What are the five main sources of switch-mode powersupply ripple?
1.Channel settings:
Coupling: the choice of channel coupling method. Ripple is an AC signal superimposed on a DC signal. Therefore, if we want to test the ripple signal, we can remove the DC signal and directly measure the superimposed AC signal.
Broadband Limit: Off
Probe: First choose the voltage probe method. Then select the attenuation ratio of the probe. It must be consistent with the attenuation ratio of the actual probe used, so that the numbers read from the oscilloscope are real data. For example, if the voltage probe used is placed in the ×10 position, then the option of the probe here must also be set to the ×10 position.
2. Trigger settings:
Type: Edge
Source: The actual selected channel. For example, if you plan to use CH1 channel for testing, then CH1 should be selected here.
Slope: rising.
Trigger mode: If you are observing the ripple signal in real time, select 'Auto' trigger. The oscilloscope will automatically follow the changes in the actual measured signal and display it. At this time, you can also set the measurement button to display the measured value you need in real time. However, if you want to capture the signal waveform during a certain measurement, you need to set the trigger mode to 'normal' trigger. At this time, you also need to set the trigger level. Generally, when you know the peak value of the signal you are measuring, set the trigger level to 1/3 of the peak value of the measured signal. If not known, the trigger level can be set slightly lower.
Coupling: DC or AC..., AC coupling is generally used.
3. Sampling length (seconds/division):
The setting of the sampling length determines whether the required data can be sampled. When the set sampling length is too large, the high-frequency components in the actual signal will be missed; when the set sampling length is too small, only part of the measured actual signal can be seen, and the real actual signal cannot be obtained. Therefore, during actual measurement, you need to rotate the button back and forth and observe carefully until the displayed waveform is a real and complete waveform.
4. Sampling method:
It can be set according to actual needs. For example, if it is required to measure the P-P value of the ripple, it is best to choose the peak measurement method. The number of sampling can also be set according to actual needs, which is related to the sampling frequency and sampling length.
5. Measurement:
By selecting the peak measurement of the corresponding channel, the oscilloscope can help you display the required data in a timely manner. At the same time, you can also select the frequency, maximum value, root mean square value, etc. of the corresponding channel.
Through reasonable settings and standardized operation of the oscilloscope, the required ripple signal can be obtained. However, during the measurement process, care must be taken to prevent other signals from interfering with the oscilloscope probe itself, lest the measured signal be unrealistic.
