Switching power supply and linear power supply

Ac current through the rectifier, can obtain dc power supply. However, due to changes in AC voltage and load current, the dc voltage obtained after rectification usually causes a voltage change of 20% to 40%.

In order to obtain stable DC voltage, the voltage regulator circuit must be used to achieve voltage regulation. According to the different implementation methods, regulated voltage power supply can be divided into linear regulated voltage power supply, phased regulated voltage power supply and switching regulated voltage power supply. Among them, switching power supply represents the development trend of low-carbon environmental protection and advanced power supply.

The commonly used low-voltage DC switching power supply is the 220 VOLT AC power through the ELECTROMAGNETIC compatibility filter, directly rectified into about 300 volt DC power supply, and then converted into high-frequency AC power for transformer transformation, so as to generate one or more required voltages, and then rectified into the required voltage DC power supply. The reason why it is converted into high frequency ALTERNATING current is that the efficiency of high frequency alternating current in transformer conversion circuit is much higher than 50Hz, so the main transformer can be made very small, with magnetic core, not too hot when working; In addition, at high frequencies, the energy storage and filter capacitance and inductance are higher than 50Hz

It's much smaller and costs much less. If not 50Hz

The power transformer doesn't make sense if it's high frequency! Switching transformers are not god dense, is a general transformer skeleton transformer! This is the power transformer. Switching power supply is achieved by electronic technology, its main link is: rectifier into DC - commutation into the required voltage alternating current (mainly regulating voltage) - and then rectifier into DC voltage output. In the structure of switching power supply, there is no bulky transformer and radiator in the middle, so the volume is very small. At the same time, switching power supply is full of high efficiency, low heat electronic components. Although, with large interference signal and other defects, but now the local market sales in Europe, America and Japan and the manufacturing industry in China but no shoddy power transformer anti-interference signal filter and shielding technology has been very timely. Switching power supply can be divided into two kinds of isolation and non-isolation, isolation type must have switching transformer, and non-isolation type must have. Briefly speaking, the principle of the power transformer is as follows :1. Ac input is filtered into AC by the rectifier; 2. Operate switch tube according to high frequency PWM(pulse width modulation) or single pulse frequency modulation (PFM). Add DC to switch transformer primary; 3. The high frequency voltage induced by the secondary switching transformer is provided to the load by rectification filter; 4. Output part through a certain circuit feedback to the control circuit, control PWM duty ratio, to achieve the purpose of stable output. When ac power is supplied, it usually passes through an inductor - capacitance filter. Overconsidering the influence of power outage on the network, and also overconsidering the influence of switching power supply on the power network; When the output power is the same, the higher the switching frequency of the power supply, the smaller the volume of the switching transformer, but the higher the regulation of the switching tube; The secondary coil of the switching transformer can have several winding resistance or a winding resistance has several taps, in order to obtain the necessary output; Generally, some maintenance power supply circuits should also be promoted, such as full load, short circuit failure and other maintenance, otherwise it is likely to damage the power transformer. The above is the general principle of the power transformer. In fact, there are very high degree of integration of special chips, can make the peripheral circuit very simple or even debugging. For example, TOP series switching power supply chips (or modules), as long as some resistance capacitor components and a switching transformer, can be made into the basic switching power supply. Power transformer & linear regulated power supply, general half bridge on the key principle of the power transformer is under the bridge and the bridge of the switch tube (high frequency switch tube VMOS) round the on and off, the first switch tube into electricity flow according to the bridge, using the inductance of the storage function, the electromagnetic energy gathered in the electromagnetic coil, eventually turn off the switch tube on the bridge, open the switch tube under the bridge, Inductors and capacitors continuously supply power to the external system. Then turn off the lower bridge switch tube, and then open the bridge to let the current into, is repeated in this way, because to turn the power switch two switch tube, so called the power transformer. Linear regulated power supply is not the same, because there is no power switch intervention, prompting the water inlet pipe has been adding water, if there is more, it will leak, this is the heat value of some linear regulated power supply regulation tube is very large, spend endless electromagnetic energy, all converted into energy. From this perspective, the conversion efficiency of linear regulated power supply is extremely low, and under the circumstance of high calorific value, the service life of components is bound to be reduced, endangering the actual application effect in the end.

The main difference between power transformers and linear regulated power supplies is the way they work. The power regulator tube of a linear power supply often operates in an expanded region where the current flows continuously. Because the regulating tube consumes a lot of output power, so it must be a large output power regulating tube and equipped with a very large volume of heat pipe radiator, hot more serious, very low efficiency. Generally in 50%~60%, also have to say that he is a very good linear voltage regulator. The working mode of linear regulated voltage power supply makes it necessary to have the voltage equipment from high voltage to bottom voltage. Generally, it is all transformer, and there are other such as KX switching power supply, and then after the rectifier output AC voltage. In this way, he was heavy, unwieldy, inefficient and hot. He also has his advantages: small harmonic distortion, good regulation rate, small influence of opening to the outside world. Suitable for analog circuits, various amplifiers, etc. Switching power supply. The power device works in the switching state, and temporarily stores energy through the inductor coil when adjusting the voltage, with small loss, high efficiency and low requirements for heat dissipation. However, it also has high requirements for transformer and energy storage inductor. Therefore, materials with low loss and high permeability should be adopted. The transformer type is small. The total efficiency is 80%~98%, the switching power supply has high efficiency but small volume, but compared with the linear power supply, the voltage and current adjustment rate has a certain discount.

1. The radio station applies a relatively standard outdoor antenna feed system. When the coaxial cable shielding layer does not participate in radio transceiver, the ESD of the power supply and the anti-interference ability of the stable part of the power supply are mainly considered. The reason is that the load impedance of the power supply changes greatly at the moment of transmission, and improper processing will lead to the disorder of sampling and execution of the stable system. Therefore, a low pass filter must be installed between sampling and output of the stable system.

2. The radio station applies casual outdoor antenna feed system software, and the coaxial line shields the layer to participate in wireless communication receiving and sending. At this point a low pass filter must be modified at the 380V input to suppress the effect.