LED Current Supply Dynamic Voltage Control
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Solution Overview
Problem
Power supply systems for light emitting diodes (LEDs) face significant power losses due to voltage drops across LED strings, which vary due to production tolerances, temperature changes, and aging, leading to inefficient energy use, especially in applications requiring dynamic voltage adaptation like automotive signaling.
Innovation Solution
A current supply system with a control circuit that dynamically adjusts the output voltage based on actual load requirements using a combination of analog-to-digital and digital-to-analog converters, feed-forward, and feedback control mechanisms to set the reference signal, allowing for real-time optimization of voltage without interrupting the illumination pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the output voltage is fixed at a maximum value to ensure all LED strings can operate, then all LED strings can be powered, but power losses increase due to excessive voltage headroom
Solution Approach 1:
The patent implements dynamic output voltage adjustment by monitoring the actual voltage requirements of LED strings and adapting the output voltage in real-time. The power supply transitions from a fixed maximum voltage to a dynamic voltage that matches the actual load requirements, reducing power losses while ensuring all LED strings can operate when needed.
Solution Approach 2:
The patent employs feedback control mechanisms where the control circuit monitors the voltage drops across LED strings and adjusts the output voltage accordingly. This feedback loop enables the system to maintain optimal voltage levels, preventing both over-voltage power losses and under-voltage operation failures.
2Loss of energy
If the output voltage is dynamically adjusted to reduce power losses, then energy efficiency improves, but the system complexity increases due to additional control circuits
Solution Approach 1:
The patent implements self-service control where the power supply system automatically monitors and adjusts its own output voltage based on the actual LED string requirements. The control circuit uses built-in sensing and feedback mechanisms to autonomously optimize voltage levels without requiring external intervention or complex external control systems.
Solution Approach 2:
The patent combines the voltage regulation and monitoring functions within the existing power supply control circuit. Rather than adding completely separate control systems, the invention integrates voltage adaptation capabilities into the existing control architecture, reducing overall system complexity while achieving dynamic voltage optimization.
3Loss of energy
If the output voltage is adjusted in real-time, then power efficiency improves, but the illumination pattern may be interrupted during voltage transitions
Solution Approach 1:
The patent ensures continuous illumination during voltage transitions by implementing smooth voltage adjustment mechanisms. The control circuit gradually modifies the output voltage rather than making abrupt changes, and coordinates with the LED driving circuitry to maintain continuous current flow through the LED strings, preventing visible flicker or interruption in the illumination pattern.
Data Source
Figure 1~3
Figure 4A~4B
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AI summary
A current supply system for strings of solid-state light sources (34) is disclosed. The current supply system comprises a plurality of terminals (OUT1..OUTn), wherein each of the terminals (OUT1..OUTn) is configured to be connected via a respective current regulator or limiter (32) to a first output terminal of a voltage source (20) and via a respective string of solid-state light sources (34) to a second output terminal of the voltage source (20). A control circuit (40) is configured to generate a reference signal (Vref) for the voltage source (20), wherein the reference signal is indicative of a requested output voltage (Vout) to be generated by the voltage source (20) between the first and the second output terminals of the voltage source (20). In particular, the control circuit (40) comprises: - a digital feed-forward control circuit (408, 410, 412) configured to compute a digital feed-forward regulation value (Vout_req) indicative of a requested output voltage by determining a maximum voltage drop (VLED_MAX) at the strings of solid-state light sources (34), -a digital feed-back control circuit (414) configured to determine (1030) a minimum voltage drop (V32_MIN) at the current regulators or limiters (32) and determine a digital feed-back correction value as a function of the minimum voltage drop (V32_MIN), and - a control circuit (40) configured to set the reference signal (Vref) after a start-up as a function of the digital feed-forward regulation value (Vout_req) and then correct the reference signal (Vref) as a function of the digital feed-back correction value.