EZ-Color controller family simplifies HB-LED-lighting system designs
By Margery Conner, Technical Editor -- EDN, June 18, 2007
All HB (high-brightness) LEDs are not created equal: Even within the same part number, their performance, including wavelength, brightness, and power, can vary. HB-LED manufacturers use a “binning” process to test each LED and sort it into a category, which becomes part of the specification. HB LEDs from different bins have visibly different colors, and designers must allow for these colors in the system’s RGB-color control. Having the capacity to allow for and adapt to different bins can save as much as 15% of the component cost, as opposed to locking your design into one bin and then finding that its price is at a premium or that it is no longer available. In addition, an HB LED degrades with temperature, and different colors degrade at different rates. Developing these color-creation and -control algorithms is a complex, time-consuming part of the design process.
Addressing that challenge, Cypress has combined the new EZ-Color family of HB-LED controllers with the PSoC Express embedded visual-design tool to allow designers to input a supported vendor’s HB-LED part number and bin. The PSoC Express software then applies the manufacturer’s bin specifications and temperature-feedback algorithms to program the EZ-Color controller to compensate for both HB LEDs’ binning characteristics and their temperature response. The family comprises the CY8CLED04/08/16, which drive as many as four, eight, or 16 HB-LED channels.
The EZ-Color controller uses Cypress’ proprietary Prism spread-spectrum power-control technology, rather than a fixed-frequency PWM signal to control LED brightness. The advantage of Prism over a PWM approach is a reduction in low-frequency flicker and EMI. The CY8CLED04 sells for less than $4 (high volumes).
