Electrical power supply device, comprising: - a DC voltage source liable to induce electrocution, applying a nominal voltage Vm between its terminals; - a device for detecting an insulation defect of the DC voltage source, comprising: - first and second input terminals (47, 48) connected to the terminals of the voltage source; - first and second resistors (41, 42) connected in series between the first and second input terminals (47, 48), and configured so that the insulation defect current between one of said terminals of the voltage source and an electrical ground passes through the first resistor or the second resistor, the first and second resistors each exhibiting an impedance value Z of between Zmin and Zmax, with Zmin= Vm/lmax and Zmax=1.5*Vm/Imax, Imax being a maximum insulation defect current of 3.5 mA; - a current-detection circuit connected between an electrical ground and an intermediate point between the first and second resistors, the current-detection circuit comprising a microcontroller comprising an input terminal connected to said intermediate point, said input terminal being connected by way of a third resistor to a power supply with a voltage level Vcc at least ten times lower than the voltage level of the DC voltage source; characterized in that said input terminal is moreover connected to the electrical ground by way of a fourth resistor, and receives a voltage proportional to the insulation defect current originating from the intermediate point, said microcontroller being configured to determine the amplitude of an insulation defect as a function of the voltage applied to its input terminal, the third and fourth resistors each exhibiting an impedance value Zt of between Ztmin and Ztmax, with Ztmin = Z*Vcc/(4*Vm) and Ztmax = Z * Vcc/2Vm. - a DC voltage source liable to induce electrocution, applying a nominal voltage Vm between its terminals; - a device for detecting an insulation defect of the DC voltage source, comprising: - first and second input terminals (47, 48) connected to the terminals of the voltage source; - first and second resistors (41, 42) connected in series between the first and second input terminals (47, 48), and configured so that the insulation defect current between one of said terminals of the voltage source and an electrical ground passes through the first resistor or the second resistor, the first and second resistors each exhibiting an impedance value Z of between Zmin and Zmax, with Zmin= Vm/lmax and Zmax=1.5*Vm/Imax, Imax being a maximum insulation defect current of 3.5 mA; - a current-detection circuit connected between an electrical ground and an intermediate point between the first and second resistors, the current-detection circuit comprising a microcontroller comprising an input terminal connected to said intermediate point, said input terminal being connected by way of a third resistor to a power supply with a voltage level Vcc at least ten times lower than the voltage level of the DC voltage source; - first and second input terminals (47, 48) connected to the terminals of the voltage source; - first and second resistors (41, 42) connected in series between the first and second input terminals (47, 48), and configured so that the insulation defect current between one of said terminals of the voltage source and an electrical ground passes through the first resistor or the second resistor, the first and second resistors each exhibiting an impedance value Z of between Zmin and Zmax, with Zmin= Vm/lmax and Zmax=1.5*Vm/Imax, Imax being a maximum insulation defect current of 3.5 mA; - a current-detection circuit connected between an electrical ground and an intermediate point between the first and second resistors, the current-detection circuit comprising a microcontroller comprising an input terminal connected to said intermediate point, said input terminal being connected by way of a third resistor to a power supply with a voltage level Vcc at least ten times lower than the voltage level of the DC voltage source;