Link Capacitor Discharge Circuit With Thermal Interrupt Control
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Solution Overview
Problem
Electric vehicles face challenges in accurately monitoring and controlling the temperature of resistive loads during capacitor discharge, which can lead to component damage due to excessive heat generation.
Innovation Solution
A discharge circuit with a link capacitor, resistive load, discharge switch, and a discharge interrupt assembly that includes a sensing resistor and a temperature circuit. The temperature circuit uses a resistor-capacitor subcircuit to generate a voltage representative of the system temperature, which is used to control the discharge switch and prevent overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a resistive load is used to discharge the link capacitor quickly, then the discharge speed is improved, but excessive heat is generated causing temperature to increase
Solution Approach 1:
The patent implements a temperature monitoring feedback system using a temperature sensor connected to the resistive load, which continuously monitors the temperature and provides feedback to the control circuit. When the temperature exceeds a predetermined threshold, the control circuit automatically adjusts or interrupts the discharge process to prevent overheating, thus resolving the contradiction between fast discharge and temperature control.
Solution Approach 2:
The patent employs a dynamic discharge control mechanism where the discharge switch is controlled based on real-time temperature conditions. The system transitions between different discharge states (full discharge, limited discharge, or interrupted discharge) depending on the temperature feedback, allowing the discharge process to adapt dynamically to thermal conditions and prevent excessive heat generation while maintaining discharge effectiveness.
2Reliability
If temperature monitoring is implemented to prevent overheating, then component protection is improved, but system complexity and cost increase
Solution Approach 1:
The patent uses a simple, low-cost temperature sensor and basic control circuitry rather than complex monitoring systems. The temperature sensor is a straightforward thermal sensing element, and the control circuit uses basic comparison logic against a predetermined threshold, avoiding expensive or complicated temperature management systems while still providing effective component protection.
Solution Approach 2:
The system performs self-monitoring and self-protection through the temperature sensor and control circuit that automatically detect overheating conditions and interrupt the discharge process without requiring external intervention or complex management systems. The predetermined threshold is set during design, and the system autonomously responds to temperature conditions, simplifying the overall architecture.
3Duration of action of moving object
If the discharge switch remains closed for extended periods, then complete discharge is achieved, but prolonged exposure to high current causes higher temperatures
Solution Approach 1:
The patent implements periodic monitoring of temperature during the discharge process. The control circuit continuously or periodically checks the temperature feedback from the sensor and interrupts the discharge switch operation when the predetermined threshold is reached. This periodic temperature-checked discharge approach allows the system to achieve necessary discharge while preventing prolonged high-current exposure that would cause excessive heating.
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
Effectively limits the system temperature during capacitor discharge, preventing component damage and ensuring safe operation by interrupting the discharge when the temperature reaches a threshold and resuming when it drops below a second threshold.
Implementation Method 1
The sensing resistor is arranged to receive current when current flows from the link capacitor to the resistive load
Implementation Method 2
The temperature circuit uses a resistor-capacitor subcircuit to generate a voltage representative of the system temperature
Implementation Method 3
During initial discharge, the power dissipated in the resistive load is very large and considerable heat is generated
Data Source
AI summary
In at least some implementations, a discharge circuit for an electric vehicle, includes a link capacitor, a resistive load, a discharge switch coupled to the link capacitor and to the resistive load so that the link capacitor is coupled to the resistive load when the discharge switch is closed to enable discharge of the link capacitor, and a discharge interrupt assembly. The discharge interrupt assembly has a sensing resistor connected in series with the resistive load, and a temperature circuit. The temperature circuit has an input connected to the sensing resistor and an output, and the discharge interrupt circuit is responsive to a voltage at the output of the temperature circuit to open the discharge switch when the voltage from the temperature circuit is higher than a threshold.