San Marino the switching frequency of the AC-DC switching power supply module?(3)

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 48V input power supply equipment will be reduced to the maximum, which is not conducive to miniaturization. When the switching 48V input 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.

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

HVDC module power supply
High-power switching high-voltage DC power supplies are widely used in large-scale equipment such as electrostatic dust removal, water quality improvement, medical X-ray machines and CT machines. The voltage is as high as 50~159kV, the current reaches more than 0.5A, and the power can reach 100kW.
Since the 1970s, some Japanese companies have begun to use inverter technology to rectify the mains and invert it to an intermediate frequency of about 3kHz, and then boost it. In the 1980s, high-frequency switching power supply technology developed rapidly. Siemens of Germany uses power transistors as the main switching elements to increase the switching frequency of the power supply to above 20kHz. And the dry-type transformer technology is successfully applied to the high-frequency high-voltage power supply, the high-voltage transformer oil tank is cancelled, and the volume of the transformer system is further reduced.

When testing electronic and electrical equipment, the electronic and electrical equipment shall be tested for conducted interference voltage emission at its 48V input 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 48V input power supply is close to 150K, and the more difficult it is to deal with the conducted disturbance.