Horological movement equipped with an oscillator comprising a piezoelectric balance-spring

An horological movement comprising:

• an analogue time display,
• a geartrain,
• a barrel kinematically linked with the analogue display via the geartrain,
• an electromechanical oscillator formed of a resonator, comprising a balance and a piezoelectric balance-spring, and a mechanical escapement coupling the balance with the geartrain, the piezoelectric balance-spring being formed at least partially from a piezoelectric material and comprising at least two electrodes of which at least one electrode is connected to an electronic control circuit, the piezoelectric material and said at least one electrode being arranged in such a way as to enable the application, managed by the electronic control circuit, of electrical stress on the piezoelectric balance-spring, and
• an electrical energy source configured to supply an electrical energy to the electronic control circuit,
• the horological movement being configured such that, when the electrical energy supplied to the electronic control circuit from the electrical energy source is not sufficient for the electronic control circuit to generate driving electrical pulses for the electromechanical oscillator, the barrel is capable of driving the analogue display and maintaining alone a functional oscillation of the electromechanical oscillator with a first amplitude which is dependent on a position of the horological movement;
• wherein the electronic control circuit, when the electrical energy supplied to the electronic control circuit from the electrical energy source is sufficient, is configured to control the application of an electrical voltage to said at least one electrode so as to generate the driving electrical pulses for the electromechanical oscillator which supply it with sufficient energy to enable a functional oscillation of said electromechanical oscillator, for each position of the horological movement, with a second amplitude which is greater than a maximum nominal value of the first amplitude for said position.