JP2525285Y2 - Output device of detection switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Field of the Invention The present invention relates to a detection switch for controlling a load device based on a detection state of an object to be detected, and particularly to a detection sensor circuit,
The present invention relates to a detection switch output device including an IC in which an NPN output circuit and another switching output circuit are integrated.

(B) Conventional technology Generally, when outputting a detection signal of a detection switch,
There are NPN output type and PNP output type. When an output device that outputs the detection signal of the detection switch is integrated into an IC, the terminal can be directly connected to a load device with an output transistor incorporated in the case of an NPN output type. On the other hand, in the case of a PNP output type, an output transistor is often externally connected. This is because the output device of the detection switch is N compared to the PNP output type.
Demand for PN output type is large, and N for PNP transistor
Since the same current flows as the PN transistor, it occupies a larger area on the IC chip than the NPN transistor, and the size of the IC chip becomes larger due to the less frequently used PNP output type output transistor. This is to prevent it.

This is because, as shown in FIG. 2, in consideration of the versatility of the output circuit, the detection sensor circuit 22, the NPN output circuit 23 and the PNP output circuit 24 (an output circuit that requires an external PNP output The same applies to the case where another switching output circuit such as an IC is integrated into an IC. The NPN output circuit 23 includes an output transistor Q21, whereas the PNP output circuit 24 includes an output transistor. Absent. Therefore, the output terminal of the NPN output circuit 23 can be directly connected to the load device 25, while the output of the PNP output circuit is input to the load device 26 via the output transistor Q22. A known short-circuit protection function is provided to each of the NPN output circuit 23 and the PNP output circuit 24. Generally, the short-circuit protection functions of the NPN output circuit 23 and the PNP output circuit 24 are linked, and when one operates, the other also operates.

Further, when the NPN output circuit 23 is configured in the IC 21, the size of the output transistor Q21 increases according to the drive current value for the load device 25. Therefore, in consideration of the miniaturization of the IC 21, the output transistor Q21 is not so large, but is capable of outputting a drive current of, for example, 100 mA at the maximum. In order to obtain a drive current of 100 mA or more using such an IC21, as shown in FIG.
The output of the output transistor Q21 of the N output circuit 23 is amplified by the transistor Q23 and the output transistor Q24. With this configuration, when the output transistor Q21 is turned on, the transistors Q23 and Q24 are turned on and the transistor Q23 is turned on.
The allowable current value of 24 can be supplied to the load device 25 as the maximum drive current.

(C) Problems to be solved by the invention However, when a large output current (for example, 100 mA or more) is realized by externally connecting the transistor Q24 to the IC21,
Since all the current flows to the load device 25 via the transistor Q24 and does not flow to the NPN output circuit 23, the NPN output circuit
The short circuit protection function of 23 cannot be used. Therefore, in order to obtain a short-circuit protection function for the load device 25, a circuit for realizing the short-circuit protection function must be externally provided to the IC 21, and the configuration of the entire output device of the detection switch becomes complicated and large, There was a problem that caused an increase in cost.

The purpose of this idea is to obtain a large output current,
Enables the use of the short-circuit protection function of the NPN output circuit built into the IC that constitutes the detection switch, eliminating the need to externally attach a circuit to realize this function to the IC, miniaturizing the device and reducing parts. Accordingly, it is an object of the present invention to provide a detection switch output device capable of realizing cost reduction.

(D) Means for Solving the Problems The output device of the detection switch of the present invention includes a detection sensor circuit that outputs a detection signal according to the presence or absence of an object to be detected, an NPN output circuit that receives the detection signal, Another switching output circuit that outputs an on / off signal linked to this NPN output circuit via an external PNP output transistor is integrated with the NPN output circuit or another switching output circuit. An output device of a detection switch that opens and closes a current path of a load device in accordance with an output of an NPN output circuit or another switching output circuit, the IC including an IC that turns off a detection signal when the output voltage exceeds the output voltage, including the external PNP output transistor; A switching circuit for outputting an on / off signal according to an on / off state of the another switching output circuit, and a PNP output transistor of the switching circuit A transistor having a collector terminal connected to a base terminal, the switching transistor opening and closing a current path of a load device based on an on / off signal output from a switching circuit, and a current value flowing from the load device to the switching transistor. And a limiter circuit that guides a current having a difference between a current value flowing from the load device to the switching transistor and a specified value to an NPN output circuit.

(E) Operation In the present invention, a current flows through the load device via the limiter circuit. The limiter circuit is turned on / off by a switching circuit including a PNP output transistor that outputs an on / off signal according to the on / off state of another switching output circuit built in the IC. Since the detection signal is similarly input from the detection sensor circuit to the NPN output circuit and another switching output circuit in the IC constituting the detection switch, the signal is output from the NPN output circuit and simultaneously from another switching output circuit. An output signal is output. The switching circuit is driven by the output signal of the other switching output circuit, and the switching circuit turns on the limiter circuit. This causes a current to flow through the load device.

When a current equal to or more than the specified value flows through the load device, the limiter circuit guides the difference between the current and the specified value to the NPN output circuit. The NPN output circuit has a short-circuit protection function, so if an excessive current flows through the load device, a large amount of current will be input to the NPN output circuit, and the short-circuit protection function of the NPN output circuit will operate. As a result, no output signal is output from the NPN output circuit. Accordingly, the output signal from another switching output circuit is also turned off.

(F) Embodiment FIG. 1 is a circuit diagram in a case where a load device is controlled using an output device of a detection switch according to an embodiment of the present invention.

The output device of the detection switch of the present invention is configured by externally attaching a limiter circuit 11 and a switching circuit 12 to IC1. IC1 has the same configuration as that used in FIGS. 2 and 3, and is configured by a detection sensor circuit 2, an NPN output circuit 3, and a PNP output circuit 4. 2 and 3 that the NPN circuit 3 and the PNP circuit 4 have a known short-circuit protection function (for example, a short-circuit protection circuit disclosed in JP-A-61-199416 can be used). It is the same as the IC shown.

The detection signal of the detection sensor circuit 2 is similarly input to the NPN output circuit 3 and the PNP output circuit 4, and the transistor Q1
And Q2 are turned on / off at the same time. Also, limiter circuit
11 is composed of transistors Q4 and Q5 and a resistor R2. The load device 5 is connected to the collector terminal of the transistor Q5 and also to the output terminal 6 of the NPN output circuit 3 of IC1. Further, the switching circuit 12 includes a transistor Q6 and a resistor R3. The base terminal of the transistor Q6 is connected to the output terminal 7 of the PNP output circuit 4.

In the above configuration, the NPN output circuit 3 of IC1 and
When the transistors Q1 and Q2 of the PNP output circuit 4 turn on, all of the transistors Q4 to Q6 forming the limiter circuit 11 and the switching circuit 12 turn on, and the current I flows through the load device 5. As a current path of a current flowing through the load device 5,
The route Ia and the route Ib shown in FIG. 1 are conceivable. Route Ia
Current flowing through, i.e. the collector current of the transistor Q5, the limiter is applied at a current value determined by the base-emitter value of the voltage V _BE and the resistor R2 of the transistor _{Q4 (I '= V BE /} R2). In other words, by appropriately selecting the value of the resistor R2, the specified value of the current flowing through the current path Ia can be set.

When the current I flowing through the load device 5 exceeds the specified value I ', the current having the specified value I' flows through the path Ia and the remaining current (I
−I ′) flows through the path Ib. As a result, the difference current (I-I ') flows into the NPN output circuit 3, and when the difference current value (I-I') exceeds a predetermined value, NP
The short-circuit protection function of the N output circuit 3 operates. For example, I '
If the value of the resistor R2 is set to be 100 mA, when the load current I is 120 mA, a current of 100 mA flows through the current path Ia and a current of 20 mA flows through the current path Ib. When the short-circuit protection function is activated, for example, if the output transistor is operated intermittently to prevent the output transistor from being damaged, the transistor Q6 also operates intermittently. Intermittent operation.

As described above, according to this embodiment, the limiter circuit 11 and the switching circuit 12 are provided between the IC 1 and the load device 5.
, The output transistor Q of the NPN output circuit
For load devices that have a drive current exceeding the capacity of 1, the IPN output circuit 3 with the short-circuit protection function still active
C1 can be used.

By changing the value of the resistor R2 provided in the limiter circuit 11, the current flowing through the path Ia, that is, the specified value of the limiter circuit 11, can be easily changed, and the load device using the detection switch is changed. 5 can be easily handled.

In this embodiment, a PNP output circuit is used as another switching output circuit. However, another switching output circuit that turns on / off in conjunction with the NPN output circuit, for example, an integration circuit or an LED driving circuit can be used. .

(G) Effects of the Invention According to the invention, a current equal to or greater than the maximum drive current value specified by the output transistor of the NPN output circuit built into the IC can flow to the load device, and the current flowing to the load device can be increased. Exceeds the sum of the specified value specified in the limiter circuit and the maximum drive current value of the NPN output transistor inside the IC, the short-circuit protection function provided in the NPN output circuit is enabled and this NPN output circuit and another The output of the switching output circuit can be turned off, and there is no need to externally connect a short-circuit protection circuit to the IC in order to realize this function, so that there is an advantage that the size and cost of the output device can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a use state of an output device of an output switch according to an embodiment of the present invention. FIGS. 2 and 3 are circuit diagrams showing the state of use of the output device of the conventional detection switch. 1 ... IC, 2 ... Detection sensor circuit, 3 ... NPN output circuit, 4 ... PNP output circuit (another switching output circuit), 11 ... Limiter circuit, 12 ... Switching circuit,
5 ... Load device.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References Japanese Utility Model Sho 63-174726 (JP, U) Japanese Utility Model Sho 63-90332 (JP, U) Japanese Utility Model Sho 61-182127 (JP, U)

Claims (1)

(57) [Scope of request for utility model registration] 1. A detection sensor circuit for outputting a detection signal in accordance with the presence or absence of an object to be detected, an NPN output circuit to which the detection signal is input, and an on / off signal interlocked with the NPN output circuit. Another switching output circuit that outputs via a PNP output transistor, and an NPN output circuit that includes an IC that turns off the detection signal when the current flowing through the NPN output circuit or another switching output circuit exceeds a certain value. Alternatively, in an output device of a detection switch that opens and closes a current path of a load device in accordance with an output of another switching output circuit, the output device includes the external PNP output transistor, and responds to an on / off state of the another switching output circuit. A switching circuit that outputs an on / off signal; and a transistor having a base terminal connected to the collector terminal of the PNP output transistor of the switching circuit. A switching transistor that opens and closes a current path of the load device based on an on / off signal output from the switching circuit; and a current limiting unit that limits a current value flowing from the load device to the switching transistor to a specified value. An output device for a detection switch, comprising: a limiter circuit that guides a current having a difference between a current value flowing from the device to a switching transistor and a specified value to an NPN output circuit.