Digital control system and method of VI source

Abstract

The invention discloses a digital control system and method of a VI source, and relates to the field of VI source control. A main loop controller and a clamping loop controller are separately arranged in a main controller, and seamless switching between the main loop controller and the clamping loop controller is realized in cooperation with a monitor; the main loop controller is responsible for accurately outputting voltage / current under a normal working condition, and the clamping loop controller is specially used for overload protection. The two controllers are provided with programmable adjusting parameters, and the response speed and the steady-state precision are dynamically optimized according to load characteristics. The monitor adopts a periodic scanning mechanism, monitors an output signal in real time and intelligently switches a control mode. According to the invention, the four-quadrant operation capability is realized, the hundred microsecond level protection response speed is realized while high-precision output is maintained, and the problems of response hysteresis and parameter solidification existing in a traditional simulation protection circuit are effectively solved.

Description

Technical Field

[0001] The present invention relates to the field of VI source control, and particularly to a digital control system and method for a VI source. Background Art

[0002] The statements in this section only provide background information related to the present disclosure and may not constitute prior art.

[0003] As a core instrument in the fields of automated test equipment (ATE) and electronic measurement, a VI source (voltage-current source) is mainly used for the electrical characteristic testing of various electronic components. It can operate in voltage source mode or current source mode. By applying a precisely controllable voltage / current excitation signal to the device under test (DUT) and synchronously collecting the response parameters of the device, the characteristics of passive / active components such as resistors, diodes, and MOSFETs can be analyzed. To ensure test accuracy, the prior art generally adopts a closed-loop feedback control architecture and is equipped with a voltage-current clamping protection mechanism to prevent the DUT from being damaged due to overload.

[0004] Traditional analog closed-loop control schemes construct feedback controllers through hardware circuits such as operational amplifiers and RC networks. The system response time is preset by the component parameters such as resistors and capacitors in the circuit. Once the hardware circuit design is completed, the dynamic response characteristics of the system are fixed, and users cannot adjust the response speed according to actual test requirements. If the response time needs to be adjusted, it must be achieved by replacing circuit components or switching preset redundant circuit modules (such as multiple groups of RC networks with different parameters and selection switches), which will lead to problems such as increased hardware costs and expanded circuit layout area. In addition, to avoid system instability caused by load changes, analog closed-loop designs often adopt a low fixed bandwidth to ensure generality, which further limits the optimization space of the system response ability.

[0005] Therefore, the existing analog closed-loop VI sources have the following technical defects: 1. Response time adjustment depends on hardware modification: Users cannot dynamically adjust the system response time and must achieve it by replacing circuit components or switching preset circuit modules, resulting in poor flexibility in use; 2. Hardware redundancy causes resource waste: To achieve a limited selection of response times, multiple groups of RC networks and switching switches need to be integrated on the circuit board, significantly increasing the manufacturing cost and PCB area; 3. It is difficult to balance performance and generality: Although a conservative bandwidth design can adapt to different loads, it sacrifices the system response speed, and the user's control over the response ability is severely restricted. Summary of the Invention

[0006] The object of the present invention is to provide a digital control system and method for a VI source, which combines a hardware circuit with a digital chip (such as a DSP, FPGA, etc.), in order to improve the limitations of the analog loop and reduce the complexity of analog circuit design. The closed-loop regulation function and the clamping control function originally implemented by hardware circuits such as operational amplifiers are transferred to the digital chip for implementation. Digital control is more flexible than analog control. The digital closed loop can easily adjust the loop parameters (bandwidth) of the system, and can provide appropriate response speed and stability for different loads. In addition, digital clamping can easily change the clamping judgment conditions and threshold values, getting rid of the limitations of hardware.

[0007] The technical solution of the present invention is as follows: A digital control system for a VI source, comprising: a digital controller, a voltage digital-to-analog converter, and a measurement unit; The voltage digital-to-analog converter converts the output of the digital controller from a digital quantity to an analog quantity, and the output voltage / current is applied to the load. The measurement unit measures the voltage / current value applied to the load. The digital controller internally integrates a main loop controller, a clamping loop controller, an output selector, and a monitor. Both the main loop controller and the clamping loop controller can adjust and output an analog quantity based on the measured value. The monitor selects the main loop controller or the clamping loop controller through the output selector according to the magnitude relationship between the measured value and the clamping threshold.

[0008] Furthermore, it further includes: an operational amplifier adjustment circuit, which adjusts the analog quantity according to requirements and then outputs it.

[0009] Furthermore, the measurement unit includes: a current measurement unit and a voltage measurement unit.

[0010] Furthermore, the current measurement unit includes: a current analog-to-digital converter and a current detection resistor; the current analog-to-digital converter, the operational amplifier adjustment circuit, and the current detection resistor measure the output current and convert the current analog quantity into a digital quantity and input it to the digital controller.

[0011] Furthermore, the voltage measurement unit includes: a voltage analog-to-digital converter; the voltage analog-to-digital converter and the operational amplifier adjustment circuit measure the output voltage and convert the voltage analog quantity into a digital quantity and input it to the digital controller.

[0012] Furthermore, a main loop feedback selector and a clamping loop feedback selector are also provided inside the digital controller; When the VI source operates in the transmitted voltage mode, the main loop feedback selector gates the voltage analog-to-digital converter, and the output selector default gates the main loop controller. By default, the main loop controller operates, and the clamp loop controller does not operate. The main loop controller compares the error between the voltage set value and the voltage measured value and sends it to the closed-loop regulator, so that under stable conditions, the output voltage value can be controlled to track the set value within the accuracy requirements. The clamp loop feedback selector gates the current analog-to-digital converter, and the monitor continuously monitors the input current of the clamp loop controller. When the input current exceeds the clamp threshold, the monitor activates the clamp loop controller, gates the output selector to the clamp loop controller, and simultaneously stops the operation of the main loop controller. The clamp loop controller compares the error between the clamp current value and the measured current value and sends it to the closed-loop regulator, thereby controlling the output current value to approach the clamp current value. When the VI source operates in the transmitted current mode, the main loop feedback selector gates the current analog-to-digital converter, and the output selector default gates the main loop controller. By default, the main loop controller operates, and the clamp loop controller does not operate. The main loop controller compares the error between the current set value and the current measured value and sends it to the closed-loop regulator, so that under stable conditions, the output current value can be controlled to track the set value within the accuracy requirements. The clamp loop feedback selector gates the voltage analog-to-digital converter, and the monitor continuously monitors the input voltage of the clamp loop controller. When the input voltage exceeds the clamp threshold, the monitor activates the clamp loop controller, gates the output selector to the clamp loop controller, and simultaneously stops the operation of the main loop controller. The clamp loop controller compares the error between the clamp voltage value and the measured voltage value and sends it to the closed-loop regulator, thereby controlling the output voltage value to approach the clamp voltage value.

[0013] Furthermore, both the main loop controller and the clamp loop controller can adjust the loop parameters according to the load to change the response speed and steady-state accuracy of the clamp current.

[0014] The present invention also proposes a digital control method for a VI source. Based on the above digital control system for a VI source, it includes: The main loop controller of the digital controller generates a voltage / current control signal, which is output to the load after being adjusted by the digital-to-analog conversion and operational amplifier adjustment circuit; The output voltage and current signals are respectively collected by the voltage analog-to-digital converter and the current analog-to-digital converter and fed back to the digital controller; The closed-loop regulator compares the error between the set value and the feedback value for closed-loop control; When the monitor detects that the output signal exceeds the preset clamp threshold, the closed-loop regulator of the clamp loop controller is switched to operate.

[0015] Further, when the VI source operates in the transmit voltage mode, the main loop feedback selector gates the voltage analog-to-digital converter, the output selector default gates the main loop controller, the default main loop controller operates, and the clamp loop controller does not operate; the main loop controller compares the error between the voltage set value and the voltage measured value and sends it to the closed-loop regulator, so that under stable conditions, the output voltage value can be controlled to track the set value within the accuracy requirement; the clamp loop feedback selector gates the current analog-to-digital converter, and the monitor continuously monitors the input current of the clamp loop controller; when the input current exceeds the clamp threshold, the monitor activates the clamp loop controller, gates the output selector to the clamp loop controller, and simultaneously stops the operation of the main loop controller; the clamp loop controller compares the error between the clamp current value and the measured current value and sends it to the closed-loop regulator, so as to control the output current value to approach the clamp current value.

[0016] Further, when the VI source operates in the transmit current mode, the main loop feedback selector gates the current analog-to-digital converter, the output selector default gates the main loop controller, the default main loop controller operates, and the clamp loop controller does not operate; the main loop controller compares the error between the current set value and the current measured value and sends it to the closed-loop regulator, so that under stable conditions, the output current value can be controlled to track the set value within the accuracy requirement; the clamp loop feedback selector gates the voltage analog-to-digital converter, and the monitor continuously monitors the input voltage of the clamp loop controller. When the input voltage exceeds the clamp threshold, the monitor activates the clamp loop controller, gates the output selector to the clamp loop controller, and simultaneously stops the operation of the main loop controller; the clamp loop controller compares the error between the clamp voltage value and the measured voltage value and sends it to the closed-loop regulator, so as to control the output voltage value to approach the clamp voltage value.

[0017] Compared with the existing technologies, the beneficial effects of the present invention are as follows: The system and method proposed by the present invention can operate in four quadrants and take into account the clamp protection function, can automatically switch between the normal operation mode and the clamp operation mode, and can flexibly adjust the response speed and accuracy of the output signal during normal operation, as well as the response speed and accuracy of the clamp output signal during clamp operation. Description of the Drawings

[0018] Figure 1 It is a block diagram of a digital control system for a VI source; Figure 2 It is an internal architecture diagram of a digital controller; Figure 3 It is a flowchart of the operation of a digital controller. Detailed Embodiments

[0019] It should be noted that relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent in such process, method, article or device. Without further limitation, an element defined by the statement "comprising a..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the element.

[0020] The features and performance of the present invention will be further described in detail below in conjunction with the embodiments.

[0021] Embodiment 1 Please refer to Figure 1 , a digital control system for a VI source, comprising: a digital controller, a voltage digital-to-analog converter, and a measurement unit; The voltage digital-to-analog converter converts the output of the digital controller from digital quantity to analog quantity, and outputs a voltage / current to be applied to the load; The measurement unit measures the voltage / current value applied to the load; The digital controller internally integrates a main loop controller, a clamping loop controller, an output selector, and a monitor; Both the main loop controller and the clamping loop controller can adjust and output an analog quantity based on the measured value; The monitor selects the main loop controller or the clamping loop controller through the output selector according to the magnitude relationship between the measured value and the clamping threshold.

[0022] In this embodiment, specifically, it further includes: an operational amplifier adjustment circuit, which adjusts (amplifies and biases) the analog quantity according to requirements and then outputs it.

[0023] In this embodiment, specifically, the measurement unit includes: a current measurement unit and a voltage measurement unit.

[0024] In this embodiment, specifically, the current measurement unit includes: a current analog-to-digital converter and a current detection resistor; the current analog-to-digital converter, the operational amplifier adjustment circuit, and the current detection resistor measure the output current and convert the current analog quantity into a digital quantity and input it to the digital controller.

[0025] In this embodiment, specifically, the voltage measurement unit includes: a voltage analog-to-digital converter; the voltage analog-to-digital converter and the operational amplifier adjustment circuit measure the output voltage and convert the voltage analog quantity into a digital quantity and input it to the digital controller.

[0026] In this embodiment, specifically, a main loop feedback selector and a clamping loop feedback selector are further provided inside the digital controller; it should be noted that the VI source can achieve closed-loop control of the transmitted voltage or current and has a clamping protection function, which is mainly realized through the internal logic of the digital controller. The internal architecture of the digital controller is as Figure 2 shown. Essentially, both the main loop controller and the clamping loop controller are VI source closed-loop controllers. The difference is that the main loop controller, as a normal working module, is used to quickly and stably generate voltage / current, while the clamping loop controller, as an abnormal protection function module, will bypass the main loop controller when the output voltage / current exceeds the clamping threshold and serve as the input source of the voltage digital-to-analog converter to stably clamp the system voltage and current at the set threshold to prevent damage to the internal components of the system or the device under test. The monitor, as a scheduler, is used to control when the main loop controller and the clamping loop controller work.

[0027] Specifically, when the VI source operates in the voltage transmission mode, the main loop feedback selector gates the voltage analog-to-digital converter, and the output selector default gates the main loop controller. By default, the main loop controller works, and the clamping loop controller does not work; the main loop controller compares the error between the voltage set value and the voltage measured value and sends it to the closed-loop regulator, so that under stable conditions, it can control the output voltage value to track the set value within the accuracy requirements; the main loop controller can adjust the loop parameters according to the load to change the response speed and steady-state accuracy of the clamping current; the clamping loop feedback selector gates the current analog-to-digital converter, and the monitor continuously monitors the input current of the clamping loop controller; when the input current exceeds the clamping threshold, the monitor activates the clamping loop controller, gates the output selector to the clamping loop controller, and at the same time stops the operation of the main loop controller; the clamping loop controller compares the error between the clamping current value and the measured current value and sends it to the closed-loop regulator to control the output current value to approach the clamping current value; at the same time, the clamping loop controller can adjust the loop parameters according to the load to change the response speed and steady-state accuracy of the clamping current; When the VI source operates in the transmit current mode, the main loop feedback selector gates the current analog-to-digital converter, and the output selector default gates the main loop controller. The default main loop controller operates, and the clamp loop controller does not operate. The main loop controller compares the error between the current set value and the current measured value and sends it to the closed-loop regulator, so that under stable conditions, it can control the output current value to track the set value within the accuracy requirements. The main loop controller can adjust the loop parameters according to the load to change the response speed and steady-state accuracy of the clamp current. The clamp loop feedback selector gates the voltage analog-to-digital converter, and the monitor continuously monitors the input voltage of the clamp loop controller. When the input voltage exceeds the clamp threshold, the monitor activates the clamp loop controller and gates the output selector to the clamp loop controller, while stopping the operation of the main loop controller. The clamp loop controller compares the error between the clamp voltage value and the measured voltage value and sends it to the closed-loop regulator, so as to control the output voltage value to approach the clamp voltage value. At the same time, the clamp loop controller can adjust the loop parameters according to the load to change the response speed and steady-state accuracy of the clamp current.

[0028] This embodiment also proposes a digital control method for a VI source. Based on the above digital control system for a VI source, it includes: Generate a voltage / current control signal through the main loop controller of the digital controller, and after being adjusted by the digital-to-analog conversion and operational amplifier adjustment circuit, output it to the load; Collect the output voltage and current signals through the voltage analog-to-digital converter and the current analog-to-digital converter respectively and feedback them to the digital controller; Perform closed-loop control by comparing the error between the set value and the feedback value through the closed-loop regulator; When the monitor detects that the output signal exceeds the preset clamp threshold, switch to the closed-loop regulator of the clamp loop controller to work.

[0029] In this embodiment, specifically, when the VI source operates in the transmit voltage mode, the main loop feedback selector gates the voltage analog-to-digital converter, and the output selector default gates the main loop controller. The default main loop controller operates, and the clamp loop controller does not operate. The main loop controller compares the error between the voltage set value and the voltage measured value and sends it to the closed-loop regulator, so that under stable conditions, it can control the output voltage value to track the set value within the accuracy requirements. The clamp loop feedback selector gates the current analog-to-digital converter, and the monitor continuously monitors the input current of the clamp loop controller. When the input current exceeds the clamp threshold, the monitor activates the clamp loop controller and gates the output selector to the clamp loop controller, while stopping the operation of the main loop controller. The clamp loop controller compares the error between the clamp current value and the measured current value and sends it to the closed-loop regulator, so as to control the output current value to approach the clamp current value.

[0030] In this embodiment, specifically, when the VI source operates in the transmit current mode, the main loop feedback selector gates the current analog-to-digital converter, and the output selector default gates the main loop controller. By default, the main loop controller operates, and the clamp loop controller does not operate. The main loop controller compares the error between the current set value and the current measured value and feeds it into the closed-loop regulator, so that under stable conditions, the output current value can be controlled to track the set value within the accuracy requirements. The clamp loop feedback selector gates the voltage analog-to-digital converter, and the monitor continuously monitors the input voltage of the clamp loop controller. When the input voltage exceeds the clamp threshold, the monitor activates the clamp loop controller, gates the output selector to the clamp loop controller, and simultaneously stops the operation of the main loop controller. The clamp loop controller compares the error between the clamp voltage value and the measured voltage value and feeds it into the closed-loop regulator, thereby controlling the output voltage value to approach the clamp voltage value.

[0031] In this embodiment, furthermore, the working process of the digital controller is as Figure 3 shown. Taking the VI source operating in the transmit voltage mode as an example: First, configure the parameters of the main loop controller and the clamp loop controller according to the desired response speed. The main loop feedback selector gates the voltage analog-to-digital converter, the clamp loop controller gates the current analog-to-digital converter, and the output selector default gates the main loop controller. By default, the main loop controller is enabled, and the clamp loop controller is disabled.

[0032] Wait for the host computer to send a start command, and then the main loop controller starts to work. By comparing the error between the voltage set value and the voltage measured value and feeding it into the closed-loop regulator, it controls the output voltage to track the given value. At the same time, the monitor starts to periodically monitor the input current of the clamp loop controller. When the clamp entry condition is met, the monitor activates the clamp loop controller, gates the output selector to the clamp loop controller, and simultaneously stops the operation of the main loop controller. The clamp loop controller controls the output current value to approach the clamp current value through the closed-loop regulator. The monitor continues to periodically monitor the input current of the clamp loop controller. When the clamp exit condition is met, the monitor activates the main loop controller, gates the output selector back to the main loop controller, and simultaneously stops the operation of the clamp loop controller, and so on in a cycle.

[0033] As long as the system starts to work, the monitor can automatically complete the scheduling and switching of the controllers until it receives the stop command from the host computer, then the loop controller stops working, and the system stops outputting voltage to the load.

[0034] The above-described embodiments merely represent the specific implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the protection scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the technical solution of the present application, several variations and improvements can still be made, and these all fall within the protection scope of the present application.

[0035] This Background of the Invention section is provided to generally present the context of the present invention. Work of the presently named inventors, to the extent it is described in this Background of the Invention section, and work that is not prior art as of the filing date of this application, are neither expressly nor impliedly admitted as prior art to the present invention.

Claims

1. A digital control system for a VI source, characterized in that, Including: A digital controller, a voltage digital-to-analog converter, and a measurement unit; The voltage digital-to-analog converter converts the output of the digital controller from digital quantity to analog quantity, and the output voltage / current is applied to the load; The measurement unit measures the voltage / current value applied to the load; The digital controller internally integrates a main loop controller, a clamping loop controller, an output selector, and a monitor; Both the main loop controller and the clamping loop controller can adjust and output analog quantity based on the measured value; The monitor selects the main loop controller or the clamping loop controller through the output selector according to the magnitude relationship between the measured value and the clamping threshold.

2. The digital control system of a VI source according to claim 1, characterized in that It also includes: An operational amplifier adjustment circuit that adjusts the analog quantity according to requirements and then outputs it.

3. The digital control system of a VI source according to claim 2, characterized in that, The measurement unit includes a current measurement unit and a voltage measurement unit.

4. The digital control system of a VI source according to claim 3, characterized in that, The current measurement unit includes a current analog-to-digital converter and a current detection resistor; the current analog-to-digital converter, the operational amplifier adjustment circuit, and the current detection resistor measure the output current and convert the current analog quantity into a digital quantity and input it to the digital controller.

5. A digital control system for a VI source according to claim 4, characterized in that, The voltage measurement unit includes a voltage analog-to-digital converter; the voltage analog-to-digital converter and the operational amplifier adjustment circuit measure the output voltage and convert the voltage analog quantity into a digital quantity and input it to the digital controller.

6. The digital control system of a VI source according to claim 5, characterized in that, The digital controller also internally has a main loop feedback selector and a clamping loop feedback selector; When the VI source works in the transmit voltage mode, the main loop feedback selector selects the voltage analog-to-digital converter, the output selector defaults to select the main loop controller, the main loop controller works by default, and the clamping loop controller does not work; the main loop controller compares the error between the voltage set value and the voltage measured value, and sends it to the closed-loop regulator, so that under stable conditions, it can control the output voltage value to track the set value within the accuracy requirements; the clamping loop feedback selector selects the current analog-to-digital converter, and the monitor continuously monitors the input current of the clamping loop controller; when the input current exceeds the clamping threshold, the monitor starts the clamping loop controller, and selects the output selector to the clamping loop controller, and at the same time stops the work of the main loop controller; the clamping loop controller compares the error between the clamping current value and the measured current value, and sends it to the closed-loop regulator, so as to control the output current value to approach the clamping current value; When the VI source works in the transmit current mode, the main loop feedback selector selects the current analog-to-digital converter, the output selector defaults to select the main loop controller, the main loop controller works by default, and the clamping loop controller does not work; the main loop controller compares the error between the current set value and the current measured value, and sends it to the closed-loop regulator, so that under stable conditions, it can control the output current value to track the set value within the accuracy requirements; the clamping loop feedback selector selects the voltage analog-to-digital converter, and the monitor continuously monitors the input voltage of the clamping loop controller. When the input voltage exceeds the clamping threshold, the monitor starts the clamping loop controller, and selects the output selector to the clamping loop controller, and at the same time stops the work of the main loop controller; the clamping loop controller compares the error between the clamping voltage value and the measured voltage value, and sends it to the closed-loop regulator, so as to control the output voltage value to approach the clamping voltage value.

7. The digital control system of a VI source according to claim 6, wherein Both the main loop controller and the clamping loop controller can adjust the loop parameters according to the load to change the response speed and steady-state accuracy of the clamping current.

8. A digital control method for a VI source, characterized in that, A digital control system for a VI source according to any one of claims 1-7, comprising: A main loop controller of a digital controller generates a voltage / current control signal, which is output to a load after being adjusted by a digital-to-analog conversion and operational amplifier adjustment circuit; The output voltage and current signals are respectively collected by a voltage analog-to-digital converter and a current analog-to-digital converter and fed back to the digital controller; Closed-loop control is performed by comparing the error between the set value and the feedback value through a closed-loop regulator; When the monitor detects that the output signal exceeds the preset clamping threshold, the closed-loop regulator of the clamping loop controller is switched to work.

9. A digital control method for a VI source according to claim 8, characterized in that, When the VI source operates in the transmitted voltage mode, the main loop feedback selector selects the voltage analog-to-digital converter, the output selector defaults to select the main loop controller, the main loop controller works by default, and the clamping loop controller does not work; the main loop controller compares the error between the voltage set value and the voltage measured value and sends it to the closed-loop regulator, so that the output voltage value can be controlled to track the set value within the accuracy requirement under stable conditions; the clamping loop feedback selector selects the current analog-to-digital converter, and the monitor continuously monitors the input current of the clamping loop controller; when the input current exceeds the clamping threshold, the monitor starts the clamping loop controller, and the output selector is selected to the clamping loop controller, and at the same time, the operation of the main loop controller is stopped; the clamping loop controller compares the error between the clamping current value and the measured current value and sends it to the closed-loop regulator, so as to control the output current value to approach the clamping current value.

10. A digital control method for a VI source according to claim 8, characterized in that, When the VI source operates in the transmitted current mode, the main loop feedback selector selects the current analog-to-digital converter, the output selector defaults to select the main loop controller, the main loop controller works by default, and the clamping loop controller does not work; the main loop controller compares the error between the current set value and the current measured value and sends it to the closed-loop regulator, so that the output current value can be controlled to track the set value within the accuracy requirement under stable conditions; the clamping loop feedback selector selects the voltage analog-to-digital converter, and the monitor continuously monitors the input voltage of the clamping loop controller. When the input voltage exceeds the clamping threshold, the monitor starts the clamping loop controller, and the output selector is selected to the clamping loop controller, and at the same time, the operation of the main loop controller is stopped; the clamping loop controller compares the error between the clamping voltage value and the measured voltage value and sends it to the closed-loop regulator, so as to control the output voltage value to approach the clamping voltage value.

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