Sensor signal output circuit and circuit board

Abstract

The application discloses a sensor signal output circuit and an integrated circuit board, and belongs to the technical field of sensor signal output circuits.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, specifically to a sensor signal output circuit and circuit board. Background Technology

[0002] In aerospace, weaponry, and marine applications, many alarm-type sensors (such as pressure alarms, temperature alarms, and vehicle water ingress alarms) need to simultaneously provide signals to multiple loads (subsystems) so that each subsystem can detect the alarm information and respond at the same time. These sensors typically output 0-5V voltage signals or 4-20mA current signals. However, when providing signals to multiple loads, the voltage signal is affected by cable length; the more loads, the greater the output voltage deviation, and it is also susceptible to electromagnetic interference. When powering multiple loads with current signals, it is also affected by load impedance. If the loads are connected in series, the current signal's load-carrying capacity is very limited, generally not exceeding 2-3 loads. If the loads are connected in parallel, the transmitted signal will cause significant distortion, similarly failing to provide reliable signals to multiple loads. Although digital signals like RS485 and CAN can achieve one master and multiple slaves, providing signals to multiple loads simultaneously, they are rarely used in sensors in aerospace, weaponry, and marine applications. Analog signals are generally used to ensure high communication reliability. Currently used voltage and current signals are insufficient to meet the requirements of supporting multiple loads, maintaining signal integrity, and ensuring high transmission reliability.

[0003] The published patent application CN201610392517.9, entitled "A Current Loop Communication System for Two-Wire Half-Duplex Multi-Machine Communication," describes a signal output circuit, such as... Figure 1 As shown: The master station transmits data by controlling the on / off state of the controlled switch K1, and the slave station receives data through the receiving module. At this time, current loop I is formed sequentially through the positive power supply, controlled switch K2, communication line I, slave station receiving module, communication line II, controlled switch K1, and GND. The slave station transmits data by controlling the on / off state of the transmitting module, and the master station receives data through the current sampling data receiving module. At this time, current loop II is formed sequentially through the positive power supply, controlled switch K2, communication line II, slave station transmitting module, communication line I, controlled switch K3, current sampling data receiving module, and GND. The order of the controlled switch K3 and the current sampling data receiving module is adjustable. Thus, when data is transmitted from the master station to the slave station and from the slave station to the master station, two current loops with opposite directions are realized on communication line I and communication line II, respectively.

[0004] Two current loops in opposite directions are used to transmit data from the master station to the slave station and from the slave station to the master station, respectively. Controlled switches are set on the DC power supply path, data transmission path, and data reception path of the master station. The number of slave stations is determined by the output power of the DC power supply and the breaking capacity of the three controlled switches: that is, when multiple slave stations are connected in parallel to two communication lines, if the current flowing through the current loop is I when there is one master and one slave, then when the number of slave stations is N and N>1, the DC power supply needs to output N×I when the master station transmits data; the DC power supply needs to output I when the slave station transmits data.

[0005] While the technical solution in the aforementioned patent application can handle multiple current loop loads, the number of slave stations is determined by the output power of the DC power supply and the breaking capacity of the three controlled switches. Specifically, when multiple slave stations are connected in parallel to two communication lines, if the current flowing through the current loop is I when there is one master and one slave, then when the number of slave stations is N and N>1, the DC power supply needs to output N×I current when the master station transmits data; and I current when the slave station transmits data. Since this current is controlled by the DC power supply, achieving automatic current adjustment and control is complex. Furthermore, additional circuitry and programming are required to integrate with this system, significantly increasing its complexity and making it unsuitable for use in sensors with limited space. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a sensor signal output circuit and circuit board with strong anti-interference ability and strong load-bearing capacity, in view of the problems existing in the prior art.

[0007] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0008] A sensor signal output circuit includes an operational amplifier unit, a voltage-to-frequency converter unit, a transistor Q1, and a constant current source unit. The input terminal of the operational amplifier unit is used to receive and amplify the sensor output signal. The input terminal of the voltage-to-frequency converter unit is connected to the output terminal of the operational amplifier unit and is used to receive the amplified sensor output signal and convert it into a frequency signal. The output terminal of the voltage-to-frequency converter unit is connected to the base of the transistor Q1 and is used to drive the transistor Q1. The transistor Q1, the constant current source unit, and the load are connected in series.

[0009] As a further improvement to the above technical solution:

[0010] The constant current source unit includes a three-terminal voltage regulator and a resistor module. The input terminal of the three-terminal voltage regulator is connected to the load, and the output terminal of the three-terminal voltage regulator is connected to one end of the resistor module. The ground terminal of the three-terminal voltage regulator and the other end of the resistor module are both connected to the collector of transistor Q1.

[0011] The resistor module includes resistors R2 and R3, which are connected in series. One end of resistor R3 is connected to the output terminal of the three-terminal regulator, and the other end of resistor R3 is connected to one end of resistor R2. The other end of resistor R2 is connected to the collector of transistor Q1.

[0012] It also includes a MOSFET Q2, the source of which is connected to one end of a resistor R3, and the drain of which is connected to the other end of a resistor R3.

[0013] It also includes an optocoupler U2 and a MOS driving unit. The input terminal of the optocoupler U2 is connected in series with one of the multiple parallel loads. The output terminal of the optocoupler U2 is connected to the input terminal of the MOS driving unit. The output terminal of the MOS driving unit is connected to the gate and drain of the MOS transistor Q2.

[0014] The output terminal of the optocoupler U2 is connected to the input terminal of the MOS driving unit via a filtering unit.

[0015] The filtering unit includes a resistor R4 and a capacitor C1. The output terminal of the optocoupler U2 is connected to the input terminal of the MOS driving unit via the resistor R4. One end of the capacitor C1 is connected to the input terminal of the MOS driving unit, and the other end is connected to the ground terminal of the optocoupler U2.

[0016] An inductor L1 is connected in series between the power supply VCC1 of the load and the load.

[0017] The inductor L1 is connected in parallel with a freewheeling diode D1. The positive terminal of the freewheeling diode D1 is connected to the power supply VCC1, and the other end is connected to the load.

[0018] The present invention also discloses an integrated circuit board, including the sensor signal output circuit described above.

[0019] Compared with the prior art, the advantages of the present invention are as follows:

[0020] The sensor output circuit of this invention can simultaneously modulate the frequency and current magnitude. The load end uses an optocoupler to receive the signal. The output signal of the sensor core can be obtained by simply demodulating the PWM frequency signal. It is independent of the current magnitude and only related to the frequency. In this way, the sensor signal will not be distorted when the load increases, and the load-carrying capacity is greatly improved. The output frequency is proportional to the output voltage of the sensor core. The output signal of the sensor core is obtained by demodulating the frequency magnitude, which has strong anti-interference ability. In addition, a constant current source unit is used, which has strong current output capability.

[0021] This invention solves the problems of insufficient load-carrying capacity and signal distortion when a sensor simultaneously provides signals to multiple loads. The circuit can simultaneously adjust the frequency and current of the sensor's output signal. The sensor's signal is only related to the frequency and not to the current magnitude, thus ensuring undistorted signal transmission and increasing signal transmission reliability. This invention is particularly suitable for applications such as aircraft and armored vehicles that require providing reliable signals to multiple subsystems simultaneously. It features a simple circuit structure and strong anti-interference capability. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a signal output circuit in the prior art.

[0023] Figure 2 This is a circuit schematic diagram of the circuit of the present invention in an embodiment.

[0024] Figure 3 The diagram shows the current waveforms on the load at different frequencies (without inductor L1).

[0025] Figure 4 The current waveform of the load at a frequency of 7kHz (with inductor L1) is shown in the figure.

[0026] Legend: 1. Operational amplifier unit; 2. Voltage to frequency conversion unit; 3. Constant current source unit; 4. MOS driver unit; 5. Filter unit. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0028] like Figure 2 As shown, the sensor signal output circuit of this embodiment includes an operational amplifier unit 1, a voltage-to-frequency conversion unit 2, a transistor Q1, and a constant current source unit 3. The input terminal of the operational amplifier unit 1 is used to receive and amplify the sensor output signal. The input terminal of the voltage-to-frequency conversion unit 2 is connected to the output terminal of the operational amplifier unit 1, and is used to receive the amplified sensor output signal and convert it into a frequency signal. The output terminal of the voltage-to-frequency conversion unit 2 is connected to the base of the transistor Q1, and is used to drive the transistor Q1. The transistor Q1, the constant current source unit 3, and the load are connected in series. During operation, the weak signal originally output by the sensor core is amplified by the operational amplifier unit 1 and then enters the voltage-to-frequency conversion unit 2 (specifically, a voltage-to-frequency conversion chip). The voltage signal is converted into a PWM frequency signal, which drives the transistor Q1, causing the transistor Q1 to operate in a switching state. The circuit where the load is located transmits a PWM current signal, generating a PWM voltage signal at both ends of the load. The load end uses an optocoupler to receive the signal, and the output signal of the sensor core can be obtained by demodulating the PWM frequency signal.

[0029] The sensor output circuit of this invention can simultaneously modulate the frequency and current magnitude. The load end uses an optocoupler to receive the signal. The output signal of the sensor core can be obtained by simply demodulating the PWM frequency signal. It is independent of the current magnitude and only related to the frequency. Thus, the sensor signal will not be distorted when the load increases, and the load-carrying capacity is greatly improved. The output frequency is proportional to the output voltage of the sensor core. The output signal of the sensor core is obtained by demodulating the frequency magnitude, which has strong anti-interference ability. In addition, a constant current source unit 3 is used, which has strong current output capability.

[0030] In one specific embodiment, the constant current source unit 3 includes a three-terminal voltage regulator U1 and a resistor module. The input terminal of the three-terminal voltage regulator U1 is connected to the load, and the output terminal of the three-terminal voltage regulator U1 is connected to one end of the resistor module. The ground terminal of the three-terminal voltage regulator and the other end of the resistor module are both connected to the collector of the transistor Q1. The constant current source unit 3, composed of a three-terminal voltage regulator, has a simple circuit structure.

[0031] In one specific embodiment, the resistor module includes resistors R2 and R3 connected in series. One end of resistor R3 is connected to the output terminal of the three-terminal regulator U1, and the other end of resistor R3 is connected to one end of resistor R2. The other end of resistor R2 is connected to the collector of transistor Q1. Additionally, a MOSFET Q2 is included, with its source connected to one end of resistor R3 and its drain connected to the other end of resistor R3.

[0032] When MOSFET Q2 is not turned on, the current in constant current source unit 3 is:

[0033] Where Vr is the internal reference voltage of the three-terminal regulator, and the circuit transmits the PWM current signal;

[0034] When MOSFET Q2 is turned on, the current in constant current source unit 3 increases to:

[0035] That is, by controlling the switching of MOSFET Q2, the current of the constant current source circuit can be adjusted, thus making it suitable for loads of different sizes.

[0036] In one specific embodiment, the system further includes an optocoupler U2 and a MOS driving unit 4. The input terminal of the optocoupler U2 is connected in series with one of the multiple parallel loads. The output terminal of the optocoupler U2 is connected to the input terminal of the MOS driving unit 4 via a filter unit 5. The output terminal of the MOS driving unit 4 is connected to the gate and drain of the MOS transistor Q2. Specifically, the filter unit 5 includes a resistor R4 and a capacitor C1. The output terminal of the optocoupler U2 is connected to the input terminal of the MOS driving unit 4 via the resistor R4. One end of the capacitor C1 is connected to the input terminal of the MOS driving unit 4, and the other end is connected to the ground terminal of the optocoupler U2. The optocoupler U2 is grounded via the resistor R5.

[0037] Specifically, assuming the circuit can drive n loads connected in parallel, as the number of loads increases, the current flowing through each load decreases. To increase the circuit's load-carrying capacity, when the n / 2th load is connected, an optocoupler U2 is connected in series. The PWM current flowing through the load forms a PWM voltage signal across R5 via the optocoupler U2. This signal is then converted into a DC voltage by the filter unit 5 composed of R4 and C1, and output as a drive signal through the MOS driver circuit. This causes the MOS transistor Q2 to conduct, increasing the total current flowing through the circuit from i1 to i2, thus increasing the circuit current and the load-carrying capacity. By configuring the parameters of R2, R3, and the loads, signals can be provided to more than 20 loads simultaneously, and each load receives a distortion-free frequency signal.

[0038] In one specific embodiment, an inductor L1 is connected in series between the load power supply VCC1 and the load. The function of inductor L1 is to reduce the inrush current of the constant current source unit 3 when transistor Q1 is turned on. This is because if the inrush current is too large at power-on, a typical three-terminal regulator-based constant current source cannot operate at frequencies above several kHz. Without inductor L1, with the three-terminal regulator (such as LM117), internal reference Vr = 1.25V, R2 = 100Ω, and MOSFET Q2 and the transistor turned on, its constant current design value is 12.5mA. With a remote load of 10Ω, the voltage across the remote load, i.e., the current flowing through the constant current source circuit, is measured at different frequencies. Figure 3 As shown: When the driving frequency of transistor Q1 is 1kHz or below, the current flowing through the circuit can reach the design value of 12.5mA. However, when the frequency rises to 3kHz or above, the current flowing through the circuit is only 2mA, far below the design value. The current is too small, and the circuit's anti-interference capability is weak. With the addition of inductor L1, when the driving frequency of transistor Q1 is 7kHz or above, the current flowing through the circuit can reach the design value, such as... Figure 4 As shown, the circuit's anti-interference capability is greatly improved.

[0039] Furthermore, a freewheeling diode D1 is connected in parallel with inductor L1. The positive terminal of freewheeling diode D1 is connected to the power supply VCC1, and the other terminal is connected to the load. The freewheeling diode is used to prevent the reverse voltage of inductor L1 from being too high when transistor Q1 is turned off, which could damage the components in the circuit.

[0040] The present invention also discloses an integrated circuit board, wherein the integrated circuit board is packaged with the sensor signal output circuit described above, which also has the advantages described above for the output circuit.

[0041] This invention solves the problems of insufficient load-carrying capacity and signal distortion when a sensor simultaneously provides signals to multiple loads. The circuit can simultaneously adjust the frequency and current of the sensor's output signal. The sensor's signal is only related to the frequency and not to the current magnitude, thus ensuring undistorted signal transmission and increasing signal transmission reliability. This invention is particularly suitable for applications such as aircraft and armored vehicles that require providing reliable signals to multiple subsystems simultaneously. It features a simple circuit structure and strong anti-interference capability.

[0042] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A sensor signal output circuit, characterized in that, It includes an operational amplifier unit (1), a voltage-to-frequency converter unit (2), a transistor Q1, and a constant current source unit (3); the input terminal of the operational amplifier unit (1) is used to receive and amplify the sensor output signal; the input terminal of the voltage-to-frequency converter unit (2) is connected to the output terminal of the operational amplifier unit (1), and is used to receive the amplified sensor output signal and convert it into a frequency signal; the output terminal of the voltage-to-frequency converter unit (2) is connected to the base of the transistor Q1, and is used to drive the transistor Q1; the transistor Q1, the constant current source unit (3), and the load are connected in series in sequence; During operation, the weak signal originally output by the sensor core is amplified by the operational amplifier unit (1) and then enters the voltage-to-frequency unit (2) to convert the voltage signal into a PWM frequency signal. The PWM frequency signal then drives the transistor Q1 to work in the switching state. The circuit where the load is located transmits the PWM current signal, which generates a PWM voltage signal at both ends of the load. The load end uses an optocoupler to receive the signal and demodulates the PWM frequency signal to obtain the output signal of the sensor core. An inductor L1 is connected in series between the power supply VCC1 of the load and the load. The constant current source unit (3) includes a three-terminal voltage regulator and a resistor module. The input terminal of the three-terminal voltage regulator is connected to the load, and the output terminal of the three-terminal voltage regulator is connected to one end of the resistor module. The ground terminal of the three-terminal voltage regulator and the other end of the resistor module are both connected to the collector of transistor Q1. The emitter of transistor Q1 is grounded. The resistor module includes resistors R2 and R3, which are connected in series. One end of resistor R3 is connected to the output terminal of the three-terminal regulator, and the other end of resistor R3 is connected to one end of resistor R2. The other end of resistor R2 is connected to the collector of transistor Q1. It also includes a MOS transistor Q2, the source of which is connected to one end of a resistor R3 and the drain of which is connected to the other end of a resistor R3; it also includes an optocoupler U2 and a MOS driving unit (4), the input of which is connected in series with one of the multiple parallel loads, the output of which is connected to the input of the MOS driving unit (4), and the output of which is connected to the gate and drain of the MOS transistor Q2.

2. The sensor signal output circuit according to claim 1, characterized in that, The output terminal of the optocoupler U2 is connected to the input terminal of the MOS driving unit (4) via the filter unit (5).

3. The sensor signal output circuit according to claim 2, characterized in that, The filter unit (5) includes a resistor R4 and a capacitor C1. The output terminal of the optocoupler U2 is connected to the input terminal of the MOS driving unit (4) via the resistor R4. One end of the capacitor C1 is connected to the input terminal of the MOS driving unit (4), and the other end is connected to the ground terminal of the optocoupler U2.

4. The sensor signal output circuit according to claim 1, characterized in that, The inductor L1 is connected in parallel with a freewheeling diode D1. The negative terminal of the freewheeling diode D1 is connected to the power supply VCC1, and the other end is connected to the load.

5. An integrated circuit board, characterized in that, Includes the sensor signal output circuit as described in any one of claims 1 to 4.

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