Working conditions and working characteristics of switching power supply

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Working conditions and working characteristics of switching power supply [Copy link]

　　Working conditions of switching power supply:

　　1. Switch: Power electronic devices work in a switching state rather than a linear state

　　2. High frequency: Power electronic devices operate at high frequencies rather than low frequencies close to the power frequency.

　　3. DC: The switching power supply outputs DC instead of AC

　　Working characteristics of switching power supply:

　　Low power consumption and high efficiency. In the switching power supply circuit, the transistor V works alternately in the on-off and off-on switching states under the stimulation of the excitation signal, with a very fast switching speed, and the frequency is generally around 50kHz. In some technologically advanced countries, it can reach several hundred or nearly 1000kHz. This makes the power consumption of the switching transistor V very small, and the efficiency of the power supply can be greatly improved, and its efficiency can reach 80%.

　　Small size and light weight. From the principle block diagram of the switching power supply, it can be clearly seen that no bulky power frequency transformer is used here. Since the power dissipation on the adjustment tube V is greatly reduced, a large heat sink is omitted. Due to these two reasons, the switching power supply is small in size and light in weight.

　　Wide voltage regulation range. The output voltage of the switching power supply 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 power supply is very wide and the voltage regulation effect is very good. In addition, there are two methods to change the duty cycle: pulse width modulation and frequency modulation. The switching power supply not only has the advantage of a wide voltage regulation range, but also has many ways to achieve voltage regulation. Designers can flexibly select various types of switching power supplies according to the requirements of actual applications.

　　The efficiency of filtering is greatly improved, which greatly reduces the capacity and volume of the filter capacitor. The operating frequency of the switching power supply is currently basically 50kHz, which is 1000 times that of the linear voltage-regulated power supply, which makes the filtering efficiency after rectification almost 1000 times higher; even if half-wave rectification is used and capacitor filtering is added, the efficiency is also increased by 500 times. Under the same ripple output voltage, when using a switching power supply, the capacity of the filter capacitor is only 1/500 to 1/1000 of the filter capacitor in the linear voltage-regulated power supply. The circuit form is flexible and diverse, including self-excitation and external excitation, width modulation and frequency modulation, single-ended and double-ended, etc. Designers can give full play to the strengths of various types of circuits and design switching power supplies that can meet different applications.