Why It's Generally Not Advisable to Choose Switching Frequencies Below 50K
We know that generally, the lower the switching frequency, the smaller the switching loss. However, on the other hand, the volume of power components increases with the decrease in switching frequency, which is不利于 miniaturization. During operation, the magnetic core of a switching power supply will vibrate due to the switching of the components. Additionally, the audible frequency range is approximately 20~20,000Hz. To minimize audible noise, we typically select frequencies well away from 20kHz.
Disadvantages of Selecting AC-DC Control ICs with Switching Frequencies Higher Than 135K
Electrical and electronic equipment must test the传导干扰voltage emission at the power terminal when assessing their electromagnetic interference emissions. Although the frequency bands tested by different standards vary, the majority of product tests occur within the range of 150K to 30M. From the lower limit of the test frequency, it can be seen that the switching power supply's operating frequency, the closer it is to 150K, the more difficult it is to handle the conducted interference. Aviation ground power 2, 36V aviation power 1, 400Hz frequency converter power 7, 115/200V power 2, 27V DC power 5, 400Hz power 12, aviation power
What specific applications require specifications for the frequency of power switches?
In certain special occasions, circuit operations are more sensitive to power switch noise, such as in power line carrier, wireless communication, and wireless identification scenarios. Let's discuss the power requirements for power line carrier applications. Currently, power line carriers are primarily used in smart home systems, long-distance meter reading systems, and long-distance streetlight control systems. In China, the power line carrier frequency range is from 9KHz to 500KHz, with a carrier bandwidth of 4KHz. Due to the changes in power line impedance and noise interference from power lines, this greatly hinders the development of power line carriers. To increase the communication distance of power line carriers, the switching frequency of the power supply for the circuit carrier unit must be far from our carrier frequency. Currently, the more commonly used carrier frequencies in China are 115KHz and 132KHz. In such cases, a power supply with a switching frequency of around 60KHz is required.
