Episode 4 Column
Episode 4 serves as an explanation of the two main regulation methods in DC power supplies: switching and linear. Power supplies implementing these methods are also known as “linear regulator” and “switch-mode” power supplies. Switching power supplies get their name from the way they “switch” DC voltage on and off at high frequencies.
This is where we decided to make use of various metaphors to help explain this complicated mechanism. In most places, people liken these two regulation methods to “flowing water” or a “water distribution system.” However, we thought this wasn’t very interesting or inventive. In other words, we thought that this concept would be easier to understand with examples that are closer to home. We’re sure that most of you know what water wheels and canals are, but examples so unfamiliar to the average person tend to not stick as well. Therefore, we decided instead to go with something a little bit more universal: bread. This comic book might even be first in the world to compare power supply circuit systems to bread!
Switching type circuits control output with intermittent electrical energy that somewhat resembles the “tear-and-share” bread that is popular in many Japanese bakeries. Linear systems, on the other hand, control output by releasing excess electrical energy (like chocolate being squeezed out of a pastry). The mechanics in switching systems responsible for ‘switching’ the voltage on and off are largely controlled by electronic components (semiconductors) integrated into the system, meaning that bulky transformers and heat sinks aren’t required like in linear systems. This is one of the factors that made compact, lightweight power supplies possible. However, this intermittent switching also produces “noise,” which is seen as a significant drawback.
Linear systems provide a continuous output of electrical energy and are practically noiseless (for the most part). Another advantage would be that because the power isn’t constantly being switched on and off, there is very little delay when responding to changes in the load. It is for these reasons that linear power supplies are still used today. That being said, they do come with the drawback of being big, bulky, and relatively energy inefficient (squeezing out chocolate = heat dissipation).
We often get inquiries from customers thinking that their DC power supply is broken when they notice malfunctions, “jitters” in the voltage, etc. during their tests. More times than not we conclude that the customer actually chose a DC power supply not suited for their application (i.e. choosing a switching power supply when they needed a linear one). There have been an unimaginable number of switching DC power supplies manufactured in recent years. The reason for this is most likely that more and more test applications use products (circuits) that are resilient to noise and don’t require extremely fast transient response speed in which cases a switching DC power supply is completely suitable. However, when your DC power supply isn’t working how you expected it to, it’s important to ask yourself if you are using the right power supply for your application.