Capacitor Discharge Device With Selectable Resistance Values
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Solution Overview
Problem
Existing capacitor discharge devices in electric vehicles and chargers face challenges in efficiently discharging high-energy capacitors, particularly when they store significant quantities of energy, as they often require bulky resistor configurations or single-use pyrotechnic switches, which are costly and inconvenient to maintain.
Innovation Solution
A device with a resistive component having selectable resistance values, connected in parallel with the capacitor, and a circuit that progressively decreases resistance values during discharge, controlled by switches, ensuring safe and efficient energy dissipation by managing the discharge based on voltage and time thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a single high-power resistor is used to discharge the capacitor, then the discharge capability is sufficient, but the device size and weight increase significantly
Solution Approach 1:
The single high-power resistor is divided into multiple lower-power resistors connected in parallel. Each resistor handles a portion of the total discharge power, allowing the use of smaller, lighter components while achieving the same overall discharge capability. The control circuit switches between different resistor combinations to optimize discharge at various power levels.
2Speed
If pyrotechnic switches are used for capacitor discharge, then the discharge speed is very fast, but the cost and maintenance complexity increase
Solution Approach 1:
Pyrotechnic switches are replaced with electronic switching devices (such as transistors or thyristors) controlled by a control circuit. This substitution eliminates the need for explosive materials and single-use components, enabling repeated use, reduced maintenance, and lower cost while maintaining fast discharge speeds through electronic control.
3Device complexity
If a fixed resistance value is used, then the circuit is simple, but the discharge efficiency is suboptimal across different voltage levels
Solution Approach 1:
The fixed resistance value is replaced with a variable resistance system where multiple resistors are switched in parallel combinations based on the capacitor's voltage level. At high voltage, fewer resistors are active (higher equivalent resistance), and as voltage decreases, more resistors are engaged (lower equivalent resistance), optimizing power dissipation throughout the discharge process and improving overall energy dissipation efficiency.
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
This solution allows for controlled and efficient discharge of capacitors, adhering to safety standards by gradually reducing resistance values, ensuring safe and rapid energy dissipation, and avoiding the need for bulky components or single-use switches.
Implementation Method 1
a resistive component having a value selectable from among at least three values, intended to be connected in parallel with the capacitor
Data Source
AI summary
A device for discharging a capacitor includes a resistive component having a resistance value selectable from among at least three resistance values. The device is configured to be connected in parallel with the capacitor. A circuit operates to select the resistance value of the resistive component.