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Important Components of the Power Adapter

1. The input voltage range of the power adapter


When the input voltage of the switching power supply changes, the input voltage variation range that keeps the output characteristics unchanged is maintained. The wider this range, the stronger the ability of the power supply to adapt to changes in the external mains 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 variation range of the switching power supply has reached 90V-270V, which can save the 110V/220V switch on many electrical appliances.


2. The voltage regulation rate of the power adapter


Voltage regulation, also known as voltage stability, is the relative change in output voltage when the output current remains unchanged (the load does not change) and the input AC operating voltage changes.


This technical indicator 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. The current regulation rate of the power adapter


The current regulation rate, also known as the load regulation rate, is the relative change of the output voltage when the input AC voltage is rated (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. The output resistance of the power adapter


There is the ratio of the change in output voltage to the change in output current. The smaller the ratio is, 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 of the power adapter


There is the ratio of output power to input power of a power supply. The higher the ratio, the higher the change efficiency, the smaller the size of the switching power supply and the higher the reliability. At present, the efficiency of switching power supply can reach more than 90%.


6. Ripple voltage of the power adapter


Since the voltage regulation process of the switching power supply is a process of continuous sampling and feedback adjustment, there will be a superimposed and fluctuating ripple voltage 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 the ripple: one is the effective value of the output ripple voltage, the other is the peak value of the output ripple voltage.


The specifications of the general 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 harsh environments, the output DC voltage of the switching power supply of the China power adapter plus the noise ripple should not exceed the output high and low voltage limits (Min value and Max value). Otherwise, it may cause the power supply voltage to exceed or be lower than the working voltage of the logic circuit (such as TTL circuit) and malfunction, which will further cause a crash.

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