1, Linear dimming (DC dimming)
Linear dimming is the most fundamental dimming method for LED linear lights, and its core principle is to achieve brightness control by adjusting the driving current. The luminous intensity of LED is linearly related to the forward current, and the brightness increases as the current increases; Conversely, it decreases. This dimming method does not require complex circuits and can be achieved by integrating variable resistors or potentiometers into the driving power supply.
However, linear dimming has significant drawbacks. Firstly, the color temperature of the LED will change during the dimming process. Taking white LED as an example, it generates white light by exciting yellow fluorescent powder through a blue light chip. When the current decreases, the luminous efficiency of the blue light chip decreases, while the excitation efficiency of the fluorescent powder does not change synchronously, resulting in an overall spectral shift towards yellow light and an increase in color temperature. Secondly, the volt ampere characteristics of LEDs are nonlinear, and small voltage fluctuations may cause exponential changes in current, thereby affecting dimming accuracy. In addition, a decrease in current can lead to a reduction in the heat generation of the LED, and changes in thermal resistance may cause temperature fluctuations in the chip, further exacerbating color temperature drift.
At the application level, linear dimming is mainly suitable for scenarios that do not require high dimming accuracy, such as home decoration lighting, advertising light boxes, etc. Its advantages lie in low cost and simple implementation, but it is difficult to meet the strict requirements for color temperature consistency in fields such as commercial lighting and stage lighting.
2, PWM dimming (pulse width modulation dimming)
PWM dimming is the mainstream dimming technology for current LED linear lights, and its core principle is to achieve brightness adjustment by controlling the switching frequency and duty cycle of the LED. Specifically, by converting the DC power supply into high-frequency pulse signals, the LED only emits light during the conduction stage in each cycle. By adjusting the ratio of conduction time to cycle (i.e. duty cycle), the average current can be linearly changed, thereby controlling the brightness.
PWM dimming has significant advantages:
Colorless temperature shift: Due to the fact that the LED only emits light when it is turned on and no current passes through during the off period, the color temperature remains constant during the dimming process.
High precision: Modern PWM controllers can achieve 16 bit resolution and dimming accuracy up to 0.01%.
Strong anti-interference ability: High frequency pulse signals have low sensitivity to power noise and are suitable for complex electromagnetic environments.
Strong compatibility: It can seamlessly integrate with digital control protocols such as DALI and DMX512 to achieve intelligent control.
However, PWM dimming should pay attention to the following issues:
Strobe issue: When the pulse frequency is below 100Hz, the human eye may perceive flicker, and it is necessary to ensure that the frequency is above 200Hz to avoid visual fatigue.
EMI interference: High frequency signals may cause electromagnetic radiation, which needs to be suppressed through filtering circuits.
Driving capability: A constant current driver that supports PWM dimming is required, which is relatively expensive.
3, Controllable silicon dimming (front edge phase cut dimming)
Controllable silicon dimming is an extension of traditional incandescent dimming technology, which achieves brightness control by adjusting the conduction angle of AC power. Specifically, during each half cycle of AC power, the thyristor conducts at a specific phase, cutting off a portion of the voltage waveform to reduce the effective value and achieve dimming.
The application of thyristor dimming in LED linear lamps faces the following challenges:
Compatibility issue: LED driver power supply is usually a switching power supply, which does not match the phase control mechanism of the thyristor dimmer, which may cause flickering or inability to dim.
Dimming range limited: Due to the microcurrent emission characteristics of LEDs, it is difficult for thyristor dimmers to completely turn off the current at low brightness, resulting in a higher minimum brightness.
Harmonic pollution: Controllable silicon dimming will introduce a large amount of harmonics, affecting the quality of the power grid.
To address compatibility issues, there have been thyristor dimming drivers specifically designed for LEDs on the market, which work in conjunction with thyristor dimmers through power factor correction (PFC) and constant current control technology. However, its cost is higher and its dimming performance is still inferior to PWM dimming.
4, 0-10V dimming
0-10V dimming is an analog dimming method that adjusts brightness by adding a 0-10V control signal line to the driving power supply. Specifically, 0V corresponds to the lowest brightness (usually 10%), and 10V corresponds to the highest brightness (100%).
The advantages of 0-10V dimming are:
Strong compatibility: Can be integrated with various traditional dimming systems, suitable for renovation projects.
Low cost: The control signal line is low-voltage DC, without the need for additional isolation circuits.
However, its drawbacks are equally evident:
Complex wiring: additional control signal lines are required, which increases the difficulty of construction.
Weak anti-interference ability: Analog signals are susceptible to electromagnetic interference, leading to unstable dimming.
Poor scalability: difficult to achieve intelligent control and scenario based applications.
5, DALI dimming (digital addressable lighting interface)
DALI is a digital communication protocol designed specifically for lighting control, which enables bidirectional communication between controllers and lighting fixtures through twisted pair cables. Each DALI lighting fixture has an independent address and supports functions such as group control and scene calling.
The advantages of DALI dimming include:
Single lamp controllable: Each lamp can be independently addressed to achieve precise control.
Bidirectional communication: supports status feedback for easy fault diagnosis.
Standardization protocol: Devices from different manufacturers can be interoperable.
However, the cost of DALI dimming is relatively high, requiring dedicated controllers and drivers, and wiring that follows specific specifications, making it suitable for high-end commercial lighting and smart building applications.
6, DMX512 dimming
DMX512 is a stage lighting control protocol that transmits data through the RS-485 bus and supports 512 channels, each of which can independently control brightness. Its characteristics are:
High real-time performance: The data refresh rate can reach 44Hz, suitable for dynamic lighting effects.
Strong flexibility: capable of implementing complex scene programming and special effects control.
But the disadvantage of DMX512 is that:
Complex wiring: specialized shielded twisted pair cables are required, and the distance between the controller and the lighting fixtures is limited.
High cost: requires professional dimming station and decoder.
Poor scalability: The number of channels is fixed, making it difficult to meet large-scale lighting needs.
7, Wireless dimming technology
With the development of IoT technology, wireless dimming has become an emerging trend. The mainstream technologies include:
Bluetooth dimming: controlled through a mobile app or voice assistant, suitable for smart home scenarios.
Wi Fi dimming: supports remote control and automation scenarios, but consumes high power.
ZigBee dimming: Low power consumption, self-organizing network, suitable for large-scale lighting systems.
The advantages of wireless dimming lie in convenience and flexibility, but it needs to address issues such as signal interference and security.
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