Photocoupler Reflective Surface Reduces Capacitance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional photocouplers experience issues with large capacitance values and low Common Mode Rejection Ratio (CMRR) due to a close distance and large overlapping area between conductive frames, which do not meet required electrical standards.
Innovation Solution
A photocoupler design featuring a transparent inner encapsulant body with a dome and extension portion, an optically reflective outer covering body, and conductive frames with a minimized overlapping area, where the light emitting and sensing elements are positioned to utilize both direct and reflected light paths, increasing the creepage distance and reducing capacitance while enhancing CMRR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the distance between the two conductive frames is reduced to make the photocoupler more compact, then the size of the photocoupler is reduced, but the capacitance value increases and CMRR decreases
Solution Approach 1:
The patent introduces a third dimension by forming an optically reflective surface on the outer encapsulant body. This creates a reflected light path that allows the light-receiving element to detect light from the light-emitting element through both direct transmission and reflection, enabling effective coupling while maintaining larger physical separation between conductive frames, thus reducing capacitance and improving CMRR
2Reliability
If the overlapping area between the two conductive frames is increased to improve electrical coupling, then the electrical characteristics improve, but the capacitance value increases and CMRR decreases
Solution Approach 1:
The patent introduces an optically reflective surface as an intermediary element on the outer encapsulant body. This reflective surface mediates the light transmission between the light-emitting and light-receiving elements, allowing effective optical coupling without requiring large overlapping area between conductive frames, thus maintaining low capacitance and high CMRR
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
The design minimizes capacitance and increases CMRR, ensuring the photocoupler meets electrical standards by optimizing the placement and reflection of light between elements, thereby improving electrical characteristics.
Implementation Method 1
an optically reflective surface is formed on the outer covering body in contact with a dome surface of the dome encapsulant portion; a portion of the light emitting from the light emitting element is reflected to a light receiving top portion of the light-sensing element through the optically reflective surface
Implementation Method 2
a light emitting element for emitting a light
Implementation Method 3
a light-sensing element for receiving the light
Data Source
AI summary
A photocoupler comprises a light emitting element, a light-sensing element, a transparent inner encapsulant body, an outer covering body, and two conductive frames. An optically reflective surface is formed on the outer covering body directly in contact with the dome encapsulant portion of the transparent inner encapsulant body. A portion of the light emitted by the light emitting element is reflected to the light-sensing element through the optically reflective surface, and the other portion of the light emitted from the light emitting element is directly emitting to the light-sensing element through the dome encapsulant portion. The present invention applies the optically reflective surface to minimize the overlapping area between the two conductive frames, and reduces the capacitance value, and increases the CMRR in a manner that the photocoupler of the present invention is able to meet the standard of electrical characteristics as required.