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Powerful SMPS for tube ampifier
Powerful SMPS for tube ampifier
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Old 14th September 2019, 07:14 PM   #61
CaterpilarSK is offline CaterpilarSK  Slovakia
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Quote:
Originally Posted by trobbins View Post
I thought it worth making that post - even though this is a diy forum, I would professionally be concerned about a smps designer that gave a project status report with


A nice aspect of smps design is that it covers such a wide range of technical aspects - of which any one can trip up a prototype until adequately appreciated and worked through. PCB design is just one aspect where noise level can increase with an output variable and then reach some limit on a feedback or local supply rail such that the controller gets confused.
which is exactly what happened. I didnt think trough the component values correctly otherwise the PCB is even shielded (using one copper layer as solid groundplain shield) running short high current lines, track lenghts kept equal.

The only thing I didnt do and I now regret not doing is givving the 494 a discrete regulator so the garbage from switching would be filtered with a fast LDO, further ensuring stability.

I found a much better IC for the job. LM5021. Im determinde to use that and this time go mains power with the coilcraft HA4060.
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Old 14th September 2019, 11:23 PM   #62
Shawnstium is offline Shawnstium  United States
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If you’re still planing a 500Vdc output be careful not to exceed the voltage at the HA4060 transformer, which is rated for 500Vdc.
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Old 15th September 2019, 09:10 AM   #63
MorbidFractal is offline MorbidFractal
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The HA4060 is rated 2A peak @ 120V. That's consistent with a 4.5uS on time which agrees with the measurement frequency of 100KHz. 50% duty cycle for a single switch convertor. At 230VAC/311DC your duty cycle will be 17%. You are strictly limited to that 2A peak current. Your convertor will operate with discontinuous current, good and bad, and your strict power limit will be 50W. If you can't do these sort of sums and prefer to thrash about in the dark then you are on a road to nowhere.
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Old 15th September 2019, 04:35 PM   #64
CaterpilarSK is offline CaterpilarSK  Slovakia
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Originally Posted by Shawnstium View Post
If you’re still planing a 500Vdc output be careful not to exceed the voltage at the HA4060 transformer, which is rated for 500Vdc.
I am aware of the 500V max output. I have yet to use it for audio on that voltage. The Mullard 20W amplifier runs of 420V I only tested if its capable of 500V at 50W
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Old 16th September 2019, 07:00 PM   #65
CaterpilarSK is offline CaterpilarSK  Slovakia
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So here is a question. For those of you who make mains powered SMPS, how do I calculate the mains side capacitor bank capacitance.

Peak current 2.5A
Voltage on the filter caps = 120VDC-380VDC
Switching frequency = 100kHz

I have absolutely no clue how to get this value. I will also build a proper mains input (noise filter and all that)
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Old 16th September 2019, 08:15 PM   #66
Shawnstium is offline Shawnstium  United States
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The amount you will need depends on what you want for the ripple (both voltage and RMS current) on DC link to be and how much reserve energy is needed for regulation, transients and holdup time. A guess a good rule of thumb would be a minimum of 1.5uF/W, if you are using a full wave bridge rectifier and single supply.

You will most likely want to construct a soft start circuit for the charging of those caps and make precautions for AC surges.
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Last edited by Shawnstium; 16th September 2019 at 08:18 PM.
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Old 16th September 2019, 09:42 PM   #67
CaterpilarSK is offline CaterpilarSK  Slovakia
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Quote:
Originally Posted by Shawnstium View Post
The amount you will need depends on what you want for the ripple (both voltage and RMS current) on DC link to be and how much reserve energy is needed for regulation, transients and holdup time. A guess a good rule of thumb would be a minimum of 1.5uF/W, if you are using a full wave bridge rectifier and single supply.

You will most likely want to construct a soft start circuit for the charging of those caps and make precautions for AC surges.
Thank you very much sir.
With more than enough reserve ill go with 150uF roughly. Using two 56uF 450V capacitors and two 10uF 450V low ESR cap. That should take care of it.

AC surge will be taken care of in the AC input filter.. PTC should be sufficient. For the secondary side the SMPS chip has a soft start pin and I will surely use it.
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Old 16th September 2019, 11:55 PM   #68
Shawnstium is offline Shawnstium  United States
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I haven’t used a PTC thermostat, only the negative verity. Is the PTC used in place of current sense resistor?
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Old 17th September 2019, 05:32 AM   #69
CaterpilarSK is offline CaterpilarSK  Slovakia
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Quote:
Originally Posted by Shawnstium View Post
I haven’t used a PTC thermostat, only the negative verity. Is the PTC used in place of current sense resistor?
ah crap sorry I'm dumb. I wanted to say NTC and then for some reason I did that. Sorry I meant to say NTC .
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