Patent ID: 9631838
Date: 2017-04-25
CPC Classifications: F24D,F24H,H02M,H03K

Claim:
1. An apparatus comprising: a sensor circuit configured to detect activation of at least one circulator arranged to circulate liquid from a boiler through at least one circulation loop and back to the boiler; an analog up/down timer circuit having an input coupled to an output of the sensor circuit and configured to generate a variable threshold signal that varies as a function of an activation time of said at least one circulator; a burner control circuit configured to receive the variable threshold signal from the analog up/down timer circuit and to generate an ignition control signal based at least in part on comparison of a temperature sensor signal of the boiler with the variable threshold signal; and an ignition driver configured to receive the ignition control signal from the burner control circuit and to generate an ignition signal for a burner configured to burn fuel to heat the liquid in the boiler based at least in part on the ignition control signal; wherein said at least one circulator comprises a plurality of circulators; and wherein the analog up/down timer circuit is configured to generate the variable threshold signal at least in part by being configured: to charge a charge storage element in a charge mode of operation for a period of time for which at least one of the plurality of circulators is activated; and to discharge the charge storage element in a discharge mode of operation for a period of time for which none of the plurality of circulators is activated.