Illuminant Dimming Circuit Using Analog Deviation Digitization
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Solution Overview
Problem
Existing methods for controlled dimming of illuminants, such as LED and gas discharge lamps, require high-resolution A/D converters that operate slowly, leading to a slow control loop due to the need to digitize analog actual values, which limits the speed and efficiency of the dimming process.
Innovation Solution
Converting digital dimming values into analog values, comparing them with analog actual values to determine an analog control deviation, and then converting this deviation into a digital control deviation, allowing for a reduced bit number A/D converter and faster control loop operation, with the aid of a PI controller to minimize control differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-resolution A/D converters are used to digitize analog actual values, then measurement precision is improved, but the control loop speed deteriorates
Solution Approach 1:
The patent segments the control loop into two distinct paths: an analog path for computing the control deviation (difference between setpoint and actual value) and a digital path for processing the corrected setpoint. This segmentation allows the A/D converter to operate at lower resolution since it only needs to digitize the small control deviation signal rather than the full-range actual value signal, thereby improving control loop speed while maintaining sufficient measurement precision for control purposes.
2Measurement precision
If high bit number A/D converters are used, then control precision is improved, but the operating speed deteriorates
Solution Approach 1:
The patent applies local quality by matching the A/D converter resolution to the specific requirements of the signal being digitized. Since the control deviation signal has a much smaller amplitude range than the actual value signal, a lower bit-number A/D converter is sufficient for this local requirement. This localized adaptation of precision requirements reduces conversion time while maintaining adequate control precision for the deviation correction function.
3Measurement precision
If analog actual values are directly digitized, then control accuracy is maintained, but device complexity increases
Solution Approach 1:
The patent extracts the control deviation computation from the digital domain and performs it in the analog domain using operational amplifiers. This extraction eliminates the need for high-resolution A/D converters and complex digital signal processing, thereby reducing device complexity while maintaining control accuracy through precise analog computation of the deviation signal before it is digitized at lower resolution.
Data Source
AI summary
Techniques for controlled dimming of an illuminant such as, for example, a light-emitting diode (LED), an organic light-emitting diode (OLED) or gas discharge lamp are described herein. In one example, a control difference formed by subtracting actual values from desired values (dimming values) is smaller than actual values fed back by the lamp. Thus, without directly digitizing an analog feedback variable, the example digitizes a control difference (control deviation) determined in the analog domain, in order to process the latter in a digital control algorithm that determines a digital manipulated variable that influences power to the illuminant.