Hot standby (redundant) power supply circuit

- G
- ganeshokade
  
  Contact options for registered users
posted
18 years ago

Wed, Apr 12, 2006 10:22 AM

Dear Experts, I have an embedded application using VMEbus backplane with one CPU and a few I/O boards. The vendor of the VME system provides one 80W

18-24 VDC input power supply which provides 3 outputs: +5V 8A(max), +12V 3A(max), -12V 1A(max). Our end customer requires a dual power supply to work in redundant/hot standby mode. He intends to power each power supply from two different 24VDC sources. So if power fails on one (or if one of the power supply fails), the other one takes over immediately (without getting the CPU's to reset/restart - i.e. hot standby). We need to now merge the outputs of the two power supplies on to another PCB which handles this switching and then power the VME backplane with the output of this board. What is the best way to achive this? Please note that designing a new redundant power supply is not an option for us. We must achieve redundancy by combining the outputs of the two power supplies in some way. Thanks.

Ganesh Okade Sunlux Technologies Ltd.

formatting link

- B
- budgie
  
  Contact options for registered users
Vote on answer
posted
18 years ago

Wed, Apr 12, 2006 2:51 PM

Unless I am missing something in the description, a pair of Schottky diodes for each PSU output rail voltage. You need to increase each voltage by the diode forward rop at load curent. That only leaves the PSU input side, where you would need to ensure that a PSU fault wouldn't take down the 24V source protection.

- G
- ganeshokade
  
  Contact options for registered users
Vote on answer
posted
18 years ago

Thu, Apr 13, 2006 5:35 AM

Dear budgie, Thanks for the response. I do not have an option of increasing the output voltage of the power supply rails itself as the power supplies are from a different vendor and provide for a fixed voltage only. Instead I can use a DC-DC converter at the output of each rail after the newly added diodes (say a 5V-5V DC-DC converter at the +5V rail) using which I can get a regulated output at the rated voltage. What do you think of this scheme? I know that adding an active component AFTER the redundancy point defeats to some extent the redundancy itself but I can't think of any other way of doing this. Thanks.

Ganesh