マンガでわかる直流安定化電源

Episode 3 Learn circuit system with image -1st-

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Episode 3 Column

Episodes 3 and 4 (next episode) are mainly centered around understanding the different circuit formulas. These differences would normally be explained using a circuit diagram, but we have banned these diagrams throughout this comic. So how should we go about this? The method we thought of involved showing the basic structure of each power supplies’ interior and using a little bit of imagination. DC power supplies used in the laboratory come from various lineups made by a wide range of manufacturers, but don’t look too incredibly different on the outside. At the end of the day, they’re still just square-shaped machines with meters, control knobs, and output terminals; and it’s nearly impossible to guess their circuit type based solely on their outward appearance (Although you might be able to guess the capacity judging by the chassis size …).

Since the interior and exterior of a power supply aren’t explicitly linked, the only thing left to do is look directly at the internal components. Here is where we used some “imagination” and thought of a few ways to help the reader associate and remember the link between a power supplies’ internal structure and its circuit characteristics. In this episode, Naoto takes apart some old power supplies he found at a junk shop in Akihabara (electronics district in Tokyo) to show Minami. Nowadays, he probably would have just ordered it online, but we thought it’d be more interesting to go the old school route. Obviously, Minami can’t tell the difference between the two circuit types just by looking at them. However, she points out that one of them has a heavy black object (transformer) attached to it, which happens to be 100% correct.

Either type will come with wiring cables and printed circuit boards, but there are certain components that stand out in linear circuits. The components in question are the extremely bulky power supply transformer and the heat sink (We’ll touch on the heat sink later in Ep. 4). Switching power supplies also utilize transformers and heat sinks, but their size in relation to output capacity is disproportionately small when compared to linear instruments. A transformer is a lump of iron with copper wire wound around it, whose size (amount of core material and winding) is dictated by the power supply frequency and circuit current. Theoretically speaking, the higher the frequency the easier it is to reduce transformer size, but linear power supplies tend to operate at a low frequency (50 to 60 Hz). As you can imagine, the transformer size directly correlates with the instrument’s overall weight. This is one of the few reasons that linear power supplies tend to be both bulkier and heavier than their switching counterparts.

In other words, it’s safe to categorize linear power supplies as “bulky and heavy”. Which begs the question: in a world where “light and compact” electronics are considered the norm, why are we even using these bulky instruments (with pound-for-pound less output power than switching types) anymore!? In the next episode, we’ll be using a few metaphors to help explain the basic principles of each circuit type, which will help you solve the mystery as to why linear power supplies are still used today. This knowledge will serve as one of the main criteria when selecting a proper DC power supply for your application.

Kikusui denshi

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