Reducing Output low frequency ripple URGENT
Hİ,
I have designed a 24 V 1.54A SMPS with TOP256YN and TL 431 feedback,
My aim is to reduce Voltage ripple below 40mV at full load both 85V and 220 V AC input.
In my design I see a 56mV 400Hz ripple at 220 V AC, and it inceases to 750 mV in 85 V AC.
Do you now the reason for the excessive increase in the output voltage ripple when the input voltage increases?
The frequency of the ripple is 400 HZ. I use TL431 and I studied on the feedback circuit but I could not solved the probelm. I investigate that when I change the capacitor connected between reference and cathode of the TL 431 the ripple increases
In the attachment you can find some output waveforms,
How can we reduce the ripple?
In one topic in the forum I see that "boosted" ripple filter aka "capacitance multiplier" should work but in my design 1,54 A current value causes 2W loss, it is not feasible,
How can I solve this ripple frequency and the magnitude,
is there any design tool with TL431,
Could you help please?
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Putting a capacitor does not cause any help, it doesn't change anything in the waveform,
The most crucial problem is ripple is increases linearly with decreasing input AC voltage, and when the input is 85V AC the ripple is greater than 1V peak to peak,
And if this is not due to feedback what can be the problem I put low ESR 100uF in the input
The line ripple can show up in the output and the feedback loop may not be able to reject all of the line ripple.
To test this theory increase the INPUT capacitance and then see what kind of output ripple you get with decreasing line voltage.
-Wesley
Hİ,
I have designed a +/-15 V 10A Power Supply using Vicor DC-DC converter. Input supply voltage is 115/220 Vac 400Hz. I am confused whether I should have to used a power factor correction at the input side?
I am not getting any PFC method at 400hz input supply and at 400hz frequency the waveform is to distorted.
My aim is to reduce this distortion and make the voltage and current waveform in phase.
Could you help please?
Hi Kemred,
It will be good if you can also send your schematic.
Usually if line frequency is reflected in the output, input bulk capacitor is not enough to deliver desired output power. Approximately, input bulk capacitor should be ATLEAST twice the output power. Example 24Vx 1.54A =36.96W , 36.96W x 2 = 74uF or greater.
If you already added bulk capacitor (above minimium bulk cap requirement) and the ripple is still too high, you have to check your transformer design. You can quickly check this on your circuit thru current probe on switch drain current. Check your current at full load and 85Vac input if it is saturated. Then redesign your transformer.
Please let us know what you got out of this.
Thanks and Best Regards.
This is quite a small value of output ripple and I believe that the feedback loop will not play as large a role as an output capacitor with low ESR and a post filter will in suppressing the ripple.
Try adding another output capacitor with low impedance at 400 Hz, say 47 uF near the output terminals of the power supply. Try an aluminum electrolytic and see if this attenuates the ripple at all.
Also do you have a schematic of the power suppl you can provide me with as this will help me give better suggestions.
-Wesley