A light hybrid drive device comprising an internal combustion engine MCI that is coupled, on the one hand, to a main receiver RP and, on the other hand, by a mechanical torque transmission means, to a fixed displacement pump/engine unit, a hydraulic circuit that contains, in addition to the pump/engine unit, a hydraulic engine for rotating a secondary take-off drive, a high-pressure accumulator that contains a certain quantity of fluid under high pressure, a low-pressure tank capable of containing a sufficient quantity of fluid to fill the high-pressure accumulator and including a main hydraulic valve between a part of the hydraulic circuit that contains the pump/engine unit and another part of the hydraulic circuit that contains the hydraulic engine, the main hydraulic valve being able to be controlled, either in a closed state, interrupting the circulation of fluid between the two parts (32, 34) of the hydraulic circuit to put the device into a state designated a state of rest, or in a parallel open state, during which the pump/engine unit is intended to function as a hydraulic pump, or in a crossed open state, during which the pump/engine unit is intended to function as a hydraulic engine, characterized in that it further comprises: • a hydraulic clutch distributor in parallel with the pump/engine unit, said clutch distributor being able to be controlled, either in a closed state to pass the fluid of the pump/engine unit, in the hydraulic circuit or in an open state to divert the passage of the fluid in the hydraulic circuit by said clutch distributor, • a hydraulic engine distributor, being able to be controlled, either in a closed state for isolating the hydraulic engine from the hydraulic circuit, or in an open state for permitting the passage of the fluid in the hydraulic engine, • a hydraulic pressure regulator comprising an inlet Er for controlling the level to which the regulator opens in order to control the flow of fluid in the hydraulic engine, • a hydraulic accumulator valve being able to be controlled either in an open state, permitting the filling or the emptying of the high-pressure accumulator through the pump/engine unit, or in a closed state for isolating the high-pressure accumulator from the hydraulic circuit, • a computer UC that is configured so as to control the states of the hydraulic valves (50, 56, 58, 60), the degree to which the pressure regulator opens, the engine speed of the internal combustion engine MCI on the basis of various operational configurations of the device. • a hydraulic clutch distributor in parallel with the pump/engine unit, said clutch distributor being able to be controlled, either in a closed state to pass the fluid of the pump/engine unit, in the hydraulic circuit or in an open state to divert the passage of the fluid in the hydraulic circuit by said clutch distributor, • a hydraulic engine distributor, being able to be controlled, either in a closed state for isolating the hydraulic engine from the hydraulic circuit, or in an open state for permitting the passage of the fluid in the hydraulic engine, • a hydraulic pressure regulator comprising an inlet Er for controlling the level to which the regulator opens in order to control the flow of fluid in the hydraulic engine, • a hydraulic accumulator valve being able to be controlled either in an open state, permitting the filling or the emptying of the high-pressure accumulator through the pump/engine unit, or in a closed state for isolating the high-pressure accumulator from the hydraulic circuit, • a computer UC that is configured so as to control the states of the hydraulic valves (50, 56, 58, 60), the degree to which the pressure regulator opens, the engine speed of the internal combustion engine MCI on the basis of various operational configurations of the device.