Load Failure Diagnosis Circuit for Inductive Switching Paths
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Solution Overview
Problem
Conventional short-circuit detection devices for inductive loads often mistakenly detect short-circuits due to excessive current flow, potentially damaging the field-effect transistor, and fail to reliably perform failure diagnosis without causing unnecessary operation of the loads.
Innovation Solution
An electronic device with a failure diagnosis unit that compares a load signal converted from current to voltage with a reference signal, using a microcontroller and op-amp circuit to determine if the load is in an abnormal state, thereby preventing damage to the switching element and avoiding unnecessary tactile feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diagnostic driving signal is given in an extremely short pulse shape to minimize current flow, then the field-effect transistor is protected from damage, but short-circuits in the inductive load may be mistakenly detected
Solution Approach 1:
The patent applies preliminary action by performing failure diagnosis during periods when the field-effect transistor is not switching (when it remains in the on-state or off-state). This allows the diagnostic current to flow through the inductive load without causing rapid changes in current that would generate harmful back-EMF, thereby preventing mistaken short-circuit detection while still enabling reliable fault detection through voltage measurements across the load.
Solution Approach 2:
The patent uses the inductive load itself as an intermediary for diagnosis by measuring the voltage across it during non-switching periods. This voltage measurement serves as an indirect indicator of load health without requiring direct current measurement that could trigger false short-circuit detection. The controller acts as an intermediary that coordinates the timing of diagnosis with the switching cycle to avoid harmful effects.
2Productivity
If the field-effect transistor is driven with a driving voltage in an extremely short pulse shape, then diagnostic speed is improved, but excessive current may flow into the field-effect transistor causing damage
Solution Approach 1:
The patent performs failure diagnosis during idle periods between switching operations or during sustained on/off states, rather than during the brief transition periods. This preliminary timing selection allows sufficient time for accurate voltage measurements without inducing excessive current flow or back-EMF that would damage the field-effect transistor, while still maintaining diagnostic productivity through efficient use of available time windows.
Solution Approach 2:
The patent implements periodic failure diagnosis by systematically selecting specific timing windows within the switching cycle (when the field-effect transistor is in stable on-state or off-state) to perform voltage measurements. This periodic approach ensures that diagnosis occurs at optimal moments that balance speed requirements with protection against excessive current, creating a reliable cyclic diagnostic routine.
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 device reliably performs failure diagnosis for loads while suppressing damage to the switching element and preventing unnecessary tactile feedback during diagnosis.
Implementation Method 1
a driving control signal that represents a result of comparison between a load signal resulting from converting a current flowing in the current path to a voltage
Data Source
AI summary
An electronic device includes: a plurality of loads, a switching element provided in a current path connected to the plurality of loads, a failure diagnosis unit that performs failure diagnosis according to voltages applied to the plurality of loads, and a driving circuit that drives the switching element. The driving circuit outputs, to the switching element, a driving control signal that represents a result of comparison between a load signal resulting from converting a current flowing in the current path to a voltage and a reference signal used as a reference for the operation of the switching element. If the failure diagnosis unit detects a voltage outside a normal voltage range, the failure diagnosis unit decides that the load is in an abnormal state.