Control circuit for relay-operated gas valves
AssigneeHoneywell International Inc.
InventorDerk Vegter
Life of this patent
Estimating the term…
Abstract
A control circuit and methods for controlling gas valves via a relay are provided. In one illustrative embodiment, a control circuit includes or is connected to a relay that controls the opening and/or closing of a gas valve. The control circuit may also include a failsafe circuit that has at least one input that can be connected to a control device and at least one output that can be connected to the relay. In some cases, the fail-safe circuit may only supply an output voltage and/or current to the replay for opening the gas valve if the input signal received from the control device includes at least two different successively applied frequency signals. Other methods and embodiments are also contemplated.
Claims13
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 charging circuit having at least one capacitor including a charging capacitor;
- a drive circuit coupled to the relay having an input transistor, a base of the input transistor being electrically connected to the charging capacitor of the charging circuit;
- and
- 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.
A fail-safe circuit for controlling a relay that controls the opening of a gas valve, the fail-safe circuit comprising:
- at least one input that can be connected to a gas valve controller;
- at least one output that can be connected to the relay;
- a charging circuit having a charging capacitor;
- and
- a drive circuit having at least one transistor and a drive capacitor;
- wherein the fail-safe circuit is configured to only supply an output signal to the relay to open the gas valve via the at least one output of the fail safe circuit if/when the gas valve controller provides an input signal having at least a first frequency signal and a different second frequency signal to the at least one input of the fail-safe circuit;
- wherein, during the period of the first frequency signal, the charging capacitor charges, and the drive capacitor discharges to provide a relay current to the relay;
- and
- further wherein, during the period of the second frequency signal, the charging capacitor discharges into the base of the at least one transistor of the drive circuit, which causes the drive circuit to charge the drive capacitor and to provide a relay current to the relay.
Dependencies are inferred from the claim text.