Before we get into the difference between a regulated and unregulated power supply, let’s first start with understanding exactly what “power supply” even means. In a general sense, a power supply is any device that supplies energy (power!) to an electrical circuit. Taken this way, batteries are power supplies for flashlights and power plants are power supplies for the electrical grid.
But that’s not usually what we have in mind when we talk about power supplies. Usually, we use “power supply” to indicate a circuit or a device that adapts available power to the specific needs of one device or a set of similar devices. In most non-industrial settings, the available power, or input power, is AC, and the output power is DC. A power supply will receive power from an electrical outlet and convert the current from AC to DC. So, is every power supply built and designed the same? The answer is no.
Power supplies can be:
Each device needs a different amount of power, or DC, to function, meaning the power supply has to somehow regulate the voltage, keeping the device from overheating.
The power supply is the first place to receive electricity, with most designed to handle fluctuations in electrical current and still provide a regulated or consistent power output. Some power supplies even include fuses that will blow if the surge of electricity is too great, as a way of protecting the equipment.
Power supplies are categorized two ways, regulated vs. unregulated power supply. When comparing a regulated vs. an unregulated power supply, what are the differences? Well, the difference between a regulated and unregulated power supply has to do with the voltage input and output needed for certain devices.
Let’s start by discovering what is regulated power supply, and why does it matter? Regulated power supplies have voltage regulators on their output. This means that the regulator ensures the output voltage will always stay at the rated value of the power supply, regardless of the current that the device is consuming. Any change in the input voltage will not affect the output voltage because of the regulators.
This works as long as the device is not drawing more than the rated output current of the power supply. In fancy electrical terms, a regulated power supply provides a constant output voltage, independent of the output current. A regulated power supply with multiple regulators can offer multiple output voltages for operating different devices. Regulated power supplies maintain the voltage at the desired level and are ideal for almost all types of electronic devices because of the smooth, steady supply of voltage they offer.
Now that we have answered what a regulated power supply is, what is an unregulated power supply? Well, just like the name implies, the difference between a regulated and unregulated power supply is that the output voltage of an unregulated power supply is not regulated. Unregulated power supplies are designed to produce a certain voltage at a particular current. That is, to use the fancy electrical terms again, unregulated power supplies provide a constant amount of power (voltage x current). The output voltage will decrease as the output current increases, and vice versa; thus, an unregulated power supply should always be matched as closely as possible to the voltage and current requirements of the device it is powering.
Unregulated power supplies by their nature do not produce a clean (i.e. constant) voltage like regulated power supplies do. Without a regulator to stabilize the output voltage, any change in input voltage will be reflected on the output voltage. These small changes in the output voltage are called “ripple voltage” and are, essentially, electrical noise. If the power supply and load requirements are closely matched, there is usually not a problem. However, if the ripple voltage is large enough in relation to the output voltage, it will impact the behavior of circuits and devices.
To reduce the impact of ripple voltage, a filter capacitor can be placed across the positive and negative outputs of the power supply. The capacitor, which resists changes to voltage, will act like a regulator, smoothing the output voltage and allowing for normal operation.
So which is the better choice? It depends on your needs. Unregulated power supplies are less expensive, but can only supply power as clean as the available input power. If you are powering equipment with sensitive electronics, clean power is an absolute requirement. You can use an unregulated power supply if it is matched closely to the voltage and current requirements of the device, allowing it to still run smoothly.
If you need a power supply that can offer multiple DC output voltages, then one regulated power supply with multiple outputs will be a better option than multiple supplies with single outputs. Regulated power supplies are also more common and easily found as it is getting easier to make regulated power supplies that are still inexpensive. Also, if the device you are using is sensitive, you may want to choose a regulated power supply, giving you more confidence that your device is receiving the correct amount of voltage no matter the input.
If you are unsure of what type of power supply you are using for your sensor, contact us today! We will help you determine if you are using a regulated or unregulated power supply and what type of sensor will be the best choice for your needs.
top image credit: U.S. Army Corps of Engineers Detroit District via flickr cc
