LED Power Supply Thermal Management via Interrupt Circuit
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Solution Overview
Problem
Existing power supply systems for LEDs in motor vehicles face challenges in maintaining constant luminosity at varying temperatures, particularly at low temperatures where the forward voltage requirement exceeds the capacity of conventional DC/DC converters, leading to insufficient voltage supply and increased complexity or component usage in existing solutions.
Innovation Solution
A system that includes a DC/DC converter and an interrupt circuit capable of short-circuiting LEDs based on ambient temperature measurements, allowing temporary short-circuiting of LEDs to adjust voltage levels and ensure the converter can supply the remaining LEDs, which heats up to reach operational temperature, thereby automatically lifting the short circuit when temperature rises.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the DC/DC converter is sized according to LED characteristics at operating temperature, then the converter is compact and cost-effective, but the converter cannot provide sufficient voltage at low temperatures when forward voltage increases
Solution Approach 1:
The interrupting circuit detects temperature drops in advance and preemptively short-circuits LEDs before the voltage deficiency becomes critical. This preliminary action prevents the converter from failing to supply adequate voltage, allowing the converter to be sized for normal operating conditions rather than worst-case low-temperature scenarios.
Solution Approach 2:
The system dynamically changes the effective number of LEDs in the series chain by short-circuiting certain LEDs when temperature drops. This parameter change (reducing the number of active LEDs) lowers the total forward voltage requirement, enabling the converter to maintain reliable operation across varying temperature conditions without oversizing.
2Reliability
If LEDs are short-circuited to compensate for voltage deficiency at low temperatures, then the converter can supply sufficient voltage, but the total forward voltage in the string varies significantly
Solution Approach 1:
The interrupting circuit continuously monitors temperature and uses this feedback to determine when to short-circuit LEDs. This closed-loop control compensates for voltage variations caused by temperature changes, maintaining stable total forward voltage across different operating conditions by dynamically adjusting the number of active LEDs based on real-time temperature data.
3Reliability
If multiple independent branches with dedicated current sources are used, then each branch can be reliably powered, but the device complexity and component count increase significantly
Solution Approach 1:
A single DC/DC converter is designed to perform multiple functions: it powers all LED branches under normal conditions and can adaptively adjust the number of active LEDs in response to temperature changes. This universal approach eliminates the need for multiple dedicated current sources per branch, reducing component count while maintaining reliability through dynamic adaptation.
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
Enables the use of standard, durable, and inexpensive components to maintain consistent LED power supply without significant space or cost additions, ensuring reliable lighting even at low temperatures by automatically adjusting voltage levels and reducing the duration of temporary luminosity reduction.
Implementation Method 1
at least one of the light sources being connected to a circuit controlled by a temperature measurement
Implementation Method 2
the circuit being capable of short-circuiting said LED connected to the circuit, in order to stabilize/compensate for the total variation of the voltage in the string of LEDs
Implementation Method 3
a DC/DC converter capable of converting an input electrical voltage into an output electrical voltage
Implementation Method 4
The forward voltage of LEDs is higher at low temperatures than at an ambient temperature of 25°C or at the LEDs' operating temperature
Data Source
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AI summary
The invention relates to a device (100) and a method for controlling the power supply of light sources, in which a DC/DC converter (110) is capable of supplying a maximum voltage (VMAX) to the light sources. The forward voltage of the light sources is temperature-dependent and can temporarily exceed VMAX at low temperatures. The invention provides means for automatically reducing the required forward voltage based on an ambient temperature measurement.