Patent ID: 8875557

Claim:
A diagnostic flame sensing circuit comprising: a chopper; a high voltage DC source connected to a first terminal of the chopper; and a filter connected to a second terminal of the chopper; and wherein: a first output of the filter is provided to a flame sensor; a second output of the filter comprises diagnostic information; when the flame sensing circuit is activated, an analysis of the second output of the filter reveals a condition of one or more circuit components of the flame sensing circuit; and the revealed condition of one or more circuit components of the flame sensing circuit includes one or more of: a resistor having leakage; a resistor being open; a capacitor being smaller than normal; a resistor to resistor ratio being incorrect; a capacitor being shorted; a frequency of a pulse width modulator being too low; a capacitor having leakage; the sensing timing of an analog-to-digital converter being out of sync with an output signal of the chopper; the chopper having stopped; a DC-DC voltage converter component not operating; a frequency of a pulse width modulator being too low; a capacitor being open; the output of the second filter containing too much noise; and a microcontroller having lost control over the chopper.