What is the difference between AC and DC power supplies?

Power supplies are designed to convert power to the type of power you need. Some of the most well-known devices convert from AC power to DC power, but you can also choose DC to DC power. Understanding the differences between these types of power supplies and when to use them will help you make an informed decision when you need to make a purchase.

What is an AC power supply?

An alternating current (AC) power supply is the standard format of electricity that comes from an electrical outlet. The name comes from the waveform used for the current. To understand what makes up an AC waveform, you need to understand that current comes from the flow of electrons. When the electrons in an AC wave move, they can move in a positive direction, which corresponds to the upward part of the sine wave produced by the current. When there is a negative flow of electrons, the wave falls.

These waves come from the alternators in power plants that produce alternating current. Inside the alternator, the coils rotate in a magnetic field. The rotation produces AC waves as the wire moves into areas of different magnetic polarity. For example, when the wire rotates from the north pole region of the magnetic field to the south pole region, the current changes direction. The waves generated in an alternator are very important for the use of AC power.

The wave-like motion of alternating current makes this form of electricity superior to direct current. Because it moves in waves, this form of electricity can travel farther than direct current. Most outlets in a building provide AC power. While many electronic devices (such as lights and appliances) use AC power, other devices require the conversion of electricity to DC format.

What is a DC power supply?

A direct current (DC) power supply uses electrons that move in a linear fashion. This linear movement, as opposed to the fluctuations of AC, gives this current its name. This form of current comes from batteries, solar cells, fuel cells, alternators equipped with commutators that produce direct energy , and rectifiers that convert electricity from AC to DC.

Since DC power is very consistent in terms of the voltage it provides, most electronic devices require this type of power. This is why most electronics have DC power in the form of batteries, or require a rectifier to convert AC power from an outlet to DC power. Power supplies usually have built-in rectifiers and transformers to raise or lower the voltage to the proper level.

For some devices, such as laptops, constant voltage is preferred. For such devices, an AC-DC power converter is required if you want to run these electronic devices from an outlet. The converter converts the waveform to a stable, straight line. It is better to use DC power for electronics because the high or low AC power can damage the precision components inside the electronics.

Why are there two different types of power supplies?

The use of AC power as the primary power source for power plants originated from a heated debate in the late 19th century. At that time, Thomas Edison, a famous inventor, and Nikola Tesla, an equally famous intellectual, fought a fierce battle over the battle for electricity.

Edison developed the DC power supply and hoped that this form would become the preferred power source for homes and businesses. His early work on DC power contributed to the use of DC power as the default power source in many cities. However, DC power was not perfect. With this power source, it is difficult to change its voltage and deliver DC power over long distances. Tesla believes AC power can solve both of these problems.

George Westinghouse, who had financial control of Tesla's induction AC motor, powered the Chicago World's Fair in 1893 at a lower price than Edison. The lower bid ensured that fairgoers would experience a shining city powered by alternating current. That same year, Buffalo, New York, began construction of a hydroelectric facility using Niagara Falls. Three years later, the entire town of Buffalo was receiving electricity from the alternating current generated by the movement of the falls. Seeing the success of AC power in Buffalo, General Electric, which had previously supported Edison's position on DC power, began selling AC power.

Today, AC power continues to dominate the market for electricity. Power outlets bring AC power into a building, and that current may be used immediately or may need to be converted to DC power. Although Edison lost the battle of the currents, the war did not end there. Many of today's electronics require smooth, even DC supply voltages. Since DC power is still in use, both energy types remain essential today.

Since both power types continue to provide power today, you may have devices that run on DC power and have AC power. For these, you will need an AC-DC power supply. These power supplies convert the voltage to DC and adjust the voltage up or down depending on the output of the device.

In addition, many portable generators store power in a battery that uses DC power. For remote applications, battery power, fuel cells, or solar cells that provide DC power are more readily available than AC power from power lines. In these cases, a DC-DC power supply may be required to vary the output voltage for use by the device.

What is the difference between AC and DC power supplies?

As mentioned earlier, the main difference between AC and DC power is the direction of electron flow. This difference leads to all the other differences between these types of power. The fluctuation of AC power helps this power to travel very efficiently farther because power plants can easily generate large amounts of AC power and deliver it through power lines and then feed it into transformers to reduce the voltage until it reaches homes and businesses. DC power does not increase or decrease easily when changing the voltage, so it cannot be transmitted efficiently over long distances.

It is also important to note the difference between AC and DC power transmission. Power sources and their power sources are different - power sources come from transmission lines that feed power directly into equipment or by converting power to another form or voltage.

When comparing the difference between AC power and DC power, consider whether the power comes from a battery or an outlet. Most outlets provide AC power, while batteries are the most common source of DC power.

How does AC-DC power work?

To power many devices in a building, you may need AC-DC power supplies. These units include transformers to change the voltage, rectifiers to convert to DC, and filters to remove some of the electronic noise from high and low AC waves. Even when the power supply changes from AC to DC, the waves are still present, resulting in higher and lower voltage output voltage ripple.

In an unregulated power supply, the ripple voltage stays in the output voltage. If you are not sure if you need a regulated or unregulated power supply, pair the unregulated power supply with the device via the output. Do not use an unregulated power supply with an output that exceeds the needs of the electrical components to avoid overloading the equipment with power, especially if that equipment has electronic components.

In fact, if you have an electrical device, you do not necessarily need an unregulated or regulated power supply; proceed with caution and choose a regulated one. While ripple voltage may have little to no effect on most conventional electrical equipment, it does affect electronic equipment. To avoid damaging components inside your electronic equipment, you need an AC-DC power supply with a voltage regulator.

Regulated power supplies may be linear or switching, depending on the mechanism they use to reduce the ripple voltage of the power supply. Switching power supplies use pulse width modification. The benefits of this technology include the ability to add adapters for foreign use, higher capacity, and boost or buck. Unfortunately, switching power supplies cost more and occasionally generate a small amount of electronic noise when switching. However, these disadvantages do not outweigh the advantages of switching power supplies.

Linear power supplies lack the efficiency and versatility of switching power supplies. These devices have a large transformer that can only be stepped down, so they are useless if you have high voltage requirements. Larger size units typically generate more heat than switching power supplies, but they are quiet and ideal for communications or medical facilities. If you have older equipment or need quiet operation, a linear regulated power supply may be a better choice for smoothing out ripple voltage in the form of output power. As the name implies, linear power supplies operate as a single line, delivering power in one direction through the system.

Switching power supplies have a more complex operation, which, contrary to intuition, makes them more efficient. With these types of power supplies, you truly get what you pay for. Poorly made regulated switching models may have only slightly less output ripple than unregulated power supplies. Evaluate power supply models and their construction carefully before investing. These power supplies start with an AC supply and send it through a rectifier to a DC supply. The transistor then converts the DC power back to AC, this time in a square wave. It can then be passed through a transformer to make the voltage rise or fall. Finally, the correct voltage is returned again through the rectifier to the DC supply, which reduces the output voltage ripple through a filter.

Adjusting the output power of the device reduces the output voltage ripple and ensures a clean DC power supply. For devices that rely heavily on the smoothest power supply without changing voltage, a regulated DC power supply is necessary. If you need a DC-DC power supply, the decision of whether you need a regulated or unregulated power supply does not go away. Because these devices work in unexpected ways, you still need to choose whether you need clean output power.

How do DC-DC power supplies work?

Some devices start with a DC power supply, such as a vehicle battery or solar cell. The voltage from the power supply may be more than what is needed for the device it is plugged into. Since it is difficult for a DC power supply to change its voltage, a DC-DC power supply usually includes an inverter and rectifier to first convert the DC power to AC power. The AC power goes into a transformer to change the voltage. After the power supply reaches the correct voltage, the current enters the rectifier where it is converted back to DC.

As with AC-DC power supplies, DC-DC models may require a voltage regulator to smooth the signal. By converting the voltage to AC, ripple voltage occurs in the current. A voltage regulator reduces the output voltage ripple, thus producing cleaner energy in the output. For devices that do not require perfectly smoothed voltages, they can use unregulated power supplies, which are usually less costly. However, if you must use a DC-DC power supply for precision equipment, you will need the cleaner output of a regulated power supply.

How to know if a power supply is AC or DC

If you have ever wondered how to tell if a power supply is AC or DC, then you must understand the difference between AC and DC power supplies and pay attention to the equipment itself.

One way to determine if you have an AC-DC power supply or a DC-DC model is to look at the device itself. Usually, the input and output information will appear somewhere on the surface. If the input is AC, you have an AC-DC power supply, and if the input and output are both DC, you have a DC-DC model.

Although you already know that AC power includes outlets, this information becomes useless if you have equipment on a boat or aircraft. How do these components get their power? An on-board generator or engine battery can generate the required power. If you are unsure of the power source for your equipment, please contact us. We have experts who can guide you in determining the type of power source you need.

The power source you have is as important as the power you have. To protect your electrical equipment from damage, provide them with power to create the correct type of voltage and current needed for your equipment without exceeding your budget constraints. If you have any questions or need to purchase an AC or DC power supply, we can help.