LED Driver Dimming Control via Offset Voltage Isolation
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Solution Overview
Problem
Existing LED drivers face challenges in accurately controlling dimming due to offset voltages in error amplifiers, which affect the precision of LED current regulation.
Innovation Solution
An LED driver system comprising an LED current controller, a comparer, and a dimming controller, which includes a voltage level limiter and a voltage divider, to maintain a constant LED current by comparing sensing and reference signals and modifying output signals to achieve precise dimming control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an error amplifier is used to compare detection voltage and reference voltage for dimming control, then the LED current can be regulated, but offset voltage in the error amplifier causes inaccurate dimming control
Solution Approach 1:
The patent extracts the harmful offset voltage effect by separating the dimming control function from the error amplifier's voltage comparison function. The dimming controller independently generates dimming signals without being affected by the error amplifier's offset voltage, allowing accurate dimming control even when the error amplifier introduces voltage errors.
Solution Approach 2:
The patent introduces an intermediary approach by using a dedicated dimming controller that receives feedback from the LED current but processes it separately from the error amplifier's voltage comparison. This intermediary control path eliminates the direct influence of offset voltage on dimming accuracy while maintaining LED current regulation.
2Ease of operation
If the resistance value of the input terminal of the error amplifier is changed to control LED current, then the LED current can be adjusted, but the offset voltage is reflected in the output voltage causing dimming control difficulty
Solution Approach 1:
The patent segments the control functions into separate modules: the error amplifier handles voltage comparison for LED current regulation, while the dimming controller independently handles dimming control. This segmentation prevents the offset voltage in the error amplifier from affecting the dimming control accuracy, as each module operates independently with its own signal path.
3Productivity
If a related art LED driver uses error amplifier voltage comparison for dimming, then the system can control LED current, but the offset voltage reflects in output voltage reducing control precision
Solution Approach 1:
The patent implements feedback by having the dimming controller receive feedback signals from the LED current while maintaining an independent control path. The feedback mechanism allows the system to monitor LED current and adjust accordingly, but the dimming control precision is maintained by preventing offset voltage from the error amplifier from contaminating the feedback signal used for dimming control.
Data Source
AI summary
A light-emitting diode (LED) driver, an LED lighting apparatus, and a method of operating the LED lighting apparatus are provided. The LED driver may include an LED current controller configured to control an LED current, which flows through an LED array including a plurality of LEDs, such that the LED current is maintained at a constant level; a comparer configured to compare a sensing signal, which corresponds to a magnitude of the LED current, and a reference signal, and to obtain a first output signal based on a comparison result; and a dimming controller configured to modify the first output signal to obtain a second output signal for dimming of the plurality of LEDs, and to provide the second output signal to the LED current controller.