Abstract: There is disclosed a combustion control circuit of a combustion apparatus with a driving signal generator, an exhaust fan controller and a gas valve controller, including: a combustion state detector for detecting the state of combustion occurring within a combustion chamber according to an output signal of a flame sensor installed in the combustion chamber, and for producing a signal corresponding to the state of combustion; a reference signal generator for producing a reference signal in response to each output signal of a temperature sensor and a flow sensor; a comparator for comparing the output signal of the combustion state detector with the output signal of the reference signal generator, and for outputting a signal corresponding to a difference therebetween; and an adder for adding the output signal of the comparator to the output signal of the driving signal-generator, and for respectively applying an output to each one of the exhaust fan controller and the gas valve controller.

Abstract: There is disclosed a combustion-state detecting circuit of a combustion apparatus installed in a combustion chamber, including: a flame detector that has a heat-emitting device for emitting heat on application of an alternating current signal, and produces a potential difference between the current applied to the heat-emitting device and flame-electric current produced by ignition occurring within the combustion chamber; a rectifier that changes the alternating current signal provided by the flame detector into a direct current signal; an inversion amplifier that inverts the direct current signal produced by the rectifier with respect to a reference signal and increases the magnitude of the inverted signal; and a flame discriminator that compares the output signal of the inversion amplifier with a flame discriminating reference signal to determine if ignition occurs.