LED Driver Average Current Estimation via Switching Instance Sampling
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Solution Overview
Problem
Existing LED drivers require extensive calculation time or additional hardware to determine the average current accurately, leading to delays and increased complexity and cost.
Innovation Solution
The LED driver employs a switched mode power supply with a control unit that estimates the average current by measuring at specific instances relative to the opening and closing of the switch, reducing computational effort and eliminating the need for multiple current measurements, and uses a calibration process to determine the optimal measurement instance for accurate feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple current measurements are taken and extensive calculations are performed to determine average current accurately, then measurement precision is improved, but loss of time increases due to extensive calculation time
Solution Approach 1:
The patent extracts only the essential information needed for average current calculation by taking measurements at specific critical instances (switching events) rather than continuously sampling. This selective extraction of measurement points reduces computational burden while maintaining accuracy.
Solution Approach 2:
The control unit is configured to measure current at predetermined instances relative to switch operation (e.g., at the moment of switching or at specific intervals therefrom). This preliminary positioning of measurement timing eliminates the need for post-processing multiple samples, reducing calculation time while preserving measurement precision.
2Measurement precision
If multiple current measurements and calculations are performed to determine average current, then measurement precision is improved, but device complexity increases due to additional hardware requirements
Solution Approach 1:
The control unit performs multiple functions: it controls the switch operation, measures current at specific instances, and calculates average current. This multi-functionality eliminates the need for separate dedicated measurement hardware, reducing device complexity while maintaining measurement precision.
Solution Approach 2:
The system uses its own existing resources (the control unit that already controls switching) to perform the measurement and calculation functions. The control unit leverages its inherent capabilities to determine average current without requiring additional external measurement devices, thereby reducing hardware complexity.
3Measurement precision
If current is measured at multiple instances to ensure accuracy, then measurement precision is improved, but productivity decreases due to processing delays
Solution Approach 1:
The control unit measures current at predetermined instances that are strategically chosen to provide accurate average current information. By positioning measurements at these optimal moments (relative to switching events), the system obtains sufficient accuracy data without requiring multiple sequential measurements, thus maintaining fast control response and high productivity.
Data Source
Figure 1a~2a
Figure 2b~3
AI summary
An LED driver for powering an LED fixture is described, the LED driver comprising: - a switched mode power supply for providing a current to the LED fixture, and - a control unit for controlling a switch of the switched mode power supply; the control unit comprising an input terminal for receiving a set point representing a desired output characteristic of the LED fixture; the control unit further being adapted to - periodically determine an opening instance of said switch and a closing instance of said switch; - determining an average current estimate based on at least one measurement of the current to the LED fixture at at least one measurement instance determined on the basis of at least one of the opening instance or the closing instance of the switch. - applying the average current estimate as a feedback signal representing the average current for controlling the LED current.