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

Power requirements can vary significantly depending on the equipment and test environment. Some applications require precise control of AC frequency and waveform, while others depend on stable and accurate DC output, giving AC power sources and DC power supplies distinct roles in system design and testing.

Understanding their output characteristics, control capabilities, and typical use cases can help engineers select the right power solution for R&D, validation, and industrial testing. Preen also explores how these power systems are applied across different operating environments.

Table of contents

• What is AC and DC in power supply?
• Understanding AC Power: What is an AC Power Source or AC Power Supply?
• What are the categories of AC power supplies?
• Related AC Power source Products
• Where is the AC power supply used?
• AC Power source FAQs
• What is DC Power?
• Related DC Power Source Products
• DC Power Source FAQs
• What is the Difference Between an AC and DC Power Supply?
• How Does an AC/DC Power Supply Work?
• How Does a DC-DC Power Supply Work?
• How to Know if a Power Supply is AC or DC?
• How to Choose a Power Supply?
• Why Choose Preen’s Power Supply products ?
• FAQs

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 standardsThe 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)

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+ SeriesThe 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

How does an AC power supply work?

When it comes to power supply, the three components, a transformer, rectifier, and filter, are primary and necessary.First, in order to meet the required voltage of power supply load, the AC voltage will be stepped down by a transformer. Second, a rectifier will transform the sinusoidal AC waveform into a set of positive troughs and crests. Last, to mediate an oscillation in the AC waveform, a filter will be used to smooth out the AC voltage into a usable DC supply.

What is the normal operating voltage for AC?

Normal operating voltage for AC is 220V and 380V respectively.

What kind of power source is AC?

Coming out of outlets, AC power is a common-see and standard electricity format. More than what kind of AC source is, AC source is a “way” that electricity transmits from a power plant to us, the users. In particular, AC source is very useful for power transportation during the complicated process of transforming.

What is AC source?

AC source is made out of power plants. Also, because AC source changes periodically, especially for the change of sinusoidally, AC circuit is the name of that circuit. For example, AC source satisfies many aspects of our life and needs, including commercial and residential power.

What are the two types of AC power sources?

AC power sources can be generally categorized into two types:

• AC Voltage Stabilizer：Applying Slidac, Tap switching, Phase control and Linear amplifier method.
• CV and CF Frequency converter：Applying switching, Inverter(Single range), Inverter(wide range), and Linear amplifier method.

What Is a Programmable AC Power Supply / Programmable AC Power Source?

A programmable AC power supply, also referred to as a programmable AC power source, is an electrical device capable of adjusting the output voltage and frequency to simulate different grid conditions across various regions. Through digital interfaces such as RS232, GPIB, USB, or analog signal input, users can remotely control and monitor real-time output voltage and current.

In addition to voltage and frequency control, a programmable AC power source allows users to define drop and rise ranges at specific points in the waveform. This enables more precise waveform control to meet testing requirements. Such devices can simulate abnormal mains conditions, including voltage sags, surges, dropouts, and spikes.

Preen’s AFV-P Series is an example of a programmable AC power source that offers DC output and precision measurement, supporting comprehensive power testing and simulation applications.

Which AC Source can be used to test EVSE?

Before EV charger's ready for installation, it's necessary to do input AC characteristic test, control signal test, performance test, safety features and etc to ensure its reliability and safety. These tests can meet the requirements through the AFV+ and PAS series of Preen. AFV+ series can provide the variable power source and PAS series can source or sink power for testing regenerative charger.

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 TestingADG-L series has excellent performance and characteristics, suitable for high voltage or high current test simulation.

DC Power source FAQs

What is programmable DC power source?

It's an electrical device which user can set each STEP’s output voltage, output current and time to meet the test requirements. Preen's ADG-L Series is a programmable DC power source with three output power levels(5kW, 10kW, 15kW) which includes several Auto Range models. Users can set each STEP’s output voltage, output current and time to generate consecutive voltage/current changes or set different rise/fall time.

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.

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 SupplySwitching AC/DC Power SupplyOutputconstant voltageregulated voltageSizeRequiring large transformers, increasing the need of spaceThe space needed of the transformers are much smaller due to the higher frequencies of switching AC/DC power supplyComplexitylarger 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 supplyNoiseUnregulated 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 SeriesADG-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 CurvePreen 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.

FAQs

What is a power supply?

A power supply is a device to provide the electric current that comes from a power source to the type of electricity you need, including motors, computers, and other electrical devices. The main objective of a power supply is to convert electric current to the proper voltage to power the load. With correct voltage and frequency, the electrical devices can function normally.

What's the need for two different power types?

Both types of power supplies have their strengths and flaws. For example, AC is the most prevalent power supply on the electricity market because DC is not able to travel the same distance that AC is , and that AC is easier to generate than DC due to the costs and the way the generators of DC operate. On the other hand, electrical devices are in favor of DC power because of its smooth flow and even voltage which AC fails to provide.

What are the advantages of AC over DC?

1. AC is the most prevalent power supply on the electricity market
2. AC is able to travel a longer distance than DC
3. The costs of AC are lower

Why is the use of AC voltage preferred over DC voltage?

1. The energy loss of AC voltage during transmission is significantly lower than DC voltage.
2. The cost for AC transmission is much lower than equivalent DC transmission.
3. AC voltage can be switched with transformers quite easily.

Which is better, AC or DC?

No matter if it is AC or DC, they both have pros and cons. And that’s the reason why they equally account for specific electric applications respectively. In terms of specific use of long-distance electricity, AC is better, whereas DC is more suitable to provide electronic items at fixed locations, including homes, working places, etc.

What is AC and DC in power supply?

Before explaining the meaning of AC and DC in power supply, let’s firstly know what power supply is. Designed to change one kind of power source into the other one, electricity will finally become the most suitable form that users need with the help of power source. To be more specific, some devices convert from AC to DC power while some devices convert from DC to DC power supply, depending on the format of electricity that devices need.

Is 12V AC or DC?

We can see 12V on DC devices. To be more specific, the output formats of voltage of AC are only 220V and 380V while the output formats of voltage of DC are numerous, such as 30V, 6.0V, 90V, 12V, etc.

More Info:

A Practical Guide to AC Power Sources: What They Are and How They Work

What is an AC power source?

DC Power Supply Solutions for Modern Applications: Features, Functions, and Use Cases

Programmable Power Supply for EV Charging: High-Precision, Scalable Solutions