Switch mode power supply (SMPS) has been widely used in various electronic devices, from computers and mobile phones to home appliances and even industrial control equipment. As an efficient power conversion device, it has gradually replaced the traditional linear power supply with its advantages such as high efficiency, lightness and stability. However, many people have doubts about its actual application scenarios and whether SMPS is needed every time. This article will explore when SMPS should be used and whether SMPS is always necessary.

What is a switched mode power supply (SMPS)? Why is it so important?

Before discussing in depth when SMPS should be used, let's first understand what SMPS is and its importance. A switch mode power supply is an electronic device that regulates voltage and current through rapid switching. It can convert input DC or AC power into outputs of different voltages and currents to meet the power needs of different devices.

Working principle of SMPS

The working method of SMPS is very different from that of traditional linear power supplies. It uses switching elements (such as MOSFET) to quickly switch the switching state of the power supply at high frequency, and uses inductors and capacitors to convert pulse voltage into a stable output voltage. This high-frequency conversion greatly improves the efficiency of SMPS, which can usually reach 80% to 95%.
Traditional linear power supplies adjust current by changing the difference between input voltage and output voltage, but a lot of heat is generated in the process, and the efficiency is low. SMPS reduces energy loss through switching action, has higher conversion efficiency, and reduces heating problems.

Main advantages of SMPS

High efficiency: The biggest advantage of SMPS is its efficient power conversion, which can convert more input power into output power and reduce energy loss. In contrast, the efficiency of linear power supplies is lower, usually between 50% and 70%.
Small size and light weight: Because SMPS uses high-frequency switching, the size of transformers and inductors can be designed to be smaller, suitable for portable and space-limited applications.
Less heat dissipation: High efficiency means that SMPS generates less heat, which not only reduces the need for heat sinks, but also extends the life of the equipment.
Multiple input power types: SMPS can accept multiple input power types, including direct current (DC) and alternating current (AC), and can flexibly adjust the output voltage.

When should a switching mode power supply be used?

In practical applications, the choice of using SMPS or linear power supply depends on the specific scenario and requirements. The following are several typical scenarios to explain in which cases SMPS should be preferred.

Occasions with high energy requirements

The high efficiency of SMPS makes it very suitable for situations with high energy efficiency requirements. For example, in data centers, servers, and communication equipment, the energy efficiency of the power supply is a key factor. When a large number of electronic devices are running at the same time, the efficiency of the power supply directly affects the energy consumption and heat dissipation of the system.
For example, in a data center, each server needs to be powered continuously. If an inefficient linear power supply is used, it will generate huge power waste in the long run. SMPS can significantly reduce power consumption and reduce the power cost of the data center.

Equipment that requires multiple output voltages

SMPS can output multiple voltages simultaneously through different conversion modules, so it is very suitable for equipment that requires multiple different voltages to power. For example, a computer requires multiple different voltages (such as 3.3V, 5V, 12V, etc.) to power different components, and SMPS can provide appropriate power for these components by adjusting the output voltage.
In addition, some household appliances, experimental equipment, and industrial control systems also require multiple voltage outputs. Using SMPS can reduce the complexity of using multiple power modules and improve the reliability of the device.

Portable and space-limited devices

Due to its small size and light weight, switching power supply is particularly suitable for devices that require portability or are space-limited. For example, laptops, mobile phone chargers, wireless devices, etc. all use SMPS extensively. The power modules of these devices need to be both small and efficient, and SMPS just meets these requirements.
For example, laptop chargers usually use SMPS to convert 220V AC power into low-voltage DC power suitable for the device, while ensuring the lightness and portability of the device. If a larger linear power supply is used, the weight and volume of the charger will increase significantly, affecting the user experience.

Heat-sensitive occasions

Another important advantage of SMPS is that it generates less heat, so it is suitable for use in temperature-sensitive occasions. For example, in medical equipment and precision instruments, excessive heat may affect the accuracy of the equipment or even damage sensitive components. SMPS can effectively protect these devices and extend their service life by reducing heat.
For example, ultrasonic equipment, laser instruments, etc. are very sensitive to temperature, and excessively high temperatures may cause the performance of the equipment to deteriorate or fail. Therefore, choosing an efficient SMPS power supply can reduce the need for heat dissipation and ensure that the device runs at a stable temperature for a long time.

Is SMPS always necessary? When is it not necessary to use SMPS?

Although SMPS has many advantages, it is not necessary in all cases. In some occasions where linear power supplies can still do the job, using SMPS may add unnecessary cost or complexity. Next, we will discuss when SMPS is not necessarily needed.

Occasions where power efficiency is not required

If the energy efficiency requirements of the device are not high, or the loss of the power supply has little impact on the overall performance of the system, then a linear power supply may be a more economical choice. For example, some simple household appliances (such as clocks, radios, etc.) have small power requirements, and power conversion efficiency is not the main concern.
In these occasions, it may be more economical to use a linear power supply because of its simple structure and low production cost, which is suitable for devices with small power requirements.

Applications of low-cost and simple designs

The design of SMPS is relatively complex, involving multiple components such as high-frequency switches, inductors, capacitors, etc., so the manufacturing cost is relatively high. If the project budget is limited and an efficient power supply system is not required, a linear power supply may be a better choice.
For example, in some low-cost small appliances or toys, the design of the power supply system can be simpler, and the linear power supply can meet their basic needs. In these devices, the use of SMPS may lead to unnecessary cost increases, while the linear power supply can achieve basic power conversion functions at a lower price.

Occasions where multiple voltage outputs are not required

If the device only needs a single voltage power supply and the power requirement is not high, the linear power supply can also do the job. For example, some small audio equipment, signal generators or experimental instruments only need a fixed voltage power supply, and the load is relatively light, so the complex design of SMPS is not required.

High-power equipment that does not need to run for a long time

For some high-power equipment that is used occasionally, such as power tools or small machinery, a linear power supply may be sufficient. If these devices do not need to run continuously for a long time, the high efficiency advantage of SMPS may not be obvious. The linear power supply has a simple structure and is easy to maintain, which is also suitable for these scenarios.

How to judge whether SMPS is needed?

When choosing a power supply, whether a switch mode power supply (SMPS) should be used depends on multiple factors, including the power demand, efficiency requirements, volume restrictions, cost budget, etc. of the device. The following will discuss in detail how to determine whether SMPS is needed and whether SMPS is the best choice in different application scenarios.

Power requirements of the device

The power requirements of the device are one of the most important considerations when choosing a power supply type. For devices that require stable high power output, SMPS is usually a better choice.
High-power device requirements If your device needs to provide a large amount of power, such as industrial equipment, communication equipment, or large-screen displays, the high power output capability and high-efficiency conversion of SMPS make it the best choice. SMPS can operate over a wide input voltage range and can maintain high efficiency under high load conditions.
Low-power portable devices In contrast, for small, low-power portable devices, although linear power supplies can also meet the needs, the advantage of SMPS is that it can minimize energy loss and extend the battery life of the device. Therefore, the use of SMPS will make small devices more endurance and portable, especially in the field of mobile devices and portable electronic products, SMPS is widely used.

Efficiency requirements

If your application scenario has high requirements for energy efficiency, SMPS is almost an indispensable choice. Due to its high-frequency switching design, SMPS can maintain high efficiency over a wide range of loads, typically 85%-95% efficiency.
Efficient power conversion In some high-efficiency power conversion applications, such as solar inverters, energy-saving lighting, etc., SMPS can greatly improve the energy efficiency of the system, reduce energy loss, and reduce operating costs. For example, in a solar system, SMPS can efficiently convert the DC power of solar panels into AC power for home or commercial use, reducing waste.
Inefficient alternatives In contrast, traditional linear power supplies waste more energy because they need to adjust the voltage through resistors. If a linear power supply is used, a large amount of energy in the system will be lost in the form of heat, which will increase operating costs over long periods of time and is not environmentally friendly.

Size and weight limitations

Another significant advantage of SMPS is its compactness and lightness. If your project has strict requirements on size and weight, such as embedded systems, handheld devices, or devices that need to be mobile, SMPS is a more suitable choice.
Applications with limited space In application scenarios where space needs to be saved, SMPS is much smaller than linear power supplies. Since SMPS operates on high-frequency switching, it uses smaller transformers and inductors, which are the components that take up the most space in traditional linear power supplies. This allows switched mode power supply to play an important role in electronic devices with limited space.
For example, mobile phone chargers, laptop power adapters and other devices all use SMPS technology precisely because they need to provide efficient power in a limited space.

Cost Budget

Although SMPS has advantages in efficiency, size and flexibility, its design and manufacturing costs are generally higher than linear power supplies. Therefore, the cost budget also needs to be considered when deciding whether to use SMPS.
Short-term vs. long-term costs In the short term, SMPS has a higher manufacturing cost than linear power supplies, especially in low-power devices, where the complex design and material costs of SMPS may not be as cost-effective as linear power supplies. However, over time, the high efficiency of SMPS can save a lot of electricity costs, and from a long-term use perspective, it can reduce overall operating expenses. Therefore, if your device needs to run for a long time, SMPS will offset the initial investment by reducing electricity bills.

Feasibility of other options

Although SMPS has many advantages, linear power supplies are still a better choice in certain specific occasions. Especially in situations where power stability is extremely demanding (such as in some high-end audio equipment), the low noise characteristics of linear power supplies make them perform better. Therefore, whether to choose SMPS should also be combined with the specific needs of the application scenario.
Noise-sensitive applications SMPS may generate certain electromagnetic interference (EMI) due to its high-frequency switching design. For noise-sensitive devices, although SMPS can also reduce interference through filtering and shielding technology, linear power supplies may still be a better choice in some scenarios. For example, high-end audio systems are often very sensitive to power supply noise, and linear power supplies can provide a more "clean" power supply signal.

Conclusion

Determining whether to use SMPS depends on the trade-off of multiple factors. Switching mode power supply is popular for its high efficiency, compactness and wide range of application scenarios. Especially in scenarios that need to save space, improve power efficiency and reduce long-term operating costs, SMPS is undoubtedly an ideal choice. However, in some applications that are sensitive to power supply noise or in low-power devices with limited budgets, linear power supplies still have certain advantages. The final choice depends on the specific needs of the device and the design goals.