Emerson Electric Co.
Safety gas valve relay driving circuits

Abstract:

A safety gas valve relay driving circuit for an HVAC system includes a gas valve relay including an output for selectively enabling and disabling a gas valve in an HVAC system according to an energization state of the gas valve relay, and a charge pump circuit to control energization of the gas valve relay. The charge pump circuit includes a charge pump capacitor. The driving circuit also includes first and second inputs for receiving first and second driving signals from at least one controller, a low-pass filter coupled between the first input and the charge pump circuit to filter the received first driving signal, and a high-pass filter watchdog circuit coupled between the second input and the charge pump circuit to filter the received second driving signal. Example methods of driving a gas valve relay for an HVAC system are also disclosed.