Opto-Emulator Input Stage With Transformer Isolation for High CMTI
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Solution Overview
Problem
Opto-couplers face limitations in data rate due to light switching times and are susceptible to common mode noise, which affects their resilience and performance in noisy environments.
Innovation Solution
The development of opto-emulators that emulate the isolation characteristics of opto-couplers without light emitting diodes, utilizing a center-tapped transformer, cross-coupled oscillator, current shunt circuitry, oscillator disable circuitry, discharge circuitry, and clamp circuitry to enhance Common Mode Transient Immunity (CMTI) and bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If opto-couplers use light emitting diodes for signal transmission, then isolation characteristics are achieved, but data rate is limited due to light switching times
Solution Approach 1:
The patent extracts the light emitting diode from the opto-coupler system, replacing it with an electrical input stage that directly drives a transformer. This removes the light switching time limitation while maintaining galvanic isolation through the transformer, thereby increasing data rate without sacrificing isolation characteristics
Solution Approach 2:
The patent substitutes the optical system (light emitting diode converting electrical signals to light and back) with a direct electrical system using a transformer. This replacement eliminates the optical conversion delay and enables faster signal transmission while preserving the isolation function through magnetic coupling
2Object-affected harmful factors
If opto-couplers are used for signal transmission, then galvanic isolation is achieved, but susceptibility to common mode noise increases
Solution Approach 1:
The patent introduces a center-tapped transformer as an intermediary between the electrical input stage and the output stage. The center tap provides a reference potential that rejects common mode noise, while the transformer maintains galvanic isolation. This intermediary structure simultaneously improves noise immunity and preserves isolation characteristics
Solution Approach 2:
The patent employs asymmetric winding configurations on the transformer with different numbers of turns on primary and secondary sides, optimized for differential signal transmission. This asymmetric design enhances common mode rejection ratio while maintaining galvanic isolation, reducing susceptibility to common mode noise
3Speed
If opto-emulators operate at higher speeds than opto-couplers, then bandwidth is increased, but Common Mode Transient Immunity decreases
Solution Approach 1:
The patent incorporates preliminary filtering and conditioning circuits in the input stage that prepare the signal before it reaches the transformer. These circuits include common mode chokes and filtering networks that preemptively reject common mode transients, allowing high-speed operation while maintaining immunity to common mode disturbances
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 increases CMTI from 25 kV/μs to 100 kV/μs and bandwidth from 15 Mbps to 25 Mbps, improving resilience to noise and data transmission speed.
Implementation Method 1
utilizing a center-tapped transformer
Data Source
AI summary
An example apparatus includes: a current mirror having first and second outputs; oscillator circuitry including: a first transistor having a first terminal coupled to the first output of the current mirror, having a second terminal, and having a control terminal; and a second transistor having a first terminal coupled to the first output of the current mirror, having a second terminal coupled to the control terminal and the second terminal of the first transistor, and having a control terminal coupled to the second terminals of the first and second transistors; and current shunt circuitry having a terminal coupled to the second output of the current mirror.