MOSFET Shutdown Mechanism for Electric Power Steering Reliability
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Solution Overview
Problem
Conventional electric power steering systems face issues with power loss, large and expensive relays, and unreliability due to high current requirements, necessitating a more efficient method to disconnect power from the electric motor.
Innovation Solution
Implementing a shutdown mechanism with a MOSFET between the power input and gate drive device, which quickly isolates power and allows regenerative energy to flow back to the battery, using a small bypass capacitor and a controlled buck-boost converter for efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electromagnetic relays are used to disconnect power from the motor, then power disconnection can be achieved, but the system suffers from power loss due to relay contact resistance, large physical size, high cost, and reduced reliability
Solution Approach 1:
The patent replaces electromagnetic relays (mechanical/electromagnetic switching devices) with power transistors (solid-state electronic switching devices). This substitution eliminates relay contact resistance and associated power losses while improving reliability through solid-state operation without moving parts or contact wear.
Solution Approach 2:
The invention changes the operating parameters of the switching device by using power transistors that can handle high currents with very low on-resistance compared to relay contacts. The transistor's electrical characteristics (low Rds(on), high current capacity) provide superior power efficiency and reliability over electromagnetic relay parameters.
2Reliability
If electromagnetic relays are used to disconnect power from the motor, then power disconnection can be achieved, but the relay components become physically large and expensive due to high current requirements
Solution Approach 1:
The patent replaces electromagnetic relays (mechanical/electromagnetic switching devices) with power transistors (solid-state electronic switching devices). This substitution eliminates relay contact resistance and associated power losses while improving reliability through solid-state operation without moving parts or contact wear.
Solution Approach 2:
The invention changes the operating parameters of the switching device by using power transistors that can handle high currents with very low on-resistance compared to relay contacts. The transistor's electrical characteristics (low Rds(on), high current capacity) provide superior power efficiency and reliability over electromagnetic relay parameters.
3Reliability
If electromagnetic relays are used to disconnect power from the motor, then power disconnection can be achieved, but multiple redundant battery measurements are required on both sides of the relay to ensure proper operation
Solution Approach 1:
The patent replaces electromagnetic relays (mechanical/electromagnetic switching devices) with power transistors (solid-state electronic switching devices). This substitution eliminates relay contact resistance and associated power losses while improving reliability through solid-state operation without moving parts or contact wear.
Solution Approach 2:
The invention changes the operating parameters of the switching device by using power transistors that can handle high currents with very low on-resistance compared to relay contacts. The transistor's electrical characteristics (low Rds(on), high current capacity) provide superior power efficiency and reliability over electromagnetic relay parameters.
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 reduces power loss, eliminates the need for redundant battery measurements, and enables quick disconnection of power, improving the reliability and efficiency of the electric power steering system.
Implementation Method 1
a gate drive device electrically connected to the at least one power device for regulating operation of the at least one power device. A shutdown mechanism is electrically connected between the gate drive device and the power input. The shutdown mechanism isolates electrical power from the gate drive device in response to a shutdown condition to prevent the at least one power device from providing electric power to the power steering motor.
Implementation Method 2
By implementing the shutdown mechanism between the power input and the gate drive device, several advantages are achieved over prior art systems. First, because of the relatively small size of a bypass capacitor (not shown), electric power is removed from the at least one power device very quickly once one of the enable signals is removed. Furthermore, electric energy generated by the motor may flow back to a battery of the vehicle.
Data Source
AI summary
An electric power steering system for a vehicle includes a motor for providing assistance in turning the wheels of the vehicle. The motor is electrically connected to a controller. The controller includes a power device, such as a power transistor, electrically connected to the motor to variably provide electric power to the motor as needed. The controller also includes a gate drive device electrically connected to the power device for regulating operation the power device. A shutdown mechanism is electrically connected between the gate drive device and a power input. In the event of a fault, the shutdown mechanism isolates electrical power from the gate drive device. This prevents the power device from providing electric power to the power steering motor.