JPS5997228A - Semiconductor device for proximity switch - Google Patents

Abstract

PURPOSE:To operate a load stably and surely without increasing the number of pins, by constituting the inside of an integrated circuit for a proximity switch as prescribed. CONSTITUTION:An oscillating circuit 21, a detecting circuit 22, a voltage comparing circuit 23, an output circuit 24, an initial reset circuit 25, and a power supply circuit 26 are incorporated in an IC28 for the proximity switch. The amplitude of the output of the oscillating circuit 21 is reduced or increased to turn on and off the output circuit 24 according as an object M to be detected approaches or separates from a detecting coil L. A constant voltage generating circuit 30 is connected between a terminal I, to which an initial reset capacitor C2 is connected, and an earth terminal E, and a reverse current preventing diode D is connected between the terminal I and the output terminal of the power supply circuit 26. A discharge circuit 29 of the capacitor C2 is connected between the output terminal of the power supply circuit 26 and the terminal I.

Description

[Detailed Description of the Invention] Kizari 1 relates to the improvement of a semiconductor device for a high-frequency oscillation type proximity switch.More specifically, it aims to reduce the residual voltage, stabilize the detection operation, and improve it compared to conventional products. In this paper, we propose an integrated circuit that realizes these functions by increasing the number of terminals compared to the conventional one.

Figure 1 is a circuit diagram showing the configuration of a conventional proximity switch.
18 (hereinafter referred to as an IC) is connected to external components to constitute a proximity switch 17 (surrounded by a two-dot chain line). When the test object M approaches the detection coil L, the switch transistor Q, which is an outward component, is turned on, and power is supplied from the power supply V to the load RL. This circuit will be explained below.

ICl3 is the oscillation circuit 11. Detection circuit 12. Voltage comparison circuit 13. Output circuit 14. It consists of an initial reset circuit] 5, a power supply circuit 16, etc. The oscillation circuit 11 includes a detection coil, a parallel circuit of a tuning capacitor C, and sensitivity (operating distance).
A series circuit with an adjustment resistor R is connected, and when the object M is absent or outside the detection range, it oscillates with a predetermined amplitude, and this output is given to the detection circuit 12. An integrating capacitor C7 is externally connected to the output terminal of the detection circuit 12, and this terminal is connected to the input terminal of the voltage comparison circuit 13. Voltage Comparison Circuit] Voltage comparator circuit 13 has a voltage that corresponds to the amplitude of the oscillation circuit 11 output, but if this is greater than a predetermined comparison reference value, the voltage comparator circuit 13 output turns off the output circuit 14, and If the voltage becomes lower than that, the output circuit 4 is turned on.

When the test object M approaches the detection range of the detection coil L, the amplitude of the oscillation output of the oscillation circuit 110 is attenuated or the oscillation stops thL, and as a result, the voltage of the voltage comparison circuit 13 becomes low level, and the output of the output circuit 14 turns on.

Conversely, when the object M moves away, the output circuit 14 is turned off.

The output circuit 14 connects one end to the proximity switch via the terminal E]7
It is connected to terminal l- of , and this l-terminal is ? 11' It is connected to the angle of source V. The middle and ends of the output circuit 14 are connected to the output terminal OUT of the ICl3.

Sixteen power supply circuits supplying power to the internal circuits of the ICs 1 and 8 are connected to external circuits via power supply terminals VT.

The positive pole of the source V is connected to another conduit t + l of the proximity switch 17 via a switch 19 and a load RL. Terminal, I! The above-mentioned switch circuit including the transistor Q2 is connected between them, and a circuit for supplying power to the switched ICl3 is connected between them. That is, the HPNPI-
The emitter of the transistor Q is connected to the terminal L-, whose collector is also connected to the emitter of the transistor Q1, whose base is connected to the emitter of the transistor Q1. The collector of transistor Q1 is connected to terminal VT, and the base is connected to terminal OUT via resistor R. An r/i resistor R2 is interposed between the emitter and base of the transistor Q. A constant current element CD is interposed between terminal /4 and terminal VT, and a constant voltage element ZD is interposed between terminals VT and E.

As mentioned above, when the object M is separated, the output circuit 1
4 is off, and when the eIM to be tested approaches, the output circuit 14 is turned on, and the switch circuit is also turned off and on accordingly.

That is, if output circuit]4 is off, transistor Q;
is off, and therefore transistor Q2 is also off. On the other hand, when the output circuit 14 is turned on, a current flows to the base of the transistor Q1, conduction occurs between the collector and the emitter, and the constant current element CD is short-circuited via the base of the transistor Q2. For this reason, transistor Q.

A base current flows, and a drive current can be supplied to the power supply terminal VT of ICl3 via transistor Q1. Then, the transistor Q2 is turned on, causing current to flow through the load RL, and the proximity of the test object M is detected.

In such a test object detection state, the voltage between l-4 and
The so-called residual voltage is the constant voltage of the constant voltage element ZD, the collector-emitter saturation voltage of the transistor Q, and the collector-emitter saturation voltage of the transistor Q.
The smaller this residual voltage is and the larger the difference from the power supply V, the more reliable and stable the operation of the load RL will be.

On the other hand, when the test object M moves away and the output circuit 14 is turned off and the transistors Q+ and Qt are turned off, no drive current flows through the load RL. At this time, a voltage determined by the constant voltage element ZD is supplied to the power supply terminal VT of the ICl3 via the constant current element CD. Constant current element CD is selected so that the current consumption in ICl3 in such a state, that is, the leakage current that also flows to load RL, is reduced.

Next, connect the initial reset capacitor C2, which is used to determine the time constant of the initial reset circuit 15 inside the IC 18, to the terminal I.
It includes a timer circuit using this capacitor C2. This timer circuit starts timing when the switch 19 is closed and power supply to the ICl 8 is started.

Then, the operation of the output circuit 14 is inhibited until the initial reset circuit 15 timer circuit reaches its expiry time, thereby restricting the output circuit 14 to the OFF state.

When the time limit is reached, this restriction is released and the device is turned on or off in accordance with the proximity or separation of the object M. Immediately after the switch 19 is closed, the amplitude of the output of the oscillation circuit 11 is small;
The amplitude returns to normal after a short delay.

Therefore, the initial reset circuit operates as described above]
5 does not exist, there is a risk that the output circuit 14 will be turned on immediately after the switch 19 is closed, similar to when the object M approaches, resulting in erroneous output. The initial reset circuit 15 prevents this.

In such a conventional circuit, it is necessary to select a constant voltage element ZD whose rated voltage value is slightly higher than the minimum operating voltage of the IC 18.

Therefore, if the minimum operating voltage of ICl3 is, for example, 475V, it is difficult to reduce the remaining voltage to 5 to 6V or less.

The present invention was made in view of the problems of certain conventional circuits, and it reduces the residual voltage to ensure stable and reliable operation of the load, and also uses a proximity switch that is housed in the same number of bottles as the conventional one. The purpose of the present invention is to provide a semiconductor device.

The present invention will be described in detail below based on drawings showing embodiments thereof.

FIG. 2 is a circuit diagram showing the configuration of a proximity switch including a proximity switch IC according to the present invention.

The number of terminals of the proximity switch IC28 is the same as that of the conventional IC shown in Figure 1.
18, the oscillation circuit 21 is connected with a terminal for connecting a detection coil and a tuning capacitor C, and a terminal for connecting a sensitivity adjustment resistor R. The trench detection circuit 22 is connected to a terminal for connecting an integrating capacitor C1.

The output terminal OUT of the IC 28 is connected to the output circuit 24, the terminal ■ for connecting the initial reset capacitor C2 is connected to the initial reset circuit 25, and the power supply terminal VT is connected to the power supply circuit 26. . The ground line of the internal circuit described above is connected to the ground terminal E.

The configuration of the power supply circuit 26 is similar to that of the conventional power supply circuit 16, and is configured to supply a required voltage to the internal circuits.

Oscillation circuit 21. Detection circuit 22. The structures of the voltage comparator circuit 23 and the output circuit lPt24 are similar to the conventional device shown in FIG. 1, and the object M is located close to the detection coil.

The amplitude of the output of the oscillation circuit 21 decreases as the distance increases,
The output circuit 24 is turned on and off.

This IC 28 is provided with a constant voltage generating circuit 30, the positive line of which is connected to the terminal I and to the anode of a diode D for preventing backflow. The cathode of diode D is connected to the output terminal of power supply circuit 26.

The initial reset circuit 25 is also the initial reset circuit 15 in FIG.
It is configured in the same manner as above, and operates so as to turn off the output circuit 24 immediately after the switch 19 is closed, but a discharge circuit WT29 is connected to the line connected to the terminal I. This discharge circuit 29 monitors the output of the power supply circuit 6, and if this becomes less than a predetermined value, a reset capacitor C connected to the terminal ■
The second charge is discharged.

The negative terminal of the power supply V is connected to the terminal l- of the proximity switch 27 or the ground line of the proximity switch 27. A transistor Q, which constitutes a switch circuit.

Of Q2, the emitter and collector of transistor Q2 are connected to the terminals z" and l!-, respectively, as in the case of the transistor Q2 in FIG. A resistor R2 is interposed between the link and the base.Transistor 1cJt
The base is connected to the emitter of transistor Q1, and the collector of transistor Q1 is connected to I&. The base of the transistor Q1 is connected to the output terminal OU'Nζ via a resistor R4. And the terminal
A series circuit consisting of a load RL, a switch 19, and a power source (2) is connected between the two.

Comparing such an external circuit with the one circuit shown in FIG. 1, the constant current element CD is not used, and the collector 75 of the transistor Q is connected to terminal 1.
I understand that it is connected to the constant voltage generation circuit inside the IC28 through this.

Next, the circuit operation of the device of the present invention as described above will be explained. I will clarify.

When the switch 19 is closed, current is supplied to the power supply terminal VT via the load RL. This is the power supply circuit 26 from ζ
A voltage for driving the circuit is emitted from the output terminals.

The initial reset circuit 25 starts charging the initial reset capacitor C2, and turns off the output circuit 1i@24 until the time limit. Since the output of the power supply circuit 26 is connected to the terminal (2) via the diode D for preventing backflow, the capacitor C2 is charged only from the initial reset circuit 25. Also, the discharge circuit 9
Since the voltage output from the power supply circuit 26 is applied to the capacitor C2, the initial reset circuit 25 does not cause the capacitor C2 to discharge. Works to prevent output. Output circuit 2 due to the function of initial reset circuit ti325.
While transistor 4 is off, transistors Q1+Q,
Of course, IC2 is off, and the load RL has IC2 turned off.
Only the leakage current consumed at 8 flows.

Next, when the object M is separated from the detection coil L and the amplitude of the oscillation output from the oscillation circuit 21 is large, the output circuit 24I/i is turned off.

Now, when the object M approaches the detection coil, the oscillation circuit 21
The amplitude of the output is attenuated (- or the oscillation stops and the output circuit 24
turns on. This causes the transistor Q1 to have a resistor R
3, current flows through its base, conduction occurs between its collector and emitter, transistor Q2 is turned on, and the load RLK drive current flows, operating as if the object under test M had been detected. . At this time, a current flows to the IC 28 through the routes of the load RL-+emitter of the transistor Q2, the emitter of the pace-transistor Q1, and the collector-terminal I. The current flowing into this terminal 3 causes the constant voltage generating circuit 30 to generate a constant voltage, and this constant voltage can be applied to the internal circuit via the diode D. Therefore, the remaining voltage between terminals M and L of the proximity switch 27 is the sum of the constant voltage If value of the constant voltage generating circuit 30, the collector-emitter saturation voltage of the transistor Q1, and the emitter-base 17 voltage of the transistor Q2.
By keeping the internal voltage low, this remaining voltage can be lowered.

Note that even if the voltage at the power supply terminal VT fluctuates lower than the minimum operating voltage of the power supply circuit 6, power can be supplied to the internal circuit from the terminal (2), that is, from the constant voltage generation circuit 30 side. In this case, it is preferable to set the output voltage of the constant voltage generating circuit 30 to be higher than the output voltage of the power supply circuit 26 during normal operation by the forward voltage of the diode D in order to stabilize the operation of the internal circuit.

When the discharge circuit 29 (switch) 9 is open, the capacitor C
Discharge the charge of 2. That is, when the voltage at the output terminal of the power supply circuit 26 decreases due to the switch 19 being opened, this is detected and the charge in the capacitor C2 is discharged. Therefore, even if the switch 19 is repeatedly turned off, charging of the capacitor C7 starts from a state where the residual electric potential is zero, so that the output circuit 24
The time limit for restricting the initial reset circuit 25 or the time limit of the timer circuit of the initial reset circuit 25 is stabilized, and malfunctions when the power is turned on are reliably avoided.

FIG. 3 is a circuit diagram showing an example of a specific configuration of the essential parts of the device of the present invention. The output circuit 24 includes transistors 115 .
It consists of 118. When no current is supplied from the transistor 116 of the current mirror circuit,
Transistor 118 is off regardless of the signal from voltage comparison circuit 23. On the other hand, transistor 1
When current is supplied from the transistor 16, the transistor 118 is turned on and off in response to a signal from the voltage comparison circuit 23. That is, the amplitude of the output of the oscillation circuit 21 is large and the voltage comparison circuit 2
If the output of 3 is 7.1, the transistor 11
7 is turned on and transistor 118 is turned off, whereas
When the amplitude of the oscillation circuit output becomes small (near the test object M) and the output of the voltage comparison circuit 23 becomes low level, the transistor 117 is turned off and the transistor 118 is turned on.

Initial reset circuit 2514) transistors 109, 11
A current mirror circuit consisting of 0, a resistor that determines the current value] 21, and a capacitor C7 that initializes the mirror current.
It consists of a resistor 122 interposed in the line supplied to the capacitor C2, and a charging current detection circuit portion that detects the charging voltage of the capacitor C2 and supplies current to the output circuit 240 and the current mirror circuit.

The charging and current detection circuit part includes diodes 103 and 104 and transistors 111 and 11 that constitute a current mirror circuit.
2, and a resistor 123 interposed between the transistor 112 and the output circuit 24, and an initial reset capacitor C
When the charging voltage of diodes 103, 104 (!--transistors 111, 112) is about to reach the threshold value determined by transistors 111, 112, the current from the collector of transistor 110 is equal to the mirror current of the current mirror circuit of transistors 111, 112. Then, a mirror current is generated from the collector of the transistor 112, thereby eliminating the inhibition of output from the output circuit 24.

In other words, after the switch 19 is turned on, while the voltage of the capacitor C7 is below the threshold value, the transistors 111 and 112
Since no mirror current is generated, the transistor 118 is kept in the off state just as the transistor 116 is turned off.

The initial reset capacitor discharge circuit 29 consists of diodes 101, 102 and a resistor 1]9 for voltage detection, and a discharge circuit 108 and a discharge resistor 120. The diodes 101 and '102 are connected in series, with their anodes connected to the output terminal of the power supply circuit 26, and their cathodes connected to the ground line via a resistor 119. The base of the transistor i08 is connected to the connection point between the cathode side and the resistor 119, its collector is connected to the ground side line, and its emitter is connected to the terminal I via the resistor 120. The base of the transistor 108 is lower than the internal circuit driver voltage, that is, the output of the power supply circuit 26, by the forward voltage drop of the diodes 101 and 102, and the emitter of the transistor 108 is lower than the base voltage by the emitter voltage. only.

Assuming that the forward voltage of one diode is equal to the base-emitter voltage, the emitter voltage of the transistor 108 is lower than the internal [01 path drive a) voltage by the forward voltage drop of one diode. It's just low and nutty. Therefore, under normal conditions, the transistor 108 is on, but if the output of the power supply circuit 26 decreases by more than the forward voltage drop of one diode due to an open circuit of the switch 19, etc., an emitter-collector current corresponding to the decrease will flow. and ζ
As a result, capacitor c2 is discharged via resistor 120.

30 constant voltage generating circuits connected in series diodes 105,
106.107, a resistor 124 interposed between the cathode side of this diode group and the ground line, a transistor 113 whose base is connected to the connection point of these, and a transistor connected to this by Darlington]14. The collector of the transistor 114 is connected to the anode side of the diode group, and the emitter is connected to the ground line. The anode of the diode group is connected to the terminal, and is connected to the output of the power supply circuit 26 via a diode D for preventing backflow. When a current is applied to terminal I from an external circuit, a constant voltage value equal to the sum of the forward voltage drops of diodes 105, 106, and 107 and the sum of base-emitter voltages of transistors 113 and 114 is obtained. It becomes a constant voltage circuit. If the forward voltage drop of one diode in this IC 28 and the base emitter voltage of one transistor are equal and are defined as vD, then the constant voltage value of this circuit is 5VD.

First, the output voltage of the power supply circuit 26 is set to be equivalent to 4vD.

When the switch 19 is opened and a voltage is applied to the power supply circuit 26 via the terminal VT, its output reaches the above-mentioned 4VD. At this time, the base of the transistor 108 of the discharge circuit 29 is lower by the forward voltage drop of two diodes, and when a voltage higher than that by one diode is applied to the emitter, a current flows to the emitter. That is, when the emitter of the transistor 108 becomes equal to or higher than [4Vo -2VD+VD], a current flows to the emitter. However, as will be described later, until the timer circuit of the initial reset circuit W425 expires, the emitter potential of the transistor 108 does not rise above 3 VD, so no current flows there.

Similarly, in the constant voltage generation circuit 30, the terminal voltage of the terminal I is 5VD.
Since the voltage is not higher than that, no circuit current flows through this, and since the voltage at the anode is lower than that at the cathode of the backflow prevention diode D, no current flows there either.

Now, in the initial reset circuit 25, when the switch 19 is closed, a mirror current flows and charges the capacitor C2. This charging voltage is applied to the charging current detection circuit section, and the sum of the forward voltage drop of two diodes and the base-emitter voltage of the transistor 112, 3VD, becomes the threshold. While the charging voltage of the capacitor C2 is below 3VD, the output circuit 24 or the transistor 118 is activated as described above.
is off.

When the charging voltage of capacitor C2 becomes 3VD or more, normal detection operation becomes possible, and when the object M approaches, oscillation [ρ
The amplitude of the 1Wj output becomes small or oscillation stops, the output circuit 24 is turned on, the transistor Q, +02 is turned on,
Drive current is supplied to the load. On the other hand, lightning and current flow into terminal I. Then, the constant voltage generation circuit 30 generates a voltage equivalent to SVD, and the power supply circuit 26 no longer supplies voltage to the internal circuits.

Therefore, a voltage is supplied to the internal circuit via the reverse current prevention diode D, but if the forward voltage of this diode D is vD, the voltage supplied from the constant voltage generation circuit 30 to the internal circuit is also 4VD. This stabilizes the internal circuit operation.

When such a test object is detected, the emitter of the transistor 108 of the discharge circuit 29 becomes Lt'13Vo, and a voltage of 2'VD is applied to the resistor 120 between this emitter and the terminal (2). , the resistance value of this resistor J20 is selected to be several tens of Ω, and the current flowing through it is set to several tens of tA.
This prevents an excessive current from flowing to the emitter of the transistor 108.

Regarding the first M IJ set circuit 25, a difference of 2vD between the voltage 5VD on the terminal I side and the threshold 1lii3Vn is applied to the resistor 122.1. This is also selected to be several tens of ohms, so that the current flowing through the resistor 122 is suppressed to several tens of tA. This current is passed through the transistor 11 as a mirror current.
However, by appropriately selecting the value of the resistor 123, the internal current consumption can be suppressed.

Note that the charging current to the capacitor C7 is the transistor 110.
The charging current flows through the resistor 122 from the collector of
A is often set to A, and when the resistance value is determined as described above, the voltage drop is about 0.1 to 0.3 V, and has no effect on timer operation.

Next, regarding the state where the test object M is separated, the power supply circuit 6
Voltage is supplied from the terminal VT to the terminal VT, and current is no longer supplied from the transistor Q1, but the initial reset circuit 25
Current flows from the collector of transistor 1]0 to the capacitor C2 and the current mirror circuit of transistors 111 and 112, and the output circuit 24 is turned on and off by the mirror current flowing from the collector of transistor 112 of this current mirror circuit. kept in a possible state.

If the switch 19 is opened during the detection operation as described above, the transistor 10 of the discharge circuit 9
8 is turned on and the charge in the capacitor C2 is discharged, but even if the resistance value of the resistor 120 is selected to be several tens of Ω as described above, the discharge current will be sufficiently large and the discharge will occur quickly. .

As described in detail above, in the case of the semiconductor device for a proximity switch according to the present invention, the terminals M, I! of the proximity switch 27 are used. - The remaining voltage between 5VD of the constant voltage generation circuit, the emitter-collector saturation voltage of transistor Q, and the transistor Q
, which is the sum of the pace-emitter voltages of about 4 V, which is extremely low, and is extremely effective in ensuring stable and reliable operation of the load. Furthermore, since this reduction in residual voltage was achieved without increasing the number of terminals, there is no need to increase the size of the product compared to conventional products.

Furthermore, if an initial reset capacitor discharge circuit is provided, the initial reset capacitor will be discharged immediately each time the switch 7M path or the power is turned off, so the output circuit off period immediately after the switch is closed or the power is turned on will be stabilized. ,
There will be no erroneous output.

[Brief explanation of the drawing]

FIG. 1 is a schematic circuit diagram of a conventional device, FIG. 2 is a schematic circuit diagram of the device of the present invention, and FIG. 3 is a circuit diagram of essential parts of the device of the present invention. 21...Oscillation circuit Wr 24...Output circuit 25...
・Initial reset circuit 26...Power supply circuit 29...
Discharge circuit 30... Constant voltage generation circuit D... Backflow prevention diode V... Power supply RL... Load Q+
, Q2... Transistor patent applicant: Koyo Electronics Industry Co., Ltd. Agent Patent attorney: Noboru Kono

Claims (1)

[Claims] 1. A detection coil, a power supply, a load switch circuit, and an initial reset capacitor are externally attached, and the output is changed in response to separation or proximity of the object to the detection coil, and this output is used to control the switch. In a semiconductor device for a proximity switch, in which the circuit is operated to intermittent power supply to the load, and the output is restrained for a time specified by an initial reset capacitor at the time of initial reset, nr of the power source and the load is connected. A series circuit includes a power supply circuit that is substantially directly connected and outputs a voltage for driving the internal circuit, a common terminal to which the initial reset capacitor and one terminal of the switch circuit are connected, and a constant circuit connected to the common terminal. The voltage circuit, the voltage output terminal of the power supply circuit, and the i+? 1. A semiconductor device for a proximity switch, comprising a backflow prevention diode connected between the positive terminal and the positive terminal. 2. A detection coil, a power supply, a load switch circuit, and an initial reset capacitor are externally attached, and the output is changed in response to the separation or proximity of the object to the detection coil, and this output operates the switch circuit to reset the load. Intermittent power supply to
Further, in a semiconductor device for a proximity switch, which restricts the output for a time specified by an initial reset capacitor at the time of initial reset, the semiconductor device is substantially directly connected to the series circuit of the power supply and load, and the voltage for driving the internal circuit is and a common terminal to which one terminal of the initial reset capacitor and the switch circuit should be connected. a constant voltage circuit connected to the common terminal; a backflow prevention diode connected between the voltage output terminal of the power supply circuit and the common terminal; and the output terminal of the power supply circuit and the common terminal. In succession,
A semiconductor device for a proximity switch I, comprising a discharge circuit that discharges the charge of an initial reset capacitor when the output voltage of the power supply circuit becomes equal to or less than a predetermined value.
f7.