LED Abnormality Detection Circuit with Integrated Pull-Up
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Solution Overview
Problem
Existing abnormality detection devices for LEDs in vehicles fail to categorize failure states such as short-to-ground, short-to-power, and disconnection accurately without user notice and consume current during detection, and require external pull-up resistors leading to unintended lighting.
Innovation Solution
An abnormality detection device with a control unit, switching elements, and a detection unit that determines the state of the load by comparing voltage levels after switching the power supply off, allowing for categorization without user notice and without consuming current, using a configuration that includes a high side or low side type driver circuit and a constant current circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an external pull-up resistor is used for IPD to detect disconnection in extinguished state, then disconnection detection is enabled, but the LED lights unintentionally during determination operation
Solution Approach 1:
The patent removes the external pull-up resistor from the circuit and integrates the pull-up function internally within the IPD through a built-in pull-up circuit. This eliminates the unintended LED lighting issue caused by external pull-up resistors while maintaining disconnection detection capability. The internal pull-up circuit is controlled to activate only during detection phases, preventing harmful unintended lighting during normal operation.
Solution Approach 2:
The IPD is designed with multi-functionality, serving both as a driver for LED control and as an abnormality detection device. The built-in pull-up circuit and detection unit enable the IPD to perform both driving and detection functions, eliminating the need for separate external detection circuits and pull-up resistors, thereby preventing unintended LED lighting while maintaining detection accuracy.
2Object-affected harmful factors
If pulse width is controlled to not light the LED during detection, then user notice is avoided, but detection time must be extended for capacitor charging
Solution Approach 1:
The patent performs preliminary charging of the capacitor during the LED on-time period before detection. The capacitor is charged while the LED is lit, so that when the LED turns off for detection, the capacitor already has sufficient charge to maintain the pull-up voltage. This eliminates the need for extended detection time and allows detection to occur immediately when the LED is off, avoiding user notice while maintaining timely detection.
3Measurement precision
If pull-up circuit with pull-up switching element is used to detect disconnection and short-to-power, then failure state categorization is enabled, but additional circuit complexity is introduced
Solution Approach 1:
The patent merges the pull-up circuit, detection unit, and failure state categorization functions into a single integrated IPD chip. The pull-up switching element is integrated within the IPD, and the detection unit analyzes voltage levels to categorize failures as disconnection, short-to-power, or short-to-ground. This integration reduces external circuit complexity while maintaining accurate failure state categorization capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate categorization of LED failure states without user awareness and reduces power consumption during detection, using standard circuits without expensive components.
Implementation Method 1
a detection unit that outputs a signal based on comparison between a voltage of the load connection terminal and a predetermined reference voltage
Data Source
AI summary
An abnormality detection device includes a load connected to a load connection terminal; a first switching element, having one end connected to the load connection terminal, that switches between connection and disconnection of a power supply to the load; a control unit that switches between an on state and an off state of the first switching element; a detection unit that outputs a signal based on comparison between a voltage of the load connection terminal and a predetermined reference voltage; an acquisition unit that acquires the signal from the detection unit; a determination unit that determines that the load is in an abnormal state when the acquisition unit acquires an abnormality detection signal, which is a signal of a predetermined level, continuously for more than a predetermined first determination time period after the control unit switches the first switching element from the on state to the off state.