Vehicle Direction Indicator Hazard Circuit Design
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Solution Overview
Problem
Existing direction indicator systems fail to reliably maintain hazard operations when the ignition switch is turned off due to inaccurate current detection thresholds and the complexity of using microcomputers or logic circuits.
Innovation Solution
A direction indicator system with a hazard detecting unit, power holding unit, and power supplying unit that uses a capacitor and resistor to maintain hazard operations by detecting the hazard switch state through direction indicator lamp connection terminals and supplying voltage from a battery connection terminal, even when the ignition switch is off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current detection threshold is set higher to avoid false hazard detection, then false detection is reduced, but hazard operation cannot be detected when battery voltage is low
Solution Approach 1:
The patent changes the detection parameter from current magnitude to current direction. By detecting the direction of current flow through the hazard switch rather than the magnitude of current through the lamps, the system avoids threshold sensitivity issues entirely. This directional detection method works reliably across all battery voltage conditions without false positives or negatives.
2Reliability
If microcomputer or logic circuit is used to maintain hazard operation, then hazard maintaining function is achieved, but circuit becomes large scaled and complicated
Solution Approach 1:
The patent extracts the essential hazard detection and maintaining function from complex microcomputer or logic circuit implementations and implements it using a simple current direction detection circuit. By taking out only the necessary functional elements (current direction sensing and switch state monitoring), the system achieves hazard maintaining capability with minimal circuit complexity.
Solution Approach 2:
The hazard maintaining function is achieved through the inherent characteristics of the electrical circuit itself rather than requiring external control systems. The circuit automatically maintains hazard operation by continuously monitoring current direction and switch state, eliminating the need for microcomputers or complex logic circuits.
3Device complexity
If determination threshold is set at midpoint between TH1 and TH2, then circuit complexity is reduced, but hazard operation cannot be detected when one lamp is disconnected
Solution Approach 1:
Instead of detecting hazard operation by measuring current magnitude (which requires threshold comparison and fails when lamps are disconnected), the patent inverts the approach by detecting current direction. This inverted method reliably identifies hazard operation regardless of lamp connection status, as the current direction through the hazard switch remains characteristic of hazard mode even when individual lamps are disconnected.
Data Source
AI summary
A direction indicator system 1 includes an ignition switch 3, a hazard switch 4, a direction indicator switch 5, direction indicator lamps 6A, 6B, direction indicator lamps 7A, 7B, and a direction indicator device 2. The direction indicator device 2 detects that the switch 4 is in an ON state via direction indicator lamp connection terminals L-SW, R-SW, performs a hazard operation to blink both the direction indicator lamps 6A, 6B and the direction indicator lamps 7A, 7B by a drive current output from a drive current output terminal LOAD with a blinking period T in a case where the switch 3 is in the ON state when the switch 4 is put into the ON state, and operates with a voltage supplied from a battery connection terminal BAT1 to output the drive current when the switch 3 is put into an OFF state during the hazard operation.