Hi guys
I am trying to design a DC-DC converter to power a Raspberry Pi 3 SBC. The spec calls for 5 volts +/- .1 volts. I am using 12 volt battery (12 V - 14.2 V). The Pi, plus some associated hardware, (GPS Unit, motor controller etc) causes a current drain of between 500 Ma and 3.5 Amps.
My initial design was based on a 7805 voltage regulator which worked fine, but was not very efficient. To improve efficiency, I have now upgraded to a buck converter based on a LM 2678T-5 switcher. The circuit is attached. It almost exactly follows the application note on the TI website (http://www.ti.com/lit/ds/symlink/lm2678.pdf). However, I find that the voltage swings between 5.65 and 4.8 volts, depending on the load.
I have damaged one Pi, and I find that even when the Pi works, it reboots every five or ten minutes, presumably a hot boot caused by fluctuating voltage.
Can anyone suggest a way to make the output more stable, or an alternative circuit.
I take the point I have seen on other posts that its easier, quicker and cheaper to buy a module to do the job, but I want to be able to put the entire project on a single board. Anyway, it surely must be possible to derive a stable 5 volt supply. Anyone got any ideas?
I am trying to design a DC-DC converter to power a Raspberry Pi 3 SBC. The spec calls for 5 volts +/- .1 volts. I am using 12 volt battery (12 V - 14.2 V). The Pi, plus some associated hardware, (GPS Unit, motor controller etc) causes a current drain of between 500 Ma and 3.5 Amps.
My initial design was based on a 7805 voltage regulator which worked fine, but was not very efficient. To improve efficiency, I have now upgraded to a buck converter based on a LM 2678T-5 switcher. The circuit is attached. It almost exactly follows the application note on the TI website (http://www.ti.com/lit/ds/symlink/lm2678.pdf). However, I find that the voltage swings between 5.65 and 4.8 volts, depending on the load.
I have damaged one Pi, and I find that even when the Pi works, it reboots every five or ten minutes, presumably a hot boot caused by fluctuating voltage.
Can anyone suggest a way to make the output more stable, or an alternative circuit.
I take the point I have seen on other posts that its easier, quicker and cheaper to buy a module to do the job, but I want to be able to put the entire project on a single board. Anyway, it surely must be possible to derive a stable 5 volt supply. Anyone got any ideas?
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