A method and system for generating a precision equivalent resistance based on duty cycle modulation

Abstract

The application discloses a precise equivalent resistance generation method and system based on duty cycle modulation, and the system comprises a main circuit and an auxiliary circuit; the main circuit comprises a test power supply, a low-pass filter, a high-speed electronic switch, a high-precision standard reference resistance and a current acquisition module which are sequentially connected; the auxiliary circuit comprises an analog-digital conversion module ADC, a digital controller and a digital pulse sequence generation unit which are sequentially connected, wherein the digital controller comprises a calibration and compensation module; the digital pulse sequence generation unit is connected with the high-speed electronic switch; the analog-digital conversion module ADC is connected with the current acquisition module; and the current acquisition module is connected with the test power supply. The application can generate an equivalent resistance with continuous resistance value, stepless, high-resolution adjustment, high absolute precision and excellent temperature stability.

Description

Technical Field

[0001] This application relates to the field of electronic technology, and in particular to a method and system for generating precision equivalent resistance based on duty cycle modulation. Background Technology

[0002] In fields such as precision measurement, sensor simulation, automated testing, and instrument calibration, high-precision resistors with adjustable resistance values ​​are often required. Existing solutions mainly include the following: 1. Precision multi-range resistance box: This type of resistance box consists of a series of high-precision, low-temperature-coefficient standard resistors that are switched between by mechanical relays or electronic switches. Its disadvantages are: the resistance values ​​vary discretely, with resolution limited to the smallest resistance range (e.g., 0.1Ω), making continuous, stepless adjustment impossible; achieving high resolution and a wide range requires a large number of precision resistors and switches, resulting in a complex, bulky, and costly system; and the mechanical relays have slow switching speeds and are prone to wear.

[0003] 2. High-resolution digital potentiometers (DigiPot): These integrate resistor strings and switch networks using CMOS technology. Their disadvantages include relatively low absolute accuracy (typically 1%~20%) and a large temperature coefficient (up to several hundred degrees). Furthermore, it exhibits significant end-to-end resistance error; its adjustable range is limited, and it can typically only be used as a voltage divider, making it difficult to directly connect to a circuit as a precision adjustable resistor.

[0004] 3. Active analog circuits based on digital-to-analog converters (DACs) and operational amplifiers: These circuits simulate resistance characteristics by controlling voltage or current sources through the DAC. Their disadvantages include: complex circuitry, extremely high requirements for parameters such as the input impedance and bias current of the operational amplifier, limited output drive capability and bandwidth, and their "equivalent resistance" characteristics are significantly affected by the load, rather than being true passive resistance characteristics.

[0005] The main problems and shortcomings of existing technologies can be summarized as follows: they cannot simultaneously achieve high absolute accuracy, high resolution (or continuous adjustability), wide adjustment range, low cost, and high reliability. In particular, existing solutions have significant shortcomings in achieving continuous, stepless, and high-precision resistance adjustment, such as sacrificing accuracy and temperature stability (e.g., digital potentiometers), failing to achieve true continuity (e.g., resistance boxes), and being extremely costly and complex. Summary of the Invention

[0006] In view of this, this application provides a method and system for generating a precision equivalent resistance based on duty cycle modulation, which uses digital pulse density modulation (PDM) technology to control the connection time of a standard resistor in order to generate a high-precision, continuously adjustable equivalent resistance.

[0007] This application discloses a precision equivalent resistance generation system based on duty cycle modulation, which includes a main circuit and an auxiliary circuit. The main circuit includes a test power supply, a low-pass filter, a high-speed electronic switch, a high-precision standard reference resistor, and a current acquisition module connected in sequence. The auxiliary circuit includes an analog-to-digital converter (ADC), a digital controller, and a digital pulse sequence generation unit connected in sequence. The digital pulse sequence generation unit is connected to the high-speed electronic switch. The ADC is connected to the current acquisition module. The current acquisition module is connected to the test power supply.

[0008] Furthermore, the test power supply is used to provide operating power to various components of the system; A low-pass filter is used to filter out high-frequency ripples generated by high-speed electronic switching operations, and to extract the time-averaged voltage signal V_avg and time-averaged current signal I_avg from the main circuit port. These two signals are collectively referred to as the time-averaged electrical signal. Simultaneously, the pulse sequence output from the digital pulse sequence generation unit is smoothed to output a pure DC voltage V_avg proportional to the average voltage drop across the equivalent resistance. V_avg is used to establish the time-averaged voltage-current relationship at the main circuit port, ensuring that the average current flowing through the main circuit and the port voltage satisfy Ohm's law, thereby achieving the electrical characteristics of the equivalent resistance R_eq in a time-averaged sense. The high-speed electronic switch is controlled by the digital pulse sequence, and its on or off state is used to control the high-precision standard reference resistor R_ref to selectively connect to or disconnect from the main circuit. The high-precision standard reference resistor R_ref is used as a reference for the resistance value of the system's equivalent resistance. The current acquisition module is used to acquire the load current signal flowing through the high-precision standard reference resistor; The analog-to-digital converter (ADC) module is used to convert the acquired analog load current signal into a digital signal and transmit it to the digital controller. The digital controller receives the user-defined target equivalent resistance value R_target and the load current digital signal output by the analog-to-digital converter module, converting the load current digital signal into a sampled current value I_meas. It calculates the ideal duty cycle D_ideal = R_ref / R_target based on the target equivalent resistance value R_target and the high-precision standard reference resistance value R_ref. During system operation, it calculates the duty cycle compensation ΔD based on the deviation between the sampled current I_meas and the theoretical current corresponding to the ideal duty cycle D_ideal, where ΔD = K·(I_meas) I_ref); where K is the proportional correction coefficient, and I_ref is the theoretical current value corresponding to the ideal duty cycle D_ideal calculated based on the target equivalent resistance value R_target and the system operating conditions; the duty cycle compensation amount ΔD is superimposed with the ideal duty cycle D_ideal to obtain the duty cycle control signal D_ctrl=D_ideal+ΔD, and the duty cycle control signal D_ctrl is output to the digital pulse sequence generation unit; The digital pulse sequence generation unit is used to generate a digital pulse sequence with a corresponding duty cycle based on the duty cycle control signal D_ctrl, where 0 <D_ctrl≤1。

[0009] Furthermore, under the condition that the switching frequency of the high-speed electronic switch is greater than the target signal frequency and the cutoff frequency of the low-pass filter is less than the switching frequency, the system makes the main circuit port exhibit equivalent resistance characteristics in the time-averaged sense, satisfying R_eq=R_ref / D_ctrl, where R_eq is the equivalent resistance of the main circuit port.

[0010] Furthermore, the digital pulse sequence generation unit is an MCU or FPGA based on Σ-Δ modulation, and its output terminal is connected to the control terminal of the high-speed electronic switch to generate a pulse density modulation sequence with adjustable duty cycle to control the on and off of the high-speed electronic switch. The high-speed electronic switch is a MOSFET or CMOS analog switch, and the source and drain of the high-speed electronic switch are connected to the low-pass filter and the high-precision standard reference resistor, respectively.

[0011] Furthermore, the low-pass filter is an active filter, a passive RC filter, or a switched capacitor filter; the active filter is a Sallen-Key filter or a multi-feedback filter. The cutoff frequency of the low-pass filter is higher than the frequency bandwidth of the target voltage or target current signal at the main circuit port, but lower than the switching frequency of the digital pulse sequence.

[0012] Furthermore, the digital controller includes a calibration and compensation module, which includes a calibration control unit, an error signal sampling circuit, an error parameter calculation unit, a software compensation unit, and a non-volatile memory, and acquires calibration signals through the current acquisition module and the analog-to-digital conversion module; The calibration and compensation module is used to acquire the error parameters of the high-speed electronic switch when the system enters calibration mode and stores the error parameters in non-volatile memory; in system operation mode, the error parameters are called to correct the ideal duty cycle; in calibration mode, the calibration control unit controls the high-speed electronic switch to be continuously turned on, so that a preset calibration current flows through the high-speed electronic switch to acquire voltage and current signals for calculating error parameters; the error signal sampling circuit collects the voltage signal across the high-speed electronic switch and the transient voltage offset at the input of the low-pass filter, converts them into digital signals by the analog-to-digital converter module, and then inputs them to the error parameter calculation unit for error parameter calculation. The unit calculates the on-resistance parameter R_on based on the voltage signal and the preset calibration current, and establishes a duty cycle correction relationship in conjunction with the transient voltage offset ΔV_sw, thereby obtaining the duty cycle calibration compensation amount ΔD_cal. The software compensation unit corrects the ideal duty cycle based on the duty cycle compensation amount ΔD, obtaining the duty cycle control signal D_ctrl=D_ideal+ΔD, wherein the duty cycle compensation amount ΔD includes the calibration compensation amount ΔD_cal and the closed-loop compensation amount ΔD_fb. The error parameters obtained from the calibration are stored in a non-volatile memory and are called during system operation to generate the duty cycle control signal D_ctrl, thereby improving the accuracy of the system's equivalent resistance.

[0013] Furthermore, the system also includes a multi-range extension module, which includes multiple high-precision standard reference resistors with different resistance values ​​and high-speed electronic switches connected in series with each high-precision standard reference resistor. The digital controller selects the corresponding high-precision standard reference resistor to connect to the main circuit according to the resistance range in which the target equivalent resistance value is located, and calculates the corresponding duty cycle according to the resistance value of the selected high-precision standard reference resistor, so as to realize the wide-range continuous adjustment of the system's equivalent resistance.

[0014] This application also discloses a method for generating a precision equivalent resistance based on duty cycle modulation, applicable to the aforementioned precision equivalent resistance generation system based on duty cycle modulation, comprising: Step 1: Set the target equivalent resistance value R_target of the system, where the resistance value of the high-precision standard reference resistor is R_ref. Calculate the ideal duty cycle D_ideal according to the formula D_ideal = R_ref / R_target, where 0 <D_ideal≤1; Step 2: The digital controller calculates the duty cycle control signal D_ctrl = D_ideal + ΔD based on the ideal duty cycle D_ideal and the duty cycle compensation amount ΔD obtained by the system compensation mechanism. The duty cycle compensation amount ΔD includes the calibration compensation amount ΔD_cal and the closed-loop compensation amount ΔD_fb. The digital pulse sequence corresponding to the duty cycle control signal D_ctrl is generated by the digital pulse sequence generation unit. Step 3: The high-speed electronic switch controls the high-precision standard reference resistor to be connected to or disconnected from the main circuit according to the high and low levels of the digital pulse sequence. When the level is high, the high-precision standard reference resistor R_ref is connected to the circuit; when the level is low, the high-precision standard reference resistor R_ref is disconnected from the circuit. Step 4: Smooth the pulse signal generated by the high-speed electronic switch using a low-pass filter to obtain the time-averaged voltage and time-averaged current signals of the main circuit port. Establish the voltage-current relationship of the main circuit port through the time-averaged voltage V_avg and time-averaged current I_avg in the time-averaged electrical signals, so that it satisfies: R_eq=V_avg / I_avg=R_ref / D_ctrl.

[0015] Furthermore, in step 2, the digital pulse sequence generation unit generates a pulse density modulation (PDM) sequence based on Σ-Δ modulation, which serves as the digital pulse sequence to drive the high-speed electronic switch. The calibration and compensation module in the digital controller acquires the on-resistance parameter R_on of the high-speed electronic switch and the transient voltage offset ΔV_sw generated at the moment of switch switching in calibration mode. Based on the error parameters, a duty cycle calibration compensation amount ΔD_cal is established, and combined with the closed-loop compensation amount ΔD_fb obtained by closed-loop optimization calculation, the duty cycle compensation amount ΔD = ΔD_cal + ΔD_fb is obtained. The ideal duty cycle is corrected to obtain the corrected duty cycle, thereby compensating for the influence of non-ideal factors on the equivalent resistance of the system and improving the accuracy of the equivalent resistance. Non-ideal factors include the on-resistance of the high-speed electronic switch and charge injection. Before step 2, a calibration compensation step and a closed-loop optimization calculation step are also included; the calibration compensation step includes: In calibration mode, error parameters of the high-speed electronic switch are acquired, and the duty cycle calibration compensation amount ΔD_cal is calculated. The closed-loop optimization calculation step is performed after the calibration compensation step. The analog signal of the main circuit load current is acquired through the current acquisition module, converted into a digital current value I_meas by the analog-to-digital conversion module, and transmitted to the digital controller. The digital controller calculates the ideal duty cycle D_ideal based on the target equivalent resistance value R_target, and calculates the actual deviation of the equivalent resistance based on the sampled current I_meas, generating the duty cycle closed-loop compensation amount ΔD_fb, where ΔD_fb is obtained by linear correction, piecewise compensation, or lookup table mapping. The digital controller superimposes the ideal duty cycle D_ideal, the calibration compensation amount ΔD_cal, and the closed-loop compensation amount ΔD_fb to obtain the duty cycle compensation amount ΔD=ΔD_cal+ΔD_fb, and accordingly obtains the duty cycle control signal D_ctrl=D_ideal+ΔD. The duty cycle control signal D_ctrl is used to drive the digital pulse sequence generation unit to generate a pulse sequence with the corresponding duty cycle.

[0016] Furthermore, if the system includes multiple high-precision standard reference resistors with different resistance values ​​and corresponding high-speed electronic switches, when it is necessary to expand the resistance range of the system's equivalent resistance, the digital controller selects the corresponding high-precision standard reference resistor as the current reference resistor according to the resistance range where the target equivalent resistance value R_target is located; and recalculates the ideal duty cycle D_ideal,i=R_ref_i / R_target based on the resistance value of the selected high-precision standard reference resistor; then, combined with the corresponding calibration compensation amount ΔD_cal,i and closed-loop compensation amount ΔD_fb, the duty cycle control signal D_ctrl,i=D_ideal,i+ΔD_cal,i+ΔD_fb is calculated; and the corresponding high-speed electronic switch is controlled to turn on and off according to the duty cycle control signal D_ctrl,i, thereby realizing the continuous adjustment of the system's equivalent resistance in multiple resistance ranges.

[0017] Due to the adoption of the above technical solution, this application has the following advantages: 1. This application proposes a technical solution that uses a digital controller to calculate the duty cycle and generate a pulse sequence to drive a high-speed electronic switch so that a high-precision standard reference resistor is connected to the main circuit according to a set time ratio. Under the action of low-pass filtering, the main circuit exhibits equivalent resistance characteristics in the time-averaged sense. At the same time, non-ideal factors such as switch on-resistance and charge injection are corrected through current sampling and error compensation mechanisms, thereby achieving high-precision, high-resolution and wide-range adjustable equivalent resistance output.

[0018] 2. Ultra-high resolution and continuity: The adjustment step size of the equivalent resistance value is only limited by the word length of the digital controller (such as 24-bit or 32-bit), which can achieve sub-ppm level resolution and truly continuous stepless adjustment, overcoming the discreteness of the resistance box.

[0019] 3. High absolute accuracy and low temperature drift: The absolute accuracy and temperature coefficient of the system depend almost entirely on a single high-precision standard reference resistor. Ultra-high precision (±0.001%) and ultra-low temperature drift resistors, such as foil resistors, can be selected. Using resistive elements, high overall system performance can be achieved at a lower cost, which is unmatched by digital potentiometers.

[0020] 4. Simple structure and controllable cost: The entire system requires only one ultra-high precision resistor, several general-purpose switches, filtering and control circuits. Compared with a precision multi-stage resistor box that achieves the same performance, the number of precision resistors required is greatly reduced, and the system structure and cost are optimized.

[0021] 5. Fully electronic and highly reliable: There are no mechanical moving parts, and the adjustment is completed electronically. It has a long life, high reliability, and is easy to achieve remote program control and automation integration.

[0022] 6. High flexibility: Complex functions such as nonlinear correction and temperature compensation can be easily implemented through software, and different R_refs can be quickly switched to change the range. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in the embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings.

[0024] Figure 1 This is a block diagram of a precision equivalent resistance generation system based on duty cycle modulation, according to an embodiment of this application. Figure 2 This is a schematic flowchart of a precision equivalent resistance generation method based on duty cycle modulation according to an embodiment of this application. Detailed Implementation

[0025] The present application will be further described in conjunction with the accompanying drawings and embodiments. The described embodiments are only some, not all, of the embodiments of the present application. All other embodiments obtained by those skilled in the art should fall within the protection scope of the embodiments of the present application.

[0026] See Figure 1This application provides an embodiment of a precision equivalent resistance generation system based on duty cycle modulation, which includes a main circuit and an auxiliary circuit. The main circuit includes a test power supply, a low-pass filter, a high-speed electronic switch, a high-precision standard reference resistor, and a current acquisition module connected in sequence. The auxiliary circuit includes an analog-to-digital converter (ADC), a digital controller, and a digital pulse sequence generation unit connected in sequence. The digital pulse sequence generation unit is connected to the high-speed electronic switch. The ADC is connected to the current acquisition module. The current acquisition module is connected to the test power supply.

[0027] The main circuit in this application is used to form an equivalent resistance characteristic and can be connected to external measurement circuits, sensor simulation circuits, or automated test circuits, including but not limited to measurement circuits, sensor simulation circuits, automated test circuits, instrument calibration circuits, or other circuit structures that require adjustable resistance. This application does not limit the specific structure of the main circuit.

[0028] This application utilizes a high-speed electronic switch to control the duty cycle of a high-precision, low-temperature drift standard reference resistor connected to the main circuit, and extracts its average effect through a low-pass filter at the input end of the circuit (usually a high-input-impedance acquisition circuit), so that the main circuit port exhibits an equivalent resistance with continuously adjustable resistance in electrical characteristics.

[0029] Optionally, the test power supply is used to provide operating power to various components of the system; A low-pass filter (LPF) is used to filter out high-frequency ripples generated by high-speed electronic switching operations, and to extract the time-averaged voltage signal V_avg and the time-averaged current signal I_avg from the main circuit port. These two signals are collectively referred to as the time-averaged electrical signal. Simultaneously, the pulse sequence output from the digital pulse sequence generation unit is smoothed to output a pure DC voltage V_avg proportional to the average voltage drop across the equivalent resistance. V_avg is used to establish the time-averaged voltage-current relationship at the main circuit port, ensuring that the average current flowing through the main circuit and the port voltage satisfy Ohm's law, thereby achieving the electrical characteristics of the equivalent resistance R_eq in a time-averaged sense. The high-speed electronic switch S1 is controlled by the digital pulse sequence, and its on or off state is used to control the high-precision standard reference resistor to selectively connect to or disconnect from the main circuit. The high-precision standard reference resistor is used as a reference for the resistance value of the system's equivalent resistance. The current acquisition module is used to acquire the load current signal flowing through the high-precision standard reference resistor; The analog-to-digital converter (ADC) module is used to convert the acquired analog load current signal into a digital signal and transmit it to the digital controller. The digital controller receives the user-defined target equivalent resistance value R_target and the load current digital signal output by the analog-to-digital converter module, converting the load current digital signal into a sampled current value I_meas. It calculates the ideal duty cycle D_ideal = R_ref / R_target based on the target equivalent resistance value R_target and the high-precision standard reference resistance value R_ref. During system operation, it calculates the duty cycle compensation ΔD based on the deviation between the sampled current I_meas and the theoretical current corresponding to the ideal duty cycle D_ideal, where ΔD = K·(I_meas) I_ref); where K is the proportional correction coefficient, and I_ref is the theoretical current value corresponding to the ideal duty cycle D_ideal calculated based on the target equivalent resistance value R_target and the system operating conditions; the duty cycle compensation amount ΔD is superimposed with the ideal duty cycle D_ideal to obtain the duty cycle control signal D_ctrl=D_ideal+ΔD, and the duty cycle control signal D_ctrl is output to the digital pulse sequence generation unit; The digital pulse sequence generation unit is used to generate a digital pulse sequence with a corresponding duty cycle based on the duty cycle control signal D_ctrl, where 0 <D_ctrl≤1。

[0030] Optionally, under the condition that the switching frequency of the high-speed electronic switch is greater than the target signal frequency and the cutoff frequency of the low-pass filter is less than the switching frequency, the system makes the main circuit port exhibit equivalent resistance characteristics in the time-averaged sense, satisfying R_eq=R_ref / D_ctrl, where R_eq is the equivalent resistance of the main circuit port.

[0031] Optionally, the digital pulse sequence generation unit is an MCU or FPGA based on Σ-Δ modulation, and its output terminal is connected to the control terminal of the high-speed electronic switch to generate a pulse density modulation sequence with adjustable duty cycle to control the on and off of the high-speed electronic switch. The high-speed electronic switch is a MOSFET or CMOS analog switch, and the source and drain of the high-speed electronic switch are connected to the low-pass filter and the high-precision standard reference resistor, respectively.

[0032] Optionally, the low-pass filter is an active filter, a passive RC filter, or a switched capacitor filter; the active filter is a Sallen-Key filter or a multi-feedback filter. The cutoff frequency of the low-pass filter is higher than the frequency bandwidth of the target voltage or target current signal at the main circuit port, but lower than the switching frequency of the digital pulse sequence.

[0033] Optionally, the digital controller includes a calibration and compensation module, which includes a calibration control unit, an error signal sampling circuit, an error parameter calculation unit, a software compensation unit, and a non-volatile memory, and acquires calibration signals through the current acquisition module and the analog-to-digital conversion module. The calibration and compensation module is used to acquire the error parameters of the high-speed electronic switch when the system enters calibration mode and stores the error parameters in non-volatile memory; in system operation mode, the error parameters are called to correct the ideal duty cycle; in calibration mode, the calibration control unit controls the high-speed electronic switch to be continuously turned on, so that a preset calibration current flows through the high-speed electronic switch to acquire voltage and current signals for calculating error parameters; the error signal sampling circuit collects the voltage signal across the high-speed electronic switch and the transient voltage offset at the input of the low-pass filter, converts them into digital signals by the analog-to-digital converter module, and then inputs them to the error parameter calculation unit for error parameter calculation. The unit calculates the on-resistance parameter R_on based on the voltage signal and the preset calibration current, and establishes a duty cycle correction relationship in conjunction with the transient voltage offset ΔV_sw, thereby obtaining the duty cycle calibration compensation amount ΔD_cal. The software compensation unit corrects the ideal duty cycle based on the duty cycle compensation amount ΔD, obtaining the duty cycle control signal D_ctrl=D_ideal+ΔD, wherein the duty cycle compensation amount ΔD includes the calibration compensation amount ΔD_cal and the closed-loop compensation amount ΔD_fb. The error parameters obtained from the calibration are stored in a non-volatile memory and are called during system operation to generate the duty cycle control signal D_ctrl, thereby improving the accuracy of the system's equivalent resistance.

[0034] Optionally, the system further includes a multi-range extension module, which includes multiple high-precision standard reference resistors with different resistance values ​​and high-speed electronic switches connected in series with each high-precision standard reference resistor. The digital controller selects the corresponding high-precision standard reference resistor to connect to the main circuit according to the resistance range in which the target equivalent resistance value is located, and calculates the corresponding duty cycle according to the resistance value of the selected high-precision standard reference resistor, so as to realize the wide-range continuous adjustment of the system's equivalent resistance.

[0035] See Figure 2 This application also provides an embodiment of a precision equivalent resistance generation method based on duty cycle modulation, applicable to the precision equivalent resistance generation system based on duty cycle modulation described in the above embodiments, comprising: Step 1: Set the target equivalent resistance value R_target of the system, where the resistance value of the high-precision standard reference resistor is R_ref. Calculate the ideal duty cycle D_ideal according to the formula D_ideal = R_ref / R_target, where 0 <D_ideal≤1; Step 2: The digital controller calculates the duty cycle control signal D_ctrl = D_ideal + ΔD based on the ideal duty cycle D_ideal and the duty cycle compensation amount ΔD obtained by the system compensation mechanism. The duty cycle compensation amount ΔD includes the calibration compensation amount ΔD_cal and the closed-loop compensation amount ΔD_fb. The digital pulse sequence corresponding to the duty cycle control signal D_ctrl is generated by the digital pulse sequence generation unit. Step 3: The high-speed electronic switch controls the high-precision standard reference resistor to be connected to or disconnected from the main circuit according to the high and low levels of the digital pulse sequence. When the level is high, the circuit is turned on and the high-precision standard reference resistor is connected to the circuit. When the level is low, the circuit is turned off and the high-precision standard reference resistor is disconnected from the circuit. Step 4: Smooth the pulse signal generated by the high-speed electronic switch using a low-pass filter to obtain the time-averaged voltage and time-averaged current signals of the main circuit port. Establish the voltage-current relationship of the main circuit port through the time-averaged voltage V_avg and time-averaged current I_avg in the time-averaged electrical signals, so that it satisfies: R_eq=V_avg / I_avg=R_ref / D_ctrl.

[0036] Optionally, in step 2, the digital pulse sequence generation unit generates a pulse density modulation (PDM) sequence based on Σ-Δ modulation, which serves as the digital pulse sequence for driving the high-speed electronic switch. The calibration and compensation module in the digital controller acquires the on-resistance parameter R_on of the high-speed electronic switch and the transient voltage offset ΔV_sw generated at the moment of switch switching in calibration mode. Based on the error parameters, a duty cycle calibration compensation amount ΔD_cal is established, and combined with the closed-loop compensation amount ΔD_fb obtained by closed-loop optimization calculation, the duty cycle compensation amount ΔD = ΔD_cal + ΔD_fb is obtained. The ideal duty cycle is corrected to obtain the corrected duty cycle, thereby compensating for the influence of non-ideal factors on the equivalent resistance of the system and improving the accuracy of the equivalent resistance (R_eq). Non-ideal factors include the on-resistance of the high-speed electronic switch and charge injection. Before step 2, a calibration compensation step and a closed-loop optimization calculation step are also included; the calibration compensation step includes: In calibration mode, error parameters of the high-speed electronic switch are acquired, and the duty cycle calibration compensation amount ΔD_cal is calculated. The closed-loop optimization calculation step is performed after the calibration compensation step. The analog signal of the main circuit load current is acquired through the current acquisition module, converted into a digital current value I_meas by the analog-to-digital conversion module, and transmitted to the digital controller. The digital controller calculates the ideal duty cycle D_ideal based on the target equivalent resistance value R_target, and calculates the actual deviation of the equivalent resistance based on the sampled current I_meas, generating the duty cycle closed-loop compensation amount ΔD_fb, where ΔD_fb is obtained by linear correction, piecewise compensation, or lookup table mapping. The digital controller superimposes the ideal duty cycle D_ideal, the calibration compensation amount ΔD_cal, and the closed-loop compensation amount ΔD_fb to obtain the duty cycle compensation amount ΔD=ΔD_cal+ΔD_fb, and accordingly obtains the duty cycle control signal D_ctrl=D_ideal+ΔD. The duty cycle control signal D_ctrl is used to drive the digital pulse sequence generation unit to generate a pulse sequence with the corresponding duty cycle.

[0037] Optionally, if the system includes multiple high-precision standard reference resistors with different resistance values ​​and corresponding high-speed electronic switches, when it is necessary to expand the resistance range of the system's equivalent resistance, the digital controller selects the corresponding high-precision standard reference resistor as the current reference resistor according to the resistance range where the target equivalent resistance value R_target is located; and recalculates the ideal duty cycle D_ideal,i=R_ref_i / R_target based on the resistance value of the selected high-precision standard reference resistor; then, combined with the corresponding calibration compensation amount ΔD_cal,i and closed-loop compensation amount ΔD_fb, the duty cycle control signal D_ctrl,i=D_ideal,i+ΔD_cal,i+ΔD_fb is calculated; and the corresponding high-speed electronic switch is controlled to turn on and off according to the duty cycle control signal D_ctrl,i, thereby realizing the continuous adjustment of the system's equivalent resistance in multiple resistance ranges.

[0038] This application provides an equivalent resistor with continuous, stepless, and high-resolution adjustable resistance. This equivalent resistor has extremely high absolute accuracy and excellent temperature stability. Its core performance is mainly determined by a single high-stability standard resistor. The implementation scheme has relatively low cost, simple structure, high reliability, and is easy to program and integrate. It can accurately simulate the characteristics of real passive resistors under DC or low frequency conditions.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and not to limit them. Although this application has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of this application. Any modifications or equivalent substitutions that do not depart from the spirit and scope of this application should be covered within the protection scope of the claims of this application.

Claims

1. A precision equivalent resistance generation system based on duty cycle modulation, characterized in that, It includes a main circuit and an auxiliary circuit; the main circuit includes a test power supply, a low-pass filter, a high-speed electronic switch, a high-precision standard reference resistor, and a current acquisition module connected in sequence; the auxiliary circuit includes an analog-to-digital converter (ADC), a digital controller, and a digital pulse sequence generation unit connected in sequence; the digital pulse sequence generation unit is connected to the high-speed electronic switch; The analog-to-digital converter (ADC) module is connected to the current acquisition module; the current acquisition module is connected to the test power supply.

2. The system according to claim 1, characterized in that, The test power supply is used to provide operating power to various components of the system; A low-pass filter is used to filter out high-frequency ripples generated by high-speed electronic switching operations, and to extract the time-averaged voltage signal V_avg and time-averaged current signal I_avg from the main circuit port. These two signals are collectively referred to as the time-averaged electrical signal. Simultaneously, the pulse sequence output from the digital pulse sequence generation unit is smoothed to output a pure DC voltage V_avg proportional to the average voltage drop across the equivalent resistance. V_avg is used to establish the time-averaged voltage-current relationship at the main circuit port, ensuring that the average current flowing through the main circuit and the port voltage satisfy Ohm's law, thereby achieving the electrical characteristics of the equivalent resistance R_eq in a time-averaged sense. The high-speed electronic switch is controlled by the digital pulse sequence, and its on or off state is used to control the high-precision standard reference resistor R_ref to selectively connect to or disconnect from the main circuit. The high-precision standard reference resistor R_ref is used as a reference for the resistance value of the system's equivalent resistance. The current acquisition module is used to acquire the load current signal flowing through the high-precision standard reference resistor; The analog-to-digital converter (ADC) module is used to convert the acquired analog load current signal into a digital signal and transmit it to the digital controller. The digital controller is used to receive the target equivalent resistance value R_target set by the user and the load current digital signal output by the analog-to-digital conversion module, and convert the load current digital signal into a sampled current value I_meas; and calculate the ideal duty cycle D_ideal=R_ref / R_target based on the target equivalent resistance value R_target and the high-precision standard reference resistance value R_ref. During system operation, the duty cycle compensation ΔD is calculated based on the deviation between the sampled current I_meas and the theoretical current corresponding to the ideal duty cycle D_ideal, where ΔD = K·(I_meas) I_ref); where K is the proportional correction coefficient, and I_ref is the theoretical current value corresponding to the ideal duty cycle D_ideal condition calculated based on the target equivalent resistance value R_target and the system operating conditions. The duty cycle compensation amount ΔD is superimposed with the ideal duty cycle D_ideal to obtain the duty cycle control signal D_ctrl=D_ideal+ΔD, and the duty cycle control signal D_ctrl is output to the digital pulse sequence generation unit. The digital pulse sequence generation unit is used to generate a digital pulse sequence with a corresponding duty cycle based on the duty cycle control signal D_ctrl, where 0 <D_ctrl≤1。 3. The system according to claim 2, characterized in that, Under the condition that the switching frequency of the high-speed electronic switch is greater than the target signal frequency and the cutoff frequency of the low-pass filter is less than the switching frequency, the system makes the main circuit port present an equivalent resistance in the time-averaged sense, satisfying R_eq=R_ref / D_ctrl, where R_eq is the equivalent resistance of the main circuit port.

4. The system according to claim 1, characterized in that, The digital pulse sequence generation unit is an MCU or FPGA based on Σ-Δ modulation. Its output terminal is connected to the control terminal of the high-speed electronic switch and is used to generate a pulse density modulation sequence with adjustable duty cycle to control the on and off of the high-speed electronic switch. The high-speed electronic switch is a MOSFET or CMOS analog switch, and the source and drain of the high-speed electronic switch are connected to the low-pass filter and the high-precision standard reference resistor, respectively.

5. The system according to claim 1, characterized in that, The low-pass filter is an active filter, a passive RC filter, or a switched capacitor filter; the active filter is a Sallen-Key filter or a multi-feedback filter. The cutoff frequency of the low-pass filter is higher than the frequency bandwidth of the target voltage or target current signal at the main circuit port, but lower than the switching frequency of the digital pulse sequence.

6. The system according to claim 1, characterized in that, The digital controller also includes a calibration and compensation module, which includes a calibration control unit, an error signal sampling circuit, an error parameter calculation unit, a software compensation unit, and a non-volatile memory, and acquires calibration signals through the current acquisition module and the analog-to-digital conversion module. The calibration and compensation module is used to acquire the error parameters of the high-speed electronic switch when the system enters the calibration mode, and store the error parameters in a non-volatile memory; In system operation mode, the error parameters are invoked to correct the ideal duty cycle; In the calibration mode, the calibration control unit controls the high-speed electronic switch to remain continuously on, allowing a preset calibration current to flow through the high-speed electronic switch to obtain voltage and current signals for calculating error parameters. The error signal sampling circuit acquires the voltage signal across the high-speed electronic switch and the transient voltage offset at the input of the low-pass filter, converts it into a digital signal via the analog-to-digital converter, and inputs it to the error parameter calculation unit. The error parameter calculation unit calculates the on-resistance parameter R_on based on the voltage signal and the preset calibration current, and establishes a duty cycle correction relationship based on the transient voltage offset ΔV_sw, thereby obtaining the duty cycle calibration compensation amount ΔD_cal. The software compensation unit corrects the ideal duty cycle based on the duty cycle compensation amount ΔD, obtaining the duty cycle control signal D_ctrl = D_ideal + ΔD, where the duty cycle compensation amount ΔD includes the calibration compensation amount ΔD_cal and the closed-loop compensation amount ΔD_fb. The error parameters obtained from the calibration are stored in a non-volatile memory and are called during system operation to generate the duty cycle control signal D_ctrl, thereby improving the accuracy of the system's equivalent resistance.

7. The system according to claim 1, characterized in that, The system also includes a multi-range extension module, which includes multiple high-precision standard reference resistors with different resistance values ​​and high-speed electronic switches connected in series with each high-precision standard reference resistor. The digital controller selects the corresponding high-precision standard reference resistor to connect to the main circuit according to the resistance range in which the target equivalent resistance value is located, and calculates the corresponding duty cycle according to the resistance value of the selected high-precision standard reference resistor, so as to realize the wide-range continuous adjustment of the system's equivalent resistance.

8. A method for generating a precision equivalent resistance based on duty cycle modulation, applicable to the precision equivalent resistance generation system based on duty cycle modulation as described in any one of claims 1-7, characterized in that, include: Step 1: Set the target equivalent resistance value R_target of the system, where the resistance value of the high-precision standard reference resistor is R_ref. Calculate the ideal duty cycle D_ideal according to the formula D_ideal = R_ref / R_target, where 0 <D_ideal≤1; Step 2: The digital controller calculates the duty cycle control signal D_ctrl = D_ideal + ΔD based on the ideal duty cycle D_ideal and the duty cycle compensation amount ΔD obtained by the system compensation mechanism. The duty cycle compensation amount ΔD includes the calibration compensation amount ΔD_cal and the closed-loop compensation amount ΔD_fb. The digital pulse sequence corresponding to the duty cycle control signal D_ctrl is generated by the digital pulse sequence generation unit. Step 3: The high-speed electronic switch controls the high-precision standard reference resistor to be connected to or disconnected from the main circuit according to the high and low levels of the digital pulse sequence. When the level is high, the high-precision standard reference resistor R_ref is connected to the circuit; when the level is low, the high-precision standard reference resistor R_ref is disconnected from the circuit. Step 4: Smooth the pulse signal generated by the high-speed electronic switch using a low-pass filter to obtain the time-averaged voltage and time-averaged current signals of the main circuit port. Establish the voltage-current relationship of the main circuit port through the time-averaged voltage V_avg and time-averaged current I_avg in the time-averaged electrical signals, so that it satisfies: R_eq=V_avg / I_avg=R_ref / D_ctrl.

9. The method according to claim 8, characterized in that, In step 2, the digital pulse sequence generation unit generates a pulse density modulation (PDM) sequence based on Σ-Δ modulation, which serves as the digital pulse sequence to drive the high-speed electronic switch. The calibration and compensation module in the digital controller acquires the on-resistance parameter R_on of the high-speed electronic switch and the transient voltage offset ΔV_sw generated at the moment of switch switching in calibration mode. Based on the error parameters, a duty cycle calibration compensation amount ΔD_cal is established, and combined with the closed-loop compensation amount ΔD_fb obtained by closed-loop optimization calculation, the duty cycle compensation amount ΔD = ΔD_cal + ΔD_fb is obtained. The ideal duty cycle is corrected to obtain the corrected duty cycle, thereby compensating for the influence of non-ideal factors on the equivalent resistance of the system and improving the accuracy of the equivalent resistance. Non-ideal factors include the on-resistance of the high-speed electronic switch and charge injection. Before step 2, a calibration compensation step and a closed-loop optimization calculation step are also included; the calibration compensation step includes: In calibration mode, error parameters of the high-speed electronic switch are acquired, and the duty cycle calibration compensation amount ΔD_cal is calculated. The closed-loop optimization calculation step is performed after the calibration compensation step. The analog signal of the main circuit load current is acquired through the current acquisition module, converted into a digital current value I_meas by the analog-to-digital conversion module, and transmitted to the digital controller. The digital controller calculates the ideal duty cycle D_ideal based on the target equivalent resistance value R_target, and calculates the actual deviation of the equivalent resistance based on the sampled current I_meas, generating the duty cycle closed-loop compensation amount ΔD_fb, where ΔD_fb is obtained by linear correction, piecewise compensation, or lookup table mapping. The digital controller superimposes the ideal duty cycle D_ideal, the calibration compensation amount ΔD_cal, and the closed-loop compensation amount ΔD_fb to obtain the duty cycle compensation amount ΔD=ΔD_cal+ΔD_fb, and accordingly obtains the duty cycle control signal D_ctrl=D_ideal+ΔD. The duty cycle control signal D_ctrl is used to drive the digital pulse sequence generation unit to generate a pulse sequence with the corresponding duty cycle.

10. The method according to claim 8, characterized in that, If the system includes multiple high-precision standard reference resistors with different resistance values ​​and corresponding high-speed electronic switches, when it is necessary to expand the resistance value range of the system's equivalent resistance, the digital controller selects the corresponding high-precision standard reference resistor as the current reference resistor according to the resistance value range where the target equivalent resistance value R_target is located. The ideal duty cycle D_ideal,i = R_ref_i / R_target is recalculated based on the resistance value of the selected high-precision standard reference resistor. Then, the duty cycle control signal D_ctrl,i = D_ideal,i + ΔD_cal,i + ΔD_fb is calculated by combining the corresponding calibration compensation amount ΔD_cal,i and closed-loop compensation amount ΔD_fb. The corresponding high-speed electronic switch is turned on and off according to the duty cycle control signal D_ctrl,i, thereby realizing the continuous adjustment of the system's equivalent resistance in multiple resistance ranges.

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