| Electronics > Repair |
| strange low frequency switching noice from diy sg3525 smps |
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| Herschel:
So I made a powersupply for an audio amp using sg3525ic and an ir2110 mosfetdriver The smps works fine, but the problem is, when i connect an amplifier+speaker to the smps, i could hear strange low frequency switching noice from the speaker output: here is a video showing the issue: https://youtube.com/shorts/UIPuuqmjZPY?feature=share so to check weather its the noice from the amplifier, I disconnected the amplifier and connected an led to the transformer output(before the full bridge rectifier) and the LED isn't constantly on, its blinking and here is a video showing that: https://youtube.com/shorts/7hwPGjBLxPw?feature=share this thing only happens when i connect the output to the feedback circuit |
| Circlotron:
Despite what looks like a common mode choke after the diode bridge, you should really have a filter choke between the bridge and the filter capacitors. One choke on each rail. Without a choke, the DC output voltage of the inverter is mostly dependent on the peak voltage of the inverter output, and the PWM for voltage regulation can't work properly. When you connect the feedback the loop is unstable because a large change in pulse width does not produce a corresponding change in DC output voltage. |
| Herschel:
--- Quote from: Circlotron on September 17, 2024, 06:52:45 am ---Despite what looks like a common mode choke after the diode bridge, you should really have a filter choke between the bridge and the filter capacitors. One choke on each rail. Without a choke, the DC output voltage of the inverter is mostly dependent on the peak voltage of the inverter output, and the PWM for voltage regulation can't work properly. When you connect the feedback the loop is unstable because a large change in pulse width does not produce a corresponding change in DC output voltage. --- End quote --- Actually i didn't used a common mode choke, I used one choke for each rail. Also the chokes I'm using have iron powder core. Are iron powder cores suitable for this purpose? |
| Herschel:
--- Quote from: Circlotron on September 17, 2024, 06:52:45 am ---the DC output voltage of the inverter is mostly dependent on the peak voltage of the inverter output, and the PWM for voltage regulation can't work properly. When you connect the feedback the loop is unstable because a large change in pulse width does not produce a corresponding change in DC output voltage. --- End quote --- I used one choke for each rail, chokes with iron powder core... can this be prevented by adding a capacitor before ther chokes or, is iron powder cores suitable for this purpose? |
| Circlotron:
Powdered iron is fine. Looks like you have used 21 material. What is the switching frequency? Definitely no capacitor before the chokes. |
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