Capacitive Isolator Circuit for High Voltage Isolation
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Solution Overview
Problem
Existing digital isolators in power conversion products face challenges such as start-up synchronization issues, error detection difficulties due to long pulse periods, lack of common mode rejection in capacitive coupling, and RF interference from cellular devices, which affect the reliability and efficiency of high-speed digital links.
Innovation Solution
An integrated circuit with capacitive isolation circuitry that uses a pair of capacitors to provide high voltage isolation between functional groups, employing frequency or amplitude modulation techniques to transmit data, and incorporating transmit and receive circuitry to manage RF signals and minimize common mode signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If magnetic pulse couplers are used for digital isolation, then voltage isolation is achieved, but start-up synchronization and error detection issues occur
Solution Approach 1:
The patent introduces a capacitor as an intermediary coupling element between the primary and secondary sides of the isolator. This capacitor enables direct capacitive coupling that eliminates the need for magnetic pulse synchronization, allowing the secondary side to directly detect voltage levels without waiting for pulse edges, thereby resolving the start-up synchronization problem while maintaining voltage isolation
2Reliability
If capacitive coupling is used for isolation, then common mode rejection is improved, but RF interference from cellular devices increases
Solution Approach 1:
The patent changes the operating parameters by using direct capacitive coupling without magnetic transformation, which fundamentally alters the frequency response characteristics. This approach provides inherent common mode rejection while the direct coupling path minimizes RF interference susceptibility compared to magnetic coupling schemes that can act as antennas at GHz frequencies
3Reliability
If magnetic resistive couplers are used, then isolation is provided, but device complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the complex magnetic resistive coupling mechanism (resistors and transformers) from the isolation circuit. By using only a capacitor for capacitive coupling, the design achieves voltage isolation with significantly reduced circuit complexity and lower component count, removing the need for wheatstone bridge circuits and magnetic resistive elements
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 solution achieves reliable high-speed digital isolation with up to 5,000 volts of voltage isolation, effectively addressing synchronization, error detection, and RF interference issues, while maintaining low power consumption and cost-effectiveness.
Implementation Method 1
capacitive isolation circuitry that uses a pair of capacitors to provide high voltage isolation between functional groups
Data Source
AI summary
An integrated circuit provides high voltage isolation capabilities. The circuit includes a first area containing a first group of functional circuitry located in a substrate of the integrated circuit. This circuit also includes a second area containing a second group of functional circuitry also contained within the substrate of the integrated circuit. Capacitive isolation circuitry located in the conductive layers in the integrated circuit provide a high voltage isolation link between the first group of functional circuitry and the second group of functional circuitry. The capacitive isolation circuitry distributes a first portion of the high voltage isolation signal across the first group of capacitors in the capacitive isolation circuitry and distributes a second portion of the high voltage isolation circuitry across the second group of capacitors in the capacitive isolation circuitry.