How to implement galvanic isolation for power and signal lines in high-voltage systems
Robust protection for devices and users is required in the presence of power and signal lines across a range of high-voltage applications, including Industry 4.0 systems like factory automation and motor drives. This extends to automotive and electric vehicles (EVs), medical systems, test and measurement applications, and green energy systems such as photovoltaic systems and grid infrastructure. To achieve this protection, some form of isolation is required. The challenge for designers is to ensure the isolation mechanism is compact, efficient, and cost effective, while also supporting bidirectional signal transmission and power transfer. Because the isolation mechanism must provide operator safety from high voltages and ensure reliable system operation, isolation devices must meet standards like International Electrotechnical Commission (IEC) 60747-5 and IEC 60747-17.
Traditional approaches to galvanic isolation using optocouplers or transformers can satisfy the IEC standards but have limitations in some applications. To more reliably meet device and user protection requirements, while also providing bidirectional signal transmission, galvanic isolation using capacitive and magnetic technologies is required. This article briefly introduces galvanic isolation. It then reviews the IEC standards and looks at how galvanic isolation can be implemented using integrated capacitive and magnetic technologies. It presents example galvanic isolation solutions from Texas Instruments for applications including general purpose isolators that combine capacitive and magnetic technologies. Evaluation
The role of galvanic isolation Galvanic isolation prevents current flow between functional sections of electronic or electrical systems, but supports the transmission of analog and digital signals and power between the sections (Figure 1). Galvanic isolation is useful for: ■ Connecting functional sections that have different ground potentials ■ Breaking ground loops by stopping current flow between functional sections sharing a ground
■ Protecting operators from shock hazards from high- voltage sections
By Jeff Shepard Contributed By DigiKey's North American Editors
boards that speed the design process are also discussed.
Figure 1: Galvanic isolation allows data and/or power flow, but no ground currents between isolated sections. (Image source: Texas Instruments)
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