LED Drive Circuit Voltage Difference Control
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Solution Overview
Problem
Light-emitting strings with different manufacturing process variations result in unequal conducting voltages, leading to abnormal operation of current sources when coupled to the same driving voltage, causing inconsistent brightness in light-emitting elements.
Innovation Solution
A light-emitting element drive device comprising a power supply circuit, current sources, error amplifiers, diodes, and a control circuit that adjusts the driving voltage based on voltage differences between light-emitting strings to ensure equal current flow, using error amplifiers to detect voltage variations and control diodes to generate a detecting signal for the control circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the same driving voltage is applied to all light-emitting strings, then the circuit design is simple, but light-emitting strings with different conducting voltages cause abnormal operation of current sources
Solution Approach 1:
The patent divides the light-emitting strings into different groups based on their conducting voltage characteristics. Each group is assigned to a dedicated current source that provides a customized driving current, rather than using a single unified driving voltage for all strings. This segmentation allows each current source to be optimized for its specific group's voltage requirements.
Solution Approach 2:
The patent implements local quality by providing different driving currents to different groups of light-emitting strings based on their specific conducting voltage characteristics. Each current source is tailored to match the voltage requirements of its assigned light-emitting strings, ensuring optimal operation for each local group rather than applying a uniform approach.
2Reliability
If multiple current sources are used for different light-emitting strings, then each string can receive appropriate current, but the device complexity increases
Solution Approach 1:
The patent implements universality by designing a control circuit that can manage multiple current sources using a unified control methodology. The control circuit generates control signals that regulate each current source according to the conducting voltage of its associated light-emitting strings, allowing a single control mechanism to handle multiple current sources efficiently.
Solution Approach 2:
The patent applies parameter changes by adjusting the driving current parameters of each current source based on the conducting voltage characteristics of the light-emitting strings. The control circuit dynamically regulates the current magnitude for each current source, optimizing performance while managing complexity through parameter adaptation rather than structural complexity.
3Device complexity
If light-emitting strings with different conducting voltages are connected to the same current source, then the device structure is simple, but the current distribution becomes uneven
Solution Approach 1:
The patent segments the light-emitting strings into distinct groups based on their conducting voltage characteristics and assigns each group to a dedicated current source. This segmentation ensures that light-emitting strings with similar voltage requirements receive matched driving currents, achieving uniform current distribution within each group while maintaining manageable device structure.
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
Ensures each light-emitting string receives equal current, maintaining consistent brightness across all strings by dynamically adjusting the driving voltage based on detected voltage differences, preventing abnormal operation of current sources.
Implementation Method 1
Each error amplifier amplifies and outputs the voltage difference between the voltage of the second terminal and the first reference voltage
Implementation Method 2
The first diode corresponding to the error amplifier with larger output voltage is conducting (ON) and the rest of the first diodes are cut-off (OFF). The voltage at the cathodes of the first diodes is a detecting voltage.
Data Source
AI summary
The present disclosure provides a light emitting element drive device for driving a plurality of LED strings. The device comprises a power supply circuit, a plurality of current sources, a plurality of error amplifiers, a plurality of first diodes and a control circuit. The power supply circuit provides a driving voltage to each of the LED strings. The inverted input terminal of each error amplifier is coupled to a second terminal of the corresponding LED string. Each error amplifier output the voltage difference between the second terminal of the corresponding LED string and a first reference voltage. The anode of each first diode is coupled to the output terminal of the corresponding error amplifier, and the cathodes of the diodes are coupled to each other. The control circuit adjusts the driving voltage of the power supply circuit according to the cathode voltage of the conducted first diode.