Circuit arrangement for flame detection

A method for detecting a flame in a burner having a transistor coil ignition system, which includes a trigger stage that triggers a power transistor located in a power circuit of a primary winding of an ignition coil, comprising the steps:

• restricting charging current flowing in the primary winding of the ignition coil to a current level below a charging current level needed to generate an ignition spark in an ignition phase;
• receiving a first signal from the primary winding, said first signal being produced when said charging current flowing in the primary winding of the ignition coil is interrupted;
• and
• processing said first signal to generate a second signal indicating whether a flame exists in the burner, wherein said step of processing said first signal to generate a second signal indicating whether a flame exists in the burner includes the steps of integrating said first signal and comparing said integrated first signal with a predetermined reference signal.

A flame detection circuit for a burner having a transistor coil ignition system that includes a trigger stage connected with a primary winding of an ignition coil for triggering a power transistor located in a power circuit of the primary winding of the ignition coil, comprising:

• current control means connected to said trigger stage for restricting charging current flowing in the primary winding of the ignition coil to a current level below a charging current level needed to generate an ignition spark in an ignition phase;
• and
• analysis means connected with the primary winding of the ignition coil, said analysis means comprising a first means for receiving a first signal from the primary winding, said first signal being produced when said charging current flowing in the primary winding of the ignition coil is interrupted, and a second means for generating a second signal indicating whether a flame exists in the burner, said analysis means further comprising:
• a rectifier connected with the primary winding of the ignition coil;
• integration means connected with said rectifier for integrating an output signal received from said rectifier;
• and
• a second comparator having a first input and a second input, wherein said first input of said second comparator is connected with said integration means, said second input of said second comparator is connected with a predetermined reference value, and said comparator produces a flame status signal that corresponds to a comparison of said signal received from said integration means and said reference value.

A flame detection circuit for a burner having a transistor coil ignition system that includes a trigger stage connected with a primary winding of an ignition coil for triggering a power transistor located in a power circuit of the primary winding of the ignition coil, comprising:

• current control means connected to said trigger stage for restricting charging current flowing in the primary winding of the ignition coil to a current level below a charging current level needed to generate an ignition spark in an ignition phase, said current control means comprising:
• a timing element;
• a first comparator having a first input and a second input;
• a switch connected with said timing element and said first input of said first comparator, said switch being actuated by said timing element and operating to apply a predetermined current level for one of a flame detection phase and an ignition phase to said first input of said first comparator;
• and
• a current sensor connected with the primary winding of the ignition coil and said second input of said first comparator, said current sensor operating to provide the current level in the primary winding of the ignition coil to said second input of said first comparator, and
• analysis means connected with the primary winding of the ignition coil, said analysis means comprising a first means for receiving a first signal from the primary winding, said first signal being produced when said charging current flowing in the primary winding of the ignition coil is interrupted, and a second means for generating a second signal indicating whether a flame exists in the burner.

A flame detection circuit for a burner having a transistor coil ignition system that includes a trigger stage connected with a primary winding of an ignition coil for triggering a power transistor located in a power circuit of the primary winding of the ignition coil, comprising:

• current control means connected to said trigger stage for restricting charging current flowing in the primary winding of the ignition coil to a current level below a charging current level needed to generate an ignition spark in an ignition phase, said current control means comprising:
• a first comparator having a first input and a second input;
• a ramp generator connected with said first input of said first comparator, said ramp generator providing a linearly rising output voltage to said first input of said first comparator;
• and
• a current sensor connected with the primary winding of the ignition coil and said second input of said first comparator, said current sensor operating to provide the current level in the primary winding of the ignition coil to said second input of said first comparator, and
• analysis means connected with the primary winding of the ignition coil, said analysis means comprising first means for receiving a first signal from the primary winding, said first signal being .produced when said charging current flowing in the primary winding of the ignition coil is interrupted, and a second means for generating a second signal indicating whether a flame exists in the burner.