Intelligent adaptive LED constant current drive source application case

Recently, artificial intelligence has been the subject of much discussion, especially with the rise of advanced robotics. Many people speculate that robots could soon replace humans entirely and even dominate them in the future, creating a world ruled by machines. These ideas often stem from science fiction, where they serve to captivate audiences rather than reflect reality. In reality, most robotic systems today, like those on assembly lines, operate strictly according to pre-programmed instructions and lack the ability to adapt dynamically to environmental changes. When faced with even slight alterations in their surroundings, these systems fail to function correctly, making them far from what we would consider "intelligent." What truly matters is how we harness smart technologies to address real-world problems and enhance our daily lives. The essence of intelligent technology lies in its capacity for self-adaptation. Technologies that automatically adjust device operations for optimal results based on environmental changes are inherently adaptive. With adaptability, we can transform traditional approaches and achieve unexpected breakthroughs. One notable example of intelligent technology is the intelligent LED constant current source. 1. Classic Linear Constant Current Source: We understand that all power supplies fall into two categories: constant voltage and constant current. A constant voltage power supply maintains a stable output regardless of fluctuations in input voltage or load, whereas a constant current power supply ensures steady current flow irrespective of changes in input voltage or load. Since LEDs are semiconductor diodes with a negative temperature coefficient, they require constant current regulation to prevent excessive current flow that could damage them. This regulation can be achieved through either switch-mode or linear-type constant current sources. Switch-mode sources offer high efficiency (around 90%) but come with drawbacks such as higher component count, lower reliability, larger size, and higher costs. Conversely, linear constant current sources feature fewer components, high reliability, compact size, and affordability but suffer from low efficiency, typically around 85%. 2. Efficiency of Linear Constant Current Sources: The efficiency of linear constant current sources diminishes as input voltage increases. Their typical efficiency curve shows a steep decline. At 220V mains voltage, efficiency drops to just 85%. Lower input voltages yield higher efficiencies. Can we make this linear constant current source highly efficient at 220V? This necessitates a deeper dive into the circuit composition and performance of linear constant current sources. 3. Linear Constant Current Source with Ordinary Constant Current Diode: The simplest linear constant current source uses an ordinary constant current diode. Its circuit diagram is as follows: [Diagram description] CRD in the diagram represents a constant current diode. Multiple CRDs are connected in parallel to achieve the desired constant current value. Alternatively, various constant current diodes with different current ratings are available, eliminating the need for parallel connections. Simply connect a single constant current diode with the desired current rating in series with all LEDs to create a constant current supply. This makes the circuit straightforward! Its operation principle can be understood from its I-V characteristics: [Diagram description] It maintains constant current from Vk up to the input DC voltage range of POV. Absolute Vk is less than 3V. Assuming rectified DC voltage is 300V and constant current value is 0.1A, total power is 30W. If the total voltage of the LED string closely matches 300V, the constant current diode operates at Vk, consuming only 0.3W of power, resulting in an efficiency of (30-0.3)/30 = 99%. However, as input voltage increases, the constant current diode must absorb excess voltages, shifting its operating point to the right, increasing power consumption, and reducing overall efficiency. This demonstrates the inherent inefficiency of constant current diodes, which require large heat sinks, seemingly unavoidable. This aligns with general textbooks. 4. Improving Efficiency of Linear Constant Current Sources with Adaptive Methods: To boost the efficiency of linear constant current sources, we need innovative solutions. Given our application powers LEDs, LEDs are the load of our constant current source. For instance, if the rectified voltage is 300V and each LED's forward voltage is 3V, then 100 LEDs must be connected in series. When the mains voltage rises, so does the rectified voltage, but the LED is powered by a constant current source, keeping its forward voltage constant. The excess rectified voltage falls on the constant current diode, inevitably lowering overall efficiency. Is there a way to prevent the constant current diode from taking on additional voltage after rectification? The best solution is adaptively adjusting the number of LEDs. When the mains voltage increases, add more LEDs; when it decreases, reduce the number. This can be easily achieved using an adaptive digital switching circuit. Here’s the schematic: [Diagram description] LED blocks can be adaptively connected to or disconnected from the main LED string, depending on input voltage changes. It senses input voltage changes and adjusts the number of LEDs accordingly, making it adaptive or intelligent. Shenzhen Effie has successfully developed such a chip capable of automatic switching, named AICS, standing for Adaptive-Intelligence-Current-Source. 5. Performance of Intelligent LED Constant Current Source: 5.1 Adaptation to Input Voltage: As mentioned, with adaptive control, this constant current source can achieve 99% efficiency. Moreover, this efficiency remains consistent across a wide range of input voltage variations. Below is the relationship between efficiency and input voltage: [Graph description] Blue represents the efficiency of the constant current source itself, while red shows total efficiency including the rectifier. Within 175V-265V mains voltage range, constant current source efficiency stays at 99%, with overall system efficiency exceeding 98%. 5.2 Temperature Adaptation: When ambient temperature changes, the power consumption of the constant current diode increases. For example, as temperature rises, the forward voltage of LEDs decreases due to their negative temperature coefficient. This lowers the forward voltage below the rectified voltage, increasing the voltage drop across the constant current diode and raising its power consumption. This intelligent constant current source adds more LEDs to the string, boosting total voltage to match the rectified voltage, maintaining high efficiency. Results: [Graph description] From the graph, as ambient temperature rises from 35°C to 85°C, overall efficiency remains nearly identical to the input voltage curve, staying above 98% (including rectifier losses). 5.3 Adaptation to LEDs with Different Forward Voltages: This intelligent LED constant current source also features adaptability to LEDs with varying forward voltages. Mixing LEDs with different forward voltages in the same string doesn’t hinder its performance. The adaptive smart LED constant current source automatically switches the number of LEDs, ensuring 99% total efficiency. This patent has been authorized by the US Patent Office. 5.4 Changing Number of LEDs Without Changing Luminous Flux: Simply changing the number of LEDs alters total luminous flux since the constant current source’s current remains unchanged. This issue is addressed in the intelligent LED constant current source’s overall design. While changing the number of LEDs, the constant current source’s current also adapts, keeping total power and luminous flux constant. [Graph description] From the figures, after this adaptive adjustment, input power, output luminous flux, and overall luminous efficiency remain largely unchanged across different input voltage ranges. 6. Integrated Photoelectric Light Engine: This intelligent LED constant current source breaks conventional understanding of linear constant current sources, achieving 99% efficiency. Thus, the constant current source and the light source can be placed on the same aluminum substrate to form an integrated photoelectric light engine. Due to its minimal power consumption, placing it on the light source’s aluminum substrate doesn’t increase the LED junction temperature. Shenzhen Effie has produced a series of light engines with varying power levels: [Image description] 7. Conclusion: This intelligent LED constant current source boasts an efficiency of 99%, essentially a non-electricity-consuming constant current source. Typically, LED constant current source efficiency is 85-90%, meaning this intelligent source saves an additional 10-15% energy. Its significance is immense! China’s lighting consumes 14.5% of total electricity. In 2014, total power generation was 564.96 billion kWh, meaning lighting consumed 819.19 billion kWh. Using Effie’s light engines, at least 10% savings can be achieved, equating to 81.92 billion kWh, equivalent to the annual power generation of the Three Gorges Power Station (84.7 billion kWh). Globally, lighting accounts for 19% of total electricity consumption. In 2014, total global power generation was 238.67 billion kWh, meaning lighting consumed 453 billion kWh. Using Effie’s light engines, savings reach 453.5 billion kWh, equivalent to five and a half Three Gorges Power Stations!

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