Inverter Fault Detection Using Pull-Down Voltage Division
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Solution Overview
Problem
Existing fault detection systems for multiphase motors require pull-up resistors for voltage monitoring, which occupy significant board space and can be affected by leakage currents, leading to potential errors.
Innovation Solution
A fault detector system that utilizes leakage currents through pull-down resistors to monitor voltages at interarm connection nodes, eliminating the need for pull-up resistors and reducing board space, while accurately detecting stuck-ON and stuck-OFF faults in upper and lower arm elements and motor relays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pull-up resistors are used for voltage monitoring, then fault detection capability is improved, but board space occupation increases
Solution Approach 1:
The patent extracts and eliminates the pull-up resistor component from the circuit by utilizing the inherent output impedance of the drive circuit as a virtual pull-up resistor. This removes the need for a separate physical pull-up resistor component, thereby reducing board space occupation while maintaining fault detection capability through the same voltage monitoring mechanism at the interarm connection node.
Solution Approach 2:
The drive circuit's output impedance is made to serve dual functions: driving the arm element and acting as a virtual pull-up resistor for voltage monitoring. This multi-functionality eliminates the need for dedicated pull-up resistor components, reducing board space while preserving fault detection capability.
2Measurement precision
If pull-up resistors are used for voltage monitoring, then voltage measurement is enabled, but leakage currents cause measurement errors
Solution Approach 1:
The patent converts the harmful leakage current into a beneficial signal by using the drive circuit's output impedance as a virtual pull-up resistor. The leakage current that would normally cause measurement errors is instead utilized to create a measurable voltage drop across the virtual pull-up resistor, enabling accurate fault detection without requiring separate pull-up resistors that would be susceptible to the same leakage issues.
Solution Approach 2:
The drive circuit's output impedance acts as an intermediary element that mediates between the power supply and the interarm connection node. This virtual pull-up resistor provides a controlled impedance path that enables voltage monitoring while isolating the measurement from the harmful effects of leakage currents that would affect traditional pull-up resistor configurations.
3Area of stationary object
If pull-up resistors are eliminated, then board space is reduced, but fault detection reliability may be compromised
Solution Approach 1:
The drive circuit serves itself by using its own output impedance as a virtual pull-up resistor for voltage monitoring. This self-service approach eliminates the need for external pull-up resistor components, reducing board space while maintaining fault detection reliability through the inherent electrical characteristics of the drive circuit itself.
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 system effectively detects faults with reduced component count and board space, minimizing errors by utilizing leakage currents for voltage monitoring, thereby enhancing reliability and efficiency.
Implementation Method 1
The pull-down resistor for each phase may have two voltage-division resistors connected in series. A determination unit may be provided to determine stuck-ON faults (short circuit faults) and stuck-OFF faults (open circuit faults) of the motor relay based on the voltage at the voltage-division node
Implementation Method 2
utilizing leakage currents for voltage monitoring
Data Source
AI summary
A fault detector includes an inverter, an upper drive circuit, a lower drive circuit, pull-down resistors, and a determination unit. The inverter has upper and lower arm elements in each phase. The upper drive circuit configured to output a gate signal to the upper arm element. Pull-down resistors being two voltage-division resistors connected between an interarm connection node and a ground in each phase. The determination unit detects whether a fault occurs in at least the upper and lower arm elements, based on a voltage at a voltage-division node being a connection node between the voltage-division resistors. The power supply line is connected to the interarm connection node without a pull-resistor between the power supply line and the interarm connection node. The determination unit detects whether stuck-ON fault and a stuck-OFF faults occur in the upper and lower arm elements, based on the voltage at the voltage-division node.