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North Korea the switching frequency of the AC-DC switching power supply module?(3)


AC-DC power module

We know that the lower the switching frequency, the smaller the switching loss, but on the other hand, with the reduction of the switching frequency, the volume of the LED advertising screen power supply equipment will be reduced to the maximum, which is not conducive to miniaturization. When the switching LED advertising screen power supply is working, due to the switching of the switching device, the magnetic core will vibrate, and the frequency range that the human ear can hear is about 20~20000Hz. In order to avoid audible noise, we usually choose to stay away from the 20 frequency KHz.

Regulation of output voltage
For module power products with TRIM or ADJ (adjustable) output pins, the output voltage can be adjusted within a certain range through resistors or potentiometers, and the general adjustment range is ±10%.
For the TRIM output pin, connect the center of the potentiometer to TRIM. In all modules with +S and -S pins, the other two ends are connected to +S and -S respectively. When there is no +S, -S, connect the two ends to the output positive and negative poles of the corresponding main circuit (+S to +Vin, -S to -Vin), and then adjust the potentiometer. The resistance value of the potentiometer is generally more appropriate to use 5 ~ 10kΩ.

2. North Korea Disadvantages of choosing an AC-DC control IC with a switching frequency higher than 135K

When testing electronic and electrical equipment, the electronic and electrical equipment shall be tested for conducted interference voltage emission at its LED advertising screen power supply terminal. Although the test frequency bands of different standards are different, the test frequency bands of most products are 150K~30M. It can be seen from the lower limit of the test frequency that the operating frequency of the switching LED advertising screen power supply is close to 150K, and the more difficult it is to deal with the conducted disturbance.