Power Supply

Table of Contents

What is a Power Supply?

A power supply is a device that converts power supplied from a source, such as a wall outlet, to a specific voltage, current, and frequency. These characteristics may vary depending on their application and the component that requires power. The power supply may need to increase or decrease voltage, convert the power to direct current, or regulate the power for a smoother output voltage [1].

How a Power Supply Works

Since the source of power (the main electrical supply) outputs a consistent amount of voltage regardless of the device connected to it, the power supply must step down the voltage to prevent overload or step up the voltage to meet the requirements of the device [1].

Aside from regulating the voltage, the power supply must convert the incoming electricity to the correct format for the device.  There are two types of power supplies, DC and AC. DC power supplies supply direct current, whereas AC power supplies supply an alternating current. Most electrical devices utilize direct current, and so a power supply can convert the AC power into DC power [1].

Fixed Power Supplies

A fixed power supply has a fixed output voltage, meaning that this voltage comes as is and cannot be changed. When the power supply is plugged into the main electrical supply and turned on, the output voltage is a particular voltage that is expected to change. These power supplies typically have DC output voltages of +3.3V, +5V, and +/- 12V. Additionally, fixed power supplies typically have a fixed current limit setting and regulate their output voltages to an accuracy of around 5% [2].

Bench Power Supplies

A bench power supply is a useful tool for testing components. Bench power supplies may be fixed power supplies or variable power supplies, where the characteristics may be changed. These power supplies may output constant voltage or constant current. One of these two will have a value specified by the user, and the other will have a specified threshold. Bench power supplies generally have similar appearances and control methods. These power supplies have a grounded metal case and a spot to plug in an AC power cord. On the front, there will be two displays: one for voltage and one for current. To set the voltage and current, there will be either knobs or buttons. Additionally, there will be buttons to turn the output on and off [4].

How to Use a Bench Top Power Supply

When a power supply is in constant voltage, the output voltage matches the voltage set by the user, and the current is determined based on the load. When a power supply is in constant current, the output current matches the current limit set by the user, and the voltage is determined by the load. The user must set either the outgoing voltage or current using the knobs or buttons on the power supply, as well as the threshold for the other. The circuit and components can then be connected to the power supply using wires.

Ensure the power supply is connected to a power source. The power cord connecting the power supply to the power source, such as a wall outlet should be in good condition. Typically, the power supply will be turned on via a switch or button [6]. 

References

[1] “What Is a Power Supply & How Does It Work?,” Advanced Conversion Technology, 19-Oct-2020. [Online]. Available: https://www.actpower.com/educational/what-is-a-power-supply-and-how-does-it-work/.

[2] G. R, “What's the difference between a fixed output power supply and a programmable output power supply?,” Watt's Up?, 06-Apr-2012. [Online]. Available: http://powersupply.blogs.keysight.com/2012/04/whats-difference-between-fixed-output.html#:~:text=A fixed output power supply has, well, a fixed output,simple bias for a circuit.

[3] “VOLTCRAFT FSP-1243 Bench PSU,” Conrad. [Online]. Available: https://www.conrad.com/p/voltcraft-fsp-1243-bench-psu-fixed-voltage-24-v-dc-max-3-a-max-72-w-no-of-outputs-1-x-511409

[4] SparkFun Electronics, YouTube, 30-Jan-2017. [Online]. Available: https://www.youtube.com/watch?v=uraPWaeAgYA&t=10s.

[5] Keysight, “Bench Power Supplies,” Keysight, 02-Jan-2018. [Online]. Available: https://www.keysight.com/ca/en/products/dc-power-supplies/bench-power-supplies.html.

[6] Tektronix Experts, “Bench Power Supply Basics,” Tektronix, 01-Apr-2021. [Online]. Available: https://www.tek.com/blog/bench-power-supply-basics.

[7] “Lab Power Supply DIY,” ezContents blog, 2019. [Online]. Available: https://ezcontents.org/lab-power-supply-diy.