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US 10,540,040 B2Granted
Architecture and driving methods for minimizing power losses in touch panel
AssigneeSTMicroelectronics Asia Pacific Pte Ltd
InventorYannick Guedon
Life of this patent
Estimating the term…
Abstract
Dual power supply and energy recovery techniques are used in a capacitive touch panel that employs a concurrent drive scheme. A dual supply output buffer boosts a capacitor from an intermediate voltage level to a high voltage level. Energy recovery exchanges stored energy between a capacitor and an inductor. When both techniques are used together, power consumption of a capacitive touch panel drive circuit can be reduced dramatically, by as much as about 80%. Such high efficiency touch panels have wide application to ultra-thin touch screens, including those suitable for use in mobile devices and flexible displays.
Claims18
A touch screen, comprising:
- a main power supply line configured to provide a main power supply voltage;
- an intermediate voltage power supply line configured to provide an intermediate power supply voltage, the intermediate power supply voltage having a value between the main power supply voltage and a reference voltage;
- a display electrically coupled to the main power supply line;
- an array of read lines overlaid on the display;
- an array of transmit lines overlaid on the display, the transmit lines extending in a direction transverse to a direction of the read lines, the transmit lines and the read lines creating capacitive junctions where they overlap one another;
- and a plurality of pairs of output buffers, each pair being respectively coupled to a respective one of the transmit lines, each pair including first and second output buffers, the first output buffer of the pair having a first supply input directly connected to the main power supply line and an output directly connected to the respective transmit line, the second output buffer of the pair having a first supply input directly connected to the intermediate voltage power supply line and an output directly connected to the respective transmit line, the second output buffer of the pair of output buffers being configured to charge the respective transmit line to the intermediate power supply voltage, and the first output buffer of the pair of output buffers being configured to charge the respective transmit line to the main power supply voltage.
3 more elements
A method, comprising:
- coupling a selected transmit line of a touch screen controller to a first power supply line during a first time interval, the selected transmit line having a transmit line voltage and the first power supply line having a first power supply voltage;
- waiting, during a first transition time interval, for the transmit line voltage to reach the first power supply voltage;
- disconnecting the selected transmit line from the first power supply line;
- connecting the selected transmit line to a second power supply line, the second power supply line having a second power supply voltage that is different than the first power supply voltage;
- and
- waiting, during a second transition time interval, for the transmit line voltage to reach the second power supply voltage, wherein the control signals further activate;
- coupling the selected transmit line of the touch screen controller to an energy recovery rail during a second time interval, the energy recovery rail coupled to an energized induction coil;
- and
- extending a third transition time interval to permit energy equalization to occur between the energized induction coil and a load capacitor coupled to the selected transmit line.
6 more elements
A touch screen controller, comprising:
- a plurality of load capacitors coupled to a touch screen;
- a plurality of drive lines configured to transmit drive signals to drive selected ones of the plurality of load capacitors;
- and
- a plurality of pairs of output buffers, each pair being respectively associated with a respective one of the drive lines, each pair including first and second output buffers, the first output buffer of the pair having a first supply input directly connected to a main power supply line at a supply voltage and an output directly connected to the respective drive line, the second output buffer of the pair having a first supply input directly connected to an intermediate voltage power supply line at an intermediate voltage and an output directly connected to the respective drive line, the intermediate voltage being a lower voltage than the supply voltage, the second output buffer of the pair of output buffers being configured to charge the respective drive line to the intermediate voltage, and the first output buffer of the pair of output buffers being configured to charge the respective drive line to the supply voltage.
1 more element
A non-transitory computer-readable memory having instructions stored thereon, the instructions being executable by a microprocessor configured to output control signals that activate:
- coupling a selected transmit line of a touch screen controller to a first power supply line during a first time interval, the selected transmit line having a transmit line voltage and the first power supply line having a first power supply voltage;
- waiting, during a first transition time interval, for the transmit line voltage to reach the first power supply voltage;
- disconnecting the selected transmit line from the first power supply line;
- connecting the selected transmit line to a second power supply line, the second power supply line having a second power supply voltage that is different than the first power supply voltage;
- and
- waiting, during a second transition time interval, for the transmit line voltage to reach the second power supply voltage, wherein the control signals further activate
- coupling the selected transmit line of the touch screen controller to an energy recovery rail during a second time interval, the energy recovery rail coupled to an energized induction coil;
- and
- extending a third transition time interval to permit energy equalization to occur between the energized induction coil and a load capacitor coupled to the selected transmit line.
6 more elements
Dependencies are inferred from the claim text.