JPH0745355A - Electric heating appliance - Google Patents

Abstract

PURPOSE:To provide an electric heating appliance which can detect voltage of the electric power source with a simple composition and at the same time which can detect short circuit between a heat radiating body and a short circuit detecting wire which short circuits. CONSTITUTION:When voltage alteration occurs in a commercial a.c. electric power source E, even if the temperature detected by heat sensitive wires T1, T2 is constant, the voltage alters. Since the resistance of short circuit detecting wires G1, G2 is kept to be a constant value independently of the temperature of the heater H1, H2, the voltage value follows the alteration of the voltage of the commercial a.c. electric power source E. The voltage of the short circuit detecting wires G1, G2 is sent to an electric power source voltage input port of a microcomputer 5 and when the voltage value deceases to 1/2 or lower, it is judged that the short circuit detecting wires G1, G2 are ruptured and at the same time voltage alteration is detected. Based on the voltage sent from the electric power source voltage input port, the voltage to be sent from a sensor temperature input port is corrected and the temperature is corrected to be actual temperature. The voltage value converted by a sensor temperature-voltage converting means 10 can be corrected to be a prescribed temperature value corresponding to the altering voltage of the commercial a.c. electric power source E and thus precise temperature control can be done.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric heating appliance capable of detecting a power supply voltage with a simple structure and detecting a disconnection of a short circuit detection line short-circuited with a heating element.

[0002]

2. Description of the Related Art Conventionally, an electric heating appliance has a structure in which, when the temperature of a heating element rises abnormally, the power supply to the heating element is stopped to prevent an accident.

In order to prevent the temperature of the heating element from rising abnormally, a short circuit is made when the temperature of the heating element is increased, which is attached to the heating element, for example, and the short circuit causes the resistance attached to the temperature fuse to overheat. A short-circuit detection line that blows a thermal fuse is known.

On the other hand, if the short-circuit detection line is broken, normal operation cannot be expected when the heating element is overheated. Therefore, the short-circuit detection line voltage is detected to detect the short-circuit detection line disconnection.

In general, the temperature of the heating element is detected by a sensor provided separately from the heating element. And
The temperature detected by the sensor is converted into a voltage to detect the voltage value, and the temperature of the heating element is controlled based on this voltage value.

However, since the power supply voltage varies,
Even if the temperature detected by the sensor is constant, the detected voltage value fluctuates, so it is also necessary to detect fluctuations in the power supply voltage.

[0007]

The short circuit detection line has an impedance of a substantially constant value regardless of temperature, and the power supply voltage and the voltage value of the short circuit detection line are in a proportional relationship.

However, as described above, although both of them detect the voltage, the circuit for detecting the disconnection of the short circuit detection line and the circuit for detecting the fluctuation of the power supply voltage are provided separately, and the circuit configuration is different. Has the problem of becoming complicated.

The present invention has been made in view of the above problems, and detects fluctuations in a power supply voltage with a simple structure.
An object of the present invention is to provide an electric heating appliance capable of detecting a disconnection of a short-circuit detection wire that short-circuits with a heating element.

[0010]

An electric heating appliance according to the present invention comprises a heating element, a switch means for turning the heating element on and off, and a short-circuit detection line for short-circuiting with the heating element when the heating element overheats. The control means detects the voltage of the short-circuit detection line to detect the fluctuation of the power supply voltage and turns off the switch means when the voltage of the short-circuit detection line is out of a predetermined range.

[0011]

According to the present invention, since the voltage of the short-circuit detection line corresponds to the power supply voltage, the control means detects the voltage of the short-circuit detection line to detect the fluctuation of the power supply voltage, and the voltage of the short-circuit detection line is out of the predetermined range. In the case of, for example, disconnection of the short-circuit detection line or abnormality of the power supply voltage, the switch means is turned off to stop the supply of electric power to the heating element, and the abnormal temperature rise is prevented. It is possible to detect fluctuation and disconnection of the short circuit detection line.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the electric heating apparatus of the present invention will be described below with reference to the electric carpet shown in the drawings.

First, the electric carpet is composed of a rectangular electric carpet body 11 as shown in FIG.
Side surfaces 11a 1 and 11a 2 are formed on both end surfaces of the electric carpet body 11 in the longitudinal direction.
A central surface 11b is formed between a and the side surfaces 11a, 11a and the central surface 11b are formed to have substantially the same area. Further, the side surfaces 11a, 11a and the central surface 11b respectively have, for example, 445 as a heating element.
The first heater H1 and the second heater H2 of W are housed,
A control box 12 is connected to the first heater H1 and the second heater H2, and the control box 12 is connected to a commercial AC power source E. Then, when the first heater H1 and the second heater H2 are simultaneously operated, the power consumption becomes 890 W, and when either the first heater H1 or the second heater H2 is used, the power consumption becomes 445 W. Power consumption.

Further, as shown in FIG. 1, a commercial AC power source E
In parallel with the first relay Ry of the first switch means 1 ₁ via the power switch SW1 and the thermal fuse F.
The series circuit of the first relay contact Ry1S of 1 and the first heater H1 and the series circuit of the second relay contact Ry2S of the second relay Ry2 of the second switch means 1 ₂ and the second heater H2 are In addition to being connected, the relay power supply circuit 2 is connected.

The relay power supply circuit 2 is composed of a series circuit of a rectifying diode D1, a resistor R1, a smoothing capacitor C1 and a resistor R2 connected in parallel with the capacitor C1.

From the connection point of the resistor R1 and the capacitor C1 of the relay power supply circuit 2, the first relay coil Ry1L of the first relay Ry1, the resistor R3 ₁ , the first relay coil Ry1L, the resistor R3 ₁ A first diode D2 ₁ and a series circuit of a _first relay drive circuit 3 ₁ connected in parallel with the second relay coil Ry2L of the second relay Ry2, a resistor R3 ₂ , A series circuit of the second relay coil Ry2L, the second diode D2 ₂ connected in parallel with the resistor R3 ₂ and the second relay drive circuit 3 ₂ is connected.

In the first relay drive circuit 3 ₁ , the collector and the emitter of the transistor Q1 ₁ are connected between the connection point of the resistor R3 ₁ and the first diode D2 ₁ and the other end of the commercial AC power source E. the transistor Q1 ₁ base, between the emitters, is connected the collector of the transistor Q2 _1, the emitter resistance R4 ₁ is connected to the collector of the transistor Q2 _1.

Further, the second relay drive circuit 3 ₂ has a resistor
Between R3 ₂ and of the second diode D2 _second connection point and the commercial AC power source E and the other end, the collector of the transistor Q1 _2, the emitter is connected, the transistor Q1 and _second base, the emitter, the collector of the transistor Q2 ₂ , The emitter is connected, and the resistor R4 ₂ is connected to the collector of the transistor Q2 ₂ .

Further, the commercial AC power supply E is connected to a power supply circuit 4 for converting AC into DC, and the power supply circuit 4 is connected to a microcomputer 5 as a control means. The microcomputer 5 includes a temperature setting circuit 6 for setting the temperatures of the first and second heaters H1 and H2, and the first and second heaters H1 and H2.
A display circuit 7 for displaying the setting contents or the operation of is connected. Furthermore, this first and second relay output ports of the microcomputer 5, the base of the transistor Q2 ₁ and transistor Q2 ₁ are respectively connected.

Further, a microcomputer runaway detection circuit 8 for detecting runaway of the microcomputer 5 is connected to the microcomputer 5. Further, the microcomputer runaway detection circuit 8 includes a resistor R5, a capacitor C2, a rectifying diode D3, a diode D4, a smoothing capacitor C3 and a resistor at the runaway detection output port of the microcomputer 5.
R6 is connected, the base of the transistor Q3 is connected to the resistor R6, the emitter is connected to the capacitor C3,
The base of the transistor Q4 is connected to the collector of C4. The power supply circuit 4 is connected to the collector of the capacitor C4, and the resistors R4 ₁ and R4 ₂ are connected to the emitter.

Further, a sensor 9 is connected to a commercial AC power source E via a power switch SW1 and a temperature fuse F via a resistor R6. The sensor 9 is composed of heat sensitive wires T1 and T2 composed of two thermistors, and these heat sensitive wires T1 and T2 are connected to a sensor temperature-voltage conversion circuit 10 via resistors R7 and R8. ing.

The sensor temperature-voltage conversion circuit 10
Is connected to the operational amplifier OP1 which forms a comparator through resistor R10, diode D5 and diode D6,
This operational amplifier OP1 consists of resistor R11, diode D7, capacitor C4, resistor R12, resistor R13 and Zener diode ZD.
It is connected via 3 to the sensor temperature input port of the microcomputer 5.

Further, the first heater H1 has a short circuit detection line G1.
Are provided via the nylon layer in a relationship between the outer winding and the inner winding, and the first heater H1 and the short-circuit detection line G1 constitute the first heater device 22 ₁ and the second heater H2 is short-circuited. Detection line
Similarly, G2 is provided through the nylon layer in a relationship between the outer winding and the inner winding, and the second heater H2 and the short-circuit detection line G2 constitute the _second heater device 222. The short circuit detection line G1 and the short circuit detection line G2 are connected to the power supply voltage detection circuit 23.

The power supply voltage detection circuit 23 is provided with a short circuit detection line G1.
Is connected to the resistor R21, the resistor R22 is connected to the short-circuit detection line G2, and is connected to the power supply voltage input port of the microcomputer 5 through the diode D10, the smoothing capacitor C11 and the resistor R23.

Further, the other ends of the short circuit detection line G1 and the short circuit detection line G2 are connected to a resistor R24 as a heat generating means which is thermally coupled to the temperature fuse F. And this resistance R2
4 is a resistor R24 and a resistor connected between both terminals of the commercial AC power source E via the power switch SW1 and the thermal fuse F.
It is connected to R25, diode D11, diode D12 and diode D13.

Further, a sensor overheat detection circuit 24 is connected to the microcomputer runaway detection circuit 8. In this sensor overheat detection circuit 24, a series circuit of a resistance R27 and a resistance R28 is connected between the power supply voltage input port of the microcomputer 5 and the other end of the commercial AC power supply E, and the resistance R28 is connected.
The capacitor C12 is connected to. Then, the non-inverting input terminal of the operational amplifier OP2 that constitutes the comparator is connected to the connection point of these resistors R27 and R28,
The inverting input terminal of the operational amplifier OP2 is connected to the sensor temperature input port and the sensor temperature-voltage conversion circuit 10. A resistor R29 is connected between the non-inverting input terminal and the output terminal of the operational amplifier OP2, the base of the transistor Q5 is connected to the output terminal of the operational amplifier OP2, and the collector of the transistor Q5 is connected to the resistor R6. , The emitter is connected to the sensor temperature-voltage conversion circuit 10.

Next, the operation of the above embodiment will be described with reference to Table 1.

[0028]

[Table 1] First, when operating the entire surface of the electric carpet, 2
When both the first and second heaters H1 and H2 are operated and only the half surface is operated, one of the two first and second heaters H1 and H2 is operated.

Here, the case where the entire surface of the electric carpet is operated will be described below. When only the half surface is operated, only one of the two first and second heaters H1 and H2 should be operated. Good.

When the temperature of the first and second heaters H1 and H2 detected by the sensor 9 is normal and lower than a set temperature, for example, 40 ° C., the microcomputer 5 determines which one 1st and 2nd relay contact Ry1
To close S and Ry2S as well, L level signals are output from the first and second relay output ports.

On the other hand, normally, the high-level pulse and the L-level pulse are output from the runaway detection output port of the microcomputer 5.
Since the level pulse is alternately output, the capacitor C3 is charged through the resistor R5, the capacitor C2, and the diode D3, and the current is supplied to the base of the transistor Q3 to turn on the transistor Q3. A current is supplied to the base of the transistor Q4 to turn on the transistor Q4.

Further, since the temperatures of the first and second heaters H1 and H2 detected by the sensor 9 are the set value of the overheated temperature, for example, 60 ° C. or less, they are output from the sensor 9 and the sensor temperature-voltage conversion circuit is output. Since the voltage converted in 10 is less than the specified value, transistor Q5 remains off and capacitor C3
Is charged as it is.

Here, if a voltage fluctuation occurs in the commercial AC power supply E, even if the temperature detected by the heat-sensitive wires T1 and T2 of the sensor 9 is constant, the voltage values of the heat-sensitive wires T1 and T2 will fluctuate, apparently. It operates as if the temperature had changed. On the other hand, the resistance values of the short-circuit detection lines G1 and G2 maintain a substantially constant value regardless of the temperatures of the first and second heaters H1 and H2.
The voltage values of the short-circuit detection lines G1 and G2 almost follow the fluctuation of the voltage of the commercial AC power supply E.

Therefore, the voltage of the commercial AC power source E is half-wave rectified by the diode D11, and this rectified current is applied to the resistor R24.
, Short-circuit detection line G1 and resistor R21 in series, or short-circuit detection line G2 and resistor R22 in series, and diode D10.
Through the capacitor C11 and the resistor R23, and a voltage corresponding to the voltage of the commercial AC power source E is applied to the resistor R23 and input to the power source voltage input port of the microcomputer 5.

Next, the operation of the microcomputer 5 based on the voltage input from the power supply voltage input port will be described with reference to the flow chart shown in FIG.

First, the microcomputer 5 detects the power supply voltage, and determines whether this voltage is 70 V or higher, that is, whether the short-circuit detection lines G1 and G2 are broken (step 1), and 70 V or higher is determined. If it is 130V
It is judged whether or not it is below (step 2), and it is below 130V, that is, above 70V within a predetermined range and above 130V.
In the following cases, calculation is performed in the microcomputer 5 and the voltage from the sensor 9 is corrected according to the power supply voltage (step 3).

As described above, in the microcomputer 5, when the detection voltage of the power supply voltage input port is 70 V or higher,
When the voltage is 0 V or less, based on the voltage input from the power supply voltage input port, for example, as shown in Table 2, the temperature is corrected to a predetermined temperature for each voltage range input from the sensor temperature input port and detected by the sensor 9. The corrected temperature is corrected to the actual temperature. That is, when the voltage value of the commercial AC power supply E decreases to the sensor temperature input port, it indicates a temperature higher than the actual temperature. Therefore, the predetermined temperature corresponding to the voltage is subtracted, and conversely, the voltage value of the commercial AC power supply E decreases. When the temperature increases, the temperature is lower than the actual temperature, so a predetermined temperature corresponding to the voltage is added. Therefore, even if the voltage of the commercial AC power source E fluctuates, the voltage value detected by the sensor 9 and converted by the sensor temperature-voltage conversion means 10 is used as a value of a predetermined temperature corresponding to the fluctuated voltage of the commercial AC power source E. Since it can be corrected to, accurate temperature control can be performed.

[0038]

[Table 2] Furthermore, when it is determined in step 1 or step 2 that the voltage is 70 V or less or 130 V or more, which is outside the predetermined range, the first and second relays Ry1 and Ry2 are opened, and the first heater H1 or the second heater H1 or the second relay is opened. The power supply to the heater H2 is stopped (step 4). That is, as will be described later, when either one of the short circuit detection line G1 or the short circuit detection line G2 is broken, either the series circuit of the short circuit detection line G1 and the resistor R21 or the series circuit of the short circuit detection line G2 and the resistor R22. Since one side is open, the voltage applied to the sensor temperature input port drops to 1/2, so the short-circuit detection line
When it is judged that the G1 or the short circuit detection line G2 is broken, the first and second relays Ry1 and Ry2 are opened, and the supply of electric power to the first heater H1 or the second heater H2 is stopped. Further, when the voltage value of the commercial AC power source E drops to 70 V or less, the microcomputer 5 may malfunction, and therefore the microcomputer 5 is similarly stopped. On the other hand, even if the voltage is too high, the voltage is rising due to a short circuit or other reasons, and for safety, the first and second relays are
Ry1 and Ry2 are opened, and the supply of electric power to the first heater H1 or the second heater H2 is stopped.

Further, by outputting an L level signal from the first and second relay output ports, the transistor Q2 ₁ and the transistor Q2 ₂ are turned off, and the transistor Q2 ₁ and the transistor Q2 ₂ are turned off.
Turning on Q4 causes transistor Q1 ₁ and transistor Q1
_Since the base is supplied to ₂ , the transistor Q1 ₁ and the transistor Q1 ₂ are turned on, current is supplied from the relay power supply circuit 2 to the first relay coil Ry1L and the second relay coil Ry2L, and the first relay contact Ry1S and The second relay contact Ry2S is closed, the first heater H1 and the second heater H2 operate, and heating is performed without any inconvenience.

When the temperature of the first and second heaters H1 and H2 detected by the sensor 9 is higher than the set temperature in the normal state, the microcomputer 5 determines which of the first and second heaters is to be used. In order to open the relay contacts Ry1S and Ry2S of, the H level signal is output from the first and second relay output ports.

Therefore, by outputting the H level signal from the first and second relay output ports, the transistor Q2
Since ₁ and transistor Q2 ₂ is turned on, the transistor Q1 ₁ and the transistor Q1 ₂ base current is not supplied, the transistor Q1 ₁ and the transistor Q1 ₂ is turned off, the relay power supply circuit 2 first relay coil Ry1L and second No current is supplied to the relay coil Ry2L, the first relay contact Ry1S and the second relay contact Ry2S are opened, and the first heater H1 and the second heater H2 are stopped.

When the microcomputer 5 is out of control and the temperatures of the first and second heaters H1 and H2 detected by the sensor 9 are lower than the set temperature, the operation of the microcomputer 5 is not fixed. An L level signal may be output from the first and second relay output ports.

On the other hand, when the microcomputer 5 runs out of control, a fixed output of H level or L level is output from the runaway detection output port of the microcomputer 5, so that the capacitor C3 is not charged and a current is supplied to the base of the transistor Q3. The transistor Q3 is turned off without supplying the current, and by turning off the transistor Q3, a current is supplied to the base of the transistor Q4 to turn off the transistor Q4.

[0044] Thus, since not supply base transistor Q1 ₁ and the transistor Q1 ₂ by turning off the transistors Q4, even if the transistors Q2 ₁ and transistor Q2 ₂ is not turned off, the transistor Q1 ₁ and the transistor Q1 ₂ is turned off, No current is supplied from the relay power supply circuit 2 to the first relay coil Ry1L and the second relay coil Ry2L, the first relay contact Ry1S and the second relay contact Ry2S are opened, and the first heater H1 and the first heater H1 The second heater H2 does not work and can handle failures without inconvenience. Even when the microcomputer 5 is out of control and when the temperatures of the first and second heaters H1 and H2 detected by the sensor 9 are higher than the set temperature, the same operation is performed and trouble can be handled without any inconvenience. it can.

Furthermore, when the sensor temperature input port of the microcomputer 5 fails or the relay output malfunctions, and the temperature of the first and second heaters H1 and H2 detected by the sensor 9 is lower than the set temperature. The microcomputer 5 includes a first relay contact Ry1 and a second relay contact Ry1.
To close both S and Ry2S, L level signals are output from the first and second relay output ports.

On the other hand, since the microcomputer 5 itself does not run out of control, an H level pulse and an L level pulse are output from the runaway detection output port of the microcomputer 5, so that the resistor R5, the capacitor C2, the diode
The capacitor C3 is charged through D3, supplying a current to the base of the transistor Q3 to turn on the transistor Q3, and turning on the transistor Q3 supplies a current to the base of the transistor Q4 to turn on the transistor Q4.

Further, since the temperatures of the first and second heaters H1 and H2 detected by the sensor 9 are the set value of the overheated temperature, for example, 60 ° C. or less, they are output from the sensor 9 and the sensor temperature-voltage conversion circuit is output. Since the voltage converted in 10 is less than the specified value, transistor Q5 remains off and capacitor C3
Is charged as it is.

Therefore, by outputting the L level signal from the first and second relay output ports, the transistor Q2
With ₁ and transistor Q2 ₂ is turned off, since the supply of the base by turning on the transistor Q4 to transistor Q1 ₁ and the transistor Q1 _2, transistors Q1 ₁ and the transistor Q1 ₂ is turned on, the first relay coil from the relay power supply circuit 2 Ry1L and second relay coil Ry2L
Is supplied with current, the first relay contact Ry1S and the second relay contact Ry2S are closed, and the first heater H1 and second heater contact Ry1S are closed.
The heater H2 of 1 operates to heat the room, but since the temperature is below a predetermined value, the room is heated without any inconvenience.

When the sensor temperature input port of the microcomputer 5 fails or the relay output malfunctions, and the temperatures of the first and second heaters H1 and H2 detected by the sensor 9 are higher than the set temperature. Then, the microcomputer 5 tries to close any of the first and second relay contacts Ry1S and Ry2S, and outputs the L level signal from the first and second relay output ports.

On the other hand, since the microcomputer 5 itself does not run out of control, the runaway detection output port of the microcomputer 5 outputs an H level pulse and an L level pulse, so that the resistor R5, the capacitor C2, and the diode.
The capacitor C3 is charged via D3.

However, the first or second heater H1, H2
Is an excessive temperature, for example, when the temperature rises to 60 ° C., the temperature detected by the sensor 9 is converted into a voltage by the sensor temperature-voltage conversion circuit 10, and the sensor temperature is converted from the voltage divided by the resistors R27 and R28. Since the output voltage of the voltage conversion circuit 10 becomes high, the operational amplifier OP2 is inverted to output the L level, and the transistor Q3 is turned on.

When the transistor Q3 is turned on, the voltage charged in the capacitor C3 is discharged. In this way, when the capacitor C3 is discharged, the transistor
Q3 is turned off, the transistor Q4 is also turned off, the current is not supplied from the relay power supply circuit 2 to the first relay coil Ry1L and the second relay coil Ry2L, and the first relay contact Ry1S and the second relay contact Ry2S It can be prevented that the first heater H1 and the second heater H2 are turned off and the temperatures of the first heater H1 and the second heater H2 are excessively raised by opening.

Further, by turning off the first heater H1 and the second heater H2, the first heater H1 and the second heater H1 are turned off.
However, the temperature of the heater H2 of
The hysteresis characteristic is given by R29, and the voltage inverted to the H level output is set lower than the voltage inverted to the L level output. Therefore, the temperature is 6
It prevents the first relay contact Ry1S and the second relay contact Ry2S from frequently turning on and off at around 0 ° C, and prevents the first heater H1 and the second heater H2 from repeatedly turning on and off. To do.

Also, the first heater H1 and the second heater H1
When the sensor 9 detects that the temperature of H2 has dropped, and the temperature has dropped to the restart temperature of, for example, about 35 ° C., the operational amplifier OP2 is inverted and outputs the H level, the transistor Q5 is turned off, and the capacitor C3 is charged again. , The transistor Q4 is turned on and the relay power supply circuit 2 moves to the first relay coil Ry1L.
And a current is supplied to the second relay coil Ry2L,
The relay contact Ry1S and the second relay contact Ry2S are closed, and the first heater H1 and the second heater H2 operate to heat again.

As described above, since the temperatures of the first heater H1 and the second heater H2 are set to, for example, 60 ° C. or less in any case, the temperatures of the first heater H1 and the second heater H2 are It is safe without overheating.

Further, the first heater H1 and the second heater H1
After the temperature of H2 reaches 60 ℃ and turns off, the first heater H1
Since the second heater H2 does not restart until the temperature of the second heater H2 drops to 35 ° C., the first heater H1 and the second heater H2
The ON and OFF intervals are very long, so you can easily know the failure.

Further, the first heater H1 and the second heater H2 are respectively provided with a first short-circuit detection line G1 and a second short-circuit detection line G2 in a relationship between the inner winding and the outer winding. Therefore, when the voltage of the first heater H1 or the second heater H2 rises, the inserted nylon layer softens, and the first short-circuit detection line G1 or the second short-circuit detection line G2 becomes the first heater
Short-circuited to H1 or the second heater H2, commercial AC power supply E, power switch SW1, temperature fuse F, resistor R25, diode D11, resistor R24, short-circuit detection line G1 or short-circuit detection line G2,
A current flows through the first heater H1 or the second heater H2, the current flowing through the resistor R24 increases, the resistor R24 generates heat, the temperature fuse F is melted, and the power is turned off. Is also safe against.

Further, the first heater H1 and the second heater H1
Regarding the temperature detection of H2, for example, the sensor 9 may detect whether or not the respective temperatures are set, or may detect based on both temperatures.

Regarding the temperature control of the first heater H1 and the second heater H2, the microcomputer 5 controls the first and second switch means 1 ₁ and 1 ₂ to control the first relay contact Ry1S. Or second relay contact Ry2S
By opening and closing, the control or the phase control based on the instantaneous temperature may be performed individually or both.

Further, according to the above embodiment, the short circuit detection line
The voltage drop and the fluctuation of the power supply voltage due to the disconnection of G1 and G2 are input and detected by the power supply voltage input port of the microcomputer 5, so that the circuit configuration is simplified and the use of the input port of the microcomputer 5 is reduced to 1 Therefore, the cost can be reduced and the software of the microcomputer 5 can be simplified.

[0061]

According to the electric heating appliance of the present invention, the control means detects the voltage of the short-circuit detection line to detect the fluctuation of the power supply voltage, and when the voltage of the short-circuit detection line is out of the predetermined range, For example, when the short-circuit detection line is broken or the power supply voltage is abnormally increased or decreased, the switch means is turned off to stop the power supply to the heating element. It is possible to detect it, prevent abnormal overheating of the heating element, and improve safety.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an electric carpet of an embodiment of an electric heating appliance of the present invention.

FIG. 2 is a perspective view showing an appearance of the electric carpet of the above.

FIG. 3 is a flowchart showing the same operation.

[Explanation of symbols]

1 ₁ , 1 ₂ Switch means 5 Microcomputers G1 and G2 as control means Short circuit detection lines H1 and H2 Heaters as heating elements

Claims (1)

[Claims] 1. A heating element, a switch means for turning the heating element on and off, a short-circuit detection line short-circuited with the heating element when the heating element overheats, and a voltage of the short-circuit detection line for detecting a power supply voltage. And a control means for turning off the switch means when the voltage of the short-circuit detection line is out of a predetermined range.