JP2008305148A - Usb power supply booster - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a USB booster for supplying a power supply voltage capable of driving a USB device even if the length of a USB cable is extended. <P>SOLUTION: In the case of supplying the power supply voltage from a USB host 1 to the USB device 7 through the USB cable, the USB power supply booster 10 is inserted into an optional position of the USB cable to monitor the power supply voltage on a power supply cable VBUS which is outputted to the USB device 7, and when the power supply voltage is reduced lower than a previously determined voltage threshold, the power supply voltage is boosted up to the voltage threshold and outputted to the USB cable 7 side through the USB cable. When the USB device 7 is disconnected or the power supply voltage outputted to the USB device 7 is boosted to the voltage threshold and higher, power supply voltage boosting operation in the USB power supply booster 10 is stopped. The USB power supply booster 10 is composed of a boost coil type DC-DC converter. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a USB power booster.

  In recent years, as described in Japanese Patent Application Laid-Open No. 2003-280771 “In-vehicle device” of Patent Document 1, in the field of a car navigation system and the like, a hard disk, a music player, and the like via USB (Universal Serial Bus) Various terminal devices (USB devices) such as sensors are connected. FIG. 4 is a connection configuration diagram showing an example of a conventional USB connection method for an in-vehicle device, and shows a case where a USB device is connected to a car navigation system.

  As shown in FIG. 4, as a USB host 1, a car navigation system equipped with a USB host controller 4 and a USB device 7 include a power cable VBUS, signal cables D +, D-, and an earth cable between the USB connectors 5 and 6. It is connected by a USB cable made of GND. In order to supply power to the USB device 7, the USB host controller 4 turns on the switch SW3, connects the power source 2 of + 5V (maximum current capacity 1.5A) to the USB connector 5, and passes through the power cable VBUS. Then, power is supplied to the connected USB device 7.

The USB device 7 operates by power supplied from the car navigation system, that is, the USB host 1 through the power cable VBUS. Here, the operation guarantee voltage range of the USB device 7 is generally DC + 5V ± 5% in accordance with the standard of the power source 2 of the USB host 1.
Japanese Patent Laying-Open No. 2003-280771 (page 5-6)

  However, in the conventional technology as shown in FIG. 4, since the USB connectors 5 and 6 are directly connected by the USB cable, when the USB cable length becomes long, the power supply is reduced by the voltage drop of the USB cable length. The power supply voltage supplied to the USB device 7 side via the cable VBUS decreases, and the USB device 7 may not operate.

  If the USB device 7 is a low power consumption device such as a USB flash memory, it can operate even if the power supply voltage drops slightly, but it is consumed by a portable hard disk or a hard disk music player. In the case of a device with a large electric power, there is a high possibility that it will not operate.

  In particular, when using an in-car car navigation system as a USB host, the car navigation system or the like must be attached to the center console of the car and the USB cable must be wired from the back. Needs to be extended over a considerable length, and the phenomenon of not operating as described above occurs.

  In other words, the power consumption from the power source 2 of the USB host 1 drops due to the power consumption consumed for the line resistance proportional to the USB cable length, and falls below the guaranteed operating voltage of the USB device 7 + 5V ± 5%. End up. If the impedance of the power cable VBUS is 1 ohm and the current consumption is 500 mA, the voltage drop is 0.5 V, and the USB device 7 drops to 4.5 V at the input point of the USB device 7. Will not work.

  The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a USB power booster that supplies power that allows a USB device to operate reliably even when the USB cable length is extended. It is aimed.

  In order to solve the above-described problems, the USB power booster according to the present invention employs the following characteristic configuration.

(1) A USB power booster that conforms to the USB (Universal Serial Bus) standard, and connects the USB host and the USB device when supplying a power supply voltage from the USB host to the USB device through a USB cable. A voltage that is inserted into an arbitrary portion of the USB cable, operates with a power supply voltage input from the USB host via the USB cable, and is output from the USB power booster to the USB device. A USB power booster that boosts to a threshold and outputs to the USB device via a USB cable.
(2) The USB power booster according to (1), wherein the power supply voltage boosting operation is suspended when the USB device is in a disconnected state.
(3) The USB power booster according to (1), wherein when the power supply voltage output to the USB device is equal to or higher than the voltage threshold, the power supply voltage boosting operation is suspended.
(4) A coil that connects one end to the power cable from the USB host, a switching transistor that connects one end to the other end of the coil, and connects the other end to ground, and one end connected to the other end of the coil. A Schottky diode that connects the other end to the output USB cable, an output capacitor that connects one end to the other end of the Schottky diode and the output USB cable, and connects the other end to the ground, and A drive control circuit connected to the gate of the switching transistor and controlling the gate according to the oscillation period of a built-in oscillator, and comparing the output voltage level of the output capacitor with the voltage threshold, The USB power source according to any one of the above (1) to (3), comprising a voltage monitoring circuit for controlling the operation of the control circuit Divider.
(5) When the voltage monitoring circuit detects that the output voltage level of the output capacitor is lower than the voltage threshold value, the voltage control circuit operates the drive control circuit and outputs the voltage from the output terminal. The USB power booster according to (4), which stops the operation of the drive control circuit when it is detected that no current is flowing.
(6) The USB power booster according to (4) or (5) above, wherein any one of an NPN transistor, a PNP transistor, or a field effect transistor is used as the switching transistor.

  According to the USB power booster of the present invention, the following effects can be obtained.

  First, since the USB power booster can be inserted and connected to any part of the USB cable, even if the cable length of the USB cable is extended long, the operation guarantee voltage of the USB device It is possible to supply a power supply voltage of + 5V ± 5%.

  Secondly, the USB power booster can be operated with the power of the USB host side, and can be configured as a small component with a small number of components as a component, for example, a small size of about 3 cm × 3 cm. And can be housed in any desired location.

  Third, even if the length of the USB cable is extended, it is possible to supply a power supply voltage of + 5V ± 5% that is the guaranteed operating voltage range at the input point of the power supply voltage to the USB device. Even a USB device with high power consumption that cannot be operated can be operated, and the number of operable USB devices can be remarkably increased. Further, the installation location of the USB device can also be an arbitrary location.

  Hereinafter, a preferred embodiment of a USB power booster according to the present invention will be described with reference to the accompanying drawings. The USB power booster according to the present invention can be used by being inserted into an arbitrary portion of the USB cable. For example, the USB power booster can be inserted and connected at a position immediately before the USB device, and boosted to a rated voltage of +5 V, It is possible to supply a USB device with a guaranteed operating voltage.

(Connection configuration of USB power booster)
FIG. 1 shows an example of a connection configuration of a USB power booster according to the present invention to a USB cable. As shown in FIG. 1, a USB power booster 10 according to the present invention is inserted and connected to an arbitrary location on a USB cable connecting a USB host 1 and a USB device 7 with USB connectors 11 and 12. FIG. 1 shows an example in which the USB device is inserted immediately before the USB device.

  Here, the USB power booster 10 incorporates a booster circuit 13 that pulls in the power cable VBUS from the USB host 1 from the USB connector 11 and boosts the power supply voltage to a predetermined rated voltage level (+5 V). The power supply voltage boosted by the circuit 13 is supplied from the USB connector 12 to the USB device 7 via the power supply cable VBUS. Further, the earth potential of the booster circuit 13 is set by the earth cable GND. On the other hand, other cables in the USB cable, that is, signal cables D + and D− are directly connected from the USB connector 11 to the USB connector 12 and pass through the USB power booster 10 through.

  Next, an example of the internal configuration of the USB power booster 10 according to the present invention will be described with reference to FIG. FIG. 2 is a circuit diagram showing an example of the internal configuration of the USB power booster 10 according to the present invention, and shows an example in which a DC-DC converter using a coil is used. Note that, instead of using a coil, the booster circuit may be configured using, for example, a charge pump system that charges up using a plurality of capacitors.

  As shown in FIG. 2, the USB power supply booster 10 includes a drive control circuit 16, a voltage monitoring circuit 17, an NPN transistor 18 and an output capacitor 19 having a coil 14, a Schottky diode 15, and an oscillator OSC 16a as a boosting circuit 13. The power cable VBUS from the USB host 1 is connected to the coil 14 through the USB connector 11, and one end of the Schottky diode 15 and the output capacitor 19 is connected from the USB connector 12 through the power cable VBUS. It is connected to the USB device 7 side.

  When the drive control circuit 16 turns on / off the NPN transistor 18 at a fixed period in which the built-in oscillator OSC 16a oscillates, energy is stored in the coil 14 during the time period when the NPN transistor 18 is turned on, and the NPN transistor 18 In the OFF time zone, the energy stored in the coil 14 is stored in the output capacitor 19 via the Schottky diode 15. The energy accumulated in the output capacitor 19 is output to the USB device 7 side as a boosted output voltage via the USB connector 12 and the power cable VBUS.

  The output voltage of the output capacitor 19 is monitored by the voltage monitoring circuit 17, and the control operation to the NPN transistor 18 of the drive control circuit 16 is performed according to whether or not the output voltage has reached a predetermined rated voltage (+5 V). By controlling, the output voltage is maintained at a predetermined rated voltage (+5 V) and supplied to the USB device 7 side.

  FIG. 2 shows the case where the NPN transistor 18 is used as the switching transistor. However, in some cases, a PNP transistor may be used, or a field effect transistor such as a CMOS type may be used. You may comprise.

(Description of operation of the embodiment)
Next, an example of an outline of the operation of the USB power booster 10 shown in FIGS. 1 and 2 will be described with reference to the flowchart of FIG. FIG. 3 is a flowchart for explaining an example of the operation outline of the USB power booster 10 according to the present invention.

  First, for example, when using a USB device 7 operating at a voltage level of the guaranteed operation voltage range + 5V ± 5% using a power source from a car navigation system, a USB cable between the USB host 1 and the USB device 7 is used. Is connected to the USB power booster 10 (step S1). As a result, the USB device 7 receives the power supply from the USB host 1 via the power cable VBUS and the USB power booster 10 and starts operation (step S2).

  The voltage monitoring circuit 17 of the USB power booster 10 constantly monitors whether or not the USB device 7 is in a disconnected state by turning off the switch depending on whether or not an output current flows (step S3). In such a case (YES in step S3), the USB power booster 10 shifts to a halt state by stopping the operation of the drive drive circuit 16 of the USB power booster 10.

  On the other hand, as long as the USB device 7 is in operation (NO in step S3), the voltage monitoring circuit 17 determines whether or not the output voltage of the output capacitor 19, that is, whether or not the power supply voltage of the power cable VBUS to the USB device 7 side has dropped. The monitoring operation is continued (step S4). When a voltage drop in the power supply voltage of the power cable VBUS is detected and falls below the rated voltage + 5V (YES in step S4), the drive control circuit 16 is driven and the NPN is generated at a constant cycle of the built-in oscillator OSC 16a. By performing ON / OFF operation of the transistor 18, the output voltage of the output capacitor 19, that is, the power supply voltage of the power cable VBUS to the USB device 7 side is boosted (step S 5). The step-up operation is repeated continuously until the output voltage of the output capacitor 19 reaches the rated voltage + 5V. When the voltage reaches the rated voltage + 5V (YES in step S4), the voltage monitoring circuit 17 stops the operation of the drive control circuit 16, whereby the USB power booster 10 shifts to a dormant state.

  The power supplied from the USB host 1 to the USB power booster 10 is set in consideration of the power consumption of the USB device 7, the amount of power loss of the USB cable, and the efficiency of the USB power booster 10. . Currently, there are many devices that satisfy the supply capability as the USB host 1 to which the present invention is applied, such as a commercially available device such as a PC.

  As described above, the USB power booster 10 has a small circuit scale such as the coil 14, the Schottky diode 15, the drive control circuit 16, the voltage monitoring circuit 17, the NPN transistor 18, and the output capacitor 19, and the USB host 1 side Since it is a structure that operates sufficiently with electric power, it is not necessary to provide a rechargeable battery, and can be sufficiently realized with a small size of about 3 cm × 3 cm.

  In the future, for example, in the field of in-vehicle equipment, in order to further improve the in-vehicle environment, the number of types that can connect various USB devices to car navigation, car audio, etc. will increase. Yes, even when the cable length of the USB cable is extended long, there is an increased number of scenes where the power supplied from the power cable VBUS needs to be sufficiently guaranteed by the power supply on the SB host 1 side. To do.

  The USB power booster 10 according to the present invention can reliably supply a power supply voltage of + 5V ± 5% of the guaranteed operating voltage range of the USB device 7 even when the cable length is extended. In addition, the circuit scale is small, the size is small, and it can be used easily regardless of location.

(Effect of this embodiment)
First, since the USB power booster 10 can be inserted and connected to an arbitrary portion of the USB cable, the operation of the USB device 7 is performed even when the cable length of the USB cable is extended. It is possible to supply a power supply voltage of + 5V ± 5% which is a guaranteed voltage.

  Second, the USB power booster 10 can be operated with the power on the USB host 1 side, and can be configured as a small component with a small number of components as a component, for example, about 3 cm × 3 cm. It can be realized in a small size and can be accommodated in any desired location.

  Third, even if the length of the USB cable is extended, it is possible to supply a power supply voltage of 5 V ± 5%, which is an operation guarantee voltage range, at the input point of the power supply voltage to the USB device 7. Can operate even the high power consumption USB device 7 that cannot be operated, and can greatly increase the number of operable USB devices. Further, the installation location of the USB device 7 can also be an arbitrary location.

  The configuration of the preferred embodiment of the present invention has been described above. However, it should be noted that such examples are merely illustrative of the invention and do not limit the invention in any way. Those skilled in the art will readily understand that various modifications and changes can be made according to a specific application without departing from the gist of the present invention.

It is a connection block diagram which shows an example of the connection structure to the USB cable of the USB power supply booster by this invention. It is a circuit diagram which shows an example of the internal structure of the USB power supply booster by this invention. It is a flowchart for demonstrating an example of the operation | movement outline | summary of the USB power supply booster by this invention. It is a connection block diagram which shows an example of the USB connection method of the conventional vehicle equipment.

Explanation of symbols

1 USB host 2 Power supply 3 Switch SW
4 USB host controller 5, 6 USB connector 7 USB device 10 USB power booster 11, 12 USB connector 13 booster circuit 14 coil 15 Schottky diode 16a oscillator OSC
16 Drive control circuit 17 Voltage monitoring circuit 18 NPN transistor 19 Output capacitor D +, D- Signal cable GND Ground cable VBUS Power cable

Claims (6)

  A USB power booster compliant with the USB (Universal Serial Bus) standard, and a USB cable for connecting the USB host and the USB device when supplying the power voltage from the USB host to the USB device through the USB cable. Inserted in any location, operates with power supply voltage input from the USB host via the USB cable, boosts the power supply voltage output from the USB power booster to the USB device to a predetermined voltage threshold A USB power booster that outputs to the USB device via a USB cable.   2. The USB power booster according to claim 1, wherein when the USB device is in a disconnected state, the power supply voltage boosting operation is suspended.   2. The USB power booster according to claim 1, wherein when the power supply voltage output to the USB device becomes equal to or higher than the voltage threshold, the power supply voltage boosting operation is suspended.   A coil having one end connected to a power cable from the USB host; a switching transistor having one end connected to the other end of the coil and the other end connected to ground; and one end connected to the other end of the coil, the other end A Schottky diode that connects to the output USB cable, an output capacitor that connects one end to the other end of the Schottky diode and the USB cable for output, and connects the other end to the ground, and the switching transistor A drive control circuit connected to the gate and controlling the gate in accordance with the oscillation period of the built-in oscillator, and comparing the output voltage level of the output capacitor with the voltage threshold value. The voltage monitoring circuit for controlling the operation is provided, and configured according to any one of claims 1 to 3. SB power booster.   When the voltage monitoring circuit detects that the output voltage level of the output capacitor is lower than the voltage threshold value, the voltage monitoring circuit operates the drive control circuit and the output current flows from the output terminal. 5. The USB power booster according to claim 4, wherein the operation of the drive control circuit is stopped when it is detected that the drive has not been detected.   6. The USB power booster according to claim 4, wherein any one of an NPN transistor, a PNP transistor, or a field effect transistor is used as the switching transistor.

Images