CN110554255B

CN110554255B - Transformer testing method and related device

Info

Publication number: CN110554255B
Application number: CN201810544189.9A
Authority: CN
Inventors: 王庆海; 赵为阳; 赵龙; 戴勇军
Original assignee: Huawei Digital Power Technologies Co Ltd
Current assignee: Huawei Digital Power Technologies Co Ltd
Priority date: 2018-05-30
Filing date: 2018-05-30
Publication date: 2022-04-22
Anticipated expiration: 2038-05-30
Also published as: CN110554255A

Abstract

The embodiment of the invention discloses a method and a related device for testing a transformer, wherein the transformer is loaded on a PCB mainboard for testing radiation interference RE, the transformer consists of a primary coil and a secondary coil which are mutually coupled, and the method comprises the following steps: acquiring scattering parameters between a first port and a second port through a network analyzer, wherein the first port is any one of two ports of a main winding in the primary coil, and the second port is any one of two ports of a main winding in the secondary coil; and determining the transformer to be a defective transformer under the condition that the scattering parameter is greater than or equal to a preset threshold value. By adopting the embodiment of the invention, the problems that the RE characteristic test fails due to the limitation of a transformer manufacturing process in the prior art can be solved.

Description

Transformer testing method and related device

Technical Field

The invention relates to the technical field of electronic circuits, in particular to a transformer testing method and a related device.

Background

With the development of the fast charging technology, the requirements on the power parameters of the switching power supply are higher and higher, so that the design structure of the transformer is more and more complex. In particular, for a transformer of a high-frequency power supply, the structure of a transformer winding is complex, the number of machining processes is large, and part of the processes are completed manually. Factors such as flatness of an enameled wire in a transformer winding, fullness of a wire slot, and deviation have a large influence on radiation interference (RE) characteristics in electromagnetic compatibility (EMC), and the factors are manually unavoidable, so that the problem that the RE characteristics of the transformer cannot pass through during testing is caused, and the product quality of the transformer is influenced to a certain extent. Fig. 1 and fig. 2 show schematic circuit diagrams of two transformer tests, respectively.

As shown in fig. 1, the transformer is composed of three inductors L1, L2, and L3. L1 and L2 are inductances on the primary coil side, L3 is an inductance on the secondary coil side, and the primary coil and the secondary coil are magnetically coupled to each other. As shown in fig. 1, pin 3 of L2 and pin 7 of L3 are floating, and pin 2 of L1 and pin 3 of L2 are grounded. Pin 6 of L3 is connected to ground through a resistor R, which may have a value of 100 kilo-ohms (K Ω). A triangular wave is applied at pin 1 of transformer L1. The frequency of the triangular wave can be 100KHz, and the peak value of the voltage is 20V. Further, the voltage across the resistor R is used to perform a RE characteristic test on the transformer to intercept a defective transformer. However, in practice, the circuit supports interception of a low-frequency transformer, and has larger deviation on interception of a high-frequency transformer.

Fig. 2 shows a schematic circuit diagram of a single transformer unit test. The transformer consists of three inductors L1, L2 and L3. L1 and L2 are inductances on the primary coil side, L3 is an inductance on the secondary coil side, and the primary coil and the secondary coil are magnetically coupled to each other. As shown in fig. 2, pin 1 of L1, pin 3 of L2, pin 4, and pin 7 of L3 are all connected to ground. The 2 pin of L1 and the 6 pin of L3 are respectively used as

test points

1 and 2. And directly obtaining scattering parameters (S parameters) between the

test points

1 and 2 by a network analyzer, and screening out bad transformers by the S parameters. However, this solution only supports testing of the transformer unit, and cannot be applied to a real circuit/product having a transformer, such as a charger including a transformer. The testing accuracy is low, and the real purpose of transformer screening cannot be achieved.

Therefore, under the condition that the transformer manufacturing process cannot solve the above problems, how to manage the RE characteristics of the transformer to realize the screening of the transformer is a hot research problem.

Disclosure of Invention

The embodiment of the invention discloses a transformer testing method and a related device, which can solve the problem that the RE characteristic of a transformer cannot pass the test caused by the limitation of a manufacturing process in the prior art, can realize the automatic interception of a bad transformer and ensure the product quality of the transformer.

In a first aspect, the embodiment of the present invention discloses a method for testing a transformer, where the transformer is loaded on a PCB motherboard for performing a test of a radiation interference RE, the PCB motherboard is configured to provide a peripheral circuit that cooperates with the transformer, so as to perform the test of the RE on the transformer under the cooperation of the peripheral circuit, and the transformer is composed of a primary coil and a secondary coil that are coupled to each other, and the method includes:

acquiring scattering parameters between a first port and a second port through a network analyzer, wherein the first port is any one of two ports of a main winding in the primary coil, and the second port is any one of two ports of a main winding in the secondary coil;

and determining the transformer to be a defective transformer under the condition that the scattering parameter is greater than or equal to a preset threshold value.

In some possible embodiments, the network analyzer includes a third port connected to the first port through a core of a first radio frequency cable, and a fourth port connected to the second port through a core of a second radio frequency cable; the rubber-covered wire of the first radio frequency cable and the rubber-covered wire of the second radio frequency cable are respectively connected with the ground.

In some possible embodiments, the PCB main board includes a first end point, a second end point, and a third end point, the core wire of the first rf cable is connected to the first port through the first end point, the rubber-covered wire of the first rf cable is connected to the ground through the second end point, the core wire of the second rf cable is connected to the second port through the third end point, and the rubber-covered wire of the second rf cable is connected to the ground through the second end point.

In some possible embodiments, the network analyzer includes a third port connected to the first port through a core of a first rf cable, and a fourth port connected to a current clamp through a second rf cable;

the current clamp is buckled on two ports of the secondary coil, the two ports of the secondary coil comprise the second port, the rubber-covered wire of the first radio-frequency cable is connected with the ground, the core wire of the second radio-frequency cable is connected with the core wire of the current clamp, and the rubber-covered wire of the second radio-frequency cable is connected with the rubber-covered wire of the current clamp.

In some possible embodiments, the PCB main board includes a first end point through which the core wire of the first radio frequency cable is connected with the first port, and a second end point through which the rubber-insulated wire of the first radio frequency cable is connected with the ground.

In some possible embodiments, before the obtaining, by the network analyzer, the scattering parameter between the first port and the second port, the method further includes:

and carrying out short circuit processing on an electromagnetic interference (EMI) device in the PCB mainboard, wherein the EMI device is a device with an electromagnetic interference suppression function in the PCB mainboard.

In some possible embodiments, the EMI device includes a common mode inductor and a device that constitutes a rectification circuit.

In a second aspect, an embodiment of the present invention provides a transformer testing apparatus, where the apparatus includes a transformer, the transformer is carried on a PCB motherboard for performing a test of a radiation interference RE, the PCB motherboard is configured to provide a peripheral circuit cooperating with the transformer, so as to perform the test of the RE on the transformer in cooperation with the peripheral circuit, the transformer is composed of a primary coil and a secondary coil that are coupled to each other,

acquiring scattering parameters between a first port and a second port through a network analyzer, wherein the transformer is a defective transformer under the condition that the scattering parameters are greater than or equal to a preset threshold value;

the first port is any one of two ports of a main winding in the primary coil, and the second port is any one of two ports of a main winding in the secondary coil.

In some possible embodiments, the transformer testing device further includes the PCB main board.

In some possible embodiments, before the scattering parameter between the first port and the second port is obtained by the network analyzer, an electromagnetic interference EMI device in the PCB main board is subjected to short-circuit processing, where the EMI device is a device in the PCB main board having an electromagnetic interference suppression function.

By implementing the embodiment of the invention, the problem that the RE characteristic of the transformer cannot pass the test due to the limitation of a manufacturing process in the prior art can be solved, the automatic interception of the bad transformer can be realized, and the product quality of the transformer can be ensured.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below.

Fig. 1 is a schematic circuit diagram of a transformer test provided in the prior art.

Fig. 2 is a schematic circuit diagram of another transformer test provided by the prior art.

Fig. 3 is a schematic view of a scenario of a transformer test according to an embodiment of the present invention.

Fig. 4 is a schematic flowchart of a transformer testing method according to an embodiment of the present invention.

Fig. 5 is a graph illustrating a variation of a scattering parameter according to an embodiment of the present invention.

Fig. 6A-6B are schematic structural diagrams of two transformers according to an embodiment of the present invention.

Fig. 7A-7B are schematic circuit diagrams of two transformer tests according to an embodiment of the present invention.

Fig. 8A-8B are schematic circuit diagrams of another two transformer tests according to the embodiment of the invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be described in detail below with reference to the accompanying drawings of the present invention.

The applicant has discovered in the course of the present application: the problem that the transformer cannot pass during the RE test is caused due to the influence of the transformer manufacturing process in the prior art. In order to solve the problem, the application provides a transformer testing method and a device applicable to the method. Specifically, the RE characteristic of the transformer can be controlled by utilizing a peripheral circuit matched with the transformer to work so as to intercept the transformer which does not meet the specification (namely, a defective transformer). Fig. 3 is a schematic view of a possible transformer test scenario provided in an embodiment of the present invention.

The scene diagram shown in fig. 3 includes a PCB main board (or a test platform). The PCB board includes a peripheral circuit for testing the transformer, two interfaces, shown as two Surface Mounting Board (SMB) heads, and a plurality of plug holes. The transformer can mount/bear the transformer to be tested on the PCB mainboard through the plugging hole shown in the figure, so as to realize the RE test of the transformer in the following. Optionally, the automatic plug transformer of this application machine to realize the intelligent screening of transformer. Two ports of the network analyzer are respectively connected with two interfaces (two SMB heads) in the diagram so as to obtain scattering parameters between the two corresponding interfaces and realize the screening of the transformer.

In the two SMB heads shown in the figure, one of the SMB heads may be connected to the first endpoint (D endpoint) and the second endpoint (S endpoint) respectively, and the other SMB head may be connected to the second endpoint (S endpoint) and the third endpoint (ground endpoint) respectively, which will be described in detail later and will not be described in detail herein.

Fig. 4 is a schematic flow chart of a transformer testing method according to an embodiment of the present invention. Wherein the transformer is composed of a primary coil and a secondary coil coupled to each other. The transformer is carried on a PCB mainboard for RE characteristic test, so as to obtain scattering parameters (or RE characteristics) reflected on the PCB mainboard by the transformer. The method as shown in fig. 4 comprises the following implementation steps:

step S102, scattering parameters between a first port and a second port are obtained through a network analyzer, the first port is any one of two ports of a main winding in the primary coil, and the second port is any one of two ports of a main winding in the secondary coil.

And step S104, determining the transformer to be a defective transformer under the condition that the scattering parameter is greater than or equal to a preset threshold value.

The following sets forth some specific embodiments and alternatives to which the present application relates.

Specifically, the transformer is composed of a primary coil and a secondary coil coupled to each other. Wherein the primary coil may be composed of one or more windings, and the secondary coil may also be composed of one or more windings. When the coil is composed of a plurality of windings, it includes one main winding, and the remaining windings are sub-windings.

In the transformer testing process, two ports of the network analyzer may be electrically connected to two ports (specifically, a first port and a second port) of the transformer, respectively, to obtain scattering parameters between the two ports. Wherein the first port (port1) may be any port of a winding in the primary coil and the second port (port2) may be any port of a winding in the secondary coil. Suppose that the network analyzer obtains a voltage signal of a first port as V₁Obtaining the voltage signal of the second port as V₂Then the scattering parameter S between the first port and the second port can be obtained by using the following formula (1)₂₁。

And after the scattering parameters are obtained, comparing the scattering parameters with a preset threshold value to identify the quality of the transformer. For example, when the scattering parameter is greater than or equal to a preset threshold value, the transformer may be determined to be a defective transformer (inferior transformer, bad transformer). Otherwise, when the scattering parameter is smaller than the preset threshold value, the transformer can be determined to be a high-quality transformer, so that the transformer meeting the specification can be screened out, and the product quality of the transformer is improved.

The preset threshold is set by a user side or a system side in a self-defined mode. Optionally, the threshold values set correspondingly may be different due to different frequencies. Fig. 5 shows a schematic diagram of the relationship between the scattering parameter and the preset threshold. As shown in fig. 5, different test frequencies correspond to different scattering parameters and different preset thresholds. And when the curves of the scattering parameters are all below the threshold curve, the test result of the transformer is a high-quality transformer, otherwise, the transformer is a defective transformer.

In an alternative embodiment, the first port is any one of two ports of a main winding in the primary coil. The second port is any one of two ports of the main winding in the secondary coil.

For example, please refer to fig. 6A and 6B, which illustrate circuit schematic diagrams of two possible transformer tests. As in fig. 6A, the primary coil and the secondary coil are each constituted by one winding (i.e., a main winding). In this case, the first port may be specifically a in the drawing₁Or C₁A port. The second port may be embodied as B in the figure₁Or D₁A port.

As in fig. 6B, the primary coil and the secondary coil are each constituted by two windings. The windings (inductor) L1 and L2 constitute a primary coil, and the windings (inductor) L3 and L4 constitute a secondary coil. L1 is the primary winding of the primary coil and L2 is your secondary winding in the primary coil. L3 is the main winding in the secondary coil and L4 is the secondary winding in the secondary coil. In this case, the first port may be specifically a in the drawing₂And C₂A port. The second port can be specifically B in the figure₂Or D₂A port.

In an alternative embodiment, the network analyzer includes a third port (port3) and a fourth port (port 4). And the two ports of the network analyzer are respectively connected with the first port and the second port through two radio frequency cables. Wherein, the radio frequency cable includes heart yearn and rubber-insulated-wire. Specifically, the third port of the network analyzer is connected with the first port through a core wire of a first radio frequency cable. The rubber-insulated wire of the first radio frequency cable is connected with the ground. And the fourth port of the network analyzer is connected with the second port through a core wire of a second radio frequency cable. The rubber-covered wire of the second radio frequency cable is connected with the ground.

In an alternative embodiment, the PCB motherboard provides (includes) three endpoints, a first endpoint (D endpoint), a second endpoint (S endpoint), and a third endpoint (secondary ground endpoint), respectively. Specifically, the chip of the first rf cable is connected to the first end (D end) to be connected to the first port of the transformer through the first end. The rubber-insulated wire of the first radio frequency cable is connected with a second end point (S end point) so as to be connected with the ground through the second end point. The core of the second radio frequency cable is connected to a third port (secondary ground point) to connect to the second port of the transformer through the third port. The rubber-insulated wire of the second radio frequency cable is connected with a second end point (S end point) so as to be connected with the ground through the second end point.

In an alternative embodiment, the network analyzer includes a third port (port3) and a fourth port (port 4). And the third port and the fourth port are respectively led out by two radio frequency cables. And the third port of the network analyzer is electrically connected with the first port of the transformer through a core wire of the first radio frequency cable. The rubber-insulated wire of the first radio frequency cable is connected with the ground. And the fourth port of the network analyzer is electrically connected with the current clamp through a second radio frequency cable. The current clamp is buckled on two ports of a secondary coil in the transformer, wherein the two ports of the secondary coil at least comprise a second port of the transformer.

Wherein the current clamp comprises a radio frequency cable, namely a core wire and a rubber-covered wire. Specifically, a core wire of the second radio frequency cable is connected with a core wire of the current clamp, and a rubber-covered wire of the second radio frequency cable is connected with a rubber-covered wire of the current clamp.

In an alternative embodiment, the PCB motherboard provides (includes) a first endpoint (D-endpoint) and a second endpoint (S-endpoint). The chip of the first rf cable is connected to the first end (D end) to be connected to the first port of the transformer through the first end. The rubber-insulated wire of the first radio frequency cable is connected with a second end point (S end point) so as to be connected with the ground through the second end point.

In an optional embodiment, before the obtaining, by the network analyzer, the scattering parameter between the first port and the second port, the method further includes: and carrying out short circuit treatment on an electromagnetic interference (EMI) device in the PCB mainboard. The EMI device is a device with an electromagnetic interference suppression function in the PCB mainboard.

Specifically, in order to better test the RE characteristic of the transformer, the EMI device in the PCB main board needs to be shorted before the test, so as to better test the RE characteristic of the transformer, and further identify the quality of the transformer. The EMI device refers to a device having an electromagnetic interference suppression function, such as a common mode inductor, a component in a rectifier circuit (rectifier bridge), and the like.

In an optional embodiment, the PCB motherboard includes a peripheral circuit therein to cooperate with the transformer to test RE characteristics, so as to identify the quality of the transformer. The specific circuit structure of the peripheral circuit is not limited and detailed in the present application.

To better assist the user in understanding, two specific embodiments are given below by way of example.

The first embodiment:

fig. 7A shows a schematic diagram of a transformer test circuit. As shown in fig. 7A, the circuit includes two common mode inductors L3 and L4, a rectifier bridge (rectifier circuit) formed by four diodes, a transformer composed of mutually coupled inductors (windings) L1 and L2, a capacitor C1 and a resistor R1 connected in parallel with L1, a diode connected to one end of L1, a capacitor C2 connected in parallel with L2, a diode connected to one end of L2, a field effect MOS transistor connected to one end of L1, and a capacitor C3 connected across two ends of the rectifier bridge. The other devices except the transformer are all devices in a peripheral circuit, and can be welded on a PCB main board and provided by the PCB main board.

Before testing the transformer, the EMI devices involved in the circuit need to be short-circuited. Here, the two common-mode inductors and the rectifier bridge may be short-circuited. Further, the MOS transistor is removed, and the illustration shows only that the G pole of the MOS transistor is suspended. The S and D poles can be considered as the S and D terminals. Accordingly, after the EMI device is shorted, the transformer test circuit schematic shown in FIG. 7B can be formed.

Accordingly, the two port3 and port4 of the network analyzer are each led out by one shielded radio frequency cable (RF cable). The RF cable is divided into a core wire and a covered wire, wherein the covered wire is grounded to reduce interference with the core wire. As shown in fig. 7B, the core wire of port3 may be connected (or soldered) to the D-terminal of the MOS transistor location to connect to the port1 port of the transformer, and the flex wire of port3 may be connected (or soldered) to the S-terminal of the MOS transistor location to connect to ground. The core of port4 is connected to ground for the low voltage output signal, i.e., port2 port of the transformer. The flex of port4 is shorted to the flex of port3 to connect to the S-endpoint, to ground.

After the operation is ready, a transformer to be tested (shown by magnetic coupling of L1 and L2) can be inserted on the PCB main board, and a network analyzer is started to measure and obtain scattering parameters between the port1 and the port2 of the transformer. And further comparing the scattering parameter with a preset threshold value, and if the scattering parameter is greater than or equal to the preset threshold value, intercepting the transformer to be regarded as an unqualified or inferior transformer.

In this embodiment, the MOS transistor position (S, D end point) provided by the PCB main board and the port1 and port2 port positions for obtaining scattering parameters may be adjusted and changed according to actual requirements, and the illustration of the present application is only an example and is not limited.

Second embodiment:

fig. 8A shows a schematic diagram of another transformer test circuit. As shown in fig. 8A, the circuit includes a transformer and peripheral circuits that work in cooperation with the transformer, and the peripheral circuits may be provided by, for example, soldered on, a PCB main board. The devices included in the peripheral circuit and the connection relationship of the devices may be as shown in the figures or referred to in the relevant explanation of the first embodiment, and are not described in detail here.

Similarly, before testing the transformer, the EMI devices involved in the peripheral circuits need to be shorted, which is illustrated as a common mode inductor and a rectifier bridge. The MOS transistors on the primary side of the peripheral circuit are removed, leaving three terminals (shown as G, S and D terminals) to which the MOS transistors are connected. Accordingly, after the EMI device is shorted, the transformer test circuit schematic shown in FIG. 8B can be formed.

Further, two port3 and port4 of the network analyzer are each led out by one shielded radio frequency cable (RF cable). The RF cable is divided into a core wire and a covered wire, wherein the covered wire is grounded to reduce interference with the core wire. As shown in fig. 8B, the core wire of port3 may be connected (or soldered) to the D-terminal of the MOS transistor location to connect to the port1 port of the transformer, and the flex wire of port3 may be connected (or soldered) to the S-terminal of the MOS transistor location to connect to ground. Port4 is connected to a current clamp that snaps onto a USB cable at the output of the peripheral circuit, shown as the output line corresponding to the two ports of the secondary coil.

The present application may also provide a transformer testing apparatus, the apparatus comprising a transformer, the transformer being carried on a PCB motherboard for testing of RE characteristics. The transformer consists of a primary coil and a secondary coil coupled to each other,

In an alternative embodiment, the device may further comprise the PCB main board.

The parts which are not shown or not described in this embodiment may refer to the related explanations in the foregoing method embodiments, and are not described here again.

The devices or circuits in the device of the embodiment of the invention can be sequentially adjusted, combined and deleted according to actual needs. The devices or circuits in the embodiments of the present invention may be implemented by a general-purpose Integrated Circuit, such as a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), or the like.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.

Claims

1. A method for testing a transformer, the transformer comprising a primary coil and a secondary coil coupled to each other, wherein the transformer is carried on a PCB board for testing radiated interference RE, the PCB board being configured to provide peripheral circuitry for cooperating with the transformer to perform RE testing on the transformer in cooperation with the peripheral circuitry, the method comprising:

performing short-circuit processing on an electromagnetic interference (EMI) device in the PCB mainboard, wherein the EMI device is a device with an electromagnetic interference suppression function in the PCB mainboard and comprises a common-mode inductor and a device forming a rectifying circuit;

acquiring a scattering parameter between a first port and a second port through a network analyzer, wherein the first port is any one of two ports of a main winding in the primary coil, the second port is any one of two ports of a main winding in the secondary coil, the network analyzer comprises a third port and a fourth port, the third port is connected with the first port through a core wire of a first radio frequency cable, and the fourth port is connected with the second port through a core wire of a second radio frequency cable; the rubber-covered wire of the first radio frequency cable and the rubber-covered wire of the second radio frequency cable are respectively connected with the ground;

2. The method of claim 1, wherein the PCB motherboard includes a first endpoint, a second endpoint, and a third endpoint, wherein a core of the first RF cable is connected to the first port via the first endpoint, wherein a rubber-covered wire of the first RF cable is connected to ground via the second endpoint, wherein a core of the second RF cable is connected to the second port via the third endpoint, and wherein a rubber-covered wire of the second RF cable is connected to ground via the second endpoint.

3. A method for testing a transformer, the transformer comprising a primary coil and a secondary coil coupled to each other, wherein the transformer is carried on a PCB board for testing radiated interference RE, the PCB board being configured to provide peripheral circuitry for cooperating with the transformer to perform RE testing on the transformer in cooperation with the peripheral circuitry, the method comprising:

acquiring a scattering parameter between a first port and a second port through a network analyzer, wherein the first port is any one of two ports of a main winding in the primary coil, the second port is any one of two ports of a main winding in the secondary coil, the network analyzer comprises a third port and a fourth port, the third port is connected with the first port through a core wire of a first radio frequency cable, and the fourth port is connected with a current clamp through a second radio frequency cable; the current clamp is buckled on two ports of the secondary coil, the two ports of the secondary coil comprise the second port, the rubber-covered wire of the first radio-frequency cable is connected with the ground, the core wire of the second radio-frequency cable is connected with the core wire of the current clamp, and the rubber-covered wire of the second radio-frequency cable is connected with the rubber-covered wire of the current clamp;

4. The method of claim 3, wherein the PCB motherboard includes a first endpoint through which a core wire of the first RF cable is connected to the first port and a second endpoint through which a flex wire of the first RF cable is connected to ground.

5. A transformer testing device comprises a transformer, wherein the transformer consists of a primary coil and a secondary coil which are coupled with each other, and is characterized in that the transformer is carried on a PCB mainboard for testing radiated interference RE, the PCB mainboard is used for providing a peripheral circuit which is matched with the transformer to test the RE of the transformer under the matching of the peripheral circuit,

acquiring scattering parameters between a first port and a second port through a network analyzer, wherein the transformer is a defective transformer under the condition that the scattering parameters are greater than or equal to a preset threshold value; before the scattering parameters between the first port and the second port are obtained through the network analyzer, an electromagnetic interference (EMI) device in the PCB main board is subjected to short-circuit processing, the EMI device is a device with an electromagnetic interference suppression function in the PCB main board, and the EMI device comprises a common-mode inductor and a device forming a rectifying circuit; the first port is any one of two ports of a main winding in the primary coil, the second port is any one of two ports of a main winding in the secondary coil, the network analyzer comprises a third port and a fourth port, the third port is connected with the first port through a core wire of a first radio frequency cable, and the fourth port is connected with the second port through a core wire of a second radio frequency cable; the rubber-covered wire of the first radio frequency cable and the rubber-covered wire of the second radio frequency cable are respectively connected with the ground.

6. The transformer testing device of claim 5, wherein the PCB motherboard comprises a first end point, a second end point and a third end point, wherein a core wire of the first RF cable is connected with the first port through the first end point, a rubber-covered wire of the first RF cable is connected with the ground through the second end point, a core wire of the second RF cable is connected with the second port through the third end point, and a rubber-covered wire of the second RF cable is connected with the ground through the second end point.

7. A transformer testing device comprises a transformer, wherein the transformer consists of a primary coil and a secondary coil which are coupled with each other, and is characterized in that the transformer is carried on a PCB mainboard for testing radiated interference RE, the PCB mainboard is used for providing a peripheral circuit which is matched with the transformer to test the RE of the transformer under the matching of the peripheral circuit,

acquiring scattering parameters between a first port and a second port through a network analyzer, wherein the transformer is a defective transformer under the condition that the scattering parameters are greater than or equal to a preset threshold value; before the scattering parameters between the first port and the second port are obtained through the network analyzer, an electromagnetic interference (EMI) device in the PCB main board is subjected to short-circuit processing, the EMI device is a device with an electromagnetic interference suppression function in the PCB main board, and the EMI device comprises a common-mode inductor and a device forming a rectifying circuit; the first port is any one of two ports of a main winding in the primary coil, the second port is any one of two ports of a main winding in the secondary coil, the network analyzer comprises a third port and a fourth port, the third port is connected with the first port through a core wire of a first radio frequency cable, and the fourth port is connected with the current clamp through a second radio frequency cable;

8. The transformer testing device of claim 7, wherein the PCB motherboard comprises a first end point and a second end point, wherein a core wire of the first RF cable is connected with the first port through the first end point, and a rubber-insulated wire of the first RF cable is connected with the ground through the second end point.