Emergency LED Driver Relay Timing to Prevent Hot Plugging
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Solution Overview
Problem
Existing emergency LED drivers face issues with relay synchronization during short mains interruptions, leading to high output voltage buildup and current surges that can damage the LED load due to 'hot plugging', particularly in high power converters.
Innovation Solution
An emergency LED driver system with load and mains side relays that delay the disconnection from the external driver by a predefined time after mains failure, allowing residual energy to dissipate, and uses a battery to maintain relay operation during this delay, ensuring zero current switching upon mains restoration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If relays are used to switch power supply from external driver to emergency converter during mains failure, then the LED load can be powered during mains interruption, but the relays can drop out during short mains interruptions causing voltage surges and hot plugging damage
Solution Approach 1:
The microcontroller detects mains failure and activates the delay mechanism before the relay switches. This preliminary detection and timing setup ensures that the relay only operates when necessary (sustained failures) and prevents premature switching during transient interruptions, avoiding voltage surges and hot plugging effects
Solution Approach 2:
The microcontroller acts as an intermediary between the mains power detection and the relay switching mechanism. It introduces intelligent control logic that mediates the switching decision based on failure duration, preventing direct mechanical relay responses that cause harmful voltage surges during short interruptions
2Adaptability or versatility
If relays are used for switching, then power supply can be switched between external driver and emergency converter, but relay contacts can weld due to high current and power surges during hot plugging
Solution Approach 1:
The system performs preliminary detection of sustained mains failure and implements a delay mechanism before relay switching. This ensures that the relay only operates when the external driver has fully shut down, preventing high current surges that would weld the contacts and extending relay lifespan while maintaining power switching capability
3Speed
If the relay switches immediately upon mains failure, then the emergency converter can take over power supply, but the external driver may still be operating causing high output voltage buildup and current surges
Solution Approach 1:
The microcontroller performs preliminary detection of mains failure and implements an intelligent delay before relay switching. This delay allows the external driver to complete its shutdown sequence and dissipate residual energy, ensuring that when the relay switches, no voltage surges or current spikes occur, thus protecting the LED load
Solution Approach 2:
The system uses feedback from the microcontroller to monitor the switching process and control the relay timing. The microcontroller receives feedback about mains status and external driver operation, adjusting the relay switching moment to occur only when it is safe, preventing harmful voltage and current surges
Data Source
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AI summary
The invention relates to an emergency LED driver (100) for supplying an LED load (300), comprising a mains connection (101) for receiving a mains voltage; an output port (105) configured to forward a driver supply voltage based on said mains voltage to an external driver (200); an input port (107) configured to receive an LED supply voltage from the external driver (200); an LED connection (113) for connecting the LED load (300) to the emergency LED driver (100); and a load side relay (111). In a non-emergency mode, the load side relay (111) is adapted to electrically connect the LED connection (113) with the input port (107), such that the LED supply voltage received at the input port (107) is forwarded to the connected LED load (300). Upon a failure of the mains voltage, the load side relay (111) is configured to maintain the connection between the LED connection (113) and the input port (107) for a predefined delay time, and, after said delay time has passed, disconnect the input port (107) from the LED connection (113) and switch over the voltage supply of the LED load (300) to a battery (110).