GOA circuit and LCD device

A GOA circuit includes a plurality of pull-up control units. An n-th stage pull-up control unit of top m-stage pull-up control units includes a signal-output-control circuit, a first switch unit, and a capacitor. The first switch unit includes a control terminal, a first terminal receiving an n-th stage clock signal, and a second terminal electrically connected with an nth-stage scanning line. The capacitor has a terminal electrically connected with the control terminal of the first switch unit and another terminal electrically connected with the second terminal of the first switch unit. The signal-output-control circuit charges the capacitor for a first time period and disconnects a discharging path of the capacitor for a second time period. The first time period and the second time period are consecutive time periods, and the second time period is subsequent to the first time period.

BACKGROUND OF THE INVENTION

This application claims the priority of an application No. 201710697384.0 filed on Aug. 15, 2017, entitled “GOA circuit and LCD device”, the contents of which are hereby incorporated by reference.

Field of Invention

The present invention relates to a liquid crystal display (LCD) device, and more particularly to a gate driver on array (GOA) and a LCD device.

Description of Prior Art

As common display devices, liquid crystal displays (LCDs) are favored by users due to its low power consumption, small size and light weight. The gate driver on array (GOA) circuit is a method in which gate driver integrated chips (ICs) are directly formed on an array substrate to replace the external chip. Because the GOA circuit can directly form the gate driving circuit around the LCD panel, the manufacturing process is reduced, thereby reducing the cost of the LCD device. In addition, since the GOA circuit forms the gate driving circuit on the array substrate, the integration of the LCD device is also improved. The conventional GOA circuit generally includes a pull-up control unit, a capacitor, and a switch unit. The switch unit comprises a control terminal, a first terminal, and a second terminal. One terminal of the capacitor is electrically connected with the pull-up control unit and the control terminal of the switch unit, and another terminal of the capacitor is electrically connected with the scanning line of the LCD device. When the scanning line is at a high level, a node between the capacitor and the control terminal of the switch unit is pulled to a higher level, due to the coupling effect of the capacitor, thereby facilitating the turn-on of the switch unit, thereby enabling the GOA circuit to work normally. However, since several stages of the pull-up control units (usually the top three stages) are often in an open state, the charges in the capacitors easily flow out via the pull-up control unit, so that the coupling effect of the capacitors becomes worse, when the coupling effect of the capacitance is poor to a specific level, the GOA circuit can not work normally.

SUMMARY OF THE INVENTION

The present invention provides a gate driver on array (GOA) circuit, applied to a liquid crystal display (LCD) device. The GOA circuit comprises a plurality of pull-up control units. An n-th stage pull-up control unit of top m-stage pull-up control units comprises a signal-output-control circuit, a first switch unit, and a capacitor. The first switch unit comprises a control terminal, a first terminal, and a second terminal. The control terminal of the first switch unit is electrically connected with one terminal of the capacitor, the first terminal of the first switch unit receives an n-th stage clock signal, and the second terminal of the first switch unit is electrically connected with an nth-stage scanning line. The terminal of the capacitor is electrically connected with the control terminal of the first switch unit and another terminal of the capacitor is electrically connected with the second terminal of the first switch unit. The signal-output-control circuit charges the capacitor for a first time period and disconnects a discharging path of the capacitor for a second time period. Wherein n is a positive integer M is a positive integer greater than or equal to n. The first time period and the second time period are consecutive time periods, and the second time period is subsequent to the first time period.

Comparing with the conventional art, the GOA circuit of the present invention comprises a plurality of pull-up control units. An n-th stage pull-up control unit of top m-stage pull-up control units comprises a signal-output-control circuit, a first switch unit, and a capacitor. The signal-output-control circuit charges the capacitor for the first time period and disconnects the discharging path of the capacitor for the second time period, so that a node between the capacitor and the control terminal of the first switch unit is pulled to a higher level due to the coupling effect of the capacitor, when the scanning line is at a high level during the first time period, which is good to turn on the first switch unit; and in a second time period, the pull-up control unit turns off the discharging path of the capacitor, so as to prevent the charge of the capacitor from being discharged, so that the coupling effect of the capacitor is not reduced, and the normal work of the GOA circuit is ensured.

The present further provides a LCD device, which comprises the GOA circuit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Please refer toFIGS. 1-2.FIG. 1is a structural illustrative diagram of a GOA circuit of a first embodiment according to the present invention.FIG. 2is a waveform diagram of all signals of the GOA circuit ofFIG. 1.

A gate driver on array (GOA) circuit10is applied to a liquid crystal display (LCD) device1. The GOA circuit10comprises a plurality of pull-up control units100. An n-th stage pull-up control unit100of top m-stage pull-up control units100comprises a signal-output-control circuit110, a first switch unit T21, and a capacitor C. The first switch unit T21comprises a control terminal g, a first terminal d, and a second terminal s. The control terminal g of the first switch unit T21is electrically connected with one terminal of the capacitor C, the first terminal d of the first switch unit T21receives an n-th stage clock signal CK(n), and the second terminal s of the first switch unit T21is electrically connected with an nth-stage scanning line G(n). The terminal of the capacitor C is electrically connected with the control terminal g of the first switch unit T21and another terminal of the capacitor C is electrically connected with the second terminal d of the first switch unit T21. The signal-output-control circuit110charges the capacitor C for a first time period t1and disconnects a discharging path of the capacitor C for a second time period t2. Wherein n is a positive integer M is a positive integer greater than or equal to n. The first time period and the second time period are consecutive time periods, and the second time period is subsequent to the first time period. In one embodiment, n is a positive integer less than or equal to 3, and m may be 3. In one embodiment, all the pull-up control units100in the top m-stage pull-up control units100are the same as the n-th stage pull-up control unit100.

In the embodiment, the signal-output-control circuit110comprises a second switch unit T12, a third switch unit T13and a fourth switch unit T14. During the first time period t1, the second switch unit T12is turned on, the third switch unit T13is turned off, the fourth switch unit T14is turned on, and the capacitor Cis charged. During the second time period t2, the second switch unit T12is turned on, the third switch unit T13is turned on, the fourth switch unit T14is turned off, and the discharging path of the capacitor C is disconnected.

Specifically, the second switch unit T12, the third switch unit T13, and the fourth switch unit T14all comprises a control terminal g, a first terminal d, and a second terminal s. Both the control terminal g of the second switch unit T12and the first terminal d of the second switch unit T12are loaded with a first signal, the second terminal s of the second switch unit T12is electrically connected with the first terminal d of the third switch unit T13. The control terminal g of the third switch unit T13receives the n-th stage clock signal CK(n), the second terminal s of the third switch unit T13is electrically connected with a first node P1to load a second signal. The control terminal g of the fourth switch unit T14is electrically connected with the second terminal s of the second switch unit T12, the first terminal d of the fourth switch unit T14is electrically connected with the first terminal d of the second switch unit T12, the second terminal s of the fourth switch unit T14is electrically connected with the first node P1, and the second terminal s of the fourth switch unit T14is electrically connected with the control terminal g of the first switch unit T21. During the first time period t1, the second switch unit T12is turned on, the third switch unit T13is turned off, the fourth switch unit T14is turned on, and the capacitor C is charged. During the second time period t2, the second switch unit T12is turned on, the third switch unit T13is turned on, the fourth switch unit T14is turned off, and the discharging path of the capacitor C is disconnected.

In the embodiment, the first switch unit T21, the second switch unit T12, the third switch unit T13, and the fourth switch unit T14are all negative thin film transistors (NTFTs). The control terminal g is a gate electrode of the NTFT, the first terminal d is a drain electrode of the NTFT, and the second terminal s is a source electrode of the NTFT; or, the control terminal g is a gate electrode of the NTFT, the first terminal d is a source electrode of the NTFT, and the second terminal s is a drain electrode of the NTFT. Correspondingly, the first signal is a high-level signal and the second signal is a low-level signal. The n-th stage clock signal CK(n) is a low-level signal during the first time period t1and the n-th stage clock signal CK(n) is a high-level signal during the second time period t2(please refer toFIG. 2). In the embodiment, both the control terminal g of the second switch unit T12and the first terminal d of the second switch unit T12are connected with a second node P2, the second node P2receives a starting signal STV of the LCD device1to load the first signal, the first node P1receives a low-level signal (Vss) of the LCD device1to load the second signal.

For the convenience of description, the first stage clock signal, the second stage clock signal, the third stage clock signal, the fourth stage clock signal, the fifth stage clock signal, the sixth stage clock signal, the seventh stage clock signal, and the eighth stage clock signal are represented as CK1, CK2, CK3, CK4, CK5, CK6, CK7, and CK8inFIG. 2. G(1) represents the signal loaded on the first stage scanning line.

Or, in other embodiment, the first switch unit T21, the second switch unit T12, the third switch unit T13, and the fourth switch unit T14are all positive thin film transistors (PTFTs). The control terminal g is a gate electrode of the PTFT, the first terminal d is a drain electrode of the PTFT, and the second terminal s is a source electrode of the PTFT; or, the control terminal g is a gate electrode of the PTFT, the first terminal d is a source electrode of the PTFT, and the second terminal s is a drain electrode of the PTFT. Correspondingly, the first signal is a low-level signal and the second signal is a high-level signal. The n-th stage clock signal CK(n) is a high-level signal during the first time period t1and the n-th stage clock signal CK(n) is a low-level signal during the second time period t2.

Comparing with the conventional art, the GOA circuit10of the present invention comprises a plurality of pull-up control units100. An n-th stage pull-up control unit100of top m-stage pull-up control units100comprises a signal-output-control circuit110, a first switch unit T21, and a capacitor C. The signal-output-control circuit110charges the capacitor C for the first time period t1and disconnects the discharging path of the capacitor C for the second time period t2, so that a node Q(n) between the capacitor C and the control terminal g of the first switch unit T21is pulled to a higher level due to the coupling effect of the capacitor C, when the scanning line is at a high level during the first time period t2, which is good to turn on the first switch unit T21; and in a second time period t2, the pull-up control unit100turns off the discharging path of the capacitor C, so as to prevent the charge of the capacitor C from being discharged, so that the coupling effect of the capacitor C is not reduced, and the normal work of the GOA circuit10is ensured.

Please refer toFIG. 3, which is a comparative diagram of waveforms of Q(1) of the GOA circuit of the present invention and Q(1) of the conventional GOA circuit. For convenience of description, a node at one terminal of the capacitor C connected with the first switch unit T21is marked as a node Q(n). In comparison with the waveform of the node Q(1) of the first level up-pull control unit100of the GOA circuit10of the present invention and the waveform of Q(1) of the conventional GOA circuit, the pull-up control unit100disconnects the discharging path of the capacitor C for the second time period t2, so as to prevent the charge of the capacitor C from being discharged, hence, a highest level of Q(1) of the GOA circuit of the present invention is higher than a highest level of Q(1) of the conventional GOA circuit.

Please refer toFIG. 4, which is a structural illustrative diagram of a GOA circuit of a second embodiment according to the present invention. The waveforms of the respective signals in the GOA circuit of the second embodiment are the same as the waveforms of the respective signals in the GOA circuit of the first embodiment, and will not be drawn here, please refer toFIG. 2. In the embodiment, the first switch unit T21, the second switch unit T12, the third switch unit T13, and the fourth switch unit T14are all NTFTs. The first signal is a high-level signal and the second signal is a low-level signal. The n-th stage clock signal CK(n) is a low-level signal during the first time period t1and the n-th stage clock signal CK(n) is a high-level signal during the second time period t2(please refer toFIG. 2). The GOA circuit of the second embodiment is basically the same as the GOA circuit of the first embodiment. The difference is that in the present embodiment, the control terminal g of the second switch unit T12is connected with a second node P2, the second node P2receives a starting signal STV of the LCD device1to load the first signal, the first terminal d of the second switch unit T12is connected with a direct current (DC) high-level power source VGH to load the first signal, the first node P1receives a low-level signal Vss of the LCD device1to load the second signal.

It is understood that the first switch unit T21, the second switch unit T12, the third switch unit T13, and the fourth switch unit T14are all NTFTs, the control terminal g is a gate electrode of the NTFT, the first terminal d is a drain electrode of the NTFT, and the second terminal s is a source electrode of the NTFT; or, the control terminal g is a gate electrode of the NTFT, the first terminal d is a source electrode of the NTFT, and the second terminal s is a drain electrode of the NTFT.

In other embodiments, the first switch unit T21, the second switch unit T12, the third switch unit T13, and the fourth switch unit T14can be all PTFTs. The control terminal g is a gate electrode of the PTFT, the first terminal d is a drain electrode of the PTFT, and the second terminal s is a source electrode of the PTFT; or, the control terminal g is a gate electrode of the PTFT, the first terminal d is a source electrode of the PTFT, and the second terminal s is a drain electrode of the PTFT. Correspondingly, the first signal is a low-level signal and the second signal is a high-level signal. The n-th stage clock signal CK(n) is a high-level signal during the first time period t1and the n-th stage clock signal CK(n) is a low-level signal during the second time period t2.

Please refer toFIG. 5, which is a structural illustrative diagram of a GOA circuit of a third embodiment according to the present invention. The waveforms of the respective signals in the GOA circuit of the third embodiment are the same as the waveforms of the respective signals in the GOA circuit of the first embodiment, and will not be drawn here, please refer toFIG. 2. The signal-output-control circuit110comprises a second switch unit T12, a third switch unit T13, a fourth switch unit T14, a fifth switch unit T15, and a sixth switch unit T16. The the second switch unit T12, the third switch unit T13, the fourth switch unit T14, the fifth switch unit T15, and the sixth switch unit T16all comprises a control terminal g, a first terminal d, and a second terminal s. Both the control terminal g of the second switch unit T12and the first terminal d of the second switch unit T12are loaded with a first signal, the second terminal s of the second switch unit T12is electrically connected with the first terminal d of the third switch unit T13. The control terminal g of the third switch unit T13receives the n-th stage clock signal CK(n), the second terminal s of the third switch unit T13is electrically connected with a first node P1to load a second signal. The control terminal g of the fourth switch unit T14is electrically connected with a second terminal s of the second switch unit T12, the first terminal d of the fourth switch unit T14receives the first signal, and the second terminal s of the fourth switch unit T14is electrically connected with the first terminal d of the fifth switch unit T15. The control terminal g of the fifth switch unit T15receives the n-th stage clock signal CK(n) and the second terminal s of the fifth switch unit T15is electrically connected with a first node P1to load the second signal. The control terminal g of the sixth switch unit T16is electrically connected with the second terminal s of the fourth switch unit T14, the first terminal d of the sixth switch unit T16is electrically connected with the first terminal d of the fourth switch unit T14, and the second terminal s of the sixth switch unit T16is electrically connected with the first node P1to load the second signal.

During the first time period t1, the second switch unit T12is turned on, the third switch unit T13is turned off, the fourth switch unit T14is turned on, the fifth switch unit T15is turned off, the sixth switch unit T16is turned on, and the capacitor C is charged. During the second time period t2, the second switch unit T12is turned on, the third switch unit T13is turned on, the fourth switch unit T14is turned off, and the discharging path of the capacitor C is disconnected.

In the embodiment, the first switch unit T21, the second switch unit T12, the third switch unit T13, the fourth switch unit T14, the fifth switch unit T15, and the sixth switch unit T16are all NTFTs. The control terminal g is a gate electrode of the NTFT, the first terminal d is a drain electrode of the NTFT, and the second terminal s is a source electrode of the NTFT; or, the control terminal g is a gate electrode of the NTFT, the first terminal d is a source electrode of the NTFT, and the second terminal s is a drain electrode of the NTFT. Correspondingly, the first signal is a high-level signal and the second signal is a low-level signal. The n-th stage clock signal CK(n) is a low-level signal during the first time period t1and the n-th stage clock signal CK(n) is a high-level signal during the second time period t2. The control terminal g of the second switch unit T12, the first terminal d of the second switch unit T12, and the first terminal d of the fourth switch unit T14are all connected with a second node P2, the second node P2receives a starting signal STV of the LCD device1to load the first signal, the second node P2receives a low-level signal Vss of the LCD device1to load the second signal.

In the embodiment, the connection between the fourth switch unit T14and the fifth switch unit T15and the connection between the fourth switch unit T14and the fifth switch unit T15and the other connection between elements in the GOA circuit100can ensure that the gate electrode of the sixth switch unit T16is turned off better, when the n-th clock signal CK(n) is a high-level signal, so that the discharging path of the capacitor C is closed better.

In other embodiments, the first switch unit T21, the second switch unit T12, the third switch unit T13, the fourth switch unit T14, the fifth switch unit T15, and the sixth switch unit T16are all PTFTs. The control terminal g is a gate electrode of the PTFT, the first terminal d is a drain electrode of the PTFT, and the second terminal s is a source electrode of the PTFT; or, the control terminal g is a gate electrode of the PTFT, the first terminal d is a source electrode of the PTFT, and the second terminal s is a drain electrode of the PTFT. Correspondingly, the first signal is a low-level signal and the second signal is a high-level signal. The n-th stage clock signal CK(n) is a high-level signal during the first time period t1and the n-th stage clock signal CK(n) is a low-level signal during the second time period t2.

Please refer toFIG. 6, which is a structural illustrative diagram of a GOA circuit of a fourth embodiment according to the present invention. The waveforms of the respective signals in the GOA circuit of the fourth embodiment are the same as the waveforms of the respective signals in the GOA circuit of the first embodiment, and will not be drawn here, please refer toFIG. 2. In the embodiment, the first switch unit T21, the second switch unit T12, the third switch unit T13, the fourth switch unit T14, the fifth switch unit T15, and the sixth switch unit T16are all NTFTs. The first signal is a high-level signal and the second signal is a low-level signal. The n-th stage clock signal CK(n) is a low-level signal during the first time period t1and the n-th stage clock signal CK(n) is a high-level signal during the second time period t2(Please refer toFIG. 2). The GOA circuit of the fourth embodiment is basically the same as the GOA circuit of the third embodiment. The difference is that in the present embodiment, the control terminal g of the second switch unit T12is connected with a second node P2, the second node P2receives a starting signal STV of the LCD device1to load the first signal, the first terminal d of the second switch unit T12and the first terminal d of the fourth switch unit T14are both connected with a direct current (DC) high-level power source VGH to load the first signal, the first node P1receives a low-level signal Vss of the LCD device1to load the second signal.

It is understood that the first switch unit T21, the second switch unit T12, the third switch unit T13, the fourth switch unit T14, the fifth switch unit T15, and the sixth switch unit T16are all NTFTs, the control terminal g is a gate electrode of the NTFT, the first terminal d is a drain electrode of the NTFT, and the second terminal s is a source electrode of the NTFT; or, the control terminal g is a gate electrode of the NTFT, the first terminal d is a source electrode of the NTFT, and the second terminal s is a drain electrode of the NTFT.

In other embodiments, the first switch unit T21, the second switch unit T12, the third switch unit T13, the fourth switch unit T14, the fifth switch unit T15, and the sixth switch unit T16can be all PTFTs. The control terminal g is a gate electrode of the PTFT, the first terminal d is a drain electrode of the PTFT, and the second terminal s is a source electrode of the PTFT; or, the control terminal g is a gate electrode of the PTFT, the first terminal d is a source electrode of the PTFT, and the second terminal s is a drain electrode of the PTFT. Correspondingly, the first signal is a low-level signal and the second signal is a high-level signal. The n-th stage clock signal CK(n) is a high-level signal during the first time period t1and the n-th stage clock signal CK(n) is a low-level signal during the second time period t2.

FIG. 7is a structural illustrative diagram of a LCD device according to the present invention. The LCD device1comprises a GOA circuit10, which can be referred to the foregoing description, which will not be further described herein. The LCD device1includes but is not limited to a mobile phone, a notebook computer, an electronic book, and the like.

The foregoing disclosure is merely one preferred embodiment of the present invention, and certainly can not be used to limit the scope of the present invention. A person having ordinary skill in the art may understand that all or part of the processes in the foregoing embodiments may be implemented, and the present invention may be implemented according to the present invention, equivalent changes in the requirements are still covered by the invention.