With the advent of highly efficient switching-mode power supplies, linear power supplies are often thought of as old-fashioned and not very useful except in a few specific applications. Nothing could be further from the truth. In fact, modern versions of linear power supplies are making their way into a wide range of industries and applications that demand clean power with very little ripple and low noise (EMI and RFI).
Let’s take a quick look at the major differences between these two styles as well as a few applications where linear power supplies really shine:
Switching power supply advantages: For higher efficiency, a smaller form factor and lighter weight, switching power supplies are the clear winner. However, this higher efficiency and lower heat dissipation comes at a cost. Not only are they more expensive than linear versions, they’re also more complex and can cause electrical noise issues. Even so, their high performance, small footprint, and proven reliability are hard to beat compared to their linear counterparts.
Linear power supply advantages: When low common mode noise is a must, making the tradeoff between the higher efficiency of switching power supplies and lower noise of linear styles makes sense. Switching power supplies just can’t offer low enough ripple for certain applications. A simpler design and lower part count also makes mean time between failures another key advantage of linear designs over the more complicated switching-mode construction.
Key applications for linear power supplies: Simply stated, linear power supplies are an ideal choice when output noise must be kept to a minimum. Applications such as high-end audio equipment, lighting designs such as LEDs, sophisticated sensors, and redundant power for power generation scenarios are all prime candidates for linear power supplies due to their minimal noise output and low ripple. Medical equipment also requires linear power supplies as well, though there are only a few products on the market certified to meet industry standards for patient and operator protection. The key is choosing the right power supply for the type of load in question, and balancing efficiency needs with noise requirements.