D1 Power Supplies

Topic

Every power supply serves as a critical support component for the rest of an electronic system. The linear regulators—previously described in the Part II power supply model—set their output voltage using an internal reference and a pair of resistors that define the desired ratio relative to that reference; while simple, low-noise, and fast-responding, they are inefficient when the difference between input and output voltage is large, as that entire difference is dissipated as heat within the regulator itself—a phenomenon of Joule heating previously established in the second model of this catalog.

This generated heat raises the component's internal temperature above ambient levels, to a degree determined by the amount of dissipated power and the package's ability to dissipate heat to the outside environment; if the internal temperature exceeds the semiconductor's safe limit, the regulator fails or sustains damage, which is why high-current applications require additional heat sinks. In contrast, switched-mode power supplies dominate applications requiring more than a few watts of power, thanks to the significantly higher efficiency previously described in the AC/DC converter model.

Uninterruptible power supply (UPS) systems incorporate batteries to maintain power delivery during grid outages, utilizing various architectures that offer different trade-offs between output voltage quality and reaction time in the event of a failure. Power factor correction in grid-connected power supplies adjusts the equipment's current consumption to approximate a purely resistive load—drawing on the concept of power factor established in the AC signals model—thereby reducing unnecessary reactive current and associated losses within the distribution network. That is why this module—which begins with a regulator that dissipates the entire voltage difference as heat—concludes by showing that designing a power supply goes beyond simply choosing between linear and switching topologies: it also requires managing the heat generated by the conversion process itself, and that heat does not vanish simply because the design was efficient on paper.

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