JPS59231618A - Temperature controller - Google Patents

Abstract

PURPOSE:To increase the upper limit of the resistance value of a temperature detection electrode line and increase the level of malfunction due to noises by accumulating a charge which flows from a DC voltage generated by a control power source circuit through the temperature electrode line and discharging an erroneous charge repeatedly through a disconnection detecting circuit. CONSTITUTION:An electric power control element 6 is connected between an AC power source VAC and a heating body 5 to control the feeding to the heating body 5. A temperature sensing element 9 is interposed between the heating body 5 and temperature detection electrode line 8, and the element 9 and a temperature detecting circuit 10 detect the temperature of the heating body 5. The charge flowing from the DC voltage generated by the detecting circuit 10 through the electrode line 8 is accumulated and discharged periodically by the disconnection detecting circuit 15 to detect the breaking of the electrode line 8. The output of this detecting circuit 15 is inputted to a pulse generation part 33, whose output pulse triggers the element 6. Then, the upper limit of the resistance value of the electrode line 8 is increased, and malfunction of the control power source circuit 38 due to noises is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a temperature control device for electric heating appliances such as electric blankets and electric carpets. The temperature control device is composed of a circuit as shown in FIG. 1, for example. vAC is an alternating current source, and a control power supply circuit 38 is configured with a diode 2, a resistor 3, and a capacitor 4 to create a direct current power source.

6 is a heating element, 6 is a power control element that controls energization to the heating element 6, 7 is a gate resistor, 8 is a temperature sensing electrode wire, and 9 is interposed between the heating element 6 and the temperature sensing electrode wire 8. A temperature sensing element 034 whose resistance, capacitance, and impedance change depending on the temperature of the heating element 6 is a resistor, which is thermally coupled to the temperature fuse 1. If the power supply to the heating element 6 is not controlled due to various malfunctions and the heating element 6 is abnormally overheated, the impedance of the temperature sensing element 9 decreases or the heating element 6 melts due to abnormal heat generation. A large current flows through the resistor 34 due to the connection with the temperature sensing electrode wire 8, causing the resistor 34 to generate heat, blowing out the temperature fuse 1, and stopping the current supply to the heating element 5. 11 is a temperature detection transistor whose base is grounded. The transistor 11 conducts when the power control element 6 is turned off, and detects the temperature determined by the impedance of the temperature sensing element 9 along the path of base → emitter → resistor 34 → temperature sensing electrode wire 8 → temperature sensing element 9 → heating element 6. Current flows. The resistance value of the resistor 34 is made sufficiently smaller than the impedance of the temperature sensing element 9. A resistor 12 and a capacitor 13 connected to the collector of the transistor 11 convert the temperature detection current into a voltage, and generate a temperature detection voltage across the capacitor 13. 14 is a base-emitter reverse voltage control diode of transistor 11; A temperature detection circuit 10 is composed of a 12° resistor and a capacitor 13.

Reference numeral 16 denotes a disconnection detection circuit that checks for disconnection of the temperature sensing electrode wire 8 by passing a loop-like disconnection detection current. 16 is a transistor for applying a disconnection detection current; 17 is a transistor for driving the transistor 16; the transistor 17 is biased by a resistor 18 connected to its collector; 19 and 20 are resistors. Reference numeral 21 denotes a transistor for driving the transistor 17, which is connected to the base of the transistor 17 via a resistor 22, and the transistor 21 is driven by the pulse Vp of the pulse generator 33. 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. diode 29,
30 and 31 are protection diodes of the disconnection detection circuit 15 against disconnection of the connector P2. 32 is a temperature control section that processes the output of the temperature detection circuit 10 and the output of the disconnection detection circuit 16 and outputs a gate trigger signal vG of the power control element 6 to control the temperature of the heating element 5.

However, with this configuration, if the electrical path from the emitter side of the transistor 16 to the emitter side of the transistor 11 is opened, including an open failure of the temperature detection electrode line, the power control element 6 is turned off and the temperature is reduced. Unsafety caused by abnormal overheating of the heating element 6 due to disconnection of the detection electrode wire 8 is prevented.

Furthermore, the disconnection detection circuit 16, the temperature control unit 32, the power control element 6, etc. fail, and the power supply to the heating element 5 becomes uncontrollable.
When the heating element 6 becomes abnormally overheated, a large current flows through the resistor 34 due to a short circuit between the heating element 5 and the temperature sensing electrode wire 8 due to the low impedance of the temperature sensing element 9 and melting of the temperature sensing element 9 due to high temperature. The temperature fuse 1 is fused to eliminate the unsafe condition. 37 is an overload fusing type resistor;
When the heating element 6 is abnormally heated, the overload fusing resistor is opened to cut the current flowing through the disconnection detection circuit 15, and a larger current flows to the resistor 34 than before the overload fusing resistor 37 was opened. This allows the temperature fuse 1 to be quickly and reliably fused.

However, the disconnection detection circuit 15 operates normally only when the potential at point A is lower than the potential at point B when the constant current flowing from the constant current 23 flows through the temperature sensing electrode wire 8.

Therefore, the resistance value of the overload fusing resistor 37 and the temperature sensing electrode wire are set to such a value that the voltage drop across the overload fusing resistor 37, the temperature sensing electrode wire 8, the resistor 34, and the diode 14 is higher than the potential at point B. If the resistance value of 8 and the resistance value of resistor 34 are selected, it will be considered that the wire is broken even if it is not broken, and the selection of constants will be extremely restricted.

In particular, the length of the temperature sensing electrode wire 8 varies depending on the number of types of electric blankets, electric carpets, etc., and there are some that are very long. In that case, the resistance value of the temperature sensing electrode wire 8 becomes large, and the conventional method has a problem in that it is regarded as a disconnection even if it is not disconnected.

Furthermore, when the heating element 6 is abnormally heated, the temperature detection electrode wire 8
If abnormal overheating occurs especially on the Pl side, and the temperature sensing element 9 melts on this side, causing a short circuit between the heating element 6 and the temperature sensing electrode wire 8, until the overload fusing resistor 37 opens. There is a problem in that a large current flows through the disconnection detection circuit 15, and the elements in the disconnection detection circuit may break down or break down.

Further, when a large negative voltage noise enters the power supply on the D side with respect to the C side, a negative voltage pulse is generated with respect to the point AKCK through the heating element 5, the temperature sensing element 9, and the temperature sensing electrode wire 8. At this time, especially when the disconnection detection circuit 15 is constructed of a semiconductor integrated circuit, the withstand voltage of the diode 31 is low, so that if a negative pulse occurs at point A, the diode 31'1
Leakage current flows from point i-B. Due to this current, even when transistor 16 is off, transistor 28
The multi-temperature control section 32 which is turned off also has the problem of causing malfunctions.

OBJECTS OF THE INVENTION The present invention eliminates these conventional drawbacks and further expands the range of applications by further increasing the upper limit of the resistance value of the temperature sensing electrode wire, and also configures a disconnection detection circuit even when there is a short circuit between the heating element and the temperature sensing electrode wire. The purpose of this is to prevent the risk of rupture of the connected elements, and to raise the noise malfunction level of the disconnection detection circuit.

Structure of the Invention In order to achieve this object, the present invention uses a disconnection detection circuit to periodically detect the accumulation of charges flowing through the temperature sensing electrode wire from the DC voltage generated by the control power supply circuit and the discharge of falsely accumulated charges. It has a repeating structure.

With this configuration, it is possible to raise the upper limit of the resistance of the temperature sensing electrode wire, and even in the event of a short circuit between the heating element and the temperature sensing electrode wire, there is no possibility of rupture of the element constituting the disconnection detection circuit. It is possible to prevent danger and raise the malfunction level of the disconnection detection circuit against noise.

DESCRIPTION OF THE EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. FIG. 2 is a circuit diagram of an embodiment of the temperature control device of the present invention. Components with the same numbers as those in FIG. 1 are the same components, and therefore, description thereof will be omitted. 39 is a capacitor, and during the period when the transistor 17 is not turned on when the temperature detection electrode wire 8 is not disconnected,
A resistor 4 is connected to the DC power supply generated by the control power supply circuit 38.
0 → Temperature Once detection electrode wire 8 → Resistor 34 → Diode 14
is charged by the current flowing through it. When the transistor 17 is on, part of the charge accumulated in the capacitor 39 flows through the transistor 17 → resistor 18 → resistor 19 and between the base and emitter of the transistor 160 and is discharged, turning on the transistor 16 and remaining in the capacitor 39. The current charge is discharged through the transistor 16 while being current limited by the constant current source 23. Therefore, the diode 24
~26→No current flows between the resistor 27 and the transistor emitter, and the transistor 28 is turned off. If the temperature sensing electrode wire 8 is disconnected, no charging current will flow to the capacitor 39. Therefore, the current flowing from the constant current source 23 flows to the diodes 24 to 26, the resistor 27, and the transistor 28, and the transistor 28 continues to be turned on. Therefore, a disconnection is detected.

Effects of the Invention The temperature control device of the present invention uses a charged charge in the disconnection detection circuit, so the resistor 40. There is a very large margin in the resistance value of the temperature sensing electrode wire and the resistor 34, and especially for temperature sensing electrode wires that have various shapes (lengths), the upper limit of the resistance value can be widened, so it is very versatile. spread.

Furthermore, by setting the resistor 40 to a large value, it is possible to suppress the current flowing to the disconnection detection circuit when the heating element and the temperature sensing electrode wire are shorted due to abnormal overheating of the heating element.
It is possible to prevent dangers such as rupture of elements constituting the disconnection detection circuit. Furthermore, even when noise enters,
Since the wire breakage detection circuit (capacitor 39) can lower the impedance of the wire breakage detection circuit as seen from point E-F, the noise malfunction level can be raised.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional temperature control device, and FIG. 2 is a circuit diagram of an embodiment of the temperature control device of the present invention. 6... Heating element, 6... Power control element,
8. River... Temperature sensing electrode wire, 9... Temperature sensing element,
10... Temperature detection circuit, 16... Disconnection detection circuit, 33... Pulse generator, 38...
...Control power supply circuit.

Claims (1)

[Claims] The heating element is formed by a power control element connected between an alternating current power source and the heating element to control the supply of electricity to the heating element, and a temperature sensing element interposed between the heating element and the temperature sensing electrode wire. Disconnection of the temperature sensing electrode wire is detected by periodically repeating the discharge of accumulated charge flowing through the temperature sensing electrode wire from a DC voltage generated by a temperature sensing circuit that detects the temperature of the temperature sensing electrode wire and a control power supply circuit. A temperature control circuit device comprising: a wire breakage detection circuit configured to trigger the power control element with a pulse output from the wire breakage detection circuit.