Electrical system allowing for the conversion of a direct voltage into another direct voltage, comprising: • a resonant DC-DC converter comprising a resonant converter circuit LLC comprising a resonance inductance (Lr), two resonance capacitors (Cr/2) and a transformer (Tr), • characterised by a control unit comprising: ∘ a first module for determining the average value (I r_avrg) of a current, referred to as "resonance current" (I r), circulating in a branch of the resonant converter circuit LLC which comprises the transformer (Tr), over a duration referred to as "evaluation duration", ∘ a second module for determining a maximum value (V r_max) of the voltage at the terminals of each resonance capacitor (Cr/2) and of a minimum value (V r_min) of the voltage at the terminals of each resonance capacitor (Cr/2) over the evaluation duration "T", using the average value (I r_avrg) of the resonance current, of the input voltage (V in) of the resonant DC-DC converter, of the switching frequency (F S) of the resonant DC-DC converter, and of the value of the resonance capacitor (Cr). ∘ a module for comparing between a maximum voltage threshold (V r_define_max) and the maximum value (V r_max) of the voltage at the terminals of each resonance capacitor (Cr/2) and between a minimum voltage threshold (V r_define_min) and the minimum value (V r_min) of the voltage at the terminals of each resonance capacitor (Cr/2), ∘ a cut-off element configured to cut off the operation of the resonant DC-DC converter if: • said maximum voltage value (V r_max) is greater than or equal to the maximum voltage threshold (V r_define_max), • said minimum voltage value (V r_min) is less than or equal to the minimum voltage threshold (V r_define_min). • a resonant DC-DC converter comprising a resonant converter circuit LLC comprising a resonance inductance (Lr), two resonance capacitors (Cr/2) and a transformer (Tr), • characterised by a control unit comprising: ∘ a first module for determining the average value (I r_avrg) of a current, referred to as "resonance current" (I r), circulating in a branch of the resonant converter circuit LLC which comprises the transformer (Tr), over a duration referred to as "evaluation duration", ∘ a second module for determining a maximum value (V r_max) of the voltage at the terminals of each resonance capacitor (Cr/2) and of a minimum value (V r_min) of the voltage at the terminals of each resonance capacitor (Cr/2) over the evaluation duration "T", using the average value (I r_avrg) of the resonance current, of the input voltage (V in) of the resonant DC-DC converter, of the switching frequency (F S) of the resonant DC-DC converter, and of the value of the resonance capacitor (Cr). ∘ a module for comparing between a maximum voltage threshold (V r_define_max) and the maximum value (V r_max) of the voltage at the terminals of each resonance capacitor (Cr/2) and between a minimum voltage threshold (V r_define_min) and the minimum value (V r_min) of the voltage at the terminals of each resonance capacitor (Cr/2), ∘ a cut-off element configured to cut off the operation of the resonant DC-DC converter if: • said maximum voltage value (V r_max) is greater than or equal to the maximum voltage threshold (V r_define_max), • said minimum voltage value (V r_min) is less than or equal to the minimum voltage threshold (V r_define_min). ∘ a first module for determining the average value (I r_avrg) of a current, referred to as "resonance current" (I r), circulating in a branch of the resonant converter circuit LLC which comprises the transformer (Tr), over a duration referred to as "evaluation duration", ∘ a second module for determining a maximum value (V r_max) of the voltage at the terminals of each resonance capacitor (Cr/2) and of a minimum value (V r_min) of the voltage at the terminals of each resonance capacitor (Cr/2) over the evaluation duration "T", using the average value (I r_avrg) of the resonance current, of the input voltage (V in) of the resonant DC-DC converter, of the switching frequency (F S) of the resonant DC-DC converter, and of the value of the resonance capacitor (Cr). ∘ a module for comparing between a maximum voltage threshold (V r_define_max) and the maximum value (V r_max) of the voltage at the terminals of each resonance capacitor (Cr/2) and between a minimum voltage threshold (V r_define_min) and the minimum value (V r_min) of the voltage at the terminals of each resonance capacitor (Cr/2), ∘ a cut-off element configured to cut off the operation of the resonant DC-DC converter if: • said maximum voltage value (V r_max) is greater than or equal to the maximum voltage threshold (V r_define_max), • 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), • said minimum voltage value (V r_min) is less than or equal to the minimum voltage threshold (V r_define_min).