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Q&A(FAQ) How to Protect a DC-DC Converter from Reverse Voltage

Avoid applying reverse-polarity input voltage, as it can damage the power supply.
The unit can be protected from reverse input voltage by adding an external diode, as shown below.

Fig. 1.1 Example of reverse input voltage protection circuit vol.1 — Fig. 1.1 Example of reverse input voltage protection circuit Version 1

Fig. 1.2 Example of reverse input voltage protection circuit vol.2 — Fig. 1.2 Example of reverse input voltage protection circuit Version 2

Fig. 1.3 Example of reverse input voltage protection circuit vol.3 — Fig. 1.3 Example of reverse input voltage protection circuit Version 3

Table 1.1 Feature of reverse input voltage protection circuit
Fig.#	Operation during applied reverse polarity voltage	Advantage	Disadvantage	Cost
1.1	Normal operation	Normal output No recovery components required	Reverse connection not detectable Constant diode power loss	High
1.2	No output	Detectable of reverse connection No recovery components required	Reverse connection detectable Constant diode power loss	Low
1.3	No output Fuse open	Reverse connection detectable No diode power loss	Fuse replacement required for recovery Overcurrent for an instant	Medium

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