Design Article
Product How-To: LED arrays are establishing themselves
Uwe Hock, Sharp Microelectronics Europe
4/3/2012 5:03 AM EDT
Long lifespan and fail-safe operation thanks to the matrix circuit
In an array, a larger amount of small LED dies is electronically coupled in series and in parallel in a matrix. This does not only have the advantage that the overall output can be scaled through the number of dies, but also that current and voltage can be controlled over a wide range — given the necessary experience — to adjust the optimal operating point for the respective application. The current density at the individual LED dies remains limited due to the matrix structure, which considerably reduces the thermal stress on the die — and therefore increases efficiency — compared to the single-chip solution.
In an array as of the 10 W Mini Zenigata, a larger amount of small LED dies is electronically coupled in series and in parallel in a matrix. This allows failure save operation and to optimize current and voltage within certain limits for a specific application.
The array structure also contributes to the longevity of the LED module; the matrix circuit in itself guarantees a fail-safe operation. Even if individual dies fail, the flow of current through the array is secured due to the circuit design, so that the module remains fully functioning overall. In addition, Sharp uses ceramic substrate with predefined solder points for its LED modules, which helps distribute the excess heat across the entire surface of the illuminant than is the case in SMD LEDs, and hence creates a highly efficient heat transfer to the cooling element. This can therefore be kept relatively small. Due to their design, the LED modules by Sharp reach a lifespan of 40,000 hours at an operating temperature of 90°C.
Ceramic substrates of Sharp LED arrays convey excess heat very efficiently through the entire surface of the module, which allows keeping cooling elements quite small ensure operation at the temperature of 90°C for the which the modules are specified.
Light quality – decision criterion for light designers and consumers
The determining factor for the acceptance of LEDs as illuminants is the quality of the light. The benchmark is still set by the Edison incandescent light bulb with a CRI value of 100 at a warm white tone, because of the high share in the red wave spectrum. White light LEDs, on the other hand, come from the opposite end of the visible spectrum, because they are based on a blue light diode, which leads to a cool, bluish color tone. This enables the production of LEDs in a broad bandwidth of different color temperatures, whereby specific color temperatures can be achieved by changing the proportions of red and green phosphor. In this manner, Sharp offers white light LED modules for general lighting applications in the color nuances "warm, neutral, pure and cold white." The color temperatures of the LEDs range from 2,700 to 6,500 Kelvin.
The different phosphor blends allow for very high color rendering indices (CRI), which result in great color fastness and true-to-life details. All LED components from Sharp, for all color temperatures, have a CRI value of at least 80; this is a significant qualitative leap, especially in the case of warm-white light LEDs, the CRI values of which were in the region of 60 - 70 until now. The high color rendering modules of the Zenigata series even achieve CRI values of up to 93. While providing efficient lighting, they therefore adhere to the requirements of the international Energy Star program and other industry standards.
In an array, a larger amount of small LED dies is electronically coupled in series and in parallel in a matrix. This does not only have the advantage that the overall output can be scaled through the number of dies, but also that current and voltage can be controlled over a wide range — given the necessary experience — to adjust the optimal operating point for the respective application. The current density at the individual LED dies remains limited due to the matrix structure, which considerably reduces the thermal stress on the die — and therefore increases efficiency — compared to the single-chip solution.
In an array as of the 10 W Mini Zenigata, a larger amount of small LED dies is electronically coupled in series and in parallel in a matrix. This allows failure save operation and to optimize current and voltage within certain limits for a specific application.
The array structure also contributes to the longevity of the LED module; the matrix circuit in itself guarantees a fail-safe operation. Even if individual dies fail, the flow of current through the array is secured due to the circuit design, so that the module remains fully functioning overall. In addition, Sharp uses ceramic substrate with predefined solder points for its LED modules, which helps distribute the excess heat across the entire surface of the illuminant than is the case in SMD LEDs, and hence creates a highly efficient heat transfer to the cooling element. This can therefore be kept relatively small. Due to their design, the LED modules by Sharp reach a lifespan of 40,000 hours at an operating temperature of 90°C.
Ceramic substrates of Sharp LED arrays convey excess heat very efficiently through the entire surface of the module, which allows keeping cooling elements quite small ensure operation at the temperature of 90°C for the which the modules are specified.
Light quality – decision criterion for light designers and consumers
The determining factor for the acceptance of LEDs as illuminants is the quality of the light. The benchmark is still set by the Edison incandescent light bulb with a CRI value of 100 at a warm white tone, because of the high share in the red wave spectrum. White light LEDs, on the other hand, come from the opposite end of the visible spectrum, because they are based on a blue light diode, which leads to a cool, bluish color tone. This enables the production of LEDs in a broad bandwidth of different color temperatures, whereby specific color temperatures can be achieved by changing the proportions of red and green phosphor. In this manner, Sharp offers white light LED modules for general lighting applications in the color nuances "warm, neutral, pure and cold white." The color temperatures of the LEDs range from 2,700 to 6,500 Kelvin.
The different phosphor blends allow for very high color rendering indices (CRI), which result in great color fastness and true-to-life details. All LED components from Sharp, for all color temperatures, have a CRI value of at least 80; this is a significant qualitative leap, especially in the case of warm-white light LEDs, the CRI values of which were in the region of 60 - 70 until now. The high color rendering modules of the Zenigata series even achieve CRI values of up to 93. While providing efficient lighting, they therefore adhere to the requirements of the international Energy Star program and other industry standards.
|
|
|
|
|
Navigate to related information