Unlike linear power supplies, switching power supplies utilize transistors that primarily switch between fully on (saturation region) and fully off (cutoff region) modes. Both modes are characterized by low dissipation. While the transition between modes involves higher dissipation, the time is very short, thus saving energy and generating less waste heat. Ideally, the switching power supply itself does not consume electrical energy. Voltage regulation is achieved by adjusting the on and off times of the transistors. Conversely, in a linear power supply, the transistors operate in the amplification region during the output voltage generation process, consuming electrical energy themselves. The high conversion efficiency of switching power supplies is a major advantage. Furthermore, because switching power supplies operate at high frequencies, they can use small, lightweight transformers, making them smaller and lighter than linear power supplies. If efficiency, size, and weight are key considerations, switching power supplies are better than linear power supplies. However, switching power supplies are more complex, with internal transistors switching frequently. If the switching current is not properly managed, it may generate noise and electromagnetic interference that could affect other devices. Moreover, without special design, the power factor of a switching power supply may be low.
What is a switching power supply used for? In daily life, people interact with switches every day, touching the switches of different objects almost daily, such as light switches, mobile phone switches, or television switches. These switches are essentially switching power supplies. Today, I'll introduce the uses of switching power supplies. With the electrification of society, the use of switching power supplies is becoming increasingly widespread. So, what is a switching power supply used for? What are its characteristics? Today, I'll give you a detailed introduction.
What is a switching power supply used for? An LED switching power supply uses circuitry to control the switching transistors, enabling high-speed switching on and off. It converts direct current (DC) into high-frequency alternating current (AC) to power a converter, producing one or more required voltages. The reason for this conversion is that high-frequency AC is more efficient in transformer circuits than 50Hz or 60Hz AC mains power. Therefore, switching power supply transformers can be very small, do not overheat during operation, and are cheaper than standard DC regulated power supplies. Without converting 50Hz or 60Hz to higher frequencies, a switching power supply would be meaningless. Switching power supplies can be broadly categorized into isolated and non-isolated types. Isolated power supplies always contain a switching power converter, while non-isolated power supplies may not. Compared to traditional DC power supplies, switching power supplies offer advantages such as smaller size, lighter weight, and higher efficiency.
What are the uses of switching power supplies? Switching power supplies are widely used in industrial automation control, military equipment, scientific research equipment, LED lighting, industrial control equipment, communication equipment, power equipment, instruments and meters, medical equipment, semiconductor refrigeration and heating, air purifiers, electronic refrigerators, LCD displays, LED lamps, communication equipment, audio-visual products, security monitoring, LED light bags, computer cases, digital products and instruments, etc.
The development trend of modern power electronics technology is shifting from traditional power electronics, which primarily addresses low-frequency problems, to modern power electronics, which primarily addresses high-frequency problems. In the applications of power electronics technology and various power supply systems, switching power supply technology occupies a core position.
From the invention of the self-oscillating push-pull transistor single transformer DC-DC converter by G.H. Roger in the United States in 1955, which marked the beginning of high-frequency conversion control circuits, to today's switching power supply technology becoming an indispensable power source in the rapid development of the electronic information industry.
Why has switching power supply technology become the core of modern power electronics technology? Is its success solely due to its miniaturization and ease of installation in electronic devices?
What is a switching power supply?
A switching power supply is short for a switching regulated power supply. It generally refers to an AC (alternating current) to DC (direct current) converter that takes AC voltage as input and outputs DC voltage. The power switching transistors inside a switching power supply operate in a high-frequency switching state, consuming very little energy. The power supply efficiency can reach 75% to 90%, which is twice that of a conventional linear regulated power supply.
1. Working principle of switching power supply
A switching power supply is a type of power supply that uses modern power technology to control the on and off time ratio of switching transistors to maintain a stable output voltage. Switching power supplies are composed of pulse width modulation (PWM) control (metal-oxide-semiconductor field-effect transistors).
A switching power supply consists of four main parts: the main circuit, the control circuit, the detection circuit, and the auxiliary circuit. As the name suggests, a switching power supply is like having a door; one door allows current to flow, and the other door stops the current. So, what is this door?
Some switching power supplies use thyristors, while others use switching transistors. These rely on pulse signals applied to the base and control electrode (thyristor) of the switching transistor to turn on and off, causing the electronic switch to continuously 'turn on' and 'turn off'. This allows the electronic switching device to pulse-modulate the input voltage, thereby achieving DC/AC and DC/DC voltage conversion, as well as adjustable and automatic voltage regulation of the output voltage.
The difference between switching power supplies and linear power supplies
In simple terms, voltage regulation in a linear power supply can be viewed as resistance regulation, which is equivalent to changing the voltage by adjusting a sliding rheostat. In contrast, a switching power supply changes the voltage by adjusting the switching frequency. Furthermore, compared to linear power supplies, the cost of both increases with output power, although the rates of increase differ.
1. The cost of a linear power supply is actually higher than that of a switching power supply at a certain output power point.
Therefore, with the development and innovation of power electronics technology, switching power supply technology has continued to break through and innovate. This cost issue has instead led to the shift of switching power supply technology towards lower output power, providing a wide range of development opportunities for switching power supplies.
2. The relationship between power electronic equipment and people's work and life is becoming increasingly close. Electronic equipment cannot function without a reliable power supply. After the 1980s, computers fully adopted switching power supplies. In the 1990s, switching power supplies entered various electronic and electrical fields.
In just ten years, switching power supply technology has rapidly taken over a core position in power electronic equipment. Is this simply because switching power supplies are small in size?
3. From the schematic diagram of a switching power supply, we can see that it doesn't use a bulky power frequency transformer. Furthermore, because the power dissipation on the regulating transistor is significantly reduced, a large heatsink is unnecessary. This makes the switching power supply smaller and lighter. However, the biggest advantage of a switching power supply is its low power consumption and high efficiency. In a switching power supply circuit, the transistor, under the excitation signal, continuously repeats the 'on' and 'off' switching states, with an extremely fast switching speed and a frequency of only 50Hz, greatly improving power efficiency.
4. Wide voltage regulation range of the switching power supply. The output voltage of the switching power supply is adjusted by the duty cycle of the excitation signal, and changes in the input signal voltage can be compensated for by frequency modulation or pulse width modulation. In this way, it can still ensure a relatively stable output voltage when the mains voltage fluctuates greatly.
Therefore, it is not unreasonable that switching power supply technology has quickly become a part of power electronic equipment.
5. Switching power supplies currently operate at approximately 50kHz, which is 1000 times that of linear regulated power supplies. This results in a nearly 1000-fold increase in filtering efficiency after rectification. Even with half-wave rectification followed by capacitor filtering, the efficiency is still increased by 500 times. Under the same ripple output voltage, the capacitance of the filter capacitor in a switching power supply is only 1/500 to 1/1000 of that in a linear regulated power supply.
Why has switching power supply technology become the core of modern power electronics technology? Is its success solely due to its miniaturization and ease of installation in electronic devices?
