Heater with duty cycle controller
First Claim
1. A heater control apparatus comprising:
- (a) a user temperature selection means for producing a signal representative of a user selected temperature;
(b) an ambient temperature sensor means for producing a signal representative of the ambient temperature;
(c) a comparator means responsive to the user selected temperature signal and ambient temperature signal for producing a difference signal, said comparator means having a positive feedback means operatively connected thereto for producing a duty cycle having a set hysteresis range, and a negative feedback means operatively connected thereto for defining a temperature range, said negative feedback means responsive to the difference signal for regulating the on and off time of the duty cycle;
(d) an alternating current zero crossing determining means operatively connected to the comparator means for producing output time periods at the zero crossings during which difference signals from the first comparator means are passed as load driver control signals; and
(e) a load driver means responsive to the load driver control signals for producing regulated power, whereby heater operation is controlled by the regulated heater supply power.
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Accused Products
Abstract
A heater including a sensing device for sensing an ambient temperature, a temperature input device for providing a user selectable input temperature both connected to a first circuit to control the heater. The first control circuit includes positive feedback and negative feedback to electrically define a temperature range. The first circuit provides an on/off time duty cycle output wherein the on to off time of the duty cycle is relative to the relationship between the temperature range and the sensed ambient temperature. A second circuit is connected to receive the duty cycle output from the first circuit and is further connected to an alternating current power source to provide a second output signal during the zero crossing of the alternating current power source and when the duty cycle output is present. A driver circuit is connected to receive this second signal and activates the heater when the second signal is active by providing a third signal to a triac which regulates power to the heater.
44 Citations
11 Claims
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1. A heater control apparatus comprising:
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(a) a user temperature selection means for producing a signal representative of a user selected temperature; (b) an ambient temperature sensor means for producing a signal representative of the ambient temperature; (c) a comparator means responsive to the user selected temperature signal and ambient temperature signal for producing a difference signal, said comparator means having a positive feedback means operatively connected thereto for producing a duty cycle having a set hysteresis range, and a negative feedback means operatively connected thereto for defining a temperature range, said negative feedback means responsive to the difference signal for regulating the on and off time of the duty cycle; (d) an alternating current zero crossing determining means operatively connected to the comparator means for producing output time periods at the zero crossings during which difference signals from the first comparator means are passed as load driver control signals; and (e) a load driver means responsive to the load driver control signals for producing regulated power, whereby heater operation is controlled by the regulated heater supply power. - View Dependent Claims (2, 3, 4, 5, 6, 8, 9, 10, 11)
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7. A heater control apparatus according to claim 13 further including a power supply circuit for providing power to said comparator means, said zero crossing means, and said driver circuit said power supply circuit including a capacitive filter connected in parallel with a zener diode for producing directly from an alternating current source the positive direct power supply voltage.
Specification