Systems for an electrostatic stylus within a capacitive touch sensor

Abstract

Systems are described for transmitting and receiving signals in an active stylus for a capacitive touch sensor, for which the systems have at least one circuit for receiving a current from an electrode and for transmitting a voltage onto the electrode. The systems include components for receiving the current in a receiving mode, a switch, and a switchmode power supply circuit having at least a transformer and a diode, for which the diode is coupled to the transformer. In a transmission mode, there is means for electrically isolating at least some of the components configured for receiving the current in the receiving mode from the voltage formed across the stray capacitance. In the receiving mode, there is a means for electrically isolating at least some of the components configured for receiving the current in the receiving mode from an inductance of the transformer in the switchmode power supply circuit.

1 - 24 . (canceled) 
     
     
         25 . A method for use with a two dimensional sensor array, the method comprising:
 in a transmission mode, configuring a device having a circuit and an electrode to transmit a voltage to a node of the two dimensional sensor array coupled electrostatically to the electrode by:
 generating a voltage using a power supply circuit, wherein the power supply circuit comprises at least a diode; 
 permitting the diode to be intermittently forward-biased, and permitting current to flow through the diode into a capacitance; and 
 configuring a switch to electrically isolate a component in the circuit; and 
   in a receiving mode, configuring the circuit to receive the current through the node coupled to the electrode by:
 configuring the switch to receive the current into the component in the circuit, and 
 configuring the diode to be reversed-biased; and 
 configuring the circuit to determine information based on a received signal. 
   
     
     
         26 . The method of  claim 25 , wherein a resistor is coupled to the diode, the method further comprising providing a reference voltage on at least one terminal of the resistor that is greater than a ground voltage of the circuit. 
     
     
         27 . The method of  claim 25 , further comprising, in the receiving mode, sending at least part of the received current into a current receiving circuit, wherein the current receiver circuit is controlled by a microcontroller. 
     
     
         28 . The method of  claim 25 , wherein configuring the switch comprises configuring the switch to open in the transmission mode to electrically isolate the component in the circuit configured to receive the current in the receiving mode from the voltage formed across a parasitic capacitance associated with one or more components on the node coupled to the electrode. 
     
     
         29 . The method of  claim 28 , further comprising placing a second deliberate capacitance in parallel with the capacitance at the node coupled to the electrode. 
     
     
         30 . The method of  claim 29 , further comprising receiving the current on an order of one microamp, and transmitting the voltage on an order of one hundred volts. 
     
     
         31 . The method of  claim 25 , wherein the power supply circuit comprises a flyback circuit. 
     
     
         32 . An apparatus for use with a two dimensional sensor array, the apparatus comprising:
 a switch configured to switch between a receiving mode and a transmission mode; and   a circuit in communication with the switch, the circuit configured to operate in a transmission mode and a receiving mode,   wherein, in the transmission mode, the circuit is configured to:
 generate a voltage using a power supply circuit comprising at least a diode, 
 permit the diode to be intermittently forward-biased, and permit current to flow through the diode into a capacitance, and 
 open the switch to electrically isolate at least some of a plurality of components configured to receive the current in the receiving mode, and 
   wherein, in the receiving mode, the circuit is configured to:
 close the switch to receive the current into the electrically isolated components configured to receive the current, 
 permit the diode to be reversed-biased, and 
 determine information based on a received signal. 
   
     
     
         33 . The apparatus of  claim 32 , wherein the power supply circuit comprises a flyback circuit. 
     
     
         34 . The apparatus of  claim 32 , further comprising a resistor, wherein the resistor is couple to the diode, wherein the circuit is configured to provide a reference voltage on at least one terminal of the resistor that is greater than a ground voltage of the circuit. 
     
     
         35 . The apparatus of  claim 32 , wherein the circuit is configured to send, in the receiving mode, at least part of the received current into a current receiver circuit, wherein the current receiver circuit is controlled with a microcontroller. 
     
     
         36 . The apparatus of  claim 32 , wherein the capacitance comprises a parasitic capacitance associated with one or more components on a node coupled to the electrode. 
     
     
         37 . The apparatus of  claim 32 , further comprising a second deliberate capacitance that is located in parallel with the capacitance at a node coupled to the electrode. 
     
     
         38 . The apparatus of  claim 32 , wherein the received current is on an order of one microamp, and wherein the transmitted voltage is on an order of one hundred volts. 
     
     
         39 . A system for use with a two-dimensional sensor array, the system comprising:
 an electrode;   components configured to receive current in a receiving mode;   a power supply circuit comprising at least a diode;   a switch configured to switch between a receiving mode and a transmission mode; and   a circuit in communication with the switch, the circuit configured to operate in a transmission mode and a receiving mode,   wherein, in the transmission mode, the circuit is configured to:
 generate a voltage using the power supply circuit; 
 permit the diode to be intermittently forward-biased, and permit current to flow through the diode into a capacitance; 
 open the switch to electrically isolate at least some of the components configured to receive the current in the receiving mode from the voltage formed across the capacitance; and 
   wherein, in the receiving mode, the circuit is configured to:
 close the switch to receive the current into the components configured to receive the current in the receiving mode, and 
 determine information based on a received signal. 
   
     
     
         40 . The system of  claim 39 , wherein the power supply circuit comprises a flyback circuit. 
     
     
         41 . The system of  claim 39 , further comprising a resistor, wherein the resistor is coupled to the diode, wherein the circuit comprises means to provide a reference voltage on at least one terminal of the resistor that is greater than a ground voltage of the circuit. 
     
     
         42 . The system of  claim 39 , wherein the circuit comprises means to send, in the receiving mode, at least part of the received current into a current receiver circuit, wherein the current receiver circuit is controlled with a microcontroller. 
     
     
         43 . The system of  claim 39 , wherein the capacitance comprises a parasitic capacitance associated with one or more components on a node coupled to the electrode. 
     
     
         44 . The system of  claim 39 , further comprising a second deliberate capacitance that is located in parallel with the capacitance at a node coupled to the electrode.