JPH04198763A - Insulation type voltage detector - Google Patents

Abstract

PURPOSE:To reduce the consumed current by providing a liquid crystal plate between light emitting and light receiving elements. CONSTITUTION:Voltage applying terminals 11a, 11b of a liquid crystal plate 11 are connected to a power source to be detected 12, and the output voltage is applied to the liquid crystal plate 11. When the output voltage is held within a normal range at the voltage threshold value V2 or above, the liquid crystal plate 11 interrupts a luminous beam from a light emitting element 13, and a light receiving element 14 is switched off. The DC voltage Vd of an output terminal 18 becomes +5V. When the output voltage is lowered to the threshold value V1 or below on the contrary, the light permeability of the liquid crystal plate 11 is increased, the element 14 is switched on, and the voltage Vd of the terminal 18 becomes +0V. The output voltage state of the power source 12 can be detected in the electrically insulated state from the power source 12. The liquid crystal plate 11 has high impedance, the change of the light permeability is determined by the applied voltage value, the power consumption on the power source 12 can be made very small.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an insulated voltage detector for detecting the power supply state of an electric circuit as a voltage change in an electrically isolated state.

2. Description of the Related Art Conventionally, as this type of isolated voltage detector, a transformer relay using an AC coupling circuit and an optical coupling element (for example, a photocoupler or a photoisolator) are known.

FIG. 7 shows a circuit configuration diagram when a conventional photocoupler is used. In the figure, a light emitting element 1 (for example, L
The cathode C of the ED) is connected to the voltage detection terminal A of the power supply to be detected 2 via the resistor 3, and the anode a is connected to the voltage detection terminal B of the power supply to be detected 2. Light receiving element (e.g.
A collector C of the phototransistor 4 is connected to a 5V terminal of a 5V DC power source and an output terminal 6 via a resistor 5, and a base b of the light receiving element 4 is connected to the circuit ground.

Here, the power source to be detected 2 is a power source that is used in various electric circuits and is a target power source whose power state is to be determined whether or not it is normal.

Next, the operation of the above conventional example will be explained.

When the detected power source 2 is ON, the output voltage between the voltage detection terminals ASB of the detected power source 2 is applied to the light emitting element 1 via the resistor 3. When the light emitting element 1 is forward biased and a forward current flows, it emits light. When this light enters, the light receiving element (phototransistor) 4 is turned on, and a collector current flows from the +5V voltage terminal through the resistor 5 to the collector C.
→Anode a→Circuit ground, and the voltage at the output terminal changes from +5V to Ov. In this way, even with the conventional insulated voltage detector described above, changes in the voltage of the power source to be detected can be detected while being electrically isolated by the photocoupler.

Problems to be Solved by the Invention However, in an insulated voltage detector such as the conventional photocoupler described above, a collector current of more than ten mA must be passed through the light emitting element l to cause it to emit light. There was a problem that the current consumption of the power supply increased.

The present invention solves these conventional problems,
It is an object of the present invention to provide an excellent low power consumption isolated voltage detector that can reduce the current consumption of a detected power supply with a simple component configuration.

Means for Solving the Problems In order to achieve the above object, the present invention provides a light emitting element that emits light with a constant amount of light, a light receiving element that outputs a voltage signal of a predetermined level depending on the amount of light received from the light emitting element, and a light emitting element that emits light at a constant amount of light. This constitutes an insulated voltage detector in which a liquid crystal plate is provided between the element and the optical path of the light-receiving element, and the amount of light transmitted changes according to changes in the voltage applied from the power source to be detected.

Function Since the present invention is configured as described above, the light emitting element is constantly caused to emit light by an external power source different from the power source to be detected, and the amount of light transmitted changes depending on the voltage change of the power source to be detected. It is detected by a light receiving element through the liquid crystal plate. Thereby, a change in the voltage of the power source to be detected can be detected as a change in the amount of light received by the light receiving element due to a change in the amount of light transmitted through the liquid crystal plate.

Therefore, since the light emitting element is not directly driven by the power source to be detected, the power consumption of the power source to be detected is as low as changing the amount of light transmitted through the liquid crystal plate provided between the light emitting element and the light receiving element.

Embodiment FIG. 1 shows a circuit diagram of two circuits of an insulated detection circuit according to a first embodiment of the present invention, and FIG. 2 shows the applied voltage and light transmission to the liquid crystal plate used in the above insulated detector. This is a characteristic that shows the relationship between the amount (photo/multiple output value). FIG. 3 is a perspective view showing the structure of the insulated detector.

In FIGS. 1 and 3, voltage terminals 11a and 11b are provided on the liquid crystal plate 11 and connected to voltage terminals A and H of the detected power source 12, respectively.

A 1-current voltage of +5 V is applied to the light emitting element (LED) 13 via a resistor 15 from an external DC power source (particularly not shown) independent of the detected power source 12 .

The light receiving element (phototransistor) 14 is arranged at a position to receive the light beam from the light emitting element 13.
Similarly, it is driven by an external DC power supply. +5V is constantly applied to the collector of the light receiving element from an external DC power supply via the resistor 16. The collector is also connected to the output terminal 18.

The liquid crystal plate 11 is placed in the optical path of the light beam from the light emitting element 13 to the light receiving element 14 so as to block the emitted beam.

The operation of the first embodiment of the present invention will be described.

In the configuration shown in FIG. 1, when a forward bias of +5V is applied to the cathode C of the light emitting element 13 from the DC power source via the resistor 15, a forward current flows from the cathode C to the anode a to the circuit ground, and the light emitting element 13 emits light.

The light-receiving element (phototransistor) 14 has +5V constantly applied to its collector C from a current power supply, and when it receives a light beam, the switch turns on, and therefore the output terminal 1
The DC voltage Vd of 8 becomes +Ov. When the light emitting element 13 is emitting light and an object is inserted into the optical path of the light beam to block the light beam, the light receiving element 14 becomes OFF because it cannot receive the light beam, and the output terminal 18 becomes a DC voltage V.
d changes from OV to +5v.

In one embodiment of the present invention, the light emitting element 13 is always in a light emitting state, so unless the light beam is interrupted, the light receiving element 14
The switch is ON, and the output terminal 18 always maintains the Ov state.

However, as shown in FIG. 1 showing the configuration of an embodiment of the present invention, a liquid crystal plate 11 is disposed in the optical path from the emitted beam of the light emitting element 13 to the light receiving element. In the characteristic curve of the liquid crystal plate shown in FIG.
When the switch is turned on, the DC voltage Vd at the output terminal 18 becomes Ov.
become. On the other hand, when the voltage value applied to the liquid crystal plate 11 exceeds v2, the amount of transmitted light decreases rapidly, and the light receiving element 14 is switched off.

Therefore, the DC voltage Vd at the output terminal 18 becomes +5v.

Voltage application terminals 11a and 11b of the liquid crystal plate 11 are connected to voltage monitor terminals A and B of the detected power supply 12, respectively, so that the output voltage of the detected power supply 12 is applied to the liquid crystal plate 11.
is applied to If the output voltage of the detected power supply 12 is maintained within the normal range and is equal to or higher than the voltage threshold value 72, the liquid crystal plate 11 blocks the emitted light beam from the light emitting element 13 at that voltage.
The light receiving element 14 is switched off.

The DC voltage Vd at the output terminal 18 becomes +5v.

Conversely, the output voltage of the detected power supply 12 decreases and reaches the voltage threshold v1.
Below, the light transmittance of the liquid crystal plate increases and the light receiving element 14
becomes the switch ON state, and the DC voltage V at the output terminal 18
d becomes +0■.

In this way, the state of the output voltage (O
(N state or OFF state) can be detected in an electrically isolated state from the detected power supply.

Furthermore, the liquid crystal plate 11 has a high impedance, and the change in light transmittance is determined by the applied voltage value (the current value is on the order of several μA). Therefore, the power consumption of the detected power source can be made very low.

In addition, in the embodiment shown in FIG. 1, the voltage applied to the liquid crystal plate 11 from the detected power supply 12 is a DC voltage at a constant level (V2
In this example, the voltage is maintained at a voltage of a pulse waveform (either above or below v1), but a pulse waveform voltage may also be used. In this case, the light transmittance changes greatly depending on whether the peak value of the pulse is greater than or equal to the voltage threshold value v2 or less than the voltage threshold value v1.

In FIG. 3, a liquid crystal plate 11 is arranged between a light emitting element 13 and a light receiving element 14, and a slit plate 20.21 having light passage holes 20h and 21h with the liquid crystal plate 11 in between.
is provided to block scattered incident light from other sources. Terminals 11a and llb of the liquid crystal board 11 are connected to the detected power supply 1.
2 (not shown in FIG. 2).

FIG. 4 is a perspective view showing a structure in which a photo ink club is used as a second embodiment of the present invention.

In this case, the photointerrupter 22 has a pair of light-emitting elements and a light-receiving element placed opposite each other, and a space is provided between the light-emitting element and the light-receiving element, so that when an object enters there, the light-receiving element receives the space. It uses changes in the amount of light received to detect the presence, position, phase, etc. of an object.

In this embodiment, instead of moving an object between the light emitting element and the light receiving element of the photointerrupter 22, the amount of light transmitted from the light emitting element to the light receiving element is changed by applying the output voltage of the detected power source as shown in FIG. Insert and fix the liquid crystal plate that changes the With such a structure, the same effect as the first embodiment can be achieved.

FIG. 5 is a perspective view showing a reflective type structure as a third embodiment of the present invention.

In the figure, a light emitting element 13 and a light receiving element 14 are arranged at an angle with respect to a slit plate 23. Further, a liquid crystal plate 11 is arranged parallel to the slit plate 23, and a reflection plate 24 is arranged in close contact with the lower surface of the liquid crystal plate 11.

Note that the lower surface of the liquid crystal plate 11 may be coated with a reflective surface in advance.

The emitted light beam from the light emitting element 13 passes through the light passage hole 23h of the slit plate 23 and enters the liquid crystal plate 11.
It passes through the slit plate 2, is reflected by the reflection plate 24, and returns to the slit plate 2.
The light passes through the light passing hole 23k of No. 3 and is received by the light receiving element 14. .

Terminals 11a and llb of the liquid crystal plate 11 are connected to voltage monitor terminals A and B of the detected power source 12.

With such a structure, the same effects as those of the first embodiment shown in FIG. 1 can be obtained, and moreover, the degree of freedom in the arrangement of components can be obtained when mounting on a circuit board or the like.

FIG. 6 shows a circuit configuration diagram in a fourth embodiment of the present invention.

In the figure, the difference from the first embodiment shown in FIG. 1 is that a photodiode 19 is used as a light receiving element instead of a phototransistor. Here, the liquid crystal plate 11 includes not only the power source to be detected but also an external electric circuit 25.
The signal monitor terminals M1 and M2 of the terminal are connected to each other.

In the case of a phototransistor, unless the voltage applied to the liquid crystal plate changes between the voltage threshold V2 or higher and the voltage threshold ■1 or lower, switching 0N10FF will not occur and a predetermined change in output voltage will not be obtained. Photodiode 19
In this case, since it has a wide sensitivity range with respect to the intensity of light incident on the light receiving element 13, it is possible to detect a change in the amount of light transmitted through the liquid crystal plate due to the voltage applied to the liquid crystal plate 11 as a wide change in the output voltage. can.

Therefore, in the embodiment shown in FIG.
It is not limited to monitoring the FF state, but can also detect analog fluctuations in the signal level of general electric circuits.

Effects of the Invention As is clear from the embodiments described above, conventionally, in monitoring the status of a power source to be detected, power is supplied from the power source to a light emitting element, which emits light and is detected by a light receiving element. The determination was made based on the change in the output voltage of the light receiving element due to a decrease in the amount of light emitted by the light emitting element.

The driving current of the light emitting element is usually more than ten mA, which is a considerable load on the power source to be detected.

In contrast, with the configuration shown in each embodiment of the present invention, both the light-emitting element and the light-receiving element are constantly driven by an external power source, and a liquid crystal plate is placed between the optical path of the light-emitting element and the light-receiving element of the emitted beam. A change in the voltage of the power source to be detected is detected as a change in the output voltage of the light receiving element due to a change in the amount of light transmitted through the liquid crystal plate. The liquid crystal plate has high impedance, and the change in light transmittance is determined by the applied voltage value, and the current value is on the order of several μA.

Therefore, the power consumption by this isolated voltage detector to the power source to be detected can be made very low.

Further, the liquid crystal plate used in the present insulated voltage detector may be a commercially available liquid crystal display (LCD), and since it has a simple structure, it can be produced at low cost.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an insulated voltage detector according to a first embodiment of the present invention, and FIG. FIG. 3 is a perspective view showing the specific configuration of the embodiment of FIG. 1, and FIG. 4 is a characteristic curve showing the relationship between output values), and FIG. 4 is a characteristic curve showing the relationship between FIG. 5 is a perspective view showing a reflective type structure as a third embodiment of the present invention, and FIG. 6 is a circuit configuration in a fourth embodiment of the present invention. 7 are circuit configuration diagrams when a conventional photocoupler is used. 11...Liquid crystal plate, 12...Power source to be detected, 13...
Light emitting element (LED), 14... Light receiving element (phototransistor), 15 and 16... Resistor, 18...
Output terminals, A and B...Voltage monitor terminal of the power supply to be detected, 19...Photodiode, 22...Photointerrupter, 23...Slit plate, 24...Reflector, 25...External Electric circuit, Ml and M2...signal monitor terminals of the external electric circuit 25. Figure 1 Figure 2 Photomultiple output Figure 3 Figure 4

Claims (1)

[Scope of Claims] A light emitting element that emits light with a constant amount of light, a light receiving element that outputs a voltage signal at a predetermined level depending on the amount of light received from the light emitting element, and a detected power source between the optical path of the light emitting element and the light receiving element. 1. An insulated voltage detector comprising: a liquid crystal plate that changes the amount of light transmitted according to changes in voltage applied from the insulated voltage detector.