AC Power Supply vs. DC Power Supply: Key Differences, Uses & How to Choose

What is AC and DC in power supply?

Understanding the Meaning of Power Source

The term power source refers to the fundamental nature and function of a device that supplies electrical energy. Understanding the meaning of a power source helps clarify how electrical energy is generated, converted, and regulated, and explains the principles behind alternating current (AC) and direct current (DC). This knowledge is essential when choosing the appropriate power supply for different applications.

Electrical power is commonly categorized into two types based on input and output: alternating current (AC) and direct current (DC). The key difference between them lies in how the current flows. In AC power, the current periodically reverses direction and varies in magnitude. In contrast, DC power flows in a single, constant direction, with electrons moving along a linear path.

AC power is the form of electricity most often used in residential and commercial environments, supplying power to household appliances through wall outlets. DC power, on the other hand, is commonly used by batteries, solar cells, fuel cells, and alternators. Many electronic devices rely on DC electricity because it provides a stable and consistent voltage.

Although both AC and DC power are used daily, their differences are not always well understood. One might wonder why two types of electrical power are necessary. The reason lies in their distinct advantages and use cases. AC power dominates electricity distribution because it can be transmitted efficiently over long distances. However, many modern electronic devices still require DC power to operate properly.

As a result, AC power delivered through outlets often needs to be converted into DC power before it can be used by electronic equipment. This makes both AC and DC power equally important, as each serves a critical role in modern electrical systems.

Preen’s AFV-P Series AC power source features transient capabilities that allow users to precisely control waveforms by inserting disturbances at user-defined points with adjustable drop and rise ranges. This functionality is useful for simulating pre-compliance tests and various power line disturbances, such as surges, sags, spikes, and dropouts, for immunity testing. The AFV-P Series can sustain inrush currents up to nine times the maximum output current, eliminating the need to purchase higher-capacity power supplies to accommodate high inrush loads. Additionally, due to the wave-like nature of AC power, it can travel farther than DC power.

The AFV-P Series is a programmable AC power supply that also provides DC output and precise measurement capabilities. It can generate AC output to simulate real-world grid conditions as well as DC output based on user-defined settings. This makes it a cost-effective and versatile power testing solution for R&D and certification laboratories. For this reason, testing both AC and DC power is essential—and the AFV-P Series is designed to support both.

AFV-P Series AC power supply is a programmable AC power source with DC output and precision measurement. It not only provides AC output to simulate real world grid conditions, but also can generate DC output based on the user's settings. It is an ideal cost-effective power testing solution for R&D and certification laboratories. That is the reason why testing for AC & DC is also important, which our AFV-P series is capable of.

(AFV-P Series High Performance Programmable AC Power Source)

AFV-P Series - How to simulate for IEC61000-4-11 standards
The AFV-P series is a high performance AC source that features fast response, high accuracy, low THD and tight regulation.

Understanding AC Power: What is an AC Power Source or AC Power Supply?

What Is AC Power and an AC Power Source?

Before explaining the meaning of an AC power source, it is important to first understand what AC power is. AC power, short for alternating current, is the standard form of electricity used in most household and commercial applications. Its defining characteristic is that the current continuously reverses direction and changes in magnitude over time, typically following a sine wave pattern. This type of power is supplied through electrical outlets and is widely used to operate lamps, household appliances, and industrial equipment.

An AC power source, also known as an AC power supply, is a device designed to deliver AC power to electrical equipment. While many household appliances can operate under the unsteady voltage conditions of general grid power, precision instruments and devices containing electronic circuits are far more sensitive. Voltage instability or waveform distortion can negatively affect their performance and may even cause malfunction or damage.

In addition to eliminating voltage fluctuations, an AC power source can also be used for testing purposes and to simulate malfunctions, including instantaneous electricity shutdown, harmonic generation, surges and sags, in the testing of electronic equipment. This is due to its capacity to supply various voltages and frequencies.

As the last paragraph states, the electricity provided by the power supply may contain various fluctuations, which can cause malfunctions in the device under test (DUT). Therefore, it is essential to verify in advance that the DUT can withstand such an environment. To conduct power supply tests, an AC power source is typically utilized, as it is best suited for testing the DUT's actual power supply. Each test must be performed separately to ensure accurate results.(Learn More: IEC-61000-4-11 Simulation)

Simply put, AC power source is a kind of power supply that meets the following three properties:

• Providing stable voltage output.
• Offering steady waveform output regardless of fluctuations of the input voltage.
• Supplying sustaining power to different types and changes of the load.

What are the categories of AC power supplies?

Single-Phase AC Power Supply

An AC power supply might be a single-phase or three-phase power supply. A single-phase power supply is the distribution of AC from the power line through the load, and back through the neutral wires. Single-phase power supply is a common method to supply AC current to individual residences and business offices. On the other hand, a three-phase power supply consists of three conductors to transfer AC with a phase difference of 120°. A three-phase power supply is a more economical and efficient way to deliver electricity, since three-phase power supplies contain less materials of conductors to transfer the same amount of power.

Three-Phase AC Power Supply

A three-phase AC is especially used for high-voltage power transmission.The AFV＋series High Power Programmable AC Power Source is featured of the three phase independent adjustment. Users can press the icon on the main page of the touch screen to quickly switch from balanced voltage setting to independent voltage adjustment setting. The AFV＋series High Power Programmable AC Power Source is ideal to simulate different regions' voltage and frequency conditions, and can cover applications for domestic appliances, motors, medical equipment, lighting and EMC laboratory.(Learn More: Worldwide Electric Power System Simulation)

Related AC Power source Products

AC Power Source

 

Where is the AC power supply used?

Single-phase power supplies are not efficient in powering large industrial equipment,however, household appliances such as coolers, small air-cons and fans commonly take advantage of single-phase power supplies since AC power supply is not polarized.On the other hand, The efficiency of a three-phase power supply is significantly higher in comparison to a single-power supply carrying the same load.Three-Phase Power Supplies are usually applied in industrial equipment such as motors, power pumps and electric heaters that require larger power supplies.

 

(AFV+ Series High Power Programmable AC Power Source)

Worldwide Electric Power System Simulation－ AFV+ Series
The AFV+ series is a high power programmable AC power source utilizing advanced PWM technology to deliver power with THD ≦ 0.5% and up to 2000kVA.

AC Power source FAQs

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What is DC Power?

Definition and Applications of DC Power Supply

A DC power supply is a device that delivers stable direct current, commonly used in electronic equipment, instrumentation, and testing systems. With precise output and strict voltage regulation, a DC power supply ensures that sensitive components operate in a stable environment, thereby preventing potential damage from voltage fluctuations.

DC Power (Direct Current power) refers to electrical power flowing in only one direction. This current mostly comes in the form of batteries, solar and fuel cells. Because DC power delivers consistent voltage, most electronics require this power type. You can see many electronics in our daily lives have batteries of the devices or need to convert AC power from the outlets to DC power through a rectifier. By doing so, the delicate components inside electronics devices will not be damaged by the highs and lows of alternating current.

(ADG-L Series Programmable DC Power Supply)

ADG-L series introduction and LED Testing
ADG-L series has excellent performance and characteristics, suitable for high voltage or high current test simulation.

Related DC Power source Products

DC Power Supply

 

DC Power source FAQs

What is the Difference Between an AC and DC Power Supply?

It’s very clear that AC power supply is a device that supplies AC power, and DC power supply is a device that supplies DC power.
As we mentioned before, the main difference between AC and DC power is the direction of electrons flow. AC power, flowing in alternating direction, uses electrons that move like waves, whereas DC uses electrons that move in a straight line, flowing in only one direction.
Because AC power moves in waves, it can travel a lot farther than DC power. Preen's AFV+ series AC power supply has the following traits which can meet the requirements, utilizing advanced PWM technology to deliver power with THD œ 0.5% and up to 2000kVA.
Power plants can easily generate large amounts of AC power and deliver it through power lines, and the voltage will be stepped down to an acceptable level when it reaches homes and businesses.

On the other hand, in many laboratories or factories, the DC power supply is located a certain distance away from the DUT, and this sometimes causes voltage drop due to the resistance of the wires. Preen's ADG-L DC power source is equipped with remote sensing to compensate voltage drops and provide a stable output voltage,and it allows users to have the desired voltage appear at DUT.
There is another easy way to tell the difference between AC power and DC power sources. Just see whether the electricity comes from an outlet or a battery. Generally, outlets supply AC power, whereas batteries supply DC power.

Items	AC power supply	DC power supply
Flowing Direction	Alternating direction.	One direction.
Electric Current	Wave-line motion (a sine wave).	Straight line.
Advantages	AC power can travel farther very efficiently. The generation of AC is cheaper than that of DC. When AC is supplied at higher voltages, the transmission losses are small compared to DC transmission. AC can easily be converted into DC with the help of rectifiers.	Consistent delivery of voltage to electrical devices. In DC System, there is no interference with other communication lines and systems. More readily available than AC power.
Disadvantages	Interference with the neighboring communication lines. At high voltages, it is more dangerous to work with AC than DC.	DC power can only run across short distances, making it unsuitable for the electrical grid. Due to commutation problems, electric power can’t be produced at High (DC) Voltage.
Electricity Comes From...	Most outlets.	Batteries, solar and fuel cells.
Applications	Preen's AC power supply can be utilized for home appliances, laboratory, industrial power supply, electric vehicles, renewable energy, military, aerospace and medical industry.	Preen’s DC power supply includes renewable energy, electric vehicle (EV), power battery IT/SMT production line and motor & compressor.

 

Why are there Two Different Types? What's the need for AC and DC Power Supply?

Although AC power can be easily converted to DC power if required, DC power still cannot be totally replaced by AC. The main reason is that AC power transmitted power through lines whose length are not limitless, so if we use everything with lines, our living space will definitely be confined. To put it in other words, battery power, fuel cells, or solar cells, which provide DC power, are more readily available than AC power from electricity lines.

As a matter of fact, AC is the most prevalent power supply on the electricity market because AC is easier to generate than DC due to the costs and the way the generators of DC operate. Despite the strengths of AC , DC still plays a vital role on power supplies. It turns out, anything battery-powered depends on storing DC power. That is, DC facilitates devices that need to store power in batteries for future use, such as smartphones,laptops and cameras.

Because both electricity types are still in use, sometimes you will need to convert the voltage. In this case, you will need an AC-DC power supply which can convert the voltage into direct current and adjust the voltage up or down according to the device you are using.

How Does an AC/DC Power Supply Work?

Whether you choose an AC-DC or a DC-DC power supply, the objective of a power supply is to power the load with the proper voltage and current. A power supply can be external, often seen in devices such as laptops and phone chargers, or internal, such as in larger devices such as desktop computers.

Each AC-DC power supply may have its different design configurations, but basically, it all has three primaries and necessary components which are transformers, rectifiers, and filters.

First of all, in order to provide a reliable source of DC electricity to a device, the AC voltage will be stepped down by transformers. Secondly, rectifiers will take AC electricity from a source (such as mains power) and convert that energy into DC electricity. Last, a filter will remove some of the electronic noise from the high and low AC power waves. These are the three main steps that how an AC-DC power supply works.

 

Types of AC/DC Power Supply

Linear AC/DC Power Supply

A linear AC/DC power supply typically utilizes linear regulators to maintain a constant voltage at the output. Compared to switching AC/DC supply, linear AC/DC works less efficiently and the size of a linear AC/DC power supply is larger.

Switching AC/DC Power Supply

A switching AC/DC power supply uses the power conversion technology to turn switching transistors on and off rapidly to provide regulated voltage. For instance, personal computer chargers, cell phone adaptors and uninterruptible power supply (UPS), are all types of switching power supplies. With the innovation of technology, switching power supplies have been widely applied in multiple industries due to its compact and lightweight characteristics.
Switching AC/DC power supplies play an essential role in the development of electronic industries. Therefore, nowadays switching power supplies are widely preferred and utilized owing to their cost, size, and efficiency.

	Linear AC/DC Power Supply	Switching AC/DC Power Supply
Output	constant voltage	regulated voltage
Size	Requiring large transformers,increasing the need of space	The space needed of the transformers are much smaller due to the higher frequencies of switching AC/DC power supply
Complexity	larger and more complex filters, as well as control and regulation circuitry for the converters.	larger and more complex filters, as well as control and regulation circuitry for the converters than linear AC/DC power supply
Noise	Unregulated power supplies can compose a loud noise due to the voltage ripple.	The noise made by its’ transistors can either be filtered out or switched into different frequencies that above the limit of human hearing

 

What will happen if you don’t use an AC/DC power supply?

As mentioned previously, the main purpose of using an AC/DC power supply is to transform the AC into a DC voltage, and then the DC can then be utilized to power different electrical devices. Without an AC/DC power supply, AC cannot be transformed into a stable voltage, which may cause electronic components to be damaged. Moreover, some high AC voltage equipment may malfunction or even explode if not using AC/DC power supply properly.

How Does a DC-DC Power Supply Work?

Sometimes, you will need a DC-DC power supply if the device starts with DC power. Unlike AC, DC power cannot be changed from one voltage to another (step up or step down) using a transformer. Therefore, a DC-DC power supply comes out to solve this problem - to generate regulated output voltage for electric and electronic applications. First of all, DC-DC power supplies often include inverters and rectifiers to convert the DC power into AC power, hence AC power can move into a transformer to change the voltage. After the power supply generates the proper voltage, the electricity needs to convert back to DC power through the rectifier, and thus you can use your devices smoothly.

In order to produce cleaner energy in the output, DC-DC power supplies require regulators to smooth out the signal. You can consider whether your devices need a perfectly smooth voltage. Preen's ADG-L series DC power source is designed for low ripple, high accuracy and tight regulation for simulating different DC voltages. With fast transient response and rise time, the ADG-L DC power sources are ideal to test DUT behavior to voltage sags, dropouts, ON/OFF tests and complex DC waveforms. Although unregulated power supplies are often cheaper than regulated, we strongly suggest you use a regulated DC-DC power supply for a delicate device.

Application of DC-DC converter

DC-DC converter is an electronic circuit or regulator that converts a source of DC from one voltage level to another. DC-DC converter is widely used in a variety of products from portable devices, including cell phones, computers, and so on. Besides, a DC-DC converter is also one of the key components for electric vehicles, since it converts voltage from the high-voltage battery pack and to low-voltage for electric devices, such as wipers, air conditioners, headlights, stereos, seat heaters, etc.

DC-DC converters influence an improvement of performance on efficiency, reliability, control and even power level. Preen’s programmable DC supply is suitable for high-voltage and low-voltage DC-DC converters testing. The built-in simulation function allows DUT to be tested for voltage and current dropout, spikes and other repetitive testing. With the outstanding stability, precise measurement and user-friendly programmable function, ADG-L series DC power source allows users to enter the test data easily and test multiple DC-DC converters in the meantime. Therefore, Preem’s programmable DC supply significantly improves the testing efficiency and productivity compared to the conventional testing solutions. ADG-L series DC power source offers output voltage up to 2000V and output power from 5kW to 300kW which is ideal for high power DC/DC converters testing applications. (Learn more details: EV Testing Solution Part II : DC/DC Converter)

(ADG-L Series Programmable DC Power Supply)

High Power Density Programmable DC Power Supply－ ADG-L Series
ADG-L Series which has 19 models and three different output power, 5kW, 10 kW and 15 kW. Utilizing PWM technology, ADG-L delivers stable output and precise measurement.

How to Simulate Solar Array IV Curve
Preen rolls out a new function on the latest programmable DC power supply: solar array IV curve simulation, which has built-in dynamic MPPT test profile of EN50530 and Sandia and can monitor the MPPT status for the PV inverters.

How to Know if a Power Supply is AC or DC?

Usually, on the surface of the device writes the form. The easiest way to tell whether it is an AC-DC power supply or a DC-DC one is to see the “input” part. When the input is AC, the device surely is AC-DC. On the other hand, when both input and output parts are DC, the device is DC-DC.

How to Choose a Power Supply?

When choosing a power supply, users should first decide the applications of the power supply. Based on the needs, users might consider some factors including certification, maximum power output, and output voltage regulation.

• Certification: Standard certifications and are required in order to ensure customers’ safety.
• Maximum Output Power: For safety, be sure of the range of output power.
• Output Voltage Regulation: Voltage determines whether the electrical devices would function normally or not. Users should pay attention to the voltage regulation standards.

 

Why Choose Preen (AC Power Corp.)’s power supply producs?

Worldwide Experience

Founded in 1989, Preen (AC Power Corp.) is a world leader in power supply systems, and has been developing AC and DC power supplies based on the core technology of power conversion. We provide advanced, reliable and cost effective power products including AC power source, DC power supply, regenerative grid simulator, power supplies for aerospace and defense, and line conditioners.
With a corporate office located in Taipei, Taiwan, Preen has three manufacturing facilities and multiple branch offices and service locations worldwide, including the U.S. office located in Irvine, California, to provide services to our customers.

Certificates and Awards

Many of Preen’s products are CE and RoHS certified, in line with international safety standards and environmental friendly development. All Preen's manufacturing facilities have ISO 9001:2015 certifications. We keep rigorous controls on manufacturing processes and plant management to ensure only the top-quality products are delivered.

Preen’s Power AC/DC Supply Products

Preen provides outstanding products and solutions to different applications, and our products cater to different expectations.
For instance, AFV-P series AC power source is a programmable AC power source with DC output and precision measurement. It is ideal for commercial, defense and aerospace test applications from design verification,quality assurance, ATE to mass production.

(AFV-P Series High Performance Programmable AC Power Source)

High Performance Programmable AC Power Source - AFV-P Series
By utilizing the Transient feature within the AFV-P series, users gain enhanced control over waveforms, allowing them to introduce disturbances at specific user-defined points along with a designated drop/rise range.

If you would like to cover a higher power application, then AFV＋ Series AC power source will be your best choice. The AFV＋series is a high power programmable AC power source, and this series is suitable to simulate different region’s voltage and frequency conditions.

(AFV+ Series High Power Programmable AC Power Source)

How to Simulate North America 1Φ 3W Power System
Preen's AFV+ series, a programmable high power AC power source, is able to simulate multiple power systems, whether it is three-phase or single-phase.

Preen Program Makes Remote Management a Breeze
Preen Program gives users a second choice to operate the product. With features of easy-to-use interface, accurate waveform preview and real-time report generator, users can put testing data at your fingertips.

To learn more about our products and determine the best power source for your application, you can visit our pages AC Power Source and DC Power Source for further information.
 

Summary

The most important objective of a power supply is to transform current from one power source to another, and in the meantime transform to proper voltage level. For specific applications, there are different solutions that can meet your needs. You can learn more about Preen’s products on our product page and our products’ applications.

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