LED Matrix Switching to Exceed Driver Voltage Limits
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Solution Overview
Problem
In LED lighting applications, especially in automotive systems, the maximum output voltage is limited, restricting the number of LEDs that can be used in a string due to the total forward voltage exceeding the driver's capability, necessitating additional drivers and increasing costs.
Innovation Solution
The implementation of a power supply with a maximum voltage and a switch arrangement with parallel switches, a switching sequencer, and a controller to generate PWM switching patterns, ensuring the total forward voltage of active LEDs never exceeds the driver's maximum capacity, allowing for a greater number of LEDs and higher drive current without exceeding the driver's capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the number of LEDs in series is increased to achieve higher illumination intensity, then the total forward voltage exceeds the power supply capability, but the illumination intensity is improved
Solution Approach 1:
The LED string is divided into multiple groups, with each group containing a subset of LEDs that can be independently controlled. This segmentation allows the total forward voltage to be distributed across different groups, enabling higher illumination intensity through selective activation without exceeding the power supply voltage capability at any given moment.
Solution Approach 2:
The patent implements periodic switching of LED groups using PWM (pulse width modulation) control. Different LED groups are activated in alternating periods, and by controlling the duty cycle of each group, the overall illumination intensity is maintained at a high level while the instantaneous voltage requirement never exceeds the power supply capability.
2Power
If additional drivers are added to handle higher voltage requirements, then the power supply capability is extended, but the device complexity and cost increase
Solution Approach 1:
A single power supply unit is designed to handle multiple LED groups through intelligent control circuitry. This multi-functional power supply can dynamically adjust its output to drive different combinations of LED groups, eliminating the need for multiple dedicated drivers while maintaining extended power capability.
Solution Approach 2:
A control circuit acts as an intermediary between the single power supply and multiple LED groups. This intermediary manages the switching and power distribution, enabling one power supply to effectively drive more LEDs than its rated voltage would normally permit, thereby avoiding the need for additional driver circuits.
3Illumination intensity
If all LEDs are activated simultaneously to achieve maximum illumination, then the illumination intensity is maximized, but the total forward voltage exceeds the driver capacity
Solution Approach 1:
The system dynamically adjusts which LED groups are active based on real-time requirements. By continuously monitoring and adjusting the activation state of different LED groups, the system achieves maximum overall illumination intensity while ensuring that the instantaneous voltage demand never exceeds the driver's capacity through adaptive switching.
Solution Approach 2:
The patent changes the operational parameters of LED groups by controlling their duty cycles and activation sequences. By varying these parameters, the system optimizes the total illumination output while maintaining the voltage demand within driver capacity limits through precise parameter management.
Data Source
AI summary
A lighting unit includes a power supply that provides a maximum voltage and multiple LED lighting circuits. Each of the LED lighting circuits includes an LED string, multiple switches, a switching sequencer and a switch controller. The LED string includes multiple series-connected emitters having a total forward voltage that exceeds the maximum voltage of the power supply. Each of the switches is coupled in parallel with a respective LED of the LED string. The switching sequencer provides a sequence of switching patterns such that a total forward voltage of simultaneously active LEDs in each switching pattern does not exceed the maximum voltage of the power supply. The switch controller actuates switches according to each of the switching patterns in the sequence. The LED string of each of the plurality of LED lighting circuits is arranged in a two-dimensional array.