JPH0690523A - Bilateral constant-current circuit - Google Patents

Abstract

PURPOSE:To obtain a bilateral constant-current circuit for driving an electrically controlled equipment or the like by a single power supply. CONSTITUTION:A first switch 14 and a second switch 16 are connected to an output of a constant-current circuit 11, and a terminal 18 of the first switch 14 and a terminal 19 of the second switch 16 are grounded. A common terminal 20 of the first switch 14 and a common terminal 22 of the second switch 16 are connected to a first output terminal 21 and a second output terminal 23, respectively. The first switch 14 and the second switch 16 are simultaneously changed by a driver circuit 24. Hence, it becomes possible to switch the direction of a current appearing on the first terminal 21 and the second terminal 23 by a current applied to a control input terminal 25. Thus, an output from the constantcurrent circuit 11 will be outputted only in one direction, and hence there is no necessity to use two power supplies, that is, a positive one and a negative one.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bidirectional constant current circuit for driving electronic control equipment and the like.

[0002]

2. Description of the Related Art A conventional bidirectional constant current circuit will be described below.

FIG. 4 is a block diagram of a conventional bidirectional constant current circuit. In FIG. 4, 1 is a constant current circuit, the first output 2 of this constant current circuit 1 is connected to the first output terminal 3, and the second output 4 is connected to the second output terminal 5. It was Then, the first output terminal 3 and the second output terminal 5
The electronic control device 6 was connected between the.

The constant current circuit 1 is connected to a positive power source 7 and a negative power source 8. The current directions of the first output 2 and the second output 4 were controlled by applying a control signal to the control input terminal 9.

[0005]

However, in the above-mentioned conventional circuit configuration, it is necessary to use the positive and negative power supplies to switch the direction of the current applied to the electronic control device 6,
There was a problem that two power supply circuits were required.

The present invention solves such problems, and an object of the present invention is to provide a bidirectional constant current circuit composed of a single power source.

[0007]

To achieve this object, a bidirectional constant current circuit of the present invention comprises a constant current circuit and a first terminal of a first switch connected to the output of the constant current circuit. And a second terminal of the second switch connected to the first terminal, and a ground connected to the second terminal of the first switch and the first terminal of the second switch. A first output terminal connected to the common terminal of the first switch and a second output terminal connected to the common terminal of the second switch
Output terminal, a drive circuit for simultaneously driving the first switch and the second switch, and a control input terminal connected to the input of the drive circuit.

[0008]

In this structure, the first switch and the second switch are simultaneously switched, so that the first output terminal and the second switch are connected.
The direction of the current appearing at the output terminal of is switched.

Therefore, the output of the constant current circuit may be a single power supply and does not require two power supplies, a positive power supply and a negative power supply.

[0010]

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a bidirectional constant current circuit according to the first embodiment of the present invention. In FIG. 1, 11
Is a constant current circuit, and this constant current circuit 11 is a positive power source 1
Connected to 2. Further, the output 13 of the constant current circuit 11 is connected to the first terminal 15 of the first switch 14 and the second terminal 17 of the second switch 16. In addition, the second terminal 1 of the first switch 14
8 and the first terminal 19 of the second switch 16 are connected to ground.

The common terminal 20 of the first switch 14 is the first
Of the second switch 16 and the common terminal 22 of the second switch 16 is connected to the second output terminal 23. The electronic control device 6 is connected between the first output terminal 21 and the second output terminal 23.

Reference numeral 24 is a drive circuit, and this drive circuit 24
Is connected so as to drive the first switch 14 and the second switch 16 at the same time to switch the current path of the constant current circuit 11.

The operation of the bidirectional constant current circuit thus configured will be described below.

First, the drive circuit 24 is actuated by the signal input to the control input terminal 25 so that the first switch 14 becomes the first switch.
To the terminal 15 side of the second switch 1 at the same time
If 6 is switched to the first terminal 19 side, the current flowing out from the constant current circuit 11 is the output 13 and the first switch 1
4, the first terminal 15, the common terminal 20, and the first output terminal 2
It flows through the electronic control device 6 in the direction A through 1 and is connected to the ground through the second output terminal 23, the common terminal 22 of the second switch 16 and the first terminal 19.

Next, when the signal at the control input terminal 25 is switched, the drive circuit 24 operates to activate the first switch 14
Switches to the second terminal 18 side, and at the same time, the second switch 16 switches to the second terminal 17 side. Therefore,
The current flowing out from the constant current circuit 11 passes through the output 13, the second terminal 17 and the common terminal 22 of the second switch 16, passes through the second output terminal 23, and flows in the electronic control device 6 in the B direction, It will be connected to the ground through the first output terminal 21, the common terminal 20 of the first switch 14 and the second terminal 18.

Therefore, the direction of the current flowing through the electronic control unit 6 can be switched according to the signal input from the control input terminal 25.

(Embodiment 2) FIG. 2 shows a second embodiment in which a transistor circuit is used instead of the first switch 14 and the second switch 16.

In FIG. 2, reference numeral 26 is a constant current circuit, and a fixed voltage is applied to the input terminals 27 and 28 of the constant current circuit 26. The constant current circuit 26 uses a single positive power source 12. The transistors 29 and 30 and the resistor 31 constitute the first switch 14, and the transistors 32 and 33 and the resistor 34 constitute the second switch 1.
6, the transistors 35, 36, 37 and the resistors 38, 39, 40, 41 constitute the drive circuit 24.

The operation of the bidirectional current circuit configured as described above will be described below. First, the operational amplifiers 42 and 43 of the constant current circuit 26 use the single power source 12, and the resistors 44 to 49 and the operational amplifiers 42 and 43 form a constant current circuit, and the input terminals 27 and 28 of the operational amplifier 42.
By fixing the constant current is constantly flowing out.

Next, the operation of the first switch 14 and the second switch 16 will be described. When the signal input to the control input terminal 25 connected to the transistor 35 is turned on, the transistors 35 and 37 are turned on, so that the transistors 29 and 30 are turned on. On the other hand, when the transistor 35 is turned on and the transistor 36 is turned off, the transistors 32 and 33 are turned off. Therefore, a current flows in the A direction.

Conversely, when the input signal input to the control input terminal 25 connected to the transistor 35 is turned off, the transistors 35 and 37 are turned off and the transistors 32 and 33 are turned on. On the other hand, since the transistor 37 is also turned off, the transistors 29 and 30 are turned off. Therefore, a current flows in the B direction.

As described above, by switching the control input signal, it is possible to flow a constant current in both directions to drive the electronic control unit 6.

As described above, according to this embodiment, since the transistors are used for the first switch 14 and the second switch 16, the switching speed is fast, and the bidirectional constant current circuit which is compact and inexpensive is provided. Can be realized. Furthermore, since the input terminal of the constant current circuit is fixed, a circuit that is not affected by the load of the electronic control device 6 can be realized.

(Embodiment 3) FIG. 3 shows a third embodiment of the present invention in which the first switch 14 and the second switch 16 are constituted by a relay having two circuits and two contacts. In FIG. 3, 50 is 2
A circuit two-contact relay, which includes a first switch 14 and a second switch.
The switch 16 of FIG. Further, the transistor 51 and the resistors 52 and 53 form a drive circuit 24. Here, the difference from the configuration of FIG. 2 is that the first switch 14 and the second switch 16 are switched by a relay 50 instead of by a transistor.

The operation of the bidirectional constant current circuit configured as described above will be described below. As in the first embodiment, the constant current flowing out from the constant current circuit 26 is applied to the relay 5 when the transistor 51 is turned on by the control input signal.
When 0 is turned on, a current flows in the A direction. On the contrary, when the transistor 51 is turned off, the relay 50 is also turned off and a current flows in the B direction. In this way, a constant drive current can be passed in both directions to drive the electronic control unit 6.

As described above, the same function can be realized by the configuration of the switching circuit which is simpler than that of the second embodiment.

[0028]

As described above, in the bidirectional constant current circuit of the present invention, the first switch and the second switch are connected to the output of the constant current circuit, and the first switch and the second switch are simultaneously switched. Therefore, the directions of the currents appearing at the first output terminal and the second output terminal are switched.

Therefore, the output of the constant current circuit may be a single power supply, and does not require two power supplies, a positive power supply and a negative power supply.

[Brief description of drawings]

FIG. 1 is a block diagram of a bidirectional constant current circuit according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a bidirectional constant current circuit according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram of a bidirectional constant current circuit according to a third embodiment of the present invention.

FIG. 4 is a circuit diagram of a conventional bidirectional constant current circuit.

[Explanation of symbols]

 11 Constant Current Circuit 13 Output of Constant Current Circuit 14 First Switch 16 Second Switch 15, 19 First Terminal 17, 18 Second Terminal 20, 22 Common Terminal 21 First Output Terminal 23 Second Output Terminal 24 Drive circuit 25 Control input terminal

Claims (3)

[Claims] 1. A constant current circuit, a first terminal of a first switch connected to the output of the constant current circuit, and a second terminal of a second switch connected to the first terminal. , A second terminal of the first switch and a first terminal of the second switch
A ground connected to a terminal of the first switch, a first output terminal connected to a common terminal of the first switch, a second output terminal connected to a common terminal of the second switch, A bidirectional constant current circuit comprising a drive circuit for simultaneously driving the first switch and the second switch, and a control input terminal connected to the input of the drive circuit. 2. The bidirectional constant current circuit according to claim 1, wherein the first switch and the second switch are constituted by a relay having two circuits and two contacts. 3. The bidirectional constant current circuit according to claim 1, wherein the first switch and the second switch are constituted by a transistor circuit.