TWI867507B - Active stylus - Google Patents

Abstract

An active stylus includes an electrode, a recycling capacitor, a first switch, an power source, and a second switch. The first switch is coupled between the recycling capacitor and the electrode. The second switch is coupled between the power source and the electrode. In a first phase, the second switch is turned on, the power source provides a current or a voltage for the electrode and the first switch is turned off. In a second phase, the second switch is turned off and the first switch is turned on. Alternatively, the recycling capacitor may be replaced with an electrode.

Description

Active stylus

The present invention relates to a touch pen, and in particular to an active touch pen.

The active stylus can be used on a capacitive touch panel for input. The operation of the active stylus includes sending signals to the capacitive touch panel, which consumes power. Therefore, there is a need to save power for the active stylus so that it can be used for a longer time.

The present invention provides an active touch pen which has the advantage of being more power-saving.

In one embodiment of the present invention, an active touch pen is provided, which includes an electrode, a recycling capacitor, a first switch, a power source and a second switch, wherein the first switch is coupled between the recycling capacitor and the electrode, and the second switch is coupled between the power source and the electrode. In a first phase, the second switch is turned on, the power source provides a voltage or current to the electrode, and the first switch is turned off. In a second phase, the second switch is turned off, and the first switch is turned on.

In one embodiment of the present invention, an active touch pen is provided, which includes a first electrode, a second electrode, a first switch, a power source and a second switch, the first switch is coupled between the first electrode and the second electrode, the second switch is coupled between the power source and the first electrode, and a coupling capacitor is formed between the second electrode and the adjacent conductor. In a first phase, the second switch is turned on, the power source provides a first voltage or a first current to the first electrode, and the first switch is turned off. In a second phase, the second switch is turned off, and the first switch is turned on, so that the charge on the first electrode is recovered to the coupling capacitor.

In order to enable the review committee to have a deeper understanding and knowledge of the structural features and effects achieved by the present invention, we would like to provide a better implementation diagram and a detailed description as follows:

1: Active stylus

10: Electrode

100:Resistance

101: Coupling capacitor

11: Recycling capacitors

12: First switch

13: Power supply

14: Second switch

15: The third switch

16: Controller

160: Digital control circuit

161:Level shifter

17: Touch pen body

18: Integrated circuits

19: Voltage regulator

1’: Active stylus

10’: First electrode

100’:Resistance

101’: first coupling capacitor

11’: Second electrode

110’:Resistance

111’: Second coupling capacitor

12’: First switch

13’: Power supply

14’: Second switch

15’: The third switch

16’: Controller

17’: The fourth switch

18’: The fifth switch

19’: Integrated Circuits

G1, G2, G3, G1’, G2’, G3’, G4’, G5’: control signal

B: Touch pen body

Figure 1 is an equivalent circuit diagram of the first embodiment of the active touch pen of the present invention.

Figures 2(a) to 2(d) illustrate the operation of the active touch pen in Figure 1. Figure 3 is a schematic diagram of the position of the electrode and the recovery capacitor in the touch pen body of the first embodiment of the present invention.

Figure 4 is a schematic diagram showing the positions of the electrodes and the recovery capacitor in the stylus body of the second embodiment of the present invention.

Figure 5 is a schematic diagram showing the positions of the electrodes and the recovery capacitor in the stylus body of the third embodiment of the present invention.

Figure 6 is a schematic diagram showing the positions of the electrodes and the recovery capacitor in the stylus body of the fourth embodiment of the present invention.

Figure 7 is an equivalent circuit diagram of the second embodiment of the active touch pen of the present invention.

Figures 8(a) to 8(c) illustrate the operation of the active stylus in Figure 7.

Figure 9 is a schematic diagram showing the positions of the electrode, recovery capacitor and voltage regulator in the stylus body of the fifth embodiment of the present invention.

Figure 10 is an equivalent circuit diagram of the third embodiment of the active touch pen of the present invention.

Figures 11(a) to 11(d) illustrate the operation of the active stylus in Figure 10.

Figure 12 is an equivalent circuit diagram of the fourth embodiment of the active touch pen of the present invention.

Figures 13(a) to 13(d) illustrate the operation of the active stylus in Figure 12.

Figure 14 is a schematic diagram showing the positions of the first electrode and the second electrode in the stylus body of an embodiment of the present invention.

The embodiments of the present invention will be further explained below with the help of the relevant drawings. As far as possible, the same reference numerals in the drawings and the specification represent the same or similar components. In the drawings, the shapes and thicknesses may be exaggerated for the sake of simplicity and convenience. It is understood that the components not specifically shown in the drawings or described in the specification have the form known to the ordinary technicians in the relevant technical field. The ordinary technicians in this field can make various changes and modifications based on the content of the present invention.

Unless otherwise specified, some conditional sentences or words, such as "can", "could", "might", or "may", are usually intended to express that the present embodiment has, but can also be interpreted as features, components, or steps that may not be required. In other embodiments, these features, components, or steps may not be required.

The description of "one embodiment" or "an embodiment" below refers to a specific component, structure or feature associated with at least one embodiment. Therefore, multiple descriptions of "one embodiment" or "an embodiment" appearing in multiple places below do not refer to the same embodiment. Furthermore, specific components, structures and features in one or more embodiments may be combined in an appropriate manner.

Certain terms are used in the specification and patent application to refer to specific components. However, those with ordinary knowledge in the relevant technical field should understand that the same components may be referred to by different terms. The specification and patent application do not use the difference in name as a way to distinguish components, but use the difference in function of the components as the basis for distinction. The "include" mentioned in the specification and patent application is an open term and should be interpreted as "include but not limited to". In addition, "coupled" includes any direct and indirect connection means. Therefore, if the text describes that the first component is coupled to the second component, it means that the first component can be directly connected to the second component through electrical connection or signal connection methods such as wireless transmission, optical transmission, etc., or indirectly electrically or signal connected to the second component through other components or connection means.

FIG. 1 provides an equivalent circuit diagram of the first embodiment of the active touch pen of the present invention. Please refer to FIG. 1, and the first embodiment of the active touch pen is introduced below. The active touch pen 1 includes an electrode 10, a recycling capacitor 11, a first switch 12, a power source 13 and a second switch 14. The first switch 12 is coupled between the recycling capacitor 11 and the electrode 10, and the recycling capacitor 11 is connected to the ground terminal. The second switch 14 is coupled between the power source 13 and the electrode 10, and the electrode 10 has a resistor 100. When the electrode 10 is close to a conductor, such as a capacitive touch panel, the electrode 10 and the conductor form a coupling capacitor 101. In some embodiments, the active stylus pen 1 may further include a third switch 15 and a controller 16, wherein the third switch 15 is coupled between the electrode 10 and the ground terminal. The controller 16 is coupled to the power supply 13, the first switch 12, the second switch 14 and the third switch 15, and is used to control the first switch 12, the second switch 14 and the third switch 15 to be disconnected or connected. The power supply 13 may be, for example, a voltage source or a current source. The combination of the controller 16, the power supply 13 and the switch 14 may be regarded as an excitation signal generator for providing an excitation signal to the electrode 10. The excitation signal may be a periodic voltage signal or a current signal. The controller 16 may control the power supply 13 to turn on or off. The controller 16 and the power supply 13 can be integrated into an integrated circuit or separately configured. In one embodiment, the controller 16 and the recycling capacitor 11 are integrated into an integrated circuit.

FIG. 2(a) to FIG. 2(d) respectively illustrate the operation of the active stylus pen 1 of FIG. 1 in the first phase to the fourth phase, wherein the control signal G1 is used to control the first switch 12, the control signal G2 is used to control the second switch 14, and the control signal G3 is used to control the third switch 15. The control signals G1 to G3 are provided by the controller 16. As shown in FIG. 2(a), in the first phase, the controller 16 controls the second switch 14 to be turned on, and disconnects the first switch 12 and the third switch 15, so that the power supply provides a voltage or current to the electrode 10. As shown in FIG. 2(b), in the second phase after the first phase, the controller 16 disconnects the second switch 14 and the third switch 15, and turns on the first switch 12. The voltage on the electrode 10 is greater than the voltage of the recovery capacitor 11, so the electrode 10 charges the recovery capacitor 11 through the first switch 12. This process can be understood as recovering the charge supplied to the electrode 10 to the recovery capacitor 11. As shown in Figure 2(c), in the third phase after the second phase, the controller 16 disconnects the first switch 12 and the second switch 14, and turns on the third switch 15. At this time, the electrode 10 is grounded. As shown in Figure 2(d), in the fourth phase after the third phase, the controller 16 disconnects the second switch 14 and the third switch 15, and turns on the first switch 12. At this time, the recovery capacitor 11 charges the electrode 10, causing the voltage of the electrode 10 to rise. From the above process, it can be understood that in the second phase, the charge is first recovered to the recovery capacitor 11, and then in the fourth phase, the recovery capacitor 11 charges the electrode 10 again, so that the voltage of the electrode 10 rises to the first level. When the active touch pen 1 returns to the operation of the first phase, the power supply 13 only needs less power to raise the voltage of the electrode 10 from the first level to the required second level. Therefore, the operation of the active touch pen 1 can be more power-saving.

The capacitance value of the recovery capacitor 11 can be designed to be much larger than the capacitance value of the coupling capacitor 101. For example, the capacitance value of the recovery capacitor 11 is at least 1 nanofarad (nF), and the capacitance value of the coupling capacitor 101 is not more than 50 picofarads (pF). In practice, the average current consumed by the first embodiment of the active touch pen 1 is 17.5 microamperes (μA), and the average current consumed by the prior art is 27.5 microamperes. Compared with the prior art, the power consumption of the active touch pen 1 is greatly reduced by 36%.

The embodiment of FIG. 1 can be realized as the structure shown in FIG. 3. In the embodiment of FIG. 3, the active touch pen 1 includes a touch pen body 17 and an integrated circuit 18, the recovery capacitor 11 and the integrated circuit 18 are arranged in the touch pen body 17, and the integrated circuit 18 can include a power supply 13 and a controller 16. In FIG. 3, the electrode 10 is arranged at the tip of the touch pen body 17 of the active touch pen 1 to serve as a tip electrode. This tip electrode is used to transmit a signal to input on the surface of the capacitive touch panel.

The electrode 10 may also be disposed at other locations of the stylus body 17. In the embodiment of FIG. 4, the electrode 10 is disposed at the tail end of the stylus body 17 of the active stylus 1 to serve as a tail electrode. This tail electrode may be used to communicate with the outside world or to perform a specific function.

The number of electrodes 10 can be varied. In the embodiment of FIG. 5, two electrodes 10 and a recovery capacitor 11 are included. The difference between FIG. 3 and FIG. 5 is that the embodiment of FIG. 5 uses two electrodes 10 to share one recovery capacitor 11.

The number of recycling capacitors 11 may be more than one. The recycling capacitor 11 may also be integrated into the integrated circuit 18. Please refer to the embodiment of FIG. 6. The difference between the embodiments of FIG. 3 and FIG. 6 is that the embodiment of FIG. 6 includes two recycling capacitors 11, and these two recycling capacitors 11 are integrated into the integrated circuit 18.

FIG. 7 is an equivalent circuit diagram of the second embodiment of the active stylus of the present invention. Please refer to FIG. 7. Compared with FIG. 1, the active stylus 1 of FIG. 7 further includes a voltage regulator 19, and the voltage regulator 19 couples the recycling capacitor 11 and the controller 16. The voltage regulator 19 can be, but is not limited to, a low voltage regulator. In different embodiments, the voltage regulator 19, the controller 16 and the power supply 13 can be integrated into an integrated circuit or separately set up.

Figures 8(a) to 8(c) respectively illustrate the operation of the active stylus pen 1 in Figure 7 from the first phase to the third phase, wherein the control signal G1 is used to control the first switch 12, the control signal G2 is used to control the second switch 14, and the control signal G3 is used to control the third switch 15. The control signals G1~G3 are provided by the controller 16. As shown in Figure 8(a), in the first phase, the controller 16 controls the second switch 14 to be turned on, and disconnects the first switch 12 and the third switch 15, so that the power supply provides a voltage or current to the electrode 10. As shown in Figure 8(b), in the second phase after the first phase, the controller 16 disconnects the second switch 14 and the third switch 15, and turns on the first switch 12. The electrode 10 charges the recovery capacitor 11 through the first switch 12. This process can be understood as recovering the charge supplied to the electrode 10 to the recovery capacitor 11. As shown in Figure 8(c), in the third phase after the second phase, the controller 16 disconnects the first switch 12 and the second switch 14, and turns on the third switch 15. At this time, the electrode 10 is grounded.

In some embodiments, the controller 16 may include, but is not limited to, a digital control circuit 160 and a level shifter 161. The digital control circuit 160 may be coupled between the level shifter 161 and the power source 13, and the level shifter 161 may be coupled to the first switch 12, the second switch 14, and the third switch 15. The digital control circuit 160 controls the level shifter 161 to generate control signals G1, G2, and G3 to control the first switch 12, the second switch 14, and the third switch 15 to be disconnected or connected. In one embodiment, the voltage regulator 19 is a low voltage regulator. The voltage regulator 19 and the recycling capacitor 11 are used to provide voltage for the digital control circuit 160. The voltage of the recycling capacitor 11 will be limited to a low voltage below a critical value, and the voltage change is very small, so the step of charging the coupling capacitor 101 by the recycling capacitor 11 as shown in Figure 2d can be omitted. The charge recovered by the recycling capacitor 11 from the electrode 10 in the second phase can be provided to the voltage regulator 19 and the digital circuit, so the power consumption of the active stylus 1 can still be reduced, and its operation can be more power-saving.

The capacitance value of the recovery capacitor 11 can be designed to be much larger than the capacitance value of the coupling capacitor 101. For example, the capacitance value of the recovery capacitor 11 is 1 microfarad (μF), and the capacitance value of the coupling capacitor 101 is 50 pF. Assume that the power source 13 generates a high voltage of 20 volts, the voltage on the recovery capacitor 11 coupled by the regulator 19 is 1.2 volts, and the charging frequency of the coupling capacitor 101 is 250 kilohertz (kHz). Therefore, the average recovery current is (20-1.2)×50× ^10-12 ×250× ¹⁰³ =235 microamperes (μA).

The embodiment of FIG. 7 can be realized as the structure shown in FIG. 9. In the embodiment of FIG. 9, the active stylus 1 includes a stylus body 17 and an integrated circuit 18, the recovery capacitor 11 and the integrated circuit 18 are arranged in the stylus body 17, and the integrated circuit 18 can include a power supply 13, a controller 16 and a voltage regulator 19. The recovery capacitor 11 is arranged outside the integrated circuit 18 and is electrically connected to the voltage regulator 19 in the integrated circuit 18. In FIG. 9, the electrode 10 is arranged at the tip of the stylus body 17 of the active stylus 1 to serve as a tip electrode and/or a ring electrode.

FIG. 10 is an equivalent circuit diagram of the third embodiment of the active touch pen of the present invention. The active touch pen 1' comprises a first electrode 10', a second electrode 11', a first switch 12', a power source 13' and a second switch 14'. The first switch 12' is coupled between the first electrode 10' and the second electrode 11', and the second switch 14' is coupled between the power source 13' and the first electrode 10'. The first electrode 10' has a resistor 100', and the second electrode 11' has a resistor 110'. The first electrode 10' and the second electrode 11' form a first coupling capacitor 101' and a second coupling capacitor 111' with adjacent conductors, respectively, wherein the conductor may be, but is not limited to, a touch panel. In some embodiments, the active stylus pen 1' may further include a third switch 15', a controller 16', a fourth switch 17' and a fifth switch 18'. The third switch 15' is coupled between the first electrode 10' and a ground terminal. The controller 16' is coupled to the power source 13', the first switch 12', the second switch 14', the third switch 15', the fourth switch 17' and the fifth switch 18', and is used to control the first switch 12', the second switch 14', the third switch 15', the fourth switch 17' and the fifth switch 18' to be disconnected or connected. The power source 13' may be, for example, a voltage source providing a first voltage, or a current source providing a first current. The combination of the controller 16', the power supply 13' and the switch 14' can be regarded as an excitation signal generator for providing an excitation signal to the first electrode 10'. The controller 16' can control the power supply 13' to turn on or off. The controller 16' and the power supply 13' can be integrated into an integrated circuit or separately set. The fourth switch 17' is coupled between the power supply 13' and the second electrode 11', and the fifth switch 18' is coupled between the second electrode 11' and the ground terminal.

Figures 11(a) to 11(d) respectively illustrate the operation of the active stylus 1' in Figure 10 in the first phase to the fourth phase, wherein the control signal G1' is used to control the first switch 12', the control signal G2' is used to control the second switch 14', the control signal G3' is used to control the third switch 15', the control signal G4' is used to control the fourth switch 17', and the control signal G5' is used to control the fifth switch 18'. The control signals G1'~G5' are provided by the controller 16.

As shown in FIG. 11(a), in the first phase, the controller 16' controls the second switch 14' to be turned on, and disconnects the first switch 12', the third switch 15', the fourth switch 17' and the fifth switch 18', so that the power source 13' provides a first voltage or a first current to the first electrode 10'. As shown in FIG. 11(b), in the second phase after the first phase, the controller 16' disconnects the second switch 14', the third switch 15', the fourth switch 17' and the fifth switch 18', and turns on the first switch 12', so that the first electrode 10' charges the second electrode 11' through the first switch 12' to increase the voltage of the second electrode 11'. This process can be understood as the charge of the first electrode 10' is recovered to the second coupling capacitor 111'. As shown in FIG. 11(c), in the third phase after the second phase, the controller 16' disconnects the first switch 12', the second switch 14', the fourth switch 17' and the fifth switch 18', and turns on the third switch 15'. At this time, the first electrode 10' is grounded. As shown in FIG. 11(d), in the fourth phase after the third phase, the controller 16' disconnects the second switch 14', the third switch 15', the fourth switch 17' and the fifth switch 18', and turns on the first switch 12. At this time, the second coupling capacitor 111' charges the first electrode 10' to increase the voltage of the first electrode 10'. From the above process, it can be understood that in the second phase, the charge is first recovered to the second coupling capacitor 111', and then in the fourth phase, the second coupling capacitor 111' charges the first electrode 10' again, so that the voltage of the first electrode 10' first rises to the first level. When the active stylus 1' returns to the operation of the first phase, the power supply 13' only needs less power to pull the voltage of the first electrode 10' from the first level to the required second level. Therefore, the operation of the active stylus 1' can be more power-saving. In one embodiment, the fourth switch 17' can be omitted, which means that the power supply 13' is not coupled to the second electrode 11'. The second electrode 11' can be used to receive signals instead of transmitting signals.

FIG. 12 provides a fourth embodiment of the active stylus of the present invention. The equivalent circuit diagram of the fourth embodiment is the same as that of the third embodiment (FIG. 10), and will not be described again here. In the fourth embodiment, the controller 16' can further control the power source 13' to provide a second voltage or a second current to the second electrode 11'.

FIG. 13(a) to FIG. 13(d) respectively illustrate the operation of the active stylus 1' in FIG. 12 in the first phase to the fourth phase, wherein the control signal G1' is used to control the first switch 12', the control signal G2' is used to control the second switch 14', the control signal G3' is used to control the third switch 15', the control signal G4' is used to control the fourth switch 17', and the control signal G5' is used to control the fifth switch 18'. The control signals G1'~G5' are provided by the controller 16. As shown in FIG. 13(a), in the first phase, the controller 16' controls the second switch 14' and the fifth switch 18' to be turned on, and disconnects the first switch 12', the third switch 15' and the fourth switch 17', so that the power source 13' provides a first voltage or a first current to the first electrode 10'. At the same time, the second electrode 11' is grounded. As shown in FIG. 13(b), in the second phase after the first phase, the controller 16' disconnects the second switch 14', the third switch 15', the fourth switch 17' and the fifth switch 18', and turns on the first switch 12', so that the first electrode 10' charges the second electrode 11' through the first switch 12' to increase the voltage of the second electrode 11'. This process can be understood as recycling the charge supplied to the first electrode 10' to the second electrode 11' for use. The capacitance values of the first coupling capacitor 101' and the second coupling capacitor 111' are of the same level, for example, not more than 50 pF, so in the second phase, the voltage on the first electrode 10' decreases rapidly and gradually to a lower voltage, and the voltage on the second electrode 11' increases rapidly and gradually to a higher voltage. As shown in FIG. 13(c), in the third phase after the second phase, the controller 16' disconnects the first switch 12', the second switch 14' and the fifth switch 18', and turns on the third switch 15' and the fourth switch 17'. At this time, the first electrode 10' is grounded. At the same time, the power source 13' provides a second voltage or a second current to the second electrode 11'. As shown in FIG. 13(d), in the fourth phase after the third phase, the controller 16' disconnects the second switch 14', the third switch 15', the fourth switch 17' and the fifth switch 18', and turns on the first switch 12. The capacitance levels of the first coupling capacitor 101' and the second coupling capacitor 111' are the same. In the fourth phase, the second coupling capacitor 111' charges the first electrode 10' to quickly increase the voltage of the first electrode 10' and quickly reduce the voltage of the second electrode 11'. This process can be understood as recycling the charge supplied to the second electrode 11' to the first electrode 10' for use. From the above process, it can be understood that in the second phase, the charge recovered from the first electrode 10' will first raise the voltage of the second electrode 11', so in the third phase, the power supply 13' only needs less power to raise the voltage of the second electrode 11' to the required level. In the fourth phase, the charge recovered from the second electrode 11' will first raise the voltage of the first electrode 10', so in the first phase, the power supply 13' only needs less power to raise the voltage of the first electrode 10' to the required level. Therefore, the operation of the active stylus 1' can be more power-saving.

The charging frequencies of the first coupling capacitor 101' and the second coupling capacitor 111' are the same, but the phases of the voltages on the first electrode 10' and the second electrode 11' differ by 180 degrees. The first electrode 10' and the second electrode 11' can be disposed at the head and the tail of the active stylus 1', respectively. As shown in FIG. 14, the active stylus 1' comprises a stylus body B and an integrated circuit 19', the integrated circuit 19' is disposed in the stylus body B, and the integrated circuit 19' can comprise a power source 13' and a controller 16'. In FIG. 14, the first electrode 10' is disposed at the head end of the stylus body B of the active stylus 1' to serve as a head end electrode (or ring electrode), and the second electrode 11' is disposed at the tail end of the stylus body B of the active stylus 1' to serve as a tail end electrode. In another embodiment, the first electrode 10' and the second electrode 11' are both disposed at the head end of the stylus body B, and a distance is separated therebetween.

In other embodiments, the number of first electrodes 10' at the tip of the stylus body B may be multiple, and/or the number of second electrodes 11' at the tail of the stylus body B may also be multiple.

According to the above-mentioned embodiment, the active touch pen utilizes recycling capacitors or electrodes to recycle charges, thereby having the advantage of being more power-saving.

For those who are familiar with this technology, it is possible to combine the above-mentioned embodiments to produce more different variations. Therefore, the above-mentioned is only a preferred embodiment of the present invention and is not used to limit the scope of implementation of the present invention. Therefore, all equivalent changes and modifications made according to the shape, structure, features and spirit described in the scope of the patent application of the present invention should be included in the scope of the patent application of the present invention.

1: Active stylus

10: Electrode

100:Resistance

101: Coupling capacitor

11: Recycling capacitors

12: First switch

13: Power supply

14: Second switch

15: The third switch

16: Controller

G1, G2, G3: control signal

Claims (18)

An active touch pen comprises: an electrode; a recycling capacitor having a first end and a second end, the second end being grounded; a first switch coupled between the first end of the recycling capacitor and the electrode; a power source; and a second switch coupled between the power source and the electrode; wherein, in a first phase, the second switch is turned on, the power source provides a voltage or current to the electrode, and the first switch is turned off; in a second phase, the second switch is turned off, and the first switch is turned on, so that the electrode charges the recycling capacitor and recovers the charge on the electrode to the recycling capacitor. The active touch pen as described in claim 1 further includes a third switch coupled between the electrode and a ground terminal, and in a third phase after the second phase, the first switch and the second switch are disconnected and the third switch is turned on. The active touch pen as described in claim 2, wherein in the fourth phase after the third phase, the first switch is turned on, and the second switch and the third switch are turned off, so that the recovery capacitor charges the electrode using the charge recovered from the electrode in the second phase. The active touch pen as described in claim 2 further includes a controller, which is coupled to the first switch, the second switch and the third switch to control the first switch, the second switch and the third switch to be disconnected or connected. An active stylus pen as described in claim 4, wherein the controller and the power source are integrated into an integrated circuit. An active stylus pen as described in claim 5, wherein the recycling capacitor is integrated into the integrated circuit. The active stylus pen as described in claim 1 further includes a voltage regulator coupled to the recycling capacitor. The active touch pen as described in claim 1, wherein the electrode is disposed at the head end or the tail end of the active touch pen. An active stylus pen as described in claim 1, wherein the power source is a current source or a voltage source. An active touch pen comprises: a first electrode; a second electrode, forming a coupling capacitor with an adjacent conductor; a first switch, coupled between the first electrode and the second electrode; a power source; and a second switch, coupled between the power source and the first electrode; wherein, in a first phase, the second switch is turned on, the power source provides a first voltage or a first current to the first electrode, and the first switch is turned off; in a second phase, the second switch is turned off, and the first switch is turned on, so that the first electrode charges the coupling capacitor and recovers the charge on the first electrode to the coupling capacitor. The active touch pen as described in claim 10 further includes a third switch coupled between the first electrode and a ground terminal, and in a third phase after the second phase, the first switch and the second switch are disconnected and the third switch is turned on. An active stylus pen as described in claim 11, wherein in a fourth phase after the third phase, the first switch is turned on, and the second switch and the third switch are turned off, so that the coupling capacitor charges the first electrode using the charge recovered from the first electrode in the second phase. The active touch pen as described in claim 12 further includes a fourth switch coupled between the power source and the second electrode. In the third phase, the fourth switch is turned on, and the power source further provides a second voltage or a second current to the second electrode. In the first phase, the second phase, and the fourth phase, the fourth switch is turned off. The active touch pen as described in claim 13 further includes a fifth switch coupled between the second electrode and the ground terminal, the fifth switch is turned on in the first phase, and the fifth switch is turned off in the second phase, the third phase and the fourth phase. The active touch pen as described in claim 14 further includes a controller coupled to the first switch, the second switch, the third switch, the fourth switch and the fifth switch, for disconnecting or connecting the first switch, the second switch, the third switch, the fourth switch and the fifth switch. An active stylus pen as described in claim 15, wherein the controller and the power source are integrated into an integrated circuit. The active touch pen as described in claim 10, wherein the first electrode and the second electrode are respectively disposed at the head end and the tail end of the active touch pen. An active touch pen as described in claim 10, wherein the power source is a voltage source or a current source.

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