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The basic introduction of the isolated DC-DC converter

wallpapers News 2021-04-29
The basic introduction of the isolated DC-DC converter
For a variety of reasons, both DC-DC converters may need to be isolated. It is often convenient to separate the input and output grounding so that the current paths are separated without interacting. A common application is to supply circuitry to the RS485 interface, where the isolated power rail for the driver can prevent the current from flowing between the host ground and the connected device.
Having a "floating" output also enables the load docking point to be connected to any DC-DC output terminal. For example, floating 12V can be configured to -12V by connecting the positive output to the ground. Similarly, 12 volts can be "stacked" on another voltage, such as an input of 12 volts, to provide a total voltage of 24 volts, which might be useful for small motor drives.
A degree of anti-EMI performance can also be provided through the power coupling of the transformer, especially against common mode noise generated by the local grounding line.
An important reason for quarantine is often the need for security. You might think that if a DC-DC converter has low input and output voltages, security is not an issue. However, the isolation layer in a DC-DC is often used as part of a broader isolation system to achieve an overall security rating. An extreme example is a "patient-connected" application in the medical market, where the DC-DC converter must have a full medical-grade isolation rating for the highest system voltage (possibly 230VAC). The reason for this is that other devices connected to the patient can fail because of the dangerous voltage applied. A DC-DC converter can allow dangerous currents to flow back to the original device through an "unspecified connection path," so it must have a high level of isolation.
Many promotional materials for DC-DC converters refer to an isolation rating simply as a voltage value, such as 3 KVDC. Users should be particularly careful because this is only a factory "test" voltage, although it is a measure of isolation robustness. DC-DC converters should not be used for security isolation systems unless a particular security agency defines their isolation level as "essential," "enhanced," or medical "protective measures.

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