Oscillation protection circuit, electronic load, power supply test system and equipment

Abstract

The invention discloses an oscillation protection circuit, an electronic load, a power supply test system and equipment, the circuit comprises a switch module and an oscillation detection circuit, and the switch module is connected with a control signal input end of a closed-loop control circuit; the oscillation detection circuit comprises a sampling unit, a coupling capacitor unit, a Schmitt trigger and a D latch, the sampling unit is used for sampling the voltage and / or current of the closed-loop control circuit, and the output end of the sampling unit is connected with the input end of the coupling capacitor unit so as to be used for obtaining an alternating current component in the sampled voltage and / or current; the output end of the coupling capacitor unit is connected with the input end of the Schmitt trigger, the output end of the Schmitt trigger is connected with the first input end of the D latch, and the output end of the D latch is connected with the control end of the switch module. Fuses and software control are not needed, the protection response time can be shortened, and the reliability of oscillation protection is improved.

Description

Technical Field

[0001] The present application relates to the field of power supply testing, and in particular to an oscillation protection circuit, an electronic load, a power supply testing system and equipment. 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 of the existing solutions is to connect a fuse in series in the closed-loop control circuit. When the loop undergoes self-oscillation, the fuse overheats and burns out, disconnecting the entire loop and protecting the electronic load from damage. The defect of using a fuse is that it takes a while for the fuse to overheat and burn out after the 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 different current and voltage scenarios, it is difficult to select a suitable fuse. Another solution is that the electronic load calculates whether the electronic load has self-oscillated based on the sampled current and oscillation model, and turns off the output when self-oscillation occurs. The defect is that the calculation and control need to be realized through software, which increases the R&D and computing power costs. In addition, in order to pursue accuracy, the DC sampling in the electronic load is usually not collected at a high speed and cannot keep up with the frequency of oscillation. Therefore, it is difficult for the electronic load to restore the oscillation model through calculation, resulting in low reliability of oscillation protection. Summary of the invention

[0005] The present application proposes an oscillation protection circuit, an electronic load, a power supply test system and equipment, which do not require the installation of fuses and do not require software control, and can shorten the protection response time and improve the reliability of oscillation protection.

[0006] According to an oscillation protection circuit of the first aspect of the present application, the 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: a switch module, which is arranged at the control signal input end of the closed-loop control circuit; an oscillation detection circuit, wherein the oscillation detection circuit includes a sampling unit, a coupling capacitor unit, a Schmitt trigger and a D latch, the sampling unit is used to sample the voltage and / or current of the closed-loop control circuit, the output end of the sampling unit is connected to the input end of the coupling capacitor unit to obtain the AC component in the sampled voltage and / or current, the output end of the coupling capacitor unit is connected to the input end of the Schmitt trigger, the output end of the Schmitt trigger is connected to the first input end of the D latch, and the output end of the D latch is connected to the control end of the switch module.

[0007] The 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, a switch module is set at the signal input end of the closed-loop control circuit, and the sampling unit inputs the collected voltage and / or current of the closed-loop control circuit to the coupling capacitor unit, and the DC component in the sampled voltage and / or current is filtered out by the coupling capacitor unit. When the closed-loop control circuit does not self-oscillate, the Schmitt trigger is not triggered, and the closed-loop control circuit works normally; 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 latter component, thereby outputting an AC signal to the Schmitt trigger, and the Schmitt trigger converts the AC signal into a pulse signal. After receiving the pulse signal, the D latch sends a fixed level control switch module to cut off the control signal input of the closed-loop control circuit, thereby realizing the shutdown of the closed-loop control circuit. The present application adopts a simple hardware circuit to realize the oscillation protection of the closed-loop control circuit, without the need to set a fuse and without software control, and can shorten the protection response time and improve the reliability of the oscillation protection.

[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 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, the output end of the first coupling capacitor circuit is connected to the input end of the Schmitt trigger through a diode D1, the output end of the voltage sampling circuit is connected to the input end of the second coupling capacitor circuit, and the output end of the second coupling capacitor circuit is connected to the input end of the Schmitt trigger through a diode D2.

[0011] According to some embodiments of the present application, the coupling capacitor unit includes a plurality of coupling capacitors connected in parallel and having different capacitances, and each of the coupling capacitors is connected to an input end of the Schmitt trigger via a diode.

[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, the electronic load includes a closed-loop control circuit and the above-mentioned oscillation protection circuit.

[0014] The electronic load according to the second aspect of the present application has at least the following beneficial effects: In the implementation mode of the present application, a switch module is set at the signal input end of the closed-loop control circuit, and the sampling unit inputs the collected voltage and / or current of the closed-loop control circuit to the coupling capacitor unit, and the DC component in the sampled voltage and / or current is filtered out by the coupling capacitor unit. When the closed-loop control circuit does not self-oscillate, the Schmitt trigger is not triggered, and the closed-loop control circuit works normally; 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 latter component, thereby outputting an AC signal to the Schmitt trigger, and the Schmitt trigger converts the AC signal into a pulse signal. After receiving the pulse signal, the D latch sends a fixed level control switch module to cut off the control signal input of the closed-loop control circuit, thereby realizing the shutdown of the closed-loop control circuit. The present application adopts a simple hardware circuit to realize the oscillation protection of the closed-loop control circuit, without the need to set a fuse and without software control, and can shorten the protection response time and improve the reliability of the oscillation protection.

[0015] According to the third aspect of the present application, a power supply testing system includes the above-mentioned electronic load and a power supply to be tested.

[0016] The power supply testing system according to the third aspect of the present application has at least the following beneficial effects: In the implementation mode of the present application, a switch module is set at the signal input end of the closed-loop control circuit, and the sampling unit inputs the collected voltage and / or current of the closed-loop control circuit to the coupling capacitor unit, and the DC component in the sampled voltage and / or current is filtered out by the coupling capacitor unit. When the closed-loop control circuit does not self-oscillate, the Schmitt trigger is not triggered, and the closed-loop control circuit works normally; 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 latter component, thereby outputting an AC signal to the Schmitt trigger, and the Schmitt trigger converts the AC signal into a pulse signal. After receiving the pulse signal, the D latch sends a fixed level control switch module to cut off the control signal input of the closed-loop control circuit, thereby realizing the shutdown of the closed-loop control circuit. The present application adopts a simple hardware circuit to realize the oscillation protection of the closed-loop control circuit, without the need to set a fuse and without software control, and can shorten the protection response time and improve the reliability of the oscillation protection.

[0017] An electronic device according to an embodiment of the fourth aspect of the present application includes the above-mentioned oscillation protection circuit.

[0018] The electronic device according to the fourth aspect of the present application has at least the following beneficial effects: In the implementation mode of the present application, a switch module is set at the signal input end of the closed-loop control circuit, and the sampling unit inputs the collected voltage and / or current of the closed-loop control circuit to the coupling capacitor unit, and the DC component in the sampled voltage and / or current is filtered out by the coupling capacitor unit. When the closed-loop control circuit does not self-oscillate, the Schmitt trigger is not triggered, and the closed-loop control circuit works normally; 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 latter component, thereby outputting an AC signal to the Schmitt trigger, and the Schmitt trigger converts the AC signal into a pulse signal. After receiving the pulse signal, the D latch sends a fixed level control switch module to cut off the control signal input of the closed-loop control circuit, thereby realizing the shutdown of the closed-loop control circuit. The present application adopts a simple hardware circuit to realize the oscillation protection of the closed-loop control circuit, without the need to set a fuse and without software control, and can shorten the protection response time and improve the reliability of the oscillation protection.

[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 is a principle block diagram of an oscillation protection circuit in an embodiment of the present application; Figure 3 : is a circuit schematic diagram of an oscillation protection circuit in an embodiment of the present application; Figure 4 4 is a circuit diagram of an 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] 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 1As shown, a current closed-loop control circuit in an electronic load includes a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), a metal-oxide-semiconductor field effect transistor (MOS), a signal conditioning module, an error amplifier U1, a current sampling resistor R1 and a differential amplifier U2, and a microcontroller (Microcontroller) of the electronic load. Unit-MCU) outputs a DC signal setting value through 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 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] One of the existing solutions is to connect a fuse in series in the closed-loop control circuit. When the loop undergoes self-oscillation, the fuse overheats and burns out, disconnecting the entire loop and protecting the electronic load from damage. The defect of using a fuse is that it takes a while for the fuse to overheat and burn out after the 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 different current and voltage scenarios, it is difficult to select a suitable fuse. Another solution is that the electronic load calculates whether the electronic load has self-oscillated based on the sampled current and oscillation model, and turns off the output when self-oscillation occurs. The defect is that the calculation and control need to be realized through software, which increases the R&D and computing power costs. In addition, in order to pursue accuracy, the DC sampling in the electronic load is usually not collected at a high speed and cannot keep up with the frequency of oscillation. Therefore, it is difficult for the electronic load to restore the oscillation model through calculation, resulting in low reliability of oscillation protection.

[0032] In order to solve the above problems, the present application proposes an oscillation protection circuit, an electronic load, a power supply test system and equipment. The oscillation protection circuit of the present application is first introduced below. Figure 2As shown, an 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, comprising: a switch module S1 and an oscillation detection circuit; wherein the switch module S1 is arranged at the control signal input end of the closed-loop control circuit, the oscillation detection circuit comprises a sampling unit, a coupling capacitor unit, a Schmitt trigger and a D latch, the sampling unit is used to sample the voltage and / or current of the closed-loop control circuit, the output end of the sampling unit is connected to the input end of the coupling capacitor unit to obtain the AC component in the sampled voltage and / or current, the output end of the coupling capacitor unit is connected to the input end of the Schmitt trigger, the output end of the Schmitt trigger is connected to the first input end of the D latch, and the output end of the D latch is connected to the control end of the switch module S1.

[0033] Specifically, the switch module S1 is arranged between the DAC and the signal conditioning module. When the switch module S1 is closed, the control signal can be normally input into the closed-loop control circuit to control the conduction of the MOS tube Q1. The control signal is the DC signal setting value output by the MCU through the DAC. When the switch module S1 is disconnected, the signal input of the signal conditioning module can be cut off. At this time, the MOS tube Q1 is cut off and the electronic load stops outputting.

[0034] 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 DC components and AC components. The DC components 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 multiple in parallel. After filtering by the coupling capacitor unit, an AC signal is output to the Schmitt trigger. The Schmitt trigger compares the AC signal with the preset voltage value, and determines whether it is triggered by the preset voltage value, that is, whether self-oscillation has occurred. After triggering, the Schmitt trigger outputs a pulse signal to the D latch. After the D latch detects the pulse signal, it latches the state and continuously outputs a fixed level to trigger the switch module S1 to turn off, thereby cutting off the control signal until the state of the D latch is reset and the switch module S1 is restored to close. The state reset of the D latch can be triggered by a reset button, or the MCU of the electronic load can output a switch signal to reset the state of the D latch after the electronic load is restarted, waiting for the next trigger protection. In this embodiment, a switch module S1 is set at the signal input end of the closed-loop control circuit, and the sampling unit inputs the collected voltage and / or current of the closed-loop control circuit to the coupling capacitor unit, and the DC component in the sampled voltage and / or current is filtered out by the coupling capacitor unit. When the closed-loop control circuit does not self-oscillate, the Schmitt trigger is not triggered, and the closed-loop control circuit works normally; 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 latter component, thereby outputting an AC signal to the Schmitt trigger, and the Schmitt trigger converts the AC signal into a pulse signal. After receiving the pulse signal, the D latch sends a fixed level control switch module S1 to cut off the control signal input of the closed-loop control circuit, thereby realizing the shutdown of the closed-loop control circuit. The present application adopts a simple hardware circuit to realize the oscillation protection of the closed-loop control circuit, without the need to set a fuse and without software control, and can shorten the protection response time and improve the reliability of the oscillation protection.

[0035] In some embodiments of the present application, the sampling unit includes a current sampling circuit, which samples the output current of the R2 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.

[0036] 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.

[0037] refer to Figure 3 As shown, in the embodiment of the present application, the current sampling circuit includes a non-inductive sampling resistor R2 and a differential amplifier U3. The non-inductive sampling resistor R2 is connected in series between the source of the MOS tube Q1 and the power supply to be measured. 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 through a first-level coupling 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 put two insulated wires together, the terminals are short-circuited, the head end is externally connected to the power supply and the application circuit, the current directions of the 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 resistance. The low-frequency to high-frequency current analog signal is obtained by the non-inductive sampling resistor, and the excellent high-frequency response performance of the non-inductive sampling resistor is used to improve the measurement accuracy.

[0038] 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.

[0039] 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.

[0040] refer to Figure 3 As shown, in the embodiment of the present application, the voltage sampling circuit includes a differential amplifier U4, and the input ends of the differential amplifier U4 are respectively connected to the output ends of the electronic load, that is, the two ends of the power supply under test. 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.

[0041] 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, the output end of the first coupling capacitor circuit is connected to the input end of the Schmitt trigger through a diode D1, the output end of the voltage sampling circuit is connected to the input end of the second coupling capacitor circuit, and the output end of the second coupling capacitor circuit is connected to the input end of the Schmitt trigger through a diode D2.

[0042] In this embodiment, the output current AC component and the output voltage AC component of the loop are sampled respectively by the current sampling circuit and the voltage sampling circuit. The current sampling circuit and the voltage sampling circuit output an AC signal to the Schmitt trigger through the circuit formed by the diode D1 and the diode D2. The triggering of the Schmitt trigger is determined by the higher of the output current AC component and the output voltage AC component. The self-oscillation is detected by simultaneously sampling the output current AC component and the output voltage AC component, thereby further improving the detection accuracy of the self-oscillation.

[0043] In some embodiments of the present application, the coupling capacitor unit includes a plurality of coupling capacitors connected in parallel and having different capacitances, and each coupling capacitor is connected to an input terminal of a Schmitt trigger via a diode.

[0044] 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.

[0045] In some embodiments of the present application, a first resistor Rc, a first capacitor Cr and a temperature switch S2 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 S2. The detection end of the temperature switch S2 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.

[0046] In this embodiment, reference Figure 4 As shown, 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, and the temperature switch S2 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 S2 is triggered to disconnect, and the loop output stops. In this embodiment, the first resistor Rc uses a power resistor. On the basis of the oscillation detection circuit and the switch module S1, the present application additionally adds an oscillation protection unit formed by an RC circuit and a temperature switch S2, which further improves the reliability of the oscillation protection.

[0047] An example of the present application is described in detail below with reference to the accompanying drawings: refer to Figure 4 As shown, in this embodiment, the sampling unit includes a current sampling circuit and a voltage sampling circuit, the first coupling capacitor circuit includes a capacitor C1, the second coupling capacitor circuit includes a capacitor C2, the source of the MOS tube Q1 is connected to the negative electrode of the power supply under test through the current sampling resistor R1 and the non-inductive sampling resistor R2 connected in series in sequence, 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 positive electrode of the diode D1 through the capacitor C1, the input end of the differential amplifier U4 is connected to the two ends of the power supply under test, the differential amplifier U4 is connected to the positive electrode of the diode D2 through the capacitor C2, the negative electrodes of the diode D1 and the diode D2 are both connected to the input end of the Schmitt trigger, the output end of the Schmitt trigger is connected to the input end of the D latch, the control end of the D latch is connected to a state clearing switch S3, and the state of the D latch is reset by key triggering, the output end of the D latch is connected to the control end of the switch module S1, and the switch module S1 adopts an analog switch.

[0048] In addition, the source of the MOS tube Q1 is connected to the negative electrode of the power supply under test through the first resistor Rc and the first capacitor Cr connected in series, the drain of the MOS tube Q1 is connected to the positive electrode of the power supply under test through the temperature switch S2, and the detection end of the temperature switch S2 is connected to the first resistor Rc.

[0049] The above circuit determines whether self-oscillation occurs by simultaneously collecting the AC current component and the AC voltage component. When self-oscillation occurs, the switch module S1 is controlled by the Schmitt trigger and the D latch to disconnect and stop the loop output. This application uses a pure hardware circuit to achieve self-oscillation protection of the loop, without the need to set a fuse or software control, with low component cost and fast response speed of oscillation protection. In addition, additional protection consisting of an RC circuit and a temperature switch S2 is also provided, which can also achieve self-oscillation protection when the oscillation detection circuit or the switch module S1 fails, with high reliability.

[0050] The present application also relates to an electronic load, comprising a closed-loop control circuit and the oscillation protection circuit of the above embodiment.

[0051] Since the electronic load of the present application is provided with the oscillation protection circuit of the above embodiment, its specific working process and principle are the same as those of the oscillation protection circuit in the above embodiment, and will not be described in detail here.

[0052] 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.

[0053] Since the power supply test system of the present application is provided with the electronic load of the above-mentioned embodiment, its specific working process and principle are the same as those of the oscillation protection circuit in the above-mentioned embodiment, which will not be described in detail here.

[0054] The present application also relates to an electronic device, comprising the oscillation protection circuit of the above embodiment.

[0055] The electronic device of the present application is provided with the oscillation protection circuit of the above-mentioned embodiment, and its specific working process and principle are the same as those of the oscillation protection circuit in the above-mentioned embodiment, which will not be described one by one here.

[0056] The embodiments of the present application are described in detail above in conjunction with the accompanying drawings, but the present application is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present application.

Claims

1. An 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: A switch module, arranged at a control signal input end of the closed-loop control circuit; An oscillation detection circuit, the oscillation detection circuit comprising a sampling unit, a coupling capacitor unit, a Schmitt trigger and a D latch, the sampling unit being used to sample the voltage and / or current of the closed-loop control circuit, the output end of the sampling unit being connected to the input end of the coupling capacitor unit to obtain the AC component in the sampled voltage and / or current, the output end of the coupling capacitor unit being connected to the input end of the Schmitt trigger, the output end of the Schmitt trigger being connected to the first input end of the D latch, and the output end of the D latch being connected to the control end of the switch module.

2. The 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 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 oscillation protection circuit according to claim 1, characterized in that: The sampling unit includes a current sampling circuit and a voltage sampling circuit, and 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 is connected to the input end of the Schmitt trigger through a diode D1. The output end of the voltage sampling circuit is connected to the input end of the second coupling capacitor circuit, and the output end of the second coupling capacitor circuit is connected to the input end of the Schmitt trigger through a diode D2.

5. The oscillation protection circuit according to claim 1, characterized in that: The coupling capacitor unit includes a plurality of coupling capacitors connected in parallel with each other and having different capacitances, and each of the coupling capacitors is connected to the input end of the Schmitt trigger via a diode.

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

8. A power supply testing system, characterized in that: It comprises the electronic load and the power supply to be tested as described in claim 7.

9. An electronic device, characterized in that: The oscillation protection circuit comprises the oscillation protection circuit according to any one of claims 1 to 6.

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