Switching power adapters do not use bulky power frequency transformers. Since the dissipated power 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 switching MOS tube is excited by the excitation signal, it works alternately in the on-off and off-on switching states, the conversion speed is very fast, the frequency is generally above 50kHz, in some advanced switches. In the power supply line, several hundred or nearly megahertz can be achieved. 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 adapter is basically above 50kHz, which is more than 1,000 times that of the linear regulated power adapter, which makes the filtering efficiency after rectification almost 1,000 times higher. Efficiency is also increased by a factor of 500.
Under the same ripple output voltage, when the switching power supply is used, the capacity of the filter capacitor is only 1/500 ~ 1/1000 of the filter capacitor in the linear regulated power supply.
The output voltage of the switching power adapter is regulated 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 power adapter is very wide, and the voltage regulation effect is very good.
In addition, there are two methods of changing the duty ratio: a pulse width modulation type and a frequency modulation type. Switching regulated power supply not only has the advantages of a wide range of voltage regulation, but also has many methods to achieve voltage regulation. Designers can flexibly select various types of switching power supply integrated circuit chip solutions according to the requirements of practical applications.
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