MC34063A: 电感L，呲呲噪声

Hello user4057332,

First I hope that I understand your questions correct as I needed to use a translator. I am sorry, but I do not speak Chinese.

1. Is it possible that you have a very low load on the output? The switch waveform seem to be ok for low output load. The converter needs to go to discontinuous conduction mode to keep the output voltage at the target.

2. You changed the inductor, so please share your schematic as I expect this is not the only change compared to the picture above.
What do you mean with "high noise on the screen"? Is the device the power supply for a display?

Hello Brigitte,

1、Application circuit diagram as follow:

2、Iload = 200mA

3、Test waveform is Obtained at the pin1;

4、hear the noise by the  ears ;

please help me.

Hello user40573332,

Thank you for the schematic.

Please check the following 2 points:

1. What happens if you remove the inductor from the board and connect it through wires. Does the acoustic noise change?

2. What happens if you reduce the capacitor C1228 to 1nF

Hello Brigitte

1、If wire instead of the inductor L1204，noise disappears;

2、If the value of the capacitor C1228 is 1nF，the switching frequency of the sc pin is faster，but the noise is still there;

3、If the value of the inductor is 47uH，the noise is  smaller than before。but the noise is still there，the test waveform is as follows:

The noise is still there，please。