JPH02156575A - Photo detector - Google Patents

Abstract

PURPOSE:To avoid complex process and cost rise, and reduce malfunction caused by in-phase inputs by arranging a plurality of light receiving parts and light shielded light-receiving parts at point-symmetric positions. CONSTITUTION:A plurality of light receiving parts 12a, 12b which are not subjected to light shielding, and the same number of light-shielded light receiving parts 13a, 13b as the light receiving parts 12, 12b are arranged at point- symmetric positions. Signals from the light receiving part 12a, 12b are synthesized and delivered to an amplifying circuit 14. On the other hand, signals from the light-shielded light receiving parts 13a, 13b also are similarly synthesized and delivered to the amplifying circuit 14. The respective signals are amplified, compared and output. Noise signal input in a photo detector is divided into four portions by the light receiving parts, and output signals of equal quantity generate on the light receiving parts 12a, 12b and on the light-shielded light receiving parts 13a, 13b, on account of the point-symmetric arrangement. As a result, the signals from the light receiving part 12a, 12b and signals from the light-shielded light receiving parts 13a, 13b are cancelled each other out by the amplifying circuit 14, so that malfunction caused by noise signal does not occur.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a light receiving device in an optically coupled semiconductor device such as a photocoupler.

<Prior Art> Conventionally, in an optically coupled semiconductor device, in order to remove noise due to disturbance etc., a light receiving device has one light receiving section 2 as a light receiving element l, an amplifier 3 and an amplifier 3, as shown in FIGS. It is formed from an amplifier circuit 5 having a comparator 4, and receives light from the input end to the output side through the human output capacity ff1cl that exists between the light emitting element 6 (input side) and the light receiving element l side (output side). A transparent conductive film 8 through which light 7 passes is arranged on the surface of the light receiving section 2 so as to remove common mode noise signals input to the section 2.

In addition, as another conventional example, as shown in FIGS. 6 and 7, a conductor 9 is arranged around the light receiving section 2, and the output signal from the conductor 9 and the output signal from the light receiving section 2 are the amplifier 3
After a and 3 b are amplified, these values are subtracted to obtain the common-mode noise signal rejection ratio (Coau++ on M
ode Rejection flatio: CM below
(referred to as RR) to reduce malfunctions caused by common-mode input.

Note that in the figure, IO is a semiconductor substrate, and 11 is a reference voltage.

Problems that the invention seeks to solve 〉However,
In the conventional configuration shown in FIGS. 4 and 5, the light receiving section 2
A process for attaching a transparent conductive film 8 thereon is required, which poses problems such as complicated processes and an unavoidable increase in price.

In addition, in the conventional configuration shown in FIGS. 6 and 7, in order to obtain high CMRR, the capacitance C3 between the input end and the light receiving section 2,
It is necessary that the capacitance ff1c2 between the input side and the conductor 9 be equal, but in practice, in an optically coupled semiconductor device such as a photocoupler, the distance between the inputs is determined by the shape of the light receiving part (usually 0,
Since the capacitance is small (less than 1 mountain river) compared to around 5 mm11), trial and error was necessary to match the capacitances C2 and 03.

In addition, even if C2 and 03 match, the amplifier 3a whose input is the light receiving section 2 and the input/output capacity fiC3 to the light receiving section 2,
With the amplifier 3b in which the capacitance C2 between the conductor 9 and the output side of the conductor 9 is manually operated, it is difficult to obtain a high CMRI't because the response characteristics of the circuits do not match.

In view of the above problems, the present invention aims 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 as shown in FIGS. 1 to 3, in a light receiving device that receives light 7 from a light emitting element 6,
A plurality of unshielded light receiving sections 12a12b and the same number of light receiving sections 12a and 12b as light-shielded light receiving sections 13a.
, 13b are arranged point-symmetrically, and includes an amplifier circuit 14 for amplifying and comparing the output signals of the unshielded light receiving sections 12a, 12b and the output signals of the shielded light receiving sections 13a, 13b. be.

<Operation> In the above problem solving means, the signals from the light receiving sections 12a and 12b are combined and output to the amplifier circuit 14. On the other hand, signals from the light shielding light receiving sections 13a and +3b are similarly combined and output to the amplifier circuit 14. The respective output signals are then amplified and compared and output.

Here, the noise signal input to the light receiving device is transmitted to the light receiving portion t because the light receiving portion is divided into four parts and arranged point symmetrically.
2a, 12b and the light-shielding light receiving sections 13a, 13b produce output signals of the same amount. Therefore, the amplifier circuit I4 combines the signals from the light receiving sections 12a and +2b with the light-shielding light receiving section 13.
Since the signals from a and +3b cancel each other out, malfunctions due to noise signals do not occur.

In addition, the amplifier of the amplifier circuit 14 has the same configuration for the light receiving section 12a12b and the light-shielding light receiving sections 13a and 13b, and each light receiving section has the same configuration, so there is no difference in circuit response. Since no in-phase input signal is generated, a higher CMRR is possible.

On the other hand, since the optical signal emitted from the light emitting element 6 enters only the light receiving sections 12a and 12b which are not shielded from light, the optical signal can be detected reliably.

Therefore, by dividing the light-receiving portion of the light-receiving element 1 into two parts, one that is not shielded and the other that is shielded, the noise signals are canceled out and removed, so that the CMRR can be increased.

Moreover, in the manufacturing process of the light receiving element 1, it is only necessary to cover the surface of the light receiving element 1 with the light shielding bodies L5a and 15b, and the manufacturing process is simple, so it is possible to easily provide a light receiving device with high CMRR. .

<Example> Hereinafter, an example of the present invention will be described based on 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, and FIG. 3 is a diagram showing the positional relationship between a light emitting element and a light receiving element.

As shown in the figure, the light-receiving element l of the light-receiving device of the present invention includes two light-receiving parts +2a and 12b that are not shielded from light on a semiconductor substrate lO.
2g of light-shielded light-receiving parts 13a, 13b, which are the same number as the light-receiving parts 12a, 12b, receive the light 7 from the light-emitting element 6.
They are placed in symmetrical positions so that they can receive light evenly.

Further, an amplifier circuit 14 is provided which amplifies and compares the output signals of the unshielded light receiving sections 12a, 12b and the output signals of the shielded light receiving sections 13a, 13b.

The light receiving sections 12a, 12b and the light-shielding light receiving section 13a.

tab is composed of a photodiode, and the light-shielding light receiving section 1
The surfaces of the elements 3a and 13b are covered with light shielding members 15a and 15b made of metal or an opaque insulator. In addition,
The light emitting cord 6 consists of a light emitting diode.

Further, the amplifying circuit 14 is mounted on a single semiconductor substrate 1O together with the light receiving sections, and the light receiving sections 12a, 1
2b, an amplifier H+516b that amplifies the output signals from the light-shielding light-receiving sections 13a and 13b, and a double-channel width transducer 16a.

The comparator 17 compares the outputs from the detector 16b and outputs a detection signal. Both tank width gauges I6a and 16b are composed of the same circuit, and the light receiving parts 12a,
12b and the light shielding light receiving sections 13a, 13b are connected in parallel to the respective amplifiers 16a, 16b.

The capacity between the light emitting element 6 and the light receiving sections 12a and 12b is C4 and C5, respectively. In addition, the capacity between the light shielding light receiving parts 13a and 13b is C
6 and C7.

In the above configuration, the signals from the light receiving sections 12a and 12b are combined and amplified by the amplifier 16a. On the other hand, signals from the light shielding light receiving sections 13a and 13b are similarly combined and amplified by the amplifier 16b.

The outputs of the respective amplifiers 16a and 16b are compared by a comparator I7 and output digitally.

Here, the common mode noise signal entering the output side from the input end through the human output capacitors IC4 to C7 has the same amount as shown in FIG. Generates a noise signal current.

That is, in FIG. 3, the noise signals are orthogonal to each other
Assuming that light enters from on the X-axis of the axial coordinates, the distances from the noise signal current section to the centers of the light receiving section 12a and the light-shielding light receiving section 13a are equal, and the capacitances C4 and 06 thereof are equal. Similarly, the capacities ff1c5 and 07 between the light receiving section 12b and the light-shielding light receiving section 13b are equal. Therefore, the same amount of noise signal current is generated in the light receiving sections 12a, 12b and the light shielding light receiving sections 13a, 13b.

Therefore, even if the same noise signal current is amplified by the amplifiers 16a and 16b having the same circuit configuration and input to the differential human power comparator 17, the output will not be inverted and the light receiving section 12
Since the signals from a and 12b and the signals from the light-shielding light receiving sections 13a and 13b cancel each other out, an output signal is output.
Malfunction of comparator I7 due to noise signals does not occur.

In addition, the human power of each amplifier 16a, 16b is the light receiving part +2a
, 12b or the light-shielding light receiving part +3a, 13b,
Since they have the same configuration consisting of two light receiving sections and there is no difference in circuit response, no in-phase input signal is output, making it possible to achieve higher CMRR.

On the other hand, since the optical signal emitted from the light emitting element 6 enters only the light receiving section 12a12b which is not shielded from light, the optical signal can be detected reliably.

Therefore, by dividing the light-receiving element l into two, one that is not shielded and the other that is shielded, the in-phase input signals are canceled out and removed, so that the CMRR can be increased.

Moreover, in the manufacturing process of the light receiving element 1, it is only necessary to cover the surface of the light receiving element l with the light shielding bodies 15a and 15b, and the manufacturing process is simpler than that of pasting a conductive film on the light receiving element l. There is no need to change the process, and an optically coupled semiconductor device having high CMRR can be easily provided.

It should be noted that 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 l is not limited to four divisions, but may be divided into six or more points symmetrically.

<Effects of the Invention> As is clear from the above description, according to the present invention, in a staggered light receiving device that receives light from a light emitting element, there are a plurality of unshielded light receiving sections and the same number of light receiving sections as the light receiving sections. The light receiving section is arranged point-symmetrically with the light receiving section, and the noise signal is canceled out and removed by providing an amplifier circuit that amplifies and compares the output signal of the unshielded light receiving section and the output signal of the light shielded light receiving section. Therefore, the CMRR can be increased.

Furthermore, since the light receiving element can be manufactured through a simple process, it has the advantageous effect that a light receiving device having a high CMRR can be easily provided.

[Brief explanation of the drawing]

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, Fig. 3 is a diagram showing the positional relationship between a light emitting element and a light receiving element, and Fig. 4 is a plan view of a conventional light receiving device. FIG. 5 is a plan view of the light receiving device, FIG. 5 is its electric circuit diagram, FIG. 6 is a plan view of another conventional light receiving device, and FIG. 7 is its electric circuit diagram. l; Light receiving element, 6: Light emitting element, 7: Light, 12a, 12b
: Light receiving section, 13a, 13b: Light shielding light receiving section, 14. Amplifier circuit, I 5a, I 5b: Light shield, I 6a, I
6b: Amplifier, 17: Comparator. Applicant Sharp Corporation

Claims (1)

[Claims] In a light-receiving device that receives light from a light-emitting element, a plurality of unshielded light-receiving parts and the same number of light-shielded light-receiving parts as the light-receiving parts are arranged in point-symmetrical positions, and the unshielded light-receiving parts 1. A light-receiving device comprising an amplifier circuit that amplifies and compares the output signal of the light-shielded light-receiving section with the output signal of the light-shielded light-receiving section.