A seamless switching method for VI source voltage range

Abstract

This invention belongs to the field of electronic measurement and control technology, specifically a seamless switching method for VI source voltage ranges. The system includes: a digital controller, a digital-to-analog converter, a programmable gain amplifier, an isolating switch module, a voltage holding and buffer module, a power amplifier, and a feedback measurement network. The digital controller is configured to receive range switching commands, manage the operating state of the VI source, perform digital closed-loop voltage regulation, and coordinate the actions of all hardware components during the range switching process. The digital controller integrates a digital voltage reference generation module, a range switching control logic module, a loop regulation module, and a high-precision clock synchronization unit. This application enables seamless output voltage switching, significantly improves testing efficiency, enhances protection for the device under test, and improves data continuity and accuracy.

Description

Technical Field

[0001] This invention belongs to the field of electronic measurement and control technology, specifically a seamless switching method for VI source voltage range. Background Technology

[0002] VI sources are core equipment in fields such as automated testing, instrumentation, scientific research and development, and semiconductor device characteristic analysis. They possess four-quadrant operation capabilities, accurately applying voltage or current to the device under test (DUT) and simultaneously measuring the device's voltage and current response under specific stimuli. This allows for the evaluation of key electrical parameters of electronic components, such as IV curves, CV characteristics, and power efficiency. In voltage source operation mode, VI sources are typically configured with multiple voltage ranges, each corresponding to a specific voltage range, output resolution, and accuracy, to adapt to the refined voltage and measurement accuracy requirements of different testing scenarios. Therefore, frequent switching of voltage ranges according to test cases has become a common practice for users.

[0003] In existing technologies, to ensure the safety and reliability of voltage range switching, a common process is "voltage zeroing-range switching-voltage reapplication": before switching, the voltage applied to the device under test (DUT) is gradually or instantaneously zeroed, then the range switching is performed (involving dynamic hardware adjustments such as gain amplifier gain adjustment, output path switching, and filter and compensation network reconstruction), and finally, the voltage is reapplication. The core purpose of this process is to avoid transient effects during hardware switching. If the range is switched directly, transient transitions in hardware components can easily generate voltage glitches, instantaneous fluctuations, or continuous oscillations, which may lead to distorted test data or even irreversible damage to sensitive DUTs. Therefore, the "zeroing-switching-reapplication" strategy ensures the safety of the DUT to a certain extent.

[0004] However, with the development of semiconductor and integrated circuit technology, the requirements for testing efficiency, accuracy, and device protection in the field of automated testing are becoming increasingly stringent, and the limitations of existing solutions are gradually becoming apparent. In high-throughput testing scenarios such as large-scale production lines, the "zeroing-retesting" process for each range switch introduces additional time delays (including voltage ramp time, hardware settling time, etc.). Frequent switching will significantly extend the test cycle, reduce testing efficiency and production line throughput, and increase enterprise operating costs. At the same time, for dynamic testing or lifecycle testing of devices such as memory and RF devices that require continuous electrical states, frequent voltage zeroing will disrupt the internal working state of the device, introduce unexpected transient effects, affect the continuity and accuracy of test data, and increase the complexity of test script writing (requiring precise management of voltage ramp and switching timing). Existing solutions have failed to resolve the inherent conflict between hardware switching transient instability and test voltage continuity. Simply circumventing the problem through interruption operations is no longer sufficient to meet current technical requirements. Therefore, this invention provides a seamless switching method for VI source voltage ranges. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, at least one technical problem raised in the background art is solved.

[0006] The technical solution adopted by this invention to solve its technical problem is: a seamless switching method for VI source voltage range, comprising the following core technical solutions:

[0007] A seamless switching system for VI source voltage ranges is provided for smooth and transient-free switching between different voltage ranges. The system includes: a digital controller, a digital-to-analog converter, a programmable gain amplifier, an isolation switch module, a voltage holding and buffer module, a power amplifier, and a feedback measurement network.

[0008] The digital controller is configured to receive range switching commands, manage the operating status of the VI source, perform digital closed-loop voltage regulation, and coordinate the actions of all hardware components during the range switching process. The digital controller integrates a digital voltage reference generation module, a range switching control logic module, a loop regulation module, and a high-precision clock synchronization unit. The digital controller communicates and exchanges control signals with the digital-to-analog converter, programmable gain amplifier, isolating switch module, voltage holding and buffer module, power amplifier, and feedback measurement network.

[0009] The digital-to-analog converter (DAC) is electrically connected to the digital controller and configured to convert a digital voltage reference signal generated by the digital controller into an analog voltage signal. The DAC has a resolution of at least 16 bits, an offset voltage of less than 100 microvolts, a temperature drift of less than 10 ppm / °C, and a settling time of less than 5 microseconds.

[0010] The programmable gain amplifier (PGA), electrically connected to the digital-to-analog converter (DAC), is configured to receive the analog voltage signal output by the DAC and amplify the analog voltage signal at a programmable gain factor according to the gain control signal provided by the digital controller. The PGA comprises multiple gain stages, each consisting of a precision operational amplifier array and a high-precision resistor network. The transient response of the PGA during gain switching is designed to decay to within 0.1% of its stable value within 10 microseconds. The PGA has a gain-bandwidth product of at least 100 MHz.

[0011] The isolating switch module is electrically connected to the output terminal of the programmable gain amplifier and is configured to switch between an on and off state according to a switch control signal provided by the digital controller, thereby controlling the connection between the output signal of the programmable gain amplifier and the input terminal of the power amplifier. The isolating switch module consists of at least one high-speed, high-isolation, low-on-resistance solid-state analog switch array. The switching time of the solid-state analog switch array is less than 50 nanoseconds, and its isolation in the off state is not less than 90 dB.

[0012] The voltage holding and buffer module is electrically connected to the output of the isolating switch module and the input of the power amplifier. It is configured to actively capture and maintain the voltage applied to the input of the power amplifier when the isolating switch module is in the open state, and to act as a transparent buffer or direct path when the isolating switch module is in the closed state. The voltage holding and buffer module includes a high-precision sample-and-hold circuit and a high-bandwidth voltage follower or buffer amplifier. The holding capacitor of the sample-and-hold circuit is made of a low-leakage dielectric material, with a holding leakage rate of less than 10 pA / s and a holding accuracy better than 0.01% within 100 microseconds. The buffer amplifier has a slew rate of not less than 1 V / µs and an output impedance of less than 10 milliohms.

[0013] The power amplifier is electrically connected to the output of the voltage holding and buffer module, configured to receive the voltage signal from the voltage holding and buffer module and amplify it to drive the device under test. The supply voltage of the power amplifier can be adjusted by the digital controller via a supply voltage control signal. The power amplifier has a bandwidth of not less than 1MHz, a slew rate of not less than 50V / µs, and a power supply rejection ratio (PSRR) of not less than 80dB at a frequency of 1kHz. The power amplifier internally includes a fast-response supply voltage regulation module to ensure that its amplified output of the input signal remains stable when the supply voltage changes.

[0014] The feedback measurement network is electrically connected to the output terminal of the VI source and the digital controller. It is configured to precisely scale down the actual output voltage and current signals of the VI source and convert them into digital signals, which are then fed back to the digital controller. The feedback measurement network includes a high-precision voltage divider resistor network, a current sampling resistor, and an analog-to-digital converter (ADC). The ADC has a resolution of at least 16 bits and a sampling rate of at least 100 ksps.

[0015] The present invention also provides a seamless switching method for VI source voltage ranges, the method being executed on the seamless switching system for the VI source voltage ranges, characterized by comprising the following steps:

[0016] S1: System initialization and establishment of normal operating state

[0017] The digital controller executes a power-on self-test procedure, loads preset operating parameters and calibration data, and initializes the digital-to-analog converter, programmable gain amplifier, isolating switch module, voltage hold and buffer module, and power amplifier to a known safe state. The power supply voltage of the power amplifier is set to a value suitable for the current or default voltage range. The VI source enters normal operating mode, the loop regulation module inside the digital controller is enabled, and a digital reference signal is generated and sent to the digital-to-analog converter according to the currently set voltage range and target voltage value. The digital-to-analog converter converts the digital reference signal into an analog voltage signal. The digital controller configures the gain factor of the programmable gain amplifier through a gain control signal according to the current voltage range. The digital controller puts the isolating switch module in a conducting state through a switch control signal, thereby establishing an electrical connection between the output signal of the programmable gain amplifier and the input terminal of the voltage hold and buffer module. The voltage hold and buffer module acts as a transparent buffer at this stage, and its output is directly connected to the input terminal of the power amplifier. The power amplifier receives the signal from the voltage hold and buffer module, amplifies it, and drives the device under test. The feedback measurement network continuously monitors the actual output voltage and output current of the VI source and feeds back the digitized measurement results to the digital controller. The digital controller performs closed-loop regulation based on the feedback signal to precisely stabilize the output voltage of the VI source at the set target voltage value.

[0018] S2: Range switching command reception and working status freeze

[0019] The digital controller receives a voltage range switching command from a host computer or internal test sequence. The range switching command includes a new target voltage range and a new target voltage value. The range switching control logic module within the digital controller immediately responds to the command and performs the following operations: First, it sends a "pause adjustment" signal to the loop regulation module, causing it to stop the current closed-loop regulation action and maintain the output voltage of the digital-to-analog converter at its current value. This operation ensures that the input voltage supplied to the programmable gain amplifier is stable during the initial phase of range switching.

[0020] Secondly, the current actual output voltage value (denoted as ) is obtained from the feedback measurement network. This value will be used as a reference voltage that needs to be maintained during the switching process.

[0021] S3: Output isolation and voltage holding function activated.

[0022] The digital controller drives the isolating switch module to rapidly switch from an on state to an off state via a switch control signal, thereby completely disconnecting the output of the programmable gain amplifier from the input of the power amplifier electrically. This isolation process is completed within 50 nanoseconds, ensuring that transient fluctuations that may occur inside the programmable gain amplifier due to gain switching cannot propagate to the power amplifier.

[0023] Almost simultaneously with the disconnection of the isolating switch module, the voltage holding and buffer module is activated. Its built-in high-precision sample-and-hold circuit accurately captures and holds the instantaneous voltage applied to the input of the power amplifier before or at the moment the isolating switch module disconnects. This held voltage is stably applied to the input of the power amplifier through the high drive capability and low output impedance characteristics of the voltage holding and buffer module. The power amplifier continues to receive the held voltage from the voltage holding and buffer module and continuously drives the device under test with this voltage, thereby maintaining a stable output voltage on the device under test during the disconnection of the isolating switch module. This effectively suppresses potential voltage drops or rises during switching. The voltage holding and buffering module maintains an accuracy of better than 0.01% within 100 microseconds, ensuring the continuity of the output voltage.

[0024] S4: Internal reconfiguration of programmable gain amplifier and power amplifier

[0025] When the isolating switch module is in the open state and the voltage is maintained synchronously with the output voltage maintained by the buffer module, the digital controller performs the following parallel operations:

[0026] On one hand, the range switching control logic module inside the digital controller sends a command to the programmable gain amplifier via a gain control signal, causing its internal gain amplifier array to switch to a preset gain multiple that matches the new target voltage range. The internal transient effects of the programmable gain amplifier during this switching period are effectively isolated by the isolating switch module, and do not affect the output of the VI source. The programmable gain amplifier stabilizes to the new gain state within 10 microseconds.

[0027] On the other hand, the digital controller adjusts the supply voltage of the power amplifier via a supply voltage control signal. This adjustment aims to optimize the efficiency of the power amplifier under new target voltage ranges, reduce power consumption, and manage thermal effects. For example, when the target voltage range is high, the supply voltage of the power amplifier is increased accordingly; when the target voltage range is low, the supply voltage is decreased. The supply voltage regulation module inside the power amplifier has a fast response capability of less than 1 microsecond, ensuring that when the supply voltage changes, the amplified output of the power amplifier to the holding voltage from the voltage holding and buffering module remains stable, and its output ripple is less than 1 mVRMS.

[0028] S5: Pre-compensation and precise matching calculation of digital reference voltage

[0029] The range switching control logic module inside the digital controller, based on the range obtained in step S2 The value, the new target voltage range, and the new gain factor of the programmable gain amplifier that has been switched (denoted as...). ( ), precisely calculate the output voltage of the programmable gain amplifier to be exactly equal to the target voltage range under the new target voltage range. The digital reference voltage value to be sent to the digital-to-analog converter (denoted as ) ).

[0030] This calculation process takes into account the actual gain of the programmable gain amplifier and the equivalent gain or attenuation factor of the power amplifier under the new supply voltage (denoted as ). This includes, as well as all possible DC offset and gain errors. The calculation formula can be expressed as:

[0031] ;

[0032] in, This is a calibration value used to eliminate the inherent DC offset of the system under new ranges and supply voltages. The digital controller transmits the calculated value via a high-speed data bus. The value is forcibly updated to the digital-to-analog converter. The digital-to-analog converter immediately outputs the value... The corresponding analog voltage, after being amplified by the programmable gain amplifier that has completed gain switching, will have an output voltage that is precisely equal to the voltage value being held by the voltage holding and buffer modules, with the difference precisely controlled within 1 millivolt.

[0033] S6: Output path reconnection and matching verification. The digital controller monitors the output voltage of the programmable gain amplifier in real time under the new gain configuration and the new digital-to-analog converter reference voltage, and compares it with the voltage value that the voltage holding and buffer module is holding.

[0034] Once the output voltage of the programmable gain amplifier stabilizes and the difference between it and the voltage value held by the voltage holding and buffer modules is less than a preset minimum threshold (e.g., less than 1 mV or 0.01% of the target range), it indicates that the output voltage of the programmable gain amplifier has achieved precise matching with the input voltage of the power amplifier. The digital controller then drives the isolating switch module to quickly switch from the off state to the on state via a switch control signal, thereby reconnecting the programmable gain amplifier, which has completed gain switching and outputs a matched voltage, to the input of the power amplifier. This reconnection process, due to the precise matching of internal and external voltages, ensures that no transient voltage spikes, steps, or current surges occur at the moment of connection, thus achieving a seamless transition of the output voltage.

[0035] S7: Restore closed-loop regulation and target voltage regulation

[0036] After the isolating switch module is fully turned on and completes its internal stabilization (stabilization time less than 50 nanoseconds), the range switching control logic module inside the digital controller immediately performs the following operations:

[0037] First, a "restore regulation" signal is sent to the loop regulation module to re-enable its closed-loop control function.

[0038] Next, the target voltage value of the VI source is updated to the final target voltage value set by the user in step S2.

[0039] The loop regulation module precisely adjusts the output of the digital-to-analog converter based on the new target voltage value and real-time feedback data from the feedback measurement network. This ensures that the actual output voltage of the VI source smoothly and continuously transitions from the current holding voltage value to the final target voltage value, maintaining high precision and stability. At this stage, since the voltage range switching is seamlessly completed, the subsequent voltage regulation process is identical to that in normal operating mode, and there are no additional transient risks.

[0040] The beneficial effects of this invention are as follows:

[0041] 1. The seamless switching method for VI source voltage range described in this invention, through the coordinated work of the isolating switch module and the voltage holding and buffering module, and the precise timing control and voltage pre-compensation of the programmable gain amplifier, power amplifier and digital-to-analog converter by the digital controller, achieves the continuity of output voltage during voltage range switching, avoids the traditional voltage zeroing operation, and eliminates voltage glitches and transient fluctuations that may occur during the switching process.

[0042] 2. The seamless switching method for VI source voltage range described in this invention eliminates the voltage zeroing and reapplication process required for each range switch, as well as the accompanying ramp-up / down and setup time. This invention significantly shortens the test cycle and is particularly suitable for automated testing scenarios with high throughput and frequent range switching, directly improving production line efficiency and equipment utilization.

[0043] 3. The seamless switching method for VI source voltage range described in this invention completely eliminates the potential damage risk to sensitive devices under test caused by voltage spikes and instabilities due to transient effects during range switching, thereby improving the safety and reliability of testing and avoiding economic losses caused by device damage.

[0044] 4. The seamless switching method for VI source voltage range described in this invention ensures a smooth transition of the test voltage for scenarios requiring continuous characteristic scanning or dynamic testing across voltage ranges. This maintains the internal working state of the device under test without interruption, thereby obtaining more realistic, continuous, and accurate test data and improving the reliability of the test results.

[0045] 5. The seamless switching method for VI source voltage range described in this invention eliminates the need for test engineers to write complex logic for voltage zeroing, delay, and voltage recovery. Instead, they can directly set the target voltage range and target voltage value. The system automatically completes the seamless switching process, reducing the development difficulty and maintenance cost of test scripts. Furthermore, through the dynamic adjustment of the power amplifier's supply voltage by the digital controller, the power amplifier always operates under power supply conditions that match its output voltage requirements, effectively reducing power loss and heat generation, and improving energy efficiency and long-term equipment stability.

[0046] 6. The seamless switching method for VI source voltage range described in this invention ensures the accuracy of the entire switching process and the stability of the output voltage after switching by utilizing the high-speed computing power of the digital controller, the high-resolution digital-to-analog converter and analog-to-digital converter, the high-precision programmable gain amplifier, and the design of a low leakage voltage holding and buffer module. Attached Figure Description

[0047] The invention will now be further described with reference to the accompanying drawings.

[0048] Figure 1 This is the overall control block diagram for seamless range switching;

[0049] Figure 2 This is an internal block diagram of the digital controller;

[0050] Figure 3 This is a schematic diagram of the seamless switching method in this invention. Detailed Implementation

[0051] This invention provides a seamless switching method for VI source voltage ranges, aiming to overcome the problems of low efficiency, data interruption, and potential damage to the device under test encountered in existing technologies during voltage range switching. The core of this technical solution lies in constructing a highly coordinated hardware and software system to ensure that the output voltage of the VI source maintains high continuity, stability, and accuracy when switching between different voltage ranges, thereby achieving a smooth transition without transient fluctuations. The following will provide a detailed description of the seamless switching system for VI source voltage ranges and its specific implementation method to ensure that those skilled in the art can fully understand and implement this technical solution.

[0052] In one specific embodiment, the seamless switching system for the VI source voltage range of the present invention, such as Figure 1 As shown, it mainly consists of a digital controller, a digital-to-analog converter, a programmable gain amplifier, an isolating switch module, a voltage holding and buffer module, a power amplifier, and a feedback measurement network. These components work together through precise electrical connections and high-speed data communication to achieve seamless switching of the voltage range.

[0053] like Figure 2As shown, the digital controller is the core intelligent unit of the entire system, typically employing a hybrid architecture of a high-performance field-programmable gate array (FPGA) and an embedded microcontroller (MCU). This digital controller is configured to receive and parse range switching commands from a host computer or other automated testing equipment, comprehensively manage the various operating states of the VI source, and execute a digital closed-loop voltage regulation algorithm. It integrates several key modules, including a digital voltage reference generation module, a range switching control logic module, a loop regulation module, and a high-precision clock synchronization unit. The digital voltage reference generation module is responsible for generating accurate digital voltage reference values ​​based on commands and calibration data, which can be achieved by consulting a pre-stored lookup table or through a high-precision direct digital frequency synthesis (DDS) algorithm. The range switching control logic module is a state machine responsible for parsing switching commands and coordinating the precise timing actions and state transitions of all hardware components during the switching process. The loop regulation module is typically implemented as a digital PID controller, used to dynamically adjust the output based on feedback data to ensure the accuracy and stability of the output voltage. The high-precision clock synchronization unit provides all the synchronization clock signals required by the entire system, ensuring strict synchronization of the actions between components, with jitter strictly controlled at the sub-nanosecond level. The digital controller communicates and interacts with the digital-to-analog converter, programmable gain amplifier, isolation switch module, voltage holding and buffer module, power amplifier, and feedback measurement network via a high-speed serial peripheral interface (SPI), I²C bus, or parallel data bus for data communication and control signal exchange. For example, the digital controller uses a Xilinx Artix-7 series FPGA (XC7A100T) and an STM32H7 series MCU with an ARM Cortex-M4 core to work together; the FPGA handles high-speed logic and real-time control, while the MCU handles communication and advanced control.

[0054] The digital-to-analog converter (DAC) is electrically connected to the digital controller. This DAC is configured to convert the digital voltage reference signal generated by the digital controller into an analog voltage signal with high precision. To meet the high-performance requirements of the VI source, the selection of the DAC is crucial; it should have a resolution of at least 16 bits to ensure fine voltage regulation steps and a wide dynamic range. Its offset voltage must be less than 100 microvolts to minimize its impact on output voltage accuracy. Temperature drift is a significant factor in high-precision applications; therefore, the temperature drift of the DAC should be less than 10 ppm / °C to ensure consistent performance under different ambient temperatures. Furthermore, to quickly respond to the digital controller's commands and shorten switching time, the DAC's settling time must be less than 5 microseconds to ensure its output can quickly stabilize to the target analog voltage. A specific DAC can be selected from Analog Devices' high-precision DAC series, such as the AD5791, which features 20-bit resolution, excellent linearity, and a settling time of less than 1 microsecond. Its output signal is buffered by a low-noise, high-bandwidth operational amplifier to provide stable drive capability and isolate the effects of subsequent loads.

[0055] The programmable gain amplifier (PGA) is electrically connected to the output of the digital-to-analog converter (DAC). This amplifier is configured to receive the analog voltage signal output by the DAC and, based on the digital gain control signal provided by the digital controller, precisely amplify the analog voltage signal at a programmable gain factor. The PGA internally contains multiple gain stages, typically composed of a precision operational amplifier array and a high-precision resistor network. The precision operational amplifier array employs a low-noise, low-offset voltage, high common-mode rejection ratio (CMRR) precision instrumentation amplifier or differential amplifier to ensure signal integrity. The high-precision resistor network is implemented using thin-film resistors or laser-trimmed resistors to ensure gain stability and accuracy, with a temperature coefficient as low as 5 ppm / °C. During gain switching, the transient response of the PGA, caused by capacitor charging / discharging and switching transient effects, is carefully designed and suppressed to ensure that it decays to less than 0.1% of its stable value within 10 microseconds, thereby reducing its impact on other parts of the system. To handle high-speed analog signals, the programmable gain amplifier should have a gain-bandwidth product (GBW) of at least 100MHz to ensure sufficient bandwidth across various gain settings. For example, an integrated programmable gain amplifier based on the AD8250 or LTC6915 can be used, combined with an external precision resistor network to achieve the required gain range and accuracy. The gain factor can be set by a digital controller via a tri-state digital input or SPI interface; typical gain factors are configurable to 0.1, 1, 10, 100, etc.

[0056] The isolating switch module is electrically connected to the output of the programmable gain amplifier. This module is configured to switch rapidly between an on and off state based on a switching control signal provided by the digital controller, thereby electrically controlling the connection between the output signal of the programmable gain amplifier and the input of the power amplifier. The isolating switch module consists of at least one high-speed, high-isolation, low-on-resistance solid-state analog switch array. The solid-state analog switch array is typically manufactured using CMOS or MEMS technology to achieve fast switching and reliability. Its switching time is designed to be less than 50 nanoseconds to ensure rapid isolation or reconnection during range switching. In the off state, to effectively prevent signal leakage and the propagation of transient interference, the isolation of the solid-state analog switch array is not less than 90 dB (e.g., at 1 MHz), meaning that only extremely low signal energy can couple from the input to the output when off. Low on-resistance (e.g., less than 1 ohm) ensures the integrity of signal transmission in the on state, reducing signal attenuation and heat generation. High-precision analog switches from Analog Devices' ADG series or Texas Instruments' TMUX series can be selected, featuring low charge injection and high isolation characteristics.

[0057] The voltage holding and buffer module is electrically connected to the output of the isolating switch module and the input of the power amplifier. Its core function is to actively and accurately capture and maintain the voltage applied to the power amplifier's input when the isolating switch module is in the off state, thus providing a stable drive signal for the power amplifier. When the isolating switch module is in the on state, the voltage holding and buffer module acts as a transparent buffer or direct path, having almost no impact on signal transmission. The voltage holding and buffer module includes a high-precision sample-and-hold circuit and a high-bandwidth voltage follower or buffer amplifier. The sample-and-hold circuit is its key component, its core being a holding capacitor made of a low-leakage dielectric material (e.g., polystyrene or polypropylene) to ensure an extremely low leakage rate, specifically below 10 pA / s, which is crucial for maintaining a precise voltage over long periods. The holding accuracy of this sample-and-hold circuit should be better than 0.01% within 100 microseconds, meaning minimal voltage drift during switching. The sample-and-hold circuit also needs extremely short aperture time and aperture jitter to accurately capture transient voltages. The buffer amplifier features high input impedance and low output impedance, with a slew rate of at least 1V / µs to ensure rapid response to voltage changes and drive the input stage of the power amplifier with an output impedance of less than 10 milliohms, ensuring stable signal transmission. For example, a design combining Linear Technology's LTC6268 (low-leakage amplifier) ​​and LTC6240 (high-slew rate buffer) with an external precision holding capacitor can be used.

[0058] The power amplifier is electrically connected to the output of the voltage holding and buffer module. This power amplifier is configured to receive the voltage signal from the voltage holding and buffer module and amplify it at high power to drive the device under test (DUT). To optimize operating efficiency and reduce power consumption, the supply voltage of the power amplifier can be programmed and adjusted by the digital controller via a supply voltage control signal. The supply voltage can be increased when the output voltage demand is high and decreased when the output voltage demand is low. The power amplifier should have a bandwidth of at least 1MHz to ensure good response to rapidly changing signals. Its slew rate should be at least 50V / µs to handle rapid changes in high voltage output. Furthermore, its power supply rejection ratio (PSRR) should be at least 80dB at a frequency of 1kHz to effectively suppress the impact of supply voltage fluctuations on the output signal. The power amplifier internally includes a fast-response supply voltage regulation module, typically employing a topology combining a high-efficiency DC-DC converter and a low-noise linear regulator. This ensures that the power amplifier maintains stable amplification of the input signal when the supply voltage changes, and its peak-to-peak output ripple voltage remains below 5mV even under dynamic adjustment. The response speed of this supply voltage regulation module should be less than 1 microsecond to meet the rapid switching requirements of the entire system. High-performance operational amplifiers (such as OPA548 or AD8397) can be used, combined with an external high-power output stage (such as a MOSFET array) and a dedicated power management IC (such as LTM8051).

[0059] The feedback measurement network is electrically connected to the output of the VI source and the digital controller. This network is configured to precisely scale down the actual output voltage and current signals of the VI source and convert them into digital signals, feeding them back to the digital controller to provide real-time data for closed-loop regulation. The feedback measurement network includes a high-precision voltage divider resistor network, a current sampling resistor, and an analog-to-digital converter (ADC). The high-precision voltage divider resistor network is used to accurately attenuate the high-voltage output to the input range of the ADC 7. It has high resistance matching and an extremely low temperature coefficient, typically using thin-film resistor pairs. The current sampling resistor is a low-resistance precision resistor connected in series in the output path. The output current is derived by measuring the voltage drop across it, and a Kelvin connection is typically used to eliminate the influence of parasitic resistance. The ADC 7 should have a resolution of at least 16 bits and a sampling rate of at least 100 ksps to ensure the accuracy and real-time performance of the measurement results, providing sufficient data for the closed-loop control of the digital controller. Multi-channel, high-resolution, high-sampling-rate ADCs such as the AD7606 from Analog Devices (ADI) or the ADS8688A from Texas Instruments (TI) can be used. To improve measurement accuracy, the input of the analog-to-digital converter 7 is usually connected to a buffer amplifier with high input impedance and low noise.

[0060] The following details the seamless switching method for the VI source voltage range described in this invention, which is executed on the aforementioned seamless switching system for the VI source voltage range. The process is as follows: Figure 3 As shown, the specific steps include:

[0061] S1: System initialization and establishment of normal operating state

[0062] Upon power-on of the VI source, the digital controller first executes a series of power-on self-test procedures to verify the functionality of the system memory, communication interface, and various hardware modules. After the self-test passes, the digital controller loads preset operating parameters and calibration data. This calibration data includes compensation parameters such as gain, offset, and linearity for each voltage range, ensuring high-precision operation of the system across different ranges. Subsequently, the digital controller initializes the digital-to-analog converter, programmable gain amplifier, isolating switch module, voltage holding and buffer module, and power amplifier, bringing them to a known safe state, such as setting the output voltage to zero or a low safe voltage. During this stage, the power amplifier's supply voltage is set to a value suitable for the current or default voltage range to optimize its efficiency. Once initialization is complete, the VI source enters normal operating mode. At this time, the loop regulation module inside the digital controller is enabled, generating a digital reference signal based on the currently set voltage range and target voltage value. This digital reference signal is then sent to the digital-to-analog converter, which converts it into an analog voltage signal. The digital controller configures the gain of the programmable gain amplifier (PLA) based on the current voltage range requirements via a gain control signal. Simultaneously, the digital controller activates the isolating switch module via a switch control signal, establishing an electrical connection between the PLA's output signal and the input of the voltage hold and buffer module. During this phase, the voltage hold and buffer module acts as a transparent buffer or direct path, its output directly connected to the power amplifier's input, transmitting the signal to the power amplifier. The power amplifier receives the signal from the voltage hold and buffer module, amplifies it, and drives the device under test (DUT). The feedback measurement network continuously monitors the actual output voltage and current of the VI source during this process, feeding back the digitized measurement results to the digital controller in real time. Based on these feedback signals, the digital controller uses its internal digital PID control algorithm for closed-loop regulation, ensuring that the actual output voltage of the VI source is precisely stabilized at the set target voltage value.

[0063] S2: Range switching command reception and working status freeze

[0064] When the system needs to switch voltage ranges, the digital controller receives a voltage range switching command from a host computer (e.g., via SCPI instructions) or an internal automated test sequence. This command typically contains two key parameters: a new target voltage range (e.g., switching from a 0-5V range to a 0-20V range) and a new final target voltage value (e.g., eventually stabilizing at 15V within a 20V range). Upon receiving this command, the range switching control logic module within the digital controller responds immediately and executes a series of predetermined actions. First, the logic module sends a "pause regulation" signal to the loop regulation module. This signal instructs the loop regulation module to temporarily halt its current closed-loop regulation action and force it to maintain the output voltage of the digital-to-analog converter at the stable value it was at when the command was first received. The purpose of this operation is to ensure that the input voltage supplied to the programmable gain amplifier is highly stable and free from transient changes during the initial stage of range switching. Second, the digital controller obtains the current actual output voltage value with high precision through the feedback measurement network. To improve accuracy and interference resistance, multiple samples are typically taken and the average value is calculated. This value is then precisely recorded as... .this The value will serve as a reference voltage that needs to be maintained throughout the switching process, and is a key benchmark for achieving seamless switching.

[0065] S3: Output isolation and voltage holding function activated.

[0066] Under precise timing control, the digital controller drives the isolating switch module to rapidly switch from the on state to the off state via a switch control signal. This switching process is completed within 50 nanoseconds, achieving electrical isolation between the output of the programmable gain amplifier and the input of the power amplifier. This rapid isolation is crucial, effectively preventing any transient fluctuations or noise that may arise within the programmable gain amplifier due to the impending gain switch from propagating to the power amplifier, thus protecting the device under test (DUT) from impact. Almost simultaneously with the disconnection of the isolating switch module, the voltage hold and buffer module is activated. Its built-in high-precision sample-and-hold circuit is triggered, accurately capturing and holding the instantaneous voltage applied to the input of the power amplifier before or at the instant the isolating switch module disconnects. The aperture time of this sampling action is extremely short, ensuring accurate sampling of the instantaneous voltage. The sampled and held voltage is stably applied to the input of the power amplifier through the high drive capability and low output impedance characteristics of the voltage hold and buffer module. During this period, the power amplifier continues to receive the held voltage from the voltage hold and buffer module and continuously drives the DUT with this voltage. This strategy effectively maintained the output voltage on the device under test stable. This value suppresses any possible voltage drops, rises, or glitches during the disconnection of the isolating switch module, ensuring the continuity of the output voltage. The voltage holding and buffering module has a holding accuracy of better than 0.01% within 100 microseconds, meaning that output voltage drift is negligible during critical switching time windows.

[0067] S4: Internal reconfiguration of programmable gain amplifier and power amplifier

[0068] When the isolating switch module is in the open state and the voltage is maintained synchronously with the output voltage maintained by the buffer module, the digital controller performs two key operations in parallel:

[0069] On one hand, the range switching control logic module inside the digital controller sends a command to the programmable gain amplifier via a gain control signal. This command switches its internal gain amplifier array to a preset gain multiple that matches the new target voltage range. For example, if switching from a low voltage range to a high voltage range, the gain of the programmable gain amplifier may decrease accordingly to accommodate the subsequent higher output voltage. Internal transient effects of the programmable gain amplifier during this switching (e.g., due to internal switch switching or capacitor charging / discharging) will not propagate to the output of the VI source due to the effective isolation of the isolation switch module. The design of the programmable gain amplifier ensures that it can stabilize to the new gain state within 10 microseconds, preparing for subsequent precise matching.

[0070] On the other hand, the digital controller dynamically adjusts the power amplifier's supply voltage via a supply voltage control signal. The fundamental purpose of this adjustment is to optimize the power amplifier's operating efficiency under new target voltage ranges, reduce unnecessary power consumption, and effectively manage thermal effects. For example, when the new target voltage range is high (e.g., switching from a 5V range to a 50V range), the power amplifier's supply voltage is correspondingly increased (e.g., from ±6V to ±55V) to provide sufficient margin for high voltage output. Conversely, when the target voltage range is low, the supply voltage is reduced to decrease static power consumption and heat dissipation requirements. The power amplifier's internal supply voltage regulation module has a fast response time of less than 1 microsecond, ensuring that when the supply voltage changes, the power amplifier maintains a stable amplified output of the holding voltage from the voltage holding and buffering module, and its output ripple voltage is less than 1 mVRMS.

[0071] S5: Pre-compensation and precise matching calculation of digital reference voltage

[0072] After the programmable gain amplifier completes gain switching and the power amplifier's supply voltage stabilizes, the range switching control logic module inside the digital controller enters the precise calculation stage. It will calculate based on the data obtained in step S2. The value, the new target voltage range, and the new gain factor of the programmable gain amplifier that has been switched (denoted as...). ( ), precisely calculate the output voltage of the programmable gain amplifier to be exactly equal to the target voltage range under the new target voltage range. The digital reference voltage value to be sent to the digital-to-analog converter (denoted as ) ).

[0073] This calculation process not only considers the nominal gain, but also comprehensively considers the programmable gain amplifier's performance. The actual gain deviation under the w setting, and the equivalent gain or attenuation coefficient of the power amplifier under the new supply voltage (denoted as w). This coefficient may include the inherent gain of the power amplifier and any fixed attenuation on its output path, as well as all DC offset and gain errors that the system may introduce under new ranges and supply voltages. These compensation parameters are typically determined through precise calibration before the system leaves the factory and are stored in the non-volatile memory of the digital controller, allowing for online temperature and aging compensation. The calculation formula can be expressed as:

[0074] ;

[0075] in, This is a calibration value used to eliminate the inherent DC offset of the system under new ranges and supply voltages. The digital controller transmits the calculated value via a high-speed data bus. The value is forcibly updated to the digital-to-analog converter. The digital-to-analog converter immediately outputs the value... The corresponding analog voltage, after being amplified by the programmable gain amplifier that has completed gain switching, will have an output voltage that is precisely equal to the voltage value being held by the voltage holding and buffer modules. The difference between them is precisely controlled within 1 millivolt, and even within 0.005% of the target range under a specific high-precision range.

[0076] S6: Output path reconnection and matching verification

[0077] After the digital controller updates the DAC reference voltage, it continuously monitors the output voltage of the programmable gain amplifier (PGA) in real time under the new gain configuration and the new digital-to-analog converter (DAC) reference voltage. This monitoring can be achieved through a dedicated high-speed comparator or through an additional channel in a feedback measurement network. The digital controller compares this real-time voltage value with the voltage value that the voltage hold and buffer module is precisely holding. The purpose of the comparison is to verify the precise match between the two. Once the output voltage of the PGA stabilizes and the difference between it and the voltage value held by the voltage hold and buffer module is less than a preset minimum threshold (e.g., less than 1 mV or 0.01% of the target range), it indicates that the output voltage of the PGA has achieved a highly precise match with the input voltage of the power amplifier. At the instant this precise match condition is met, the digital controller immediately drives the isolation switch module to quickly switch from the off state to the on state via a switch control signal, thereby reconnecting the PGA, which has completed gain switching and outputs a matched voltage, to the input of the power amplifier. This reconnection process, thanks to the precise matching of internal and external voltages, ensures that no transient voltage spikes, jumps, or current surges occur at the moment of connection. This achieves a seamless transition of the output voltage at the range switching point without disturbing the operating state of the device under test.

[0078] S7: Restore closed-loop regulation and target voltage regulation

[0079] After the isolating switch module is fully turned on and completes its internal stabilization (its stabilization time is less than 50 nanoseconds), the range switching control logic module inside the digital controller immediately executes subsequent operations. First, it sends a "restore regulation" signal to the loop regulation module, re-enabling its closed-loop control function. At this time, the loop regulation module will... The corresponding voltage value initiates the adjustment process. Next, the digital controller updates the final target voltage value of the VI source to the final target voltage value set by the user in step S2. The loop adjustment module precisely adjusts the output of the digital-to-analog converter based on the new target voltage value and real-time feedback data from the feedback measurement network. Because the switching process is seamless, the actual output voltage of the VI source can smoothly and continuously transition from the current holding voltage value to the final target voltage value, maintaining high precision and stability. At this stage, since the voltage range switching is seamlessly completed, the subsequent voltage adjustment process is no different from the adjustment process in normal operating mode, and there are no additional transient risks; the system can quickly reach and maintain the new target voltage.

[0080] Example 1: Switching from 5V range to 20V range

[0081] In one specific embodiment, the VI source described in this invention is configured for testing a precision analog chip. The VI source has multiple voltage ranges, including ±5V, ±20V, and ±50V. Currently, the VI source is operating at the +5V range, with the output voltage stabilized at +3.000V, and providing a 10mA current to a resistive load. At this point, the user issues a range switching command, requesting a switch from +5V to +20V, ultimately setting the target output voltage to +15.000V.

[0082] S1: System initialization and establishment of normal operating state

[0083] The VI source is in normal working order, and the digital controller (using a Xilinx Artix-7 FPGA and STM32H7 MCU combination) has been loaded with calibration data. The positive output of the digital-to-analog converter (ADI AD5791, 20-bit) drives the programmable gain amplifier (AD8250 with a precision resistor network) to output 3.000V. The isolating switch module (ADG5408 high-speed analog switch) is in the ON state. The voltage holding and buffer module (LTC6268+LTC6240) acts as a transparent buffer. The power amplifier (OPA548 with MOSFET output stage) is supplied with ±6V, and the output is stable at +3.000V. The feedback measurement network (AD7606, 16-bit, 200ksps) continuously monitors and feeds back data, and the PID loop of the digital controller maintains the output at 3.000V.

[0084] S2: Range switching command reception and working status freeze

[0085] The digital controller receives a command from the host computer: the new range is +20V, and the new target voltage is +15.000V. The range switching control logic module immediately sends a "pause adjustment" signal to the loop adjustment module, locking the digital-to-analog converter output at the current value, thus maintaining the input voltage of the programmable gain amplifier unchanged. Simultaneously, the digital controller accurately measures the current actual output voltage through a feedback measurement network, averaging multiple samples to obtain the final voltage. =+3.00005V.

[0086] S3: Output isolation and voltage holding function activated.

[0087] The digital controller sends a switch control signal to the isolating switch module, causing it to switch from the on state to the off state within 45 nanoseconds, disconnecting the programmable gain amplifier from the voltage holding and buffer module. Almost simultaneously, the high-precision sample-and-hold circuit of the voltage holding and buffer module is triggered, capturing the voltage applied to the power amplifier input (assuming it is +0.25V) 10 nanoseconds before the isolating switch module disconnects. This voltage is precisely held by a holding capacitor (using a polystyrene capacitor with a leakage current <5pA / s). The buffer amplifier of the voltage holding and buffer module applies this +0.25V stably to the power amplifier input with high drive capability. The power amplifier continues to output +3.00005V (assuming a power amplifier gain of 12, then the input is 0.25V), maintaining voltage stability on the device under test. During the 100-microsecond hold period, the hold voltage drift is less than 0.005%.

[0088] S4: Internal reconfiguration of programmable gain amplifier and power amplifier

[0089] While the isolating switch module is disconnected and the voltage is maintained, and the buffer module maintains the output voltage, the digital controller performs the following in parallel: .

[0090] Programmable gain amplifier reconfiguration: The digital controller sends a command to the programmable gain amplifier to switch its gain from the current +5V range-matched gain (e.g., 12x) to the +20V range-matched gain (e.g., 2x). This switching is done internally, transient effects are isolated, and stabilization occurs within 8 microseconds.

[0091] Power amplifier supply voltage adjustment: The digital controller sends a command to the power amplifier's internal supply voltage adjustment module to increase its supply voltage from ±6V to ±24V. This adjustment is completed within 800 nanoseconds, and the output ripple remains below 0.8mVRMS after the switch.

[0092] S5: Pre-compensation and precise matching calculation of digital reference voltage

[0093] Digital controller according to New target range (+20V), new programmable gain amplifier gain and the equivalent gain of the power amplifier under ±24V supply. (Assuming there is a slight deviation at this point) and the offset compensation value in the calibration lookup table. Accurately calculate the digital reference voltage value to be sent to the digital-to-analog converter. .

[0094] Calculation process: First, calculate the analog voltage required at the input of the programmable gain amplifier:

[0095] .

[0096] Convert this analog voltage to a digital value for the DAC (assuming a DAC reference voltage of 5V, 20-bit):

[0097] .

[0098] Consider offset compensation:

[0099] .

[0100] The digital controller transmits via high-speed SPI Updated to digital-to-analog converter. The digital-to-analog converter outputs the corresponding analog voltage within 3 microseconds. After being amplified by a process-controlled gain amplifier, its output voltage is precisely stabilized at +0.25001V, with a voltage difference of only +10 microvolts from the +0.25V voltage held by the voltage holding and buffer modules.

[0101] S6: Output path reconnection and matching verification

[0102] The digital controller compares the output voltage (+0.25001V) of the programmable gain amplifier with the holding voltage (+0.25000V) of the voltage holding and buffer module in real time. When the difference between the two is less than 0.5 millivolts (preset threshold), it indicates that the matching is accurate.

[0103] The digital controller immediately sends a switching control signal, driving the isolating switch module to switch from the off state to the on state within 45 nanoseconds, reconnecting the output of the programmable gain amplifier to the input of the power amplifier. Due to the high matching of internal and external voltages at the time of connection, the output voltage of the VI source remains smooth at the moment of connection, without generating any measurable transient glitches.

[0104] S7: Restore closed-loop regulation and target voltage regulation

[0105] After the isolating switch module is fully turned on and stabilized, the range switching control logic module sends a "restore adjustment" signal to the loop adjustment module and updates the target voltage of the VI source to +15.000V. The loop adjustment module adjusts the output of the digital-to-analog converter based on the new target voltage and real-time feedback from the feedback measurement network. The actual output voltage of the VI source smoothly and continuously transitions from +3.00005V to the final target voltage of +15.000V, with the voltage change slope controlled at 5V / ms. The entire transition process takes approximately 2.4 milliseconds, with no overshoot or undershoot.

[0106] Comparative Example 1: Range Switching of Traditional VI Source

[0107] As a comparative example of the present invention, consider a VI source employing a conventional range switching method. When switching ranges, this conventional VI source typically requires the output voltage to first return to zero, then the range to be switched, and finally the target voltage to be reapplied. Assume the same scenario as in Example 1: the VI source is currently operating at the +5V range, with an output voltage of +3.000V; the target range is switched to +20V, with a final target voltage of +15.000V.

[0108] Traditional switching steps:

[0109] Zeroing command: When the digital controller receives the range switching command, it first sends a zeroing command to the output module.

[0110] Voltage ramp descent: The output voltage of the VI source drops from +3,000V to 0V at a preset ramp (e.g., 10V / ms). This process takes approximately 300 microseconds.

[0111] Voltage stabilized at zero: The output voltage stabilizes at 0V (e.g., 1 millisecond) to ensure that the device under test enters a safe state.

[0112] Range hardware switching: The digital controller sends a command to switch the supply voltage of the internal gain amplifier and power amplifier to the configuration corresponding to the new range (+20V). This process may be accompanied by transient noise, and an additional wait (e.g., 5 milliseconds) is usually required for it to stabilize.

[0113] Reapplying the target voltage: The digital controller sends a command to increase the output voltage from 0V to the new target voltage +15,000V at a preset slope (e.g., 10V / ms). This process takes approximately 1.5 milliseconds.

[0114] Voltage settling and stabilization: The output voltage oscillates around +15,000V and requires additional time (e.g., 10 milliseconds) to fully stabilize to the required accuracy.

[0115] Problems with traditional methods:

[0116] Voltage interruption: The output voltage is forced to zero, causing the working state of the device under test to be interrupted, affecting the continuity of test data.

[0117] Inefficiency: The additional zeroing, waiting, re-rise, and setup time significantly increases the test cycle. The total switching time (including zeroing, stabilization, hardware switching, re-rise, and stabilization) is much longer than that of this invention.

[0118] Transient risks: The ramp process of returning to zero and reapplying voltage may cause overshoot or undershoot in the output voltage, as well as glitches that may occur during range hardware switching, posing a potential risk to sensitive devices under test.

[0119] Data reliability: The discontinuity of the output voltage during the test makes it difficult to analyze continuous data across the range, or reduces the authenticity of the data.

[0120] Comparison of experimental data

[0121] To quantify the superiority of this invention, we conducted a range switching performance comparison test between the VI source implemented in this invention and a VI source employing a traditional zero-switching method. The test conditions were both for switching from +3.000V (5V range) to +15.000V (20V range) with a load of 300 ohms. The following is a comparison of experimental data for key performance parameters:

[0122] Performance parameters Seamless switching method of the present invention Traditional zeroing switching method Improvement level Remark Total switching time (ms) 2.8 17.8 Reduced by 84.3% The time from issuing the command to the output stabilizing at the new target voltage Voltage interruption time (ms) 0 15.0 Eliminate interruption The time when the output voltage is 1% below the target range or returns to zero Switching transient voltage spike peak value (mV) <0.5 >50 Reduced by more than 99% Maximum transient deviation of output voltage at the switching point Output voltage recovery time to 0.01% accuracy (ms) <0.2 >10 Reduced by more than 98% Time from switchover completion to stabilization at the new target voltage The operating state of the device under test Uninterrupted Complete interruption Significantly improve test continuity Improved efficiency of automated testing high Low Significant Especially suitable for scenarios with frequent range switching Data continuity Excellent Difference Significant improvement Especially beneficial for continuous characteristic curve scanning

[0123] The experimental data comparison clearly demonstrates that the seamless switching method for the VI source voltage range proposed in this invention significantly outperforms the traditional zero-switching method in key performance indicators such as total switching time, voltage interruption time, transient voltage glitches, and output voltage recovery accuracy time. By eliminating the voltage zero-switching operation, this invention maintains a high degree of continuity in the output voltage during range switching, greatly improving testing efficiency and data reliability, and effectively protecting the device under test from transient voltage surges.

[0124] Furthermore, as a preferred embodiment of the present invention, the digital voltage reference generation module in the digital controller can employ a combination of high-performance lookup table method and interpolation algorithm to accurately generate the digital code required by the DAC based on the set target voltage value, the current range, and calibration data. To further improve accuracy, the lookup table can store calibration coefficients for different temperatures and load conditions, and the system temperature is monitored in real time by a thermistor array, with dynamic compensation performed in conjunction with the load current detection results.

[0125] Specifically, the high-precision resistor network in the programmable gain amplifier can be manufactured using thin-film resistor technology, achieving a temperature coefficient (TCR) as low as ±5ppm / ℃. To ensure smooth gain switching, a break-before-make switching timing strategy can be employed, supplemented by a soft-start circuit to suppress transient current spikes during switching. Gain programming can be completed within 1 microsecond via a serial peripheral interface (SPI), ensuring fast switching speed.

[0126] The solid-state analog switch array in the disconnecting switch module can be designed to include multiple parallel high-speed CMOS switching units to reduce total on-resistance and improve current carrying capacity. In the off state, to maximize isolation, the control signals of the switching units can be designed to be pulled high or low simultaneously, and parasitic capacitive coupling is reduced through guard rings and shielding layers. Its switching time of less than 50 nanoseconds is one of the keys to achieving "seamless" operation.

[0127] The selection of the hold capacitor in the sample-and-hold circuit of the voltage holding and buffer module is crucial. Besides using a low-leakage dielectric material, its capacitance value needs to be precisely calculated based on the required hold time and the allowable voltage drift. For example, if a hold time of 100 microseconds is required and a drift of 0.01% is allowed (assuming a 10V output), the drift voltage is 1mV. If the leakage current is 10pA, the required capacitor is at least 1nF. Simultaneously, the buffer amplifier must be a high-impedance amplifier with JFET or CMOS input to minimize the load effect on the hold capacitor and ensure hold accuracy.

[0128] The fast-response power supply voltage regulation module inside the power amplifier can employ a combination of a multi-stage DC-DC converter and a linear regulator. For example, a high-efficiency switching regulator provides a coarse supply voltage, while a low-noise linear regulator performs fine adjustment and ripple suppression to ensure a fast and stable supply voltage for the output stage. The timing of the power supply voltage adjustment should be closely coordinated with the range switching control logic module to ensure that the adjustment is completed during output isolation, avoiding interference to the output.

[0129] In one specific embodiment, the analog-to-digital converter 7 in the feedback measurement network can be a synchronous sampling multi-channel ADC to simultaneously acquire voltage and current data, ensuring the timing synchronization of the measurement results. To improve measurement accuracy, the voltage divider resistor network can use precision resistor pairs with a ratio matching accuracy of 0.005%, and temperature drift can be further reduced through a temperature compensation circuit. The current sampling resistor can be an ultra-low resistance (e.g., 10mΩ) precision resistor with a four-wire Kelvin connection to minimize the impact of its own voltage drop on the output path and ensure high-precision current measurement.

[0130] In summary, this invention achieves seamless, transient-free voltage range switching by comprehensively and meticulously designing the hardware and software of the VI source voltage range switching system. Specifically, it utilizes a digital controller to achieve highly coordinated control of the digital-to-analog converter, programmable gain amplifier, isolating switch module, voltage holding and buffer module, power amplifier, and feedback measurement network. This method not only significantly improves testing efficiency and enhances protection for the device under test, but also improves the continuity and accuracy of test data, representing a significant advancement in the field of precision VI source technology.

[0131] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A system for seamless switching of VI source voltage ranges, comprising: The application relates to a digital controlled VI source, comprising: a digital controller configured to receive a range switching instruction, manage the working state of a VI source, execute digital closed-loop voltage regulation, and coordinate the actions of all hardware components during the range switching process; the digital controller is configured to, after receiving the range switching instruction, suspend the closed-loop regulation to maintain the output voltage of a digital-to-analog converter, and obtain the current actual output voltage as a maintenance reference voltage; a drive isolation switch module is driven to be turned off, and a voltage maintenance and buffer module is simultaneously activated; during the voltage maintenance, a programmable gain amplifier is controlled to be switched to a gain matched with a new target range, the power supply voltage of a power amplifier is adjusted, and the pre-compensation digital reference voltage of the digital-to-analog converter is calculated according to the maintenance reference voltage, the new gain and the new power supply voltage; when the difference between the output of the programmable gain amplifier and the maintenance voltage is less than a preset threshold, the drive isolation switch module is driven to be turned on, the closed-loop regulation is restored, and the output voltage is smoothly transitioned to the new target voltage; a digital-to-analog converter is electrically connected to the digital controller and is configured to convert the digital voltage reference signal generated by the digital controller into an analog voltage signal; a programmable gain amplifier is electrically connected to the digital-to-analog converter and is configured to receive the analog voltage signal output by the digital-to-analog converter and amplify the analog voltage signal by a programmable gain multiple according to the gain control signal of the digital controller; an isolation switch module is electrically connected to the output end of the programmable gain amplifier and is configured to switch between the on and off states according to the switch control signal of the digital controller, thereby controlling the connection between the output signal of the programmable gain amplifier and the input end of the power amplifier; a voltage maintenance and buffer module is electrically connected to the output end of the isolation switch module and the input end of the power amplifier and is configured to capture and maintain the voltage applied to the input end of the power amplifier when the isolation switch module is turned off, and to act as a transparent buffer or a straight-through path when the isolation switch module is turned on; a power amplifier is electrically connected to the output end of the voltage maintenance and buffer module and is configured to receive the voltage signal of the voltage maintenance and buffer module and amplify it to drive the measured device, and the power supply voltage of the power amplifier can be programmed and adjusted by the digital controller through a power supply voltage control signal; a feedback measurement network is electrically connected to the output end of the VI source and the digital controller and is configured to accurately scale down the actual output voltage and output current signals of the VI source and convert them into digital signals for feedback to the digital controller.

2. A system for seamless switching of voltage ranges of a VI source according to claim 1, wherein, The digital controller is internally integrated with a digital voltage reference generation module, a range switching control logic module, a loop regulation module and a high-precision clock synchronization unit; the digital voltage reference generation module generates an accurate digital voltage reference value, the range switching control logic module analyzes the switching instruction and coordinates the timing actions and state transitions of the hardware components during switching, the loop regulation module dynamically adjusts the output according to the feedback data to ensure accurate and stable voltage, and the high-precision clock synchronization unit provides a system synchronization clock signal; the digital controller communicates data and interacts control signals with the digital-to-analog converter, the programmable gain amplifier, the isolation switch module, the voltage maintenance and buffer module, the power amplifier and the feedback measurement network through a high-speed serial peripheral interface, an I2C bus or a parallel data bus.

3. A system for seamless switching of voltage ranges of a VI source as claimed in claim 1, wherein, The output signal of the digital-to-analog converter is buffered through a low-noise, high-bandwidth operational amplifier to provide stable driving capability and isolate the influence of subsequent loads.

4. The system for seamless switching of voltage ranges of a VI source according to claim 1, wherein, The programmable gain amplifier comprises multiple gain stages formed by a precision operational amplifier array and a high-precision resistance network.

5. The system for seamless switching of voltage ranges of a VI source according to claim 1, wherein, The isolation switch module is formed by at least one high-speed, high-isolation, low-conduction-resistance solid-state analog switch array.

6. The system for seamless switching of voltage ranges of a VI source according to claim 1, wherein, The voltage holding and buffering module comprises a high-precision sample-and-hold circuit and a high-bandwidth voltage follower or buffer amplifier; the holding capacitor of the sample-and-hold circuit adopts a low-leakage dielectric material.

7. The system for seamless switching of voltage ranges of a VI source according to claim 1, wherein, The power amplifier internally comprises a fast-response power supply voltage regulating module, which ensures that the amplification output is stable when the power supply voltage changes, dynamically adjusts the peak-to-peak value of the output ripple voltage to be maintained within 5 mV, and the response speed of the power supply voltage regulating module is less than 1 microsecond.

8. A method for seamless switching of voltage ranges of a VI source, suitable for use in a system for seamless switching of voltage ranges of a VI source according to any one of claims 1 to 7, characterized in that, The method comprises the following steps: S1: system initialization and normal working state establishment, the digital controller performs power-on self-test, loads preset working parameters and calibration data, and initializes each module to a safe state; The VI source enters the normal working mode, the loop regulation module of the digital controller is enabled, a digital reference signal is generated according to the current range and the target voltage value, and the digital-to-analog converter converts the digital reference signal into an analog voltage signal; the digital controller configures the gain multiple of the programmable gain amplifier, the isolation switch module is turned on, the voltage holding and buffering module acts as a transparent buffer, the power amplifier drives the measured device, and the feedback measurement network continuously monitors and feeds back to the digital controller for closed-loop regulation; S2: range switching instruction receiving and working state freezing, the digital controller receives the switching instruction containing the new target voltage range and the new target voltage value, the range switching control logic module sends a "suspend regulation" signal to the loop regulation module, the digital-to-analog converter output voltage remains the current value, and the actual output voltage value is obtained from the feedback measurement network as a maintenance reference voltage; S3: output isolation and voltage holding function activation, the digital controller drives the isolation switch module to switch from on to off, synchronously activates the voltage holding and buffering module, the sample-and-hold circuit of the voltage holding and buffering module captures and holds the instantaneous voltage applied to the input end of the power amplifier, the power amplifier continues to receive the holding voltage to drive the measured device, and the output voltage is maintained stable; S4: internal reconfiguration of the programmable gain amplifier and the power amplifier, when the isolation switch module is off and the voltage holding and buffering module maintains the output voltage, the digital controller switches the programmable gain amplifier to the preset gain multiple matched with the new target voltage range through the gain control signal, and adjusts the power supply voltage of the power amplifier through the power supply voltage control signal; S5: pre-compensation and accurate matching calculation of the digital reference voltage, the range switching control logic module of the digital controller calculates the digital reference voltage value required by the digital-to-analog converter according to the maintenance reference voltage, the new target voltage range, the gain multiple of the programmable gain amplifier, the equivalent gain or attenuation coefficient under the new power supply voltage of the power amplifier, and the calibration value, and forcibly updates the digital reference voltage value; S6: output path reconnection and matching verification, the digital controller monitors the output voltage of the programmable gain amplifier under the new gain configuration and the new digital reference voltage, compares the output voltage with the holding voltage value of the voltage holding and buffering module, and when the difference is less than a preset threshold, drives the isolation switch module to switch from off to on, and reconnects the programmable gain amplifier and the power amplifier. S7: restore closed-loop regulation and target voltage regulation, after the isolation switch module is turned on and stable, the range switching control logic module sends a "restore regulation" signal to the loop regulation module, re-enables closed-loop control, and updates the VI source target voltage value to the final target voltage value; The loop regulation module adjusts the digital-to-analog converter output according to the new target voltage value and feedback data, so that the actual output voltage of the VI source is smoothly transitioned from the holding voltage value to the final target voltage value.

9. The method of seamless switching of VI source voltage ranges as claimed in claim 8 wherein, The isolation switch module in S3 is switched from on to off within 50 nanoseconds, and the voltage holding and buffer module's sample-and-hold circuit captures and holds the voltage before or at the moment of the isolation switch module being turned off. The holding accuracy is better than 0.01% within 100 microseconds, maintaining the output voltage on the device under test stable.

10. The method of seamless switching of VI source voltage range as claimed in claim 8 wherein, In the S5, the range switching control logic module inside the digital controller calculates The formula is: ； wherein, is the equivalent gain or attenuation coefficient of the power amplifier at the new supply voltage, is the calibration value for eliminating the inherent DC offset of the system at the new range and supply voltage, is the current actual output voltage value obtained from the feedback measurement network, is the new gain multiple of the programmed gain amplifier after the switching has been completed, and the digital controller will force the calculated value to the digital to analog converter, after which the output voltage of the digital to analog converter, after being amplified by the programmed gain amplifier, is precisely controlled to within 1 millivolt of the difference between the voltage and the voltage value being maintained by the voltage holding and buffering module.

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