Control unit of a circuit breaker, said control unit being intended to be associated with an electric circuit breaker and to be electrically connected to input terminals of the circuit breaker and comprising: - a safety module containing an integrated circuit which is configured to transmit a command for switching of the circuit breaker when the safety module detects an operating anomaly, - a plurality of programmable computation modules which are to perform functions of managing the circuit breaker when the unit is associated with the circuit breaker, - a power supply management system comprising a connection interface which is to be connected to distinct power supply sources in order to receive an incoming electrical power delivered by the power supply sources, the interface being electrically connected to the safety module and to the computation modules in order to selectively redistribute the received electrical power to the safety module and the computation modules , the control unit being characterised in that the power supply management system is configured to switch automatically, according to the level of electrical power received from the power supply sources and according to a predefined power supply programme, between: - at least one active power supply mode (M1, M2, M3, M4), in which the safety module and at least some of the computation modules are electrically supplied with the incoming electrical power, and - a safety power supply mode (M0), in which the safety module is supplied with the incoming electrical power of at least one of the power supply sources and in which said computation modules are isolated from the connection interface and are not supplied with the incoming electrical power, and in that the power supply management system is configured to switch to the safety power supply mode (M0) when the electrical power received at the connection interface falls below a predefined minimum threshold, the predefined minimum threshold being fixed according to the electrical power consumed by the computation modules . - a safety module containing an integrated circuit which is configured to transmit a command for switching of the circuit breaker when the safety module detects an operating anomaly, - a plurality of programmable computation modules which are to perform functions of managing the circuit breaker when the unit is associated with the circuit breaker, - a power supply management system comprising a connection interface which is to be connected to distinct power supply sources in order to receive an incoming electrical power delivered by the power supply sources, the interface being electrically connected to the safety module and to the computation modules in order to selectively redistribute the received electrical power to the safety module and the computation modules , - at least one active power supply mode (M1, M2, M3, M4), in which the safety module and at least some of the computation modules are electrically supplied with the incoming electrical power, and - a safety power supply mode (M0), in which the safety module is supplied with the incoming electrical power of at least one of the power supply sources and in which said computation modules are isolated from the connection interface and are not supplied with the incoming electrical power, <EOS>