The power adapter does not use bulky industrial frequency transformers. After the power dissipation on the switch MOS tube is greatly reduced, a larger heat sink is omitted. Due to these two reasons, the switching power adapter is small in size and light in weight.
In the switching power supply adapter circuit, the switch MOS tube is activated by the excitation signal, it alternately works in the on-off and off-on switching state. The conversion speed is very fast and the frequency is generally above 50kHz. In some advanced switches in the power line, it can be several hundred or near mega Hz. This makes the power consumption of the switch MOS tube very small, and the efficiency of the power supply can be greatly improved, and its efficiency can reach 90%.
The operating frequency of the switching power supply adapter is basically above 50kHz, which is more than 1000 times that of the power adapter that is linear stabilized. This makes the filter efficiency after rectification almost 1000 times higher. Even if half-wave rectification is used and capacitor filtering is added, the efficiency has also been increased by 500 times. Under the same ripple output voltage, when the switching desktop ac adapter is used, the capacity of the filter capacitor is only 1/500～1/1000 of the filter capacitor in the linear stabilized power supply.
The output voltage of the switching power supply adapter is adjusted by the duty cycle of the excitation signal, and the change of the input signal voltage can be compensated by frequency modulation or width modulation. In this way, when the power frequency grid voltage changes greatly, it can still ensure a relatively stable output voltage. Therefore, the voltage regulation range of the switching wall mount power adapter is very wide, and the voltage regulation effect is very good.
In addition, there are two methods for changing the duty cycle: pulse width modulation and frequency modulation. Switching regulated power supply not only has the advantages of a wide voltage regulation range, but also has many ways to realize voltage regulation. Designers can flexibly choose various power supply types of switching power supply integrated circuit chip schemes according to the requirements of actual applications.