The hottest LED dimming technology what are the pr

  • Detail

LED dimming technology what are the problems with LED dimming

led dimmer is an LED electrical device that changes the light flux of the light source in the lighting device, which is bad for the billet, and adjusts the illumination level. The purpose of LED dimmer is to adjust the brightness of different lights. By reducing or increasing the RMS voltage, the average power of the light produces different intensity light output. Although variable voltage devices can be used for various purposes, this regulation is designed to control lighting. Next, we will introduce the LED dimming technology and the problems of LED dimming

led dimming technology:

in today's LED industry, I am most optimistic about LED dimming technology and LED drive power supply for the time being. LED driving power supply is mainly oriented to LED street lamp power supply. This time we mainly talk about LED dimming technology. LED dimming technology mainly includes the following:

1: silicon controlled dimming, a dimming technology developed in incandescent lamps, can smoothly realize dimming because incandescent lamps are pure resistive loads, but it is not practical for LEDs. From the dimming power supply compatible with silicon controlled rectifier, the efficiency is usually very low, and 80% is difficult to achieve, which is contrary to the original intention of LED energy saving. Secondly, it is difficult to achieve high-power factors. Again, It can only work under a single input voltage, and this dimming technology will die out due to the demise of incandescent lamps. However, due to the high market penetration, it will exist for some time

2: linear dimming uses the special dimming foot of the constant current chip to adjust the current of the led to achieve the purpose of dimming. This technology has a good effect, but the wiring is complex, which is not conducive to the lighting of fluorescent lamps, street lamps and so on. Many desk lamps use this method

3: PWM dimming this method is similar to linear dimming, and together with linear dimming, it occupies most of the territory of dimming table lamps. The PWM dimming users and customers are also very happy

4: remote control dimming is divided into infrared remote control and wireless remote control. It is relatively complex to realize, but it can achieve the effect that cannot be achieved by changing color temperature, color and other dimming methods. It is mainly used for panel lamp dimming, and some bulb lamps adopt some dimming methods

5: segmented dimming this dimming method uses the switch on the wall to achieve the purpose of dimming within the specified time. The advantage of this method is that there is no need for additional dimming elements. According to the existing installation method, each lamp can realize dimming. On the other hand, because the dimming is completely controlled by the power source switch chip, high efficiency and high power factors can be achieved in the full voltage range, regardless of the brightness of the work, The disadvantage is that it can only be adjusted according to the preset brightness cycle, and can not achieve stepless dimming. In addition, there are few types of such ICs, and the current adjustment rate is not satisfactory. However, I think that with the maturity of technology, IC manufacturers will be more perfect. Personally, I think this dimming technology will become the mainstream of dimming technology in the future

what is the problem with LED dimming:

LED lamps used to replace standard incandescent lamps usually contain an LED array, and this basically constant stress (yield platform stress) is called the yield point σ S ensure uniform illumination. These LEDs are connected together in series. The brightness of each LED is determined by its current. The forward voltage drop of the LED is about 3.4 V, usually between 2.8 V and 4.2 v. The LED light string should be driven by a constant current power supply, and the current must be strictly controlled to ensure a high degree of matching between adjacent LED lights

in order to realize dimmable LED light, its power supply must be able to analyze the variable phase angle output of the SCR controller in order to adjust the constant current flowing to the LED in one direction. It is very difficult to do this while maintaining the normal operation of the dimmer, which often leads to poor performance. The problem can be shown as slow startup speed, flickering, uneven illumination, or flickering when adjusting the brightness. In addition, there are also problems such as inconsistencies between components and unwanted audio noise from LED lights. These negative conditions are usually caused by factors such as false triggering or premature shutdown of thyristor and improper control of LED current. The root cause of false triggering is the current oscillation when the thyristor is turned on

when the thyristor is turned on, the AC mains voltage is applied to the LC input filter of the LED lamp power supply almost at the same time. The voltage step applied to the inductor will cause oscillation. If the dimmer current is lower than the thyristor current during oscillation, the thyristor will stop conducting electricity. The thyristor trigger circuit charges, and then turns on the dimmer again. This irregular multiple thyristor restart can make the LED light produce unnecessary audio noise and flicker. Designing simpler EMI filters can help reduce such unnecessary oscillations. To achieve successful dimming, the inductance and capacitance of the input EMI filter must also be as small as possible

the worst condition of oscillation is a 90 degree phase angle (at this time, the input voltage reaches the peak of sine wave and is suddenly applied to the input of LED lamp), and it is a high input voltage (at this time, the forward current of dimmer reaches the lowest level). When deep dimming is required (such as the phase angle is close to 180 degrees) and the input voltage is low to prevent blocking the pipeline of the circulating system, premature shutdown will occur. To reliably lower the luminosity, the thyristor must be monotonically turned on and stay at the point where the AC voltage is almost reduced to zero volts. For thyristors, the sustaining current required to maintain conduction is usually between 8 Ma and 40 ma. Incandescent lamps are relatively easy to maintain this current, but for LED lamps whose power consumption is only 10% of the equivalent incandescent lamp, this current can be reduced below the thyristor maintenance current, resulting in the thyristor turning off prematurely. This will cause flickering and/or limit the dimmable range

Copyright © 2011 JIN SHI