Abstract:
An ESD protection circuit for a charge pump circuit, wherein the charge pump circuit provides a first voltage pin and a second voltage pin, and the absolute value of a voltage provided by the first voltage pin being greater than or equal to the absolute value of a voltage provided by the second voltage pin, and the two voltages have the same phase. The ESD protection circuit comprises a first diode reversely connected between the second voltage pin and ground, and a second diode reversely connected between the second voltage pin and the first voltage pin.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of Invention  
         [0002]     The present invention relates in general to an electrostatic discharge (ESD) protection circuit. More particularly, the invention relates to an ESD protection circuit for a charge pump integrated in an LCD panel, and an electronic device and system using the same.  
         [0003]     2. Description of Related Art  
         [0004]     For commercial consideration, circuits are integrated together to reduce the total device size and production cost. However, as circuits are integrated together, problem arise with discharging electrostatic charge.  
         [0005]     ESD protection circuits are commonly used to preventing the circuit from being damaged by discharging electrostatic charges. Generally, ESD protection circuits are applied on a signal I/O pad/pin that receives or outputs signals. Referring to  FIG. 1 , an exemplary ESD protection circuit is presented. As shown in  FIG. 1 , VDD and VSS are power sources in the electronic device  10 , and each of the signal pins  100 ,  110 , and  120  are connected to an ESD protection circuit  130 ,  140  and  150 , respectively. Generally, ESD protection circuits are connected between the power sources VDD and VSS. For example, ESD protection circuit  130  has two diodes  132  and  134 . Diode  132  is reversely connected between VSS and signal pin  100 , and diode  134  is reversely connected between VDD and signal pin  100 . By using the ESD protection circuit  130 , the discharged electrostatic charges from signal pin  100  are released to VDD or VSS via diode  134  or  132 , respectively.  
         [0006]     However, the ESD protection circuit shown in  FIG. 1  could not be used for a charge pump because a signal I/O pin may output or receive a voltage either higher than VDD or lower than VSS. The diodes in the ESD protection circuit are engaged when the received or output voltage is higher than VDD or lower than VSS. This results in abnormal operation of the ESD protection circuit.  
       SUMMARY OF THE INVENTION  
       [0007]     According to various embodiments there is an ESD protection circuit for a charge pump integrated in LCD panel to protect the charge pump from being damaged by electrostatic discharging.  
         [0008]     According to various embodiments there is an ESD protection circuit for a charge pump circuit that includes diodes in the ESD protection circuit that are reversely connected between ground and a signal pin or reversely connected between two signal pins that provide different voltages.  
         [0009]     According to various embodiments there is an ESD protection circuit for a charge pump circuit. The charge pump circuit can include a source pin set, a target pin set, and a grounding pin electrically connected to ground. According to various embodiments each of the source and target pin set can include a first positive pin that provides a first positive voltage, a second positive pin that provides a second positive voltage, a first negative pin that provides a first negative voltage, and a second negative pin that provides a second negative voltage. According to various embodiments the ESD protection circuit can comprise a first diode set, which is reversely connected between the first/second positive pins of the source pin set and the grounding pin, a second diode set, which is reversely connected between the first/second positive pins of the source pin set and the first positive pin of the target pin set, a third diode set, which is reversely connected between the first/second negative pins of the source pin set and the grounding pin, and a fourth diode set, which is reversely connected between the first/second negative pins of the source pin set and the first negative pin of the target pin set. Further, the first positive pin can provide a voltage that is greater than or equal to the voltage provided by the second positive pin. Moreover, the first negative pin can provide a voltage that is less than or equal to the voltage provided by the second negative pin.  
         [0010]     According to various embodiments there is an ESD protection circuit for a charge pump circuit, where the charge pump circuit can provide a first voltage pin and a second voltage pin. Further, the absolute value of a voltage provided by the first voltage pin being greater than or equal to the absolute value of a voltage provided by the second voltage pin. According to various embodiments the two voltages can have the same phase. The ESD protection circuit can also comprise a first diode, which is reversely connected between the second voltage pin and ground, and a second diode, which is reversely connected between the second voltage pin and the first voltage pin.  
         [0011]     According to various embodiments there is an electronic device with a charge pump circuit having an ESD protection circuit. The electronic device can comprise a charge pump circuit, including a first voltage pin and a second voltage pin, the absolute value of a voltage provided by the first voltage pin being greater than or equal to the absolute value of a voltage provided by the second voltage pin. According to various embodiments the two voltages can have the same phase. Moreover, according to various embodiments the ESD protection circuit can comprise a first diode reversely connected between the second voltage pin and ground and a second diode reversely connected between the second voltage pin and the first voltage pin.  
         [0012]     According to various embodiments there is an electronic system with a charge pump circuit having ESD protection circuit. The electronic system can comprise a power source for providing a power; a charge pump circuit, electrically connecting to the power source that can receive the power, generate voltages, and output voltages having the same phase via a first voltage pin and a second voltage pin respectively. According to various embodiments the absolute value of the voltage output by the first voltage pin being greater than or equal to the absolute value of the voltage output by the second voltage pin. Moreover, according to various embodiments the ESD protection circuit, comprising a first diode reversely connected between the second voltage pin and ground and a second diode reversely connected between the second voltage pin and the first voltage pin.  
         [0013]     According to various embodiments diodes in the ESD protection circuit can always be reversely connected between two voltages. As such, the ESD protection circuit only works when an abnormal voltage caused by discharging of electrostatic charge occurs. Charge pumps can be protected by using the ESD protection circuit provided by the present invention.  
         [0014]     It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.  
         [0016]      FIG. 1  is a block diagram of an electronic device having ESD protection circuit according to prior art.  
         [0017]      FIG. 2  depicts a block diagram of an electronic system having ESD protection circuit for charge pump circuit according to an embodiment of the present invention.  
         [0018]      FIG. 3  depicts a circuit diagram of an ESD protection circuit according to an embodiment of the present invention.  
         [0019]      FIG. 4A  depicts an example of a diode used in an ESD protection circuit according to an embodiment of the present invention.  
         [0020]      FIG. 4B  depicts an example of a diode used in an ESD protection circuit according to an embodiment of the present invention.  
         [0021]      FIG. 5  depicts a block diagram of an electronic device having ESD protection circuit for charge pump circuit according to an embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]     Reference will now be made in detail to various embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.  
         [0023]      FIG. 2  is a block diagram of an electronic system  20  having an ESD protection circuit  270  for a charge pump circuit  200  according to an embodiment of the present invention. In the embodiment, electronic system  20  includes an electronic device  22  and a power source  24 . Power source  24  provides power to the electronic device  22 . The electronic device  22  includes charge pump circuit  200  and ESD protection circuit  270 . The charge pump circuit  200  further includes a source pin set  202  and target pin set  250  each comprising positive pins  210 - 212 ,  260 - 262  and negative pins  214 - 216 ,  264 - 266 . The power provided by the power source  24  is transmitted to the charge pump circuit  200 . Charge pump circuit  200  pumps the voltage of the power to different voltage levels and outputs these pumped voltages via the source pin set  202  and target pin set  250  to other circuits.  
         [0024]     According to various embodiments ESD protection circuit  270  can be electrically connected between the source pin set  202  and the target pin set  250 . More particularly, the ESD protection circuit  270  is reversely connected in the electronic device  22 .  FIG. 3  depicts an exemplary circuit diagram of an ESD protection circuit according to an embodiment of the present invention. In this embodiment, VDD 1  and VDD 2  are positive voltages, and VDD 1  can be greater than or equal to VDD 2 . Further, VEE 1  and VEE 2  are negative voltages, and VEE 1  can be less than or equal to VEE 2 , i.e., the absolute value of VEE 1  is greater than or equal to VEE 2 . According to various embodiments the ESD protection circuit  370  can include several diode sets  372 ,  374 ,  376  and  378 , and, for each diode set, two diodes can be included therein. For example, diode set  372  can include two diodes  372   a  and  372   b , diode set  374  can include two diodes  374   a  and  374   b , diode set  376  can include two diodes  376   a  and  376   b , and diode set  378  can include two diodes  378   a  and  378   b.    
         [0025]     In the embodiment depicted in  FIG. 3 , diodes are reversely connected, that is, the diodes are reverse biased. For example, the, anode and cathode of the diode is connected to the same voltage. Also for example, in the diode set  372 , diode  372   a  can be reversely connected since VDD 1  is greater than GND (which represents grounding), and anode/cathode of diode  372   b  are connected to VDD 1  so that diode  372   b  is reversely connected as well. In the diode set  374 , diode  374   a  is reversely connected since VDD 1  is greater than VDD 2 , and diode  374   b  is reversely connected since VDD 2  is greater than GND. In the diode set  376 , anode/cathode of diode  376   a  are connected to VEE 1  so that diode  376   a  is reversely connected, and diode  376   b  is reversely connected since VEE 1  is lower than GND. In the diode set  378 , diode  378   a  is reversely connected since VEE 1  is less than or equal to VEE 2 , and diode  378   b  is reversely connected since VEE 2  is lower than GND.  
         [0026]     Accordingly, diode sets  372 - 378  do not work when VDD 1 , VDD 2 , VEE 1  and VEE 2  are in normal situations. However, when electrostatic discharge occurs, one of the diode sets  372 - 378  works to protect other circuits. According to various embodiments MOS devices, such as NMOS  402  or PMOS  404  shown in  FIG. 4A  or  FIG. 4B , can be employed as the diodes in the diode sets  372 - 378 . Moreover, TFTs may be employed as the diodes as well.  
         [0027]     Referring to  FIG. 5 , which is a block diagram of an electronic device  50  having ESD protection circuit for charge pump circuit according to an embodiment of the present invention. In the electronic device  50 , charge pump  530  generates several voltages and outputs these voltages via a source pin set  510 . Target pin set  520  receives the voltages via FPC  560  and transmits these voltages to other circuits, such as a display panel. The FPC  560  provides several lines for electrically connecting pin  512  to pin  522  (in the embodiment shown in  FIG. 5  both are named as VDD 1 ), pin  514  to pin  524  (in the embodiment shown in  FIG. 5  both are named as VDD 2 ), pin  516  to pin  526  (in the embodiment shown in  FIG. 5  both are named as VEE 1 ) and pin  518  to pin  528  (in the embodiment shown in  FIG. 5  both are named as VEE 2 ). Further, one terminal of each capacitor  562 - 568  can be electrically connected to the source pin set  510  and target pin set  520  via the FPC  560 . Further, for protecting the charge pump  530  or other panel circuits from being damaged by electrostatic discharging, ESD protection circuit including diode sets  542 - 548 , part of which are reversely connected between source pin set  510  and target pin set  520 , and another part of the diode sets  542 - 548  are reversely connected between the source pin set  510  and GND.  
         [0028]     While array testing or light-on testing is proceeding before the FPC  560  being connected to both the source pin set  510  and the target pin set  520 , a tester (not shown) provides a highest voltage to pin  522  (VDD 1 ) and a lowest voltage to pin  526  (VEE 1 ) for providing working voltages to the panel circuit. Therefore, under the circumstance that the FPC  560  is not connected, diode set  542  is reversely connected between the pins  512 / 514  and GND, diode set  544  is reversely connected between the pins  512 / 514  and pin  522 , diode set  546  is reversely connected between the pins  516 / 518  and GND, and diode set  548  is reversely connected between the pins  516 / 518  and pin  526 . According to various embodiments these diodes do not work because voltages on pin  512  and  514  are less than or equal to the voltage provided on the pin  522 , and voltages on pin  516  and  518  are greater than or equal to the voltage provided on the pin  526 . Diode sets  542 - 548  therefore do not affect the normal test operation but can protect the charge pump  510  from being damaged by electrostatic discharging.  
         [0029]     Accordingly, an ESD protection circuit provided by the present invention would not affect the normal operation of a charge pump.  
         [0030]     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing descriptions, it is intended that the present invention covers modifications and variations of this invention if they fall within the scope of the following claims and their equivalents.