A temperature drift resistant charge-voltage conversion circuit based on a t-type bootstrap network

Abstract

The application discloses a temperature-drift-resistant charge-voltage conversion circuit based on a T-type bootstrap network, comprising an input protection circuit, a two-wire charge amplifier and a T-type alternating-current bootstrap network. The T-type alternating-current bootstrap network comprises a bootstrap resistor in series, and an alternating-current signal of a source electrode of a field effect transistor is fed back to a series common point of the bootstrap resistor through a coupling capacitor. The T-type alternating-current bootstrap network can reduce temperature drift and thermal noise of a conventional measurement circuit caused by environmental temperature change, while maintaining high alternating-current input impedance required for measurement. The input protection circuit can discharge transient high-voltage peaks to prevent damage to core devices. The circuit is composed of discrete components, has the characteristics of temperature-drift resistance, transient high-voltage impact resistance, easy integration and good frequency response characteristics, and is particularly suitable for shock wave overpressure measurement and vibration monitoring in harsh environments.

Description

Technical Field

[0001] This invention relates to the field of vibration and shock wave measurement technology, and in particular to a temperature drift-resistant charge-voltage conversion circuit based on a T-type bootstrap network. Background Technology

[0002] Piezoelectric sensors are widely used in dynamic mechanical measurements, but their output raw charge signal is weak, their output impedance is high, and they are easily affected by external environmental interference. Current conventional technology integrates the piezoelectric sensing element and the charge-to-voltage conversion circuit within the same shielded housing, achieving localized conversion of high-impedance charge signals to low-impedance voltage signals. This approach shortens the transmission distance of high-impedance signals and reduces the risk of charge leakage associated with long-distance cable transmission.

[0003] In existing charge conversion circuit designs, large-value bias resistors are typically used to increase the circuit's input impedance in order to achieve impedance matching of the sensor and prevent the weak AC charge signal from dissipating too quickly. However, when this conventional circuit is applied in environments such as shock wave measurement and complex industrial monitoring, it faces the following challenges:

[0004] 1. In test scenarios with drastic temperature changes, the resistance of large-value bias resistors will change due to their inherent temperature coefficient, causing the DC operating point of the charge conversion circuit to shift, resulting in zero-point drift of the measurement signal, which in turn affects the normal operation of subsequent amplification circuits.

[0005] 2. In shock wave overpressure measurement, transient mechanical impact forces cause the sensor to output a large amount of charge instantaneously, establishing a transient voltage spike at the circuit input. Simultaneously, complex testing environments are often accompanied by strong electromagnetic radiation, which may couple to generate transient high voltages. These transient high voltages, generated by mechanical force conversion and electromagnetic coupling, can easily exceed the withstand voltage limits of core components, reducing the reliability of the measurement system. Summary of the Invention

[0006] The purpose of this invention is to provide a temperature drift-resistant charge-to-voltage conversion circuit based on a T-type bootstrap network to solve the problems of poor temperature stability caused by the use of large-value resistors to construct high input impedance and susceptibility to breakdown damage from transient high-voltage spikes in the environment when existing measurement circuits are used for dynamic mechanical testing and shock wave measurement or vibration monitoring in industrial environments. At the same time, it takes into account the design requirements of easy circuit integration, good high-frequency response characteristics and wide dynamic range.

[0007] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0008] A temperature-drift-resistant charge-to-voltage conversion circuit based on a T-type bootstrap network includes the following circuit units: a power supply and output interface for connecting a constant current drive power supply and serving as the voltage output terminal of the temperature-drift-resistant charge-to-voltage conversion circuit based on the T-type bootstrap network to transmit a low-impedance voltage signal; an input protection circuit connected between the charge input terminal of the temperature-drift-resistant charge-to-voltage conversion circuit based on the T-type bootstrap network and the charge amplification and impedance transformation circuit; a charge amplification and impedance transformation circuit connected between the input protection circuit and the power supply and output interface, including a field-effect transistor (Q1) and a bipolar transistor (Q2); a T-type AC bootstrap network connected between the gate and source of the field-effect transistor (Q1) and connected to the power supply and output interface to obtain DC bias; and a feedback compensation circuit connected across the power supply and output interface and the gate of the field-effect transistor (Q1).

[0009] Furthermore, the input protection circuit includes a current-limiting resistor (R0) and a transient suppression diode (Z1); the current-limiting resistor (R0) is connected in series between the charge input terminal and the gate of the field-effect transistor (Q1), and the transient suppression diode (Z1) is connected in parallel between the charge input terminal and ground.

[0010] Furthermore, in the charge amplification and impedance transformation circuit, the field-effect transistor (Q1) is an N-channel junction field-effect transistor, and the bipolar transistor (Q2) is a PNP transistor; the drain of the N-channel junction field-effect transistor (Q1) is connected to the base of the PNP transistor (Q2), and is connected to the power supply and output interface through a load resistor (R4); the source of the N-channel junction field-effect transistor (Q1) is connected to ground through a source resistor (R5); the emitter of the PNP transistor (Q2) is connected to the power supply and output interface, and the collector is grounded.

[0011] Further, the T-type AC bootstrap network includes a first voltage divider resistor (R1), a second voltage divider resistor (R2), a first bootstrap resistor (R3A), a second bootstrap resistor (R3B), a bypass capacitor (C2), and a coupling capacitor (C4); the first voltage divider resistor (R1) and the second voltage divider resistor (R2) are connected in series between the power supply and output interface and ground; the common connection point of the first voltage divider resistor (R1) and the second voltage divider resistor (R2) forms a DC bias node; the bypass capacitor (C2) is connected between the DC bias node and ground; the first bootstrap resistor (R3A) and the second bootstrap resistor (R3B) are connected in series, and one end of the main branch after series connection is connected to the gate of the field-effect transistor (Q1), and the other end is connected to the DC bias node; one end of the coupling capacitor (C4) is connected to the common point of the series connection of the first bootstrap resistor (R3A) and the second bootstrap resistor (R3B), and the other end is connected to the source of the field-effect transistor (Q1).

[0012] Furthermore, the first bootstrap resistor (R3A) and the second bootstrap resistor (R3B) have the same resistance value, and the first voltage divider resistor (R1) has a greater resistance value than the second voltage divider resistor (R2).

[0013] Furthermore, the feedback compensation circuit includes a feedback capacitor (C1), a phase compensation resistor (R6), and a high-frequency bypass capacitor (C3); the feedback capacitor (C1) is connected in series between the power supply and output interface and the gate of the field-effect transistor (Q1); the phase compensation resistor (R6) is connected in series with the high-frequency bypass capacitor (C3) and then in parallel with the feedback capacitor (C1).

[0014] Compared with the prior art, the significant advantages of this invention are:

[0015] 1. Traditional methods for suppressing temperature drift include using differential amplifier circuits, selecting components with low temperature coefficients, and using diodes for temperature compensation. This invention optimizes the circuit structure by employing a T-type AC bootstrap network. The AC signal from the source is fed back to the common point of the series connection between the first and second bootstrap resistors via the coupling capacitor, causing the AC voltage drop across the first bootstrap resistor to approach zero. The circuit can use conventional low-to-medium resistance resistors in the DC loop, while achieving extremely high input impedance in the AC equivalent circuit, preventing the rapid discharge of weak charge signals. No complex external compensation circuit is required, improving the stability and reliability of the circuit in a wide temperature range measurement environment.

[0016] 2. To address transient high-voltage surges generated by the measurement environment, the front end of this invention integrates an input protection circuit. By utilizing the synergistic effect of a current-limiting resistor and a transient suppression diode, it absorbs and discharges transient high-voltage spikes generated by transient impact pressure conversion and electromagnetic interference coupling, preventing downstream core components from being damaged and burned out, thus improving the system's survivability.

[0017] 3. The circuit of this invention is composed entirely of simple discrete components, which is inexpensive and easy to integrate and package. With the cooperation of a closed-loop feedback compensation circuit, it can achieve stable two-wire long-distance transmission while having a wide dynamic response range and good high-frequency response characteristics. It is particularly suitable for high-fidelity extraction of shock wave and vibration signals in harsh monitoring environments. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a temperature drift-resistant charge-to-voltage conversion circuit based on a T-type bootstrap network.

[0019] Figure 2 It is a graph showing the amplitude-frequency response of the circuit.

[0020] Figure 3It is a circuit temperature scan analysis curve. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings.

[0022] like Figure 1 As shown, this invention proposes a temperature-drift-resistant charge-to-voltage conversion circuit based on a T-type bootstrap network, comprising the following circuit units: an input protection circuit, connected to the charge input terminal, for receiving the charge signal generated by the piezoelectric sensor and providing overvoltage protection; and a charge amplification and impedance transformation circuit, including a field-effect transistor. and bipolar transistor It is used to convert high-impedance input signals to low-impedance output signals; a T-type AC bootstrap network is connected between the gate and source of the field-effect transistor, including a first voltage divider resistor. Second voltage divider resistor First bootstrap resistor Second bootstrap resistor Bypass capacitor and coupling capacitor Feedback compensation circuit, connected between the voltage output terminal of the circuit and the gate of the field-effect transistor, is used to expand the circuit bandwidth and stabilize the frequency response; power supply and output interface, used to connect to the constant current drive power supply and transmit low impedance voltage signals to the outside at the voltage output terminal.

[0023] Specifically, the input protection circuit includes a current-limiting resistor. and transient suppression diodes Current-limiting resistor A transient suppression diode connected in series between the charge input terminal and the gate of the field-effect transistor. It is connected in parallel between the charge input terminal and ground. When a transient high-voltage spike reaches the measurement circuit, the transient suppression diode... Able to discharge it to ground, current-limiting resistor It can further limit the residual current flowing into the gate of the field-effect transistor, thus protecting the core amplifier.

[0024] Specifically, in this embodiment, the field-effect transistor is an N-channel junction field-effect transistor, and the bipolar transistor is a PNP transistor. In the charge amplification and impedance transformation circuit, the N-channel junction field-effect transistor... The drain of the PNP transistor The base is connected and through the load resistor Connected to the voltage output terminal; N-channel junction field-effect transistor The source of the PNP transistor is grounded through a source resistor. The emitter is connected to the voltage output terminal, and the collector is grounded. The two-wire circuit architecture multiplexes the power line and signal output line, simplifying the transmission link. This is beneficial for sensor integration and packaging, reduces noise introduced by long cable transmission, and ensures the quality of the output signal.

[0025] Specifically, the feedback compensation circuit includes a feedback capacitor. Phase compensation resistor and high-frequency bypass capacitor Phase compensation resistor With high frequency bypass capacitor After being connected in series, with the feedback capacitor Parallel connection forms high-frequency compensation; feedback capacitor Connected in series with the N-channel junction field-effect transistor at the voltage output terminal The distance between the gate and the electrode determines the gain of the circuit, and the output voltage can be expressed by the following formula:

[0026]

[0027] in, It is the amount of charge input to the circuit. It is a feedback capacitor The capacitance value.

[0028] Specifically, the T-type AC bootstrap network in this embodiment is the core design element for suppressing temperature drift caused by large-value resistors in wide-temperature measurement environments. In conventional signal conditioning circuits, gigaohm-level high-value bias resistors are typically used to prevent the discharge of the weak AC high-frequency charge signal output by the piezoelectric sensor. However, in measurement environments with large temperature variations, the gate leakage current of the field-effect transistor may change drastically. If a large-value bias resistor is used, it can easily generate DC offset voltage, leading to saturation of subsequent circuits or severe signal baseline shift.

[0029] The T-type AC bootstrap network proposed in this invention can resolve this technical contradiction. Its dynamic working principle is as follows:

[0030] For DC signals, the supply voltage passes through the first voltage divider resistor. Second voltage divider resistor Voltage divider, forming a stable DC bias node at the common terminal of both. Bypass capacitor. The AC interference at this node is filtered out to ground. At this time, the equivalent input impedance of the MOSFET gate is the first bootstrap resistor. With the second bootstrap resistor The sum of the resistance values, through reasonable setting and With a standard medium resistance value, it can effectively suppress DC voltage drift caused by drastic changes in leakage current with temperature, achieving excellent anti-temperature drift performance.

[0031] For AC signals, the field-effect transistor (FET) and its subsequent circuitry exhibit voltage following characteristics; the AC voltage at the source will follow the AC voltage at the gate in phase and with almost equal amplitude. Coupling capacitor. Under high-frequency AC signals, this is equivalent to a short circuit, directly coupling the source voltage of the field-effect transistor to the common point of the series connection of the bootstrap resistors. At this time, the first bootstrap resistor... Since the AC voltages at both ends are approximately equal, according to the impedance equivalence principle, the AC equivalent input impedance of this branch can be expressed as:

[0032]

[0033] in, This represents the AC voltage gain from the gate to the feedback node. Due to the bootstrap effect, As the denominator approaches 0, the circuit exhibits an input impedance much greater than the actual resistance value when the AC equivalent is applied.

[0034] An AC voltage source was applied to the circuit input terminal, and the amplitude frequency response and phase frequency response within a 10 MHz range were analyzed. The AC frequency sweep results are as follows: Figure 2 As shown in the figure, the frequency sweep results show that the lower cutoff frequency of the circuit is approximately 1.78 Hz, the upper cutoff frequency is approximately 1.58 MHz, and it has a flat frequency response characteristic within the passband, which meets the measurement requirements for shock waves and high-frequency vibration signals.

[0035] Temperature scanning analysis was performed on the circuit, and the results are as follows: Figure 3 As shown in the figure, the final output voltage Vout after the DC blocking capacitor and the output waveform V1 without the DC blocking capacitor are respectively shown. The latter can intuitively reflect the drift of the DC operating point with temperature. The simulation results show that as the ambient temperature increases, the fluctuation of the static baseline of the output signal is within a controllable range. In addition, the amplitude and phase of the final output signal remain consistent under different temperature conditions, and the waveform does not show obvious distortion, indicating that the circuit has good reliability under extreme temperature environments.

[0036] In summary, the circuit in this embodiment utilizes a T-type bootstrap network, which avoids baseline drift and thermal noise caused by using large-value resistors under high-temperature conditions, and provides a new solution for applying traditional measurement circuits to shock wave overpressure and vibration measurement.

Claims

1. A temperature-drift-resistant charge-to-voltage conversion circuit based on a T-type bootstrap network, characterized in that, Includes the following circuit units: The power supply and output interface is used to connect to a constant current drive power supply and to transmit low-impedance voltage signals to the outside as the voltage output terminal of the temperature drift-resistant charge-to-voltage conversion circuit based on a T-type bootstrap network. The input protection circuit is connected between the charge input terminal of the temperature drift-resistant charge-to-voltage conversion circuit based on a T-type bootstrap network and the charge amplification and impedance transformation circuit. The charge amplification and impedance transformation circuit is connected between the input protection circuit and the power supply and output interface, and includes a field-effect transistor (Q1) and a bipolar transistor (Q2). A T-type AC bootstrap network is connected between the gate and source of the field-effect transistor (Q1) and connected to the power supply and output interface to obtain DC bias. The feedback compensation circuit is connected between the power supply and output interface and the gate of the field-effect transistor (Q1).

2. The temperature-drift-resistant charge-to-voltage conversion circuit based on a T-type bootstrap network according to claim 1, characterized in that: The input protection circuit includes a current-limiting resistor (R0) and a transient suppression diode (Z1); the current-limiting resistor (R0) is connected in series between the charge input terminal and the gate of the field-effect transistor (Q1), and the transient suppression diode (Z1) is connected in parallel between the charge input terminal and ground.

3. The temperature-drift-resistant charge-to-voltage conversion circuit based on a T-type bootstrap network according to claim 1, characterized in that: In the charge amplification and impedance transformation circuit, the field-effect transistor (Q1) is an N-channel junction field-effect transistor, and the bipolar transistor (Q2) is a PNP transistor. The drain of the N-channel junction field-effect transistor (Q1) is connected to the base of the PNP transistor (Q2), and is connected to the power supply and output interface through a load resistor (R4). The source of the N-channel junction field-effect transistor (Q1) is connected to ground through a source resistor (R5). The emitter of the PNP transistor (Q2) is connected to the power supply and output interface, and the collector is grounded.

4. The temperature-drift-resistant charge-to-voltage conversion circuit based on a T-type bootstrap network according to claim 1, characterized in that: The T-type AC bootstrap network includes a first voltage divider resistor (R1), a second voltage divider resistor (R2), a first bootstrap resistor (R3A), a second bootstrap resistor (R3B), a bypass capacitor (C2), and a coupling capacitor (C4). The first voltage divider resistor (R1) and the second voltage divider resistor (R2) are connected in series between the power supply and output interface and ground. The common connection point of the first voltage divider resistor (R1) and the second voltage divider resistor (R2) forms a DC bias node. The bypass capacitor (C2) is connected between the DC bias node and ground. The first bootstrap resistor (R3A) and the second bootstrap resistor (R3B) are connected in series. One end of the main branch is connected to the gate of the field-effect transistor (Q1), and the other end is connected to the DC bias node. One end of the coupling capacitor (C4) is connected to the common point of the series connection of the first bootstrap resistor (R3A) and the second bootstrap resistor (R3B), and the other end is connected to the source of the field-effect transistor (Q1).

5. The temperature-drift-resistant charge-to-voltage conversion circuit based on a T-type bootstrap network according to claim 4, characterized in that: The first bootstrap resistor (R3A) and the second bootstrap resistor (R3B) have the same resistance value, and the first voltage divider resistor (R1) has a greater resistance value than the second voltage divider resistor (R2).

6. The temperature-drift-resistant charge-to-voltage conversion circuit based on a T-type bootstrap network according to claim 1, characterized in that: The feedback compensation circuit includes a feedback capacitor (C1), a phase compensation resistor (R6), and a high-frequency bypass capacitor (C3); the feedback capacitor (C1) is connected in series between the power supply and output interface and the gate of the field-effect transistor (Q1); the phase compensation resistor (R6) and the high-frequency bypass capacitor (C3) are connected in series and then in parallel with the feedback capacitor (C1).

Images