Optical Coupler Frame Segmentation for Offset Voltage Reduction
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Solution Overview
Problem
Optical coupling devices used in circuits for power semiconductor elements, such as IGBTs, face challenges in managing offset voltage, which varies with temperature, making correction difficult due to its temperature-dependent nature.
Innovation Solution
The optical coupling device is designed with specific frame configurations and wire arrangements to minimize electromotive force and mutual inductance, including longer distances between input signal lines and power/ground lines, orthogonal wire orientations, and protrusions as electromagnetic shields, to reduce offset voltage and its temperature variability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the light-emitting element and drive circuit are integrated on the same frame, then device complexity is reduced, but electromagnetic interference increases causing higher offset voltage
Solution Approach 1:
The device is divided into two separate frames: a power frame for the light-emitting element and a ground frame for the drive circuit. This segmentation physically separates the high-current power lines from the sensitive signal lines, reducing electromagnetic interference and offset voltage while maintaining manageable device complexity through modular architecture.
Solution Approach 2:
A magnetic shield is introduced as an intermediary component between the power frame and ground frame. This magnetic shield acts as a mediator that blocks electromagnetic fields from the power lines from interfering with the signal lines, thereby reducing offset voltage without requiring complete physical separation of the frames.
2Area of stationary object
If the input signal line is placed closer to the drive circuit for compact design, then area is reduced, but electromagnetic interference from power lines increases
Solution Approach 1:
The frame structure is segmented into distinct functional zones: the power frame contains only the light-emitting element and power lines, while the ground frame contains the drive circuit and signal lines. This segmentation allows the signal line to be positioned close to the drive circuit for compact area while maintaining sufficient distance from power lines to minimize electromagnetic interference.
Solution Approach 2:
The magnetic shield serves as an intermediary that enables closer positioning of the signal line to the drive circuit. By blocking electromagnetic fields, the magnetic shield allows compact layout without sacrificing signal integrity, thus reducing area while controlling electromagnetic interference.
3Measurement precision
If correction circuitry is added to compensate for offset voltage, then measurement precision is improved, but device complexity increases
Solution Approach 1:
Offset voltage is reduced at the source through preliminary design choices: separating power and signal lines onto different frames and positioning the signal line optimally close to the drive circuit. This preliminary action minimizes the need for subsequent correction, maintaining measurement precision while avoiding the complexity of additional correction circuitry.
Solution Approach 2:
The design converts the potential harm of electromagnetic interference into a benefit by using the magnetic shield and frame separation to actively reduce offset voltage. This approach transforms what would require complex correction into a simpler passive solution, maintaining accuracy without increasing device complexity.
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 configuration effectively reduces offset voltage and its temperature-induced variations, enhancing the stability and accuracy of signal transmission across varying temperature ranges.
Implementation Method 1
a magnetic shield is disposed between the power frame and the ground frame
Implementation Method 2
a light-emitting element, a transmission integrated circuit (IC), and a receiving IC. When the light-emitting element emits an optical signal based on an electrical signal
Data Source
AI summary
An optical coupling device includes a power lead with a first portion and a power line portion. A light-emitting element is disposed on the first portion. A ground lead includes a ground line portion and a second portion with a drive circuit disposed thereon. A first input frame in the device includes a first input terminal portion and a first input signal line portion. A second input frame in the device includes a second input terminal portion and a second input signal line portion. The first and second input frames are adjacent to each other and a minimum distance from the first input signal line portion to the first installation portion is greater than a minimum distance from the first input signal line portion to the power line portion.