LED Channel Current Control via Offset Voltage Setting
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Solution Overview
Problem
Existing LED light emitting devices with multiple channels face challenges in uniformly sustaining the magnitude of channel current due to errors in offset voltage, reference current, and resistor values, leading to inconsistencies in current flow across LED channels.
Innovation Solution
The solution involves a constant current source with multiple operating amplifiers, offset voltage setting units, and reference current generators to ensure each LED channel receives a predetermined setting channel current, using feedback and reference voltages to adjust and synchronize channel currents across all channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a constant current source with operating amplifier is used to control LED channel current, then the channel current can be set to a desired magnitude, but errors in offset voltage, reference current, and resistor values cause the actual current to deviate from the preset value
Solution Approach 1:
The patent applies preliminary action by pre-calculating and setting the offset voltage of the operating amplifier before actual LED operation. The offset voltage is set to a specific value that compensates for errors in reference current and resistor values, so that when the LED channel operates, the current is already corrected to match the preset value accurately
Solution Approach 2:
The patent uses feedback by continuously monitoring the actual LED channel current and comparing it with the preset current value. The operating amplifier adjusts its output based on the difference between these values, and the offset voltage is set to ensure that the feedback loop compensates for component errors, achieving accurate current control
2Reliability
If detection resistor is trimmed to achieve preset channel current, then current uniformity can be improved, but the process is complex and errors still occur when channel current differs from preset value
Solution Approach 1:
The patent extracts the error compensation function from the detection resistor trimming process and transfers it to the operating amplifier's offset voltage setting. Instead of adjusting the detection resistor to compensate for errors, the system sets the offset voltage to achieve the same compensation effect, simplifying the overall process
Solution Approach 2:
The patent changes the parameter being adjusted from detection resistor value to operating amplifier offset voltage. By setting the offset voltage to a specific value that compensates for component errors, the system achieves accurate current control without the complexity of resistor trimming
3Measurement precision
If offset voltage of operating amplifier is canceled, then current control accuracy can be improved, but errors in reference current and resistor values still limit uniformity
Solution Approach 1:
The patent converts the harmful effect of offset voltage into a beneficial compensation mechanism. Instead of trying to eliminate the offset voltage, the system sets it to a specific value that compensates for errors in reference current and resistor values, turning a source of error into a correction tool
Data Source
AI summary
An LED light emitting device and a method of driving the same are provided, and technology that can uniformly sustain the magnitude of a channel current flowing to a plurality of LED channels is disclosed. The LED light emitting device includes: a plurality of LED channels that are formed with a plurality of LED elements that are continuously connected in series; and a constant current source that controls each channel current flowing to the plurality of LED channels according to a predetermined channel reference current to be a predetermined setting channel current, wherein the constant current source includes a plurality of operating amplifiers that control the magnitude of each of the channel currents, and a feedback voltage generating according to a predetermined offset reference current is input to a second input terminal of an operating amplifier for an offset setting period that sets an offset voltage of the plurality of operating amplifiers, a reference voltage generating according to a channel reference current is input to a first input terminal of the operating amplifier, and an offset voltage of each of the plurality of operating amplifiers is set so that an actual channel current may be identical to a predetermined setting channel current.