JP2006148340A - Power line carrier communication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power line carrier communication apparatus capable of reducing spurious radiation from power lines without the need for using a high-order low pass filter. <P>SOLUTION: The power line carrier communication apparatus includes: a modulation-demodulation circuit 2 for outputting a differential output signal for expressing transmission data in terms of a differential signal; a feedback amplifier section 3 for differentially amplifying the differential output signal outputted from the modulation-demodulation circuit 2; a buffer unit 4 for outputting a communication signal for communication purpose in response to the signal amplified by the feedback amplifier section 3; and a coupling unit 5 for transmitting the communication signal outputted from the buffer unit 4 to another power line carrier communication apparatus via conductor lines LN1, LN2, and the feedback amplifier section 3 includes a resistor R4 for feeding back the communication signal outputted from the buffer unit 4 to the input of the feedback amplifier section 3 and carries out feedback amplification to provide a signal level in response to the differential output signal of the modulation-demodulation circuit 2 to the communication signal on the basis of a feedback amount by the resistor R4. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power line carrier communication apparatus that performs power line carrier communication.

  In a power line carrier communication device that performs power line communication, a transmission signal output from a modulation circuit that modulates transmission data to be transmitted is generated inside the modulation circuit in addition to the normal noise component due to harmonic distortion of the signal component. Common mode noise component is included. If this signal is amplified as it is, superimposed on the power line and transmitted, unnecessary radiation from the power line increases, and the regulation value stipulated in Article 44 of the Radio Law Construction Rules may not be satisfied. In order to improve this problem, the order of the low-pass filter is changed according to the transmission power, and the characteristics of the low-pass filter are optimized to reduce normal mode noise and common mode noise, thereby reducing unnecessary radiation. The technique which performs is known (for example, refer patent document 1).

  FIG. 6 is a block diagram showing another configuration of the power line carrier communication apparatus according to the background art. The power line carrier communication apparatus 101 shown in FIG. 6 includes a modulation / demodulation circuit 102, a transmission amplifier 103, a coupling unit 104, and a reception filter 116. The modem circuit 102 outputs a modulated signal representing transmission data to the transmission amplifier 103 as a differential signal. The transmission amplifier 103 amplifies the modulated signal from the modulation / demodulation circuit 102 and outputs the amplified signal to the coupling unit 104 as a differential signal. The differential signal output from the transmission amplifier 103 is applied to both ends of the secondary winding 106 of the transformer 105 in the reception filter 116 and the transformer 105, and the voltage between both ends generated in the primary winding 107 of the transformer 105 is the capacitor 108. Are output to the power lines 109 and 110 via the.

  For example, the transmission amplifier 103 is integrated to reduce the circuit size, and the withstand voltage value at the signal output terminal of the transmission amplifier 103 is lower than that of the discrete component. On the other hand, for example, a noise voltage of about several tens of volts is output from the electric equipment to the power lines 109 and 110. Therefore, the power line carrier communication apparatus 101 controls the transmission amplifier 103 from the voltage such as noise received from the power lines 109 and 110. In order to protect the transmission amplifier 103, a Zener diode 111 as a voltage amplitude limiting element is provided in the primary winding 107 of the transformer 105, or the output terminal portion of the transmission amplifier 103 is voltage clamped by the diodes 112, 113, 114, and 115. For example, the voltage applied to the output terminal portion is limited.

7 and 8 are explanatory diagrams for explaining the operation of the power line carrier communication apparatus 101. FIG. FIG. 7A shows an example of a noise waveform. For example, the frequency is 10 kHz and the amplitude is ± 5V. FIG. 7B is an example of a power line carrier communication signal, and shows an example in which the frequency is 100 kHz and the amplitude is ± 1 V, for example. Such a power line carrier communication signal has a signal waveform superimposed on a noise signal on the power lines 109 and 110.
JP 2004-56275 A

  By the way, as described above, when normal mode noise and common mode noise are reduced by changing the order of the low-pass filter according to the transmission power, the order of the low-pass filter is detected by detecting the transmission power. The circuit scale increases because the number of control circuits to be changed and the number of filter circuit elements required to increase the order of the low-pass filter increases, making it difficult to reduce the cost and size of the power line carrier communication device. There was the inconvenience of becoming.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a power line carrier communication device that can reduce unnecessary radiation from a power line without using a high-order low-pass filter. And

  In order to achieve the above object, a power line carrier communication apparatus according to the present invention represents transmission data as a differential signal in a power line carrier communication apparatus that performs communication using a conductor line shared for power supply and communication. A data output unit that outputs a differential output signal; a feedback amplification unit that differentially amplifies the differential output signal output from the data output unit; and a communication amplifier configured to perform communication according to the signal amplified by the feedback amplification unit. A buffer unit that outputs a communication signal; and a coupling unit that transmits the communication signal output by the buffer unit to another power line carrier communication device via the conductor line, the feedback amplification unit including the buffer A first feedback resistor that feeds back the communication signal output by the feedback amplifier to the input of the feedback amplification unit, and the communication signal is responsive to the differential output signal based on a feedback amount by the first feedback resistor. It is characterized by performing feedback amplification in order to the signal level.

  In the above power line carrier communication apparatus, the feedback amplification unit amplifies the differential output signal and outputs the amplified differential output signal to the buffer unit as a single-ended signal.

  In the above power line carrier communication device, the coupling unit further receives a communication signal transmitted from another power line carrier communication device connected to the conductor line, and the other power line carrier communication device. A receiving unit that receives the communication signal transmitted from the coupling unit, and a first control unit that causes the buffer unit to enter a high impedance state when the communication signal is received by the receiving unit. Furthermore, it is characterized by providing.

  Further, in the above power line carrier communication device, the feedback amplification unit feeds back the signal amplified by the feedback amplification unit to the input of the feedback amplification unit, and has a second resistance value larger than that of the first feedback resistor. A feedback resistor is further provided, and the feedback amplification is performed based on a feedback amount by the first and second feedback resistors.

  In the above power line carrier communication device, the feedback amplification unit may supply a differential amplifier and one phase of the differential output signal output by the data output unit to the inverting input terminal of the differential amplifier. A second resistor having a resistance value equal to that of the first resistor, a non-inverting input terminal of the differential amplifier, and a non-inverting input terminal of the differential amplifier. A third resistor that supplies a predetermined reference voltage set in advance to the inverting input terminal, and a combined resistance value of the first and second feedback resistors is equal to a resistance value of the third resistor It is characterized by.

  And in the above-mentioned power line carrier communication device, the coupling part is provided between a signal output part in the buffer part and the conductor wire, and between the signal output part in the buffer part and the ground. And a high-pass filter including an interposed inductor.

  Further, in the above power line carrier communication device, the coupling unit includes a capacitor, a first secondary winding is connected between the signal output unit in the buffer unit and the ground, and one end of the primary winding is the capacitor. And a transformer connected to one phase side of the power source in the conductor line and the other end connected to the other phase side of the power source in the conductor line. Yes.

  In the power line carrier communication device described above, the switch is opened when the communication signal is received by the switch interposed between the first secondary winding and the ground and the receiving unit. And a second control unit, wherein the reception unit receives a voltage across the first secondary winding of the transformer as a differential signal indicating the communication signal.

  Furthermore, in the above-described power line carrier communication device, the transformer includes a second secondary winding in addition to the primary winding and the first secondary winding, and the receiving unit includes a second winding in the transformer. The voltage across the secondary winding is received as a differential signal indicating the communication signal.

  In the power line carrier communication device having such a configuration, the data output unit outputs a differential output signal representing transmission data as a differential signal, and the feedback output unit outputs the differential output signal from the data output unit as a differential signal. A communication signal for communication is output in accordance with the signal amplified and amplified by the feedback amplification unit by the buffer unit, and the communication signal output from the buffer unit by the coupling unit is transmitted to another power line carrier communication device via the conductor line. Sent. Then, the communication signal output from the buffer unit by the first feedback resistor is fed back to the input of the feedback amplification unit, and the communication signal is changed according to the differential output signal by the feedback amplification unit based on the feedback amount by the first feedback resistor. Therefore, the common mode noise component in the communication signal is reduced, and unnecessary radiation from the power line can be reduced without using a high-order low-pass filter.

  Embodiments according to the present invention will be described below with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted.

  FIG. 1 is a circuit diagram illustrating an example of a configuration of a power line carrier communication apparatus according to an embodiment of the present invention. The power line carrier communication apparatus 1 shown in FIG. 1 performs power line carrier communication with other power line carrier communication apparatuses connected to the conductor lines LN1 and LN2, using the conductor lines LN1 and LN2 that supply the commercial power supply AC. It is a power line carrier communication device, and includes a modulation / demodulation circuit 2, a feedback amplification unit 3, a buffer unit 4, a coupling unit 5, and a reception filter circuit 6.

  The modulation / demodulation circuit 2 is a modulation / demodulation circuit configured using, for example, an ASIC (Application Specific Integrated Circuit) that modulates and demodulates a communication signal of power line carrier communication. For example, the modulation / demodulation circuit 2 modulates transmission data received from outside and transmits a differential signal. Function as an example of a data output unit (not shown) that converts the differential output signals Tx + and Tx− and outputs the differential output signals to the feedback amplification unit 3, or receives and demodulates the signal output from the reception filter circuit 6. First, it functions as an example of a receiving unit (not shown) that outputs received data obtained in the outside, or when the signal Rx output from the receiving filter circuit 6 is received, the buffer unit 4 is set to a high impedance state. Function as an example of the control unit (not shown).

  The feedback amplification unit 3 is a feedback amplification circuit that differentially amplifies the differential output signals Tx + and Tx− output from the modulation / demodulation circuit 2 and outputs the differential output signals Tx + and Tx− to the buffer unit 4 as a single-ended signal, for example, capacitors C1, C2, Resistor R1 (first resistor), resistor R2 (second resistor), resistor R3 (third resistor), resistor R4 (first feedback resistor), resistor R5 (second feedback resistor), and differential An amplifier 31 is provided.

  The buffer unit 4 is a signal driving circuit that amplifies the signal amplified by the feedback amplification unit 3 and outputs a communication signal for power line carrier communication. For example, the transistors Tr1, Tr2, Tr3, Tr4, resistors R6, R7, R8 , R9 and switches S1, S2. The transistors Tr1, Tr2, Tr3, Tr4 are, for example, numbers output to the conductor lines LN1, LN2 from electrical devices connected to the conductor lines LN1, LN2, for example, home appliances such as IH cooking appliances, air conditioners, microwave ovens, and vacuum cleaners. A bipolar transistor having a withstand voltage exceeding a noise voltage of about 10 V, for example, a voltage rating of 100 V or more is used. The buffer unit 4 is composed of discrete components so as to make it easy to use, for example, high voltage transistors Tr1, Tr2, Tr3, Tr4, and withstand voltage of, for example, 100 V or more with respect to the output voltage from the coupling unit 5 Have a value.

  Further, for example, the transistors Tr1 and Tr4 are PNP transistors, and the transistors Tr2 and Tr3 are NPN transistors. The pair of the transistor Tr1 and the transistor Tr2 and the pair of the transistor Tr3 and the transistor Tr4 are electrically opposite in polarity. Transistors that are commercially available as so-called complementary products with uniform characteristics are used. The switches S1 and S2 are configured by transistors such as FET (Field Effect Transistor), analog switches, relays, and the like.

  The buffer unit 4 uses a complementary two-stage directly connected emitter follower. However, any buffer circuit having another configuration may be used as long as the output impedance can be maintained in a high impedance state in the reception state according to the control signal Ts. It may be used.

  The coupling unit 5 receives the communication signal output from the buffer unit 4 via the capacitor C3 that removes the DC component, and transmits the high-frequency component to other power line carrier communication devices via the conductor lines LN1 and LN2. And includes an inductor L1, a capacitor C4, and external connection terminals 51 and 52. The conductor lines LN1 and LN2 are connected to the external connection terminals 51 and 52, respectively.

  The reception filter circuit 6 shapes the reception signal received by the coupling unit 5 from other power line carrier communication devices connected to the conductor lines LN1 and LN2, or removes noise and outputs the signal to the modulation / demodulation circuit 2, for example, a passive element It is a filter circuit comprised by these.

  In the feedback amplifier 3, the output terminal of the differential output signal Tx + in the modulation / demodulation circuit 2 is connected to the inverting input terminal of the differential amplifier 31 via the capacitor C1 and the resistor R1 connected in series. The output terminal of the differential output signal Tx− in the circuit 2 is connected to the non-inverting input terminal of the differential amplifier 31 via a capacitor C2 and a resistor R2 connected in series. The output terminal of the differential amplifier 31 is connected to the inverting input terminal of the differential amplifier 31 via the resistor R5, and the non-inverting input terminal of the differential amplifier 31 is set to a predetermined constant via the resistor R3. The reference voltage Vref is supplied. The reference voltage Vref is set to be a target output voltage of the feedback amplification unit 3 when the power line carrier communication device 1 does not transmit, for example.

  The buffer unit 4 includes a series circuit of a switch S1, a resistor R6, and a transistor Tr1, and a series circuit of a transistor Tr2, a resistor R7, and a switch S2 between the power supply E for operation in the power line carrier communication device 1 and the ground. Are connected in parallel to a series circuit of a transistor Tr3, a resistor R8, a resistor R9, and a transistor Tr4, a connection point between the resistor R6 and the transistor Tr1 is connected to a base of the transistor Tr3, and a connection between the transistor Tr2 and the resistor R7. The point is connected to the base of the transistor Tr4, and the bases of the transistors Tr1 and Tr2 and the output terminal of the differential amplifier 31 are connected to form a complementary two-stage directly connected emitter follower circuit. The switches S1 and S2 are turned on and off according to the control signal Ts from the modem circuit 2.

  Further, the connection point between the resistor R8 and the resistor R9 is the output unit of the buffer unit 4, and is connected to the inverting input terminal of the differential amplifier 31 via the resistor R4 and externally connected via the capacitors C3 and C4. It is connected to the terminal 51. The external connection terminal 52 is connected to the ground, the inductor L1 is connected between the connection point of the capacitors C4 and C3 and the ground, and the connection point of the capacitors C4 and C3 is connected to the signal input terminal of the reception filter circuit 6. The signal output terminal of the reception filter circuit 6 is connected to the modem circuit 2.

  Next, the operation of the power line carrier communication apparatus 1 configured as described above will be described. First, the transmission operation of the power line carrier communication apparatus 1 will be described. First, the switches S1 and S2 are turned on by the control signal Ts from the modulation / demodulation circuit 2, and the buffer unit 4 is activated. Then, after elapse of a certain time until the operation of the buffer unit 4 becomes stable, for example, the signal delay time of the emitter follower circuit in the buffer unit 4, transmission data received from the outside is modulated by the modem circuit 2. At the same time, the differential output signals Tx + and Tx− are output to the capacitors C1 and C2, respectively.

  Then, the DC voltage component is removed from the differential output signal Tx + by the capacitor C1, so that only the high frequency component used for power line carrier communication is output to the inverting input terminal of the differential amplifier 31 via the resistor R1. By removing the DC voltage component from the dynamic output signal Tx− by the capacitor C2, only the high frequency component used for power line carrier communication is output to the non-inverting input terminal of the differential amplifier 31 via the resistor R2.

  Then, the signal voltage between the inverting input terminal and the non-inverting input terminal is differentially amplified by the differential amplifier 31 and converted into a single-ended signal and output to the bases of the transistors Tr1 and Tr2, and the difference is made by the resistor R4. Feedback is made to the inverting input terminal of the dynamic amplifier 31. Next, in the buffer unit 4, the switches S 1 and S 2 are turned on by the control signal Ts from the modulation / demodulation circuit 2, so that the buffer unit 4 is in an active state and corresponds to the output signal from the differential amplifier 31. A voltage appears at the emitters of the transistors Tr1 and Tr2, respectively.

  Since the emitters of the transistors Tr1 and Tr2 are connected to the bases of the transistors Tr3 and Tr4 and have a two-stage direct-coupled emitter follower configuration, the emitters of the transistors Tr3 and Tr4 have the same base voltage as the transistors Tr1 and Tr2. Are respectively output. The voltage between the emitter of the transistor Tr3 and the emitter of the transistor Tr4 is divided by resistors R8 and R9, and the divided voltage is used as an output voltage of the buffer unit 4, that is, a capacitor as a power line carrier communication signal (communication signal). It is output to C3 and fed back to the inverting input terminal of the differential amplifier 31 through the resistor R4. In this case, the output signal from the differential amplifier 31 is amplified by the buffer unit 4, and the pair of transistors Tr1 and Tr2 and the pair of transistors Tr3 and Tr4 have complementary electrical characteristics. Therefore, distortion of the power line carrier communication signal due to variations in transistor characteristics is suppressed.

  Further, when the buffer unit 4 is in an active state, the transistors Tr3 and Tr4 operate in the non-saturation region in accordance with the output signal from the differential amplifier 31, so that neither of them is completely turned off. An idling current flows from the power supply E to the ground through the transistor Tr3, the resistors R8 and R9, and the transistor Tr4. The resistors R8 and R9 are resistors that limit the idling current. For example, a resistor of about 1 to 10Ω is used to suppress the idling current while suppressing the influence on the output impedance.

  On the other hand, the power line carrier communication signal from the buffer unit 4 is fed back to the inverting input terminal of the differential amplifier 31 via the resistor R4, and the feedback amplifier unit 3 converts the power line carrier communication signal according to the differential output signals Tx + and Tx−. Since feedback control is performed so as to obtain a high voltage, distortion of the power line carrier communication signal is further reduced.

  Next, the power line carrier communication signal output from the buffer unit 4 is output to the conductor line LN1 via the capacitors C3 and C4 and the external connection terminal 51, and is superimposed between the conductor lines LN1 and LN2 to be superimposed on the conductor lines LN1, LN1. It is transmitted to another power line carrier communication device connected to LN2. In this case, an effective signal frequency component in the power line carrier communication signal output from the buffer unit 4 is extracted by the high-pass filter configured by the capacitor C3 and the inductor L1, and thus is superimposed between the conductor lines LN1 and LN2. The S / N ratio (signal to noise ratio) of the signal can be improved. Further, since the capacitor C4 has an impedance that increases with respect to the commercial power supply frequency and decreases with respect to the frequency of the power line carrier communication signal, the power line carrier communication signal is superimposed between the conductor lines LN1 and LN2. However, the application of the commercial power supply voltage between the conductor lines LN1 and LN2 to the buffer unit 4 is suppressed.

  Since various load devices are connected to the conductor lines LN1 and LN2, the impedances of the conductor lines LN1 and LN2 change according to the connection state of the load devices. However, since the impedances of the conductor lines LN1 and LN2 viewed from the buffer unit 4 are combined impedances with the inductor L1, fluctuations in the impedances of the conductor lines LN1 and LN2 caused by changes in the connection state of the load device are reduced by the inductor L1. It is possible to stabilize the communication state of the power line carrier communication.

  Furthermore, even when the impedance of the conductor lines LN1 and LN2 varies due to a change in the connection state of the load device, the power line carrier communication signal output from the buffer unit 4 is inverted by the differential amplifier 31 via the resistor R4. Since feedback control is performed to feed back the power line carrier communication signal to the voltage corresponding to the differential output signals Tx + and Tx− by the feedback amplifier 3 by feedback to the input terminal, regardless of the fluctuation of the impedance of the conductor lines LN1 and LN2. As a result of the voltages corresponding to the differential output signals Tx +, Tx− being output to the conductor lines LN1, LN2, the apparent output impedance of the power line carrier communication device 1 viewed from the conductor lines LN1, LN2 can be reduced.

  Further, since the buffer unit 4 has a withstand voltage value of, for example, 100 V or more, the buffer unit 4 is destroyed by a noise voltage output to the conductor lines LN1 and LN2 from the electrical equipment connected to the conductor lines LN1 and LN2. Therefore, it is not necessary to separately provide a protection circuit for protecting the buffer unit 4 from destruction due to overvoltage.

  For example, in the power line carrier communication apparatus according to the background art shown in FIG. 6, assuming that the amplitude limiting voltage by a voltage amplitude limiting element or the like provided to protect the transmission amplifier 103 from an overvoltage due to noise is ± 2 V, for example, FIG. The power line carrier communication signal superimposed on the noise waveform shown in a) becomes a signal waveform shown in FIG. 8A as a result of being clamped at ± 2V. Further, the signal waveform shown in FIG. 8A is a signal received by the modem circuit 102 when the commercial power supply frequency is removed from the power lines 109 and 110 by the coupling unit 104 and the noise frequency is further removed by the reception filter 116. As shown in FIG. 8B, the waveform of FIG. 7B, which is the original power line carrier communication signal waveform, becomes a missing signal waveform as shown in FIG. There was an inconvenience that communication could not be performed normally.

  On the other hand, in the power line carrier communication apparatus 1 shown in FIG. 1, since it is not necessary to provide a protection circuit with a voltage amplitude limiting element or the like, the power line carrier communication signal waveform is lost due to voltage clamping with a protection circuit such as a voltage amplitude limiting element or a diode clamp. Therefore, the stability of power line carrier communication can be improved. When it is necessary to protect the buffer unit 4 from lightning surge or the like, a circuit is formed using a voltage amplitude limiting element having a high voltage limiting voltage that does not operate with a voltage output from an electric device such as a home appliance. You may make it protect.

  Further, in the power line carrier communication apparatus 1 shown in FIG. 1, the output signal modulated by the modulation / demodulation circuit 2 is converted into differential output signals Tx +, Tx− and differentially amplified by the feedback amplification unit 3. Common mode noise components generated inside are reduced, and unnecessary radiation from the power line can be reduced without using a high-order low-pass filter. Further, the feedback amplifier 3 amplifies the differential output signals Tx + and Tx− output from the modulation / demodulation circuit 2 as a single-ended signal and outputs the amplified signal to the buffer unit 4. Compared to the case where Tx + and Tx− are amplified with the differential signals and the differential positive and negative signals are amplified by the buffer unit 4, the number of signals amplified by the buffer unit 4 is 1 / Since the circuit of the buffer unit 4 can be simplified, the power line carrier communication apparatus 1 can be downsized and the cost can be reduced.

  Further, since feedback control is performed by the feedback amplifier 3 so that the power line carrier communication signal output from the buffer unit 4 becomes a voltage corresponding to the differential output signals Tx + and Tx−, distortion of the power line carrier communication signal is reduced. can do.

  Next, the operation of the resistor R5 that feeds back the output signal of the differential amplifier 31 to the inverting input terminal of the differential amplifier 31 will be described. First, in a state before the power line carrier communication apparatus 1 starts a transmission operation, the switches S1 and S2 are turned off. Then, if there is no resistor R5, the feedback path from the output terminal of the differential amplifier 31 to the inverting input terminal of the differential amplifier 31 via the buffer unit 4 and the resistor R4 by turning off the switches S1 and S2 Becomes an open state, and the output voltage of the differential amplifier 31 rises to a maximum value, for example, near the power supply voltage for operation supplied to the differential amplifier 31. When the switches S1 and S2 are turned on by the control signal Ts from the modulation / demodulation circuit 2 to start the transmission operation in this state, the output voltage of the differential amplifier 31, that is, the base voltage of the transistors Tr1 and Tr2 has already reached the maximum value. Since it is in the raised state, a signal corresponding to the maximum output voltage from the differential amplifier 31 is passed from the buffer unit 4 via the capacitor C3 and the coupling unit 5 in a transient state until feedback control by the resistor R4 is performed. The noise is output between the conductor lines LN1 and LN2.

  On the other hand, in the power line carrier communication apparatus 1 shown in FIG. 1, since the resistor R5 that feeds back the output signal of the differential amplifier 31 to the inverting input terminal of the differential amplifier 31 is provided, the switches S1 and S2 are turned off. Even in the state, as a result of the feedback by the resistor R5, the output voltage of the differential amplifier 31 is maintained at the reference voltage Vref, and even when the switches S1 and S2 are turned on to start the transmission operation, the differential amplifier 31 Is prevented from being output between the conductor lines LN1 and LN2.

  Further, during the transmission operation, feedback control is performed in the feedback amplification unit 3 by a route passing through the resistor R4 and a route passing through the resistor R5, but the route through the resistor R5 that does not feed back the output signal of the buffer unit 4 is controlled. When the feedback amount is larger than the feedback amount of the path passing through the resistor R4, the effect of reducing distortion of the output signal from the buffer unit 4 is diminished. Therefore, the resistor R4 is set to a lower resistance than the resistor R5, and the output from the buffer unit 4 is set so that the feedback amount of the path via the resistor R4 is larger than the feedback amount of the path via the resistor R5. It is intended to reduce signal distortion.

The resistance values of the resistors R1, R2, R3, R4, and R5 are set such that the resistance values of the resistors R1 and R2 are equal to, for example, the resistance value Ra, and the combined resistance value of the resistors R4 and R5 and the resistance value of the resistor R3 are, for example, It is desirable that the resistance values Rb be equal. In this case, when the output voltage of the feedback amplifier 3 is Vout and the differential input voltage is Vin, the relationship of the following equation (1) is established.
Vout = Rb × Vin / Ra (1)
Then, for example, if the resistance value Ra is 10 kΩ and the resistance value of the resistor R4 is 11 kΩ, the resistance value of the resistor R5 is 120 kΩ, and the output voltage Vout of the feedback amplifier 3 can be calculated based on the equation (1). Therefore, the output voltage Vout of the feedback amplifier 3 can be calculated using a simple calculation formula, and the design of the feedback amplifier 3 can be facilitated.

  Next, the receiving operation of the power line carrier communication apparatus 1 will be described. First, the switches S1 and S2 are turned off by the control signal Ts from the modulation / demodulation circuit 2, and the output impedance of the buffer unit 4 is set to a high impedance state. Then, the impedance of the buffer unit 4 viewed from the external connection terminals 51 and 52 side is increased as compared with the time of transmission operation, and the power line carrier communication signal transmitted from the other power line carrier communication device 1 via the conductor lines LN1 and LN2 is increased. For example, it is several kΩ or more with respect to the frequency.

  Then, the power line carrier communication signal transmitted from the other power line carrier communication device 1 while being superimposed on the commercial power source voltage is received by the external connection terminals 51 and 52 via the conductor lines LN1 and LN2, and the commercial power source is supplied by the coupling unit 5. The frequency is removed and output to the reception filter circuit 6. At this time, since the impedance of the buffer unit 4 is increased as compared with that during the transmission operation, the power line carrier communication signal is suppressed from being attenuated by the influence of the impedance of the buffer unit 4. Further, the power line carrier communication signal received by the reception filter circuit 6 is subjected to noise removal and waveform shaping, and is output to the modulation / demodulation circuit 2 as a reception signal Rx, demodulated by the modulation / demodulation circuit 2 and output to the outside as reception data. .

  As a result, when the modulation / demodulation circuit 2 performs a reception operation, the modulation / demodulation circuit 2 puts the buffer unit 4 into a high impedance state, thereby suppressing the attenuation of the power line carrier communication signal due to the influence of the impedance of the buffer unit 4. it can.

  As shown in FIG. 2, in the modulation / demodulation circuit 2a, the reception circuit for the reception signal Rx is configured to receive the differential signals Rx + and Rx−, and the reception terminal for the differential signal Rx + is connected to the reception filter circuit 6. The receiving terminal for the differential signal Rx− may be connected to the ground via the capacitor C5.

  Further, as in the power line carrier communication device 1a shown in FIG. 3, for example, a transformer T1 is used in place of the inductor L1 in the coupling unit 5 shown in FIG. One end of the secondary winding 1) is connected to the output portion of the buffer unit 4 through the capacitor C3, that is, the connection point of the resistors R8 and R9, the other end of the secondary winding N2 is connected to the ground, and the transformer T1 One end of the primary winding N1 may be connected to the external connection terminal 51 via the capacitor C4, and the other end of the primary winding N1 may be connected to the external connection terminal 52 to form a high-pass filter.

  In this case, the conductor lines LN1 and LN2 connected to the commercial power supply AC and the internal circuit in the power line carrier communication device 1 can be insulated by the coupling portion 5a. For example, when installing the power line carrier communication device 1 indoors The safety against electric shock is improved when an operator touches an internal circuit of the power line carrier communication device 1, such as the modulation / demodulation circuit 2, the feedback amplification unit 3, the buffer unit 4, and the reception filter circuit 6 during maintenance, adjustment, etc. be able to.

  For example, as shown in FIG. 4, the other end of the secondary winding N2 in the transformer T1 is connected to the ground via the switch S3. The switch S3 is connected to the modulation / demodulation circuit 2a which is an example of the second control unit. The reception filter circuit 6a is configured to be turned off at the time of transmission operation by the control signal Ts and to be turned off at the time of reception operation. The reception filter circuit 6a uses a differential signal indicating a power line carrier communication signal as a voltage across the secondary winding N2 in the transformer T1. As a differential signal Rx +, Rx− may be output to the modulation / demodulation circuit 2a. As the switch S3, a switch that is bidirectional and has a low impedance with respect to the output current from the buffer unit 4, such as an FET, an analog switch, and a relay switch, can be used.

  As a result, the switch S3 is turned off during the reception operation, whereby the voltage across the secondary winding N2 in the transformer T1 can be output to the reception filter circuit 6a as a differential signal indicating the power line carrier communication signal. Since the differential signal Rx +, Rx− can be output to the modulation / demodulation circuit 2a by filtering the differential signal in 6a, the signal inside the power line carrier communication device 1 from the external connection terminals 51, 52 to the modulation / demodulation circuit 2a The influence of common mode noise on the path can be reduced, and the S / N ratio of the differential signals Rx + and Rx− received by the modem circuit 2a can be improved.

  Further, for example, as shown in FIG. 5, a switch S3 using a transformer T1a having a secondary winding N2 and a secondary winding N3 (second secondary winding) instead of the transformer T1 in FIG. It is good also as a structure which outputs the both-ends voltage of the secondary winding N3 to the reception filter circuit 6a as a differential signal which shows a power line carrier communication signal, without providing.

  As a result, the voltage across the secondary winding N3 in the transformer T1 can be output to the reception filter circuit 6a as a differential signal indicating the power line carrier communication signal, and the reception filter circuit 6a performs a filtering process with the differential signal. Since the differential signals Rx + and Rx− can be output to the modulation / demodulation circuit 2a, the influence of common mode noise on the signal path inside the power line carrier communication device 1 from the external connection terminals 51 and 52 to the modulation / demodulation circuit 2a is reduced. The S / N ratio of the differential signals Rx + and Rx− received by the modem circuit 2a can be improved.

It is a circuit diagram for demonstrating an example of a structure of the power line carrier communication apparatus which concerns on one Embodiment of this invention. It is a circuit diagram for demonstrating the modification of the power line carrier communication apparatus shown in FIG. It is a circuit diagram for demonstrating the modification of the power line carrier communication apparatus shown in FIG. It is a circuit diagram for demonstrating the modification of the power line carrier communication apparatus shown in FIG. It is a circuit diagram for demonstrating the modification of the power line carrier communication apparatus shown in FIG. It is a circuit diagram which shows the power line carrier communication apparatus which concerns on background art. It is a signal waveform diagram for demonstrating operation | movement of the power line carrier communication apparatus shown in FIG. It is a signal waveform diagram for demonstrating operation | movement of the power line carrier communication apparatus shown in FIG.

Explanation of symbols

1, 1a Power line carrier communication device 2, 2a Modulation / demodulation circuit 3 Feedback amplification unit 4 Buffer unit 5, 5a Coupling unit 6, 6a Reception filter circuit 31 Differential amplifier 51, 52 External connection terminals C1, C2, C3, C4, C5 Capacitor L1 Inductor LN1, LN2 Conductor wire N1 Primary winding N2, N3 Secondary winding R1, R2, R3, R4, R5, R6, R7, R8, R9 Resistance S1, S2, S3 Switch T1, T1a Transformer Tr1, Tr2, Tr3, Tr4 transistor

Claims (9)

In a power line carrier communication device that performs communication using a conductor line shared for power supply and communication,
A data output unit that outputs a differential output signal representing transmission data as a differential signal;
A feedback amplifier for differentially amplifying the differential output signal output from the data output unit;
A buffer unit that outputs the communication signal for communication according to the signal amplified by the feedback amplification unit;
A coupling unit that transmits the communication signal output by the buffer unit to another power line carrier communication device via the conductor line;
With
The feedback amplification unit includes a first feedback resistor that feeds back the communication signal output from the buffer unit to the input of the feedback amplification unit, and the communication signal is transmitted based on a feedback amount by the first feedback resistor. A power line carrier communication apparatus, wherein feedback amplification is performed to obtain a signal level corresponding to a differential output signal.   2. The power line carrier communication apparatus according to claim 1, wherein the feedback amplification unit amplifies the differential output signal and outputs the amplified signal as a single-ended signal to the buffer unit. The coupling unit further receives a communication signal transmitted from another power line carrier communication device connected to the conductor line,
A receiving unit that receives a communication signal transmitted from the other power line carrier communication device via the coupling unit;
A first control unit that causes the buffer unit to be in a high impedance state when the communication unit receives the communication signal;
The power line carrier communication apparatus according to claim 1, further comprising:   The feedback amplification unit further includes a second feedback resistor having a resistance value larger than that of the first feedback resistor that feeds back the signal amplified by the feedback amplification unit to the input of the feedback amplification unit. 4. The power line carrier communication apparatus according to claim 3, wherein the feedback amplification is performed based on a feedback amount by the second feedback resistor. The feedback amplifier is
A differential amplifier;
A first resistor for supplying one phase of the differential output signal output by the data output unit to the inverting input terminal of the differential amplifier;
A second resistor having a resistance value equal to that of the first resistor, supplying the other one phase of the differential output signal to a non-inverting input terminal of the differential amplifier;
A third resistor for supplying a predetermined reference voltage to the non-inverting input terminal of the differential amplifier;
With
5. The power line carrier communication apparatus according to claim 4, wherein a combined resistance value of the first and second feedback resistors is equal to a resistance value of the third resistor.   The coupling unit includes a capacitor interposed between the signal output unit in the buffer unit and the conductor wire, and an inductor interposed between the signal output unit in the buffer unit and the ground. It is a high pass filter, The power line carrier communication apparatus in any one of Claims 1-5 characterized by the above-mentioned.   In the coupling unit, a capacitor and a first secondary winding are connected between a signal output unit in the buffer unit and a ground, and one end of the primary winding is connected to the power source in the conductor line via the capacitor. 6. A high-pass filter comprising: a transformer connected to the phase side and having the other end connected to the other phase side of the power source in the conductor wire. The power line carrier communication device described. A switch interposed between the first secondary winding and the ground;
A second control unit that opens the switch when the communication unit receives the communication signal;
8. The power line carrier communication device according to claim 7, wherein the receiving unit receives a voltage across the first secondary winding in the transformer as a differential signal indicating the communication signal. 9. The transformer includes a second secondary winding in addition to the primary winding and the first secondary winding,
8. The power line carrier communication device according to claim 7, wherein the receiving unit receives a voltage across the second secondary winding in the transformer as a differential signal indicating the communication signal.

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