Michael A. Terrell wrote on Jan 4 2007 in the s.e.d. thread, "job thing, maybe"
We had already taken a quality hit from a high failure rate on Vicor
> dual output supplies built with their VI-260-IY modules for dual 5 VDC
> 50 W outputs and VI-261-IY modules for dual 12 VDC 50 W outputs.
> $20,000 radios still in warranty, and just out of warranty were having
> lots of problems, all wich were traced back to their crappy modules
> and whole power supplies.
>
Vicor's rev 1.7 datasheet says, "Vicor's broad series of zero- current-switching component-level DC-DC converters, with over 12 million units shipped..."
Vicor generally has a good reputation. So I have to ask, I notice your modules were 300V-input (i.e. offline), 5V and 12V output, with their lowest power rating, 50 watts. The other modules in the VI-200 series are rated at 75, 100, 150 and 200 watts. Is it possible the problem wasn't actually the modules, but something else, like improper DC-input conditioning, or lack of proper heat-sink cooling? Or perhaps your power circuit allowed the 12V supply to pull the 5V module output above +5 under certain circumstances, such as at power-up or power-down. Just asking.
They were part of Vicor built power supplies. The ac line was doubled to get the 300 volts inside the supply. The case was cast aluminum, with fins. Vicor said our product's case had plenty of air flow, yet they couldn't tell us why they were failing. I may still have a complete, scrap supply for the model numbers, but all I could find the other day was a bad module. Either one of the two module's output would die, or the regulation would go to crap and have a lot of noise on the output. The only load that came close to 50 watts was the +5 volts, and I think it was only 7 amps or 35 watts. We tried for six months to find a solution before we removed them from the qualified vendor list. They may have been cause by the defective electrolytic problem, but the modules are cast in epoxy so we couldn't take a look, in house. We had too many angry customers to wait any longer. We paid for a bunch of new supplies that were out of warranty to keep them happy, but the problem kept growing.
The replacement power supplies had a built in fan, and were through hole PCB construction. We tested over 20 different OEMs before we decided on the new supplier. This was some time late in 2000, or early
2001. The replacement supply also ended up being a good choice for a newer DSP based receiver design. I might have a datasheet on the replacement power supply in my files. Changing the power supply vendor meant a change in the bare aluminum chassis, a new wiring harness, and designing a field conversion kit for high security locations that did some self service in house. I don't know what conclusion Vicor finally came to as the cause of the failures, because the company didn't want to switch back to the old design and take a chance.
It was like the problems we had with a well known SMD trimpot manufacturer. The failure rate was over 2% because their o-rings on the shafts were defective. They insisted that we were damaging the pots, even though we hadn't made any changes to our process in over five years.
After we switched to Bourns, they finally admitted the O-rings were undersized, and didn't have enough lubricant applied during manufacturing. As soon as we switched to Bourns the failure rate dropped to almost zero in a six month period. Two pots were damaged by a QC inspector on a finished board, but they were still classed as defective parts.
--
Service to my country? Been there, Done that, and I\'ve got my DD214 to
prove it.
Member of DAV #85.
Michael A. Terrell
Central Florida
Vicor spent a lot of money on advertising and litigation, but I've yet to hear anything positive about their products from end-users - and have done good business revisioning them out of other people's products.
There's reason why they shouldn't be able to come up with superior products, given the decades they've had to get it right.
I'd stay clear of anything producing output voltages above 5V that they make, no matter what power level, and wouldn't use any module that wasn't second-sourced. It's not worth the risk, and it's not necessary.
Do you know how many names they have had over the decades, or the different fields they dabbled in? My first experience with their CATV line equipment back in the '70s was no better. It seems like every time they screwed up bad enough, they changed their name, and their product lines.
--
Service to my country? Been there, Done that, and I\'ve got my DD214 to
prove it.
Member of DAV #85.
Michael A. Terrell
Central Florida
Since 1981, Vicor has engaged in the development, manufacture and sale of power conversion components and systems.
Vicor also manufactures and sells complete configurable power systems, accessory products and custom power solutions. It also licenses certain rights to its technology in return for ongoing royalties. The principal markets for Vicor's power converters and systems are large original equipment manufacturers (OEMs) and smaller, lower volume users, which are broadly distributed across several major market areas.
I gutted a couple of their modules once. They had some beautiful magnetics with integrated shields (formed from thic Cu). They did things like run the switches from the +ve rather than -Ve DC bus, so the drains dont bounce up and down. Some very nice tricks to reduce EMI.
Of course the converters themselves sucked; a close read of the datasheet shows they achieved high power levels by requiring ludicrous heatsinks. We had nothing but trouble with the ones we used (hence I got to gut some).
I imagine the required heatsinks may seem ludicrous when compared to the module's size, but not so much when compared to the maximum delivered power level. Vicor "eats their own food" by using these modules in their six-module (did I get that right?) power system, but this uses a fan, doesn't it? I've got a few of them, I'll take a look.
what vicor have (or at least had, I havent looked this century) was a not particularly great topology, coupled with some fabulous production engineering. Their efficiencies werent that great (cf eg syncor), but they compensated for it with very good thermal design internally - the heat spreaders on the bigger modules are huge, comparable with BIG igbts. Likewise they dealt with EMC by pulling clever tricks like floating the switch, making really nice ES shields in their magnetics, and of course the DCB-style construction. basically well done brute force engineering (you dont develop modules like that without spending a LOT of money)
other manufacturers achieve high power density by making their devices more efficient. If you care about the resultant volume of the final equipment, this approach is best.
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