Digital Isolator Input Stage Emulating Optocoupler Diode Behavior
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Solution Overview
Problem
Existing optocoupler emulators fail to completely mimic the operational characteristics of optocouplers employing LEDs with diode current-voltage characteristics, leading to inefficiencies and higher costs in digital isolators.
Innovation Solution
A diode emulating oscillator comprising bipolar junction transistors and an inductor-capacitor (LC) oscillator, which generates modulated signals based on current flow, is used to create a digital isolator that mimics the behavior of an optocoupler, including spread spectrum modulation, without requiring separate power or active voltage regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If optocoupler emulators are used to replace optocouplers, then cost and complexity are reduced, but the operational characteristics (diode IV characteristic) are not completely mimicked
Solution Approach 1:
The patent changes the operating parameters of bipolar junction transistors to emulate diode IV characteristics. By controlling the current flow through the BJT in a specific manner (using the relationship Ic = β*Ib and the exponential relationship between base-emitter voltage and collector current), the circuit mimics the nonlinear voltage-current characteristics of a diode, thereby resolving the contradiction between simplified structure and authentic operational behavior
Solution Approach 2:
The patent creates a functional copy of the optocoupler's input stage behavior using bipolar junction transistors configured to replicate the diode's current-voltage characteristics. The BJT circuit copies the essential electrical behavior (exponential I-V relationship) without requiring an actual diode, achieving cost reduction while maintaining operational fidelity
2Reliability
If CMOS transistors and active voltage regulation are used in digital isolators, then performance is improved, but cost increases
Solution Approach 1:
The patent replaces expensive CMOS transistors and active voltage regulation circuits with a simpler bipolar junction transistor configuration that naturally provides the required voltage regulation through its inherent exponential I-V characteristics. This substitution uses cheaper components (standard BJT vs. CMOS) while maintaining the necessary performance, directly addressing the cost-performance contradiction
Solution Approach 2:
The bipolar junction transistor circuit provides self-regulation of voltage and current through its intrinsic properties without requiring external active voltage regulation components. The BJT's natural exponential relationship between base-emitter voltage and collector current automatically establishes the correct operating point, eliminating the need for additional regulation circuitry and reducing overall system cost
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 allows for efficient signal transmission and isolation while reducing costs by eliminating the need for expensive CMOS transistors and active internal voltage regulation, effectively emulating the behavior of an optocoupler with improved electromagnetic radiation control.
Implementation Method 1
an inductor capacitor (LC) oscillator coupled to the set of bipolar junction transistors, and a current mirror transistor coupled to the set of bipolar junction transistors and the LC oscillator, wherein the LC oscillator is configured to generate a modulated signal based on a current flowing through the current mirror transistor
Implementation Method 2
A diode emulating oscillator comprising a set of bipolar junction transistors coupled in series... configured to generate a modulated signal when a current flows through the set of bipolar junction transistors
Implementation Method 3
a current mirror transistor coupled to the set of bipolar junction transistors and the LC oscillator
Data Source
AI summary
A digital isolator comprising a set of bipolar transistors and an inductor capacitor (LC) oscillator coupled to the set of bipolar transistors in series, wherein the LC oscillator is configured to be turned on and off based on the current applied to the set of bipolar transistors or the LC oscillator and generate a set of differential signals based on the current flowing through the set of bipolar transistors and mimicking the operational characteristics of an optocoupler.