Structural analysis of switching power supply

Posted on Feb 7, 2014    3495

Daily switching power supply, mainly offer the direct current power supply for electronic device and supply power. The required direct-current volts of the electronic device, ranges are generally all between several volts and more than ten volts, and the voltage of exchanging Piower supply of city power is 220V 110V, The frequency is 50Hz 60Hz. T

Structural analysis of switching power supply
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he function of switching power supply is to vary the mains frequency alternating current of a high voltage class into the direct current of a low voltage class. The alternating current of mains frequency is commutated directly, save bulky mains frequency with big weight and commutate the voltage transformer after entering the switching power supply. The rectifier is outputted for very high direct current of voltage, the voltage after commutating passes the capacitor filtering, the mean value of the voltage is 300V 310V. The direct current of the high voltage class is sent to the input end of the inverter, vary by the inverter, turn into upper voltage, high-frequency alternating current. The variety operating frequency of the inverter of the switching power supply is in dozens of to several hundred KHz ranges at present. The exchange electric energy that the inverter exported, connect the primary side of the high-frequency step-down transformer, exchange the mains frequency of the electric frequency ratio much higher because of the high frequency that is produced by the inverter, so the volume of the high-frequency voltage transformer is much smaller than with the mains frequency voltage transformer of the capacity, have reduced volume and weight of the whole power fundamentally. The high-frequency alternating current that the inverter produce, after the high-frequency voltage transformer steps down, links such as commutating, voltage regulation, etc. , can vary the undervoltage direct current which accords with the load requirement out, supply load. The rectifying circuit of mains frequency is generally uncontrolled rectifying circuit, according to the magnitude of the power capacity, can single-phase commutate, generally choose the structure of single-phase bridge, the high-capacity switching power supply can use the three-phase a. c. voltage supply. The switching power supply is in inputting the interference-free characteristic, because the characteristic multistep connects in series of its one`s own circuit structure, It is passed that general input interference such as surge voltage is very difficult, have the advantage of being greater compared with linear power in outputting voltage stability this technical indicator, it outputs reachable 0. 5% to 1% of voltage stability. The switch power module is as a kind of electric and electronic integrated device, should pay attention to the following several points in application. Because the operating efficiency of the switching power supply is high, can generally be more than 80%, so on the choice of its output current, should measure or calculate and use the maximum absorption current of the electrical equipment accurately, in order to make the switching power supply that is chosen have high performance-cost ratio, Switching power supply will produce more interference than linear power, responsive to spend the electrical equipment to common-mode interference, should take and earth and shield the measure, so there are EMC electromagnetic compatibility electric-wave filters in the switching power supply. The switching power supply must have excessive load, excessive heating, short out etc. to protect the function in the design, so should first choose to protect the switch power module with complete function during design, and the technical parameter of its protective circuit answers and uses the operating characteristic of the electrical equipment to be assorted, in order to avoid damaging and using the electrical equipment or switching power supply. The electric motor, under

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