JP2012109990A - Power supply circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply circuit capable of supplying power to a transmission part from a reception part, with no constraint on the power supply condition of a receiver device.SOLUTION: The power supply circuit includes a transmission part 10 for transmitting video, a reception part 20 for receiving the video transmitted from the transmission part 10, and a connection means which connects the transmission part 10 to the reception part 20, containing a power supply wiring for transferring a power supply voltage and a third wiring. The reception part 20 includes a power supply switch SWA for switching connection to a voltage source and to a power supply wiring. The transmission part 10 includes a power supply circuit 16 which outputs a predetermined voltage to the power supply wiring, and a switching circuit 18 which changes the potential of the third wiring to a predetermined potential if a predetermined voltage is not being outputted to the power supply wiring from the power supply circuit 16. The power supply switch SWA, in the case where the third wiring is not at a predetermined potential, turns on the connection between the voltage source and the power supply wiring, so that the voltage from the voltage source is outputted to the transmission part 10 by way of the power supply wiring. In the case the third wiring is at the predetermined potential, it turns off the connection between the voltage source and the power supply wiring.

Description

  Embodiments described herein relate generally to a power supply circuit.

In recent years, HDMI (High-Definision Multimedia Interface) cables, I ² C (Inter-Integrated Circuit) communication cables, and the like have been proposed as communication interfaces for transmitting signals between devices.

  Conventionally, in a transmission device (Source device), for example, a maximum of 55 mA can be supplied to a PW + 5 V line that supplies a power supply voltage in an HDMI cable. Further, since 5 mA is consumed to drive the HPD line, the receiving device (Sink device) can consume 50 mA at maximum.

JP 2009-44706 A

  Conventionally, an HDMI cable has not been configured to supply power from a receiving device to a transmitting device. For this reason, when a mobile device is connected as a transmission device using an HDMI cable, the operation time may be limited due to the power supply situation on the mobile device side. For example, when a mobile phone or a mobile device that reproduces moving images is connected as a transmission device, the power supply on the transmission device side is consumed, and the signal transmission operation time may be limited.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a power supply circuit that can supply power from a receiving unit to a transmitting unit and is not restricted by the power supply situation of a receiving device. To do.

  A power supply circuit according to an embodiment of the present invention includes a transmission unit that transmits video, a reception unit that receives video transmitted from the transmission unit, and a connection unit that connects the transmission unit and the reception unit. A power supply circuit including a power supply wiring for transmitting a power supply voltage and a third wiring, wherein the receiving unit switches power between the voltage source and the power supply wiring. A power supply circuit that outputs a predetermined voltage to the power supply wiring; and a potential of the third wiring in response to the fact that the predetermined voltage is not output from the power supply circuit to the power supply wiring. A switch circuit that changes the voltage source to a predetermined potential, and the power supply switch turns on the connection between the voltage source and the power source wiring when the third wiring is not at the predetermined potential. Voltage to the power distribution Is output to the transmission unit via the third wiring is configured to turn off the connection between the voltage source and the power supply line when a predetermined potential.

It is a figure which shows roughly the example of 1 structure of the power supply circuit which concerns on one Embodiment of this invention. It is a figure for demonstrating an example of operation | movement of the power supply circuit shown in FIG. FIG. 6 is a diagram for explaining another example of the operation of the power supply circuit shown in FIG. 1. FIG. 3 is a diagram for explaining an example of an operation of stopping power supply in the power supply circuit shown in FIG. 1.

  Hereinafter, a power supply circuit according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration example of a power supply circuit according to the present embodiment.

  The power supply circuit has a first communication function (for example, an HDMI function) that transmits video and audio signals mainly by a transition time minimum differential signal transmission (TMDS) method, and a second communication that mutually transmits the party line. A function (for example, HDMI-CEC function) and a power supply wiring are provided.

  The power supply circuit includes a transmission unit (Source) 10, a reception unit (Sink) 20, and a plurality of signal lines for transmitting video signals, control signals, and the like between the transmission unit 10 and the reception unit 20. I have.

  The transmission unit 10 and the reception unit 20 are connected by connection means such as an HDMI cable or an I2C communication line. The plurality of signal lines include, for example, a video signal transmission line, a power supply line (PW + 5V), an HPD line, a UTIL line, a CEC line, a DDC line, an SCL line, and an SDA line.

  Both ends of the plurality of signal lines are connected to the connectors 10B and 20B. The connector 10 </ b> B is attached to the receptor 10 </ b> A of the transmission unit 10, and a plurality of signal lines are connected to the transmission unit 10. The connector 20 </ b> B is attached to the receptor 20 </ b> A of the receiving unit 20, and a plurality of signal lines are connected to the receiving unit 20.

  The transmission unit 10 is mounted on, for example, a video signal transmission device and encodes a video signal, a buffer 14 that outputs a signal output from the encoder 12 by a differential transmission method, a power supply circuit 16, and a control circuit CTR1. A power disconnection switch SWC, a power supply notification switch SWD, a switch circuit 18, and a receptor 10A.

  Video signals R, G, and B are input to the encoder 12. The encoder 12 encodes the input video signals R, G, and B, and outputs the encoded video signal as a serial signal to the buffer 14 disposed in the subsequent stage.

  The encoded video signal and the clock signal CK are input to the buffer 14. The buffer 14 outputs the encoded video signal and the inverted signal of the encoded video signal to the video signal transmission line in synchronization with the clock signal CK by the differential transmission method.

  The power supply circuit 16 is configured to convert the voltage supplied from the battery BT as necessary to output the voltage Vcc, and to charge the battery BT with the supplied power. The voltage Vcc is supplied to an IO (Input / output) port of the receptor 10 </ b> A of the transmission unit 10 and the switch circuit 18. The transmitter 10 can be mounted on an electronic device that can be used as a portable device by charging the battery BT. The transmitter 10 may be mounted on an electronic device that is used by connecting an external power supply (AC adapter).

  The power cut switch SWC is provided on an output line from the power supply circuit 16 to one terminal of the receptor 10A. The operation of the power cut switch SWC is controlled by the control circuit CTR1.

  The power supply notification switch SWD is provided on an input line from one terminal of the receptor 10A to the power supply circuit 16. The operation of the power supply notification switch SWD is controlled by the control circuit CTR1.

  The switch circuit 18 includes analog switches 18A and 18B configured to be able to short-circuit a terminal connected to the connection line SCL of the receptor 10A and a terminal connected to the connection line SDA. The switch circuit 18 is supplied with the voltage Vcc from the power supply circuit 16. The analog switches 18A and 18B short-circuit the connection lines with the receptor 10A when the voltage Vcc is not supplied.

  The control circuit CTR1 is configured to control the operations of the encoder 12, the power supply circuit 16, the power cut switch SWC, and the power supply notification switch SWD.

  The power supply circuit 16 is connected to the power supply wiring (PW + 5V) of the HDMI cable via the power cut switch SWC. In the transmission unit 10, the power supply wiring (PW + 5V) is connected to the HPD line and the IO port of the control circuit CTR1 via the power supply notification switch SWD and the resistor.

  The receiving unit 20 is mounted on, for example, a video receiving device, and includes a decoder 22, a buffer 24 that outputs an input signal to the decoder 22, a power supply switch SWA, a power direction notification switch SWB, a control circuit CTR2, a recording circuit A ROM as means 26 and a monitoring circuit 28 are provided.

  The buffer 24 receives the encoded video signal from the video signal transmission line, and outputs the encoded video signal and the clock signal. The encoded video signal is input to the decoder 22. The decoder 22 decodes the encoded video signal and outputs it in parallel.

  The power supply switch SWA is configured to switch the connection between the power supply voltage supply line (PW + 5V) and the voltage source of the voltage Vcc. The operation of the power supply switch SWA is controlled by the control circuit CTR2. A resistor defined by the HDMI standard is connected between the power supply voltage supply line (PW + 5V) and the HPD line via a power direction notification switch SWB.

  In the receiving unit 20, the voltage Vcc is connected to the power supply wiring (PW + 5V) via the power supply switch SWA, and the power supply to the transmission unit 10 is controlled by switching the power supply switch SWA.

  In the recording unit 26, an address (Physical Address) representing a position in the entire system is recorded. The transmission unit 10 and the reception unit 20 access the recording unit 26 and acquire an address, thereby confirming where the device itself is located in the HDMI system.

  An SCL (clock signal) line and an SDA (data signal) line are connected to the IO port of the monitoring circuit 28. A pull-up resistor R1 (4.7 KΩ) is connected to the SCL line. A pull-down resistor R2 (4.7 KΩ) is connected to the SDA line. The monitoring circuit 28 monitors the potentials of the SCL line and the SDA line.

The control circuit CTR2 controls operations of the decoder 22, the power supply switch SWA, the power direction notification switch SWB, the recording unit 26, and the monitoring circuit 28. The HPD line is connected to the IO port of the control circuit CTR2, and the potential of the HPD line is monitored by the control circuit CTR2.
Note that the UTIL (Utility) line of the HDMI cable shown in FIG. 1 may be connected to a circuit (not shown).

FIG. 2 is a timing chart for explaining an operation example of supplying power from the receiving unit 20 to the transmitting unit 10 in the power supply circuit.
First, the control circuit CTR2 of the receiving unit 20 turns on the power direction notification switch SWB and turns off the power supply switch SWA. The control circuit CTR1 of the transmission unit 10 turns on the power disconnect switch SWC and turns off the power supply notification switch SWD.

  When the transmission unit 10 and the reception unit 20 are connected by the connecting means and the transmission unit 10 is activated, the power supply circuit 16 operates to supply the power supply voltage to the power supply voltage supply line (PW + 5V). At this time, a current flows from the power supply voltage supply line (PW + 5V) to the IO port of the control circuit CTR2 through the power supply direction notification switch SWB, the resistor, and the HPD line, and the potential of the HPD line becomes high. Become. Thus, initially, the environment is the same as that of a normal HDMI cable.

  Next, in order to request power supply from the transmission unit 10 to the reception unit 20, the transmission unit 10 inquires of the reception unit 20 about the power supply function using the CEC line. At this time, not only the presence / absence of the power supply function but also the amount of current requested by the transmitter 10 may be included in the inquiry command. The receiving unit 20 responds to an inquiry from the transmitting unit 10 if there is a power supply function. For the response, the supply current amount that can be handled by the receiving unit 20 may be added to the response command. The inquiry command system on the CEC line uses, for example, an extension of CDC (Capability Discovery and Control) defined in HDMI 1.4.

  Next, the receiving unit 20 notifies the transmitting unit 10 that the communication of the function related to HDCP is replaced with the CDC-HPD command defined in HDMI 1.4. The transmission unit 10 returns a response that acknowledges communication by CDC-HPD to the reception unit 20.

  Next, the control circuit CTR1 of the transmission unit 10 turns on the power supply notification switch SWD and turns off the power disconnection switch SWC. After preparing for power supply, the power supply circuit 16 requests the control circuit CTR2 of the receiving unit 20 to start power supply with a CDC command. The control circuit CTR2 of the receiving unit 20 turns on the power supply switch SWA to start power supply, turns off the power supply direction notification switch SWB, and notifies the control circuit CTR1 of the transmission unit 10 of the start of power supply with a CDC command. To do.

  In response to the power supply start command, the control circuit CTR1 of the transmission unit 10 turns on the power cut switch SWC and starts receiving power. That is, the power supply voltage is supplied from the voltage source of the voltage Vcc of the receiving unit 20 to the control circuit CTR1 of the transmitting unit 10 through the path of the power supply voltage supply line (PW + 5V), the power reception notification switch SWD, and the HPD line. During the period in which the HPD line potential remains high, power supply from the receiving unit 20 side is continued.

  Next, a case where power supply is stopped will be described. First, the control circuit CTR1 of the transmission unit 10 turns off the power disconnect switch SWC and temporarily stops receiving power from the power supply voltage supply wiring (PW + 5V).

  Subsequently, the control circuit CTR1 prepares that the power supply circuit 16 generates the voltage Vcc and supplies it to the power supply voltage supply wiring (PW + 5V). Subsequently, a CDC command for stopping power supply is transmitted. The control circuit CTR2 of the receiving unit 20 receives the power supply stop command, turns on the power direction notification switch SWB, turns off the power supply switch SWA, and notifies the transmission unit 10 of the stop of power supply. The transmitter 10 turns on the power disconnect switch SWC and starts supplying the voltage Vcc to the power supply voltage supply wiring (PW + 5V).

Next, the control circuit CTR2 of the receiving unit 20 sends a command for canceling the use of CDC-HPD, and the control circuit CTR1 of the transmitting unit 10 returns a response that acknowledges the use of CDC-HPD. When the power supply request is stopped as described above, the supply of the power supply voltage Vcc from the reception unit 20 to the transmission unit 10 is stopped, and the supply of the power supply voltage Vcc from the transmission unit 10 to the reception unit 20 is started.
Note that the start and end commands for use of CDC-HPD shown in the above example may or may not be used.

  Next, an operation example in the case where the voltage Vcc is not supplied from the transmission unit 10 when the transmission unit 10 and the reception unit 20 are connected by the connection unit will be described.

  First, the control circuit CTR2 of the receiving unit 20 causes the monitoring circuit 28 to monitor the potentials of the SCL line and the SDA line, and acquires the state of the transmitting unit 10. When the voltage Vcc is not output from the power supply circuit 16, the SCL line and the SDA line are electrically connected by the switch circuit 18. At this time, the monitoring circuit 28 detects that the SCL line is at a high level and the SDA line is at a low level, and the voltage Vcc is not supplied from the transmission unit 10 to the control circuit CTR2. A signal to notify that is output. In this case, the control circuit CTR2 of the reception unit 20 turns on the power supply switch SWA and turns off the power supply direction notification switch SWB, and supplies the voltage Vcc to the transmission unit 10.

  When the voltage Vcc is supplied from the transmitter 10, the switch circuit 18 connects the SCL line and the SDA line to the control circuit CTR1 and supplies a predetermined signal. When the monitoring circuit 28 detects that the SCL line is at a high level and the SDA line is at a predetermined potential (for example, 2.5 V), the voltage Vcc is supplied from the transmission unit 10 to the control circuit CTR2. Output a signal to notify that In this case, the control circuit CTR2 of the receiving unit 20 performs the power supply voltage supply operation shown in FIG.

  When the transmitting unit 10 is not electrically connected to the IO port to which the SCL line and the SDA line of the receiving unit 20 are connected, the monitoring circuit 28 detects that the IO port is open, A signal notifying that the transmission unit 10 is not connected to the control circuit CTR2 is output.

  As described above, when the switch circuit 18 and the monitoring circuit 28 are provided, for example, when the battery BT cannot be discharged and the voltage Vcc cannot be supplied from the transmission unit 10, the voltage from the reception unit 20. By supplying Vcc, the transmitter 10 can be activated to perform signal transmission processing.

  Next, a case where the power supply voltage supply amount from the receiving unit 20 to the transmitting unit 10 is increased will be described. FIG. 3 is a timing chart for explaining an operation example in which the power supply voltage supply amount is increased while the power supply voltage is being supplied from the reception unit 20 to the transmission unit 10.

  In this example, an HDMI selector (including a transmission unit 10 and a reception unit 20) that connects between a stationary transmission device such as a set-top box or a recorder and a stationary device such as a digital television receiver. Is assumed. Such a device may be used with an external power supply (AC adapter) attached thereto, but if this embodiment is applied, an external power supply becomes unnecessary.

  First, the control circuit CTR2 of the receiving unit 20 inquires of the control circuit CTR1 of the transmitting unit 10 with a CDC command whether the power supply amount can be increased. The control circuit CTR1 of the transmission unit 10 responds to the control circuit CTR2 of the reception unit 20 that there is a function of increasing the power supply amount. Information indicating the suppliable amount may be added to the inquiry or response at this time.

  Next, the control circuit CTR2 of the receiving unit 20 notifies the control circuit CTR1 of the transmitting unit 10 that the communication of the function related to HDCP is replaced with the CDC-HPD command defined by HDMI 1.4. The control circuit CTR1 of the transmission unit 10 returns a response that acknowledges communication using the CDC-HPD command to the control circuit CTR2 of the reception unit 20.

  Next, the control circuit CTR2 of the receiving unit 20 requests an increase in power supply amount with a CDC-HPD command. The control circuit CTR1 of the transmitter 10 increases the power supply amount after turning on the power supply notification switch SWD, and responds to the control circuit CTR2 of the receiver 20 with the completion of the power supply amount with a CDC-HPD command.

  Next, the control circuit CTR2 of the receiving unit 20 turns off the power direction notification switch SWB. The control circuit CTR1 of the transmission unit 10 and the control circuit CTR2 of the reception unit 20 continue to detect the HPD line, and the amount of power supplied from the transmission unit 10 during the period when the potential of the HPD line is kept high. Increase.

  Subsequently, an operation example of the power supply amount increase stop will be described. First, a stop request for the power supply increasing function is transmitted from the transmission unit 10 using a CDC-HPD command. The control circuit CTR2 of the receiving unit 20 turns on the power supply direction notification switch SWB, and then returns a response that approves the stop of power supply increase to the control circuit CTR1 of the transmitting unit 10.

  Next, it is confirmed that the state where the potential of the HPD line is high (High) is continued, and a command for stopping the use of CDC-HPD is issued from the control circuit CTR2 of the receiving unit 20 to the control circuit of the transmitting unit 10 Send to CTR1. The control circuit CTR1 of the transmission unit 10 returns a response that acknowledges the use stop of the CDC-HPD. As described above, the power supply amount increase stop is completed.

  In addition, although the example which transmits the increase cancellation request command from the transmission part 10 was shown, you may transmit a cancellation command from control circuit CTR2 of the receiving part 20 conversely.

  FIG. 4 shows an example of a cancel operation applicable in the power supply voltage supply operation and the power supply voltage increase operation.

  The control circuit CTR1 of the transmission unit 10 and the control circuit CTR2 of the reception unit 20 continue to detect the potential of the HPD line after the start of power supply from the transmission unit 10 or the start of increase in the amount of power supply, and the potential of the HPD line is high. When the (High) level changes to the low (Low) level, the transmitting unit 10 and the receiving unit 20 immediately stop the operation related to power supply, turn off the power supply switch SWA, and turn on the power direction notification switch SWB. The power cut switch SWC is turned on, the power supply notification switch SWD is turned off, and the voltage Vcc is supplied from the power supply circuit 16 to the power supply voltage supply line (PW + 5V).

  As described above, according to the power supply circuit according to the present embodiment, power can be supplied to the connected device (transmitting device side) via connection means such as an HDMI cable, and signal transmission is performed in the operation mode of the connected device (battery operation). ) Is no longer dependent on. In addition, even when signal transmission is not performed from the connected device, it is possible to charge the battery simply by connecting an HDMI cable or the like, and user convenience can be improved. Further, it is possible to reliably determine whether the HDMI cable is disconnected during a signal transmission operation from the transmitting device.

  That is, according to the power supply circuit according to the present embodiment, it is possible to provide a power supply circuit that can supply power from the receiving unit to the transmitting unit and is not restricted by the power supply situation of the receiving device.

  In the above power supply circuit, the HDMI communication and the HDMI-CEC communication are used for searching for the power supply function and controlling the power supply function. For example, either or both of the HPD line and the UTIL line are used. May be. Even in this case, the same effect as that of the power supply circuit according to the embodiment can be obtained.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  SWC ... Power disconnection switch (switch), SWD ... Power supply notification switch, SWA ... Power supply switch, SWB ... Power direction notification switch, BT ... Battery, Vcc ... Voltage, SCL ... Connection line, SDA ... Connection line, R1 ... Resistor, R2 ... Resistor, CTR1, CTR2 ... Control circuit, 10 ... Transmitter, 10B, 20B ... Connector, 12 ... Encoder, 14 ... Buffer, 16 ... Power supply circuit, 18 ... Switch circuit, 18A, 18B ... Analog switch , 20: receiving unit, 10A, 20A ... receptor, 22 ... decoder, 24 ... buffer, 26 ... recording means (ROM), 28 ... monitoring circuit.

Claims (1)

A transmission unit for transmitting video;
A receiver for receiving the video transmitted from the transmitter;
A connecting means for connecting the transmitting section and the receiving section, comprising: a power supply wiring for transmitting a power supply voltage; and a third wiring;
A power supply circuit comprising:
The receiver includes a power supply switch that switches a connection between a voltage source and the power supply wiring,
The transmission unit changes a potential of the third wiring to a predetermined potential in response to a power supply circuit that outputs a predetermined voltage to the power supply wiring and a predetermined voltage not being output from the power supply circuit to the power supply wiring. A switch circuit
The power supply switch turns on the connection between the voltage source and the power supply wiring and outputs the voltage from the voltage source to the transmitting unit via the power supply wiring when the third wiring is not at the predetermined potential. A power supply circuit that turns off the connection between the voltage source and the power supply wiring when the third wiring is at the predetermined potential.

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