JP3335927B2 - Optoelectronic circuit - Google Patents

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. 8 has been known, and is applied to a power measuring apparatus having an optical sensor 1 whose parameter of light 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, so that P = P
Represented by _{0 (1} + m), the measurement signal Vout, the DC voltage component corresponding to the average received optical power P _0, the waveform of the AC voltage component corresponding to the modulation index m is superimposed. 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 at all times. 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, the optoelectronic circuit shown in FIG. 8 employs a feedback method 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.

In the above-mentioned optoelectronic circuit, the above-described feedback control is realized by the DC voltage component V2 in the voltage signal V1 output from the current / voltage conversion circuit 2. However, when the voltage signal V1 is integrated, the feedback control is performed. There is also a problem that the DC voltage component V2 becomes a measurement error factor, and the integrated value of the AC voltage component originally sought cannot be obtained with high accuracy.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in order to solve such a problem, and an optical sensor whose light parameter changes depending on an object to be measured, and a light emitting element which emits light to the optical sensor. And a light receiving element for receiving the modulated light modulated by the optical sensor, and a feedback to the light emitting element based on the DC component of the light receiving element output so that the average light receiving power on the light receiving surface of the light receiving element becomes constant. A driving circuit for causing the light emitting element to emit light by a driving current generated by a difference voltage between a voltage fed back to the light emitting element and a reference voltage other than the ground voltage, and a light generated in the light receiving element. A reference current generation circuit that generates a reference current equal in magnitude to the DC component of the current, and a current comparison that generates a comparison current by comparing the photocurrent generated in the light receiving element with the reference current And road, live by the current comparator circuit
Output voltage that is amplified in proportion to the generated comparison current.
And a current-voltage conversion circuit .

In 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. 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.

Since the reference current is set equal to the DC component in the photocurrent generated in the light receiving element, the DC component of the comparison current becomes zero. Therefore, the current comparison circuit outputs an output current including only the AC current component corresponding to the modulated light, and the measurement signal output does not include the DC component. At this time, the voltage fed back to the light emitting element becomes zero, but a reference voltage other than the ground voltage is applied to the light emitting element, so that the light emitting element is generated by a difference voltage between the feedback voltage and the reference voltage. A drive current is applied.

[0012]

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

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 drive circuit 9 receives the DC voltage component ΔVdc output from the DC component extraction circuit 15 and supplies a drive current Id to the light emitting diode LED. As a result, the outgoing light hν having the optical power Pin corresponding to the drive current Id is introduced into the optical sensor 8, and the photodiode PD receives the modulated light hν ′ modulated by the optical sensor 8 in response to a change in a magnetic field or an electric field. It is supposed to.

The current comparison circuit 10 is constituted by an addition / subtraction circuit for performing current addition (or current subtraction). Then, by adding (or subtracting) the light current Ip generated in the photodiode PD and the reference current Iref generated by the current generation circuit 11, a comparison current that is a comparison result between the light current Ip and the reference current Iref is obtained. 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, since the current addition or the current subtraction is performed in accordance with the polarity of the reference current Iref, in the optoelectronic circuit of the present embodiment, the comparison current ΔIp can be obtained by both the current addition and the current subtraction. I have.

The current generation circuit 11 includes a reference voltage generation circuit 1
A reference current Iref is generated based on a reference voltage Vref set in advance to the reference voltage Vref. The magnitude of this reference current Iref is
It is set equal to the magnitude of the DC component in the photocurrent Ip generated in the photodiode PD.

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, by applying the feedback to the drive circuit 9 to extract the DC voltage component ΔVdc in voltage signal? Vp ', such that the average received optical power P ₀ of the light receiving surface of the photodiode PD is constant , The drive current Id. That is, the DC component extraction circuit 15 includes the light emitting diode LE.
To compensate for the D and photodiode PD and drift such as an optical sensor 8, and a feedback loop for the average received optical power P ₀ the constant.

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 includes 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 reference voltage Vref. This reference voltage Vr
ef is also provided to the drive circuit 9 as described later.

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 based on a reference voltage Vref generated at the connection point x, a reference current Iref. Generate

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. 3A shows a more specific circuit example of the DC component extraction circuit 15 and the drive circuit 9. The DC component extraction circuit 15 includes resistors 22 and 2 for setting a voltage amplification factor.
3, a resistor 25 connected between the inverting input terminal of the inverting amplifier 24 and the output terminal of the low-pass filter 14, and the non-inverting input terminal of the inverting amplifier 24 and the output terminal of the low-pass filter 14. It comprises a resistor 26 and a coupling capacitor 27 connected in series between them. The driving circuit 9 for driving the light emitting diode LED is constituted by a resistor 28, and the resistor 28 has a ground voltage, that is, a reference voltage V other than zero volt.
ref is given from the reference voltage generation circuit 12.

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.

As will be described later, since the DC voltage component ΔVdc extracted by the DC component extraction circuit 15 is set to zero, the light emitting diode LED has a voltage between the zero volt feedback voltage and the reference voltage Vref. The drive current Id generated by the difference voltage is applied.

FIG. 3B shows another example of the drive circuit 9. In FIG. 3B, the same or corresponding parts as those in FIG. 5A is different from FIG. 5A in that the reference voltage Vref supplied from the reference voltage generating circuit 12 to the drive circuit 9 is negative, and the drive current Id is zero volts. This is a point caused by a difference voltage between the voltage Vref.

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 DC voltage component ΔVdc becomes zero volt as described above (see FIG. 4 (a)), and the difference voltage between this zero volt and the reference voltage Vref is obtained. The above-described drive current Id (see FIG. 4B) for driving the light emitting diode LED is generated. This drive current Id
Is supplied from the driving circuit 9 to the light emitting diode LED, the emitted light hν of the optical power Pin (see FIG. 4C) is introduced from the light emitting diode LED to the optical sensor 8, and The modulated light hν ′ (see FIG. 4D) is incident on the light receiving surface of the photodiode PD. Here, the received light power P on the light receiving surface of the photodiode PD is obtained by using the average received light power P ₀ and the modulation m of the modulated light hν ′ by the optical sensor 8 as 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 compared. The comparison current ΔIp represented by the sum is generated (see FIG. 5B). At this time, the reference current Iref
Is set equal to the magnitude of the DC current component Idc in the photocurrent Ip generated in the photodiode PD, the DC current component (Iref-Idc) in the current comparison result becomes zero.

Further, the current / voltage conversion circuit 13 calculates the sum of the AC voltage component ΔVac proportional to the AC current component (−Iac) and the DC voltage component (−ΔVdc) proportional to the DC current component (Iref−Idc). A voltage signal ΔVp represented is generated (see FIG. 5C). However, as described above, since the comparison current ΔIp is only the AC current component (−Iac),
The DC signal (-ΔVdc) does not appear in the voltage signal ΔVp, but only the AC voltage component ΔVac. Then, the voltage signal ΔVp containing no DC component is applied to the low pass filter 14.
, And the voltage signal ΔVp ′ from which the noise component has been removed is output to the integrating circuit as a measurement signal. Therefore, only the AC voltage component ΔVac corresponding to the modulation degree m of the optical sensor 8 can be integrated, and a measurement target such as a magnetic field or an electric field can be measured with high accuracy based on the integration result.

Further, the DC signal extracting circuit 15 generates a voltage signal Δ
The DC voltage component ΔVdc in Vp ′ is extracted. But,
Since the DC signal component ΔVdc is not included in the voltage signal ΔVp ′, the output voltage of the DC component extraction circuit 15 becomes zero volt, and the feedback voltage to the drive circuit 9 becomes zero volt as described above (see FIG. 4 (a)).

In the present embodiment, the feedback of the light emitting diode LED is performed based on the DC component of the comparison current ΔIp, thereby suppressing the fluctuation of the average light receiving power P _{0 on} the light receiving surface of the photodiode PD due to drift or the like. Can be The DC component of the comparison current ΔIp is the photodiode P
Since the dynamic range is generated by current comparison between the photocurrent Ip generated in D and a preset reference current Iref, the dynamic range is widened regardless of the power supply voltage.

In this embodiment, even if the voltage signal ΔVp output from the current / voltage conversion circuit 13 does not include the DC voltage component ΔVdc, the light emitting diode LED is driven. For this reason, the measurement signal appears on the basis of zero volt, the influence of the DC voltage component ΔVdc on the AC voltage component ΔVac is eliminated, and it is possible to accurately measure even a small measurement signal.

Next, a description will be given of a second embodiment in which the optoelectronic circuit according to the present invention is applied to an electronic watt-hour meter.

FIG. 6 is a block diagram showing the configuration of the optoelectronic circuit of this embodiment. In this figure, the same or corresponding parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

The difference between the present embodiment and the first embodiment is that the feedback loop between the DC component extraction circuit 15 and the drive circuit 9 includes a voltage / current conversion circuit 31, a current addition circuit 3
(2) that a current generation circuit 33 and a temperature compensation circuit 34 are provided. According to this configuration, the DC voltage component (−ΔVdc) due to the variation of the components of the circuit in the output voltage ΔVp ′ of the optoelectronic circuit according to the above-described first embodiment.
Appears, this DC voltage component (−ΔVdc) is removed from the output voltage ΔVp ′.

That is, the DC component extraction circuit 15 extracts the DC voltage component (-ΔVdc) in the voltage signal ΔVp ′ generated due to the variation of the circuit components, and outputs the DC voltage component ΔVdc whose polarity is inverted. The voltage / current conversion circuit 31 converts the DC voltage component ΔVdc output from the DC component extraction circuit 15 into a current ΔIdc proportional thereto and outputs the current.

The current adding circuit 32 adds a constant value of the correction current Iad supplied from the current generating circuit 33 provided with the temperature compensating circuit 34 and the above-mentioned current ΔIdc, and calculates the added current If (= Iad + ΔIdc). The drive circuit 9 is fed back.

FIG. 7 shows a DC component extracting circuit 15, a voltage / current converting circuit 31, a current adding circuit 32, and a current generating circuit 33.
3 shows a more specific circuit example of the temperature compensation circuit 34.

As shown in FIG.
As in the first embodiment, the inverting amplifier 24, the resistors 22, 23, 25, and 26 and the coupling capacitor 2
7 With the DC component extraction circuit 15 having 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 DC voltage in the voltage signal ΔVp ′ is supplied to the output terminal of the inverting amplifier 24. A DC voltage component ΔVdc whose component (−ΔVdc) is inverted in polarity is output.

The voltage / current conversion circuit 31 includes the inverting amplifier 2
4 is realized by a resistor 29 connected to the output terminal of the fourth output terminal.
The current generating circuit 33 includes a voltage regulator 41 that outputs a constant voltage Vdd1, resistors 42 to 49, and an inverting amplifier 50. The temperature compensating circuit 34 is implemented by a diode 51 connected between the resistor 42 and a ground terminal. Have been.

The current generation circuit 33 having such a configuration
In the degree compensation circuit 34, the voltage regulator 41
Supplied from the resistor to the diode 51 via the resistor 42
As a result, the diode voltage V_DOccurs
I do. This diode voltage V _DAre divided by resistors 43 and 44
I do. The divided voltage V_D’And the inverting amplifier 50
Amplification based on the voltage amplification rate set in 5, 46
Generates a constant voltage Vdd2.

Further, the resistors 47 and 48 divide the voltage (Vdd1−Vdd2) generated between the voltage Vdd1 and the constant voltage Vdd2 to generate a reference voltage Vad having a constant value. The conversion generates a compensation current Iad. Here, when the environmental temperature changes, depending on the temperature characteristics of the diode 51, the diode voltage V _D varies, further reference voltage Vad is changed in accordance therewith, so as also to vary the compensation current Iad.

The current adding circuit 32 is realized by a connection point x between the resistors 29 and 49 and the driving circuit 9. That is, in the present embodiment, the driving circuit 9 includes the resistor 28 to which the reference voltage Vref output from the reference voltage generating circuit 12 is applied, the resistor 53 connected between the cathode of the light emitting diode LED and the connection point x, and An inverting input terminal of the inverting amplifier 54 and a resistor 29,
A current adding circuit 32 is realized by a connection point x with 49.

In such a configuration, for example, the resistor 4
9 is a variable resistor, and the voltage regulator 41 is capable of variably outputting. By finely adjusting the correction current Iad supplied to the current adding circuit 32, the voltage signal ΔVp ′ output from the low-pass filter 14 is formed. Initial settings are made so that the DC voltage component ΔVdc does not occur due to variations in components. The addition current If based on the correction current Iad and the current ΔIdc flowing into the connection point x is output by the inverting amplifier 54.
, The corrected drive current Id is supplied to the light emitting diode LED. The DC component in the photocurrent Ip generated in the photodiode PD is adjusted by the corrected drive current Id, and the DC voltage component (-ΔVdc) generated in the output voltage ΔVp ′ due to the variation in the components is removed.

As a result, even if the components vary, feedback control is performed so that the average light receiving power P _{0 on the} light receiving surface of the photodiode PD is constant, and the voltage signal Δ
The feedback control is performed so that the DC voltage component (−ΔVdc) does not appear in Vp ′ and only the AC voltage component ΔVac is present.

FIG. 1 according to the first embodiment described above.
In the optoelectronic circuit shown in (1), the DC voltage component (−ΔVdc) due to the variation of the circuit components can be removed from the output voltage ΔVp ′ by giving the current generating circuit 11 an output variable function. That is, the magnitude of the reference current Iref generated by the current generation circuit 11 is changed by the variation of the components, and the light current Ip
By making the magnitude equal to the magnitude of the DC current component (−Idc), the comparison current ΔI
p is only the alternating current component (−ΔIac). Therefore, the DC voltage component (−ΔVdc) can be removed from the output voltage ΔVp ′.

In the above description, the embodiment of the optoelectronic circuit applied to the electronic watt-hour meter 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.

[0053]

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.

Further, the measurement signal appears on the basis of zero volt, so that even a small measurement signal can be accurately measured.

[Brief description of the drawings]

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

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 that constitute the optoelectronic circuit of the first embodiment.

FIG. 3 is a circuit diagram illustrating a specific circuit example of a DC component extraction circuit and a drive circuit that constitute the optoelectronic circuit according to the first embodiment.

FIG. 4 is a graph for explaining an operation example of the first embodiment.

FIG. 5 is a graph for further explaining an operation example of the first embodiment.

FIG. 6 is a block diagram illustrating a configuration of an optoelectronic circuit according to a second embodiment of the present invention.

FIG. 7 is a circuit diagram showing specific circuit examples of a DC component extraction circuit, a voltage / current conversion circuit, a current addition circuit, a current generation circuit, a temperature compensation circuit, and a drive circuit that constitute the optoelectronic circuit of the second embodiment. It is.

FIG. 8 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 (58) Field surveyed (Int. Cl. ⁷ , DB name) G01R 19/00 G01R 15/24 G01R 33/032 G01R 21/08

Claims (5)

(57) [Claims] 1. An optical sensor whose light parameter changes according to a measurement object, a light emitting element that emits light to the optical sensor, a light receiving element that receives modulated light modulated by the optical sensor, and an output of the light receiving element. A feedback loop for feeding back the light emitting element based on the DC component of the light emitting element and controlling the average light receiving power on the light receiving surface of the light receiving element to be constant. A driving circuit for causing the light emitting element to emit light by a driving current generated by a difference voltage between the light emitting element and a reference voltage other than a ground voltage; and a reference for generating a reference current having a magnitude equal to a DC component in a photocurrent generated in the light receiving element. a current generating circuit, and a current comparison circuit for generating a to compare current comparing the photocurrent generated in the light receiving element and the reference current, is generated by the current comparator circuit Proportional to the comparison current
An opto-electronic circuit comprising: a current-to-voltage conversion circuit that outputs a voltage that has been amplified . 2. The feedback loop according to claim 1, further comprising a current addition circuit having an output current variable function for outputting a correction current for canceling a DC component generated in an output current of the current comparison circuit to the drive circuit. An optoelectronic circuit according to claim 1. 3. The optoelectronic circuit according to claim 1, wherein said reference current generation circuit has an output current variable function. 4. The optoelectronic circuit according to claim 1, wherein the optical sensor has a magneto-optical effect element whose light parameter changes according to a magnetic field. 5. The optoelectronic circuit according to claim 1, wherein the optical sensor includes an electro-optic effect element whose light parameter changes according to an electric field.