LED Driver IC Resistance Control for Beam Switching Overcurrent
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Solution Overview
Problem
Existing light emitting devices, such as those described in Patent Document 1, experience overcurrent issues when switching between high and low beam modes due to voltage drops, leading to potential damage of LEDs, and require experimental optimization of voltage values and retention times to mitigate this, which is not universally applicable across different LED specifications.
Innovation Solution
A semiconductor integrated circuit with a variable resistor controller that increases the resistance value of a variable resistor connected in series with light emitting elements before or simultaneously with reducing the number of lit elements, to prevent high currents from passing through the elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the number of light emitting elements that are lit is reduced to switch between high beam and low beam modes, then the illumination pattern is changed, but an overcurrent occurs due to voltage drop that damages the LEDs
Solution Approach 1:
The variable resistor controller increases the resistance value of the variable resistor immediately before or at the same time as the number of lit light emitting elements is reduced. This preliminary action prevents the voltage drop from causing overcurrent by having the resistance already increased when the circuit configuration changes, thereby protecting the LEDs from damage during beam mode switching.
Solution Approach 2:
The variable resistor controller applies a counter-action to the voltage drop by increasing the resistance value before the voltage drop occurs. This preliminary anti-action counteracts the harmful effect of voltage drop causing overcurrent, preventing the harmful current surge from damaging the LEDs when switching between high and low beam modes.
2Device complexity
If the output voltage of the DC-DC converter is allowed to drop when switching beam modes, then the circuit operation is simplified, but an overcurrent occurs that damages the light emitting elements
Solution Approach 1:
The variable resistor acts as an intermediary element between the DC-DC converter output and the light emitting elements. By controlling the variable resistor's resistance value, the system can allow the output voltage to drop during beam mode switching while the variable resistor compensates by increasing its resistance, thereby preventing overcurrent from reaching the LEDs. This intermediary approach maintains circuit simplicity while protecting the light emitting elements.
3Reliability
If experimental optimization is used to determine voltage values and retention times, then overcurrent can be reduced for specific LED specifications, but the solution is not universally applicable across different LED variations
Solution Approach 1:
The variable resistor controller dynamically adjusts the resistance value in real-time based on the switching event, rather than relying on fixed experimental optimization for specific LED specifications. This dynamic adjustment occurs immediately before or during the beam mode switch, automatically adapting to different LED variations without requiring re-optimization, thereby providing universal applicability across different LED specifications while maintaining overcurrent protection.
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 approach effectively prevents high currents and minimizes LED damage by proactively adjusting resistance values, ensuring consistent overcurrent prevention regardless of LED variations.
Implementation Method 1
a variable resistor controller to control a resistance value of the variable resistor. The adjuster is configured to change the number of light emitting elements that are lit among a plurality of light emitting elements connected in series. The variable resistor controller is configured to increase the resistance value of the variable resistor immediately before, or at the same time as, the time point at which the number of light emitting elements that are lit is reduced
Data Source
AI summary
A semiconductor integrated circuit for driving a light emitting element forms at least part of a light emitting element driving device configured to change the number of light emitting elements that are lit among a plurality of light emitting elements connected in series. The semiconductor integrated circuit includes a variable resistor controller configured to increase the resistance value of a variable resistor connected in series with the plurality of light emitting elements immediately before, or at the same time as, the time point at which the number of light emitting elements that are lit is reduced.