Abstract:
An overcurrent protection circuit includes a universal serial bus (USB) controller having an overcurrent detection pin, and a plurality of USB connectors each electronically connected to a USB device and the overcurrent detection pin. The USB controller communicates with the USB devices respectively via the USB connectors. When the overcurrent detection pin detects an overcurrent occurrence in one of the USB devices, the USB controller stops communicating with all of the USB devices.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The exemplary disclosure generally relates to overcurrent protection circuits, particularly to an overcurrent protection circuit for universal serial bus (USB) devices. 
         [0003]    2. Description of Related Art 
         [0004]    A typical USB controller used in a computer communicates with a plurality of USB devices via a respective plurality of USB connectors. The USB controller usually has a plurality of overcurrent detecting pins each configured for detecting whether an overcurrent occurs in a USB device. When the overcurrent occurs in a USB device, the USB controller stops communicating with the USB device to prevent the USB connector and the USB device from burning out due to the occurrence of the overcurrent. 
         [0005]    However, because the USB controller is typically integrated within a south bridge chip, some overcurrent detecting pins of the USB controller may be used as general purpose input output (GPIO) pins of the south bridge chip occasionally, and cannot be used for overcurrent detection. Thus, at this time, some USB connectors of the computer cannot be protect from overcurrent by the USB controller. 
         [0006]    Therefore, there is room for improvement within the art. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Many aspects of the embodiments can be better understood with reference to the drawing. In the drawing, the emphasis is placed upon clearly illustrating the principles of the disclosure. 
           [0008]    The FIGURE is a schematic circuit diagram of an exemplary embodiment of an overcurrent protection circuit. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    The FIGURE is a schematic circuit diagram of an exemplary embodiment of an overcurrent protection circuit  10 . The overcurrent protection circuit  10  includes a USB controller  11 , a first power supply VCC 1 , a second power supply VCC 2 , a pull-up resistor R 1 , a plurality of USB connectors, a plurality of fuses, a plurality of diodes, and a plurality of filter capacitors. Each USB connector is electronically connected to a USB device  20 . The USB controller  11  communicates with the USB devices  20  respectively via the USB connectors. In one embodiment, the USB overcurrent protection circuit  10  includes three USB connectors J 1 -J 3 , three fuses F 1 -F 3 , three diodes D 1 -D 3 , and three filter capacitors C 1 -C 3 . 
         [0010]    The USB controller  11  has an overcurrent detection pin OC. The first power supply VCC is electronically connected to the overcurrent detection pin OC via the pull-up resistor R 1 . A node between the pull-up resistor R 1  and the overcurrent detection pin OC is electronically connected to anodes of the diodes D 1 -D 3 . The cathodes of the diodes D 1 -D 3  are electronically connected to power pins VCC respectively of the USB connectors J 1 -J 3 . A node between the diode D 1  and the USB connector J 1  is electronically connected to the second power supply VCC 2  via the fuse F 1 , and is grounded via the filter capacitor C 1 . Similarly, a node between the diode D 2  and the USB connector J 2  is electronically connected to the second power supply VCC 2  via the fuse F 2 , and is grounded via the filter capacitor C 2 . A node between the diode D 3  and the USB connector J 3  is electronically connected to the second power supply VCC 2  via the fuse F 3 , and is grounded via the filter capacitor C 3 . 
         [0011]    Each USB connector further includes a forward differential signal pin D+, and a reverse differential signal D−. The forward differential signal pins D+, and a reverse differential signal pins D− are electronically connected to the USB controller  11  to allow the USB connectors J 1 -J 3  to communicate with the USB controller  11 . Since the forward differential signal pins D+ and the reverse differential signal pins D− are connected to the USB controller  11  in a well-know way, the connection circuit between the USB controller  11  and the differential signal pins D+ and D− are not shown in the FIGURE. 
         [0012]    The voltage of the first power supply VCC 1  is lower than the voltage of the second power supply VCC 2 . In one embodiment, the voltage of the first power supply VCC 1  is 3.3 volts, and the voltage of the second power supply VCC 2  is 5 volts. When all of the USB devices  20  are working in a normal state, since the voltage of the first power supply VCC 1  is lower than the voltage of the second power supply VCC 2 , the diodes D 1 -D 3  are cut off, the voltage of the overcurrent detection pin OC is a high level voltage (e.g. logic 1). At this time, the USB controller  11  communicates with the USB devices  20  normally, and the USB devices  20  are powered by the second power supply VCC 2  respectively via the USB connectors J 1 -J 3 . If an overcurrent occurs in any one of the USB device  20 , that is, the current of one USB device  20  obtained from the second power supply VCC 2  exceeds a threshold current, the USB controller  11  cuts off all communications with the USB devices  20 . For example, when an overcurrent occurs in the USB device  20  connected to the USB connector J 1 , the fuse F 1  connected between the USB connector J 1  and the second power supply VCC is fused, to make the diode D 1  to switch on. At this time, the voltage of the overcurrent detection pin OC is switched to a low level voltage (e.g. logic 0), the USB controller  10  stops communicating with all of the USB devices  20 . Therefore, the plurality of USB connectors J 1 -J 3  can share one overcurrent detection pin OC to obtain overcurrent protection, and the other overcurrent detection pins of the USB controller  11  can be always used as GPIO pins. 
         [0013]    It is believed that the exemplary embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the disclosure or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the disclosure.