Classification and characteristics of switching power supplies
Classification of switching power supplies
With the popularity of switching power supplies, switching power supplies have begun to be widely used in various fields, and the classification of switching power supplies is also varied. According to different application fields and focus points, the same switching power supply can also be divided into several different categories. The following is a brief introduction to several common classifications of switching power supplies.
AC/DC power supply
AC/DC switching power supply is a switching power supply that converts AC voltage into DC voltage. This type of power supply usually converts 220V, 50Hz or 60Hz AC grid voltage into a lower DC voltage, and at the same time realizes electrical isolation between the AC grid and the DC output. There are many types of AC/DC switching power supplies, and their power range can range from a few watts to several kilowatts, which belongs to the first category of switching power supplies.
DC/DC power supply
DC/DC switching power supply is a switching power supply that converts one DC voltage into another DC voltage. At the same time, it realizes electrical isolation between the DC input power supply and the DC output voltage. Its power range is usually from a few watts to several hundred watts, which belongs to another major category of switching power supplies.
Switching Regulator
A switching regulator is a simple DC/DC switching power supply. The input voltage and output voltage of this power supply are not electrically isolated, but the power efficiency can reach more than 95%. It is mostly used for voltage conversion inside electrical equipment. For example, various voltage converters on laptop motherboards.
Module power supply
This type of switching power supply is usually made into a module form, with both AC/DC modules and DC/DC modules. Its input voltage and output voltage have many specifications for users to choose. The power range of the module power supply is small, generally only a few watts to tens of watts.
Power adapter
The power adapter is one of the most common switching power supplies at present and is widely used in our daily life. For example, mobile phones, digital cameras and tablet charging adapters, router power adapters, etc.
Special power supply
Special power supply is a switching power supply with a specific purpose. Electric bicycle charger is one of them. This type of switching power supply is designed for specific loads and usually has constant voltage and constant current output characteristics, as well as battery reverse connection protection and other functions.
Characteristics of switching power supplies
Compared with linear power supplies, switching power supplies have the following advantages:
Low power consumption, high efficiency, and significant energy-saving effects
The power loss of switching power supplies is low, and its efficiency is usually above 80%, while that of linear power supplies is generally only about 40%. Switching power supplies have significant energy-saving effects.
Small size and light weight
Switching power supplies do not have bulky power frequency transformers, and do not require large heat sinks, thereby reducing the size and weight of the power supply. Its size and weight are usually only about 30% of that of linear power supplies.
Wide input voltage range
The input voltage range of switching power supplies can be made very wide, such as 90~260V, which is called universal input voltage. It can be used in the civil power grid of any country in the world without considering voltage matching.
Application of switching power supply in PFC
PFC (power factor correction) is a technology to improve the power factor of power supply equipment and reduce reactive power loss. Switching power supplies are particularly widely used in PFC. Here is a typical example to illustrate:
Example: PFC application of computer power supply
Background: In order to meet energy efficiency standards and reduce pollution to the power grid, modern computer power supplies usually integrate PFC circuits. PFC circuits can be divided into passive PFC and active PFC.
Features of active PFC circuit:
High power factor: Active PFC circuit can increase the power factor to close to 1 (usually above 0.95
Low harmonic distortion: Active PFC can effectively reduce the harmonic components in the input current and reduce pollution to the power grid.
High efficiency: Since the active PFC circuit can correct the input current waveform to a sine wave, its efficiency is usually higher than that of passive PFC.
Working principle
Rectification: The input AC voltage is first converted into DC voltage through a rectifier circuit.
PFC controller: The PFC controller adjusts the input current through a switch tube (such as MOSFET) to make its waveform the same as the waveform of the input voltage, thereby achieving the purpose of power factor correction.
Filtering: The DC voltage output by the PFC circuit is then passed through a filtering circuit and provided to the subsequent DC/DC conversion circuit.
Specific application: In a computer power supply, the active PFC circuit usually consists of a boost converter (Boost Converter). It increases the rectified DC voltage by adjusting the on-time of the switch tube and adjusts the input current waveform to make it in phase with the input voltage, thereby achieving high power factor and low harmonic distortion.
For example: Assume a high-efficiency computer power supply with a rated power of 500W and an integrated active PFC circuit.
Input voltage: 220V AC
Rectified voltage: about 310V DC
PFC circuit output voltage: 380V DC
Power factor: 0.98
Efficiency: 92%
Advantages:
High efficiency and energy saving: High power factor reduces the loss of reactive power and has higher overall efficiency.
Low grid pollution: Reduce harmonic components and reduce interference to the grid.
