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Different Types of Switching Power Supplies

Views: 14     Author: Site Editor     Publish Time: 2023-06-13      Origin: Site

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What is the difference between a switching power supply and a SMPS?

The exploration and advancement of power supplies employing a "switching" technique to enhance efficiency compared to traditional linear power supplies can be traced back to the 1950s when early devices incorporated vacuum tubes. However, the official patent for the term "switch-mode power supply" was granted in 1976 to Howard Scott of RCA. Presently, the terms "switching power supply" and "switch-mode power supply" (SMPS) are commonly used interchangeably.

What are Switching Power Supplies?

Switching power supplies, also known as switched-mode power supplies or SMPS, are highly efficient devices widely utilized in personal electronics as well as the powering of industrial equipment. They have revolutionized the field of power supply with their energy-saving capabilities.

Unlike linear power supplies that regulate voltage by dissipating energy as heat within a device, usually through a resistor, switching power supplies employ high-frequency switching of an electronic circuit to achieve voltage regulation without energy loss. This fundamental distinction renders them significantly more efficient than traditional linear power supplies.

Since their inception in the 1950s, switching power supplies have undergone significant advancements. The continuous evolution of technology has resulted in modern switching power supplies that offer enhanced reliability, efficiency, and safety.

Contemporary switching power supplies can generate a wide range of voltages to cater to diverse applications. Furthermore, they can be customized with features such as over-voltage protection to safeguard against voltage spikes or surges, bolstering their reliability and safety.

The term "modular" frequently appears in discussions about power supplies. In the context of power supplies, modular refers to the utilization of interchangeable components to achieve the desired voltage output. This versatility sets modular power supplies apart from regular switching power supplies, enabling their application in a broader range of scenarios. Additionally, modular power supplies are comparatively easier to repair or upgrade.

When designed effectively, switching power supplies tend to have a longer lifespan than other types of power supplies, translating to reduced long-term ownership costs. Consequently, they find extensive usage across various industries and applications, including medical devices, home appliances, electronics, telecommunications systems, and energy-efficient lighting systems. Now, let's delve into a detailed explanation of how switching power supplies function.

Linear Power Supplies

Before diving into switching power supplies, it's essential to understand their counterpart, linear power supplies. Linear power supplies regulate the output voltage by dissipating excess power as heat. Although they are relatively simple and inexpensive, they are not as efficient as switching power supplies, especially when dealing with high voltage differences.

Linear power supply

Switched-mode principles

The principles of switched-mode conversion are applicable to both AC-DC and DC-DC power supplies. When it comes to an AC-DC power supply, there are several stages involved, such as rectifying a single-phase 230Vac or 3-phase 400Vac 50Hz mains voltage, prior to the DC-DC conversion process.

In both scenarios, during the DC-DC conversion stage, a primary circuit consisting of power semiconductors (known as a power switch circuit) generates a high-frequency alternating voltage that is then transferred to a transformer. This results in the generation of a current in the primary windings, which, in turn, induces an alternating current in the secondary windings, leading to the development of a secondary voltage. The winding ratio of the transformer determines whether the voltage is stepped up or stepped down. A secondary circuit rectifies the high-frequency voltage and may generate a feedback signal to regulate the primary electronics.

Switching Power Supplies

Switching power supplies operate on the principle of rapidly switching the input voltage on and off to achieve the desired output voltage. This switching is controlled by pulse-width modulation (PWM) signals. The four main types of switching power supplies are:

Switching Power Supply

Buck Converter

The buck converter, also known as a step-down converter, is one of the most common types of switching power supplies. It converts a higher input voltage to a lower output voltage. This type of converter finds extensive use in applications where a lower voltage is required, such as in laptops and mobile phones.

Boost Converter

The boost converter, or step-up converter, does the opposite of the buck converter. It increases the input voltage to a higher output voltage. Boost converters are commonly employed in applications like battery charging, renewable energy systems, and LED drivers.

Buck-Boost Converter

The buck-boost converter can either step up or step down the input voltage based on the requirements. It provides flexibility by allowing both voltage reduction and voltage increase, making it suitable for a wide range of applications, including battery-powered devices and automotive electronics.

Flyback Converter

The flyback converter is a popular choice when isolation between the input and output is necessary. It stores energy in the inductor during the "on" time of the switching cycle and releases it to the output during the "off" time. This type of converter is commonly found in applications such as televisions, computer monitors, and low-power offline devices.

Components of a Switching Power Supply

A typical switching power supply comprises several key components, each serving a specific purpose. Let's take a closer look at these components:

Power Input Stage

The power input stage is responsible for receiving the incoming AC power from the main source. It usually consists of an input connector, a fuse, and transient protection components to safeguard the power supply and connected devices from voltage surges and spikes.

Rectification Stage

In the rectification stage, the alternating current (AC) input is converted into direct current (DC) through a rectifier circuit. This circuit typically consists of diodes that allow the flow of current in one direction, resulting in a pulsating DC waveform.

Filtering and Smoothing Stage

After rectification, the DC waveform passes through a filter, which removes unwanted ripple and noise. Capacitors are commonly used in this stage to smooth the waveform and provide a stable DC voltage.

Power Switching Stage

The power switching stage is the heart of a switching power supply. It utilizes a high-frequency switch, such as a transistor or a MOSFET, to control the energy flow and regulate the output voltage. This stage operates by rapidly switching the input voltage on and off, transforming it into a high-frequency waveform.

Output Stage

The output stage of a switching power supply is responsible for regulating the final DC output voltage and providing protection features. It usually includes an output filter to further reduce ripple and noise, as well as voltage regulation and feedback circuits to maintain a stable output voltage.

Working Principle of a Switching Power Supply

The working principle of a switching power supply involves a process known as pulse-width modulation (PWM). The power switching stage rapidly switches the input voltage on and off at a high frequency. The duration of each ON and OFF cycle is adjusted to control the output voltage. By varying the width of the ON cycle (duty cycle), the average voltage delivered to the load is regulated.

During the ON cycle, energy is stored in an inductor or transformer. This energy is then transferred to the output stage during the OFF cycle. Through this switching action, the switching power supply can efficiently convert and regulate the input voltage to provide a stable output voltage.

How do you reduce the noise in switching power supply circuits?

Achieving complete elimination of noise or electromagnetic interference (EMI) from your power supply design is not realistically attainable. Instead, the goal is to minimize noise as much as possible to ensure electromagnetic compatibility. By doing so, your power supply board not only becomes a considerate neighbor to nearby electronic devices but also ensures that the presence of EMI does not adversely affect functionality. To effectively reduce noise on printed circuit board assemblies (PCBAs), it is advisable to implement the following best practices: employ impedance matching, restrict trace lengths, and adhere to appropriate creepage and clearance distances. Furthermore, one of the crucial factors that significantly affects both performance objectives for connected loads and noise reduction is the implementation of filtering techniques.

Applications of Switching Power Supplies

Switching power supplies find extensive use in various industries and applications, including:

1. Consumer Electronics

From smartphones and laptops to televisions and gaming consoles, switching power supplies are widely used to provide efficient and compact power solutions for consumer electronic devices.

2. Industrial Automation:


Switching power supplies are employed in industrial automation systems, powering control panels, motor drives, robotics, and other equipment.

3. Telecommunications

Switching power supplies are crucial in telecommunications infrastructure, supporting the efficient operation of routers, switches, and communication devices.

4. Renewable Energy Systems

Solar inverters and wind turbines utilize switching power supplies to convert and regulate DC power generated from renewable sources.

Advantages of Switching Power Supplies

Switching power supplies offer several advantages over traditional linear power supplies. Here are some key benefits:

● High Efficiency:

Switching power supplies can achieve higher efficiency levels, typically above 80% and often exceeding 90%. This efficiency translates to reduced power loss and heat generation, making them more energy-efficient and environmentally friendly.

● Compact Size:

Compared to linear power supplies, switching power supplies are much smaller and lighter. This compactness is advantageous in applications where space is limited, such as portable electronic devices and compact equipment.

● Wide Input Voltage Range:

Switching power supplies can handle a wide range of input voltages, allowing them to operate efficiently even in situations where the input voltage fluctuates or varies significantly.

● Regulation and Stability:

Switching power supplies provide excellent voltage regulation and stability, ensuring a consistent and reliable power output regardless of variations in the input voltage or load conditions.

● Flexibility

With various types of switching power supplies available, designers have the flexibility to choose the most suitable type for their specific application. This adaptability enables the efficient power management of different electronic devices and systems.

● Reduced Heat Dissipation

As switching power supplies are more efficient, they generate less heat compared to linear power supplies. This feature reduces the need for additional cooling mechanisms and enhances the overall reliability of the system.

Common Challenges and Solutions

While switching power supplies offer numerous benefits, they also present certain challenges. Here are a few common challenges and their solutions:

● Electromagnetic Interference (EMI)

Switching power supplies can introduce EMI due to the high-frequency switching operation. Proper shielding, filtering, and layout techniques can mitigate EMI issues and ensure compliance with electromagnetic compatibility (EMC) standards.

● Switching Noise

The switching action of these power supplies can create noise, which may interfere with sensitive electronic components. Careful circuit design, component selection, and proper grounding techniques help minimize switching noise.

● Complexity of Design

Switching power supply design requires careful consideration of various parameters, such as component selection, feedback loop design, and thermal management. Working with experienced designers and utilizing simulation tools can simplify the design process.

● Component Stress

High-frequency switching can subject components to stress and increased wear. Selecting components with appropriate voltage and current ratings, as well as implementing adequate protection circuits, can help mitigate component stress and prolong the lifespan of the power supply.

The Development Trend and Current Situation of Switching Power Supply

In recent times, power supplies have experienced a surge in applications across various sectors such as e-sports products, automotive electronics, Internet of Things (IoT), and industrial automation. There are three primary categories of power supply and components: automation, infrastructure, and manufacturers based in Taiwan have emerged as leaders in the global switching power supply industry.

Taiwanese manufacturers currently dominate the production of switching power supplies (SMPS), which find extensive usage in communication products, computers, and related equipment. As Taiwan's information industry has flourished, the output of switching power supplies has secured the top position globally. The raw materials involved in their production can be categorized as ICs, semiconductors, magnetic components, capacitors, other types of electronic components, chassis, and printed circuit boards.

For ICs and power semiconductors, the majority of the supply comes from the United States and Japan, while Taiwan excels in manufacturing other raw materials. The downstream PC, electronics, communications, and other industries generate a wide range of business opportunities and applications for switching power supplies. With the continuous expansion of this field, users now demand increased portability. Consequently, there has been a concerted effort to reduce the size of switching power supplies, making it a major area of development and enhancing product value and competitiveness.


Switching power supplies are vital components in modern electronic devices, providing efficient and reliable power conversion. Their various types, including buck converters, boost converters, buck-boost converters, and flyback converters, offer versatility and flexibility in meeting the diverse power requirements of different applications. With their high efficiency, compact size, and stability, switching power supplies have revolutionized the field of power electronics.


1. How can I mitigate electromagnetic interference (EMI) caused by switching power supplies?

Proper shielding, filtering, and layout techniques can help reduce EMI caused by switching power supplies.

2. What are some common challenges in designing switching power supplies?

Common challenges include managing electromagnetic interference, mitigating switching noise, dealing with the complexity of design, and addressing component stress.

3. Are switching power supplies more efficient than linear power supplies?

Yes, switching power supplies are generally more efficient than linear power supplies, resulting in reduced power loss and improved energy efficiency.

4. Can I use a switching power supply for both step-up and step-down voltage conversion?

Yes, a buck-boost converter is capable of both stepping up and stepping down the input voltage, providing flexibility for different applications.

5. What are the key considerations when selecting a switching power supply for my application?

Important factors include input voltage range, output voltage and current requirements, efficiency, size, and specific application needs.

6. Are switching power supplies suitable for sensitive electronic components?

Yes, switching power supplies can be designed to minimize noise and provide stable power, making them suitable for sensitive electronic components.

In conclusion, understanding the different types of switching power supplies is essential for anyone involved in electronics design or maintenance. These power supplies offer numerous advantages, including high efficiency, compact size, and flexibility in voltage conversion. By addressing the challenges associated with switching power supplies and utilizing proper design techniques, engineers can create reliable and efficient power solutions for a wide range of applications.

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