![]() If connected to single phase or three phase AC, an earth connection may also be present (see below) at the input side as a connection in an input EMI filter circuit. Primary ground (PGND): This is the ground region on the primary side of the transformer, i.e., the input side of the power supply.In an isolated power supply, there may be up to 3 ground regions: ![]() The above topology doesn't explicitly show you something important: how isolation is actually implemented and the overall grounding strategy. This is also done in a flyback converter, which is a common type of isolated DC-DC switching converter, although the topology may be different. ![]() ![]() The pulsating output from this circuit is then stepped down to a lower voltage with a transformer and smoothed with a capacitor bank. This is basically what is done in a resonant LLC converter. In the above topology, a step-down transformer is shown at the input (between any input EMI filtering and the rectifier circuit) as part of AC-DC conversion, but often times this will be placed after the rectifier and PFC stages, particularly in an isolated DC-DC switching converter. Typically, in high current switching DC-DC converters that require isolation, the strategy in isolated DC-DC power supply design requires driving a half-bridge or full-bridge array of MOSFETs with a pulse stream supplied by a gate driver circuit. Simple topology for the output stage of an isolated power supply via an isolation transformer. A typical topology for converting AC to DC with an isolated power supply is shown below. In other words, they may need to plug or unplug wires, adjust some settings on the front panel, or otherwise handle the power supply unit. By isolating the input from the output, the end user of the power supply is at lower risk of shock when they work with the power supply. Subsequent PFC and regulator stages might be used to limit the output current to a stable value, which ensures the downstream components are protected from large voltage and current surges at the power supply input.įor a lab-grade DC or AC power supply, the user will need to interact with the output stage of the isolated power supply. These power supplies can accept a large input voltage from AC mains and convert the input down to a lower voltage. This means that power and voltage is transferred from the input to the output without a direct electrical connection between the two sections. What is an Isolated Power Supply?Īn isolated power supply is a power supply that is electrically isolated from the rest of the circuit that it is powering, often by an isolation transformer. non-isolated power supply before starting your design. So let’s all do ourselves a favor, and consider the difference between an isolated vs. Power supply isolation, even when integrated into the board or into a multi-board system, will help protect the end user and other equipment. For many digital and embedded systems, the power supply is integrated into the board, and it doesn't appear as a single integrated circuit. Here, we're not talking about only the AC or DC power supply units you find the lab. non-isolated power supplies is all about designer and user safety. For example, with a non-isolated power supply powering your medical PCB, there is a greater risk for dangerous shocks or surges surge through the supply and into your device, potentially harming the user (and maybe even the patient!).Īn understanding of isolated vs. This is a common measure in power systems, and for good reason. What is power isolation, and what is an isolated power supply? Power isolation is essentially what it sounds like: the power supply is isolated from the rest of the circuits in your system. Oftentimes, when these regulations are in effect, power isolation (or lack thereof) suddenly becomes a very popular topic. Whether it be medical, automotive, military, or anything of the sort, your design could end up being scrutinized and held to very high standards. There may come a time in your career as a PCB designer when your designs will fall under the purview of some kind of regulatory requirements.
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