As modern electronic equipment continues to increase its requirements for power efficiency, volume and performance, Switched Mode Power Supply (SMPS) has gradually become the mainstream power supply technology, replacing the traditional linear power supply (Linear Power Supply). SMPS has been widely used in industrial, consumer electronics, communications and other fields due to its high efficiency, light weight and flexibility. This article will explore the significant advantages of SMPS over linear power supplies from multiple perspectives and explain how these characteristics affect the design and use of electronic devices.

Why is SMPS efficiency much higher than linear power supply?

In power supply design, energy conversion efficiency is a core indicator. The high efficiency of SMPS makes it the first choice for many application scenarios, while linear power supplies are generally less efficient due to their technical limitations. Here are the reasons for the difference in efficiency between the two.

1. Differences in energy conversion methods

Linear power supplies adjust the output voltage by changing the size of the resistor, and the remaining energy is dissipated as heat. Although this method is simple, it is extremely inefficient, especially when the difference between the input voltage and the output voltage is large. For example, when the input voltage is 24V and the output voltage is 5V, most of the energy is wasted on heat.

In contrast, SMPS uses high-frequency switching and pulse width modulation (PWM) technology to convert electrical energy into the required voltage and current through switching circuits. This approach minimizes energy waste, with efficiency typically between 85% and 95%. Therefore, SMPS can still maintain high efficiency even when there is a large difference between input and output voltages.

2. Low heat generation, reducing heat dissipation requirements

Since linear power supplies generate a large amount of heat during the energy conversion process, they need to be equipped with larger heat sinks or even active cooling devices. This not only increases the size and weight of the device, but also results in increased overall energy consumption. The high-efficiency energy conversion of SMPS makes it generate extremely low heat. In most cases, only a small heat sink or natural heat dissipation is needed to meet the demand, thus further optimizing the system design.

Calculation example

Assume a device requires 10W of output power:

Linear power supply: input voltage 24V, output voltage 5V, current 2A, the efficiency is calculated as follows:

Efficiency = output power/input power =5V×2A/ (24V×2A)=41.7%

SMPS: Assuming an efficiency of 90%, the input power is:

Input power = output power/efficiency = 10W/0.9 =11.1W

It can be seen that SMPS significantly reduces input power requirements and reduces energy waste.

Why are SMPS smaller and lighter than linear power supplies?

In modern electronic devices, size and weight are important considerations in design. The structural characteristics of SMPS enable more compact and lightweight designs.

1. Advantages of high-frequency switching technology

SMPS utilizes high-frequency switching technology to significantly reduce the size of transformers and inductors. High-frequency signals can achieve the same energy transfer on smaller magnetic cores, so the magnetic components of SMPS are much smaller than the transformers of linear power supplies. Linear power supplies use 50Hz or 60Hz power frequency AC power, and their transformers must be larger to handle the energy transfer of low-frequency signals.

2. Simplify heat dissipation design

Because switching mode power supply is more efficient, its cooling needs are lower, so there is no need for large heat sinks like linear power supplies. This not only reduces equipment weight, but also provides greater flexibility in system layout.

Application examples

For example, the power adapter of a laptop computer may weigh more than 1 kilogram and be very bulky if it uses a linear power supply. Modern SMPS power adapters usually weigh only 200-300 grams and are small and easy for users to carry.

This lightweight advantage is particularly important in the fields of portable devices and aerospace, where reducing device weight can significantly improve user experience or reduce operating costs.

Why is SMPS more suitable for diverse power needs?

The diversity and complexity of electronic equipment places higher demands on power supplies. The flexible design and wide adaptability of SMPS enable it to meet the needs of a variety of different applications, while linear power supplies are more limited in this regard.

1. Adapt to multiple input and output voltages

SMPS can easily implement requirements from different input voltage ranges to multiple outputs. For example, an SMPS can output 5V, 12V and 24V voltages at the same time to meet the multi-voltage requirements of complex equipment. Linear power supplies, on the other hand, require a separate transformer and conditioning circuit to be designed for each voltage, which is neither economical nor flexible.

2. Support wide input voltage range

SMPS can handle an extremely wide range of input voltages, such as AC from 90V to 264V or DC from 10V to 60V. This makes it more convenient for global applications, while linear power supplies can usually only accommodate a narrow input voltage range.

3. Quick response to load changes

The power requirements of modern electronic devices tend to change dynamically over time, such as processors consuming different amounts of power when performing different tasks. By quickly adjusting the output voltage and current, SMPS can respond instantly to load changes and maintain stable operation of the equipment. The linear power supply has a slow response speed and is difficult to meet such high dynamic performance requirements.

Application scenarios

For example, in data centers, servers' power requirements fluctuate as task loads change. SMPS can quickly adjust output to meet the dynamic power needs of servers, ensuring efficient operation of data centers.

Why is SMPS safer and more environmentally friendly?

As people pay more attention to equipment safety and environmental impact, switching power supply has shown more obvious advantages in these aspects.

1. Improve device security

SMPS usually have built-in overcurrent, overvoltage, short circuit and overheating protection functions, which can quickly cut off the output when the power supply is abnormal to prevent equipment damage. In addition, the isolation design of SMPS (such as the use of high-frequency transformers) can effectively prevent electric shock and other potential hazards, while linear power supplies have weaker protection capabilities in this regard.

2. Reduce electromagnetic interference (EMI)

Although the high-frequency switching of SMPS may produce electromagnetic interference, modern SMPS can effectively reduce EMI levels through input filtering and shielding design to meet international electromagnetic compatibility standards. In contrast, the low efficiency of linear power supplies results in more heat dissipation, which is not conducive to electromagnetic compatibility.

3. Comply with energy efficiency and environmental protection standards

SMPS can meet multiple energy efficiency regulations including US DoE Level VI and EU EcoDesign. Its standby power consumption is usually less than 0.1 watt, significantly reducing energy waste. Due to technical limitations, linear power supplies are difficult to meet these strict energy efficiency standards.

Environmental significance

From a global perspective, using high-efficiency SMPS to replace traditional linear power supplies can significantly reduce power consumption. For example, assuming that 50 million devices in a country use SMPS and each device saves 10 kWh of electricity per year, a total of 500 million kWh can be saved, significantly reducing greenhouse gas emissions.

Conclusion

Switch-mode power supplies (SMPS) have unparalleled advantages over linear power supplies. Its high efficiency significantly reduces energy consumption; its small size and light weight meet the needs of modern electronic equipment for compact design; and its flexible output capabilities adapt to diverse application scenarios. In addition, SMPS also performs better in terms of safety and environmental protection, in line with the global trend of energy conservation and emission reduction. It is foreseeable that with the further development of technology, SMPS will exert its unique value in more fields and bring more convenience and possibilities to our lives and work.