JP4122596B2 - Reed relay drive circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a reed relay drive circuit that measures the contact resistance of a reed switch contact of a reed relay.
[0002]
[Prior art]
First, a conventional reed relay drive circuit will be described with reference to FIG.
First, the configuration will be described.
FIG. 3 is a diagram for explaining a conventional reed relay drive circuit.
3 includes a buffer circuit 101 constituting the reed relay drive circuit 100, a reed switch 200a, and a coil 200b for exciting the reed switch 200a from the outside. The on / off operation of the reed switch 200a is controlled by the buffer circuit 101. The reed relay 200 and the DC power source 300 are included.
[0003]
The buffer circuit 101 constituting the reed relay drive circuit 100 is composed of an npn transistor and has an open collector output. The collector of the npn transistor of the buffer circuit 101 is connected to one end of the coil 200b of the reed relay 200, the emitter is grounded, and a control signal for controlling the on state and off state of the buffer circuit 101 is input to the base. . The buffer circuit 101 is turned off when the input to the base of the npn transistor of the buffer circuit 101 is “L” level, and is turned on when the input to the base is “H” level. The on / off state of the reed switch 200a of the reed relay 200 is controlled by controlling the current flowing through the coil 200b, in other words, the driving voltage applied to the coil 200b.
[0004]
In the reed relay 200, a DC power source 300 is connected to the other end of the coil 200b. In the reed relay 200, the reed switch 200a is turned on when a current of a certain value or more flows through the coil 200b, and the reed switch 200a is turned off when the current of a certain value or more does not flow through the coil 200b.
[0005]
The voltage value of the DC voltage 300 and the voltage value when the input voltage to the buffer circuit 101 is “H” level are the values of the reed relay 200 when the “H” level voltage value is input to the buffer circuit 101. Each is set so that the reed switch 200a is turned on.
[0006]
Next, the operation will be described.
When the reed switch 200a of the reed relay 200 is controlled to be turned on, an “H” level voltage signal is input to the base of the npn transistor of the buffer circuit 101, and the buffer circuit 101 is turned on. When the buffer circuit 101 is turned on, a current flows through the coil 200b of the reed relay 200, and the reed switch 200a of the reed relay 200 is turned on.
[0007]
When the reed switch 200a of the reed relay 200 is controlled to be turned off, an “L” level voltage signal is input to the base of the npn transistor of the buffer circuit 101, and the buffer circuit 101 is turned off. When the buffer circuit 101 is off, no current flows through the coil 200b of the reed relay 200, and the reed switch 200a of the reed relay 200 is turned off.
[0008]
As described above, the on / off control of the reed switch 200a of the reed relay 200 is performed by controlling the voltage level (“H” level, “L” level) of the input voltage to the buffer circuit 101.
[0009]
Here, when confirming that the contact resistance of the contact of the reed switch 200a has deteriorated due to a glass tube crack or the like of the reed relay 200, the voltage applied to the coil 200b of the reed relay 200 is operated (off). It is effective to measure the contact resistance of the reed switch 200a of the relay relay 200 when it is the minimum voltage (operational voltage) that switches from ON to ON.
[0010]
[Problems to be solved by the invention]
However, in the conventional reed relay drive circuit 100, the drive voltage of the reed relay 200 cannot be arbitrarily set after being mounted on a printed circuit board, and the reed switch 200a of the reed relay 200 is contacted with the minimum voltage at which the reed relay 200 operates. There was a problem that it was difficult to measure resistance.
[0011]
An object of the present invention is to provide a reed relay drive circuit capable of measuring the contact resistance of a reed switch of a reed relay with a minimum voltage (an emotional voltage) at which the reed relay operates. For the purpose.
[0012]
[Means for Solving the Problems]
The invention according to claim 1 is connected to a coil of a reed relay, and is connected to a transistor for controlling on / off of a current flowing through the coil by an on / off operation, to a base of the transistor, and to turn on / off the reed relay. The on / off state of the transistor is controlled by an on / off operation during off control, and the buffer circuit that is off when measuring the contact resistance of the contact of the reed relay, and the magnitude of the voltage value of the input voltage to the transistor A D / A converter that converts an input digital signal to be controlled into an analog signal, one end connected to the output of the D / A converter, and the other end connected to the output of the buffer circuit and the base of the transistor And a pull-up resistor .
[0013]
According to the first aspect of the invention, it is possible to on / off control of the re Dorire, be measured at the minimum voltage reed relay contact resistance of the reed relay reed switch is operated (touched voltage) it can.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
A reed relay drive circuit according to an embodiment to which the present invention is applied will be described with reference to FIG.
[0015]
First, the configuration will be described.
FIG. 1 is a diagram for explaining a reed relay drive circuit 1 according to an embodiment.
FIG. 1 shows a reed relay drive circuit 1, a reed switch 2a, and a coil 2b for exciting the reed switch 2a from the outside. The reed relay drive circuit 1 controls the on / off operation. DC power supply 3 connected to two coils 2b. The reed relay drive circuit 1 includes a transistor 11, a buffer circuit 12, a D / A (Digital to Analog) converter 13, and a pull-up resistor 14.
[0016]
The reed relay drive circuit 1 has two operation modes, one of which is an operation mode for performing on / off control of the reed relay 2 with a rated voltage. The other is an operation mode in which the contact resistance of the contact point of the reed switch 2a of the reed relay 2 is measured at the minimum voltage (operation voltage) at which the reed relay 2 operates (operation that switches from off to on).
Each of these operation modes will be described in detail after each component is described.
[0017]
The transistor 11 is a pnp transistor, the emitter is connected to one end of the coil 2b of the reed relay 2, and the collector is grounded. The transistor 11 is turned on when the input to the base is at the “L” level, and is turned off when the input to the base is at the “H” level. The on / off state of the reed switch 2b is controlled by controlling the current flowing through the coil 2b of the reed relay 2 by the on / off state of the transistor 11.
[0018]
The buffer circuit 12 uses an npn transistor and has an open collector output. The collector is connected to the base of the transistor 11 and one end of the pull-up resistor 14, the emitter is grounded, and the base includes the buffer circuit 12. A control signal for controlling the on state and the off state is input. The buffer circuit 12 is turned off when the input to the base is at “L” level, and is turned on when the input to the base is at “H” level.
[0019]
The D / A converter 13 has an output connected to the other end of the pull-up resistor 14, converts an input digital signal into an analog signal, and outputs the analog signal. The D / A converter 13 and the pull-up resistor 14 constitute an input voltage changing circuit unit that controls changing the input voltage to the base of the transistor 11.
[0020]
Next, the drive voltage applied to the coil 2b of the reed relay 2 when the buffer circuit 12 is in the off state will be briefly described.
Since the buffer circuit 12 is off, the output of the D / A converter 13 is input to the base of the transistor 11.
Here, if V1 is the DC voltage value of the DC power supply 3, VDAC is the output voltage value of the D / A converter 13, and VBE is the voltage value between the base and emitter of the transistor 11, the coil 2b of the reed relay 2 has A voltage of (V1-VDAC-VBE) is applied.
[0021]
Therefore, in the case of the reed relay drive circuit 1 of this configuration, the voltage value of the drive voltage applied to the coil 2b of the reed relay 2 is controlled by changing the output voltage value VDAC of the D / A converter 13, that is, D This can be controlled by changing and controlling the input digital signal to the / A converter 13.
[0022]
Further, the circuit operation will be described.
First, an operation mode in which the reed switch 2a of the reed relay 2 is turned on / off with the rated voltage will be described.
The input digital signal of the D / A converter 13 is set so that the voltage value of the DC voltage 3 and the output voltage value of the D / A converter 13 are equal.
[0023]
When the reed switch 2a of the reed relay 2 is controlled to be in an on state, an “H” level voltage signal is input to the base of the buffer circuit 12, and the buffer 12 is turned on. As a result, a current flows from the output of the D / A converter 13 via the pull-up resistor 14 from the collector to the emitter of the transistor of the buffer circuit 12, and the input to the base of the transistor 11 is at "L" level. Since the “L” level voltage signal is input to the base of the transistor 11, the transistor 11 is turned on. When the transistor 11 is turned on, a current flows through the coil 2b of the reed relay 2, and the reed switch 2a of the reed relay 2 is turned on.
[0024]
When the reed switch 2a of the reed relay 2 is controlled to be in an off state, an “L” level voltage signal is input to the base of the buffer circuit 12, and the buffer circuit 12 is in an off state, that is, a high impedance. As a result, the output voltage of the D / A converter 13 is input to the base of the transistor 11, and the input to the base of the transistor 11 is at the same voltage value level (“H” level) as the voltage value of the DC power supply 3. Since the voltage signal having the same voltage value level (“H” level) as the voltage value of the DC power supply 3 is input to the base of the transistor 11, the transistor 11 is turned off. When the transistor 11 is off, no current flows through the coil 2b of the reed relay 2, so that the reed switch 2a of the reed relay 2 is turned off.
[0025]
As described above, the on / off control of the reed switch 2a of the reed relay 2 is performed by controlling the voltage level (“H” level, “L” level) of the input voltage to the buffer circuit 12.
[0026]
Next, an operation mode for measuring the contact resistance of the reed switch 2a of the reed relay 2 at the minimum voltage (moving voltage) at which the reed relay 2 operates will be described.
In this operation mode, since the input to the base of the transistor 11 is used as the output voltage of the D / A converter 13, the input to the base of the buffer circuit 12 is set to "L" level, the buffer circuit 12 is turned off, and D The output voltage of the / A converter 13 is input to the base of the transistor 11.
[0027]
As an initial setting, the output voltage of the D / A converter 13 is set so that the drive voltage applied to the coil of the reed relay 2 is less than the minimum voltage (moving voltage) value at which the reed relay 2 operates. .
[0028]
The input digital signal to the D / A converter 13 is controlled so that the output voltage of the D / A converter 13 is reduced, for example, by 30 mV. Then, it is confirmed whether or not the reed switch 2a of the reed relay 2 has been turned on, for example, by measuring the resistance value of the reed switch 2a. Then, until it is confirmed that the reed switch 2a of the reed relay 2 is turned on, the input digital signal to the D / A converter 13 is sequentially controlled so that the output signal of the D / A converter 13 is reduced by 30 mV. The process is repeated.
[0029]
When it is confirmed that the reed switch 2a of the reed relay 2 has been turned on, that is, when the minimum voltage (operation voltage) at which the reed relay 2 operates is applied to the coil 2b of the reed relay 2. This state is maintained, a current is passed through the reed switch 2a of the reed relay 2, and the contact resistance of the reed switch 2a of the reed relay 2 is measured.
[0030]
As described above, while the output of the D / A converter 13 is gradually reduced, that is, the drive voltage applied to the coil 2b of the reed relay 2 is gradually increased, the minimum voltage (at which the reed relay 2 operates) ( Reed relay 2 that has been impossible in the past is detected by detecting the state in which the moving voltage is applied to the coil 2b of the reed relay 2 and measuring the contact resistance of the reed switch 2a of the reed relay 2 with the minimum voltage. It is possible to measure the contact resistance of the reed switch 2a of the reed relay 2 with the minimum voltage (moving voltage) that operates.
[0031]
Since the current flowing through the coil 2b of the reed relay 2 is about 30 mA, an error corresponding to (base current of the transistor 11 × resistance value of the pull-up resistor 14) occurs when the HFE of the transistor 11 is small. It is desirable that the HFE is 200 or more and the resistance value of the pull-up resistor 14 is 1 K ohm or less.
[0032]
Further, a reed relay drive circuit when a large number of relays are mounted on the substrate will be described with reference to FIG.
FIG. 2 is a diagram for explaining a reed relay drive circuit according to another embodiment. Note that FIG. 2 illustrates an example in which there are two reed relays, but it goes without saying that the configuration can be the same even if there are three or more.
[0033]
In FIG. 2, the reed relay 2-1a and the coil 2-1b of the reed relay 2-1 connected to the reed switch 2-1a and the coil 2-1b for exciting the reed switch 2-1a from the outside are connected. A power supply 3-1, a drive circuit unit 1-1 comprising a transistor 11-1 which is a pnp transistor, a buffer circuit 12-1 comprising an npn transistor and a pull-up resistor 14-1, a reed switch 2 -2a and a coil 2-2b for exciting the reed switch 2-2a from the outside, a power supply 3-2 connected to the coil 2-2b of the reed relay 2-2, a pnp transistor Drive circuit composed of a transistor 11-2, a buffer circuit 12-2 composed of an npn transistor, and a pull-up resistor 14-2. Part 1-2, a D / A converter 13, an operational amplifier 4, and a current buffer circuit 5.
[0034]
The reed relays 2-1 and 2-2 have the same function as the reed relay 2 described in the above embodiment, and the transistors 11-1 and 11-2 have the same function as the transistor 11 described in the above embodiment. Further, the buffer circuits 12-1 and 12-2 are the buffer circuit 12 described in the above embodiment, and the pull-up resistors 14-1 and 14-2 are the pull-up resistors described in the above embodiment. It has the same function as the device 14.
[0035]
The D / A converter 13 has an output connected to the + input terminal of the operational amplifier 4, converts an input digital signal into an analog signal, and outputs the analog signal.
[0036]
In the operational amplifier 4, the output of the D / A converter 4 is input to the + input terminal, and the output of the current buffer circuit 5 is input to the − input terminal and the current buffer circuit 5 to constitute a voltage follower circuit.
[0037]
The output of the current buffer circuit 5 is connected to the pull-up resistors 14-1 and 14-2 of the drive circuit units 1-1 and 1-2.
The circuit operation of the circuit shown in FIG. 2 is substantially the same as the circuit operation of the circuit shown in FIG.
[0038]
By configuring the circuit as shown in FIG. 2, it is possible to control the on / off of the reed switches of a large number of reed relays with a single D / A converter, and to cope with the contact resistance of the reed switches of a plurality of reed relays. It is possible to measure at the minimum voltage (moving voltage) at which the reed relay operates, and it becomes highly practical.
[0039]
【The invention's effect】
According to the first aspect of the present invention, the reed relay drive circuit is connected to the coil of the reed relay and connected to the transistor for controlling on / off of the current flowing through the coil by the on / off operation, and to the base of the transistor. A buffer circuit that controls an on / off state of the transistor by an on / off operation at the time of on / off control of the reed relay, and an off state at the time of measuring a contact resistance of the contact of the reed relay, and an input to the transistor A D / A converter that converts an input digital signal that controls the magnitude of a voltage value into an analog signal, one end connected to the output of the D / A converter, and the other end connected to the output of the buffer circuit and the output due to the structure by a pull-up resistor connected to the base of the transistor, a reed relay on / off control Preparative it is, it can be measured at the minimum voltage reed relay contact resistance of the reed relay reed switch is operated (touched voltage).
[0040]
Also, a D / A converter that converts an input digital signal that controls the magnitude of the voltage value of the input voltage to the transistor into an analog signal, one end connected to the output of the D / A converter, and the other end is a buffer circuit The pull-up resistor connected to the output of the transistor and the base of the transistor makes it possible to control the change of the input voltage to the base of the transistor.
[0041]
According to the second aspect of the present invention, the on / off state of the reed relay can be easily controlled by using a pnp transistor as the transistor.
[0042]
According to the third aspect of the invention, at the time of the contact resistance measurement of the reed switch of Li Dorire, the D / A converter under the control of the input digital signal be lowered sequentially input voltage to the transistor by a predetermined voltage Thus, since the control for sequentially increasing the drive voltage of the coil of the reed relay is performed, the contact resistance of the reed switch of the reed relay can be measured with the minimum voltage (the moving voltage) at which the reed relay operates.
[0043]
According to the fourth aspect of the present invention, the reed relay drive circuit is connected to the coil of the reed relay and connected to the transistor for controlling on / off of the current flowing through the coil by the on / off operation, and to the base of the transistor. The on / off state of the transistor is controlled by an on / off operation when the reed relay is on / off controlled, and the buffer circuit is turned off when the contact resistance of the contact of the reed relay is measured. A plurality of drive circuit units composed of pull-up resistors connected to each other, a D / A converter that converts an input digital signal that controls the magnitude of a voltage value of an input voltage to the transistor into an analog signal, and the D An operational amplifier to which the output of the A / A converter is input, and an input is connected to the output of the operational amplifier, and the output is And a current buffer circuit connected to a pull-up resistor of the drive circuit section of the drive circuit section, so that on / off control of the reed switches of a plurality of reed relays is possible and a reed switch of the plurality of reed relays It is possible to measure the contact resistance at the minimum voltage (moving voltage) at which the corresponding reed relay operates.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a reed relay drive circuit 1 according to an embodiment;
FIG. 2 is a diagram for explaining a reed relay drive circuit according to another embodiment.
FIG. 3 is a diagram for explaining a conventional reed relay drive circuit;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Reed relay drive circuit 11 Transistor 12 Buffer circuit 13 D / A converter 14 Pull-up resistor 2 Reed relay 2a Reed switch 2b Coil 3 DC power supply

Claims (4)

A transistor connected to the coil of the reed relay and controlling on / off of a current flowing through the coil by an on / off operation;
A buffer circuit that is connected to the base of the transistor, controls the on / off state of the transistor by an on / off operation when the reed relay is on / off controlled, and is turned off when the contact resistance of the contact of the reed relay is measured; ,
A D / A converter that converts an input digital signal that controls the magnitude of a voltage value of an input voltage to the transistor into an analog signal;
A pull-up resistor having one end connected to the output of the D / A converter and the other end connected to the output of the buffer circuit and the base of the transistor;
A reed relay drive circuit comprising:   The reed relay drive circuit according to claim 1, wherein the transistor is a pnp transistor. When measuring the contact resistance of the contact of the reed relay, the D / A converter sequentially reduces the input voltage to the transistor by a predetermined voltage based on the control of the input digital signal, thereby driving the coil of the reed relay. 3. The reed relay drive circuit according to claim 2, wherein the voltage is sequentially increased. A transistor connected to the coil of the reed relay and connected to the base of the transistor for controlling on / off of the current flowing through the coil by the on / off operation. A buffer circuit that controls the on / off state of the transistor and is turned off when measuring the contact resistance of the contact of the reed relay; and a plurality of drive circuit units including a pull-up resistor having one end connected to the base of the transistor; ,
A D / A converter that converts an input digital signal that controls the magnitude of a voltage value of an input voltage to the transistor into an analog signal;
An operational amplifier to which the output of the D / A converter is input;
A current buffer circuit having an input connected to an output of the operational amplifier and an output connected to a pull-up resistor of the plurality of drive circuit units;
A reed relay drive circuit comprising:

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