Patent Publication Number: US-2016226483-A1

Title: Control circuit and electronic device using the same

Description:
FIELD 
     The subject matter herein generally relates to control circuitry. 
     BACKGROUND 
     A universal serial bus (USB) device is usually charged by a battery of a notebook computer through a USB connector coupled to the notebook computer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       Implementations of the present technology will now be described, by way of example only, with reference to the attached FIGURE. 
       The FIGURE is a circuit diagram of an embodiment of an electronic device using a control circuit. 
     
    
    
     DETAILED DESCRIPTION 
     Numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures, and components have not been described in detail so as not to obscure the related relevant feature being described. Also, the description is not to be considered as limiting the scope of the embodiments described herein. 
     Several definitions that apply throughout this disclosure will now be presented. 
     The term “coupled” is defined as connected, whether directly or indirectly through intervening components, and is not necessarily limited to physical connections. The connection can be such that the objects are permanently connected or releasably connected. The term “comprising” when utilized, means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in the so-described combination, group, series and the like. 
     The FIGURE shows an electronic device  100  comprising a control circuit  10 , a power module  20 , and a connecting module  30 . The control circuit  10  can comprise a control module  40  and a switch module  50 . 
     In the embodiment, the electronic device  100  can be a notebook computer. The power module  20  can be a battery of the notebook computer. The power module  20  supplies power for the electronic device  100 . The control module  40  can be an integrated controller in the notebook computer. The connecting module  30  can be a universal serial bus (USB) connector. The power module  20  supplies power for the connecting module  30  when the power module  20  is coupled to the connecting module. The connecting module  30  comprises a power pin  1 , a signal pin  2 , a signal pin  3 , and ground pins  4 - 8 . The signal pin  2  and the signal pin  3  are used to transmit signals when the electronic device  100  is coupled to an external USB device through the connecting module  30 . 
     The control module  40  can comprise a first port  1  and a second port  2 . The first port  1  is coupled to the power module  20  and the second port  2  is coupled to the switch module  50 . 
     The switch module  50  can comprise power terminals V 1  and V 2 , a resistor R, a capacitor C, and transistors Q 1  and Q 2 . In the embodiment, the transistor q 1  is a NPN transistor and the transistor Q 2  is an n-channel FET. A base of the transistor Q 1  as a control terminal is coupled to the second port  2  of the control module  40 . An emitter of the transistor Q 1  as a second terminal is grounded. A collector of the transistor Q 1  as a first terminal is coupled to the power terminal V 1  through the resistor R. A gate of the transistor Q 2  as a control terminal is coupled to the collector of the transistor Q 1 . A drain of the transistor Q 2  as a first terminal is coupled to the power terminal V 2 . A source of the transistor Q 2  as a second terminal is coupled to the power pin of the connecting module  30 . The drain of the transistor Q 2  is also grounded through the capacitor C. In the embodiment, the power terminal V 1  receives a first voltage from the power module  20  through a motherboard of the electronic device  100 . The second power terminal V 2  receives a second voltage from the power module  20  through the motherboard of the electronic device  100 . 
     In use, the control module  40  detects a level of power in the power module  20  and outputs a control signal to the second port  2 . 
     When the level of power in the power module  20  exceeds a preset value, the control signal is at a low level, such as logic 0. The transistor Q 1  is turned off and the FET Q 2  is turned on. The power terminal V 2  is connected to the power pin  1  of the connecting module  30  and the second voltage is output to the connecting module  30 . 
     When the level of power in the power module  20  does not exceed the preset value, the control signal is at a high level, such as logic 1. The transistor Q 1  is turned on and the transistor Q 2  is turned off. The power terminal V 2  is disconnected from the power pin  1  of the connecting module  30  and the second voltage is not output to the connecting module  30 , thus the power module stops supplying power for the connecting module. 
     While the disclosure has been described by way of example and in terms of the embodiment, it is to be understood that the disclosure is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements as would be apparent to those skilled in the art. Therefore, the range of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.