural lighting project, since the DC line is weak, it is required to install a controller at about 12 meters, and the control bus is in parallel mode. Therefore, the controller has a lot of traces and it is impossible to construct in many occasions.

The receiver of the DMX512 needs to set the address so that it can explicitly receive the dimming command, which is also very inconvenient in practical applications. Multiple controllers are interconnected to control complex lighting schemes, and operational software design can be complex.

Therefore, DMX512 is more suitable for occasions where lamps are concentrated, such as stage lighting.

In summary, the main disadvantage of the DMX controller is that it requires special wiring layout and type, and requires some programming to set the basic color and scene, which is more costly for later maintenance.

Figure: DMX512 wiring principle