Ignition boost and rectification flame detection circuit

Rectification flame detection circuit for detecting the presence of flame in a burner of a gas furnace, and in which pulsating current is applied to a relay coil in order to actuate the furnace, the flame detection circuit comprising

• a capacitor having first and second electrodes, the first electrode being connected to one end of said relay coil;
• a transistor having a control electrode, a common electrode and a power electrode, with a signal impedance being connected in series with said power electrode and a junction therebetween defining an output;
• a first resistor having one end connected to the second electrode of said capacitor and a another electrode connected to the control electrode of said transistor;
• a second resistor connected between the control and common electrodes of said transistor;
• and
• a flame detection conductor disposed in said burner and being electrically connected to the one electrode of said first resistor;
• such that the output is in one of an oscillating state or non-oscillating state if flame is present, and in the other state if flame is not present in the burner.

Combination gas burner igniter circuit and rectification flame detection circuit, in which an igniter and flame detection conductor starts a flame and also detects the presence of flame in a burner of a gas furnace, and in which pulsating current signals are applied respectively a first and second relay coils in order to actuate the furnace, the igniter circuit and flame detection circuit comprising

• a flyback rectifier having a first electrode connected to the first relay coil and a second electrode;
• charge storage means coupled to the second electrode of the flyback rectifier to accumulate a flyback voltage;
• a step-up transformer having a primary winding and a secondary winding, the secondary winding being connected to the igniter and flame detection conductor to provide a high voltage thereto;
• switching means coupled between the charge storage means and the primary winding of the step-up transformer for discharging the charge storage means through the primary winding whenever the stored flyback voltage reaches a suitable level to produce ignition;
• a capacitor having first and second electrodes, the first electrode being connected to one end of the second relay coil;
• a transistor having a control electrode, a common electrode and a power electrode, with a signal impedance being connected in series with said power electrode and a junction therebetween defining an output;
• a first resistor having one end connected to the second electrode of said capacitor and a another end connected to the control electrode of said transistor;
• a second resistor connected between the control and common electrodes of said transistor;
• and
• one end of said transformer secondary being connected to the one end of said first resistor, so that the igniter and flame detection conductor is connected through said transformer secondary and through said first resistor to said transistor;
• such that the output is in one of a first state and a second state if flame is present, and in the other state if flame is not present in the burner.