Here is an elegant (insane?) way of converting 220V to 110V - diyAudio
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Old 6th December 2010, 03:45 PM   #1
Elvee is offline Elvee  Belgium
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Default Here is an elegant (insane?) way of converting 220V to 110V

Here is a possible answer (the mad scientist version) to this problem:

What is the elegant way to convert 220? to 110V? - diyAudio

This circuit is basically a phase control system allowing the power to flow for 30 on either side of the zero crossing of the 230V input waveform (sin 30 = 0.5).
It uses a MOS rather than an SCR or triac to improve flexibility and to conduct twice per half-cycle.
Doing so has a number of advantages: it reduces the stress on the circuit elements and almost doubles the ripple frequency seen at the output of the transformer.
The conduction is a little larger than 30, because the V.s product with this waveform is smaller and allows it, and because the leakage inductance of the transformer will cause a larger drop wrt. to the peak voltage than a regular sinusoid.
One screenshot shows the result with a simulated transformer, and the other on a pure resistive load.
The IC can be a LM393. The ground connection is for simulation purposes only.
Note that the circuit also acts as a soft- start.

Disclaimer:

If you choose to build this circuit, it is your sole responsibilty, etc etc
Attached Images
File Type: gif 220V110V1.GIF (65.6 KB, 782 views)
File Type: gif 220V110V2.GIF (65.9 KB, 764 views)
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Old 6th December 2010, 05:55 PM   #2
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I suspect phase control will not produce a very happy audio system. Think of having light dimmers nearby, and the trouble they create. Now feed your system off a light dimmer, and get ready for some real buzz.
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Old 6th December 2010, 06:22 PM   #3
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Still think the easiest way is to stroll down to your local building supplies merchant and buy one of those fetching yellow step-down transformers they use for 110V power tools.

On ebay they frequently pop up for next to nothing s/h and they come in all conceivable sizes..
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Old 6th December 2010, 09:04 PM   #4
Elvee is offline Elvee  Belgium
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One more thing:

Thanks to the frequency-doubling effect, the peak voltage (and consequently the useful output power from the transformer) can be susbtantially increased:
The conduction angle can be increased to 60 without risk of causing the core material to saturate, leading to a peak primary voltage of 280V in a 230/115V system.

On the other hand, the ripple can be optimized by choosing a 45 angle, thus making 4*F the dominant ripple frequency, yielding 230V peak primary voltage.

The conduction angle can be modified by increasing the value of R9.
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Old 6th December 2010, 11:23 PM   #5
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Quote:
Originally Posted by Charles Darwin View Post
Still think the easiest way is to stroll down to your local building supplies merchant and buy one of those fetching yellow step-down transformers they use for 110V power tools.
If you are tempted to try it, be prepared for odds sounds. Those 240:110Vac site isolation transformers (in the UK) have massive leakage inductance designed-in - it's part of the fault current limiting strategy, and doesn't matter to 50Hz power tools. It's also mostly why they run so damn hot even when unloaded.
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Old 7th December 2010, 11:10 AM   #6
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The following example compares the situation of a conventional 115V sinusoid solution with the voltage converter set at a higher conduction angle.

The average output voltage rises from 32V to 48V, a 50% increase, while the ripple voltage goes down by 1V pp (much more as a percentage).
Yet, the transformer's core utilization is still lower, meaning lower iron losses.
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Old 7th December 2010, 11:31 AM   #7
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Quote:
Originally Posted by martin clark View Post
If you are tempted to try it, be prepared for odds sounds. Those 240:110Vac site isolation transformers (in the UK) have massive leakage inductance designed-in - it's part of the fault current limiting strategy, and doesn't matter to 50Hz power tools. It's also mostly why they run so damn hot even when unloaded.
I haven't tried it personally but whenever I see american musicians here they almost invariably have the instruments amps plugged into those.
Friend of mine uses an US-made SWR bass amp which kept breaking down. He eventually had it back-converted to 110V and is using one of those now without problems. Similarly I know of a few people who bought US studio equipment using them. All without odd noises or problems.
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Old 9th December 2010, 09:01 AM   #8
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In addition, the circuit also acts as a line voltage regulator: because the conduction time is decided by comparing the incoming waveform with a fixed reference, the output voltage has a constant peak value.
It is therefore a universal power supply front-end, accepting mains voltages from 100 to 300V~, depending on the MOS rating.
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Old 9th December 2010, 09:32 AM   #9
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And in addition will act like a huge voltage-spike generator on the secondary side of the transformers that are fed with such a voltage shape (due to the switching on non-zero transitions).
I would not tie that output to an equipment that has any kind of transformer or even direct rectifier/switched power supply.
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Old 9th December 2010, 10:13 AM   #10
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by SoNic_real_one View Post
And in addition will act like a huge voltage-spike generator on the secondary side of the transformers that are fed with such a voltage shape (due to the switching on non-zero transitions).
I would not tie that output to an equipment that has any kind of transformer or even direct rectifier/switched power supply.
Have you read the title?

Quote:
Here is an elegant (insane?)

By the way, SMPS based supplies see even larger spikes, and 1,000 times more often too.
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