JPS6147088A - Temperature controller - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a temperature control device that particularly improves safety in electric heating appliances such as electric blankets and electric floor heaters.

Conventional configuration and its problems Conventional temperature control devices such as electric blankets and electric floor heaters use a heating circuit consisting of a heater connected to an AC power source and a power control element connected in series to adjust the temperature change of the heater. Control is generally performed by controlling a power control element using a temperature detection signal from a temperature sensor whose resistance and capacitance change depending on the temperature, and safety against disconnection of the temperature sensor's temperature detection electrode wire is particularly important. .

Figure 1 (al) is a structural diagram of a temperature sensor used in electric blankets, electric floor heaters, etc. A temperature sensing electrode wire 2 is wound around a core yarn 1, and a temperature sensing element 3 made of a plastic thermistor is placed on top of the wire 2. is coated, one wL electrode wire is wound on top of it, and a sheathing jacket 5' is further coated on top of it. Figure 1(b) shows the temperature characteristics of the sensor impedance. As is clear from the figure, it exhibits negative temperature characteristics.

In the conventional circuit shown in FIG. 1 tc+, 1 is an alternating current power supply. A circuit power supply A is composed of a diode (2), a resistor (3), and a capacitor (4). 5 is a heater, 6 is a power control element for controlling the energization of the heater 5, 7 is a temperature sensor, and 8 is a temperature detection electrode wire of the temperature sensor 7. Furthermore, 9 transistors, 10 resistors, and 11 capacitors constitute a temperature detection circuit B that converts a temperature detection current determined by the impedance of the temperature sensor 7 into a DC voltage. C is a temperature control unit that processes the signal of the temperature detection circuit B and determines the gate trigger signal of the power control element 6;
12 is a gate resistor, 13 is a base of the transistor 9, an emitter reverse voltage suppression diode, and 14 is a temperature detection current limiting resistor.

In the above configuration, the temperature sensor 7 exhibiting negative temperature characteristics
If the temperature sensing electrode wire 8 is disconnected, the impedance becomes larger than normal, and the control temperature may become abnormally high. Depending on the situation, there is a risk that the heater may continue to be energized without being controlled. There is a danger of burns and fire, especially when using electric blankets that come into direct contact with the human body.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned conventional problems and aims to detect a disconnection failure in a temperature sensing electrode wire of a temperature sensor.

Structure of the Invention In order to achieve the above object, the present invention supplies a pulse current to the temperature detection electrode wire of a temperature sensor, detects the pulse current value, converts it to voltage, and monitors the voltage value to prevent disconnection failures. , and processes the output and a temperature signal output that changes depending on the temperature of the temperature sensor, and uses the obtained output as a control signal for a power control element that controls energization of the heater.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 2, 15 is an AC power source and 16 is a power switch. A circuit power supply is constructed with 17 diodes, 18 resistors, and 19 capacitors. 20 is a heater, 2
1 is a power control element that controls energization of the heater 2o, 2
2 is a gate resistor, 23 is a temperature sensing electrode wire, 24 is the other electrode wire, and 25 is a temperature sensing element interposed between the electrode wires. Element 2
5 constitutes a temperature sensor E whose impedance changes depending on the temperature, and is thermally coupled to the heater 20. 26 is a temperature detection transistor whose base is grounded. The transistor 26 is conductive when the power control element 21 is turned off, and a current flows through the path of the base, emitter, temperature sensing element 11 polar wire 23, temperature sensing element 25, the other electrode wire 24, and the resistor 27. The temperature detection current is determined by the impedance formed by the resistance and capacitance of the element 25. A resistor 28 and a capacitor 29 connected to the collector of the transistor 26 convert the temperature detection current into a voltage, and generate a temperature detection voltage across the capacitor 29.

A temperature detection circuit F is composed of a transistor 26, a resistor 28, and a capacitor 29.

G is a zero-cross pulse generation circuit that generates a zero-cross pulse using the zero volt voltage of the AC power supply 15, and a resistor 3
0 to the AC power source 15.

31 is a transistor, which is connected to the zero-cross pulse generation circuit G.
It operates based on the output v1 of. The emitter of the transistor 31 is connected to a circuit power source, and a resistor 32 is connected between the emitter and the base. The collector of the transistor 31 is connected to one end of the temperature sensing electrode line 23 via a resistor 33. A diode-connected transistor 34 constitutes a current mirror circuit together with the transistor 35. The collector (base) of the transistor 34 is connected to the temperature sensing electrode wire 23
At the other end, the collector of transistor 35 is connected via a resistor 36 to the circuit power supply. 37 is a comparator, resistor 38
．． The voltage value from the connection point 39 is compared with the voltage v2 obtained at the resistor 36, and an output v3 is output. Resistor 32, transistor 31, resistor 33, transistor 34, transistor a5, resistor 36, comparator 37, resistor 38, resistor 3
9 constitutes a disconnection detection circuit H for detecting a disconnection failure of the temperature sensing electrode wire 23. 3 is a temperature side "control circuit" which processes the output of the temperature detection circuit F and the output of the disconnection detection circuit H and outputs a gate trigger signal for the power control element 21, and controls the temperature of an electric blanket or the like.

The operation of the above configuration will be explained with reference to FIG.

The case when the temperature sensing electrode wire 23 is not disconnected will be explained. The transistor 31 outputs the output v of the zero-cross pulse generation circuit G.
-1, and is off during the Hi period of vl and on during the La period. Therefore, during the ON period of the transistor 310, a pulse current flows along with the alternating current flowing to the temperature sensor E to the temperature sensing electrode wire 23 and the transistor 34 via the circuit power supply D1, the emitter and collector of the transistor 31, and the resistor 33. . Since the transistor 34 and the transistor a5 have a current mirror circuit configuration, a current equivalent to the pulse current flowing through the collector of the transistor 34 flows through the collector of the transistor 35, and the voltage of the resistor 36 due to the pulse current value is 2. is generated, and this voltage V·2 becomes an input signal to the inverting input terminal of the comparator 37. A voltage v5 determined by the division ratio of the resistors 38 and 39 is input to the non-inverting input terminal of the comparator 37. In the slave I, the output of the comparator 37 is Lo during the Hi period and Hi- during the La period.
A signal v3 is obtained. This signal v3 is input to the temperature control circuit I together with the output of the temperature detection circuit F.

The temperature control circuit I processes these signals and outputs a gate trigger signal (4) for the power control element 21 to control the temperature of the electric blanket or the like.

Next, the case when the temperature sensing electrode wire 23 is disconnected will be explained. The transistor 31 is operated by the output v1 of the zero-cross pulse generation circuit G in the same way as when there is no disconnection, but since the temperature detection electrode wire 23 is disconnected, the transistor 31 operates during the La period of vl, that is, during the ON period of the transistor 31. Even if there is, no current from the circuit power supply will flow to the transistor 34.

Therefore, no pulse voltage is generated across the resistor 36 either.

Therefore, the output V3 of the comparator 37 always remains at [Lo J, the output v4 of the temperature control circuit l also remains at [Lo J, the gate trigger signal of the power control element 21 is not output, and the heater 20 receives an alternating current. Power source 15 is not supplied.

Effects of the Invention As described above, according to the present invention, the following effects can be obtained.

(1) A pulse current is passed through the temperature detection electrode wire of the temperature sensor, the pulse current value is detected and converted to voltage, and the voltage value is monitored to detect a disconnection failure in the temperature detection w1 pole wire. Since the power control element is rendered non-conductive, safety is extremely high.

(2) Since this is a disconnection detection circuit that detects current and converts it to voltage, the potential on the input side can be realized at an extremely low 0 level.
Easy to integrate into semiconductor integrated circuits.

(3) When configured with a semiconductor integrated circuit, the number of terminals can be reduced because it can also be used as the input side terminal of the temperature detection circuit.

[Brief explanation of the drawing]

FIG. 1(a) is a structural diagram of the temperature sensor, FIG. 1(b) is a temperature characteristic diagram of the temperature sensor, FIG. Fig. 3 is a timing chart of the temperature control device in Fig. 2. 15... AC power supply, 2o... Heater,
21... Power control element, 23... Temperature sensing electrode wire, 25... Temperature sensing element, 31...
...Transistor, 33...Resistor, 34,35
...Transistor, 36...Resistor, 3
7...Comparator, D...Circuit power supply, E.
...Temperature sensor, F...Temperature detection circuit,
G...Zero cross pulse generation circuit, H...
...Disconnection detection circuit, temperature control circuit for engineering. Name of agent: Patent attorney Toshi Nakao, Idiot 1
Figure 1 Haruka Jun (-(:) 0 Figure 1

Claims (1)

[Claims] The negative side of the circuit power source is grounded to one side of the AC power source, and a temperature sensing element is provided between a first electrode wire connected to the ground side of the AC power source and a second electrode wire connected to the non-grounded side of the AC power source. a temperature sensor with a temperature sensor interposed therebetween, a pulse generation circuit that generates a pulse synchronized with the AC power source, a temperature detection circuit that detects a signal of the temperature sensor, and a temperature sensor that receives the output of the pulse generation circuit as an input. a disconnection detection circuit that detects a disconnection failure in the first electrode wire; and a power control element that processes the output of the temperature detection circuit and the output of the disconnection detection circuit and controls energization of a heater connected to an AC power source. and a control circuit that outputs a signal, and the disconnection detection circuit causes a pulse current to flow through the first electrode wire of the temperature sensor in accordance with the output signal of the pulse generation circuit, and passes the pulse current through a current mirror circuit. A temperature control device configured to detect, convert to voltage, and monitor the voltage level.