Sensor circuit and display apparatus
A sensor circuit or a display apparatus from which a highly accurate sensor output can be obtained includes a photodiode, a capacitor that is connected to the photodiode via an accumulation node and accumulates charges according to an electric current in the photodiode; a sensor switching element transistor that causes the accumulation node and an output line to be conductive with respect to each other in response to a readout signal and outputs an output signal according to the potential of the accumulation node to the output line; a variable capacitor that is provided between the accumulation node and an input electrode, and whose capacitance varies when a pressure is applied by a touching operation; and a control switching element transistor to which a control signal for switching conduction and non-conduction between the variable capacitor and the accumulation node is input.
1. A sensor circuit comprising:
a photodetecting element that receives incident light;
an accumulation part that is connected to the photodetecting element via an accumulation node and accumulates charges according to an electric current having flown through the photodetecting element;
a reset signal line to which a reset signal for initializing a potential of the accumulation node is supplied;
a readout signal line to which a readout signal for outputting the potential of the accumulation node is supplied;
a sensor switching element that is connected to between the accumulation node and an output line, so as to make the accumulation node and the output line conductive with each other in response to the readout signal, and to output an output signal according to the potential of the accumulation node to the output line;
a variable capacitor that is provided between the accumulation node and an input electrode to which a voltage is input, and whose capacitance varies when a pressure is applied; and
a control switching element that is connected to the variable capacitor and the accumulation node, and has a control electrode to which a control signal for switching conduction and non-conduction between the variable capacitor and the accumulation node is input.
2. A sensor circuit comprising:
a photodetecting element that receives incident light;
an accumulation part that accumulates a potential according to an electric current having flown through the photodetecting element, in an accumulation node;
a reset signal line to which a reset signal for initializing a potential of the accumulation node is supplied;
a readout signal line to which a readout signal for reading out the potential of the accumulation node is supplied;
a sensor switching element that reads out the potential of the accumulation node in response to the readout signal and outputs an output signal according to the potential;
a variable capacitor whose capacitance varies with a pressure applied thereto; and
a control switching element that controls conduction and non-conduction between the variable capacitor and the accumulation node,
wherein the sensor circuit operates in at least two operation modes among an imager mode, a touch mode, and a hybrid mode,
wherein in the imager mode, the potential of the accumulation node depends on an electric current that has flown through the photodetecting element during a period from the initialization by the reset signal to the readout in response to the readout signal,
in the touch mode, the potential of the accumulation node depends on a capacitance of the variable capacitor upon the readout, and
in the hybrid mode, the potential of the accumulation node depends on both of the electric current having flown through the photodetecting element and the capacitance of the variable capacitor.
3. The sensor circuit according to claim 2 , wherein in the imager mode, a voltage of the reset signal is set so that charges according to the electric current having flown through the photodetecting element are accumulated in the accumulation part during the period from the initialization of the accumulation node by the reset signal to the readout in response to the readout signal, and
the control switching element is controlled so that it is non-conductive at least upon the readout.
4. The sensor circuit according to claim 2 , wherein in the touch mode, a voltage of the reset signal is set so that the accumulation node assumes an initialized state upon the readout, and
the control switching element is controlled so that it is conductive upon the readout.
5. The sensor circuit according to claim 2 , wherein in the hybrid mode, the control switching element is controlled so that the control switching element is conductive upon the readout,
a voltage of the reset signal is set so that charges according to the electric current having flown through the photodetecting element are accumulated in the accumulation part during the period from the initialization of the accumulation node by the reset signal to the readout in response to the readout signal, and
in the case where the variable capacitor is made conductive with the accumulation node by the control switching element upon the readout, a voltage is applied to the variable capacitor so that the accumulation node has a predetermined voltage.
6. A display apparatus comprising:
an active matrix substrate having a pixel region;
a counter substrate, and
the sensor circuit according to claim 1 provided in the pixel region of the active matrix substrate.
7. A display apparatus comprising:
an active matrix substrate having a pixel region;
a counter substrate, and
the sensor circuit according to claim 2 provided in the pixel region of the active matrix substrate.