Electrical system which makes it possible to convert one DC voltage into another DC voltage, comprising: • a resonant DC-to-DC voltage converter comprising a resonant LLC converter circuit comprising a resonant inductor, two resonant capacitors (Cr/2) and a transformer (Tr), • a control unit comprising: ∘ a first determination module for determining a maximum value (V r_max) of the voltage across the terminals of each resonant capacitor (Cr/2) and a minimum value (V r_min) of the voltage across the terminals of each resonant capacitor (Cr/2) as a function of an output voltage (V out) of the resonant DC-to-DC voltage converter, ∘ a comparison module for comparing said maximum value (V r_max) of the voltage across the terminals of each resonant capacitor (Cr/2) with a high voltage threshold (Vr limit_max) corresponding to said output voltage (V out) and said minimum value (V r_min) of the voltage across the terminals of each resonant capacitor (Cr/2) with a low voltage threshold (Vr limit_min) corresponding to said output voltage (V out), ∘ a failure detection element configured to detect a failure of the resonant DC-to-DC voltage converter if: ▪ said maximum value (V r_max) of the voltage across the terminals of each resonant capacitor (Cr/2) is greater than or equal to the high voltage threshold (Vr limit_max), or ▪ said minimum value (V r_min) of the voltage across the terminals of each resonant capacitor (Cr/2) is less than or equal to the low voltage threshold (Vr limit_min). • a resonant DC-to-DC voltage converter comprising a resonant LLC converter circuit comprising a resonant inductor, two resonant capacitors (Cr/2) and a transformer (Tr), • a control unit comprising: ∘ a first determination module for determining a maximum value (V r_max) of the voltage across the terminals of each resonant capacitor (Cr/2) and a minimum value (V r_min) of the voltage across the terminals of each resonant capacitor (Cr/2) as a function of an output voltage (V out) of the resonant DC-to-DC voltage converter, ∘ a comparison module for comparing said maximum value (V r_max) of the voltage across the terminals of each resonant capacitor (Cr/2) with a high voltage threshold (Vr limit_max) corresponding to said output voltage (V out) and said minimum value (V r_min) of the voltage across the terminals of each resonant capacitor (Cr/2) with a low voltage threshold (Vr limit_min) corresponding to said output voltage (V out), ∘ a failure detection element configured to detect a failure of the resonant DC-to-DC voltage converter if: ▪ said maximum value (V r_max) of the voltage across the terminals of each resonant capacitor (Cr/2) is greater than or equal to the high voltage threshold (Vr limit_max), or ▪ said minimum value (V r_min) of the voltage across the terminals of each resonant capacitor (Cr/2) is less than or equal to the low voltage threshold (Vr limit_min). ∘ a first determination module for determining a maximum value (V r_max) of the voltage across the terminals of each resonant capacitor (Cr/2) and a minimum value (V r_min) of the voltage across the terminals of each resonant capacitor (Cr/2) as a function of an output voltage (V out) of the resonant DC-to-DC voltage converter, ∘ a comparison module for comparing said maximum value (V r_max) of the voltage across the terminals of each resonant capacitor (Cr/2) with a high voltage threshold (Vr limit_max) corresponding to said output voltage (V out) and said minimum value (V r_min) of the voltage across the terminals of each resonant capacitor (Cr/2) with a low voltage threshold (Vr limit_min) corresponding to said output voltage (V out), ∘ a failure detection element configured to detect a failure of the resonant DC-to-DC voltage converter if: ▪ said maximum value (V r_max) of the voltage across the terminals of each resonant capacitor (Cr/2) is greater than or equal to the high voltage threshold (Vr limit_max), or ▪ said minimum value (V r_min) of the voltage across the terminals of each resonant capacitor (Cr/2) is less than or equal to the low voltage threshold (Vr limit_min). ▪ said maximum value (V r_max) of the voltage across the terminals of each resonant capacitor (Cr/2) is greater than or equal to the high voltage threshold (Vr limit_max), or ▪ said minimum value (V r_min) of the voltage across the terminals of each resonant capacitor (Cr/2) is less than or equal to the low voltage threshold (Vr limit_min).