Bhutan the switching frequency of the AC-DC switching power supply module?(2)

Bhutan Choosing the switching frequency of the LED advertising screen power supply does not mean choosing the switching frequency of the LED advertising screen power supply with a good switching frequency, but the choice is suitable for your own use. Most of the current market is like this. The frequency of the AC-DC switching LED advertising screen power supply module is between 50K and 135K, and this frequency range can meet most applications. Let's discuss it. Some of the problems that AC-DC encounters when choosing switching frequency:

Remote control switch circuit
The remote control switch operation of the module power supply is carried out through the REM terminal. There are two general control methods:
(1) REM is connected to -VIN (reference ground), the remote control is turned off, and VREF<0.4V is required. REM is suspended or connected to +VIN, the module works, and VREM>1V is required.
(2) REM is connected to VIN, the remote control is turned off, and VREM<0.4V is required. REM is connected to +VIN, the module works, VREM>1V is required. REM is suspended, and the remote control is turned off, that is, the so-called "suspended shutdown" (-R).
If the control is to be isolated from the input, an optocoupler can be used to pass the control signal

1. Why generally do not choose a switching frequency lower than 50K

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.