The main raw materials for switching power supplies are transformers, power devices, inductors, reactors, etc. Switching power supplies are the basic products of the electronics industry. The downstream involves many areas of the national economy, including telecommunications, postal services, banking, securities, railways, civil aviation, taxation, industry and commerce, petroleum, shipping, aerospace, and military.
At present, the switching power supply industry has formed a complete industrial chain. The upstream international mainstream component suppliers control the manufacturing technology of switching power supply IC chips. The midstream power supply manufacturers are downstream according to their different levels of power supply manufacturing expertise and production capacity. Customers offer power products of different skill levels and types. The downstream of the switching power supply industry is industrial automation control, military equipment, scientific research equipment, LED lighting, industrial control equipment, communication equipment, power equipment, instrumentation, medical equipment, semiconductor refrigeration and heating, air purifiers, electronic refrigerators, liquid crystal displays, LED lamps. , communications equipment, audio-visual products, security monitoring, LED light bags, computer chassis, digital products and instruments.
In the process of development, China's power switches have shown a trend of miniaturization, thinning, light weight and high frequency. Because, with the continuous expansion of power switch applications, users are increasingly demanding portability of switching power supplies. In a certain range, the increase of the switching frequency can not only effectively reduce the size of the capacitor, the inductor and the transformer, but also suppress the interference and improve the dynamic performance of the system, so that the size, thickness, weight, and frequency are reduced. It will be the main development direction of switching power supply.
Switching power supply module is a new generation of switching power supply products, mainly used in civil, industrial and military applications, including switching equipment, access equipment, mobile communications, microwave communications, optical communications, routers and other communications fields and automotive electronics, aerospace Wait. Due to the short design cycle, high reliability and easy system upgrade, the module power supply system has more and more applications. Especially in recent years, due to the rapid development of data services and the continuous promotion of distributed power supply systems, module power supply has developed rapidly.
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There are also many types of control chips for switching power supplies, which are mainly divided into two types: current control type and voltage control type. The voltage control type only samples the output voltage, stops the closed-loop control as the reaction signal, and uses PWM technology to regulate the output voltage. From the perspective of control theory, this is a single-loop control system. The current control type is based on the voltage control type, adding a current negative reaction link, making it a dual-loop control system, thereby improving the performance of the power supply.
Product classification, roughly divided into AD / DC, DC / DC two categories. Over the years, the technology application of product application has formed a certain misunderstanding of the industry's understanding of DC/DC power supply, thinking that DC/DC is difficult to do, AC/DC is easy to do.
Nevertheless, there is still a big difference between AC/DC and DC/DC. From the aspects of product design, device selection request, and reliable purpose, AC/DC is far more complicated than DC/DC, which is difficult for many years. Engaged in the development of AC / DC power supply, the deep understanding of consumption.
First of all, from the input side comparison, AC / DC is much harder than DC / DC. AC/DC is directly connected to the public network. It is well known that the public network is very complicated. Some mains are directly small hydropower, and can be up to 350VAC at night. Some direct phase voltages are 380VAC, and low voltage can reach Below 130 volts. In addition, there are many devices with different input characteristics, such as rational load, capacitive load, a lot of spike noise on the power grid, and repeated harmonic components, lightning thunderstorms and other elements. The combined impact makes the public network more complex. The DC/DC input voltage is usually from a rectifier or a battery. The commonly used voltages are 12V/24V/48V/60V, etc. The rectifier is AC/DC, which has been isolated once.
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Secondly, from the perspective of device selection and reliability, AC/DC design is more difficult than DC/DC. From the above description, AC/DC directly faces high voltage, the choice of input devices, especially power MOSFETs, the higher the voltage, the higher the turn-on voltage drop and the switching loss, the harder the thermal design of the power supply is, the other diodes, Triodes also have such problems, high voltage is difficult to choose, low voltage is good choice. At the same time, the safety level of AC/DC power supply requirements is much higher than DC/DC. From the circuit configuration point of view, AC/DC usually requires two-stage transformation, and DC/DC only needs one-stage transformation, and the main power conversion circuit used by DC/DC is relatively simple.
The switching power supply is a kind of power supply that uses a modern power electronic technology to control the ratio of the time when the switch is turned on and off, and maintains a stable output voltage. The switching power supply is generally composed of a pulse width modulation control IC and a MOSFET. With the development and innovation of power electronics technology, switching power supply technology is constantly innovating. At present, switching power supply chips are widely used in almost all electronic devices due to their small size, light weight and high efficiency. It is an indispensable power supply method for the rapid development of the electronic information industry. Next, Xiaobian will pay attention to the following matters when using the switching power supply chip:
1) Before using the power chip, first determine whether the input and output voltage specifications match the nominal value of the power supply used;
2) Before power-on, check whether the input and output leads are connected correctly to avoid damage to the user equipment;
3) Check whether the installation is firm, whether the mounting screws are in contact with the power board device, and measure the insulation resistance of the housing and the input and output to avoid electric shock;
4) To ensure the safety of use and reduce interference, please ensure that the grounding terminal is reliably grounded;
5) Multi-output power supply is generally divided into main and auxiliary outputs. The main output characteristic is better than the auxiliary output. Under normal circumstances, the output current is large as the main output. In order to ensure the output load regulation rate and output dynamics and other indicators, it is generally required to have at least 10% load per channel. If the auxiliary road is not used, the main road must be added with a proper dummy load. For details, refer to the specifications of the corresponding model;
6) Please note: frequent power switch will affect its life;
7) The working environment and the degree of loading will also affect its life.
despite this. Engineers know that despite the rapid development of switching power supply applications, the linear power supply is also the highlight!
The DC power is different according to the requirements. The linear power supply is best to output linear DC power. It can be used in high requirements. The switching power supply is second. It is a transformer and switch tube with high switching speed. It is characterized by weight. Small, large capacity, high output quality, phase control power is used in occasions where the requirements are not high and the current is very large.
The adjustment tube of the linear power supply works in an amplified state, so the heat generation is large and the efficiency is low (about 35%). It is necessary to add a bulky heat sink, and also requires a large-sized power frequency transformer, when multiple voltage outputs are to be produced. The transformer will be bigger.
The regulating tube of the switching power supply operates in saturation and cut-off state, so the heat generation is small, the efficiency is high (more than 75%) and the large-volume transformer is omitted. However, the DC output of the switching power supply will be superimposed with a large ripple (50mV at 5V output typical), and the Zener diode can be improved at the output end. In addition, since the switching tube works, it will generate a large spike interference. The magnetic beads are connected in series in the circuit to improve. Relatively speaking, the linear power supply has no such defects, and its ripple can be made very small (below 5mV).
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Switching power supplies are preferred where power efficiency and installation volume are required. Linear power supplies are often used where electromagnetic interference and power purity are required (eg, capacitive leakage detection). In addition, when the circuit needs to be isolated, most of the DC-DC is used to supply the isolated part (DC-DC is the switching power supply from its working principle). Also, the high-frequency transformer used in the switching power supply may be troublesome to wind up.
The switching power supply and the linear power supply are completely different in internal structure. As the name suggests, switching power supply has a switching action. It uses variable duty ratio or frequency conversion to realize different voltages. The implementation is more complicated, and the biggest advantage is high efficiency. More than 90%, the disadvantage is that the Wenbo and switching noise is large, suitable for occasions where the requirements of Wenbo and noise are not high; while the linear power supply has no switching action, which belongs to continuous analog control, the internal structure is relatively simple, and the chip area is also small. The cost is lower, the advantage is low cost, the noise of the ripple is small, and the biggest disadvantage is the low efficiency. They each have their own shortcomings that complement each other in application!
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