Circuit for controlling a relay for the coupling of a reactive load with capacitive character, to a low-voltage network

摘要

The control circuit is intended to prompt the closure of the contacts 3b of a relay 3, in order to couple a load 1, such as a capacitive fluorescent tube ballast, which exhibits, in addition to an active component, a reactive component with capacitive character, closure occurring at zero voltage. It includes a switching circuit 5 capable of becoming conducting in response to the cancelling of the alternating voltage on its input 5c, and of remaining conducting if a current, provided by a source 2, passes through the coil 3a of the relay 3. A phase-shifting stage 6, adjustable, makes it possible to regulate the phase on the input 5c with respect of that of the voltage network between conductors P, N. An AND gate 4 becomes conducting when the switching circuit 5 becomes conducting and when a control signal C is applied. This occurs on the first active instance of cancellation of voltage on the input 5c. The phase-shifting stage 6 is adjusted so that the duration of closure of the contacts 3b corresponds to the phase-shift to within K pi . IMAGE