Vehicle Lighting Control Circuit for Switch Discrimination
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Solution Overview
Problem
Existing vehicular lighting control systems face issues with accurately distinguishing between the turning-on of winker and hazard switches, especially when connected in parallel, leading to potential erroneous energization of LED lighting due to leakage currents and asynchronous input voltages, while also requiring a reduction in the number of harnesses.
Innovation Solution
A lighting control system with separate input ports for left and right switch signals, a judging mechanism to differentiate between winker and hazard switch activations based on signal timing, and a three-contact hazard switch to simplify the circuit arrangement, ensuring accurate switch differentiation and reduced harness usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If winker switch and hazard switch are connected in parallel between controller and ground, then the number of harnesses is reduced, but leakage current may erroneously turn on LED lighting
Solution Approach 1:
The patent introduces a current detection circuit as an intermediary between the parallel-connected switches and the LED lighting. This circuit monitors the current flowing through each switch path and only activates the LED when current exceeds a predetermined threshold, effectively filtering out leakage currents while maintaining the simplified parallel harness structure
Solution Approach 2:
The patent changes the parameter for LED activation from simple voltage presence to current magnitude threshold. By monitoring whether current exceeds a predetermined value, the system can distinguish between legitimate switch activation and leakage current, maintaining reliability while using the simpler parallel harness configuration
2Device complexity
If winker switch and hazard switch are connected in parallel with common wires, then harness quantity is reduced, but mechanical hazard switch action generates asynchronous input voltages that prevent accurate switch discrimination
Solution Approach 1:
The patent introduces a timing detection mechanism as an intermediary that processes the asynchronous voltage signals from the parallel switches. By measuring the timing relationship between signals on different wires and comparing against predetermined time intervals, the system can accurately distinguish between winker and hazard switch activations despite asynchronous voltage generation
Solution Approach 2:
The patent implements preliminary timing analysis of incoming signals before determining switch activation. By detecting whether signals appear simultaneously or with time delay, and comparing this timing pattern against expected patterns for each switch type, the system can accurately discriminate between winker and hazard modes despite the asynchronous nature of mechanical switch operation
Data Source
AI summary
A lighting control system is provided with a blinker switch, a hazard switch, and a control circuit which controls the flashing of blinker lamps. The CPU of the control circuit, after detecting an input signal from one switch input port among a left side and a right side switch input port, determines that the hazard switch is switched on when an input signal from the other of the switch input ports is detected within a predetermined time, and determines that the blinker switch is switched on when no input signal from the other of the switch input ports is detected.