LED Driver Circuit for Motorcycle Switch Detection
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Solution Overview
Problem
Conventional LED driver circuits face issues such as heating, timing adjustments, and increased costs due to the use of resistors, constant current circuits, magnets, or Hall devices, which can lead to erroneous detection of the on/off state of a switch device when wetted with water, especially in motorcycle applications.
Innovation Solution
An LED driver circuit that eliminates the need for timing adjustments and expensive components like Hall devices, utilizing a detection circuit with a pMOS transistor, detection capacitor, and comparison circuit to accurately determine the on/off state of a mechanical switch device, even when wet, by comparing detection voltage with a threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional techniques use resistors or constant current circuits to prevent erroneous detection, then reliability is improved, but heating occurs and manufacturing cost increases
Solution Approach 1:
The patent replaces conventional passive components (resistors, constant current circuits) with an active MOSFET-based detection circuit. The MOSFET operates in saturation region to provide high-impedance current path, eliminating the need for power-dissipating resistors while maintaining detection accuracy. This substitution of mechanical/passive components with active semiconductor devices resolves the heating issue while preserving reliability.
Solution Approach 2:
The patent changes the operating parameters by using MOSFET threshold voltage characteristics and saturation region operation to create a high-impedance state during detection. By controlling the MOSFET to operate in specific regions (cutoff, linear, saturation), the circuit dynamically adjusts its impedance to prevent erroneous detection without requiring continuous power dissipation, thus eliminating heating while maintaining detection reliability.
2Reliability
If conventional techniques use Hall devices or magnets to detect switch state, then reliability is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive Hall devices and magnets with inexpensive MOSFET transistors and standard capacitors. These semiconductor components are mass-producible and significantly cheaper than magnetic sensing components. The circuit achieves the same detection function using readily available, low-cost electronic components, thereby reducing manufacturing cost while maintaining detection reliability.
Solution Approach 2:
The patent substitutes magnetic field-based detection (Hall devices, magnets) with electrical field-based MOSFET switching detection. This replacement eliminates the need for expensive magnetic components and their associated alignment and calibration requirements, using instead standard semiconductor devices that are easier and cheaper to manufacture and integrate into the circuit.
3Reliability
If conventional techniques use sampling methods to detect switch state, then reliability is improved, but device complexity and timing adjustment requirements increase
Solution Approach 1:
The patent performs detection action immediately upon switch actuation by connecting the detection circuit directly to the switch terminals. The MOSFET-based circuit is designed to detect the presence or absence of switch closure in real-time without requiring delayed sampling or complex timing sequences. This preliminary and immediate detection approach simplifies the circuit by eliminating timing control logic and synchronization requirements.
Solution Approach 2:
The patent extracts and eliminates the timing control and sampling logic from the detection circuit. By using the MOSFET's natural switching characteristics and direct connection to the switch, the circuit achieves detection without requiring microcontroller intervention, sampling timers, or complex state machine logic, thereby reducing overall device complexity.
4Reliability
If conventional techniques use elaborate wiring to pass leak current, then reliability is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent merges the leak current path detection function with the main switch detection circuit by using the same MOSFET and capacitor components to detect both normal switch operation and leak current conditions. The detection circuit is integrated into the existing switch terminal connections, eliminating the need for separate wiring paths for leak current detection. This consolidation reduces wiring complexity while maintaining the ability to distinguish between legitimate switch signals and leak currents.
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
This solution reduces manufacturing costs and minimizes erroneous detections caused by leak currents, enabling reliable operation of LED lamps in wet conditions without requiring expensive components or timing adjustments.
Implementation Method 1
a detection circuit periodically detects a current flowing to a first terminal
Implementation Method 2
a comparison circuit compares a detection voltage responsive to the detection signal with a threshold voltage
Data Source
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AI summary
An LED driver circuit includes a first terminal to which a current path of the switch device is connected at one end thereof; a second terminal to which the current path of the switch device is connected at another end thereof, the switch device and a battery being connected in series between the first terminal and the second terminal; a detection circuit that periodically detects a current flowing to the first terminal and outputs a detection signal responsive to a result of the detection at a first node; a comparison circuit that compares a detection voltage responsive to the detection signal with a threshold voltage and outputs a comparison result signal responsive to a result of the comparison; and a control circuit that controls a current detection operation of the detection circuit and controls driving of the LED lamp based on the comparison result signal.