MC33063A-Q1: 在使用MC33063作BOOST时，轻载情况下电感会啸叫

您好，我在使用MC33063AQ1作为boost升压电路时，在轻载（12V输入，30V输出时<70mA，14V输出时<200mA）的情况下电感会啸叫，测量其电感SW引脚的波形发现其落在人耳可听的频率范围内（20-20khz），但是随着负载电流的升高，SW引脚的频率会随之升高，30V输出时在超过70mA后就不会再啸叫，基本可以确定芯片应该是使用的PFM模式进行调制的。采用的解决包括：逐步增大时间电容CT至2nF、逐步增加输出电容至320uF、更换一体成型电感器，有所改善但是无法解决此问题。因有负载电流会变化的需求，请问在使用此款芯片时有没有办法解决在轻载情况下开关频率落在人耳可听见的范围之内的问题，感谢。

Hi, when I use MC33063AQ1 as a  boost circuit, the inductor will howl under light load (12V input,&lt;70mA at 30V output,&lt;200mA at 14V output). When measuring the waveform of the  SW pin, it was found that it falls within the audible frequency range (20-20khz). And as the load current increases, the frequency of the SW pin will increase accordingly, and the inductor will no longer howl after exceeding 70mA at 30V output, It can be basically considered that the chip should be modulated by using the PFM mode. The solutions adopted include gradually increasing the time capacitance CT to 2nF, gradually increasing the output capacitance to 320uF, and replacing the inductor with the integrated inductor, which has improved but cannot solve this problem. Due to the demand for variable load current, may I ask if there is a solution to the problem of switching frequency falling within the audible range of the human ear under light load when using this chip? Thank you.

如下为原理图和PCB：

The following pictures are schematic diagram and PCB: