Method for controlling a device for modulating the supply voltage (Ue) of an electrical current that is supplied by a traction battery of a hybrid motor vehicle and that is provided to an electric machine of the motor vehicle, said hybrid motor vehicle including a thermal powertrain and an electric powertrain, the method comprising: - a step of determining an optimal electrical torque (T e opt) that the electric machine must produce, according to an energy value (Pr) requested to propel the motor vehicle and an equivalence factor (λ) associated with the traction battery, said equivalence factor (λ) being a function of a relative value of the cost of an electrical energy relative to the cost of a thermal energy, - a step of analytical calculation of an optimal supply voltage (U e opt) according to said optimal electrical torque (T e opt) and the speed (ω e) of the electric machine, said optimal supply voltage (U e opt) minimising the electrical losses in an assembly comprising at least the modulation device and the electric machine, and - a step of controlling said modulation device so as to deliver said optimal supply voltage (U e opt) characterised in that said optimal electrical torque (T e opt) is determined by analytical calculation, according to the formula: T e opt = a − λ. b 1 / 2. λ. ωe. b 2, such that: a = a 1 if P r - P m opt ≤ P lim and a = a 2 if P r - P m opt > P lim b 1 = b 1 - and b 2 = b 2 - if P m opt ≤ 0 and b 1 = b 1 + and b 2 = b 2 + if P m opt > 0 and where: T e opt is the optimal electrical torque, ω e is the speed of the electric machine, λ the equivalence factor of the traction battery, P r the power at the wheels, P lim a variable depending on the speed of the electric machine, and a 1, a 2, b 1 -, b 2 -, b 1 +, b 2 + predetermined constants. - a step of determining an optimal electrical torque (T e opt) that the electric machine must produce, according to an energy value (Pr) requested to propel the motor vehicle and an equivalence factor (λ) associated with the traction battery, said equivalence factor (λ) being a function of a relative value of the cost of an electrical energy relative to the cost of a thermal energy, - a step of analytical calculation of an optimal supply voltage (U e opt) according to said optimal electrical torque (T e opt) and the speed (ω e) of the electric machine, said optimal supply voltage (U e opt) minimising the electrical losses in an assembly comprising at least the modulation device and the electric machine, and - a step of controlling said modulation device so as to deliver said optimal supply voltage (U e opt) characterised in that said optimal electrical torque (T e opt) is determined by analytical calculation, according to the formula: T e opt = a − λ. b 1 / 2. λ. ωe. b 2, such that: a = a 1 if P r - P m opt ≤ P lim and a = a 2 if P r - P m opt > P lim b 1 = b 1 - and b 2 = b 2 - if P m opt ≤ 0 and b 1 = b 1 + and b 2 = b 2 + if P m opt > 0 and where: T e opt is the optimal electrical torque, ω e is the speed of the electric machine, λ the equivalence factor of the traction battery, P r the power at the wheels, P lim a variable depending on the speed of the electric machine, and a 1, a 2, b 1 -, b 2 -, b 1 +, b 2 + predetermined constants. such that: a = a 1 if P r - P m opt ≤ P lim and a = a 2 if P r - P m opt > P lim b 1 = b 1 - and b 2 = b 2 - if P m opt ≤ 0 and b 1 = b 1 + and b 2 = b 2 + if P m opt > 0 a = a 1 if P r - P m opt ≤ P lim and a = a 2 if P r - P m opt > P lim b 1 = b 1 - and b 2 = b 2 - if P m opt ≤ 0 and b 1 = b 1 + and b 2 = b 2 + if P m opt > 0 and where: T e opt is the optimal electrical torque, ω e is the speed of the electric machine, λ the equivalence factor of the traction battery, P r the power at the wheels, P lim a variable depending on the speed of the electric machine, and a 1, a 2, b 1 -, b 2 -, b 1 +, b 2 + predetermined constants. T e opt is the optimal electrical torque, ω e is the speed of the electric machine, λ the equivalence factor of the traction battery, P r the power at the wheels, P lim a variable depending on the speed of the electric machine, and a 1, a 2, b 1 -, b 2 -, b 1 +, b 2 + predetermined constants.