Adaptive transmit voltage in active stylus

A system comprising:

• an active stylus;
• and
• a touch sensor controller, operable with a touch sensor configured to transmit signals to and receive signals from the active stylus, the touch sensor controller comprising a computer-readable non-transitory storage medium embodying logic that is configured when executed to:
• detect signal levels at intersections between first electrodes and second electrodes of the touch sensor according to an operation cycle, wherein the first electrodes extend in a first direction and the second electrodes extend in a second direction different from the first direction, and
• detect the active stylus based on the detected signal levels,
• wherein the operation cycle includes a synchronization timing interval and an integration timing interval,
• in the synchronization timing interval, the logic instructs the touch sensor to transmit signals to the active stylus and does not detect the active stylus, and in the integration timing interval, the logic instructs the touch sensor to not transmit signals to the active stylus and to receive signals from the active stylus, wherein
• the active stylus includes an adaptive voltage generation circuit including:
• a boost voltage controller configured to perform a boost by controlling the adaptive voltage generation circuit to generate output voltage (Vout) from a voltage of a power source;
• a comparator configured to measure Vout;
• a switch control configured to shut off the boost when Vout is above a threshold voltage level and to allow the boost when Vout is below the threshold voltage level;
• and
• a bleeder circuit configured to regulate Vout within a defined time, and
• the active stylus is operable in:
• an idle mode, in which a transmitter of the active stylus is turned off and a receiver of the active stylus is turned on and operable to receive signals from the touch sensor,
• a sleep mode, in which the transmitter of the active stylus is turned off and the receiver of the active stylus is turned off, and
• an active mode, in which the adaptive voltage generation circuit is controlled and the transmitter of the active stylus is turned on and operable to transmit signals to the touch sensor, such that:
• (a) if a tip of the stylus is not pressed, the transmitter of the active stylus transmits signals, at a second transmit voltage determined based at least on a strength of an electric field between the tip of the stylus and the touch sensor, and
• (b) if the tip of the stylus is pressed, instructs the transmitter to transmit signals indicative of a state of the tip being pressed, from the tip of the stylus to the touch sensor, at a first transmit voltage weaker than the second transmit voltage.