A test circuit and a test method

Abstract

The present invention discloses a test circuit and a test method. The test circuit includes: an AC power supply, an impedance stabilization circuit and a spectrum analyzer; the first end of the impedance stabilization circuit is connected to the AC power supply, the second end of the impedance stabilization circuit is connected to the switching power supply, and is used to isolate the AC power supply from the switching power supply; the first end of the spectrum analyzer is connected to the third end of the impedance stabilization circuit, the second end of the spectrum analyzer is grounded, and the spectrum analyzer is used to display the interference information spectrum of the switching power supply. In an embodiment of the present invention, by connecting the test circuit of the switching power supply to the spectrum analyzer, the spectrum analyzer analyzes the interference information spectrum of the switching power supply, reduces the testing cost of the switching power supply, and can be applied to the full coverage test of the finished product.

Description

Technical Field

[0001] The invention relates to a switch power supply electromagnetic interference radiation test circuit, and in particular to a test circuit and a test method. Background Art

[0002] Almost all electronic devices require a DC regulated power supply. The switching power supply is a widely used power supply mode, which has the advantages of small size, light weight, and high energy conversion efficiency. However, the switching power supply operates at a higher frequency, and its radiation interference to the outside world is relatively strong. Therefore, the switching power supply needs to be tested for radiation in an electromagnetic interference darkroom, and the radiation value in the electromagnetic interference darkroom must meet the requirements of regulations.

[0003] Since the testing cost of switching power supplies in an EMI darkroom is very high and takes a long time, it cannot be applied to full coverage testing of finished products. Summary of the invention

[0004] The embodiment of the present invention provides a test circuit and a test method to implement the analysis of the interference information spectrum of a switching power supply by a spectrum analyzer, thereby reducing the test cost of the switching power supply.

[0005] An embodiment of the present invention provides a test circuit, including:

[0006] AC power supply, impedance stabilization circuit and spectrum analyzer;

[0007] A first end of the impedance stabilization circuit is connected to an AC power source, and a second end of the impedance stabilization circuit is connected to a switching power source, for isolating the AC power source from the switching power source;

[0008] The first end of the spectrum analyzer is connected to the third end of the impedance stabilization circuit, the second end of the spectrum analyzer is grounded, and the spectrum analyzer is used to display the interference information spectrum of the switching power supply.

[0009] Optionally, the third terminal of the impedance stabilization circuit includes a live line output terminal and a neutral line output terminal;

[0010] The impedance stabilization circuit includes a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a first inductor, a second inductor, a first resistor and a second resistor. The first end of the first capacitor is electrically connected to the live wire end of the AC power supply and the first end of the first inductor, respectively, and the second end of the first capacitor and the first end of the second capacitor are both grounded; the second end of the first inductor is electrically connected to the first end of the third capacitor and the switching power supply, respectively; the second end of the third capacitor is electrically connected to the first end of the first resistor and the live wire output end, respectively; the second end of the second capacitor is electrically connected to the neutral wire end of the AC power supply and the first end of the second inductor, and the second end of the second inductor is electrically connected to the first end of the fourth capacitor; the second end of the fourth capacitor is electrically connected to the first end of the second resistor and the neutral wire output end, respectively; the second end of the second resistor is electrically connected to the second end of the first resistor.

[0011] Optionally, the test circuit further includes a toggle switch; a first end of the toggle switch is electrically connected to a first end of the spectrum analyzer; a second end of the toggle switch is electrically connected to a live wire output end or the neutral wire output end;

[0012] When the second end of the toggle switch is electrically connected to the live wire output end, the spectrum analyzer obtains a first common mode current; when the second end of the toggle switch is electrically connected to the neutral wire output end, the spectrum analyzer obtains a second common mode current; the spectrum analyzer is also used to display the interference information spectrum corresponding to the larger of the first common mode current and the second common mode current.

[0013] Optionally, the test circuit further includes a load and a rectifier circuit, and two ends of the load are connected to two ends of the switching power supply to simulate the load capacity of the switching power supply;

[0014] One end of the rectifier circuit is connected to the second end of the impedance stabilization circuit, and the other end is connected to the switching power supply, so as to convert the alternating current into direct current.

[0015] Optionally, the test circuit further includes a grounded metal plate, one end of the grounded metal plate is connected to the second end of the impedance stabilization circuit, and the other end of the grounded metal plate is connected to the second end of the spectrum analyzer.

[0016] Optionally, the spectrum analyzer is further used to determine that the switching power supply is qualified when the maximum amplitude of the interference information spectrum of the switching power supply is smaller than the reference spectrum amplitude, otherwise, determine that the switching power supply is unqualified.

[0017] Optionally, the spectrum analyzer is further used to determine that the switching power supply is qualified when the maximum amplitude of the interference information spectrum corresponding to the larger one of the first common mode current and the second common mode current is less than the reference spectrum amplitude, otherwise determine that the switching power supply is unqualified.

[0018] An embodiment of the present invention further provides a testing method, which is applied to the testing circuit described in any of the above embodiments, comprising:

[0019] The impedance stabilization circuit isolates the AC power supply from the switching power supply;

[0020] The spectrum analyzer acquires and displays the interference information spectrum of the switching power supply.

[0021] Optionally, the testing method further includes: the spectrum analyzer determines that the switching power supply is qualified when the maximum amplitude of the interference information spectrum of the switching power supply is smaller than the reference spectrum amplitude, otherwise, determines that the switching power supply is unqualified.

[0022] Optionally, the third terminal of the impedance stabilization circuit includes a live line output terminal and a neutral line output terminal;

[0023] The impedance stabilization circuit includes a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a first inductor, a second inductor, a first resistor and a second resistor. The first end of the first capacitor is electrically connected to the live wire end of the AC power supply and the first end of the first inductor, respectively, and the second end of the first capacitor and the first end of the second capacitor are both grounded; the second end of the first inductor is electrically connected to the first end of the third capacitor and the switch power supply, respectively; the second end of the third capacitor is electrically connected to the first end of the first resistor and the live wire output end, respectively; the second end of the second capacitor is electrically connected to the neutral wire end of the AC power supply and the first end of the second inductor, and the second end of the second inductor is electrically connected to the first end of the fourth capacitor; the second end of the fourth capacitor is electrically connected to the first end of the second resistor and the neutral wire output end, respectively; the second end of the second resistor is electrically connected to the second end of the first resistor; the test circuit also includes a toggle switch; the first end of the toggle switch is electrically connected to the first end of the spectrum analyzer; the second end of the toggle switch is used to be electrically connected to the live wire output end or the neutral wire output end; when the second end of the toggle switch is electrically connected to the live wire output end, the spectrum analyzer obtains a first common mode current; when the second end of the toggle switch is electrically connected to the neutral wire output end, the spectrum analyzer obtains a second common mode current;

[0024] The test methods also include:

[0025] The spectrum analyzer displays the interference information spectrum corresponding to the larger one of the first common-mode current and the second common-mode current; and when the maximum amplitude of the interference information spectrum corresponding to the larger one of the first common-mode current and the second common-mode current is less than the reference spectrum amplitude, the switching power supply is determined to be qualified, otherwise the switching power supply is determined to be unqualified.

[0026] In the embodiment of the present invention, the test circuit of the switching power supply is connected to the spectrum analyzer, so that the spectrum analyzer can analyze the interference information spectrum of the switching power supply, reduce the test cost of the switching power supply, and can be applied to full coverage test of finished products. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the structure of the test circuit in the first embodiment of the present invention;

[0028] Figure 2 is a schematic diagram of the structure of a test circuit in Embodiment 2 of the present invention;

[0029] Figure 3 Schematic diagram of the structure of the test circuit in the third embodiment of the present invention;

[0030] Figure 4 This is a flow chart of the test issuing party in the fourth embodiment of the present invention;

[0031] Figure 5 Schematic diagram of the test method in Embodiment 5 of the present invention;

[0032] Figure 6 It is a flowchart diagram of the test circuit in the sixth embodiment of the present invention. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0034] Embodiment 1

[0035] Figure 1 A schematic diagram of the structure of a test circuit provided in Embodiment 1 of the present invention is shown in FIG. Figure 1 As shown, the test circuit includes: an AC power supply 10, an impedance stabilization circuit 20 and a spectrum analyzer 30; a first end 21 of the impedance stabilization circuit 20 is connected to the AC power supply 10, and a second end 22 of the impedance stabilization circuit 20 is connected to the switching power supply 40, for isolating the AC power supply 10 from the switching power supply 40; a first end 31 of the spectrum analyzer 30 is connected to a third end 23 of the impedance stabilization circuit 20, and a second end 32 of the spectrum analyzer 30 is grounded, and the spectrum analyzer 30 is used to display the interference information spectrum of the switching power supply 40.

[0036] In the technical solution of the above embodiment, on the one hand, the first end 21 of the impedance stabilization circuit 20 is connected to the AC power supply 10, the second end 22 of the impedance stabilization circuit 20 is connected to the switching power supply 40, the AC power supply 10 provides the switching power supply 40 with a gate AC voltage and frequency through the impedance stabilization circuit 20, and the third end 23 of the impedance stabilization circuit 20 is connected to the spectrum analyzer 30 to display the interference information spectrum of the switching power supply 40 on the spectrum analyzer 30; on the other hand, the impedance stabilization circuit 20 between the AC power supply 10 and the switching power supply isolates the AC power supply 10 and the switching power supply 40, thereby ensuring that the spectrum analyzer 30 displays the interference information spectrum of the switching power supply 40.

[0037] The technical solution of this embodiment connects the test circuit of the switching power supply with the spectrum analyzer, thereby realizing the analysis of the interference information spectrum of the switching power supply by the spectrum analyzer, reducing the testing cost of the switching power supply, and can be applied to full coverage testing of finished products.

[0038] Embodiment 2

[0039] Figure 2 A schematic diagram of the structure of a test circuit provided in the second embodiment of the present invention, such as Figure 2 As shown, the third end 23 of the impedance stabilization circuit 20 includes a live line output terminal OUTL and a neutral line output terminal OUTN; the impedance stabilization circuit 20 includes a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a first inductor L1, a second inductor L2, a first resistor R1 and a second resistor R2, the first end of the first capacitor C1 is electrically connected to the live line terminal Line of the AC power source 10 and the first end of the first inductor L1, the second end of the first capacitor C1 and the first end of the second capacitor C2 are both grounded; the second end of the first inductor L1 is electrically connected to the third inductor L2, and the second end of the first inductor L1 is electrically connected to the third inductor L3. The first end of the capacitor C3 is electrically connected to the switching power supply 40; the second end of the third capacitor C3 is electrically connected to the first end of the first resistor R1 and the live line output terminal OUTL respectively; the second end of the second capacitor C2 is electrically connected to the neutral line terminal Neutral of the AC power supply 10 and the first end of the second inductor L2, and the second end of the second inductor L2 is electrically connected to the first end of the fourth capacitor C4; the second end of the fourth capacitor C4 is electrically connected to the first end of the second resistor R2 and the neutral line output terminal OUTN respectively; the second end of the second resistor R2 is electrically connected to the second end of the first resistor R1.

[0040] It should be noted that the first end of the first capacitor C1 of the impedance stabilization circuit 20 is connected to the live line terminal Line of the AC power supply 10, and a high-pass filter of the live line circuit is formed by the first inductor L1, the third capacitor C3 and the first resistor R1 components. The other end of the first inductor L1 is connected to the switching power supply 40, and the second end of the third capacitor C3 is electrically connected to the live line output terminal OUTL, so that the interference information spectrum of the live line terminal of the switching power supply 40 is coupled to the spectrum analyzer 30; the second end of the second capacitor C2 of the impedance stabilization circuit 20 is connected to the neutral line terminal NEUTRAL of the AC power supply 10, and a high-pass filter of the neutral line circuit is formed by the second inductor L2, the fourth capacitor C4 and the second resistor R2 components. The other end of the second inductor L2 is connected to the switching power supply 40, and the second end of the fourth capacitor C4 is electrically connected to the neutral line output terminal OUTN, so that the interference information spectrum of the neutral line terminal of the switching power supply 40 is coupled to the spectrum analyzer 30.

[0041] On the other hand, the first end of the first inductor L1 of the impedance stabilization circuit 20 is also connected to the first capacitor C1 and grounded through the first capacitor C1, so as to protect the live line in the impedance stabilization circuit 20; the first end of the second inductor L2 of the impedance stabilization circuit 20 is also connected to the second capacitor C2 and grounded through the second capacitor C2, so as to protect the neutral line in the impedance stabilization circuit 20.

[0042] Optionally, the test circuit further includes a toggle switch 50; a first end 51 of the toggle switch 50 is electrically connected to a first end 31 of the spectrum analyzer 30; a second end 52 of the toggle switch 50 is electrically connected to a live output terminal OUTL or a neutral output terminal OUTN;

[0043] When the second end 52 of the toggle switch 50 is electrically connected to the live line output terminal OUTL, the spectrum analyzer 30 obtains a first common mode current; when the second end 52 of the toggle switch 50 is electrically connected to the neutral line output terminal OUTN, the spectrum analyzer 50 obtains a second common mode current; the spectrum analyzer 30 is also used to display the interference information spectrum corresponding to the larger of the first common mode current and the second common mode current.

[0044] It should be noted that when the second end 52 of the toggle switch 50 is electrically connected to the live wire output terminal OUTL, the AC power supply 10 supplies power to the switching power supply 40 through the first inductor L1, and to the live wire output terminal OUTL through the first inductor L1 and the third capacitor C3. The live wire output terminal OUTL is connected to the second end 52 of the toggle switch 50, and to the first end 31 of the spectrum analyzer 30 through the first end 51 of the toggle switch 50, and the spectrum analyzer 30 obtains the first common-mode current; when the second end 52 of the toggle switch 50 is electrically connected to the neutral wire output terminal OUTN, the AC power supply 10 supplies power to the switching power supply 40 through the second inductor L2, and to the neutral wire output terminal OUTN through the second inductor L2 and the fourth capacitor C4. The neutral wire output terminal OUTN is connected to the second end 52 of the toggle switch 50, and to the first end 31 of the spectrum analyzer 30 through the first end 51 of the toggle switch 50, and the spectrum analyzer 30 obtains the second common-mode current.

[0045] On the other hand, the spectrum analyzer 30 displays the interference information spectrum corresponding to the larger one of the first common mode current and the second common mode current according to the acquired magnitudes of the first common mode current at the live output terminal OUTL and the second common mode current at the neutral output terminal OUTN.

[0046] Optionally, the spectrum analyzer 30 is further configured to determine that the switching power supply 40 is qualified when the maximum amplitude of the interference information spectrum of the switching power supply 40 is smaller than the reference spectrum amplitude, otherwise, determine that the switching power supply 40 is unqualified.

[0047] It should be noted that the spectrum analyzer 30 in the switching circuit determines that the switching power supply 40 is qualified when the maximum amplitude of the interference information spectrum of the switching power supply 40 is less than the reference spectrum amplitude, otherwise the switching power supply 40 is determined to be unqualified. When the switching power supply 40 is working, the MOSFET and the transformer will generate a ringing of about 12MHz, which is a triple frequency of 36MHz. The larger the amplitude of the ringing, the smaller the radiation margin will be, and the smaller the amplitude of the ringing, the larger the radiation margin will be. By setting the spectrum analyzer 30, when the maximum amplitude of the frequency point of 11.5M~19MHz exceeds the reference spectrum amplitude, the spectrum analyzer 30 determines that the finished switching power supply 40 is unqualified, and when the amplitude of the frequency point of 11.5M~19MHz is lower than the reference spectrum amplitude, the spectrum analyzer 30 determines that the finished switching power supply 40 is qualified.

[0048] Optionally, the spectrum analyzer 30 is further configured to determine that the switching power supply 40 is qualified when the maximum amplitude of the interference information spectrum corresponding to the larger one of the first common mode current and the second common mode current is less than the reference spectrum amplitude, otherwise determine that the switching power supply 40 is unqualified.

[0049] When the second end 52 of the toggle switch 50 is electrically connected to the live line output terminal OUTL, the spectrum analyzer 30 obtains the first common mode current. When the second end 52 of the toggle switch 50 is electrically connected to the neutral line output terminal OUTN, the spectrum analyzer 50 obtains the second common mode current. By setting the spectrum analyzer 30, the spectrum analyzer 30 obtains the interference information spectrum corresponding to the larger of the first common mode current and the second common mode current. When the maximum amplitude of the frequency point of 11.5M~19MHz exceeds the reference spectrum amplitude, the spectrum analyzer 30 determines that the finished switching power supply 40 is unqualified. When the amplitude of the frequency point of 11.5M~19MHz is lower than the reference spectrum amplitude, the spectrum analyzer 30 determines that the finished switching power supply 40 is qualified.

[0050] According to the technical solution of this embodiment, when the third output terminal of the impedance stabilization circuit is connected to the spectrum analyzer through the live line output terminal, the spectrum analyzer obtains the first common-mode current; when the third output terminal of the impedance stabilization circuit is connected to the spectrum analyzer through the neutral line output terminal, the spectrum analyzer obtains the second common-mode current; the spectrum analyzer obtains the interference information spectrum corresponding to the larger of the first common-mode current and the second common-mode current, and determines whether the switching power supply is qualified or unqualified based on the relationship between the maximum amplitude of the interference information spectrum corresponding to the larger of the first common-mode current and the second common-mode current and the amplitude of the reference spectrum.

[0051] Embodiment 3

[0052] Figure 3 The schematic diagram of the structure of the test circuit provided in the third embodiment of the present invention is as follows: Figure 3 As shown, the test circuit further includes a load 70 and a rectifier circuit 60 . Two ends of the load 70 are connected to two ends of the switching power supply 40 to simulate the load capacity of the switching power supply 40 .

[0053] It should be noted that the test circuit also includes a load 70, which is connected to both ends of the switching power supply 40 to simulate the load capacity of the switching power supply 40. The load 70 can be a resistor. By connecting to the resistor, it is simulated whether the switching power supply 40 operates normally under load conditions.

[0054] One end of the rectifier circuit 60 is connected to the second end 22 of the impedance stabilization circuit 20 , and the other end is connected to the switching power supply 40 , so as to convert the AC power into the DC power.

[0055] One end of the rectifier circuit 60 is connected to the second end 22 of the impedance stabilization circuit 20, and the other end is connected to the switching power supply 40, so that the AC power supply 10 supplies power to the switching power supply 40, wherein the rectifier circuit 60 is used to convert the AC power of the AC power supply 10 into DC power to supply power to the switching power supply 40.

[0056] It should be noted that the rectifier circuit 60 may be a rectifier diode or a rectifier circuit including other components, as long as it can convert the AC power of the AC power source 10 into the DC power required by the switching power supply 40 .

[0057] Optionally, the test circuit further includes a grounded metal plate 80 , one end of the grounded metal plate 80 is connected to the second end 22 of the impedance stabilization circuit 20 , and the other end of the grounded metal plate 80 is connected to the second end 32 of the spectrum analyzer 30 .

[0058] It should be noted that the test circuit includes a grounded metal plate 80, one end of the grounded metal plate 80 is connected to the second end 22 of the impedance stabilization circuit 20, and the other end is connected to the second end 32 of the spectrum analyzer 30. The other end of the first inductor L1 of the impedance stabilization circuit 20 is connected to one end of the switching power supply 40 after passing through the rectifier circuit 60, and the other end of the switching power supply 40 is grounded through the grounded metal plate 80. The first end of the first capacitor C1 of the impedance stabilization circuit 20 is connected to the live wire terminal Line of the AC power supply 10, and a high-pass filter of the live wire line is formed by the first inductor L1, the third capacitor C3 and the first resistor R1. The second end of the third capacitor C3 is electrically connected to the live wire output terminal OUTL, so as to couple the interference information spectrum of the live wire terminal of the switching power supply 40 to the spectrum analyzer 30; the second end of the impedance stabilization circuit 20 The other end of the inductor L2 is connected to one end of the switching power supply 40 after passing through the rectifier circuit 60. The other end of the switching power supply 40 is grounded through the grounding metal plate 80. The second end of the second capacitor C2 of the impedance stabilization circuit 20 is connected to the neutral line terminal NEUTRAL of the AC power supply 10. A high-pass filter of the neutral line is formed by the second inductor L2, the fourth capacitor C4 and the second resistor R2. The other end of the second inductor L2 is connected to the switching power supply 40, and the second end of the fourth capacitor C4 is electrically connected to the neutral line output terminal OUTN, thereby coupling the interference information spectrum of the neutral line terminal of the switching power supply 40 to the spectrum analyzer 30.

[0059] In the technical solution of this embodiment, the grounded metal plate is connected to the switching power supply to collect the capacitance of the switching power supply to ground, and is connected to the spectrum analyzer to display the interference information spectrum of the switching power supply in the spectrum analyzer. The rectifier circuit converts the AC power supply into DC to supply power to the switching power supply, and the load is used to test the load capacity of the switching power supply.

[0060] Embodiment 4

[0061] Embodiment 4 of the present invention provides a testing method, including any one of the testing circuits in the above embodiments, Figure 4 A flow chart of a test method provided in Embodiment 4 of the present invention is shown in FIG. Figure 4 As shown, the test methods include:

[0062] S100, the impedance stabilization circuit isolates the AC power supply from the switching power supply;

[0063] The first end of the impedance stabilization circuit is connected to the AC power supply, and the second end is connected to the switching power supply. The switching power supply under test is isolated from the AC power supply through the impedance stabilization circuit, ensuring the interference information spectrum of the switching power supply under test displayed on the spectrum analyzer.

[0064] S200: The spectrum analyzer obtains and displays the interference information spectrum of the switching power supply.

[0065] The spectrum analyzer obtains and displays the interference information spectrum of the switching power supply under test, and the radiation intensity of the switching power supply can be judged based on the interference information spectrum of the switching power supply under test.

[0066] In the technical solution of this embodiment, the impedance stabilization circuit ensures that the spectrum analyzer displays the interference information spectrum of the switching power supply under test, and the spectrum analyzer obtains and displays the interference information spectrum of the switching power supply, thereby realizing the analysis of the interference information spectrum of the switching power supply by the spectrum analyzer.

[0067] Embodiment 5

[0068] Figure 5 A flow chart of a test method provided in Embodiment 5 of the present invention is shown in FIG. Figure 5 As shown, the test method also includes:

[0069] S300: When the maximum amplitude of the interference information spectrum of the switching power supply is smaller than the reference spectrum amplitude, the spectrum analyzer determines that the switching power supply is qualified; otherwise, the spectrum analyzer determines that the switching power supply is unqualified.

[0070] The spectrum analyzer in the switching circuit determines that the switching power supply is qualified when the maximum amplitude of the interference information spectrum of the switching power supply is less than the reference spectrum amplitude, otherwise the switching power supply is determined to be unqualified. When the switching power supply 40 is working, the MOSFET and the transformer will generate a ringing of about 12MHz, which is a triple frequency of 36MHz. The larger the amplitude of the ringing, the smaller the radiation margin will be, and the smaller the amplitude of the ringing, the larger the radiation margin will be. By setting the spectrum analyzer, when the maximum amplitude of the frequency point of 11.5M~19MHz exceeds the reference spectrum amplitude, the spectrum analyzer determines that the finished switching power supply is unqualified, and when the amplitude of the frequency point of 11.5M~19MHz is lower than the reference spectrum amplitude, the spectrum analyzer determines that the finished switching power supply is qualified.

[0071] The technical solution of this embodiment realizes the judgment of whether the finished switching power supply is qualified or unqualified by setting the spectrum analyzer.

[0072] Embodiment 6

[0073] Figure 6 A flow chart of a test method provided in Embodiment 6 of the present invention is shown in FIG. Figure 6 As shown, the test method also includes:

[0074] S400, the spectrum analyzer displays the interference information spectrum corresponding to the larger one of the first common-mode current and the second common-mode current; and when the maximum amplitude of the interference information spectrum corresponding to the larger one of the first common-mode current and the second common-mode current is less than the reference spectrum amplitude, the switching power supply is determined to be qualified, otherwise the switching power supply is determined to be unqualified.

[0075] It should be noted that the third terminal of the impedance stabilization circuit includes a live line output terminal and a neutral line output terminal;

[0076] The impedance stabilization circuit includes a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a first inductor, a second inductor, a first resistor and a second resistor. The first end of the first capacitor is electrically connected to the live wire end of the AC power supply and the first end of the first inductor, respectively, and the second end of the first capacitor and the first end of the second capacitor are both grounded; the second end of the first inductor is electrically connected to the first end of the third capacitor and the switching power supply, respectively; the second end of the third capacitor is electrically connected to the first end of the first resistor and the live wire output end, respectively; the second end of the second capacitor is electrically connected to the neutral wire end of the AC power supply and the first end of the second inductor, and the second end of the second inductor is electrically connected to the first end of the fourth capacitor; the second end of the fourth capacitor is electrically connected to the first end of the second resistor and the neutral wire output end, respectively; the second end of the second resistor is electrically connected to the second end of the first resistor; the test circuit also includes a toggle switch; the first end of the toggle switch is electrically connected to the first end of the spectrum analyzer; the second end of the toggle switch is used to be electrically connected to the live wire output end or the neutral wire output end; when the second end of the toggle switch is electrically connected to the live wire output end, the spectrum analyzer obtains a first common mode current; when the second end of the toggle switch is electrically connected to the neutral wire output end, the spectrum analyzer obtains a second common mode current.

[0077] When the second end 52 of the toggle switch 50 is electrically connected to the live wire output terminal OUTL, the AC power supply 10 supplies power to the switching power supply 40 through the first inductor L1, and to the live wire output terminal OUTL through the first inductor L1 and the third capacitor C3. The live wire output terminal OUTL is connected to the second end 52 of the toggle switch 50, and to the first end 31 of the spectrum analyzer 30 through the first end 51 of the toggle switch 50, and the spectrum analyzer 30 obtains the first common-mode current; when the second end 52 of the toggle switch 50 is electrically connected to the neutral line output terminal OUTN, the AC power supply 10 supplies power to the switching power supply 40 through the second inductor L2, and to the neutral line output terminal OUTN through the second inductor L2 and the fourth capacitor C4. The neutral line output terminal OUTN is connected to the second end 52 of the toggle switch 50, and to the first end 31 of the spectrum analyzer 30 through the first end 51 of the toggle switch 50, and the spectrum analyzer 30 obtains the second common-mode current. By setting the spectrum analyzer 30, the spectrum analyzer 30 obtains the interference information spectrum corresponding to the larger one of the first common-mode current and the second common-mode current. When the maximum amplitude of the frequency point of 11.5M~19MHz exceeds the reference spectrum amplitude, the spectrum analyzer 30 determines that the finished switching power supply 40 is unqualified; when the amplitude of the frequency point of 11.5M~19MHz is lower than the reference spectrum amplitude, the spectrum analyzer 30 determines that the finished switching power supply 40 is qualified.

[0078] The technical solution of this embodiment, by setting the spectrum analyzer, obtains the interference information spectrum corresponding to the larger one of the live wire end and the neutral wire end of the switching power supply, thereby realizing the qualified or unqualified judgment of the finished switching power supply.

[0079] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A test circuit, characterized in that: include: AC power supply, impedance stabilization circuit and spectrum analyzer; A first end of the impedance stabilization circuit is connected to the AC power supply, and a second end of the impedance stabilization circuit is connected to the switching power supply, for isolating the AC power supply from the switching power supply; The first end of the spectrum analyzer is connected to the third end of the impedance stabilization circuit, the second end of the spectrum analyzer is grounded, and the spectrum analyzer is used to display the interference information spectrum of the switching power supply; The spectrum analyzer is further used to determine that the switching power supply is qualified when the maximum amplitude of the interference information spectrum of the switching power supply is less than the reference spectrum amplitude, otherwise, the switching power supply is determined to be unqualified; The third terminal of the impedance stabilization circuit includes a live line output terminal and a neutral line output terminal; The test circuit further comprises a toggle switch; a first end of the toggle switch is electrically connected to a first end of the spectrum analyzer; a second end of the toggle switch is electrically connected to the live line output end or the neutral line output end; When the second end of the toggle switch is electrically connected to the live wire output end, the spectrum analyzer obtains a first common-mode current; when the second end of the toggle switch is electrically connected to the neutral wire output end, the spectrum analyzer obtains a second common-mode current; the spectrum analyzer is also used to display an interference information spectrum corresponding to the larger of the first common-mode current and the second common-mode current.

2. The test circuit according to claim 1, characterized in that: The impedance stabilization circuit includes a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a first inductor, a second inductor, a first resistor and a second resistor. The first end of the first capacitor is electrically connected to the live wire end of the AC power supply and the first end of the first inductor, respectively, and the second end of the first capacitor and the first end of the second capacitor are both grounded; the second end of the first inductor is electrically connected to the first end of the third capacitor and the switching power supply, respectively; the second end of the third capacitor is electrically connected to the first end of the first resistor and the live wire output end, respectively; the second end of the second capacitor is electrically connected to the neutral wire end of the AC power supply and the first end of the second inductor, respectively, and the second end of the second inductor is electrically connected to the first end of the fourth capacitor; the second end of the fourth capacitor is electrically connected to the first end of the second resistor and the neutral wire output end, respectively; the second end of the second resistor is electrically connected to the second end of the first resistor.

3. The test circuit according to claim 1, characterized in that: It also includes a load and a rectifier circuit, wherein two ends of the load are connected to two ends of the switching power supply to simulate the load capacity of the switching power supply; One end of the rectifier circuit is connected to the second end of the impedance stabilization circuit, and the other end is connected to the switching power supply, and is used for converting alternating current into direct current.

4. The test circuit according to claim 1, characterized in that: It also includes a grounding metal plate, one end of which is connected to the second end of the impedance stabilization circuit, and the other end of which is connected to the second end of the spectrum analyzer.

5. The test circuit according to claim 1, characterized in that: The spectrum analyzer is further configured to determine that the switching power supply is qualified when the maximum amplitude of the interference information spectrum corresponding to the larger one of the first common mode current and the second common mode current is less than the reference spectrum amplitude, otherwise determine that the switching power supply is unqualified.

6. A testing method, characterized in that: The test circuit according to any one of claims 1 to 5 comprises: The impedance stabilization circuit isolates the AC power supply from the switching power supply; The spectrum analyzer acquires and displays the interference information spectrum of the switching power supply.

7. The testing method according to claim 6, characterized in that: Also includes: The spectrum analyzer determines that the switching power supply is qualified when the maximum amplitude of the interference information spectrum of the switching power supply is smaller than the reference spectrum amplitude, and otherwise determines that the switching power supply is unqualified.

8. The testing method according to claim 6, characterized in that: The third end of the impedance stabilization circuit includes a live line output end and a neutral line output end; the impedance stabilization circuit includes a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a first inductor, a second inductor, a first resistor, and a second resistor. The first end of the first capacitor is electrically connected to the live line end of the AC power supply and the first end of the first inductor, respectively, and the second end of the first capacitor and the first end of the second capacitor are both grounded; the second end of the first inductor is electrically connected to the first end of the third capacitor and the switching power supply, respectively; the second end of the third capacitor is electrically connected to the first end of the first resistor and the live line output end, respectively; the second end of the second capacitor is electrically connected to the neutral line end of the AC power supply and the second The first end of the inductor is electrically connected, and the second end of the second inductor is electrically connected to the first end of the fourth capacitor; the second end of the fourth capacitor is electrically connected to the first end of the second resistor and the neutral line output end respectively; the second end of the second resistor is electrically connected to the second end of the first resistor; the test circuit also includes a toggle switch; the first end of the toggle switch is electrically connected to the first end of the spectrum analyzer; the second end of the toggle switch is used to be electrically connected to the live line output end or the neutral line output end; when the second end of the toggle switch is electrically connected to the live line output end, the spectrum analyzer obtains a first common mode current; when the second end of the toggle switch is electrically connected to the neutral line output end, the spectrum analyzer obtains a second common mode current; The method further comprises: The spectrum analyzer displays the interference information spectrum corresponding to the larger of the first common-mode current and the second common-mode current; and when the maximum amplitude of the interference information spectrum corresponding to the larger of the first common-mode current and the second common-mode current is less than the reference spectrum amplitude, the switching power supply is determined to be qualified; otherwise, the switching power supply is determined to be unqualified.

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