In electronic devices and power supply systems, power supply plays a vital role. Whether it is home appliances, industrial equipment, or portable electronic devices, a stable and reliable power supply is the basis for the normal operation of the equipment. With the development of technology, the types of power supplies have gradually increased, among which switching power supplies (SMPS) and traditional linear power supplies are two common forms of power supplies. So, what is the difference between switching power supplies and traditional power supplies? Which power supply should be selected in different application scenarios? This article will explore these issues in depth to help readers better understand the difference between the two.

1. What are switching power supplies and traditional power supplies?

To understand the difference between the two, we first need to clarify their basic definitions and working principles.

What is a switching power supply (SMPS)?

A switching power supply, or SMPS for short, is a power supply device that converts input voltage into the required output voltage through a high-speed switching circuit. Its working principle is based on switching regulation technology, using pulse width modulation (PWM) to control power transmission. Switching power supplies have the advantages of high efficiency, small size, and light weight, and are widely used in home appliances, industrial equipment, communication equipment and other fields.

During operation, the switching power supply converts the input AC power into DC power through rectification and filtering, and then adjusts the output voltage through high-frequency switching elements. Its efficient power conversion method enables SMPS to maintain stable output under various voltage and load conditions.

What is a traditional power supply (linear power supply)?

Traditional power supplies usually refer to linear power supplies. The working principle of a linear power supply is to step down the AC power through a transformer, and then adjust the voltage to the required output voltage through a linear regulator. Unlike a switching power supply, a linear power supply relies on adjusting the voltage difference to stabilize the voltage, which consumes more energy, so its efficiency is low.

The advantage of a linear power supply is that the voltage fluctuation is small and the output current is relatively smooth, which is suitable for devices that are sensitive to power supply noise. However, due to the low conversion efficiency of linear power supplies, they are usually larger in size and heavier in weight.

2. What are the main differences between a switching mode power supply and a traditional power supply?

There are significant differences between switching power supplies and traditional power supplies in many aspects, including efficiency, volume, weight, cost, and application scenarios. The following will analyze the differences between the two in detail from multiple perspectives.

Difference in efficiency

Efficiency is an important indicator for evaluating power supply performance. Switching power supplies have significant advantages in this regard because they adjust the output voltage through high-speed switching elements, reducing energy losses. The typical efficiency of switching power supplies can reach 85% to 95%, which means that a large part of the input power can be converted into effective output power, reducing heat generation.

In contrast, the efficiency of traditional linear power supplies is usually lower, generally around 50% to 60%. This is because linear power supplies adjust the voltage through linear regulators, and in this process, a lot of energy is consumed to maintain a stable output, resulting in energy wasted in the form of heat.

For example, if a device requires an output power of 12V 1A, if 100% efficiency is used for calculation, the power demand of the device is:

Power demand = voltage × current = 12V × 1A = 12W

Assuming a switching power supply with an efficiency of 90%, the input power is:

Input power = output power / efficiency = 12W / 0.90 = 13.33W

If a linear power supply with an efficiency of 50% is used, the input power is:

Input power = output power / efficiency = 12W / 0.50 = 24W

From this simple calculation, it can be seen that the switching power supply significantly saves input energy and reduces power waste.

Difference in volume and weight

The high efficiency of the switched mode power supply makes its volume and weight relatively small. Since the switching power supply operates at high frequency, the size of the required transformer and other components can be greatly reduced. This makes the switching power supply particularly suitable for portable devices, compact electronic devices and application scenarios with high space requirements.

In contrast, traditional linear power supplies require larger transformers and heat sinks to cope with energy loss, so they are larger in size and weight. Especially in high-power applications, the size of linear power supplies may become very bulky. This also limits the application of linear power supplies in some modern electronic devices.

Cost Difference

The production cost of switching power supplies is usually higher than that of linear power supplies because of the complex high-frequency switching circuits and sophisticated control systems used inside them. However, due to the high efficiency and long life of switching power supplies, the total cost in actual use may be lower than that of linear power supplies. Especially in devices that run for a long time, switching power supplies can save a lot of power consumption.

Although linear power supplies are lower in cost, they require larger heat sinks and heavier transformers in high-power applications, which increases material costs and maintenance costs. Therefore, in long-term use, switching power supplies usually have better cost performance.

3. What are the application scenarios of switching power supplies and linear power supplies?

Different types of power supplies are suitable for different application scenarios. Switching power supplies and linear power supplies each have their own advantages and disadvantages, and how to choose depends on the specific application requirements.

Typical applications of switching power supplies

Due to their high efficiency and small size, SMPS are widely used in various modern electronic devices. Common application scenarios include:

Computers and servers: Computers and servers usually require a stable DC power supply and have high power requirements. Switching power supplies can provide efficient and stable power supply while reducing energy loss and heat dissipation requirements.
Portable devices: Due to their small size and light weight, switching power supplies are ideal for portable devices such as mobile phone chargers and laptop adapters. These devices usually require high power conversion efficiency to extend battery life and reduce heat generation.
Industrial equipment: Many industrial equipment require high-power power supplies and require long-term operation at high efficiency. Switching power supplies can meet these requirements while reducing the size and weight of the equipment, facilitating equipment integration and maintenance.
Communication equipment: Equipment such as communication base stations, routers and switches require a stable power supply. Switching power supplies have become the main power supply solution for these devices due to their high efficiency, low noise and stability.

Typical applications of linear power supplies

Although linear power supplies have low efficiency, their output current is smooth and noise is low, making them suitable for application scenarios that are sensitive to power supply noise. Common application scenarios include:

Audio equipment: High-end audio and recording equipment are usually very sensitive to power supply noise. Linear power supplies can provide high-quality power supply for these devices due to their low noise and stable voltage output, avoiding power supply noise from interfering with audio signals.
Laboratory equipment: Test equipment and instruments in the laboratory usually require precise and stable power output, and linear power supplies are widely used in this field. Due to its small voltage fluctuation, it can provide higher power stability for precision instruments.
Medical equipment: Some medical devices are very sensitive to power fluctuations and interference. The low noise and low ripple characteristics of linear power supplies make them suitable for medical devices with high requirements for power quality.

4. When to choose a switching power supply and when to choose a linear power supply?

In practical applications, the choice of switching power supply or linear power supply needs to be determined based on the specific needs, budget and application scenarios of the equipment. Here are a few suggestions to help users make the best choice in different situations.

Choose a switch mode power supply when efficiency and size are the main considerations

If the application scenario requires the device to be small and light, and has high requirements for power efficiency, then the switching power supply is undoubtedly the best choice. For example, in portable electronic devices, mobile device chargers and embedded systems, switching power supplies can provide efficient power conversion while saving space and power costs.

Choose a linear power supply when a smooth, noise-free power supply is required

If the application scenario is very sensitive to power supply noise or requires a very smooth output voltage, then a linear power supply may be a better choice. For example, in high-end audio equipment and precision test equipment, the smooth output of a linear power supply can prevent power supply noise from interfering with the normal operation of the equipment.

Choose a linear power supply when the budget is limited

When a linear power supply can meet basic power needs, choosing a linear power supply can reduce the initial purchase cost. Although the switching power supply has higher efficiency, its initial cost is higher, while the linear power supply has a relatively simple structure and lower production cost, which is suitable for application scenarios with limited budgets.

Conclusion

There are significant differences between switching power supplies and traditional linear power supplies in terms of working principles, efficiency, volume and application scenarios. Switching power supplies are widely used in various modern electronic devices due to their advantages of high efficiency, small size and light weight, while linear power supplies still occupy an important position in certain specific application scenarios due to their smooth output voltage and low noise.

When actually choosing a power supply, users need to comprehensively consider which power supply to choose based on factors such as the specific needs of the equipment, power requirements, volume restrictions and budget. For applications that require efficient power conversion and compact design, switching power supplies are the best choice; for equipment that requires smooth output and low noise, linear power supplies still have irreplaceable advantages.