Reversible Current Mirror for Bidirectional Communication
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Solution Overview
Problem
Existing electromechanical motor vehicle power steering mechanisms require multiple contacts and signal lines for bidirectional communication, which are error-prone due to low voltages and increase complexity and cost.
Innovation Solution
A current mirror arrangement using pairs of identical transistors with additional MOSFETs to reverse circuit topology, allowing bidirectional communication with only one contact per end, utilizing n-channel and p-channel enhancement-mode MOSFETs to manage signal transmission between circuit units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate signal lines are used for bidirectional communication between MCU and ECU, then communication reliability is improved, but device complexity and cost increase due to requiring multiple contacts and wires
Solution Approach 1:
The patent combines bidirectional signal transmission into a single wire by using current mirror circuits that can operate in both directions. The first and second current mirrors enable the same physical wire to carry signals from MCU to ECU and from ECU to MCU alternately, eliminating the need for separate signal lines and reducing the number of contacts required.
Solution Approach 2:
The patent implements dynamic direction control where the current mirrors can be switched between forward and reverse operation modes. Control signals activate specific transistors (Q1-Q4 in first current mirror, Q5-Q8 in second current mirror) to change the conduction direction, allowing the communication interface to adaptively switch between transmitting and receiving modes on the same wire.
2Use of energy by moving object
If low voltage contacts are used for signal transmission, then power consumption is reduced, but reliability deteriorates due to error-prone contacts
Solution Approach 1:
The patent introduces current mirror circuits as intermediary devices that enable reliable signal transmission at low voltages. The current mirrors amplify and condition the signals passing through the contacts, ensuring that even with low voltage operation, the signal integrity is maintained and contact errors are minimized through the active circuitry that regens and conditions the signals.
3Measurement precision
If current mirrors are used for signal transmission, then signal integrity is improved, but circuit complexity increases due to requiring additional transistors
Solution Approach 1:
The patent designs the current mirror circuits to serve multiple functions: they provide signal transmission, signal amplification, direction control, and level shifting all within the same circuit structure. The same current mirror circuitry that ensures signal integrity also handles the bidirectional switching and impedance matching, reducing the need for separate dedicated circuits for each function.
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 cost-effective and reliable bidirectional communication with reduced wiring, using current mirrors to maintain constant output current and adjust for potential differences, simplifying signal transmission in electromechanical motor vehicle power steering mechanisms.
Implementation Method 1
a current mirror arrangement for bidirectional communication between two circuit units is provided, said arrangement comprising, in each circuit unit, a pair of first identical transistors with their bases connected together and their bases and their collectors connected to each other respectively
Implementation Method 2
Each MOSFET switches the assigned phase winding to the on-board vehicle power-supply voltage or the earth potential. This occurs at a high frequency so that the temporal average value acts as the effective voltage in the phase windings.
Implementation Method 3
wherein parasitic diodes formed between the drain-source-connection of the pair of second transistors of each circuit unit are arranged in series in opposite polarity directions
Data Source
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AI summary
The present invention relates to a current mirror arrangement for duplex bidirectional communication between two circuit units (A, B), said arrangement comprising in each circuit unit (A, B) two identical transistors (34, 34', 35, 35') with their bases (36, 37) connected together and their bases and their collectors connected to each other respectively, wherein each of the connections between the bases and the collectors is formed via a MOSFET (38, 39, 40, 41) and the MOSFETs (38, 39, 40, 41) of both circuit units (A, B) are connected together, wherein the MOSFETs' parasitic diodes of each circuit unit (A, B) are arranged in opposite direction with respect to the current system.