Motor Control Device Discharge Circuit Overheat Protection
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Solution Overview
Problem
In automotive vehicles, the motor control device fails to detect abnormal conditions in the discharge device due to the inability to transmit signals from the discharge device to the motor control device, leading to potential issues during vehicle collisions or other critical situations.
Innovation Solution
A motor control device that includes a discharge portion with a switching element and a discharge resistor connected in series, and an overheat protection portion, allowing the motor control device to determine the normalcy of the discharge device by controlling the switching element's ON and OFF states based on diagnostic conditions, including the presence of electric current flow through the discharge resistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the discharge device is separated from the inverter circuit and connected only from the motor control device to the discharge device, then the overall structure is simplified, but the motor control device fails to detect abnormal conditions of the discharge device
Solution Approach 1:
The patent introduces a feedback mechanism where the discharge device transmits signals back to the motor control device to report its operational status. This allows the motor control device to detect abnormal conditions (such as overheat or malfunction) of the discharge device by receiving and processing feedback signals, thereby resolving the contradiction between structural simplification and abnormal condition detection capability.
2Measurement precision
If the switching element is controlled to turn on and off frequently for diagnostic purposes, then the abnormal condition detection precision is improved, but the discharge device reliability deteriorates due to increased wear and potential failures
Solution Approach 1:
The patent implements preliminary diagnostic actions by controlling the switching element to turn on briefly before actual discharge operations to check the operational status of the discharge device. This preliminary check allows the motor control device to detect potential abnormalities early without requiring frequent on-off cycling during normal operation, thus maintaining detection precision while reducing wear and improving reliability.
3Object-affected harmful factors
If the switching element remains turned off after overheat protection activates, then the safety is improved by preventing further overheating, but the loss of time increases due to inability to reset and resume normal operation
Solution Approach 1:
The patent implements a self-service mechanism where the discharge device automatically resets after the overheat condition is resolved. When the temperature drops below the threshold, the switching element automatically turns on again without requiring manual intervention or system shutdown, allowing the discharge device to resume normal operation. This resolves the contradiction by maintaining safety through automatic overheat protection while minimizing operational downtime through automatic recovery.
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 the motor control device to accurately determine the normal or abnormal status of the discharge device, preventing unnecessary discharges and ensuring proper operation during vehicle travel and collision scenarios, thereby enhancing safety and reliability.
Implementation Method 1
a discharge resistor and a high-voltage capacitor both of which are connected in parallel between positive and negative electrode buses of a power line
Data Source
AI summary
After turning on a switching element by receiving a discharge command from a motor ECU via a control circuit, a drive circuit of a discharge device causes, upon receipt of an overheat protection command from an overheat protection circuit, the switching element to turn off and keeps the resulting state thereof. And, the motor ECU sends the discharge command, after establishment of a diagnostic condition, to the control circuit of the discharge device and determines that the discharge device is abnormal if an electric current will not flow through a discharge resistor and the switching element.