Current-mode analog output device with dynamic power regulation

Abstract

The application provides a current-mode analog output device with dynamic power consumption adjustment. The device comprises a processor for generating a digital control quantity; a digital-to-analog conversion circuit for converting the digital control quantity into a first analog voltage; a power consumption dynamic adjustment circuit comprising a current detection circuit for amplifying a sampling voltage and outputting a detection voltage; a reference voltage circuit for outputting a reference voltage representing an output current threshold; a comparison circuit for comparing the detection voltage with the reference voltage and outputting a comparison result signal; a switch selection circuit for selecting between a first feedback branch and a second feedback branch; a power tube voltage detection circuit for converting a voltage across a power tube into a first feedback voltage; and a voltage division feedback circuit for providing a second feedback voltage to a step-down power supply module. The application can reduce output stage power consumption and temperature rise, improve small current and no-load working condition stability, reduce processor load and improve system reliability.

Description

Technical Field

[0001] This application relates to the field of novel circuit design technology, and in particular to a current-type analog output device with dynamic power consumption regulation. Background Technology

[0002] Current-type analog output devices (such as 0-20mA and 4-20mA current loops) are widely used in industrial control and measurement systems for process quantity regulation, status monitoring, and remote signal transmission due to their advantages such as strong anti-interference capability, long transmission distance, and low signal attenuation. These devices typically consist of a processor, digital-to-analog converter, voltage-to-current converter, and constant current output circuitry, achieving analog output by providing a constant current to the field load.

[0003] In existing technologies, some solutions address the issue of high internal power consumption in current-type analog output devices by proposing low-power analog current output systems that manage the step-down power supply through a microcontroller's built-in power control algorithm. This involves the processor periodically detecting the output status and adjusting the power supply output voltage or operating mode to reduce internal losses to some extent. However, such solutions rely on embedded software algorithms and processor resources, resulting in tight coupling between circuit structure and software logic, complex implementation and maintenance, and high requirements for processor computing power and program reliability.

[0004] On the other hand, due to the significant variations in voltage drop across the power transistor and related devices in the current output circuit under different load impedance and output current combinations, existing devices may still experience excessively high internal voltage drops and concentrated power consumption on the output stage devices when the load impedance is low or under conditions of low current or no load. This leads to large device temperature rise, shortened lifespan, and instability and whistling issues in switching power supplies under light load conditions, thus affecting the overall reliability of the system. Therefore, it is necessary to provide a current-type analog output device that achieves dynamic power consumption adjustment through hardware circuitry without relying on software algorithms. Summary of the Invention

[0005] In view of this, the present application provides a current-type analog output device with dynamic power consumption adjustment to solve the problems of large internal power consumption in the current output circuit and difficulty in adjusting with load changes, uncontrollable voltage drop and temperature rise of power transistors, reliance on processor software for power consumption management, and unstable power supply and current output under low current and no-load conditions in the prior art.

[0006] This application provides a dynamic power consumption regulating current-type analog output device, including: a processor for generating a digital control quantity for setting the output current according to external instructions; a digital-to-analog conversion circuit for converting the digital control quantity into a first analog voltage; a voltage-to-current conversion circuit for generating a control current signal according to the first analog voltage; a current output circuit including a step-down power supply module, a power transistor, a sampling resistor, and a load port, wherein the output terminal of the step-down power supply module is connected to the load port in sequence via the power transistor and the sampling resistor, and the control current signal is applied to the control terminal of the power transistor to form a current-type analog quantity set by the processor at the load port; the sampling resistor is used to generate a sampling voltage proportional to the output current; and a power consumption dynamic regulation circuit for switching and dynamically regulating the output voltage of the step-down power supply module according to the output current and the voltage across the power transistor, including: a current detection circuit for amplifying the sampling voltage and outputting a detection voltage; and a reference voltage circuit. The system comprises the following components: a reference voltage outputting a threshold current; a comparator circuit comparing the detected voltage with the reference voltage and outputting a comparison result signal; a switch selection circuit with its control terminal connected to the output of the comparator circuit and its signal terminal connected to the feedback terminal of the buck power supply module, used to select between the first and second feedback branches; a power transistor voltage detection circuit with its input terminal bridging the two ends of the power transistor and its output terminal connected to the signal terminal of the switch selection circuit via the first feedback branch, used to convert the voltage across the power transistor into the first feedback voltage; and a voltage divider feedback circuit connected between the feedback terminal of the buck power supply module and the reference potential, and connected to the signal terminal of the switch selection circuit via the second feedback branch, used to provide the buck power supply module with a second feedback voltage; wherein, under the control of the switch selection circuit, the buck power supply module switches between the first and second feedback branches to provide an adjustable supply voltage to the current output circuit, driving the load port to output current based on the current-type analog quantity.

[0007] The technical solutions adopted in the embodiments of this application can achieve the following beneficial effects: The system includes: a processor for generating a digital control quantity to set the output current based on external instructions; a digital-to-analog conversion circuit for converting the digital control quantity into a first analog voltage; a voltage-to-current conversion circuit for generating a control current signal based on the first analog voltage; a current output circuit, including a buck power supply module, a power transistor, a sampling resistor, and a load port, wherein the output terminal of the buck power supply module is connected to the load port in sequence via the power transistor and the sampling resistor, and the control current signal is applied to the control terminal of the power transistor to form a current-type analog quantity set by the processor at the load port; the sampling resistor is used to generate a sampling voltage proportional to the output current; and a power consumption dynamic adjustment circuit for switching and dynamically adjusting the output voltage of the buck power supply module based on the output current and the voltage across the power transistor, including: a current detection circuit for amplifying the sampling voltage and outputting a detection voltage; and a reference voltage circuit for outputting a voltage representing the output current threshold. The system includes: a reference voltage; a comparator circuit for comparing the detected voltage with the reference voltage and outputting a comparison result signal; a switch selection circuit, with its control terminal connected to the output of the comparator circuit and its signal terminal connected to the feedback terminal of the buck power supply module, used to select between a first feedback branch and a second feedback branch; a power transistor voltage detection circuit, with its input terminal connected across the power transistor and its output terminal connected to the signal terminal of the switch selection circuit via the first feedback branch, used to convert the voltage across the power transistor into a first feedback voltage; and a voltage divider feedback circuit connected between the feedback terminal of the buck power supply module and the reference potential, and connected to the signal terminal of the switch selection circuit via the second feedback branch, used to provide a second feedback voltage to the buck power supply module. The buck power supply module, under the control of the switch selection circuit, switches between the first and second feedback branches to provide an adjustable supply voltage to the current output circuit, driving the load port to output current based on the current-type analog signal. This application can reduce output stage power consumption and temperature rise, improve stability under low current and no-load conditions, reduce processor load, and improve system reliability. Attached Figure Description

[0008] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0009] Figure 1 This is a schematic diagram of the internal circuit structure of the current-type analog output device with dynamic power consumption adjustment provided in the embodiments of this application; Figure 2 This is a schematic diagram of the overall structure of the current-type analog output device with dynamic power consumption adjustment provided in the embodiments of this application. Detailed Implementation

[0010] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0011] Current-type analog output devices (typical output: 0-20mA) are widely used in industrial control and measurement due to their strong anti-interference, long transmission distance, and low signal attenuation. However, different current-type analog output devices have different output impedances due to variations in their circuit design principles. During the drive control process of a current-type analog output device, if the product of the load impedance and the output current is small, it will result in a large voltage drop inside the device. This leads to a significant amount of power being consumed internally, wasting a large amount of electrical energy and causing a substantial increase in the internal temperature of the device. This greatly shortens the lifespan of electronic components, makes the system prone to various malfunctions, and reduces system reliability.

[0012] This application enables dynamic adjustment of device power consumption through hardware circuit verification and control, without consuming CPU resources. It also reduces power loss in current-type analog output devices, resulting in stable and interference-resistant current-type analog output. For example, existing technology discloses a low-cost, low-power analog current output system. This solution implements the low-power analog current output system through a power control algorithm within the MCU, requiring algorithm support from embedded software.

[0013] In contrast, this application utilizes pure hardware control technology, eliminating the need for embedded software algorithm support, to achieve a low-power analog current output system. Moreover, it features low internal power consumption, small circuit size, and lower overall module cost. Power regulation does not consume CPU resources, thus freeing up CPU resources. The channel ports are equipped with protective circuitry, providing strong anti-interference capabilities.

[0014] In view of the problems existing in the prior art, this application provides a current-type analog output device with dynamic power consumption adjustment. This application relates to current-type analog output control technology. Current-type analog output devices (typical output: 0-20mA) are widely used in industrial control and measurement fields due to their strong anti-interference, long transmission distance, and low signal attenuation. This application can achieve dynamic power consumption adjustment of the current-type analog output device through hardware circuit verification and control, reducing the internal losses of the current-type analog output device; power consumption adjustment does not occupy CPU resources, thus freeing up CPU resources; the current-type analog output device can also operate stably under low current output (near 0mA) or no load conditions; this current-type analog output device has low internal power consumption, good output stability, and strong anti-interference characteristics.

[0015] The current-type analog output device of this application mainly consists of a protection circuit, a current output circuit, a power consumption dynamic adjustment circuit, a processor (CPU), a voltage-to-current conversion circuit (V / I), and a digital-to-analog converter (DAC). This application primarily reduces the power loss of the current-type analog output device through hardware circuit detection and control. Its main feature is that the processor (CPU) controls the DAC to output an analog voltage, which is then converted into an analog current via the voltage-to-current conversion circuit (V / I). This analog current controls the current magnitude in the current output circuit's current output loop. The power consumption dynamic adjustment circuit detects the power loss of the main components in the current output loop of the current-type analog output device and dynamically adjusts the output voltage of the BUCK power supply, thereby reducing the voltage across the main components of the current-type analog output device.

[0016] The power loss of a component is equal to the product of the voltage across the component and the output current. When the output current remains constant, reducing the voltage across the component can reduce the power loss of the device. The power consumption dynamic adjustment circuit can also dynamically adjust the stability of the BUCK power supply. In the case of low current output (near 0mA) or no load, the BUCK power supply in the current-type analog output device is in a light load state, which can easily lead to power instability, inductor and capacitor whistling, seriously affecting the service life of the device. In this application, under the condition of low current output (near 0mA) or no load, the power consumption dynamic adjustment circuit can adjust the power consumption according to the set value (V). T The system automatically adjusts the preset value of the BUCK power supply FB to output a stable voltage, ensuring the stability of the BUCK power supply. The protection circuit primarily prevents damage to the internal circuitry from static electricity and surges, providing greater circuit reliability.

[0017] Before providing a detailed description of the embodiments of this application, the internal circuit structure and principle of the current-type analog output device with dynamic power consumption adjustment of this application will be explained in conjunction with the accompanying drawings and embodiments. Figure 1This is a schematic diagram of the internal circuit structure of the current-type analog output device with dynamic power consumption adjustment provided in the embodiments of this application, as shown below. Figure 1 As shown, the internal circuit structure and principle of the device include the following: The device comprises a CPU processor, a DAC (Digital-to-Analog Converter), a V / I (Voltage-to-Current Converter), a current output circuit, a power consumption dynamic adjustment circuit, a protection circuit, and a load RL. The CPU outputs a digital control signal to the DAC based on external instructions. The DAC converts the digital control signal into a first analog voltage and sends it to the V / I circuit. The V / I circuit converts the first analog voltage into a control current signal and applies it to the control terminal of the power transistor Q1. Q1, the sampling resistor R2, and the load RL are connected in series to form a current output loop. Current flows from the Vout terminal of the buck power supply module BUCK through Q1 and R2 to the load port, thus generating a current-type analog output on the load RL.

[0018] The current output circuit uses BUCK as its power supply core, and its V in The terminal is connected to a DC input power supply, V out The output terminal serves as the power supply node for the current output circuit and is connected to the collector of Q1. The emitter of Q1 is connected to one end of the sampling resistor R2, and the other end of R2 is connected to the output terminal and in series with the load RL. Capacitors C2 and C3 are also connected in parallel in the output circuit to filter the output current. When current flows through R2, a sampling voltage proportional to the output current is generated across it. This sampling voltage is fed back to the current detection circuit in the power consumption dynamic adjustment circuit, and also suppresses output ripple and interference through the network formed by C2, C3 and ground.

[0019] The power consumption dynamic adjustment circuit is connected to the sampling resistor R2, power transistor Q1, and the feedback terminal FB of BUCK. It is used to switch modes and dynamically adjust the output voltage of BUCK based on the output current and the voltage across Q1. The current detection circuit consists of operational amplifier B and resistors R25, R26, R27, and R32. R25 and R26 sample the voltage across R2 and feed the samples into the input of operational amplifier B. R27 and R32 form a feedback and bias network, differentially amplifying the voltage drop across R2 to output the detection voltage V. B The reference voltage circuit consists of a reference voltage V. ref Composed of resistors R12 and R18, a reference voltage corresponding to a preset current threshold is obtained through voltage division. The two input terminals of comparator A receive the detected voltage V. B The reference voltage is supplied through resistor R10 and filtered and stabilized by capacitor C5. Its output serves as the control signal for the switch selection circuit, used to select the voltage based on V. B The conduction state of analog switch S is controlled by the relationship between the magnitude of the reference voltage and the voltage.

[0020] The analog switch S has a common terminal So and two selection terminals S1 and S2. So is connected to the feedback terminal FB of BUCK. S1 and S2 are connected to the first feedback branch and the second feedback branch, respectively. The first feedback branch is a dynamic feedback path, which includes a power transistor voltage detection circuit and a first voltage divider resistor network: the power transistor voltage detection circuit consists of an operational amplifier A and resistors R19, R20, R21, and R31. Its input terminal is connected across the collector and emitter of Q1 via R20 and R21, and measures the voltage V across Q1. CE The signal is amplified, and the output is stabilized via feedback through R19 before being sent to the first voltage divider network composed of R14 and R16. The voltage divider point of this network is connected to S1. When So and S1 are connected, the FB terminal of BUCK receives voltage based on V... CE The first feedback voltage is formed, and BUCK adjusts V internally. out The voltage across Q1 is dynamically adjusted to limit the voltage drop across Q1 within a set range. The second feedback branch is a fixed feedback path. The second voltage divider network, consisting of resistors R7 and R8, is connected between the feedback terminal of BUCK and ground. Its voltage divider point is connected to S2. When S0 and S2 are on, the FB terminal of BUCK receives the fixed feedback voltage and outputs V. out The value remains fixed as set by R7 and R8. The control signal output by comparator A is based on the detected voltage V. B The relationship between the reference voltage and the control So is connected to S1 or S2 respectively, so that BUCK can automatically switch between dynamic feedback mode and fixed feedback mode.

[0021] 5. Protection circuits and interfaces At the end of the current output circuit, a protection circuit is set between the sampling resistor R2 and the load port. One end of the protection diode D1 is connected to the output terminal and the other end is grounded. It is used to clamp the energy to ground when there is a surge, voltage spike or electrostatic discharge on the load side. The capacitor C3 is connected in parallel between the output terminal and ground. It is used to perform high-frequency filtering on the output current signal. Together with R2 and C2, it forms a low-pass filter network at the output end, which improves the stability of the current-type analog output and protects the internal components.

[0022] Through the above structure Figure 1 The current-type analog output device with dynamic power consumption adjustment shown in the figure maintains the output current set by the processor through DAC and V / I, while using the power dynamic adjustment circuit to detect the output current and the voltage across the power transistor, automatically switches the BUCK power feedback mode and adjusts its output voltage, thereby realizing hardware-based dynamic control of the power consumption inside the current output loop.

[0023] The specific structure and function of the current-type analog output device with dynamic power consumption adjustment provided in this application will be described in detail below with reference to the accompanying drawings and specific embodiments. Figure 2This is a schematic diagram of the overall structure of the dynamic power consumption regulation current-type analog output device provided in the embodiments of this application, as shown below. Figure 2 As shown, the dynamic power consumption regulation current-type analog output device of this application specifically includes the following circuits and components: Processor 201 is used to generate digital control quantities for setting the output current according to external instructions; The digital-to-analog converter circuit 202 is used to convert digital control quantities into a first analog voltage; The voltage-to-current conversion circuit 203 is used to generate a control current signal based on the first analog voltage; The current output circuit 204 includes a step-down power supply module, a power transistor, a sampling resistor, and a load port. The output terminal of the step-down power supply module is connected to the load port in sequence via the power transistor and the sampling resistor. The control current signal is applied to the control terminal of the power transistor to form a current-type analog quantity set by the processor at the load port. The sampling resistor is used to generate a sampling voltage that is proportional to the output current. The power consumption dynamic adjustment circuit 205 is used to switch modes and dynamically adjust the output voltage of the buck power supply module according to the output current and the voltage across the power transistor. It includes: a current detection circuit for amplifying the sampled voltage and outputting a detection voltage; a reference voltage circuit for outputting a reference voltage characterizing the output current threshold; a comparison circuit for comparing the detection voltage with the reference voltage and outputting a comparison result signal; and a switch selection circuit, with its control terminal connected to the output of the comparison circuit and its signal terminal connected to the feedback terminal of the buck power supply module, for selecting between the first feedback branch and the second feedback branch. The power transistor voltage detection circuit 206 has an input terminal connected across the two ends of the power transistor and an output terminal connected to the signal terminal of the switch selection circuit via the first feedback branch, used to convert the voltage across the power transistor into the first feedback voltage. The voltage divider feedback circuit 207 is connected between the feedback terminal and the reference potential of the buck power supply module, and is connected to the signal terminal of the switch selection circuit through the second feedback branch, and is used to provide a second feedback voltage to the buck power supply module. The step-down power supply module switches between the first feedback branch and the second feedback branch under the control of the switch selection circuit to provide an adjustable power supply voltage to the current output circuit, and drives the load port to output current according to the current-type analog quantity.

[0024] In some embodiments, the buck power supply module is constructed using a switching buck chip. The chip integrates a switching transistor, a driver circuit, and an error amplifier. Its output terminal serves as the power supply node for the current output circuit. The chip's feedback pin, FB, receives external feedback voltage and compares it with the chip's internal reference voltage, thereby adjusting the duty cycle and stabilizing the output voltage. The feedback pin FB switches between the first and second feedback branches via a switching selection circuit, allowing different feedback methods to control the output voltage of the buck power supply module under different operating conditions.

[0025] Specifically, to achieve dynamic feedback that changes with the voltage across the power transistor, in this embodiment, the first feedback branch includes a power transistor voltage detection circuit and a first voltage divider resistor network connected thereto. The power transistor voltage detection circuit is connected between the collector and emitter of the power transistor, and detects the voltage V across the power transistor through an operational amplifier and a resistor network. CE Perform differential amplification to obtain the result with V CE Proportional detection voltage V A The first voltage divider resistor network will divide V A After being divided according to a predetermined ratio, the voltage is sent to the first selection terminal of the switch selection circuit. When the switch selection circuit, under the control signal output by the comparator circuit, connects the feedback terminal FB to the first selection terminal, the first feedback voltage received by the feedback terminal of the BUCK power module changes with V. CE The voltage changes synchronously with the change. The internal error amplifier of the BUCK power module compares this first feedback voltage with the internal reference voltage, and when V... CE When the increase causes the first feedback voltage to rise, the BUCK power module automatically reduces the duty cycle to lower the output voltage V. out This makes V CE Controlled within a set range; when V CE When the voltage decreases, the first feedback voltage decreases, and the BUCK power module correspondingly increases the voltage. out This keeps the voltage drop across the power transistor basically stable.

[0026] To maintain stable power output under low current or no-load conditions, the second feedback branch in this embodiment uses a voltage divider feedback circuit to achieve fixed feedback. The voltage divider feedback circuit consists of a series-connected network of second voltage divider resistors, with one end connected to the output terminal of the BUCK power module and the other end grounded. Its voltage divider node is connected to the second selection terminal of the switch selection circuit.

[0027] By appropriately selecting the resistance values ​​of each resistor in the second voltage divider network, the voltage at the voltage divider node is made equal to the feedback level corresponding to the internal reference voltage of the BUCK power module. When the switch selection circuit connects the feedback terminal FB to the second selection terminal, the second feedback voltage obtained at the feedback terminal is a fixed value. The BUCK power module operates in constant output mode based on this fixed feedback voltage, and the output voltage V... out It maintains a preset fixed voltage value and no longer adjusts with changes in the voltage across the power transistor.

[0028] In practical applications, the detected voltage output by the current detection circuit can be compared with the reference voltage generated by the reference voltage circuit. When the detected voltage is less than the reference voltage and the output current is in a low current or no-load range, the comparator circuit controls the switch selection circuit to select the second feedback branch, causing the BUCK power module to operate according to the fixed feedback set by the voltage divider feedback circuit. When the detected voltage is greater than the reference voltage and the output current exceeds the set threshold, the comparator circuit controls the switch selection circuit to switch to the first feedback branch, causing the BUCK power module to operate according to the dynamic feedback provided by the power transistor voltage detection circuit. With this structure, when the load current is large, the output voltage of the BUCK power module can automatically adjust with the voltage across the power transistor to limit the power transistor voltage drop and power consumption; when the load current is small or open circuit, the BUCK power module maintains a fixed output voltage to avoid instability under light load.

[0029] Through the design of the above embodiments, the switching buck power supply module uses a structure with feedback pins in conjunction with two feedback branches with different characteristics, so that the first feedback voltage can dynamically change with the voltage across the power transistor, and the second feedback voltage is fixedly set by the voltage divider feedback circuit. Thus, on the same hardware platform, both power consumption control under high current conditions and power supply stability under low current conditions are taken into account, improving the adaptability and overall reliability of the current-type analog output device under different load conditions.

[0030] In some embodiments, the current detection circuit includes a first operational amplifier and a first resistor and a second resistor respectively connected to the two ends of the sampling resistor. The output of the first operational amplifier is fed back to the input via a third resistor so as to differentially amplify the sampling voltage across the sampling resistor and output a detection voltage.

[0031] Specifically, the current detection circuit, as a key component of the dynamic power consumption adjustment circuit, works in conjunction with the sampling resistor and the comparator circuit to convert the output current in the current output loop into a stable and reliable detection voltage signal. Specifically, the sampling resistor is connected in series between the power transistor and the load port. When the current-type analog output device operates according to the current set by the processor, the output current flowing through the sampling resistor forms a sampling voltage proportional to the current magnitude across its terminals. The current detection circuit differentially amplifies this sampling voltage, outputting a detection voltage linearly corresponding to the output current. This detection voltage is then sent to the comparator circuit and compared with a reference voltage provided by the reference voltage circuit to determine whether the output current exceeds a set threshold. This provides a basis for subsequent feedback branch switching and buck power supply module output voltage adjustment.

[0032] In some examples, the current sensing circuit includes a first operational amplifier and a first resistor, a second resistor, and a third resistor. Two sampling signals are led out from both ends of the sampling resistor and connected to the two input terminals of the first operational amplifier through the first resistor and the second resistor, respectively.

[0033] The first resistor feeds the potential of the sampling resistor near the power transistor to the inverting input of the first operational amplifier, while the second resistor feeds the potential of the sampling resistor near the load port to the non-inverting input of the first operational amplifier. The first operational amplifier forms a differential amplifier structure to amplify the voltage difference across the sampling resistor. One end of the third resistor is connected to the output of the first operational amplifier, and the other end is fed back to its inverting input, forming a negative feedback loop used to set the amplification factor and stabilize the operating point of the operational amplifier.

[0034] By appropriately selecting the resistance values ​​of the first, second, and third resistors, a predetermined linear proportional relationship can be maintained between the output detection voltage of the first operational amplifier and the voltage drop across the sampling resistor, thereby achieving accurate detection of the output current.

[0035] For example, in some specific examples, the sampling resistor is set to R2, the first and second resistors are set to R25 and R26 respectively, the third resistor is set to R27, and the first operational amplifier uses a low-noise, rail-to-rail input / output precision operational amplifier chip to ensure good linearity and resolution in the low current region near 0mA. The output current is I. O At that time, the voltage difference across the sampling resistor is I. O ×R2, after being amplified by the first operational amplifier, has an output detection voltage V. B It can be represented as V B =I O×R²×(R²⁷ / R²⁵), where R²⁷ / R²⁵ is the magnification factor. During the design, the ratio of R²⁷ to R²⁵ is set to an appropriate magnification factor, for example, a magnification factor of 10, so that in I... O The detection voltage V is within the range of 2mA to 20mA. B The input falls within the matching range of the comparator circuit and the reference voltage circuit, thus facilitating accurate discrimination by the subsequent comparator. To improve common-mode rejection capability, the second resistor R26 and the first resistor R25 can be set to be equal or proportionally matched, making the first operational amplifier insensitive to changes in the common-mode voltage across the sampling resistor, amplifying only the voltage difference.

[0036] In practical applications, the output of the current detection circuit is connected to ground through an appropriate filter capacitor to suppress high-frequency noise and ripple introduced by the switching buck power supply module and load changes, thus keeping the detection voltage smooth and stable. The detection voltage V after differential amplification and filtering... B The input is given to the comparator circuit, which will input V. B Compared with the reference voltage generated by the reference voltage circuit, when V B The corresponding output current exceeds the preset threshold I T When V is in the correct position, the output level of the comparator circuit flips, driving the switch selection circuit to switch the feedback terminal to the first feedback branch; when V... B The corresponding output current is lower than or equal to the threshold I. T When the comparison circuit maintains or switches to another level, the control switch selection circuit selects the second feedback branch, thereby realizing automatic switching of feedback mode under different current ranges.

[0037] Through the current detection circuit design of the above embodiments, the differential amplification structure composed of the first operational amplifier and the first, second, and third resistors is used to accurately amplify the small voltage drop across the sampling resistor and output the detection voltage. This enables the output current to be accurately converted into a voltage signal for use by the comparison circuit, thereby improving the accuracy and stability of the output current threshold judgment. This provides a reliable basis for the switching of the feedback branch of the buck power supply module and is conducive to the accurate execution of subsequent dynamic power consumption adjustment.

[0038] In some embodiments, the reference voltage circuit includes a reference voltage source and a resistor divider network connected to the reference voltage source. The voltage division ratio of the resistor divider network is adjustable and is used to set the magnitude of the reference voltage according to a preset current threshold.

[0039] Specifically, the reference voltage circuit, as an important component of the power consumption dynamic adjustment circuit, is used to generate a reference voltage corresponding to a preset current threshold and provide this reference voltage to the comparator circuit for comparison with the detection voltage output by the current detection circuit. The reference voltage circuit includes a reference voltage source and a resistor divider network connected to the reference voltage source. The voltage division ratio of the resistor divider network is adjustable. When setting the operating range of the current-type analog output device, the user only needs to adjust the resistor division ratio according to the desired output current threshold to complete the calibration of the reference voltage.

[0040] Specifically, the reference voltage source in the reference voltage circuit can be implemented using conventional bandgap reference chips or Zener diodes, such as a reference power supply chip with a stable output voltage of 2.5V or 3.0V, whose output terminal serves as the input terminal of the voltage divider network. The resistor voltage divider network consists of resistors R12 and R18 connected in series. One end of R12 is connected to the output terminal of the reference voltage source, and one end of R18 is grounded. The connection point between the two serves as the reference voltage output node V. ref_out And connected to one side input terminal of the comparator circuit (corresponding to) Figure 1 (The input terminal of comparator A in the circuit). To make the voltage division ratio adjustable, R12 or R18 can be designed as a multi-stage adjustable resistor, a variable resistor, or a combination resistor selected by several resistors via jumpers or DIP switches. This allows for adjustment of V without changing the output of the reference voltage source itself. ref_out Make detailed adjustments.

[0041] In one specific embodiment, it is assumed that the detection voltage V output by the current detection circuit is... B Satisfying relation V B =I O ×R2×(R27 / R25), where I O R2 is the output current, R2 is the sampling resistor, and R27 and R25 are resistors within the current detection circuit. To ensure the comparator circuit flips when the output current reaches a preset current threshold IT, the target reference voltage V can be determined based on the above relationship. T =I T ×R2×(R27 / R25), then adjust the resistance values ​​of R12 and R18 in the voltage divider network to make V ref_out ≈VT. For example, when the reference voltage source output is 2.5V, by selecting an appropriate resistance ratio of R12 and R18, V can be made... ref_out A value of 1.0V or 1.2V corresponds to different current thresholds I. T During commissioning, production personnel can connect a standard load to the output circuit and apply a target current I. T By finely adjusting the variable resistor, the output of the comparator circuit is made to flip exactly at the current point, thereby achieving precise setting of the threshold current.

[0042] In another implementation, to improve long-term stability and consistency, R12 and R18 can be high-precision metal film resistors, and fine-tuning can be achieved by connecting a small-value adjustable resistor in series at the output of the reference voltage source or by connecting a fine-tuning potentiometer in parallel at the voltage divider node. Alternatively, the voltage divider network can be split into two stages: a coarse-tuning resistor and a fine-tuning resistor. The coarse-tuning part allows for rapid configuration of different ranges by replacing the fixed resistor, while the fine-tuning part performs precise calibration using a small-range variable resistor to adapt to the current threshold configuration requirements of different systems.

[0043] Through the reference voltage circuit design of the above embodiments, by using a stable reference voltage source in conjunction with an adjustable voltage divider network, the reference voltage corresponding to the preset current threshold can be flexibly set under a unified hardware structure. This enables the comparison circuit to accurately distinguish the threshold point in different output current ranges, ensuring both the accuracy and consistency of dynamic power consumption adjustment switching conditions, and facilitating the adjustment of the current threshold for different application scenarios. This improves the adaptability and field adjustability of the current-type analog output device.

[0044] In some embodiments, the switch selection circuit is an analog switch device with a common terminal, a first selection terminal and a second selection terminal. The common terminal is connected to the feedback terminal of the step-down power supply module, the first selection terminal is connected to the first feedback branch, and the second selection terminal is connected to the second feedback branch. The comparison result signal output by the comparison circuit is used to control the common terminal to be connected to the first selection terminal or the second selection terminal.

[0045] The switch selection circuit is implemented using a single-pole double-throw analog switch device, which has three terminals: a common terminal, a first selection terminal, and a second selection terminal. The common terminal is directly connected to the feedback terminal FB of the buck power supply module, used to send the feedback voltage of the selected feedback branch into the buck power supply module. The first selection terminal is connected to the first feedback branch, whose node is a dynamic feedback voltage node based on the output of the power transistor voltage detection circuit processed by the first voltage divider network. The second selection terminal is connected to the second feedback branch, whose node is a fixed feedback voltage node generated by the voltage divider feedback circuit. In this way, the analog switch device constitutes a selection path for switching between two feedback voltages.

[0046] The control terminal of the analog switching device is connected to the output terminal of the comparator circuit. The two input terminals of the comparator circuit receive the detection voltage output by the current detection circuit and the reference voltage output by the reference voltage circuit, respectively. After comparing the detection voltage with the reference voltage, the comparator circuit outputs either a high level or a low level, which is used to drive the conduction direction of the internal switching transistor of the analog switching device.

[0047] For example, in one implementation, when the output current corresponding to the detected voltage is less than or equal to a preset current threshold, the comparator circuit outputs a low level, and the analog switching device connects the common terminal to the second selection terminal, allowing the FB terminal to receive the fixed feedback voltage provided by the second feedback branch. At this time, the buck power supply module operates according to the fixed feedback set by the voltage divider feedback circuit, and the output voltage remains at a preset fixed value. When the output current corresponding to the detected voltage is greater than the preset current threshold, the comparator circuit outputs a high level, and the analog switching device connects the common terminal to the first selection terminal, allowing the FB terminal to receive the dynamic feedback voltage provided by the first feedback branch. The buck power supply module automatically adjusts the output voltage according to the feedback signal output by the power transistor voltage detection circuit in the first feedback branch. By designing the output polarity of the comparator circuit and the control logic relationship of the analog switching device, the device can automatically select the corresponding feedback mode in different output current ranges.

[0048] In some examples, the analog switching devices are selected from single-pole double-throw analog switch chips with operating voltage ranges covering the system power supply voltage, low on-resistance, and low leakage current. Their power supply pins are connected to the same power supply Vcc as the operational amplifier and comparator to ensure switch control level compatibility. To avoid frequent switching of the analog switching devices caused by output jitter in the comparator circuit when the detection voltage approaches the threshold, a current-limiting resistor can be connected in series between the comparator circuit output and the analog switch control terminal, and a small capacitor can be connected in parallel with ground at the control terminal to form a simple RC filter network. This network is used for edge buffering and transient filtering of the comparison result signal. Alternatively, a small amount of hysteresis can be added internally or externally to the comparator circuit, causing a slight difference between the rising and falling edges of the switching point, thereby improving the stability of the feedback branch switching.

[0049] During the production and commissioning phase, users can observe the output voltage changes of the buck power supply module and the simulated switch conduction state under different load and output current conditions to verify whether the common terminal accurately switches between the first selection terminal and the second selection terminal when the output current crosses the preset threshold. If necessary, the switching point position can be optimized by fine-tuning the parameters of the reference voltage circuit or the current detection circuit.

[0050] Through the switch selection circuit design in the above embodiments, the common terminal is hardware-based to switch between the first feedback branch and the second feedback branch using analog switching devices. Automatic control is achieved through the comparison result signal output by the comparison circuit, enabling the buck power supply module to maintain stable output in a fixed feedback mode under low current or no-load conditions. When the output current exceeds the threshold, it switches to a dynamic feedback mode based on the power transistor voltage. This achieves fast and reliable switching of the feedback path without relying on software control, which helps to ensure the timeliness of power consumption adjustment in the current output circuit and the stability of the whole machine operation.

[0051] In some embodiments, the first feedback branch includes a first voltage divider resistor network connected in series with the feedback terminal of the buck power supply module and the output terminal of the power transistor voltage detection circuit. The input terminal of the power transistor voltage detection circuit is connected across the two ends of the power transistor to amplify the voltage across the power transistor. The first voltage divider resistor network is used to feed back the output voltage of the power transistor voltage detection circuit to the buck power supply module so as to adjust the output voltage of the buck power supply module according to the voltage across the power transistor.

[0052] Specifically, the first feedback branch, as one of the core paths of the power consumption dynamic adjustment circuit, works in conjunction with the feedback terminal of the buck power supply module, the power transistor, and the power transistor voltage detection circuit to adjust the output voltage of the buck power supply module according to the voltage across the power transistor when the output current is large, thereby performing voltage constraint control on the main power consumption components in the current output circuit.

[0053] The output terminal V of the buck power supply module BUCK in the current output circuit out The collector of power transistor Q1 is connected to the collector, and the emitter of Q1 is connected to the load port via sampling resistor R2. The voltage V between the collector and emitter of Q1 is... CE This represents the voltage drop across the main power loss components in the current output circuit. To obtain a detection signal proportional to VCE, the power transistor voltage detection circuit in this embodiment uses an operational amplifier A and related resistors. Its input is connected across the collector and emitter of Q1 via resistors R20 and R21, respectively. Operational amplifier A amplifies the voltage difference across Q1, and its output is fed back to its input via resistor R19. Resistor R31 is used to set the amplification factor and operating point of the operational amplifier, thereby obtaining a voltage signal proportional to VCE. CE The corresponding linear output voltage V A During the design process, the resistance values ​​of R19, R20, R21, and R31 can be selected based on the maximum allowable voltage drop of Q1 and the desired detection range, so that V... A In V CE When the voltage changes, it falls within the allowable operating level of the feedback terminal of the step-down power supply module.

[0054] To make V A In the feedback control link of the step-down power supply module, the first feedback branch in this embodiment further includes a first voltage divider resistor network. The first voltage divider resistor network consists of resistors R14 and R16 connected in series, with one end connected to the output terminal V of operational amplifier A. A One end is connected to the ground, and the voltage divider node between R14 and R16 serves as the output node of the first feedback branch. It is connected to the feedback terminal FB of the step-down power supply module via the first selection terminal of the analog switch. Thus, when the switch selection circuit, under the control of the comparator circuit, connects the common terminal to the first selection terminal, the first feedback voltage received by the feedback terminal FB is V. AThe voltage V after voltage division by R14 and R16 FB V FB The size varies with V CE It changes with the changes. The error amplifier inside the buck power supply module will change this V. FB V is compared with an internal reference voltage, and the duty cycle of the internal switching transistor is adjusted to change the voltage. out , making V CE The changes are compensated for within a certain range.

[0055] In some examples, the feedback reference voltage V of the BUCK chip in the circuit can be used as a reference. FB_ref And the expected target pressure drop V CE_target Select the resistance values ​​of R14, R16, and the resistors in the power transistor voltage detection circuit. For example, set the amplification factor of operational amplifier A so that V A ≈k×V CE Where k is the amplification factor, and then the ratio of R14 to R16 is selected so that when V CE At the target pressure drop V CE_target At that time, the first feedback voltage V obtained by voltage division through R14 and R16 is FB Exactly equal to the feedback reference V of the BUCK chip FB_ref Thus, when the load decreases, causing V across Q1 to... CE When there is an increasing trend, V A and V FB Accordingly, when the BUCK chip detects that the feedback voltage is higher than the reference voltage, it will reduce the duty cycle and lower V. out Thus, V CE It is pulled back to the set range; when the load increases, V CE When V decreases, FB To reduce V, the BUCK chip increases the duty cycle. out , making V CE It keeps the voltage near the desired range. Through this linear mapping relationship, the output voltage of the buck power supply module can be automatically adjusted under different load conditions, so that the voltage drop across the power transistor is maintained within a reasonable range.

[0056] In practical applications, the first feedback branch is usually used in conjunction with the second feedback branch. When the output current detection circuit and the comparison circuit determine that the output current is greater than the preset threshold I... T At that time, the comparator circuit outputs a control signal to drive the analog switch to switch to the first feedback branch, causing the buck power supply module to enter the V-based mode. CE Dynamic feedback mode; when the output current is lower than or equal to the threshold I T When the voltage is constant, the second feedback branch provides a fixed feedback voltage, and the buck power supply module maintains a fixed output.

[0057] In this embodiment, the voltage across the power transistor is effectively introduced into the feedback control loop of the buck power supply module through the first feedback branch formed by the power transistor voltage detection circuit and the first voltage divider resistor network. This allows the output voltage of the buck power supply module to automatically adjust with the change in the voltage drop of the power transistor, thereby limiting the change in the voltage drop of the power transistor when the output current is large, reducing the voltage stress and power consumption of the output stage devices under heavy load conditions, and improving the working stability and safety margin of the circuit under different load conditions.

[0058] In some embodiments, the second feedback branch includes a second voltage divider resistor network connected between the feedback terminal of the buck power supply module and ground, for providing a fixed feedback voltage to the buck power supply module so that the buck power supply module outputs a preset fixed voltage.

[0059] Specifically, the second feedback branch serves as a fixed feedback path for the buck power supply module under low current output or no-load conditions. It works in conjunction with the first feedback branch to provide a stable, fixed feedback voltage to the buck power supply module when dynamic adjustment based on the voltage across the power transistor is not required, thus enabling it to output a preset fixed voltage. In the current output circuit, the buck power supply module BUCK uses a switching buck chip with a feedback pin. The chip integrates an error amplifier and a reference voltage source. The voltage at the feedback pin FB is compared with the internal reference voltage to determine the duty cycle of the power switch, thereby adjusting the output voltage V. out The voltage magnitude.

[0060] Specifically, the second feedback branch includes a second voltage divider resistor network connected between the feedback terminal of the buck power supply module and ground. The second voltage divider resistor network consists of resistors R7 and R8 connected in series, with one end of R7 connected to the BUCK output terminal V. out One end of R8 is grounded, and the connection point between R7 and R8 serves as a voltage divider node, connected to the feedback terminal FB via the second selection terminal of the switch selection circuit. When the switch selection circuit, under the control of the comparator circuit, connects the common terminal to the second selection terminal, the feedback terminal FB receives the fixed feedback voltage V generated by the voltage divider formed by R7 and R8. FB_fix By appropriately selecting the values ​​of R7 and R8, the voltage at the voltage divider node corresponds to the reference feedback voltage inside the BUCK chip, that is, when V... out When the preset fixed value is reached, V FB_fix When the voltage level equals the chip reference level, the buck power supply module is in steady-state operation.

[0061] In some examples, the internal feedback reference voltage of the BUCK chip is set to V. FB_ref For example, 0.8V or 1.2V, the desired preset fixed voltage at the output terminal is V. out_fix For example, 12V or 15V can be calculated using the formula V. out_fix ≈V FB_ref×(R7+R8) / R8 Select the resistance values ​​of R7 and R8 such that when V out When the preset fixed value is reached, the voltage at the voltage divider node is exactly equal to V. FB_ref During production debugging, a standard load or no-load can be connected to the output terminal, and V can be monitored using an oscilloscope or multimeter. out By fine-tuning the resistance combination of R7 or R8 and the feedback terminal voltage, the BUCK output voltage is ensured to remain stable near the designed fixed value when the second feedback branch is connected. In this embodiment, under low current output (close to 0mA) or no-load conditions, if the BUCK power supply operates under light load and is combined with dynamic feedback, phenomena such as inductor and capacitor howling and output jitter are likely to occur. Therefore, using a fixed feedback mode is particularly important under such conditions.

[0062] In this embodiment, the second feedback branch, together with the current detection circuit, the reference voltage circuit, and the comparator circuit, constitutes the operating mode selection mechanism. When the detection voltage V output by the current detection circuit... B After comparing the current with the reference voltage generated by the reference voltage circuit, the comparator circuit determines whether the output current is less than or equal to the preset current threshold I. T When the detected voltage is not higher than the reference voltage, the comparator circuit outputs a corresponding control level, causing the switch selection circuit to connect the feedback terminal FB to the second selection terminal where the second voltage divider resistor network is located. The buck power supply module then switches from the first feedback branch to the second feedback branch. In this state, the BUCK no longer dynamically adjusts based on the voltage across the power transistor, but operates according to the fixed feedback set by R7 and R8. The output voltage remains at a preset fixed value, providing stable power for light load, no-load, and low-current output conditions.

[0063] Through the second feedback branch design in the above embodiment, the second voltage divider resistor network connected between the feedback terminal of the step-down power supply module and ground provides a fixed feedback voltage to the step-down power supply module under specified operating conditions, so that the step-down power supply module outputs a preset fixed voltage. This avoids the problems of power supply instability, howling and output fluctuation caused by dynamic feedback under low current or no load conditions, and ensures the power supply stability and interface reliability of the current-type analog output device in the low load range.

[0064] In some embodiments, the power transistor voltage detection circuit includes a second operational amplifier and a fourth resistor and a fifth resistor connected to both ends of the power transistor. The input terminal of the second operational amplifier is connected across both ends of the power transistor via the fourth resistor and the fifth resistor, respectively, and the output terminal is fed back to the input terminal via a sixth resistor, so as to amplify the voltage across the power transistor and form a first feedback voltage.

[0065] Specifically, the power transistor voltage detection circuit, as the front-end detection unit of the first feedback branch, is used to convert the voltage change across the power transistor in the current output circuit into a first feedback voltage with appropriate amplitude and high linearity, and then send it to the feedback channel of the buck power supply module through the first voltage divider resistor network. In conjunction with the circuit structure described above, the power transistor Q1 is the main power device in the current output loop, and its collector is connected to the output terminal V of the buck power supply module BUCK. out The emitter is connected to the load port via sampling resistor R2, and the voltage V between the collector and emitter of Q1 is... CE It reflects the voltage drop of the output stage under the current load and output current conditions, and is also a key measured parameter for dynamic power consumption adjustment in this application.

[0066] The power transistor voltage detection circuit includes a second operational amplifier and a fourth and a fifth resistor connected to both ends of the power transistor. The second operational amplifier uses a common operational amplifier chip to implement differential amplification. One end of the fourth resistor is connected to the collector of the power transistor Q1, and the other end is connected to one input terminal of the second operational amplifier (e.g., the inverting input terminal). One end of the fifth resistor is connected to the emitter of the power transistor Q1, and the other end is connected to the other input terminal of the second operational amplifier (e.g., the non-inverting input terminal), thereby acquiring the voltage difference between the collector and emitter of Q1. To set the amplification factor and form negative feedback, the output terminal of the second operational amplifier is also fed back to one of its input terminals through a sixth resistor, for example, to the inverting input terminal, so that the second operational amplifier constitutes a differential amplification structure, linearly amplifying the voltage across Q1 and outputting it as the first feedback voltage V. A .

[0067] In some examples, to achieve higher detection sensitivity, the fourth and fifth resistors can be designed to have equal resistance values, for example, both 10kΩ. This allows the second operational amplifier to have better suppression of the common-mode voltage across the power transistor, only affecting V. CE A response is generated. The sixth resistor can be selected with an appropriate value based on the required amplification factor. For example, selecting a 100kΩ sixth resistor will result in an amplification factor of approximately 10. In this configuration, when the voltage drop across the power transistor V... CE When the voltage varies within the range of 0.5V to 2V, the output of the second operational amplifier can generate a first feedback voltage V in the range of approximately 5V to 20V. A To accommodate the operating voltage range of the first voltage divider resistor network and the feedback pin of the buck power supply module, a current-limiting resistor or clamping diode can be connected in series at the output of the second operational amplifier to limit V. A The maximum amplitude should be controlled to prevent exceeding the chip's rated input voltage.

[0068] For example, in some specific examples, the second operational amplifier and its peripheral resistors correspond to operational amplifier A and resistors R19, R20, R21, R31, etc., and the second operational amplifier will V CE Amplified output V A Satisfying similar V A =(R19 / R20)×V CE The relationship is then used to obtain the feedback voltage V through the first voltage divider resistor network formed by R14 and R16. FB This is used for comparison by the internal error amplifier of the buck power supply module. With the above structure, when the load RL decreases and the output current remains at a large value, the voltage drop V across Q1 is... CE There is an upward trend, and the output V of the second operational amplifier is... A As it increases, the feedback voltage V after voltage division increases. FB As the voltage rises, the buck power supply module detects that the feedback voltage is higher than the internal reference value and automatically reduces the output voltage V. out , making V CE The increase in V is suppressed; conversely, when the load increases, causing V to increase, the increase in V is suppressed. CE It tends to decrease, V A With V FB As a result, the step-down power supply module increases V. out This keeps Q1 near the set voltage drop range.

[0069] In practical applications, the combination of the fourth, fifth, and sixth resistors can be adjusted according to the voltage rating and allowable power dissipation level of different power transistors to set an appropriate detection sensitivity and operating range. For example, for power transistors with higher voltage ratings, the amplification factor can be set to a lower value to avoid V A Premature saturation; for those who wish to finely limit V CE In certain scenarios, the amplification factor can be appropriately increased so that the second operational amplifier can produce a significant feedback voltage difference even for small voltage drop changes, thereby improving the precision of the buck power supply module's adjustment.

[0070] Through the power transistor voltage detection circuit design in the above embodiment, using the differential amplifier structure composed of the second operational amplifier and the fourth, fifth, and sixth resistors, the voltage drop V across the power transistor Q1 can be detected. CE The stable and linear conversion to a first feedback voltage with appropriate amplitude not only improves the detection accuracy and response sensitivity of output stage voltage drop changes, but also lays the foundation for the first feedback branch to provide a reliable dynamic feedback signal to the buck power supply module. This is conducive to effectively constraining the voltage drop and power consumption of the power transistor, and ensuring the working safety and stability of the current output circuit under different load conditions.

[0071] In some embodiments, the voltage-to-current conversion circuit includes a third operational amplifier and a sensing resistor. The input terminal of the third operational amplifier is connected to a first analog voltage output by the digital-to-analog conversion circuit, and the output terminal is connected to the control terminal of the power transistor via the sensing resistor. The third operational amplifier and the sensing resistor constitute a constant current source structure for generating a control current signal.

[0072] Specifically, the voltage-to-current conversion circuit, as a key link connecting the digital-to-analog conversion circuit and the power transistor, is used to accurately convert the first analog voltage output by the digital-to-analog conversion circuit into a control current signal for driving the power transistor, thereby forming a current-type analog quantity in the subsequent current output circuit that corresponds to the processor's set value.

[0073] Based on the overall structure of this device described above, the processor outputs a digital value to the digital-to-analog converter circuit according to the set value issued by the host system. The digital-to-analog converter circuit converts the digital value into a first analog voltage, which is between 0V and V. REF The voltage varies linearly between these values, corresponding to a current output range of 0mA to 20mA. The voltage-to-current conversion circuit receives this first analog voltage and generates a control current signal proportional to the first analog voltage through a constant current source structure. This control current signal is applied to the control terminal of the power transistor, causing the power transistor to adjust the output current according to the set value in the subsequent current output circuit.

[0074] The voltage-to-current conversion circuit includes a third operational amplifier and a sensing resistor. The third operational amplifier is preferably a precision operational amplifier with rail-to-rail input and output. One of its input terminals (e.g., the non-inverting input terminal) is directly connected to the first analog voltage output by the digital-to-analog conversion circuit, and the other input terminal (e.g., the inverting input terminal) is connected to one end of the sensing resistor, and the other end of the sensing resistor is grounded.

[0075] The output of the third operational amplifier is connected to the control terminal of the power transistor via the branch containing the sensing resistor or with an additional current-limiting resistor, thus forming a constant current source structure that converts input voltage into output current. The third operational amplifier adjusts its output voltage to ensure that the voltage at the inverting input terminal is consistent with the first analog voltage at the non-inverting input terminal. In stable operation, the voltage across the sensing resistor is equal to the first analog voltage, and the current flowing through the sensing resistor is the control current signal, the magnitude of which is approximately the ratio of the first analog voltage to the resistance value of the sensing resistor.

[0076] In some examples, the non-inverting input of the third operational amplifier can be connected to the output of a digital-to-analog converter, the inverting input can be connected to ground through a sense resistor, and the output of the third operational amplifier can be connected to the base or gate of the power transistor Q1 through a series current-limiting resistor. Simultaneously, the upper end of the sense resistor can be led out from the output of the third operational amplifier as a feedback point, forming a typical transresistive constant current source structure. Assume the resistance of the sense resistor is R.det If the first analog voltage output by the digital-to-analog converter circuit ranges from 0V to 5V, then the third operational amplifier will automatically adjust the output voltage to make the voltage across the sensing resistor equal to the first analog voltage. At this time, the current through the sensing resistor is I. ctrl ≈V dac / R det By selecting the appropriate R det For example, select R det It is 2.5kΩ, which can achieve when V dac When the voltage varies between 0V and 5V, the control current signal changes linearly between 0mA and 2mA. This control current signal is then amplified by the power transistor, and together with the sampling resistor and feedback link in the current output circuit, the output current at the load end varies within the range of 0mA to 20mA.

[0077] In another implementation, to improve control accuracy and stability, a small resistor can be connected in series between the inverting input of the third operational amplifier and the sensing resistor, or a protective resistor can be connected in series between the output of the third operational amplifier and the control terminal of the power transistor. This limits transient current and reduces the impact of noise on the control loop. Furthermore, a small capacitor can be connected in parallel between the input of the third operational amplifier and ground to form a simple compensation network, improving the phase margin of the voltage-to-current conversion loop and preventing oscillations when coupled to the subsequent current output feedback loop.

[0078] During production and debugging, a standard resistor can be connected to the load end and different digital set values ​​can be set. The corresponding output current and the first analog voltage can be measured to check whether the control current signal output by the voltage-to-current conversion circuit and the first analog voltage maintain the expected proportional relationship. If necessary, the overall output can be calibrated by fine-tuning the resistance value of the detection resistor or the output range parameter of the digital-to-analog conversion circuit.

[0079] In the specific implementation of this application, the voltage-to-current conversion circuit composed of the third operational amplifier and the sensing resistor works closely with the pre-processor, the digital-to-analog converter circuit, and the subsequent power transistor, sampling resistor, and power consumption dynamic adjustment circuit to form a complete closed-loop link from the digital setpoint to the output current. Through the voltage-to-current conversion circuit design of the above embodiment, the first analog voltage output by the digital-to-analog converter circuit is accurately converted into a control current signal in a constant current source manner. This not only ensures the linear correspondence between the output current and the digital setpoint, facilitating fine resolution and calibration from 0mA to 20mA, but also improves the stability of the current setting link under different operating temperatures and power supply conditions, providing an accurate and reliable front-end drive foundation for subsequent power consumption dynamic adjustment based on power transistor voltage drop and output current.

[0080] In some embodiments, the device further includes a protection circuit disposed at the interface between the sampling resistor and the load port. The protection circuit includes a protection diode and a capacitor connected in parallel between the load port and the reference potential, and a current-limiting resistor connected in series with the signal path. The protection circuit is used to provide electrical protection and filtering for the interface signal of the load port.

[0081] The device incorporates a protection circuit between the sampling resistor and the load port to provide electrical protection and filtering for interface signals input to the field. The emitter of power transistor Q1 is connected to the output terminal via sampling resistor R2, and the output terminal is then connected to the field load RL. The protection circuit, located at the interface between R2 and the output terminal, absorbs abnormal energy such as surges, electrical fast pulses, and electrostatic discharges from the field lines, and filters high-frequency interference components in the output current signal, thereby protecting core components such as the internal power transistor Q1, operational amplifier, and buck power supply module.

[0082] In some examples, the protection circuitry includes a protection diode and capacitor connected in parallel between the load port and the reference potential, and a current-limiting resistor connected in series with the signal path. One end of the protection diode is connected to the load port, and the other end is connected to the reference potential (typically system ground). A transient voltage suppressor diode (TVS) or a device with ESD protection is preferred. When a high-amplitude surge, voltage spike, or electrostatic discharge occurs on the field line, the protection diode quickly conducts near its clamping voltage, dissipating excess energy to the reference potential and preventing high voltage from being directly applied to the sampling resistor R2 and subsequent internal circuitry.

[0083] One end of the capacitor is connected to the load port, and the other end is connected to the reference potential. It is connected in parallel with the protection diode to bypass and filter high-frequency interference signals at the load port. Under the influence of ripple, electromagnetic interference and external long-line coupling interference generated by the operation of the switching buck power supply module, the capacitor provides a low-impedance path for high-frequency components, making the output voltage change smoother.

[0084] In addition to the protection diode and capacitor connected in parallel, this embodiment also connects a current-limiting resistor in series in the signal path between the sampling resistor R2 and the load port. This current-limiting resistor can be in the range of several ohms to tens of ohms. When an external short circuit, surge, or instantaneous high voltage occurs, the current-limiting resistor initially limits the current flowing into the internal circuit. Combined with the clamping effect of the protection diode, the surge current and voltage are significantly attenuated before reaching R2 and the internal precision operational amplifier.

[0085] In addition, the current-limiting resistor and the capacitor connected in parallel at the output end together form an RC low-pass filter network, which smooths out high-frequency glitches and noise in the output current waveform under normal operating conditions, making the changes in the current-type analog quantity sent to the field load more gradual, which is beneficial to improving the stability of measurement and control of the controlled equipment.

[0086] For example, in some specific examples, the protection diode is selected as a unidirectional TVS diode with a rated reverse working voltage of 24V and a clamping voltage of approximately 40V. The capacitor capacity can be selected as a high-frequency bypass capacitor of 10nF to 100nF, and the current-limiting resistor value can be set to approximately 10Ω. In use, even if the field line is long, there is an inductive load, or a switching operation, the reverse electromotive force and spike interference generated at the load end will first be attenuated by the voltage division of the current-limiting resistor, and then discharged or bypassed to ground by the protection diode and capacitor, thereby effectively reducing the impact of transient overvoltage on the internal circuit.

[0087] Through the protection circuit design in this embodiment, an interface protection and filtering network consisting of a protection diode, a capacitor, and a current-limiting resistor is constructed between the sampling resistor and the load port. On the one hand, it can limit and absorb the effects of surges, electrical fast transients, and electrostatic discharges from the field, reducing the voltage and current impacts on internal components such as the power transistor Q1, the sampling resistor R2, and the operational amplifier, thereby improving the surge and electrostatic discharge resistance of the interface. On the other hand, the RC network is used to perform high-frequency filtering on the output signal, improving the smoothness and anti-interference performance of the current-type analog output, thereby improving the reliability and long-term stable operation capability of the current-type analog output device in complex industrial field environments.

[0088] The above embodiments have provided a detailed description of the circuit structure, principle, and function of the current-type analog output device of this application. The following will explain the circuit, components, and working principle of the current-type analog output device of this application in conjunction with specific scenario examples. The specific content is as follows: 1. Current output control principle The processor (CPU) controls the digital-to-analog converter (DAC) to output analog voltage. The analog voltage is converted into analog current by a voltage-to-current converter (V / I). The analog current controls the current magnitude in the current output circuit through transistor Q1. The processor (CPU) controls the current magnitude in the current output circuit by outputting the analog voltage through the digital-to-analog converter (DAC). The current output circuit consists of a BUCK power supply, transistor Q1, sampling voltage R2, and load RL.

[0089] 2. Principle of Dynamic Power Consumption Adjustment Dynamic power consumption adjustment control determines the output voltage V of the BUCK power supply by controlling the analog switch S. out Is the output fixed or dynamically adjustable? The switching of analog switch S is determined by the output of comparator A, and the output of comparator A is determined by the reference voltage V. ref The magnitude of the output V of operational amplifier B B Decision, V B The value of is determined by the product of the output current of the current-type analog output device and the sampling resistor R2, and the specific calculation formula is as follows: V B =Io*R2* (R27 / R25); Among them, V B This represents the output voltage value of operational amplifier B.

[0090] The BUCK power supply has two feedback loops: the first feedback loop consists of transistor Q1, operational amplifier A, R14, R16, analog switch S, and the BUCK power supply. Switching to this feedback loop allows the BUCK power supply to output a dynamically adjustable value. The second feedback loop consists of R7, R8, analog switch S, and the BUCK power supply. Switching to this feedback loop allows the BUCK power supply to output a fixed value. If V B ≥V ref The output S of analog switch S O When connected to input S2, the BUCK power supply switches to the second feedback loop, and the output V out It is a fixed value; If V B <V ref The output S of analog switch S O When connected to input S1, the BUCK power supply switches to the first feedback loop, and the output V out This is a dynamically adjusted value.

[0091] When the current-type analog output device outputs a small current (around 0mA), under no-load conditions, or less than the set value (I), T When the feedback loop is unstable, the set reference voltage V is used. ref The output So of the control analog switch S is connected to the input S2, and the output voltage Vout of the BUCK power supply is fixed to ensure the stability of the current-type analog output device.

[0092] When the output current of the current-type analog output device is greater than the set value (I) T When ), through the set reference voltage V ref Control the output S of analog switch S O Connected to input S2, the output V of the BUCK power supply out This is a dynamically adjusted value.

[0093] Adjustment threshold V for fixed output and dynamically adjusted output T From the reference voltage V ref With operational amplifier B output voltage value V B The size is determined by.

[0094] V T =V B = I T *R2*(R27 / R25) If V T ≥V ref The output S of analog switch S O When connected to input S2, the BUCK power supply switches to the second feedback loop, and the output V out It is a fixed value; If V T <V ref The output S of analog switch S O When connected to input S1, the BUCK power supply switches to the first feedback loop, and the output V out This is a dynamically adjusted value; Therefore, V can be adjusted ref and V T The size is used to set the switching of the BUCK power feedback loop.

[0095] Reference voltage V ref Greater than the output voltage V of operational amplifier B B The comparator's analog switch controls the analog switch output S. O Connected to S2, feedback is sent to the FB pin of BUCK, and the BUCK power supply output V... out It is a fixed value, and its size is determined by the values ​​of R7 and R8; the specific calculation formula is as follows: V out =(R7+R8)*VFB / R8 Among them, V out This indicates the output voltage value of the BUCK power supply; V FB This indicates the BUCK power supply feedback voltage value, which can be obtained by referring to the manual of the selected BUCK power supply.

[0096] If the reference voltage V ref If the voltage is less than the output voltage VB of operational amplifier B, the analog switch of the comparator controls the analog switch output So to connect with S1, which feeds back to the FB pin of BUCK, and the BUCK power supply output V. out The output is dynamically adjusted based on the output of the operational amplifier; its magnitude is determined by the values ​​of R14 and R16, as well as the output V of operational amplifier A. A Decision; specific calculations are as follows: V out =(R14+R16)*V FB / R16; V FB =V A *R16 / (R14+R16); V A =(R19 / R20)*V CE .

[0097] Among them, V outThis indicates the output voltage value of the BUCK power supply; V FB This indicates the BUCK power supply feedback voltage value, which can be obtained by referring to the manual of the selected BUCK power supply; V CE This represents the voltage between the collector and emitter of transistor Q1.

[0098] V out The output is determined by V CE It is determined that transistor Q1 is the main power loss component, and the power loss is: P w =V CE *Io.

[0099] If the BUCK power supply always provides a fixed output, the voltage V across transistor Q1 will change as the load RL varies. CE It also changes; when the load increases, i.e., the resistance of RL decreases, V CE The power loss will increase, therefore the power loss P w It will increase.

[0100] If the BUCK power supply is a dynamically adjustable output, check V. CE The voltage across the two ends is adjusted by the detection V. CE The voltage across the terminals can be adjusted V out The output of V makes V CE The voltage across the terminals is a constant value and will not decrease as the resistance of RL decreases. V CE Increase; ensure that the loss of transistor Q1 varies within the specified range, and reduce the power loss of transistor Q1; under low current output (near 0mA) and no load conditions, the BUCK power supply output is fixed, and since Io is small, the power loss of transistor Q1 is also small; thus, dynamic adjustment of power consumption is achieved.

[0101] 3. High reliability and strong anti-interference ability The protection circuit is placed at the interface of the current-type analog output device; it mainly absorbs static electricity and surge energy through the protection diode D1, and filters interference signals through capacitors C3, R2, and C2; preventing static electricity from damaging the internal core components.

[0102] Existing current-type analog output devices consume a large amount of power, resulting in significant energy waste and a substantial increase in internal temperature, which greatly shortens the lifespan of electronic components, makes the system prone to various malfunctions, and reduces system reliability. This application addresses this by enabling dynamic adjustment of device power consumption through hardware circuit verification and control, without consuming CPU resources. Simultaneously, it reduces power consumption in the current-type analog output device, providing stable output and strong anti-interference capabilities.

[0103] Through the technical solutions provided in the above embodiments of this application, this application has at least the following advantages: 1. Dynamically adjust the power consumption of the current-type analog output device through pure hardware circuit testing and control, thereby reducing the internal losses of the current-type analog output device; 2. Power consumption adjustment is implemented in hardware, requiring no software control. Power consumption adjustment does not occupy CPU resources, thus freeing up CPU resources. 3. Solve the problem of unstable output current when outputting a small current (around 0mA); 4. Solve problems such as circuit instability and inductor / capacitor squealing under no-load (output open circuit) conditions; 5. High reliability and strong anti-interference ability.

[0104] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although the technical solutions of this application have been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A current-type analog output device with dynamic power consumption regulation, characterized in that, include: The processor is used to generate digital control quantities for setting the output current based on external instructions; A digital-to-analog converter circuit is used to convert the digital control quantity into a first analog voltage; A voltage-to-current conversion circuit is used to generate a control current signal based on the first analog voltage; The current output circuit includes a step-down power supply module, a power transistor, a sampling resistor, and a load port. The output terminal of the step-down power supply module is connected to the load port in sequence via the power transistor and the sampling resistor. The control current signal is applied to the control terminal of the power transistor to form a current-type analog quantity set by the processor at the load port. The sampling resistor is used to generate a sampling voltage that is proportional to the output current. A power consumption dynamic adjustment circuit is used to switch modes and dynamically adjust the output voltage of the buck power supply module according to the output current and the voltage across the power transistor. It includes: a current detection circuit for amplifying the sampled voltage and outputting a detection voltage; a reference voltage circuit for outputting a reference voltage characterizing the output current threshold; a comparison circuit for comparing the detection voltage with the reference voltage and outputting a comparison result signal; and a switch selection circuit, with its control terminal connected to the output of the comparison circuit and its common terminal connected to the feedback terminal of the buck power supply module, for selecting between a first feedback branch and a second feedback branch. The power transistor voltage detection circuit has an input terminal connected across the two ends of the power transistor and an output terminal connected to the signal terminal of the switch selection circuit via the first feedback branch, used to convert the voltage across the power transistor into a first feedback voltage. A voltage divider feedback circuit is connected between the feedback terminal of the step-down power supply module and the reference potential, and is connected to the signal terminal of the switch selection circuit through the second feedback branch, for providing a second feedback voltage to the step-down power supply module; The step-down power supply module switches between the first feedback branch and the second feedback branch under the control of the switch selection circuit to provide an adjustable power supply voltage to the current output circuit and drive the load port to output current according to the current-type analog quantity.

2. The apparatus according to claim 1, characterized in that, The step-down power supply module is a switching step-down power supply module, which is provided with a feedback pin as the feedback terminal. The first feedback voltage provided by the first feedback branch changes with the voltage across the power transistor, and the second feedback voltage provided by the second feedback branch is a fixed voltage determined by the voltage divider feedback circuit.

3. The apparatus according to claim 1, characterized in that, The current detection circuit includes a first operational amplifier and a first resistor and a second resistor respectively connected to the two ends of the sampling resistor. The output of the first operational amplifier is fed back to the input via a third resistor so as to differentially amplify the sampled voltage across the sampling resistor and output the detection voltage.

4. The apparatus according to claim 1, characterized in that, The reference voltage circuit includes a reference voltage source and a resistor divider network connected to the reference voltage source. The voltage division ratio of the resistor divider network is adjustable and is used to set the magnitude of the reference voltage according to a preset current threshold.

5. The apparatus according to claim 1, characterized in that, The switch selection circuit is an analog switch device with a common terminal, a first selection terminal, and a second selection terminal. The common terminal is connected to the feedback terminal of the step-down power supply module, the first selection terminal is connected to the first feedback branch, and the second selection terminal is connected to the second feedback branch. The comparison result signal output by the comparison circuit is used to control the common terminal to be connected to the first selection terminal or the second selection terminal.

6. The apparatus according to claim 1, characterized in that, The first feedback branch includes a first voltage divider resistor network connected in series with the feedback terminal of the buck power supply module and the output terminal of the power transistor voltage detection circuit. The input terminal of the power transistor voltage detection circuit is connected across the two ends of the power transistor to amplify the voltage across the power transistor. The first voltage divider resistor network is used to feed back the output voltage of the power transistor voltage detection circuit to the buck power supply module so as to adjust the output voltage of the buck power supply module according to the voltage across the power transistor.

7. The apparatus according to claim 1, characterized in that, The second feedback branch includes a second voltage divider resistor network connected between the output terminal of the buck power supply module and ground, which is used to provide a fixed feedback voltage to the buck power supply module so that the buck power supply module outputs a preset fixed voltage.

8. The apparatus according to claim 1, characterized in that, The power transistor voltage detection circuit includes a second operational amplifier and a fourth resistor and a fifth resistor connected to both ends of the power transistor. The input terminal of the second operational amplifier is connected across both ends of the power transistor via the fourth resistor and the fifth resistor, respectively, and the output terminal is fed back to the input terminal via a sixth resistor, so as to amplify the voltage across the power transistor and form the first feedback voltage.

9. The apparatus according to claim 1, characterized in that, The voltage-to-current conversion circuit includes a third operational amplifier and a sensing resistor. The input terminal of the third operational amplifier is connected to the first analog voltage output by the digital-to-analog conversion circuit, and the output terminal is connected to the control terminal of the power transistor via the sensing resistor. The third operational amplifier and the sensing resistor constitute a constant current source structure for generating the control current signal.

10. The apparatus according to claim 1, characterized in that, The device further includes a protection circuit disposed at the interface between the sampling resistor and the load port. The protection circuit includes a protection diode and a capacitor connected in parallel between the load port and the reference potential, and a current-limiting resistor connected in series with the signal path. The protection circuit is used to provide electrical protection and filtering for the interface signal of the load port.

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