AC power control

Claim 1

A device for regulating delivery of ac power from an ac voltage source to a load in response to changes in the state of a predetermined condition, the ac voltage source having an instantaneous phase angle, the device comprising: a switching means for controlling flow of current through the load in response to the ac voltage, the switching means having a conductive state in which the switching means permit flow of current through the load and a non-conductive state in which the switching means prevent flow of current through the load, the switching means requiring application of a triggering signal in each half cycle of the ac voltage to assume the conductive state; phase angle signal generating means responsive to the ac voltage for generating a phase angle signal corresponding to the instantaneous phase angle of the ac voltage relatie to the most recent zero crossover of the ac voltage; sensor means for sensing the current state of the predetermined condition, the sensor means comprising a sensor whose resistance varies with the current state of the predetermined condition; threshold signal generating means responsive to the sensor means for generating a threshold signal varying with the sensed current state of the predetermined condition, the threshold signal generating means comprising: (a) means defining a voltage divider, the sensor being an element of the voltage divider; (b) dc supply means adapted to be powered by the ac voltage for so applying a dc voltage to the voltage divider that a divider voltage whose magnitude is dependent on the resistance of the sensor is generated; and (c) amplifier means for amplifying the divider voltage; and, comparison means for comparing the phases angle signal with the threshold signal and for applying a triggering signal to the switching means whenever the phase angle signal corresponds to the threshold signal.

Claim 2

A device for regulating delivery of ac power from an ac voltage source to a load in response to changes in the state of a predetermined condition, the ac voltage source having an instantaneous phase angle, the device comprising: a switching means for controlling flow of current through the load in response to the ac voltage, the switching means having a conductive state in which the switching means permit flow of current through the load and a non-conductive state in which the switching means prevent flow of current through the load, the switching means requiring application of a triggering signal in each half cycle of the ac voltage to assume the conductive state; phase angle signal generating means responsive to the ac voltage for generating a phase angle signal corresponding to the instantaneous phase angle of the ac voltage relatie to the most recent zero crossover of the ac voltage; sensor means for sensing the current state of the predetermined condition, the sensor means comprising a sensor whose resistance varies with the current state of the predetermined condition; threshold signal generating means responsive to the sensor means for generating a threshold signal varying with the sensed current state of the predetermined condition, the threshold signal generating means comprising: (a) means defining a voltage divider, the sensor being an element of the voltage divider; (b) dc supply means adapted to be powered by the ac voltage for so applying a dc voltage to the voltage divider that a divider voltage whose magnitude is dependent on the resistance of the sensor is generated; and (c) amplifier means for amplifying the divider voltage; and, comparison means for comparing the phases angle signal with the threshold signal and for applying a triggering signal to the switching means whenever the phase angle signal corresponds to the threshold signal.

Claim 6

A device for regulating delivery of ac power from an ac voltage source to a load in response to changes in the state of a predetermined condition, the ac voltage source having an instantaneous phase angle, the device comprising: a switching means for controlling flow of current through the load in response to the ac voltage, the switching means having a conductive state in which the switching means permit flow of current through the load and a non-conductive state in which the switching means prevent flow of current through the load, the switching means requiring application of a triggering signal in each half cycle of the ac voltage to assume the conductive state; phase angle signal generating means responsive to the ac voltage for generating a phase angle signal corresponding to the instantaneous phases angle of the ac voltage relative to the most recent zero crossover of the ac voltage, the phase angle generating means comprising: (a) zero crossover detection means for detecting zero crossovers of the ac voltage, the zero crossover detection means comprising: (1) full-wave rectification means for producing a fullwave rectified signal corresponding to the ac voltage; and (2) pulse-generating means for producing a pulse whenever the magnitude of the full-wave rectified signal is less than a predetermined threshold value; (b) resettable signal generating means for generating a predetermined signal of continuously increasing magnitude whenever the signal generating means are reset, the predetermined signal corresponding to the phase angle signal; the resettable signal generating means comprising an RC charging circuit, the RC charging circuit having a time constant substantially determined by the product of the resistance of a single resistor and the capacitance of a single capacitor; and (c) resetting means responsive to the zero crossover detection means for resetting the resettable signal generating means whenever a zero crossover of the ac voltage has been detected, the resetting means comprising a semiconductor switching means triggered to discharge the capacitor whenever the pulse generating means produces a pulse, the semiconductor switching means comprising a transistor; and sensor means for sensing the current state of the predetermined condition; threshold signal generating means responsive to the sensor means for generating a threshold signal varying with the sensed current state of the predetermined condition; comparison means for comparing the phase angle signal with the threshold signal and for applying a triggering signal to the switching means whenever the phase angle signal corresponds to the threshold signal.

Claim 7

A device for regulating delivery of ac power from an ac voltage source to a load in response to changes in the state of a predetermined condition, the ac voltage source having an instantaneous phase angle, the device comprising: a switching means for controlling flow of current through the load in response to the ac voltage, the switching means having a conductive state in which the switching means permit flow of current through the load and a non-conductive state in which the switching means prevent flow of current through the load, the switching means requiring application of a triggering signal in each half cycle of the ac voltage to assume the conductive state; phase angle signal generating means responsive to the ac voltage for generating a phase angle signal corresponding to the instantaneous phases angle of the ac voltage relative to the most recent zero crossover of the ac voltage, the phase angle generating means comprising: (a) zero crossover detection means for detecting zero crossovers of the ac voltage, the zero crossover detection means comprising: (1) full-wave rectification means for producing a fullwave rectified signal corresponding to the ac voltage; and (2) pulse-generating means for producing a pulse whenever the magnitude of the full-wave rectified signal is less than a predetermined threshold value; (b) resettable signal generating means for generating a predetermined signal of continuously increasing magnitude whenever the signal generating means are reset, the predetermined signal corresponding to the phase angle signal; the resettable signal generating means comprising an RC charging circuit, the RC charging circuit having a time constant substantially determined by the product of the resistance of a single resistor and the capacitance of a single capacitor; and (c) resetting means responsive to the zero crossover detection means for resetting the resettable signal generating means whenever a zero crossover of the ac voltage has been detected, the resetting means comprising a semiconductor switching means triggered to discharge the capacitor whenever the pulse generating means produces a pulse, the semiconductor switching means comprising a transistor; and sensor means for sensing the current state of the predetermined condition; threshold signal generating means responsive to the sensor means for generating a threshold signal varying with the sensed current state of the predetermined condition; comparison means for comparing the phase angle signal with the threshold signal and for applying a triggering signal to the switching means whenever the phase angle signal corresponds to the threshold signal.