LED String Over-Temperature Handling via Switch Control
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Solution Overview
Problem
Solid-state lighting devices face challenges in managing over-temperature conditions, which can lead to damage or hazardous situations due to excessive heat generation, and existing solutions do not adequately prevent reapplication of excessive power voltages after an over-temperature event.
Innovation Solution
A solid-state lighting device with a system controller that couples LEDs in series with a switch, incorporating a temperature sensor to detect over-temperature conditions and prevent switch closure until reset, ensuring safe power reapplication and logging information for diagnostic purposes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the first switch is closed to deliver drive current to the string of LEDs, then the lighting device operates normally and provides illumination, but over-temperature conditions can occur due to heat generation from the LEDs and control electronics
Solution Approach 1:
The temperature sensor continuously monitors the temperature of the LED array and provides feedback to the system controller. When the temperature exceeds a predetermined threshold, the controller opens the first switch to stop current flow, thereby reducing heat generation. This closed-loop feedback mechanism dynamically balances illumination output with temperature control.
Solution Approach 2:
The system implements periodic temperature monitoring and switch control. The temperature sensor periodically checks the temperature, and the switch is opened/closed based on temperature thresholds. This periodic action allows the system to operate at high illumination levels when cool while preventing dangerous temperature accumulation.
2Reliability
If the first switch is opened to stop drive current during over-temperature conditions, then heat generation is reduced and components are protected, but the lighting device cannot operate during the over-temperature state
Solution Approach 1:
The system proactively opens the first switch before critical temperature damage can occur to LED components. By anticipating the damage threshold and acting in advance, the system protects components from irreversible harm. The switch remains open during over-temperature conditions to prevent damage, then resets when safe conditions return.
Solution Approach 2:
The system takes preliminary protective action by opening the switch at the first sign of over-temperature conditions, preventing the escalation to dangerous temperature levels. This preliminary intervention stops the harmful process before it can cause component failure, ensuring reliability while minimizing operational interruption.
3Productivity
If the system allows immediate reset and switch closure after over-temperature conditions abate, then operational continuity is maintained, but excessive power supply voltages may be reapplied to the string of LEDs causing damage
Solution Approach 1:
The system requires a reset action before allowing the first switch to close again after an over-temperature event. This preliminary reset requirement ensures that the system explicitly acknowledges the over-temperature condition has cleared and authorizes safe reoperation. The reset mechanism prevents automatic reclosure that could expose damaged LEDs to excessive voltage.
Solution Approach 2:
The system implements preliminary anti-action by blocking switch closure and preventing current flow until a reset occurs. This anti-action counteracts the tendency to immediately restore power after over-temperature shutdown, thereby preventing the harmful effect of applying excessive voltage to potentially damaged LED components.
4Reliability
If a temperature sensor and control system are added to monitor and respond to over-temperature conditions, then safety and component protection are improved, but device complexity increases
Solution Approach 1:
The system controller performs multiple functions: it controls the first switch for normal operation, monitors temperature through the sensor, detects over-temperature conditions, and manages the reset process. By making the controller multi-functional, the patent avoids adding separate dedicated circuits for each function, thereby limiting the increase in overall device complexity while achieving comprehensive protection.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively manages over-temperature conditions by preventing further power application until safe, reducing the risk of damage from excessive voltages and allowing for diagnostic logging of events.
Implementation Method 1
The system controller is further associated with a temperature sensor and is configured to detect an over-temperature condition based on information provided by the temperature sensor
Data Source
AI summary
A lighting device employs at least one string of LEDs as a lighting source. The string of LEDs is coupled in series with a first switch, wherein the string of LEDs and the first switch are coupled between a power supply node and ground. During a normal operation mode, a system controller is configured to close the first switch to deliver a drive current to the string of LEDs from the power supply node. The system controller is further associated with a temperature sensor and is configured to detect an over-temperature condition based on information provided by the temperature sensor. Upon detecting the over-temperature condition, the system controller will open the first switch to stop the drive current from flowing through the string of LEDs.