JPH07105524B2 - Light receiving device - Google Patents

Description

The present invention relates to a light receiving device in an optically coupled semiconductor device such as a photo coupler.

<Prior Art> Conventionally, in an optically coupled semiconductor device, in order to remove noise due to disturbance or the like, as shown in FIG. 4 and FIG. 5, a light receiving device has one light receiving portion 2 as a light receiving element 1, an amplifier 3, and A light receiving unit on the output side from the input side through an input / output capacitance C1 formed between an amplifier circuit 5 having a comparator 4 and existing between the light emitting element 6 side (input side) and the light receiving element 1 side (output side). 2 to remove the common-mode noise signal input to
A transparent conductive film 8 that allows light 7 to pass therethrough is disposed on the surface of the.

Further, as another conventional example, as shown in FIG. 6 and FIG. 7, a conductor 9 is arranged around the light receiving section 2, and an output signal from the conductor 9 and an output signal from the light receiving section 2 are provided. The amplifier 3a, 3
After amplification in b respectively, by subtracting these values, the common-mode noise signal rejection ratio (common mode rejection ratio: hereinafter referred to as CMRR) is increased, and malfunctions due to common-mode input are reduced.

In the figure, 10 is a semiconductor substrate and 11 is a reference voltage.

<Problems to be Solved by the Invention> However, in the conventional configuration shown in FIGS. 4 and 5, a process of attaching the transparent conductive film 8 on the light receiving portion 2 is necessary, which complicates the process and reduces the price. There is a problem that rising is inevitable.

In addition, in the conventional configuration shown in FIG. 6 and FIG.
In order to obtain CMRR, it is necessary that the capacitance C2 between the input side and the light receiving portion 2 and the capacitance C3 between the input side and the conductor 9 be equal. However, in an optical coupling semiconductor device such as a photo coupler, Since the distance between the inputs is as small as 1 mm or less compared to the shape of the light receiving part (usually around 0.5 mmR), trial and error was required to match the capacitances C2 and C3.

Further, even when C2 and C3 match, the light receiving unit 2 and the amplifier 3a to which the input / output capacitance C2 to the light receiving unit 2 is input, and the amplifier to which the conductor 9 and the input / output capacitance C3 of the conductor 9 are input It is difficult to obtain high CMRR because the response characteristics of the circuits do not match with those of 3b.

In view of the above problems, it is an object of the present invention to provide a light receiving device that can easily achieve high CMRR.

<Means for Solving the Problems> The means for solving the problems according to the present invention is a light receiving device for receiving the light 7 from the light emitting element 6 as shown in FIGS. A plurality of light-shielding parts 12a, 12b that are not shielded from light-receiving device 7 and that detect a common-mode noise signal from the light-emitting device 6, and the same number of common-mode noise signals from the light-emitting device 6 as the light-receiving parts 12a, 12b. A light-shielding light-receiving portion 13a, 13b that detects light, and an amplifier circuit 14 that amplifies and compares the output signal of the light-receiving portion 12a, 12b and the output signal of the light-shielding light-receiving portion 13a, 13b. , 12b and the light-shielding light-receiving parts 13a, 13b, the light-receiving parts 12a, 12b and the light-shielding light-receiving parts 13a, 13b.
It is arranged alternately on the outer circumference of the center of the light-receiving portion area constituted by b and b.

<Operation> In the above problem solving means, the signals from the light receiving portions 12a and 12b are combined and output to the amplifier circuit 14. On the other hand, the signals from the light-shielding and light-receiving parts 13a and 13b are also synthesized in the same manner and the amplification circuit 1
Output to 4. Then, the respective output signals are amplified, compared and output.

Here, in the noise signal input to the light receiving device, the light receiving area is divided into four, and the light receiving areas 12a and 12b and the light shielding light receiving areas 13a and 13b are alternately arranged on the outer periphery of the center of the light receiving area, that is, the point symmetrical arrangement. Therefore, the light receiving parts 12a, 12b and the light blocking light receiving parts 13a, 1
3b produces the same amount of output signal. Therefore, by the amplifier circuit 14, the signals from the light receiving parts 12a and 12b and the light-shielding light receiving part 1
Since the signals from 3a and 13b cancel each other out, no malfunction occurs due to the noise signal.

Further, the amplifier of the amplifier circuit 14 has the same configuration for the light receiving portions 12a, 12b and the light-shielding light receiving portions 13a, 13b, and each input has the same light receiving portion. Since there is no difference, the in-phase input signal is not output, and higher CMRR is possible.

On the other hand, with respect to the optical signal emitted from the light emitting element 6, since the signal enters only the light receiving portions 12a and 12b which are not shielded,
The optical signal is detected reliably.

Therefore, by dividing the light receiving portion of the light receiving element 1 into a non-light-shielded one and a light-shielded one, the noise signal is canceled and removed, so that the CMRR can be increased.

Moreover, in the manufacturing process of the light-receiving element 1, it is sufficient to cover the surface of the light-receiving element 1 with the light shields 15a and 15b, and the light-receiving element 1 can be manufactured by a simple process. Therefore, it is possible to easily supply a light-receiving device having a high CMRR.

<Embodiment> An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a plan view of a light receiving device showing an embodiment of the present invention, FIG. 2 is an electric circuit diagram of the same light receiving device, and FIG. 3 is a diagram showing a positional relationship between a light emitting element and a light receiving element.

As shown in the figure, the light receiving element 1 of the light receiving device of the present invention includes two light receiving portions 12a and 12b which are not light-shielded on the semiconductor substrate 10 and two light-shielding light receiving portions which are the same number as the light receiving portions 12a and 12b. Part 13
a and 13b are alternately arranged on the outer periphery of the center of the light receiving area formed by the light receiving sections 12a and 12b and the light shielding light receiving sections 13a and 13b so that the light 7 from the light emitting element 6 can be received evenly. Specifically, the light receiving portions 12a and 12b and the light shielding light receiving portions 13a and 13b are arranged in point symmetry positions. Then, an amplifier circuit 14 that amplifies and compares the output signals of the light-receiving portions 12a and 12b that are not shielded with the output signals of the shielded light-receiving portions 13a and 13b that are shielded.
Is equipped with.

The light-receiving portions 12a, 12b and the light-shielding light-receiving portions 13a, 13b are made of photodiodes, and the light-shielding light-receiving portions 13a, 13b have light-shielding members 15a, 15b such as metal or opaque insulators on their surfaces.
Is covered with. The light emitting element 6 is a light emitting diode.

Further, the amplifier circuit 14 is mounted on the one semiconductor substrate 10 together with the light receiving portion, the amplifier 16a for amplifying the output signal from the light receiving portion 12a, 12b, and the light shielding light receiving portion 13a, 1.
Amplifier 16b that amplifies the output signal from 3b, and both amplifiers 16b
Comparator 1 that outputs the detection signal by comparing the outputs from a and 16b
It is composed of 7 and. Both amplifiers 16a and 16b are composed of the same circuit, and the light receiving parts 12a and 12b and the light shielding and light receiving parts 13a and 13b are connected in parallel to the respective amplifiers 16a and 16b.

The input-output capacitances between the light emitting element 6 and the light receiving portions 12a and 12b are C4 and C5, respectively. Further, the input-output capacitances between the light-shielding light-receiving parts 13a and 13b are C6 and C7.

In the above configuration, the signals from the light receiving units 12a and 12b are combined and amplified by the amplifier 16a. On the other hand, the light-shielding light receiving unit 1
The signals from 3a and 13b are similarly combined and amplified by the amplifier 16b.

The outputs of the amplifiers 16a and 16b are compared with each other by the comparator 17
Are compared and output digitally.

Here, the common-mode noise signal that enters the output side from the input side through the input-output capacitances C4 to C7 has the same amount as shown in FIG. 3 because the light receiving element 1 is divided into four parts and arranged in point symmetry. It produces a noise signal current. That is, in FIG. 3, assuming that light is incident from the X axis of the X and Y axis coordinates where the noise signal is orthogonal, the distances from the noise signal incident portion to the centers of the light receiving portion 12a and the light shielding light receiving portion 13a are equal. And its capacity C4 and C
Is equal to 6. Similarly, the light receiving section 12b and the light blocking light receiving section 13b
The capacitances C5 and C7 between and are equal. Therefore, the light receiving part
The same amount of noise signal current is generated in 12a, 12b and the light-shielding light receiving parts 13a, 13b.

Therefore, the same amount of noise signal current is amplified by the amplifiers 16a and 16b having the same circuit configuration, and the differential input comparator 1
Even when input to 7, the output is not inverted, the signals from the light receiving sections 12a, 12b and the signals from the light-shielding light receiving sections 13a, 13b cancel each other out, and an output signal is output.
Malfunction does not occur.

Further, the inputs of the amplifiers 16a and 16b have the same configuration including two light receiving portions such as the light receiving portions 12a and 12b or the light shielding light receiving portions 13a and 13b, and there is no difference in the circuit response. Since the common mode input signal is not output, higher CMRR is possible.

On the other hand, with respect to the optical signal emitted from the light emitting element 6, since the signal enters only the light receiving portions 12a and 12b which are not shielded,
The optical signal is detected reliably.

Therefore, by dividing the light receiving element 1 into a non-light-shielded element and a light-shielded element, the in-phase input signal is canceled and removed, so that the CMRR can be increased.

Moreover, in the manufacturing process of the light receiving element 1, it is sufficient to cover the surface of the light receiving element 1 with the light shields 15a and 15b.
Since it can be manufactured by a simple process as compared with the process of attaching a conductive film to, it is possible to easily supply an optically coupled semiconductor device having a high CMRR without changing the manufacturing process.

The present invention is not limited to the above embodiments, and it goes without saying that many modifications and changes can be made to the above embodiments within the scope of the present invention.

For example, the light receiving element 1 is not limited to four divisions, but may be divided into six or more divisions in point symmetry.

<Effects of the Invention> As is apparent from the above description, according to the present invention, a plurality of light-shielding portions that receive light from a light-emitting element and that detect a common-mode noise signal from the light-emitting element, and a plurality of light-receiving portions that are not shielded, And a light-shielding light-shielding light-receiving unit that detects the same-phase noise signal from the light-emitting element, and an amplifier circuit that amplifies and compares the output signal of the light-receiving unit and the output signal of the light-shielding light-receiving unit, By arranging the light-receiving unit and the light-shielding light-receiving unit alternately on the outer periphery of the center of the light-receiving unit region formed by the light-receiving unit and the light-shielding light-receiving unit, even if a common-mode noise signal is input, the light-receiving unit and the light-shielding light-receiving unit Since the same amount of output signal is generated in each section, the noise signal can be canceled and removed, the CMRR can be increased, and the noise resistance can be improved.

Moreover, since the light receiving element can be manufactured by a simple process in the manufacturing process, there is an excellent effect that a light receiving device having a high CMRR can be easily supplied.

[Brief description of drawings]

FIG. 1 is a plan view of a light receiving device showing an embodiment of the present invention, and FIG.
The figure is also an electric circuit diagram of the light receiving device, FIG. 3 is a diagram showing the positional relationship between the light emitting element and the light receiving element, FIG. 4 is a plan view of a conventional light receiving device, FIG. 5 is its electric circuit diagram, and FIG. Is a plan view of another conventional light receiving device, and FIG. 7 is an electric circuit diagram thereof. 1: light receiving element, 6: light emitting element, 7: light, 12a, 12b: light receiving section, 13a,
13b: light-shielding light-receiving part, 14: amplifier circuit, 15a, 15b: light-shielding body, 16a, 1
6b: amplifier, 17: comparator.

Claims (1)

[Claims] 1. A light-receiving device for receiving light from a light-emitting element, wherein a plurality of light-shielding portions that receive light from the light-emitting element and that detect a common-mode noise signal from the light-emitting element are not shielded; And a light-shielding light-shielding light-receiving portion that detects the same-mode noise signal from the light-emitting element in the same number as the number of parts,
The center of the light-receiving part region, which includes an amplifier circuit for amplifying and comparing the output signal of the light-receiving part and the output signal of the light-shielding light-receiving part, and the light-receiving part and the light-receiving part A light-receiving device characterized in that the light-receiving device is alternately arranged on the outer periphery of the.