BJT Bidirectional IO Circuit for Ground-Shifted Data Links
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Solution Overview
Problem
Conventional galvanic isolators are expensive and unsuitable for bidirectional communication, particularly in automotive applications where ground shifts can cause signal distortion and require costly isolation, and they are not effective for bidirectional communication lines like I2C buses.
Innovation Solution
A communication circuit using bipolar junction transistors (BJTs) for bidirectional communication, with a switching part, transmitter part, and receiver part configured to activate BJTs in response to input signals, and a diode to impede current, allowing data transmission without ground-related disturbances, using a single IO line and reducing costs compared to galvanic isolators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If galvanic isolators are used to protect against ground voltage differences, then signal isolation and protection are improved, but cost increases significantly
Solution Approach 1:
The patent uses bipolar junction transistors as intermediary elements to transfer signals between circuits with different ground potentials. The BJTs act as mediators that couple the input and output circuits through current control without requiring direct galvanic isolation, thereby eliminating the need for expensive isolators while maintaining signal integrity and protection against ground voltage differences.
Solution Approach 2:
The invention replaces expensive galvanic isolators with inexpensive bipolar junction transistors. The BJTs are standard, low-cost semiconductor components that can be easily integrated into the circuit, providing the same protective function at a fraction of the cost of traditional isolators like optocouplers or iCouplers.
2Reliability
If galvanic isolators are used for signal isolation, then protection against ground loops is improved, but bidirectional communication capability deteriorates
Solution Approach 1:
The patent employs dynamic switching of BJT operating states to enable bidirectional communication. By controlling the base currents of the BJTs, the circuit can dynamically switch between transmitting and receiving modes, allowing signal flow in both directions along the same communication line while maintaining isolation from ground potential differences.
Solution Approach 2:
The BJT-based circuit performs multiple functions: it provides signal isolation, enables bidirectional communication, and protects against ground voltage differences all within a single integrated structure. The same transistors that provide isolation also facilitate bidirectional signal transmission, eliminating the need for separate isolator components.
3Adaptability or versatility
If separate ground connections are used for distributed circuit modules, then system flexibility and distribution are improved, but signal distortion from ground shifts increases
Solution Approach 1:
The BJTs serve as intermediary elements that transfer signals between distributed modules with separate ground connections. By using current-controlled BJTs rather than voltage-based signal transmission, the circuit eliminates the harmful effect of ground potential differences, allowing distributed modules to communicate without signal distortion despite having independent ground references.
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 bidirectional communication between separated circuit modules with reduced sensitivity to ground voltage differences, supporting data transfer rates for I2C bus transmissions and voltage level shifts, while protecting against signal distortion and potential damage.
Implementation Method 1
a switching part including a first bipolar junction transistor, BJT, having a first base, a first collector, and a first emitter connected to the IO line at a first position, wherein the switching part is configured to activate the first BJT in response to an input data signal on the IO line
Implementation Method 2
a diode in the IO line between the first and second positions for impeding current associated with an input data signal in the IO line and conducting a current associated with an output data signal in the IO line
Data Source
Figure 1
AI summary
Communication circuit (2) for bidirectional communication. A switching part (202) is provided including a first BJT (10) having a first base (11), a first collector (12), and a first emitter (13) connected to an IO line (7). The first BJT (10) is activated in response to an input data signal. A transmitter part (201) is provided including a second BJT (20) having a second base (21) connected to the first collector (12), and a second collector (22) connected to an output (104). A receiver part (203) is provided comprising a third BJT (30) having a third base (31) connected to an input (106), and a third collector (32) connected to the first base (12) and to the IO line (7). A diode (91) is provided in the IO line (7) for impeding current associated with an input data signal and conducting a current associated with an output data signal.