Parallel Load Failure Detection Using Predefined Current Pulse
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing circuit arrangements for lighting devices with consumers connected in parallel, such as LEDs, face challenges in accurately detecting individual failures due to the high variability of the K-factor (up to 200% to 300%) in semiconductor switch devices, leading to inaccuracies in load current measurement and inability to reliably distinguish between different load currents.
Innovation Solution
A circuit arrangement that generates a predefined current pulse at the load current output of the semiconductor switch device to determine the transfer factor, allowing for precise calculation of a diagnostic current limit value, enabling reliable detection of consumer failures by comparing the detected diagnostic current with the determined limit value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the diagnostic current provided by the semiconductor switch device is used to measure load current, then the measurement can be implemented without additional hardware, but the measurement precision deteriorates due to K-factor variability of up to 200% to 300%
Solution Approach 1:
The patent applies preliminary action by pre-determining the transfer factor through a calibration process before actual operation. A test current is applied to the semiconductor switch device, and the resulting diagnostic current is measured to calculate the actual transfer factor. This pre-calibrated transfer factor is then stored and used for accurate load current measurement during normal operation, eliminating the need for complex real-time calibration hardware.
Solution Approach 2:
The patent changes the operational parameters by introducing a test current mode that switches the semiconductor switch device between normal operation and calibration mode. During calibration, a known test current is applied and the diagnostic current response is measured to determine the actual transfer factor. This parameter change enables accurate measurement without requiring complex hardware, as the system adapts its operating state to perform self-calibration.
2Measurement precision
If additional hardware components such as measuring resistors and integrated circuits are added to accurately measure load current, then the measurement precision improves, but the device complexity and cost increase significantly
Solution Approach 1:
The patent implements self-service by enabling the semiconductor switch device to perform its own calibration and measurement functions using its existing diagnostic current output. The system uses itself as the calibration object by applying a known test current and measuring its own diagnostic current response to determine the transfer factor. This eliminates the need for external measuring resistors, integrated circuits, or other additional hardware components.
Solution Approach 2:
The patent applies universality by making the semiconductor switch device perform multiple functions: it acts as both the power switch for the load and the measurement object for calibration. The same diagnostic current output intended for monitoring purposes is repurposed for calibration, and the same control circuitry is used for both switching and measurement functions. This multi-functionality eliminates the need for separate dedicated measurement hardware.
3Ease of manufacture
If the manufacturer's specified K-factor range is used for load current calculation, then the implementation is simple, but the reliability deteriorates due to the large tolerance range of up to 200% to 300%
Solution Approach 1:
The patent implements feedback by using the actual diagnostic current response of the specific semiconductor switch device to determine its unique transfer factor. Instead of relying on the manufacturer's general K-factor range, the system measures the actual diagnostic current output for a known test current and uses this feedback to calculate the precise transfer factor. This feedback mechanism ensures reliable failure detection by using device-specific rather than manufacturer-average parameters.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present invention discloses a circuit arrangement in a control unit 100 for controlling parallel connected consumers V1, V2, in particular light sources of a lighting device.The circuit arrangement comprises a semiconductor switching device 10, which in turn comprises a load current output 13 for supplying a load current IL to the consumers V1, V2, and a diagnostic current output 13 for outputting a diagnostic current ID, ID1, ID2, ID3, which is proportional to a current flowing at the load current output 12, wherein the control unit 100 is configured to generate a predefined current pulse IP, which can be superimposed on the load current IL at the load current output 12, to determine a transfer factor K based on the load current IL and the predefined current pulse IP, to determine a limit value G based on the transfer factor K and the load current IL, to determine a diagnostic current limit value IDG from a predefined load current limit value ILG and the transfer factor K, and to output a consumer failure signal depending on a comparison of the diagnostic current ID, ID1, ID2, ID3 with the limit value G and the diagnostic current limit value IDG.