In daily life and work, switched mode power supplies (SMPS) are widely used in various devices, such as computers, TVs, mobile phone chargers, etc. How to choose a suitable SMPS has become a concern for many people. This article will start with several common questions to help you understand in depth how to choose a SMPS that suits your needs.

What is the output power you need?

The first factor in choosing a switched mode power supply is power demand. Different devices and application scenarios have different power requirements. Understanding the output power you need is the key to ensuring that the SMPS can work properly and avoid failure or equipment damage.

Clarify the power requirements of the device

Before buying an SMPS, you first need to clarify the power requirements of the required device. The unit of power is watts (W), which can usually be found on the back of the device, in the manual or on the label. For most electronic devices, such as computers, monitors, routers, etc., the input power of the device is usually marked. For example, a laptop power adapter may require 90W of power, while a desktop power supply may require more power, such as 400W or more.

If you need to power multiple devices, it is recommended to add up the power of these devices and ensure that the rated power of the SMPS can meet the needs of all devices. Generally, the rated power of the SMPS should be slightly higher than the total power demand of the devices to ensure that it can still provide stable power when the load fluctuates.

Consider the instantaneous power at startup

Some electrical devices will have a higher instantaneous power demand at startup, which may exceed the power of the device during normal operation. For example, motor-driven devices or high-power lighting devices may have several times the power demand of their normal operation at startup. Therefore, when selecting an SMPS, make sure it can withstand these startup current peaks, otherwise it may cause the power supply to malfunction or damage the device.

Reserve power margin for future expansion

In some applications, you may gradually add new devices or functions. In this case, choosing a slightly higher power SMPS will reserve space for future expansion. For example, in industrial automation, you may gradually add new sensors, displays, or other control devices. If the current power supply power can only meet the needs of existing devices, once the device is added, it may cause insufficient power. Therefore, choosing an SMPS with a power slightly higher than the current demand will provide protection for future upgrades or expansions.

2. How to choose input voltage and output voltage?

In addition to power requirements, the input and output voltage of the power supply are also important factors that must be considered when selecting an SMPS. If the input voltage and output voltage are not appropriate, the device may not work properly, and may even cause permanent damage to the device.

Input voltage range

The input voltage of the SMPS usually has a wide range to adapt to the power standards of different countries and regions. For example, a universal SMPS usually supports 100V to 240V AC input, which means that it can be used in both the 110V American power system and the 220V Asian or European power system. If you need to provide power support for a device used globally, it is very important to choose an SMPS with a wide range of input voltages.

In addition, some SMPS may require direct current (DC) input, in which case the input voltage range and polarity are equally important. If the input voltage is not within the design range of the power supply, it may cause the power supply to fail to start properly or even be damaged.

Output voltage selection

The output voltage of the SMPS is critical and should be exactly matched to the rated input voltage of the device being powered. Common output voltages include 5V, 12V, 24V, 48V, etc. These voltage levels are suitable for different types of electronic devices. For example, 5V is often used for USB devices such as mobile phone chargers; 12V is often used for LED lights, cooling fans and other devices; 24V and 48V are often used for industrial equipment or communication equipment.

When purchasing an SMPS, make sure that its output voltage matches the input requirements of the device. Too high or too low output voltage will damage the device. In some cases, a regulated SMPS can provide an adjustable output voltage range, which you can adjust according to the needs of the device, but be sure to be careful when adjusting to avoid incorrect settings that cause equipment failure.

Voltage stability and accuracy

Voltage stability and accuracy are critical for some precision electronic devices. Many modern devices are very sensitive to fluctuations in input voltage, especially computers, medical equipment or some industrial control equipment. Therefore, choosing an SMPS with good voltage stability to ensure that it can maintain a stable output voltage when the load changes is the key to protecting the normal operation of the device.

Do you need to consider efficiency and heat dissipation issues?

Choosing an efficient SMPS can not only reduce energy waste, but also reduce the heat generation of the power supply and extend its service life. Power efficiency and heat dissipation performance are two important factors that affect the performance and reliability of the power supply.

Importance of efficiency rating

The efficiency of an SMPS refers to the efficiency of its conversion of input AC power into DC power. An efficient SMPS has less energy loss and generates less heat during the conversion process. In contrast, a less efficient power supply wastes more power and dissipates it as heat. Typically, the efficiency rating of an SMPS is between 70% and 90%, and high-end products can even reach more than 95%.

In the long-term use process, choosing an efficient SMPS can significantly reduce power consumption, especially in industrial or data center applications that require long-term continuous power supply. The improvement in efficiency can not only save a lot of energy costs, but also reduce the demand for cooling equipment and reduce overall operation and maintenance costs.

Choice of cooling method

SMPS generates heat when working, so the cooling method is an important factor affecting the life of the power supply. Generally speaking, the cooling methods of SMPS are divided into active cooling and passive cooling. Active cooling SMPS is usually equipped with a fan that can quickly discharge the heat inside the power supply, which is suitable for high-power and high-load application scenarios. However, fan noise and mechanical losses also need to be considered, which may increase the maintenance requirements of the equipment.

Passive cooling relies on the heat dissipation design of the power supply housing and natural convection, and is suitable for scenarios with low power or silent operation, such as home entertainment systems or medical equipment. If you consider the use environment of the equipment when choosing a switch mode power supply, especially a quiet working environment, the passive cooling design may be more suitable for your needs.

Operating temperature and environmental adaptability

In some extreme environments, such as high temperature, low temperature or high humidity, the operating temperature range of the SMPS will directly affect its performance and life. If you need to use an SMPS in industrial equipment or outdoor equipment, it is very important to ensure that it can operate over a wide temperature range. Most standard SMPSs can work normally between -10°C and 50°C, but if the ambient temperature exceeds this range, you may need to choose a more durable industrial-grade power supply.

What kind of safety protection function is needed?

Safety protection function is an important aspect that cannot be ignored when purchasing an SMPS. Good safety protection measures can not only protect the power supply itself, but also effectively prevent the equipment from being damaged due to power problems.

Overvoltage, overcurrent, and short-circuit protection

Overvoltage protection prevents the voltage output by the SMPS from exceeding the range that the device can withstand, thus preventing voltage fluctuations from damaging the device. Overcurrent protection prevents the current from exceeding the rated value, thus preventing the device circuit from burning out due to excessive current. Short-circuit protection cuts off the power supply in time when a short circuit occurs, preventing damage to the power supply or causing a fire. These three protection functions are basic configurations in most SMPSs to ensure the safety of the power supply and the device.

Overheat protection

When working at high load for a long time, the temperature of the SMPS will rise. Overheat protection can automatically shut down the power supply when the power supply temperature reaches a dangerous level, preventing the power supply or the device from being damaged by overheating. Especially when using SMPS in outdoor or industrial environments, the overheat protection function is particularly important to ensure that the device can operate safely under harsh conditions.

EMI/EMC compliance

Switching power supplies may generate electromagnetic interference (EMI) during operation, which may affect some sensitive equipment (such as medical equipment or communication equipment). Therefore, when purchasing an SMPS, it is very important to check whether it meets the electromagnetic compatibility (EMC) standards. Compliant SMPS can effectively reduce electromagnetic interference and ensure that other devices will not be affected.

Certification and quality standards

When purchasing SMPS, check whether the product has passed relevant certifications and tests, such as CE, UL, FCC and other international safety standards. These certifications indicate that the product meets safety and quality standards during the design and manufacturing process, and can provide users with more protection in practical applications.

What are the practical application scenarios of switch mode power supplies?

After understanding power, input and output voltage, efficiency and safety, we can finally look at the practical application scenarios of SMPS. These scenarios can help you better understand the diverse uses of SMPS and make the most suitable choice according to your needs.

Home appliances and electronic devices

In the home, SMPS is widely used in TVs, computers, laptop chargers, routers and other devices. These devices usually require power between 50W and 500W. Choosing an SMPS with appropriate power can ensure stable power supply for these devices while reducing energy consumption and noise.

Industrial equipment and automation control systems

In the industrial field, the power demand of SMPS is usually high, and common applications include motor drive, control system, sensor power supply, etc. Industrial-grade switching power supply requires high reliability and durability to adapt to harsh working environments, such as high temperature, humidity, dust and other conditions.

Communication and data center equipment

Communication equipment and data centers have extremely high requirements for the reliability of power supply. The high efficiency and stable performance of SMPS can provide long-term uninterrupted power support for servers, network switches, fiber optic equipment, etc. In addition, the modular design of SMPS also makes it easier to expand to meet the needs of large data centers.

LED lighting and renewable energy systems

In renewable energy systems, such as solar photovoltaic power generation and wind power generation, SMPS is used to convert direct current into stable alternating current for home or industrial use. LED lighting systems also widely use SMPS to provide efficient low-voltage power supply to ensure long-term stable lighting of lamps.

Conclusion

Choosing a suitable switching mode power supply (SMPS) requires comprehensive consideration of power requirements, input and output voltages, efficiency, heat dissipation and safety protection functions. Through reasonable selection, you can not only ensure the normal operation of the equipment, but also improve energy efficiency and extend the service life of the power supply and equipment. I hope this article can provide you with valuable reference when purchasing SMPS, so that you can make the most suitable choice. Whether it is for home, industrial or other professional applications, finding an ideal SMPS will provide you with continuous and reliable power support.