JP2011188457A - Transmission-path termination circuit, data receiving device having the same, and image formation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission-path termination circuit capable of obtaining electric power from the signal that comes through a transmission path even when an external device side is not provided with a special mechanism that supplies electric power to the receiving side. <P>SOLUTION: The transmission-path termination circuit 10 is a circuit connected to an end of the transmission path 2 instead of a termination resistor, and the circuit has: an electric-power collecting circuit 11 and an impedance adjusting circuit 12. The electric-power collecting circuit 11 collects electric power from the current which flows in accordance with the signal that comes from the transmission path 2. The impedance adjusting circuit 12 controls the amount of the current that flows to the transmission-path termination circuit 10 so that the impedance viewed from the transmission path 2 side is equal to a predetermined termination resistance value. The electric-power collecting circuit 11 is composed of a diode bridge circuit, a switched capacitor circuit or the like. The impedance adjusting circuit 12 is composed of, for example, a constant-current element such as a MOSFET and a voltage-dividing circuit, which provides a divided voltage of a termination voltage v as a control voltage of the constant-current element. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a transmission line termination circuit connected to the termination of a transmission line, a data receiving apparatus including the transmission line termination circuit, and an image forming apparatus.

  Generally, a termination resistor is connected to the end of the transmission line in order to prevent signal reflection. The electric power consumed by this termination resistor was converted into heat and discarded without being used as energy. In particular, in the case where the voltage is high and the transmission path is composed of a plurality of transmission lines, power consumption at the terminating resistor is remarkable.

  By the way, in the device that monitors the signal coming from the network during the power saving mode and returns to the normal mode, the normal mode is monitored by checking whether the signal addressed to the own device has arrived even in the power saving mode. It is necessary to operate at least a circuit that determines whether or not it is necessary to return to the state. For this reason, normally, the power supply to the circuit is performed from the power supply circuit of its own device even in the power saving mode.

  In addition, as a technology for using power supplied from outside during the power saving mode, for example, when there are network signal lines and power supply lines in the communication connector, the power supplied from the outside through the power supply lines is stepped down. An electronic device that is used as a power source in the power saving mode has been proposed (see, for example, Patent Document 1).

  In addition, as a method of supplying power from the outside through a transmission line, a method of supplying power by superimposing the signal on the same transmission line as a telephone line, or between two transmission lines as in Power over Ether technology A method of supplying power by applying a voltage to the battery is known.

JP 2007-27866 A

  As described above, conventionally, in order to receive power supply from the outside through the transmission line, a mechanism for supplying power to the external device side is necessary. In the case of a communication method without such a mechanism, In the power saving mode, the power supply to the circuit that monitors the return signal must be supplied by the power supply circuit of the device itself.

  The present invention is intended to solve the above problems, and a transmission line that can obtain power from a signal arriving through the transmission line without a special mechanism for supplying power to the receiving side on the external device side. It is an object of the present invention to provide a termination circuit, a data reception device including the termination circuit, and an image forming apparatus.

  The gist of the present invention for achieving the object lies in the inventions of the following items.

[1] A transmission line termination circuit connected to the termination of a transmission line that performs data communication,
A power recovery circuit that recovers power from the flowing current;
An impedance adjustment circuit for controlling the amount of current flowing through the transmission line termination circuit so that the impedance viewed from the transmission line side becomes a predetermined termination resistance value;
A transmission line termination circuit comprising:

  In the above invention, the power recovery circuit recovers the power from the current flowing from the signal arriving from the transmission line, and the impedance adjustment circuit shows the impedance viewed from the transmission line side even if the impedance of the power recovery circuit varies with the power recovery. Is controlled to have a predetermined termination resistance value. In other words, the power recovery circuit recovers the power consumed as heat in the conventional termination resistor while fulfilling the function as the termination resistor.

[2] The impedance adjustment circuit includes:
A voltage detector for detecting a voltage applied to the transmission line termination circuit;
A current detector for detecting a current flowing in the transmission line termination circuit;
A variable resistor connected in series to the power recovery circuit and whose resistance is electronically controlled;
A feedback circuit that controls the resistance value of the variable resistor so that the current value detected by the current detection unit = the voltage value detected by the voltage detection unit ÷ the predetermined termination resistance value;
The transmission line termination circuit according to [1], characterized by comprising:

  In the above invention, the impedance adjustment circuit detects the voltage v applied to the transmission line termination circuit and the current i flowing through the transmission line termination circuit, and recovers power so that the relationship of i = v ÷ termination resistance value is maintained. Controls the resistance value of a variable resistor connected in series with the circuit.

[3] The impedance adjustment circuit includes:
A constant current element that is connected in series with the power recovery circuit and flows a current according to an applied control voltage;
A voltage dividing circuit for providing a divided voltage of a voltage applied to the transmission line termination circuit as a control voltage of the constant current element;
The transmission line termination circuit according to [1], characterized by comprising:

  In the above invention, a constant current element such as a MOSFET is connected in series with the power recovery circuit, and a divided voltage applied to the transmission line termination circuit is given as a control voltage of the constant current element.

[4] A bypass circuit that bypasses the power recovery circuit and flows current when the impedance viewed from the transmission line side cannot be adjusted to a predetermined termination resistance value by the impedance adjustment circuit due to a decrease in the current flowing through the power recovery circuit The transmission line termination circuit according to any one of [1] to [3], characterized by comprising:

  In the above invention, when the amount of power storage increases and the current flowing through the power recovery circuit decreases, even if the impedance of the impedance adjustment circuit is zero, it becomes impossible to pass a current corresponding to the termination resistance value through the transmission line termination circuit. Therefore, when the adjustment range of the impedance adjustment circuit is exceeded, the bypass circuit is operated to bypass the power recovery circuit, and the current is allowed to flow, so that the impedance adjustment circuit can be adjusted and the transmission line viewed from the transmission line side. Control so that the impedance of the termination circuit becomes the termination resistance value.

[5] The bypass circuit includes:
A second variable resistor connected in parallel with the power recovery circuit and whose resistance is controlled electronically;
When the impedance viewed from the transmission line side can be adjusted to a predetermined termination resistance value by the impedance adjustment circuit in a state where the resistance value of the second variable resistor is controlled to be infinite, the second variable resistor is set. A control circuit for controlling the resistance value to be infinite, and when the adjustment cannot be performed in the state, a control circuit for reducing the resistance value of the second variable resistor so that the adjustment is possible;
The transmission line termination circuit according to any one of [1] to [3], characterized by comprising:

  In the above invention, when adjustment is possible with the impedance adjustment circuit, current is prevented from flowing through the bypass circuit to prevent a decrease in power recovery efficiency and only when the adjustment range of the impedance adjustment circuit is exceeded. To control the current to flow.

[6] a fixed resistor having a predetermined termination resistance value;
A switching circuit that switches between a state in which the impedance adjustment circuit and the power recovery circuit are functioned to recover power and a state in which only the fixed resistor is in an impedance viewed from the transmission line side;
The transmission line termination circuit according to any one of [1] to [5], wherein:

  In the above invention, the switching circuit has a state in which the impedance adjustment circuit and the power recovery circuit function to recover power, and a state in which only the fixed resistor is connected to the end of the transmission line without functioning them. Switch. For example, when high-speed response is required, only the fixed resistor is connected, and when priority is given to power recovery over high-speed response, the impedance adjustment circuit and the power recovery circuit function to operate the power. Switch to the state of collecting. In this way, an operation according to the purpose can be performed.

[7] The power recovery circuit includes a circuit in which a capacitor is connected to the output of the diode bridge, or a switched capacitor or a charge pump. The power recovery circuit is any one of [1] to [6] A transmission line termination circuit according to 1.

  In the above invention, the power recovery circuit recovers the electric power by preventing the backflow of the current from the capacitor side to the transmission line side while accumulating the flowing current (charge) in the capacitor.

[8] The power recovery circuit includes a switched capacitor or a charge pump.
Any one of [1] to [6], wherein the pulse signal received from the transmission path is a switching signal for switching between a switched capacitor or a charge pump connected to the transmission path side and a disconnected state. The transmission line termination circuit according to one.

  In the above invention, the pulse signal received from the transmission line is used as a switching signal for switching the switched capacitor or the charge pump between the state where the switched capacitor or the charge pump is connected to the transmission line side and the state where it is disconnected. In addition, charging and discharging can be switched at an appropriate timing.

[9] A receiving circuit that receives a signal through a transmission line;
The transmission line termination circuit according to any one of [1] to [8] connected to the termination of the transmission line;
A storage battery for storing the power recovered by the transmission line termination circuit;
A return determination circuit for determining return from the main power source and the power saving mode based on a received signal from the transmission path;
A power supply control circuit that switches the power supply source from the main power supply to the storage battery when the power saving mode is entered;
A data receiving device comprising:

  In the data receiving apparatus of the above invention, the power recovered by the transmission line termination circuit is supplied as the operating power of the return determination circuit that determines the return from the power saving mode based on the received signal from the transmission line in the power saving mode. To do.

[10] The data receiving device according to [9];
An image forming unit that operates by receiving power supply from the main power source and forms an image based on image data received by the data receiving device on a recording sheet;
An image forming apparatus comprising:

  According to the transmission line termination circuit, the data receiving apparatus and the image forming apparatus including the transmission line termination circuit according to the present invention, the transmission line termination circuit collects power from a signal sent through the transmission line while serving as a termination resistor. Therefore, even if there is no special mechanism for supplying power to the receiving side on the external device side, power can be obtained through the transmission line.

It is a block diagram which shows the basic composition of the transmission line termination circuit which concerns on embodiment of this invention. It is a circuit diagram which shows the electric power recovery circuit comprised by connecting a capacitor | condenser to the output of a diode bridge. It is a circuit diagram which shows the electric power recovery circuit using a switched capacitor circuit. It is explanatory drawing which shows the state at the time of charge of the circuit shown in FIG. It is explanatory drawing which shows the state at the time of discharge of the circuit shown in FIG. It is a circuit diagram which shows the structural example of the impedance adjustment circuit which adjusts an impedance with the variable resistor which can control resistance value electronically. It is a characteristic view which shows the relationship between the control voltage and resistance value in the variable resistor of the circuit shown in FIG. It is a circuit diagram which shows the structural example of the impedance adjustment circuit which uses a constant current element. FIG. 2 is a circuit diagram illustrating a configuration example of a transmission line termination circuit in which a bypass circuit is added to the transmission line termination circuit illustrated in FIG. 1. It is explanatory drawing which shows the case where the thing which connected in series the resistor with a fixed resistance value and the variable resistor which can control a resistance value electronically is made into a subtermination resistor. 1 is a block diagram illustrating a schematic configuration of an image forming apparatus including a transmission line termination circuit according to the present invention. It is explanatory drawing which shows the structure and operation | movement of a return judgment circuit. It is a block diagram which shows a link bypass circuit. FIG. 7 is an explanatory diagram showing a return sequence for transmitting a dummy packet from the PC side and collecting power necessary for recovery by transmitting a dummy packet from the PC side when the power of the transmission line termination circuit is turned off during standby. It is a circuit diagram which shows the structural example of the impedance adjustment circuit corresponding to positive / negative voltage. FIG. 16 is a characteristic diagram illustrating a relationship between a control voltage and a resistance value in the variable resistor of the circuit illustrated in FIG. 15. It is a circuit diagram which shows the structural example of the impedance adjustment circuit (a constant current element is used) corresponding to positive / negative voltage.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a basic configuration of a transmission line termination circuit 10 according to an embodiment of the present invention. The transmission line termination circuit 10 is a circuit connected to the termination of the transmission line 2 instead of the termination resistor, and functions as a termination resistor and a function of recovering power from a signal arriving through the transmission line 2. A receiving circuit 20 that receives a signal arriving through the transmission path 2 is connected to the end of the transmission path 2 in parallel with the transmission path termination circuit 10.

  The transmission line termination circuit 10 includes a power recovery circuit 11 that recovers power from a current that flows in response to arrival of a signal from the transmission line 2, and an impedance when the amount of current flowing through the transmission line termination circuit 10 is viewed from the transmission line 2 side. Is configured to include an impedance adjustment circuit 12 that controls the value to be equal to a predetermined termination resistance (termination resistance value). The power recovered by the power recovery circuit 11 is output from the output terminal 13 of the power recovery circuit 11 to the power usage side (for example, the receiving circuit 20 or the storage battery).

  When the potential difference (voltage) at the end of the transmission line 2 is v and the current flowing through the transmission line termination circuit 10 is i, the current i is impedance so that the relationship of i = v ÷ predetermined resistance value is established. It is controlled by the adjustment circuit 12. Thereby, the transmission line termination circuit 10 performs power recovery while serving as a termination resistor.

  Next, a configuration example of the power recovery circuit 11 will be described.

  The power recovery circuit 11 may be a circuit having a function of preventing the backflow of current from the storage battery side to the transmission line 2 side while accumulating the flowing current i in the storage battery. For example, the diode bridge circuit shown in FIG. A charge pump circuit (not shown), a switched capacitor circuit shown in FIG.

  FIG. 2 shows a power recovery circuit 11 (11a) configured by connecting a capacitor 32 to the output of the diode bridge 31.

  FIG. 3 shows a configuration example of the power recovery circuit 11 (11b) using a switched capacitor circuit. At the time of charging, the switch 34A is closed and the switch 34B is opened, so that the states shown in FIGS. 4A and 4B are formed. Thus, during charging, the capacitor 35 other than the output stage is connected in parallel with the power recovery side, the capacitor 36 of the output stage is disconnected from the power recovery side, and the current i is supplied to the capacitor 35 other than the output stage from the power recovery side. It flows in and charges are accumulated.

  At the time of discharging, the switch 34A is opened and the switch 34B is closed, and the states shown in FIGS. 5A and 5B are formed. As a result, the power recovery circuit 11 (11b) is disconnected from the power recovery side, and the capacitors 35 at each stage are connected in series to form a booster circuit and connected to the capacitor 36 at the output stage.

  In this way, the power recovery circuit 11b has its output side (power usage side) disconnected during charging, and its input side (power recovery side) disconnected during discharge, and the input and output are insulated. It can also be used when the ground level between outputs is different.

  When the signal arriving from the transmission path 2 is a pulse signal, a drive clock signal (switching signal for opening and closing the switch 34A and the switch 34B) such as a switched capacitor is generated from the pulse signal. As a result, the power recovery circuit 11 does not need to include an oscillation circuit for a drive clock signal, and power can be recovered with less power consumption.

  Next, a configuration example of the impedance adjustment circuit 12 will be described.

  In the power recovery circuit 11, the impedance and back electromotive force change depending on the storage amount of the storage battery (capacitors 32 and 35), the non-resistance component of the internal circuit, and the like. Therefore, the impedance adjustment circuit 12 is provided to maintain the impedance viewed from the transmission line 2 side constant (predetermined termination resistance value).

  FIG. 6 shows a configuration example of the impedance adjustment circuit 12 (12a) that adjusts the impedance by a variable resistor whose resistance value can be electronically controlled. The impedance adjustment circuit 12a includes a voltage detection unit that detects a voltage applied to the transmission line termination circuit 10, a current detection unit that detects a current flowing through the transmission line termination circuit 10, and an electronic circuit connected in series to the power recovery circuit 11. And the resistance value of the variable resistor so that the current value detected by the current detection unit = the voltage value detected by the voltage detection unit ÷ the predetermined termination resistance value. And a feedback circuit for controlling.

  More specifically, the impedance adjustment circuit 12a includes a first resistor 41 for current detection, a variable resistor 42 whose resistance value is electronically controlled, and an amount of current flowing through the first resistor 41 as a first resistor. A first differential amplifier 43 that detects based on a potential difference between both ends of the resistor 41 (the resistance value of the first resistor 41 is R1), and a voltage dividing resistor 44 that is inserted at the end of the transmission line 2 The voltage difference (voltage v) obtained by dividing the potential difference (voltage v) at the end of the transmission line 2 by the voltage dividing ratio of the voltage dividing resistor 44 and the potential difference between the both ends of the first resistor 41 (first differential amplifier 43). And a second differential amplifier 45 for controlling the resistance value of the variable resistor 42 so that the output voltage of the variable resistor 42 becomes equal.

  The first resistor 41, the variable resistor 42, and the power recovery circuit 11 are connected in series and are inserted at the end of the transmission line 2. The voltage dividing resistor 44 is connected to the terminal of the transmission line 2 in parallel with a circuit in which the first resistor 41, the variable resistor 42, and the power recovery circuit 11 are connected in series. The first resistor 41 and the first differential amplifier 43 function as a current detection unit that detects a current flowing through the transmission line termination circuit 10. The voltage dividing resistor 44 functions as a voltage detection unit that detects a voltage v (actually a voltage va proportional to the voltage v) applied to the transmission line termination circuit 10. The second differential amplifier 45 functions as a feedback circuit that controls the resistance value of the variable resistor 42.

  By inserting the impedance adjustment circuit 12a and the power recovery circuit 11 in series at the end of the transmission line 2, a relationship of a predetermined termination resistance value R = v / i is maintained regardless of the state of the power recovery circuit 11. Therefore, it is possible to recover power from the incoming signal while maintaining a characteristic like a fixed resistance when viewed from the transmission line 2 side.

  In the impedance adjustment circuit 12a shown in FIG. 6, the output of the second differential amplifier 45 is positive when the current i becomes larger than v / R (that is, when R1 × i> va) (that is, R1). Since x becomes negative (when i <va), the characteristic of the resistance value with respect to the control voltage of the variable resistor 42 is as shown in FIG. The impedance adjustment circuit 12a is preferably integrated in order to increase the response speed.

  FIG. 8 shows an example of the impedance adjustment circuit 12 (12b) using a constant current element. The impedance adjusting circuit 12b divides the constant current element 51 for supplying a current according to the applied control voltage and the voltage v applied from the transmission line 2 to the transmission line termination circuit 10 at a predetermined ratio to determine the divided voltage. A voltage dividing circuit (voltage dividing resistor) 52 provided as a control voltage for the current element 51 is provided. The constant current element 51 is inserted at the end of the transmission line in series with the power recovery circuit 11.

  The constant current element 51 is configured by an FET (Field Effect Transistor) or the like. The constant current element 51 preferably has a constant current characteristic (linear characteristic) in which the control voltage and the flowing current value are proportional to each other. However, the constant current element 51 has non-linearity in a range where the terminal resistance value is within an allowable fluctuation range. It doesn't matter. The constant current element 51 is not limited to the FET.

  In the impedance adjustment circuit 12b, constant current operation is performed on the constant current element 51 so that the current flowing through the constant current element 51 becomes a current value obtained by dividing the voltage v by the voltage dividing ratio of the voltage dividing circuit 52. Let it be done. Accordingly, the relationship of the termination resistance value R = v / i is maintained regardless of the state of the power recovery circuit 11. Because of the simple configuration utilizing the characteristics of the constant current element 51, the power consumption is less than that of the circuit configuration shown in FIG. 6, and the frequency response is excellent.

  By the way, when the amount of stored electricity increases and the back electromotive force of the power recovery circuit 11 increases, the current flowing through the power recovery circuit 11 becomes too small and exceeds the adjustment range of the impedance adjustment circuit 12 (impedance adjustment circuit 12 The desired current does not flow even if the resistance value is 0). Therefore, in order not to exceed the adjustment range of the impedance adjustment circuit 12, a bypass circuit that bypasses the power recovery circuit 11 and flows current when the current flowing through the power recovery circuit 11 becomes too small is provided. It is preferable to control the amount of current to be bypassed by the bypass circuit so as to decrease within a range not exceeding the adjustment range of the impedance adjustment circuit 12.

  FIG. 9 shows a configuration example of a transmission line termination circuit 10b in which a bypass circuit is added to the transmission line termination circuit 10 shown in FIG. The bypass circuit is connected in parallel to the power recovery circuit 11, the second variable resistor 61 whose resistance value R <b> 2 is electronically controlled, and the amount of current flowing through the impedance adjustment circuit 12 from the potential difference between both ends of the impedance adjustment circuit 12. And a third differential amplifier circuit 62 for detecting. Then, the output voltage of the third differential amplifier circuit 62 is supplied as a control voltage to the second variable resistor 61, and the resistance value R2 of the second variable resistor 61 is proportional to the potential difference v1 across the impedance adjustment circuit 12. Control to do.

  In the transmission line termination circuit 10b provided with such a bypass circuit, when the current i1 flowing through the power recovery circuit 11 decreases, v1 also decreases, and as a result, the resistance value R2 of the second variable resistor 61 is controlled to decrease. As a result, the current i2 flowing through the second variable resistor 61 increases and can be within the adjustment range of the impedance adjustment circuit 12 (preventing the resistance value of the impedance adjustment circuit 12 from being close to 0).

  When the relationship of the termination resistance value R = v / i can be formed within the adjustment range of the impedance adjustment circuit 12, the resistance value of the second variable resistor 61 is controlled to infinity. In this state, the impedance adjustment circuit 12 Only when the relationship of the termination resistance value R = v / i cannot be formed within the adjustment range, control is performed so that the resistance value of the second variable resistor 61 is decreased from infinity to a magnitude at which the above relationship can be established. It is preferable. Hereinafter, a resistor that flows a current that bypasses the power recovery circuit 11, such as the second variable resistor 61, is referred to as a sub-termination resistor.

  The bypass circuit is not limited to the configuration shown in FIG. 9. For example, a sub-termination resistor having a fixed resistance value is provided, and the sub-termination resistor is normally disconnected, and in this disconnected state, the adjustment range of the impedance adjustment circuit 12 Therefore, the sub-termination resistor may be connected in parallel with the power recovery circuit 11 or connected in place of the power recovery circuit 11 only when the relationship of the termination resistance value R = v / i cannot be formed. Absent.

  Even if the bypass circuit is provided, the magnitude of the current i is controlled by the impedance adjustment circuit 12 to be proportional to the voltage v, as in the case where there is no bypass circuit, so that the impedance of the entire transmission line termination circuit 10 is constant. Kept.

  For example, as shown in FIG. 10, a resistor 63 having a fixed resistance value and a variable resistor 64 capable of electronically controlling the resistance value are connected in series instead of the second variable resistor 61 in FIG. You may comprise so that things may be connected as a subtermination resistor. By controlling the resistance value of the resistor 63 as a desired termination resistance value and controlling the resistance value of the variable resistor 64 to zero, the resistor 63 can be operated as a normal resistor. Can be small.

  Furthermore, it is preferable to provide a termination resistance mode in which the resistance value of the impedance adjustment circuit 12 is set to zero, the resistance value of the power recovery circuit 11 is set to infinity, and the resistance value of the variable resistor 64 is set to zero. In the termination resistance mode, a state in which the impedance viewed from the transmission line 2 side is only the resistor 63, that is, a circuit equivalent to a termination resistance using a normal fixed resistor is formed. The termination resistance mode is effective when it is desired to reduce the signal distortion as much as possible, such as in the case of high-speed communication or communication using multiple values.

  Switching between the power recovery mode in which the impedance adjustment circuit 12 and the power recovery circuit 11 are functioned to recover power and the termination resistance mode in which power recovery is not performed and only the function of the termination resistance is performed is performed by an external control signal. It is good also as a structure and it is good also as a structure switched according to the amount of electrical storage. For example, since 1000Base-T has an analog waveform and is easily affected by non-linearity, when communicating with 1000Base-T, it is preferable to stop power recovery and operate in the termination resistance mode. In addition, a configuration may be provided in which a storage circuit is provided for monitoring the storage amount and switching to the power recovery mode when the storage amount is equal to or less than a predetermined amount and automatically switching to the termination resistance mode when the storage amount exceeds the predetermined amount.

  In addition, the transmission line termination circuit shown in FIG. 1, FIG. 6, FIG. 9, etc., a fixed resistor having a desired termination resistance value, or a transmission line termination circuit is connected to the termination of the transmission line 2, or a fixed resistor is used. A circuit having a switching circuit for switching connection is used as a transmission line termination circuit with a switching function, and the transmission line termination circuit shown in FIGS. 1, 6, 9, etc. is connected to the termination of the transmission line to recover power. The switching circuit may be configured to switch between a state to be performed and a state in which only the fixed resistor is connected and functions only as a termination resistor.

  FIG. 11 shows a schematic configuration of an image forming apparatus 70 provided with the transmission line termination circuit 10. The image forming apparatus 70 is a copy job that optically reads a document and prints the duplicate image on a recording paper, a scan job that stores image data of the read document as a file, or transmits the file to an external terminal via a network, This is a device that executes a print job or the like that forms and outputs an image related to print data received from an external terminal via a network on a recording sheet.

  The image forming apparatus 70 includes a main control circuit 71 that performs overall control of the operation of the image forming apparatus 70. Connected to the main control circuit 71 are a scanner unit 72, a printer unit (image forming unit) 73, an operation display unit 74, an image processing unit 75, a hard disk device (HDD) 76, and a communication unit 78. . A transmission line termination circuit 10 is connected to the end of the transmission line 2 connected to the communication unit 78.

  The communication unit 78 includes a reception unit 81 including a reception circuit 20 that receives a signal arriving from the reception transmission path 2 and a return determination circuit 80, and a transmission circuit 82 that transmits a signal to an external device through the transmission transmission path. It has. In addition, the image forming apparatus 70 includes a main power supply 83 that supplies power obtained from a commercial power supply, a storage battery 84 that stores power collected by the transmission line termination circuit 10, and a receiver 81. A changeover switch 85 for switching whether or not to connect a power supply line from the power supply 83 and a power supply control circuit 86 for controlling opening and closing of the changeover switch 85 are provided.

  The main control circuit 71 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like as main parts. Various programs are stored in the ROM, and control related to each function of the image forming apparatus 70 is performed when the CPU executes processing according to these programs. The RAM is used as a work memory that temporarily stores various data when the CPU executes a program, an image memory that stores image data, a communication buffer that temporarily stores data related to transmission and reception, and the like.

  The scanner unit 72 performs a function of optically reading a document and acquiring image data. The scanner unit 72 sequentially moves, for example, a light source that irradiates light on a document, a line image sensor that receives the reflected light for one line in the width direction, and a reading position in line units in the length direction of the document. An optical path composed of a lens, a mirror, and the like for guiding the reflected light from the document to the line image sensor to form an image, a conversion unit for converting the analog image signal output from the line image sensor into digital image data, etc. It is prepared for.

  The printer unit 73 has a function of printing an image corresponding to the image data on a recording sheet. Here, it has a recording paper transport device, a photosensitive drum, a charging device, a laser unit, a developing device, a transfer separation device, a cleaning device, and a fixing device, and forms an image by an electrophotographic process. It is configured as a so-called laser printer. Other types of printers may be used.

  The operation display unit 74 has a function of displaying various operation screens, setting screens, and the like and a function of receiving various operations from the user. The operation display unit 74 includes a display unit configured by a liquid crystal display, for example, and the screen. A touch panel provided on the touch panel for detecting a pressed coordinate position, and operation units such as a numeric keypad, a character input key, and a start key are provided.

  The image processing unit 75 performs enlargement / reduction, rotation, compression / decompression, and the like of the image. The hard disk device 76 is a large-capacity non-volatile storage device that stores image data and the like.

  In the image forming apparatus 70, for example, a copy job is realized by optically reading a document image by the scanner unit 72 to acquire image data and performing printing based on the image data by the printer unit 73. The print job receives print data sent from the external terminal through the transmission path 2 by the receiving unit 81, rasterizes the received print data in the main control circuit 71, and develops it into image data. This is realized by performing printing based on the printer unit 73.

  The image forming apparatus 70 has a power saving mode for reducing power consumption, and the main control circuit 71 is normal when a state in which there is no job execution, data reception, or operation from the operation display unit 74 continues for a predetermined time or longer. Switch from mode to power saving mode.

  In addition, here, the communication unit 78 corresponds to Ethernet (registered trademark), assumes an IEEE (Institute of Electrical and Electronic Engineers) 802.3az power saving technology, and is equivalent to 10Base-T when shifting to the power saving mode. Note that the transmission line termination circuit is not particularly dependent on the communication speed, and since the Ethernet is a differential signal, the termination resistor must correspond to positive and negative voltages. A configuration example of the transmission line termination circuit 10 corresponding to positive and negative voltages will be described later.

  In the normal mode, the changeover switch 85 is closed, and power is supplied to each unit from the main power supply 83. In addition, charging from the main power supply 83 to the storage battery 84 is also performed. At this time, the transmission line termination circuit 10 can also recover the electric power from the transmission line 2 and keep the storage battery 84 charged.

  Basically, in the power saving mode, the power supply control circuit 86 opens the changeover switch 85 to disconnect circuit parts necessary for monitoring received data, such as the reception unit 81 and the transmission line termination circuit 10, from the main power supply 83. Is switched so as to supply power from the storage battery 84. In the power saving mode, the main control circuit 71 operates in the low power consumption mode with little power consumption, and the function of waiting for the return signal from the return determination circuit 80 or the return signal from the operation display unit 74 operates. The other operations are not performed. In the power saving mode, the operation display unit 74 turns off the display. Further, power supply to the scanner unit 72, the printer unit 73, the image processing unit 75, the hard disk device 76, and the transmission circuit 82 is stopped.

  In the power saving mode, the transmission line termination circuit 10 collects a signal from the transmission line 2 as electric power, and charges the storage battery 84. The reception circuit 20 and the return determination circuit 80 analyze the received data, and if it is determined that the return is necessary, a return signal is sent to the main control circuit 71.

  When receiving the return signal, the main control circuit 71 determines the received data, and if necessary, controls the power supply control circuit 86 to supply power to each unit to return to the normal mode.

  When the capacity (charge amount) of the storage battery 84 has decreased below a predetermined amount in the power saving mode, the power supply control circuit 86 connects the part disconnected from the main power supply 83 with the changeover switch 85 closed. Then, it may be controlled to disconnect again after the charging is completed.

  Moreover, when the capacity | capacitance of the storage battery 84 has decreased, you may comprise so that the transmission line termination circuit 10 and the receiving part 81 may be turned off, without connecting the main power supply 83 again. In this case, in order to operate as a termination resistor even when the transmission line termination circuit 10 is OFF, (1) the transmission line termination circuit 10 has a configuration that does not require operating power other than the signal of the transmission line 2, or ( 2) The power supply may be switched to a circuit that does not require operating power when the power is turned off.

  For example, to achieve the above (1), the power recovery circuit 11 is a power recovery circuit 11a using a diode bridge shown in FIG. 2, and the impedance adjustment circuit 12 is a circuit using a constant current element shown in FIG. do it. For the above (2), a circuit that operates in the above-described power recovery mode when the power is turned on and is in the termination resistance mode when the power is turned off, such as the power recovery shown in FIGS. A transmission line termination circuit 10 having a function, a fixed termination resistor, and a changeover switch for switching whether the transmission line termination circuit 10 is connected to the termination of the transmission line 2 or to connect the termination resistor. Sometimes, the switch may be a circuit that connects the terminating resistor to the transmission line.

  Further, in the operation of the apparatus, when it is not necessary to operate as a normal termination resistor during a period in which the received data is not judged, the impedance adjustment circuit 12 is set so that the termination resistance value is higher than that in the normal state. By setting so as to be reduced to an allowable range, more power can be extracted from the transmission line. In other words, even if the waveform of the received signal collapses during the period when the received data is not judged, there is no problem as the device. After that, the power recovery is achieved by reducing the termination resistance value within the allowable range of the transmission line and circuit. Charging efficiency can be improved by increasing the amount of current flowing into the circuit.

  Next, the return determination circuit 80 will be described.

  10Base-T uses a Manchester code, but a Manchester decoding circuit normally has to sample a signal with a clock several times the signal frequency, resulting in a problem that the power consumption increases due to high frequency driving. is there. Therefore, here, attention is paid to the fact that the Manchester code has two kinds of long and short pulse widths, and the return determination circuit 80 with low power consumption is used without preparing a clock generation circuit.

  FIG. 12 shows a schematic configuration of the return determination circuit 80 and an outline of its operation. The return determination circuit 80 includes a pulse width measurement unit 91, a wakeup pattern register 92, a pulse width shift register 93, and a pattern comparison unit 94.

  The pulse width measuring unit 91 identifies whether the pulse width of the received pulse signal is longer or shorter than a predetermined value. For example, a capacitor is charged by the received pulse signal, and when the charge potential from the start edge to the end edge of the pulse signal exceeds a predetermined threshold, it is identified as a long pulse signal, otherwise it is identified as a short pulse signal. To do. As the discrimination signal 95, for example, 1 is output to the input side of the pulse width shift register 93 when it is identified as a long pulse and 0 is identified as a short pulse.

  The pulse width measurement unit 91 outputs a clock 96 for shifting by 1 bit to the pulse width shift register 93 in synchronization with the determination signal 95. For example, the edge of the received Manchester code is used as the shift clock 96. Further, when the received signal has a length exceeding the upper limit value, it is determined that there is no signal, and the reset signal 97 is output to the pulse width shift register 93.

  The wakeup pattern register 92 is loaded from the main control circuit 71 with a predetermined return bit pattern for determining that the signal is addressed to itself. The pulse width shift register 93 sequentially shifts and accumulates the determination signal 95 input from the pulse width measurement unit 91 according to the clock 96 input from the pulse width measurement unit 91. The pattern comparison unit 94 compares the return bit pattern stored in the wake-up pattern register 92 with the bit pattern stored in the pulse width shift register 93, and outputs a return signal when all bits match.

  With such a configuration, a high frequency clock is not required, and the power consumption of the return determination circuit 80 can be reduced.

  If a plurality of sets of wakeup pattern registers 92 and pattern comparison units 94 are prepared, a plurality of return bit patterns can be handled.

  When returning using the return determination circuit 80, the main control circuit 71 receives the contents of the pulse width shift register 93 after returning by the return signal, and then connects the received signal to the received signal. Is required. When the return bit pattern is fixed, instead of receiving the contents of the pulse width shift register 93, a known return bit pattern and a signal received thereafter may be connected.

  Even if the return determination circuit 80 shown in FIG. 12 is not used, if the amount of power that can be extracted from the transmission line 2 is sufficiently higher than the power consumption of the reception circuit 20, the reception circuit 20 receives the same reception as in the normal mode. Processing may be performed to determine a packet addressed to itself, and a return signal may be sent to the main control circuit 71.

  Next, the case where the estimation of the amount of electricity stored by the transmission line termination circuit 10 is estimated using Ethernet's 10Base-T will be exemplified. In 10Base-T, the minimum value of the receiving end voltage at the end of 100Ω is determined to be about 2.2V to 2.8V. Assuming that the signal is a rectangular wave of 2.2 V, the power that can be extracted per hour is 2.2 V2 / 100Ω / 2 = 24.2 mW.

  Since this is a state in which data continuously flows, the power per packet is theoretically 24.2 mW × (packet time). In 10Base-T, the N-byte packet time is N × 800 ns, and thus the power that can be extracted from the N-byte packet is N × 24.2 mW / s × 800 ns = N × 19.36 nW. For example, in a 1500-byte packet, a maximum of 29.04 μW of power can be extracted. If a 10Base-T pulse is always received without interruption, there is a possibility that 24.2 mW of power can be extracted per second.

  Next, a method for maintaining a link with the network in the power saving mode will be described.

  Some Ethernet switching hubs have a mechanism that detects a link state for each port and does not send a signal to a port that has not established a link. In such a case, it is necessary to output link pulses periodically to maintain the link. However, only the power recovered by the transmission line termination circuit 10 from the transmission line cannot cover the power for link pulse transmission. There is no possibility. For such a case, as shown in FIG. 13, a link bypass circuit may be provided in which the link pulse received by the receiving device side is sent back to the transmission path as it is.

  The link bypass circuit includes a bypass switch 101 interposed between a transmission line on the reception side and a transmission line on the transmission side, and a link bypass control unit 102 that controls opening and closing of the bypass switch 101. The link bypass control unit 102 turns the bypass switch 101 ON (closed) when there is no reception signal for a predetermined time, and turns OFF (opens) after only one pulse of the reception signal or reception pulse has passed. By passing only one pulse, when a packet that is not a link pulse is received, the received packet can be prevented from being sent back to the transmitting side as it is, and at the same time, power can be recovered from the remaining portion by the transmission line termination circuit 10. it can. Note that in the case of a normal signal that is not a link pulse, a synchronization pulse is added to the head of a plurality of bits, so no problem occurs even if the first 1 bit is lost by the link bypass circuit.

  In the receiving unit or the transmission line termination circuit 10, the termination resistance value viewed from the transmission side of the counterpart device is set to a steady state by setting the termination resistance to be infinite while the bypass switch is ON (closed). Can look the same. In other words, when the bypass switch is ON (closed), the receiving end of the counterpart device is the end of the transmission line, so if the receiving end of the counterpart device has a normal termination resistor, Terminated.

  Next, a description will be given of a return method when the capacity of the storage battery 84 is reduced and the power of the receiving unit 81 and the transmission line termination circuit 10 is turned off during the power saving mode.

  In this case, there is an advantage that the standby power can be reduced to almost zero. However, since the received data cannot be determined, it is necessary to recover the power for operating the part necessary for recovery from the transmission path. Therefore, as shown in FIG. 14, from the terminal device 120 side such as a personal computer that transmits data to the image forming apparatus 70, a dummy packet is continuously transmitted for a predetermined time prior to transmission of a use start packet (P1). Then, by collecting power from the dummy packet, a function of executing a procedure of transmitting a use start packet after the receiving unit 81 on the image forming apparatus 70 side becomes operable (P2) is provided.

  Further, when there is no response from the image forming apparatus 70 even if the use start packet is transmitted, the terminal apparatus 120 may be configured to retry sending the dummy packet several times. Further, the dummy packet itself is composed of data that is a return condition of the image forming apparatus 70 and requests a response from the image forming apparatus 70, and the terminal device 120 side receives the dummy packet from the image forming apparatus 70 until a response is received. You may employ | adopt the procedure of continuing sending out. That is, in the image forming apparatus 70, when the transmission line termination circuit 10 is charged by repeatedly arriving dummy packets, and the charge amount increases and becomes operable, the return determination circuit 80 receives the dummy packet and needs to return from its contents. And the return response is transmitted from the transmission circuit to the terminal device 120.

  In this case, it is desirable to provide a certain response timeout period, and to stop sending dummy packets when there is no response from the image forming apparatus 70 within the response timeout period. As a result, for example, when there is no response to a failure on the image forming apparatus 70 side or a transmission path failure, transmission of dummy packets is prevented from continuing indefinitely.

  Next, a configuration example of the transmission line termination circuit 10 corresponding to positive and negative voltages will be described. Since a signal to be transmitted is a differential signal in a transmission line such as Ethernet, the termination resistor needs to correspond to a positive / negative voltage. FIG. 15 is a circuit example when the circuit of FIG. 6 is adapted to positive and negative voltages. The same parts as those in FIG. 6 are denoted by the same reference numerals, and the description thereof is omitted. The circuit of FIG. 15 includes a current detection unit 140 instead of the first resistor 41 and the first differential amplifier 43 of FIG. 6, and a voltage detection unit 150 instead of the voltage dividing resistor 44 of FIG. . In the circuit shown in FIG. 15, the voltage and current are determined with signs, and the characteristics of the variable resistance section are switched depending on the direction of the current. Specifically, circuit constants are selected so that the output Vi of the current detection unit 140 is a value proportional to i × R. If | Vi |> | v |, the resistance value is increased. | Vi | < If | v |, the variable resistor 42 changes in a decreasing direction to form a feedback loop for controlling v / i to be constant. FIG. 16 shows the relationship between the resistance value of the variable resistor 42 and its control voltage.

  FIG. 17 is a circuit example when a circuit using the constant current element of FIG. 8 is made to correspond to positive and negative voltages. When a MOSFET or the like is used as the current control element, the reverse current is not limited by the action of the parasitic diode. If this is utilized, the impedance adjustment circuit corresponding to a positive / negative voltage can respond | correspond by the structure which connected the constant current elements (current control elements) 51 and 53 from which polarity differs as shown in FIG.

  The embodiment of the present invention has been described with reference to the drawings. However, the specific configuration is not limited to that shown in the embodiment, and there are changes and additions within the scope of the present invention. Are also included in the present invention.

  For example, in the image forming apparatus 70, the case where the network is Ethernet has been described as an example. However, the transmission line targeted by the transmission line termination circuit 10 is not limited to this, and various types of terminals that require a termination resistor may be used. It can be applied to other transmission lines.

  The apparatus incorporating the transmission line termination circuit 10 is not limited to the image forming apparatus 70, and may be a data receiving apparatus having a configuration that does not include the scanner unit 72, the printer unit (image forming unit) 73, and the like.

DESCRIPTION OF SYMBOLS 2 ... Transmission path 10, 10b ... Transmission path termination circuit 11, 11a, 11b ... Power recovery circuit 12, 12a, 12b ... Impedance adjustment circuit 13 ... Output terminal 20 ... Reception circuit 31 ... Diode bridge 32 ... Capacitor 34A, 34B ... Switch DESCRIPTION OF SYMBOLS 35, 36 ... Capacitor 41 ... 1st resistor 42 ... Variable resistor 43 ... 1st differential amplifier 44 ... Voltage dividing resistor 45 ... 2nd differential amplifier 51, 53 ... Constant current element 52 ... Voltage dividing circuit (Partial resistor)
DESCRIPTION OF SYMBOLS 61 ... 2nd variable resistor 62 ... 3rd differential amplifier circuit 63 ... Resistor 64 ... Variable resistor 70 ... Image forming apparatus 71 ... Main control circuit 72 ... Scanner part 73 ... Printer part (image forming part)
74 ... Operation display section 75 ... Image processing section 76 ... Hard disk device (HDD)
DESCRIPTION OF SYMBOLS 78 ... Communication part 80 ... Return determination circuit 81 ... Reception part 82 ... Transmission circuit 83 ... Main power supply 84 ... Storage battery 85 ... Changeover switch 86 ... Power supply control circuit 91 ... Pulse width measurement part 92 ... Wake-up pattern register 93 ... Pulse width shift Register 94 ... Pattern comparison unit 95 ... Discrimination signal 96 ... Clock 97 ... Reset signal 101 ... Bypass switch 102 ... Link bypass control unit 120 ... Terminal device 140 ... Current detection unit 150 ... Voltage detection unit

Claims (10)

A transmission line termination circuit connected to the termination of a transmission line for data communication,
A power recovery circuit that recovers power from the flowing current;
An impedance adjustment circuit for controlling the amount of current flowing through the transmission line termination circuit so that the impedance viewed from the transmission line side becomes a predetermined termination resistance value;
A transmission line termination circuit comprising: The impedance adjustment circuit is
A voltage detector for detecting a voltage applied to the transmission line termination circuit;
A current detector for detecting a current flowing in the transmission line termination circuit;
A variable resistor connected in series to the power recovery circuit and whose resistance is electronically controlled;
A feedback circuit that controls the resistance value of the variable resistor so that the current value detected by the current detection unit = the voltage value detected by the voltage detection unit ÷ the predetermined termination resistance value;
The transmission line termination circuit according to claim 1, wherein: The impedance adjustment circuit is
A constant current element that is connected in series with the power recovery circuit and flows a current according to an applied control voltage;
A voltage dividing circuit for providing a divided voltage of a voltage applied to the transmission line termination circuit as a control voltage of the constant current element;
The transmission line termination circuit according to claim 1, wherein: A bypass circuit that bypasses the power recovery circuit and flows current when the impedance viewed from the transmission line side cannot be adjusted to a predetermined termination resistance value by the impedance adjustment circuit due to a decrease in the current flowing through the power recovery circuit. The transmission line termination circuit according to any one of claims 1 to 3. The bypass circuit is:
A second variable resistor connected in parallel with the power recovery circuit and whose resistance is controlled electronically;
When the impedance viewed from the transmission line side can be adjusted to a predetermined termination resistance value by the impedance adjustment circuit in a state where the resistance value of the second variable resistor is controlled to be infinite, the second variable resistor is set. A control circuit for controlling the resistance value to be infinite, and when the adjustment cannot be performed in the state, a control circuit for reducing the resistance value of the second variable resistor so that the adjustment is possible;
The transmission line termination circuit according to any one of claims 1 to 3, characterized by comprising: A fixed resistor having a predetermined termination resistance value;
A switching circuit that switches between a state in which the impedance adjustment circuit and the power recovery circuit are functioned to recover power and a state in which only the fixed resistor is in an impedance viewed from the transmission line side;
The transmission line termination circuit according to any one of claims 1 to 5, wherein: The transmission line according to any one of claims 1 to 6, wherein the power recovery circuit includes a circuit in which a capacitor is connected to an output of a diode bridge, or a switched capacitor or a charge pump. Termination circuit. The power recovery circuit includes a switched capacitor or a charge pump,
The pulse signal received from the transmission path is a switching signal for switching between a switched capacitor or a charge pump connected to the transmission path side and a disconnected state. A transmission line termination circuit according to 1. A receiving circuit for receiving a signal through a transmission line;
The transmission line termination circuit according to any one of claims 1 to 8, which is connected to a termination of the transmission line;
A storage battery for storing the power recovered by the transmission line termination circuit;
A return determination circuit for determining return from the main power source and the power saving mode based on a received signal from the transmission path;
A power supply control circuit that switches the power supply source from the main power supply to the storage battery when the power saving mode is entered;
A data receiving device comprising: A data receiving device according to claim 9,
An image forming unit that operates by receiving power supply from the main power source and forms an image based on image data received by the data receiving device on a recording sheet;
An image forming apparatus comprising:

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