LED Drive Circuit Defect Mode Using Input Nodes
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Solution Overview
Problem
Existing LED drive circuits require additional communication pins to report failures, increasing system complexity and cost.
Innovation Solution
The drive circuit monitors the LED string for shorts and changes to a defect mode, operating in a cycle that deactivates and activates the string to detect persistent faults, using only existing input nodes to communicate failure detection without additional pins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dedicated communication channel is used to report LED failures, then failure detection capability is improved, but device complexity and cost increase due to additional pins
Solution Approach 1:
The existing input nodes are made multi-functional by allowing them to serve both their original purpose (receiving input voltage) and a new purpose (communicating failure status). The drive circuit leverages the existing bidirectional nature of the input nodes to transmit defect information back to the control circuit without requiring dedicated communication pins, thus achieving universal use of existing components.
Solution Approach 2:
The drive circuit autonomously monitors the LED string for shorts and self-detects defects without external assistance. Upon detecting a defect, it automatically changes to defect mode and uses the existing input nodes to communicate the failure status back to the control circuit, enabling the system to self-report errors without additional communication infrastructure.
2Loss of information
If the LED string remains continuously activated in defect mode, then visibility is maintained, but current consumption increases
Solution Approach 1:
Instead of continuous activation, the LED string is activated periodically in defect mode according to a defect cycle. The drive circuit switches between activating and deactivating the LED string, allowing status visibility during activation periods while reducing overall current consumption through deactivation periods. This periodic operation balances information visibility with energy efficiency.
Solution Approach 2:
The drive circuit maintains continuous monitoring and communication capability even when the LED string is deactivated. The defect mode operation ensures that failure status is continuously communicated to the control circuit through the input nodes, while the LED string itself is activated only when necessary for visibility, thus maintaining useful action continuity in terms of fault detection while optimizing energy use.
Data Source
AI summary
An electronic circuit and a method are disclosed. The electronic circuit includes an LED circuit, wherein the LED circuit (1) includes: an input (11, 12) configured to receive an input voltage (VIN); a drive circuit (2A) connected to the input (11, 12); and an LED module (3A) connected to the drive circuit (2A) and comprising an LED string (41) with at least one LED. The drive circuit (2A) is configured to monitor the LED module (3A) for the occurrence of an LED short in the LED string (41) and to change from a normal mode to a defect mode upon detection of the LED short, and the drive circuit (2A) is configured, in the defect mode, to operate the LED string (41) in at least one defect cycle that includes deactivating the LED string (41) for a deactivation period, activating the LED string for an activation period, and checking for the persistence of the LED short in the activation period.