Compared with switching power supply, the biggest advantage of linear power supply is that its semiconductor devices are in a linear state, and the output voltage will not have great ripple.
Therefore, linear power supply has the characteristics of small interference and good EMI.
When used in noise-sensitive equipment such as speakers, the performance of the equipment can be improved.
Question 2: Where should linear power supply be given priority, and where should switching power supply be given priority, depending on whether it is centralized power supply or independent power supply? Choose to do linearity alone, focusing on switching power supply.
Question 3: What is the difference between switching power supply and linear power supply? Where have they seen this zhidao.baidu/...016244?
Question 4: The difference between linear power supply and switching power supply 1. Switching power supply converts direct current into high-frequency pulse current, stores electric energy in inductance and capacitance elements, and releases electric energy according to predetermined requirements by using the characteristics of inductance and capacitance to change output voltage or current; Linear power supply has no high-frequency pulse and energy storage elements. It uses the linear characteristics of components to feedback and control the input immediately when the load changes, and realizes stable voltage and current.
2. Switching power supply can step down or step up; Linear power supply can only step down.
3, the switching power supply has high efficiency; Linear power supply is inefficient.
4. The linear power supply has fast control speed and small ripple; The switching power supply has large ripple.
Advantages and disadvantages of linear power supply and switching power supply
They are all direct current, and they are used according to different requirements. Linear power supply outputs linear DC, which can be used in demanding occasions, followed by switching power supply. It is composed of transformer and switch tube, with fast switching speed, light weight, large capacity and high output quality. Phased power supply was originally used in occasions with low requirements and high current.
The difference between linear power supply and switching power supply
The regulating tube of linear power supply works in amplification state, so the calorific value is high and the efficiency is low (about 35%). It needs to add a huge radiator and a large power frequency transformer. When multiple sets of voltage outputs are made, the transformer will be larger.
The regulating tube of the switching power supply works in a saturated off state, so the calorific value is low and the efficiency is high (above 75%), and a large transformer is saved. However, the DC output of the switching power supply will have a large ripple (typical value is 50mV for 5V output), which can be improved by connecting a zener diode in parallel at the output terminal. In addition, because the switching tube will produce great peak interference, it is necessary to connect magnetic beads in series in the circuit to improve it. Relatively speaking, linear power supply does not have the above defects, and its ripple can be made very small (below 5mV).
It is best to use switching power supply where there are requirements for power supply efficiency and installation volume, and linear power supply where there are requirements for electromagnetic interference and power supply purity (such as capacitance leakage detection). In addition, when the circuit needs isolation, DC-DC is mostly used to supply power to the isolated part (DC-DC is a switching power supply from its working principle). Also, the high-frequency transformer for switching power supply may be troublesome to wind.
Switching power supply and linear power supply are completely different in internal structure. As the name implies, switching power supply has switching function. It uses variable duty ratio or frequency conversion to realize different voltages, which is more complicated. The biggest advantage is high efficiency, generally above 90%. The disadvantage is that the noise of the museum and switch is large, which is suitable for occasions with low requirements for the museum and noise. Linear power supply has no switching action and belongs to continuous analog control. Its internal structure is relatively simple, the chip area is small and the cost is low. Its advantages are low cost and low noise, and its biggest disadvantage is low efficiency. They each have their own shortcomings, and they complement each other in application!
First, the principle of linear power supply:
Linear power supply mainly includes power frequency transformer, output rectifier filter, control circuit and protection circuit. Linear power supply converts alternating current through transformer, and then rectifies and filters through rectifier circuit to get unstable DC voltage. In order to obtain high-precision DC voltage, the output voltage must be adjusted by voltage feedback. This power supply technology is very mature, which can achieve high stability, small ripple, no interference with switching power supply and no noise. But its disadvantage is that it needs a huge and bulky transformer, and the volume and weight of the filter capacitor are also quite large. Moreover, the voltage feedback circuit works in a linear state, and there is a certain voltage drop on the regulating tube. When outputting large working current, the power consumption of the regulating tube is too large, the conversion efficiency is low, and a large heat sink is installed. This kind of power supply is not suitable for computers and other equipment, and will be gradually replaced by switching power supply.
Second, the principle of switching power supply:
Switching power supply mainly includes input power grid filter, input rectifier filter, inverter, output rectifier filter, control circuit and protection circuit. Their functions are:
1, input power grid filtering: eliminate interference from the power grid, such as motor start-up, electrical switch, lightning strike, etc. It also prevents the high-frequency noise generated by switching power supply from spreading to the power grid.
2. Input rectifier filter: rectifies and filters the input voltage of the power grid to provide DC voltage for the converter.
3. Inverter: It is the key component of switching power supply. It converts DC voltage into high frequency AC voltage and isolates the output part from the input power grid.
4. Output rectification and filtering: rectify and filter the high-frequency AC voltage output by the frequency converter to obtain the required DC voltage, and at the same time ... & gt
Question 5: What is the difference between linear power supply and switching power supply? What specific aspects are used more? The voltage feedback circuit of linear power supply works in linear state, and switching power supply means that the tube used for voltage regulation works in saturation cutoff region, that is, switching state. Linear power supply usually samples the output voltage and sends it to a comparative voltage amplifier with a reference voltage. The output of this voltage amplifier is used as the input of the voltage regulator, which controls the regulator to make its junction voltage change with the input, thus adjusting its output voltage. The switching power supply changes the output voltage by changing the switching time of the regulator, that is, the duty cycle! From its main characteristics, linear power supply has mature technology, low manufacturing cost, high stability, small ripple and no interference and noise with switching power supply, but its volume is relatively large compared with switching power supply and its input voltage range is high; Switching power supply is the opposite.
Question 6: Those appliances use linear power supply. What about switching power supply? Linear power supply generally refers to the power supply obtained after the mains electricity or power supply is stepped down, rectified and filtered by a transformer or a step-down element, and requires a voltage stabilizing circuit. This circuit is inefficient (compared with switching power supply), but because of its low frequency, convenient filtering and better insulation performance than switching power supply (in theory, it is almost completely insulated, and it will not supply power to people regardless of whether the ground wire is connected or not). If the switching power supply is not connected to the ground wire, people will get an electric shock if they come into contact with any metal part that is not insulated from the ground (because most switching power supplies have primary and secondary coupling capacitors for anti-interference). It is used for sensitive appliances with interference and sensitive appliances with special requirements for insulation, such as high-end audio, medical instruments and measuring instruments. If the components are selected reasonably, they will rarely break.
Switching power supply Unless there are special requirements, almost all general appliances use switching power supply. In Japan, it is stipulated that switching power supply must be used unless there are special requirements. Its characteristics are high efficiency, small size and less use of non-ferrous metals. , but it is relatively easy to decompose. Especially when it thunders.
Question 7: What is the difference between switching power supply and linear power supply? Switching power supply is to control the high-speed switching of switching tube through circuit. It converts direct current into high-frequency alternating current and provides it to the transformer for transformation, thus generating one or more required voltages! The reason for switching to Huawei's high-frequency alternating current is that the efficiency of high-frequency alternating current in transformer transformation circuit is much higher than 50Hz, so the switching transformer can be made very small and will not be very hot when working! ! The cost is very low. If you don't turn 50Hz into high frequency, switching power supply is meaningless! ! Switching transformers are not mysterious. Just an ordinary transformer! This is a switching power supply.
Switching power supply is realized by electronic technology, and the main link is: rectifying to DC- alternating current with required voltage (mainly regulating voltage)-and then rectifying to DC voltage output.
The structure of switching power supply is very small, because there is no transformer and heat sink in the middle. At the same time, the switching power supply is all electronic components, with high efficiency and low heat generation. Although there are disadvantages such as electromagnetic interference, the current shielding technology is already available.
Switching power supply can be roughly divided into isolated and non-isolated types. The isolated type must have a switching transformer, but the non-isolated type may not.
Simply put, the working principle of switching power supply is:
1. AC power input enters DC after rectification and filtering;
2. The switch tube is controlled by high frequency PWM (pulse width modulation) signal, and the DC is added to the primary of the switching transformer;
3. The secondary of the switching transformer induces high-frequency voltage, which is provided to the load through rectification and filtering;
4. The output part is fed back to the control circuit through a certain circuit to control the PWM duty ratio and achieve the purpose of stable output.
When the AC power supply is input, it usually passes through something similar to the current loop to filter out the interference on the power cut-off network, and at the same time, it also filters out the interference of the power supply on the power grid; Under the same power, the higher the switching frequency, the smaller the size of the switching transformer, but the higher the requirements for the switching tube; The secondary of the switching transformer can have multiple windings, or one winding has multiple taps to obtain the required output; Generally, it is necessary to add some protection circuits, such as no-load and short-circuit protection, otherwise it may burn out the switching power supply.
The above is the general working principle of switching power supply.
In fact, there are special chips with very high integration, which can make the peripheral circuits very simple and even debugging-free.
For example, TOP series switching power supply chips (or modules) can be made into a basic switching power supply as long as they are equipped with some resistance-capacitance components and a switching transformer.
Switching power supply &; linear power supply
The main working principle of switching power supply is that the Mos transistors of the upper bridge and the lower bridge are turned on in turn. First, the current flows in through the Mos tube of the upper bridge, and the energy is concentrated in the coil by using the energy storage function of the coil. Finally, the Mos tube of the upper bridge is turned off, and the Mos tube of the lower bridge is turned on, and the coil and capacitor continuously supply power to the outside. Then turn off the bridge Mos tube, and then turn on the upper bridge to let the current in. This is repeated, because Mos tubes have to be switched on and off in turn, which is called switching power supply.
Linear power supply is different. Because there is no switch to intervene, the water supply pipe has been draining. Too much will leak out. This is what we often see. Mos tubes of some linear power supplies generate a large amount of heat, and all the inexhaustible electric energy is converted into heat energy. From this point of view, the conversion efficiency of linear power supply is very low, and when the calorific value is high, the life of components is bound to decline, which will affect the final use effect.
The difference between switching power supply and linear power supply is mainly the working mode.
The power device of linear power supply works in a linear state, that is to say, the power device has been working since it is used, which leads to its low working efficiency, generally 50%~60%. I have to say that it is a good linear power supply. The working mode of linear power supply makes him need to change from high voltage to low voltage with a voltage regulator, which is usually a transformer and other power supplies like KX, and then output DC voltage through rectification. This makes him bulky, heavy, inefficient and calorific. He also has his advantages: small ripple, good regulation rate and small external interference. Suitable for analog circuits, various amplifiers, etc.
Switching power supply. His power devices work in the switching state (one is turned on and one is turned off, and the frequency is very fast. Generally, the frequency of flat-panel switching power supply is 100~200KHz, and the module power supply is 300 ~ 500 kHz). In this way, its loss is small and its efficiency is high, which requires the transformer to be made of high permeability materials ...
Question 8: What is the difference between linear power supply and switching power supply? Simply put, the linear DC power supply is transformed by a transformer first, and then filtered and rectified into DC; Switching DC power supply is rectified to DC first, and then DC-DC conversion is realized through transformer and PWM. According to the different topology, switching power supply can be flyback, forward, bridge, LLC, push-pull and so on.
Linear DC power supply, simple structure and circuit, low efficiency, large mass and volume; But the working frequency is low (power frequency), so the high frequency interference is also small.
Switched DC power supply circuit has complex structure, high efficiency, small volume, multiple functions and high cost.
Question 9: What are the advantages and disadvantages of switching power supply and linear power supply? Advantages of linear power supply: there are no switching devices in the circuit, so there is no switching noise and the output is very clean.
Linear power supply has many disadvantages, as follows:
1, only step down;
2. Only the same voltage polarity can be converted;
3. Input and output cannot be isolated;
4. It is difficult to realize multi-channel output;
5. Low efficiency and large transistor loss;
6. The input voltage range is narrow;
7. Severe fever;
8, large volume.
Advantages of switching power supply:
1, high efficiency and ideal no power consumption;
2, small size, miniaturization due to the increase of frequency;
3, can step down or step up the output;
4, the input and output are easily isolated;
5, it is easy to realize multi-channel output;
6, can output negative voltage;
7. The input voltage range is very wide.
Switching power supply has only one disadvantage, that is, it has output noise and electromagnetic radiation is greater than linear power supply.
Question 10: What is a linear regulated power supply? The regulating tube of linear power supply works in amplification state, so the heat generation is large and the efficiency is low (about 35%). It needs to add a huge radiator and a large power frequency transformer. When multiple sets of voltage outputs are made, the transformer will be larger. The regulating tube of the switching power supply works in a saturated off state, so the calorific value is low and the efficiency is high (above 75%), and a large transformer is saved. However, the DC output of the switching power supply will have a large ripple (typical value is 50mV for 5V output), which can be improved by connecting a zener diode in parallel at the output terminal. In addition, because the switching tube will produce great peak interference, it is necessary to connect magnetic beads in series in the circuit to improve it. Relatively speaking, linear power supply does not have the above defects, and its ripple can be made very small (below 5mV). It is best to use switching power supply where there are requirements for power supply efficiency and installation volume, and linear power supply where there are requirements for electromagnetic interference and power supply purity (such as capacitance leakage detection). In addition, when the circuit needs isolation, DC-DC is mostly used to supply power to the isolated part (DC-DC is a switching power supply from its working principle). Also, the high-frequency transformer for switching power supply may be troublesome to wind.