TWI708235B - Pixel sensor circuit - Google Patents

Abstract

A pixel sensor circuit includes a piezoelectric material, an amplitude sensing circuit, and a reading circuit. The piezoelectric material is configured to generate a vibration signal according to an input voltage, and the vibration signal changes a amplitude during a enabling time. The amplitude sensing circuit is configured to receive the vibration signal and obtain a maximum value and a minimum value of the amplitude during the enabling time. The reading circuit is configured to output an output current according to the maximum value and the minimum value of the amplitude.

Description

Pixel sensing circuit

This disclosure relates to a pixel sensing circuit, especially a pixel sensing circuit capable of sensing AC signals whose amplitude changes with time.

Ultrasonic recognition technology is the mainstream trend of fingerprint recognition technology. Many high-end smart electronic devices are successively equipped with ultrasonic fingerprint recognition technology, such as under-screen fingerprint recognition. Major technology companies are developing fast and accurate fingerprint recognition technology, such as successful recognition even when the fingers are wet. An ultrasonic signal is similar to an AC signal, and is different from a DC signal. The amplitude of the ultrasonic signal changes with time. Therefore, it is necessary to design a sensing technology that can correctly recognize ultrasonic signals.

In an embodiment of the present disclosure, a pixel sensing circuit includes a piezoelectric material, an amplitude sensing circuit, and a reading circuit. The piezoelectric material is used to generate a vibration signal according to the input voltage, and the vibration signal changes its amplitude during the receiving time. The amplitude sensing circuit is used to receive the vibration signal and obtain the maximum and minimum amplitudes within the receiving time. The reading circuit is used for outputting an output current according to the maximum value and the minimum value of the amplitude.

To sum up, the special characteristics of piezoelectric materials produce vibration signals similar to AC signals. The amplitude sensing circuit obtains the maximum and minimum amplitudes of the vibration signal. The output current of the reading circuit is based on the maximum value of the vibration signal. Value and minimum value.

100, 100a, 100b, 100c, 100d, 100e‧‧‧Pixel sensing circuit

110‧‧‧Piezoelectric material

120, 120b, 120c, 120d‧‧‧Amplitude sensing circuit

130, 130b, 130c, 130d, 130e‧‧‧Reading circuit

V _BIAS ‧‧‧Input voltage

A, G, B, H‧‧‧node

T1~T7‧‧‧Transistor

FVDD, FVSS, V _P , V _N ‧‧‧Voltage

S _H , S _INT ‧‧‧input signal

V _INT ‧‧‧Initial voltage

V _REF ‧‧‧Reference voltage

S _READ ‧‧‧Read signal

D1, D2‧‧‧Diode

C1, C2‧‧‧Capacitor

TP1‧‧‧Reset time

TP1a‧‧‧Send time

TP2‧‧‧Receiving time

TP3‧‧‧Read time

FIG. 1 is a functional block diagram of a pixel sensing circuit according to an embodiment of the disclosure.

FIG. 2 is a partial circuit diagram of a pixel sensing circuit according to an embodiment of the disclosure.

FIG. 3 shows a signal timing diagram according to an embodiment of the present disclosure.

FIG. 4 is a schematic diagram illustrating the operation of the pixel sensing circuit according to an embodiment of the present disclosure.

FIG. 5 is a schematic diagram illustrating the operation of the pixel sensing circuit according to an embodiment of the present disclosure.

FIG. 6 is a schematic diagram illustrating the operation of the pixel sensing circuit according to an embodiment of the present disclosure.

FIG. 7 is a pixel sensing circuit diagram according to an embodiment of the disclosure.

FIG. 8a shows an amplitude sensing circuit diagram according to an embodiment of the present disclosure.

FIG. 8b shows an amplitude sensing circuit diagram according to an embodiment of the present disclosure.

FIG. 8c is a circuit diagram of an amplitude sensing circuit according to an embodiment of the present disclosure.

FIG. 9 shows a signal timing diagram according to an embodiment of the present disclosure.

FIG. 10 is a schematic diagram illustrating the operation of the pixel sensing circuit according to an embodiment of the present disclosure.

FIG. 11a shows a pixel sensing circuit diagram according to an embodiment of the present disclosure.

FIG. 11b shows a pixel sensing circuit diagram according to an embodiment of the disclosure.

FIG. 12a shows a pixel sensing circuit diagram according to an embodiment of the present disclosure.

FIG. 12b is a circuit diagram of a pixel sensing circuit according to an embodiment of the present disclosure.

The terms "include", "have" and so on used in this article are all open terms, meaning "including but not limited to". In addition, the "and/or" used in this article includes any one of one or more of the related listed items and all combinations thereof.

In this text, when an element is referred to as "connected" or "coupled", it can be referred to as "electrical connection" or "electrical coupling." "Link" or "coupling" can also be used to indicate the coordinated operation or interaction between two or more components. In addition, although terms such as "first", "second", ... are used herein to describe different elements, the terms are only used to distinguish elements or operations described in the same technical terms. Unless the context clearly indicates, the terms do not specifically refer to or imply the order or sequence, nor are they used to limit this disclosure.

Please refer to FIG. 1, which illustrates a functional block diagram of the pixel sensing circuit 100 according to an embodiment of the present disclosure. The pixel sensing circuit 100 includes a piezoelectric material 110, an amplitude sensing circuit 120 and a reading circuit 130. The piezoelectric material 110 is used to generate a vibration signal according to the input voltage V _BIAS , and the vibration signal changes its amplitude during the enabling time. The amplitude sensing circuit 120 is used to receive the vibration signal and obtain the maximum and minimum amplitudes during the enabling period. The reading circuit 130 is used for outputting an output current according to the maximum value and the minimum value of the amplitude. In one embodiment, the vibration signal may be an ultrasonic signal.

The piezoelectric material 110 inputs the vibration signal to the node A (depicted in FIG. 4) in the amplitude sensing circuit 120, and the amplitude sensing circuit 120 receives the vibration signal through the node A.

Please refer to FIG. 2. FIG. 2 illustrates a partial circuit diagram of the pixel sensing circuit 100 according to an embodiment of the present disclosure. The reading circuit 130 includes a transistor T1 and a transistor T2. The transistor T1 and the transistor T2 each include a first terminal, a second terminal, and a control terminal. The first terminal of the transistor T1 is used to receive the voltage FVDD, the second terminal of the transistor T1 is coupled to the first terminal of the transistor T2, the control terminal of the transistor T1 is coupled to the node G, and the transistor T1 is based on the The voltage is selectively turned on, and the voltage FVDD can be a system high voltage.

The first end of the transistor T2 is coupled to the second end of the transistor T1, the second end of the transistor T2 is coupled to the reading end of the pixel sensing circuit 100, and the control end of the transistor T2 is used to receive reading With the signal S _READ , the transistor T2 is selectively turned on according to the read signal S _READ .

Please refer to FIG. 3. FIG. 3 shows a signal timing diagram according to an embodiment of the present disclosure. The pixel sensing circuit 100 operates in a first operation mode, which includes a reset time TP1, a receiving time TP2, and a reading time TP3. Figure 3 contains the timings of the input signal S _H , the input signal S _INT , the voltage of the node A, and the read signal S _READ at the reset time TP1, the reception time TP2 and the read time TP3.

Please refer to FIG. 4. FIG. 4 shows a schematic diagram of the operation of the pixel sensing circuit 100 according to an embodiment of the present disclosure. The amplitude sensing circuit 120 includes a transistor T3, a transistor T4, a transistor T5, and a transistor T6. , Transistor T7, Diode D1, Diode D2, Capacitor C1 and Capacitor C2.

Transistor T3, Transistor T4, Transistor T5, Transistor T6, and Transistor T7 each include a first terminal, a second terminal, and a control terminal. The first end of the transistor T3 is coupled to the node H of the amplitude sensing circuit 120, the second end of the transistor T3 is used to receive the initial voltage V _INT , the control end of the transistor T3 is used to receive the input signal S _H , and according to input signal S _H is selectively turned on.

The first end of the transistor T4 is coupled to the node B, the second end of the transistor T4 is used to receive the reference voltage V _REF , and the control end of the transistor T4 is used to receive the read signal S _READ , and according to the read signal S _READ Selectively turn on.

The first end of the transistor T5 is coupled to the node A, the second end of the transistor T5 is coupled to the node G, and the control end of the transistor T5 is used to receive the input signal S _INT and is selectively turned on according to the input signal S _INT .

The first end of the transistor T6 is coupled to node A, the second end of the transistor T6 is coupled to node B, and the control end of the transistor T6 is used to receive the input signal S _INT and is selectively turned on according to the input signal S _INT .

The first end of the transistor T7 is coupled to the node A, the second end of the transistor T7 is used to receive the initial voltage V _INT , the control end of the transistor T7 is used to receive the input signal S _INT , and is selectively based on the input signal S _INT地转通.

The capacitor C1 and the capacitor C2 each include a first terminal and a second terminal. The first terminal of the capacitor C1 is coupled to the node G, and the second terminal of the capacitor C1 is coupled to the node H. The first end of the capacitor C2 is coupled to the node H, and the second end of the capacitor C2 is coupled to the node B.

The diode D1 is used to obtain the maximum amplitude of the vibration signal. The diode D1 includes a first end and a second end. The first end of the diode D1 is coupled to the node A, and the second end of the diode D1 It is coupled to the node G of the amplitude sensing circuit 120. The first end of the diode D1 is used to receive the vibration signal, and the diode D1 is selectively turned on according to the vibration signal and the voltage of the node G.

For example, when the amplitude of the vibration signal reaches the maximum voltage V _P , when the voltage V _{P is} greater than the voltage of the node G, the diode D1 is turned on, and the voltage of the node G becomes the voltage V _P.

The diode D2 is used to obtain the minimum amplitude of the vibration signal. The diode D2 includes a first end and a second end. The first end of the diode D2 is coupled to the node A, and the second end of the diode D2 Coupled to node B. The first end of the diode D2 is used to receive the vibration signal, and the diode D2 is selectively turned on according to the vibration signal and the voltage of the node B. For example, when the amplitude of the vibration signal reaches the minimum voltage V _N and the voltage V _{N is} less than the voltage of the node B, the diode D2 is turned on and the voltage of the node B becomes the voltage V _N.

Please refer to FIG. 3, while the second 4, FIG. 4 of the sensing pixel circuit 100 operates in the reset time TP1, input signal S _INT input signal S _H and a low potential, and the transistor T5, the transistor T6, Transistor T7 and transistor T3 are turned on, and the voltages of node A, node G, node B, and node H are reset to the initial voltage V _INT .

Please refer to FIG. 3 and FIG. 5 at the same time. FIG. 5 is a schematic diagram of the operation of the pixel sensing circuit 100 according to an embodiment of the present disclosure. Pixel sensing circuit operates in the reception time TP2, the input signal S _INT to the high level, the input signal S _H to a low level, the diode D1 acquired amplitude of vibration thereof the voltage signals of the node G is the maximum value of the amplitude of the voltage V _P, The diode D2 obtains the amplitude of the vibration signal so that the voltage at the node B becomes the minimum amplitude voltage V _N.

In actual operation, since the diode D1 and the diode D2 have the turn-on voltage required for conduction, the diode D1 and the diode D2 are turned on and enter the forward bias region, and the node G The voltage of V becomes the voltage V _P minus the critical voltage of the diode D1, for example, the voltage of the node G becomes the voltage V _P minus 0.7V. The voltage of the node B becomes the voltage V _N plus the critical voltage of the diode D2. For example, the voltage of the node B becomes the voltage V _N plus 0.7V.

。 Please refer to FIGS. 3 and 6 at the same time. FIG. 6 is a schematic diagram illustrating the operation of the pixel sensing circuit 100 according to an embodiment of the present disclosure. The pixel sensing circuit operates at the read time TP3, the input signal S _INT and the input signal S _{H are} at a high level, and the read signal S _READ is at a low level. The transistor T4 is turned on to minimize the voltage of the node B from the amplitude of the vibration signal The value (voltage V _N ) becomes the reference voltage V _REF , so that the voltage of node G changes from the maximum amplitude of the vibration signal (voltage V _P ) to the maximum amplitude plus a variable voltage (voltage V _P +△V) , The variable voltage is the reference voltage minus the minimum value of the vibration signal amplitude (△ V=V _REF -V _N ). Since node G is coupled to the control terminal of transistor T1, when the voltage of node G fluctuates by a variable voltage value, according to the formula of transistor current, the output current I _OUT flowing through transistor T1 and transistor T2 will also vary according to Voltage change

.

。 Please refer to FIG. 7, which is a circuit diagram of the pixel sensing circuit 100a according to an embodiment of the present disclosure. The pixel sensing circuit 100a includes an amplitude sensing circuit 100a. The difference between the amplitude sensing circuit 100a and the amplitude sensing circuit 100 is that the first end and the second end of the diode D1 are exchanged, and the first end of the diode D2 is The end and the second end are exchanged so that the diode D1 is used to obtain the minimum value of the vibration signal amplitude, and the diode D2 is used to obtain the maximum value of the vibration signal amplitude. The pixel sensing circuit 100a has the same piezoelectric material 110 and the reading circuit 130 as the pixel sensing circuit 100 in FIGS. 4 to 6, and will not be repeated here. In this embodiment, the difference between the output current and the output current of the amplitude sensing circuit 100 is that the variable voltage in the formula of the output current differs by a negative sign

.

The amplitude sensing circuit 120 has different implementations according to different coupling methods of the internal transistors. At the reset time TP1, the amplitude sensing circuit 120 has different reset methods due to different implementations. Please refer to FIG. 8a, FIG. 8b and FIG. 8c at the same time. FIG. 8a shows a circuit diagram of the amplitude sensing circuit 120b according to an embodiment of the present disclosure, and FIG. 8b shows a circuit diagram according to an embodiment of the present disclosure. A circuit diagram of the amplitude sensing circuit 120c, FIG. 8c shows the circuit diagram of the amplitude sensing circuit 120d according to an embodiment of the present disclosure Road map.

The difference between the amplitude sensing circuit 120b and the amplitude sensing circuit 120 is that the coupling method of the transistor T5 and the transistor T6 is changed. The first terminal of the transistor T5 is used to receive the initial voltage V _INT , the first terminal of the transistor T6 is coupled to the second terminal of the transistor T7, and the second terminal of the transistor T6 is coupled to the first terminal of the transistor T4 . At the reset time TP1, the transistor T5 is turned on to make the node G change to the initial voltage V _INT , and the transistor T6 is turned on to make the voltage of the node B change to the initial voltage V _INT . .

The difference between the amplitude sensing circuit 120c and the amplitude sensing circuit 120 is that the coupling mode of the transistor T7 is changed. The first terminal of the transistor T7 is used to receive the initial voltage V _INT , and the second terminal of the transistor T7 is coupled to the node G. At the reset time TP1, the transistor T7 is turned on so that the voltage of the node G becomes the initial voltage V _INT . The other operations are the same as those in FIG. 4, and will not be repeated here.

The difference between the amplitude sensing circuit 120d and the amplitude sensing circuit 120 is that the coupling method of the transistor T7 is changed. The first end of the transistor T7 is coupled to node B, and the second end of the transistor T7 is coupled to the second end of the transistor T3. At the reset time TP1, the transistor T7 is turned on so that the voltage of the node B becomes the initial voltage V _INT . The other operations are the same as those in FIG. 4 and will not be repeated here.

Please refer to FIG. 9, which illustrates a signal timing diagram according to an embodiment of the present disclosure. The pixel sensing circuit 100 operates in a second operation mode, which includes a sending time TP1a, a receiving time TP2, and a reading time TP3. Figure 9 includes the input voltage V _BIAS , the input signal S _H , the input signal S _INT , the voltage of the node A, and the timing of the read signal S _READ at the sending time TP1a, the receiving time TP2 and the reading time TP3.

Please refer to FIG. 9 and FIG. 10 at the same time. FIG. 10 is a schematic diagram of the operation of the pixel sensing circuit 100 according to an embodiment of the present disclosure. When the pixel sensing circuit 100 operates at the transmission time TP1a, the voltage of the node A becomes the initial voltage V _INT due to the conduction of the transistor T7, and the input voltage V _BIAS of the other end of the piezoelectric material 110 becomes a continuous pulse. Different from the operation at the reception time TP2, the operation of the pixel sensing circuit 100 at the transmission time TP1a is similar to being a transmitting end.

The reading circuit 130 has different implementations according to the coupling method of the internal transistor and the use of different transistor elements. Please refer to FIG. 11a and FIG. 11b at the same time. FIG. 11a shows a circuit diagram of a pixel sensing circuit 100b according to an embodiment of the present disclosure, and FIG. 11b shows a pixel sensing circuit according to an embodiment of the present disclosure. Circuit diagram of test circuit 100c.

The pixel sensing circuit 100b in FIG. 11a includes a reading circuit 130b. In the reading circuit 130b, the first terminal of the transistor T1 in Figures 4 to 6 is changed to be coupled to the output terminal, and the second terminal of the transistor T1 is changed to receive a voltage FVSS. The voltage FVSS can be a system low voltage. For the convenience of description, in FIGS. 11a and 11b, other transistor elements that are the same as those in FIGS. 4 to 6 are replaced with switch symbols, which will not be repeated here.

The pixel sensing circuit 100c in FIG. 11b includes a reading circuit 130c. In the reading circuit 130c, the transistor T1 in Figs. 4 to 6 is changed to an N-type transistor. Other components are the same as those in Fig. 4 to Fig. 6, and will not be repeated here.

Please refer to FIG. 12a and FIG. 12b at the same time. FIG. 12a shows a circuit diagram of a pixel sensing circuit 100d according to an embodiment of the present disclosure, and FIG. 12b shows a pixel sensing circuit according to an embodiment of the present disclosure. Test circuit 100e circuit diagram. The pixel sensing circuit 100d in FIG. 12a includes a reading circuit 130d. The pixel sensing circuit 100e in FIG. 12b includes a reading circuit 130e.

To sum up, the special characteristics of piezoelectric materials generate vibration signals similar to AC signals. The pixel sensing circuit uses two diodes in different directions to obtain the maximum and minimum values of the vibration signal, so that it can be read. The output current of the circuit changes according to the maximum and minimum values of the vibration signal. The pixel sensing circuit can correctly sense the input signal whose amplitude changes with time, such as ultrasonic signal.

100‧‧‧Pixel sensing circuit

110‧‧‧Piezoelectric material

120‧‧‧Amplitude sensing circuit

130‧‧‧Reading circuit

V _BIAS ‧‧‧Input voltage

Claims (10)

A pixel sensing circuit includes: a piezoelectric material for generating a vibration signal according to an input voltage, wherein the vibration signal changes an amplitude within a consistent energy time; an amplitude sensing circuit for receiving the vibration signal , And obtain a maximum value and a minimum value of the amplitude during the enabling time; and a reading circuit for outputting an output current according to the maximum value and the minimum value of the amplitude, wherein the piezoelectric material is input to the The vibration signal is sent to a first node in the amplitude sensing circuit, the amplitude sensing circuit receives the vibration signal through the first node, and the amplitude sensing circuit includes: a first diode for obtaining the The maximum value of the amplitude, wherein the first diode includes a first end and a second end, the first end of the first diode is coupled to the first node, and the The second end is coupled to a second node of the amplitude sensing circuit, wherein the first end of the first diode is used for receiving the vibration signal, and the first diode is based on the vibration signal and the second node The voltages of the two nodes are selectively turned on; a second diode is used to obtain the minimum value of the amplitude, wherein the second diode includes a first end and a second end, and the second diode The first end of the second diode is coupled to the first node, the second end of the second diode is coupled to a third node of the amplitude sensing circuit, and the first end of the second diode For receiving the vibration signal, the second diode is selectively turned on according to the vibration signal and the voltage of the third node. The pixel sensing circuit according to claim 1, wherein the amplitude sensing circuit further comprises: a first transistor including a first terminal, a second terminal and a control terminal, wherein the first transistor The first end is coupled to the first node, the second end of the first transistor is coupled to the second node, the control end of the first transistor is used to receive a first input signal, and according to The first input signal is selectively turned on; a second transistor includes a first terminal, a second terminal, and a control terminal, wherein the first terminal of the second transistor is coupled to the first node, The second terminal of the second transistor is used for receiving an initial voltage, and the control terminal of the second transistor is used for receiving the first input signal, and is selectively turned on according to the first input signal; a third The transistor includes a first terminal, a second terminal and a control terminal, wherein the first terminal of the third transistor is coupled to the first node, and the second terminal of the third transistor is coupled to The third node, the control terminal of the third transistor is used for receiving the first input signal, and selectively conducting according to the first input signal; a fourth transistor including a first terminal, a second terminal Terminal and a control terminal, wherein the first terminal of the fourth transistor is coupled to the third node, the second terminal of the fourth transistor is used to receive a reference voltage, the control of the fourth transistor The terminal is used to receive a read signal and selectively turn on according to the read signal; a fifth transistor includes a first terminal, a second terminal and a control terminal, wherein the first terminal of the fifth transistor One end is coupled to one of the amplitude sensing circuit The fourth node, the second terminal of the fifth transistor is used to receive the initial voltage, and the control terminal of the fifth transistor is used to receive a second input signal, and is selectively turned on according to the second input signal ; A first capacitor includes a first terminal and a second terminal, wherein the first terminal of the first capacitor is coupled to the second node, and the second terminal of the first capacitor is coupled to the fourth Node; and a second capacitor, including a first terminal and a second terminal, wherein the first terminal of the second capacitor is coupled to the fourth node, and the second terminal of the second capacitor is coupled to the The third node. The pixel sensing circuit according to claim 2, wherein the reading circuit includes: a sixth transistor including a first terminal, a second terminal and a control terminal, wherein the second terminal of the sixth transistor One end is used to receive a system voltage, the control end of the sixth transistor is coupled to the second node and is selectively turned on according to the voltage of the second node; and a seventh transistor including a first Terminal and a second terminal and a control terminal, wherein the first terminal of the seventh transistor is coupled to the second terminal of the sixth transistor, and the second terminal of the seventh transistor is coupled to the A reading terminal of the pixel sensing circuit, and the control terminal of the seventh transistor are used for receiving the reading signal and selectively conducting according to the reading signal. The pixel sensing circuit according to claim 3, wherein the pixel sensing circuit is operated in a first operation mode, and the first operation mode It includes a reset time, a receiving time and a reading time. The pixel sensing circuit according to claim 4, wherein the pixel sensing circuit operates during the reset time, the first input signal and the second input signal are at low potentials, so that the first transistor, the The second transistor, the third transistor, and the fifth transistor are turned on, and the voltages of the first node, the second node, the third node, and the fourth node are reset to the initial voltage. The pixel sensing circuit according to claim 5, wherein the pixel sensing circuit operates at the receiving time, the first input signal is a high potential, the second input signal is a low potential, and the first diode Obtain the amplitude of the vibration signal so that the voltage of the second node is the maximum value of the amplitude, and the second diode obtains the amplitude of the vibration signal such that the voltage of the third node is the minimum value of the amplitude. The pixel sensing circuit according to claim 6, wherein the pixel sensing circuit is operated at the reading time, the first input signal and the second input signal are high, and the reading signal is low, The fourth transistor is turned on so that the voltage of the third node changes from the minimum value of the amplitude to the reference voltage, and the voltage of the second node changes from the maximum value of the amplitude to the maximum value of the amplitude plus A fluctuating voltage, the size of the output current changes according to the fluctuating voltage. The pixel sensing circuit according to claim 7, wherein the pixel sensing circuit operates in a second operation mode, and the second operation mode includes a sending time, the receiving time, and the reading time. The pixel sensing circuit according to claim 8, wherein the pixel sensing circuit operates during the sending time, the input voltage includes a plurality of pulse signals, and the first input signal and the second input signal are low potentials , Reset the voltages of the first node, the second node, the third node, and the fourth node to the initial voltage. The pixel sensing circuit according to claim 2, wherein the first end and the second end of the first diode are exchanged, and the first end and the second end of the second diode are exchanged, The first diode is used to obtain the minimum value of the amplitude, and the second diode is used to obtain the maximum value of the amplitude.

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