Current Mirror Circuit for LED String Fault Isolation
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Solution Overview
Problem
Current mirror circuits fail to operate when an open circuit fault occurs in parallel LED strings, leading to current imbalance and incorrect selection of the faulty string as the current reference, which affects the overall LED system's light uniformity and lifetime.
Innovation Solution
A current mirror circuit with a selection circuit that connects the circuit branch with the smallest current to the bases of balancing transistors and an isolation circuit that detects and isolates open circuit faults, using opamps for feedback assistance and isolation switches to disconnect faulty branches, preventing incorrect current reference selection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the circuit selects the current source with smallest current as reference, then current balancing is achieved, but open circuit faults cause incorrect selection of faulty string as reference
Solution Approach 1:
The patent introduces an intermediary fault detection circuit and isolation mechanism between the current sources and the current reference selection. This intermediary layer monitors the status of each LED string and prevents faulty strings from being selected as current references, ensuring that the smallest current selection criterion operates only on healthy strings.
2Adaptability or versatility
If selection switches are included in the current mirror circuit, then re-configurability is improved, but complexity of the circuit increases
Solution Approach 1:
The patent applies self-service by implementing a self-diagnosing and self-isolating current mirror circuit. The fault detection circuit automatically identifies open circuit faults without external intervention, and the isolation switches automatically disconnect faulty strings, enabling the circuit to re-configure itself to maintain operation of healthy LED strings.
Data Source
AI summary
Provided is a current mirror circuit (1) for balancing respective currents in a plurality of parallel circuit branches (2) in a target circuit (3), the current mirror circuit (1) including: a plurality of balancing transistors (4), each having a connector (5), an emitter (6), and a base (7), the collector (5) and emitter (6) of each balancing transistor (4) connected in series with a respective circuit branch (2); a selection circuit (8) that connects the circuit branch (2) having the smallest current amongst the circuit branches (2) to the bases (7) of each balancing transistor; and an isolation circuit (9) that isolates circuit branches (2) having an open circuit fault from the rest of the target circuit (3). An associated method of balancing respective currents in a plurality of parallel circuit branches (2) in a target circuit (3) is also provided.