Stylus and stylus circuitry for capacitive touch screens

• US 9,519,363 B2
• Filed: 08/18/2015
• Issued: 12/13/2016
• Est. Priority Date: 09/08/2011
• Status: Active Grant

• Current Assignee: Jcm Electronic Stylus LLC
• Original Assignee: Jcm Electronic Stylus LLC
• Inventors: Mann, John Conrad
• Primary Examiner(s): Sternbane, Larry
• Assistant Examiner(s): Michaud, Robert
• Application Number:
  US14/829,007
• Publication Number:
  US 20150355732A1
• Time in Patent Office: 483 Days
• US Class Current: 1/1
• CPC Class Codes: G06F 3/03543 Mice or pucks G06F3/03541 takes precedence
• CPC Class Codes: G06F 3/03545 Pens or stylus
• CPC Class Codes: G06F 3/0383 Signal control means within the pointing device
• CPC Class Codes: G06F 3/0442 using active external devices, e.g. active pens, for transmitting changes in electrical potential to be received by the digitiser

Abstract

A stylus for a capacitive touch screen includes an inverting charge integrator circuit is connected to a conductive tip for providing an output signal proportional to a charge induced at the conductive tip. An inverting amplifier generates an amplified signal proportional to the signal output from the inverting charge integrator. A conductive contact provides electrical or capacitive coupling between the amplified signal and an exterior of the stylus which may provide electrical or capacitive coupling with a person holding the stylus. In other embodiments, the order of the inverting charge integrator and the inverting amplifier may be reversed. A power supply circuit powers the inverting charge integrator and the inverting amplifier. Shielding may be implemented to isolate the stylus circuitry and prevent oscillation. The provided circuitry may enable a ball point or other fine point stylus tip configurations.

Claims

1. A circuit for a capacitive touch screen stylus, the circuit comprising:

a. a conductive tip for providing capacitive coupling with a capacitive touch screen;

b. an amplifier circuit for providing an output signal proportional to a current induced at the conductive tip when it is placed near the capacitive touch screen;

c. an integrator circuit for generating an output voltage proportional to the output signal of the amplifier circuit; and

d. a conductive contact for providing electrical or capacitive coupling between the output voltage and an exterior of the stylus.

2. The circuit of claim 1 wherein a positive transition in potential at the conductive tip results in a positive transition in voltage at the conductive contact.

3. The circuit of claim 1 wherein a negative transition in potential at the conductive tip results in a negative transition in voltage at the conductive contact.

4. The circuit of claim 1, further comprising shielding between the conductive tip and the integrator circuit for isolating at least the connection between the tip and the integrator circuit.

5. The circuit of claim 4 wherein the shielding is connected to a ground of the stylus circuit.

6. The circuit of claim 4 wherein the shielding comprises a conductive enclosure having a circular cross-section and extending along an axis of at least a portion of the stylus.

7. The circuit of claim 4 wherein the shielding comprises a conductive wrapping around at least a portion of the stylus circuit.

8. The circuit of claim 4 wherein the shielding comprises a substantially continuous conducting layer of a circuit board for the stylus circuit.

9. The circuit of claim 4 wherein the shielding comprises one or more conducting planes above and/or below a plane of the stylus circuit.

10. The circuit of claim 4 wherein the shielding comprises one or more conducting planes in a plane of the stylus circuit.

11. The circuit of claim 1 wherein the conductive contact is connected or coupled to an external surface of a stylus.

12. The circuit of claim 1 wherein the integrator circuit and the amplifier circuit are combined.

13. The circuit of claim 1 wherein the conductive tip is metallic.

14. The circuit of claim 1 wherein the conductive tip comprises a conductive polymer.

15. A stylus for a capacitive touch screen, the stylus comprising:

an elongated barrel with an opening therein adapted to receive a stylus circuit;

a conductive tip extending through an end of the elongated barrel;

an amplifier circuit housed within the elongated barrel, the amplifier circuit providing an output signal proportional to a current induced at the conductive tip when the conductive tip is placed near a voltage source;

an integrator circuit housed within the elongated barrel, the integrator circuit generating an output voltage at an output proportional to the output signal of the amplifier circuit; and

a conductive contact on an exterior surface of the elongated barrel, the conductive contact electrically or capacitively coupled to the output of the integrator circuit.

16. The stylus of claim 15, wherein the conductive tip has a cross-section projected onto the touch screen of less than 3.5 millimeters.

17. The stylus of claim 15, further comprising a power supply circuit housed within the elongated barrel, the power supply circuit comprises one or more batteries.

18. The stylus of claim 17, wherein the one or more batteries are rechargeable.

19. The stylus of claim 15, wherein the conductive tip comprises a ball point.

20. The stylus of claim 15, wherein a positive change in voltage at the conductive tip results in a positive change in voltage at the conductive contact and a negative change in voltage at the conductive tip results in a negative change in voltage at the conductive contact.