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US 6,794,771 B2Granted
Fault-tolerant multi-point flame sense circuit
AssigneeRanco Incorporated of Delaware
InventorBrian L. Orloff
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AssigneeRanco Incorporated of Delaware
InventorBrian L. Orloff
Estimating the term…
A fault-tolerant multi-point flame sense circuit utilizes a single electronic switch to signal the presence or absence of flame to an electronic controller. Multiple flame sense electrodes may be input to this circuit. By configuring these electrodes in accordance with the present invention, cross-contamination of a single failed flame sense electrode will not affect the other flame sense electrodes' ability to sense a flame at their associated burner. The circuit provides inputs for a number of flame sense electrodes via input channels that are capacitively coupled to the line voltage and resistively coupled to an RC network that controls the state of an electronic switch. When a flame is present at any one of the electrodes, the resulting unbalance current flow through the RC network turns the switch off to indicate the presence of flame. This operation is not affected by a short on any other electrode in the circuit.
A fault-tolerant multi-point flame sense circuit, comprising:
A fault-tolerant multi-point flame sense circuit, comprising:
A fault-tolerant multi-point flame sense circuit, comprising:
A fault-tolerant multi-point flame sense circuit, comprising:
A flame sense circuit, comprising a first flame sense electrode coupled through a first resistor to a first node coupling a first capacitor and a second resistor, the first capacitor being coupled to a line voltage input and the second resistor being coupled to a flame sense input node, the flame sense input node being coupled to a third resistor that is coupled to a gate of a junction field effect transistor, a drain of which is coupled through a resistor to a control voltage input and a source of which is coupled to ground, the flame sense input node further being coupled to a fourth resistor and to a second capacitor, both of which are also coupled to ground, and a second flame sense electrode coupled through a sixth resistor to a second node coupling a third capacitor and a seventh resistor, the third capacitor being coupled to the line voltage input and the seventh resistor being couple to the flame sense input node.
Dependencies are inferred from the claim text.