Low power touch screen
AssigneeSTMicroelectronics Asia Pacific Pte Ltd
InventorYannick Guedon
Life of this patent
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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.
Claims17
A touch screen, comprising:
- a main power supply;
- a display electrically coupled to the main power supply;
- 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;
- a pair of output buffers coupled to each one of the transmit lines, a first output buffer of the pair being coupled to the main power supply and a second output buffer of the pair being coupled to an intermediate voltage power supply, the pair of output buffers controlling an amount of charge stored in one or more of the capacitive junctions of the transmit line to which the pair of output buffers is coupled.
A method, comprising:
- coupling a selected transmit line of a touch screen controller to a first power supply during a first time interval, the selected transmit line having a transmit line voltage and the first power supply 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;
- connecting the selected transmit line to a second power supply, the second power supply having a second power supply voltage;
- and
- waiting, during a second transition time interval, for the transmit line voltage to reach the second power supply voltage.
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 pair of output buffers associated with each one of the drive lines, a first output buffer coupled to a main power supply and a second output buffer coupled to an intermediate voltage power supply that supplies a lower power than the main power supply.
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 the touch screen controller to a first power supply during a first time interval, the selected transmit line having a transmit line voltage and the first power supply 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;
- connecting the selected transmit line to a second power supply, the second power supply having a second power supply voltage;
- and
- waiting, during a second transition time interval, for the transmit line voltage to reach the second power supply voltage.
Dependencies are inferred from the claim text.