Uses, advantages and working principle of a switching power supply

What is a power supply?

A power supply is an electrical device, it converts the current that comes from the power supply to the voltage value required by the load, such as an electronic motor or an electronic device.

There are two main designs for power supplies: a linear power supply and a switching power supply.

Linear: Linear power supply designs use a transformer to lower the input voltage. Then the voltage is rectified into DC voltage and then filtered to improve the waveform quality.

Linear power supplies use linear regulators to maintain a constant voltage at the output. These linear regulators dissipate any additional energy in the form of heat.

Switching: Switching power supply design is a relatively new method, It is designed to solve many problems associated with linear power supply design, including transformer size and voltage regulation.

In switching power supply designs, the input voltage is no longer reduced. Instead, it’s calibrated and filtered at the input. Then the voltage goes through a chopper, which converts it into a high-frequency pulse train. Before the voltage reaches the output, it’s filtered and rectified once again.

Topology of switching power supply

Switching power supplies (SMPS) have four topologies, such as AC-DC converter, DC-DC converter, Fly-back Converter, and Forward Converter.

AC-DC converter: In this type of SMPS, the input power is AC and the output power is DC. we get DC supply. Rectifiers and filters are used to convert this alternating current to a direct current.

DC-DC converter: The input power of this power supply is directly from the high voltage DC power directly.

Fly-back Converter: Any SMPS with output power less than 100W is called flyback converter SMPS. Compared to other SMPS, the circuit of these SMPS is simple and straightforward. This type of SMPS is used for low power consumption.

Forward Converter: The design of this type of SMPS is almost identical to the anti-shock converter SMS. In this SMPS, the switch is connected to the output of the transformer secondary winding for control.

Compared with flyback converters, filtering and correction circuits are more complex. These SMPS, also known as DC-DC buck converters, are also used for transformer scaling and isolation.

How does a switching power supply work?

AC/DC switching power supply is the most effective way to convert AC power supply to DC power supply. Power conversion is divided into three stages: input rectification, power factor correction (PFC), and isolation.

A switching power supply (switching-mode power supply, switch-mode power supply, switched power supply, SMPS, or switcher) is an electronic power supply. It incorporates a switching regulator to convert electrical power efficiently.

Like other power supplies, an SMPS transfers power from a DC or AC source (often mains power) to DC loads, such as a personal computer, while converting voltage and current characteristics.

The pass transistor of a switching supply continually switches between low-dissipation, full-on and full-off states. It spends very little time in the high dissipation transitions, which minimizes wasted energy. Ideally, a switched-mode power supply dissipates no power.

Voltage regulation is achieved by varying the ratio of on-to-off time. In contrast, a linear power supply regulates the output voltage by continually dissipating power in the pass transistor. This higher power conversion efficiency is an important advantage of a switched-mode power supply.

Advantages of switching power supply

The use of any technology is often a careful balance of several advantages and disadvantages. This is true for switch-mode power supplies which offer some distinct advantages but also have their drawbacks.

SMPS advantages

High efficiency: A switch action means that the series regulator element is on or off. So very little energy is given off as heat, and very high levels of efficiency can be achieved.

Compact: Due to high efficiency and low heat dissipation level, Switching mode power supplies can be made more compact.

Costs: One of the things that makes switching power very attractive is cost. The higher efficiency and switching characteristics of the design mean that less heat is required than a linear power supply, resulting in lower costs. Over time, the switching nature of the power supply means that many components cost less.

Flexible technology: Switching power supply technology can be used to provide high-efficiency voltage conversions in voltage step-up or “Boost” applications or step-down “Buck” applications.

On balance, switching power supplies are ideal for a host of applications from computers to chargers, and laboratory equipment to many items of domestic electronic gadgetry. Cost, size, and efficiency are key factors in ensuring that they become a major technology for many applications.

Applications of SMPS:

For many years, Linear AC/DC power supplies have been converting alternating current from the utility grid to DC voltage, and fit is used to run household appliances or lighting. High-power applications require smaller power supplies.

This means that linear power supplies have been relegated to specific industrial and medical uses. Because of their low noise, they are still needed in these uses. But switching power supplies have taken over because they are smaller, more efficient, and capable of handling high power.

Switching power supplies have many applications, such as computers which are the most common use, security systems, railway systems, battery chargers, and machine tool industries.

Switching power supply is widely used downstream. Recently, switching power supply has become more and more important in the LED industry, medical equipment, mobile phone charger, automobile, consumer electronics, and other fields.

Globally, the switching power supply market is driven primarily by the growing demand for consumer electronics, which accounted for nearly 52% of the total downstream consumption of SWITCHING power supplies.

Summary

There are many different aspects to consider when designing a switching power supply, especially related to safety, performance, size, weight, and so on. Switching power supplies also have more complex control circuits than linear power supplies, which is why many designers find it useful to implement integrated modules in their power supplies.

WEHO offers a wide variety of modules that can simplify switching power supply design, such as NDR EDR Din-rail Power supply, LRS Slim type power supply, LPV IP67 Waterproof LED drive, DC-DC converter, etc.