![]() The transformer facilitates generating multiple output rails, and you can easily modify output voltages by varying the turns ratio to accommodate your design needs. This topology is traditionally used to isolate low-power applications. ![]() Each one offers distinct benefits depending on the application.Ī flyback power supply combines a buck-boost converter and a split inductor to form a transformer. Let’s explore the different topologies used to generate an isolated power supply. ![]() ![]() Designers usually elect to design isolated supplies that are optimized for logic and system noise performance. While the use of existing secondary supplies is an option, noise coupling and supply regulation often become an issue. These include power-supply voltage levels matching the input- and output-signal levels, each offering a separate ground. In some cases, two separate power-supply rails may already be available within the system for primary- and secondary-side power, as long as you can meet some minimal requirements of the isolator logic. 2).ĭoes a Secondary-Side Supply Work for Isolated Power? Be sure to review the digital isolator datasheet carefully for power-supply requirements before finalizing supply input and output requirements and optimize the output of the digital isolator for the logic levels of interfacing components.įor example, when powering a digital isolator with 5 V that interfaces to a microcontroller, select signals that also are operating at or close to 5-V logic levels on the secondary side (Fig. The input and output signal voltages of a digital isolator often depend on their applied power-supply voltage, and they usually have a direct relationship to the supply voltage (V CC) on the secondary side. Industry end-equipment standards define many of these requirements. Among other considerations for isolated power solutions compared to non-isolated power solutions are system insulation ratings and required creepage and clearance distances, along with electromagnetic-compatibility requirements such as electrostatic discharge and the emissions performance of the system. What Are the Power Requirements for a Digital Isolator?īefore selecting a power topology for a digital isolator solution, you will need to determine the basic requirements of the supply, including the input voltage range, output voltage, output power needed for the secondary side, and the number of output rails. This need is independent of whether a device supports basic or reinforced isolation, and it applies to digital isolators as well as isolated devices with integrated interfaces. Each IC requires a separate power supply and ground for both the primary and secondary sides of the device, with no physical connection between them. The internal architecture of a digital isolator consists of two separate digital integrated circuits (ICs) on a split leadframe with a high-voltage isolation dielectric barrier between them (Fig. But first, let’s address the need for isolated power. This article will introduce some of the most popular topologies-flyback, half-bridge (H-bridge) inductor-inductor-capacitor (LLC), push-pull, and integrated isolated data and power solutions-along with design considerations. ![]() Many options are available when designing an isolated power supply for digitally isolated circuits. While a digital isolator’s secondary side typically requires little power, system designers often include an additional power allowance to supply power for multiple devices. Maintaining the integrity of a signal across an isolation barrier requires the isolation of all coupling paths between the primary and secondary sides of the circuit, including the power supplies. Digital isolators offer a simple and reliable path toward achieving high-voltage isolated communication in industrial and automotive applications. A high-voltage circuit design requires isolation to protect human operators, enable communication to lower-voltage circuitry, and eliminate unwanted noise within the system. ![]()
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