How to filter out the AC component noise mixed in the 24V DC?

天天1

How to filter out the AC component noise mixed in the 24V DC? [Copy link]

 

At present, the 24V input of the device is powered by the 220V to 24V power module of Mingwei. After entering, I used TI's LMR23630DCDC chip to convert it to 5V to power the module. The device frequency read by the module jumps a lot. I use the 5V from the USB port of the laptop to power the device. The module on the device can read normally and the data read is very stable. At first I thought it was the problem of the DCDC chip. After changing to 7812 plus 7805, it still doesn't work. At present, I suspect that there is a problem with the 24V power module of Mingwei. The output 24V is also mixed with AC components. Is there any way to remove this?

maychang

First, use an oscilloscope to check the ripple output of the 24V power module to see the ripple amplitude and frequency. The 24V power module should be properly loaded during the test.

tagetage

The poster must be an electronics novice to ask such a question. Generally, there is no problem with Mean Well 24V power supply module. It depends on the on-site interference.

天天1

maychang posted on 2021-3-13 10:08 First use an oscilloscope to look at the ripple output of the 24V power module to see the ripple amplitude and frequency. The 24V power module should be properly loaded during the test.

The ripple of the 24V power supply of Meanwell is 344mV. The ripple of the 24V to 6V output by LMR23630 chip is 92mV. The ripple of the 6V output by 7812 plus 7806 is 56mV.

chunyang

If the power supply is functioning properly, there shouldn't be such a large ripple. Use an oscilloscope to check or replace it with a known power supply of the same type for comparison. Also, pay attention to the correct use of this type of power supply. If there is a Y capacitor connected to the power ground, the power ground must be reliably connected to the ground, otherwise it will seriously affect the output.

maychang

天天1 posted on 2021-3-13 14:10 maychang posted on 2021-3-13 10:08 First use an oscilloscope to look at the ripple output of the 24V power module to see the ripple amplitude and frequency. During the test, 24V ...

Like relatively strong common mode interference.

In addition to what Chunyang said on the 5th floor, "If there is a Y capacitor connected to the power ground, the power ground must be reliably connected to the ground", if you want to filter the 24V power output, it is recommended to use common-mode inductors to form common-mode filtering, and then perform differential-mode filtering.

maychang

天天1 posted on 2021-3-13 14:10 maychang posted on 2021-3-13 10:08 First use an oscilloscope to look at the ripple output of the 24V power module to see the ripple amplitude and frequency. During the test, 24V ...

Since I haven't seen the real thing, I don't know the specific wiring of your wrench, so it's hard to analyze. The ground wire layout on your circuit board may not be good enough.

tagetage

Mean Well power supply does not have such a large ripple. The two masters above have already given you suggestions. I personally think that the main issues to consider are grounding and interference. If the power of the equipment is not large, you can also consider using a 220V/220V isolation transformer.

天天1

tagetage posted on 2021-3-14 11:56 Mean Well power supply does not have such a large ripple. The two masters above have already given you suggestions. I personally think that the main considerations are grounding and interference.

The power is very low. I think it should be a problem with my schematic design or drawing board.

annysky2012

Do you actually use a filter circuit in the board you use? Mean Well's power supply is a switching power supply, so it is normal to have a little ripple. So you should fully consider your own circuit.

天天1

chunyang posted on 2021-3-13 16:46 If the power supply function is intact, there should not be such a large ripple. Use an oscilloscope to check or replace it with a known good power supply of the same type for comparison. Also pay attention to this type of power supply...

I went to the site today to confirm that this is probably the problem.

btty038

Learn about common mode inductors

sxd1234

Try using differential mode