Touch sensing device and touch sensing system

1. A touch sensing device for sensing at least one active pen using touch electrodes, comprising:

a driving circuit configured to transmit an uplink signal; and

a sensing circuit configured to receive a downlink signal corresponding to the uplink signal,

wherein, the sensing circuit receives a first downlink signal from a first active pen through a first touch electrode in order to sense a touch or an approach of the first active pen, and

wherein, if reception of the first downlink signal from the first active pen through the first touch electrode is stopped and the first downlink signal is not received for a predetermined time, the sensing circuit starts to search for the first active pen within an area corresponding to the first touch electrode or touch electrodes near the first touch electrode from among an entire area of a panel, in order to recognize the first active pen.

2. The touch sensing device of claim 1 , wherein, when the reception of the first downlink signal through the first touch electrode is stopped, the driving circuit transmits a first uplink signal in order to search for the first active pen through the first touch electrode or the touch electrodes near the first touch electrode.

3. The touch sensing device of claim 1 , wherein the sensing circuit restarts to receive the first downlink signal through the first touch electrode or the touch electrodes near the first touch electrode and resumes sensing a touch or approach of the first active pen.

4. The touch sensing device of claim 1 , wherein the sensing circuit receives a synchronization signal which defines display intervals and touch intervals and receives the first downlink signal in order to sense the first active pen in some of the touch intervals.

5. The touch sensing device of claim 1 , wherein the driving circuit transmits a second uplink signal to a second active pen and the sensing circuit receives a second downlink signal, corresponding to the second uplink signal, from the second active pen through a second touch electrode and starts to search for the second active pen by waiting for the reception of the second downlink signal through the second touch electrode or touch electrodes near the second touch electrode when the reception of the second downlink signal through the second touch electrode is stopped.

6. The touch sensing device of claim 5 , wherein the sensing circuit senses both the first active pen and the second active pen in every frame.

7. The touch sensing device of claim 6 , wherein the sensing circuit receives a synchronization signal which defines display intervals and touch intervals and senses the first active pen in some of the touch intervals of one frame and senses the second active pen in others of the touch intervals thereof.

8. The touch sensing device of claim 1 , wherein the driving circuit transmits a touch driving signal to the touch electrodes and the sensing circuit senses a touch or approach of an object for the panel in response to a response signal of the touch electrodes for the touch driving signal.

9. A touch sensing system for sensing a plurality of active pens, comprising:

a panel including a first touch area and a second touch area; and

a touch sensing device configured to sense a touch or approach of a first active pen by receiving a first downlink signal from the first active pen in the first touch area and to sense a touch or approach of a second active pen receiving a second downlink signal from the second active pen in the second touch area,

wherein, if the sensing of the first active pen in the first touch area is stopped and the first active pen is not sensed for a predetermined time, the touch sensing device performs a search to recognize the first active pen within the first touch area or within a vicinity of the first touch area from among an entire area of the panel.

10. The touch sensing system of claim 9 , wherein, when the sensing of the second active pen in the second touch area is stopped, the touch sensing device performs both the search for the first active pen in the first touch area and the search for the second active pen in the second touch area.

11. The touch sensing system of claim 10 , wherein the touch sensing device receives a synchronization signal which defines display intervals and touch intervals, searches for the first active pen in some of the touch intervals of one frame, and searches for the second active pen in others of the touch intervals thereof.

12. The touch sensing system of claim 11 , wherein, when the sensing of the first active pen and the second active pen is resumed, the touch sensing device senses the first active pen in the some of the touch intervals, and senses the second active pen in the others of the touch intervals.

13. The touch sensing system of claim 9 , wherein the touch sensing device identifies a location of the first active pen through the search.

14. The touch sensing system of claim 9 , wherein the touch sensing device transmits touch driving signals to the first touch area and the second touch area and senses a touch or approach of an object for the panel in response to response signals for the touch driving signals.