JPH0320768B2 - - Google Patents

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 floor heaters.

Configuration of conventional examples and their problems Conventional temperature control devices such as electric blankets and electric floor heaters use a heat generating circuit consisting of a heater connected to an AC power source and a power control element connected in series to control changes in the heater. Generally, a power control element is controlled by a temperature detection signal from a temperature sensor whose resistance and capacitance change depending on the temperature, and safety against disconnection of the temperature detection line of the temperature sensor is particularly important.

Figure 1 is a structural diagram of a temperature sensor used in electric blankets, electric floor heaters, etc., in which an electrode wire 2 is wound around a core thread 1, and a temperature sensing element 3 made of a plastic thermistor is covered thereon. An electrode wire 4 is wound thereon, and an insulating jacket 5 is further coated thereon.

Figure 2 shows the temperature characteristics of the sensor impedance, which consists of the resistance (Ω) and capacitance (F) between the electrode wires 2 and 4.As is clear from the figure, it shows negative temperature characteristics, and the resistance The component impedance is very large compared to the capacitance impedance, and the sensor impedance is determined by the capacitance. By the way, if the electrode wire 2 or 4 is disconnected, the sensor impedance will become larger than normal, and the control temperature may become abnormally high. In some cases, there is a risk that the heater will continue to be energized without being controlled. It was hot.

Conventionally, as a method for detecting disconnection of an electrode wire, there is a circuit shown in FIG. The conventional circuit shown in Fig. 3 is an application of the integrated heater and temperature sensor shown in Japanese Patent Application Laid-Open No. 57-103518 to a temperature control device in which the heater and temperature sensor are independent. It is something. In the figure, 6 constitutes an AC power supply, 7 constitutes a power switch, and 8 constitutes a circuit power supply. 9
10 is a heater, 10 is a power control element that controls energization of the heater 9, 11 is a temperature sensor, and 12 is a temperature detection circuit that converts a temperature detection current determined by the impedance of the temperature sensor 11 into a DC voltage.
13 is a temperature sensor 11 connected to the ground side of the circuit
Disconnection detection circuit for checking disconnection of electrode wire, 1
4 is a zero cross pulse generation circuit that generates pulses with zero volt voltage of AC power supply 6; 15 is a temperature control circuit that connects the output of temperature detection circuit 12 and disconnection detection circuit 1;
3 and outputs a gate trigger signal for the power control element 10 to control the temperature of an electric blanket or the like.

In the above configuration, the zero-cross pulse Zp generated by the zero-cross pulse generation circuit 14 is input to the disconnection detection circuit 13, and a zero-cross pulse current is caused to flow through the electrode wire of the temperature sensor 11 connected to the ground side of the circuit. The disconnection detection circuit 13 generates different outputs depending on whether the ground electrode wire of the temperature sensor 11 is disconnected or disconnected, and inputs the output to the temperature control circuit 15 and processes it with the output of the temperature detection circuit 12 for power control. A gate trigger signal V _G of element 10 is determined.
That is, when the ground electrode wire of the temperature sensor 11 is not disconnected, a zero cross pulse current flows and the power control element 1
0 is triggered and the heater 9 is energized, but when the wire is disconnected, the zero-cross pulse current does not flow and the power control element 10 is not triggered and the energization to the heater 9 is stopped. Therefore, it is safe if the grounding side electrode wire breaks, but if the other non-grounding electrode wire breaks, the heater temperature will rise abnormally and the electric power that comes into direct contact with the human body will be safe. Blankets, etc. pose a risk of burns and fire.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned conventional drawbacks, and aims to control a power control element with zero volts of an AC power source and detect a disconnection failure in a non-grounded electrode wire of a temperature sensor.

Composition of the Invention In order to achieve the above object, the present invention detects a disconnection failure of the non-grounded electrode wire of a temperature sensor by detecting a signal in which the phase of the temperature sensor differs between when the wire is not disconnected and when the wire is disconnected, and synchronizes it with an AC power source. The output is compared with a temperature signal output that changes depending on the temperature of the temperature sensor, and the output is used 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. 4, 16 is an AC power supply, 17 is a power switch, 18 is a diode, 19 is a resistor, 20 is a
The circuit power supply A is composed of the capacitors. 21 is a heater, 22 is a power control element for controlling energization of the heater 21, 23 is a gate resistor, 24 is a non-grounded electrode wire, 25 is a grounded electrode wire, and 26 is connected to the non-grounded electrode wire 24 on the ground side. Temperature sensor B is a temperature sensing element interposed between the electrode wire 25, and the resistance, capacitance, and impedance of the non-grounded electrode wire 24, the grounded electrode wire 25, and the temperature sensing element 26 change depending on the temperature. Configure. 27 is a temperature detection transistor whose base is grounded. The transistor 27 has a base that is conductive when the power control element 22 is at a non-conducting voltage;
A current flows through the path of the emitter, the ground electrode wire 25, the temperature sensing element 26, the non-ground electrode wire 24, and the resistor 28, and becomes a temperature detection current determined by the impedance formed by the resistance and capacitance of the temperature sensing element 26. A resistor 29 and a capacitor 30 connected to the collector of the transistor 27 convert the temperature detection current into a voltage and generate a temperature detection voltage across the capacitor 30. 31 is a base and emitter reverse voltage suppression diode of transistor 27;
7. Temperature detection circuit C with resistor 29 and capacitor 30
Configure. 32 and 33 are resistors; the resistor 32,
33 is connected in series with one end of the non-grounded electrode wire 24 and grounded. The voltage generated at the connection point between the resistors 32 and 33 is set as the base voltage of the transistor 34, the emitter of the transistor 34 is grounded, and the collector is connected via the resistor 35 to the circuit power supply Vcc.
36 is a base and emitter reverse voltage suppression diode of the transistor 34, and the resistors 32, 33, the transistor 34, and the resistor 35 constitute a disconnection detection circuit D. Reference numeral E denotes a zero-cross pulse generation circuit that generates a zero-cross pulse using the zero volt voltage of the AC power source 16, and is connected to the AC power source 16 via a resistor 37. 38 is a logic circuit which receives the output V _k of the disconnection detection circuit D and the output Z _p of the zero cross pulse generation circuit E as inputs. F is a temperature control circuit that processes the output of the temperature detection circuit C and the output V _S of the AND circuit 38 to generate a gate trigger signal for the power control element 22.
Outputs V _G to control the temperature of electric blankets, etc.

The operation of the above configuration will be explained with reference to FIGS. 5 and 6.

The case when the non-ground side electrode wire 24 is not disconnected will be explained. The temperature sensor B consists of a resistance 39 and a capacitance 40 between the non-grounded electrode wire 24 and the grounded electrode wire 25, as shown in the equivalent circuit of FIG. 6a.
The impedance of the resistance component 39 is very large, and the impedance of the temperature sensor B is almost determined by the capacitance component 40. The resistance portion 39 and the capacitance portion 40 are an equivalent circuit of the temperature sensing element 26. Therefore, the phase of the current i _S flowing to the temperature sensing element 26 side is advanced by the capacitance 40, and the phase of the current flowing to the resistors 32 and 33 is delayed, which occurs at the connection point between the resistors 32 and 33. The phase of the AC voltage V _A also lags behind the AC power supply 16 . Since the AC voltage V _A generated at the connection point between the resistor 32 and the resistor 33 is input to the base of the transistor 34, the collector voltage V _K of the transistor 34 is the AC voltage V _A
When the potential is positive, the transistor 34 is turned on and becomes "L", and when the potential is negative, the transistor 34 is turned off and becomes "H". Collector voltage of transistor 34
V _K becomes "H" because the capacitance of the temperature sensing element 26 is 4
Since the phase is delayed by 0, it becomes a zero cross portion of the AC power supply 16, and becomes one input signal of the AND circuit 38. The other input of the AND circuit 38 is
The output Z _P of a zero cross generation circuit E that generates a zero cross pulse with the zero volt voltage of the AC power supply 16 is input, and the output Z _P is an "H" signal at the zero cross. Therefore, the output V _S of the AND circuit 38
also becomes "H" at the zero cross and is input to the temperature control circuit F, and by the output from the temperature detection circuit C,
When the temperature is low, the gate trigger signal of the power control element 7
V _G is output to energize the heater 21, and when the temperature is high, the gate trigger signal V _G is not output, so the AC power source 16 is not supplied to the heater 21, so the energization of the heater 21 is controlled at the set temperature.

Next, a case where the non-grounded side electrode wire 24 is disconnected will be explained. FIG. 6b shows an equivalent circuit of the temperature sensor B when the non-grounded electrode wire 24 is disconnected. As shown in the figure, a temperature sensing element 26 is also interposed between both ends of the disconnected part, and the resistance is 41
A capacitive component 42 occurs, and the impedance of the resistive component 41 is very large compared to the impedance of the capacitive component 42, and the impedance of the part where the disconnection failure occurs is also almost determined by the capacitive component 42. Therefore, due to the capacitance 42 of the part where the disconnection occurred, the resistors 32 and 33
The phase of the current ia flowing through the resistor 32 and the resistor 3 advances.
The phase of the AC voltage V _A generated at the connection point with AC power supply 3 also leads that of AC power supply 16 . The phase of the AC voltage V _A is determined by the capacitance 42, and the zero cross generation circuit E
The output Z goes further from the rising phase of _P , and the maximum is
It will be close to 90°. Since the AC voltage V _A generated at the connection point between the resistors 32 and 33 is input to the base of the transistor 34, the collector voltage V _K of the transistor 34 is such that when the AC voltage V _A is at a positive potential, the transistor 34 is The transistor 34 is turned on and becomes "L", and when the potential is negative, the transistor 34 is turned off and becomes "H". Collector voltage V _K of transistor 34 is “L”
Since the phase is advanced by the capacitance 42 of the disconnected part, it becomes the zero-crossing part of the AC power supply 16, and becomes one input signal of the AND circuit 38. The other input of the AND circuit 38 receives the output Z _P of the zero cross generation circuit E that generates a zero cross pulse with the zero volt voltage of the AC power supply 16.
The output Z _P is an "H" signal at zero cross. Therefore, the output V _S of the AND circuit 38 always becomes an "L" signal and is input to the temperature control circuit F, and even if the temperature detection circuit C outputs an output indicating that the temperature is low, the AND circuit 38 Since the output V _S of the temperature control circuit F is always "L", the output of the temperature control circuit F is also always "L" and does not trigger the power control element 22. That is, when the non-ground side electrode wire 24 has a disconnection failure, the gate trigger signal to the power control element 22 is always set to "L".

As described above, according to this embodiment, a disconnection failure of the electrode wire 24 on the non-grounded side can be detected by a phase change caused by a difference in the distribution of the capacitance of the temperature sensor, and the zero volt of the power control element 22 can be detected. Switch control and disconnection failure detection of the non-grounded electrode wire 24 can be instantaneously performed, and an extremely safe temperature control device can be provided. In the above embodiment, only the disconnection detection on the non-grounding side was explained, but the disconnection of the grounding side electrode wire 25 is detected in the third example of the conventional example.
It can be detected using the circuit shown in the figure.

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

(1) It is extremely safe because it detects the phase based on the capacitance of the temperature sensor and can detect disconnection failures in the electrode wire from the non-grounded side.

(2) When configured with a semiconductor integrated circuit, etc., the disconnection detection signal input voltage can be achieved at an extremely low level even for non-grounded electrode lines, so it is easy to implement the semiconductor integrated circuit (3) Power control The device's zero-volt switch control and disconnection detection of the non-grounded electrode wire can be instantaneously performed every cycle of the AC power supply, resulting in high safety and excellent noise resistance.

[Brief explanation of drawings]

FIG. 1 is a structural diagram of a temperature sensor, FIG. 2 is a temperature characteristic diagram of the temperature sensor, FIG. 3 is a conventional temperature control device, and FIG. 4 is a temperature control device according to an embodiment of the present invention. 5 is a timing chart of the temperature control device in FIG. 4, and FIG. 6 is an equivalent circuit diagram of the temperature sensor. 16... AC power supply, 21... Heater, 22...
Power control element, 24... Non-grounding side electrode wire, 25...
...Ground side electrode wire, 26...Temperature sensing element, 32...Resistor, 33...Resistor, 34...Transistor, 38
...Logic product circuit, 39...Resistance component, 40...Capacitance component, 41...Resistance component of disconnection failure section, 42...Capacitance component of disconnection failure section, A...Circuit power supply, B...Temperature sensor, C...Temperature detection circuit, D...Disconnection detection circuit, E...Zero cross pulse generation circuit, F...Temperature control circuit.

Claims (1)

[Scope of Claims] 1. A negative side of the circuit power source is grounded to one side of the AC power source, and 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 having a temperature sensing element interposed between the temperature sensor, a temperature detection circuit for detecting a signal of the temperature sensor, a disconnection detection circuit for detecting a disconnection failure of a second electrode wire of the temperature sensor; a pulse generation circuit that generates pulses synchronized with an AC power supply; a comparison circuit that compares the output of the disconnection detection circuit with the output of the pulse generation circuit; and a comparison circuit that compares the output of the temperature detection circuit with the output of the comparison circuit and a control circuit that outputs a control signal to a power control element that controls energization of a heater connected to a power source, and the disconnection detection circuit detects a signal that has a different phase when the temperature sensor is not disconnected and when the temperature sensor is disconnected. Temperature control device configured to cut off power to the heater. 2 Connect one end of the second electrode wire of the temperature sensor to the non-grounded side of the AC power source via a resistor, connect the other end to the grounded side via the first resistor and the second resistor, and The signal voltage at the connection point between the resistor and the second resistor is
Claim 1: The emitter is connected to the ground side, and the collector is connected to the positive side of the circuit power supply via a resistor, etc. as the base voltage of a transistor, and a disconnection fault is detected by a signal from the collector of the transistor. Temperature control device as described in section. 3. The temperature control device according to claim 1, wherein the pulse generation circuit is configured with a zero-cross pulse generated at zero volt voltage of an AC power source as an output to be compared with the output of the disconnection detection circuit.