Linear vs. Switch-Mode Power Supply Design

by | Jun 26, 2017 | Electronics and Electrical

DC power supplies are out there in either linear or switch-mode designs. While both kinds supply DC power, the technique utilized to generate this power is different. Depending upon the application, each kind of power supply has benefits over the other one. Let us discuss the differences between the two technologies and each design’s disadvantages and advantages.

Switch-mode power supplies convert AC line powers right to DC voltages without transformers, and the raw DC voltage then is converted to a higher frequency AC signal, used within the regulator circuit to generate the desired current and voltage. It’ll result in a much lighter, smaller transformer for lowering or raising the voltage than what might be needed at the AC line frequency of 60 Hz. The smaller transformers also are significantly more efficient than a 60 Hz transformer; therefore, the power conversion ratio is greater.

Linear power supply designs apply AC line voltages to power transformers to lower or raise voltages prior to being applied to regulator circuitry. As the size of the transformer indirectly is proportional to the operation’s frequency, it’ll result in a heavier, larger power supply.

Each kind of power supply operation will have its own set of disadvantages and advantages. Switch-mode power supplies are as much as 80 percent lighter and smaller than corresponding linear power supplies, but they generate high-frequency noises which interfere with sensitive electronic equipment. Switch-mode power supplies, unlike linear power supplies, have the ability to stand up to small AC power losses within the range of 10 to 20 ms without having to affect the outputs.

Linear power supplies require large semiconductor devices that regulate the output voltage and thereby generate more heat, and results in reduced energy efficiency. Linear power supplies usually operate around 60 percent efficiency for 24V outputs, whereby switch-mode power supplies operate at 80 percent and up. Linear power supplies have transient response times of around 100 times greater than their switch-mode counterpart– critical within specialized areas.

Generally, switch-mode power supplies are better suited for portable equipment, as they’re more compact and lighter. Because the electrical noise is easier to contain and lower, linear power supplies are more appropriate for operating sensitive analog circuity.

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