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US 7,256,371 B2Granted
Temperature control method for positive temperature coefficient type heating element
AssigneeIntegrated Electronic Solutions Pty Ltd.
InventorsJohn Crawford, Mark Potter, Kevin Altschwager
Life of this patent
Estimating the term…
Abstract
A controller adapted to control the temperature of a heating elements with a wide range of positive temperature coefficient of resistance, including very low values, using a sensor in line with the heating element. The controller is able to take account of non-constant mains power supplies and variation in the element resistance over time.
Claims19
A controller adapted to control the temperature of a heating element within a selected temperature range wherein the instantaneous electrical resistance of the element is measured to determine the instantaneous temperature of the element, comprising:
- a heating element of a type where the electrical resistance of the element increases with increasing element temperature;
- a switch adapted to electrically couple a sinusoidal alternating current power source to the heating element when a switch controller is in an ON state, and to decouple the sinusoidal alternating current power source from the heating element when the switch controller is in an OFF state;
- a current sensor coupled in series with the heating element and adapted to provide as an output a voltage, wherein the current sensor comprises a sense resistor, wherein said voltage is dependent on the magnitude of a electrical current passing through the heating element and said sense resistor;
- a zero set point controller adapted to supply a first voltage proportional to a supply voltage of the sinusoidal alternating mains current power source;
- a difference sensor with a first input connected to the current sensor, and
- a second input connected to the zero set point controller adapted to produce an output signal which is dependent on the difference between voltage signals received at the first and second inputs,
- an operational set point controller adapted to supply a second voltage proportional to the supply voltage of the sinusoidal alternating mains current power source, the value of the second voltage being dependent on a selected desired temperature of operation of the heating element;
- a timer adapted to supply timing pulses of a selected pulse duration and period;
- a threshold detector electrically connected to receive the output signal of the difference sensor and the output signal of the operational set point controller and adapted to provide a selected output when an extent of magnitude and direction of difference between the said signals is greater than a selected extent;
- and
- logic circuitry adapted to set the switch controller to an ON state in response to a said timing pulse, and to reset the switch controller to an OFF state in response to the selected output from the threshold detector.
8 more elements
A controller adapted to control the temperature of a heating element within a selected temperature range wherein the instantaneous electrical resistance of the element is measured to determine the instantaneous temperature of the element, comprising:
- a heating element of a type where the electrical resistance of the element increases with increasing element temperature;
- a switch adapted to control the flow of an alternating current to the heating element when a switch controller is in an ON state, and to decouple the sinusoidal alternating current power source from the heating element when the switch controller is in an OFF state;
- a current sensor coupled in series with the heating element and adapted to provide as an output a voltage, wherein the current sensor comprises a sense resistor, wherein said voltage is dependent on the magnitude of an electric current passing through the heating element and said sense resistor;
- a zero set point controller adapted to supply a first voltage proportional to a supply voltage of the sinusoidal alternating current power source;
- a difference sensor with a first input connected to the current sensor, and
- a second input connected to the zero set point controller adapted to produce an output signal which is dependent on the difference between voltage signals received at the first and second inputs,
- an operational set point controller adapted to supply a second voltage proportional to the supply voltage of the sinusoidal alternating current power source, the value of the second voltage being dependent on a selected desired temperature of operation of the heating element;
- further including a microcontroller including software to provide a timing function generating timing pulses having a predetermined pulse duration and period, said pulses causing the switch controller to turn the switch ON at predetermined intervals, the microcontroller being further adapted to receive the output signal of the difference sensor and the output signal of the operational set point controller and to provide a selected output when an extent of magnitude and direction of difference between the said signals is greater than a selected extent;
- and
- logic circuitry adapted to set the switch controller to an ON state in response to a said timing pulse, and to reset the switch controller to an OFF state in response to the selected output from the threshold detector.
7 more elements
Dependencies are inferred from the claim text.