I am creating an add-on board for my raspberry pi. I want to power up the raspberry pi from a voltage regulator (LM-2576 o/p is 5v and 3-A). I also want to drive two dc motors, 3-servo motors, an ultrasonic sensor, and 4 proximity sensors. I am using two LM-2576 regulators: one is for the raspberry pi, the other is for the drive sensors and actuators.

I believe my regulator is safe, but the inductor is getting hot after a few minutes. Why is my inductor getting hot? According to the data sheet I am using, it is 100microhenry and can support 3A at 5V.

Is the LM2576 sufficient for the raspberry pi and other sensors?

Is there a regulator available that I can replace both of my LM-2576 regulators with?

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    \$\begingroup\$ 100uH inductor of sufficient current handling capabilities is of course a requirement and not any old 100uH choke. \$\endgroup\$ – Andy aka Nov 3 '15 at 19:15
  • \$\begingroup\$ A thumb rule for switching PS inductor is that it should be rated twice as the load current. \$\endgroup\$ – Eugene Sh. Nov 3 '15 at 19:25
  • \$\begingroup\$ Typical information to add to your question: Input voltage. Load currents of dc motors, 3-servo motors, sensors. Is the regulator burning up without any load? \$\endgroup\$ – Dejvid_no1 Nov 3 '15 at 20:13
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    \$\begingroup\$ Please add link to the datasheet of the inductor (or at least mfgr&part# or a photo). SMPS use inductor to pump energy, so must have enough "Li-squared" to handle the power. Most SMPS inductors I've seen/used are wound on standard TDK magnetic cores, so in this case a photo would help show if it's at least a reasonable core. \$\endgroup\$ – MarkU Nov 3 '15 at 21:42

More details are needed but the inductor heats up due to two loss mechanisms:

1) Resistive losses. Make sure you did not select an inductor with too low current rating. I'd guess that this is the cause for the inductor to heat up.

2) Core losses. An inductor is typically formed by a coil wound around a magnetic core. As the current through the inductor looks like a triangle due to switching, the magnetic core flux fluctuates as well. Since the magnetic material B-H curve is not perfect, some energy is lost each switching cycle. The higher the switching frequency, the higher the loss. Make sure your inductor can operate at the frequency of the LM-2576 regulator (52 kHz).

Mainly, make sure your inductor meets the rated current requirements.

From the LM-2576 datasheet, page 17:

An inductor should not be operated beyond its maximum rated current because it may saturate. When an inductor begins to saturate, the inductance decreases rapidly and the inductor begins to look mainly resistive (the DC resistance of the winding). This will cause the switch current to rise very rapidly. Different inductor types have different saturation characteristics, and this should be kept in mind when selecting an inductor. The inductor manufacturer's data sheets include current and energy limits to avoid inductor saturation.


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