Multicircuit control apparatus and control method therefor

Abstract: In a multicircuit control apparatus (10) including a mechanical main contact (125) and plural semiconductor switching devices such as triacs (13a, ---, 13d) each connected in series to the main contact, the main contact is closed by a control circuit 15 prior to turning-on of any of the semiconductor switching devices and is also opened by the control circuit 15 after completion of turning-off of all the semiconductor devices.

Description: The present invention relates to a multicircuit control apparatus for frequently opening/closing many lighting feeder circuits or the like. A circuit control apparatus is disclosed in FR-A 2 563 394 comprising a main contact connected to a power source. A load comprising an electric motor is connected to the main contact via a plurality of semi-conductor switching devices, each being connected in series to the main contact. A control circuit closes the main contact before turning on the semi-conductor switches in response to on-command signals supplied thereto. In addition, the main contact is opened only after turning off the semi-conductor switches in response to an off-command signal. FIG.6 is a connection diagram showing another conventional multicircuit control apparatus which is disclosed in the gazette of JP-A-62-193481. In FIG.6, a multicircuit 100 includes plural (e.g. four) remote-controlled relays 3A, 3B, 3C and 3D, each of which has a main contact 35 for opening and closing a load circuit (not shown) connected opening and closing a load circuit (not shown) connected therewith. These remote-controlled relays 3A, 3B, 3C and 3D are connected with four remote control switches 6A, 6B, 6C and 6D via a power source 7, respectively, thereby constituting a multicircuit control apparatus in which each of the remote-controlled relays 3A, ---, 3D is controlled by corresponding one of remote control switches 6A, ---, 6D. FIG.7 is a circuit diagram showing only the circuit concerning the remote-controlled relay 3A and the remote control switch 6A in FIG.6. In the remote-controlled relay 3A, an end of an operation coil 31 is connected to the power source 7, and the other end is connected to both a cathode of a diode 32 and an anode of a diode 33. An anode of the diode 32 and a cathode of the diode 33 are connected to a changeover switch 34. This changeover switch 34 alternately makes connection with one of the diodes 32 and 33 at every inverting excitations of the operation coil 31. The main contact 35, which is to be connected to the load circuit, makes or breaks contact in response to the alternate connecting states of the changeover switch 34. In the remote control switch 6A, an anode of a diode 61 and a cathode of a diode 62 are connected to the changeover switch 34 of the remote-controlled relay 3A, and a cathode of the diode 61 and an anode of the diode 62 are connected to the power source 7 through switches 63a and 63b, respectively. A cathode of a diode 65 is connected to the changeover switch 34 via a resistor 64, and an anode of the diode 65 is connected to a cathode of an LED 66. An anode of a diode 68 is also connected to the changeover switch 34 via a resistor 67, and a cathode of the diode 68 is connected to an anode of an LED 69. Both an anode of the LED 66 and a cathode of the LED 69 are connected to the power source 7. Next, operation of the above-mentioned conventional remote control switch 6A and remote-controlled relay 3A is described. In a state shown in FIG.7, current flows in a closed loop which includes the power source 7, the LED 66, the diode 65, the resistor 64, the changeover switch 34, the diode 32 and the operation coil 31. Flowing of the current is allowed in only one direction because of presence of the diodes 65 and 32, and the LED 66 emits light. Since the current is limited by the resistor 64, excitation of the operation coil 31 is not enough to actuate the changeover switch 34. From this state, when the switch 63b is closed, current flows through the switch 63b, the diode 62, the changeover switch 34, the diode 32 and the operation coil 31. Since this current is not limited by any resistor, the operation coil 31 is sufficiently excited, thereby causing the changeover motion of the changeover switch 34. Thus, the changeover switch 34 instantaneously changes the connection from terminal 34b to a terminal 34a, and the main contact 35 breaks contact at the same time. Once the changeover switch 34 makes connection to the terminal 34a, the current flow is stopped due to the reverse polarity of the diode 33. In this state, current flows in a closed loop which includes the power source 7, the operation coil 31, the diode 33, the changeover switch 34, the resistor 67, the diode 68 and the LED 69. Flowing of the current is allowed in only one direction due to presence of the diodes 33 and 68, and the LED 69 emits light. Since the current is limited by the resistor 67, excitation of the operation coil 31 is not sufficient to actuate the changeover switch 34. From this state, when the switch 63a is closed, current flows through the operation coil 31, the diode 33, the changeover switch 34, the diode 61 and the switch 63a. Since this current is not limited by any resistor, the operation coil 31 is sufficiently excited, thereby causing the changeover motion of the changeover switch 34. Thus, the changeover switch 34 instantaneously changes the connection from the terminal 34a to the terminal 34b, and the main contact 35 makes contact at the same time. Once the changeover switch 34 makes connection to the terminal 34b, the current does not flow any more because of the reverse polarity of the diode 32, thus returning to the initial state shown by FIG.7. The above-mentioned control is carried out in substantially only one loop with two wires connected to the remote control switch 6A by utilizing respective half waves of AC power source 7 as two directional signals. This has been known as the "two-wire" control method. In the above-mentioned conventional multicircuit control apparatus, the main contact 35 is a mechanical contact which is mechanically actuated by electromagnetic force generated by the operation coil 31. Since the operation coil 31 necessitates a comparatively large amount of energy to generate such an electromagnetic force, the total energy required becomes large for control of many circuits such as the lighting feeder circuits. Therefore, the power source 7, which is the energy only for the control, has to be of large capacity. This is of course undesirable in respect of saving energy. In order to save energy, one could replace the mechanical contact with a solid state device such as a solid state relay. However, employment of the solid state device brings another serious problem that insulation between the primary line (power source) and the secondary line (load) of the solid state device is not reliable. This is caused by leakage current through the solid state device or a protection circuit such as a snubber circuit provided in parallel with the solid state device. Therefore, even after completion of opening the circuit, should an operator touch the secondary line with his fingers, he receives an unexpected electrical shock. Besides, the leakage current could cause an accident such as a fire. Under these circumstances, it has been difficult in practice to use solid state devices in place of the mechanical contacts. An object of the present invention is to provide a multicircuit control apparatus which has a very long lifetime and high insulating ability of off time and reduces the energy required for operation. In order to achieve the above-mentioned object, a multicircuit control apparatus is provided by the present invention as defined in claim 1. The invention will be better understood and appreciated from the following detailed description of embodiments taken in conjunction with the drawings. FIG.1 is a single-line diagram showing a multicircuit control apparatus in one embodiment of the present invention. FIG.2 is a circuit diagram showing connections between the multicircuit control apparatus 10 in FIG.1 and four remote control switches 6A, ---, 6D. FIG.3 is a circuit diagram showing an internal circuit of an electromagnetic switch 12 in FIG.1. FIG.4(a) and FIG.4(b) are circuit diagrams showing two types of an internal circuit of the remote control switch 6A in FIG.2. FIG.5 is a graph showing each on or off state of a main contact 125 and plural triacs 13a, ---, 13d in FIG.2. FIG.5a is a flow chart which is to be executed by a microcomputer 152 in FIG.1. FIG.6 is a circuit diagram showing the conventional multicircuit control apparatus. FIG.7 is a circuit diagram showing the conventional two-wires control circuit extracted from FIG.7. Hereafter, a preferred embodiment of the present invention is described with reference to the accompanying drawings. FIG.1 is a single-line diagram showing a multicircuit control apparatus 10. The multicircuit control apparatus 10 includes an electromagnetic switch 12, plural (e.g. four) semiconductor control devices such as triacs 13a, 13b, 13c, 13d and a control circuit 15 and has a primary terminal 11, four secondary terminals 14a, 14b, 14c, 14d and four control terminals 16a, 16b, 16c, 16d with a common terminal 17. A main contact 125 of the electromagnetic switch 12 is connected to the primary terminal 11, and each of the triacs 13a, 13b, 13c and 13d is connected in series with the main contact 125 of the electromagnetic switch 12. Secondary lines of the triacs 13a, 13b, 13c and 13d are connected to the secondary terminals 14a, 14b, 14c and 14d, respectively. A control section 12a of the electromagnetic switch 12 and gate lines of the triacs 13a, ---, 13d are connected to the control circuit 15 which receives signals from the control terminals 16a, ---, 16d and its common terminal 17. The primary terminal 11 is connected to a main power source (not shown), and the secondary terminals 14a, ---, 14d are connected to respective loads such as lighting equipments. The control circuit 15 is composed of an input signal processing circuit 151, a microcomputer 152, a gate control circuit 153, a power source circuit 154, a switch control circuit 155 and plural diodes 156a, ---, 156d. Input signals coming from the remote control switch 6A, ---, 6D are supplied to the microcomputer 152 through the input signal processing circuit 151. The microcomputer 152 takes the present on/off states of the main contact 125 and the triacs 13a,---, 13d into consideration and forwards control signals to the gate control circuit 153 and the switch control circuit 155, thereby controlling the triacs 13a, ---, 13d and the electromagnetic switch 12, respectively. Four diodes 156a, ---, 156d are provided in order to separate signals given to the control terminals 16a, ---, 16d from one another. FIG .2 is a circuit diagram showing connections between the above-mentioned multicircuit control apparatus 10 and four remote control switches 6A, ---, 6D each having two terminals 601x and 602x (x = a, b, c, d) for the two-wire control. The terminals 602x (x = a, b, c, d) are connected to the common terminal 17 via a power source 7 of 24V AC, and the terminals 601x (x = a, b, c, d) are connected to the control terminals 16a, 16b, 16c and 16d, respectively. The triacs 13a, ---, 13d are switched on or off by the corresponding remote control switches 6A, ---, 6D, respectively. FIG.3 is a circuit diagram showing an internal circuit of the electromagnetic switch 12 which is composed of the main contact 125 and the control section 12a. In FIG. 3, a cathode of a diode 121, an anode of a diode 122 and one end of an operation coil 124 are connected to the control circuit 15 (FIG.1). The other end of the operation coil 124 is connected to a common terminal of a changeover switch 123 which alternately makes connection with one of the diodes 121 and 122 at every inversions of excitation of the operation coil 124. The main contact 125 is also actuated by the operation coil 124 to make/break contact in response to the alternate state of the changeover switch 123. That is, when the changeover switch 123 makes connection with the diode 121 as shown in FIG. 3, the main contact 125 is opened. When the changeover switch 123 makes connection with the diode 122, the main contact 125 is closed. FIG. 4(a) and FIG. 4(b) are circuit diagrams showing two types of an internal circuit, for instance, of the remote control switch 6A. Other remote control switches 6B, ---, 6D have the same internal circuit as that of the remote control switch 6A. In FIG.4(a), an anode 61 of a diode 61 and a cathode of a diode 62 are connected to the terminal 601a. One end of a switch 63a and one end of a switch 63b are connected to the diodes 61 and 62, respectively, and both the other ends of the switches 63a and 63b are connected to the terminal 602a. A resistor 64 is connected between the terminals 601a and 602a. In another circuit shown by FIG.4(b), the diodes 61, 62 and the switches 63a, 63b are provided in the similar way to the above. Further, between the terminals 601a and 602a, operation indicator circuits are provided. That is, an anode of an LED 66 is connected to the terminal 602a via a resistor 64, and its cathode is connected to the terminal 601a. A cathode of an LED 69 is connected to the terminal 602a, and its anode is connected to the terminal 601a via a resistor 67. Next, operation of the above-mentioned embodiment is described with reference to FIGs. 1 --- 5. FIG.S is a graph showing each on or off state of the main contact 125 and the triacs 13a, ---, 13d. A time chart "M" represents an on or off state of the main contact 125, and time charts A, B, C and D represent on or off states of the triacs 13a, 13b, 13c and 13d, respectively. In a state that all the triacs 13a, ---, 13d are off, for example, when the remote control switch 6A (FIG.2) turns on by closing the switch 63b (FIG.4(a) or 4(b)) at the time T₁ (FIG.5), a certain voltage based on half waves of the power source 7 is applied to the terminal 16a of the multicircuit control apparatus 10. The control circuit 15 receives the above-mentioned voltage and gives the operation coil 124 (FIG. 3) of the electromagnetic switch 12 an excitation signal. The main contact 125 is thereby closed at the time T₂. Since all the triacs 13a, ---, 13d are off yet at this point in time, the main contact 125 does not close any load circuit but merely makes connection. Subsequently, the control circuit 15 gives a gate of the triac 13a a turn-on signal at the time T₃. The triac 13a is thereby turned on, and the power is supplied to the load (not shown) connected therewith. In case where one of other triacs 13b, 13c and 13d is turned on instead of the triacs 13a, the similar operation to that mentioned above is carried out. After turning-on of one triac (e.g. 13a), it is possible to quickly turn on another triac upon receipt of an on-command from any of the remote control switches 6B, ---, 6D. Hereupon, once the control circuit 15 makes the electromagnetic switch 12 on, the control circuit 15 maintains the on-state of the electromagnetic switch 12 as long as at least one triac is on. This will be described in detail about an example shown in FIG.5 wherein four triacs 13a, ---, 13d are turned on and subsequently off in turn with an overlap time when two triacs are on. That is, the triac 13c is turned on as shown by the time chart C before the triac 13a (the time chart A) is turned off. Next, the triac 13b (the time chart B) is turned on before the triac 13c is turned off. Further, the triac 13d (the time chart D) is turned on before the triac 13b is turned off. In the above-mentioned process, since at least one triac is always on, the main contact 125 (the time chart M) is maintained to be on-state by the control circuit 15. When the remote control switch 6D is switched off at the time T₄, the control circuit 15 shuts off the gate signal for the triac 13d. The triac 13d is thereby turned off at the time T₅. At that moment, the control circuit 15 detects a state that all gate voltages of the triac 13a, ---, 13d are zero, and subsequently, the control circuit 15 actuates the electromagnetic switch 12 to open its main contact 125 at the time T₆. Since the load current has been already broken by the triacs 13a, ---, 13d, the main contact 125 does not break the current in substance but makes disconnection only. Owing to the mechanical "open" state of the main contact 125, secondary lines of the main contact 125 is fully insulated from the primary lines. When one or more on-command signal is given from the remote control terminals 6A, ---, 6D again, the control circuit 15 makes the main contact on and subsequently turns the corresponding triac on. While the main contact 125 is closed, on or off control can be frequently carried out by the triacs 13a, ---, 13d which are opened/closed by a small power consumption without arc. That is, insulation of the secondary line in the off-time, which is important to safety, is secured by the main contact 125, and both saving energy and long lifetime are secured by the triacs 13a, ---, 13d which are the semiconductor control devices. In this embodiment, the above-mentioned on-operation procedure and off-operation procedure are executed in accordance with a flow chart shown in FIG.5a which is stored in the microcomputer 152.

Claims: A multicircuit control apparatus comprising: a main contact (125) connectable to a line (11) from a power source; a plurality of semiconductor switching devices (13a - 13d), each being connected in series to said main contact (125) and connectable to a load (14a - 14b); and a control circuit (15) which closes said main contact (125) before turning on the switching devices (13a - 13d) in response to on-command signals supplied thereto and opens said main contact (125) after turning off said switching devices in response to off-command signals supplied thereto, characterized in that said apparatus further comprises control terminals (16a - 16d) for separately receiving an on- or off-command signal for each one of said switching devices (13a - 13d), said control circuit (15), when all of said switching devices are in the off state, closes said main contact (125) in response to an on-command signal for turning on only one of said switching devices (13a - 13d) and thereafter turns on said one of the switching devices, and said control circuit (15) opens said main contact (125) upon detecting the condition that all of said switching devices (13a - 13d) have first been turned off.

Inventors: ARINOBU ICHIRO, ARINOBU, ICHIRO, ARINOBU, ICHIRO, C/O FUKUYAMA SEISAKUSHO
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1990
Main classification: H01H9
IPC codes: H01H9