What Makes Linear Power Supplies Different than Switching Power Supplies?

Linear power supply

The two most popular DC power supply designs are switching power supplies and linear power supplies. Linear power supplies feature a sizable steel or iron-laminated transformer that provides a safety barrier for the low voltage output from the AC input and reduces the input voltage. The transformer also provides excellent isolation by separating the the AC line neutral or ground from the power power supply’s output. A linear power supply is usually much heavier than a switching power supply due to the size of the transformer. Linear power supplies deliver constant voltage at all times, whereas a switching power supply operates by constantly switching the source on and off at a rate determined by the necessary voltage.

Linear power supplies are often selected because of certain performance advantages and their simplicity of use — linear regulator ICs are widely available and the designer only needs a rectified voltage source to operate. A switching power supply, on the other hand, is usually more complex and requires more integrated circuits as well as several inductors.

Switching power supply

The advantage of a switching power supply over a linear power supply is its efficiency. A linear supply operates like a voltage divider that constantly changes resistance to regulate the output voltage, so the energy that goes into the linear power supply will diminish by the time it exits from the outputs. A switching power supply, however, has fewer resistive elements and the energy is mainly stored in its capacitors. The voltage in a switching power supply constantly oscillates at a very minute amount and the circuitry uses this oscillation to gauge when to connect and disconnect from the source.

The disadvantage of a switching power supply is noise. The voltage oscillations and the constant connection and disconnection from the source creates additional electrical noise that can interfere with other nearby electronic devices. Adequate shielding helps reduce the noise in a switching power supply. Although linear power supply designs also create some noise, their design produces much less noise than is typical of a switching power supply. For this reason, many users of lab-grade or bench power supplies prefer a linear power supply over a switching design.

In summation, linear power supplies have been proven to be reliable but less efficient than switching power supplies. Because they require a large transformer, linear power supplies produce comparatively less noise and are both larger and heavier than switching power supplies.

A switching power supply is smaller, lighter, and more efficient than its linear counterparts. They do produce more noise than a linear power supply, so the choice between the two technologies should consider all the factors mentioned above. If you are not concerned about noise or size, a switching model may be the better choice.

Wayne

It was 1971 when an amazing new device called the Integrated Circuit became the new big thing in electronic design and manufacturing, and the Thorpe family started their mail order catalog, Superconductor Supermart. Wayne is still active on a daily basis with Circuit Specialists, serving as a consultant and intermediary to all of its international vendors.

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