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Lowering 54vdc to 48-50vdc

Kyleag89

Oct 9, 2023
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Hello, just as the title states I have an unregulated linear power supply that is 54vdc 8a and would like to lower it to 48v max 50vdc to power a small amplifier. What's the simplest way to do this? Thanks
 

Kyleag89

Oct 9, 2023
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A quick look and all I'm seeing is low voltage and very low amp selections. Would you happen to know a model #?
 

danadak

Feb 19, 2021
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I dont think you can buy charge pump converters at this W / V / I ratings ? But then
I saw this and learned -


But ratings needed = $ 10+ kinds of cost.....

You can do this with a linear solution which results in a lot of Pdiss/heat/wasted
energy. Or a switching solution. Or discrete, a power transistor, zener, couple of
R's, a low power transistor to implement current limiting.....

1699811917777.png

Note above circuits needs an R from input to base/zener connection to supply
base and zener current.


Regards, Dana.
 
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Kyleag89

Oct 9, 2023
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Thanks Dana, I tried a simple voltage divider using 2 resistors but it didn't work. I would get exactly 50.1v from it but as soon as the amplifier switched on it dropped to 3vdc and the amp didn't power on. I'm guessing that's because the impedance of the amp is much greater than the resistors I used?
 

Kyleag89

Oct 9, 2023
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The amplifier is a tpa3255 chip amp from Wuzhi audio model #zk-3002. It turns on with the 54vdc BT I only tried it briefly because I didn't want to burn anything out. How can I tell if it will be safe to run at 54v? Would I have to look up the data sheets on everything on the board and make sure they can handle 54v?
 

Kyleag89

Oct 9, 2023
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Hey thanks I can use the 24v 15a or even the 20a and still get the output im after. Does anyone have any experience with those buck converters? I've seen them all over eBay and Amazon as well as AliExpress but was hesitant to try one. I plan on putting this amp and PSU inside a custom subwoofer enclosure I'm building. The amp/PSU will be in a separated compartment with holes cut out for air flow. It it gets too hot I can figure out the best way to add a fan in there as well which would be easier if I used 24v vs 48v.
 

Delta Prime

Jul 29, 2020
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Hey thanks I can use the 24v 15a or even the 20a and still get the output im after
That would be a boost converter from a low voltage DC to a high voltage DC
A buck converter is high voltage DC to low voltage DC
And you can even get a buck boost DC to DC converter. Look at the specifications do not try to buy the most inexpensive one try to buy local so you can return it. They are pretty reliable.
Forgive the grammar about speech to text
Also make sure the amperage is above the amperage your device is using it'll run cooler no fan needed I normally double it the amperage
 

danadak

Feb 19, 2021
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Thanks Dana, I tried a simple voltage divider using 2 resistors but it didn't work. I would get exactly 50.1v from it but as soon as the amplifier switched on it dropped to 3vdc and the amp didn't power on. I'm guessing that's because the impedance of the amp is much greater than the resistors I used?
No a divider would not work. As soon as amp turns on and pulls 8A
the divider output would collapse if you had designed it for outout V
of 54 with no load.

Slightly better way is just a series R, it has to handle 54 - 48 V, a drop
of 6 volts, and 8 A thru it, so R = 6 / 8 = .75 ohms. Its power = V x I =
6 x 8 = 48W. But it too suffers from V too high when no load. Thats why'
a regulator of some sort is needed, as previously discussed.


Regards, Dana.
 

Delta Prime

Jul 29, 2020
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Make model of power supply? photos of the specifications? same with your amplifier?
have an unregulated linear power supply that is 54vdc 8a and would like to lower it to 48v max 50vdc to power a small amplifier. What's the simplest way to do this?
@danadak solution I would prefer and use myself.
I plan on putting this amp and PSU inside a custom subwoofer enclosure I'm building
That's your plan you didn't ask for advice so I can't say that plan would being amateur mistake.
The amp/PSU will be in a separated compartment with holes cut out for air flow
If isolated totally separated from the woofer if not you run into trouble.
If it's in included with the woofer then Helmholtz resonance comes into play with those holes you're drilling called "ports"
Speech to text sorry
 

kellys_eye

Jun 25, 2010
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What form is the 'unregulated' power supply you currently have? There's no requirement to run it at its absolute maximum voltage and obtaining a lower voltage PSU (with appropriate current) would likely be simpler and cheaper than creating a regulation circuit for the existing unit.
 

AnalogKid

Jun 10, 2015
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Did I miss the post with the amplifier current rating? Without this, there is no way to reduce the large number of possible methods.

OK - looking at the datasheet, the part can run on 53.5 V. At high current levels, that's less than one diode Vf voltage drop from your 54 V source.

Use two or three diodes in series between the 54 V source and the chip, and multiple parallel decoupling capacitors from the chip to GND. The diodes should be rated for 100 V, and twice the operating current of the amp. Depending on the amp power level, the diodes might need heatsinks.

BUT -

The amp chip requires two power supply voltages, and has a specific power-up sequence requirement. A simple series regulator is not going to be sufficient.

ak
 
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Martaine2005

May 12, 2015
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Hello, just as the title states I have an unregulated linear power supply that is 54vdc 8a and would like to lower it to 48v max 50vdc to power a small amplifier. What's the simplest way to do this? Thanks
What does the voltage drop to when the amp turns on with your unregulated 54V? I would have thought about 50V or below.

Martin
 

Kyleag89

Oct 9, 2023
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What does the voltage drop to when the amp turns on with your unregulated 54V? I would have thought about 50V or below.

Martin
Just sitting idle without music playing it stayed right at 54v when switched on. I didn't try it more than maybe 3 seconds, just long enough to get a meter reading then switched power back off. I too thought that with the loaf of the amplifier the voltage would drop to 50 or so but it didn't. If it were playing music I'm sure it would drop but I was worried about the times it's sitting muted and creeps back to 54v.
 

Kyleag89

Oct 9, 2023
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Did I miss the post with the amplifier current rating? Without this, there is no way to reduce the large number of possible methods.

OK - looking at the datasheet, the part can run on 53.5 V. At high current levels, that's less than one diode Vf voltage drop from your 54 V source.

Use two or three diodes in series between the 54 V source and the chip, and multiple parallel decoupling capacitors from the chip to GND. The diodes should be rated for 100 V, and twice the operating current of the amp. Depending on the amp power level, the diodes might need heatsinks.

BUT -

The amp chip requires two power supply voltages, and has a specific power-up sequence requirement. A simple series regulator is not going to be sufficient.

ak
The chop is in a finished pcb board and accepts a 19v-50v DC input and the company suggests a 48v 10a plus supply for full power. They don't give a maximum amp rating. I'll try and post a link to the model I have.
 
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