LED Driver with Programmable NTC Temperature Foldback
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Solution Overview
Problem
Conventional LED power drivers with remotely coupled negative thermal coefficient (NTC) sensors are not adjustable or configurable, leading to fixed temperature breakpoints and ending currents, which can result in damage to LED lighting fixtures during elevated ambient temperatures, increasing warranty returns and reducing product life.
Innovation Solution
An LED driver with a programmable interface that incorporates a temperature sensing circuit and controller circuit to derate output current based on adjustable temperature derating parameters, eliminating the need for external NTC sensors and allowing for customizable temperature ranges and ending currents to prevent overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a remotely coupled NTC sensor is used to measure LED load temperature, then temperature measurement accuracy is improved, but device complexity and wiring requirements increase
Solution Approach 1:
The patent combines the temperature sensing circuit and controller circuit into the LED driver housing, eliminating the need for separate remote NTC sensors and their associated lead wires. The temperature sensing circuit is positioned to measure temperature at critical points within the driver housing, integrating multiple functions into a single unit.
Solution Approach 2:
The patent uses the driver housing structure itself as an intermediary thermal measurement medium. By placing temperature sensing circuits within the housing and using programmable transfer functions, the system indirectly measures LED load temperature through the housing temperature correlation, avoiding direct remote sensing complexity.
2Device complexity
If hard-coded transfer functions are used in conventional LED power drivers, then device complexity is reduced, but adaptability to different LED loads and temperature conditions deteriorates
Solution Approach 1:
The patent implements dynamic programmability in the controller circuit, allowing temperature derating parameters, transfer functions, and breakpoints to be configured and adjusted based on specific LED load requirements and operating conditions. This enables the system to adapt to different thermal characteristics while maintaining a relatively simple base hardware architecture.
Solution Approach 2:
The patent allows modification of key parameters including temperature derating parameters, transfer function coefficients, and breakpoint temperatures through programming. This enables the same hardware platform to serve multiple LED load types by changing software parameters rather than redesigning the control circuitry for each application.
3Reliability
If external NTC sensors are remotely coupled to LED power drivers, then temperature sensing capability is improved, but manufacturing precision and development time increase due to experimental placement requirements
Solution Approach 1:
The patent integrates the temperature sensing circuit directly into the driver housing, eliminating the need for separate external NTC sensor placement. This integration ensures consistent and reproducible thermal measurement positioning during manufacturing, removing the variability associated with manual or experimental sensor placement.
Solution Approach 2:
The driver housing structure itself serves as the thermal measurement reference point. By embedding the temperature sensing circuit within the housing and using programmable transfer functions that account for the thermal relationship between housing and LED load, the system self-calibrates thermal measurements without requiring external sensor placement experimentation.
4Device complexity
If fixed temperature breakpoints and ending currents are used, then device complexity is reduced, but product reliability under varying ambient conditions deteriorates
Solution Approach 1:
The patent implements programmable temperature breakpoints and ending currents that can be adjusted based on ambient temperature conditions, LED load characteristics, and desired thermal protection profiles. This dynamic parameter adjustment enables the system to maintain effective thermal protection across varying operating conditions while using a unified control architecture.
Solution Approach 2:
The patent allows programming of multiple temperature breakpoints and corresponding ending current values to create customized derating curves. This enables the system to adapt protection parameters to different ambient temperature ranges and LED thermal characteristics, improving reliability without significantly increasing hardware complexity through software-based parameter management.
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 solution reduces the risk of damage to LED lighting fixtures by dynamically adjusting output current in response to temperature changes, prolonging product life and reducing warranty returns, while also simplifying the development process and reducing costs by eliminating the need for additional wiring and experimental setup.
Implementation Method 1
incorporating the temperature sensor into the LED driver having programmable interface configured to make the temperature ranges and the current level at an ending temperature adjustable
Data Source
AI summary
An LED driver includes a temperature sensing circuit integrated within its housing. The sensing circuit generates signals corresponding to actual temperature values within the driver housing to a controller. The controller receives programmable temperature derating parameters at least partially related to a light fixture receiving the driver housing, converts the temperature sensor signal into the actual temperature value, and derates the output current in linear fashion according to a transfer function when the actual temperature value falls within the temperature derating parameters. The parameters may include starting and ending temperatures, and an ending current parameter. The temperature sensing circuit may include a voltage divider with a negative thermal coefficient (NTC) device, preferably as the high side resistor. The temperature sensing circuit may typically provide a non-linear output across the temperature range, wherein the controller converts the non-linear output from the sensing circuit into a linear output for the transfer function.