With the increasing demand for lighting, the control of lighting fixtures has changed from simple switch control to 0-100% brightness adjustment, achieving smooth transition and high-precision dimming effects.
The method used to transmit the dimming signal from the intelligent lighting dimming controller to the dimming driver (commonly known as "dimming technology") can be divided into analog dimming and digital dimming. This is different from the dimming technology between the dimming driver and the lamps. Today we will mainly talk about the dimming technology of the dimmer.

I Analog Dimming
1. SCR Front Phase-Cut (FPC) Dimming
SCR front phase-cut dimming is widely used in the fields of smart lighting, hotel guest control and smart home. The technology is derived from the dimming of incandescent lamps and halogen light sources with pure resistive loads, and the principle is relatively simple.
It is also relatively common in LED applications, but due to the different matching degrees of the driving power, the compatibility of FPC dimming in LED applications varies greatly.
FPC dimming is to use an SCR circuit, the input voltage is chopped from AC phase 0, and there is no voltage input until the SCR 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.
FPC dimmers have the advantages of high adjustment accuracy, high efficiency, small size, light weight, and easy long-distance manipulation. They dominate the market, and most manufacturers' dimmer products are of this type. FPC dimmers generally use SCRs as switching devices, so they are also called SCR dimmers
The advantages of using FPC dimmers on LED lighting are low dimming cost, compatible with existing circuits, and no need for rewiring.
The disadvantage is that the FPC's dimming performance is poor, which usually leads to a reduction in the dimming range, causing the minimum required load to exceed the rated power of a single or a small number of LED lighting lamps.
Because of the properties of the SCR half controlled switch, we can only turn on the current, but not completely turn off the current. Even if it is adjusted to the lowest level, there is still a weak current flowing. And because of the light-emitting characteristics of the LED's micro-current, after the LED is turned off, there is still a weak light emission, which has become a problem in the promotion of the wiring-free LED dimming method.
2. Intelligent Lighting Rear Phase-Cut (RPC) MOS Dimming
Rear phase-cut control dimmer is made of field-effect transistor (FET) or insulated gate bipolar transistor (IGBT) equipment. The rear phase-cut dimmer generally uses MOSFET as a switching device, so it is also called MOSFET dimmer, commonly known as "MOSFET"
MOSFET is a fully controlled switch, which can control the on or off, so there is no situation that the SCR dimmer cannot be completely turned off. In addition, MOSFET dimming circuits are more suitable for capacitive load dimming than SCRs. However, because it has a high cost and relatively complex dimming circuits, and it is not easy to stabilize, the MOS dimming method has not been developed, and the SCR dimmers still occupy most of the dimming system market.
Compared with the front phase-cut dimmer, the rear phase-cut dimmer is applied to LED lighting equipment. Since there is no minimum load requirement, it can achieve better performance on single lighting equipment or a very small load.
However, MOS tubes are rarely used in dimming systems, and are generally only made into knob-type single-lamp dimming switches. This low-power rear phase-cut dimmer is not suitable for engineering. Many lighting manufacturers use this dimmer to test their own dimming drives and lamps, and promote its own dimming products to the engineering market. So the SCR dimming system is often used to modulate phase-cut dimming drive in engineering. The mismatch of this dimming mode leads to a dimming flicker, which can quickly damage the power supply or dimmer.
3. 0-10V dimming
The basic principle of 0-10V dimming is to change the effective value of the input light source current to achieve the purpose of dimming, that is, converting the 0-10V analog signal into a PWM dimming signal, which is an analog-to-digital conversion process.
There are two independent circuits in the 0-10V dimming device, one is an ordinary switch circuit, used to turn on or off the power to the lighting equipment, and the other is a low-voltage circuit, which provides a reference voltage to tell the dimming level of the lighting equipment.
Converting the 0-10V analog signal into a PWM dimming signal is a process of analog-to-digital conversion, and the dimming is smooth and uniform, which is unmatched by the SCR dimming. The 0-10V dimming controller was commonly used in the dimming control of fluorescent lamps. Now, because the constant power supply is added to the LED drive module and there are special control circuits, the 0-10V dimmer can also support a large number of LED lighting.
However, application shortcomings are also very obvious. The low-voltage control signal requires an additional set of lines, which also increases the requirements for construction.

II Digital Dimming
1. DALI (Digital Addressable Lighting Interface)
DALI is the acronym for "Digital Addressable Lighting Interface" and is a data transmission protocol. DALI defines the digital communication method between lighting appliances and system equipment controllers.
The DALI standard has defined a DALI network, including the largest 64 units (independent addresses), 16 groups and 16 scenes. 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 up to 40 to 50 lights, which can be divided into 16 groups and can process some actions at the same time. In a DALI network, 30-40 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 replaces the 1-10V voltage interface control ballast. Compared with the traditional 1-10V dimming, the advantage of DALI is that each node has a unique address code with feedback, and longer-distance dimming will not have signal attenuation, but this distance should still not exceed 200 meters.
The disadvantages of DALI are the complex signal line layout and the high cost. It is worth mentioning that the current DALI dimming driver still needs to be in the standby mode when the light is off to ensure that the microcontroller is always on standby.
2. DMX512 (or DMX) Dimming
The DMX512 protocol was first developed by the USITT to control the dimmer from the standard digital interface used in the console. DMX512 surpasses the analog system, but it cannot completely replace the analog system. The simplicity, reliability (if it can be installed and used correctly) and flexibility of DMX512 make it a protocol of choice when funds permit.
3. SLC(Single Line Carrier) Dimming Technology and Ready2mains Dimming
If we want to upgrade the non-dimmable traditional lighting system to the intelligent lighting system of dimmable LED, there is always complicated wiring, and it will lead to high cost. The SLC(Single Line Carrier) dimming technology and ready2mains dimming technology of Tridonic realize the transmission of digitally coded dimming signals through the AC FireWire, which simplifies the wiring requirements and provides convenience for traditionally switchable lighting solutions.
The single-fire-wire dimming technology adopts full digital transmission, which can completely eliminate flicker, realizes 0-100% dimming in the full load range, and is perfectly compatible with the existing decoration and use environment. The wiring method follows the traditional single-fire-wire wiring method. In the renovated apartments, smart dimmer switches and LED digital dimming drivers are used to give full play to the excellent performance of smart lighting, without the need to re-decorate and adding wiring.

Related Article:
https://www.utmel.com/blog/categories/semiconductor/introduction-to-triac-and-triac-dimmer