Lighting System Current Measurement Using Single Sensor and PWM Switching
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Solution Overview
Problem
Existing lighting systems face challenges in efficiently monitoring and managing the operation of multiple lighting modules connected to a voltage source, particularly in accurately measuring current and detecting failures, which often requires multiple current sensors and measurement channels.
Innovation Solution
A lighting system that employs a single current sensor connected in series with the voltage source and a control unit generating PWM drive signals to selectively connect and disconnect lighting modules, allowing for the estimation of total and individual currents using a single measurement channel, thereby reducing the need for multiple sensors and improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple current sensors and measurement channels are used to monitor each lighting module, then measurement precision and reliability are improved, but device complexity and cost increase
Solution Approach 1:
The patent merges multiple measurement functions into a single measurement channel by sequentially switching between different lighting modules using electronic switches. The control unit coordinates the switches to isolate individual modules for measurement, allowing one current sensor to capture current data for all modules at different time points, thereby reducing hardware complexity while maintaining measurement precision
Solution Approach 2:
The system employs periodic switching of electronic switches to sequentially connect different lighting modules to the measurement channel. The control unit generates periodic drive signals that switch modules on and off in a predetermined sequence, enabling time-multiplexed current measurements. This periodic action allows a single sensor to capture data from multiple modules over time, resolving the contradiction between measurement accuracy and system complexity
2Device complexity
If a single current sensor is used with sequential switching, then device complexity is reduced, but measurement precision may deteriorate due to temporal separation of measurements
Solution Approach 1:
The control unit implements feedback by continuously monitoring current measurements from the single sensor and using this data to adjust and coordinate the switching of electronic switches. The measured current values feed back to the control unit, which processes the information to determine module status and control subsequent switching actions, ensuring accurate individual module monitoring despite temporal separation of measurements
Solution Approach 2:
The system performs preliminary actions by pre-coordinating the switching sequence of electronic switches before measurements are taken. The control unit establishes a predetermined switching pattern that ensures each lighting module is isolated and measured in turn, preparing the measurement channel in advance for each module. This preliminary coordination ensures that measurements are taken under optimal conditions, maintaining precision while using a single sensor
3Ease of operation
If all lighting modules are connected simultaneously to the voltage source, then ease of operation is improved, but the ability to detect individual module failures is reduced
Solution Approach 1:
The patent applies segmentation by dividing the monitoring function into sequential segments through electronic switching. While all modules remain connected to the voltage source for normal operation, the electronic switches enable the system to segment the current path for measurement purposes, isolating individual modules one at a time. This allows the system to maintain simple parallel operation while periodically segmenting the circuit for individual module monitoring and failure detection
Solution Approach 2:
The system employs dynamic switching to transition between different operational states. The electronic switches dynamically reconfigure the circuit topology based on measurement requirements, allowing all modules to be connected simultaneously during normal operation, then dynamically isolating individual modules for measurement. This dynamic reconfiguration enables the system to adapt between ease of operation and failure detection capabilities as needed
Data Source
Figure 1~2b
Figure 2c~3
Figure 4~5b
AI summary
There is described a lighting system. The lighting system comprises a voltage source (12) configured to generate a constant direct current adapted to supply a plurality of lighting modules (20a..20n). Moreover, the system comprises a number n of electronic switches (SWa..SWn), wherein each electronic switch (SWa..SWn) is configured to selectively connect a respective lighting module (20a..20n) to the voltage source (12) as a function of respective drive signals (PWMa..PWMn) generated by a control unit (102). A current sensor (104) is connected in series with the voltage source (12), in order to detect a measurement signal (CS) indicative of the current provided by the voltage source (12). Specifically, the control unit (102) varies the drive signals (PWMa..PWMn), such that: - in a first instant, all lighting modules (20a..20n) are connected to the voltage source (12); and - during a sequence of (n - 1) instants, each time a different set of lighting modules (20a..20n) is connected to the voltage source (12). The control unit (102) then determines the current flowing through all lighting modules (20a..20n) as a function of the measurement signal (CS) detected in the first instant, and determines the currents which flow through the various lighting modules (20a..20n) as a function of the measurement signals (CS) detected during the sequence of instants.