A multifunction PWM control isolated module integrated circuit

Abstract

This invention relates to the field of integrated circuit technology, and more particularly to a multifunctional PWM-controlled isolated modular integrated circuit, comprising a PWM isolation input module, a multi-stage passive filter network, a 4~20mA current output circuit, and a 0~10V voltage output circuit. The PWM isolation input module is connected to the multi-stage passive filter network through an isolation device U3, electrically isolating the external PWM signal and converting it into a DC reference signal. The 4~20mA current output circuit includes a V / I conversion circuit and a rectifier bridge B1 connected in series at the output terminal, and the feedback loop of the V / I conversion circuit is equipped with an RC compensation circuit. In this invention, the rectifier bridge connected in series in the 4~20mA current output circuit provides basic reverse connection protection, avoiding the risk of circuit burnout due to incorrect wiring polarity during construction, and improving the wiring fault tolerance of the module.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit technology, and in particular to an isolated modular integrated circuit with multifunctional PWM control. Background Technology

[0002] In industrial automation control systems, the main control unit often needs to output analog signals to drive field actuators. To prevent high-voltage surge crosstalk, electrical isolation must be performed between the main control unit and the field side. Traditional solutions often use PWM signals that are isolated and then filtered for conversion. However, industrial sites present challenges such as harsh electromagnetic environments, complex wiring, and diverse load types. These factors place extremely high engineering requirements on the isolation and conditioning accuracy, anti-self-oscillation capability, load-carrying drive strength, and field wiring compatibility of the analog output module.

[0003] Existing analog output circuits are often simple in structure, lack adaptive polarity and deep stabilization mechanisms, and cannot be compatible with internal and external power supply modes. In the field, the module is easily burned out due to reverse connection of positive and negative terminals. At the same time, when faced with long cable distributed capacitance or inductive loads, the output current is prone to self-excited oscillation, which leads to control instability and cannot adapt to harsh industrial environments with low fault tolerance. Summary of the Invention

[0004] To overcome the above deficiencies, this invention provides an isolated modulus integrated circuit with multifunctional PWM control, which aims to improve the self-excited oscillation and control instability caused by the circuit when driving inductive loads or long cables.

[0005] In a first aspect, the present invention provides the following technical solution: a multi-functional PWM-controlled isolated modulus integrated circuit, comprising, PWM isolated input module, multi-stage passive filter network, 4~20mA current output circuit and 0~10V voltage output circuit; The PWM isolation input module is connected to the multi-stage passive filter network through the isolation device U3, which electrically isolates the external PWM signal and converts it into a DC reference signal; The 4~20mA current output circuit includes a V / I conversion circuit and a rectifier bridge B1 connected in series at the output terminal, and the feedback circuit of the V / I conversion circuit is provided with an RC compensation circuit. The 0~10V voltage output circuit includes a driver operational amplifier U5A and a push-pull output stage composed of symmetrical transistor groups. The push-pull output stage is connected to a negative feedback network composed of resistors R30 and R31.

[0006] Preferably, the rectifier bridge B1 is arranged between the current inflow and outflow terminals of the 4~20mA current output circuit to keep the current direction of the V / I conversion circuit constant, while being compatible with both internal and external power supply modes and providing reverse connection protection.

[0007] Preferably, the V / I conversion circuit includes operational amplifiers U4A and U4B and a power transistor Q1, and the RC compensation circuit includes integrating capacitors C15 and C17 connected across the feedback terminals of the operational amplifiers U4A and U4B to suppress self-excited oscillations caused by external inductive loads and cable distributed capacitance.

[0008] Preferably, the 4~20mA current output circuit is also equipped with an energy storage and decoupling circuit, which includes a voltage regulator chip U1 and a filter inductor L1 to compensate for the voltage drop caused by the rectifier bridge B1 and maintain internal power supply stability during long cable transmission.

[0009] Preferably, the multi-stage passive filter network is an RC low-pass filter consisting of at least two stages of resistors R5 and R3 and capacitors C11 and C12, which filters out the high-frequency carrier of the isolated PWM signal and smoothly integrates it into a low-ripple DC reference voltage to provide to the subsequent circuit.

[0010] Preferably, the push-pull output stage adopts a composite transistor structure composed of transistors Q2, Q3, Q4, and Q5, and integrates a hardware current limiting protection sub-circuit. In the event of a short circuit or overload at the output terminal, the base current of the main drive transistor is pulled down by feedback to protect the circuit.

[0011] Preferably, the push-pull output stage further includes bias diodes D1 and D2, which are connected in series between the output terminal of the driving operational amplifier U5A and the base of the transistor to provide a static bias voltage to eliminate crossover distortion of the output signal.

[0012] Preferably, the resistors R30 and R31 in the 0~10V voltage output circuit are high-precision, low-temperature drift metal film resistors with a resistance accuracy better than 0.1% and a temperature coefficient lower than 25ppm.

[0013] Preferably, the output terminal of the 4~20mA current output circuit is further provided with a dual protection circuit, which includes a self-resetting fuse F1 connected in series in the circuit and a transient voltage suppressor TV1 connected in parallel.

[0014] Preferably, the terminal side of the 0~10V voltage output circuit is provided with a surge protection and backflow protection network, which includes a bidirectional transient voltage suppressor U6, a clamping diode D3, and a self-resetting fuse F3.

[0015] The present invention has the following beneficial effects: 1. In this invention, a rectifier bridge is connected in series in the 4~20mA current output circuit, so that the current direction inside the V / I conversion circuit always remains constant. This effectively supports both internal and external power supply modes in industrial sites and provides basic reverse connection protection, avoiding the risk of circuit burnout due to incorrect wiring polarity during construction and improving the wiring fault tolerance of the module.

[0016] 2. In this invention, an RC compensation circuit composed of an integrating capacitor is added to the feedback loop through the V / I conversion circuit, which increases the phase margin of the closed-loop control and directly suppresses the self-excited oscillation caused by the distributed capacitance of external inductive loads or long transmission cables, thereby ensuring the stability of the current output of the equipment in complex field environments.

[0017] 3. In this invention, the 0~10V voltage output circuit adopts a composite push-pull output stage composed of transistors, which improves the load driving capability of the circuit. At the same time, the hardware current limiting protection sub-circuit integrated inside can quickly pull down the base current of the main drive transistor through feedback when a short circuit or overload occurs at the output end, preventing the components from being damaged by thermal breakdown and ensuring the safe operation of the circuit. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the circuit structure of an isolated modulus integrated circuit for multifunctional PWM control proposed in this invention. Figure 2 This is a schematic diagram of a 4~20mA current output circuit of an isolated modulus integrated circuit with multifunctional PWM control proposed in this invention. Figure 3 This is a schematic diagram of the 0~10V voltage output circuit of an isolated modular integrated circuit with multifunctional PWM control proposed in this invention. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] This invention provides an isolated modular integrated circuit for multifunctional PWM control, comprising the following steps: Reference Figure 1 ,include: PWM isolated input module, multi-stage passive filter network, 4~20mA current output circuit and 0~10V voltage output circuit; The PWM isolation input module is connected to a multi-stage passive filter network through the isolation device U3 to electrically isolate the external PWM signal and convert it into a DC reference signal; The 4~20mA current output circuit includes a V / I conversion circuit and a rectifier bridge B1 connected in series at the output terminal, and the feedback loop of the V / I conversion circuit is equipped with an RC compensation circuit. The 0~10V voltage output circuit includes a driver operational amplifier U5A and a push-pull output stage composed of symmetrical transistor groups. The push-pull output stage is connected to a negative feedback network composed of resistors R30 and R31.

[0021] Specifically, the circuit's hardware topology includes a PWM isolation input module and a multi-stage passive filter network connected in series, as well as a 4~20mA current output circuit and a 0~10V voltage output circuit connected in parallel to the output of the multi-stage passive filter network. The signal input terminal of the PWM isolation input module receives the PWM digital signal sent by the external main control chip; the internal circuit of the PWM isolation input module is equipped with an isolation device U3; the isolation device U3 is preferably an optocoupler; the external PWM digital signal drives the light-emitting diode on the primary side of the isolation device U3 to emit light, so that the phototransistor on the secondary side is synchronously turned on and off according to the frequency of the received light signal; the above structure cuts off the direct electrical connection between the external control side and the field output side, blocking the path of high voltage surges in the industrial field to the main control chip along the signal line; the isolation device U3 converts the primary PWM signal into a pulse voltage signal with an adjustable duty cycle on the secondary side; the signal output terminal of the isolation device U3 is connected to the signal input terminal of the multi-stage passive filter network through copper traces; A multi-stage passive filter network receives the aforementioned pulse voltage signal and performs smooth integration processing on it. The multi-stage passive filter network filters out the high-frequency switching carrier component in the pulse voltage signal through series and parallel resistor and capacitor components. After the aforementioned low-pass filtering processing, the pulse voltage signal is converted into a continuous and smooth DC reference signal. The voltage amplitude of this DC reference signal is proportional to the duty cycle of the external PWM signal. The output node of the multi-stage passive filter network simultaneously leads out two branches, which are respectively connected to a 4~20mA current output circuit and a 0~10V voltage output circuit to provide a controlled reference voltage for the subsequent analog output. The 4~20mA current output circuit receives the aforementioned DC reference signal and performs a linear conversion from voltage to current. Physically, this circuit includes a V / I conversion circuit and a rectifier bridge B1. The V / I conversion circuit controls the base current of the power transistor through an operational amplifier, adjusting the on-resistance of the power transistor to convert the DC reference signal into a 4~20mA analog current at a fixed ratio. The rectifier bridge B1 is composed of four rectifier diodes connected in series. The rectifier bridge B1 is connected in series to the external terminals of the V / I conversion circuit. The rectifier bridge B1 ensures that regardless of how the external terminals are connected (positive or negative), the direction of the current flowing into the V / I conversion circuit remains singular and constant. This rectifier bridge B1 structure allows the current output circuit to be compatible with both internal and external power supply modes and solves the technical problem of component burnout due to reverse polarity connections. An RC compensation circuit is arranged in the feedback loop of the V / I conversion circuit. The RC compensation circuit includes compensation resistors and integrating capacitors connected in series and parallel. The RC compensation circuit is connected between the inverting input and output terminals of the operational amplifier inside the V / I conversion circuit. The RC compensation circuit increases the phase margin of the closed-loop control system by changing the pole and zero distribution of the closed-loop feedback network. The increase in the phase margin is used to suppress loop self-excited oscillation caused by the distributed capacitance of long-distance transmission cables in industrial sites and external inductive loads, and maintain the stability of the 4~20mA output current. The 0~10V voltage output circuit receives the aforementioned DC reference signal and performs voltage following and power amplification. This circuit includes a driver operational amplifier U5A and a push-pull output stage. The DC reference signal is connected to the non-inverting input terminal of the driver operational amplifier U5A. The push-pull output stage is constructed from a group of NPN and PNP transistors arranged in a symmetrical structure. The signal output terminal of the driver operational amplifier U5A is connected to the base of the aforementioned transistors. The push-pull output stage provides current sourcing through NPN transistors and current sinking through PNP transistors, thereby increasing the load driving capability of the 0~10V voltage output terminal. A negative feedback network is connected to the output pin of the push-pull output stage; the negative feedback network is composed of resistors R30 and R31 connected in a voltage divider configuration; resistors R30 and R31 are preferably metal film resistors with a temperature coefficient of less than 25ppm; one end of resistor R30 is connected to the output node of the push-pull output stage, and the other end is connected to the inverting input of the driving operational amplifier U5A; one end of resistor R31 is connected to the inverting input of the driving operational amplifier U5A, and the other end is grounded to the common terminal; the above resistor voltage divider structure sets the closed-loop voltage amplification factor of the 0~10V voltage output circuit, so that the accuracy of the final output analog voltage signal is controlled, and the output voltage drift caused by changes in ambient temperature is reduced by using low temperature coefficient materials.

[0022] Reference Figure 2The rectifier bridge B1 is arranged between the current inflow and outflow terminals of the 4~20mA current output circuit to keep the current direction of the V / I conversion circuit constant, while being compatible with both internal and external power supply modes and providing reverse connection protection.

[0023] Specifically, rectifier bridge B1 is positioned between the current inflow and outflow terminals of the 4~20mA current output circuit; the hardware topology of rectifier bridge B1 consists of four rectifier diodes connected in a bridge circuit configuration; rectifier bridge B1 has two AC input nodes, a positive DC output node, and a negative DC output node; the two AC input nodes of rectifier bridge B1 are connected to the aforementioned current inflow and outflow terminals via traces on the printed circuit board; the positive DC output node of rectifier bridge B1 is connected to the high-potential input terminal of the V / I conversion circuit; the negative DC output node of rectifier bridge B1 is connected to the low-potential return terminal of the V / I conversion circuit. When the polarity of the line connected to the external terminal changes, the four rectifier diodes inside the rectifier bridge B1 automatically switch between on and off states based on the potential difference across the terminals. In the forward polarity connection state, the first set of diagonal diodes in the rectifier bridge B1 is forward biased and conducting, while the second set of diagonal diodes is reverse biased and cut off. In the reverse polarity connection state, the second set of diagonal diodes in the rectifier bridge B1 is forward biased and conducting, while the first set of diagonal diodes is reverse biased and cut off. This physical switching mechanism of diode conduction states ensures that the current flowing out of the rectifier bridge B1 always flows from the positive DC output node to the V / I conversion circuit and back from the negative DC output node. This structure keeps the polarity of the receiving electrode and the direction of the current in the components inside the V / I conversion circuit absolutely constant. The aforementioned structural features of rectifier bridge B1 are used to solve the hardware matching problem of different system power supply architectures in 4~20mA signal transmission. In internal power supply mode, the internal power supply loop of the device containing this integrated circuit provides the drive voltage to the external load. In external power supply mode, the independent power supply of the external control system provides the drive voltage to this integrated circuit. Regardless of whether the drive voltage source is located at the internal node or the external node of the current loop, rectifier bridge B1 uses its cross conduction path to convert the bidirectional possible current flowing through the terminals into a unidirectional internal current. The above hardware design enables the 4~20mA current output loop to be synchronously compatible with both internal power supply mode and external power supply mode without relying on relay switching or manual changes to physical wiring. In industrial field construction wiring, there is a technical problem where reverse connection of positive and negative wires can cause reverse breakdown damage to internal core components. The rectifier bridge B1 constructs a bottom-level reverse connection protection barrier through the aforementioned constant current flow mechanism. When a polarity reversal error occurs at the external terminal, the rectifier bridge B1 automatically cuts off the DC path of the reverse voltage entering the downstream components of the V / I conversion circuit and reroutes the current to the correct positive power supply path. This technical means prevents polarity-sensitive components such as operational amplifiers, power transistors, and capacitors inside the V / I conversion circuit from thermal breakdown damage due to reverse voltage, thereby maintaining the electrical safety operation of the 4~20mA current output module in complex field environments.

[0024] Reference Figure 2 The V / I conversion circuit includes operational amplifiers U4A and U4B and power transistor Q1. The RC compensation circuit includes integrating capacitors C15 and C17 connected across the feedback terminals of operational amplifiers U4A and U4B to suppress self-excited oscillations caused by external inductive loads and cable distributed capacitance.

[0025] Specifically, the V / I conversion circuit in the 4~20mA current output loop physically includes a first-stage operational amplifier U4A, a second-stage operational amplifier U4B, and a power transistor Q1. The non-inverting input of operational amplifier U4A receives the DC reference voltage signal output from the preceding module. The output of operational amplifier U4A is electrically connected to the input of operational amplifier U4B via a printed circuit board trace. The output of operational amplifier U4B is electrically connected to the control electrode of power transistor Q1. The main current path of power transistor Q1 is connected in series in the 4~20mA current output loop. Operational amplifiers U4A and U4B form a cascaded amplification architecture to output a drive signal. Power transistor Q1 adjusts its own on-resistance according to the aforementioned drive signal. The above hardware components work together to linearly convert the input DC voltage signal into a 4~20mA current signal according to a predetermined ratio. An RC compensation circuit is incorporated into the closed-loop control network of the V / I conversion circuit. This RC compensation circuit includes a first integrating capacitor C15 and a second integrating capacitor C17. One end of the first integrating capacitor C15 is connected to the inverting input of operational amplifier U4A, and the other end is connected to the output of operational amplifier U4A. One end of the second integrating capacitor C17 is connected to the inverting input of operational amplifier U4B, and the other end is connected to the output of operational amplifier U4B. The first integrating capacitor C15 and the second integrating capacitor C17 form two independent local AC negative feedback branches within the V / I conversion circuit. In industrial field signal transmission circuits, the distributed capacitance introduced by external long-distance transmission cables and the inductive load introduced by external access terminals alter the pole distribution of the V / I conversion circuit closed-loop system. This change in pole distribution leads to a decrease in the phase margin of the closed-loop system, causing a technical problem of high-frequency self-oscillation of the output current. The integrating capacitors C15 and C17 in the RC compensation circuit utilize the physical characteristic that their capacitive reactance is inversely proportional to the signal frequency to increase the negative feedback depth when the system is operating at high frequencies. This increase in negative feedback depth reduces the high-frequency closed-loop gain of operational amplifiers U4A and U4B, providing feedforward compensation for the main pole frequency position of the closed-loop system. This technique increases the overall phase margin of the V / I conversion circuit, eliminates the loop self-oscillation phenomenon caused by external capacitive and inductive distributed parameters, and ensures that the 4~20mA current output circuit maintains a stable output current waveform when connected to an external load with parasitic capacitance and inductance characteristics.

[0026] Reference Figure 2 The circuit's 4~20mA current output circuit is also equipped with an energy storage and decoupling circuit, which includes a voltage regulator chip U1 and a filter inductor L1 to compensate for the voltage drop caused by the rectifier bridge B1 and maintain internal power supply stability during long cable transmission.

[0027] Specifically, the physical topology of the 4~20mA current output circuit includes an energy storage and decoupling circuit. This energy storage and decoupling circuit comprises a voltage regulator chip U1 and a filter inductor L1. The voltage input pin of the voltage regulator chip U1 is electrically connected to the DC output node of the aforementioned rectifier bridge B1 via copper traces. The voltage output pin of the voltage regulator chip U1 is connected to the first terminal of the filter inductor L1. The second terminal of the filter inductor L1 is electrically connected to the power supply input terminal of the active device inside the V / I conversion circuit. The reference ground pin of the voltage regulator chip U1 is connected to the common reference ground network of this current output circuit. The rectifier diodes inside the aforementioned rectifier bridge B1 generate a forward voltage drop when in the conducting state; this forward voltage drop causes a fixed percentage decrease in the amplitude of the DC voltage transmitted to the subsequent circuit; the voltage regulator chip U1 is preferably a low-dropout linear regulator; the voltage regulator chip U1 receives the DC voltage signal after being stepped down by the rectifier bridge B1; the voltage regulator chip U1 performs voltage conversion and voltage regulation on the DC voltage signal through an internal closed-loop feedback loop, and outputs an internal operating voltage with a constant amplitude; the above hardware design compensates for the voltage drop caused by the physical characteristics of the rectifier bridge B1, so that the V / I conversion circuit can obtain a supply voltage that meets its rated operating parameters when the external bus feed voltage is at the lower limit of the operating value; A 4~20mA current signal is connected to an external receiving terminal through a long-distance transmission cable; the long-distance transmission cable has distributed resistance and distributed inductance characteristics; the above-mentioned distributed parameters generate fluctuations in the power supply voltage when transmitting transient current, which leads to a technical problem of degrading the power supply quality inside the integrated circuit; the filter inductor L1 utilizes the physical characteristic that its inductive reactance increases with the signal frequency to generate a high-frequency impedance in the power supply path; this high-frequency impedance is used to attenuate the high-frequency ripple and transient spike voltage coupled by the long-distance cable; The energy storage and decoupling circuit also includes a decoupling capacitor connected in parallel. This decoupling capacitor and the filter inductor L1 form an LC low-pass filter network in the circuit topology. When the power supply voltage drops transiently due to environmental interference from the external long-distance cable, the decoupling capacitor releases the charge stored on its plates to provide local transient current replenishment for the subsequent V / I conversion circuit. The filter inductor L1 and the decoupling capacitor work together to maintain a constant power supply voltage value in the time dimension, eliminating the influence of external cable parasitic parameters on the power supply stability of the internal circuit.

[0028] Reference Figure 1 The multi-stage passive filter network consists of at least two-stage RC low-pass filters composed of resistors R5 and R3 and capacitors C11 and C12. These filters remove the high-frequency carrier of the isolated PWM signal and smoothly integrates it into a low-ripple DC reference voltage, which is then provided to the subsequent circuit.

[0029] Specifically, the multi-stage passive filter network includes a first-order filter sub-circuit and a second-order filter sub-circuit in its circuit physical topology; the first-order filter sub-circuit and the second-order filter sub-circuit are cascaded and electrically connected; the first-order filter sub-circuit includes a first resistor R5 and a first capacitor C11; the second-order filter sub-circuit includes a second resistor R3 and a second capacitor C12; the signal output pin of the aforementioned isolation device is electrically connected to the first terminal of the first resistor R5 through printed circuit board traces; the second terminal of the first resistor R5 is connected to the first terminal of the first capacitor C11 and the first terminal of the second resistor R3 respectively; the second terminal of the first capacitor C11 is electrically connected to the common ground network of the circuit; the second terminal of the second resistor R3 is connected to the first terminal of the second capacitor C12 and the signal input terminal of the subsequent loop respectively; the second terminal of the second capacitor C12 is electrically connected to the common ground network of the circuit; all the above-mentioned components are passive electronic components. The aforementioned isolated input PWM signal is composed of a low-frequency effective control signal and a high-frequency switching carrier component superimposed; the multi-stage passive filter network utilizes the current-limiting physical characteristics of resistors and the physical characteristic that the voltage across a capacitor cannot change abruptly to perform signal integration processing; during the high-level period of the PWM signal, current flows through the first resistor R5 and the second resistor R3 to charge the plates of the first capacitor C11 and the second capacitor C12; during the low-level period of the PWM signal, the first capacitor C11 and the second capacitor C12 release the charge stored on their plates to the subsequent circuit; the above-mentioned charging and discharging physical process converts the discrete pulse duty cycle parameter into a continuous voltage amplitude signal; In scenarios where a single-stage RC filter circuit processes low-frequency PWM signals, there is a technical problem where the output DC voltage ripple coefficient exceeds the common-mode rejection range of the subsequent operational amplifier. A multi-stage passive filter network increases the total stopband attenuation of high-frequency signals by connecting the first-stage and second-stage filter sub-circuits in series. The first capacitor C11 and the second capacitor C12 exhibit low AC impedance characteristics for the high-frequency switching carrier component in the PWM signal, guiding this high-frequency carrier component to the common ground network. The first-stage filter sub-circuit performs initial high-frequency attenuation and voltage smoothing on the input signal. The second-stage filter sub-circuit receives the initially smoothed voltage signal and performs secondary high-frequency attenuation and integration. The aforementioned multi-stage cascaded physical structure reduces the overall high-frequency cutoff frequency of the multi-stage passive filter network; this technique filters out the switching frequency harmonics in the PWM signal and converts the original pulse signal into a DC reference voltage; the peak-to-peak ripple of this DC reference voltage is controlled by the total resistance-capacitance time constant of the aforementioned two-order RC network; the aforementioned smoothed low-ripple DC reference voltage is led out through physical nodes and divided into two physical branches for synchronous transmission to the subsequent 4~20mA current output circuit and 0~10V voltage output circuit, providing a DC reference level signal for the subsequent analog output.

[0030] Reference Figure 3 The push-pull output stage adopts a composite transistor structure consisting of transistors Q2, Q3, Q4, and Q5, and integrates a hardware current limiting protection sub-circuit. In the event of a short circuit or overload at the output terminal, the base current of the main drive transistor is pulled down by feedback to protect the circuit.

[0031] Specifically, the push-pull output stage in the 0~10V voltage output circuit adopts a composite transistor structure in circuit topology, consisting of a first transistor Q2, a second transistor Q3, a third transistor Q4, and a fourth transistor Q5 electrically connected. The first transistor Q2 and the second transistor Q3 are preferably complementary and symmetrical power output transistors. The emitters of the first transistor Q2 and the second transistor Q3 are electrically connected to the signal output node of the push-pull output stage. The collector of the third transistor Q4 is electrically connected to the base of the first transistor Q2. The collector of the fourth transistor Q5 is electrically connected to the base of the second transistor Q3. The push-pull output stage integrates a hardware current limiting protection sub-circuit. This hardware current limiting protection sub-circuit monitors the output current value in real time through a feedback path constructed by physical connection. When an external load short circuit or overload fault occurs at the output terminal of the 0~10V voltage output circuit, the current flowing through the emitter of the first transistor Q2 or the second transistor Q3 increases instantaneously. The increased current generates a voltage drop across the preset current sensing resistor. When the voltage drop reaches the base conduction voltage threshold of the third transistor Q4 or the fourth transistor Q5, the third transistor Q4 or the fourth transistor Q5 enters the conduction state. During the physical process of turning on the third transistor Q4 or the fourth transistor Q5, the impedance between its collector and emitter decreases, thereby shunting the base current of the main driving transistor, i.e., the first transistor Q2 or the second transistor Q3, to the ground level or the power supply terminal; after the base current is pulled low by feedback, the first transistor Q2 or the second transistor Q3 switches from the saturated conduction state or the deep amplification state to the restricted conduction state, and the equivalent impedance between its collector and emitter increases linearly. The hardware current limiting protection sub-circuit forcibly limits the current amplitude at the output terminal to a preset safety threshold range through the aforementioned physical feedback mechanism. This technique avoids thermal breakdown damage to transistors Q2 to Q5 caused by transient large currents generated by short circuits at the output terminal, thereby maintaining the hardware safety of the 0~10V voltage output circuit under electrical fault conditions. The composite transistor structure achieves real-time current limiting protection without software intervention through the coordinated work of the aforementioned components, and ensures that the push-pull output stage can automatically return to the normal linear voltage output operating mode after the fault is removed.

[0032] Reference Figure 3 The push-pull output stage also includes bias diodes D1 and D2, which are connected in series between the output terminal of the driver operational amplifier U5A and the base of the transistor to provide static bias voltage to eliminate crossover distortion of the output signal.

[0033] Specifically, the push-pull output stage of the 0~10V voltage output circuit also includes a first bias diode D1 and a second bias diode D2 in the hardware circuit; the first bias diode D1 and the second bias diode D2 are electrically connected in series in the physical topology; the series branch formed by the first bias diode D1 and the second bias diode D2 is connected between the signal output node of the driving operational amplifier U5A and the base of the transistor inside the push-pull output stage; the node of the branch containing the first bias diode D1 is connected to the base of the NPN transistor in the push-pull output stage; the node of the branch containing the second bias diode D2 is connected to the base of the PNP transistor in the push-pull output stage. In a conventional push-pull circuit topology driven solely by an alternating signal, the physically configured complementary symmetric transistors have an inherent base-emitter conduction voltage dead zone. When the amplitude of the control signal voltage output by the driving operational amplifier U5A does not reach the aforementioned conduction voltage dead zone threshold, both the upper and lower sets of transistors inside the push-pull output stage are physically cut off. This device cutoff phenomenon causes the output voltage to be unable to linearly follow the changes in the input signal, resulting in a crossover distortion problem in the output voltage waveform at the zero-point junction. After the first bias diode D1 and the second bias diode D2 are connected to the circuit, they utilize the physical characteristic of generating a fixed voltage drop by forward conduction of their internal semiconductor PN junctions to provide a static DC bias voltage for compensation of the transistors inside the push-pull output stage. The total forward voltage drop generated by the series connection of the first bias diode D1 and the second bias diode D2 matches the conduction dead zone voltage of the corresponding transistor inside the push-pull output stage. This static DC bias voltage allows the complementary transistor in the push-pull output stage to cross the dead zone voltage range in advance when there are no external signal fluctuations, and maintains a preset static basic conduction current inside. When a small voltage signal change occurs at the output terminal of the driving operational amplifier U5A, the transistor in the basic conduction state adjusts its emitter output current in real time according to the voltage change parameter. This hardware circuit configuration eliminates the response delay and waveform distortion caused by the repeated switching between the conduction and cutoff states of the transistor, eliminates the crossover distortion of the analog output signal, and thus maintains the voltage linearity of the 0~10V voltage output circuit in the entire output range.

[0034] Reference Figure 3 The resistors R30 and R31 in the 0~10V voltage output circuit are high-precision, low-temperature drift metal film resistors with a resistance accuracy better than 0.1% and a temperature coefficient less than 25ppm.

[0035] Specifically, the negative feedback network of the 0~10V voltage output circuit includes a first resistor R30 and a second resistor R31; the first resistor R30 and the second resistor R31 are physically constructed using a metal film material manufacturing process; the initial physical resistance error of the first resistor R30 and the second resistor R31 is set to be less than 0.1%; the temperature coefficient parameter of the first resistor R30 and the second resistor R31 is physically limited to be less than 25ppm per degree. The closed-loop voltage amplification factor of the 0~10V output circuit is determined by the ratio of the physical resistance of the first resistor R30 to the physical resistance of the second resistor R31. In the application of conventional resistor components, there is a technical problem that the final output analog voltage deviates from the target value due to initial manufacturing errors. The initial resistance error of the first resistor R30 and the second resistor R31 of less than 0.1% physically controls the initial voltage division accuracy of the negative feedback network. The above hardware parameter limitations cause the amplitude of the output voltage signal after amplification by the subsequent circuit to be mapped and output according to a preset fixed proportional coefficient. Industrial operating environments are subject to objective physical conditions of fluctuating operating temperatures. These fluctuations alter the lattice vibration state of conventional electronic components, leading to random drift in the physical resistance values ​​of resistors. The first resistor R30 and the second resistor R31 utilize the low-temperature sensitivity of metal film materials to limit the rate of resistance change caused by temperature variations to below 25 ppm per degree Celsius. When the external operating temperature changes, the amount of thermodynamic change in the physical resistance values ​​of the first resistor R30 and the second resistor R31 is controlled by the aforementioned parameters. The first resistor R30 and the second resistor R31 exhibit resistance changes in the same direction and proportion when exposed to changes in ambient temperature. This physical mechanism maintains a constant voltage division ratio at the series voltage divider node in the negative feedback network. These technical measures counteract the gain drift of the closed-loop circuit caused by changes in the external thermodynamic environment, solve the problem of voltage output value deviation caused by ambient temperature interference in the 0~10V voltage output circuit, and maintain the consistency of voltage output parameters of this modular integrated circuit within its nominal operating temperature range.

[0036] Reference Figure 2 The output terminal of the 4~20mA current output circuit is also equipped with a dual protection circuit, which includes a self-resetting fuse F1 connected in series in the circuit and a transient voltage suppressor TV1 connected in parallel.

[0037] Specifically, a dual protection circuit is arranged at the physical output terminal of the 4~20mA current output circuit; this dual protection circuit is composed of a resettable fuse F1 and a transient voltage suppressor TV1 electrically connected in hardware topology; the resettable fuse F1 is connected in series in the main signal transmission circuit of the 4~20mA current output circuit; the transient voltage suppressor TV1 is connected in parallel between the positive output terminal and the negative output terminal of the 4~20mA current output circuit; the above components together construct a physical protection architecture against external electrical faults. In industrial field equipment operation, there is a technical problem where an external load short circuit causes the loop current to exceed the rated upper limit. The self-resetting fuse F1 is preferably a positive temperature coefficient thermistor component. Under normal operating current conditions, the polymer structure inside the self-resetting fuse F1 maintains a low impedance state, allowing the 4~20mA analog current signal to pass through without attenuation. When an external loop short circuit causes a surge in the current flowing through the self-resetting fuse F1, the increased Joule heating changes its internal crystal structure, resulting in a step increase in the physical impedance of the self-resetting fuse F1. This high impedance state limits the continuous current in the loop to the microampere level, cutting off the physical path of overload current flowing into the internal V / I conversion circuit. When the external short circuit fault is removed and the component temperature decreases, the internal structure of the self-resetting fuse F1 is physically reset and returns to the initial low impedance state, maintaining the continuous availability of the circuit. The external long-distance transmission cable is subject to interference from spatial electromagnetic fields, which can cause transient high-voltage surges. The transient voltage suppressor TV1 has reverse breakdown physical characteristics. Within the normal operating voltage range, the transient voltage suppressor TV1 presents a high-impedance cutoff state, maintaining normal signal transmission of the 4~20mA current loop. When a transient surge voltage higher than the breakdown threshold of the transient voltage suppressor TV1 appears at the external output terminal, its internal semiconductor PN junction undergoes avalanche breakdown within a picosecond time period. The above-mentioned avalanche breakdown physical process causes its equivalent impedance to decrease sharply, bypassing the high-voltage surge current to the common grounding network and clamping the voltage amplitude at both ends of the output terminal within the safe withstand voltage range of the subsequent active electronic components. The aforementioned dual protection circuit utilizes the overcurrent thermal blocking mechanism of the self-resetting fuse F1 in conjunction with the overvoltage clamping mechanism of the transient voltage suppressor TV1. The transient voltage suppressor TV1 prevents the transient high voltage from causing electrical stress breakdown damage to the internal integrated circuit. The self-resetting fuse F1 avoids the thermal stress generated by continuous overcurrent from burning out the aforementioned rectifier bridge and operational amplifier. This physical combination technology solves the problem of dual electrical protection under complex field conditions, maintaining the integrity and functional stability of the physical hardware of the 4~20mA current output circuit.

[0038] Reference Figure 3The 0~10V voltage output circuit is equipped with a surge and backflow protection network on the terminal side. This protection network includes a bidirectional transient voltage suppressor U6, a clamping diode D3, and a resettable fuse F3.

[0039] Specifically, the physical terminal side of the 0~10V voltage output circuit is equipped with a surge protection and backflow prevention network; this surge protection and backflow prevention network includes a resettable fuse F3, a bidirectional transient voltage suppressor U6, and a clamping diode D3 in the circuit physical topology; the resettable fuse F3 is connected in series between the physical output node of the push-pull output stage and the external terminal; the bidirectional transient voltage suppressor U6 is connected in parallel between the external terminal and the common ground network; the anode of the clamping diode D3 is electrically connected to the signal transmission node between the resettable fuse F3 and the push-pull output stage, and the cathode of the clamping diode D3 is electrically connected to the internal positive power supply network of the integrated circuit; In external industrial field wiring environments, there is a technical problem of transient high-voltage surges introduced by electromagnetic coupling. The bidirectional transient voltage suppressor U6 has bidirectional avalanche breakdown physical characteristics. When positive and reverse high-voltage surge signals appear at the external terminals, the semiconductor PN junction inside the bidirectional transient voltage suppressor U6 conducts within a picosecond time period. This physical process makes the bidirectional transient voltage suppressor U6 present a low impedance state, bypassing the surge current to the common ground network and clamping the transient voltage amplitude at the terminals within the safe withstand voltage range of the transistors inside the push-pull output stage. This hardware design blocks the physical path of high-voltage surges to the core components inside the 0~10V voltage output circuit. In scenarios involving incorrect wiring of field equipment and external power supply failures, there is a technical problem of high-potential signals exceeding the rated voltage of 10V being reverse-coupled into the output terminals. This reverse-coupled voltage forces current to flow back into the internal transistors of the push-pull output stage, causing the transistors to undergo physical breakdown due to reverse voltage stress. The clamping diode D3 utilizes its unidirectional conductivity to construct an anti-reverse-current discharge path. When the amplitude of the external reverse-intrusion voltage is higher than the sum of the voltage of the internal positive power supply network and the forward conduction voltage drop of the clamping diode D3, the clamping diode D3 enters a forward-biased conduction state. This conduction state forces the charge flowing back into the signal node to be diverted to the internal positive power supply network. This technical means limits the voltage peak of the output node of the push-pull output stage, preventing the internal transistors from burning out due to reverse current. The resettable fuse F3 is preferably a polymer positive temperature coefficient thermistor assembly. During the physical operation of the clamping diode D3 conducting to discharge reverse current and the bidirectional transient voltage suppressor U6 discharging surge current, the circuit current flowing through the resettable fuse F3 continuously surges. This surge current generates Joule heating inside the resettable fuse F3, causing a change in its polymer crystal structure, resulting in a step increase in its physical impedance. The high impedance state of the resettable fuse F3 limits the short-circuit current to the microampere level, cutting off the continuous energy transfer path between the external fault source and the internal clamping protection device. The bidirectional transient voltage suppressor U6, the clamping diode D3, and the resettable fuse F3 work together at the physical level to solve the hardware failure problem of the 0~10V voltage output terminal when facing transient overvoltage, continuous overcurrent, and voltage reverse faults, maintaining the integrity of the physical structure of the voltage output circuit and the stability of its electrical parameters.

[0040] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A multi-functional PWM control isolated modular integrated circuit, characterized in that, include: PWM isolated input module, multi-stage passive filter network, 4~20mA current output circuit and 0~10V voltage output circuit; The PWM isolation input module is connected to the multi-stage passive filter network through the isolation device U3, which electrically isolates the external PWM signal and converts it into a DC reference signal; The 4~20mA current output circuit includes a V / I conversion circuit and a rectifier bridge B1 connected in series at the output terminal, and the feedback circuit of the V / I conversion circuit is provided with an RC compensation circuit. The 0~10V voltage output circuit includes a driver operational amplifier U5A and a push-pull output stage composed of symmetrical transistor groups. The push-pull output stage is connected to a negative feedback network composed of resistors R30 and R31.

2. The isolated modular integrated circuit for multifunctional PWM control according to claim 1, characterized in that, The rectifier bridge B1 is arranged between the current inflow and outflow terminals of the 4~20mA current output circuit to keep the current direction of the V / I conversion circuit constant, while being compatible with both internal and external power supply modes and providing reverse connection protection.

3. The isolated modular integrated circuit for multifunctional PWM control according to claim 1, characterized in that, The V / I conversion circuit includes operational amplifiers U4A and U4B and a power transistor Q1. The RC compensation circuit includes integrating capacitors C15 and C17 connected across the feedback terminals of the operational amplifiers U4A and U4B to suppress self-excited oscillations caused by external inductive loads and cable distributed capacitance.

4. The isolated modular integrated circuit for multifunctional PWM control according to claim 1, characterized in that, The 4~20mA current output circuit is also equipped with an energy storage and decoupling circuit. The energy storage and decoupling circuit includes a voltage regulator chip U1 and a filter inductor L1 to compensate for the voltage drop caused by the rectifier bridge B1 and maintain internal power supply stability during long cable transmission.

5. The isolated modular integrated circuit for multifunctional PWM control according to claim 1, characterized in that, The multi-stage passive filter network is an RC low-pass filter consisting of at least two stages, composed of resistors R5 and R3 and capacitors C11 and C12. It filters out the high-frequency carrier of the isolated PWM signal and smoothly integrates it into a low-ripple DC reference voltage to provide to the subsequent circuit.

6. The isolated modular integrated circuit for multifunctional PWM control according to claim 1, characterized in that, The push-pull output stage adopts a composite transistor structure composed of transistors Q2, Q3, Q4, and Q5, and integrates a hardware current limiting protection sub-circuit. In the event of a short circuit or overload at the output terminal, the base current of the main drive transistor is pulled down by feedback to protect the circuit.

7. The isolated modular integrated circuit for multifunctional PWM control according to claim 6, characterized in that, The push-pull output stage also includes bias diodes D1 and D2, which are connected in series between the output terminal of the driving operational amplifier U5A and the base of the transistor to provide a static bias voltage to eliminate crossover distortion of the output signal.

8. The isolated modular integrated circuit for multifunctional PWM control according to claim 1, characterized in that, The resistors R30 and R31 in the 0~10V voltage output circuit are high-precision, low-temperature drift metal film resistors with a resistance accuracy better than 0.1% and a temperature coefficient lower than 25ppm.

9. The isolated modular integrated circuit for multifunctional PWM control according to claim 1, characterized in that, The output terminal of the 4~20mA current output circuit is also equipped with a dual protection circuit, which includes a self-resetting fuse F1 connected in series in the circuit and a transient voltage suppressor TV1 connected in parallel.

10. The isolated modular integrated circuit for multifunctional PWM control according to claim 1, characterized in that, The 0~10V voltage output circuit is equipped with a surge and backflow protection network on the terminal side. This protection network includes a bidirectional transient voltage suppressor U6, a clamping diode D3, and a self-resetting fuse F3.

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