White LED Driver Regulating Voltage to Minimize Power Loss
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Solution Overview
Problem
White LEDs in parallel configurations experience poor current and brightness matching due to variance in forward voltage, requiring complex current regulation and DC-DC converters, which lead to inefficiencies and increased die area in integrated circuits.
Innovation Solution
A switchable current sink and DC-DC converter system that adjusts driving voltage and current to white LEDs, using a reference circuit to generate a second reference voltage for the DC-DC converter, allowing for regulated currents and minimized voltage drop, thereby optimizing efficiency and reducing die area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a DC-DC converter is used to regulate the driving voltage of white LEDs, then the voltage regulation is achieved, but the power loss increases and efficiency decreases
Solution Approach 1:
The patent dynamically adjusts the reference voltage parameter based on the actual forward voltage of the white LED. By changing the reference voltage to match the LED's actual voltage characteristics, the system achieves accurate voltage regulation without requiring excessive voltage headroom, thereby reducing power loss in the DC-DC converter and improving overall efficiency.
2Device complexity
If the voltage drop across the current source is kept constant for all load conditions, then the current regulation is simplified, but the efficiency varies considerably under different load conditions
Solution Approach 1:
The patent implements a dynamic reference voltage adjustment mechanism that adapts to different load conditions and LED forward voltage characteristics. Instead of using a fixed voltage drop assumption, the system continuously monitors and adjusts the reference voltage to match actual operating conditions, thereby maintaining high efficiency across varying load conditions while keeping the current source design relatively simple.
3Measurement precision
If each white LED is provided with an exclusive current source, then the current regulation precision is improved, but the die area occupied increases considerably
Solution Approach 1:
The patent combines multiple current source functions into a single shared current source that serves all white LEDs. By implementing a common current source with dynamic reference voltage adjustment, the system achieves precise current regulation for each LED without requiring separate current source circuits, thereby significantly reducing the die area while maintaining regulation precision.
4Device complexity
If white LEDs are connected in parallel, then the circuit complexity is reduced, but the current and brightness matching becomes poor due to forward voltage variance
Solution Approach 1:
The patent implements a feedback mechanism where the actual forward voltage of the white LED is measured and used to dynamically adjust the reference voltage. This feedback loop compensates for forward voltage variance between parallel-connected LEDs, ensuring accurate current and brightness matching while maintaining the simplicity of parallel circuit configuration.
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 system achieves high efficiency and reduced power loss by dynamically adjusting the driving voltage and current to white LEDs, ensuring consistent performance across varying load conditions and minimizing die area occupancy.
Implementation Method 1
a DC-DC converter coupled to anodes of the plurality of LEDs for providing the driving voltage to the plurality of LEDs
Implementation Method 2
a plurality of light emitting diodes (LEDs)
Data Source
AI summary
The present invention is an apparatus for driving white LEDs. The apparatus includes a switchable current sink, a DC-DC converter and a reference circuit. The DC-DC converter provides a driving voltage to a plurality of LEDs. The switchable current sink regulates currents through the plurality of LEDs, and the switchable current sink further provides a first reference voltage and outputs a plurality of voltage drops. The reference circuit receives the first reference voltage and the plurality of voltage drops to provide a second reference voltage to the DC-DC converter. The DC-DC converter adjusts the driving voltage provided to the plurality of LEDs according to the second reference voltage. In this way, the driving voltage is regulated to a minimum possible value and consequently the voltage drops across the switchable current sink is minimized. Hence, the LED driving system maintains higher efficiency.