LED Driver Timer Calibration Using AC Mains Zero-Crossings
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Solution Overview
Problem
Existing operating devices for lighting means, such as LEDs, face challenges in achieving high accuracy for time measurement without the space and cost disadvantages of external crystal timers, as internal timers provide lower accuracy.
Innovation Solution
The operating device uses an internal timer calibrated based on the stable and known frequency of the AC mains voltage, employing a detection unit to detect zero-crossings and a processing unit to assign oscillations of an internal oscillator to time intervals, thereby ensuring high accuracy without an external crystal timer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an external crystal timer is used for time measurement, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The invention extracts the time measurement function from a separate external crystal timer component and integrates it into the existing microcontroller unit. The MCU's internal timer is calibrated using AC mains voltage zero-crossing detections, eliminating the need for an external crystal timer while maintaining measurement precision.
Solution Approach 2:
The invention makes the AC mains voltage serve multiple functions: it provides power to the operating device and simultaneously serves as a calibration reference for the internal timer. By detecting zero-crossings of the AC voltage, the system achieves accurate time measurement without requiring additional dedicated components.
2Device complexity
If an internal timer is used for time measurement, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The invention implements a feedback mechanism where the microcontroller detects zero-crossings of the AC mains voltage and uses this information to校准 the internal timer. The system continuously monitors the AC voltage phase and adjusts the timer calibration accordingly, ensuring accurate time measurement despite using only the internal timer.
Solution Approach 2:
The invention changes the operational parameters of the internal timer by calibrating it based on the known frequency characteristics of the AC mains voltage. By establishing a relationship between the AC voltage zero-crossings and the internal timer counts, the system achieves high measurement precision without increasing device complexity.
Data Source
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AI summary
The present invention provides an operating device (1) for operating one or more lighting means (8), the operating device (1) comprising: an power input (IN, IN') electrically connectable to an external AC voltage source (7), preferably mains, an power output (OUT, OUT') to which the one or more lighting means are electrically connectable, a supply circuitry (2) configured to supply via the power output (OUT, OUT') the one or more lighting means (8) with DC power from an AC voltage provided by the external AC voltage source (7) via the power input (IN, IN') to the supply circuitry (2), and a control circuitry (3) comprising a processing unit (3a) configured to control the supply circuitry (2) and an internal timer (3b) configured to provide to the processing unit (3a) a first clock signal; wherein the processing unit (3a) is configured to calibrate the internal timer (3b) on the basis of the temporal course of the AC voltage. In addition a luminaire comprising the operating device according to the present invention and a calibration method are provided.