Power Switch On-Failure Diagnosis Using Motor-Induced Voltage Change
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Solution Overview
Problem
Conventional power switch failure diagnosis in power supply systems is complicated by the need to control inverter voltage, making it difficult to accurately diagnose the on-failure state without causing voltage changes.
Innovation Solution
A diagnostic device that outputs a shutdown command to the power switch with inverter control stopped, acquiring voltage changes due to motor revolutions, and using smoothing capacitors to stabilize path voltage, allowing for accurate diagnosis of power switch failures without inverter control-induced voltage changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If inverter control is used to maintain path voltage at target voltage during power switch diagnosis, then voltage stability is improved, but device complexity and diagnostic difficulty increase due to the need to coordinate inverter control with diagnosis timing
Solution Approach 1:
The patent extracts the inverter control function from the diagnosis process by stopping inverter control during power switch diagnosis. This allows the path voltage to naturally reflect the power switch state without being actively regulated, simplifying the diagnostic mechanism while maintaining voltage stability through the capacitor's inherent energy storage capability
Solution Approach 2:
The patent applies preliminary action by pre-charging the capacitor to a voltage higher than the motor's back-EMF voltage before diagnosis. This preliminary voltage setup ensures that when inverter control is stopped, the path voltage remains stable long enough to accurately detect power switch state without immediate voltage collapse
2Ease of operation
If inverter control is stopped during power switch diagnosis, then diagnostic simplicity is improved, but path voltage stability deteriorates due to loss of active voltage regulation
Solution Approach 1:
The patent introduces a capacitor as an intermediary energy storage element between the power supply and the diagnosis circuit. This capacitor acts as a voltage buffer that maintains path voltage stability during the brief period when inverter control is stopped, enabling simple diagnosis operations without sacrificing voltage stability
Solution Approach 2:
The patent applies beforehand cushioning by pre-charging the capacitor to a voltage level higher than the motor's back-EMF voltage before stopping inverter control. This voltage cushion ensures that the path voltage remains stable throughout the diagnosis period, preventing voltage collapse and enabling accurate detection
3Device complexity
If path voltage is allowed to change during motor revolution changes, then measurement simplicity is improved, but measurement precision deteriorates due to voltage changes masking the actual power switch state
Solution Approach 1:
The patent applies preliminary anti-action by pre-charging the capacitor to a voltage higher than the motor's back-EMF voltage before diagnosis begins. This preliminary voltage setup counteracts the natural voltage changes that would occur during motor revolution changes, ensuring that voltage remains stable and any detected changes accurately reflect power switch state rather than being masked by voltage fluctuations
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 reliable and simple power switch failure diagnosis by stabilizing path voltage and analyzing voltage changes, improving diagnostic accuracy and reducing system complexity.
Implementation Method 1
a smoothing capacitor connected in parallel to the power supply in the power supply path on the inverter side than the power switch
Implementation Method 2
the path voltage lower than an electromotive force voltage of the motor
Data Source
AI summary
A diagnostic device includes: a shutdown command unit that outputs a shutdown command to shut down a power switch with the control of an inverter stopped when a switch diagnostic condition is satisfied in the conduction state of the power switch, an acquisition unit that acquires a voltage change, which is the change in the detected voltage of a voltage sensor in response to the change in the number of revolutions of the motor after the output of the shutdown command by the shutdown command unit, and a diagnostic unit that diagnoses whether the power switch is in an on-failure state based on the voltage change.