JP2000101125A - Optical communication device and waveform forming circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide optical communication device which surely and automati cally adjusts a transmission output level, while a processing operation is speeded up. SOLUTION: A reception circuit 1 is constituted of a light reception means 2, an amplifier 3 converting received current I1 generated in the light reception means 2 into a voltage signal V1 and comparator 4 which binarizes the voltage signal V1 of the amplifier 3, based on a threshold VTH and outputting the binary signal to an inner circuit as a reception signal RX. A transmission circuit 5 is constituted of a light emitting means 6, and a current driver circuit 7 inputting the binary signal outputted from the inner circuit as a transmission signal TX for converting the transmission signal TX into a current signal, amplifying it and supplying amplified current to the light emitting means 6 as a transmission current I2. A voltage holding circuit 8 holds the peak voltage of the voltage signal V1 of the amplifier 3 in the reception circuit 1 as a holding voltage V2. A transmission current control circuit 9 controls the amplification level of the current driver circuit 7 of the transmission circuit 5, based on the holding voltage V2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical communication apparatus for transmitting and receiving data using light represented by infrared rays between electronic devices provided via a space, and a waveform shaping method suitable for the apparatus. Circuit.

In recent years, personal computers, PDAs (Personal Digit)
al Assistants), and some electronic devices such as digital still cameras are equipped with an optical communication device that transmits and receives data through space using infrared light. In such an optical communication device, in order to reduce the power consumption of electronic devices,
There is a demand for reducing its own power consumption. Therefore, in such an optical communication device, it is necessary to automatically adjust the transmission output level according to the communication distance, the communication state, and the like. On the other hand, in recent electronic devices, high-speed data processing is desired, and in this optical communication device, it is necessary to increase the processing speed.

[0003]

2. Description of the Related Art FIG. 10 shows an example of an optical communication apparatus 10 having an automatic transmission output level adjusting function. The optical communication device 10 includes a receiving circuit 10a including a photodiode 11, an amplifier 12, and a comparator 13, and a transmitting circuit 10b including a current driver circuit 14 and a light emitting diode 15.

In the receiving circuit 10a, a photodiode 11 is connected between input terminals of an amplifier 12, and the diode 11 generates a reception current Ipd corresponding to received light.
The amplifier 12 converts the received current Ipd into a voltage signal VA,
The voltage signal VA is output to the plus input terminal of the comparator 13. The DC reference voltage VR is input to the minus input terminal of the comparator 13 as the threshold value VTH. Then, the comparator 13 binarizes the voltage signal VA from the amplifier 12 based on the threshold value VTH and converts the binary signal into the received signal RX.
To an internal circuit (not shown).

In the transmission circuit 10b, the binary signal output from the internal circuit is input to the current driver circuit 14 as a transmission signal TX. The light emitting diode 15 is connected between the output terminals of the current driver circuit 14. The current driver circuit 14 converts and amplifies the transmission signal TX into a current signal, and supplies the amplified current to the light emitting diode 15 as a transmission current Idrv. The light emitting diode 15 repeats light emission and light extinction based on the pulsed transmission current Idrv.

The light emission level control section 16 changes the light emission level of the light emitting diode 15 according to the light receiving level of the photodiode 11. That is, the light emission level control unit 16
When the light receiving level is high, it is determined that the communication distance is short or the communication state is good, and the current driver circuit 14 is controlled so that the light emitting level of the light emitting diode 15 becomes low. On the other hand, when the light reception level is low, the light emission level control unit 1
6 determines that the communication distance is long or the communication state is not preferable, and controls the current driver circuit 14 so that the light emitting level of the light emitting diode 15 becomes high.

The light emission level control section 16 specifically includes a light reception level detection circuit 16a, a control circuit 16b, an arithmetic circuit 16c, and a light emission level adjustment circuit 16d. The light receiving level detection circuit 16a includes the amplifier 12
Is input. Light reception level detection circuit 16
a detects the level of the voltage signal VA and outputs a detection signal SG1 corresponding to the level to the control circuit 16b. The control circuit 16b calculates the light receiving level of the photodiode 11 in the calculation circuit 16c based on the detection signal SG1, and the calculation circuit 16c calculates the communication distance and the communication distance based on the calculation result.
Determine the communication state. The arithmetic circuit 16c calculates the light emission level of the light emitting diode 15 and the light emission timing based on the determination, and outputs the calculation result to the control circuit 16b.

[0008] The control circuit 16b outputs a control signal SG2 based on the calculation result to the light emission level adjustment circuit 16d.
The light emission level adjustment circuit 16d outputs an adjustment signal SG3 based on the control signal SG2 to the current driver circuit 14, and controls the amplification degree of the circuit 14. Then, the current driver circuit 14 determines the communication distance based on the adjustment signal SG3,
Transmission current Idr for setting the light emission level according to the communication state
Generate v.

In the optical communication device 10 configured as described above, the light emission level control unit 16 optimally adjusts the light reception level, that is, the light emission level of the light emitting diode 15 according to the communication distance, the communication state, and the like. Thus, the power consumption of the optical communication device 10 is reduced.

[0010]

However, the optical communication device 10 described above is configured to calculate the light emission level by calculating based on the light reception level, so that the calculation requires time. In particular, in optical communication, the communication state, that is, the light receiving level is easily changed due to the communication distance, the angle of the receiving surface, disturbance, and the like, so that the calculation of the light emission level is increased. In such a case, the time required for the calculation becomes very long, which has hindered the speeding up of the processing operation of the optical communication apparatus 10.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an optical communication device and a device capable of reliably and automatically adjusting a transmission output level while speeding up a processing operation. It is to provide a suitable waveform shaping circuit.

[0012]

FIG. 1 is a diagram for explaining the principle of claim 1. That is, the receiving circuit 1 converts the light receiving means 2 and the received current I1 generated by the light receiving means 2 into a voltage signal V1.
And a comparator 4 which binarizes the voltage signal V1 of the amplifier 3 based on the threshold value VTH and outputs the binary signal as a received signal RX to an internal circuit. The transmission circuit 5 receives the light emitting means 6 and the binary signal output from the internal circuit as a transmission signal TX, converts the transmission signal TX into a current signal, and amplifies the current signal.
The amplified current is used as the transmission current I2 in the light emitting unit 6.
And a current driver circuit 7 for supplying the current to the current driver. The voltage holding circuit 8 holds the peak voltage of the voltage signal V1 of the amplifier 3 in the receiving circuit 1 as holding information V2.
The transmission current control circuit 9 controls the amplification degree of the current driver circuit 7 in the transmission circuit 5 based on the held information V2 held in the voltage holding circuit 8.

According to a second aspect of the present invention, in the optical communication device according to the first aspect, the transmission current control circuit adjusts an amplification degree of the current driver circuit in a part of the transmission current. The transmission current level is set to the maximum value or the fixed value regardless of the held information.

According to a third aspect of the present invention, in the optical communication device according to the first aspect, the voltage holding circuit charges a capacity based on the voltage signal, and uses the charging voltage as holding information as the transmission current. Output to the control circuit.

According to a fourth aspect of the present invention, in the optical communication device according to the third aspect, the voltage holding circuit starts charging a capacitor by the voltage signal based on a reception signal output from a comparator. I did it.

According to a fifth aspect of the present invention, in the optical communication device according to the fourth aspect, the voltage holding circuit supplies a charge to the capacitor based on a voltage signal of the amplifier when the voltage holding circuit is turned on. A second switch circuit, a second switch circuit that discharges the charge of the capacitor when the switch circuit is turned on, and a non-conductive state of the first switch circuit based on a reception signal output from the comparator. And, after a predetermined time has elapsed, the first switch circuit is turned on, the second switch circuit is maintained in a non-conductive state, and further, a switch control circuit for inhibiting operation by a received signal, A reset circuit for canceling the inhibition of the operation of the switch control circuit by the received signal based on the output transmission signal.

According to a sixth aspect of the present invention, in the optical communication device according to the first aspect, the transmission current control circuit gradually controls the amplification degree of the current driver circuit when switching between control and non-control. I did it.

According to a seventh aspect of the present invention, in the optical communication device of the first aspect, a switch is provided immediately after an output terminal of the amplifier in the receiving circuit, and a voltage signal output from the amplifier during transmission is transmitted to a subsequent stage. No output to the circuit.

According to an eighth aspect of the present invention, in the optical communication device according to the first aspect, the amount of the transmission current supplied to the light emitting means is controlled so as to sharpen rising and falling edges thereof, A waveform shaping circuit for shaping the transmission current waveform is provided.

According to a ninth aspect of the present invention, in the optical communication device according to the eighth aspect, the waveform shaping circuit converts a transmission signal output from the internal circuit into a differentiated waveform signal; Based on the differentiated waveform signal of the differentiator,
A complementary current generating circuit for generating a complementary current that complements the rising and falling currents of the transmission current supplied to the light emitting means.

According to a tenth aspect of the present invention, the pulse signal is converted and amplified into a current signal, the amplified current is supplied to the light emitting means, and the rising and falling edges of the current supplied to the light emitting means are detected. A waveform shaping circuit that controls the amount of current to make the current steep, and shapes the current waveform, wherein the differentiation circuit converts the pulse signal into a differentiated waveform signal; A complementary current generating circuit for generating a complementary current that complements the rising and falling currents of the current supplied to the light emitting means.

(Operation) According to the first aspect of the present invention,
In the voltage holding circuit 8, the amplifier 3 is controlled based on the reception current I1.
The peak voltage of the voltage signal V1 output from the
2 is retained. Then, the transmission current control circuit 9
The amplification degree of the current driver circuit 7 of the transmission circuit 5 is controlled based on the held information V2 held by the voltage holding circuit 8. That is, the transmission current control circuit 9 controls the amplification degree of the current driver circuit 7 based on the held information V2,
The light emitting means 6 is driven at a light emitting level corresponding to the level of the light received by the light receiving means 2 (corresponding to the communication state). Therefore, it is possible to drive the light emitting means at a light emission level corresponding to the level of the received light without calculating the light emission level.

According to the second aspect of the present invention, in the transmission current control circuit, the amplification degree of the current driver circuit is set to a maximum value or a fixed value irrespective of information held in the voltage holding circuit in a part of the transmission current, The transmission current level is set to a maximum value or a fixed value. In the case where the optical communication device having such a transmission current control circuit is provided in both the local station and the partner station, the light emitting level of the light emitting element becomes a maximum value or a fixed value in a part thereof. It will be easier.

According to the third aspect of the invention, in the voltage holding circuit, the capacitance is charged based on the voltage signal, and the charged voltage is output to the transmission current control circuit as holding information. Then, the amplification degree of the current driver circuit is controlled based on the held information, and the light emitting unit is driven at a light emitting level suitable for the communication state based on the light received by the light receiving unit.

According to the fourth aspect of the invention, in the voltage holding circuit, the charging of the capacitance by the voltage signal is started based on the reception signal output from the comparator. Therefore, no special signal is required to start charging the capacity.

According to the fifth aspect of the present invention, the first switch circuit supplies a charge to the capacitor based on the voltage signal of the amplifier when the first switch circuit is turned on. The second switch circuit discharges the charge of the capacitor when the second switch circuit is turned on. The switch control circuit turns off the first switch circuit based on the received signal output from the comparator, turns on the second switch circuit, and turns on the first switch circuit after a lapse of a predetermined time. , The second switch circuit is maintained in a non-conductive state, and further, the operation by the received signal is prohibited. The reset circuit releases the prohibition of the operation of the switch control circuit based on the reception signal based on the transmission signal output from the internal circuit. In such a voltage holding circuit, the charge stored in the capacitor is discharged through the second switch circuit based on the received signal output from the comparator, and the held information (charge voltage) is reset. After a lapse of a predetermined time, a charge is supplied to the capacitor via the first switch circuit based on the voltage signal of the amplifier, and the charge voltage of the capacitor is output to the transmission current control circuit as holding information. Then, the charging voltage of this capacity, that is, the held information, is maintained without being affected by other received signals until the next transmission signal is input.

According to the present invention, in the transmission current control circuit, the amplification degree of the current driver circuit is gradually controlled at the time of switching between control and non-control. Therefore, in the receiving circuit of the partner station, the first-stage amplifier to which the receiving current generated by the light receiving means is input easily follows.

According to the seventh aspect of the present invention, the switch is provided immediately after the output terminal of the amplifier in the receiving circuit so that the voltage signal output from the amplifier during transmission is not output to the subsequent circuit. Therefore, even if the light emission of the light emitting means is input to the light receiving element of the own station, the voltage signal from the amplifier based on the received current is prevented from being output to the subsequent circuit, so that the subsequent circuit may malfunction. Is prevented.

According to the eighth aspect of the present invention, in the waveform shaping circuit, the amount of the transmission current supplied to the light emitting means is controlled so that the rising and falling edges thereof are steep, and the transmission current waveform is controlled. Is molded. Therefore, the light emitting means can emit light accurately.

According to the ninth aspect, the differentiating circuit converts the transmission signal output from the internal circuit into a differentiated waveform signal. The complementary current generation circuit generates a complementary current that complements the rising and falling currents of the transmission current supplied to the light emitting unit, based on the differentiated waveform signal of the differentiating circuit. Then, the amount of the transmission current supplied to the light emitting means is controlled so that the rising and falling edges thereof become steep, and the transmission current waveform is shaped. Therefore, the light emitting means can emit light accurately.

According to the tenth aspect, the differentiating circuit converts the pulse signal into a differentiated waveform signal. The complementary current generation circuit generates a complementary current that complements the rising and falling currents of the current supplied to the light emitting unit, based on the differentiated waveform signal of the differentiating circuit. Then, the amount of the current supplied to the light emitting means is controlled so that the rising and falling edges thereof become steep, and the current waveform is shaped. Therefore, the light emitting means can emit light accurately.

[0032]

(First Embodiment) A first embodiment of the present invention will be described below with reference to FIGS. Note that, for convenience of description, the same components as those in FIG. 10 are denoted by the same reference numerals, and description thereof is partially omitted.

FIG. 2 shows an optical communication device 20 according to the present embodiment. In this optical communication device 20, a light emission level control unit 21
Comprises a voltage holding circuit 22, a transmission current control circuit 23, and a timing control circuit 24.

The voltage signal VA output from the amplifier 12 is input to the voltage holding circuit 22, and the peak voltage of the voltage signal VA at the time of reception is held. The holding voltage VM as the holding information held by the voltage holding circuit 22 is input to the terminal CNT1 of the transmission current control circuit 23.

The transmission signal (binary signal) TX output from the internal circuit is input to the timing control circuit 24. The timing control circuit 24 generates a timing signal SG4 based on the transmission signal TX, and outputs the timing signal SG4 to the terminal CNT0 of the transmission current control circuit 23. The timing signal SG4 changes from the L level to the H level after a lapse of the time t1 from the rise of the transmission signal TX during the period when the transmission signal TX is the H level, and after the lapse of the time t2 when the transmission signal TX falls after the lapse of the time t1. This is a signal that goes to the L level.

The transmission current control circuit 23 generates an adjustment signal SG5 based on the holding voltage VM and the timing signal SG4, outputs the adjustment signal SG5 to the current driver circuit 14, and controls the amplification degree of the circuit 14. I do.

More specifically, when the timing signal SG4 is at the L level, the transmission current control circuit 23 outputs an adjustment signal SG5 that maximizes the amplification of the current driver circuit 14. When the timing signal SG4 is at the H level, the transmission current control circuit 23
4 to output an adjustment signal SG5 for adjusting the amplification degree to be in inverse proportion to the holding voltage VM.

Therefore, during the period when the transmission signal TX is at the H level, the transmission current control circuit 23 outputs the adjustment signal SG5 for maximizing the amplification of the current driver circuit 14 for a time t1 from the rise. In this case, the light emission level of the light emitting diode 15 becomes maximum based on the driving of the current driver circuit 14. At the time t2 when the transmission signal TX falls after the elapse of the time t1, the transmission current control circuit 23 controls the current driver circuit 1
4 to output an adjustment signal SG5 for adjusting the amplification degree to be in inverse proportion to the holding voltage VM. In this case, the light emission level of the light emitting diode 15 is controlled to a level inversely proportional to the holding voltage VM based on the driving of the current driver circuit 14.

That is, when the light receiving level is high, that is, when the communication distance is short or the communication state is good, the holding voltage VM becomes high. Therefore, the transmission current control circuit 23 sets the light emitting level of the light emitting diode 15 to the communication distance. Alternatively, an adjustment signal SG5 for suppressing the degree of amplification of the current driver circuit 14 is generated in order to lower the level to a predetermined level according to the communication state.
On the other hand, when the light reception level is low, that is, when the communication distance is long or the communication state is not favorable, the holding voltage VM becomes low. Therefore, the transmission current control circuit 23 sets the light emission level of the light emitting diode 15 to the communication distance or the communication state. Current driver circuit 14 to raise the level to a predetermined level corresponding to
To generate an adjustment signal SG5 for increasing the degree of amplification.

Next, the operation of the optical communication device 20 configured as described above will be described with reference to FIG. 1. The case where the optical communication device 20 described above is used in the own station, and the optical communication device that does not have the automatic adjustment function of the transmission output level is used in the partner station.

In this case, a burst signal based on the transmission current supplied to the light emitting diode is transmitted from the optical communication device of the partner station, for example, as shown in FIG. In the optical communication device 20 provided in the own station, the receiving circuit 10a
, A reception current Ipd corresponding to the transmitted burst signal is generated, and the amplifier 12 converts the reception current Ipd into a voltage signal VA. This voltage signal VA is supplied to the comparator 1 in the subsequent stage.
The signal is binarized at 3 and output to the internal circuit as a received signal RX. On the other hand, the voltage holding circuit 22 holds the peak voltage of the voltage signal VA at the time of reception.

Next, when the optical communication device 20 of the local station transmits, the binary signal output from the internal circuit is transmitted as a transmission signal TX in the current driver circuit 1 in the transmission circuit 10b.
4 is input. The transmission signal TX is converted into a timing signal SG4 by the timing control circuit 24 and input to the terminal CNT0 of the transmission current control circuit 23.

The transmission current control circuit 23 controls the transmission signal T
During a period in which X is at the H level, an adjustment signal SG5 that maximizes the amplification degree of the current driver circuit 14 for a time t1 from the rise of the transmission signal TX is output based on the timing signal SG4 at the L level. Then, the current driver circuit 14 transmits the transmission current Idrv as shown in FIG.
Is supplied to the light emitting diode 15. Therefore, at that time t1, the light emitting diode 15 emits light at the maximum level based on the driving of the current driver circuit 14.

Then, after the lapse of time t1, the transmission signal TX
, The transmission current control circuit 23 adjusts the amplification degree of the current driver circuit 14 so as to be inversely proportional to the holding voltage VM input to the terminal CNT1 based on the falling time t2, that is, the H level timing signal SG4. Signal SG
5 is output.

That is, at the time t2, the holding voltage VM is high, that is, the light receiving level is high, the communication distance is short, or the communication state is good.
The transmission current control circuit 23 generates an adjustment signal SG4 for suppressing the amplification of the current driver circuit 14 in order to lower the light emission level of the light emitting diode 15 to a predetermined level according to the communication distance or the communication state. Therefore, in this case, the light emission level of the light emitting diode 15 is kept low.

On the other hand, when the holding voltage VM is low, that is, when the light receiving level is low, the communication distance is long, or the communication state is not favorable, the transmission current control circuit 23
Generates an adjustment signal SG5 for increasing the amplification of the current driver circuit 14 in order to increase the light emission level of the light emitting diode 15 to a predetermined level according to the communication distance or the communication state. Therefore, in this case, the light emitting level of the light emitting diode 15 is increased.

As described above, in the optical communication device 20 of the present embodiment, the light emission level control unit 21 controls the light reception level,
That is, the light emitting diode 15 according to the communication distance, the communication state, etc.
Is adjusted optimally. Thus, the power consumption of the optical communication device 20 is reduced.

2. When both the own station and the opposite station use the optical communication device 20 described above. In this case, from the optical communication device 20 of the partner station, for example, FIG.
As shown in (b), a burst signal based on the transmission current Idrv supplied to the light emitting diode 15 is transmitted. Therefore, the voltage holding circuit 22 holds the peak voltage of the voltage signal VA at the time of reception, that is, the peak voltage within the time t1.

At the time of transmission, based on the holding voltage VM held at the time of reception by the voltage holding circuit 22, the light emitting diode 1 corresponding to the communication distance, communication state, etc.
5, the light emission level of the optical communication device 5 is optimally adjusted, and the power consumption of the optical communication device 20 is reduced.

As described above, when the above-mentioned optical communication device 20 is used for both the local station and the partner station, the light-emitting level of the light-emitting diode 15 is maximized at the time t1 so that the light-receiving levels of the optical communication devices 20 of both stations are increased. Can be easily detected.

As described above, in the present embodiment, the following functions and effects can be obtained. (1) The voltage holding circuit 22 holds the peak voltage of the voltage signal VA output from the amplifier 12 based on the received current Ipd as the holding voltage VM. The transmission current control circuit 23
At a predetermined time t2, control is performed so that the amplification degree of the current driver circuit 14 of the transmission circuit 10b is inversely proportional to the holding voltage VM. Then, the light emitting diode 15 is driven at a light emission level corresponding to the level of the light received by the photodiode 11 (corresponding to the communication state). Therefore, in the present embodiment, since the light emission level of the light emitting diode 15 can be determined without requiring any operation, the processing operation can be speeded up.

(2) When the above-mentioned optical communication device 20 is used for both the local station and the partner station, the light emitting diode 1 is used at time t1.
Since the light emission level of No. 5 is maximized, it is possible to easily detect the light reception level in the optical communication devices 20 of both stations.

(Second Embodiment) Hereinafter, a second embodiment of the present invention will be described with reference to FIGS. For the sake of convenience, the same components as those of the first embodiment shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is partially omitted.

As shown in FIG. 4, the voltage holding circuit 22 of the present embodiment includes a holding circuit 22a including two buffer circuits 25 and 26, two switches SW1 and SW2, and a capacitor C, an AND circuit 27, One shot circuit 2
8, flip-flop circuit 29 and inverter circuit 3
And a reset circuit 22b of zero.

In the hold circuit 22a, the buffer circuit 2
The voltage signal VA of the amplifier 12 is inputted to an input terminal of the amplifier 5. The output terminal of the buffer circuit 25 is connected to the switch SW1.
To the input terminal of the buffer circuit 26 at the next stage. A positive terminal of the capacitor C is connected to a node N between the switch SW1 and the input terminal of the buffer circuit 26.
The negative terminal of the capacitor C is connected to the ground GND. The node N is connected to the ground GND via the switch SW2. These switches SW1, SW2
Are turned on by an H level signal and turned off by an L level signal. Then, from the output terminal of the buffer circuit 26, the potential of the node N is output as the holding voltage VM.

In the reset circuit 22b, the AND circuit 27
The reception signal RX output from the comparator 13 is input to one of the input terminals. The output signal Q of the flip-flop circuit 29 is input to the other input terminal of the AND circuit 27. The transmission signal TX output from the internal circuit is input to the flip-flop circuit 29 as a clock signal. Then, the output signal of the AND circuit 27 is input to the one-shot circuit 28.

The one-shot circuit 28 includes an AND circuit 27
A so-called one-shot signal SG6, which shortens the pulse width of the H-level output from the control circuit to a predetermined width, is generated. The one-shot circuit 28 outputs the generated one-shot signal SG6 to the switch SW2 and outputs the generated one-shot signal SG6 to the switch SW1 via the inverter circuit 30. That is, the switches SW1 and SW2 are configured to perform complementary operations by the one-shot signal SG6.

The one-shot circuit 28 outputs the one-shot signal SG6 to the flip-flop circuit 29 as a reset signal. When the transmission signal TX rises, the flip-flop circuit 29 outputs an H-level output signal Q until an H-level one-shot signal SG6 is input, and outputs the H-level one-shot signal SG.
When 6 is input, an output signal Q of L level is output until the transmission signal TX rises.

The voltage holding circuit 22 thus configured operates as shown in FIG. First, at the start of reception of the optical communication device 20, the flip-flop circuit 29 outputs an H-level output signal Q based on the rise of the transmission signal TX at the previous transmission.

In this state, when the reception signal RX is input, the AND circuit 2 is activated at the first rise of the reception signal RX.
7 becomes H level, and the one-shot circuit 28
Outputs an H-level one-shot signal SG6. While the one-shot signal SG6 is at the H level, the switch SW2 is turned on and the switch SW1 is turned off. Then, the charge stored in the positive terminal of the capacitor C is discharged to the ground GND via the switch SW2, and the potential of the node N becomes the level of the ground GND. That is, the hold voltage VM output from the buffer circuit 26 is at the ground GND level.

At this time, the flip-flop circuit 29 outputs the L-level output signal Q in response to the H-level one-shot signal SG6. Then, the output signal of the AND circuit 27 is fixed at the L level regardless of the received signal RX.

When the one-shot signal SG6 goes low, the switch SW1 is turned on and the switch SW2 is turned off. Then, based on the H-level voltage signal VA output from the amplifier 12, a charge is supplied to the positive terminal of the capacitor C from the output terminal of the buffer circuit 25, and the potential of the node N becomes the level of the voltage signal VA. To rise. That is, at the time of reception, the potential of the node N is held at the peak voltage of the voltage signal VA, and the held voltage VM is output from the buffer circuit 26. This holding voltage VM is
At the time of transmission, as described above, it is used to optimally adjust the light emission level of the light emitting diode 15 according to the communication distance, communication state, and the like.

When the optical communication device 20 enters the transmission state and the transmission signal TX is output from the internal circuit, the output signal Q of the flip-flop circuit 29 is switched to the H level based on the rise of the transmission signal TX. . Then, the voltage holding circuit 22 waits for the next input of the reception signal RX.

As described above, in this embodiment, the following operation and effect can be obtained in addition to the operation and effect shown in the first embodiment. (1) The voltage holding circuit 22 charges the capacitor C based on the voltage signal VA, and outputs the charged voltage to the transmission current control circuit 23 as a holding voltage VM. Therefore, the voltage holding circuit 22 can be configured relatively easily.

(2) The voltage holding circuit 22 is provided with the comparator 1
3, the voltage signal VA based on the received signal RX output from
Of the capacitor C is started. Therefore, a special signal for starting the charging of the capacitor C is not required, so that the circuit configuration can be simplified.

(Third Embodiment) Hereinafter, a third embodiment of the present invention will be described with reference to FIG. still,
For convenience of explanation, the same components as those in the first embodiment shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is partially omitted.

In the transmission current control circuit 23 of the present embodiment, the control of the amplification degree of the current driver circuit 14 during transmission is different. That is, the transmission current control circuit 23 of the first embodiment maximizes the amplification degree of the current driver circuit 14 for the time t1 from the rise of the transmission signal TX during the period when the transmission signal TX is at the H level, and after the elapse of the time t1 At the time t2 when the transmission signal TX falls from the holding voltage V
The amplification degree of the current driver circuit 14 is limited based on M. Therefore, from the current driver circuit 14, FIG.
As shown in (a), a transmission current Idr composed of a burst signal
The amplitude of v greatly changes between times t1 and t2.

On the other hand, the transmission current control circuit 2 of the present embodiment
Numeral 3 is configured to gradually control the amplification degree of the current driver circuit 14 so that the amplitude of the transmission current Idrv does not greatly change between times t1 and t2. That is, the transmission current control circuit 23 calculates the peak value of the transmission current Idrv shown in FIG.
The transmission current Idr that gradually changes as shown in FIG.
v

In this way, in the receiving circuit of the partner station, the first-stage amplifier to which the current generated by the photodiode is input easily follows. Therefore, erroneous detection of the comparator provided at the subsequent stage is prevented.

(Fourth Embodiment) Hereinafter, a fourth embodiment of the present invention will be described with reference to FIG. still,
For convenience of explanation, the same components as those in the first embodiment shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is partially omitted.

In the optical communication device 20 of the present embodiment, FIG.
As shown in the figure, a switch SW3 is interposed immediately after the output terminal of the amplifier 12 constituting the receiving circuit 10a. The switch SW3 is configured to turn off when the transmission signal TX goes high and turn on when the transmission signal TX goes low.

In this manner, the transmission signal T at the H level
Even if the light emitting diode 15 emits light by driving the current driver circuit 14 based on X, the switch SW3 is turned off based on the transmission signal TX, so that the receiving circuit 10a
The voltage signal VA of the amplifier 12 at the time
Is not output to As a result, malfunction of the receiving circuit 10a due to light emission of the light emitting diode 15 of the own station can be prevented.

(Fifth Embodiment) A fifth embodiment of the present invention will be described below with reference to FIGS. For the sake of convenience, the same components as those of the first embodiment shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is partially omitted.

As shown in FIG. 9A, the cathode of the light emitting diode 15 is connected to a waveform shaping circuit 31 for shaping the waveform of the transmission current Idrv supplied to the diode 15. Here, as shown in FIG. 8A, the equivalent circuit of the light emitting diode 15 has a parasitic element 15b composed of a resistor and a capacitor with respect to the diode 15a. for that reason,
As shown in FIG. 8B, the transmission current Idrv generated based on the transmission signal TX by these parasitic elements 15b.
Rising and falling edges become dull. In particular, when the level of the transmission current Idrv is low, the dullness appears remarkably. Therefore, the waveform shaping circuit 31 outputs the transmission current I
The edge of the current Idrv is prevented from dulling in accordance with the level of drv.

More specifically, the cathode of the light emitting diode 15 is connected to the ground GND via the NMOS transistors TN1 and TN2 and to the ground GND via the NMOS transistors TN3 and TN4. NM
The transmission signal TX is input to the gate of the OS transistor TN1 via two buffer circuits 32a and 32b. A buffer circuit 32c, a differentiating circuit 33 including a capacitor and a resistor are provided at the gate of the NMOS transistor TN3.
And the transmission signal TX is input via the buffer circuit 32d. The reference voltages Vg1 and Vg2 are input to the gates of the NMOS transistors TN2 and TN4, respectively, and the transistors TN2 and TN4 form a constant current source.

In this way, the drain current IN1 of the NMOS transistor TN1 has a waveform whose rising and falling edges are dull based on the H-level transmission signal TX as shown in FIG. The drain current IN3 of TN3 has a differential waveform that complements the rising and falling portions of the drain current IN1. Therefore, the transmission current Idr flowing through the light emitting diode 15 is
Since v is a combination of the drain currents IN1 and IN3, its rise and fall sharply change. Therefore, in the present embodiment, the waveform shaping circuit 31
This prevents the edge of the transmission current Idrv from becoming dull, and allows the light emitting diode 15 to emit light accurately. Therefore, erroneous detection in the receiving circuit of the partner station can be prevented.

The embodiment of the present invention may be modified as follows. In the second embodiment, the voltage holding circuit 22
The capacitor C is charged based on the voltage signal VA, and the charged voltage is set to the holding voltage VM. However, the capacitor C may be replaced with a latch circuit or the like.

In the fifth embodiment, the transmission circuit 1
0b light emitting diode 15 and its diode 1
The waveform shaping circuit 31 for shaping the waveform of the transmission current Idrv supplied to the transmission circuit 5 is provided. However, the waveform shaping circuit 31 is not limited to the transmission circuit 10b, and may be used for light emitting elements such as light emitting diodes used in other circuits. May be provided.

In each of the above embodiments, the photodiode 11 is used. However, the photodiode 11 may be replaced with another light receiving element. In the above embodiments, the light emitting diode 15 is used. However, the light emitting diode 15 may be replaced with another light emitting element, for example, a semiconductor laser.

In each of the above embodiments, the voltage holding circuit 2
In 2, the peak voltage of the voltage signal VA at the time of reception is held as the holding voltage VM, but the peak voltage may be held instead of holding information other than the voltage. In the above embodiments, the transmission current control circuit 23 outputs the adjustment signal SG5 that maximizes the amplification degree of the current driver circuit 14 for the time t1 from the rise of the transmission signal TX. The timing at which the adjustment signal SG5 for maximizing the amplification degree is output is not limited to this. In addition, the current driver circuit 14 only for the time t1.
May be output as an adjustment signal SG5 that sets the amplification degree of the control signal to a predetermined fixed value.

[0081]

As described in detail above, according to the present invention,
It is possible to provide an optical communication device capable of reliably and automatically adjusting a transmission output level while speeding up a processing operation, and a waveform shaping circuit suitable for the device.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a schematic configuration diagram of an optical communication device according to the first embodiment.

FIG. 3 is a waveform chart showing an operation of the optical communication device according to the first embodiment.

FIG. 4 is a circuit diagram of a voltage holding circuit according to a second embodiment.

FIG. 5 is a waveform chart showing an operation of the voltage holding circuit according to the second embodiment.

FIG. 6 is a waveform chart showing an operation of the transmission current control circuit according to the third embodiment.

FIG. 7 is a circuit diagram of a receiving circuit according to a fourth embodiment.

FIG. 8 is an explanatory diagram for explaining an equivalent circuit and characteristics of a light emitting diode.

9A and 9B are a circuit diagram of a waveform shaping circuit according to a fifth embodiment and a waveform diagram showing an operation thereof.

FIG. 10 is a schematic configuration diagram of a conventional optical communication device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Receiving circuit 2 Light receiving means 3 Amplifier 4 Comparator 5 Transmitting circuit 6 Light emitting means 7 Current driver circuit 8 Voltage holding circuit 9 Transmission current control circuit I1 Receiving current I2 Sending current RX Receiving signal TX Sending signal V1 Voltage signal V2 As holding information Holding voltage VTH threshold

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H04B 10/26 H04B 9/00 S 10/14 10/04 10/06 F term (reference) 5F041 AA02 AA24 BB08 FF14 5F088 BA02 BB01 KA02 KA03 KA06 LA01 5K002 AA05 BA14 CA09 FA03 5K011 BA10 EA03 FA07 KA03 KA13 5K046 AA07 BA06 BA07 BB05 CC11 DD01 DD20

Claims (10)

[Claims] 1. A light receiving means, an amplifier for converting a reception current generated by the light receiving means into a voltage signal, a voltage signal of the amplifier is binarized based on a threshold value, and the binary signal is converted to a reception signal. A receiving circuit composed of a comparator that outputs to an internal circuit, a light emitting unit, and a binary signal output from the internal circuit are input as a transmission signal, and the transmission signal is converted into a current signal and amplified. And a current driver circuit for supplying the amplified current as a transmission current to the light emitting means. A voltage holding circuit, and based on the held information held by the voltage holding circuit,
An optical communication device comprising: a transmission current control circuit that controls an amplification degree of a current driver circuit in the transmission circuit. 2. The optical communication device according to claim 1, wherein the transmission current control circuit sets the amplification degree of the current driver circuit in a part of the transmission current to a maximum value regardless of information held in the voltage holding circuit. Alternatively, the optical communication device is characterized in that the transmission current level is a maximum value or a fixed value. 3. The optical communication device according to claim 1, wherein the voltage holding circuit charges a capacity based on the voltage signal, and outputs the charging voltage to the transmission current control circuit as holding information. An optical communication device, comprising: 4. The optical communication device according to claim 3, wherein the voltage holding circuit starts charging a capacitor by the voltage signal based on a reception signal output from a comparator. Optical communication device. 5. The optical communication device according to claim 4, wherein the voltage holding circuit comprises: a first switch circuit for supplying a charge to the capacitor based on a voltage signal of the amplifier when conducting; A second switch circuit for discharging a charge of a capacitor; and a first switch circuit based on a reception signal output from the comparator.
The second switch circuit is turned on, the second switch circuit is turned on, and after a lapse of a predetermined time, the first switch circuit is turned on, the second switch circuit is kept off, and the reception signal An optical communication device, comprising: a switch control circuit that prohibits the operation of the switch control circuit based on a transmission signal output from the internal circuit; . 6. The optical communication device according to claim 1, wherein the transmission current control circuit gradually controls the amplification degree of the current driver circuit when switching between control and non-control. Optical communication device. 7. The optical communication device according to claim 1, wherein a switch is provided immediately after an output terminal of the amplifier in the receiving circuit, so that a voltage signal output from the amplifier during transmission is not output to a subsequent circuit. An optical communication device, comprising: 8. The optical communication device according to claim 1, wherein the amount of the transmission current supplied to the light emitting means is controlled so as to sharpen the rising and falling edges thereof, and the transmission current waveform is shaped. An optical communication device comprising a waveform shaping circuit. 9. The optical communication device according to claim 8, wherein the waveform shaping circuit converts a transmission signal output from the internal circuit into a differential waveform signal, and a differential waveform signal of the differential circuit. An optical communication device, comprising: a complementary current generation circuit that generates a complementary current that complements the rising and falling currents of the transmission current supplied to the light emitting unit based on the current. 10. A pulse signal is converted and amplified into a current signal, the amplified current is supplied to a light emitting means, and the amount of the current supplied to the light emitting means is increased in order to sharpen rising and falling edges of the current supplied to the light emitting means. And a waveform shaping circuit for shaping the current waveform. A differentiation circuit for converting the pulse signal into a differentiated waveform signal, and a current supplied to the light emitting means based on the differentiated waveform signal of the differentiation circuit. And a complementary current generating circuit for generating a complementary current that complements the current at the time of rising and falling of the waveform.