Patent Publication Number: US-2007121308-A1

Title: Electronic device capable of releasing ESD

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention generally relates to an electronic device, and more specifically, to an electronic device that is capable of releasing ESD.  
      2. Description of the Prior Art  
      There is electrostatic everywhere. Though the electrostatic discharge (ESD) is almost insensible and not commonly taken seriously, it does cause damage to circuits and electronic products, especially the circuits operated at high frequencies may be damaged by only tens of volts. Therefore, it becomes an important issue. to control the ESD in circuit design and manufacturing electronic products.  
      In the safety certifications, there are requirements about ESD resistance as well. It is easy for the electrostatic charges to enter the inside of a product along a seam on the housing and to discharge electricity. The elements located in the path of discharge are destroyed thereof. Please refer to  FIG. 1 .  FIG. 1  is a diagram of a conventional notebook  10 . The housing of the notebook  10  is not hermetically sealed and having many seams as other common electronic devices. For example, as illustrated in  FIG. 1 , there are a seam  101  and a seam  102  on the housing of the main machine, and there is a seam  103  between the display panel and the surrounding housing. When an ESD test is held, or ESD just happens spontaneously around the notebook  10 , charges are shot into the notebook  10  through the seams on the housing and destroy the circuits and components of the notebook  10 . For instance, charges that enter the notebook  10  through the seam  103  will possibly destroy a controller of the display panel of the notebook  10 .  
      In the prior art, one of the most common methods to resist the destruction by ESD is to install capacitors on the circuit board. Please refer to  FIG. 2 .  FIG. 2  illustrates a cross-section view of an electronic device  200  of the prior art. There is a seam  201  on the housing  20  of the electronic device  200 , right above an IC  203  installed on a circuit board  205  of the electronic device  200 . When an ESD test is held, or ESD happens spontaneously around the electronic device  200 , it is easy for charges to enter the electronic device  200  through the seam  201  and hence to destroy the IC  203 . As shown in  FIG. 2 , the conventional electronic device  200  adopts a capacitor  206  installed on the circuit board  205  in order to release the ESD.  
     SUMMARY OF THE INVENTION  
      It is therefore an objective of the claimed invention to provide an electronic device equipped with a shielding unit to change the path of discharge in order to keep important components away from being destroyed by the electrostatic discharge.  
      The claimed invention discloses an electronic device capable of releasing ESD. The present electronic device includes a shielding unit and related discharging circuit. The shielding unit is installed within a housing having a seam, between the seam of the housing and a component to be protected. The shielding unit is utilized to conduct the charges that are shot into the housing through the seam.  
      The spirit of the present invention is to install a shielding unit between a seam of the housing and a component to be protected in order to conduct charges to discharge elsewhere, that is, to change the discharge path, hence to protect the important components from ESD.  
      The present electronic device capable of releasing ESD further includes a filter having a first end coupled with the shielding unit and a second end coupled to ground.  
      The present electronic device capable of releasing ESD further includes a transient voltage suppressor having a first end coupled with the shielding unit and a second end coupled to ground.  
      The present electronic device capable of releasing ESD further includes a varistor having a first end coupled with the shielding unit and a second end coupled to ground.  
      The present electronic device capable of releasing ESD further includes a first point discharge unit having a first end coupled to the shielding unit and a second end being a point, and a second point discharge unit having a first end being a point and a second end coupled to ground.  
      In the present electronic device capable of releasing ESD, the shielding unit may include a piece of metal net, a piece of metal foil, or metallic compound plated on the housing.  
      In the present electronic device capable of releasing ESD, the component to be protected could be a circuit, a chip, an integrated circuit or a frame of a liquid crystal display panel.  
      In the present electronic device capable of releasing ESD, the seam may be an outlet for heat sinking.  
      The present electronic device capable of releasing ESD may be a mobile phone, a notebook or a personal digital assistant.  
      These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a diagram of a conventional notebook.  
       FIG. 2  is a sectional diagram of an electronic device of the prior art.  
       FIG. 3  is a sectional diagram of a first embodiment of the present electronic device capable of releasing ESD.  
       FIG. 4  is a sectional diagram of a second embodiment of the present electronic device capable of releasing ESD.  
       FIG. 5  is a sectional diagram of a third embodiment of the present electronic device capable of releasing ESD. 
    
    
     DETAILED DESCRIPTION  
      Please refer to  FIG. 3 .  FIG. 3  is a sectional diagram of a first embodiment of the present electronic device capable of releasing ESD. The present electronic device  300  includes a housing  30  with a seam  301 , a circuit board  305 , and a component installed on the circuit board  305 , e.g. an IC  303 . In the present invention, a shielding unit  304  is installed between the seam  301  and the IC  303 , and is coupled to ground. The shielding unit  304 , being a conductor, may include a piece of metal net, a piece of metal foil, metallic compound plated or sputtered on the housing  30 , or other conductive matter. The shielding unit  304  is utilized to conduct the charges that enter the electronic device  300  from outside the housing  30  through the seam  301  to ground such that the IC  303  can be saved from being destroyed by the ESD.  
      Please refer to  FIG. 4 .  FIG. 4  is a sectional diagram of a second embodiment of the present electronic device capable of releasing ESD. In the second embodiment illustrated in  FIG. 4 , a filter  40  is coupled to the shielding unit  304  and ground. Since the electrostatic discharge is a burst and the discharge voltage may exceed tens of kilovolts, the filter  40  is adopted in the second embodiment in order to prevent the burst of ESD from releasing to ground directly and hence destroying the surrounding components. Beside of the filter  40 , a transient voltage suppressor (TVS) or a varistor may also be utilized to achieve the goal in other embodiments.  
      Please refer to  FIG. 5 .  FIG. 5  is a sectional diagram of a third embodiment of the present electronic device capable of releasing ESD. In the third embodiment, the electronic device  300  of the present invention further adopts a set of point discharge device including a first point discharge unit  501  and a second point discharge unit  502 . One end of the first point discharge unit  501  is coupled to the shielding unit  304 , and the other end of the first point discharge unit  501  is a point part called the first point part. One end of the second point discharge unit  502  is coupled to ground, and the other end of the second point discharge unit  502  is also a point part called the second point part. The first point part and the second point part are opposite to each other but not connected to each other, utilized to conduct charges on the shielding unit  304  to ground. Similarly, the point discharge units  501  and  502  help the charges of the electrostatic waves not to release to ground directly. Hence the surrounding components are kept away from the burst of the ESD.  
      In summary, the present invention provides an electronic device capable of releasing ESD. A simple shielding unit and related components are installed between the seam of the housing and circuits. Hence the discharge path is changed and the charges would be conducted to ground instead of hitting ICs or circuits. The present invention may further adopt filters coupled to the shielding unit such that the electrostatic charges may be conducted to ground indirectly. Point discharge devices may also help the present invention to prevent the burst of ESD from destroying circuits of other components of the electronic device. To prevent circuits, ICs and other components from being destroyed by ESD, the shielding unit introduced by the present invention may be installed between a display panel and a seam of the housing, next to a heat outlet, or near other seams of the housing. The present invention can be applied to mobile phones, notebooks, personal digital assistants (PDAs), or any other electronic devices.  
      Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.