A high-frequency and high-power multi-power supply voltage dc/dc converter block comprising a power circuit whose output constitutes the output of the dc/dc converter block, the power circuit comprising N depletion high-electron-mobility (HEMT) transistors (T3_1, T3_2, T3_N), N being a positive integer greater than or equal to 3, the dc/dc converter block further comprising a driving circuit of the gates of the N depletion HEMT transistors (T3_1, T3_2, T3_N) of the power circuit, the driving circuit comprising depletion HEMT transistors (T1_1, T2_1, T1_2, T2_2, T1_N, T2_N) configured to drive the gates of the N depletion HEMT transistors (T3_1, T3_2, T3_N) of the power circuit, characterized in that the power circuit is power supplied with N non-zero and positive power supply voltages, namely, a low power supply voltage (VDD_1), a high power supply voltage (VDD_N) and (N-2) intermediary power supply voltage(s) (VDD-2), the high power supply voltage (VDD_N) being greater than the low power supply voltage (VDD_1), each intermediary power supply voltage (VDD_2) being different from the low (VDD_1) and high (VDD_N) power supply voltages and the (N-2) intermediary power supply voltages (VDD_2) being different to each other and comprised between the low (VDD_1) and high (VDD_N) power supply voltages, the driving circuit further comprising, for each gate of depletion HEMT transistor (T3_1; T3_2; T3_N) of the power circuit to be driven, a first depletion HEMT driving transistor (T1_1; T1_2; T1_N), a second depletion HEMT driving transistor (T2_1; T2_2; T2_N), first, second and third resistors (R1_1, R2_1, R3_1; R1_2, R2_2, R3_2; R1_N, R2_N, R3_N), a Schottky diode (D1_1; D1_2; D1_N) and an auxiliary power supply voltage (V AUX ), the source of the first driving transistor (T1_1; T1_2; T1_N) being connected to the ground, the drain of the first driving transistor (T1_1; T1_2; T1_N) being connected to one of the terminals of the first resistor (R1_1; R1_2; R1_N) and to one of the terminals of the second resistor (R2_1 ; R2_2 ; R2_N), the gate of the first driving transistor (T1_1; T1_2; T1_N) being connected to a corresponding input (V IN_1 ; V IN_2 ; V IN_N ) of the driving circuit, the gate of the second driving transistor (T2_1; T2_2; T2_N) being connected to the other of the terminals of the first resistor (R1_1; R1_2; R1_N), the source of the second driving transistor (T2_1; T2_2; T2_N) being connected to the other of the terminals of the second resistor (R2_1; R2_2; R2_N), to the cathode of the Schottky diode (D1_1; D1_2; D1_N) and to one of the terminals of the third resistor (R3_1; R3_2; R3_N), the anode of the Schottky diode (D1_1; D1_2; D1_N) being connected to the auxiliary power supply voltage (V AUX ), the other of the terminals of the third resistor (R3_1; R3_2; R3_N) being connected to the gate of the corresponding depletion HEMT transistor (T3_1; T3_2; T3_N) of the power circuit to be driven, the drain of the second driving transistor (T2_1; T2_2; T2_N) being connected to the low power supply voltage (VDD_1) if it is connected to the conduction output terminal of the corresponding depletion HEMT transistor (T3_1) of the power circuit to be driven, or being connected to the corresponding intermediary or high power supply voltage (VDD_2; VDD_N) if it is connected to the conduction input terminal of the corresponding depletion HEMT transistor (T3_2; T3_N) of the power circuit to be driven, the auxiliary power supply voltage (V AUX ) being greater than the pinch-off voltage of the second driving transistor (T2_1; T2_2; T2_N), and the low power supply voltage (VDD_1) being greater than the auxiliary power supply voltage (V AUX ) plus the pinch-off voltage of the corresponding depletion HEMT transistor (T3_1; T3_2; T3_N) of the power circuit to be driven. <EOS>