TECHNICAL FIELD
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The present invention relates to lighting systems, particularly systems using LED drivers in parallel configurations (i.e. with combined DC output), and methods for load adaptation in the event of driver failure or overload. Specifically, the invention pertains to automatic load management in stacked driver systems, ensuring continued operation and light output in the case of driver malfunction.
BACKGROUND
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LED drivers are commonly used in lighting systems to regulate the electrical current required by LEDs. In certain applications, LED drivers are operated in parallel configurations to increase the overall system power capacity and ensure higher system availability. This configuration is often over-dimensioned, providing redundancy such that if one or more drivers fail, the remaining drivers can maintain system operation without interruption.
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However, in situations where systems are not over-dimensioned, a failure of one or more drivers results in the remaining drivers being unable to support the full load, leading to system overload and shutdown. This causes the entire lighting system to stop functioning, resulting in a complete blackout. This is a significant limitation, especially in environments where continuous lighting is critical for safety or operations, such as hospitals, emergency exits, or public spaces.
SUMMARY
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In view of the above-discussed limitations, the objective of this invention is to introduce a method for automatic and autonomous load adaptation in stacked driver systems. One objective is to allow the system to automatically reduce the load in the event of driver failure or overload, thereby allowing the lighting system to continue operating with reduced capacity, and preventing a total blackout.
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These and other objectives are achieved by the solution of this disclosure as described in the independent claims. Advantageous implementations are further defined in the dependent claims.
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According to a first aspect of the invention, a DC/DC converter is provided having output terminals for supplying a LED load. The DC/DC converter is configured to supply power to an associated LED load, and is supplied by a central DC bus voltage from one or more AC/DC converters. The DC/DC converter is configured to receive a control signal indicating a trigger event associated with a failure or reduced performance of the one or more AC/DC converters of the parallel arrangement. In response to the control signal, the DC/DC converter is further configured to adjust its power consumption, thereby ensuring continued operation with reduced power output.
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The invention provides a DC/DC converter adapted to supply a LED load that can adjust its power consumption in response to a detected trigger event, such as a failure or reduction in performance of the supplying AC/DC converters. This ability to autonomously react to such conditions ensures that the system continues to provide reduced lighting output, preventing a total loss of lighting. This feature is particularly useful in applications like emergency lighting, where maintaining at least partial illumination is critical.
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According to an implementation form of the first aspect of the invention, the trigger event is defined as the failure of the central DC bus voltage to reach or maintain a predefined nominal voltage level.
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This allows the system to precisely identify when the AC/DC converters are not providing adequate voltage to the DC/DC converter, which triggers the necessary response to reduce power consumption and maintain system stability.
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According to a further implementation form of the first aspect of the invention, the DC/DC converter is configured to reduce its power consumption by at least one of the following operations: switching off part or all of the associated LED load; or dimming the power supplied to the associated LED load.
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This flexibility allows the system to implement power reduction strategies tailored to the specific lighting requirements of the environment. In critical areas, the converter can dim the lighting to ensure continued visibility, while in non-critical areas, it can completely switch off the lighting to conserve power.
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According to a further implementation form of the first aspect of the invention, the control signal is generated either by a central control system monitoring the performance of the one or more AC/DC converters, or by local control circuitry integrated with the DC/DC converter. This configuration provides the system with adaptability to various control architectures, ensuring that the invention can be implemented in both centralized and decentralized systems.
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According to a further implementation form of the first aspect of the invention, the local control circuitry is configured to: detect attempts by the one or more AC/DC converters to raise the central DC bus voltage to the predefined nominal value; monitor the number of unsuccessful attempts; and detect the trigger event when the number of unsuccessful attempts exceeds a predetermined threshold.
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This provides an advanced monitoring mechanism within the DC/DC converter, allowing it to autonomously detect when the AC/DC converters are repeatedly failing to reach the desired voltage. By monitoring these failed attempts, the converter can accurately determine when to adjust its power consumption, ensuring robust performance in degraded system conditions.
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According to a further implementation form of the first aspect of the invention, the local control circuitry is powered by the central DC bus voltage. This ensures that the control circuitry remains operational even when the system is experiencing a failure condition, allowing it to continue monitoring and reacting to changing conditions without interruption.
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According to a second aspect of the invention, a lighting system is provided. The system comprises one or more AC/DC converters arranged to supply a central DC bus voltage, and at least one local DC/DC converter according to the first aspect or any of the implementation form of the first aspect.
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This lighting system can maintain reduced lighting output during AC/DC converter failures by ensuring that the local DC/DC converters dynamically adjust their power consumption based on the detected trigger events.
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According to a third aspect of the invention, another lighting system is provided. The system comprises one or more AC/DC converters arranged to supply a central DC bus voltage, at least one local DC/DC converter, and control circuitry configured to: detect a trigger event associated with a failure or reduced performance of the one or more AC/DC converters; and in response to the detected trigger event, control the at least one local DC/DC converter to adjust its power consumption.
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This embodiment provides centralized control of multiple DC/DC converters within the lighting system, allowing for coordinated responses to AC/DC converter failures. The centralized control system ensures that the overall system can prioritize critical lighting areas and optimize power usage during failure conditions.
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According to an implementation form of the third aspect of the invention, the control circuitry is further configured to: detect attempts by the one or more AC/DC converters to raise the central DC bus voltage to the predefined nominal value; monitor the number of unsuccessful attempts to determine if they exceed a predetermined threshold; and detect the trigger event if the threshold is exceeded.
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This provides a robust fault detection system within the control circuitry, allowing the lighting system to automatically respond to ongoing issues with the AC/DC converters and adjust the lighting load accordingly.
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According to a fourth aspect of the invention, a method for controlling a DC/DC converter supplying power to an associated LED load is provided. The method comprises: detecting a trigger event associated with a failure or reduced performance of one or more AC/DC converters that supply a central DC bus voltage to the DC/DC converter; and in response to the trigger event, adjusting the power consumption of the DC/DC converter to ensure continued operation with reduced power output.
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This method allows the system to dynamically react to failures or reductions in performance in real time, ensuring that the lighting system can maintain some level of functionality even under degraded conditions.
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According to an implementation form of the fourth aspect, the step of adjusting the power consumption comprises at least one of: switching off part or all of the associated LED load; or dimming the power supplied to the associated LED load.
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This allows for a flexible approach to managing power consumption, ensuring that lighting in critical areas can be maintained while non-essential lighting is reduced or turned off to conserve power.
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According to a further implementation form of the fourth aspect, the method further comprises: detecting multiple attempts by the one or more AC/DC converters to raise the central DC bus voltage to the predefined nominal value; monitoring the number of unsuccessful attempts; and determining whether the number of unsuccessful attempts exceeds a predetermined threshold, and detecting the trigger event if the threshold is exceeded.
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This ensures that the system can reliably detect ongoing failures and adjust its power output based on real-time monitoring of the central DC bus voltage.
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All steps that are performed by the various components described in this application, as well as the functionalities described to be performed by the various components, are intended to mean that the respective component is adapted to or configured to perform the respective steps and functionalities. Even if, in the following description of specific embodiments, a specific functionality or step to be performed by external components is not reflected in the description of a specific detailed element of that component that performs that specific step or functionality, it should be clear to a skilled person that these methods and functionalities can be implemented in respective software or hardware elements, or any kind of combination thereof.
BRIEF DESCRIPTION OF DRAWINGS
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The above-described aspects and implementation forms are now further explained with respect to the drawings by way of example only, and not for limitation. In the drawings:
- Fig. 1
- shows an exemplary DC/DC converter for supplying a LED load according to an embodiment of this invention.
- Fig. 2
- shows the detection of a trigger event according to an embodiment of this invention.
- Fig. 3
- shows a lighting system according to an embodiment of this invention.
- Fig. 4
- shows a lighting system according to another embodiment of this invention.
- Fig. 5
- shows a method according to an embodiment of this invention.
DETAILED DESCRIPTION OF EMBODIMENTS
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Illustrative embodiments of a DC/DC converter for LED applications, a lighting system, and a method for controlling a DC/DC converter supplying power to an associated LED load are described with reference to the figures. Although this description provides a detailed example of possible implementations, it should be noted that the details are intended to be exemplary and in no way limit the scope of the application.
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An embodiment/example may refer to other embodiments/examples. For example, any description including but not limited to terminology, element, process, explanation, and/or technical advantage mentioned in one embodiment/example is applicable to the other embodiments/examples. The same elements are labeled with the same reference signs and may function similarly or likewise.
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With respect to Fig. 1, a DC/DC converter 10 for supplying power to an associated LED load 11 is illustrated. The DC/DC converter 10 is supplied by a central DC bus voltage 12, which is generated by one or more AC/DC converters 13. The primary function of this DC/DC converter 10 is to maintain continuous lighting operation, even during failures or reduced performance of the AC/DC converters.
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The DC/DC converter 10 is configured to receive a control signal indicating a trigger event associated with a failure or reduced performance of the one or more AC/DC converters 13. In response to the control signal, the DC/DC converter 10 is configured to reduce its power consumption.
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In one embodiment, the DC/DC converter 10 is equipped with local control circuitry that can detect a trigger event associated with a reduction in the performance of the AC/DC converters 13 or a failure to maintain the nominal central DC bus voltage.
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In another embodiment, control circuitry integrated with a central control system provides the control signal to the DC/DC converter 10. The central control system is able to monitor the performance of the one or more AC/DC converters 13.
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Upon detecting such a trigger event, the DC/DC converter 10 adjusts its power consumption, which may involve either dimming the LED load 11 or switching off some or all of the LED loads 11. This ensures that a minimal level of light output is maintained even in the case of degraded AC/DC converter operation, thereby enhancing system reliability in critical applications such as emergency lighting.
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Notably, Fig. 1 also depicts an embodiment of a lighting system 1 comprising the DC/DC converter 10. The system further comprises one or more AC/DC converters 13 arranged to supply a central DC bus voltage 12.
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Fig. 2 illustrates the detection of a trigger event and the response of the DC/DC converter 10, in conjunction with the behavior of the AC/DC drivers shown in Fig. 3. The two graphs in Fig. 2 correspond to the output voltage (Vout) of the central DC bus over time (top graph) and the current supplied by the three drivers (I_drv1, I_drv2, and I_drv3) over time (bottom graph).
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In the system depicted in Fig. 3, there are three AC/DC drivers (DRV1, DRV2, and DRV3), each rated at 1000W, which supply power to six spotlights (SPOT 1 to SPOT 6). Each spotlight is paired with a local DC/DC converter 10 and is controlled by intelligent Load Management Interfaces (LMIs). These LMIs autonomously manage the power supplied to each spotlight based on the real-time central DC bus voltage and are pre-configured to detect overloads or voltage fluctuations.
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Initially, as shown in Fig. 2, the central DC bus voltage 12 (Vout) is stable at 48V, which is the nominal operating voltage, and all three drivers (DRV1, DRV2, and DRV3) function normally, distributing power evenly across the six spotlights.
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However, at a certain point, as illustrated in Fig. 3, DRV2 and DRV3 experience failures. This causes a sudden drop in the central DC bus voltage, as seen in Fig. 2 where Vout dips below a critical shutdown threshold, referred to as the "Abschaltschwelle LMI" (the shutdown threshold for the Load Management Interface). In response, the system initiates multiple restart attempts, shown in Figure 2 as Restart 1, Restart 2, and Restart 3.
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During each restart attempt, DRV1 (I_drv1 in Fig. 2) remains the only active driver, attempting to supply current to the system. However, due to the overload condition, DRV1 alone cannot maintain the bus voltage, and the restart attempts fail, as shown by the current interruption for I_drv1 in the bottom graph of Fig. 2. Meanwhile, DRV2 and DRV3 (I_drv2 and I_drv3) remain inactive, as reflected in both Fig. 2 (near-zero currents) and Fig. 3 (the failure of these drivers).
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The LMIs (local control circuitry) of the local DC/DC converters are designed to detect these cyclical restart attempts and the associated voltage fluctuations. Upon recognizing that DRV1 cannot handle the full load, the LMIs initiate load reduction strategies to prevent a complete system shutdown. These strategies are illustrated in Fig. 3 :
- Non-critical spotlights (SPOT 1 to SPOT 4) are switched off (labeled as "AUS"), effectively reducing the load on DRV1.
- The system prioritizes critical lighting loads, such as SPOT 5 and SPOT 6, which remain operational, marked as "Priorität" in the figure. This ensures that essential areas continue to receive power even during the failure of multiple drivers.
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The local control circuitry of the DC/DC converter 10 counts the number of failed restart attempts (Restart 1, Restart 2) and detects a trigger event when the system voltage fails to stabilize. Once the system detects this event, the LMIs autonomously manage the load by reducing power to non-critical spotlights, as reflected in Fig. 3.
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After the third restart attempt (Restart 3), the system voltage stabilizes at 48V, as shown in the top graph of Fig. 2. At this point, the LMIs recognize the recovery of the system, allowing DRV1 to resume supplying power to the essential loads (SPOT 5 and SPOT 6), while SPOT 1 to SPOT 4 remain switched off. This behavior prevents a total blackout and ensures that critical lighting remains operational.
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Possibly, the LMIs are pre-programmed to monitor the central DC bus voltage and detect voltage instability caused by repeated restart attempts. Even when the drivers shut down temporarily, the bus voltage 12 remains above a certain threshold, allowing the LMIs to continue functioning. By consuming minimal power, the LMIs remain operational during these failures and take corrective action by dimming lights or switching off non-critical spotlights, as needed.
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This embodiment, as illustrated in both Figures 2 and 3, demonstrates a fault-tolerant system capable of maintaining essential lighting during multiple driver failures. The coordination between the voltage and current monitoring (see Fig. 2) and the autonomous load management through the LMIs (see Fig. 3) ensures that the system avoids a complete shutdown and continues to function at a reduced capacity, maintaining emergency lighting when necessary.
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Fig. 4 represents a lighting system 2 according to an embodiment of the invention, where a centralized control system, such as a Building Management System (BMS), manages the power distribution across multiple drivers and spotlights. Unlike the autonomous Load Management Interfaces (LMIs) depicted in Figures 2 and 3, which operate locally and independently, Fig. 4 introduces a centralized approach for dynamic power and load management. This central control system adds a layer of intelligent coordination across the entire lighting infrastructure, providing greater flexibility and control in adjusting the lighting based on available power resources.
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In Fig. 4, the system 2 includes two AC/DC drivers 13 (DRV1 and DRV2), each rated at 1000W, and four spotlights (SPOT 1 to SPOT 4), each consuming 500W. Each spotlight is paired with a local DC/DC converter 10. The drivers and spotlights are managed by a central control unit 21, which communicates with them via a wired or wireless interface, such as DALI or a wireless communication protocol.
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The central control system continuously monitors the health of the drivers and the power distribution across the system. In this particular scenario, DRV2 has failed, reducing the total available power from 2000W to 1000W. As a result, the system needs to adjust the lighting load to match the reduced power capacity provided by the remaining operational driver (DRV1).
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The centralized control system is designed to detect when one of the drivers fails, either through direct monitoring of the driver's operational status or by receiving a failure report from the driver itself. In this case, the system 2 detects the failure of DRV2, leaving only 1000W available from DRV1. This failure detection triggers the system 2 to initiate a power management strategy to ensure that the remaining load does not exceed the available capacity.
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Upon detecting the reduction in available power, the central control system can employ one of two strategies to balance the load: either dimming all lights or selectively turning off non-essential loads. These strategies provide flexibility depending on the priorities of the environment, such as whether uniform lighting is needed or if certain areas are more critical than others.
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The first option is to dim all lights to match the reduced system capacity. In this example, since each spotlight normally consumes 500W, dimming them to 50% brightness reduces their power consumption to 250W each. This way, all four spotlights (SPOT 1 to SPOT 4) remain operational, and the total power consumption is reduced to 1000W, which matches the available capacity of DRV1.
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This option ensures that all areas of the building remain lit, though at a reduced brightness. This solution is particularly suitable for environments where uniform lighting is required across all areas, such as in large public spaces, factories, or commercial buildings where some light is better than none in all areas.
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The second option, shown in Fig. 4, is selective load reduction. In this approach, the control system prioritizes certain critical areas while turning off non-essential lights. In the figure, SPOT 1 and SPOT 2 have been turned off (marked as "AUS"), while SPOT 3 and SPOT 4 remain fully operational (marked as "Priorität"). This reduces the total power demand to exactly 1000W, allowing DRV1 to supply full power to the remaining two spotlights.
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This approach is particularly useful in emergency situations or in environments where certain areas must remain fully lit, such as in emergency exits, hallways, or operating rooms, while less critical areas (like storage rooms or low-priority areas) can be left unlit. Selective load reduction ensures that priority lighting areas remain fully functional, which is crucial for safety and operational continuity.
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The central control system communicates with both the drivers and spotlights through a communication interface, which could be either a wired protocol like DALI (Digital Addressable Lighting Interface) or wireless communication. The system can receive real-time status reports from the drivers and the spotlights, allowing it to dynamically adjust the power distribution based on the available capacity.
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This communication interface also enables centralized decision-making for power management. Instead of relying on local, autonomous decisions as seen in Figures 2 and 3, the central system 2 can optimize lighting at a broader level, ensuring that the entire network of lights and drivers is managed efficiently and coherently.
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With reference to Fig. 5, an embodiment of a method 500 for controlling a DC/DC converter 10 that supplies power to an associated LED load 11, is illustrated. This method focuses on fault detection and power management in the case of failures or reduced performance of the AC/DC converters 13, which are responsible for supplying the central DC bus voltage 12 to the DC/DC converter 10. The DC/DC converter 10 and the AC/DC converters 13 may be the converter described in the previous embodiments, as shown in Fig. 1, Fig. 3, or Fig. 4.
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The method 500 starts with detecting a trigger event (step 501), which occurs when one or more AC/DC converters fail or perform below expected levels, leading to a drop in the central DC bus voltage.
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The detection of this trigger event may be carried out by either:
- The local control circuitry of the DC/DC converter, as described in Figures 2 and 3, where autonomous Load Management Interfaces (LMIs) monitor the system locally.
- A central control circuitry 21, as described in Fig. 4, where a central Building Management System (BMS) manages and monitors the power distribution for multiple drivers and spotlights.
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Both control approaches can detect the voltage fluctuations or failures in the AC/DC converters 13 that indicate the need to reduce power consumption.
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Once the trigger event is detected, the method 500 further includes a step 502 of reducing the power consumption of the DC/DC converter 10.
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Optionally, this power reduction can be achieved in two main ways:
- Switching off part or all of the associated LED load 11, which would reduce the power demand on the system.
- Dimming the power supplied to the associated LED load 11, allowing the lights to continue operating at a lower power level, maintaining minimal illumination while conserving energy.
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These options give flexibility depending on the system's operational requirements. The choice between dimming or switching off the load may depend on the environment and the criticality of the lighting.
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The method 500 may further include a monitoring process for multiple restart attempts made by the AC/DC converters 13. When the AC/DC converters 13 fail to restore the central DC bus voltage 12 to the predefined nominal value, the system tracks these attempts and counts the number of unsuccessful attempts.
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Further, the system evaluates whether the number of unsuccessful restart attempts exceeds a predetermined threshold. This threshold acts as a decision point to confirm if the system is experiencing a sustained failure that requires further action.
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If the threshold is exceeded, the system detects the trigger event. This step finalizes the detection process, leading to the reduction of power consumption as described in Step 502.
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The method 500 presented in Fig. 5 ensures that the lighting system (e.g., the lighting system 1 as shown in Fig. 3, or the lighting system 2 as shown in Fig. 4) continues operating in a reduced capacity even when AC/DC converters 13 experience failures. By detecting trigger events and reducing the power load through dimming or switching off part of the LED load, the method maintains energy efficiency and prevents system overloads. Additionally, by monitoring and responding to repeated unsuccessful restart attempts, the system intelligently adapts to ongoing failures, ensuring a resilient and fault-tolerant power supply solution for LED lighting systems. Whether managed locally by the DC/DC converter or centrally by a BMS, this method ensures that lighting systems can maintain emergency or critical lighting levels in the face of failures.
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While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not by limitation. Numerous changes to the disclosed embodiments can be made in accordance with the disclosure herein without departing from the spirit or scope of the invention. Thus, the breadth and scope of the present invention should not be limited by any of the above described embodiments. Rather, the scope of the invention should be defined in accordance with the following claims and their equivalents.
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Although the invention has been illustrated and described with respect to one or more implementations, equivalent alterations, and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application.