JPH11352159A - Photoelectronic circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectronic circuit having a wide dynamic range. SOLUTION: Light hν is introduced from a light emitting diode LED to an optical sensor 8 by feeding a driving current Id from a driving circuit 9 to the light emitting diode LED and light hν' modulated in the optical sensor 8 is received by a photodiode PD. A photocurrent Ip generated in the photodiode PD is compared with a reference current Iref by a current comparison circuit 10 and a comparison current ΔIp generated by the comparison is converted to a voltage signal ΔVp by a current/voltage conversion circuit 13 to carry it through a low-pass filter 14. A direct current voltage component ΔVdc in a voltage signal ΔVp ' outputted from the low pass filter 14 is extracted by a direct current component extraction circuit 15 and an average light receiving power on the light receiving surface of the photodiode PD is kept constant by returning the direct current voltage component ΔVdc to the driving circuit 9. A dynamic range is enlarged by comparing the photocurrent Ip with the reference current Iref .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light receiving element for receiving light emitted from a light emitting element, and a feedback loop for feeding back the light emitting element so that the average light receiving power on the light receiving surface of the light receiving element is constant. The present invention relates to an opto-electronic circuit provided with:

[0002]

2. Description of the Related Art Conventionally, an optoelectronic circuit as shown in FIG. 6 is known, and is applied to a power measuring device having an optical sensor 1 whose light parameter changes depending on an object to be measured such as a magnetic field or an electric field. .

In this optoelectronic circuit, light hν emitted from a light emitting element LED is introduced into an optical sensor 1, and modulated light hν ′ modulated by the optical sensor 1 is received by a light receiving element PD and converted into a photocurrent Ip. Further, the photocurrent Ip is converted into a voltage signal V1 by a current / voltage conversion circuit 2, and a measurement signal Vout is output via a low-pass filter 3 for removing noise.

According to this configuration, the light receiving power P on the light receiving surface of the light receiving element PD is calculated by using the average light receiving power P ₀ and the modulation m of the modulated light hν ′ by the optical sensor 1 to obtain P = P
₀ (1 + m), and the measurement signal Vout has a waveform in which an AC voltage component corresponding to the modulation factor m is superimposed on a DC voltage component corresponding to the average received light power P ₀ . Therefore, the modulation degree m of the modulated light hν ′ can be measured based on the AC voltage component of the measurement signal Vout, and the magnetic field, the electric field, and the like can be measured based on the modulation degree m.

However, as a condition for measuring the degree of modulation m with high accuracy, the average received light power P ₀ in the above equation P = P ₀ (1 + m) must be kept constant. If this condition is not satisfied, the light emitting element LED and the light receiving element PD
And the optical sensor 1 may drift. When this drift occurs, the received light power P also fluctuates with the fluctuation of the average received light power P _0. Therefore, it is determined whether the change in the AC voltage component of the measurement signal Vout is due to a change in the measurement target or due to the drift. Can not be done. As a result,
There is a problem that the modulation m cannot be measured with high accuracy.

Therefore, in the optoelectronic circuit shown in FIG. 6, a feedback method is employed as a drift compensation method. The DC voltage component V2 in the voltage signal V1 is extracted by the DC component extraction circuit 4, and the DC voltage component V2 is a reference voltage Vref that is set in advance by the reference voltage generating circuit 5 is compared in the comparator circuit 6, by applying the feedback to drive circuit 7 in the comparison voltage V3, such that the average received optical power P ₀ is constant Drive current Id supplied from the drive circuit 7 to the light emitting element LED
Is controlling.

[0007]

However, in the feedback system in the optoelectronic circuit, the comparison voltage for applying feedback to the drive circuit 7 is obtained by comparing the DC voltage component V2 and the reference voltage Vref within the power supply voltage range. Since V3 is generated,
There was a problem that the dynamic range was narrowed.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to overcome the above problems, and has an optoelectronic circuit having a light emitting element and a light receiving element for receiving the light emitted by the light emitting element. A current comparison circuit that generates a comparison current by comparing a photocurrent generated in the light receiving element with a preset reference current, and feeds back the light emitting element based on a DC component of the comparison current, A feedback loop for controlling the average light receiving power on the light receiving surface of the element to be constant is provided.

According to this configuration, the feedback of the light emitting element based on the DC component of the comparison current suppresses the fluctuation of the average light receiving power on the light receiving surface of the light receiving element due to drift or the like. Further, since the DC component of the comparison current is generated by comparing the photocurrent generated in the light receiving element with a preset reference current, the dynamic range is widened.

[0010] Also, in an optoelectronic circuit comprising an optical sensor whose light parameter changes according to a measurement object, a light emitting element for emitting light to the optical sensor, and a light receiving element for receiving modulated light modulated by the optical sensor. A current comparison circuit that generates a comparison current by comparing a photocurrent generated in the light receiving element with a preset reference current, and feeds back the light emitting element based on a DC component of the comparison current,
And a feedback loop for controlling the average light receiving power on the light receiving surface of the light receiving element to be constant.

According to this configuration, the fluctuation of the average light receiving power on the light receiving surface of the light receiving element due to drift or the like is suppressed by the feedback loop having a wide dynamic range, so that a highly accurate measuring device using the optical sensor can be provided. Is achieved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which an optoelectronic circuit according to the present invention is applied to an electronic wattmeter will be described below.

FIG. 1 is a block diagram showing the configuration of the optoelectronic circuit of the present embodiment. In the figure, an optical sensor 8 is inserted between a light emitting diode LED as a light emitting element and a photodiode PD as a light receiving element. A driving circuit 9 is connected to the light emitting diode LED, and a current comparison circuit 10 is connected to the photodiode PD. Have been.

The optical sensor 8 is provided with a magneto-optical effect element such as a Faraday element whose light parameter changes according to a magnetic field, and an electro-optical effect element such as a Pockels element whose light parameter changes according to an electric field.

The driving circuit 9 is constituted by an active amplifier having a predetermined amplification factor, and supplies a driving current Id proportional to the DC voltage component ΔVdc output from the DC component extracting circuit 15 to the light emitting diode LED. As a result, the drive current Id
Is output to the optical sensor 8, and the photodiode PD receives modulated light hν 'modulated by the optical sensor 8 in response to a change in a magnetic field or an electric field. .

The current comparison circuit 10 is constituted by an addition / subtraction circuit for performing current addition (or current subtraction). Then, the current Ip generated in the light emitting diode LED and the reference current Iref generated by the current generation circuit 11 are added (or subtracted) to obtain a comparison current that is a comparison result between the photocurrent Ip and the reference current Iref. ΔIp is output to the current / voltage conversion circuit 13.

The current generation circuit 11 to the current comparison circuit 1
When the reference current Iref is supplied toward 0, the above-described current addition is performed. When the reference current Iref is pulled (sinked) from the current comparison circuit 10 to the current generation circuit 11, the above-described current subtraction is performed. Therefore, the current addition or the current subtraction is performed in accordance with the polarity of the reference current Iref. Therefore, in the optoelectronic circuit of the present embodiment, the comparison current ΔIp is obtained regardless of the configuration of the current addition or the current subtraction. You can get it.

The current generation circuit 11 includes a reference voltage generation circuit 1
The reference current Iref is generated based on the constant voltage Vref set in advance to 2.

The current / voltage conversion circuit 13 outputs a comparison current ΔI
p is converted into a voltage signal ΔVp proportional thereto, and integrated via a low-pass filter 14 for noise removal (not shown).
Output to As a result, high-frequency noise superimposed on the voltage signal ΔVp is removed by the low-pass filter 14, and a noise-free voltage signal ΔVp ′ is output to the integrating circuit as a measurement signal.

A DC component extraction circuit 15 is provided between the low pallet filter 14 and the drive circuit 9. The DC component extraction circuit 15 extracts the DC voltage component ΔVdc from the voltage signal ΔVp ′ and feeds it back to the drive circuit 9 so that the average light receiving power P _{0 on the} light receiving surface of the photodiode PD becomes constant. , The drive current Id. That is, the DC component extraction circuit 15 includes the light emitting diode LED.
By compensating for drifts of the photodiode PD, the optical sensor 8 and the like, a feedback loop for making the average received light power P ₀ constant is formed.

FIG. 2 shows a current comparison circuit 10, a current generation circuit 11, a reference voltage generation circuit 12, and a current / voltage conversion circuit 1.
3 shows a more specific circuit example.

In FIG. 1, a reference voltage generating circuit 12
The voltage regulator 16 is composed of a voltage regulator 16 and resistors 17 and 18. The constant voltage Vreg generated in the voltage regulator 16 is divided by the resistors 17 and 18 to generate a predetermined constant voltage Vref.

The current generating circuit 11 is composed of a resistor 19 connected between a connection point x of the resistors 17 and 18 and a cathode of the photodiode PD, and a constant voltage V generated at the connection point x.
A reference current Iref is generated based on ref.

The current / voltage conversion circuit 13 is composed of a T-type inverting amplifier 21 having a large amplification factor obtained by resistors 20a, 20b, and 20c having small resistance values. The inverting input terminal of the inverting amplifier 21 has a photodiode PD. Connected to the cathode.

The current comparison circuit 10 includes a photodiode P
This is realized by a connection point y where the cathode of D is connected to the resistor 19 and the inverting input terminal of the inverting amplifier 21. That is, at the connection point y, the photocurrent Ip and the reference current Iref
The current addition (or current subtraction) is performed to generate the comparison current ΔIp. Then, the inverting amplifier 21 outputs a voltage signal ΔVp proportional to the comparison current ΔIp.

FIG. 3 shows a more specific circuit example of the DC component extraction circuit 15. This DC component extraction circuit 15
Is an inverting amplifier 24 having resistors 22 and 23 for setting a voltage amplification factor, and a resistor 25 connected between an inverting input terminal of the inverting amplifier 24 and an output terminal of the low-pass filter 14.
And a resistor 26 and a coupling capacitor 27 connected in series between the non-inverting input terminal of the inverting amplifier 24 and the output terminal of the low-pass filter 14.

According to this configuration, the voltage signal ΔVp ′ from the low-pass filter 14 is supplied to the inverting input terminal of the inverting amplifier 24, and the voltage signal ΔVp ′ passing through the coupling capacitor 27 is supplied to its non-inverting input terminal. Only the middle AC voltage component ΔVac is supplied. The AC voltage component ΔVac is removed by the inverting amplifier 24 having a large in-phase signal removal ratio (CMRR), so that the voltage signal ΔV
Only the DC voltage component ΔVdc in p ′ is extracted and supplied to the drive circuit 9.

Next, the operation of the optoelectronic circuit having such a configuration will be described with reference to FIGS. FIG. 4 (a)
(D) schematically shows the waveforms of the DC voltage component ΔVdc and the drive current Id, and the optical power of the emitted light hν and the modulated light hν ′. FIGS. 5A to 5C schematically show waveforms of the photocurrent Ip, the comparison current ΔIp, and the voltage signal ΔVp.

4 (a) to 4 (d), the drive current Id is proportional to the DC voltage component ΔVdc (see FIG. 4 (a)).
(Refer to FIG. 4B).
The outgoing light h of the optical power Pin is supplied to the ED.
ν (see FIG. 4C) is introduced into the optical sensor 8 from the light emitting diode LED, and the modulated light hν ′ (see FIG. 4D) modulated by the optical sensor 8 is converted to the photodiode P.
D enters the light receiving surface. Here, the photodiode PD
The light-receiving power P on the light-receiving surface is represented by an average light-receiving power P ₀ ,
Using the degree of modulation m of the modulated light hν ′ by the optical sensor 8,
It is represented by P = P ₀ (1 + m).

The alternating current component corresponding to the photodiode PD receives the received optical power P, the DC current component corresponding to average received light power P ₀ and (-Idc) the modulation index m (-Ia
A photocurrent Ip represented by the sum of (c) and (c) is generated (FIG. 5A).
reference).

Further, the current addition (or current subtraction) between the photocurrent Ip and the reference current Iref is performed in the current comparison circuit 10, so that the AC current component (-Iac) and the DC current component (Iref-Idc) are converted. The comparison current ΔIp represented by the sum is generated (see FIG. 5B).

Further, the current / voltage conversion circuit 13 calculates the sum of an AC voltage component ΔVac proportional to the AC current component (−Iac) and a DC voltage component (−ΔVdc) proportional to the DC current component (Iref−Idc). After the generated voltage signal ΔVp is generated (see FIG. 5C), the voltage signal ΔVp ′ from which the noise component has been removed by the low-pass filter 14 is output to the integrating circuit as a measurement signal.

Then, the DC component extraction circuit 15 extracts the DC voltage component ΔVdc from the voltage signal ΔVp ′, and performs feedback control to the drive circuit 9.

According to the present embodiment, the current comparison circuit 10
Compares the photocurrent Ip with the reference current Iref, and feeds back the DC voltage component ΔVdc obtained by this to the drive circuit 9 via the DC component extraction circuit 15, so that the average light reception power P at the light receiving surface of the photodiode PD is obtained. _The driving current I supplied to the light emitting diode LED so that ₀ is constant
d can be controlled.

As a result, the drift of the light emitting diode LED, the photodiode PD, the optical sensor 8 and the like can be compensated, and the modulation degree m of the modulated light hν ′ can be accurately determined based on the AC voltage component of the voltage signal ΔVp ′. Measurement can be performed, and further, a magnetic field, an electric field, and the like can be measured with high accuracy based on the modulation degree m.

Further, the current comparison circuit 10 performs current addition or current subtraction between the photocurrent Ip and the reference current Iref, thereby comparing the current between the photocurrent Ip and the reference current Iref. The dynamic range of the optoelectronic circuit can be widened without being limited to the above.

Although the embodiment of the optoelectronic circuit applied to the electronic wattmeter has been described, the optoelectronic circuit of the present invention is not limited to this. That is, the optoelectronic circuit of the present invention is not limited to an optical sensor using a Faraday element or a Pockels element in which the parameter of light changes due to a magnetic field or an electric field, and applies an optical sensor for measuring other physical or chemical phenomena. It can also be used for various measuring instruments and the like. In addition to measurement equipment, control systems for improving transmission quality by maintaining a constant average light receiving power of light incident on a light receiving element in an optical transmission system including a light emitting element and a light receiving element. Can also be applied.

[0038]

As described above, according to the present invention,
A comparison current is generated by comparing a photocurrent generated in the light receiving element with a preset reference current, and feedback is applied to the light emitting element based on a DC component of the comparison current. The fluctuation of the average light receiving power on the light receiving surface of the light receiving element can be suppressed, and the dynamic range can be widened.

When an optical sensor whose light parameter changes depending on the object to be measured is interposed between the light emitting element and the light receiving element, a feedback loop having a wide dynamic range causes a light receiving surface of the light receiving element due to drift or the like to be generated. By suppressing the fluctuation of the average received light power, a highly accurate measuring device can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an optoelectronic circuit according to an embodiment.

FIG. 2 is a circuit diagram showing specific circuit examples of a current comparison circuit, a current generation circuit, a reference voltage generation circuit, and a current / voltage conversion circuit.

FIG. 3 is a circuit diagram showing a specific example of a DC component extraction circuit.

FIG. 4 is an explanatory diagram for explaining an operation example of the embodiment;

FIG. 5 is an explanatory diagram for further explaining an operation example of the present embodiment;

FIG. 6 is a block diagram illustrating a configuration of a conventional optoelectronic circuit.

[Explanation of symbols]

 Reference Signs List 8 optical sensor 9 drive circuit 10 current comparison circuit 11 current generation circuit 12 reference voltage generation circuit 13 current / voltage conversion circuit 14 low-pass filter 15 DC component extraction circuit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI G01R 33/032 G01R 33/032

Claims (4)

[Claims] 1. An optoelectronic circuit having a light-emitting element and a light-receiving element for receiving light emitted from the light-emitting element, wherein a photocurrent generated in the light-receiving element is compared with a preset reference current. A current comparison circuit that generates a current; and a feedback loop that performs feedback to the light emitting element based on a DC component of the comparison current and controls the average light receiving power on a light receiving surface of the light receiving element to be constant. An optoelectronic circuit, comprising: 2. An optoelectronic circuit comprising: an optical sensor whose light parameter changes according to an object to be measured; a light emitting element that emits light to the optical sensor; and a light receiving element that receives modulated light modulated by the optical sensor. A current comparison circuit that generates a comparison current by comparing a photocurrent generated in the light receiving element with a preset reference current; and applying feedback to the light emitting element based on a DC component of the comparison current, the light receiving element A feedback loop for controlling the average light receiving power on the light receiving surface of the light emitting element to be constant. 3. The optoelectronic circuit according to claim 2, wherein the optical sensor has a magneto-optical effect element whose light parameter changes according to a magnetic field. 4. The optoelectronic circuit according to claim 2, wherein the optical sensor includes an electro-optic effect element whose light parameter changes according to an electric field.