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An improved timed-off control apparatus and method are provided to prevent excessive cycling of an electrically operated device, such as an air conditioning compressor. The timed-off control apparatus provides a predetermined timed-off period (e.g., five minutes), during which the electrically opera

An improved timed-off control apparatus and method are provided to prevent excessive cycling of an electrically operated device, such as an air conditioning compressor. The timed-off control apparatus provides a predetermined timed-off period (e.g., five minutes), during which the electrically operated device is constrained to remain in an off state after the device is deactivated by a loss of power. For example, in an air conditioning system, fluctuations in power supply voltage and thermostat switch bounces may result in excessive cycling of the system compressor. By constraining the compressor to remain deactivated for the selected timed-off period, the compressor is protected against excessive cycling. In order to achieve consistent and predictable timed-off periods, a field effect transistor (FET) is used in conjunction with a resistance/capacitance (RC) circuit. When the power supply is interrupted, the FET is turned off state and remains off during the timed-off period. When the FET is off, the compressor remains off, even if electrical power becomes available during the timed-off period. The FET monitors the voltage across the capacitor of the RC circuit while the capacitor is being discharged and when the voltage drops below a predetermined threshold, the FET is turned on to allow resumption of compressor operation. The time at which the voltage across the capacitor reaches the predetermined threshold is a function of the capacitor discharge rate. Because the FET does not draw biasing current, the capacitor discharge rate is not affected by the FET. Therefore, consistent and predictable timed-off periods are achieved.

대표청구항 ▼

Apparatus for controlling start-up of an electrically operated device after an electrical power supply outage, said apparatus comprising: resistor means having a predetermined electrical resistance; capacitor means having a predetermined electrical capacitance and being electrically connected to sai

Apparatus for controlling start-up of an electrically operated device after an electrical power supply outage, said apparatus comprising: resistor means having a predetermined electrical resistance; capacitor means having a predetermined electrical capacitance and being electrically connected to said resistor means, said capacitor means being chargeable by an electrical power supply and being dischargeable at a predetermined rate in response to an electrical power supply outage; field effect transistor means electrically connected to said capacitor means and to said resistor means and being responsive to voltage across said capacitor means when said capacitor means is being discharged, said field effect transistor means being turned off in response to a first voltage indicating that said capacitor means is being discharged and being turned on in response to a second voltage indicating that said capacitor means has been discharging for a predetermined time; and switch means electrically connected in series between the electrical power supply and the device, said switch means being opened by said field effect transistor means in response to said first voltage for isolating the electrical power supply from the device and being closed by said field effect transistor means in response to said second voltage for electrically connecting the electrical power supply to the device.