TW201812398A - Piezoelectric sensor readout circuit - Google Patents

Abstract

A piezoelectric sensor readout circuit includes an input unit and a subtracting unit. The input unit includes a first transistor and a second transistor. The first transistor and the second transistor all include a first terminal, a second terminal, and a control terminal. The control terminal of the first transistor is configured to receive a first constant voltage, and the second terminal of the first transistor is configured to output a first output voltage. The control terminal of the second transistor is configured to receive a piezoelectric voltage, and the second terminal of the second transistor is configured to output a second output voltage. The subtracting unit is coupled to the input unit, and performs a subtracting calculation to generate a readout voltage based on the first and second output voltages.

Description

   Piezo Inductor Reading Circuit   

This case relates to a reading circuit, and more particularly to a piezoelectric sensor reading circuit.

It is known that an Active Pixel Sensor (APS) circuit is used to sense a light source and convert the light source into a photoelectric voltage according to the intensity of the light source. The active pixel sensing circuit generates a voltage change after the light is irradiated. Then, the photoelectric voltage is obtained by the reading circuit, and the actual voltage value is the difference between the photoelectric voltage value and the threshold voltage (Vth).

The industry will integrate the active pixel sensing circuit and configure it into an array light sensing panel. However, because the critical voltage values of the relevant components in the active pixel sensing circuit may vary depending on the conditions of use, or due to process differences, the critical voltage values of the relevant components in each active pixel sensing circuit are different. Errors in light detection information.

It can be seen that the above existing methods obviously still have inconveniences and defects, and need to be improved. In order to solve the above-mentioned problems, the related fields have made every effort to find a solution, but a suitable solution has not been developed for a long time.

This summary is intended to provide a simplified summary of this disclosure so that readers may have a basic understanding of this disclosure. This summary is not a comprehensive overview of this disclosure, and it is not intended to point out important / critical elements of the embodiments of the invention or to define the scope of the invention.

A technical aspect of the content of this case relates to a piezoelectric sensor reading circuit, which includes an input unit and a subtraction unit. The input unit includes a first transistor and a second transistor. Each of the first transistor and the second transistor includes a first terminal, a second terminal, and a control terminal. The control terminal of the first transistor is used to receive a first constant voltage, and the second terminal of the first transistor is used to output a first output voltage. The control terminal of the second transistor is used to receive a piezoelectric voltage, and the second terminal of the second transistor is used to output a second output voltage. The subtraction unit is electrically connected to the input unit, and is configured to perform a subtraction operation according to the first and second output voltages to generate a read voltage.

Another technical aspect of the present invention relates to a piezoelectric sensor reading circuit, which includes an input unit, a buffer unit, and a subtraction unit. The input unit includes a first transistor and a second transistor. The buffer unit includes a first comparator and a second comparator. Each of the first transistor and the second transistor includes a first terminal, a second terminal, and a control terminal. A first terminal of the first transistor is used to receive a first constant voltage, a control terminal of the first transistor is used to receive a piezoelectric voltage, and a second terminal of the first transistor is used to receive a first current. The first terminal of the second transistor is used to receive a first constant voltage. The control terminal of the second transistor is used to receive a second constant voltage, and the second terminal of the second transistor is used to receive a second current. The first comparator is electrically coupled to the second terminal of the first transistor, and is configured to output a first output voltage according to the first current and the third constant voltage. The second comparator is electrically coupled to the second terminal of the second transistor, and is configured to output a second output voltage according to the second current and the third constant voltage. The subtraction unit is configured to perform a subtraction operation according to the first output voltage and the second output voltage to generate a read voltage.

Therefore, according to the technical content of the present case, an embodiment of the present case provides a piezoelectric sensor reading circuit, so as to improve various error problems caused by differences in threshold voltage values in the reading circuit.

After referring to the following embodiments, those with ordinary knowledge in the technical field to which this case belongs can easily understand the basic spirit and other inventive objectives of this case, as well as the technical means and implementation patterns used in this case.

100, 100A‧‧‧ Piezoelectric sensor reading circuit

110‧‧‧input unit

120‧‧‧ buffer unit

130‧‧‧ Subtraction unit

300, 300A‧‧‧ Piezoelectric sensor reading circuit

310‧‧‧Input unit

320‧‧‧ buffer unit

322, 324‧‧‧ Comparator

330‧‧‧ Subtraction Unit

IVin, IV1‧‧‧ current

N1 ~ N2‧‧‧node

R1‧‧‧ resistance

T1 ~ T4‧‧‧Transistors

V1 ~ V3‧‧‧constant voltage

VA ~ VD‧‧‧Output voltage

VDD‧‧‧ Power supply voltage

Vin‧‧‧Piezoelectric Voltage

VSS‧‧‧ ground voltage

Vout‧‧‧read voltage

In order to make the above and other objects, features, advantages, and embodiments of this case more comprehensible, the description of the drawings is as follows: FIG. 1 is a schematic diagram of a piezoelectric sensor reading circuit according to an embodiment of the present case. .

FIG. 2 is a schematic diagram illustrating a piezoelectric sensor reading circuit according to another embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating a reading circuit of a piezoelectric sensor according to another embodiment of the present invention.

FIG. 4 is a schematic diagram illustrating a reading circuit of a piezoelectric sensor according to another embodiment of the present invention.

According to the usual operation method, the various features and components in the figure are not drawn to scale. The drawing method is to present the specific features and components related to this case in the best way. In addition, between different drawings, the same or similar element symbols are used to refer to similar elements / components.

In order to make the description of this disclosure more detailed and complete, the following provides an illustrative description of the implementation mode and specific embodiments of this case; but this is not the only form of implementing or using the specific embodiments of this case. The embodiments include the features of a plurality of specific embodiments, as well as the method steps and their order for constructing and operating these specific embodiments. However, other specific embodiments can also be used to achieve the same or equal functions and sequence of steps.

Unless otherwise defined in this specification, the meanings of scientific and technical terms used herein are the same as those understood and used by those having ordinary knowledge in the technical field to which this case belongs. In addition, when not in conflict with the context, the singular noun used in this specification covers the plural form of the noun; and the plural noun used also covers the singular form of the noun.

In addition, as used in this document, "coupling" may mean that two or more elements make direct physical or electrical contact with each other, or indirectly make physical or electrical contact with each other, or that two or more elements operate mutually Or action.

FIG. 1 is a schematic diagram of a piezoelectric sensor reading circuit 100 according to an embodiment of the present invention. As shown in the figure, the piezoelectric sensor reading circuit 100 includes an input unit 110, a buffer unit 120, and a subtraction unit 130. The input unit 110 includes a first transistor T1, a second transistor T2, and a third transistor T3. The first transistor T1, the second transistor T2, and the third transistor T3 of the input unit 110 each include a first terminal, a second terminal, and a control terminal.

The control terminal of the first transistor T1 is used to receive a first constant voltage V1, and the second terminal of the first transistor T1 is used to output a first output voltage VA. The control terminal of the second transistor T2 is used to receive the piezoelectric voltage Vin, and the second terminal of the second transistor T2 is used to output a second output voltage VB. The subtraction unit 130 can be electrically connected to the input unit 110 through, but not limited to, the buffer circuit 120, and performs a subtraction operation according to the first and second output voltages VA, VB to generate a read voltage Vout.

Because the first output voltage VA output from the second terminal of the first transistor T1 includes the first voltage difference (V1-Vth1) of the constant voltage V1 and the threshold voltage Vth1 of the first transistor T1, the The second output voltage VB output from the two terminals includes a second voltage difference (Vin-Vth2) between the piezoelectric voltage Vin and the threshold voltage Vth2 of the second transistor T2, and the threshold voltage Vth1 of the first transistor T1 and the second transistor The threshold voltage Vth2 of T2 is almost the same. Therefore, the subtraction unit 130 in this case performs a subtraction operation according to the first voltage difference (V1-Vth1) and the second voltage difference (Vin-Vth2) to eliminate the threshold voltage, so as to generate a voltage without the threshold voltage. Read voltage Vout. According to this, the reading voltage Vout output by the piezoelectric sensor reading circuit 100 in this case does not have a threshold voltage, so that the reading voltage Vout output by the piezoelectric sensor reading circuit 100 will not be caused by the variation of the threshold voltage. error.

In this embodiment, the first terminal of the first transistor T1 is used to receive the power supply voltage VDD, the second terminal of the first transistor T1 and the first terminal of the second transistor T2 are connected to the first node N1, and The control terminal of the first transistor T1 is used to receive a first constant voltage V1, and the first node N1 outputs a first output voltage VA. Furthermore, the second terminal of the second transistor T2 and the first terminal of the third transistor T3 are connected to the second node N2, and the control terminal of the second transistor T2 is used to receive the piezoelectric voltage Vin and is provided by the second node. N2 outputs a second output voltage VB. In addition, the control terminal of the third transistor T3 is used to receive the second constant voltage V2, and the second terminal of the third transistor T3 is used to be coupled to the ground voltage VSS.

In this embodiment, the buffer unit 120 of the read circuit 100 is coupled between the nodes N1, N2 and the subtraction unit 130, and is used for receiving and buffering the first output voltage VA and the second output voltage VB to be provided to the subtraction unit. 130. Subsequently, the subtraction unit 130 may be electrically connected to the input unit 110 through, but not limited to, the buffer unit 120. The subtraction unit 130 is configured to perform a subtraction operation according to the first and second output voltages VA and VB to generate the read voltage Vout.

FIG. 2 is a schematic diagram illustrating a piezoelectric sensor reading circuit 100A according to another embodiment of the present invention. Compared with the piezoelectric sensor reading circuit 100 shown in FIG. 1, the structure of the input unit 110A of the piezoelectric sensor reading circuit 100A is different here, and the description is as follows. As shown in FIG. 2, the input unit 110A includes a first transistor T1, a second transistor T2, a third transistor T3, and a fourth transistor T4. The first transistor T1, the second transistor T2, the third transistor T3, and the fourth transistor T4 all include a first terminal, a second terminal, and a control terminal.

The first terminal of the third transistor T3 and the second terminal of the first transistor T1 are coupled to the first node N1. The control terminal of the first transistor T1 is used to receive the first constant voltage V1, and the first node N1 The first output voltage VA is output. The first terminal of the fourth transistor T4 and the second terminal of the second transistor T2 are coupled to the second node N2. The control terminal of the second transistor T2 is used to receive the piezoelectric voltage Vin and output by the second node N2. The second output voltage VB. Subsequently, the subtraction unit 130 may be electrically connected to the input unit 110A through, but not limited to, the buffer unit 120. The subtraction unit 130 is configured to perform a subtraction operation according to the first and second output voltages VA and VB to generate the read voltage Vout.

Similar to the piezoelectric sensor reading circuit 100 shown in FIG. 1, the piezoelectric sensor reading circuit 100A shown in FIG. 2 can also eliminate the critical voltage by the above electrical operation. The reading voltage Vout output by the electrical sensor reading circuit 100A does not have a threshold voltage, so that the reading voltage Vout output by the piezoelectric sensor reading circuit 100A does not cause an error due to the variation of the threshold voltage.

In this embodiment, the first terminals of the first transistor T1 and the second transistor T2 are respectively used to receive the power supply voltage VDD, and the second terminals of the third transistor T3 and the fourth transistor T4 are respectively used to couple Connected to ground voltage VSS. In addition, the coupling method and the electrical operation method of the buffer unit 120 of the reading circuit 100A of FIG. 2 are similar to the buffer unit 120 of the reading circuit 100 of FIG. 1, and will not be repeated here.

FIG. 3 is a schematic diagram of a piezoelectric sensor reading circuit 300 according to another embodiment of the present invention. As shown in the figure, the piezoelectric sensor reading circuit 300 includes an input unit 310, a buffer unit 320, and a subtraction unit 330. The input unit 310 includes a first transistor T1 and a second transistor T2. The buffer unit 320 includes a first comparator 322 and a second comparator 324. Each of the first transistor T1 and the second transistor T2 includes a first terminal, a second terminal, and a control terminal.

The first terminal of the first transistor T1 is used to receive a constant voltage, such as the ground voltage VSS, the control terminal of the first transistor T1 is used to receive the piezoelectric voltage Vin, and the second terminal of the first transistor T1 is used to receive the first Current IVin. A first terminal of the second transistor T2 is used to receive a ground voltage VSS, a control terminal of the second transistor T2 is used to receive a first constant voltage V1, and a second terminal of the second transistor is used to receive a second current IV1. The first comparator 322 is coupled to the second terminal of the first transistor T1 and configured to output a first output voltage VA according to a first current IVin and a second constant voltage V2. The second comparator 324 is coupled to the second terminal of the second transistor T2 and configured to output a second output voltage VB according to the second current IV1 and the second constant voltage V2. The subtraction unit 330 is configured to perform a subtraction operation according to the first output voltage VA and the second output voltage VB to generate a read voltage Vout.

Since the first output voltage VA output by the first comparator 322 includes the product of the second constant voltage V2 plus the first current IVin and the resistance of the first comparator 322 (V2 + IVin × R1), the second comparator 324 outputs The second output voltage VB includes the product of the second constant voltage V2 plus the second current IV1 and the resistance of the second comparator 324 (V2 + IV1 × R1). Therefore, the subtraction unit 330 in this case is based on the first output voltage VA After performing a subtraction operation with the second output voltage VB, a read voltage Vout without a threshold voltage is generated. According to this, the reading voltage Vout output by the piezoelectric sensor reading circuit 300 in this case does not have a threshold voltage, so that the reading voltage Vout output by the piezoelectric sensor reading circuit 300 will not be caused by the variation of the threshold voltage. Something went wrong.

In this embodiment, the first comparator 322 and the second comparator 324 of the buffer unit 320 each include an inverting terminal, a non-inverting terminal, and an output terminal. The reverse terminal of the first comparator 322 is coupled to the second terminal of the first transistor T1. The first transistor T1 transmits a first current IVin from its second terminal to the first terminal according to the piezoelectric voltage Vin. The non-inverting terminal of the first comparator 322 is configured to receive a second constant voltage V2. The first comparator 322 is used for outputting the first output voltage VA from the output terminal of the first comparator 322 according to the first current IVin and the second constant voltage V2. In addition, the inverting terminal of the second comparator 324 is coupled to the second terminal of the second transistor T2. The second transistor T2 transmits the second current IV1 from the second terminal to the first terminal according to the first constant voltage V1. The non-inverting terminal of the second comparator 324 is used to receive a second constant voltage V2. The second comparator 324 is configured to output a second output voltage VB from the output terminal of the second comparator 324 according to the second current IV1 and the second constant voltage V2.

In this embodiment, the buffer unit 320 further includes a plurality of first resistors R1. The first resistor R1 of the first comparator 322 is coupled between the reverse terminal and the output terminal of the first comparator 322, so that the first comparator 322 is based on a first voltage corresponding to the first current IVin and the first resistor R1. (IVin × R1) and the second constant voltage V2 to output the first output voltage VA. For example, the first output voltage VA includes a first voltage sum (V2 + IVin × R1) of a first voltage (IVin × R1) and a second constant voltage V2. Another first resistor R1 is coupled between the inverting terminal and the output terminal of the second comparator 324, so that the second comparator 324 is based on a second voltage (IV1 × R1) corresponding to the second current IV1 and the first resistor R1. ) And the second constant voltage V2 to output a second output voltage VB. For example, the second output voltage VB includes a second voltage (IV1 × R1) and a second voltage sum (V2 + IV1 × R1) of the second constant voltage V2. The subtraction unit 330 performs a subtraction operation according to the first voltage sum (V2 + IVin × R1) and the second voltage sum (V2 + IV1 × R1) to generate a read voltage Vout.

In this embodiment, the voltage value of the second constant voltage V2 is greater than the voltage value of the ground voltage VSS, and the voltage value of the first constant voltage V1 is greater than the voltage value of the ground voltage VSS. In this way, by adjusting the voltage difference between the second constant voltage V2 and the ground voltage VSS, both the first transistor T1 and the second transistor T2 can operate in the linear region. The formula for the current in the linear region is as follows:

As described above, by adjusting the voltage difference between the second constant voltage V2 and the ground voltage VSS to make the first transistor T1 and the second transistor T2 operate in the linear region, the first output voltage VA and the second output voltage VB are as follows: VA = V2 + IVin × R1; VB = V2 + IV1 × R1; read voltage Vout is as follows: Vout = VA-VB = (IVin-IV1) × R1; Moreover, because the first transistor T1 and the second transistor T2 has the same size, so the read voltage Vout can be organized as:

It can be known from the above formula 2 that by the above-mentioned electrical operation, the read voltage Vout output by the piezoelectric sensor reading circuit 300 of the present case does not have a threshold voltage, so that the piezoelectric sensor reading circuit 300 does not vary due to the threshold voltage , Which results in an error in the output voltage Vout.

FIG. 4 is a schematic diagram of a piezoelectric sensor reading circuit 300A according to another embodiment of the present application. Compared with the piezoelectric sensor reading circuit 300 shown in FIG. 3, the structure of the input unit 310A of the piezoelectric sensor reading circuit 300A is different here, and the description is as follows. As shown in FIG. 4, the input unit 310A includes a first transistor T1, a second transistor T2, a third transistor T3, and a fourth transistor T4. The first transistor T1, the second transistor T2, the third transistor T3, and the fourth transistor T4 all include a first terminal, a second terminal, and a control terminal.

The first terminal of the first transistor T1 is used to receive a constant voltage, such as the ground voltage VSS, the control terminal of the first transistor T1 is used to receive the piezoelectric voltage Vin, and the second terminal of the first transistor T1 is used to receive the first Current IVin. A first terminal of the third transistor T3 is coupled to a second terminal of the first transistor T1, and a control terminal of the third transistor T3 is used to receive a third constant voltage V3. In addition, the first terminal of the second transistor T2 is used to receive the ground voltage VSS, the control terminal of the second transistor T2 is used to receive the first constant voltage V1, and the second terminal of the second transistor T2 is used to receive the second current. IV1. A first terminal of the fourth transistor T4 is coupled to a second terminal of the second transistor T2. The control terminal of the fourth transistor T4 is used to receive a third constant voltage V3.

Furthermore, the first comparator 322 is coupled to the second terminal of the first transistor T1 through the third transistor T3, and is configured to output the first output voltage VA according to the first current IVin and the second constant voltage V2. The second comparator 324 is coupled to the second terminal of the fourth transistor T4 and configured to output a second output voltage VB according to the second current IV1 and the second constant voltage V2. The subtraction unit 330 is configured to perform a subtraction operation according to the first output voltage VA and the second output voltage VB to generate a read voltage Vout.

Similar to the piezoelectric sensor reading circuit 300 shown in FIG. 3, the piezoelectric sensor reading circuit 300A shown in FIG. 4 can also perform the electrical operation described above to subtract the unit 330 according to the first output voltage VA. And a second output voltage VB to generate a read voltage Vout that does not include a threshold voltage. According to this, the reading voltage Vout output by the piezoelectric sensor reading circuit 300A in this case does not have a threshold voltage, so that the reading voltage Vout output by the piezoelectric sensor reading circuit 300A will not be caused by the variation of the threshold voltage. Something went wrong. In an embodiment, the coupling method and the electrical operation method of the buffer unit 320 of the reading circuit 300A in FIG. 4 are similar to the buffer unit 320 of the reading circuit 300 in FIG. 3, and are not described herein.

It can be known from the foregoing embodiments of the present application that the application of the present application has the following advantages. The embodiment of the present invention provides a piezoelectric sensor reading circuit, so as to improve various error problems caused by the difference in threshold voltage values in the reading circuit.

Although the specific embodiments of the present case are disclosed in the above embodiments, they are not intended to limit the present case. Those who have ordinary knowledge in the technical field to which this case belongs can be carried out without departing from the principles and spirit of this case. Various changes and modifications, so the scope of protection in this case shall be defined by the scope of the accompanying patent application.

Claims (13)

    A reading circuit for a piezoelectric sensor includes an input unit including a first transistor including a first terminal, a second terminal, and a control terminal. The control terminal of the first transistor is used to receive a first transistor. Constant voltage, and the second terminal of the first transistor is used to output a first output voltage; and a second transistor including a first terminal, a second terminal and a control terminal, wherein the second transistor The control terminal is used for receiving a piezoelectric voltage, and the second terminal of the second transistor outputs a second output voltage; and a subtraction unit, which is electrically connected to the input unit, and is configured to be based on the first and the second The output voltage is subtracted to generate a read voltage.         The piezoelectric sensor reading circuit according to claim 1, wherein the second terminal of the first transistor is electrically connected to the first terminal of the second transistor.         The piezoelectric sensor reading circuit according to claim 2, wherein the input unit further includes a third transistor including a first terminal, a second terminal and a control terminal, and the first terminal of the third transistor It is electrically connected to the second terminal of the second transistor, and the control terminal of the third transistor is used to receive a second constant voltage.         The piezoelectric sensor reading circuit according to claim 3, wherein the first terminal of the first transistor is used to receive a power supply voltage; the second terminal of the third transistor is used to be coupled to a Ground voltage.         The piezoelectric sensor reading circuit according to claim 4, wherein the first output voltage includes a first voltage difference between the first constant voltage and a threshold voltage of the first transistor, and the second output voltage includes the A second voltage difference between the piezoelectric voltage and a threshold voltage of the second transistor, wherein the subtraction unit is configured to subtract the first voltage difference from the second voltage difference to generate the read voltage.         The piezoelectric sensor reading circuit according to claim 1, wherein the input unit further includes a third transistor including a first terminal, a second terminal and a control terminal, and the first terminal of the third transistor Electrically coupled to the second terminal of the first transistor; and a fourth transistor including a first terminal, a second terminal and a control terminal, the first terminal of the fourth transistor and the second transistor The second terminal of the crystal is electrically coupled.         The piezoelectric sensor reading circuit according to claim 6, wherein the first terminal of the first transistor and the first terminal of the second transistor are respectively used to receive a power supply voltage; The second terminal of the crystal and the second terminal of the fourth transistor are respectively used to be coupled to a ground pressure, and the control terminal of the third transistor and the control terminal of the fourth transistor are respectively used to Receive a second constant voltage.         The piezoelectric sensor reading circuit according to any one of claims 2 to 7, further comprising: a buffer unit coupled between the input unit and the subtraction unit to buffer the first output voltage and the Second output voltage.         A piezoelectric sensor reading circuit includes: an input unit including: a first transistor including: a first terminal for receiving a first constant voltage; a control terminal for receiving a piezoelectric voltage And a second terminal for receiving a first current; and a second transistor including: a first terminal for receiving the first constant voltage; a control terminal for receiving a second constant voltage And a second terminal for receiving a second current; a buffer unit including: a first comparator electrically coupled to the second terminal of the first transistor for using the first current according to the first current; And a third constant voltage to output a first output voltage; and a second comparator, which is electrically coupled to the second terminal of the second transistor, and is configured to be based on the second current and the third constant voltage A second output voltage is output; and a subtraction unit is configured to perform a subtraction operation according to the first output voltage and the second output voltage to generate a read voltage.         The piezoelectric sensor reading circuit according to claim 9, wherein the input unit further comprises: a third transistor including: a first terminal coupled to the second terminal of the first transistor; A control terminal for receiving a fourth constant voltage; and a second terminal coupled to the first comparator; and a fourth transistor including: a first terminal coupled to the second transistor; The second terminal; a control terminal for receiving the fourth constant voltage; and a second terminal coupled to the second comparator.         The piezoelectric sensor reading circuit according to claim 9 or 10, wherein the first comparator comprises: a reverse terminal, which is electrically coupled to the second terminal of the first transistor, wherein the first comparator The transistor transmits the first current from the second terminal to the first terminal according to the piezoelectric voltage; a non-inverting terminal for receiving the third constant voltage; and an output terminal for the first comparator for Outputting the first output voltage according to the first current and the third constant voltage; wherein the second comparator includes: a reverse terminal coupled to the second terminal of the second transistor, wherein the second The transistor transmits the second current from the second terminal to the first terminal according to the second constant voltage; a non-inverting terminal for receiving the third constant voltage; and an output terminal for the second comparator To output the second output voltage according to the second current and the third constant voltage.         The piezoelectric sensor reading circuit according to claim 9 or 10, wherein a voltage value of the third constant voltage is greater than a voltage value of the first constant voltage, wherein a voltage value of the second constant voltage is greater than the first constant voltage The voltage value of the voltage.         The piezoelectric sensor reading circuit according to claim 9 or 10, wherein the buffer unit further comprises: a first resistor coupled between the inverting terminal and the output terminal of the first comparator; and A second resistor is coupled between the inverting terminal and the output terminal of the second comparator.