Highly accurate synchronized charge pump for capacitive touch screen system

• US 10,747,382 B2
• Filed: 10/29/2018
• Issued: 08/18/2020
• Est. Priority Date: 10/29/2018
• Status: Active Grant

• Current Assignee: STMicroelectronics Asia Pacific Pte Limited (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Asia Pacific Pte Limited (STMicroelectronics NV)
• Inventors: Gicquel, Hugo, Singh, Abhishek
• Primary Examiner(s): Edwards, Mark
• Application Number:
  US16/173,267
• Publication Number:
  US 20200133411A1
• Time in Patent Office: 659 Days
• Field of Search: 345173
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/0416 Control or interface arrangements specially adapted for digitisers
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2330/028 Generation of voltages supplied to electrode drivers in a matrix display other than LCD
• CPC Class Codes: H02M 1/0003 Details of control, feedback or regulation circuits
• CPC Class Codes: H02M 1/44 Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
• CPC Class Codes: H02M 3/07 using capacitors charged and discharged alternately by semiconductor devices with control electrode , e.g. charge pumps

Abstract

Disclosed herein is a touch screen controller including a driver circuit applying a drive signal to a drive line of a capacitive touch sensing panel. The driver circuit is powered by an accurate supply voltage. A driver supply circuit receives an input supply voltage and outputs the accurate supply voltage. The driver supply circuit includes a clocked comparator comparing a divided version of the accurate supply voltage to a reference voltage and outputting a comparison signal based thereupon. A voltage control circuit (e.g. a charge pump circuit) generates the accurate supply voltage in response to the comparison signal. The clocked comparator and voltage control circuit are both clocked by a driver supply circuit clock.

Claims

1. A touch screen controller, comprising:

a driver circuit configured to apply a drive signal to a drive line of a capacitive touch sensing panel, the driver circuit being powered by an accurate supply voltage; and

a driver supply circuit configured to receive an input supply voltage and output the accurate supply voltage, the driver supply circuit comprising;

a clocked comparator configured to compare a divided version of the accurate supply voltage to a reference voltage and to output a comparison signal based thereupon, in response to the clocked comparator receiving a signal edge of a driver supply circuit clock; and

a voltage control circuit configured to generate the accurate supply voltage in response to the comparison signal, in response to the voltage control circuit receiving the signal edge of the driver supply circuit clock.

2. The touch screen controller of claim 1, wherein the voltage control circuit comprises a charge pump circuit;

and wherein the accurate supply voltage comprises a boosted supply voltage.

3. The touch screen controller of claim 1, wherein the driver supply circuit further comprises a compensation impedance coupled between the input supply voltage and ground, and wherein the compensation impedance is coupled to the clocked comparator to provide the reference voltage to the clocked comparator.

4. The touch screen controller of claim 1, wherein the driver supply circuit further comprises a voltage divider coupled between the accurate supply voltage and ground, and wherein the divided version of the accurate supply voltage is produced at a tap of the voltage divider.

5. The touch screen controller of claim 4, further comprising a capacitor coupled between the tap of the voltage divider and ground.

6. The touch screen controller of claim 1, wherein the clocked comparator comprises a regenerative clocked comparator.

7. The touch screen controller of claim 1, wherein the voltage control circuit converts the comparison signal to a continuous time signal.

20. The touch screen controller of claim 1, further comprising a clock generator configured to generate the driver supply circuit clock, wherein the clock generator is directly electrically connected to both the clock comparator and to the voltage control circuit.

8. A driver supply circuit for powering a driver circuit of a touch screen controller, the driver supply circuit, comprising:

a voltage control circuit configured to generate an accurate supply voltage from an input supply voltage in response to the voltage control circuit receiving a signal edge of a clock signal, the voltage control circuit being controlled via a comparison signal; and

a comparator configured to compare a divided version of the accurate supply voltage to a reference voltage and to output the comparison signal based thereupon, in response to the comparator receiving the signal edge of the clock signal.

9. The driver supply circuit of claim 8, wherein the voltage control circuit comprises a charge pump circuit.

10. The driver supply circuit of claim 8, wherein the driver supply circuit further comprises a compensation impedance coupled between the input supply voltage and ground, and wherein the compensation impedance is coupled to the comparator to provide the reference voltage to the comparator.

11. The driver supply circuit of claim 8, wherein the driver supply circuit further comprises a voltage divider coupled between the accurate supply voltage and ground, and wherein the divided version of the accurate supply voltage is produced at a tap of the voltage divider.

12. The driver supply circuit of claim 11, further comprising a capacitor coupled between the tap of the voltage divider and ground.

13. The driver supply circuit of claim 8, further comprising a clock signal node;

wherein the comparator comprises a clocked comparator having a clock input coupled to the clock signal node;

wherein the voltage control circuit has a clock input coupled to the clock signal node; and

wherein the operation of the voltage control circuit and clocked comparator are synchronized to an edge of a clock signal received from the clock signal node.

14. The driver supply circuit of claim 8, wherein the comparator comprises a regenerative clocked comparator.

15. The driver supply circuit of claim 8, wherein the voltage control circuit converts the comparison signal to a continuous time signal.

16. A circuit, comprising:

a clocked comparator having a clock input directly electrically receiving a clock signal, a non-inverting input, and an inverting input;

a charge pump circuit powered by an input supply voltage and outputting a boosted supply voltage, the charge pump circuit having a clock input directly electrically receiving the clock signal;

a voltage divider coupled between the boosted supply voltage and ground;

wherein the inverting input of the clocked comparator is coupled to a tap of the voltage divider; and

an impedance circuit coupled between the input supply voltage and ground;

wherein the non-inverting input of the clocked comparator is coupled to a tap of the impedance circuit.

17. The circuit of claim 16, wherein the impedance circuit comprises:

first and second resistors coupled in parallel between the input supply voltage and the tap of the impedance circuit; and

a capacitor coupled between the tap of the impedance circuit and ground.

18. The circuit of claim 17, wherein the voltage divider comprises:

first and second resistors coupled between the boosted supply voltage and ground, wherein a tap between the first and second resistors is the tap of the voltage divider; and

a capacitor coupled between the tap between the first and second resistors and ground.

19. A method, comprising:

powering a driver circuit with an accurate supply voltage;

applying a voltage generated by the driver circuit to a drive line of a capacitive touch sensing panel; and

changing an input supply voltage to the accurate supply voltage by;

in response to a comparator receiving an edge of a driver supply circuit clock, comparing a divided version of the accurate supply voltage to a reference voltage and outputting a comparison signal based thereupon; and

in response to a voltage control circuit receiving the edge of the driver supply circuit clock, generating the accurate supply voltage in response to the comparison signal.