85-265VAC and 24VDC combined power supply

Christian Walter · 2007-08-10T09:25:41+00:00

Hello,I am currently working on a device where I am evaluating options for the design of the power supply. On the secondary side we need two power supply output with 5V/4A and 13,8V/2A (uncommon voltage). The input voltages are the standard 85V-265VAC range and 24VDC.We want every unit to be capable of being used in both environments. Therefore the power supply should allow both inputs. Because of 24VDC input I will need two DC/DC converters at the output side. One from 24VDC/5VDC and one from 24VDC/13,8VDC. These converters are easy to design and can have a high efficiency (>90-95%).What I am unsure about is how to handle the transformation from the primary 85V-265V to the intermediate internal voltage of 24V. A regulated switched mode power supply is certainly a overkill because I don't need the 24V to be regulated. So I thought I could use a standard 50/60Hz input stage with a simple full bridge rectifier and a good transformer. Size is not the problem but power efficiency and costs are. Or are there any better options? I searched for quite some time in goggle for possible AC input stages but did not come up with a good solution.Kind regards, Christian Walter-- \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ \\\\\\ \\email: \ Friends don't let friends drink and su(1)web: \ -- Kevin Harris

Aug 10, 2007 21 Replies

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Spehro Pefhany 18 years ago

You particularly want French products? Try SSAC, owned (like a lot of such companies) by the mighty ABB.

Best regards, Spehro Pefhany

"it\'s the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com

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Christian Walter 18 years ago

Hello,

I decided to go with this approach. Unfortunately if used as a backup supply the 24V input will have a slightly higher voltage assuming fully charged batteries (Maybe 25V-26V). If I would simply use two schottky diodes the power would be drawn from the backup source. I just thought about using the MID400 device from fairchild (AC Line Monitor -

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to switch off a MOSFET on the 24V rail if the primary power is available. The switch from 110V/230V to 24V should not be a problem because the SMPS will still have enough stored energy to supply the secondary DC/DC converters. I have not yet an idea on how to switch back because I don't want to be dependent on the power up time of the SMPS.

Kind regards, Christian Walter

\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ \\\\\\\\\\\\ \\\\ email: wolti@sil.at \\ Friends don\'t let friends drink and su(1) web: www.freemodbus.org \\ -- Kevin Harris

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