LED lamp power supply is driven by constant current. Why is it constant current instead of constant voltage? Because LED is inherently clamping, its voltage does not change much within a certain range. Therefore, to achieve dimming, it is necessary to adjust the current flowing through the LED.
1. Dimming methods mainly include DALI, 0-10V, silicon controlled rectifier, PWM, etc.
2. DALI and 0-10V are generally used in commercial areas with dimming systems, such as hotels or airports, where light control and energy conservation requirements are required.
3. Silicon controlled rectifier is the most basic method to adjust current. It changes the input energy through the phase switching of silicon controlled rectifier (called thyristor in Taiwan), so as to realize the change of power. Because the LED lamp has the characteristics of basically unchanged voltage as a load, the input current will naturally decrease when the input supply decreases, and finally the brightness of the LED lamp will decrease. For specific principles, please refer to the explanation of dimmer on Baidu Encyclopedia or Wikipedia_ Baidu Encyclopedia; The disadvantage of SCR dimming is that different dimmers will flicker; The advantage is that the cost is relatively low. Generally, the rear cut dimmer is not cheap, and the dimming effect is good, which is mainly liked in Europe and the United States. The front cut dimmer is relatively cheap, but it flickers.
4. PWM dimming is a method to adjust the LED current by pulse width. PWM is a rectangular wave whose width can be adjusted. It can change the pulse width in many ways. PWM is generally completed in the power supply, and it needs a control method to achieve width adjustment, such as Bluetooth, WIFI, or power line communication.
5. Regardless of the dimming mode, it is required to realize the brightness change by turning on the power supply in a unit time. It depends on the application situation and reliability requirements.
6. Relatively speaking, the silicon controlled dimming technology for LED dimming is more common, but there is a fatal problem that the performance of various manufacturers is uneven, which is often referred to as the compatibility problem, such as the domestic dimmer brands TCL, Lonone and Manco; Philips, Lutron, Liviton, ABB, ELCO, Schneider, Clipsal, etc.
7. Philips and Osram have good compatibility with foreign dimming spotlight brands; In China, there are Xiamen Sunshine, Huizhou Henghui, Shenghui Lighting, etc.