A cascade type gallium nitride high-voltage current sampling circuit and a power conversion topology circuit

Abstract

The application discloses a cascade gallium nitride high-voltage current sampling circuit and a power conversion topology circuit, and relates to the field of power device circuits.The cascade gallium nitride high-voltage current sampling circuit comprises a first cascade gallium nitride device, a second cascade gallium nitride device, a driving resistor and a sampling resistor; the gate of the first cascade gallium nitride device is connected with the driving resistor; the source of the first cascade gallium nitride device is grounded; the gate of the second cascade gallium nitride device is connected with the driving resistor; the source of the second cascade gallium nitride device is connected with one end of the sampling resistor; the other end of the sampling resistor is grounded; and the on-resistance of the second cascade gallium nitride device is at least two orders of magnitude larger than the on-resistance of the first cascade gallium nitride device.The application can guarantee the integrity of a current sampling signal.

Description

TECHNICAL FIELD

[0001] The application relates to the field of power device circuits, in particular to a cascaded gallium nitride high-voltage current sampling circuit and a power conversion topology circuit. BACKGROUND

[0002] The traditional current sampling circuit is realized by using a Hall current sensor, a current transformer of a high-frequency pulse transformer and the like, noise interference signals are usually introduced, and the sampling delay of the high-impedance inductive device, the signal amplitude attenuation, the phase change and the magnetic coupling leakage of the magnetic coupling result in the serious loss of the integrity of the signal in the transmission process. SUMMARY

[0003] The application aims to provide a cascaded gallium nitride high-voltage current sampling circuit and a power conversion topology circuit, which can guarantee the integrity of the current sampling signal.

[0004] To achieve the above-mentioned purpose, the application provides the following scheme.

[0005] In a first aspect, the application provides a cascaded gallium nitride high-voltage current sampling circuit, comprising: a first cascaded gallium nitride device, a second cascaded gallium nitride device, a driving resistor and a sampling resistor.

[0006] The gate of the first cascaded gallium nitride device is connected with the driving resistor; the source of the first cascaded gallium nitride device is grounded; the gate of the second cascaded gallium nitride device is connected with the driving resistor; the source of the second cascaded gallium nitride device is connected with one end of the sampling resistor; the other end of the sampling resistor is grounded.

[0007] The on-resistance of the second cascaded gallium nitride device is at least two orders of magnitude larger than the on-resistance of the first cascaded gallium nitride device.

[0008] In an embodiment, the driving resistor comprises: a first driving resistor and a second driving resistor.

[0009] One end of the first driving resistor is connected with the gate of the second cascaded gallium nitride device; one end of the second driving resistor is connected with the gate of the first cascaded gallium nitride device.

[0010] In an embodiment, the cascaded gallium nitride high-voltage current sampling circuit further comprises: a control signal input end.

[0011] The control signal input end is connected with the first driving resistor and the second driving resistor respectively.

[0012] In an embodiment, the cascaded gallium nitride high-voltage current sampling circuit further comprises: a high-voltage input end.

[0013] The high-voltage input end is connected with the drain of the first cascode gallium nitride device and the drain of the second cascode gallium nitride device respectively.

[0014] In an embodiment, the control signal input end is at the gate of the first cascode gallium nitride device, and the frequency of the input control signal is in the order of kilohertz; the control signal input end is at the gate of the second cascode gallium nitride device, and the frequency of the input control signal is in the order of megahertz.

[0015] In an embodiment, the branch composed of the second cascode gallium nitride device and the sampling resistor in series has a current in the order of microamperes.

[0016] In a second aspect, the application provides a power conversion topology circuit, comprising: a current sampling processing module, a current compensation module, and a cascode gallium nitride high-voltage current sampling circuit.

[0017] The current sampling processing module is connected with the cascode gallium nitride high-voltage current sampling circuit; and the current compensation module is connected with the current sampling processing module.

[0018] The current sampling processing module is configured to collect the current of the cascode gallium nitride high-voltage current sampling circuit.

[0019] The current compensation module is configured to perform compensation processing on the current to obtain a compensated current.

[0020] The current sampling processing module is further configured to perform filtering processing on the compensated current by using a two-stage first-order RC network to obtain a mirror current.

[0021] In an embodiment, the current compensation module comprises: a resistive compensation submodule and a capacitive compensation submodule.

[0022] The resistive compensation submodule and the capacitive compensation submodule are both connected with the current sampling processing module.

[0023] The resistive compensation submodule is configured to perform direct current bias compensation on a sampling resistor in the cascode gallium nitride high-voltage current sampling circuit.

[0024] The capacitive compensation submodule is configured to perform capacitive compensation by driving the frequency, duty cycle, and amplitude of a square wave under different alternating current input voltages.

[0025] In an embodiment, the current sampling processing module comprises: a current sampling submodule and a current processing submodule.

[0026] The current sampling submodule is connected with the cascode gallium nitride high-voltage current sampling circuit; the current processing submodule is connected with the current compensation module; and the current sampling submodule is connected with the current processing submodule.

[0027] The current sampling sub-module is used for collecting the current of the cascaded gallium nitride high-voltage current sampling circuit.

[0028] The current processing sub-module is used for:

[0029] The compensation current is obtained; the compensation current includes the current after direct current bias compensation and capacitive compensation.

[0030] The two-stage first-order RC network is used for filtering processing based on the compensation current, and the mirror current is obtained.

[0031] In an embodiment, the power conversion topology circuit includes a transformer.

[0032] The transformer is connected with the cascaded gallium nitride high-voltage current sampling circuit.

[0033] According to the specific embodiments provided in the application, the following technical effects are disclosed:

[0034] The application provides a cascaded gallium nitride high-voltage current sampling circuit and a power conversion topology circuit, the cascaded gallium nitride high-voltage current sampling circuit includes a first cascaded gallium nitride device, a second cascaded gallium nitride device, a driving resistor and a sampling resistor; the gate of the first cascaded gallium nitride device is connected with the driving resistor; the source of the first cascaded gallium nitride device is grounded; the gate of the second cascaded gallium nitride device is connected with the driving resistor; the source of the second cascaded gallium nitride device is connected with one end of the sampling resistor; the other end of the sampling resistor is grounded; the application adopts a power semiconductor gallium nitride device, since the on-resistance of the second cascaded gallium nitride device is at least two orders of magnitude larger than the on-resistance of the first cascaded gallium nitride device, that is, in addition to the introduction of a very small junction capacitance, it almost works in a pure resistance state, so the integrity of the current sampling signal is greatly guaranteed, thereby the integrity of the current sampling signal is guaranteed. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0036] Figure 1 It is a structure diagram of the cascaded gallium nitride high-voltage current sampling circuit.

[0037] Figure 2 It is a circuit structure diagram of the simulation circuit.

[0038] Figure 3This is a simulation diagram of the voltage across the sampling resistor R3;

[0039] Figure 4 This is a voltage simulation diagram of the drain D of the first cascaded gallium nitride device Q1;

[0040] Figure 5 This is a schematic diagram of the circuit structure of a power conversion topology.

[0041] Figure 6 This is a schematic diagram of a modified circuit structure for a power conversion topology.

[0042] Figure 7 A schematic diagram of a 100W power supply circuit;

[0043] Figure 8 This is a schematic diagram of the measured waveforms for a 100W power supply circuit.

[0044] Figure label:

[0045] First cascaded gallium nitride device - Q1, second cascaded gallium nitride device - Q2, first driving resistor - R1, second driving resistor - R2, sampling resistor - R3, high voltage input terminal - HV, transformer - T1. Detailed Implementation

[0046] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0047] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] In one exemplary embodiment, such as Figure 1 As shown, a cascaded gallium nitride (GaN) high-voltage current sampling circuit is provided. This cascaded GaN high-voltage current sampling circuit includes: a first cascaded GaN device Q1, a second cascaded GaN device Q2, a driving resistor, and a sampling resistor R3; wherein the driving resistor includes: a first driving resistor R1 and a second driving resistor R2.

[0049] The gate of the first cascaded gallium nitride device Q1 is connected to the driving resistor; the source of the first cascaded gallium nitride device Q1 is grounded; the gate of the second cascaded gallium nitride device Q2 is connected to the driving resistor; the source of the second cascaded gallium nitride device Q2 is connected to one end of the sampling resistor; the other end of the sampling resistor R3 is grounded.

[0050] One end of the first driving resistor R1 is connected to the gate of the second cascaded gallium nitride device Q2; one end of the second driving resistor R2 is connected to the gate of the first cascaded gallium nitride device Q1.

[0051] The on-resistance of the second-cascaded gallium nitride device Q2 is at least two orders of magnitude greater than the on-resistance of the first-cascaded gallium nitride device Q1.

[0052] The branch consisting of the second-cascaded gallium nitride device Q2 and the sampling resistor R3 connected in series corresponds to a current level in the microampere range.

[0053] In one embodiment, the cascaded gallium nitride high-voltage current sampling circuit further includes: a control signal input terminal; the control signal input terminal is connected to a first driving resistor and a second driving resistor respectively.

[0054] The control signal input terminal is located at the gate of the first cascaded gallium nitride device Q1, and the frequency of the input control signal is in the kilohertz range; the control signal input terminal is located at the gate of the second cascaded gallium nitride device Q2, and the frequency of the input control signal is in the megahertz range.

[0055] In addition, the cascaded gallium nitride high-voltage current sampling circuit also includes: a high-voltage input terminal HV; the high-voltage input terminal HV is connected to the drain of the first cascaded gallium nitride device Q1 and the drain of the second cascaded gallium nitride device Q2, respectively.

[0056] This application utilizes the extremely low on-resistance, switching characteristics, high voltage withstand capability, and high temperature resistance of cascaded gallium nitride (GaN) to significantly improve the accuracy, high-temperature drift, and simplification of circuit architecture, circuit efficiency, and PCB layout of current sampling circuits in high-voltage circuits and power conversion circuits. Because the circuit design mentioned in this application uses power semiconductor GaN devices, it operates almost purely resistively except for the extremely small junction capacitance, thus greatly ensuring the integrity of the current sampling signal.

[0057] like Figure 1 As shown, the circuit consists of a first cascaded gallium nitride device Q1 with extremely low on-resistance, a second cascaded gallium nitride device Q2 with high on-resistance (its on-resistance is at least two orders of magnitude greater than the on-resistance of the first cascaded gallium nitride device Q1), a first driving resistor R1, a second driving resistor R2, and a sampling resistor R3. In one embodiment, the second driving resistor R2 is connected to the control signal GT1, and the first driving resistor R1 is connected to the control signal GT2.

[0058] This circuit performs two functions:

[0059] 1. AC / DC high voltage input current sampling circuit.

[0060] In the high-voltage input Vin circuit based on the high-voltage input terminal HV, a first cascaded gallium nitride device Q1 with extremely low on-resistance, a second cascaded gallium nitride device Q2 with large on-resistance (two orders of magnitude larger than Q1), and a sampling resistor R3 are connected in series in the main circuit. Then, they are connected in parallel with the first cascaded gallium nitride device Q1 in the main circuit. The control signal GT1 (typically a frequency of several hundred kilohertz) connected to the gate (G) of the first cascaded gallium nitride device Q1 and the control signal GT2 (typically a frequency of megahertz) connected to the gate (G) of the second cascaded gallium nitride device Q2 are connected to the circuit, and the current signal is detected on the current sampling resistor R3.

[0061] A second cascaded gallium nitride (GaN) device, Q2, is connected in series in the high-voltage AC / DC input circuit. A sampling resistor, R3, is connected in series with the first cascaded GaN device, Q1, in parallel. The proportional relationship between the on-resistance of the cascaded GaN device and the parallel network mirrors the current detection from the high-voltage side to the low-voltage side of the sampling resistor R3 in the series network. This achieves low-voltage detection of high-voltage current. Because the current in the series branch of the second cascaded GaN device Q2 and sampling resistor R3 is very small, almost in the microamplitude range, the power consumption in the current detection circuit is virtually zero. The higher the current in the main power circuit, the better the effect, truly achieving green detection.

[0062] 2. By changing the magnitude and phase of the control signal, the amplitude and phase of the sampled current are detected. This process employs methods such as... Figure 2 The simulation circuit shown is used to obtain the simulation waveform. The simulation circuit consists of: a high-voltage input voltage source V2, a first cascaded gallium nitride device Q1 that is fed into the main power circuit, a current sensing network connected in parallel with it, namely a second cascaded gallium nitride device Q2 and a sampling resistor R3, the gate control signal V1 of the first cascaded gallium nitride device Q1, the gate control signal V3 of the second cascaded gallium nitride device Q2, and the sampling resistor R3.

[0063] The circuit simulation described above primarily defines the current flowing through the first cascaded gallium nitride (GaN) device Q1 by detecting the voltage at the drain of Q1 in the main circuit. Figure 3 and Figure 4The simulation results are shown in the figure. V3 is the voltage across the sampling resistor R3. The slopes of the two curves are the same, only the amplitudes are different. This amplitude ratio represents the impedance of the first cascaded gallium nitride device Q1, the second cascaded gallium nitride device Q2, and the sampling resistor R3. To achieve higher sampling accuracy, the high-frequency characteristics of gallium nitride can be utilized by increasing the switching frequency of the gate (G) control signal (operating frequency of 1MHz). The higher the frequency, the higher the sampling accuracy. High sampling accuracy is achieved by utilizing the high-frequency switching characteristics of the cascaded gallium nitride. Alternatively, it can be achieved by increasing the operating frequency of the gate (G) control signal of the first cascaded gallium nitride device Q1 (operating frequency of 100kHz) and using a pulse drive waveform with a large duty cycle. A small Rds-on on-resistance of the cascaded gallium nitride device is selected to weaken the influence of the introduced circuit impedance (the on-resistance of the first cascaded gallium nitride device Q1) on the main circuit. Based on the characteristics (amplitude, frequency, phase, rise time, fall time, etc.) of the voltage waveform V3 signal across the sampling resistor R3, the true voltage and current characteristics of the drain D of the first cascaded gallium nitride device Q1 can be restored by processing the distribution of the V1 control signal, the on-resistance of the first cascaded gallium nitride device Q1, and the junction capacitance of the second cascaded gallium nitride device Q2 using an algorithm.

[0064] In one exemplary embodiment, such as Figure 5 As shown, a power conversion topology circuit is provided. This power conversion topology circuit includes: a current sampling and processing module, a current compensation module, and a cascaded gallium nitride high-voltage current sampling circuit.

[0065] The current sampling and processing module is connected to the cascaded gallium nitride high-voltage current sampling circuit; the current compensation module is connected to the current sampling and processing module.

[0066] The current sampling and processing module is used to collect the current of the cascaded gallium nitride high-voltage current sampling circuit.

[0067] The current compensation module is used to compensate the current to obtain the compensated current.

[0068] The current compensation module includes a resistive compensation submodule and a capacitive compensation submodule; both the resistive and capacitive compensation submodules are connected to the current sampling and processing module; the resistive compensation submodule is used to perform DC bias compensation on the sampling resistor in the cascaded gallium nitride high-voltage current sampling circuit; the capacitive compensation submodule is used to perform capacitive compensation by driving a square wave at different AC input voltages with varying frequencies, duty cycles, and amplitudes.

[0069] The current sampling and processing module is also used to perform filtering processing using a two-stage first-order RC network based on the compensation current to obtain the mirror current.

[0070] The current sampling and processing module includes a current sampling submodule and a current processing submodule. The current sampling submodule is connected to the cascaded gallium nitride high-voltage current sampling circuit. The current processing submodule is connected to the current compensation module. The current sampling submodule is used to collect the current of the cascaded gallium nitride high-voltage current sampling circuit. The current processing submodule is used to obtain the compensation current. The compensation current includes the current after DC bias compensation and capacitive compensation.

[0071] The current processing submodule is also used to perform filtering based on the compensation current using a two-stage first-order RC network to obtain the mirror current.

[0072] As an optional implementation, the power conversion topology circuit includes: a transformer T1; the transformer T1 is connected to a cascaded gallium nitride high-voltage current sampling circuit.

[0073] In power conversion topologies, primarily used in flyback circuits and critical-mode PFC circuits, a common characteristic is the need for a main current sampling signal. A common application involves connecting a high-power sampling resistor in series with the source and source of the first cascaded gallium nitride (GaN) device Q1 for current sampling. Since the main current increases with the power supply's output, the power dissipation of the resistor connected in series with the main current also increases. For a 60W power supply with a 90V AC input, there is a minimum loss of 0.3% across this current sampling resistor. For this reason, for... Figure 5 The circuit can be modified as follows to eliminate the sampling resistor, reduce the power consumption of the main power circuit, and improve the overall system efficiency. Specifically, the control signal GT2 is changed to control signal GT1. This means that the control of both gallium nitride (GaN) power transistors is now controlled by the main circuit's control signal GT1, which controls the gates (G) of the first cascaded GaN device Q1 and the second cascaded GaN device Q2. Since the current signal sampled by the secondary circuit, consisting of the second cascaded GaN device Q2 and the sampling resistor R3 connected in series, is relatively small, it needs to be compensated and amplified to match the equal current magnitude in the main circuit. The overall circuit structure is modified as follows: Figure 6 As shown.

[0074] Several key points in this circuit: 1. There are two forms of current compensation network: a) Pure resistive compensation, which is to directly compensate the weak current signal sampled by R3 from the high voltage side through a pure resistive network, that is, DC bias compensation. b) Capacitive compensation, which is to perform capacitive compensation by driving a square wave with different frequencies, duty cycles, and amplitudes under different AC input voltages.

[0075] 2. Processing of sampled current: Since the noise amplitude of the sampled current signal is large, it needs to be filtered by a two-stage first-order RC network. The signal processed by the compensation algorithm has the same magnitude as the mirror current of the main circuit.

[0076] Based on the above modifications and theoretical deductions, a 100W power supply was designed, and its schematic diagram is shown below. Figure 7 As shown.

[0077] Figure 7 The section with the dashed line represents the current sampling circuit consisting of a gallium nitride device Q3 and a resistor R22 connected in series.

[0078] Figure 7 This application is in flyback high-frequency switching power supplies. The purpose is to eliminate the traditional current sensing resistor and apply the concept of a mirror current model. The module consists of diode D201, resistors R205, R208, FB201, resistor R209, and gallium nitride device Q4 to form the main power circuit. Diode D201, resistors R205, R208, FB201, and resistor R209 form the driving circuit for gallium nitride device Q4. The mirror circuit consists of gallium nitride device Q3, resistors R22 and R210, capacitor C14, resistor R21, diode D2, resistors R15 and R18. Diode D2, resistors R15 and R18 form the driving circuit for gallium nitride device Q3. Capacitor C14 and resistor R21 form the compensation circuit for sampling the current signal. Resistor R22 is the current sampling resistor.

[0079] The working principle is as follows: When the drive signal of the control IC is valid, the gallium nitride (GaN) devices Q3 and Q4 are turned on by the drive circuit. The current of the main power GaN device Q4 is mirrored to the resistor R22 connected in series with the secondary circuit and GaN device Q3 through an algorithm based on the impedance of the two paths. The current sampling signal on resistor R22 is amplified and compensated by a compensation network composed of capacitor C14 and resistor R21. Then, it is filtered by a first-order RC filter network composed of resistor R211 and capacitor C208 before being sent to the current sampling pin of the control IC. The control IC identifies the magnitude of the current sampling signal and the magnitude of the feedback signal from the main circuit and adjusts the operating frequency or pulse width accordingly to achieve output voltage stability.

[0080] The significant features of this circuit are: 1. The high-current sampling resistor in the main power circuit is eliminated, reducing heat sources and energy losses. 2. A simple RC compensation network achieves signal amplification and compensation. 3. The power transistors of the main and auxiliary circuits share a single drive signal, achieving synchronization between the two circuits.

[0081] The corresponding measured waveform is as follows Figure 8 As shown. Among them,Figure 8 In The bandwidth of the oscilloscope used to detect the waveform.

[0082] The above waveform, after being processed by a capacitive compensation network consisting of C14 and R21 connected in series, basically restored the current waveform of the main circuit.

[0083] The efficiency test comparison is shown in Table 1.

[0084] Table 1. Efficiency Comparison of 100W Traditional Current Sampling Circuit and New Current Sampling Circuit

[0085]

[0086] Where n(%) represents the efficiency at the corresponding power, i.e., the power conversion efficiency. load(%) refers to the percentage of the total load carried by the power supply. For example, for a power supply with an output power of 100W, load(%) is 10, which means that the power of the power supply's output load is 10W. The meaning of Uin(V) in Table 1 is equivalent to the high voltage input Vin.

[0087] Based on the efficiency comparison results in Table 1, the average efficiency of the power supply is improved by 0.471% when the input is 230Vac, and by 0.394% when the input is 115Vac.

[0088] The technical features in the above examples can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0089] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A power conversion topology circuit, characterized in that, include: Current sampling and processing module, current compensation module, and cascaded gallium nitride high-voltage current sampling circuit; The current sampling and processing module is connected to the cascaded gallium nitride high-voltage current sampling circuit; the current compensation module is connected to the current sampling and processing module. The current sampling and processing module is used to collect the current of the cascaded gallium nitride high-voltage current sampling circuit; The current compensation module is used to compensate the current to obtain a compensated current; The current sampling and processing module is also used to perform filtering processing using a two-stage first-order RC network based on the compensation current to obtain the mirror current; A cascaded gallium nitride high-voltage current sampling circuit includes: a first cascaded gallium nitride device, a second cascaded gallium nitride device, a driving resistor, and a sampling resistor; The gate of the first cascaded gallium nitride device is connected to the drive resistor; the source of the first cascaded gallium nitride device is grounded; the gate of the second cascaded gallium nitride device is connected to the drive resistor; the source of the second cascaded gallium nitride device is connected to one end of the sampling resistor; the other end of the sampling resistor is grounded. The on-resistance of the second-cascaded gallium nitride device is at least two orders of magnitude greater than the on-impedance of the first-cascaded gallium nitride device.

2. The power conversion topology circuit according to claim 1, characterized in that, The current compensation module includes: a resistive compensation submodule and a capacitive compensation submodule; Both the resistive compensation submodule and the capacitive compensation submodule are connected to the current sampling and processing module; The resistive compensation submodule is used to perform DC bias compensation on the sampling resistor in the cascaded gallium nitride high-voltage current sampling circuit. The capacitive compensation submodule is used to perform capacitive compensation by driving a square wave with different frequencies, duty cycles, and amplitudes under different AC input voltages.

3. The power conversion topology circuit according to claim 2, characterized in that, The current sampling and processing module includes: a current sampling submodule and a current processing submodule; The current sampling submodule is connected to the cascaded gallium nitride high-voltage current sampling circuit; the current processing submodule is connected to the current compensation module; the current sampling submodule is connected to the current processing submodule. The current sampling submodule is used to collect the current of the cascaded gallium nitride high-voltage current sampling circuit; The current processing submodule is used for: Obtain the compensation current; the compensation current includes: the current after DC bias compensation and capacitive compensation; The compensation current is filtered using a two-stage first-order RC network to obtain the mirror current.

4. The power conversion topology circuit according to claim 1, characterized in that, The power conversion topology circuit includes: a transformer; The transformer is connected to the cascaded gallium nitride high-voltage current sampling circuit.

5. The power conversion topology circuit according to claim 1, characterized in that, The driving resistor includes: a first driving resistor and a second driving resistor; One end of the first driving resistor is connected to the gate of the second cascaded gallium nitride device; one end of the second driving resistor is connected to the gate of the first cascaded gallium nitride device.

6. The power conversion topology circuit according to claim 5, characterized in that, The cascaded gallium nitride high-voltage current sampling circuit further includes: a control signal input terminal; The control signal input terminal is connected to the first driving resistor and the second driving resistor, respectively.

7. The power conversion topology circuit according to claim 1, characterized in that, The cascaded gallium nitride high-voltage current sampling circuit further includes: a high-voltage input terminal; The high-voltage input terminal is connected to the drain of the first cascaded gallium nitride device and the drain of the second cascaded gallium nitride device, respectively.

8. The power conversion topology circuit according to claim 6, characterized in that, The control signal input terminal is located at the gate of the first cascaded gallium nitride device, and the frequency of the input control signal is in the kilohertz range; the control signal input terminal is located at the gate of the second cascaded gallium nitride device, and the frequency of the input control signal is in the megahertz range.

9. The power conversion topology circuit according to claim 1, characterized in that, The branch consisting of a second-cascaded gallium nitride device connected in series with a sampling resistor corresponds to a current level in the microampere range.

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