Pump up the charge: Getting -5V from a 5V power supply

Re:Pump up the charge: Getting -5V from a 5V power supply by peterburkimsher on Sunday October 10, 2021 @06:52PM (#28822699)

Thank you! The Bose Sounddock for iPod that I found in a recycling bin uses a dual +/- 18V power supply, and I was wondering how to power it from batteries. That link taught me that the extra voltage headroom may not be required, it might run on 12V, and it would in theory be possible to build a +/- dual voltage circuit. Now I just have to decide whether it's worth building that and learning more about power electronics, or buying a new speaker and having a somewhat safer device.

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Re:Pump up the charge: Getting -5V from a 5V power supply by analog31 on Sunday October 10, 2021 @07:05PM (#28822764)

Here's another take on a similar theme. I've built a few of these:

https://www.maximintegrated.com/en/design/technical-document...

In my case, I was looking for a way to get decent analog power from a USB port for a non audio related project, but a LiPo battery would present a similar challenge.

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Re:Pump up the charge: Getting -5V from a 5V power supply by kevin_thibedeau on Sunday October 10, 2021 @09:25PM (#28823623)

Charge pump ICs can't supply high currents on their own and their output is unregulated. It's unlikely you would get acceptable results from the speaker if you followed this blog for guidance.

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Re:Pump up the charge: Getting -5V from a 5V power supply by nitrogen on Monday October 11, 2021 @01:26PM (#28830706)

Would four 9V batteries in series with ground drawn from the middle supply enough current?

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Re:Pump up the charge: Getting -5V from a 5V power supply by tuatoru on Monday October 11, 2021 @05:37PM (#28833402)

Enough current for what?

Power = voltage x current = (voltage) squared / resistance.

The little rectangular 9V batteries have very high internal resistance as well as low energy capacity. The nominal 9V can easily fall below 6V with heavy loads.

If you only need 1 watt (times 2 for stereo), loud enough for average rooms with speakers of reasonable efficiency, then one 9V battery would be enough. It wouldn't last long though.

With two in series you can go louder, provided the amplifier is rated for the higher voltage.

Remember to put fuses in your power leads (except the ground return). Good quality batteries can get hot trying to power a short circuit.

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