Variable Discharge Circuit for High-Voltage DC Link Safety
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Solution Overview
Problem
Conventional high-voltage vehicle electrical systems lack effective methods for safely and efficiently discharging high-voltage networks, particularly in hybrid and electric vehicles, where voltages exceed 60 volts, posing safety risks if not properly managed.
Innovation Solution
A discharge circuit is introduced that adjusts discharge current variably based on high-voltage voltage levels, using components like DC-DC converters, flyback converters, and logic units to ensure safe operation by increasing discharge current when the voltage drops below a specified threshold and minimizing it when safe operation is no longer possible, incorporating a load resistor for rapid energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a passive discharge circuit with a fixed resistor is used, then the circuit structure is simple, but the discharge time is long (usually 120 seconds) and the discharge speed is slow
Solution Approach 1:
The patent applies dynamics by making the discharge current variable rather than fixed. The control unit dynamically adjusts the discharge current based on real-time voltage measurements from the intermediate circuit capacitor, transitioning from a static passive discharge circuit to a dynamic active discharge system that adapts to changing voltage conditions.
Solution Approach 2:
The patent changes the parameter of discharge current from a fixed value to a variable value that depends on the intermediate circuit voltage. By using a control unit that adjusts the discharge current based on voltage levels, the system optimizes discharge speed across different operating conditions while maintaining safety requirements.
2Speed
If a high discharge current is applied continuously, then the discharge speed is fast, but energy is wasted when the voltage is already low and discharge is not needed
Solution Approach 1:
The patent implements feedback by using a control unit that continuously monitors the intermediate circuit voltage and adjusts the discharge current accordingly. When voltage drops below a threshold, the control unit reduces or stops the discharge current, preventing energy waste while maintaining fast discharge capability when high voltage is present.
Solution Approach 2:
The system dynamically adjusts the discharge current based on real-time voltage conditions, increasing discharge current when voltage is high for fast discharge, and reducing it when voltage is low to avoid energy waste, thereby optimizing both discharge speed and energy efficiency.
3Reliability
If the discharge circuit is always active, then safety is maintained, but operational flexibility is reduced when rapid discharge is needed below operating voltage
Solution Approach 1:
The patent makes the discharge circuit dynamically controllable rather than always active. The control unit enables the discharge circuit to be activated or deactivated based on operational requirements and voltage levels, providing both safety through controlled discharge and flexibility by allowing the system to remain operational when conditions permit.
Solution Approach 2:
The system changes the operational state of the discharge circuit from always active to conditionally active based on voltage thresholds and safety requirements, allowing the circuit to adapt between safety-critical discharge mode and operational flexibility mode.
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 solution ensures rapid and safe discharge of high-voltage intermediate circuits, reducing the risk of electrical hazards and maintaining operational safety by adjusting discharge current dynamically in response to voltage changes, ensuring efficient energy dissipation and preventing damage to the high-voltage battery.
Implementation Method 1
an intermediate circuit capacitor, which is connected on the high-voltage side between a pulse-controlled inverter and a high-voltage battery for smoothing the current and voltage peaks
Implementation Method 2
A passive discharge usually consists of at least one resistor that is connected in parallel to the energy storage device and the high-voltage grid
Data Source
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AI summary
The invention relates to a discharge circuit (10) for discharging a high-voltage DC link (20) of a vehicle. The high-voltage DC link (20) comprises a DC link capacitor (30) to which a high voltage (U_H) is applied. The discharge circuit (10) is designed to adjust the level of the discharge current (I_D) provided by the discharge circuit (10) depending on the high voltage (U_H).