Thermal measurement switching loss circuit and method for top thermally dissipated gan devices

Abstract

This invention discloses a thermal measurement switching loss circuit and method for top-heat-dissipated GaN devices. In the thermal measurement switching loss circuit, the drain of the GaN device under test T1 and the drain of the auxiliary GaN device T3 are connected to a voltage source V. DC The positive electrode of T1 is connected to the source of auxiliary gallium nitride device T2, and the source of T3 is connected to the drain of auxiliary gallium nitride device T4. The sources of T2 and T4 are both connected to V. DC The negative terminal of T1, the source of T1 and the drain of T2 are connected by a first node N1, the source of T3 and the drain of T4 are connected by a second node N2, the two ends of the inductor L are connected to N1 and N2 respectively, and the capacitor C DC With V DC The circuit is connected in parallel, with T1 being the top-mounted component. In this invention, when testing with a thermal measurement switching loss circuit, the heat from T1 is conducted into the ceramic substrate, while the heat from T2, T3, and T4 is dissipated from the bottom of the printed circuit board. This allows the ceramic substrate to effectively extract the heat loss of the gallium nitride device under test (GaN) T1, improving the accuracy of the thermal loss measurement of GaN T1.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor switching technology, specifically relating to a circuit and method for measuring the switching loss of top-heat-dissipating GaN devices. Background Technology

[0002] Currently, the demand for high power density and high efficiency in power converters is becoming increasingly urgent. One way to improve power density is to increase the switching frequency, thereby reducing the size of the output capacitor and inductor. Since the performance of Si-based devices has reached its theoretical limit with technological advancements, their switching speed is insufficient to support the high-frequency switching requirements of power converters. In contrast, third-generation semiconductor GaN devices offer faster switching frequencies, lower on-resistance, and higher breakdown voltage, and are therefore widely used in power converters. However, accurately evaluating the switching losses of GaN devices remains a problem that urgently needs to be solved by those skilled in the art.

[0003] In related technologies, dual-pulse circuits are mainly used to evaluate the switching losses of GaN devices. However, dual-pulse circuits are more suitable for Si-based devices with low switching speeds and insensitivity to parasitic parameters. Studies have shown that when using dual-pulse circuits to test the switching losses of silicon carbide and gallium nitride devices, the error can be as high as 40%.

[0004] In addition, there is a thermal testing method in the related technology that is suitable for silicon carbide devices in TO220 packages, but gallium nitride devices are mostly surface-mount packages in order to reduce parasitic parameters, so this thermal testing method is not suitable for gallium nitride devices. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this invention provides a circuit and method for measuring the switching loss of top-heat-dissipated GaN devices.

[0006] In a first aspect, the present invention provides a thermal measurement switching loss circuit suitable for top-heat-dissipated GaN devices, including a voltage source V DC Capacitor C DC Inductor L, gallium nitride device under test T1, and auxiliary gallium nitride devices: T2, T3, and T4; among which,

[0007] The drain of the gallium nitride device under test T1 and the drain of the auxiliary gallium nitride device T3 are connected to the voltage source V. DC The positive terminal of the device is connected to the source of the gallium nitride device under test (GNT) T1, and the drain of the auxiliary GNT T2 is connected to the source of the auxiliary GNT T3, and the drain of the auxiliary GNT T4 is connected to the source of the auxiliary GNT T2 and T4. The sources of the auxiliary GNT devices T2 and T4 are both connected to the voltage source V. DCThe negative terminal of the device is connected to the source of the gallium nitride device T1 under test and the drain of the auxiliary gallium nitride device T2, which includes a first node N1. The source of the auxiliary gallium nitride device T3 and the drain of the auxiliary gallium nitride device T4 include a second node N2. The two ends of the inductor L are connected to the first node N1 and the second node N2 respectively. The capacitor C... DC With voltage source V DC The devices are connected in parallel, and the gallium nitride device under test T1 is a top package.

[0008] In one embodiment of the present invention, auxiliary gallium nitride device T2, auxiliary gallium nitride device T3 and auxiliary gallium nitride device T4 are all bottom-packaged.

[0009] In one embodiment of the present invention, a ceramic substrate is also included;

[0010] The voltage source V DC Capacitor C DC The inductor L, the gallium nitride device under test T1, and the auxiliary gallium nitride devices T2, T3, and T4 are located on the first surface of the printed circuit board, and the ceramic substrate is bonded to the first surface of the printed circuit board.

[0011] In one embodiment of the present invention, the tops of auxiliary gallium nitride devices T2, T3 and T4 are covered with thermal resistance material.

[0012] In one embodiment of the present invention, the thermal resistance material is plastic.

[0013] In one embodiment of the present invention, the electrical connection lines of the gallium nitride device T1 under test are all traced at the top.

[0014] In one embodiment of the present invention, the printed circuit board includes three preset regions, each preset region including a plurality of through holes;

[0015] The three preset areas correspond to the heat dissipation surfaces of the bottom packages of the auxiliary gallium nitride device T2, auxiliary gallium nitride device T3, and auxiliary gallium nitride device T4, respectively.

[0016] In one embodiment of the present invention, the printed circuit board has windows at corresponding positions of the auxiliary gallium nitride device T2, auxiliary gallium nitride device T3 and auxiliary gallium nitride device T4.

[0017] In a second aspect, the present invention provides a method for measuring the switching loss of a top-heat-sinking GaN device, applied to the circuit for measuring the switching loss of a top-heat-sinking GaN device described in the first aspect, comprising:

[0018] After fixing the ceramic substrate in the thermal measurement switching loss circuit onto the copper heat sink of the thermal testing device, the thermal measurement switching loss circuit is turned on; wherein, the thermal testing device includes an air supply module and a cavity connected to the air outlet of the air supply module, and the copper heat sink is located on the surface of the cavity.

[0019] After the thermal measurement switching loss circuit reaches a thermally stable state, the temperature T at the first test point located on the side of the copper heat sink near the air supply module is measured. air,in The temperature T at a second test point located on the side of the copper radiator furthest from the air supply module was measured. air,out ;

[0020] Based on the temperature T at the first test point air,in and the temperature T at the second test point air,out The thermal measurement switching loss of the gallium nitride device T1 under test was calculated.

[0021] In one embodiment of the present invention, based on the temperature T at the first test point air,in and the temperature T at the second test point air,out The steps for calculating the thermal measurement switching loss of the gallium nitride device T1 under test include:

[0022] Calculate the temperature T at the second test point. air,out With the temperature T at a test point air,in The difference is used to obtain the thermal measurement switching loss result of the gallium nitride device T1 under test.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] This invention provides a thermal measurement switching loss circuit and method for top-heat-dissipated GaN devices. For a top-heat-dissipated GaN device T1 under test, this invention selects bottom-heat-dissipated auxiliary GaN devices T2, T3, and T4 for testing using the thermal measurement switching loss circuit. In this way, the heat of the GaN device T1 under test will be conducted into the ceramic substrate, while the heat of the auxiliary GaN devices T2, T3, and T4 will be dissipated from the bottom of the printed circuit board. This allows the ceramic substrate to effectively extract the heat loss of the GaN device T1 under test, thereby improving the accuracy of the thermal loss measurement of the GaN device T1 under test.

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a dual-pulse test circuit in related technologies;

[0027] Figure 2This is a schematic diagram of a thermal measurement switching loss circuit for top-heat-dissipated GaN devices provided in an embodiment of the present invention;

[0028] Figure 3 This is a schematic diagram of the positional relationship of the ceramic substrate provided in an embodiment of the present invention;

[0029] Figure 4 This is another schematic diagram of the positional relationship of the ceramic substrate provided in an embodiment of the present invention;

[0030] Figure 5a This is a PCB layout diagram of the gallium nitride device under test and the auxiliary gallium nitride device provided in an embodiment of the present invention;

[0031] Figure 5b This is another PCB layout diagram of the gallium nitride device under test and the auxiliary gallium nitride device provided in the embodiment of the present invention;

[0032] Figure 6 This is a flowchart of a method for measuring the switching loss of a top-heat-dissipated GaN device, provided in an embodiment of the present invention.

[0033] Figure 7 This is a schematic diagram of a thermal testing device provided in an embodiment of the present invention;

[0034] Figure 8 This is an overall temperature field distribution diagram of a thermal measurement switching loss circuit for top-heat-dissipating GaN devices provided in an embodiment of the present invention;

[0035] Figure 9a This is a temperature field distribution diagram of the first surface of a printed circuit board provided in an embodiment of the present invention;

[0036] Figure 9b This is a temperature field distribution diagram of the second surface of a printed circuit board provided in an embodiment of the present invention;

[0037] Figure 10 This is a temperature field distribution diagram of the ceramic substrate provided in an embodiment of the present invention. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0039] Figure 1 This is a schematic diagram of a dual-pulse test circuit in related technologies. Specifically, as shown... Figure 1As shown, when evaluating switching losses using a dual-pulse test circuit, two pulse signals need to be supplied to the transistor under test (S1). The first pulse signal is used to test the turn-off loss, and the second pulse signal is used to test the turn-on loss. Specifically, S1 is first turned on and S2 is turned off to charge the inductor L1 to the required test current. Then, the turn-off loss is tested at the falling edge of the first pulse (S1 is turned off), while S2 is turned on to form a freewheeling circuit. Next, S1 is turned on and S2 is turned off, and the turn-on loss is tested at the rising edge of the second pulse.

[0040] Because the freewheeling side element S2 body diode switches from on to off during the second turn-on, its reverse recovery characteristics are poor, which will increase the measured turn-on loss. When using the above-mentioned dual-pulse test circuit to test wide bandgap semiconductors, the error can be as high as 40%.

[0041] In view of this, the present invention provides a circuit and method for measuring the switching loss of top-heat-dissipated GaN devices.

[0042] Figure 2 This is a schematic diagram of a thermal measurement switching loss circuit for top-heat-dissipated GaN devices provided in an embodiment of the present invention. Figure 2 As shown, this embodiment of the invention provides a thermal measurement switching loss circuit suitable for top-heat-dissipated GaN devices, including a voltage source V. DC Capacitor C DC Inductor L, gallium nitride device under test T1, and auxiliary gallium nitride devices: T2, T3, and T4; among which,

[0043] The drain of the gallium nitride device under test T1 and the drain of the auxiliary gallium nitride device T3 are connected to the voltage source V. DC The positive terminal of the device is connected to the source of the gallium nitride device under test (GNT) T1, and the drain of the auxiliary GNT T2 is connected to the source of the auxiliary GNT T3, and the drain of the auxiliary GNT T4 is connected to the source of the auxiliary GNT T2 and T4. The sources of the auxiliary GNT devices T2 and T4 are both connected to the voltage source V. DC The negative terminal of the device is connected to the source of the gallium nitride device T1 under test and the drain of the auxiliary gallium nitride device T2, which includes a first node N1. The source of the auxiliary gallium nitride device T3 and the drain of the auxiliary gallium nitride device T4 include a second node N2. The two ends of the inductor L are connected to the first node N1 and the second node N2 respectively. The capacitor C... DC With voltage source V DC The devices are connected in parallel, and the gallium nitride device under test, T1, is a top-packaged device.

[0044] Specifically, this embodiment adopts Figure 2The full-bridge topology shown is used for testing. The gallium nitride device under test (GaN) T1 is a top-packaged device. The gates of GaN T1 and auxiliary GaN devices T2, T3, and T4 are all connected to the driving circuit. During the test, the above-mentioned thermal measurement switching loss circuit includes four operating stages: t1 to t4. In the t1 operating stage, GaN T1 and auxiliary GaN device T4 are turned on, while auxiliary GaN devices T2 and T3 are turned off. In the t2 operating stage, auxiliary GaN devices T2 and T4 are turned on, while GaN T1 and auxiliary GaN device T3 are turned off. In the t3 operating stage, auxiliary GaN devices T2 and T3 are turned on, while GaN T1 and auxiliary GaN device T4 are turned off. In the t4 operating stage, auxiliary GaN devices T2 and T4 are turned on, while GaN T1 and auxiliary GaN device T3 are turned off.

[0045] It should be understood that the switching loss of the gallium nitride device under test (DUT) T1 is generated during its turn-on to turn-off process. However, the duration of a typical circuit operating cycle is only on the order of microseconds, making it difficult to measure the losses generated by the DUT during the turn-on to turn-off period. Analysis of the various operating stages of the circuit shows that the DUT T1 only operates during the t1 operating stage. This design minimizes the duty cycle of the DUT (i.e., the gallium nitride device under test T1). In other words, this embodiment, through the above operating process, can reduce the on-time of the gallium nitride device T1 while ensuring continuous circuit operation, thereby reducing the switching loss error when testing the gallium nitride device T1.

[0046] Figure 3 This is a schematic diagram illustrating the positional relationship of the ceramic substrate provided in an embodiment of the present invention. For example... Figure 3 As shown, in the above-mentioned thermal measurement switching loss circuit, the auxiliary gallium nitride device T2, auxiliary gallium nitride device T3 and auxiliary gallium nitride device T4 are all bottom-packaged.

[0047] Figure 4 This is another schematic diagram illustrating the positional relationship of the ceramic substrate provided in an embodiment of the present invention. Figures 5a-5b This is a PCB layout diagram of the gallium nitride device under test and the auxiliary gallium nitride device provided in an embodiment of the present invention. For example... Figure 3-5b As shown, the above-mentioned thermal measurement switching loss circuit for top-heat-dissipating GaN devices also includes a ceramic substrate;

[0048] Voltage source V DC Capacitor C DC The inductor L, the gallium nitride device under test T1, and the auxiliary gallium nitride devices T2, T3, and T4 are located on the first surface of the printed circuit board, and the ceramic substrate is bonded to the first surface of the printed circuit board.

[0049] Further reading is available upon request. Figure 5aThe printed circuit board includes three preset areas, and each preset area includes multiple through holes;

[0050] Among them, the three preset areas correspond to the heat dissipation surfaces of the bottom packages of auxiliary gallium nitride device T2, auxiliary gallium nitride device T3, and auxiliary gallium nitride device T4, respectively.

[0051] Optionally, the printed circuit board has windows at corresponding positions of the auxiliary gallium nitride devices T2, T3, and T4.

[0052] Specifically, voltage source V DC Capacitor C DC The circuit consists of an inductor L, a gallium nitride (GaN) device under test (GNT) T1, and auxiliary GaN devices T2, T3, and T4, all located on the first surface of a printed circuit board (PCB). GNT T1 is a top-heat-dissipating device, while auxiliary GaN devices T2, T3, and T4 are all bottom-heat-dissipating devices. The ceramic substrate is attached to the first surface of the PCB. Since the ceramic substrate needs to be fixed to the thermal testing apparatus during thermal measurements, a thermal path needs to be created on the PCB for these three auxiliary GaN devices to prevent heat dissipation through the ceramic substrate, thus ensuring test accuracy.

[0053] Generally, during the packaging of gallium nitride (GaN) devices, the heat dissipation of the bare GaN die is concentrated on the package surface, i.e., the heat dissipation surface. Therefore, in this embodiment, through-holes are drilled in three preset areas corresponding to the heat dissipation surfaces of auxiliary GaN devices T2, T3, and T4 on the printed circuit board. It should be understood that if through-holes are not drilled in the preset areas of the PCB board, the heat flow of auxiliary GaN devices T2, T3, and T4 cannot be conducted vertically downwards, but will be conducted laterally along the plane of the PCB board, which can easily lead to thermal coupling with the heat flow of the GaN device under test T1. Therefore, by drilling through-holes in the preset areas of the PCB board to form a thermal path, the heat flow of auxiliary GaN devices T2, T3, and T4 can be guided to the second surface of the PCB board, avoiding adverse effects on the heat loss measurement of the GaN device under test T1.

[0054] Optionally, there are also openings at the corresponding positions of the printed circuit board and the auxiliary gallium nitride devices T2, T3 and T4. This design further reduces the thermal resistance at the bottom of the auxiliary gallium nitride devices T2, T3 and T4, and also helps to increase heat dissipation at the bottom.

[0055] Furthermore, the tops of the auxiliary gallium nitride devices T2, T3, and T4 are covered with a thermal resistance material, which can optionally be made of plastic.

[0056] Specifically, considering that the ceramic substrate has a high thermal conductivity and easily absorbs the heat of gallium nitride devices, this embodiment wraps the top of the three auxiliary gallium nitride devices with thermal resistance material to prevent the heat of the auxiliary gallium nitride devices from being conducted into the ceramic substrate. In addition, the gallium nitride device under test T1 dissipates heat from the top, while the auxiliary gallium nitride devices T2, T3, and T4 dissipate heat from the bottom. Therefore, the ceramic substrate can effectively extract the heat loss of the gallium nitride device under test T1, thereby improving the accuracy of the heat loss measurement of the gallium nitride device under test T1.

[0057] Of course, other high thermal resistance materials may be selected in some other embodiments of this application, and this application does not limit them.

[0058] In addition, in the above-mentioned thermal measurement switching loss circuit for top-heat-dissipating GaN devices, the electrical connection lines of the GaN device under test T1 are all traced on the top, so that the high thermal resistance material FR-4 in the printed circuit board can prevent heat from dissipating from the bottom.

[0059] Figure 6 This is a flowchart of a method for measuring the switching loss of top-heat-dissipated GaN devices, provided by an embodiment of the present invention. Figure 7 This is a schematic diagram of a thermal testing apparatus provided in an embodiment of the present invention. Figure 6-7 As shown, this embodiment of the invention also provides a method for measuring the switching loss of a top-heat-sinking GaN device, applied to the aforementioned circuit for measuring the switching loss of a top-heat-sinking GaN device, comprising:

[0060] S1. After fixing the ceramic substrate in the thermal measurement switching loss circuit to the copper heat sink of the thermal testing device, turn on the thermal measurement switching loss circuit; wherein, the thermal testing device includes an air supply module and a cavity connected to the air outlet of the air supply module, and the copper heat sink is located on the surface of the cavity.

[0061] S2. After the switching loss measurement circuit reaches thermal stability, measure the temperature T at the first test point located on the side of the copper heat sink near the air supply module. air,in The temperature T at a second test point located on the side of the copper radiator furthest from the air supply module was measured. air,out ;

[0062] S3, based on the temperature T at the first test point air,in and the temperature T at the second test point air,out The thermal measurement switching loss of the gallium nitride device T1 under test was calculated.

[0063] like Figure 7 As shown, the thermal testing apparatus includes an air supply module and a cavity. The cavity is connected to the air outlet of the air supply module, and a copper heat sink is provided on the outer surface of the cavity. Please continue to see... Figure 2 A ceramic substrate is fixed on a copper heat sink, and then a thermal measurement switching loss circuit is turned on. The thermal measurement switching loss circuit includes operating stages t1, t2, t3, and t4. In operating stage t1, the gallium nitride device under test (GaN) T1 and the auxiliary GaN device T4 are turned on, while the auxiliary GaN devices T2 and T3 are turned off. In operating stage t2, the auxiliary GaN devices T2 and T4 are turned on, while the GaN device under test (GaN) T1 and the auxiliary GaN device T3 are turned off. In operating stage t3, the auxiliary GaN devices T2 and T3 are turned on, while the GaN device under test (GaN) T1 and the auxiliary GaN device T4 are turned off. In operating stage t4, the auxiliary GaN devices T2 and T4 are turned on, while the GaN device under test (GaN) T1 and the auxiliary GaN device T3 are turned off.

[0064] Optionally, after multiple operating cycles t1 to t4, the circuit reaches a thermally stable state. During the aforementioned operation, the heat from the gallium nitride device under test (GaN) T1 is dissipated into the cavity through the ceramic substrate and the copper heat sink. The copper heat sink has a first test point on the side near the air supply module and a second test point on the side away from the air supply module. The air supplied by the air supply module passes sequentially through the first test point, the copper heat sink area, and the second test point. Because the heat dissipated by the GaN device under test T1 is concentrated at the copper heat sink, the temperature T of the air supplied by the air supply module at the first test point is... air,in And the temperature T at the second test point air,out There are variations; in this embodiment, the temperature T at the first test point is considered. air,in and the temperature T at the second test point air,out The thermal measurement switching loss of the gallium nitride device T1 under test can be calculated.

[0065] In step S3, based on the temperature T at the first test point... air,in and the temperature T at the second test point air,out The steps for calculating the thermal measurement switching loss of the gallium nitride device T1 under test include:

[0066] Calculate the temperature T at the second test point. air,out With the temperature T at a test point air,in The difference is used to obtain the thermal measurement switching loss result of the gallium nitride device T1 under test.

[0067] The following simulation experiment further illustrates the thermal measurement switching loss circuit and method for top-heat-dissipated GaN devices provided by this invention.

[0068] Specifically, this embodiment simulates a thermal measurement switching loss circuit suitable for top-heat-dissipated GaN devices. Figure 8 This is an overall temperature field distribution diagram of a thermal measurement switching loss circuit for top-heat-dissipating GaN devices provided in an embodiment of the present invention, such as... Figure 8 As shown, the ceramic substrate on top of the printed circuit board conducts heat very quickly and has a low temperature, which allows most of the heat from the tube under test to be transferred from the top to the thermal measurement device. Figure 9a This is a temperature field distribution diagram of the first surface of a printed circuit board provided in an embodiment of the present invention. Figure 9b This is a temperature field distribution diagram of the second surface of the printed circuit board provided in an embodiment of the present invention, such as... Figures 9a-9b As shown, most of the heat from the bottom-heat-dissipating auxiliary gallium nitride device is extracted to the second surface of the printed circuit board, while the bottom of the top-heat-dissipating gallium nitride device under test has very little heat passing through the printed circuit board, and almost all of the heat is dissipated through the top. Figure 10 This is a temperature field distribution diagram of the ceramic substrate provided in an embodiment of the present invention, by... Figure 10 It is known that the top temperature of the auxiliary gallium nitride device is close to room temperature, which means that almost no heat is dissipated from the top. This greatly improves the accuracy of heat loss measurement of the gallium nitride device under test with top heat dissipation.

[0069] As can be seen from the above embodiments, the beneficial effects of the present invention are as follows:

[0070] This invention provides a thermal measurement switching loss circuit and method for top-heat-dissipated GaN devices. For a top-heat-dissipated GaN device T1 under test, this invention selects bottom-heat-dissipated auxiliary GaN devices T2, T3, and T4 for testing using the thermal measurement switching loss circuit. In this way, the heat of the GaN device T1 under test will be introduced into the ceramic substrate, while the heat of the auxiliary GaN devices T2, T3, and T4 will be dissipated from the bottom with the printed circuit board. This allows the ceramic substrate to effectively extract the heat loss of the GaN device T1 under test, thereby improving the accuracy of the thermal loss measurement of the GaN device T1 under test.

[0071] In the description of this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0072] Although this application has been described herein in conjunction with various embodiments, other variations of the disclosed embodiments can be understood and implemented by those skilled in the art in carrying out the claimed application by reviewing the accompanying drawings, the disclosure, and the appended claims.

[0073] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A thermal measurement switching loss circuit suitable for top-heat-dissipated GaN devices, characterized in that, Including ceramic substrate, voltage source V DC Capacitor C DC ,inductance L The gallium nitride device under test, T1, and auxiliary gallium nitride devices, T2, T3, and T4, are included. The drain of the gallium nitride device under test T1 and the drain of the auxiliary gallium nitride device T3 are connected to the voltage source V. DC The positive terminal of the device is connected to the source of the gallium nitride device under test (GNT) T1, and the drain of the auxiliary GNT T2 is connected to the source of the auxiliary GNT T3, and the drain of the auxiliary GNT T4 is connected to the source of the auxiliary GNT T2 and T4. The sources of the auxiliary GNT devices T2 and T4 are both connected to the voltage source V. DC The negative electrode of the GaN device under test (T1) and the drain of the auxiliary GaN device (T2) are connected by a first node N1, and the source of the auxiliary GaN device (T3) and the drain of the auxiliary GaN device (T4) are connected by a second node N2. The inductor... L The two ends are connected to the first node N1 and the second node N2 respectively, and the capacitor C DC With voltage source V DC The gallium nitride device under test, T1, is in parallel and is top-packaged. Auxiliary gallium nitride devices T2, T3, and T4 are all bottom-packaged; the voltage source V DC Capacitor C DC ,inductance L The gallium nitride device under test, T1, and auxiliary gallium nitride devices, T2, T3, and T4, are located on the first surface of the printed circuit board, and the ceramic substrate is bonded to the first surface of the printed circuit board.

2. The thermal measurement switching loss circuit for top-heat-dissipated GaN devices according to claim 1, characterized in that, The tops of auxiliary gallium nitride devices T2, T3, and T4 are covered with thermally resistive material.

3. The thermal measurement switching loss circuit for top-heat-dissipated GaN devices according to claim 2, characterized in that, The thermal resistance material is plastic.

4. The thermal measurement switching loss circuit for top-heat-dissipated GaN devices according to claim 1, characterized in that, The electrical connection lines of the gallium nitride device T1 under test all follow the top trace.

5. The thermal measurement switching loss circuit for top-heat-dissipated GaN devices according to claim 1, characterized in that, The printed circuit board includes three preset areas, and each preset area includes multiple through holes; The three preset areas correspond to the heat dissipation surfaces of the bottom packages of the auxiliary gallium nitride device T2, auxiliary gallium nitride device T3, and auxiliary gallium nitride device T4, respectively.

6. The thermal measurement switching loss circuit for top-heat-dissipated GaN devices according to claim 1, characterized in that, The printed circuit board has openings at corresponding positions of the auxiliary gallium nitride devices T2, T3, and T4.

7. A method for measuring the switching loss of a top-heat-dissipated GaN device, characterized in that, The thermal measurement switching loss circuit for top-heat-dissipated GaN devices, as described in any one of claims 1 to 6, comprises: After fixing the ceramic substrate in the thermal measurement switching loss circuit onto the copper heat sink of the thermal testing device, the thermal measurement switching loss circuit is turned on; wherein, the thermal testing device includes an air supply module and a cavity connected to the air outlet of the air supply module, and the copper heat sink is located on the surface of the cavity. After the thermal measurement switching loss circuit reaches a thermally stable state, the temperature at the first test point located on the side of the copper heat sink near the air supply module is measured. T air,in The temperature at a second test point located on the side of the copper radiator furthest from the air supply module was measured. T air,out ; Based on the temperature at the first test point T air,in and the temperature at the second test point T air,out The thermal measurement switching loss of the gallium nitride device T1 under test was calculated.

8. The method for measuring the switching loss of a top-heat-dissipated GaN device according to claim 7, characterized in that, Based on the temperature at the first test point T air,in and the temperature at the second test point T air,out The steps for calculating the thermal measurement switching loss of the gallium nitride device T1 under test include: Calculate the temperature at the second test point. T air,out Temperature at a test point T air,in The difference is used to obtain the thermal measurement switching loss result of the gallium nitride device T1 under test.

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