LED Temperature Sensing via Superimposed Current Pulse
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Solution Overview
Problem
Conventional LED temperature measurement devices are inaccurate as they measure temperature near the LED rather than directly measuring the LED die temperature, and they require additional wires, which can be inconvenient and introduce measurement inaccuracies.
Innovation Solution
A method and device that superimpose a current pulse on the operating current of the LED to generate a voltage pulse, allowing for the determination of the LED's operating temperature based on the current and voltage pulse magnitudes, or using a thermistor in parallel with the LED to measure the temperature by distinguishing between forward and reverse bias currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermocouples or thermistors are placed near the LED to measure temperature, then temperature monitoring is enabled, but the measurement accuracy deteriorates because they measure temperature near the LED rather than directly measuring the LED die temperature
Solution Approach 1:
The LED itself serves as the temperature sensing element by utilizing its inherent electrical characteristics (forward voltage or reverse leakage current) that vary with temperature. The existing LED structure and electrical connections are used for both light emission and temperature measurement, eliminating the need for separate temperature sensing devices and their associated wiring.
2Measurement precision
If thermocouples or thermistors are connected to a monitoring system using additional wires, then temperature data can be transmitted, but the device complexity increases and measurement accuracy deteriorates due to wire-related inaccuracies
Solution Approach 1:
The temperature measurement function is merged with the existing LED power supply and control circuitry. The same electrical connections used to power the LED are also used to sense its temperature through measurements of forward voltage or reverse leakage current, eliminating the need for separate temperature sensing wires and reducing overall system complexity.
Solution Approach 2:
The LED and its electrical connections serve multiple functions: light emission, current control, and temperature sensing. By making the electrical connections universal for both power delivery and temperature measurement, the patent eliminates the need for dedicated temperature sensing wires, thereby reducing device complexity and potential sources of measurement error.
3Illumination intensity
If multiple LEDs are grouped together in a light fixture to increase light output, then illumination intensity improves, but heat buildup increases causing thermal runaway risk
Solution Approach 1:
The patent implements temperature feedback by continuously monitoring the LED's temperature through its electrical characteristics (forward voltage or reverse leakage current). When the temperature approaches unsafe levels, the system provides feedback to reduce the drive current, preventing thermal runaway and enabling safe operation of multiple LEDs in close proximity.
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
This approach provides an accurate measurement of the LED's temperature without additional wires, ensuring the LED operates within a safe temperature range and prolongs its operational lifetime by preventing thermal runaway.
Implementation Method 1
A current pulse is superimposed on the operating current to the LED, through the first and second LED conductors resulting in a voltage pulse that is superimposed on the operating voltage. The voltage pulse is sensed across the first and second LED conductors resulting from the applied pulse of current to determine a voltage magnitude of the voltage pulse.
Implementation Method 2
A thermistor is positioned in a thermal pathway of the LED to receive heat produced by the LED during operation of the LED. The temperature of the thermistor is measurable by determining the thermistor resistance.
Implementation Method 3
The LED is operable to generate light in response to receiving the operating current in a range of operating currents and receiving the operating voltage in a range of operating voltages.
Data Source
AI summary
A control system is disclosed for determining an actual temperature of a light emitting diode. The control system uses conductor that supply power to the light emitting diode to supply a pulse to the light emitting diode. The pulse is determined along with a reaction caused by the pulse and the information gained is used in determination of the light emitting diode die temperature which can then be used in controlling current to the light emitting diode to control the temperature of the light emitting diode.