How to measure discontinuous mode and continuous waveform in switching power supply?

Knight97538

How to measure discontinuous mode and continuous waveform in switching power supply? [Copy link]

 

May I ask, has anyone tested the measurement of discontinuous mode and continuous waveform?

The inductor works in continuous mode and discontinuous mode. Although I know the theory, I have never had the opportunity to measure it. How do you measure the waveform? ? !

maychang

[Excuse me, has anyone tested the measurement of discontinuous mode and continuous waveform? ]

Most of the people in this forum who are engaged in switching power supplies have measured the voltage waveforms at various points in the switching power supply circuit, but fewer of them have measured the current waveform.

maychang

[How do you measure the waveform? ? ! ]

Do you want to measure the voltage waveform or the current waveform? The voltage waveform is easier to measure, while the current waveform is more difficult to measure.

As for what equipment to use, it is of course an oscilloscope.

乱世煮酒论天下

maychang posted on 2024-6-13 13:54 [How do you measure the waveform? ? ! ] Do you want to measure the voltage waveform or the current waveform? The voltage waveform is easier to measure, and the current waveform...

The oscilloscope uses a current loop to measure current. Is the accuracy sufficient for such a small current?

maychang

Talking about the world in a chaotic world published on 2024-6-13 16:42 The oscilloscope uses a current loop to measure current. Is it accurate enough for such a small current?

[The oscilloscope uses a current loop to measure current. Is the accuracy for such a small current? 】

The oscilloscope you are using should have this marked on its manual.

不亦心

There are many ways to analyze current from the voltage waveform, measure voltage with a series resistor, use a current probe, or make a current transformer with a magnetic ring.

tagetage

The OP asked how to measure the continuous mode and discontinuous mode. I want to ask why the OP wants to measure this? ? ? ?

Knight97538

Bu Yixin published on 2024-6-13 17:08 There are many ways to analyze current from the voltage waveform, measure voltage with a series resistor, use a current probe, or make a current transformer with a magnetic ring.

Thank you teacher for your reply

When measuring with an oscilloscope, how can we prevent the interference of switching tube and other signals on the oscilloscope probe?

Knight97538

tagetage posted on 2024-6-13 21:30 The OP asked how to measure the continuous mode and discontinuous mode. I would like to ask why the OP wants to measure this? ? ? ?

I just want to know how to analyze the performance of the power supply under different working conditions, such as ripple, efficiency, etc.

I would like to know the performance of a switching power supply under full load and partial load. Is there any trick?

Knight97538

maychang posted on 2024-6-13 16:46 [The oscilloscope uses a current loop to measure current. Is the accuracy for such a small current? ] The manual of the oscilloscope you are using should have a mark...

To ensure accurate measurement results, what are the specific requirements for oscilloscopes and probes? Is it necessary to use high-frequency probes?

Knight97538

Talking about the world in a chaotic world published on 2024-6-13 16:42 The oscilloscope uses a current loop to measure current. Is it accurate enough for such a small current?

How to use current loop to measure current? How to use current loop in oscilloscope?

maychang

Knight97538 posted on 2024-6-14 13:45 To ensure accurate measurement results, what are the specific requirements for oscilloscopes and probes? Is it necessary to use high-frequency probes?

[To ensure accurate measurement results, what are the specific requirements for oscilloscopes and probes? Is it necessary to use high-frequency probes? ]

Oscilloscopes have accuracy indicators, and so do probes. The measurement results will certainly not exceed the accuracy of the oscilloscope and probe.

As for whether a high-frequency probe is needed, it should be said that the operating frequency of the switching power supply is not high, and usually an oscilloscope bandwidth of 20MHz is sufficient.

tagetage

Knight97538 posted on 2024-6-14 13:42 I just want to know how to analyze the performance of the power supply under different working conditions, such as ripple, efficiency, etc. I want to know the performance of the switching power supply under full load and partial load...

What you need to know has little to do with the work mode. Your question is too broad. Just search the Internet.

乱世煮酒论天下

Knight97538 posted on 2024-6-14 13:48 Use current loop to measure current? How to use current loop in oscilloscope?

It's the same as the probe, but I don't know what kind of probe should be used to measure the current in such a small size and space as this switching power supply, as well as such a small and relatively high frequency bandwidth?

Knight97538

tagetage posted on 2024-6-14 16:43 What you want to know has little to do with the work mode. The question you asked is too broad, just search on the Internet,

The output voltage in discontinuous mode is greatly affected by the load, and the duty cycle must be adjusted for voltage regulation.

Do you mean that measuring this waveform is meaningless? The working mode has nothing to do with efficiency?

tagetage

Knight97538 posted on 2024-6-14 17:02 The output voltage in discontinuous mode is greatly affected by the load, and the duty cycle needs to be adjusted for voltage regulation. Do you mean that measuring this waveform is meaningless? The working mode and efficiency are not...

Measuring this waveform is meaningless for your needs. What you can do is to choose a good chip, draw a good circuit, choose important components such as inductors, and draw a good PCB. The working efficiency and other things are in the chip data sheet. The working mode is that the chip automatically adjusts. You use an oscilloscope to measure the working mode. I ask you, what can you do? ? ? ? ?

不亦心

Knight97538 posted on 2024-6-14 17:02 The output voltage in discontinuous mode is greatly affected by the load, and the duty cycle needs to be adjusted for voltage regulation. Do you mean that measuring this waveform is meaningless? The working mode and efficiency are not...

You are doing the right thing, no doubt. To make a good power supply, you must be familiar with the voltage and current of each node, otherwise there is no way to talk about the optimized design. It is easy to make a power supply with output, but it is difficult to make a good power supply.