Although DC power supplies are rather basic electronic devices, there are hundreds of DC power supply products on the market from dozens of manufacturers. Narrowing down the products that best fit your application and budget can be a daunting task. This article discusses the differentiators of DC power supplies, their features, and the applications for which they are best suited. The focus of this article is on dc power supplies used by engineers, manufacturers, quality professionals, and electronics enthusiasts for R&D, manufacturing, and test purposes.
Power supplies range in price from 50 to 20,000, and the cost is often directly proportional to the amount of power the unit outputs. The main function of a power supply is to regulate the output voltage and current. It receives input power and regulates output power to maintain a constant voltage and current. For dc power supplies, the input power is converted from alternating current (AC) to direct current (DC). There are two basic types of regulated DC power supplies: linear and switching.
A linear power supply cannot output a higher voltage than its input source. In theory, a linear power supply powered by a typical 110V wall outlet can only output 110V, assuming the unit is 100% efficient. Realistically, no power supply is 100% efficient. This is because power conversion always results in energy loss (usually in the form of heat dissipation). Therefore, linear power supplies typically output a much lower voltage than their input.
A switching power supply can step up, step down, or invert an input voltage. Switching power supplies are usually larger, noisier, and more expensive than their linear counterparts, but switching power supplies are usually more efficient.
To select the right DC power supply for your application, you need to define some basic design specifications such as voltage range, current range, number of outputs, power cleanliness (referred to as “ripple”), and programmability. Generally, the higher the output voltage and the lower the ripple, the more expensive the DC power supply. Multiple outputs and programming capabilities also add to the cost.
The cheapest DC power supplies are ideal for electronics hobbyists and basic electromechanical applications that require only raw power. In these applications, the powered devices likely already have power conditioning capabilities that do not require precision input power. Low power, single output, DC power supplies range in price from 50 to 200.
Mid-range power supplies are best suited for non-critical laboratory projects involving advanced electromechanical applications or basic board-level testing. Mid-range power supplies can have multiple outputs, higher power ratings, lower ripple and precision, and digital metering (+/- .001V, +/- .01A). Mid-range DC power supplies can be linear or switching and cost between 200 and 1,000.
Advanced applications that require high output voltages, advanced programmability (GPIB PC interface), versatile outputs, and very low ripple should budget in excess of 1,000 for DC power supplies. Many lab, R&D, and test applications can easily spend 5,000 to 10,000 per power supply.