Automatic temperature control device for an electric appliance such as an electric blanket
First Claim
1. An automatic temperature control device for an electric appliance comprising:
- a heater element connected to an alternating current source to be fed therefrom;
a sensor made of a thermosensitive material having an impedance, which changes as the temperature varies, for detecting the temperature of said heater element;
a temperature responsive circuit including a grounded-base transistor with its base-emitter circuit connected in series with said sensor, the series connection being connected across said alternating current source, and a diode connected across the base-emitter junction of said transistor so that the P-N junction of said diode and the base-emitter junction of said transistor are coupled in the direction opposite to each other, whereby a collector current of said grounded-base transistor is used as a sensed signal;
an electric potential setting circuit for producing an electric potential for setting a desired temperature;
a comparison circuit for comparing an output signal of said temperature responsive circuit with an output signal of said electric potential setting circuit; and
switching means driven by an output of said comparison circuit and connected in series with said heater element for regulating the supply of electric power to said heater element.
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Accused Products
Abstract
The automatic temperature control device for an electric appliance such as an electric blanket comprises a heater element, a sensor made of a thermosensitive material having an impedance, which changes as the temperature varies, for detecting the temperature of the heater element, switching means for regulating the supply of electric power to the heater element, and a plurality of electric circuits for driving the switching means in response to the output signal from the sensor. The plurality of electric circuits function to prevent the sensor from being polarized and to detect a temperature signal by applying thereto an alternating current, to detect a failure occurring in the electric circuits in synchronism with zero-crossing pulses, and to detect a failure occurring in the switching means, thereby assuring a safe operation of the automatic temperature control device against the occurrence of any failure.
70 Citations
10 Claims
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1. An automatic temperature control device for an electric appliance comprising:
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a heater element connected to an alternating current source to be fed therefrom; a sensor made of a thermosensitive material having an impedance, which changes as the temperature varies, for detecting the temperature of said heater element; a temperature responsive circuit including a grounded-base transistor with its base-emitter circuit connected in series with said sensor, the series connection being connected across said alternating current source, and a diode connected across the base-emitter junction of said transistor so that the P-N junction of said diode and the base-emitter junction of said transistor are coupled in the direction opposite to each other, whereby a collector current of said grounded-base transistor is used as a sensed signal; an electric potential setting circuit for producing an electric potential for setting a desired temperature; a comparison circuit for comparing an output signal of said temperature responsive circuit with an output signal of said electric potential setting circuit; and switching means driven by an output of said comparison circuit and connected in series with said heater element for regulating the supply of electric power to said heater element. - View Dependent Claims (2, 3, 4, 5)
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6. An automatic temperature control device for an electric appliance comprising:
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a heater element connected to an alternating current source to be fed therefrom; switching means triggered by a triggering pulse for regulating the supply of ac power to said heater element; a sensor made of a thermosensitive material having an impedance, which changes as the temperature varies, for detecting the temperature of said heater element; a temperature responsive circuit for detecting the temperature of said heater element by detecting a change in the impedance of said sensor; an electric potential setting circuit for producing an electric potential for setting a desired temperature; a pulse supply circut for producing a zero-crossing pulse; a comparison circuit for comparing an output signal of said temperature responsive circuit with an output signal of said electric potential setting circuit in synchronism with the zero-crossing pulse and producing another zero-crossing pulse when the temperature of said heater element is lower than the set desired temperature; and a pulse discriminating circuit which comprises a circuit formed of resistors, a capacitor and switching elements operating such that in the absence of said another zero-crossing pulse supplied thereto from said comparison circuit, the capacitor stores electric charge supplied from a dc power supply through a resistor, and, upon receipt of said another zero-crossing pulse, the switching elements are turned on to discharge the electric charge stored in the capacitor through said switching means to supply the triggering pulse thereto. - View Dependent Claims (7, 8, 9, 10)
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Specification