Floating Ground Potential Divider for Electric Power Steering Signal Exchange
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Solution Overview
Problem
Dual lane isolated power supply control and drive circuits for electric power steering systems face challenges in signal exchange between lanes due to potential differences in ground lines, leading to unintelligible digital signals and reduced system availability upon faults.
Innovation Solution
The implementation of a potential divider network connecting the floating grounds of two isolated power supplies, along with Zener diodes, ensures both floating grounds are held at a similar potential, allowing reliable digital signal exchange between control circuits, even with noise or voltage surges, and providing redundancy for continued operation after faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two isolated power supplies are used for dual lane control circuits, then system reliability is improved through redundancy, but signal exchange between lanes becomes problematic due to ground potential differences
Solution Approach 1:
The patent connects the floating grounds of two isolated power supplies through a potential divider network, establishing a common reference potential between the two lanes. This allows digital control signals to be exchanged reliably between control circuits while maintaining the isolation and redundancy benefits of separate power supplies.
Solution Approach 2:
The potential divider network acts as an intermediary element between the two isolated power supply systems. It provides a controlled electrical connection that enables signal exchange while maintaining the isolation architecture, serving as a mediator that reconciles the need for both independence and communication.
2Ease of operation
If floating grounds of isolated power supplies are connected directly, then signal exchange is simplified, but voltage surges and noise from one lane can affect the other lane
Solution Approach 1:
The potential divider network provides impedance matching and voltage division that cushions against voltage surges and noise. By distributing the voltage connection through resistive elements rather than a direct connection, the system prepares in advance to absorb and attenuate harmful voltage transients before they can affect the other lane.
3Reliability
If digital isolation devices are used to enable signal exchange between isolated lanes, then signal reliability is maintained, but device complexity and cost increase
Solution Approach 1:
The patent replaces expensive digital isolation devices with a simple potential divider network using basic resistive elements. This economical approach achieves the same functional goal of enabling reliable signal exchange between isolated lanes without the complexity and cost of sophisticated isolation technology.
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 enables reliable digital communication between control circuits, maintaining system functionality and availability by stabilizing floating ground potentials, allowing for simple and effective inter-lane communication and increased redundancy in electric power steering systems.
Implementation Method 1
the two floating grounds and the two lane grounds are connected together through a potential divider network that holds the two floating grounds at a potential that is between the potential of the lane grounds for the two lanes
Implementation Method 2
The potential divider may comprise a first resistance connecting the floating ground of the first lane to the associated first ground for the first lane, a second resistance connecting the floating ground of the second lane to the associated second ground for the second lane, and a third resistance connecting the two floating grounds together
Data Source
AI summary
An electric circuit for use in the control and drive of at least one electric motor, the circuit comprises a first lane comprising a first set of motor windings that are driven by a motor drive bridge that comprises a network of drive stage switches that selectively connect each phase of the lane to either a first supply voltage or a first supply ground, and further comprising a control circuit that controls the switches of the drive stage, the control circuit being powered by an isolated first lane power supply that has a first floating ground, and a second lane comprising a second set of motor windings that are driven by a motor drive bridge that comprises a network of drive stage switches that selectively connect each phase of the lane to either a supply voltage or a supply ground, and further comprising a control circuit that controls the switches of the drive stage, the control circuit being powered by an isolated second lane power supply that has a second floating ground. The first and second control circuits in use exchange digital control signals such that the control circuit of each lane can monitor the function of the other lane, and the two floating grounds and the two lane grounds are connected together through a potential divider network that holds the two floating grounds at a potential that is between the potential of the lane grounds for the two lanes.