Backup Power Circuit for EV Gate Drive Overvoltage Protection
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Solution Overview
Problem
Electric vehicles with permanent magnet motors face over-voltage faults when the main contactor is open, potentially damaging components like high-voltage DC capacitors, and existing solutions to short circuit the motor require a 12V power supply, which may not be available in failure scenarios.
Innovation Solution
A circuit with a primary and secondary power supply, where the secondary power supply draws from the high voltage DC capacitor to enable a 3-phase short function, ensuring safety even if the primary power supply fails, using a flyback converter and integrated switch controller to manage voltage and maintain the output capacitor charged.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the main contactor is open to isolate the battery, then the battery is protected from fault conditions, but the motor can overcharge the high voltage DC bus capacitor causing component damage or fire
Solution Approach 1:
The system performs a 3-phase short of the motor windings before the overvoltage condition can damage the capacitor. This preliminary protective action prevents the harmful effect by creating a safe discharge path for the generated voltage, ensuring the capacitor remains within safe voltage limits even when the main contactor is open.
2Object-affected harmful factors
If the 12V power supply is used to short circuit the motor terminals, then the motor can be protected from overvoltage, but the system becomes vulnerable if the 12V power supply fails
Solution Approach 1:
The invention introduces an intermediary power supply mechanism that can draw power from the high voltage DC bus itself to drive the 3-phase short function. This intermediary solution ensures that even when the primary 12V power supply fails, the protection function remains available by using the bus voltage to power the gate drives that control the shorting transistors.
3Use of energy by moving object
If the motor functions as a generator during regenerative braking, then energy is recovered to charge the battery, but overvoltage faults occur when the main contactor is open
Solution Approach 1:
The invention converts the potentially harmful overvoltage condition into a beneficial protective action. When the main contactor opens during regenerative braking, instead of allowing the generated voltage to damage the capacitor, the system automatically activates the 3-phase short function to safely dissipate the energy, turning a dangerous situation into a controlled protective event.
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 3-phase short function to prevent overcharging of the high voltage DC bus capacitor, reducing the risk of component damage and ensuring safety by providing backup power to the gate drives, even in the absence of the primary 12V power supply, with minimal power loss and few components.
Implementation Method 1
a flyback converter and integrated switch controller to manage voltage
Data Source
AI summary
In a first aspect, the invention is directed to a circuit for powering a gate drive for an electric motor for a vehicle with an electric motor. The circuit provides a primary power supply and a secondary power supply that powers the gate drive in the event the primary power supply fails. The primary power supply may draw power from the 12V battery on the vehicle. The secondary power supply may draw power from a high voltage battery pack on the vehicle that is normally used to provide power to the electric motor. By providing the secondary power supply to the gate drive, a 3-phase short can be applied to the motor in the event that it is needed as a safety measure even if there is a failure in the primary power supply.