App note: Measuring inrush current

an_aimtec_inrush

Inrush current evaluation from Aimtec. Link here

In AC/DC power converters beyond a few watts, during the initial application of power an excessive inrush current will flow when the input capacitors are suddenly charged. If unhindered the inrush current can easily exceed 50 A at the peak of the AC cycle and severely stress the converter’s fuse and input rectifiers, thereby significantly reducing the reliability and life expectancy of the modules. Universal power supplies (supplies which accept a wide range of input voltages) are particularly susceptible to high inrush current since their input capacitors must be large enough to handle line voltages as low as 110 VAC, as well as voltages as high as 305 VAC at start-up. In these environments, a power-supply failure or a tripped circuit breaker can be inconvenient at best, and expensive or dangerous at worst.

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