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Old 15th June 2015, 07:26 AM   #1
sajti is offline sajti  Hungary
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Default Cooling of bridge rectifier

Hi,

I'm working on a high power amplifier. I will use Vishay PB5008 rectifier, which is PCB mounted version. My question is the cooling.
Most of the high current rectifier is the usual square metal case version, with 6.3mm connectors. And these are mainly fixed on the box of the amplifier.

The PB5008 is designed to attach to heatsink. I found some solution using small attachable aluminium heatsinks. This solutions looks weak to me, as the datasheet define the dissipation, which can be up to 80-100W with high current.

Is there anybody who use this type of rectifier? How to cool it? Is the small heatsink is enough?

Thanks:Sajti
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Old 15th June 2015, 07:50 AM   #2
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"High power amplifier" - how high? I would say that any more than 200W into 4 ohms and you need to be using either low Vf diodes or a case-mounted block to get rid of the heat.
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Old 15th June 2015, 07:52 AM   #3
sajti is offline sajti  Hungary
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Originally Posted by richie00boy View Post
"High power amplifier" - how high? I would say that any more than 200W into 4 ohms and you need to be using either low Vf diodes or a case-mounted block to get rid of the heat.
It will be 2x600W/4ohm.

Sajti
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Old 15th June 2015, 09:14 AM   #4
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That means the rectifier will be dissipating about 12Watts at full load.
Hardly worth worrying about. A 12W/degree heat sink will keep it well below 70C.
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Old 15th June 2015, 09:25 AM   #5
MarianB is offline MarianB  Romania
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I'd say it's more like 20W or so power lost on the rectifier, that is not negligible, at that power the case still can safely reach a high enough temperature without fail ( according to it's datasheet ), still it needs a good heatsink, 20W are not very easy to get rid of. I think it would be better to mount it on the amplifier case and connect it with wires to the board, because fitting an heatsink capable to dissipate 20W on the board may not be easy or even possible.
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Old 15th June 2015, 09:48 AM   #6
sajti is offline sajti  Hungary
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Originally Posted by JonSnell Electronic View Post
That means the rectifier will be dissipating about 12Watts at full load.
Hardly worth worrying about. A 12W/degree heat sink will keep it well below 70C.
Hi,

the datasheet shows about 40W dissipation for 22A rectified current. It needs about 0.8K/W heatsink to dissipate.

Sajti
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Old 15th June 2015, 09:49 AM   #7
sajti is offline sajti  Hungary
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I think it would be better to mount it on the amplifier case and connect it with wires to the board, because fitting an heatsink capable to dissipate 20W on the board may not be easy or even possible.
I want to avoid it, as I choose this rectifier to reduce the internal cabling in the amplifier.

Sajti

Last edited by sajti; 15th June 2015 at 09:52 AM.
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Old 15th June 2015, 09:57 AM   #8
MarianB is offline MarianB  Romania
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For 600W onto 4 Ohms you would have about 11A for both channels, so about 20W of power loss on the rectifier. As for what size of a heatsink is needed and what can be fitted on to the board, they may be 2 different things, it depends on your supply board, it's layout and size. You could design it as so the rectifier bridge gets positioned on the side, so you can actually fix it on the case or on some big enough heatsink.
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Old 15th June 2015, 10:00 AM   #9
sajti is offline sajti  Hungary
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For 600W onto 4 Ohms you would have about 11A for both channels,
That is true, sorry it was my mistake with the calculation.

Sajti
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Old 15th June 2015, 10:02 AM   #10
MarianB is offline MarianB  Romania
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No problem, everyone makes mistakes at some point...

Do you already have the supply board fitted, or it is still on the drawing board?
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