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I have a device plugged into the USB port of my car stereo. Occasionally, the device crashes, and I believe it is caused by power fluctuations in the USB port. I want to create a circuit that regulates the voltage between the USB port and the device that it's powering. I need to protect against power surges, and if possible, dips in the voltage. What kind of circuit would I need to create to accomplish this?

  • https://electronics.stackexchange.com/a/316988/290114
    This answer is similar to what I'm looking for, if I use a 7805 regulator. The problem is that it sounds like the 7805 regulator requires a higher input voltage (maybe 7v) than the output voltage (5v) to operate correctly, but the input and output voltage will normally both be 5v. The answer also talks about using a polyswitch to cut off the power, but since I'm trying to keep my device from turning off, this would defeat the purpose.

  • https://electronics.stackexchange.com/a/107346/290114
    This answer sounds like it would be more suitable for my application because it suggests using an ADP1613 to regulate the voltage, which does not require a high input voltage. However, it looks like the device would be hard to work with, and I'm concerned that a USB port would not be able to handle the current that this might draw, especially a USB port in a car (although I could be wrong).

Note that there is always data being transferred between the device and the stereo, so it must be plugged into the USB port. This may also further complicate the problem.

Am I on the right track? I'd greatly appreciate any guidance you can provide. Sorry if the question seems elementary... hardware is not really my area.

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    \$\begingroup\$ The correct way to fix this is to fix the faulty USB port. \$\endgroup\$
    – Hearth
    Commented Jul 2, 2021 at 5:07
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    \$\begingroup\$ "I believe it is caused by power fluctuations in the USB port" How did you come to that conclusion? Have you recorded the voltage dips with a scope? Can you post the pic? \$\endgroup\$
    – Lundin
    Commented Jul 2, 2021 at 6:11
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    \$\begingroup\$ The fuse should not blow during voltage measurements - maybe you have connected it to the current measurement points? And additionally a multimeter reacts too slow to see anything useful; as the readings are averaged across a second or so. Therefore an oscilloscope is essential. \$\endgroup\$
    – Jakob Halskov
    Commented Jul 2, 2021 at 6:38
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    \$\begingroup\$ "It read 5 volts for several minutes until the fuse eventually blew on the multimeter." It sounds like you were on current measurement range and short-circuited the 5 V supply with your meter. (Don't do that!) Usually there is no fuse in the voltage measurement range. \$\endgroup\$
    – Transistor
    Commented Jul 2, 2021 at 6:39
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    \$\begingroup\$ @JacobG. Well... at this point I'd politely advise you to hand over the problem to professionals. The fuse in a multimeter blows from a current rush when you have it set to measure current. The "power surges" you should be measuring are voltage surges. The fuse cannot blow if you measure voltage, nor from extended use. The fuse blowing is likely an indication of you short-circuiting something with the probes during measurement and not an indication of a problem in the car. There may now be a problem in the car which wasn't there when you started though... \$\endgroup\$
    – Lundin
    Commented Jul 2, 2021 at 6:47

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It is possible your usb plug or socket, especially if cheap got oxidized over time and making a bad connection.

Simplest first is always the better, try to add a large cap (200-500uF) on the power lines of the USB and see if it keeps having issue.

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