Several important parts of switching power supply

　　Switching power supplies are favored by people for their obvious advantages such as low power consumption, high efficiency, and small size, and are widely used in computer equipment, electronic instruments, communication equipment and household appliances. The following will introduce the main technical indicators of the switching power supply.

　　1. Input voltage range: When the input voltage of the switching power supply changes, the input voltage change range that keeps the output characteristics unchanged. The wider the range, the stronger the ability of the power supply to adapt to changes in the external city power, and the wider the working range of the switching power supply. It is related to the error amplifier inside the switching power supply, the gain of the sampling feedback adjustment circuit and the adjustment range of the duty cycle. At present, the input voltage range of the switching power supply has been 90V-270V, which can save the 110V/220V switch on many electrical appliances.

　　2. Voltage regulation rate: The voltage regulation rate is also called voltage stability, which is the relative change of the output voltage when the output current does not change (that is, the load does not change) and the input AC working voltage changes. This technical index is used to verify whether the stability of the output voltage of the switching power supply meets the required specifications under the worst power supply voltage environment.

　　3. Current regulation rate: The current regulation rate is also called the load regulation rate. It is the relative change of the output voltage when the input AC voltage is at the rated value (such as 220VAC) and the output current changes from the minimum value of 0 to the maximum value. This indicator is used to verify whether the output voltage stability of the switching power adapter meets the required specifications under the worst load environment.

　　4. Output internal resistance: The ratio of the change in output voltage to the change in output current. The smaller the ratio, the smaller the change of the output voltage of the power supply with the size of the load, and the better the voltage regulation performance.

　　5. Conversion efficiency: the ratio of the output power of the power supply to the input power. The higher the ratio, the higher the efficiency of the change, the smaller the size of the switching power supply, the higher the reliability. The efficiency of the current switching power supply can reach more than 90%.

　　6. Ripple of the output voltage: Since the voltage stabilization process of the switching power supply is a process of continuous sampling and feedback adjustment, a superimposed and fluctuating ripple voltage will appear on the output DC voltage, that is, the output ripple voltage. The smaller the value, the better the output characteristics. There are two ways to express ripple: one is the effective value of the output ripple voltage; the other is the peak-to-peak value of the output ripple voltage. Generally, the specifications of the switching power supply are required to be less than 1% of the output DC voltage, and its bandwidth is 20Hz-20MHz or other higher frequencies, such as 100MHz. In the harsh environment of the switching power supply, the output instantaneous voltage after the output DC voltage plus the noise ripple should not exceed the output high and low voltage boundary (Min value and Max value), otherwise it may cause the power supply voltage to exceed or fall below the logic The circuit (such as TTL circuit) malfunctions due to the working voltage, which further causes the phenomenon of crash.

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