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Author Topic: DC Power Supplies  (Read 744 times)

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Offline ratbotTopic starter

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DC Power Supplies
« on: April 02, 2013, 08:27:11 PM »
Hi Everyone;

I was hoping you all could give me some advice here. My company (I won't mention the name because I don't mean to advertise here) is developing a new DC power supply for robotics/ general electronics. Would you folks mind telling me some of the things you would like to see in a power supply?

Thanks,
Tom

Offline Azraels

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Re: DC Power Supplies
« Reply #1 on: April 02, 2013, 09:21:52 PM »
When I am in the middle of working on a bot, I usually end up needing more than a few different voltages at the same time. Right now I'm using a converted CPU power supply which can give me +12, +5, +3.3, -12, -5. 200W. This has worked well but it would be better to have multiple adjustable outputs from 0 to +24V and would be nice to be able to handle decent amps at all those voltages. Say at least 6 amps? Also the ability to switch off each output independent of the other and then a master switch for them all and the ability to recover from shorts. I have noticed my CPU supply is great at this, just switches itself off if I cross wires somewhere.
If your first post is, "I want to build a super complex robot with object recognition, etc..but I have never done programming or electronics...etc." 
Your doing it wrong. Start Simple and Work Up.

Offline waltr

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Re: DC Power Supplies
« Reply #2 on: April 03, 2013, 09:01:15 PM »
For Robotics a high efficiency DC-DC supply from either a 12V or 24V battery with multiple Voltage outputs and adjustable current limits would be nice.

Offline Billy

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Re: DC Power Supplies
« Reply #3 on: April 04, 2013, 02:07:52 PM »
My company ... is developing a new DC power supply for robotics/ general electronics.

Which is it, robotics or general electronics? It is concerning that you think they are related.

Both those market segments are so fully populated by established companies that enjoy efficient supply chains and have reliable products, I can't imagine why you would even consider getting into that market.

That said, I have noticed a few gaps in current offerings:
  • Usually linear power supplies are open frame which makes post ramp add-ons more complicated than I like. I'd like to see a Linear power supply with a full enclosure, power inlet, and over-current protection built in.
  • Multi-output switching supplies already have connectors for enabling/disabling individual outputs, but I'd like to see one that could be programmed prior to integration to control start-up and shutdown sequence.
  • Some POU modules include blackbox recording for post failure diagnostics but the memory space is limited. I'd like to see the programmable supply above with deep memory to track temp, volt, current, and noise levels going back hours, not seconds or minutes.

Don't get into linear supplies, the number of companies offering linear supplies decreases overtime for a reason. There is no money to be made in that market.
You could probably sell the programmable one but so few people need those features you'd go broke trying to find them.

Offline jwatte

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Re: DC Power Supplies
« Reply #4 on: April 06, 2013, 11:16:19 AM »
I' thinking DC/DC converter, rather than "power supply." The input is batteries, not wall A/C. The battery chemistry is typically LiPo, sometimes LiFePO4, and very unlikely to be NiMH or SLA these days.

So, problems I've solved myself because I couldn't buy ready-made solutions for them:

- Input is 4S LiPo, so between 12.8V and 16.8V. Output is 19V +/- 5%. Output current is 3.5A max.
- Input is 4S LiPo. Output is 12V +/- 5%. Output current is up to 30 A.
- Input is 3S LiPo, so between 12.6V and 9.6V. Output is 12V +/- 5%. Output current is up to 10A.
- Soft/remote on/off for up to 30 A.

Things I like, in general:
- High-efficiency switching converters. 90% is needed; 95% is good.
- High current capacity! Motors draw lots of power, as do high-capacity computers.
- Wide input range -- anything from 2S to 6S LiPo would be ideal. If you can't get sufficient efficiency with buck/boost or CUK or similar topology, step-down-only is acceptable.
- Lightweight!
- Constant current limiting -- rather than hiccupping, and resetting my entire system, letting the voltage drop and emit a warning when current draw goes over the design limit.
- Robust -- should be able to run at stated capacity in an indoors environment for an hour without overheating; this includes running in current-limited mode for an hour.
- Matching to particular power needs. 12V is common in industry, but 19V is also common for laptops/computers and not readily available off the shelf.
- LiPo power awareness -- warn when voltage is at 3.4V per cell, and turn off when voltage is at 3.2V per cell.
- Latching remote off (and, ideally, on.)
- Adjustable output voltage. In some designs, allowing any output voltage between, say, Vbat/2 and Vbat, isn't that hard to design in, and would be a useful feature.
- High-current connectors. Dean-style T-connectors, or XC-60 bullet connectors would be great. Screw terminals are good, too, if they're rated for sufficient current.

Some of these requirements are a bit conflicting -- especially the connectivity and supply range versus weight ones. I'd rather go for an open frame converter with bare solder holes, and add whatever shield/cabling is needed myself, than find myself with a steel-encased, screw-clamped supply that adds half a pound of extra weight.

Offline waltr

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Re: DC Power Supplies
« Reply #5 on: April 06, 2013, 01:39:29 PM »
Jwatt nailed requirements nicely.

Offline felipe80

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Re: DC Power Supplies
« Reply #6 on: May 16, 2013, 01:49:02 PM »
Normally we look for power supply with following features: Output voltage of 0 to 30V which is preferably adjustable. Current output should be at least 5A or more with current controlling option, short circuit protection, and thermal shutdown. It should be light weight and of small size.

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« Last Edit: May 21, 2013, 08:52:45 AM by felipe80 »

 


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