LED color mixing technology

In order to obtain a wider range of colors, the LED color mixing design has shifted from the one-sided current or voltage control method to the use of intelligent technologies such as microcontrollers or field programmable gate arrays (FPGAs), such as the selection of various colors and the real-time adjustment of color accuracy during operation. LED color mixing design faces two obstacles, namely the inconsistency of various LED parameters and the change of LED performance with temperature, which requires that LED model specifications and temperature compensation must be considered in LED color mixing design. However, this compensation is not only complex in algorithm, but also requires design engineers to have relatively professional color theory knowledge. At present, there is a quick and simple way, which is to use the LED color mixing design solution based on Cypress EZ-Color controller.

The EZ-Color controller is a programmable system-on-chip for high-brightness LED color mixing applications. It is mainly composed of an 8-bit microprocessor, programmable analog and digital modules, and external hardware multiplier accumulators, IC, Flash, SRAM and other peripheral modules. To use the EZ-Color controller for color mixing design, you must use Cypress's code-free graphical design software - PSoC exprESS. PSoC express is an embedded system design tool that does not require designers to write code. This tool itself runs at the system level rather than the design level. It uses a special function rather than a circuit, and the function itself is a real device, but a sensor, thermistor or LED driver.

The EZ-Color controller consists of input, output drive and transfer function relationship. The implementation mechanism of the color mixing scheme is shown in Figure 1. As shown in Figure 1, the EZ-Color color mixing scheme uses (y, y, Y) as input and the output is RGB three-color LED. The hardware driver of the three-color LED uses the random signal forced modulation (SSDM) user module. The input (x, y, Y) represents the color input request information of EZ-Color according to the characterization method of the CIE 1931 chromaticity diagram, that is, x, y represent hue and color saturation, reflecting color chromaticity information; and y represents luminous flux, reflecting color brightness information. The SSDM user module is the hardware implementation of Cypress's Precision Illuminance Signal Modulation (PrISM) technology. PrISM technology is a dedicated LED brightness adjustment technology that is superior to the traditional PWM method. It can effectively solve the problems of electromagnetic interference and low-frequency flicker.

Figure 1 EZ-Color solution implementation block diagram

The combination of EZ-Color controller and software PSoC express fit fundamentally changes the threshold for companies to enter the LED market. This solution not only eliminates the need for operators to learn color mixing (a discipline that requires a lot of input and is complex in itself), but also eliminates the need to compile multi-dimensional lookup tables for components such as thermistors or LED product grading. The more prominent advantage is that EZ-Color can complete these tasks in just a few minutes. With this LED color mixing technology, there is no need to execute C language coding because the language used itself simulates standard lighting technology. The new color mixing solution not only has the characteristics of high integration, low cost, great flexibility and ease of use, but also effectively solves the problems of low-frequency flicker and electromagnetic interference.