Passive HVDC Bus Discharge Circuit for Vehicle Safety
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Solution Overview
Problem
Conventional methods for discharging a high-voltage DC bus in vehicles are inefficient in terms of component and energy costs, requiring optimal solutions for safe state discharge within calibrated durations.
Innovation Solution
A passive discharge circuit utilizing a microprocessor and semiconductor switch, connected across the positive and negative rails of the HVDC bus, which automatically disables discharge during normal operation and enables it during predetermined events like key-off or electrical faults, using a resistor to dissipate voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional discharge methods are used, then the HVDC bus can be discharged to a safe state, but component costs and energy costs increase
Solution Approach 1:
The patent extracts the discharge function from complex conventional systems and implements it using a simple semiconductor switch (IGBT or MOSFET) with a resistor, eliminating the need for complex discharge controllers or multiple contactors while achieving reliable discharge to safe states
Solution Approach 2:
The microprocessor controls the semiconductor switch to automatically discharge the HVDC bus when voltage exceeds the threshold, enabling the system to self-regulate and discharge without external intervention or complex monitoring circuits
2Reliability
If conventional discharge methods are used, then the HVDC bus can be discharged to a safe state, but energy costs increase
Solution Approach 1:
The discharge circuit operates periodically only when needed (when HVDC bus voltage exceeds the threshold), rather than continuously, minimizing energy loss while ensuring the bus reaches safe states. The microprocessor monitors and triggers discharge only during necessary events
Solution Approach 2:
The patent changes the resistance parameter dynamically by using a semiconductor switch that can be turned on/off, allowing the discharge resistor to be connected only when high voltage exists, thereby minimizing continuous energy dissipation while ensuring safe discharge when required
3Device complexity
If a passive discharge circuit with semiconductor switch is used, then component costs and energy costs are reduced, but the system requires precise voltage threshold control
Solution Approach 1:
The microprocessor continuously monitors the HVDC bus voltage and compares it against a predetermined threshold, providing feedback control that automatically activates the semiconductor switch when the threshold is exceeded, ensuring precise voltage control without complex analog circuitry
Solution Approach 2:
The microprocessor acts as an intermediary between the HVDC bus voltage monitoring and the semiconductor switch control, using software-based voltage threshold comparison to achieve precise control without requiring precision analog voltage reference circuits or complex comparator networks
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 approach reduces hardware components and energy costs while ensuring efficient and controlled discharge of the HVDC bus, minimizing system losses and improving fuel economy.
Implementation Method 1
The closed switch discharges the HVDC bus through the resistor
Data Source
AI summary
A vehicle includes a rechargeable energy storage system (RESS), an electric traction motor, a traction power inverter module (TPIM), a high-voltage direct current (HVDC) bus that electrically connects the RESS to the TPIM, a passive discharge circuit connected across the positive and negative rails of the bus, and a microprocessor. The circuit includes a semiconductor switch. The microprocessor provides an output signal at a first voltage level that opens the switch and prevents discharge of the HVDC bus when the microprocessor is operating normally, and at a default second voltage level that closes the switch in the presence of a predetermined vehicle condition to thereby discharge the HVDC bus. An optocoupler may receive the output signal, and a zener diode may be in electrical parallel with an output side of the optocoupler. The switch may be an insulated gate bipolar transistor or a thyristor in different embodiments.