LED Bypass Control for Automotive Voltage Fluctuations
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Solution Overview
Problem
Lighting devices with series-connected light-emitting diodes face significant light emission impairment or complete shutdown due to variations in supply voltage, particularly in automotive applications where voltage fluctuations occur during engine starting, leading to unreliable operation.
Innovation Solution
A circuit arrangement with a controllable power source unit and a bypass element connected in parallel with each light-emitting diode, where the bypass element's conductivity is controlled based on the supply voltage, allowing it to take over the current and maintain light emission even at reduced voltages, and an overvoltage detection unit to protect the power source unit from excessive voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If series-connected light-emitting diodes are supplied with predetermined current to achieve uniform light emission, then light emission uniformity is improved, but the system becomes vulnerable to supply voltage variations causing light emission impairment or shutdown
Solution Approach 1:
The circuit divides the series-connected LED string into individually controllable segments. Each LED or group of LEDs can be independently controlled through separate control signals, allowing the system to maintain uniform light emission while adapting to voltage fluctuations by adjusting individual segment brightness or selectively activating/deactivating segments.
Solution Approach 2:
The patent implements dynamic control of LED current through controllable switching elements (such as transistors or MOSFETs) that adjust the current flow in real-time based on supply voltage conditions. This dynamic adjustment allows the system to maintain reliable operation across varying voltage conditions while preserving light emission uniformity when voltage is stable.
2Reliability
If bypass elements are added in parallel with each light-emitting diode to maintain operation at reduced voltages, then operational reliability is improved, but device complexity increases
Solution Approach 1:
The patent introduces controllable switching elements as intermediary components between the power source and LED strings. These switches act as mediators that can redirect current flow or provide alternative conduction paths when voltage drops, enabling reliable operation without requiring complex parallel bypass circuits for each LED. The intermediary elements simplify the overall circuit architecture while maintaining reliability.
3Illumination intensity
If multiple series-connected light-emitting diodes are used to reach predetermined luminous flux, then light output is improved, but the minimum required supply voltage increases making the system sensitive to voltage collapse
Solution Approach 1:
The patent employs parameter changes by using controllable switching elements to dynamically adjust the effective forward voltage requirements of the LED string. Through techniques such as PWM (pulse width modulation) or analog dimming, the system can maintain the same luminous flux output while operating at lower average voltages, reducing sensitivity to voltage collapse during engine starting or other transient conditions.
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
The solution ensures continued light emission and extended operational reliability of light-emitting diodes by managing voltage fluctuations, maintaining functionality even at lower supply voltages and preventing damage from overvoltage conditions.
Implementation Method 1
a bypass element connected in parallel with one of the at least two light-emitting diodes, and a control unit for controlling an electrical conductivity of the bypass element on the basis of a supply voltage
Implementation Method 2
at least two series-connected light-emitting diodes, a controllable power source unit, connected in series with the at least two light-emitting diodes, for supplying a predeterminable electric light-emitting diode current to the series-connected light-emitting diodes
Data Source
AI summary
A method for controlling at least two light-emitting diodes connected in series of a circuit assembly of a lighting device may include supplying the light-emitting diodes with a specifiable current by means of a controllable current source unit. The method may include connecting a bypass element in parallel with at least one of the light emitting diodes. The method may include detecting an electric supply voltage to the series circuit of the light-emitting diodes and the current source circuit, and controlling an electric conductivity of the bypass element based on the detected electric supply voltage and/or the light-emitting diode current.