JPH0241262B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a load selection device suitable for connecting two electrical devices to one electrical outlet and selecting one of the electrical devices.

BACKGROUND ART Conventionally, large-capacity electrical devices such as air conditioners and microwave ovens are usually connected to electrical outlets that are wired with dedicated wiring in a 1:1 correspondence with wiring connections and disconnectors. However, even if you want to use two electrical devices in a room or place such as a condominium where there is only one outlet with dedicated wiring, it is often not possible to easily add additional dedicated wiring or outlets. Furthermore, since it is not possible to energize two electrical devices at the same time from one outlet for safety reasons, it is extremely inconvenient for the user to operate the devices by alternately inserting plugs into the same outlet.

Therefore, the present applicant proposed in an earlier application that it is possible to connect two electrical devices to one electrical outlet and select one of the electrical devices by providing a switch for each branch circuit branching from one electrical outlet. has been done.

However, in this proposal, each branch circuit must be provided with an opening/closing section, which results in a relatively high cost.

An object of the present invention is to provide a load selection device that solves the above-mentioned problems and makes it possible to reduce costs.

To achieve this objective, the present invention provides that between a main circuit connected to a power supply and a first and second branch circuit to which two loads are respectively connected, a common contact is connected to the main circuit and a normally open contact is connected to the main circuit. A first current detection means for detecting a load current in the first branch circuit, wherein the double-throw switching section is arranged so that the normally closed contact is connected to the first branch circuit and the normally closed contact is connected to the second branch circuit, respectively. A second current detection means for detecting the load current is provided in each of the second branch circuits, and a high impedance voltage detection means is connected between the common contact and the normally open contact of the double throw switching section, When the second current detection means does not detect the load current, the normally open contact is turned on for the double-throw switching section according to either the detection output of the first current detection means or the detection output of the voltage detection means. The present invention is characterized in that it includes a control means for outputting a signal, so that two branch circuits are opened and closed by one double-throw switching section.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

The drawing shows one embodiment of the present invention, in which one of two loads is selected. Two branch circuits 4a and 4b branched from the main circuit 3 are provided between the power supply side terminal 1 and the load side terminals 2a and 2b, and a double-throw switching section 5 is provided between the main circuit 3 and the branch circuits 4a and 4b. is provided. The double-throw switching section 5 includes a normally open contact 6a, a normally closed contact 6b, and a common contact 6c, and also has a contact that turns on between the normally open contact 6a and the common contact 6c by excitation of the relay coil 7. 8. As this double-throw opening/closing part 5, a switching contact of a relay is used which is switched by energizing and de-energizing the relay coil 7. Branch circuit 4a,
The current flowing through 4b is detected by current transformers 9a, 9b. Loads 10a and 10b are connected to the load side terminals 2a and 2b, respectively. A resistor 1 whose impedance is higher than the impedance of the load 10a is installed between the common contact 6c and the normally open contact 6a of the double-throw switching section 5.
1 and a photocoupler 14 consisting of a light emitting diode 12 and a phototransistor 13,
connected in parallel. The output from the photocoupler 14 is input to a monostable multivibrator 16 via a logic converter 15.

An amplifier 17 is installed on the output side of the current transformers 9a and 9b.
a, 17b are connected to rectifiers 18a, 18b and comparators 19a, 19b. A reference voltage generation circuit 20 generates a reference voltage for comparators 19a and 19b. An on/off command signal generation circuit 21 is connected to the output sides of the comparators 19a, 19b, and the on/off command signal generation circuit 21 includes an OR gate 22 and an AND gate 23. The or gate 22 is the load 10a
The normally open contact 6a of the double-throw switching section 5 is turned on only when the current transformer 9a is in the on state, or when the current is detected by the current transformer 9b and no current is detected by the current transformer 9b. AND gate 23 is load 10a,
The normally closed contact 6b is preferentially turned on when the contact 10b is in the ON state at the same time.

The switching circuit 24 stops the excitation of the relay coil 7 by inputting a low-level OFF command signal, turns on the normally closed contact 6b, and energizes the relay coil 7 by inputting a high-level ON command signal. Turn on the normally open contact 6a.

Next, the operation will be explained. The double throw opening/closing part 5 is
When the relay coil 7 is not energized, the normally closed contact 6b is turned on and the normally open contact 6a is turned off. First, a case where the load 10a is in the on state will be described. . Approximately the power supply voltage is applied between the common contact 6c of the double-throw switching section 5, the resistor 11 connected in parallel between the normally open contact 6a, and the photocoupler 14. Note that the resistor 11 is the load 1
It has a considerably high low resistance value compared to the impedance of load 10a (impedance of load 10a << resistance 1
1). When a power supply voltage is applied, a current flows through the light emitting diode 12 and it emits light, and the light hits the phototransistor 13 and is converted to a logic level by the logic converter 15, which is then input to the monostable multivibrator 16. A high level signal is output to the OR gate 22 for a certain period of time. Therefore, the output of the OR gate 22 becomes high level and is input to one input terminal of the AND gate 23. At this time, since the load 10b is not energized to the other input terminal of the AND gate 23, the output from the comparator 19b is is input at a low level, and therefore, a high level signal is output from the AND gate 23. By outputting a high-level signal from the AND gate 23, the switching circuit 24 excites the relay coil 7, and the contact 8 of the double-throw switching section 5 changes from the normally closed contact 6b to the normally open contact 6.
Switch to a.

When the normally open contact 6a is turned on, the load 10a is energized and detected by the current transformer 9a. Due to this detection signal, a high level signal is input to one input terminal of the AND gate 23 via the amplifier 17a, rectifier 18a, comparator 19a and OR gate 22, so the output of the monostable multivibrator 16 is inverted to low level. However, one input of the AND gate 23 is held at a high level. Since the low level signal from the comparator 19b is input to the other input terminal of the AND gate 23 as described above, the output of the AND gate 23 is held at a high level. This causes the switching circuit 24
continues to excite the relay coil 7, and the normally open contact 6a
Keep it on. Therefore, energization of the load 10a continues.

Next, a case where the load 10b is in the on state will be explained. Since the contact 8 of the double-throw opening/closing section 5 turns on the normally closed contact 6b, current flows through the branch circuit 4b and is detected by the current transformer 9b. The detection signal passes through the amplifier 17b and the rectifier 18b, and the comparator 19b outputs a high-level signal, so the output of the AND gate 23 becomes low level, and the switching circuit 24 does not excite the relay coil 7. The contact 8 of the throw-open/close portion 5 does not switch and keeps the normally closed contact 6b turned on.

Next, a case will be described in which the loads 10a and 10b are turned on at the same time. Since the normally closed contact 6b is on, a detection signal is output from the current transformer 9b,
A high level signal is output from the comparator via the amplifier 17b and the rectifier 18b. Therefore, since a low level signal is always output from the AND gate 23, the switching circuit 24 does not excite the relay coil 7, and the load 10b is energized preferentially.

According to this embodiment, the two branch circuits 4a and 4b can be opened and closed by one double-throw opening/closing section 5, so that the cost can be reduced.

In the illustrated embodiment, current transformers 9a and 9b correspond to current detection means, and resistor 11 and photocoupler 14
corresponds to the voltage detection means of the present invention, and the on/off command signal generation circuit 21 corresponds to the control means of the present invention.

In this embodiment, a current transformer 9 is used to detect the current.
a and 9b are used, but the present invention is not limited to this, and a current shunt may be used, and a transformer may be used in place of the resistor 11 and the photocoupler 14. Note that the DC power supply section is omitted.

As explained above, according to the present invention, a common contact is connected to the main circuit between the main circuit connected to the power supply and the first and second branch circuits to which two loads are respectively connected. A first current detection device that detects a load current in the first branch circuit by arranging a double-throw switch so that the contact is connected to the first branch circuit and the normally closed contact is connected to the second branch circuit. and a second current detection means for detecting the load current in the second branch circuit, and a high impedance voltage detection means is connected between the common contact and the normally open contact of the double throw switching section. , in a state where the second current detection means does not detect the load current, depending on either the detection output of the first current detection means or the detection output of the voltage detection means,
Since the double-throw switching section is equipped with a control means that outputs a normally open contact ON signal, and the two branch circuits are opened and closed by one double-throw switching section, it is possible to open and close two branch circuits as in the previous application. Furthermore, compared to a circuit in which two branch circuits are opened and closed by two opening/closing parts, the circuit configuration can be made at a lower cost.

[Brief explanation of drawings]

The drawing is a circuit diagram showing an embodiment of the present invention. 1... Power supply side terminal, 4a, 4b... Branch circuit,
5...Double throw opening/closing part, 6a...Normally open contact, 6b...
Normally closed contact, 6c... Common contact, 7... Relay coil, 8... Contact, 9a, 9b... Current transformer, 10
a, 10b...Load, 11...Resistor, 14...Photocoupler, 19a, 19b...Comparator, 21...
...On-off command signal generation circuit, 24...Switching circuit.

Claims (1)

[Claims] 1. Between a main circuit connected to a power source and first and second branch circuits to which two loads are respectively connected, a common contact is connected to the main circuit, and a normally open contact is connected to the first branch circuit. A double-throw switching section is arranged in the circuit so that the normally closed contacts are respectively connected to the second branch circuit, and the first current detection means for detecting the load current is connected to the first branch circuit. A second current detection means for detecting the load current is provided in each branch circuit, a high impedance voltage detection means is connected between the common contact and the normally open contact of the double-throw switching section, and the second current detection means is connected to the common contact and the normally open contact of the double-throw switching section. Control for outputting a normally open contact ON signal to the double-throw switching section in accordance with either the detection output of the first current detection means or the detection output of the voltage detection means in a state where the means does not detect a load current. Load selection device comprising means.