Touch screen display circuit and voltage measurement circuit

• US 6,961,015 B2
• Filed: 11/14/2002
• Issued: 11/01/2005
• Est. Priority Date: 11/14/2002
• Status: Expired due to Term

• Current Assignee: Exar Corporation (Maxlinear Incorporated)
• Original Assignee: FYRE Storm Incorporated (Maxlinear Incorporated)
• Inventors: Kernahan, Kent, Thomas, John Carl
• Primary Examiner(s): Tokar, Michael
• Assistant Examiner(s): Nguyen, Khai M.
• Application Number:
  US10/295,559
• Publication Number:
  US 20040095266A1
• Time in Patent Office: 1,083 Days
• Field of Search: 341/53, 341/155, 341/158, 341/165, 323/225, 323/283
• US Class Current: 341/165
• CPC Class Codes: G05F 3/262 using field-effect transistors only
• CPC Class Codes: H02J 2207/20 Charging or discharging characterised by the power electronics converter
• CPC Class Codes: H02M 1/0012 Control circuits using digital or numerical techniques in DC/DC converters H02M3/157, H02M3/33515; in DC-AC converters H02M7/53873
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 1/008 Plural converter units for generating at two or more independent and non-parallel outputs, e.g. systems with plural point of load switching regulators
• CPC Class Codes: H02M 1/0845 digitally controlled (or with digital control)
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H02M 3/157 with digital control
• CPC Class Codes: H02M 3/1588 comprising at least one synchronous rectifier element H02M3/1582, H02M3/1584 take precedence
• CPC Class Codes: H03M 5/08 Code representation by pulse width
• CPC Class Codes: H05B 41/2828 using control circuits for the switching elements H05B41/2827 takes precedence
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A touch screen display circuit is disclosed which includes means for measuring a voltage at two separate input terminals which represent a location on a touch screen where pressure was applied. The display circuit includes means for defining a time period during which the voltage is measured and means for converting the measured voltage to a digital value. The means for measuring a voltage includes an amplifier and a capacitor which are configured as an integrator. The means for converting comprises a counter that measures an amount of time required for the capacitor to dissipate its charge. A touch screen display system having a touch screen which includes first and second sheets of conductive materials positioned in a spaced apart relationship is disclosed. The touch screen display system utilizes a means coupled to the first and second sheets for measuring a voltage at two separate input terminals, a means for defining a time period during which the voltage is measured and a means for converting the voltage to a digital value.

Claims

1. A circuit comprising:

an analog circuit adapted to measure a voltage at two separate input terminals relative to a reference voltage;

a counter; and

a digital controller, coupled to the analog circuit and the counter, the digital controller adapted to control the counter and the analog circuit to define a time period during which the voltage is measured and convert the voltage measured to a digital value.

2. The circuit of claim 1, wherein the analog circuit comprises:

an amplifier;

a capacitor coupled to the amplifier; and

a comparator coupled to the amplifier and the capacitor, the capacitor storing a charge corresponding to the voltage, wherein the time measured by the counter required by the capacitor to dissipate its charge represents the digital value.

3. The circuit of claim 1, wherein the circuit determines a location on a touch screen display.

4. The circuit of claim 1, wherein the circuit comprises a quad-slope analog-to-digital converter.

5. A touch screen display circuit comprising:

means for measuring a voltage at two separate input terminals which represent a location on a touch screen display where pressure was applied;

means for defining a time period during which the voltage is measured; and

means for converting the voltage to a digital value.

6. The circuit of claim 5, wherein the means for measuring a voltage comprises an amplifier and capacitor which are configured as an integrator, and the means for converting comprises a counter that measures an amount of time required for the capacitor to dissipate its charge.

7. The circuit of claim 5, wherein the means for measuring a voltage comprises an amplifier and a capacitor which are configured as an integrator.

8. The circuit of claim 7, wherein the means for converting comprises a counter that measures an amount of time required for the capacitor to dissipate its charge.

9. The circuit of claim 5, wherein the circuit is adapted for use in a system which includes a source of light for the touch screen, the source of light being driven by an alternating current signal, and further wherein the means for defining a time period during which the voltage is measured is adapted to define the time period such that it includes an even number of cycles of the alternating current signal.

10. The circuit of claim 5, wherein the means for measuring a voltage and the means for converting the voltage use a common set of electrical components for the measuring and converting.

11. A touch screen display system comprising:

a touch screen comprising first and second sheets of conductive materials positioned in a spaced apart relationship;

means coupled to the first and second sheets for measuring a voltage at two separate input terminals which represent a location on the touch screen where pressure was applied;

means for defining a time period during which the voltage is measured; and

means for converting the voltage to a digital value.

12. The system according to claim 11, wherein:

the means for measuring a voltage comprises an amplifier and a capacitor.

13. The system according to claim 12, wherein the means for converting comprises a counter that measures an amount of time required for the capacitor to dissipate its charge.