Abstract: A protection circuit (PD1) enables a load (L) to withstand a transient power supply failure. It comprises: inputs connected to at least one electrical power supply (B1, B2), outputs connected to the load (L), at least two storage capacitors (SC1, SC2), and first switching means (D1 to D4, SW3, CU) such that the two storage capacitors are: connected in parallel to at least one power supply (B1, B2) when the voltage of at least one power supply is greater than a fixed value; and isolated from any power supply (B1, B2) and connected in series to the outputs of the circuit (PD1) when the voltage of each power supply is less than or equal to the fixed value. Application to electronic equipment, in particular telecommunications equipment.