Coplanar Photocoupler Design for Voltage Isolation
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Solution Overview
Problem
Conventional photocouplers face challenges in achieving high voltage resistance, complex manufacturing processes, poor production yield, high defective rates, and inadequate common mode rejection noise characteristics due to the difficulty in aligning light-emitting and light-sensing chips, as well as issues with encapsulant body shaping and attachment.
Innovation Solution
A photocoupler design featuring light-emitting and light-sensing chips mounted coplanarly with a light-transmissive encapsulant body and a light-reflective encapsulant body formed by double molding and epoxy molding, reducing parasitic capacitance and improving high-voltage resistance, while allowing for easier shaping and tighter attachment of encapsulant bodies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If light-emitting chip and light-sensing chip are oppositely disposed in conventional photocoupler, then voltage isolation is achieved, but alignment accuracy is difficult to achieve and manufacturing complexity increases
Solution Approach 1:
The patent inverts the conventional opposite arrangement of light-emitting chip and light-sensing chip to a coplanar arrangement where both chips are mounted on the same lead frame in the same plane. This inversion simplifies the manufacturing process by eliminating the need for complex alignment between oppositely disposed chips while maintaining voltage isolation through the lead frame structure.
Solution Approach 2:
The patent merges the light-emitting chip and light-sensing chip onto the same lead frame in a coplanar configuration, combining what were previously separate mounting structures. This merging simplifies the overall device structure and manufacturing process while achieving both alignment accuracy and voltage isolation.
2Reliability
If light-emitting chip and light-sensing chip are oppositely disposed, then voltage isolation is achieved, but production yield decreases and defective rate increases
Solution Approach 1:
By inverting the conventional opposite arrangement to a coplanar arrangement on the same lead frame, the patent significantly improves production yield. The coplanar configuration eliminates complex alignment steps that cause defects, allowing for easier manufacturing and higher productivity while maintaining voltage isolation through the lead frame design.
3Reliability
If opposite arrangement packaging structure is used, then voltage isolation is achieved, but capacitance characteristic increases and common mode rejection noise characteristic deteriorates
Solution Approach 1:
The patent inverts the conventional packaging structure from opposite arrangement to coplanar arrangement, which reduces the parasitic capacitance between the light-emitting chip and light-sensing chip. This inversion improves common mode rejection noise characteristics while maintaining voltage isolation through the lead frame structure that electrically isolates the two chips.
4Reliability
If inner encapsulant body and outer encapsulant body are used in conventional photocoupler, then protection is achieved, but shaping difficulty increases and attachment tightness is difficult to achieve
Solution Approach 1:
The patent merges the inner and outer encapsulant bodies into a single integrated encapsulant structure. This merging eliminates the complexity of shaping and attaching two separate encapsulant bodies while maintaining the protective function. The single encapsulant body is easier to manufacture and ensures tight attachment without the alignment and bonding difficulties of multi-layer encapsulation.
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 coplanar design simplifies manufacturing, enhances high-voltage resistance, reduces size, and improves common-mode interference immunity, meeting safety regulations and market demands for thinner designs while maintaining efficient light transmission.
Implementation Method 1
the light-emitting chip is driven by an input electrical signal to convert an electrical signal into an optical signal
Implementation Method 2
the light-sensing chip receives the optical signal and converts it into the electrical signal as output
Implementation Method 3
a light-reflective encapsulant body being a light-reflective material with a light reflection of 70%-99%
Data Source
AI summary
Disclosed is a photocoupler comprising: at least two lead frames; an optical channel structure including a light-emitting chip, a light-sensing chip, and a light-transmissive encapsulant body, wherein the light-emitting chip and the light-sensing chip are mounted and bonded on the lead frame and are coplanar, a light-emitting surface of the light-emitting chip and a light-sensing surface of the light-sensing chip face toward the same direction, the light-transmissive encapsulant body encloses the light-emitting chip and the light-sensing chip; and a light-reflecting package encloses the light-transmitting package, and all enclosing contact surface where the light-reflecting outer package contacts the light-transmissive encapsulant body is an optical reflective surface, wherein the light-reflecting encapsulant body and the light-transmissive encapsulant body are formed by double molding and epoxy molding, so that the light-transmissive encapsulant body and the light-reflecting encapsulant body are easy to be shaped.