Hybrid Analog-Digital Dimming Circuit for Fast High-Resolution Control
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Solution Overview
Problem
Existing methods for controlled dimming of light sources, such as LEDs and gas discharge lamps, are hindered by slow control loops due to the need for high-bit A/D converters, which slow down the entire dimming process.
Innovation Solution
Converting digital dimming setpoint values into analog values, comparing them with actual values to determine an analog control deviation, and then converting this deviation into a digital control signal, allowing for a reduced-bit A/D converter that speeds up the control loop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-bit A/D converters are used to maintain dimming resolution, then measurement precision is improved, but control loop speed deteriorates
Solution Approach 1:
The patent segments the control loop into two distinct paths: an analog path for high-precision measurement of the control deviation (using a high-bit A/D converter only when necessary), and a digital path for standard control operations. This segmentation allows the system to maintain high dimming resolution while avoiding the continuous speed penalty of high-bit conversion, as the high-precision path is only activated when fine resolution is actually needed.
Solution Approach 2:
The patent dynamically changes the bit depth parameter of the A/D converter based on operating conditions. When the control deviation is large, a lower-bit converter is used for faster response. When the control deviation approaches zero and fine dimming resolution is needed, the system switches to a higher-bit converter. This parameter change allows the system to optimize between speed and precision in real-time.
2Measurement precision
If high-bit A/D converters are used for converting actual values, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts the high-precision conversion function from the main control loop and places it in a separate, optional path that is only activated when fine dimming resolution is required. This allows the majority of control operations to use simpler, lower-bit converters, reducing overall device complexity while maintaining the capability for high-precision measurement when needed.
3Measurement precision
If analog control deviation is converted to digital using high-bit A/D converter, then control precision is improved, but productivity decreases
Solution Approach 1:
The patent makes the A/D converter bit depth dynamic rather than static. The converter adapts its resolution based on the magnitude of the control deviation and the current dimming state. When high precision is not critical for productivity, the system operates with lower-bit conversion for faster throughput. When precision becomes critical (e.g., near minimum dimming levels), the system dynamically switches to higher-bit conversion, thus optimizing the trade-off between control precision and productivity in real-time.
Data Source
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AI summary
The invention relates to a method and to a circuit arrangement for dimming an illuminant (1) according to digital dimming values (Dd) by regulation. In order to ensure that slow dimming is possible at high resolution, but the regulation takes place quickly at the same time, according to the invention the controller (7) operates digitally but the target value/actual value comparison in the comparator (13) takes place with analog signals. To this end, the digital dimming values (Dd) are first converted to analog dimming values (Da) in a D/A converter (11). The analog control deviation (xa) ascertained by the analog operating comparator (13) is then again converted by means of an A/D converter (14) to a digital control deviation (xd) so that the digital controller (7) can process it. The A/D converter (14) must only process the control deviation - small, in comparison to the returned actual values - and ends up with a relatively low bit count. The D/A converter (11) should additionally distort exponentially in order to compensate for the logarithmic dependence of the subjectively received brightness of the physically measurable light strength of the illuminant (1).