Loop response testing device of step-down switching power supply
By designing a loop response test device for a step-down switching power supply, and utilizing components such as MOSFETs, inductors, capacitors, and bandwidth oscilloscopes, the test process is simplified, solving the problems of poor feasibility, high equipment requirements, and complex operation in existing technologies, thus achieving low-cost and efficient loop response testing.
Patent Information
- Application Number
- CN202422643209.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-31
- Publication Date
- 2025-11-14
- Estimated Expiration
- 2034-10-31
AI Technical Summary
Existing switching power supply loop response testing devices suffer from poor feasibility, high equipment requirements, high technical barriers, and complex operation, making them difficult to implement on high-density circuit boards and costing a lot.
A loop response test device for a step-down switching power supply was designed. It uses MOSFETs, inductors, capacitors, amplifier units, bandwidth oscilloscopes, and load branches. By setting up switches on the load branches and using the bandwidth oscilloscope, the signal of a node can be tested, which simplifies the testing process and lowers the equipment threshold.
It enables simple and low-cost switching power supply loop response testing on high-density circuit boards, reducing equipment requirements and operational complexity, and improving the feasibility of testing.
Smart Images
Figure CN223551855U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of loop response testing technology for switching power supplies, and specifically to a loop response testing device for a step-down switching power supply. Background Technology
[0002] In the operation of electronic systems, a stable power supply is fundamental to their reliable operation. If the loop of a switching power supply is unstable, it may lead to abnormal power output, thereby causing the entire electronic system to malfunction. For example, in communication systems, an unstable switching power supply may cause distortion or interruption of communication signals; or in industrial control systems, a power supply failure may cause production equipment to shut down or malfunction. By testing the loop response of the switching power supply, the reliability of the power supply can be ensured, reducing the probability of system failure.
[0003] The existing loop response test structure for switching power supply 1 is as follows: Figure 1 As shown, the switching power supply is actually an amplifier containing a negative feedback control loop. This means that although the switching power supply can be regarded as a DC amplifier, it actually amplifies AC signals and responds to changes in output conditions, such as load changes.
[0004] exist Figure 1 In order to perform control loop response testing, an error signal needs to be injected into the feedback path of the control loop. This feedback path refers to the resistor divider network composed of resistors R1 and R2. During testing, a smaller resistor Rinj needs to be connected in series with the feedback loop to inject an error signal. Additionally, an injection transformer (such as a Picotest J2101A) is used to isolate this AC interference signal, thus preventing any DC bias.
[0005] The measurement setup here is an InfiniiVision X-Series oscilloscope 3 with a built-in function / arbitrary waveform generator, used to measure the AC voltage level at the top of the feedback network (Vin) and the DC power output (Vout). The oscilloscope 3 calculates the gain at each test frequency point within the scanned frequency band, dB = 20Log(Vout / Vin). The phase difference between Vin and Vout is also measured.
[0006] for Figure 1 The testing device shown has the following defects in actual use:
[0007] 1. Poor feasibility: In actual design, due to the large variety and quantity of power supplies, it is basically impossible to implement a high-density circuit board if each power supply requires an additional resistor and a test point for the isolation transformer.
[0008] Second: High equipment requirements. It requires relatively professional testing equipment, such as high-quality oscilloscopes and signal generators. These devices are expensive, which can be costly for small businesses or individual developers.
[0009] Third: The technical threshold is high, and the testing process requires certain professional knowledge and skills; operators need to be familiar with the use of testing equipment, signal injection techniques, etc.; for people without relevant experience, learning and mastering these technologies requires a certain amount of time and effort.
[0010] Fourth: The operation is complex. The testing process involves multiple steps, including signal injection, measurement, data processing and analysis. Each step requires careful operation, otherwise errors are likely to occur.
[0011] Figure 1 A test waveform diagram of the test structure shown is as follows: Figure 2 As shown, Figure 2 The upper and lower test waveform lines in the image represent the gain and phase curves within the 10Hz to 1MHz scanning frequency band, respectively, yielding the crossover frequency f. c Phase margin φ m . Utility Model Content
[0012] In view of the shortcomings of the background technology, the present invention provides a loop response test device for step-down switching power supplies. The technical problem to be solved is that the existing loop test devices for switching power supplies have defects such as poor feasibility, high equipment requirements, high technical requirements and complex operation.
[0013] To solve the above technical problems, this utility model provides the following technical solution: a loop response testing device for a buck switching power supply, wherein the buck switching unit includes a MOSFET N1, an inductor L1, a capacitor C1, a capacitor C2, and an amplification unit; the drain of the MOSFET N1 is used to input the operating voltage, the source of the MOSFET N1 is electrically connected to one end of the inductor L1, and the other end of the inductor L1 is electrically connected to one end of the capacitor C1; the amplification unit includes an amplifier and a modulator, the output terminal of the amplifier is electrically connected to the input terminal of the modulator and one end of the capacitor C2, the other end of the capacitor C2 is grounded, and the output terminal of the modulator is electrically connected to the gate of the MOSFET N1;
[0014] It also includes a bandwidth oscilloscope, a voltage feedback branch, and a load branch. The other end of the inductor L1 is electrically connected to the voltage feedback branch, the load branch, and the bandwidth oscilloscope, respectively. The voltage feedback branch is used to feed back the voltage at the other end of the inductor L1 to the negative input terminal of the amplifier proportionally. The load branch includes a switch, which is used to control whether the load branch is grounded. The bandwidth oscilloscope is used to display the signal at the other end of the inductor L1.
[0015] In one embodiment, the MOS transistor N1 is an NMOS transistor.
[0016] In one embodiment, the voltage feedback branch includes at least two resistors connected in series, one end of the first resistor is electrically connected to the other end of the inductor L1, one end of the last resistor is grounded, and an intermediate node of the voltage feedback branch is electrically connected to the negative input terminal of the amplifier.
[0017] In one implementation, the voltage feedback branch includes three resistors connected in series.
[0018] In one embodiment, the load branch further includes a resistor RL, one end of which is electrically connected to the other end of the inductor L1, and the other end of which is grounded through the switch.
[0019] In one embodiment, the switch is an NMOS transistor, the drain of the NMOS transistor is electrically connected to the other end of the resistor RL, the source of the NMOS transistor is grounded, and the gate of the NMOS transistor is used to input the driving voltage.
[0020] In one embodiment, the switch is a relay, and a pair of normally open contacts of the relay are electrically connected to the other end of the resistor RL and grounded, respectively. One end of the relay's control coil is grounded, and the other end is used to input the driving voltage.
[0021] In one embodiment, the present invention further includes a microcontroller and an optocoupler. The output terminal of the microcontroller is electrically connected to the input terminal of the primary side of the optocoupler, and is used to input a control signal to the input terminal of the primary side of the optocoupler. The control signal is used to control the conduction of the secondary side of the optocoupler. The other end of the primary side of the optocoupler is grounded. The input terminal of the secondary side of the optocoupler is connected to a power supply through a resistor R10. The output terminal of the secondary side of the optocoupler is used to output a driving voltage.
[0022] In one embodiment, the microcontroller is electrically connected to the intermediate node of the voltage feedback branch, and outputs the control signal after detecting the voltage fed back by the voltage feedback branch.
[0023] In one embodiment, the present invention further includes a remote terminal, which sends control commands to a microcontroller via a communication unit, and the microcontroller responds to the control commands by outputting the control signals.
[0024] Compared with the prior art, the advantages of this utility model are as follows: In actual use, this utility model can perform loop response testing of switching power supply by setting up a load branch and a switch on the load branch. Moreover, only a bandwidth oscilloscope is needed to test and display the signal of a single node. Testing can be performed without transformers and professional equipment, which has good feasibility and lowers the equipment threshold, making testing simple. Attached Figure Description
[0025] Figure 1 A schematic diagram of the structure for loop response testing of an existing switching power supply;
[0026] Figure 2 for Figure 1 A waveform diagram during circuit testing;
[0027] Figure 3 This is a schematic diagram of the structure of the present invention in the embodiment;
[0028] Figure 4 This is a schematic diagram of a microcontroller output drive voltage in an embodiment.
[0029] Figure 5 This is a schematic diagram of another structure for the microcontroller output drive voltage in the embodiment;
[0030] Figure 6 for Figure 3 Waveform diagram during circuit testing;
[0031] Figure 7 for Figure 1 A schematic diagram of the phase margin curve set for circuit testing. Detailed Implementation
[0032] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the present invention, and therefore only show the components relevant to the present invention.
[0033] like Figure 3 As shown, a loop response testing device for a buck switching power supply is disclosed. The buck switching unit 10 includes a MOSFET N1, an inductor L1, a capacitor C1, a capacitor C2, and an amplification unit. The drain of the MOSFET N1 is used to input the operating voltage VDD. The source of the MOSFET N1 is electrically connected to one end of the inductor L1, and the other end of the inductor L1 is electrically connected to one end of the capacitor C1. The amplification unit includes an amplifier 101 and a modulator 100. The output terminal of the amplifier 101 is electrically connected to the input terminal of the modulator 100 and one end of the capacitor C2, respectively. The other end of the capacitor C2 is grounded. The output terminal of the modulator 100 is electrically connected to the gate of the MOSFET N1.
[0034] It also includes a bandwidth oscilloscope 13, a voltage feedback branch 11, and a load branch 12. The other end of the inductor L1 is electrically connected to the voltage feedback branch 11, the load branch 12, and the bandwidth oscilloscope 13, respectively. The voltage feedback branch 11 is used to feed back the voltage at the other end of the inductor L1 proportionally to the negative input terminal of the amplifier 101. The positive input terminal of the amplifier 101 is electrically connected to the reference voltage source Vref. The load branch 12 includes a switch SW1, which is used to control whether the load branch 12 is grounded. The bandwidth oscilloscope 13 is used to display the signal Vout at the other end of the inductor L1.
[0035] In practical use, this utility model can perform loop response testing of switching power supply by setting up load branch 12 and setting up switch SW1 on load branch 12 and controlling switch SW1 to conduct. Moreover, only a bandwidth oscilloscope 13 is needed to test and display the signal of one node. Testing can be performed without transformers and professional equipment, which has good feasibility, lowers the equipment threshold, and makes testing simple.
[0036] Specifically, in this embodiment, MOS transistor N1 is an NMOS transistor.
[0037] Specifically, in this embodiment, the voltage feedback branch 11 includes at least two resistors connected in series. One end of the first resistor is electrically connected to the other end of the inductor L1, one end of the last resistor is grounded, and an intermediate node of the voltage feedback branch is electrically connected to the negative input terminal of the amplifier.
[0038] exist Figure 3 In the circuit, the voltage feedback branch 11 includes resistors R1 and R2. One end of resistor R1 is electrically connected to the other end of inductor L1. The other end of resistor R1 is electrically connected to the negative input terminal of amplifier 101 and one end of resistor R2, respectively. The other end of resistor R2 is grounded.
[0039] In one implementation, the voltage feedback branch 11 may also include three resistors connected in series.
[0040] Specifically, in this embodiment, in Figure 3 In the load branch 12, there is also a resistor RL. One end of the resistor RL is electrically connected to the other end of the inductor L1, and the other end of the resistor RL is grounded through a switch.
[0041] More specifically, in this embodiment, the switch is an NMOS transistor, the drain of the NMOS transistor is electrically connected to the other end of the resistor RL, the source of the NMOS transistor is grounded, and the gate of the NMOS transistor is used to input the driving voltage.
[0042] More specifically, in this embodiment, the switch is a relay, and a pair of normally open contacts of the relay are electrically connected to the other end of the resistor RL and grounded, respectively. One end of the control coil of the relay is grounded, and the other end is used to input the driving voltage.
[0043] Other examples Figure 4 As shown, this utility model also includes a microcontroller 13 and an optocoupler 14. The output terminal of the microcontroller 13 is electrically connected to the input terminal of the primary side of the optocoupler 14, and is used to input a control signal to the input terminal of the primary side of the optocoupler 14. The control signal is used to control the conduction of the secondary side of the optocoupler 14. The other end of the primary side of the optocoupler 14 is grounded. The input terminal of the secondary side of the optocoupler 14 is connected to the power supply VCC through a resistor R10. The output terminal of the secondary side of the optocoupler 14 is used to output a drive voltage.
[0044] In practical applications, different power supply VCC values can be selected to match the drive voltage with the NMOS transistor or relay.
[0045] Specifically, in this embodiment, the microcontroller 13 is electrically connected to the intermediate node of the voltage feedback branch 11, and outputs a control signal after detecting the voltage fed back by the voltage feedback branch 11. In actual use, by having the microcontroller 13 detect the voltage fed back by the voltage feedback branch 11 and output the control signal, the automatic conduction test of switch SW1 can be realized.
[0046] Specifically, in this embodiment, as Figure 5 As shown, this utility model also includes a remote terminal 15, which sends control commands to the microcontroller 13 via a communication unit 16. The microcontroller 13 responds to the control commands and outputs control signals. The remote terminal 15 can be a computer, a mobile phone, or a host computer.
[0047] In practical use, Figure 3 The testing process for the structure shown is as follows:
[0048] A load resistor RL and a switch SW1 are connected to the other end of inductor L1. After switch SW1 is turned on, the load current I increases. The waveforms of the signal Vout and the load current I are observed simultaneously using a bandwidth oscilloscope 13. Figure 4 As shown, the frequency of the voltage offset waveform's response to the load transient is f≈fc. In this example, the frequency f of the transient ripple is approximately 15kHz, so the crossover frequency fc≈15kHz. Additionally, in some testing processes, the waveform of the load current I may not need to be observed.
[0049] Additionally, refer to Figure 5 , Figure 5 This is a collection of phase margin curves for buck converters tested using traditional methods. More curves could be included (for a single test only). This example provides curves for four different phase margins, allowing for a sufficiently approximate estimation of the phase margin of the test loop. (Comparison) Figure 4 and Figure 5As can be seen, the transient response measured in this example is closest to the number of oscillations of the blue trace, exhibiting only a small number of oscillations. This means that the loop phase margin φm measured in this example is approximately 30°.
[0050] Based on the above description and inspired by this utility model, those skilled in the art can make various changes and modifications without departing from the technical concept of this utility model. The technical scope of this utility model is not limited to the contents of the specification, but must be determined according to the scope of the claims.
Claims
1. A loop response testing device for a buck switching power supply, wherein the buck switching power supply includes a MOSFET N1, an inductor L1, a capacitor C1, a capacitor C2, and an amplification unit; the drain of the MOSFET N1 is used for input operating voltage, the source of the MOSFET N1 is electrically connected to one end of the inductor L1, and the other end of the inductor L1 is electrically connected to one end of the capacitor C1; the amplification unit includes an amplifier and a modulator, the output terminal of the amplifier is electrically connected to the input terminal of the modulator and one end of the capacitor C2, the other end of the capacitor C2 is grounded, and the output terminal of the modulator is electrically connected to the gate of the MOSFET N1, characterized in that... It also includes a bandwidth oscilloscope, a voltage feedback branch, and a load branch. The other end of the inductor L1 is electrically connected to the voltage feedback branch, the load branch, and the bandwidth oscilloscope, respectively. The voltage feedback branch is used to feed back the voltage at the other end of the inductor L1 to the negative input terminal of the amplifier proportionally. The load branch includes a switch, which is used to control whether the load branch is grounded. The bandwidth oscilloscope is used to display the signal at the other end of the inductor L1.
2. The loop response testing device for a step-down switching power supply according to claim 1, characterized in that, The MOS transistor N1 is an NMOS transistor.
3. The loop response testing device for a step-down switching power supply according to claim 1, characterized in that, The voltage feedback branch includes at least two resistors connected in series. One end of the first resistor is electrically connected to the other end of the inductor L1, and one end of the last resistor is grounded. An intermediate node of the voltage feedback branch is electrically connected to the negative input terminal of the amplifier.
4. The loop response testing device for a step-down switching power supply according to claim 3, characterized in that, The voltage feedback branch includes three resistors connected in series.
5. The loop response testing device for a step-down switching power supply according to claim 1, characterized in that, The load branch also includes a resistor RL, one end of which is electrically connected to the other end of the inductor L1, and the other end of the resistor RL is grounded through the switch.
6. The loop response testing device for a step-down switching power supply according to claim 5, characterized in that, The switch is an NMOS transistor. The drain of the NMOS transistor is electrically connected to the other end of the resistor RL. The source of the NMOS transistor is grounded, and the gate of the NMOS transistor is used to input the driving voltage.
7. The loop response testing device for a step-down switching power supply according to claim 5, characterized in that, The switch is a relay. A pair of normally open contacts of the relay are electrically connected to the other end of the resistor RL and grounded, respectively. One end of the relay's control coil is grounded, and the other end is used to input the driving voltage.
8. A loop response testing device for a step-down switching power supply according to claim 6 or 7, characterized in that, It also includes a microcontroller and an optocoupler. The output terminal of the microcontroller is electrically connected to the input terminal of the primary side of the optocoupler, and is used to input a control signal to the input terminal of the primary side of the optocoupler. The control signal is used to control the conduction of the secondary side of the optocoupler. The other end of the primary side of the optocoupler is grounded. The input terminal of the secondary side of the optocoupler is connected to the power supply through a resistor R10. The output terminal of the secondary side of the optocoupler is used to output a drive voltage.
9. The loop response testing device for a step-down switching power supply according to claim 8, characterized in that, The microcontroller is electrically connected to the intermediate node of the voltage feedback branch, and outputs the control signal after detecting the voltage fed back by the voltage feedback branch.
10. A loop response testing device for a step-down switching power supply according to claim 8, characterized in that, It also includes a remote terminal, which sends control commands to the microcontroller through a communication unit, and the microcontroller responds to the control commands by outputting the control signals.