JPH11144590A - Load control circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly detect the closing failure caused by fusion of a relay contact for switching a heater load and the opening failure caused by contact failure. SOLUTION: Heater loads 1a, 1b, 1c are opened/closed with relay contacts 3a, 3b, 3c of main relays 2a, 2b, 2c. A relay contact 5 of an auxiliary relay 4 for opening/closing in a bundle the heater loads 1a, 1b, 1c is inserted between a power source 6 and the heater loads 1a, 1b, 1c. A voltage detecting means 13 comprising a resistance 14 and the light emitting side 15a of a photocoupler is connected in parallel to the relay contact 5. The light receiving side 15b of the photocoupler is connected to a control signal processing part 7. For example, when the relay contact 5 is opened, and relay coil parts 8a, 8b, 8c of the main relays 2a, 2b, 2c are made off, if the light receiving side 15b of the photocoupler is in the on state, the occurrence of the closing failure of the relay contacts 3a, 3b, 3c caused by fusion can be seen.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a load control circuit for controlling a load such as a heater load of an air conditioner.

[0002]

For example, in an air conditioner having a heating or drying function, when opening / closing control of a heater load by a relay as opening / closing means, it is detected by a thermistor or the like whether or not a predetermined temperature has been reached. The current supply to the heater load is controlled. During the operation of the air conditioner, the relay constantly repeats the opening and closing operations. Therefore, as the air conditioner is operated for a long period of time, the relay contacts wear and may eventually cause contact welding. In a conventional heater load control circuit, when contact welding occurs, the heater load is usually continuously energized, and finally the overheat prevention device operates. Thereby, the air conditioner is safely stopped.
However, if the over-temperature protection device is activated,
It is necessary not only to replace the relay, but also to replace or reset the overheating prevention device.

[0003] In addition, contact welding rarely leads to a completely welded state immediately, and the welded state is reached after repeated minor welding, so that the contacts do not always remain closed during repair. If the contacts return to the open state, the repair worker cannot identify the cause of the failure.

An object of the present invention is to provide a load control circuit capable of monitoring a short-circuit fault or an open fault such as welding of a contact of a switching means for switching a load. Aim. It is a second object of the present invention to provide a load control circuit that can stop energizing a load when a short-circuit fault occurs.

[0005]

According to a first aspect of the present invention, there is provided a switching means for opening and closing a load, detecting a current or a voltage in a circuit including the opening and closing means, in order to achieve the first object. An opening / closing monitoring means for monitoring whether the opening / closing means is closed or open based on the driving state of the opening / closing means.

[0006] This makes it possible to quickly detect a short-circuit fault or an open fault such as welding of a contact point of the switching means, and it is also possible to detect a malfunction of the switching means.

In order to achieve the first and second objects, the invention according to claim 2 includes a single or a plurality of first opening / closing means for opening / closing a single or a plurality of loads, respectively, A second opening / closing means which can be opened / closed at once, a voltage detection means provided in parallel with the second opening / closing means, an output signal of the voltage detection means, the first opening / closing means and the second opening / closing means Open / close monitoring means for monitoring the closed / open state of the first opening / closing means or the second opening / closing means according to the driving state of the first opening / closing means.

In this configuration, for example, if the voltage detecting means detects a predetermined voltage in a state where the second opening / closing means is opened, it is found that the first opening / closing means is in a closed state, and the first opening / closing means is in a closed state. If the opening / closing means should be in the open state, it is known that the first opening / closing means has a short-circuit failure. Further, when the second opening / closing means is originally in the open state and the first opening / closing means should be in the closed state, if the voltage detecting means does not detect a predetermined voltage, the first opening / closing means is opened. It can be seen that a failure has occurred, the second switching means has a short-circuit failure, or the voltage detection means itself has a failure. When a short-circuit failure of the first opening / closing means is detected, the second opening / closing means can be opened to stop energizing the load.

According to a third aspect of the present invention, in the load control circuit according to the second aspect of the present invention, the voltage is controlled by closing the first opening / closing means at the start of energization of the load control circuit or at an arbitrary timing during operation. It is provided with a confirmation means for confirming whether or not the output signal of the detection means is correctly outputted.

As described above, a short-circuit failure, an open failure, and a failure of the voltage detecting means itself can be detected from the output signal of the voltage detecting means and the driving state of the switching means. By checking whether the output is correct or not, the reliability of the failure detection is improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of a load control circuit according to the present invention will be described.
An embodiment will be described with reference to FIGS. First, the configuration of the load control circuit will be described based on the circuit block diagram of FIG. The load control circuit of the present embodiment is for an air conditioner, and the loads are heater loads 1a, 1b, 1c and 3
There are two. Each of these heater loads 1a, 1b, 1c has
Relay contacts 3a, 3b, 3c of main relays 2a, 2b, 2c as first opening / closing means are connected in series, and a series circuit of these heater loads 1a, 1b, 1c and relay contacts 3a, 3b, 3c. Are connected in parallel. A relay contact 5 of a sub-relay 4 as a second switching means is connected in series to these load circuits, and a series circuit of this load circuit and the relay contact 5 is connected between both poles of a commercial AC power supply 6. It has become so. That is,
Each of the heater loads 1a, 1b, 1c has a corresponding main relay 2a,
2b and 2c open and close individually, and one sub-relay 4 opens and closes all at once.

A control signal processor 7 is also connected between the two poles of the commercial AC power supply 6. The control signal processing section 7 includes relay coil sections 8a, 8a of the relays 2a, 2b, 2c, 4
b, 8c, 9 are connected, and the control signal processing unit 7 controls the opening and closing of the relay contacts 3a, 3b, 3c, 5 by controlling the energization of the relay coil units 8a, 8b, 8c, 9. further,
The control signal processing unit 7 is also connected with a thermistor 11 for temperature detection and an operation switch 12.

Further, a commercial AC power supply 6 and heater loads 1a, 1
A series circuit of a resistor 14 constituting a voltage detecting means 13 and a light emitting side 15a of a photocoupler is connected in parallel to a relay contact 5 of the sub-relay 4 inserted between b and 1c. On the other hand, the light receiving side 15b of the photocoupler is connected to the control signal processing unit 7. If the voltage between both poles of the relay contact 5, that is, both ends of the series circuit of the resistor 14 and the light emitting side 15a of the photocoupler is equal to or more than a predetermined value, the light receiving side of the photocoupler
15b turns on, otherwise the photocoupler light-receiving side
b turns off. Then, the control signal processing unit 7 determines the relay contacts 3a, 3b, 3c, 5 based on the output signal of the voltage detection means 13 obtained from the light receiving side 15b of the photocoupler and the driving state of the coil units 8a, 8b, 8c, 9 It has a function as opening / closing monitoring means for detecting and monitoring the closed and open states of the device.
As will be described later in detail, the control signal processing unit 7 closes the relay contacts 3a, 3b, 3c at the start of energization of the load control circuit or at an arbitrary timing during operation, so that the voltage detection unit 13 is closed. Also has a function as a confirmation means for confirming whether or not the output signal is correctly output.

Although not shown, the load control circuit includes heater loads 1a, 1b, 1c when the temperature exceeds a predetermined temperature.
There is also provided an over-temperature prevention device as a safety device for forcibly stopping energization of the device.

Next, the operation of the above configuration will be described. Figure 2 shows the relay contacts 3 when the air conditioner is operating.
The timing chart when a, 3b, and 3c open and close normally is shown. When the operation is started by turning on the operation switch 12, the temperature of the air to be controlled is
When the detected temperature is lower than the predetermined temperature, the relay contacts 5 are closed, and then the heater loads 1a, 1b,
All or part of the relay contacts 3a, 3b, 3c connected to 1c are closed to start heating. When the thermistor 11 detects that the temperature of the air has reached a predetermined temperature, the relay contacts 3a, 3b, and 3c are first opened, and then the relay contact 5 is opened. In addition, the relay contact 5 is replaced with the relay contact
The reason why the relay contacts 5 are closed earlier and opened later than 3a, 3b, and 3c is to prevent the relay contacts 5 from being burdened with opening and closing actual loads. After opening the relay contact 5, the control signal processing unit 7 confirms that the light receiving side 15b of the photocoupler is not turned on. As shown in FIG. 2, it is normal that the light receiving side 15b of the photocoupler is not turned on. That is, if the relay contacts 3a, 3b, and 3c are actually opened, no voltage is generated across the series circuit of the resistor 14 and the light-emitting side 15a of the photocoupler, so that the light-receiving side 15b of the photocoupler is turned off. Become. If the light receiving side 15b of the photocoupler is not turned on, when the temperature detected by the thermistor 11 becomes lower than a predetermined temperature, the relay contacts 3a, 3b, 3c, 5 are closed again in the same order and heated. To start.

FIG. 3 shows, as an example, a timing chart when the relay contact 3a is temporarily and slightly welded. The same applies to other relay contacts 3b and 3c. When the temperature detected by the thermistor 11 reaches a predetermined temperature, the control signal processing unit 7 switches the relay contacts 3a, 3b, 3c
The relay coil sections 8a, 8b and 8c are turned off in order to open the relay. However, if only the relay contact 3a is actually kept closed for welding, the resistance 14 Then, a predetermined voltage is applied between both ends of the series circuit on the light emitting side 15a of the photocoupler, and the light receiving side 15b of the photocoupler is turned on. The control signal processing unit 7
Based on this signal, it is detected that the relay contacts 3a, 3b, 3c have a short-circuit failure due to welding or the like, and the subsequent operation is stopped. That is, even if the temperature detected by the thermistor 11 becomes lower than the predetermined temperature, the relay coil portions 8a, 8b,
8c and 9 are not turned on. This continues until the power is turned off and then back on.

FIG. 4 is a timing chart showing the operation when the power is turned on. When power is turned on, relay contact 3
a, 3b, and 3c are sequentially closed and opened, and the voltage detection circuit 13
Check that the relay contacts 3a, 3b, and 3c are open (failure that cannot be closed due to poor contact) and that the relay contacts 5 are short-circuited due to welding or the like. Monitor for any. The signal on the light receiving side 15b of the photocoupler shown in FIG. 4 is for a normal case, and the light receiving side 15b of the photocoupler is turned on at the same timing as the closing of the relay contacts 3a, 3b, 3c. One of the relay contacts 3a, 3b, 3c is actually open, the relay contact 5 is closed, or the resistor 14 or the photocoupler is open due to a failure. 4, the signal as shown in FIG. 4 cannot be obtained, but in this case, the control signal processing unit 7 determines that a failure has occurred,
Subsequent driving is prohibited. More specifically, if the light receiving side 15b of the photocoupler is off when the relay coil unit 9 is off and the relay coil units 8a, 8b, 8c are on, it is possible that the corresponding relay Contacts 3a, 3
Either b, 3c has an open fault, the relay contact 5 has a short-circuit fault, or the resistor 14 or the photocoupler itself is open.

According to the configuration of the first embodiment, a failure such as a closing failure of the relay contacts 3a, 3b, 3c of the relays 2a, 2b, 2c serving as switching means for the heater loads 1a, 1b, 1c is immediately performed. Can be detected. It is also possible to detect temporary light welding of the relay contacts 3a, 3b, 3c. In particular, when the power is turned on, the relay contacts 3a, 3b, and 3c are sequentially closed and opened, and by checking whether the voltage detection circuit 13 outputs a signal correctly, the relays 2a, 2b, 2c, 4 and the malfunction of the voltage detection means 13 itself can be detected, and the reliability of failure detection is improved. Further, the auxiliary relay 4 that can open and close the three heater loads 1a, 1b, and 1c collectively allows the heater loads 1a, 1b, and 3c to operate even when the relay contacts 3a, 3b, and 3c of the main relays 2a, 2b, and 2c cause a short-circuit failure. Since the power supply to 1b and 1c can be stopped, it is possible to prevent the temperature from reaching an abnormal temperature, and it is safe. In addition, since the power supply to the heater loads 1a, 1b, 1c can be stopped before the temperature reaches an abnormal temperature and the overheat prevention device operates, the relays 2a, 2b, 2c, 4 and the voltage detecting means 13 When repairing, there is no need to replace or reset the overheating prevention device. The current flowing through the heater loads 1a, 1b, 1c via the voltage detecting means 13 is very small.
1a, 1b, and 1c are substantially in a non-energized state.

FIG. 5 is a timing chart showing a second embodiment of the present invention. In the second embodiment, before the heater loads 1a, 1b, and 1c are energized during operation, and each time, the voltage detection circuit 13 confirms whether or not the voltage detection circuit 13 correctly outputs a signal to determine whether there is a failure. Is to monitor.
This check is the same as that of FIG. 4 described above. The relay contacts 3a, 3b, and 3c are sequentially closed and opened, and it is checked whether the voltage detection circuit 13 correctly outputs a signal. It monitors whether 3a, 3b, 3c has an open failure, whether the relay contact 5 has a short-circuit failure, and whether the voltage detection circuit 13 itself has a failure. When a failure is detected, the subsequent operation is prohibited, and the heater loads 1a, 1b, and 1c are not energized. As in the second embodiment, by monitoring the presence or absence of a failure at any time during operation, if a failure occurs during operation, the failure can be detected while the operation is continued,
The failure can be quickly detected, and the air conditioner can be stopped.

It should be noted that the present invention is not limited to the above embodiment, and various modifications can be made. For example,
In the above embodiment, the number of loads is three, but the number of loads is not limited thereto, and may be one. In particular, when the number of loads is one, only one first opening / closing means for opening / closing the load may be provided. In the above embodiment, the switching means is a relay, but the switching means may be a semiconductor type such as a bidirectional thyristor. Further, in the above-described embodiment, the failure such as welding is detected using the voltage detecting means connected in parallel to the second switching means inserted between the power supply and the load. It is also possible to detect a failure such as welding by a current detection means inserted between the first and second electrodes. However, with the configuration using the voltage detecting means as in the above embodiment, there is no power loss due to the detecting means during operation. Further, it is also possible to store data relating to a failure in a memory and use it for repair or the like. Furthermore, in the above embodiment, the load is the heater load of the air conditioner, but the present invention can be applied to various loads of various electric devices. For example, a motor load of a ventilator in a factory or the like,
It may be a load of an electric pump of an oil lifter that pumps kerosene into a tank on a floor higher than the floor.

[0021]

According to the load control circuit of the first aspect of the present invention, the open / close means for opening / closing the load, the detection of the current or voltage in the circuit including the open / close means, and the driving state of the open / close means depend on the drive state of the open / close means. The provision of the open / close monitoring means for monitoring the closed / open state of the means makes it possible to quickly detect a short-circuit failure or an open failure such as contact welding of the open / close means, and also detects a malfunction of the open / close means. be able to.

According to the load control circuit of the second aspect of the present invention,
A single or a plurality of first opening / closing means for respectively opening / closing a single or a plurality of loads, a second opening / closing means capable of opening / closing all the loads collectively, and a plurality of the first / opening means provided in parallel with the second opening / closing means The closed / open state of the first opening / closing means or the second opening / closing means is determined by the voltage detecting means, the output signal of the voltage detecting means, and the driving states of the first opening / closing means and the second opening / closing means. The provision of the open / close monitoring means for monitoring makes it possible to quickly detect a short-circuit failure or an open failure such as welding of a contact of the first open / close means, and to detect a malfunction of the open / close means. Further, when a short circuit failure or the like of the first opening / closing means is detected, it is also possible to open the second opening / closing means and stop energizing the load.

According to the load control circuit of the third aspect of the present invention,
In addition to the effect of the invention of claim 2, by closing the first opening / closing means at the start of energization of the load control circuit or at any timing during operation, the output signal of the voltage detection means is correctly output. Providing the confirmation means for confirming whether the short circuit failure or the open failure of the opening / closing means is more reliable.

[Brief description of the drawings]

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

FIG. 2 is a timing chart showing a control circuit operation during the same operation.

FIG. 3 is a timing chart showing an operation when the opening / closing means fails.

FIG. 4 is a timing chart showing the operation of the control circuit when the power is turned on.

FIG. 5 is a timing chart showing a second embodiment of the load control circuit of the present invention.

[Explanation of symbols]

 1a, 1b, 1c Heater load (load) 2a, 2b, 2c Main relay (first opening / closing means) 4 Secondary relay (second opening / closing means) 7 Control signal processing section (opening / closing monitoring means, checking means) 13 Voltage detection means

Claims (3)

[Claims] An opening / closing means for opening / closing a load, and an opening / closing monitoring means for monitoring a closed / open state of the opening / closing means by detecting a current or a voltage in a circuit including the opening / closing means and a driving state of the opening / closing means. A load control circuit comprising: 2. A single or a plurality of first opening / closing means for respectively opening / closing a single or a plurality of loads, a second opening / closing means capable of opening / closing all of the loads at once, and the second opening / closing means Voltage detecting means provided in parallel with the first switching means or the second switching means depending on the output signal of the voltage detecting means and the driving states of the first switching means and the second switching means. A load control circuit comprising: an opening / closing monitoring unit that monitors an open state and an open state. 3. Checking whether the output signal of the voltage detecting means is correctly output by closing the first opening / closing means at the start of energization of the load control circuit or at an arbitrary timing during operation. 3. The load control circuit according to claim 2, further comprising means.