ESD protection circuit for charge pump and electronic device and system using the same

1. Field of Invention

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.

2. Description of Related Art

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

FIG. 1 is a block diagram of an electronic device having ESD protection circuit according to prior art.

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.

FIG. 3 depicts a circuit diagram of an ESD protection circuit according to an embodiment of the present invention.

FIG. 4A depicts an example of a diode used in an ESD protection circuit according to an embodiment of the present invention.

FIG. 4B depicts an example of a diode used in an ESD protection circuit according to an embodiment of the present invention.

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.

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.

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.

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.

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.

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.

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.

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.

Accordingly, an ESD protection circuit provided by the present invention would not affect the normal operation of a charge pump.

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.