Bidirectional protection circuit capable of configuring current limiting gear and signal output module

Abstract

The invention discloses a bidirectional protection circuit capable of configuring current limiting gears and a signal output module. The bidirectional protection circuit comprises a first signal end, a second signal end, a pair of depletion mode field effect transistors and a current-limiting resistor network, the first ends of the depletion mode field effect transistors are respectively connected with the first signal end and the second signal end, the current-limiting resistor network is bridged between the second ends of the depletion mode field effect transistors and the second signal end, and the third control end of the current-limiting resistor network communicates with the MCU / FPGA. And adjusting the equivalent resistance value according to the control signal. When the current between the terminals is increased, the voltage at the two ends of the current-limiting resistance network enables the gate-source voltage of the depletion-mode field effect transistor on one side to reach a threshold value and to be converted from conduction to cut-off, and the path current is limited below the ratio of the threshold voltage to the equivalent resistance value. The signal output module connects the bidirectional protection circuit in series between a digital-to-analog converter and an output, and a digital communication interface and a current-limiting resistor network are utilized to configure a plurality of current-limiting gears so as to realize bidirectional current-limiting protection of an analog quantity output channel and flexible setting of current-limiting parameters.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electronic circuit, and particularly relates to a bidirectional protection circuit with configurable current-limiting gear and a signal output module. BACKGROUND

[0002] In an industrial data acquisition system, analog signals are generally weak signals with low voltage. In such an analog output channel, a digital-to-analog converter is usually used to generate a target voltage or current in cooperation with an operational amplifier or other driving circuit, and then the target voltage or current is connected to a field load through a terminal.

[0003] In actual engineering applications, the analog output channel often faces various working condition risks. On the one hand, field wiring errors or debugging misoperations may cause the output end to be short-circuited to ground, short-circuited to the positive pole of a power supply or misconnected to other high-voltage signal lines, thereby introducing a large current impact or reverse current, which is easy to cause damage to the digital-to-analog converter, the operational amplifier or peripheral driving devices. On the other hand, field loads are various, and different devices have differences in the upper limit of the allowed input current, the short-circuit bearing capacity and the response strategy in abnormal conditions, and it is difficult for a fixed current-limiting value to simultaneously meet the application requirements of various types. In addition, the temperature in an industrial field environment changes greatly, and the working life of an analog channel is relatively long, and the precision and temperature drift characteristics of a current-limiting circuit directly affect the precision and protection margin of a small current output.

[0004] In the prior art, to protect the analog output channel and prevent overcurrent damage, a common structure is to connect a fixed resistor, fuse or self-recovery fuse and other current-limiting elements in series at the analog output end, to increase the series impedance in the output loop and roughly limit the current in the case of short circuit or abnormality. This structure is simple to implement, but the current-limiting value is completely determined by the single element parameter, it is difficult to adjust the current-limiting level according to different loads and application scenarios, and it will introduce an additional voltage drop in the normal working state, affecting the output accuracy, and the current control capability under the conditions of external power backflow, voltage abnormality and the like is also limited. Another structure uses a protection circuit with one-way overcurrent detection and shutdown function, for example, a single metal oxide semiconductor field effect transistor is connected in series at the output end, a sampling resistor is used to detect the current flowing through the output channel, and a comparator or control logic is used to shut down the transistor when the current exceeds the preset threshold, to realize overcurrent protection. This scheme is mostly designed for the direction of the current pulled out by the microcontroller or digital-to-analog converter, and has insufficient protection capability for the reverse current poured into the output end by the external power supply or other modules, and it is difficult to effectively limit the current in both directions. In addition, the current-limiting threshold of this scheme is usually fixed in the hardware design stage, and it is difficult to flexibly configure different current-limiting gears by software afterwards. Another structure adds symmetric clamping diodes, transient suppression diodes and other clamping elements at the analog output end, to limit the voltage amplitude of the output end, and at the same time, a fixed impedance device is connected in series in the output path, to balance the overvoltage clamping and current limiting functions to some extent. This structure can suppress overvoltage and surges to some extent, but its current limiting capability still mainly depends on the fixed impedance, it is difficult to set the current limiting characteristics in different directions, and it is also impossible to flexibly set multiple current gears through control signals according to different needs of field applications.

[0005] In summary, the existing protection schemes for analog output channels still have deficiencies in current limiting methods, protection directions and current limiting configuration flexibility, and there is a lack of a protection circuit with relatively simple structure, which can limit the current in both directions of the output channel and flexibly configure the current limiting current gear. SUMMARY

[0006] Embodiments of the present application provide a bidirectional protection circuit with configurable current limiting gears and a signal output module to overcome the limitations of unidirectional protection circuits and improve the adaptability of the protection circuit to different application scenarios.

[0007] To solve the above technical problems, embodiments of the present application disclose the following technical solutions: In one aspect, a configurable current-limiting range bidirectional protection circuit is provided, comprising: a first signal terminal and a second signal terminal; a first depletion-mode field effect transistor having a first terminal, a second terminal and a first control terminal, wherein the first terminal is coupled to the first signal terminal; a second depletion-mode field effect transistor having a first terminal, a second terminal and a second control terminal, wherein the first terminal is coupled to the second signal terminal, the second terminal is coupled to the first control terminal, and the second control terminal is coupled to the second terminal of the first depletion-mode field effect transistor; a current-limiting resistor network having a first terminal, a second terminal and a third control terminal, wherein the first terminal is coupled to the second terminal of the first depletion-mode field effect transistor, the second terminal is coupled to the second terminal of the second depletion-mode field effect transistor, and the third control terminal is configured to receive a control signal from a microcontroller and / or a programmable logic array and adjust an equivalent resistance value of the current-limiting resistor network according to the control signal; wherein when a bidirectional current flowing between the first signal terminal and the second signal terminal increases, a current flowing through the current-limiting resistor network generates a voltage between the first terminal and the second terminal of the current-limiting resistor network, and when the voltage causes an absolute value of a potential difference between the control terminal and the second terminal of any depletion-mode field effect transistor to reach a threshold voltage of the depletion-mode field effect transistor, the depletion-mode field effect transistor is switched from an on state to an off state, and a current between the first signal terminal and the second signal terminal is limited within a current-limiting range set by the equivalent resistance value and the threshold voltage, and a current value of the current-limiting range is equal to a ratio of the threshold voltage to the equivalent resistance value.

[0008] Further, the current-limiting resistor network comprises: a plurality of resistor branches, each of the resistor branches comprising one or more resistor elements; and an analog switch having a plurality of switch terminals and a GPIO interface, wherein the plurality of switch terminals are respectively coupled to the plurality of resistor branches, and the GPIO interface constitutes the third control terminal; and the analog switch selectively connects at least one resistor branch according to a control signal received by the GPIO interface, so that the current-limiting resistor network has different equivalent resistance values under different control signals.

[0009] Further, the resistor elements in the plurality of resistor branches are precision resistors with a resistance accuracy not higher than 0.1% and a temperature coefficient not higher than 25ppm / ℃, so that a tolerance of a current-limiting current between the first signal terminal and the second signal terminal under any current-limiting range is not more than ±0.1%, and a relative change rate of the current-limiting current with respect to temperature is not more than 25ppm / ℃.

[0010] Further, the first signal end is coupled to an internal driving node of an analog output channel, and the second signal end is coupled to an external output terminal of the analog output channel; an output driving current of the analog output channel in a normal working state is not more than 10 mA, and an equivalent resistance value of the current-limiting resistor network is configured to make current values corresponding to respective current-limiting gears in a range of 1 mA to 10 mA.

[0011] Further, the first depletion-mode field effect transistor and the second depletion-mode field effect transistor are both N-type tubes or both P-type tubes.

[0012] Further, threshold voltages of the first depletion-mode field effect transistor and the second depletion-mode field effect transistor are equal.

[0013] Further, threshold voltages of the first depletion-mode field effect transistor and the second depletion-mode field effect transistor are not equal.

[0014] In another aspect, a signal output module with configurable current-limiting gears is provided, including: a digital-to-analog converter, at least one bidirectional protection circuit with configurable current-limiting gears as described in any of the above first aspects, and an analog output terminal connected with an external load; an analog output end of the digital-to-analog converter is electrically connected with a first signal end of the at least one bidirectional protection circuit with configurable current-limiting gears, and the analog output terminal is electrically connected with a second signal end of the at least one bidirectional protection circuit with configurable current-limiting gears; the digital-to-analog converter communicates with a microcontroller and / or a programmable logic array through a digital communication interface, for setting an output voltage of the digital-to-analog converter to generate a target analog output signal; a current-limiting resistor network of the at least one bidirectional protection circuit with configurable current-limiting gears is coupled to the microcontroller and / or the programmable logic array through a third control end, to receive a control signal output by the microcontroller and / or the programmable logic array, and configure a current-limiting gear of a current path between the analog output end of the digital-to-analog converter and the analog output terminal.

[0015] Further, a driving circuit is further included, the driving circuit including an operational amplifier and a feedback resistor; a non-inverting input end of the operational amplifier is electrically connected with the analog output end of the digital-to-analog converter, an inverting input end of the operational amplifier is electrically connected with the second signal end through the feedback resistor, and an output end of the operational amplifier is electrically connected with the first signal end, so that a voltage of the second signal end in a non-current-limiting state follows an output voltage of the digital-to-analog converter.

[0016] Further, the multiple analog output channels each include a digital-to-analog converter output channel, a driving circuit corresponding to the digital-to-analog converter output channel, and a two-way protection circuit of the configurable current limiting gear; the driving circuit is coupled between the digital-to-analog converter output channel and the two-way protection circuit of the configurable current limiting gear to drive the two-way protection circuit of the configurable current limiting gear; the multiple analog output channels are configured to respectively and independently communicate with the microcontroller and / or the programmable logic array through multiple digital communication interfaces and multiple third control terminals to determine the output voltage of the digital-to-analog converter output channel in each analog output channel and configure the equivalent resistance value of the current limiting resistor network, so as to independently configure the current limiting gear of each analog output terminal current path.

[0017] The technical solutions have at least the following beneficial effects: the two depletion-mode field effect transistors and the current limiting resistor network constitute a protection unit, the drain and source ends of the two depletion-mode field effect transistors are connected in series between the first signal end and the second signal end, and the control ends are cross-coupled to the two ends of the current limiting resistor network, so that current clamping can be formed in two current directions, thereby, no matter whether the output end is short-circuited to the ground or pulled to a high potential by an external power supply or other signal line, the two-way protection circuit can limit the path current within the current limiting gear range, effectively preventing the driving circuit and the subsequent devices from being damaged due to overcurrent, and the current limiting value can be flexibly adjusted according to the digital control signal, compared with the existing protection scheme with only a single current limiting direction and fixed current limiting value, the protection capability and configuration flexibility of the output channel under various wiring conditions are improved.

[0018] The technical solutions have the following advantages: by matching the threshold voltage of the depletion-mode field effect transistor with the equivalent resistance value of the current limiting resistor network, the current value corresponding to each current limiting gear is determined by the ratio of the threshold voltage and the equivalent resistance value, and multiple resistance branches are arranged in the current limiting resistor network to form multiple current limiting gears, which can be matched and designed according to the upper limit of the allowable current of different loads and interface standards, and is particularly suitable for configuring current limiting current by gear in a small current range of the analog output channel, so that the same hardware platform can better adapt to different types of field devices; The use of precision resistor devices can improve the consistency and temperature stability of the current limiting current under each current limiting gear, which is beneficial to determining a reasonable protection margin during the system design phase, so that the current limiting action has good predictability and repeatability, and the reliability of the analog output channel under long-term operating conditions is improved; The first depletion mode field effect transistor and the second depletion mode field effect transistor can use N-type or P-type, and the threshold voltage can be set to be equal or unequal, so as to flexibly select the device type according to the system power supply mode and the interface polarity, and to obtain the protection characteristics of the two-direction current limiting currents which are basically symmetrical through the equal threshold value, or to configure different upper limits of the current limiting currents in two directions through the unequal threshold value, so as to adapt to different risk scenarios such as output shorting to ground and external backflow current. Based on the microcontroller and / or programmable logic array cooperating with the digital-to-analog converter and the driving circuit to form an analog output channel, only a small number of peripheral devices are added on the basis of maintaining the sequential architecture of the traditional MCU / FPGA, DAC and operational amplifier, so as to realize the bidirectional current limiting protection and independent configuration of the current limiting gears of the multi-channel analog output, and to balance the simplicity of the circuit structure and the scalability of the system-level protection function. BRIEF DESCRIPTION OF DRAWINGS

[0019] The technical solutions and other beneficial effects of the present application will be apparent from the following detailed description of specific embodiments of the present application, combined with the accompanying drawings.

[0020] Figure 1 A schematic diagram of a configurable current limiting gear bidirectional protection circuit 100 provided by the present application; Figure 2 A schematic diagram of a signal output module 10 provided by the present application; Figure 3 A schematic diagram of a multi-channel analog output channel provided by the present application. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and beneficial effects of the present application clearer and more apparent, the present application will be further described in detail below, combined with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described in the present description are only for the purpose of explaining the present application, and are not intended to limit the present application.

[0022] In the description of the present application, it should be understood that the terms "first" and "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first" and "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited. The terms "connection", "connection", "coupling", "electrical connection", "signal connection" and the like, unless otherwise specifically limited, can be generally understood in a broad sense, which can be a direct connection between elements or an indirect connection through intermediate elements, devices, wires, printed circuits or networks, or can be an electrical or signal connection realized by wired or wireless means.

[0023] In this application, the term "microcontroller" or "microcontroller unit" can refer to a microcontroller unit (MCU), usually a single-chip computer or system-on-chip with computing and control capabilities, which can integrate a processor core, memory, and various peripheral interfaces. The term "programmable logic array" can refer to a field programmable gate array (FPGA), which is usually used to implement configurable logic operations and timing control. The term "digital-to-analog converter" can refer to a digital-to-analog converter (DAC), which is used to convert digital quantities into corresponding analog voltage or current outputs. The term "GPIO interface" can refer to a general-purpose input / output interface (GPIO), which is usually provided by an MCU and / or FPGA, and can be configured to output control signals or input status signals for signal interaction with analog switches, current limiting resistor networks, and other peripheral circuits. The term "analog output channel" can refer to a circuit path composed of an MCU and / or FPGA, a digital-to-analog converter, a driving circuit, and a protection circuit, etc., which is used to output analog voltage or current signals to external loads. The term "analog output terminal" can refer to the electrical connection endpoint between the analog output channel and external instruments, signal acquisition modules, or actuators, such as terminal connections or connector pins on the terminal block. The term "internal driving node" usually refers to a node located on the output side of the digital-to-analog converter and inside the driving circuit, which is used to drive the analog output terminal, and its voltage or current can be adjusted according to the control signal. The term "resistance accuracy" usually refers to the allowable deviation of the actual resistance value of a resistance element from its nominal resistance value under specified reference temperature and test conditions, commonly expressed in percentage form. The lower the resistance accuracy value, the smaller the deviation between the actual resistance value of the resistance element and its nominal resistance value. The term "temperature coefficient" usually refers to the rate of relative change in the resistance value of a resistance element with temperature, commonly expressed in terms of relative change per degree Celsius, for example, several ppm / °C.

[0024] The current limiting scheme of existing signal acquisition circuits relies on fixed impedance or one-way overcurrent protection circuits, making it difficult to simultaneously implement bidirectional current limiting and multi-gear, configurable current limiting control under the architecture of general-purpose microcontrollers and / or programmable logic arrays in conjunction with digital-to-analog converters.

[0025] To this end, the present application proposes a bidirectional protection circuit with configurable current limiting gears and a signal output module, which implements bidirectional current limiting protection for the output channel and flexibly configures the current limiting gears according to the control signal through the cooperation of depletion-mode field effect transistors and current limiting resistor networks.

[0026] Figure 1 A schematic diagram of a bidirectional protection circuit 100 with configurable current limiting levels provided in this application is shown. Figure 1 As shown, the exemplary bidirectional protection circuit 100 with configurable current limiting levels provided in this application includes: a first signal terminal 101, a second signal terminal 102, a first depletion-type field-effect transistor Q1, a second depletion-type field-effect transistor Q2, and a current-limiting resistor network 110. In this embodiment, the first depletion-type field-effect transistor Q1 has a first terminal, a second terminal, and a first control terminal, wherein the first terminal is coupled to the first signal terminal 101; the second depletion-type field-effect transistor Q2 has a first terminal, a second terminal, and a second control terminal, wherein the first terminal is coupled to the second signal terminal 102, the second terminal is coupled to the first control terminal, and the second control terminal is coupled to the second terminal of the first depletion-type field-effect transistor Q1; the current-limiting resistor network 110 has a first terminal, a second terminal, and a third control terminal, wherein the first terminal is coupled to the second terminal of the first depletion-type field-effect transistor Q1, the second terminal is coupled to the second terminal of the second depletion-type field-effect transistor Q2, and the third control terminal is used to receive control signals from a microcontroller and / or a programmable logic array, and adjust the equivalent resistance value Req of the current-limiting resistor network 110 according to the control signals.

[0027] In the above embodiments, both the first depletion-type field-effect transistor Q1 and the second depletion-type field-effect transistor Q2 are N-type transistors, with their first terminals being drains, their second terminals being sources, and their control terminals being gates. It should be understood that the first depletion-type field-effect transistor Q1 and the second depletion-type field-effect transistor Q2 can also be P-type transistors, and the circuit topology is similar to... Figure 1 Similarly, this will not be elaborated upon here.

[0028] Reference Figure 1 As can be seen, in the above-described exemplary bidirectional protection circuit 100 with configurable current limiting levels, the current limiting resistor network 110 includes multiple resistor branches and an analog switch 111. In the embodiments provided in this application, the resistor branches of the current limiting resistor network 110 may include one or more resistor elements, the analog switch 111 has multiple switching terminals and a GPIO interface, and the multiple switching terminals are respectively coupled to multiple resistor branches. The GPIO interface constitutes the third control terminal of the current limiting resistor network 110. After receiving the control signal from the GPIO interface, the analog switch 111 selectively connects at least one resistor branch, so that the current limiting resistor network 110 has different equivalent resistance values ​​Req under different control signals.

[0029] In the embodiment, four resistors R1 to R4 are used to represent the four branches of the current-limiting resistor network 110, which are connected in parallel to one end of the source of the first depletion-mode field effect transistor Q1 as the first end of the current-limiting resistor network 110. The switch ends of the analog switch 111 are represented by S1 to S4, and the GPIO interface is represented by A0 and A1, which receive the control signals Ctrl0 and Ctrl1 output by the MCU / FPGA, respectively. The enable end EN is connected to a conventional enable level of 5V, and the output port D is used as the second end of the current-limiting resistor network 110, which is connected to the second end of the second depletion-mode field effect transistor Q2 as shown in Figure 1

[0030] When the bidirectional current flowing between the first signal end 101 and the second signal end 102 increases, the current flowing through the current-limiting resistor network 110 generates a voltage between the first end and the second end of the current-limiting resistor network 110. When the absolute value of the potential difference between the control end and the second end of any depletion-mode field effect transistor reaches its threshold voltage Vth, the depletion-mode field effect transistor changes from the on state to the off state, limiting the current between the first signal end 101 and the second signal end 102 within the current-limiting gear range set by the equivalent resistance value Req of the current-limiting resistor network 110 and the threshold voltage Vth. The current value Ilim of the current-limiting gear is equal to the ratio of the threshold voltage Vth to the equivalent resistance value Req. Taking the example of controlling the analog switch 111 to select the resistor R1 branch by Ctrl0 and Ctrl1, when the DAC is coupled to the first signal end 101 and the output signal increases, the current output from the first signal end 101 to the second signal end 102 flows through the current path composed of Q1, R1, and Q2. At this time, the voltage across R1 increases, resulting in a negative gate-source voltage VGS of Q1 with an increasing absolute value. When |VGS| grows to be greater than the threshold voltage Vth1 of Q1, the channel of Q1 gradually depletes, the conduction ability gradually weakens, and eventually the channel is pinched off and Q1 changes from the on state to the off state. At this time, the current flowing through Q1, Vth1 / R1, is the current value of the current-limiting gear. Similarly, the remaining resistor branches and the case of reverse current flow are not described here.

[0031] ​In the above embodiments, it is readily understood that if the threshold voltages Vth1 and Vth2 of Q1 and Q2 are equal, then regardless of whether the current flows from the first signal port 101 to the second signal port 102 or from the second signal port 102 to the first signal port 101, the current limiting value of the current path is equal at the same level. However, if the threshold voltages Vth1 and Vth2 of Q1 and Q2 are not equal, then the current limiting values ​​of the current path under the above two current directions are different when the same resistance branch is conducting. Therefore, those skilled in the art can set different Vth1 and Vth2 according to the needs of actual application scenarios and the risk situations of different signal acquisition directions to adapt to situations such as output short grounding wires and external reverse current.

[0032] Based on the above embodiments, the resistor elements in the multiple resistor branches are precision resistors with a resistance accuracy of no more than 0.1% and a temperature coefficient of no more than 25ppm / ℃, so that the tolerance of the current limiting current between the first signal terminal 101 and the second signal terminal 102 does not exceed ±0.1% under any current limiting position, and the relative change rate of the current limiting current with temperature does not exceed 25ppm / ℃.

[0033] In the embodiments provided in this application, the first signal terminal 101 is coupled to the internal drive node of the analog output channel, and the second signal terminal 102 is coupled to the external output terminal of the analog output channel. The output drive current of the analog output channel under normal operating conditions does not exceed 10mA, and the equivalent resistance value Req of the current-limiting resistor network 110 is configured to ensure that the current value corresponding to each current-limiting level is within the range of 1mA to 10mA. Figure 1 As shown, in the above exemplary embodiment, the analog output channel is exemplified by a DAC. In high-precision signal acquisition applications, the output drive current of the internal drive node of the DAC is generally less than 10mA. Taking the current-limiting resistor network 110 with four resistor branches as an example, four current-limiting values ​​can be set as 1mA, 5mA, 8mA, and 10mA. These four current-limiting values ​​can be used to select the switching ports S1 to S4 of the analog switch 111 by controlling the control signals Ctrl0 and Ctrl1 as 00, 01, 10, and 11, respectively, thereby connecting different resistor branches between Q1 and Q2, and thus realizing the switching of current-limiting levels.

[0034] Figure 2 A schematic diagram of a signal output module 10 with configurable current limiting levels provided in this application is shown. Figure 2As shown, the signal output module 10 provided by the present application includes a digital-to-analog converter 200, at least one configurable current-limiting gear bidirectional protection circuit 100, and an analog output terminal 11 connected with an external load. The analog output terminal VOUT of the digital-to-analog converter 200 is electrically connected with the first signal terminal 101 of the at least one configurable current-limiting gear bidirectional protection circuit 100, and the analog output terminal 11 is electrically connected with the second signal terminal 102 of the at least one configurable current-limiting gear bidirectional protection circuit 100. The digital-to-analog converter 200 communicates with an MCU / FPGA through a digital communication interface, for setting the output voltage of the digital-to-analog converter 200 to generate a target analog output signal. As shown in the figure, Figure 2 As shown, in the embodiment, the digital communication interface of the digital-to-analog converter 200 is an IIC interface, including an IIC clock communication IIC_SCL and an IIC data communication IIC_SDA. In addition, the digital-to-analog converter 200 also has an address port AD, which receives an address selection level of 5V through a pull-up resistor R6. The current-limiting resistor network 110 of the configurable current-limiting gear bidirectional protection circuit 100 is coupled to the MCU / FPGA through the third control terminals A0 and A1, to control the signal Ctrl0 and Ctrl1, and configure the current-limiting gear of the current path between the analog output terminal VOUT of the digital-to-analog converter 200 and the analog output terminal 11. It should be understood that the digital communication interface in the embodiment is an IIC interface, and SPI interface, serial peripheral interface or other digital communication bus known to those skilled in the art can also be used.

[0035] Further, on the basis of the above-mentioned embodiment, the signal output module 10 also includes a driving circuit 300. The driving circuit includes an operational amplifier and a feedback resistor R5. The non-inverting input terminal of the operational amplifier is electrically connected with the analog output terminal VOUT of the digital-to-analog converter 200, the inverting input terminal is electrically connected with the second signal terminal 102 through the feedback resistor R5, and the output terminal of the operational amplifier is electrically connected with the first signal terminal 101, so that the voltage of the second signal terminal 102 in the non-current-limiting state follows the output voltage of the digital-to-analog converter 200.

[0036] In order to facilitate those skilled in the art to understand the working principle of the driving circuit 300, the following describes the working principle of the driving circuit 300. Figure 2The voltage following characteristics of the driving circuit 300 shown will be further explained. In this embodiment, the inverting input terminal of the operational amplifier is electrically connected to the second signal terminal 102 through the feedback resistor R5, thereby forming a negative feedback loop with the second signal terminal 102 as the feedback node. When the current-limiting resistor network 110 is not in the current-limiting working state and the first depletion-type field-effect transistor Q1 and the second depletion-type field-effect transistor Q2 remain on, a slight voltage difference will be generated between the non-inverting input terminal and the inverting input terminal of the operational amplifier when the voltage of the second signal terminal 102 deviates slightly from the output voltage of the digital-to-analog converter 200. As a high-gain amplifier, the operational amplifier will automatically adjust its output voltage so that the voltage fed back to the inverting input terminal through the feedback resistor R5 gradually approaches the voltage of the non-inverting input terminal, thereby stabilizing the potential of the second signal terminal 102 at a level that is basically equal to the output voltage of the digital-to-analog converter 200. Through the above negative feedback control, the drive circuit 300 forms a voltage follower in the non-current limiting state, so that the voltage of the second signal terminal 102 corresponding to the analog output terminal 11 follows the output voltage change of the digital-to-analog converter 200. At the same time, the operational amplifier provides the necessary current driving capability to reduce the pressure of the digital-to-analog converter 200 directly driving the external load.

[0037] Figure 3 This is a schematic diagram of a multi-channel analog output channel provided in this application. Figure 3 As shown, in this embodiment, based on the configurable current-limiting signal output module 10 described above, one output channel of the digital-to-analog converter 200, the corresponding drive circuit 300, and a bidirectional protection circuit 100 with configurable current-limiting levels are packaged into an analog output channel T1. The configurable current-limiting signal output module 10 of this embodiment includes multiple analog output channels (T1, T2, ...). Figure 3 The circuit topology and device configuration of T2 are the same as those of the other analog output channels, and will not be shown again. In each analog output channel, the drive circuit 300 is coupled between the output channel VOUT of the corresponding digital-to-analog converter 200 and the corresponding bidirectional protection circuit 100 with configurable current limiting level, so as to drive the bidirectional protection circuit 100 with configurable current limiting level. In this embodiment, the multiple analog output channels are configured to communicate independently with the MCU / FPGA through multiple digital communication interfaces and multiple third control terminals to determine the output voltage of the output channel of the digital-to-analog converter 200 in each analog output channel and configure the equivalent resistance value Req of the current limiting resistor network 110 so as to independently configure the current limiting level of the current path corresponding to each analog output terminal 11. Without significantly increasing the hardware complexity, the signal output module 10 with configurable current limiting level in this embodiment can realize centralized control of multiple analog outputs and flexible allocation of current limiting strategies, improving the modularity and scalability of the system.

[0038] In summary, the embodiment of the application introduces a bidirectional protection circuit composed of a pair of depletion-mode field effect transistors and a current-limiting resistor network 110 between the first signal terminal 101 and the second signal terminal 102, so that when the bidirectional current flowing between the signal terminals increases, a voltage is generated across the current-limiting resistor network 110, and when the voltage causes the gate-source voltage of the corresponding depletion-mode field effect transistor to reach the threshold voltage, the transistor changes from the on state to the off state, thereby limiting the path current within the current-limiting gear determined by the threshold voltage Vth and the equivalent resistance value Req of the current-limiting resistor network 110. By designing the current-limiting resistor network 110 as a configurable resistor network composed of multiple resistance branches and analog switches 111, and preferably using high-precision, low-temperature-coefficient resistor elements, the current-limiting current of each current-limiting gear can be flexibly configured under the action of digital control signals, with good precision and temperature stability. At the same time, according to whether the threshold voltages of the pair of depletion-mode field effect transistors are equal, the bidirectional current limiting value can be symmetric or asymmetric. At the signal output module level, the application connects the digital-to-analog converter output, the driving circuit and the bidirectional protection circuit in series to form an analog output channel, forms a voltage following structure by using an operational amplifier and a feedback resistor to ensure that the output terminal voltage follows the output voltage of the digital-to-analog converter in the non-current limiting state, and uses a microcontroller and / or a programmable logic array to digitally configure the output voltage and the equivalent resistance value of the current-limiting resistor network, respectively. Thus, without significantly increasing the hardware complexity, the bidirectional current limiting protection of the multi-channel analog output channel and the flexible and independent setting of the current-limiting gear are realized, and the circuit structure in the module is simple, adaptable and controllable in protection performance.

[0039] The specific embodiments provided in the above are only used to help understand the technical features, structures and core ideas of the technical solutions of the application. For those skilled in the art in the technical field, some improvements and modifications can be made to the application without departing from the principles of the application, and these improvements and modifications also belong to the protection scope of the claims of the application.

Claims

1. A configurable current-limited range bidirectional protection circuit, characterized in that, The current limiting resistor network comprises: a first signal terminal and a second signal terminal; a first depletion-mode field effect transistor having a first terminal, a second terminal and a first control terminal, wherein the first terminal is coupled to the first signal terminal; a second depletion-mode field effect transistor having a first terminal, a second terminal and a second control terminal, wherein the first terminal is coupled to the second signal terminal, the second terminal is coupled to the first control terminal, and the second control terminal is coupled to the second terminal of the first depletion-mode field effect transistor; a current limiting resistor network having a first terminal, a second terminal and a third control terminal, wherein the first terminal is coupled to the second terminal of the first depletion-mode field effect transistor, the second terminal is coupled to the second terminal of the second depletion-mode field effect transistor, and the third control terminal is configured to receive a control signal from a microcontroller and / or a programmable logic array and adjust the equivalent resistance value of the current limiting resistor network according to the control signal; wherein when the bidirectional current flowing between the first signal terminal and the second signal terminal increases, the current flowing through the current limiting resistor network generates a voltage between the first terminal and the second terminal of the current limiting resistor network, and when the voltage makes the absolute value of the potential difference between the control terminal and the second terminal of any depletion-mode field effect transistor reach its threshold voltage, the depletion-mode field effect transistor changes from the on state to the off state, thereby limiting the current between the first signal terminal and the second signal terminal within a current limiting range set by the equivalent resistance value and the threshold voltage, and the current value of the current limiting range is equal to the ratio of the threshold voltage to the equivalent resistance value.

2. The configurable current limited range bidirectional protection circuit of claim 1, wherein, The current limiting resistor network comprises: a plurality of resistance branches, each resistance branch comprising one or more resistance elements; an analog switch having a plurality of switch terminals and a GPIO interface, wherein the plurality of switch terminals are respectively coupled to the plurality of resistance branches, and the GPIO interface constitutes the third control terminal; the analog switch selectively connects at least one resistance branch according to the control signal received by the GPIO interface, so that the current limiting resistor network has different equivalent resistance values under different control signals.

3. The configurable current limited range bidirectional protection circuit of claim 2, wherein, The resistance elements in the plurality of resistance branches are precision resistors with a resistance accuracy not higher than 0.1% and a temperature coefficient not higher than 25ppm / ℃, so that the tolerance of the current limiting current between the first signal terminal and the second signal terminal at any current limiting range does not exceed ±0.1%, and the relative change rate of the current limiting current with temperature does not exceed 25ppm / ℃.

4. The configurable current limited range bidirectional protection circuit of any one of claims 1-3, wherein, The first signal terminal is coupled to an internal driving node of an analog output channel, and the second signal terminal is coupled to an external output terminal of the analog output channel. The output driving current of the analog output channel in a normal working state does not exceed 10mA, and the equivalent resistance value of the current limiting resistor network is configured so that the current value corresponding to each current limiting range is within the range of 1mA to 10mA.

5. The configurable current limited range bidirectional protection circuit of any one of claims 1-3, wherein, The first depletion-mode field effect transistor and the second depletion-mode field effect transistor are both N-type transistors or both P-type transistors.

6. The configurable current limited range bidirectional protection circuit of any one of claims 1-3, wherein, The threshold voltages of the first depletion-mode field effect transistor and the second depletion-mode field effect transistor are equal.

7. The configurable current limited range bidirectional protection circuit of any one of claims 1-3, wherein, Threshold voltages of the first depletion-mode field effect transistor and the second depletion-mode field effect transistor are not equal.

8. A configurable current-limited range signal output module, comprising: Comprise: a digital-to-analog converter, at least one configurable current-limiting gear bidirectional protection circuit according to any one of claims 1-7, and an analog output terminal connected with an external load; an analog output terminal of the digital-to-analog converter is electrically connected with a first signal terminal of the at least one configurable current-limiting gear bidirectional protection circuit, and the analog output terminal is electrically connected with a second signal terminal of the at least one configurable current-limiting gear bidirectional protection circuit; the digital-to-analog converter communicates with a microcontroller and / or a programmable logic array through a digital communication interface, for setting the output voltage of the digital-to-analog converter to generate a target analog output signal; a current-limiting resistor network of the at least one configurable current-limiting gear bidirectional protection circuit is coupled to the microcontroller and / or the programmable logic array through a third control terminal, to receive a control signal output by the microcontroller and / or the programmable logic array, and configure the current-limiting gear of the current path between the analog output terminal of the digital-to-analog converter and the analog output terminal.

9. The configurable current-limited range signal output module of claim 8, wherein, Further comprise: a driving circuit, wherein the driving circuit comprises an operational amplifier and a feedback resistor; a non-inverting input terminal of the operational amplifier is electrically connected with the analog output terminal of the digital-to-analog converter, an inverting input terminal of the operational amplifier is electrically connected with the second signal terminal through the feedback resistor, and an output terminal of the operational amplifier is electrically connected with the first signal terminal, so that the voltage of the second signal terminal in a non-current-limiting state follows the output voltage of the digital-to-analog converter.

10. A configurable current-limited range signal output module as claimed in claim 8 or 9, wherein, comprise multiple analog output channels, each analog output channel comprising a digital-to-analog converter output channel, a driving circuit corresponding to the digital-to-analog converter output channel, and a configurable current-limiting gear bidirectional protection circuit; the driving circuit is coupled between the digital-to-analog converter output channel and the configurable current-limiting gear bidirectional protection circuit, to drive the configurable current-limiting gear bidirectional protection circuit; the multiple analog output channels are configured to respectively and independently communicate with the microcontroller and / or the programmable logic array through multiple digital communication interfaces and multiple third control terminals, to determine the output voltage of the digital-to-analog converter output channel in each analog output channel and configure the equivalent resistance value of the current-limiting resistor network, so as to independently configure the current-limiting gear of the current path of each analog output terminal.

Images