Timing study of automotive LED dimming and color adjustment downlights and LED large display screens

CYT recently launched a color-dimming downlight with full digital dimming control, which has received a lot of attention. For this reason, we believe that the new generation of smart home products will gain strong differentiated competitiveness in the later stage of LED lighting popularization.

It is predictable that the development of LED may go through three stages: cultivation stage, popularization stage and differentiation stage. The cultivation stage has passed, which should be from 2008 to 2012; the popularization stage is about to come in 2012, and the popularization storm will trouble manufacturers at the end of the popularization stage. How to highlight homogeneity? We believe that incorporating LED lighting into smart home and smart commercial lighting is a good way out.

The dimming and color-adjusting downlight was born for such a purpose. We integrated the "dimming and color-adjusting" technology into the downlight to give the product more added value. We conducted an in-depth analysis of LED dimming and color-adjusting, that is, this is a product that must highlight the key points: dimming (brightness) and color adjustment (color temperature can be continuously changed from 3000K to 6000K), and must have a good human-machine interface and bus expansion capabilities (in order to be included in the universal interface of smart homes).

As a system, the dimming and color adjustment scheme is composed of a "digital controller" and a "controlled dimming and color adjustment downlight group". The first thing to do is to design a transmission protocol to ensure that the user's operation can be finally accepted and responded to by the downlight. In the process, we found that the timing protocol of LED dimming and color adjustment downlights is different from that of current LED display screens, and their relationship is like the difference between FTP and UTP.

For example, the key point of LED lighting requirements is: user operation is reflected effectively and reliably, which is different from the requirements of LED large-screen display. The signal of LED lighting must first be reliable and avoid bit errors as much as possible, while LED display screens can continue to operate after bit errors and frame losses.

Second, the data stream transmitted by LED lighting is much shorter, because it does not have a lot of content like the display screen, so fewer data packets can adapt to longer transmission distances, and it is also possible to transmit and control through wireless methods (such as GPRS, WIFI, ZIGBEE, power line transmission, etc. for smart homes);

Third, the data of LED lighting is bursty and allows for delay. In other words, compared with LED point light source landscape lighting and large-screen display, the data transmission of LED lighting is bursty rather than sustainable, and is idle most of the time. Only when the user operates the LED does the controlled lamp need to respond. The allowable delay mentioned here means that most users can accept a delay of hundreds of milliseconds for LED lighting control.

Fourth, the surge needs to be suppressed through timing. Therefore, we can use certain software operations (such as sequential delay) to effectively suppress the impact on the power grid when the dimming and color-changing downlight group is suddenly turned on and off.

Since the timing is so important, we can simply design a timing to explain some of the characteristics of LED dimming and color-changing downlights. For example, in the hardware of the downlight receiving end, we can build a single-chip microcomputer, which is used to receive the data packets transmitted from the transmitter.