Vehicle Door Latch Switch Diagnosis in Power Save Mode
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Solution Overview
Problem
Existing diagnosable switches in vehicle door latches do not adequately address safety aspects, particularly in power save modes, failing to provide continuous diagnostic capabilities.
Innovation Solution
A vehicle door latch with a diagnosable switch comprising a parallel resistor, a series resistor, and a diagnosis circuit that includes a diode, a pull-up resistor, a voltage divider, and a microcontroller, which determines if the midpoint voltage correlates to the switching position of the switch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diagnosable switch with inner parallel and series resistors is used, then diagnostic capability is improved, but power consumption increases and reliability in power save mode deteriorates
Solution Approach 1:
The diagnosis circuit performs diagnostic measurements periodically rather than continuously. The microcontroller activates the pull-up resistor and measures the voltage at the midpoint only when needed (e.g., when a door event occurs or on scheduled intervals), allowing the circuit to remain in a low-power state during idle periods while maintaining diagnostic capability when required.
Solution Approach 2:
The diagnostic function is extracted as a separate, on-demand operation rather than being continuously active. The measurement circuit is designed to be activated only when diagnostic information is needed, separating the diagnostic function from continuous operation and enabling power save modes while maintaining reliability.
2Reliability
If continuous diagnostic is performed in normal operation mode, then reliability is improved, but power consumption increases
Solution Approach 1:
The system transitions from continuous diagnostic to periodic diagnostic, where the microcontroller enters sleep mode between measurement cycles. Diagnostic measurements are performed at specific intervals or triggered by events, maintaining system reliability while dramatically reducing average power consumption during power save modes.
Solution Approach 2:
The diagnostic system uses the existing switch and resistor components already present in the door latch circuit to perform self-diagnostics. The microcontroller leverages the existing hardware infrastructure (switch, parallel resistor, series resistor) to conduct measurements without requiring additional active components, enabling autonomous health monitoring with minimal power overhead.
3Measurement precision
If a diagnosis circuit with diode, pull up resistor, and voltage divider is implemented, then detection precision is improved, but device complexity increases
Solution Approach 1:
The diagnosis circuit components serve multiple functions: the pull-up resistor provides both a current path for measurement and a defined voltage reference; the voltage divider network enables both fault detection and switch position sensing; the diode provides both protection and signal isolation. This multi-functionality reduces the need for additional dedicated components, managing complexity while maintaining high detection precision.
Solution Approach 2:
The voltage divider acts as an intermediary between the high-voltage domain (power source through series resistor) and the low-voltage domain (microcontroller input). This intermediary network enables safe measurement of switch states and fault conditions by providing a scaled-down, protected version of the voltage signals, improving detection precision while isolating the microcontroller from potentially harmful voltage levels.
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
The proposed solution enables continuous diagnostic capabilities during normal operation and power save modes, detecting open load, short to battery, and short to ground failures, thereby ensuring safety and reliability.
Implementation Method 1
a diagnosis circuit comprising a diode, a pull up resistor configured for receiving a pull up voltage from a power source
Implementation Method 2
a diagnosable switch comprising a parallel resistor, a switch configured for determining a position of the door and a series resistor
Data Source
Figure 1
AI summary
The invention relates to a vehicle door latch (1) for locking a door (3) of a motor vehicle (2), comprising a diagnosable switch (4) comprising a parallel resistor (6), a switch (7) configured for determining a position of the door (3) and a series resistor (8), whereby the parallel resistor (6) is connected in parallel to the switch (7) and in series with the series resistor (8), and a diagnosis circuit (5) comprising a diode (10), a pull up resistor (11) configured for receiving a pull up voltage from a power source (16), a voltage divider (12) comprising a midpoint (13) and a microcontroller (14), whereby the diode (10) is connected between the series resistor (8) and the voltage divider (12), the midpoint (13) is connected to the microcontroller (14), an anode of the diode (10) facing the voltage divider (12) is connected to the pull up resistor (11) and the microcontroller (14) is configured for determining if a midpoint voltage of the midpoint (13) correlates to a switching position of the switch (7).