Patent Application
20130186882
The present invention relates to a temperature control method for a heating line and, more particularly, to a temperature control method for a heating line, which is capable of controlling the temperature effectively and adjusting the working temperature and is suitable for heaters such as electrothermal furnaces and heating pads for hot compression.
Heaters such as heating pads are widely available in the market currently. Usually, the heating of a heating line will be automatically interrupted on condition that the temperature reaches a certain value preset by users. Thereby, the temperature of the heaters can be kept within a preset range in order to provide functions such as hot compression while ensure the safety of the users.
In order to control temperature effectively, as described in a US patent (U.S. Pat. No. 5,861,610), an element of positive temperature coefficient (abbreviated as PTC hereinafter) is used as a detection line. As described in a US patent (U.S. Pat. No. 6,943,327), an element of negative temperature coefficient (abbreviated as NTC hereinafter) is used as a detection line for sensing the temperature change, and consequently the element can be used together with a heating line for temperature-controlled heating. In this case, when the temperature of the detection line increases with the temperature of the heating line or the resistance of the detection line changes as a result of the high temperature, the comparison will occurs in the comparison circuit of the processor. On the basis of the comparison result, the current flowing into the heating line is adjusted so as to control and keep the temperature within a range preset by users.
Another US patent (U.S. Pat. No. 7,180,037) disclosed other application examples of PTC elements or NTC elements. In this patent, the technical feature distinguished from above conventional techniques is as follows: a first zero cross signal in response to the detection of a zero crossing of the AC power signal; a second zero cross signal in response to the zero crossing of the phase shifted AC power signal produced by detecting that the resistor of a PTC or NTC element is changed due to temperature; a time difference determinator circuit used to measure the phase-shift time of the first zero cross signal and the second zero cross signal continually; a controller used for calculation and outputting a control signal to render the circuit in conducting or disconnecting state; consequently, the temperature of the heating can be kept within a certain range.
The whole circuit configuration disclosed in above US patent (U.S. Pat. No. 7,180,037) is quiet complicated. Moreover, the temperature-control function can be performed only by the detection and calculation of the time difference determinator circuit and the controller. However, the manufacturing cost is inevitably increased.
In order to overcome above shortcomings, inventor had the motive to study and develop the present invention to provide a temperature control method for a heating line, which is distinguished from above prior arts and have advantages of effectively controlling temperature, simplifying the structure, and reducing the manufacturing cost.
An object of the present invention is to provide a temperature control method for a heating line, where it is capable of forming synthesized pulse wave signals from the continuous and changing pulse wave signals produced by the heated heating wire and the continuous reference pulse wave signals. Besides, by means of detecting the pulse width of the synthesized pulse wave signals, it is able to control the heating of the heating wire in order to keep the temperature within a preset range. Moreover, it is also able to simplify the structure and consequently reduce the manufacturing cost.
Another object of the present invention is to provide a temperature control method for a heating line, where it is capable of adjusting the time point in which the logic high state terminates for continuous reference pulse wave signals, so as to stop the heating of the heating wire. Thereby, it is easy for users to adjust the working temperature of the heating line.
In order to achieve above objects, the present invention provides a temperature control method for a heating line, where the heating line includes a heating wire and an insulation-and-meltable layer covering the peripheries of the heating wire; one end of the heating wire is coupled with one polarity of a power while another end of the heating wire is coupled with a switch, and the switch is coupled with a reverse polarity of the power; the switch is in conducting or disconnecting condition by means of the control of a control circuit having a processor; the temperature control method comprising steps of: a. having the power output continuous reference pulse wave signals via a pulse wave output circuit; b. utilizing a pulse wave detection circuit to detect continuous and changing pulse wave signals produced according to the temperature change of the heating wire during the heating process of the heating wire; c. utilizing an And-gate to obtain continuous synthesized pulse wave signals from the continuous reference pulse wave signals and the continuous and changing pulse wave signals, where each synthesized pulse wave signal has a pulse width that spans from a time point in which a logic high state begins to a time point in which the logic high state terminates; and d. controlling the control circuit to stop triggering the switch so as to stop the heating of the heating wire when the time point in which the logic high state begins moves in relative to the time point in which the logic high state terminates during the heating process of the heating wire and when the pulse width of the synthesized pulse wave signals reaches a value preset by the processor.
In implementation, the heating line is a positive temperature coefficient (PTC) or a negative temperature coefficient (NTC).
In implementation, in step b, the pulse wave detection circuit utilizes a temperature sensing element to detect the temperature change of the heating wire, so as to produce continuous and changing pulse wave signals by means of voltage comparison.
In implementation, the temperature sensing element is a sensing line or a thereto-sensitive resistor.
In implementation, the present invention further comprises a step for temperature adjustment by means of adjusting the time point in which the logic high state terminates for any reference pulse wave signal in order to stop the heating of the heating wire.
The following detailed description, given by way of examples or embodiments, will best be understood in conjunction with the accompanying drawings.
Please refer to
In this case, the heating wire 11 is a positive temperature coefficient (PTC) conducting wire. However, the heating wire 11 also can be a negative temperature coefficient (NTC) conducting wire, so as to increase or decrease the resistance when the temperature rises during the heating process.
As shown in
Each synthesized pulse wave signal has a pulse width W. The width W spans from a time point T1 in which a logic high state begins to a time point T2 in which the logic high state terminates. As to the synthesized pulse wave signals synthesized by And-gate, the time point T2 in which the logic high state terminates for the synthesized pulse wave signal is immovable. When the temperature of the heating wire 11 rises, the time point T1 in which a logic high state begins will move toward the time point T2 in which the logic high state terminates. In this way, the pulse width W of each synthesized pulse wave signal will decrease gradually until it reaches to the pulse width W1 of the synthesized pulse wave signal preset by the processor. Consequently, the control circuit stops triggering the switch 2 to stop the heating of the heating wire 11. When the temperature of the heating wire 11 declines, the time point T1 in which a logic high state begins will gradually move away from the time point T2 in which the logic high state terminates. In other words, the pulse width W of each synthesized pulse wave signal will increase gradually until it reaches to the pulse width W of the synthesized pulse wave signal preset by the processor. Consequently, the control circuit 3 will trigger the switch 2 again to restore the heating of the heating wire 11.
If the heating wire 11 is a negative temperature coefficient (NTC) conducting wire, the pulse width W of each synthesized pulse wave signal will increase with the increase of the temperature of the heating wire 11. When the temperature of the heating wire 11 decreases, the pulse width W of each synthesized pulse wave signal will decrease as well. In this way, when the pulse width reaches the value of the pulse width W1 of the synthesized pulse wave signal preset by the processor, it is able to stop or continue the heating of the heating wire 11 in order to keep the temperature within a preset range.
Moreover, the present invention further comprises a step for temperature adjustment by means of adjusting the time point T3 in which the logic high state terminates for any reference pulse wave signal. For example, the time point T3 in which the logic high state terminates is moved rightward. In this case, because the control circuit will not trigger switch until the same pulse width W is reached, it is able to make adjustment to increase the temperature at which the heating of the heating wire is stopped in order to adjust the temperature range.
In this embodiment, the pulse wave detection circuit 5 is used to detect directly the resistance change of the heating wire 11. As shown in
Please refer to
As shown in
The And-gate 6 includes a first diode D1 and a second diode D2 both of which are in parallel connection. The negative pole of the first diode D1 is connected to the output end of the first voltage comparator U1A. The positive pole of the first diode D1 is connected to the power 9. Besides, a first node P1 is provided between the first diode D1 and the power 9. The positive pole of the second diode D2 is coupled to the output end of the second voltage comparator U2A. The negative pole of the second diode D2 is coupled with the first node P1.
Thereby, the continuous reference pulse wave signals and the continuous and changing pulse wave signals can be synthesized by the And-gate 6 to produce continuous synthesized pulse wave signals. By means of adjusting the variable resistor VR1, it is able to adjust the time point T3 in which the in which the logic high state terminates for any reference pulse wave signal and consequently to adjust the heating temperature.
In implementation, the And-gate can be replaced by any microprocessor with the same function. Besides, the switch 2 is a thyristor, such as a SCR or a TRIAC.
Please refer to
Thereby, it is also able to obtain the continuous synthesized pulse wave signals from the continuous and changing forward pulse wave signals (that are output after being under the voltage comparison via the first voltage comparator U1A of the pulse wave detection circuit 5) and the continuous reverse reference pulse wave signals (that are output via the third voltage comparator U3A of the pulse wave output circuit 4). Besides, when the pulse width W of the synthesized pulse wave signals reaches the value of the pulse width W1 for synthesized pulse signals preset by the processor, it will prevent the control circuit 3 from triggering the switch 2 and consequently stop the heating of the heating wire 11.
Therefore, the present invention has following advantages:
1. According to the present invention, the heating of the heating line is controlled by the detection of the pulse width of a synthesized pulse wave signal. Consequently, it is able to keep effectively the temperature within a certain range, to simplify the structure, and to reduce manufacturing cost.
2. According to the present invention, the temperature at which the heating of the heating wire is stopped can be adjusted by making adjustment to the time point in which the logic high state terminates for a continuous reference pulse wave signal and by detecting the pulse width of a synthesized pulse wave signal. Consequently, users are capable of adjusting the working temperature to a much greater extent.
As disclosed in above descriptions and attached drawings, the present invention provides a temperature control method for a heating line, which is effective to control the temperature, has simple structure, and has reduced manufacturing cost. It is new and can be put into industrial use.
Although the embodiments of the present invention have been described in detail, many modifications and variations may be made by those skilled in the art from the teachings disclosed hereinabove. Therefore, it should be understood that any modification and variation equivalent to the spirit of the present invention be regarded to fall into the scope defined by the appended claims.
