In this presentation by Sam Ben-Yaakov on power flow considerations in power filters, the speaker distinguishes between signal filters and power filters. Signal filters are used to remove noise from a signal without affecting the power flow, whereas power filters smooth out the fluctuating or pulsating power from sources like rectifiers to deliver a stable output to the load. For example, an active power factor correction (APFC) front end produces pulsating power, which is then filtered by a capacitor to store and release energy as needed, ensuring a more constant output. The function of the power filter, particularly capacitors, is to manage energy storage and release based on the power flow, maintaining stability for the load.
The presentation further explores various filtering solutions for smoothing out power. One option is the use of a large capacitor to reduce ripple, though this can result in high current spikes. Alternative methods, such as a BJT-based filter, provide lower losses and can handle larger ripples with minimal energy dissipation. However, each approach comes with trade-offs in terms of efficiency, ripple rejection, and cost. For instance, LDOs offer quick adjustments but suffer from higher losses when the input voltage fluctuates. Meanwhile, DC-DC converters provide high efficiency and a constant output but may struggle with ripple rejection at certain frequencies. The speaker concludes that while DC-DC converters are ideal for efficiency, the choice of filter depends on the specific requirements, including ripple handling and cost considerations.
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Source: Sam Ben-Yaakov in EPCI Blog
