Digital closed-loop oscillation protection circuit, method, electronic load and system

Abstract

The invention discloses a digital closed-loop oscillation protection circuit, method, electronic load and system, the circuit comprises an oscillation signal acquisition circuit, the oscillation signal acquisition circuit comprises a sampling unit and a coupling capacitor unit, the sampling unit is used for acquiring current and / or voltage data of a closed-loop control circuit, and the output end of the sampling unit is connected with the coupling capacitor unit; the control module is used for outputting a control signal of the closed-loop control circuit, the output end of the coupling capacitor unit is connected with the signal input end of the control module through a first ADC, and the control module judges whether oscillation occurs or not according to the amplitude of the alternating-current component signal and stops output of the control signal to close the closed-loop control circuit under the condition that oscillation occurs. Oscillation protection can be realized without arranging a fuse, and the protection response time is short.

Description

Technical Field

[0001] The present application relates to the field of power supply testing, and in particular to a digital closed-loop oscillation protection circuit, method, electronic load and system. Background Art

[0002] Closed-loop control circuits automatically adjust output through feedback. Many electronic devices are equipped with closed-loop control circuits, such as electronic loads.

[0003] When the closed-loop control parameters of existing electronic loads are not properly selected, or when the voltage of the power supply under test is unstable, self-oscillation may occur. Self-oscillation refers to a steady and continuous oscillation that is generated without an external excitation signal. If there is no input signal at the input end of the amplifier, there is still an output signal with a certain amplitude and frequency at the output end. This phenomenon is self-oscillation. Self-oscillation may break down components such as power tubes in the closed-loop control circuit, causing damage to the electronic load or short circuit damage to the power supply under test.

[0004] One existing solution is to connect a fuse in series in a closed-loop control circuit. When the loop self-oscillates, the fuse overheats and burns out, disconnecting the entire loop and protecting the electronic load from damage. The disadvantages of using a fuse are that it takes a while for the fuse to overheat and burn out after self-oscillation occurs. During this period, other components may have been damaged, and the protection response time is long. In addition, since the fuse must not only meet the requirements of not being damaged during normal DC operation, but also meet the requirements of overheating and melting as quickly as possible after oscillation, and needs to adapt to scenarios with different currents and voltages, it is difficult to select a suitable fuse. Summary of the invention

[0005] The present application proposes a digital closed-loop oscillation protection circuit, method, electronic load and system that can achieve oscillation protection without setting a fuse and has a short protection response time.

[0006] According to the digital closed-loop oscillation protection circuit of the first aspect of the present application, a closed-loop control circuit is connected, and the output end of the closed-loop control circuit is connected to the power supply under test, including: an oscillation signal acquisition circuit, the oscillation signal acquisition circuit includes a sampling unit and a coupling capacitor unit, the sampling unit is used to collect current and / or voltage data of the closed-loop control circuit, the output end of the sampling unit is connected to the coupling capacitor unit for obtaining the AC component signal in the sampled voltage and / or current; a control module, which is used to output the control signal of the closed-loop control circuit, the output end of the coupling capacitor unit is connected to the signal input end of the control module through a first ADC for inputting the AC component signal, the control module determines whether oscillation occurs according to the amplitude of the AC component signal, and stops the output of the control signal to close the closed-loop control circuit when oscillation occurs.

[0007] The digital closed-loop oscillation protection circuit according to the first aspect of the present application has at least the following beneficial effects: In the implementation mode of the present application, the voltage and / or current of the closed-loop control circuit collected is input to the coupling capacitor unit through the sampling unit, and the DC component in the sampled voltage and / or current is filtered out through the coupling capacitor unit. When the closed-loop control circuit self-oscillates, the coupling capacitor unit can obtain the AC component in the sampled voltage and / or current after filtering out the component. After the control module obtains the AC component signal through the first ADC, it determines whether oscillation occurs according to the amplitude of the AC component signal. In the event of oscillation, the output of the control signal is stopped to close the closed-loop control circuit. The present application uses digital signals to detect self-oscillation. Since the control module itself is the sending end of the control signal of the closed-loop control circuit, the output of the control signal can be stopped immediately after the self-oscillation is detected. Oscillation protection can be achieved without setting a fuse, and the protection response time is short.

[0008] According to some embodiments of the present application, the sampling unit includes a current sampling circuit, which samples the output current of the closed-loop control circuit through a non-inductive sampling resistor, and the output end of the current sampling circuit is connected to the input end of the coupling capacitor unit.

[0009] According to some embodiments of the present application, the sampling unit includes a voltage sampling circuit, which is used to sample the voltage at the output end of the closed-loop control circuit, and the output end of the voltage sampling circuit is connected to the input end of the coupling capacitor unit.

[0010] According to some embodiments of the present application, the sampling unit includes a current sampling circuit and the voltage sampling circuit, the coupling capacitor unit includes a first coupling capacitor circuit and a second coupling capacitor circuit, the output end of the current sampling circuit is connected to the input end of the first coupling capacitor circuit, and the output end of the first coupling capacitor circuit and the output end of the second coupling capacitor circuit are respectively connected to the signal input end of the control module through a first ADC.

[0011] According to some embodiments of the present application, the coupling capacitor unit includes multiple coupling capacitors with different capacitances, the output end of the sampling unit is respectively connected to the input end of a coupling capacitor, and the coupling capacitors are respectively connected to the signal input end of the control module through a first ADC for inputting AC component signals of different frequencies.

[0012] According to some embodiments of the present application, it also includes a first resistor, a first capacitor and a temperature switch, the output end of the closed-loop control circuit is connected to the negative electrode of the power supply under test through the first resistor and the first capacitor connected in series, the output end of the closed-loop control circuit is connected to the positive electrode of the power supply under test through the temperature switch, and the detection end of the temperature switch is connected to the first resistor for detecting the temperature of the first resistor and disconnecting the output of the closed-loop control circuit when the temperature reaches a threshold.

[0013] According to the second aspect of the present application, a digital closed-loop oscillation protection circuit control method includes: Acquire first amplitude information and second amplitude information, wherein the first amplitude information is used to indicate the AC amplitude of the AC component signal, and the second amplitude information is used to indicate the amplitude of the rated DC output of the second amplitude information closed-loop control circuit; The first amplitude information is compared with the second amplitude information, and if the first amplitude information exceeds N% of the second amplitude information, it is determined that the closed-loop control circuit oscillates.

[0014] The digital closed-loop oscillation protection circuit control method according to the second aspect of the present application has at least the following beneficial effects: In the implementation mode of the present application, the voltage and / or current of the closed-loop control circuit collected is input to the coupling capacitor unit through the sampling unit, and the DC component in the sampled voltage and / or current is filtered out through the coupling capacitor unit. When the closed-loop control circuit self-oscillates, the coupling capacitor unit can obtain the AC component in the sampled voltage and / or current after filtering out the component. After the control module obtains the AC component signal through the first ADC, it determines whether oscillation occurs according to the amplitude of the AC component signal. In the event of oscillation, the output of the control signal is stopped to close the closed-loop control circuit. The present application uses digital signals to detect self-oscillation. Since the control module itself is the sending end of the control signal of the closed-loop control circuit, the output of the control signal can be stopped immediately after the self-oscillation is detected. Oscillation protection can be achieved without setting a fuse, and the protection response time is short.

[0015] According to the third aspect of the present application, the electronic load includes a closed-loop control circuit and the above-mentioned digital closed-loop oscillation protection circuit.

[0016] The electronic load according to the third aspect of the present application has at least the following beneficial effects: In the implementation mode of the present application, the voltage and / or current of the closed-loop control circuit collected is input to the coupling capacitor unit through the sampling unit, and the DC component in the sampled voltage and / or current is filtered out through the coupling capacitor unit. When the closed-loop control circuit self-oscillates, the coupling capacitor unit can obtain the AC component in the sampled voltage and / or current after filtering out the component. After the control module obtains the AC component signal through the first ADC, it determines whether oscillation occurs according to the amplitude of the AC component signal. In the event of oscillation, the output of the control signal is stopped to close the closed-loop control circuit. The present application uses digital signals to detect self-oscillation. Since the control module itself is the sending end of the control signal of the closed-loop control circuit, the output of the control signal can be stopped immediately after the self-oscillation is detected. Oscillation protection can be achieved without setting a fuse, and the protection response time is short.

[0017] According to the fourth aspect of the present application, the power supply testing system includes the above-mentioned electronic load and the power supply under test.

[0018] The power supply testing system according to the fourth aspect of the present application has at least the following beneficial effects: In the implementation mode of the present application, the voltage and / or current of the closed-loop control circuit collected is input to the coupling capacitor unit through the sampling unit, and the DC component in the sampled voltage and / or current is filtered out through the coupling capacitor unit. When the closed-loop control circuit self-oscillates, the coupling capacitor unit can obtain the AC component in the sampled voltage and / or current after filtering out the component. After the control module obtains the AC component signal through the first ADC, it determines whether oscillation occurs according to the amplitude of the AC component signal. In the event of oscillation, the output of the control signal is stopped to close the closed-loop control circuit. The present application uses digital signals to detect self-oscillation. Since the control module itself is the sending end of the control signal of the closed-loop control circuit, the output of the control signal can be stopped immediately after the self-oscillation is detected. Oscillation protection can be achieved without setting a fuse, and the protection response time is short.

[0019] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present application is further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 It is a circuit schematic diagram of a current closed-loop control circuit in the related art; Figure 2 It is a principle block diagram of a digital closed-loop oscillation protection circuit in an embodiment of the present application; Figure 3This is a circuit schematic diagram of the first digital closed-loop oscillation protection circuit in the embodiment of the present application; Figure 4 1 is a circuit schematic diagram of a second digital closed-loop oscillation protection circuit in an embodiment of the present application; Figure 5 1 is a circuit schematic diagram of a third digital closed-loop oscillation protection circuit in an embodiment of the present application; Figure 6 : is a circuit schematic diagram of a fourth digital closed-loop oscillation protection circuit in an embodiment of the present application; Figure 7 4 is a circuit schematic diagram of a digital oscillation protection circuit with an RC circuit in an embodiment of the present application. DETAILED DESCRIPTION

[0021] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0022] In the description of the present application, it should be understood that the descriptions involving orientation, such as the orientation or positional relationship indicated as up, down, etc., are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0023] In the description of this application, "a plurality" means more than two. If there is a description of "first" or "second", it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0024] In the description of this application, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in this application based on the specific content of the technical solution.

[0025] In this article, relational terms such as first and second, etc. are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "include..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0026] The present application is to solve the self-oscillation problem of the closed-loop control circuit. The following first introduces some background of the present application. The closed-loop control circuit includes a current closed-loop control circuit, a voltage closed-loop control circuit, a current-voltage closed-loop control circuit, etc. Figure 1 As shown, a current closed-loop control circuit in an electronic load includes a digital-to-analog converter (DAC), an analog-to-digital converter (ADAC), and a Converter, first ADC), Metal-Oxide-Semiconductor Field Effect Transistor (MOS) tube, signal conditioning module, error amplifier U1, current sampling resistor R1 and differential amplifier U2. The MCU of the electronic load outputs a DC signal setting value through the DAC, and enters the error amplifier U1 through the signal conditioning module. The output end of the error amplifier U1 is connected to the gate of the MOS tube. The drain and source of the MOS tube are respectively connected to the positive and negative electrodes of the power supply under test. The source of the MOS tube is connected in series with the current sampling resistor R1. The input end of the differential amplifier U2 is connected to the two ends of the current sampling resistor R1. The output end of the differential amplifier U2 is input to the feedback end of the MCU through the second ADC. The MCU collects the current of the MOS tube through the feedback end, and then controls the conduction of the MOS tube through the proportional-integral-derivative control (Proportional-Integral-Derivative-PID) algorithm, thereby realizing closed-loop constant current control.

[0027] During the operation of the electronic load, the closed-loop control circuit may have the problem of self-oscillation. Self-oscillation refers to the steady and continuous oscillation that is generated without an external excitation signal. If there is no input signal at the input end of the amplifier, but there is still an output signal with a certain amplitude and frequency at the output end, this phenomenon is self-oscillation.

[0028] The formation principle of self-oscillation is mainly based on amplitude balance conditions and phase balance conditions. Specifically, there are many natural poles inside an actual operational amplifier, which may cause additional phase shift, causing the output phase shift to exceed -180°. When negative feedback is used, if the additional phase shift reaches ±180°, the feedback signal is in phase with the input signal, and the negative feedback becomes positive feedback, thereby causing self-oscillation.

[0029] In a self-excited oscillation circuit, there is usually a positive feedback loop to continuously enhance the oscillation signal. For example, in the closed-loop control circuit of an electronic load, after the voltage or current is set, the DAC outputs an analog quantity, and after the MOS tube is slightly turned on, the circuit is started. The positive feedback loop is composed of feedback resistance, parasitic inductance and capacitance. When the current in the initial loop changes, the feedback winding will induce a voltage, which is coupled to the op amp's in-phase terminal through the capacitor, thereby enhancing the conduction ability of the switch tube. Under the action of continuous positive feedback, the power tube will quickly reach a saturated conduction state. After that, the voltage induced by the feedback resistor disappears, and the feedback voltage of the op amp decreases, resulting in a decrease in its conduction ability, which in turn reduces the conduction amount of the MOS tube and reduces the loop current. This process will be repeated continuously, resulting in continuous oscillation.

[0030] In the closed-loop control of electronic loads, if the PID parameters are not properly selected, self-oscillation may occur. In addition, when the voltage of the power supply under test is unstable, the voltage noise is converted into current noise and fed back to the control terminal of the operational amplifier, causing the output of the operational amplifier to be unstable, which can also form self-oscillation.

[0031] Self-excited oscillation may break down components such as power tubes in the closed-loop control circuit, causing damage to the electronic load or short circuit damage to the power supply under test.

[0032] One existing solution is to connect a fuse in series in a closed-loop control circuit. When the loop self-oscillates, the fuse overheats and burns out, disconnecting the entire loop and protecting the electronic load from damage. The disadvantages of using a fuse are that it takes a while for the fuse to overheat and burn out after self-oscillation occurs. During this period, other components may have been damaged, and the protection response time is long. In addition, since the fuse must not only meet the requirements of not being damaged during normal DC operation, but also meet the requirements of overheating and melting as quickly as possible after oscillation, and needs to adapt to scenarios with different currents and voltages, it is difficult to select a suitable fuse.

[0033] In order to solve the above problems, the present application proposes a digital closed-loop oscillation protection circuit, method, electronic load and system. The digital closed-loop oscillation protection circuit of the present application is first introduced below. Figure 2As shown, a digital closed-loop oscillation protection circuit is connected to a closed-loop control circuit, and the output end of the closed-loop control circuit is connected to a power supply under test, including: an oscillation signal acquisition circuit and a control module. Specifically, the oscillation signal acquisition circuit includes a sampling unit and a coupling capacitor unit. The sampling unit is used to collect current and / or voltage data of the closed-loop control circuit. The output end of the sampling unit is connected to the coupling capacitor unit to obtain the AC component signal in the sampled voltage and / or current.

[0034] The control module is used to output a control signal of a closed-loop control circuit. The output end of the coupling capacitor unit is connected to the signal input end of the control module through a first ADC for inputting an AC component signal. The control module determines whether oscillation occurs based on the amplitude of the AC component signal, and stops outputting the control signal to close the closed-loop control circuit when oscillation occurs.

[0035] In this embodiment, the control module includes a microcontroller unit (MCU), a field programmable gate array (FPGA) and a human-computer interaction module. The FPGA calculates and outputs a control signal of a closed-loop control circuit through a PID algorithm to control the conduction of the MOS tube, thereby realizing closed-loop control. The control signal is the DC signal setting value output by the FPGA through the DAC. The human-computer interaction module is connected to the FPGA through the MCU. The human-computer interaction module includes a liquid crystal display (LCD) and buttons. Parameter setting and data reading operations can be performed through the MCU. The MCU communicates with the FPGA to read parameters and data. The control module can also only use the FPGA and be connected to the FPGA through a host computer.

[0036] Among them, the sampling unit can be current sampling, voltage sampling or current + voltage sampling. Taking the sampling current as an example, when the loop self-oscillates, the sampling current contains a DC component and an AC component. The DC component in the sampling current can be filtered out by the coupling capacitor in the coupling capacitor unit. The coupling capacitor in the coupling capacitor unit can be one or more. After filtering by the coupling capacitor unit, an AC component signal is output. The analog quantity of the AC component signal is converted into a digital quantity by the first ADC and enters the FPGA. The FPGA calculates the amplitude and frequency of the AC component through the Fast Fourier Transform (Fast Fourier Transform -FFT) algorithm. The FPGA determines whether oscillation occurs based on the amplitude. When a normal DC load pulls the current, the AC component signal collected by the first ADC is close to 0V. When self-oscillation occurs, the FPGA will collect an AC component of a certain amplitude. After the FPGA determines that self-oscillation occurs, the output of the control signal is stopped, and the closed-loop control circuit stops working, thereby protecting the safety of the electronic load.

[0037] In the implementation mode of the present application, the voltage and / or current of the closed-loop control circuit collected is input to the coupling capacitor unit through the sampling unit, and the DC component in the sampled voltage and / or current is filtered out through the coupling capacitor unit. When the closed-loop control circuit self-oscillates, the coupling capacitor unit can obtain the AC component in the sampled voltage and / or current after filtering out the component. After the control module obtains the AC component signal through the first ADC, it determines whether oscillation occurs according to the amplitude of the AC component signal. In the event of oscillation, the output of the control signal is stopped to close the closed-loop control circuit. The present application uses digital signals to detect self-oscillation. Since the control module itself is the sending end of the control signal of the closed-loop control circuit, the output of the control signal can be stopped immediately after the self-oscillation is detected. Oscillation protection can be achieved without setting a fuse, and the protection response time is short.

[0038] In some embodiments of the present application, the sampling unit includes a current sampling circuit, which samples the output current of the closed-loop control circuit through a non-inductive sampling resistor, and the output end of the current sampling circuit is connected to the input end of the coupling capacitor unit.

[0039] In this implementation, the output current of the closed-loop control circuit is sampled by the non-inductive sampling resistor R2, so that the detection accuracy of the self-oscillation can be improved.

[0040] refer to Figure 3As shown, the current sampling circuit includes a non-inductive sampling resistor R2 and a differential amplifier U3, and the coupling capacitor unit includes a capacitor C1. The non-inductive sampling resistor R2 is connected in series between the source of the MOS tube Q1 and the power supply under test, and the input end of the differential amplifier U3 is respectively connected to the two ends of the non-inductive sampling resistor R2. The voltage at both ends of the non-inductive sampling resistor R2 is amplified by the differential amplifier U3, and then passes through the first-level coupling of the capacitor C1, and enters the FPGA through the first ADC to realize the acquisition of the AC component of the output current. The present application adopts the non-inductive sampling resistor R2 as the current sampling resistor to reduce the parasitic inductance of the resistor to form a phase shift, and avoid the problem that the resistor suppresses the AC component and cannot be collected. The non-inductive resistor only needs the resistance on the wire or coil to work, and there should be no inductance or voltage generated by induction. The common non-inductive resistor is to use two insulated wires together, the terminals are short-circuited, and the head end is externally connected to the power supply and application circuit. The current directions of these two insulated wires are opposite, there is no external mutual inductance, and they can be wound into a coil for use, and only play the role of a resistor. The low-frequency to high-frequency current analog signal is obtained through the non-inductive sampling resistor, and the excellent high-frequency response performance of the non-inductive sampling resistor can be used to improve the measurement accuracy.

[0041] In some embodiments of the present application, the sampling unit includes a voltage sampling circuit, which is used to sample the voltage at the output end of the closed-loop control circuit, and the output end of the voltage sampling circuit is connected to the input end of the coupling capacitor unit.

[0042] In this embodiment, the voltage at the output end of the closed-loop control circuit is sampled by a voltage sampling circuit, and the self-oscillation is identified by collecting the AC component of the voltage, which can improve the measurement accuracy in the scenario of unstable voltage of the power supply under test.

[0043] refer to Figure 4 As shown, in the embodiment of the present application, the voltage sampling circuit includes a differential amplifier U4, the coupling capacitor unit includes a capacitor C3, the input end of the differential amplifier U4 is respectively connected to the output end of the electronic load, that is, the two ends of the power supply under test, and the output end of the differential amplifier U4 is connected to the FPGA through the capacitor C3 and the first ADC. Because the power supply under test must have internal resistance, when the circuit current oscillates, an AC voltage will be generated at the port. After amplification by the differential amplifier U4, it is coupled at a first level to realize the acquisition of the AC component of the output voltage. Since the port voltage is collected, the self-excited oscillation of the power supply under test in the voltage instability scenario can be more accurately reflected.

[0044] In some embodiments of the present application, the sampling unit includes a current sampling circuit and a voltage sampling circuit, the coupling capacitor unit includes a first coupling capacitor circuit and a second coupling capacitor circuit, the output end of the current sampling circuit is connected to the input end of the first coupling capacitor circuit, and the output end of the first coupling capacitor circuit and the output end of the second coupling capacitor circuit are respectively connected to the signal input end of the control module through a first ADC.

[0045] In this embodiment, the output current AC component and the output voltage AC component of the loop are sampled respectively through the current sampling circuit and the voltage sampling circuit. The FPGA detects self-oscillation by simultaneously sampling the output current AC component and the output voltage AC component, and respectively calculating the amplitude of the AC voltage and the AC current, thereby further improving the detection accuracy of self-oscillation.

[0046] refer to Figure 5 As shown, the current sampling circuit includes a non-inductive sampling resistor R2 and a differential amplifier U3, the voltage sampling circuit includes a differential amplifier U4, the coupling capacitor unit includes a capacitor C1 and a capacitor C3, the non-inductive sampling resistor R2 is connected in series between the source of the MOS tube Q1 and the power supply under test, the input end of the differential amplifier U3 is respectively connected to the two ends of the non-inductive sampling resistor R2, the output end of the differential amplifier U3 is connected to the capacitor C1, the capacitor C1 is connected to the SPI3 port of the FPGA through a first ADC, the input end of the differential amplifier U4 is respectively connected to the output end of the power supply under test, the output end of the differential amplifier U4 is connected to the capacitor C3, and the capacitor C3 is connected to the SPI5 port of the FPGA through another first ADC.

[0047] In some embodiments of the present application, the coupling capacitor unit includes multiple coupling capacitors with different capacitances, the output end of the sampling unit is respectively connected to the input end of a coupling capacitor, and the coupling capacitors are respectively connected to the signal input end of the control module through a first ADC for inputting AC component signals of different frequencies.

[0048] In this embodiment, the coupling capacitor unit includes a plurality of coupling capacitors connected in parallel and having different capacitances. By setting coupling capacitors with different capacitances, AC components of different frequencies can be collected respectively, further improving the detection accuracy of self-oscillation.

[0049] refer to Figure 6 As shown, taking the sampling unit including the current sampling circuit and the voltage sampling circuit as an example, the coupling capacitor unit includes capacitor C1, capacitor C2, capacitor C3 and capacitor C4, capacitor C1 and capacitor C2 correspond to the current sampling circuit, capacitor C3 and capacitor C4 correspond to the voltage sampling circuit, capacitor C1 and capacitor C2 have different capacitance values, capacitor C3 and capacitor C4 have different capacitance values, the output end of the differential amplifier U3 is respectively connected to capacitor C1 and capacitor C2, capacitor C1 is connected to the SPI3 port of the FPGA through the first first ADC, capacitor C2 is connected to the SPI4 port of the FPGA through the second first ADC, the output end of the differential amplifier U4 is respectively connected to capacitor C3 and capacitor C4, capacitor C3 is connected to the SPI5 port of the FPGA through the third first ADC, capacitor C4 is connected to the SPI6 port of the FPGA through the fourth first ADC.

[0050] Exemplarily, in this embodiment, capacitors C1 and C3 are 10uF capacitors for collecting low-frequency AC components, and capacitors C2 and C4 are 10nF capacitors for collecting high-frequency AC components.

[0051] It should be understood that in this embodiment, the number of coupling capacitors of different capacitance values ​​in each group is not limited to two, but may be three, four or more, and the sampling unit may be only any one of the current sampling circuit and the voltage sampling circuit. The above capacitance selection of C1-C4 is only an example, and capacitors of other capacitance values ​​may also be selected to achieve the acquisition of AC components of different frequencies. The selection of capacitance value can be calculated by the formula f=1 / 2πRC, where R is the resistance value of the load resistor, that is, the input resistance of the coupling next-level circuit, f is the frequency of the signal, and C is the capacitance value of the coupling capacitor. The corresponding coupling capacitor is selected according to different frequencies to meet different test requirements.

[0052] In some embodiments of the present application, a first resistor, a first capacitor and a temperature switch are also included. The output end of the closed-loop control circuit is connected to the negative electrode of the power supply under test through the first resistor and the first capacitor connected in series, and the output end of the closed-loop control circuit is connected to the positive electrode of the power supply under test through the temperature switch. The detection end of the temperature switch is connected to the first resistor to detect the temperature of the first resistor and disconnect the output of the closed-loop control circuit when the temperature reaches a threshold value.

[0053] In some embodiments of the present application, a first resistor Rc, a first capacitor Cr and a temperature switch S1 are also included. The output end of the closed-loop control circuit is connected to the negative electrode of the power supply under test through the first resistor and the first capacitor connected in series, and the output end of the closed-loop control circuit is connected to the positive electrode of the power supply under test through the temperature switch S1. The detection end of the temperature switch S1 is connected to the first resistor Rc to detect the temperature of the first resistor Rc and disconnect the output of the closed-loop control circuit when the temperature reaches a threshold.

[0054] In this embodiment, reference Figure 7As shown, the sampling unit includes a current sampling circuit and a voltage sampling circuit. The source of the MOS tube Q1 is connected to the negative electrode of the power supply under test through an RC circuit constructed by a first resistor Rc and a first capacitor Cr. The temperature switch S1 is set between the drain of the MOS tube Q1 and the positive electrode of the power supply under test. When the loop does not self-oscillate, the loop output normally pulls the DC, the first capacitor Cr is cut off, and the RC circuit is not effective. When the loop self-oscillates, the first capacitor Cr is turned on, and the first resistor Rc generates heat due to the current flowing through it. When the temperature reaches the threshold, the temperature switch S1 is triggered to disconnect, and the loop output stops. In this embodiment, the first resistor Rc uses a power resistor. In the embodiment of the present application, on the basis of the current sampling circuit and the voltage sampling circuit, an oscillation protection unit formed by an RC circuit and a temperature switch S1 is additionally added, which can realize triple protection against self-oscillation and further improve the reliability of oscillation protection.

[0055] It should be understood that, in this embodiment, the sampling unit may also be only a current sampling circuit or a voltage sampling circuit.

[0056] The present application also relates to a digital closed-loop oscillation protection circuit control method using the circuit of the above embodiment, comprising: S101, obtaining first amplitude information and second amplitude information, wherein the first amplitude information is used to indicate the AC amplitude of the AC component signal, and the second amplitude information is used to indicate the amplitude of the rated DC output of the second amplitude information closed-loop control circuit; S102: Compare the first amplitude information with the second amplitude information. If the first amplitude information exceeds N% of the second amplitude information, determine that the closed-loop control circuit oscillates.

[0057] In this embodiment, by comparing the first amplitude information with the second amplitude information, if the first amplitude information exceeds N% of the second amplitude information, it is determined that the closed-loop control circuit oscillates, which can improve the stability of the closed-loop control circuit operation and reduce the probability of misjudgment.

[0058] The logic judgment of the above steps S101 and 102 is implemented by the program in the control module. Since the power supply under test may generate source ripples during the test, the control module may also collect a certain amount of AC components, and this part of the AC components belongs to the ripple influence of the power supply under test, not self-oscillation. Therefore, if the amplitude judgment threshold of the control module for the AC component is too low, there may be misjudgment. Therefore, in this application, the AC amplitude of the AC component signal is compared with the amplitude of the rated DC output of the closed-loop control circuit. If the first amplitude information exceeds N% of the second amplitude information, it is determined that the closed-loop control circuit oscillates. That is, N% of the amplitude lower than the rated DC output is considered to be the ripple influence of the power supply under test, and it is not determined that self-oscillation has occurred. Only when the amplitude of the AC component exceeds N% of the rated DC output amplitude, it is considered that self-oscillation has occurred. At this time, the control module stops the output of the control signal and performs self-oscillation protection.

[0059] It should be noted that after a lot of testing and verification, when N is 5, the ripple effect of the power supply under test can be filtered out more accurately, that is, the source ripple of the power supply under test on the market will not exceed 5% at worst. Therefore, when the AC component exceeds 5%, the FPGA will judge it as oscillation, and if it is less than 5%, it is considered to be the ripple of the power supply under test and will not affect the normal operation of the electronic load.

[0060] The present application also relates to an electronic load, comprising a closed-loop control circuit and the digital closed-loop oscillation protection circuit of the above embodiment.

[0061] The present application also relates to a power supply testing system, comprising the electronic load of the above embodiment and a power supply to be tested.

[0062] In summary, the present application realizes self-oscillation protection for the closed-loop control circuit. When the loop oscillates, the triple protection takes effect, stops the oscillation of the loop, protects the control device from damage, and avoids the explosion or even fire caused by the short-circuit state of the electronic load, thereby ensuring the safety of the power supply under test. Especially in the field of high-voltage and high-power high-voltage charging pile testing, once the loop oscillates, the short circuit formed after the electronic load device is damaged can easily cause the machine to explode, and it is more likely to catch fire. The circuit of the present application can protect the safety of the electronic load and the power supply under test without affecting the performance of the electronic load under normal operation.

[0063] The above is only a specific implementation of the present application. Those skilled in the art can clearly understand that for the convenience and simplicity of description, the specific working processes of the systems, modules and units described above can refer to the corresponding processes in the aforementioned method embodiments, and will not be repeated here. It should be understood that the protection scope of the present application is not limited to this. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in this application, and these modifications or replacements should be included in the protection scope of this application.

Claims

1. A digital closed-loop oscillation protection circuit, connected to a closed-loop control circuit, wherein the output end of the closed-loop control circuit is connected to a power supply under test, characterized in that: include: An oscillation signal acquisition circuit, the oscillation signal acquisition circuit comprising a sampling unit and a coupling capacitor unit, the sampling unit being used to collect current and / or voltage data of the closed-loop control circuit, and the output end of the sampling unit being connected to the coupling capacitor unit to obtain an AC component signal in the sampled voltage and / or current; A control module is used to output a control signal of the closed-loop control circuit. The output end of the coupling capacitor unit is connected to the signal input end of the control module through a first ADC for inputting an AC component signal. The control module determines whether oscillation occurs based on the amplitude of the AC component signal, and stops outputting the control signal to close the closed-loop control circuit when oscillation occurs.

2. The digital closed-loop oscillation protection circuit according to claim 1, characterized in that: The sampling unit comprises a current sampling circuit, and the current sampling circuit samples the output current of the closed-loop control circuit through a non-inductive sampling resistor, and the output end of the current sampling circuit is connected to the input end of the coupling capacitor unit.

3. The digital closed-loop oscillation protection circuit according to claim 1, characterized in that: The sampling unit comprises a voltage sampling circuit, and the voltage sampling circuit is used to sample the voltage at the output end of the closed-loop control circuit, and the output end of the voltage sampling circuit is connected to the input end of the coupling capacitor unit.

4. The digital closed-loop oscillation protection circuit according to claim 1, characterized in that: The sampling unit includes a current sampling circuit and a voltage sampling circuit, the coupling capacitor unit includes a first coupling capacitor circuit and a second coupling capacitor circuit, the output end of the current sampling circuit is connected to the input end of the first coupling capacitor circuit, and the output end of the first coupling capacitor circuit and the output end of the second coupling capacitor circuit are respectively connected to the signal input end of the control module through a first ADC.

5. The digital closed-loop oscillation protection circuit according to claim 1, characterized in that: The coupling capacitor unit includes a plurality of coupling capacitors with different capacitances. The output end of the sampling unit is respectively connected to the input end of a coupling capacitor. The coupling capacitors are respectively connected to the signal input end of the control module through a first ADC for inputting AC component signals of different frequencies.

6. The digital closed-loop oscillation protection circuit according to claim 1, characterized in that: It also includes a first resistor, a first capacitor and a temperature switch. The output end of the closed-loop control circuit is connected to the negative electrode of the power supply under test through the first resistor and the first capacitor connected in series. The output end of the closed-loop control circuit is connected to the positive electrode of the power supply under test through the temperature switch. The detection end of the temperature switch is connected to the first resistor to detect the temperature of the first resistor and disconnect the output of the closed-loop control circuit when the temperature reaches a threshold.

7. A digital closed-loop oscillation protection circuit control method applied to the digital closed-loop oscillation protection circuit according to any one of claims 1 to 6, characterized in that: include: Acquire first amplitude information and second amplitude information, wherein the first amplitude information is used to indicate the AC amplitude of the AC component signal, and the second amplitude information is used to indicate the amplitude of the rated DC output of the second amplitude information closed-loop control circuit; The first amplitude information is compared with the second amplitude information, and if the first amplitude information exceeds N% of the second amplitude information, it is determined that the closed-loop control circuit oscillates.

8. An electronic load, characterized in that: It comprises a closed-loop control circuit and the digital closed-loop oscillation protection circuit according to any one of claims 1 to 6.

9. A power supply testing system, characterized in that: It comprises the electronic load and the power supply to be tested as described in claim 8.

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