Switching power supply circuit design, these four typical circuits are the most important

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Selection of working mode of switching power supply: In the switching power supply circuit, there are four basic types: single-ended flyback, single-ended forward, half-bridge and full-bridge. For switching power supplies below 100 W, single-ended flyback converters are used. The transformers in the flyback power conversion circuit have the function of energy storage in addition to isolation. The structure of the flyback power conversion circuit is relatively simple, the output voltage is not limited by the input voltage, and the multi-channel voltage output TOPSwitchII series can also be applied to the single-ended flyback converter. The typical usage is as follows:
Four typical switching power supply circuit design

Figure a
Four typical switching power supply circuit design

Figure b
Four typical switching power supply circuit design

Figure c
Four typical switching power supply circuit design

Figure d
Circuit analysis: (a) the bias coil is directly used as the input of the TOPSwitch II control electrode through the current limiting resistor; (b) the voltage regulator tube is added on the basis of (a), which is an enhanced type of (a); The output voltage is applied to the TOPSwitch II control electrode through the optocoupler, which improves the output voltage feedback accuracy. (d) The precision reference TL431 is added on the basis of (c), so that the output voltage regulation accuracy and load regulation rate can be higher. Precision. The effects of the four conversion circuits are shown in the table:

The four typical switching power supply circuits are designed with a single-ended flyback switching power supply. The most important feature of this feedback control circuit is that it has a faster dynamic response speed and automatically limits the load current when the input voltage and load current vary greatly. The compensation circuit is simple. The flyback circuit is adapted to a small power switching power supply.