Advantages and disadvantages of linear and switching power supply

DC are different according to different requirements to use the power of his best linear DC output is linear , can be used in demanding situations , switching power supply , followed by his high switching speed of transformers and switches , is characterized by weight small , large capacity, high output quality , original phased electricity used in less demanding , the current king of the occasion
Linear power supplies, switching power difference
Adjust the tube work in linear power amplification status , and therefore heat, low efficiency ( about 35% ) , need to add bulky heat sink , but also need equally bulky frequency transformer , when you want to make multiple voltage output when the transformer will be more substantial.
Adjustment of the switching power supply pipe work and ended in a saturated state , and thus heat a small, high efficiency ( over 75% ) and eliminating the need for bulky transformers. But above DC switching power supply output ripple superimposed larger (50mV at 5V output typical), and connected at the output diode voltage regulator can be improved , in addition to the work because the switch will have a huge spike interference, also need chained beads improvement in the circuit. Relatively more linear power no defect , it can do very little ripple (5mV or less ) .
For power efficiency and installation volume requirements where there is better use of switching power supply for electromagnetic interference and power requirements of the purity of a place ( such as a capacitor leakage detection ) multi-use linear power . In addition, when the time required for isolation of the circuit is now the majority do with the isolated DC-DC power supply part (DC-DC therefrom , it is the principle of the switching power supply ) . Also, switching power supply may be used in high-frequency transformer winding up more trouble
Switching and linear power supply on the internal structure is completely different , as the name suggests switching power supply with a switch action, it becomes the duty cycle or frequency using the method to achieve different voltages to achieve more complex , the biggest advantage is the high efficiency, typically more than 90% , the disadvantage is the text of a large wave and switching noise , suitable for text wave and noise less demanding situations ; while no switching linear power belongs to the continuous analog control , the internal structure is relatively simple , the chip area is also smaller, lower cost , the advantage of low cost , small text -wave noise , the biggest drawback is the low efficiency. They have their own shortcomings in the application of complementary coexistence !
A linear power principle:
Linear power supply including frequency transformer , rectifier output filter , the control circuit , the protection circuit. Linear power through the AC adapter is the first transformer , rectifier circuit and then through the filter to be non-stabilized DC voltage, DC voltage to achieve high precision , must adjust the output voltage of the feedback voltage , the power supply technology is mature , it can be achieved high stability , the ripple is small , and no interference with the power switch and noise . But its disadvantage is the need huge and bulky transformers required filter capacitor size and weight are also quite large, and the voltage feedback circuit is operating in the linear state , there are certain adjustments on the tube voltage drop in the output current of the larger work when , resulting in too much power to adjust the tube , low conversion efficiency , but also to install a large heat sink. This power is not suitable for computers and other equipment needed , will gradually be replaced by the switching power supply .
Second, the principle of switching power supply :
The main switching power supply includes an input grid filter , the filter input rectifier , inverter, rectifying the filter output , the control circuit , the protection circuit . Their functions are:
1, the input power filters : eliminate interference generated from the power grid , such as starting the motor , electrical switches , lightning, etc. , but also to prevent high-frequency noise generated by switching power spread to the grid.
2, the input rectifier filter : the power input voltage is rectified and filtered to provide a DC voltage converter .
3 , the inverter : the switching power supply is a key part . It is the high-frequency AC voltage into a DC voltage, and an output portion serves to isolate the effect of the input grid .
4 , the output of the rectifier filter : the frequency of the inverter output AC voltage is rectified and filtered DC voltage to be obtained , and also to prevent high frequency interference noise on the load .
5, the control circuit : detecting the output DC voltage , and compared with a reference voltage and amplified . Pulse width modulated oscillator to thereby control the inverter to maintain a stable output voltage .
6 , the protection circuit : When the switching power supply overvoltage , short circuit overcurrent protection circuit switching power supply stop working to protect the load and the power supply itself.
Switching the first AC power supply is rectified into direct current, direct current is inverted into the alternating current into a direct current output voltage of the rectifier needed . This eliminates the need for switching power supply transformer Linear and voltage feedback circuit . The switching power inverter circuit is completely digital adjustment , the same can be adjusted to achieve very high accuracy .
The main advantage of the switching power supply :
Small size, light weight ( 20 to 30 % by volume and weight of only linear power supply ) , high efficiency ( typically 60 to 70 percent , while linear power only 30 to 40% ) , their strong anti-interference , wide output voltage range, modular .
The main drawback of the switching power supply :
Since the inverter circuit generates a high frequency voltage , the device has some of the surrounding interference . Need good shielding and grounding
Huawei switching power supply is to use a high-frequency alternating current through the switch circuit for high-speed channel switch on and off control . Direct current into high frequency AC power to the transformer the transformer , one or more groups to produce the required voltage ! 's the reason is that the efficiency of a high-frequency AC transformer transformer circuit is much higher than 50Hz , so switching transformer can do very little , but when the job is not very hot ! ! very low cost , if not then switch to 50Hz into high frequency power does not make sense ! ! switching transformer nor mysterious. was an ordinary transformer ! that's switching power supply.
Switching power supply, through electronic technology , the main link : rectified into DC - reverse into AC voltage required ( mainly to adjust the voltage ) - then rectified to a DC voltage output.
Due to the structure of the switching power supply in the middle of no transformers and heat sinks , so the volume is very small . Meanwhile, the switching power supply is internal electronic components, high efficiency, low heat. Although , with the disadvantage of electromagnetic interference and so on, but now the technology is already in place shielding .
Switching power supply can be divided into two kinds of isolated and non-isolated , isolation type must have a switching transformer , rather than isolation is not necessarily there .
Simply put , switching power supply works :
1 AC power into DC input rectifier filter through ;
(2) high-frequency PWM ( pulse width modulation ) signal control switch, the switch on the transformer primary current applied ;
3 induces a high frequency switching transformer secondary voltage supplied by the rectifier filter load ;
4 through the output section of the circuit is fed back to a control circuit for controlling the PWM duty cycle in order to stabilize the output .
Generally after Eritrea asthenosphere AC power input or something , web filtering -down interference , but also filter out interference on the power grid ; at the same power , the higher the switching frequency , the smaller the volume switch of the transformer, However, the requirements for the switch higher ; switching transformer secondary winding or can have more than one winding has multiple taps to get the desired output ; general should also increase the number of protection circuits , such as load , short circuit protection, otherwise, you may burn switching power supply.
Above that is the switching power supply roughly works.
In fact, now has a very high degree of integration of a dedicated chip, can make the external circuit is very simple to do even free debugging.
TOP series such as switching power supply chip (or module ) , as long as with some RC components , and a switching transformer , you can make a basic switching power supply.
Linear & Switching Power supply
The main principle is that the power switch on the bridge and the bridge Mos tube turns conducting , the current through the first pipe into the bridge Mos , storage function of the coil , the energy gathered in the coil , and finally close the bridge Mos tube , open the bridge Mos tube , coil and capacitor continued to external power supply. Then close the bridge Mos tube , then open the bridge to allow current to enter , so be repeated , because the switch to turn Mos tube , so called switching power supply.
The linear power supply is not the case , because there is no switch to intervene so that the drain pipe has been , if there are multiple , it will leak out , and this is Mos tube heat we often see some of the linear power supply is large, with endless electricity, all converted into heat . From this perspective , linear power conversion efficiency is very low, and the heat is high, the life element is bound to decline , affecting the final results.
Difference between switching and linear power supply is mainly the way they work .
Linear power supply power devices operating in the linear state, that he has used up the power device is working, so his work will lead to low efficiency , typically 50% to 60% , had said he was a good linear power . Work linear power , so he must have changed from high to low- pressure device , generally are transformers , there are other like KX power , through the rectified output DC voltage. So that he also large volume , bulky , inefficient , heat is also large . He also has his advantages: small ripple , regulation is good, little outside interference. Analog circuit suitable for use with various types of amplifiers.
Switching power supply. His work in the off state power devices , ( opening and closing , opening and closing , the frequency is very fast, usually flat frequency switching power supply 100 ~ 200KHz, module power at 300 ~ 500KHZ). So his loss is small , also high efficiency , the transformer has also been required to use high permeability materials do . bit of ink , and his word is a small transformer efficiency 80% to 90 % of it is said that the best American VICOR module up 99% high efficiency switching power , small size, however , and linear power than his ripple voltage and current regulation will have discount.
 
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