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DCDC Buck Converter

Power supply for the Raspberry Pi

DC/DC buck converter DC/DC Buck down converter

12V to 5V and 9V to 5V using a Buck converter

In order to get the Raspberry Pi power manager to work it is necessary to generate a 5V supply for the Raspberry Pi. The 5V supply needs to be generated from the 12V supply and then switch seamlessly to the 9V supply when the power fails.

This useful little circuit is a Buck - DC/DC down converter. It's a switch mode power supply capable of producing an output of 1.5V to 35V from an input of 3V to 40V provided that the input is a few volts higher than the output.

When I tested one of these converters under load I found that there was a few tens of millivolts of ripple at the switching frequency on the output. Noise at this level should not pose a problem but if it does then a large electrolytic capacitor across the output should quieten it down.

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Comments (1)

Topic: A Power Off Delay For Computer Shutdown
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Jacob (US) says...
In your Power Failure Detection Circuit you reference D12 and D13. I see them in the closeup of your circuit, however, they are missing in your overall layout. What happened to D6? Did it go away or is it in series just before D13?
17th February 2017 7:01pm

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