Power Inductor Applications
- Power supply filtration. As one of the most straightforward applications for inductors, power supply filters (also known as chokes) must have a high enough level of inductance to keep current from dipping to zero at a circuit’s minimum load. The difficulty of calculating the appropriate inductance for power supply filters will vary based on the details of the intended application.
- EMI filters in AC inputs. In power supplies and electronic equipment, an EMI filter helps to keep internally generated
noise contained within the device in question. Virtually any electrical equipment can function as a source of EMI. An inductor can be employed to prevent external AC line noise from entering the device. Likewise, the inductive component of an EMI filter behaves as a low-frequency pass device for AC line frequencies.
- Low-frequency ripple current noise filters. Inductor ripple current presents as a percentage of the full output current. A power inductor provides the ability to filter low-frequency ripple currents to produce the smoothest possible current flow within the circuit.
How to Select a Custom Power Inductor
- Application and circuit. Charging inductors will require analysis of the circuit design/schematics, whereas filter inductors are easier to specify and only require identification of the type of circuit.
- Tolerance and inductance. While off-the-shelf inductors typically allow a 20% inductance tolerance, a custom inductor should feature a lower tolerance of 10% to account for additional design complexity and demanding application variables.
- AC frequency and operating voltage. AC power supply filters operate only at the AC power switching frequency, while other applications may vary more widely.
- DC current. Determine the size of the DC current range required by the coil to ensure proper coil selection.
- DC resistance (DCR). While not all inductors require DCR, any inductor that must operate at or near frequencies of 0 Hz (or if tolerances overlap 0 Hz) will need appropriate specification.
- Max working voltage and/or dielectric strength. Review application requirements to understand the maximum allowed voltage of the inductor before dielectric breakdown will occur.
- Case type. Establish the size and dimensions of the case to ensure the inductor will work within the design.
- Terminals. Take any associated terminals into account, like wire leads, turrets, lugs and more.
- Environmental requirements. The conditions of the operating environment, such as ambient temperatures, humidity levels, altitude levels, and various other properties will help to specify the appropriate power inductor.
- Industry/application specifications. Power inductors are not universal. Select an inductor approved for use in the specific commercial, industrial, or military application.