Electrical system for converting a DC voltage into another DC voltage, comprising: • a DC/DC resonant converter comprising an LLC resonant converter circuit comprising a resonance inductor, two resonance capacitors (Cr/2) and a transformer (Tr), • a control unit comprising: ∘ a first determination module for determining the average value (I s_avg) of the output current (I s) of the DC/DC resonant converter over a time called "evaluation time", characterized in that the control unit also comprises: ∘ a second determination module for determining a maximum value (V r_max) of the voltage across the terminals of each resonance capacitor (Cr/2) and a minimum value (V r_min) of the voltage across the terminals of each resonance capacitor (Cr/2) over the evaluation time from the average value (I s_avg) of the output current (I s) by expressing the maximum value (V r_max) and the minimum value (V r_min) of the voltage across the terminals of each resonance capacitor (Cr/2) as a function of the RMS value of the resonance current (I r_RMS), the RMS value of the resonance current (I r_RMS) being expressed as a function of the average value (I s_avg) of the output current (I s), ∘ a comparison module for comparing a maximum voltage threshold (V r_define_max) with the maximum value (V r_max) of the voltage across the terminals of each resonance capacitor (Cr/2) and for comparing a minimum voltage threshold (V r_define_min) with the minimum value (V r_min) of the voltage across the terminals of each resonance capacitor (Cr/2), ∘ a fault detection element configured to detect a fault of the DC/DC resonant converter if: ▪ said maximum voltage value (V r_max) is greater than or equal to the maximum voltage threshold (V r_define_max), or ▪ said minimum voltage value (V r_min) is less than or equal to the minimum voltage threshold (V r_define_min). • a DC/DC resonant converter comprising an LLC resonant converter circuit comprising a resonance inductor, two resonance capacitors (Cr/2) and a transformer (Tr), • a control unit comprising: ∘ a first determination module for determining the average value (I s_avg) of the output current (I s) of the DC/DC resonant converter over a time called "evaluation time", characterized in that the control unit also comprises: ∘ a second determination module for determining a maximum value (V r_max) of the voltage across the terminals of each resonance capacitor (Cr/2) and a minimum value (V r_min) of the voltage across the terminals of each resonance capacitor (Cr/2) over the evaluation time from the average value (I s_avg) of the output current (I s) by expressing the maximum value (V r_max) and the minimum value (V r_min) of the voltage across the terminals of each resonance capacitor (Cr/2) as a function of the RMS value of the resonance current (I r_RMS), the RMS value of the resonance current (I r_RMS) being expressed as a function of the average value (I s_avg) of the output current (I s), ∘ a comparison module for comparing a maximum voltage threshold (V r_define_max) with the maximum value (V r_max) of the voltage across the terminals of each resonance capacitor (Cr/2) and for comparing a minimum voltage threshold (V r_define_min) with the minimum value (V r_min) of the voltage across the terminals of each resonance capacitor (Cr/2), ∘ a fault detection element configured to detect a fault of the DC/DC resonant converter if: ▪ said maximum voltage value (V r_max) is greater than or equal to the maximum voltage threshold (V r_define_max), or ▪ said minimum voltage value (V r_min) is less than or equal to the minimum voltage threshold (V r_define_min). ∘ a first determination module for determining the average value (I s_avg) of the output current (I s) of the DC/DC resonant converter over a time called "evaluation time", ∘ a second determination module for determining a maximum value (V r_max) of the voltage across the terminals of each resonance capacitor (Cr/2) and a minimum value (V r_min) of the voltage across the terminals of each resonance capacitor (Cr/2) over the evaluation time from the average value (I s_avg) of the output current (I s) by expressing the maximum value (V r_max) and the minimum value (V r_min) of the voltage across the terminals of each resonance capacitor (Cr/2) as a function of the RMS value of the resonance current (I r_RMS), the RMS value of the resonance current (I r_RMS) being expressed as a function of the average value (I s_avg) of the output current (I s), ∘ a comparison module for comparing a maximum voltage threshold (V r_define_max) with the maximum value (V r_max) of the voltage across the terminals of each resonance capacitor (Cr/2) and for comparing a minimum voltage threshold (V r_define_min) with the minimum value (V r_min) of the voltage across the terminals of each resonance capacitor (Cr/2), ∘ a fault detection element configured to detect a fault of the DC/DC resonant converter if: ▪ said maximum voltage value (V r_max) is greater than or equal to the maximum voltage threshold (V r_define_max), or ▪ said minimum voltage value (V r_min) is less than or equal to the minimum voltage threshold (V r_define_min). ▪ said maximum voltage value (V r_max) is greater than or equal to the maximum voltage threshold (V r_define_max), or ▪ said minimum voltage value (V r_min) is less than or equal to the minimum voltage threshold (V r_define_min).