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| The technology in green and blue LEDs progressed since 1994. The chromaticity and color gamut of LEDs with their high durability and reliability, hence, provides an alternative for commercial large-panel displays. The luminosity and the efficacy of LEDs have been continuously improved. The applications thus are believed to be prevalent. |
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To provide high-quality displays, the issue of driving LEDs with current or voltage with minimal deviation among adjacent pixels must be addressed particularly.
However, LED devices, with the nature of the deviations in electrical and optical characteristics, will need a specific method to light them up.
The deviation in electrical characteristics is almost caused by the uncertainty in Forward Current vs. Forward Voltage. That is, when we apply a Forward Voltage to a LED, we cannot precisely obtain a current.
The deviation in optical characteristics is caused by the uncertainty in Luminosity vs. Forward Current. It reveals that we cannot obtain a precise luminosity even when we apply a Forward Current.
The additional deviations, such as LED aging effect, LED wavelength shift effect, temperature effect, etc, are considered as a total deviation. The total deviation makes video quality difficult to reach the excellence when using LED array as a flat panel display and driving the LED array in a straightforward method.
Macroblock is devoted to developing the most adequate method and the most effective driver ICs to support the high quality goals of LED displays.
PrecisionDrive™ is the solution to the issue of the deviation in electrical characteristics. Macroblock develops Constant-Current Driver ICs, as a kernel of the mentioned - PrecisionDrive™ technology. |
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The output characteristics of the driver ICs, with adequate bias, are designed to be constant. The delivered currents are invariant to the variation of LED electrical characteristics, the supply voltage, and also the ambient temperature.
Instead, the driver ICs deliver designated current to light LEDs to the expected brightness. The designated current is deliberately specified by the built-in feedback control circuit. Within a wide current range, the accuracy is fulfilled.
Uniformity is as important as constancy. The LED Drivers drive arrays of LEDs. Non-uniformity among drivers causes degradation in displayed video quality. For 8-bit and 16-bit Drivers, bit-to-bit uniformity is concerned. For mass production, chip-to-chip uniformity challenges the design robustness to the IC process deviation. |
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LED Device is truly reliable and durable. However, for certain severe application, LED error is very crucial. As a result, a function of detecting LED errors is required.
Conventionally, some extra circuits are required to implement the detection. Based on the infrastructure of PrecisionDrive™ technology, the driver IC has the efficiency to detect the LED characteristics, open-circuit or short-circuit, when the driver IC lights the LED.
Macroblock develops proprietary algorithms to detect the LED Errors. The algorithms are specifically designed to effectively explore the errors occurring in LED. The algorithms use less of supporting resources and have a robust coverage of LED faults. |
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By nature of the uncertainty of epitaxy process and diffusion, LED manufacturers produce LEDs with large-span of characteristics. To make the produced LED within controlled and limited deviations, LED manufacturers categorize LED devices with various ranks. LEDs from the same ranks have smaller deviation in luminosity, when biased with a fixed Forward Current. However, the deviation ranges +/- 15% typically.
Macroblock's PrecisionDrive™ with programmable Gain Control serves this purpose. Macroblock develops digital-to-analog converter working together with PrecisionDrive™. By changing the digital codes, the effective output current could be obtained with the same accuracy. 256-step current output with 1200% total dynamic range is the technology goal achieved. |
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Higher color depth and more frequent video refresh rate are expected to achieve the higher video fidelity to build LED video displays. 16-bit color depth and 600 frames per second are usually targeted. To achieve such aggressive quality goal, the developers have to build a fast controller structure that performs the PWM outside the LED drivers. Macroblock develops a novel PWM architecture inside the driver. Such architecture greatly simplifies the computation needs in the conventional controller. The novel architecture also exploits various PWM counting algorithms and thus provides options for optimizing either the color depth or refresh rate.
For versatile LED display applications, LED devices sometimes are assembled in dot-matrix module forms. The LED modules are defined as Smart LED Modules. Macroblock develops LED Drivers for Smart LED Modules. Based on PrecisionDrive™ and Pulse Width Modulation (PWM), Macroblock provides features of individual Gain Control, and Pixel Image Data processing. The former equalizes the LED optical deviation to obtain a uniform quality for the whole module. The latter provides a straightforward access by the display system controller, by eliminating the sophisticated timing design of control signals. |
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In certain applications, LEDs are placed in distance of feet away. The LEDs are packaged as a cluster and viewed as a super pixel. When a pack of LED clusters or super pixels are used to build a huge display, the high speed signal transmission across the distance become necessary to form a vivid visual effect.
Macroblock develops technology for the long-distance signal transmission that transmits the control signals across hundreds of LED clusters. The transmission rate is pushed to 10 MHz with ordinary cable. The transmission is reliable to command the LED clusters working in the right way. |
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| The progress in LED technologies extends the applications of LEDs, from display fields to Backlighting and also lighting. Due to the popularity in Internet technology and wireless communication technology, the demands of mobile, handheld appliances emerge. LEDs, especially white LEDs, serves the appliances, like Cellular Phones, PDAs, and Digital Still Cameras. Power management, considering the LED Backlighting, is concerned by Macroblock. |
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LED Lighting, illumination, starts from niche applications, like Channel Letter, and Traffic Sign. Due to the LED characteristics, a dedicated AC-DC power conversion is required.
Lighting is a typical situation where power does not consume too much, but it is twenty-four hours operating. The electronic ballast with dimming control function has the important piece of power factor controller for starting up the fluorescence lamp, and which also provides the PFC functions to drive the fluorescence lamp efficiently.
It will be a trend that in the future all the electronic devices, no matter how small power it use, must have a power factor greater than 0.9. To achieve such high power factor, a power factor controller has to be used in the switch-mode power supply to manipulate the current waveform such that voltage and current are completely in phase.
Macroblock is devoted itself in Power Conversion fields and is innovating various topologies, feedback architectures and switching decision algorithms in its switching power conversion technologies. It is dubbed as LaurenBoost™. |
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The Forward Voltage of white LEDs ranges around 3.20V and is not a constant. To light the white LEDs, a DC-DC converter IC with current-feedback and constant-current output is required.
Macroblock develops the DC-DC converter ICs, concerning the LED characteristics, conversion efficiency, stand-by current, switching noise, current matching and usage cost. Conversion efficiency is critical for battery-powered appliances. As well, switching noise is purposely suppressed. The novel charge-pump and boost mechanism are developed to achieve those two key factors. |
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LED Backlighting is a trend for LCD monitors and LCD-TV. The color gamut and the fast response time are the advantages. Macroblock develops driver ICs for LED array Backlighting, concerning the current matching and control flexibility. The control is necessary to manage the characteristics variation of LEDs, especially the colors.
The LED array should be brightness-equalized and color-balanced by the controller. A power conversion is also considered to provide the best power efficiency in a space-limited and heat-conducting-limited environment. To be synchronized with the LCD controller, the attribute of the fast response time of LED enhances the video fidelity. |
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LED is promising for general lighting in the near future. Compared with the traditional (incandescent) bulb or fluorescence light source, LED is compact, consumes less power, and has longer life times.
Concerning the cost and performance, LEDs would be first used in accent lighting, decoration, etc. 5 to 10 Watt DC-DC converter would be developed and optimized for. Macroblock innovates various topologies, feedback architectures and switching decision algorithms in its switching power conversion technologies. Various devices and semiconductor processes are also involved. |
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To use LED as a house-held lighting device, a small form factor, as well as stable DC "current source", is especially required for driving the LEDs. Macroblock, based on various topologies, feedback architectures and switching decision algorithms, proposes a transformer-less architecture.
Traditionally, a switch-mode power supply is used to provide the necessary voltage supply for the electronic devices. However, no matter how we simplify the circuit, the switch-mode power supply still looks very bulky due to the huge piece of transformer. The only way to down size the transformer is to design a power supply operating in a very high frequency.
Transformer-less architecture is the solution to achieve the small form factor. It is usually required for LED Lighting applications where the size is mostly concerned. As named, it is a power solution without using the transformer. To overcome the challenges of designing a small size power solution for LED Lighting, new circuit architecture must be used. Several kinds of compact size AC-DC converters are now under development. |
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