JPH0830990B2 - Temperature control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a temperature control device for an electric heating appliance such as an electric blanket or an electric carpet.

(Prior Art) A conventional temperature control device for an electric heating appliance such as an electric blanket or electric carpet will be described with reference to FIGS. 3 to 5.

FIG. 3 is a block diagram of a heating element integrated with a temperature sensor used for an electric blanket. Reference numeral 1'denotes a core wire, on which a heating element 2'is wound, on which a sensor (temperature sensitive element) 3'by a plastic thermistor is coated, and a temperature detecting electrode wire 4'is wound on it. An insulating jacket 5'is coated on it. The temperature sensing element 3'and the temperature detection electrode wire 4'constitute a temperature sensor. The blanket usually uses a heating element integrated with a temperature sensor with a length of about 25 m.

FIG. 4 shows the characteristics of the temperature sensor. The vertical axis represents the impedance Z of the temperature sensor, the horizontal axis represents the temperature T, L represents the low temperature side, and H represents the high temperature side. The characteristic of the temperature sensor can be shown as a combined value Z _T of the impedance Z _{C formed} by the capacitance between the heating element 2 ′ and the impedance Z _{R formed by} the resistance.

FIG. 5 shows a conventional example of a temperature control device using this heating element and temperature sensor. This conventional example was introduced in Japanese Patent Laid-Open Publication No. 59-231618. In the figure, V _AC is an AC power supply, 1 is a DC power supply circuit, and is composed of a diode 2, a resistor 3 and a capacitor 4, and produces a DC voltage V _CC . Reference numeral 5 is a heating element, 6 is a power control element for controlling energization of the heating element 5, 7 is a gate resistor, and 8
Is a temperature detecting electrode wire, 9 is a temperature sensitive element interposed between the heat generating element 5 and the temperature detecting electrode wire 8, and the impedance consisting of resistance and capacitance changes depending on the temperature of the heat generating element 5. The temperature sensor is composed of 8 and the temperature sensitive element 9.

Reference numeral 10 is a temperature detection circuit, which is composed of a temperature detection transistor 11, a resistor 12, a capacitor 13 and a diode 14. The transistor 11 conducts when the power control element 6 is in a non-conducting voltage, and collector → emitter → temperature detection electrode wire. A temperature detection current determined by the impedance of the temperature sensitive element 9 flows through the path of 8 → the temperature sensitive element 9 → the heating element 5. A resistor 12 and a capacitor 13 connected to the collector of the transistor 11 convert the temperature detection current into a voltage and convert the temperature detection voltage into a capacitor.
It is generated at both ends of 13 and is the detection signal V _T. Reference numeral 14 is a base-emitter reverse voltage control diode of the transistor 11.
Reference numeral 15 is a disconnection detection circuit for checking the disconnection of the temperature detection electrode wire 8 and outputs a detection signal V _S. Reference numeral 16 is a transistor for applying a disconnection detection current, and 17 is a transistor for driving the transistor 16, which is biased by a resistor 18 connected to the collector. Reference numerals 19 and 20 are base-emitter resistors. Reference numeral 21 is a transistor that drives the transistor 17, and is connected to the base of the transistor 17 via the resistor 22. A constant current source 23 biases the disconnection detection circuit output transistor 28 via a shift circuit composed of diodes 24, 25, 26 and a resistor 27. Further, the constant current source 23 is bypassed as a disconnection detection current via the transistor 16. 29 is a capacitor, and when the temperature detection electrode line 8 is not disconnected, the transistor 17
During the period when it is not turned on, from the DC voltage V _{CC generated} by the DC power supply circuit 1, the capacitor 29 → the resistor 30 → the temperature detection electrode wire 8
→ Charged by the current flowing through the diode 14. When the transistor 17 is turned on, a part of the charge accumulated in the capacitor 29 flows in the order of capacitor 29 → transistor 17 → resistor 18 → resistor 19 and the base-emitter of transistor 16 → diode 31 → capacitor 29. Then, the transistor 16 is turned on, and the electric charge remaining in the capacitor 29 is discharged through the transistor 16 and the diode 31 while the current is limited by the constant current source 23. Therefore, diodes 24, 25, 26 → resistor 27 and transistor
The current flowing through the base of 28 disappears and transistor 28
When turned off, the detection signal V _S becomes a Hi signal. When the temperature detection electrode wire 8 is broken, the charging current does not flow to the capacitor 29. Therefore, since electric charge is not accumulated in the capacitor, the electric current flowing from the constant current source 23 passes through the transistor 16 and the capacitor 29 through the transistor 16 even while the transistor 17 is ON.
Discharge current of the diode 24,25,26, resistor 2
7. Continue to flow towards transistor 28, transistor 28
Keeps on all the time. Therefore, at the time of disconnection, the detection signal V _S remains Lo, so that disconnection can be detected. Reference numeral 32 denotes a control circuit, which processes the detection signal V _T of the temperature detection circuit 10 and the detection signal V _S of the disconnection detection circuit 15 to generate the power control element 6
The gate trigger signal V _G is output to control the temperature of the heating element 5. V _H indicates the anode waveform of the power control element 6, and when the temperature detection electrode wire 8 is not disconnected and the temperature of the heating element 5 is lower than the set temperature, the power control element 6 is controlled by the gate trigger signal V _G of the control circuit. Is turned on, and the power control element 6 is turned on even when the temperature of the heating element 5 is lower than the set temperature when the wire is disconnected.
It means that it does not become. Reference numeral 33 is a pulse generation circuit that generates an output pulse V _P synchronized with the _AC power supply V _AC .

(Problems to be Solved by the Invention) In the above temperature control device, when the length of the temperature sensor used is further increased and the impedance is lowered, or when the material of the temperature sensing element is changed and the impedance is lowered. When the temperature detection electrode wire is broken, the capacitor 29 is connected to the capacitor 29 → resistor 30 → temperature detection electrode wire 8 → temperature sensing element 9 → heating element from the DC voltage V _CC created by the DC power supply circuit 1. 5 → become large current flows through a path of the AC power source V _AC, by the current, the capacitor 29 will be charged. Then, when the transistor 17 is turned on, a part of the electric charge accumulated in the capacitor 29 is transferred to the transistor 17 → resistor 18 → resistor 19 and the transistor 19.
While flowing between the base and emitter of 16 to discharge, the transistor 16 is turned on, and the electric charge remaining in the capacitor 29 is discharged via the transistor 16 and the diode 31 while limiting the current with the constant current source 23. Therefore, the diodes 24,2
The current flowing through 5, 26, the resistor 27 and the base of the transistor 28 disappears, the transistor 28 turns off, and the detection signal V
_S becomes a Hi signal. In this way, the disconnection outstanding circuit 15 outputs the pulse signal in the same manner as when the temperature detection electrode wire 8 is disconnected, as in the case of no disconnection. On the other hand, the detection signal V _T of the temperature detection circuit becomes high because the current flowing through the collector of the transistor 11 decreases due to the disconnection of the temperature detection electrode line 8. This means erroneous detection that the temperature of the heating element 5 is considered to be low even if it is high. Therefore, the control circuit 32 has a drawback that the gate trigger continues to output the signal V _G and the temperature of the heating element 5 becomes higher than the set temperature, and in some cases, it is not controlled and becomes a very dangerous state.

An object of the present invention is to solve the conventional drawbacks and to provide a temperature control device which can be used even with a low impedance temperature sensor while maintaining safety.

(Means for Solving Problems) A temperature control device of the present invention comprises a heating element, a temperature detection electrode wire and a temperature sensing element which are in a state of being thermally coupled to the heating element, A temperature sensor for detecting a temperature, a DC power supply circuit for generating a DC voltage from an AC power supply, a pulse generation circuit for generating a pulse synchronized with the AC power supply, a temperature detection circuit for detecting a signal from the temperature sensor, and A capacitor connected between the DC power supply circuit and the temperature detection electrode wire, a resistor connected between the capacitor and the temperature detection electrode wire, an emitter on the resistor side, and a collector on the DC power supply circuit side. A transistor connected to the capacitor, the capacitor is charged by a current flowing from the DC power supply circuit through the resistor and the temperature detection electrode wire, and the output pulse of the pulse generation circuit is output. In imming, a disconnection detection circuit that drives the transistor to discharge the charge stored in the capacitor through the transistor, and detects the state of the temperature detection electrode line depending on the presence or absence of a discharge current of the capacitor through the transistor, A detection circuit of the temperature detection circuit and a control circuit that outputs a control signal to a power control element that controls energization to the heating element based on the detection signal of the disconnection detection circuit, wherein the disconnection detection circuit detects the temperature. When the electrode wire is broken, the charge charged in the capacitor by the current flowing from the DC power supply circuit to the AC power supply through the capacitor, the resistor and the temperature sensor, the AC power supply, the temperature sensor, and the resistor. Is forcibly over-discharged by a current flowing through the DC power supply circuit through the diode and the capacitor connected in parallel, The emitter voltage of the serial transistor to be higher than the collector voltage is obtained by a structure for turning off the transistor.

(Operation) The temperature control device of the present invention is a diode in which the charge charged in the capacitor by the current flowing from the DC power supply circuit to the AC power supply via the capacitor, the resistor and the temperature sensor is connected in parallel to the temperature sensor and the resistor from the AC period. ， When the temperature detection electrode wire of the temperature sensor is disconnected, the voltage on the side connected to the temperature detection electrode wire of the disconnection detection circuit becomes high by forcibly overdischarging the current flowing to the DC power supply circuit via the capacitor. Then, the transistor for flowing the disconnection detection current of the disconnection detection circuit is turned off, the detection signal is always Lo, the disconnection of the temperature detection electrode wire can be detected, and the energization of the power control element is stopped.

(Embodiment) An embodiment of the present invention will be described with reference to FIGS. 1 and 2. The same parts as those of the conventional example are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 1 is a circuit diagram of a temperature control device according to an embodiment of the present invention. In the figure, numeral 34 is a diode and resistor 30
And connect in parallel. When the temperature detection electrode wire 8 is not disconnected, the impedance of the temperature detection electrode wire 8 is the temperature sensitive element 9
Since it is much smaller than the impedance of the diode, it operates in the same manner as the conventional example, and the diode 34 is irrelevant. Next, the operation when the temperature detection electrode wire 8 is broken will be described. In the half cycle in which the A side of the _AC power supply V _AC is more negative than the E side, the DC voltage V _CC of the DC power supply circuit 1 → capacitor 29
→ resistor 30 → temperature detection electrode wire 8 → temperature sensing element 9 → heating element 5
→ Current flows through the _AC power supply V _AC (A) path, and capacitor 2
9 charge. This current path is designated as (1). Also, in the half cycle where the A side of the _AC power supply V _AC is more positive than the E side,
An electric current flows in the path of AC power supply V _AC → heating element 5 → temperature sensing element 9 → temperature detection electrode wire 8 → diode 34 and resistor 30 → capacitor 29 → DC voltage V _CC . This current path (2)
And Since the current flowing through the current path (2) hardly flows through the resistor 30 and flows through the diode 34, a current larger than the current flowing through the current path (1) flows. Therefore, the capacitor 29 is over-discharged by the current difference between the current path (2) and the current path (1), and a high voltage is generated at the connection point B between the capacitor 29 and the diode 34. Since this voltage is higher than the collector voltage of the transistor 16 generated by the diodes 24, 25, 26 and the base-emitter voltage of the transistor 28, the transistor 16 is turned off. Therefore, the current of the constant current source 23 continues to flow to the base of the transistor 28, and the detection signal V _S of the disconnection detection circuit 15 is always Lo. In this way, the disconnection of the temperature detection electrode wire 8 is detected.

FIG. 2 shows a second embodiment of the resistor 30.
A resistor 35 is further connected in series to a diode 34 connected in parallel with. The operation is similar to that of the first embodiment, and there is an advantage that the withstand voltage of the capacitor 29 and the diodes 31, 34 is small.

(Effect of the Invention) According to the present invention, when detecting the disconnection of the temperature detection electrode wire of the temperature sensor, at the time of the disconnection, the current flowing from the DC power supply circuit to the AC power supply through the capacitor, the resistor and the temperature sensor is used. Disconnection that turns off the transistor that passes the disconnection detection current by forcibly over-discharging the charged charge of the capacitor with the current that flows from the AC power supply to the DC power supply circuit through the diode connected in parallel with the temperature sensor and the resistor, and the capacitor. Since this is a detection circuit, disconnection can be reliably detected even when a temperature sensor with low impedance is used. As described above, it is possible to eliminate the limitation of the impedance of the temperature sensor while maintaining the safety, so that the practical effect is great.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a temperature control device according to an embodiment of the present invention, FIG. 2 is a circuit diagram of a main part of the temperature control device according to the second embodiment, FIG. 3 is a structural diagram of a heating element, and FIG. Is a temperature characteristic diagram of a temperature sensor, and FIGS. 5A and 5B are a circuit diagram and a waveform diagram of each part of a conventional temperature control device, respectively. 1 ... DC power supply circuit, 2, 24, 25, 26, 31, 34 ... Diode, 3,
7,12,18,19,20,22,27,30,35 ... Resistor, 4,13,29 ... Capacitor, 5 ... Heating element, 6 ... Power control element, 8 ... Temperature detection electrode wire, 9 ... Temperature element, 10 ... Temperature detection circuit, 11,14,16,17,
21, 28 ... Transistor, 15 ... Disconnection detection circuit, 23 ... Constant current source, 32 ... Control circuit, 33 ... Pulse generation circuit.

Claims (1)

[Claims] 1. A heating element, a temperature sensor which is in thermal connection with the heating element and which comprises a temperature detection electrode wire and a temperature sensitive element, and which detects the temperature of the heating element, and a DC voltage from an AC power source. A DC power supply circuit that generates a pulse, a pulse generation circuit that generates a pulse synchronized with the AC power supply, a temperature detection circuit that detects a signal of the temperature sensor, and a connection between the DC power supply circuit and the temperature detection electrode wire. And a resistor connected between the capacitor and the temperature detection electrode line, and a transistor having an emitter on the resistor side and a collector on the DC power supply circuit side, the DC power supply circuit to The capacitor is charged by the current flowing through the resistor and the temperature detecting electrode wire, and the transistor is driven at the timing of the output pulse of the pulse generating circuit. A disconnection detection circuit that discharges the charge stored in the capacitor through the transistor, and detects the state of the temperature detection electrode line depending on the presence or absence of a discharge current of the capacitor through the transistor; a detection signal of the temperature detection circuit and the disconnection. And a control circuit that outputs a control signal to a power control element that controls energization to the heating element based on a detection signal of a detection circuit, the disconnection detection circuit, when the temperature detection electrode wire is disconnected, the DC power supply circuit To the capacitor, the resistor, and further the charge charged in the capacitor by the current flowing to the AC power supply through the temperature sensor, the diode connected in parallel from the AC power supply to the temperature sensor, and the resistor, further the capacitor Through the DC power supply circuit via the DC power supply circuit forcibly overdischarge, the emitter voltage of the transistor is Temperature control device being characterized in that a structure to turn off the transistor and higher than Kuta voltage.