Technical Information Site of Power Supply Design

2015.09.03 DC/DC

Advantages vs Disadvantages, and Applications

Linear Regulator Basics

The greatest advantage that the linear regulator offers is the ease of use. Because a linear regulator operates when one capacitor each is simply attached to the input and output sides, in substance little design is needed. If you must be between the two, thermal dissipation design may be more complicated than circuit design (for thermal calculations, see Subsection 1-6). Also, unlike the switching power supply, the linear regulator is free of any switching noise, having ripple rejection capability and its low voltage noise, which makes the linear regulator of choice in such noise-averse applications as audio-visual, communication, medical, and measurement devices.

Figure 7. Example applications

Figure 7. Example applications

On the downside, the linear regulator produces substantial loss when the voltage difference between the input and output is large. Because most of the loss occurs in the form of heat, depending on the condition under which it is used, the linear regulator generates extremely large amounts of heat. Using a linear regulator adroitly with power consumption greater than a few watts requires overcoming the heat issue. In addition, linear regulators are applicable only to step-down operations. This holds true for the case of negative voltage applications. Since confusion often arises with respect to the step-down operation of negative voltage in particular, a little discussion in this regard may be in order. Given a -5V input, a negative-voltage linear regulator cannot produce a further lower output of -12V, for example. Here, the potential declines from -5V to -12V, but the voltage increases in a negative direction from -5V to -12V, amounting to a step-up change in the negative direction. Therefore, what a linear regulator is capable of performing is an operation in which the input is -12V and the output is -5V, for example.

Figure 8. Advantages vs. Disadvantages

Figure 8. Advantages vs. Disadvantages

Key Points:

・With a solid understanding of advantages and disadvantages, the potential use of a linear regulator should be examined by comparing it with the switching type.

・Under suitable conditions, the linear regulator may prove to be the best choice.

Basic of Linear Regulators and Switching Regulators

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