Abstract:
The present invention is to provide a voltage input circuit applied to a notebook computer, which includes a first voltage terminal for receiving and outputting voltage, a first protection loop connected to the first voltage terminal and a second voltage terminal, a second protection loop connected between the first protection loop and the second voltage terminal, and a discharge loop connected between the second protection loop and the second voltage terminal. When a short condition occurs in the notebook computer, the first protection loop electrically cuts the connection between the first and second voltage terminals and outputs voltage to the discharge loop through the second protection loop, so as to prevent circuits or electronic components in the notebook computer from being burned or damaged.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a voltage input circuit, and more particularly to a voltage input circuit of an note book. 
       BACKGROUND OF THE INVENTION 
       [0002]    To operate an electronic product successfully anytime and anywhere, it is necessary to overcome a voltage supply issue of the design and development of various electronic products. Regardless of home electric appliances or portable electronic devices, a voltage supply is required for their operations. Particularly for portable electronic devices, it is necessary to have a design of supplying sufficient voltage to the devices all the time anywhere, and thus a perfect circuit design for inputting or converting voltage is required to ensure that the portable electronic devices can receive voltage safely. In addition, it is necessary to prevent an abnormal loop caused by a short condition of a circuit board of a portable electronic device due to water, dust, or other factors, since a surge current usually has an adverse impact on the electronic components of the circuit board or damages the circuit or electronic components. Therefore, some manufacturers provide a protection circuit to prevent short conditions. 
         [0003]    Referring to  FIG. 1  for a protection circuit applied to an electronic device, the protection circuit comprises a switch chip  100  and a comparator  102 . The switch chip  100  is disposed between a voltage input terminal  12  and a working circuit  14  of the electronic device. The voltage input terminal  12  is provided for receiving and outputting voltage for the operation of the electronic device. The comparator  102  is coupled separately to the voltage input terminal  12  and the switch chip  100 . If the voltage inputted from the voltage input terminal  12  is higher than a predetermined voltage in the comparator  102 , then the comparator  102  will continue outputting a control signal to switch chip  100 , such that the switch chip  100  will conduct the voltage input terminal  12  and the working circuit  14 , and the voltage will be outputted to the electronic device. If a short condition occurs in the electronic device, then the current will be increased and the voltage will be decreased. If the voltage is lower than the predetermined voltage, then the comparator  102  will interrupt outputting the control signal to the switch chip  100  and disconnect the voltage input terminal  12  and the working circuit  14 . Therefore, the voltage will not be outputted to the electronic device to prevent the increased current from damaging a circuit or an electronic component. 
         [0004]    Although the aforementioned protection circuit can interrupt outputting the voltage to the electronic device when a short condition occurs in the electronic device, the comparator  102  still receives the voltage transmitted from the voltage input terminal  12 . If the voltage received by the comparator  102  is higher than the predetermined voltage, then the comparator  102  will continue outputting a control signal to the switch chip  100 . So that the switch chip  100  will conduct the voltage input terminal  12  and the working circuit  14 , and continue outputting the voltage to the electronic device. Since a short condition has already occurred in the electronic device by then, an increase of current and a decrease voltage will recur. If the voltage is still lower than the predetermined voltage, the comparator  102  will interrupt outputting the control signal to the switch chip  100  to disconnect the voltage input terminal  12  and the working circuit  14 . Therefore, the switch chip  100  switches the electronic device between a conducting status and an interrupt status repeatedly, and finally the increased current will damage a circuit or an electronic component of the electronic device. 
       SUMMARY OF THE INVENTION 
       [0005]    In view of the foregoing shortcomings of the prior art protection circuit that cannot thoroughly prevent an increased current from damaging a circuit or an electronic component of an electronic device, the inventor of the present invention based on years of experience in the related industry to conduct extensive researches and experiments, and finally developed a voltage input circuit in accordance with the present invention. 
         [0006]    It is a primary objective of the present invention to provide a voltage input circuit, and the voltage input circuit is applied to a notebook computer. The voltage input circuit comprises a first voltage terminal separately coupled to a first protection loop and a second protection loop, and a first protection loop and a second protection loop are coupled separately to a second voltage terminal, and a discharge loop is coupled between the second protection loop and the second voltage terminal. The first voltage terminal is provided for receiving and outputting voltage, and the second voltage terminal is provided for receiving voltage outputted from the first voltage terminal and outputting the voltage to the notebook computer. If no short condition occurs in the electronic device, the first protection loop will conduct the first voltage terminal and the second voltage terminal, such that the voltage will be outputted to the notebook computer through the first protection loop and the second voltage terminal. If a short condition occurs in the electronic device, the first protection loop will electrically cut the connection between the first voltage terminal and the second voltage terminal, so that the voltage will be outputted to the discharge loop through the second protection loop. Therefore, an increase of current and a decrease of voltage will not recur, so as to prevent an increased current from damaging a circuit or an electronic component of the notebook computer. 
         [0007]    To make it easier for our examiner to understand the objective, technical characteristics and effects of the present invention, preferred embodiment will be described with accompanying drawings as follows: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a schematic view of a conventional protection circuit; 
           [0009]      FIG. 2  is a schematic view of a voltage input circuit of the present invention; and 
           [0010]      FIG. 3  is a circuit diagram of a voltage input circuit of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0011]    Referring to  FIG. 2  for a schematic view of a voltage input circuit of the invention, the voltage input circuit is applied to a notebook computer. The voltage input circuit comprises a first voltage terminal  2 , a second voltage terminal  3 , a first protection loop  4 , a second protection loop  5  and a discharge loop  6 . The first voltage terminal  2  is provided for receiving voltage outputted from the voltage input circuit, and outputting the voltage to the voltage input circuit. The second voltage terminal  3  is provided for receiving the voltage outputted by the first voltage terminal  2  and outputting the received voltage to the notebook computer, such that the notebook computer can receive the voltage for its operation. The first protection loop  4  comprises a switch module  40  and a control module  42 . The switch module  40  is disposed between the first voltage terminal  2  and the second voltage terminal  3 , and the control module  42  is coupled separately to the first voltage terminal  2  and the switch module  40 . An input terminal of the second protection loop  5  is coupled between the first voltage terminal  2  and the control module  42 , and an output terminal of the second protection loop  5  is coupled between the switch module  40  and the second voltage terminal  3 . The discharge loop  6  is coupled to an output terminal of the second protection loop  5  and the second voltage terminal  3 . 
         [0012]    If no short condition occurs in the electronic device, then the voltage received by the control module  42  will be compliant with a predetermined voltage in the control module  42 , and the control module  42  will keep conducting the switch module  40 , so that the voltage received by the first voltage terminal  2  can be transmitted to the notebook computer through the second voltage terminal  3 . If a short condition occurs in the electronic device, then the current will be increased and the voltage will be decreased, and thus the voltage received by the control module  42  will be incompliant with the predetermined voltage, and the control module  42  will disconnect the switch module  40 , and voltage incompliant with the predetermined voltage cannot be transmitted to the second voltage terminal  3  through the switch module  40 , but the voltage is transmitted to the discharge loop  6  through the second protection loop  5  for an electric discharge. The invention not only avoids the recurrence of increasing the current and decreasing the voltage, but also transmits the voltage that is incompliant with the predetermined voltage to the discharge loop  6 , so as to prevent an increased current from damaging a circuit or an electronic component of the notebook computer. 
         [0013]    Referring to  FIGS. 2 and 3  for a preferred embodiment of the present invention, the second protection loop  5  installs at least one Zener diode  50 , such that if no short condition occurs in the electronic device, the voltage passing through the switch module  40  is prevented from being transmitted to the control module  42  through the second protection loop  5 . If a short condition occurs in the electronic device, voltage incompliant with the predetermined voltage will be outputted to the discharge loop  6  through the Zener diode  50  continuously to prevent an increased current from impacting a circuit or an electronic component of the notebook computer. 
         [0014]    In the preferred embodiment as shown in  FIG. 3 , the control module  42  comprises a voltage receiving pin  421  and an electric conduction pin  422 . The voltage receiving pin  421  is coupled between a first voltage terminal  2  and a Zener diode  50 , for receiving the voltage transmitted from the first voltage terminal  2 . If the voltage received by the voltage receiving pin  421  is incompliant with the predetermined voltage, then the control module  42  will continue generating an electric conduction signal. The electric conduction pin  422  is coupled to the switch module  40 , and the electric conduction signal is transmitted to the switch module  40  through the electric conduction pin  422 , so that the switch module  40  can be controlled to conduct the first voltage terminal  2  and the second voltage terminal  3 , or the switch module  40  can be controlled to cut the connection between the first voltage terminal  2  and the second voltage terminal  3 . 
         [0015]    In the preferred embodiment as shown in  FIG. 3 , the switch module  40  is a metal oxide semiconductor field effect transistor (MOSFET). The switch module  40  comprises a first pin  401 , a second pin  402  and a control pin  403 . The first pin  401  is coupled to the first voltage terminal  2  for receiving a voltage transmitted from the first voltage terminal  2 , and the second pin  402  is coupled to the second voltage terminal  3  for outputting the voltage transmitted from the first voltage terminal  2  to the second voltage terminal  3 . The control pin  403  is coupled to the electric conduction pin  422 . If the control pin  403  continues receiving an electric conduction signal, the first pin  401  and the second pin  402  will be conduced continuously, and the voltage will be transmitted to the second voltage terminal  3  through the switch module  40 . If the control pin  403  has not received an electric conduction signal, the first pin  401  and the second pin  402  will be disconnected, and the voltage cannot be transmitted to the second voltage terminal  3  through the switch module  40 . 
         [0016]    In the preferred embodiment as shown in  FIGS. 2 and 3 , the discharge loop  6  comprises a capacitor  60  and a ground terminal  62 . The capacitor  60  is coupled between an output terminal of the second protection loop  5  and the second voltage terminal  3 , and the ground terminal  62  is coupled to the capacitor  60 . Therefore, a surge voltage transmitted to the voltage input circuit can be absorbed by the capacitor  60  to prevent the unstable voltage from impacting a circuit or an electronic component of the notebook computer. If a short condition occurs in the electronic device, the voltage will pass through the capacitor  60 . If the capacitor  60  is fully charged, the voltage will be outputted to the ground terminal  62  for an electric discharge to prevent a circuit or an electronic component of the notebook computer from being damaged. 
         [0017]    In the preferred embodiment as shown in  FIG. 3 , the voltage input circuit further comprises a current limit loop  7 . An input terminal of the current limit loop  7  is coupled between the first voltage terminal  2  and the switch module  40 , and an output terminal of the current limit loop  7  is coupled between the switch module  40  and the second voltage terminal  3 , such that the current limit loop  7  and the switch module  40  are connected in parallel, so as to reduce the time for boosting the voltage received by the control module  42  to the predetermined voltage, and boot a notebook computer in a shorter time. Further, the current limit loop  7  installs at least one resistor  70 , or two resistors  70  connected in parallel with each other, such that the quantity of resistors  70  is controlled to select the time required for boosting the voltage received by the control module  42  to the predetermined voltage. 
         [0018]    In the preferred embodiment as shown in  FIG. 3 , the voltage input circuit further comprises a first voltage divider  8  and a second voltage divider  9 . The first voltage divider  8  is coupled between the first voltage terminal  2  and the first pin  401 , and the second voltage divider  9  is coupled between the first voltage terminal  2  and the control module  42 . With the first voltage divider  8  and the second voltage divider  9 , voltage (such as 1.3 volt) is transmitted to the control module  42  and provided for the control module  42  to determine whether or not the received voltage exceeds the predetermined voltage (such as 1.2 volts). 
         [0019]    In summation of the description above, the voltage input circuit of the invention can prevent an increase current from damaging a circuit or an electronic component of a notebook computer, if a short condition occurs in the electronic device. In addition, low-priced electronic components (such as resistor or Zener diode) are used for the voltage input circuit of the present invention, and the overall manufacturing cost for applying the voltage input circuit to a notebook computer is less than U.S. $0.009. 
         [0020]    While the invention herein disclosed has been described by means of specific embodiments, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope and spirit of the invention set forth in the claims.