Patent ID: 7586213
Filing Date: 2009-09-08
Classification: F23N,H01H

Abstract:
1. A control circuit for relay-operated gas valves comprising: a relay for opening and/or closing a gas valve; a failsafe circuit for the relay, the failsafe circuit including: a control device being connectable to an input of the failsafe circuit, the failsafe circuit only supplying the relay with a voltage and/or current necessary for opening the gas valve when an input signal having at least two different frequency signals succeeding each other in time is supplied at the input of the failsafe circuit by the control device; wherein, upon the application of a first frequency signal at the input of the failsafe circuit, the charging circuit charges the charging capacitor, and upon the application of a second frequency signal at the input of the failsafe circuit, the second frequency signal having a different frequency that the first frequency signal, the charging circuit does not charge the charging capacitor, and the charging capacitor when sufficiently charged, provides a bias to the input transistor of the drive circuit that enables the input transistor of the drive circuit; wherein the drive circuit, upon the application of the second frequency signal at the input of the failsafe circuit, supplies the relay with a voltage and/or current necessary for opening the gas valve but only if the charging capacitor is sufficiently charged by the first frequency signal to provide the necessary bias to the input transistor of the drive circuit to enable the input transistor of the drive circuit to pass the second frequency signal.