JP2007141928A - Device of controlling photo coupler and method of controlling the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily compensate the variation of current transmission ratio in high accuracy to either or both of a transmission/reception route for signals with an optional modulation mode. <P>SOLUTION: One of controllers (46 and 49) of the photo couplers (22, D1, P2, 43; 27, D2, P1, 48) is integrally provided with an optical transmitter (22, D1) including light emitting elements (D1) such as a light emitting diode or the like, and an optical receiver (P2, 43) including an optical detector (P2) to receive optical signal output which the optical transmitter transmits according to the light emission of the light emitting element. Then, it emits a light at the maximum output and the minimum output from the light emitting element before the start of transmission of the optical signal output from the optical transmitter, and determines the amplification rate of the photo coupler on the basis of a difference between the maximum output and the minimum output. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a photocoupler, and more particularly to a photocoupler control apparatus and a control method for a photocoupler that perform control for automatically correcting fluctuations in a current transfer ratio (CTR) of the photocoupler.

  Conventionally, various low-voltage devices connected to power lines, such as automatic meter reading (AMR) systems, power line modems, home automation / control, security / monitoring systems, general-purpose insulated transceivers (transceivers), Internet devices, etc. Is widely used. In addition to the original signal transmission / reception and signal processing functions, these low voltage circuits must have a common function for dealing with high voltage and high noise from the power line. In the following, a general-purpose isolation transceiver (transceiver) will be described, which is considered to be sufficient for understanding the present invention. However, it is easily understood by those skilled in the art that the concept applicable to the other low-voltage devices and their circuits is described. I understand.

  The analog front end (AFE) circuit, which is the tip of connecting the general-purpose isolated transceiver to the power line, is in the harshest environment, especially on the power line side so that the high voltage from the power line does not reach the low voltage equipment. And an insulating means for insulating the low-voltage device side. Typical AFEs include transmission filters, transmission line drivers (amplifiers), coupling transformers (isolation transformers), coupling capacitors, reception filters, reception amplifiers and surge protection devices. Thus, an insulating transformer (isolation transformer) has been frequently used as an insulating means. However, the insulation transformer is relatively large, and these AFEs using the insulation transformer have many individual parts. Therefore, the AFE becomes large, hinders downsizing of the equipment, is expensive, and is easy to handle. There was a problem of inconvenience.

  On the other hand, using an optical coupling element (optocoupler or photocoupler) to insulate the high-voltage circuit from the low-voltage circuit, the insulation transformer is removed, and the circuit elements are integrated to reduce the size and cost. Efforts to make it easier have been made. For example, Agilent HCPL-800J DAA (Data Access Arrangement; hereinafter referred to as “data access device” and abbreviated as “DAA”) commercially available from Agilent Technologies, Inc. described in Non-Patent Document 1. Is an IC that can be directly connected to a commercially available PLM (power line modem) transceiver / ENDEC (encoder-decoder) IC (integrated circuit). The DAA is connected to the power line by externally attaching a transmission filter, a coupling capacitor, a reception filter, a surge protection device, and the like.

  FIG. 1 is a simplified block diagram of the DAA 10. The DAA 10 has a configuration in which a control IC on the low-voltage side and a line IC on the high-voltage side face each other via an optical coupling element. The control IC and line IC are driven by different power sources. When the transmission mode is set by the signal TX-EN, the transmission signal (TX-IN) from the modem modulator is input to the transmission amplifier / driver 2 which is a cascade circuit of the input amplifier and the LED driver, and the light emitting element D1 Is converted into an optical signal. Next, the optical signal is detected by the light receiving element P2 through an insulating portion (represented by a dotted line in the figure). The output current of the light receiving element P2 is amplified by a transmission transfer impedance amplifier (TX-TIA) 3 and output as a transmission output signal (TX-OUT) through a filter (not shown) and a switch (Hi-Z SW) 5. On the other hand, the received input signal (RX-IN) is amplified by the receiving amplifier / driver 7 and then converted into an optical signal by the light emitting element D2, and detected by the light receiving element P1 through the insulating portion (shown by a dotted line in the figure). The The output current of the light receiving element P1 is amplified by a reception transfer impedance amplifier (RX-TIA) 8 and output as a reception output signal (RX-OUT). Further, information such as the power supply voltage on the line IC side is transmitted to the control IC side via the state logic circuit 6 and detected and output by the state detection circuit 9.

The DAA 10 in FIG. 1 corrects fluctuations in the transmission output signal (TX-OUT) due to fluctuations in the transmission signal TX-IN from the modem modulator, temperature characteristics and aging characteristics of the DAA 10 itself, or deviations between components during manufacture. Therefore, an AGC circuit 4 is provided. The AGC circuit 4 detects the output of the transmission transfer impedance amplifier (TX-TIA) 3 and feeds it back to the amplifier 3 to change the amplification factor of the amplifier 3 so that the output has a predetermined amplitude (for example, 3V _PK-PK ). It is controlled to become. Many of the causes of fluctuations in the transmission output signal (TX-OUT) by the DAA 10 itself are the current transfer ratio (CTR: Current) of the optical coupler formed by the light emitting element D1 and the light receiving element P2 (or the light emitting element D2 and the light receiving element P1). Transfer Ratio), that is, a variation in the product of the light emitting efficiency of the light emitting element and the light receiving efficiency of the light receiving element.

In the control of the peak value of the transmission output signal by the AGC circuit 4 of the DAA 10 in FIG. 1, a signal having a constant amplitude is transmitted and works well in frequency modulation, phase modulation, pulse modulation, etc., but the amplitude and amplitude envelope fluctuate. In amplitude modulation and other methods (OFDM, DSB, SSB, multicarrier, ASK, QPSK, etc.) in which information is included in the amplitude fluctuation, the modulation wave is ignored when the control speed and the modulation speed that change the amplification factor approach each other. It may cause distortion that cannot be done. Therefore, in the light receiving circuit described in Patent Document 1, an operating point control circuit for the light receiving element is provided, the operating point of the light receiving element is placed in the unsaturated region, and the operating point is moved and converted in order to obtain a required conversion gain. An apparatus is disclosed that achieves stability of gain and operating point.
Agilent HCPL-800J Application Note 5074 (http://cp.literature.agent.com/literweb/pdf/5989-1242EN.pdf; 2004-07-25 update) JP-A-9-260712

  In the compensation method for reducing the fluctuation of the output signal described in Non-Patent Document 1, it is only possible to correct the signal having a constant amplitude on the transmission side, and naturally it is not possible to compensate for the fluctuation on the reception side. The compensation method described in Patent Document 1 can compensate for a variable amplitude signal only on the reception side, but naturally has a problem that fluctuation on the transmission side cannot be compensated.

  Accordingly, an object of the present invention is to solve or alleviate the above-mentioned problems, and to compensate for fluctuations in the current transfer ratio with high accuracy over one or both of the transmission and reception paths for a signal of a desired modulation method. It is an object of the present invention to provide a simple photocoupler control device and control method that can be easily performed. In the description of the present invention, a photo including an optical transmitter including a light emitting element and an optical receiver including a light detecting element that receives an optical signal transmitted from the optical transmitter based on light emission of the light emitting element. It is called a coupler.

  Another object of the present invention is to make the gain of the photocoupler constant by compensating for variations in the current transfer ratio of the photocoupler through which the analog waveform passes.

  Still another object of the present invention is to make it easy to maintain a constant amplification factor for a transmission / reception waveform even when frequent switching occurs, such as switching between transmission and reception in power line communication.

  One of the photocoupler control devices for solving the above problems is an optical transmitter including a light emitting element such as a light emitting diode, and an optical signal output transmitted from the optical transmitter based on light emission of the light emitting element. An optical receiver including a photodetecting element is integrally provided. And before the start of transmission of the optical signal output from the optical transmitter, it generates light emission that becomes the maximum output and the minimum output of the light emitting element, and based on the difference between the maximum output and the minimum output of the photocoupler The amplification factor is determined.

  It is preferable that the light emission at the minimum output by the light emitting element is continuously performed immediately after the light emission at the maximum output. Further, the light emission with the maximum output and the light emission with the minimum output may be repeated a plurality of times.

  In addition, when the optical receiver receives the optical signal that has exceeded a predetermined intensity before the signal transmission starts, the optical signal is a signal output by the maximum output, and You may make it provide the trigger detection means which enables it to identify that the said optical signal with comparatively small intensity | strength received following the said optical signal is a signal by the said minimum output.

  Further, at least a part of the control device may constitute an IC device integrated with the photocoupler.

  In the photocoupler control method for solving the above-described problem, the photocoupler includes an optical transmitter including a light emitting element, and optical detection for receiving an optical signal transmitted from the optical transmitter based on light emission of the light emitting element. An optical receiver integrally including an element, and before starting signal transmission from the optical transmitter, generating light emission that is a maximum output and a minimum output of the light-emitting element; and the maximum output and the minimum output And a step of determining an amplification factor of the photocoupler based on the difference.

  The light emission at the minimum output by the light emitting element is preferably performed immediately after the light emission at the maximum output. Moreover, such a continuation may be repeated a plurality of times.

  A step of identifying the optical signal as a signal output by the maximum output when the optical receiver receives the optical signal in which the photodetector exceeds a predetermined intensity before the signal transmission is started; And a step of discriminating that the optical signal having a relatively low intensity received after the optical signal is a signal output by the minimum output.

  A simple photocoupler control device and control that can easily compensate for fluctuations in the current transfer ratio with high accuracy over the entire transmission / reception path for a signal of a desired modulation method by means of solving or reducing the above problems A method is provided.

  Moreover, even if switching frequently occurs, such as switching between transmission and reception in power line communication, the gain of the photocoupler is made constant by compensating for fluctuations in the current transfer ratio of the photocoupler through which the analog waveform passes. There is an effect that the amplification factor can be easily maintained constant. The details of other features and effects of the present invention will become clear from the following description.

  The embodiments of the present invention described below are for understanding the present invention and are not intended to limit the present invention to the embodiments. Therefore, the size and shape of the device and its elements are not intended to have a specific geometric relationship with the size or shape of the device or element that is actually manufactured. In addition, devices that exhibit similar functions and components thereof are given the same reference numerals as long as they do not completely coincide, but are considered to have no problem in understanding the present invention. In the following description of the embodiments, only the range necessary for understanding the invention is described for the wiring, electrical, and mechanical elements that connect the components. Further, the description of the parts belonging to the prior art is omitted or simplified.

  FIG. 2 is a block diagram showing an outline of the photocoupler, its control device, and DAA 20 according to one embodiment of the present invention. In the following description, the DAA 20 is described as being installed between the modem and the power line, but it will be easily understood that the DAA 20 can be used between other devices. The DAA 20 includes a transmission-side photocoupler (22, D1, P2, 13, 25) and a reception-side photocoupler (27, D2, P1, 18, 28), and control circuits 26 and 29 that are control devices perform control. Is doing. The transmission-side photocoupler (22, D1, P2, 13, 25) has a portion (22, D1) to be an optical transmitter and a portion (P2, 13, 25) to be an optical receiver, The coupler (27, D2, P1, 18, 28) also has a portion (27, D2) that becomes an optical transmitter and a portion (P1, 18, 28) that becomes an optical receiver. DAA 20 is preferably integrated in the same manner as conventional DAA 10. The DAA 20 is set to the transmission mode and the reception mode according to the activation (ON) and inactivation (OFF) of the mode switching signal TX-EN.

  The transmission amplifier / driver 22 buffers and amplifies the transmission signal TX-IN from the modem in response to the activation of the mode switching signal TX-EN from the modem (not shown), and drives the light emitting element D1 such as a light emitting diode. The optical signal output transmitted based on the light emission of the light emitting element D1 is detected as a current by the light detecting element P2, and the current is buffered and amplified by the transmission TIA (transmission transfer impedance amplifier) 13, and then the attenuator with output buffer 25 Then, the transmission output signal TX-OUT is transmitted to the power line. In response to switching to the transmission mode, the control circuit 29 forces the input of the transmission amplifier / driver 22 to a predetermined value at a predetermined cycle so that the light emission of the light emitting element D1 takes the maximum output value and the minimum output value, and continues to the predetermined value. The transmission signal TX-IN from the modem can be transmitted through the idle period. The transmission signal TX-IN is converted into an optical signal and detected as a current by the light detection element P2, and the current is buffered and amplified by a transmission TIA (transmission transfer impedance amplifier) 13. The control circuit 26 detects the output of the transmission TIA 13 and determines the output value corresponding to the predetermined value, and determines the amplification factor (transmission ratio) from the transmission amplifier / driver 22 to the transmission TIA 13. The amplification factor varies depending on the variation of the current transfer ratio (CTR) between the light emitting element D1 which may be a light emitting diode (LED) and the light receiving element P1 which may be a photodiode (PD) or a phototransistor (PTR). Therefore, the control circuit 26 adjusts the attenuation rate of the attenuator 25 with output buffer to compensate for fluctuations in the amplification rate, and the transmission signal TX-IN is amplified at a constant predetermined amplification rate to obtain the transmission output signal TX-OUT. To be. It is well known that the output buffer attenuator 25 has a high attenuation rate accuracy by placing an attenuator in front and a buffer amplifier. Further, the control circuit 26 may detect the power supply voltage and the like as in the conventional state logic circuit, transmit the detected voltage via the reception amplifier / driver 27, and detect and output it by the control circuit 29. Further, the maximum output value and the minimum output value of the light emission should be selected so that the transmission signal TX-IN is set in a linear amplification range.

  Further, the reception amplifier / driver 27 buffers and amplifies the reception signal RX-IN and drives the light emitting element D2 such as a light emitting diode in response to the inactivation of the mode switching signal TX-EN, based on the light emission of the light emitting element D2. The optical signal output transmitted in this manner is detected as a current by the light detection element P1, and the current is buffered and amplified by a reception TIA (reception transfer impedance amplifier) 18 and then passed through an attenuator 28 with an output buffer to receive a reception output signal RX-OUT. And sent to the modem. The control of the amplification factor is the same for both the transmission-side photocoupler and the reception-side photocoupler. Hereinafter, the transmission side will be described with reference to FIG. In FIG. 3, the horizontal axis represents time t, and the vertical axis represents amplitude relative to an arbitrary scale.

  In FIG. 3, the DAA 20 transmits (triggered) when the mode switching signal (TX-EN) 32 in the reception mode (RX) of the DAA 20 changes from the inactive (OFF) state to the active (ON) state. The mode (TX) is entered, and the light emission intensity (LOP) 34 of the light emitting diode (LED) D1 passes through the maximum output value (LOPmax) period 34a and then reaches the period 34b in which the minimum output value (LOPmin) is obtained. The standby extinction state is maintained until a period of emission intensity 38 corresponding to the signal modulated by raising (TX-IN). Next, the modem raises the transmission signal (TX-IN) from the time when the set period Txs has passed from the time when the mode switching signal 32 becomes active, and transmits the modulated signal 38. The mode switching signal (TX-EN) 32 changes from the active (ON) state to the inactive (OFF) state in response to the end of transmission of the transmission signal (TX-IN) or the elapse of a fixed time. Accordingly, the light emission of the light-emitting diode D2 on the reception side may be similarly controlled.

  According to the periods 34a, 34b, 34c of the emission intensity 34 of the LED D1, the output (IPD) 36 of the transmission TIA 13 is modulated by taking the period 36a of the output intensity IPDmax, the period 36b of IPDmin, and the period 36c of no signal. A signal 39 modulated in response to the signal 38 is produced. The control circuit 26 measures the output 36, sets an output pulse corresponding to the period 36a (or an integrated value thereof) as an output pulse having a width greater than a predetermined level and exceeding a predetermined width as IPDmax, and at the end of the period 36a. IPDmax and IPDmin are stored, with output 36 representing the output IPDmin corresponding to period 36b, triggered and sampled within a predetermined period. Then, IPDmax−IPDmin is calculated to obtain a ratio with the value IPDs corresponding to a predetermined amplification factor. The setting of the attenuator is IPDs / (IPDmax−IPDmin).

  Alternatively, if the period 36a is equal to the period 36b, and the output (IPD) 36 is integrated for the period 36a + the period 36b by an integrator that inverts and integrates the input in the period 36a and the period 36b, the influence of noise is small. IPDmax-IPDmin is obtained. Various other devices will be known.

  FIG. 4 is a schematic block diagram of a DAA 40 according to another embodiment to which the present invention is applied. Components similar to those of the DAA 20 in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted here. Also in the DAA 40, the transmission side and the reception side perform the same operation, and the transmission transfer impedance amplifier (TX-TIA) 43 and the reception transfer impedance amplifier (RX-TIA) 48 have the same function and performance. Further, the control circuit 46 can detect and transmit a state parameter such as a power supply voltage, and the control circuit 49 can detect and output the parameter. However, unlike the DAA 20, the DAA 40 does not have the output buffer attenuators 25 and 28, and the TX-TIA 43 having a variable amplification degree is set like the TX-TIA 3 in the prior art of FIG. Is.

  In both the DAA 20 and the DAA 40, the transmission output signal TX-OUT may be output via a switch as shown in FIG. 1, and may not be output during the period Txs. Both the DAA 20 and the DAA 40 can be integrated in the same manner as the DAA 10, and the low-voltage side and the power line side may be formed as monolithic integrated circuits, and then integrated on one die.

  FIG. 5 is an embodiment of the present invention, an optical transmitter including a light emitting element, and an optical receiver including a light detecting element that receives an optical signal transmitted from the optical transmitter based on light emission of the light emitting element. It is the flowchart 50 showing the control method of the photocoupler with which a machine is integrated. In step 52, before starting the signal transmission from the optical transmitter, light emission that produces the maximum output and the minimum output of the light emitting element is generated. In step 54, the gain of the photocoupler is determined based on the difference between the maximum output and the minimum output.

  FIG. 6 is an embodiment of the present invention different from the method shown in FIG. 5 and shows an optical transmitter including a light emitting element, and an optical signal transmitted from the optical transmitter based on light emission of the light emitting element. It is the flowchart 60 showing the control method of the photocoupler which is provided with the optical receiver containing the photon detection element to receive integrally. In step 62, the optical transmitter sets the light emission of the light emitting element to the maximum output before starting the signal transmission from the optical transmitter. In step 64, the optical detection element of the optical receiver receives an optical signal exceeding a predetermined intensity, and the optical signal is identified as a signal output by the maximum output. In step 66, the optical transmitter sets the light emission of the light emitting element to the minimum output. In step 68, the optical receiver identifies that the relatively low intensity optical signal received following the optical signal is a signal output by the minimum output. In step 70, the amplification factor of the photocoupler is determined from the difference between the signal output by the maximum output and the signal output by the minimum output.

  Although the embodiments have been described above, various modifications are possible, and the present invention is not limited to the above embodiments.

1 is a schematic block diagram of a DAA (Data Access Device) 10 including a photocoupler and its control device according to the prior art. It is a block diagram which shows the outline of DAA20 including the photocoupler of one Example of this invention, and its control apparatus. FIG. 4 is a timing diagram of signals related to the DAA 20 including the photocoupler and its control device according to an embodiment of the present invention. It is a block diagram which shows the outline of DAA40 containing the photocoupler of one Example of this invention, and its control apparatus. It is a flowchart which shows the control method of the photocoupler of one Example of this invention. 3 is a flowchart showing a method of controlling a photocoupler according to an embodiment of the present invention.

Explanation of symbols

10, 20, 40 DAA (data access device)
2,22 Transmission amplifier / driver 7,27 Reception amplifier / driver 3,13,43 Transmission TIA (transmission transfer impedance amplifier)
8, 18, 48 Receiving TIA (Receiving Transfer Impedance Amplifier)
26, 29, 46, 49 Control circuit D1, D2 Light emitting element P1, P2 Light receiving element

Claims (8)

In a control device for a photocoupler integrally including an optical transmitter including a light emitting element, and an optical receiver including a light detection element that receives an optical signal output transmitted from the optical transmitter based on light emission of the light emitting element,
Before starting the transmission of the optical signal output from the optical transmitter, the light emitting element emits light having the maximum output and the minimum output, and the amplification factor of the photocoupler is based on the difference between the maximum output and the minimum output. A control device for a photocoupler, characterized by:   2. The photocoupler control device according to claim 1, wherein the light emission of the minimum output by the light emitting element is continuously performed immediately after the light emission of the maximum output. 3.   Before the start of signal transmission, when the optical receiver receives the optical signal that has exceeded a predetermined intensity, the optical signal is a signal output by the maximum output, and the light 3. The photocoupler according to claim 2, further comprising: a trigger detection unit that makes it possible to identify that the optical signal having a relatively low intensity received following the signal is a signal with the minimum output. Control device.   The photocoupler control device according to claim 1, wherein at least a part of the control device constitutes an IC device integrated with the photocoupler.   The photocoupler control device according to claim 1, wherein the light emitting element includes a light emitting diode. In a control method of a photocoupler integrally including an optical transmitter including a light emitting element and an optical receiver including a light detection element that receives an optical signal transmitted from the optical transmitter based on light emission of the light emitting element.
Before starting signal transmission from the optical transmitter, generating light emission that is the maximum output and minimum output of the light emitting element;
And a step of determining an amplification factor of the photocoupler based on a difference between the maximum output and the minimum output.   The photocoupler control method according to claim 6, wherein the light emission of the minimum output by the light emitting element is continuously performed immediately after the light emission of the maximum output.   Identifying the optical signal as the signal output by the maximum output when the optical receiver receives the optical signal that has exceeded a predetermined intensity by the optical detection element before the start of the signal transmission; and 7. The method of controlling a photocoupler according to claim 6, further comprising the step of identifying that the optical signal having a relatively low intensity received following the optical signal is a signal output by the minimum output.

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