Inverter Lamp Current Regulation via Active Component Extraction
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Solution Overview
Problem
Existing methods for regulating lamp current in lighting systems using DC voltage and inverters are ineffective due to the interference of capacitive currents, which leads to incorrect dimming operations, especially under heavy dimming conditions.
Innovation Solution
Determining the actual lamp current by forming a quotient from the power supplied to the inverter and the voltage drop across the light source, and using this value to generate control signals for the inverter's clocked switches, thereby isolating the active current component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the lamp current is determined by measuring the voltage drop across a shunt resistor connected in series with the lamp, then the current measurement is obtained, but the capacitive current component outweighs the ohmic current component causing incorrect dimming operation
Solution Approach 1:
The patent extracts only the active current component from the total current by measuring it at the specific moment when the lamp voltage reaches its peak value. This eliminates the capacitive current component that causes measurement errors during dimming operations.
Solution Approach 2:
The control circuit is configured to take the measurement at the predetermined point in time when the lamp voltage reaches its peak value, which occurs before the capacitive current component becomes dominant. This preliminary timing ensures accurate active current measurement before distortion occurs.
2Ease of operation
If the total current is measured through the shunt resistor, then current data is obtained, but the current is out of phase with the lamp current making correct dimming impossible
Solution Approach 1:
The measurement is performed at the specific moment when the lamp voltage reaches its peak value, which is a predetermined point in the AC cycle. This timing ensures that the measured current is in phase with the lamp current, eliminating phase displacement errors while maintaining measurement simplicity.
3Measurement precision
If the measurement is taken at the point when lamp voltage reaches peak value, then the active current component is correctly detected, but this solution is only available for specific waveforms
Solution Approach 1:
The control circuit is designed to detect the lamp voltage peak and perform current measurement at that specific moment. This preliminary timing action ensures accurate active current detection regardless of the waveform shape, as it always measures at the point where voltage and current are in phase.
Data Source
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AI summary
The invention relates to a method and to an operating device for operating a lighting means (61), wherein the current flowing through the lighting means (61) is regulated. The lighting means (61) is provided with an alternating power output from an inverter (4). To regulate the current, a measurement signal UL is generated which corresponds to the voltage across the lighting means (61), said signal being sent to the control circuit section (7). The power output from the inverter (4) to the lighting means (61) is measured in the form of a measurement signal PI which drops across a shunt resistor (43) and is fed to the control circuit section (7). The control circuit section (7) determines the actual value of the current flowing through the lighting means (61) from the power and from the voltage drop across the lighting means (61), and compares said value with a current setpoint. The control circuit section (7) generates clock signals for the electronic switches (41, 42) of the inverter as a control value.