KR100711006B1 - Apparatus for Controlling VBUS Power in USB Device - Google Patents

Abstract

The present invention relates to a VBUS power control device in a USB device.

The present invention is a device for controlling the power of the VBUS according to the operation mode of the USB device in a USB device having both a USB host function and a USB device function, which is connected to the USB device while periodically switching the operation mode A micro controller unit (MCU) configured to sense an external host or an external device to determine the operation mode of the USB device, and generate a control signal for controlling the power of the VBUS according to the determined operation mode; And receiving the control signal from the MCU and receiving power from the external host through the VBUS if the determined operation mode is a device mode, and powering the external device through the VBUS if the determined operation mode is a host mode. Provides a VBUS power control unit for controlling the VBUS so as to reduce the leakage current and the power supplied to the VBUS is not fed back to the USB device provides a device for power control of the VBUS do.

According to the present invention, it is possible to implement host and device operation in one USB device by controlling VBUS power and sensing a state.

 USB, VBUS, Power Control, Host, Device

Description

USB power control device in USB device {Apparatus for Controlling VBUS Power in USB Device}

1 is a diagram schematically illustrating an internal configuration of a USB device having both a host function and a device function according to the present invention;

2 is a circuit diagram illustrating a VBUS power control unit according to the present invention.

<Explanation of symbols for the main parts of the drawings>

100: USB device 110: power generation unit

120: MCU 130: USB host unit

140: USB device unit 150: VBUS power control unit

The present invention relates to a VBUS power control device in a USB device. More specifically, a USB device having both a USB host function and a USB device function periodically switches the operation mode and detects an externally connected host or device to determine the operation mode of the USB device, and the USB device is a device mode. Detects whether the VBUS is powered externally and supplies power from the external host through the VBUS to use as the total system power.If the USB device operates in host mode, it supplies power to the VBUS but does not leak itself. A VBUS power control device in a USB device that controls VBUS to reduce current and prevent VBUS power from being fed back into the USB device.

The Universal Serial Bus (USB) is an interface device for connecting a computer with a peripheral device such as a mouse, a printer, a modem, a speaker, and the like. When connecting peripherals to a computer, USB connects all peripherals to the same connector without setting up software or hardware, which is easy to install and has the advantage of connecting up to 127 devices in a chain. In addition, since USB supports a Plug and Play function that recognizes even when a peripheral device is connected while using a computer, it is easy to connect a small digital device having a USB interface to the computer.

Although USB 1.1, the conventional USB standard, supports data transfer speeds of 12 Mbps, the USB 2.0 standard supports data transfer rates of up to 480 Mbps while maintaining compatibility with USB 1.1 devices. It is possible.

The USB device is classified into a host device and a device device. The host device performs functions such as power supply and signal control to the device device, and the device device analyzes a signal received from the host device and operates in a corresponding response form. Therefore, the computer corresponds to a host device for the USB interface, and various peripheral devices connected to the computer correspond to the device device.

However, a USB interface in which a computer acts as a host device has a limitation in that the device device must be connected to the computer. Therefore, in order to solve such a problem, a USB system having both a host function and a device function has been proposed to solve such a problem, and a typical example is On-The-Going (OTG).

OTG is a non-dependent USB interface that allows USB device devices to have their own host function and send and receive data without going through a computer. There is an advantage to increase.

However, when both the host function and the device function are used using one USB port, there is a problem in that power control of the power signal VBUS is not easy according to an operation mode. In order to solve this problem, conventionally, a USB device for adopting a mode switching method and manually selecting a host mode or a device mode to perform a corresponding mode operation has been proposed, but has the following problems.

The conventional mode switching method is inconvenient in terms of user interface, and when the USB device is turned off and connected to an external host device, the power does not turn on automatically. Therefore, the USB device must be powered on and switched to device mode. There is this. In addition, when the USB device operates in the host mode, there are many leakage currents, and since a plurality of control signals are required for operation, the configuration of the USB device is complicated.

In order to solve this problem, the present invention, in the USB device having both a USB host function and a USB device function periodically detects a host or device connected from the outside while determining the operation mode of the USB device, When the USB device operates in device mode, it receives power from an external host through VBUS. When the USB device operates in host mode, it supplies power to VBUS, reducing leakage current and preventing VBUS power from feeding back into the USB device. An object of the present invention is to provide a VBUS power control device in the USB device for controlling the.

According to an object of the present invention, a device for controlling the power of the VBUS according to the operation mode of the USB device in a USB device having both a USB host function and a USB device function, the USB device while periodically switching the operation mode A micro controller unit (MCU) configured to detect an external host or an external device connected to the device to determine the operation mode of the USB device, and generate a control signal for controlling the power of the VBUS according to the determined operation mode; And receiving the control signal from the MCU and receiving power from the external host through the VBUS if the determined operation mode is a device mode, and powering the external device through the VBUS if the determined operation mode is a host mode. And a VBUS power control unit for controlling the VBUS such that the leakage current is reduced and power supplied to the VBUS is not fed back to the USB device. to provide.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First of all, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are used as much as possible even if displayed on different drawings. In addition, in describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted.

According to the USB standard, when a USB device device is connected to a USB host device, it is regulated to supply power from the host device to the device device, and generally 5 V power is supplied through VBUS.

Therefore, when a USB device supports both host function and device function by using one USB port, the device mode detects VBUS and receives power from an external host through VBUS to use as internal power of the USB device. In host mode, it is necessary to control the VBUS so that it is powered by the VBUS but the power of the VBUS is not fed back into the USB device.

1 is a diagram briefly illustrating an internal configuration of a USB device having both a host function and a device function according to the present invention.

As shown in FIG. 1, the USB device 100 having both a host function and a device function includes a system power generator 110, a microcontroller unit 120, and a USB host unit 130. ), The USB device unit 140, the VBUS power control unit 150, and the like.

The power generator 110 supplies power required to the USB device 100, and when the USB device 100 operates as a host, supplies power to the external device device connected to the USB device 100 through VBUS. .

The MCU 120 controls the overall operation of the USB device 100. The MCU 120 determines an operation mode of the USB device 100 according to the type of external device connected to the USB device 100. That is, the MCU 120 operates in the device mode when the external host is connected, and controls the USB device 100 to operate in the host mode when the external device is connected. To this end, the MCU 120 periodically switches the mode of the USB device 100 and detects whether there is an external USB device connected to the USB device 100. For example, if there is no external device connected to the USB device 100, the periodic mode switching is continued. If the external device is connected in the host mode period or the external host is connected in the device mode period, the periodic mode switching is stopped. The USB device 100 operates in the corresponding mode.

The MCU 120 generates a control signal for controlling the power of the VBUS according to a mode (host mode / device mode) in which the USB 100 device operates and transmits the control signal to the VBUS power controller 150. Here, the control signal is transmitted to the VBUS power control unit 150 through the GPIO (General Purpose Input / Output) of the MCU 120, the GPIO of the MCU 120 has an Open-Drain port function for the output and for the input Designed to be 5V tolerant and have edge or level detector interrupt capability, one port can control both host and device modes.

The USB host unit 130 and the USB device unit 140 perform a USB host function and a USB device function, respectively, under the control of the MCU 120. Functions as a USB host and a USB device are well known to those skilled in the art, so a detailed description thereof will be omitted.

The VBUS power controller 150 controls the VBUS to perform both the host function and the device function in the USB device 100. The VBUS power controller 150 receives the control signal from the MCU 120 and receives power from the external host through the VBUS if the determined operation mode is the device mode. If the determined operation mode is the host mode, the VBUS power controller 150 receives the control signal from the MCU 120. The power is supplied, but the leakage current is reduced and the VBUS is controlled so that the power supplied to the VBUS is not fed back to the USB device 100. An internal configuration of the VBUS power controller 150 will be described in detail with reference to FIG. 2.

2 is a circuit diagram illustrating a VBUS power control unit according to the present invention.

As shown in FIG. 2, the VBUS power controller 150 is connected to the VBUS and the power generator 110, and control signals from the MCU 120 are transmitted to the transistors Q0 and Q2. Description of the components of the circuit diagram shown in FIG. 2 is as follows.

The DO is a Schottky diode, which serves to prevent the power supplied from the external host to the VBUS from being transferred to the power generator 110 of the USB device 100. The transistor Q0 is controlled by a control signal from the MCU 120, and is turned on when the USB device 100 operates in the host mode, and is turned off when the USB device 100 operates in the device mode, which is turned off by an internal diode. It connects host and VBUS.

When the USB device 100 operates in the host mode, the transistor Q1 is turned on to transfer the power of the power generator 110 to VBUS and to block the power of the VBUS from being fed back to the power generator 110. OFF when the device operates in device mode. Transistor Q2 is controlled by a control signal from MCU 120 and controls transistor Q1.

Resistors R1, R2, R3, R4 and R5 can be used to reduce the leakage current of USB device 100. The leakage current generated when the USB device 100 operates in the host mode can be expressed as I = 5V / R1 + 5V / R2 + 5V / R4. If the value of R1, R2, and R4 is set large enough, the leakage current can be reduced. Can be. For example, if R1 = 800k, R2 = 800k, R3 = 800k, the leakage current is about 18.75 μA. When the USB device 100 operates in the device mode, since the power is supplied from the external host through VBUS, the leakage current may not be considered. In this case, the leakage current I = 5V / R5 may be expressed as If the value is large enough, the effect of leakage current is negligible.

Meanwhile, the USB device 100 of the present invention may perform an automatic power-on function by using the VBUS power controller 150. When the external host device is connected to the USB device while the power supply of the USB device 100 is turned off, the power supplied to the VBUS from the external host device is transferred through the R1 and the R4 so that the transistors Q2 and Q1 are turned on. The USB device 100 may be automatically driven by being connected to the power supply 110 through the transistor Q1.

On the other hand, CONTROL SIGNAL1 can be connected to the ground (Ground) of the system or controlled through the MCU (120), when controlling through the MCU (120) when the host mode in the GPIO state of the MCU (120) as input To quickly discharge VBUS power when switching from host mode to device mode, the GPIO state can be switched to an output that will output a '0' and then switch back to an input. That is, in a preferred embodiment of the present invention, when switching from the host mode to the device mode, to use the CONTROL SIGNAL1 control signal to quickly discharge the power of the VBUS, to ground the CONTROL SIGNAL1 control signal or through the CONTROL SIGNAL1 control signal It can be used to detect external hosts.

The above description is merely illustrative of the present invention, and those skilled in the art to which the present invention pertains may various modifications without departing from the essential characteristics of the present invention. Accordingly, the embodiments disclosed herein are not intended to limit the present invention but to describe the present invention, and the spirit and scope of the present invention are not limited by these embodiments. It is intended that the scope of the invention be interpreted by the following claims, and that all descriptions within the scope equivalent thereto shall be construed as being included in the scope of the present invention.

As described above, the present invention automatically detects a host or device connected externally while periodically switching the operation mode without having to manually specify the operation mode in a USB device having both host and device functions. There is an effect that can be determined.

In addition, the present invention is effective to increase the efficiency of the USB device by controlling the VBUS power to minimize the leakage current when the USB device is operating in the host mode so that the power supplied to the VBUS is not fed back into the USB device have.

Claims (6)

In the device for controlling the power of the VBUS according to the operation mode of the USB device in the USB device having both USB host function and USB device function, The MCU for periodically detecting the external host connected to the USB device while switching the operation mode to determine the operation mode of the USB device, and generates a control signal for controlling the power of the VBUS according to the determined operation mode ( Micro Controller Unit); And The controller receives the control signal from the MCU and receives power from the external host through the VBUS when the determined operation mode is a device mode. When the determined operation mode is the host mode, power is supplied to the external device through the VBUS. And a VBUS power control unit for controlling the VBUS so as to reduce leakage current and prevent the power supplied to the VBUS from being fed back to the USB device. The VBUS power control unit may include: a Schottky diode D0 for blocking power supplied from the external host to the VBUS from being transferred to the power generation unit of the USB device; A transistor Q0 controlled by the control signal, the transistor Q0 being turned off when the determined operation mode is a device mode and connected to the external host and the VBUS by a diode inside the transistor, and controlled to be turned on when the determined operation mode is the host mode; A transistor Q1 that is turned OFF when the determined mode is a device mode, and is turned ON when the determined mode is a host mode, and transfers power of the power generator to the VBUS and blocks the power of the VBUS from being fed back to the power generator; A transistor Q2 controlled by the control signal and controlling the transistor Q1; And resistors R1, R2, R3, R4, and R5 for reducing leakage current of the USB device, The control signal is transmitted to the VBUS power control unit through the GPIO (General Purpose Input / Output) of the MCU. (Edge) or Level Detector Interrupt function, the MCU detects whether the external host is connected based on the input from the VBUS power control unit via the GPIO Apparatus for power control of the VBUS, characterized in that. delete delete The method of claim 1, When the external host is connected to the USB device while the power supply of the USB device is turned off, the power supplied from the external host to the VBUS is transferred through the resistor R1 and the resistor R4 to the transistor Q2 and the transistor. Transistor Q1 is in an ON state, the device for power control of VBUS, characterized in that connected to the power generation unit of the USB device via the transistor Q1 to drive the USB device automatically. delete delete

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