Introduction to Power Supply

Selecting the right power source is a crucial factor that can affect electronic system performance. AC (alternating current) to DC (direct current) power supplies and DC/DC converters are the two primary options for powering these systems.

Direct current is often needed for engine-driven equipment, whereas alternating current is commonplace in households. In this case, you’d be needing an AC/DC power supply to make the suitable conversion — you might have used one before without even knowing it!

AC Power

Alternating Current (AC) is the form of electrical power used by most homes and businesses connected to the electricity grid. An AC current changes direction periodically at a frequency, which is typically 60 Hz in the United States and 50 Hz in Europe, and voltage, which is typically 120 V in the US and 240v in Europe. These different frequencies and voltages generate a waveform that shifts from positive to negative over time.

Power is generated and transferred from sources to residential and commercial sites with the help of generators. Generators create AC power by spinning a magnet inside a coil of wire, thus inducing current in the wire.

This alternating current (AC) power is then transmitted across a system of power lines to transformers that step down the voltage, allowing it to be safely utilized in homes and businesses.

DC Power

DC is a reliable form of electricity characterized by its direct current flow and stable voltage. In contrast to AC, DC has a unidirectional path for electrons. Generated from sources such as fuel cells, solar panels, batteries, and alternators, it has become the ideal choice for many electronic devices that require a constant power source.

Additionally, DC provides cleaner energy delivery than AC power which makes it highly sought after when powering up sensitive electrical equipment.

Unfortunately, this type of electricity is limited only over short distances so using it in power grids may be difficult or even impossible. Nevertheless, DC still remains one of the premier choices when delivering electrical energy efficiently and reliably.

Converting mains electricity from AC to DC power has been a key component in powering our modern electronics. This process dates back to the late 19th century and has developed in sophistication since then.

An AC-DC power supply is necessary for devices like computers, smartphones, tablets, and more – this type of power supply can be configured differently depending on the particular electronics being used, but the basic elements are always present.

AC Power vs DC Power Comarison

Type	AC Power	DC Power
Definition	Mains electricity is the most common form of electrical power supplied to homes and businesses from the electrical grid.	The alternate form of electrical power is commonly employed in different applications.
Electric current	Waveform	Linear
Advantage	AC power is an efficient, effective means of delivering electrical energy more than long distances. An AC electricity grid system, which enables connectivity between multiple power sources and users, is the primary method of distributing AC power.	A dependable and consistent way to produce electricity, although the tradeoff is it doesn’t travel as far.
Applications	Powering electronic items at home or in the workplace.	Batteries, solar and fuel cells, and alternators.

What is AC/DC Power Supply

AC/DC power supplies are important for a variety of electronic devices, such as computers, lights, motors, laptops, and televisions.

There are two main designs for AC/DC power supplies: a linear power supply and a switching power supply. It can be difficult to decide which is the best option.

Type	AC-DC Power Supply
Definition	A device that takes AC electricity from an input source and converts it into DC electricity. This technique greatly enhances the efficiency of the output and powers various electronic devices
Electric current	From waveform to linear
Advantage	Essential for ensuring a consistent and stable supply of DC electricity to devices. They are designed to adjust voltage levels as required to ensure efficient operation at all times.
Applications	An integral part of many everyday devices, from DVD players to medical equipment, as they provide the necessary electrical current to operate them.

Linear AC/DC Power Supply

Linear AC/DC power supplies are straightforward in their design. To use the alternating current (AC) input voltage, a transformer is included to reduce it to an appropriate value for the given application.

This reduced AC voltage is then subjected to rectification and converted into a direct current (DC) voltage for a better waveform quality; filtering of the DC voltage follows.

A traditional linear AC/DC power supply is not always the ideal choice due to its requirements for efficient integration. The transformer size and weight can be quite significant since the input voltage must be changed at the input point.

Plus, a larger core is needed for higher levels of energy transfer. Linear regulators provide a consistent voltage output but all excess energy would go to waste as heat.

For low-wattage applications, this wouldn’t be an issue, but high levels of energy transfer create excessive amounts of heat that may require extraordinary cooling systems or heatsinks to counterbalance the rising temperature.

Switching AC/DC Power Supply

The development of high-power MOSFET transistors has made switching AC/DC power supplies an attractive alternative to linear or traditional designs. By utilizing these transistors, converters can be created that are more efficient and only dissipate the necessary power.

The ultimate result is a switched-mode AC/DC power supply, which relies on a rectified and filtered voltage at the input, then on a chopper to convert this voltage into a high-frequency pulse train.

This new design methodology has been instrumental in reducing transformer size and improving voltage regulation for AC/DC power converters.

After passing through a rectifier and filter, the wave is converted back to direct current (DC) with no remaining alternating current (AC) portion.

Because of its ability to transfer more power at higher frequencies without saturation, the transformer used for a switching AC/DC power supply can be smaller than one needed for a linear version. This allows less space to be taken up in the converter unit while achieving the desired voltage level.

How does an AC-DC power supply work?

Today’s electronic devices rely on AC-DC power supplies. From laptop external adapters to DVD players and medical equipment, these converters come in a variety of formats. The main components of an AC-DC power supply—transformers, rectifiers, and filters—all work together to support the reliable delivery of DC electricity.

AC-DC power supplies work by using a rectifier to convert AC to DC. A rectifier is a device that contains a set of diodes. Diodes are semiconductor devices that allow electrical current to flow in one direction only.

The rectifier converts the AC current to DC by only allowing the positive portion of the AC waveform to pass through while blocking the negative portion.

This results in a pulsed DC output, which is typically smoothed out using a capacitor to produce a more consistent DC voltage. The DC voltage is then regulated to the desired level using a voltage regulator circuit.

Applications of AC/DC Power Supplies

Switching AC/DC power supplies are commonly used in household items such as computers to handle different voltages and frequencies. Manual voltage range switching may be necessary for certain applications, like cell phone chargers, where the demand for cost efficiency is high.

Linear power supplies were formerly the most common type but now ringing choke converters are widely used due to their greater efficiency.

Flyback topology is becoming more popular when low no-load power is needed, and primary-side sensing controllers can help reduce component costs by removing optocouplers from the secondary side.

AC/DC power supplies offer tremendous cost-efficiency and performance benefits for a variety of applications. These ruggedly designed systems evenly divide loads across 24V battery cells while supplying DC/DC voltages at high capacities.

They act as “electronic transformers” for low power loads, making them ideal solutions for commercial fleets, industrial settings, and low-voltage lighting installations.

Challenges in AC-DC Power Supply Design

The design of AC-DC power supplies has traditionally been focused on maximizing efficiency and minimizing cost.

However, in recent years there has been a shift towards designing power supplies that are also smaller in size and lighter in weight.

This has led to new challenges for power supply designers, as they must now balance these competing demands.

One of the biggest challenges facing power supply designers is finding ways to reduce the size and weight of power supplies without sacrificing too much in terms of efficiency or cost. Another challenge is designing power supplies that can handle the increasing demands of modern electronic devices.

As devices get more powerful, they require more power from their power supplies. This can be a difficult balancing act for designers, as they try to find the right balance between power output and efficiency.

The challenges in AC-DC power supply design are constantly evolving, but the one constant challenge is to maintain high efficiency and reliability. This means balancing the trade-offs of size, cost, performance, and safety requirements to deliver the required power levels in a compact, cost-effective, and robust design.

Other technical challenges in AC-DC power supply design include:

♦ Power factor correction:
Designing power supplies that comply with power factor correction standards to reduce harmonic distortion and increase efficiency.

♦ EMC and EMI compliance:
Meeting electromagnetic compatibility and electromagnetic interference standards to reduce noise and prevent interference with other electronic equipment.

♦ Thermal management:
Choosing the right cooling solutions such as heatsinks or fans to keep the power supply components within safe operating temperature limits.

♦ Voltage regulation:
Maintaining a stable output voltage despite changes in input voltage, load current, and other environmental factors.

♦ Isolation and safety:
Providing adequate isolation between primary and secondary circuits and meeting safety standards such as UL, CSA, and IEC.

♦ Cost optimization:
Designing power supplies that use the most cost-effective components and manufacturing processes while maintaining high efficiency and reliability.

Overall, AC-DC power supply design requires a thorough understanding of electrical engineering principles, power electronics, and application requirements to deliver the best possible solution.

Summary

Electrical devices rely on AC/DC power supplies to transform alternating current (AC) into a steady direct current (DC).  Crafting an efficient power supply is challenging due to market demand for high-power, energy-efficient designs that withstand varying load levels.

WEHO is a global leader when it comes to AC/DC power supplies and other power supply products that serves as both an OEM supplier to businesses.

Our AC/DC power supply solutions are used daily by companies and solution providers across the globe. Each product boasts ultra-high efficiency, optimal life, and exemplary reliability.