JPH05307991A - Load controller - Google Patents

Abstract

PURPOSE:To provide an operationally safe load controller which can not be set in unsafeness even if relay-contact welding and a malfunction in a controlling means overlap each other in the case where a power failure is judged from a malfunction in a power synchronism detecting means. CONSTITUTION:A thermal fuse 13, a relay contact 7b and a neater 1 are respectively connected in series to an a.c. power source 14, the electrification of a heating resistance 12 disposed in close proximity to the thermal fuse 13 is controlled by a second power controlling means 11, and then a relay coil 7a is driven by a controlling means 4 in accordance with signals for turning on and off the heater 1. A make-and-break contact condition detecting means 9 detects the make-and-break condition of the relay contact 7b on the basis of a pulse signal incoming from a power synchronism detecting means 8 which generates the pulse signal synchronized with the output of the a.c. power source 14. When a power failure detecting means 15 detects the absence of the pulse signal incoming from the power synchronism detecting means 8 due to a power failure, a malfunction in the power synchronism detecting means 8 or the like, a safety means 10 energizes the second controlling means 11 so that the heating resistance 12 may be heated, with the thermal fuse 13 blown in order to shut off circuit power.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a load control device provided with safety means such as an electric carpet for controlling temperature and floor heating.

[0002]

2. Description of the Related Art Conventionally, a load control device of this type, for example, a control device for an electric carpet has been constructed as shown in FIG. The configuration will be described below.

As shown in the figure, the heater 1 constitutes a load, and the temperature of the heater 1 is detected as a voltage change by the temperature detecting means 3 via the temperature detecting body 2. The control means 4 controls the detection voltage VT and the set voltage V set by the temperature setting means 5.
If the detected temperature is higher than the set temperature, the transistor 6 is turned off, the relay coil (first power control means) 7a is turned off, and the relay contact (first power control means) is compared.
7b is opened to stop energizing the heater 1. On the contrary, if the detected temperature is lower than the set temperature, the relay coil 7a is turned on, the relay contact 7b is closed, and the heater 1 is energized.

Since the relay coil 7a and the relay contact 7b are used for controlling the energization of the heater 1 in this way, when the relay contact 7b has a welding failure, the result of the temperature comparison in the control means 4 and the transistor 6 are performed. The heater 1 continues to be energized irrespective of the control signal to, and finally there is a problem that the temperature of the equipment rises and the user is burned. As means for preventing this, there are a method of detecting welding of the relay contact 7b and cutting off the circuit power supply, and a method of judging excessive temperature by the detection voltage VT and cutting off the circuit power supply. It goes without saying that it is safer to detect the welding of 7b because it is possible to detect the abnormality earlier. Therefore, the power supply synchronization detection means 8 and the contact state detection means (energized state detection means) 9 detect the state of the relay contact 7b, determine whether or not the relay contact 7b is welded, and the relay contact 7b is welded. Then, the safety means 10 turns on the second power control means 11 to energize the heating resistor 12. Since the heating resistor 12 is arranged close to the thermal fuse 13, the temperature fuse 13 is melted by the temperature rise of the heating resistor 12, and the AC power source 14
To stop energizing the heater 1.

A mechanism for detecting the state of the relay contact 7b is shown in FIG.
And (Table 1). FIG. 3 shows the waveform of the AC power supply and the waveform of the input signal VPNT to the contact state detecting means 9 (Table 1).
Is the judgment of the relay contact state based on the result.

[0006]

[Table 1]

When the relay contact 7b is turned on, the waveform of the input signal VPNT to the contact state detecting means 9 is as shown in FIG.
As described above, the pulse signal is synchronized with the output waveform from the power supply synchronization detecting means 8 as shown in FIG. Since the point (A) on the positive cycle side is Lo and the point (A) on the negative cycle side is Hi, it is determined that the relay contact 7b is on.
When the relay contact 7b is off, the waveform of VPNT becomes a constant voltage as shown in FIG. 3 (d). In this case, since both the positive cycle side (A) point and the negative cycle side (A) point are Hi, it is determined that the relay contact 7b is off. If the signals VRLY and VPNT to the transistor 6 are outputting the relay-off signal to the transistor 6 and the relay contact 7b is on, it is determined that the relay contact 7b is welded, and the security means 10 causes the second power control means. 11 is turned on, the heating resistor 12 is energized to melt the temperature fuse 13, and the energization from the AC power supply 14 to the heater 1 is stopped.

[0008]

In such a load control device, since the power supply synchronization signal is not input when the power supply synchronization detection means 8 determines that there is a power failure, the point (A) on the positive cycle side, the negative point The point (a) on the cycle side cannot be specified, and the state of the relay contact 7b cannot be detected normally. If there is a real power failure, it is not dangerous because the relay power supply 7b and the heater 1 are not energized from the AC power supply 14, but a normal waveform cannot be output due to a circuit failure of the power supply synchronization detection means 8. , AC power supply 14 to relay contact 7
b. Although the heater 1 is energized, the state of the relay contact 7b cannot be detected and the safety means 10 cannot be operated. if,
At this time, if the relay contact 7b is welded or the control means 4 fails, the relay is kept on, which is extremely dangerous.

The present invention solves the above problems and provides a safe load control device which does not become unsafe due to welding of relay contacts or failure of control means even if a power failure is determined due to a failure of the power supply synchronization detection means. Is provided.

[0010]

In order to achieve the above object, the present invention has a first power control means connected to an AC power source through a temperature fuse to control the energization of a load, and arranged in the vicinity of the temperature fuse. Second power control means for controlling energization of the heat generation resistor, control means for controlling the first power control means based on a signal for turning on / off the load, and a power supply for producing a pulse signal in synchronization with the AC power supply. Synchronization detection means, conduction state detection means for detecting the conduction state to the load based on the pulse signal from the power supply synchronization detection means, and the AC power supply due to the disappearance of the pulse signal from the power supply synchronization detection means And a security means for energizing the second power control means when a power failure is detected by the power failure detecting means. To have.

[0011]

According to the present invention, the second power control means is operated by the above-mentioned problem solving means not only when the relay contacts are welded during the normal control but also when the power failure is detected due to the failure of the power failure detecting means. Even if the first power control means continues to turn on due to a short circuit failure of the power control means or a failure of the control means, the heating resistor can generate heat, the temperature fuse can be blown, and the circuit power can be turned off.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An electric carpet according to an embodiment of the present invention will be described below with reference to FIG. The same components as those in the conventional example are designated by the same reference numerals and the description thereof will be omitted.

As shown in the figure, the power failure detection means 15 detects whether or not there is a power failure by the input of the power supply synchronization detection means 8 and inputs the output to the security means 10, and when the power failure occurs, the security means 10 outputs the second power. The control means 11 is turned on.

The operation of the security means 10 in the above structure will be described with reference to (Table 2) and (Table 3). First, the power failure detection means 15 detects that there is no power failure by the pulse signal from the power supply synchronization detection means 8. At this time, as shown in (Table 2), the state of the relay contact 7b is discriminated from the state of the signal VRLY to the transistor 6 and the state of the input signal VPNT to the contact state detecting means 9, and VRLY is VPNT despite the relay OFF output. Is the relay contact 7b ON state,
Assuming that the relay contact 7b is welded, the second power control means 11 is turned on. This operation is the same as the conventional example.

[0015]

[Table 2]

Next, when the output from the power supply synchronization detecting means 8 becomes a pulse waveform and the power failure detecting means 15 detects a power failure, the state of the relay contact 7b cannot be detected normally. Therefore, in this embodiment, in this case, the security means 10 turns on the second power control means 11. The operation in this case is roughly divided into the following three, as shown in (Table 3). That is, A. If there is a power outage.

B. In the case where the power failure detection means 15 has a failure and there is no actual power failure, and the relay contact 7b is not welded.

C. When the power supply synchronization detection means 8 or the power failure detection means 15 has a failure and no power failure actually occurs, and the relay contact 7b is welded. There are three cases.

[0019]

[Table 3]

Explaining each case, when the power is cut off in A, the temperature fuse 13 is blown even if the second power control means 11 is turned on because the power supply of the entire circuit is cut off. There is no. Next, when the power failure of B and the relay contact 7b are not welded, even if the second power control means 11 is turned on, the AC power supply 1
4, the path of the heating resistor 12, the second power control means 11, and the AC power supply 14 is broken at the relay contact 7b. Therefore, the heating resistor 12 is not energized and the thermal fuse 13 is not blown. Furthermore, when the power failure of C has not occurred and the relay contact 7b is welded, the AC power supply 14,
Relay contact 7b, heating resistor 12, second power control means 1
1. Since the energization path of the AC power supply 14 is configured, the heating resistor 12 is energized and the temperature fuse 13 is blown. In this way, the power of the entire circuit can be cut off and safety can be maintained.

In this embodiment, a relay is used as the first power control means 7a and 7b, but even if a semiconductor power control element or the like is used for this, the same effect can be obtained against a short circuit of the element. It is clear that there is. Further, by configuring the security means 10, the power failure detection means 15, etc. using the microcomputer 16, it is possible to provide a safe load control device inexpensively without increasing the number of circuit components.

[0022]

As is apparent from the above embodiments, according to the present invention, the power failure detection means for detecting a power failure of the AC power supply due to the loss of the pulse signal from the power supply synchronization detection means and the power failure detection means are provided. Since a safety means for energizing the second power control means when a power failure is detected is provided,
It is possible to cope with a failure of the power supply synchronization detection means or the power failure detection means, and to reliably fuse the temperature fuse when the first power control means has a short circuit failure or when the control means has a failure, thereby improving safety.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of a load control device according to an embodiment of the present invention.

FIG. 2 is a circuit block diagram of a conventional load control device.

[Fig. 3] (a) to (d) Voltage waveform diagrams of essential parts of the same load control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 heater (load) 4 control means 7a relay coil (first power control means) 7b relay contact (first power control means) 8 power supply synchronization detection means 9 contact state detection means (energization state detection means) 10 security means 11 Second power control means 12 Heating resistance 13 Thermal fuse 14 AC power supply 15 Blackout detection means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshishi Yamamoto 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] 1. A first power control means for controlling the energization of a load by connecting to an AC power source via a temperature fuse, a second power control means for controlling the energization of a heating resistor arranged in the vicinity of the temperature fuse, and A control means for controlling the first power control means based on a signal for turning on and off a load, a power supply synchronization detection means for producing a pulse signal synchronized with the AC power supply, and a pulse signal from the power supply synchronization detection means. An energized state detecting means for detecting an energized state to the load based on a reference, a power failure detecting means for detecting a power failure of the AC power source due to the disappearance of a pulse signal from the power source synchronization detecting means, and the power failure detecting means. A load control device comprising: a security means for energizing the second power control means when a power failure is detected.