A undervoltage release circuit comprising a solenoid and a spring, the solenoid acting against the spring and being connected to a trip-latch which trips a circuit-breaker as soon as a control voltage drops under a voltage level, characterized in that it comprises a voltage determining device and a switching element controlled by a command signal, the switching element being connected in series with the solenoid, the voltage determining device comprising means for measuring the control-voltage and means for generating a signal according to the control voltage measured, the signal according to the control voltage measured constituting the command signal so that the switching element is closed when the control voltage measured is equal or higher than the voltage level and opened as soon as the control voltage is less than the voltage level.