Method, device and circuit for obtaining absorption circuit parameters of a bridge converter

Abstract

An embodiment of the present invention discloses a method, device and circuit for obtaining absorption circuit parameters of a bridge converter. The method includes: performing simulation according to a preset high-frequency equivalent circuit through a preset damping value gradient to generate an absorption circuit parameter mapping diagram; determining a target area according to the absorption circuit parameter mapping diagram; calculating the minimum power consumption of the preset high-frequency equivalent circuit according to the target area to obtain target absorption circuit parameters. Through the present invention, the problem in the related art that the voltage oscillation in the switching process of a Cascode-type GaN bridge converter cannot be effectively suppressed is solved, and combined with the minimum power consumption constraint condition of the absorption circuit, the optimal RC value for oscillation suppression is determined therefrom, achieving the technical effect of obtaining the optimal voltage oscillation suppression effect and maximizing the reduction of the power loss of the power tube and the absorption circuit, thereby improving the efficiency of the converter.

Description

Technical Field

[0001] The present invention relates to the field of live broadcast accident handling, and in particular to a method, device and circuit for obtaining absorption circuit parameters of a bridge converter. Background Art

[0002] In recent years, power devices made of the third-generation wide-bandgap semiconductor material gallium nitride (GaN) have gradually emerged in high-speed and high-power-density power electronic applications. Compared with silicon (Si) and silicon carbide (SiC), GaN power devices have higher switching frequencies, smaller on-resistances, and smaller gate charges, which means that GaN devices have obvious advantages in high-power-density and high-efficiency converters.

[0003] Since depletion-mode GaN devices are normally-on devices, it is not easy to perform driving and fault protection, and they are not suitable for bridge converter applications. To solve this problem, cascode GaN and enhancement-mode GaN are introduced to endow GaN switches with the characteristics of normally-off devices. Cascode GaN is formed by connecting a low-voltage silicon MOSFET in series with a high-voltage depletion-mode GaN. This structure can not only achieve the normally-off state of the device, but also alleviate the Miller effect, improve the switching speed, and reduce the turn-off loss under high-current conditions. Therefore, cascode GaN devices are strong candidates for high-power and high-frequency switching applications. However, the connection between the Si MOSFET and the GaN device will lead to an increase in parasitic inductance, resulting in an excessive oscillation effect at high switching frequencies, thereby limiting high-frequency operation. In addition, during the large-current turn-off process, the inherent capacitance and parasitic inductance between the Si and GaN devices may generate large oscillations during the turn-off process. Multiple parasitic elements in cascode GaN devices and parasitic inductance in external circuits may cause large oscillations at high switching frequencies, leading to serious voltage overshoot, additional power loss, electromagnetic interference (EMI) noise, and even device breakdown, reducing the reliability of the system. The complex structure of cascode GaN devices and the coupling between multiple parasitic parameters make it very difficult to model and suppress switching oscillations. In existing engineering technologies, the method of experimental trial and error is generally used to find parameters for suppressing switching oscillations, which consumes a large amount of man-hours to search. At the same time, it cannot be guaranteed that the matching parameters are the optimal circuit parameters. Sometimes, the switching speed of the device is sacrificed and the switching loss is increased. Sometimes, the switching oscillations can only be suppressed under limited working conditions, and it cannot be guaranteed that cascode GaN devices operate in the best working state.

[0004] Current research on suppressing switching oscillations of GaN power devices mainly focuses on suppressing switching oscillations of depletion-mode GaN and enhancement-mode GaN. These methods for determining absorption circuit parameters for suppressing switching oscillations are not applicable to cascode GaN power devices.

[0005] In the current related technologies, it is impossible to effectively suppress the voltage oscillation during the switching process of a Cascode-type GaN bridge converter. Combining with the minimum power consumption constraint condition of the absorption circuit, the problem of determining the optimal RC value for oscillation suppression has not been effectively solved yet. Summary of the Invention

[0006] An embodiment of the present invention provides a method, device, and circuit for obtaining the parameters of the absorption circuit of a bridge converter, so as to at least solve the problem in the related technologies that it is impossible to effectively suppress the voltage oscillation during the switching process of a Cascode-type GaN bridge converter, and combining with the minimum power consumption constraint condition of the absorption circuit, determine the optimal RC value for oscillation suppression.

[0007] According to one aspect of the embodiment of the present invention, a method for obtaining the parameters of the absorption circuit of a bridge converter is provided, including: performing simulation through a preset damping value gradient based on a preset high-frequency equivalent circuit to generate an absorption circuit parameter mapping diagram; determining a target area based on the absorption circuit parameter mapping diagram; calculating the minimum power consumption of the preset high-frequency equivalent circuit according to the target area to obtain the target absorption circuit parameters.

[0008] Optionally, the absorption circuit parameter mapping diagram is used to indicate the stability of the resistance and capacitance in the absorption circuit parameters. Among them, the horizontal axis of the absorption circuit parameter mapping diagram represents the absorption resistance, the vertical axis represents the absorption capacitance, and the specified area with a damping ratio ζ>1 is the non-oscillation area.

[0009] Optionally, performing simulation through a preset damping value gradient based on a preset high-frequency equivalent circuit to generate an absorption circuit parameter mapping diagram includes: using the root locus analysis method to determine the damping values under the values of each resistance and capacitance in the absorption circuit; quantitatively obtaining the damping change law according to the damping values under the values of each resistance and capacitance by using the gradient field to obtain the values of the resistance and capacitance of each oscillation suppression gradient; obtaining the absorption circuit parameter mapping diagram according to the distribution of the values of the resistance and capacitance of each oscillation suppression gradient.

[0010] Further, optionally, calculating the minimum power consumption of the preset high-frequency equivalent circuit according to the target area to obtain the target absorption circuit parameters includes: respectively calculating the power consumption according to the turn-off process, off-state process, and turn-on process of the preset high-frequency equivalent circuit, and calculating the power consumption according to the first resistance value mode and the second resistance value mode to obtain the minimum power consumption of the preset high-frequency equivalent circuit; obtaining the target absorption circuit parameters according to the minimum power consumption.

[0011] Optionally, calculating the power consumption according to the first resistance value mode includes:

[0012]

[0013] Among them, Esn is the power consumption of sn in the preset high-frequency equivalent circuit, Rsn is the resistance of sn in the preset high-frequency equivalent circuit, isn is the current of sn in the preset high-frequency equivalent circuit, VDC is the power supply voltage, Ceq is the capacitance of eq in the preset high-frequency equivalent circuit, and Csn is the capacitance of sn in the preset high-frequency equivalent circuit.

[0014] Optionally, the power consumption calculation according to the second resistance value mode includes:

[0015]

[0016] Among them, Esn is the power consumption of sn in the preset high-frequency equivalent circuit, Rsn is the resistance of sn in the preset high-frequency equivalent circuit, isn is the current of sn in the preset high-frequency equivalent circuit, VDC is the power supply voltage, Ceq is the capacitance of eq in the preset high-frequency equivalent circuit, and Csn is the capacitance of sn in the preset high-frequency equivalent circuit.

[0017] According to one aspect of the embodiments of the present invention, a device for obtaining the absorption circuit parameters of a bridge converter is provided, including: a simulation module for simulating through a preset damping value gradient according to a preset high-frequency equivalent circuit to generate an absorption circuit parameter mapping diagram; a region determination module for determining a target region according to the absorption circuit parameter mapping diagram; an acquisition module for calculating the minimum power consumption of the preset high-frequency equivalent circuit according to the target region to obtain the target absorption circuit parameters.

[0018] Optionally, the simulation module includes: a damping value determination unit for determining the damping values at the values of each resistor and capacitor in the absorption circuit by using the root locus analysis method; an acquisition unit for quantitatively obtaining the damping change rule by using the gradient field according to the damping values at the values of each resistor and capacitor to obtain the values of the resistors and capacitors of each oscillation suppression gradient; a simulation unit for obtaining the absorption circuit parameter mapping diagram according to the distribution of the values of the resistors and capacitors of each oscillation suppression gradient.

[0019] Further, optionally, the acquisition module includes: a first acquisition unit for calculating the power consumption respectively according to the turn-off process, the off-state process and the turn-on process of the preset high-frequency equivalent circuit, and calculating the power consumption according to the first resistance value mode and the second resistance value mode to obtain the minimum power consumption of the preset high-frequency equivalent circuit; a second acquisition unit for obtaining the target absorption circuit parameters according to the minimum power consumption.

[0020] According to one aspect of the embodiments of the present invention, a circuit is provided, which is applied to the preset high-frequency equivalent circuit in the above method, and includes: a power supply, a first resistor set, a first inductor set and a first capacitor connected in series, a specific inductor is connected in parallel to the output end of the first resistor in the first resistor set, the output end of the specific inductor is connected to the input end of a target resistor, the output end of the target resistor is connected to the input end of a target capacitor, and the output end of the target capacitor is connected to the output end of the first capacitor.

[0021] In the embodiments of the present invention, according to the preset high-frequency equivalent circuit, simulation is performed through a preset damping value gradient to generate an absorption circuit parameter mapping diagram; according to the absorption circuit parameter mapping diagram, a target area is determined; according to the target area, the minimum power consumption of the preset high-frequency equivalent circuit is calculated to obtain the target absorption circuit parameters. That is to say, the embodiments of the present invention can quantitatively determine the optimal RC parameters of the absorption circuit of the bridge converter based on the Cascode-type GaN device, and then can obtain the optimal voltage oscillation suppression effect, and can minimize the power loss of the power tube and the absorption circuit, thereby achieving the technical effect of improving the efficiency of the converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings described herein are used to provide a further understanding of the present invention, and constitute a part of this application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0023] Figure 1 It is a schematic flowchart of a method for obtaining the absorption circuit parameters of a bridge converter provided by an embodiment of the present invention;

[0024] Figure 2 It is a schematic flowchart of another method for obtaining the absorption circuit parameters of a bridge converter provided by an embodiment of the present invention;

[0025] Figure 3 It is an RC-map diagram in a method for obtaining the absorption circuit parameters of a bridge converter provided by an embodiment of the present invention;

[0026] Figure 4 It is a schematic diagram of a preset high-frequency equivalent circuit in a method for obtaining the absorption circuit parameters of a bridge converter provided by an embodiment of the present invention;

[0027] FIG. 5(a) is a root locus diagram of D(s)=0 when the absorption circuit resistor Rsn changes from 1Ω to 19Ω in a method for obtaining the absorption circuit parameters of a bridge converter provided by an embodiment of the present invention;

[0028] FIG. 5(b) is an enlarged root locus diagram of D(s)=0 in a method for obtaining the absorption circuit parameters of a bridge converter provided by an embodiment of the present invention;

[0029] Figure 6(a) is an enlarged root locus diagram of D(s)=0 when the absorption resistor Rsn is small (Rsn = 1 - 7Ω) in a method for obtaining the absorption circuit parameters of a bridge converter provided by an embodiment of the present invention;

[0030] Figure 6(b) is an enlarged root locus diagram of the parameter Csn when Rsn is medium (Rsn = 9Ω) in a method for obtaining the absorption circuit parameters of a bridge converter provided by an embodiment of the present invention;

[0031] Figure 6(c) is an enlarged root locus diagram of D(s)=0 when the absorption resistor Rsn is large (Rsn = 11 - 19Ω) in a method for obtaining the absorption circuit parameters of a bridge converter provided by an embodiment of the present invention;

[0032] Figure 7 It is a schematic diagram of the design region of Csn with ζ>0.7 when the absorption resistor Rsn varies from 1 to 19Ω in a method for obtaining the absorption circuit parameters of a bridge converter provided by an embodiment of the present invention;

[0033] Figure 8(a) is a schematic diagram of the waveform of the absorption circuit current in the first resistance value mode in a method for obtaining the absorption circuit parameters of a bridge converter provided by an embodiment of the present invention;

[0034] Figure 8(b) is a schematic diagram of the waveform of the absorption circuit current in the second resistance value mode in a method for obtaining the absorption circuit parameters of a bridge converter provided by an embodiment of the present invention;

[0035] Figures 9(a) and (b) are schematic diagrams of the time-domain waveform and frequency-domain spectrum of the drain-source voltage waveform in a method for obtaining the absorption circuit parameters of a bridge converter provided by an embodiment of the present invention;

[0036] Figure 10 It is a schematic diagram for comparing the oscillation suppression effect of the switching waveform in the time domain in a method for obtaining the absorption circuit parameters of a bridge converter provided by an embodiment of the present invention;

[0037] Figure 11 It is a schematic diagram of the experimental device in a method for obtaining the absorption circuit parameters of a bridge converter provided by an embodiment of the present invention;

[0038] Figure 12 It is a schematic diagram of the experimental results with and without an RC buffer circuit in a method for obtaining the absorption circuit parameters of a bridge converter provided by an embodiment of the present invention;

[0039] Figure 13 It is a schematic diagram of the comparison result of the oscillation suppression effect inside and outside the RC design region in a method for obtaining the absorption circuit parameters of a bridge converter provided by an embodiment of the present invention;

[0040] Figure 14 (a) Schematic diagram for comparing the test results of the power loss of the GaN transistor at different inductive currents and different RC values in a method for obtaining the absorption circuit parameters of a bridge converter provided by an embodiment of the present invention;

[0041] Figure 14 (b) Schematic diagram for comparing the test results of the power loss of the buffer resistor at different inductive currents and different RC values in a method for obtaining the absorption circuit parameters of a bridge converter provided by an embodiment of the present invention;

[0042] Figure 15 Schematic diagram of a device for obtaining the absorption circuit parameters of a bridge converter provided by an embodiment of the present invention. Detailed implementation manners

[0043] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0044] It should be noted that the terms "first", "second", etc. in the specification, claims and drawings of the present invention are used to distinguish different objects, rather than to limit a specific order.

[0045] An embodiment of the present invention provides a method for obtaining the absorption circuit parameters of a bridge converter, Figure 1 Schematic flowchart of a method for obtaining the absorption circuit parameters of a bridge converter provided by an embodiment of the present invention.

[0046] As Figure 1 shown, the method for processing a service request provided by an embodiment of the present application includes the following steps:

[0047] According to one aspect of the embodiments of the present invention, there is provided a method for obtaining the absorption circuit parameters of a bridge converter, including:

[0048] S102, performing simulation through a preset damping value gradient according to a preset high-frequency equivalent circuit to generate an absorption circuit parameter mapping diagram;

[0049] Optionally, the absorption circuit parameter mapping diagram is used to indicate the stability of the resistance and capacitance in the absorption circuit parameters. Among them, the horizontal axis of the absorption circuit parameter mapping diagram represents the absorption resistance, the vertical axis represents the absorption capacitance, and the specified area with a damping ratio ζ>1 is the non-oscillation area.

[0050] Optionally, in step S102, simulation is performed according to a preset high-frequency equivalent circuit through a preset damping value gradient to generate an absorption circuit parameter mapping diagram, including: determining the damping value under the values of each resistor and capacitor in the absorption circuit by using the root locus analysis method; quantitatively obtaining the damping change rule by using the gradient field according to the damping value under the values of each resistor and capacitor, and obtaining the values of the resistor and capacitor corresponding to each oscillation suppression gradient; and obtaining the absorption circuit parameter mapping diagram according to the distribution of the values of the resistor and capacitor corresponding to each oscillation suppression gradient.

[0051] Among them, in the embodiment of the present application, the bridge converter may be a bridge converter based on Cascode-type GaN devices, such as Figure 2 shown Figure 2 is a schematic flow chart of another method for obtaining the absorption circuit parameters of a bridge converter provided by an embodiment of the present invention. First, based on the established high-frequency equivalent circuit model of the integration of Cascode-type GaN devices and the external circuit (i.e., the preset high-frequency equivalent circuit in the embodiment of the present application), the root locus analysis method is used to extract features. By designing the damping value gradient, the damping value under different RC values of the absorption circuit is determined, and an RC-map diagram (i.e., the absorption circuit parameter mapping diagram in the embodiment of the present application) is generated, which can reflect the stable region of the RC absorption circuit.

[0052] In the embodiment of the present application, the root locus analysis method is used to determine the damping value under different RC values of the absorption circuit, and the gradient field is used to quantitatively describe the damping change rule, and an RC value distribution diagram corresponding to different oscillation suppression gradients (i.e., the absorption circuit parameter mapping diagram in the embodiment of the present application) is obtained. Figure 3 is an RC-map diagram in a method for obtaining the absorption circuit parameters of a bridge converter provided by an embodiment of the present invention. In Figure 3 , the abscissa represents R, the ordinate represents C, the lines represent the same damping gradient, and the gradients with different shades represent the oscillation suppression effect of the RC plane. The specified area with a damping ratio ζ>1 is the non-oscillation area.

[0053] Specifically, Figure 4 is a schematic diagram of the preset high-frequency equivalent circuit in a method for obtaining the absorption circuit parameters of a bridge converter provided by an embodiment of the present invention. As Figure 4 shown, the high-frequency equivalent circuit of the bridge converter based on Cascode-type GaN devices is used for high-frequency oscillation analysis and quantitative design of the RC absorption circuit. One of the methods to suppress parasitic oscillation is to use an RC absorption circuit connected in parallel to the switch node. However, traditionally, the absorption capacitor and resistor are obtained by trial and error, which is very time-consuming. Therefore, the present invention uses a parallel RC to suppress the oscillation of Cascode-type GaN devices, and realizes the quantitative design of oscillation suppression through root locus analysis, and optimally selects the absorption capacitor and resistor.

[0054] S104. Determine the target area according to the absorption circuit parameter mapping diagram;

[0055] S106. Calculate the minimum power consumption of the preset high-frequency equivalent circuit based on the target area to obtain the target absorption circuit parameters.

[0056] Furthermore, optionally, calculating the minimum power consumption of the preset high-frequency equivalent circuit based on the target area in step S106 to obtain the target absorption circuit parameters includes: calculating the power consumption respectively according to the turn-off process, off-state process and turn-on process of the preset high-frequency equivalent circuit, and calculating the power consumption according to the first resistance mode and the second resistance mode to obtain the minimum power consumption of the preset high-frequency equivalent circuit; obtaining the target absorption circuit parameters according to the minimum power consumption.

[0057] Optionally, calculating the power consumption according to the first resistance mode includes:

[0058]

[0059]

[0060] Among them, E sn is the power consumption of sn in the preset high-frequency equivalent circuit, R sn is the resistance of sn in the preset high-frequency equivalent circuit, i sn is the current of sn in the preset high-frequency equivalent circuit, V DC is the power supply voltage, C eq is the capacitance of eq in the preset high-frequency equivalent circuit, C sn is the capacitance of sn in the preset high-frequency equivalent circuit.

[0061] Optionally, calculating the power consumption according to the second resistance mode includes:

[0062]

[0063] Among them, E sn is the power consumption of sn in the preset high-frequency equivalent circuit, R sn is the resistance of sn in the preset high-frequency equivalent circuit, i sn is the current of sn in the preset high-frequency equivalent circuit, V DC is the power supply voltage, C eq is the capacitance of eq in the preset high-frequency equivalent circuit, C sn is the capacitance of sn in the preset high-frequency equivalent circuit.

[0064] Specifically, combined with Figures 1 to 4 , the oscillation of v ds (t) is the oscillation of the Cascode type GaN device, C sn and R snThe value (i.e., the target absorption circuit parameter in the embodiments of the present application) can be determined by v ds (t). First, through the established high-frequency equivalent circuit (i.e., the Figure 4 preset high-frequency equivalent circuit shown), the loop equation of the circuit is established according to KVL and KCL:

[0065] i p (t) = i ds (t) + i sn (t) (1)

[0066]

[0067]

[0068]

[0069] Under the initial conditions of i p (0) = i d (0) = i0, i sn (0) = 0, the Laplace transform is performed to obtain:

[0070] I p (s) = I ds (s) + I sn (s) (5)

[0071]

[0072]

[0073] V ds (s) = -R ex I p (s) - L loop [sI p (s) - i0] (8)

[0074] Solve to obtain the analytical equation of V ds (s):

[0075]

[0076] Among them,

[0077]

[0078]

[0079] R ex is the sum of R ESR , R sens , R loop and R DS(on) .

[0080] The value of the RC absorption circuit can be obtained by analyzing the s function of formula (11). According to control theory, when v ds (t) does not oscillate, that is, when the oscillation is suppressed, the solutions of the characteristic equation D(s) = 0 are all negative real numbers. Therefore, obtaining the values of C sn and R sn to suppress the oscillation is equivalent to determining the region mapped by R sn -C sn when all the solutions of D(s) = 0 are negative real numbers. It is necessary to study all the solutions of the equation D(s) = 0. When C sn is regarded as a variable, the equation D(s) = 0 can be expressed as follows:

[0081]

[0082] By changing the value of the capacitance C sn from zero to infinity, the root locus of the characteristic equation D(s) = 0 can be obtained. Figure 5(a) shows the root locus diagram of D(s) = 0 when the resistance R sn of the absorption circuit changes from 1Ω to 19Ω. It can be seen that as the absorption resistance R sn increases, the zeros z3 and z4 move to the left half plane of s and approach the real axis, and P1, P1 * are still the two main poles determining the system stability. Figure 5(b) is the enlarged root locus diagram of D(s) = 0. It can be seen that when R sn is small (R sn = 1 - 7Ω), R sn is at an intermediate value (R sn = 9Ω), and R sn is large (R sn = 11 - 19Ω), the root locus. When R sn is small, the root locus and the breakaway point move to the left as R sn increases. As R sn increases, the value of C sn at the breakaway point also becomes smaller. When R sn is large, the zeros z3 and z4 move towards the real axis, while z1 and z2 move away from the real axis. No matter how C sn changes, the root locus of p1 and p1 * will never reach the real axis, and the root locus moves to the right as R sn increases. Therefore, as R sn increases, the oscillation cannot be completely suppressed, and the damping effect will become worse and worse.

[0083] Figure 6(a) shows that the absorption resistance R sn is small (R snThe enlarged root locus plot of D(s)=0 when R sn is in the range of 1 - 7Ω. The root locus and the breakaway point move to the left as R sn increases. Taking ζ>0.7 as an example, it shows how to obtain the R-C absorption value plot. As can be seen from the figure, there is an intersection between the straight line (ζ = 0.7) and the root locus. Taking the blue line root locus above the horizontal axis as an example, when ζ>0.7, the absorption resistance R sn is 1Ω, 3Ω, 5Ω, 7Ω, the values of C

[0084] Figure 6(b) is the enlarged root locus plot of D(s)=0 when R sn is medium (R sn =9Ω). Different from the root locus when R sn is small, as C sn increases, the damping ratio ζ will decrease and the zero point z2 will move away from the real axis. Similarly, draw the straight line ζ = 0.7. There is an intersection between the straight line and the root locus. Taking the root locus above the horizontal axis as an example, when ζ>0.7, R sn is 8Ω and 9Ω, the values of C sn are greater than 1.64nF and 1.4nF respectively. The value of C sn in the root locus below the horizontal axis is the same as that above the horizontal axis. sn

[0085] Figure 6(c) is the enlarged root locus plot of D(s)=0 when R sn is large (Rsn = 11 - 19Ω). It can be seen that the zero points z1 and z2 move away from the real axis. No matter how C sn changes, the root locus of p1 and p1 * will never reach the real axis. As R sn increases, the root locus moves to the right, and the oscillation cannot be completely suppressed, and the damping effect becomes worse and worse. Similarly, taking ζ>0.7 as an example, it shows how to obtain the R-C absorption value plot. Draw the straight line ζ = 0.7. When R sn is 11Ω, the straight line and the root locus have an intersection. Taking the root locus above the horizontal axis as an example, when ζ>0.7, the value of C sn varies from 1.1nF to 3.68nF; when R sn is 12Ω, the straight line and the root locus have only one intersection, and C sn is 1.4nF. When R sn is greater than 12Ω, no matter how the value of C sn changes, the damping ratio of the root locus of D(s)=0 is less than 0.7. Therefore, these RC values cannot suppress the oscillation.

[0086] Based on the above analysis, when the absorption resistance R sn varies from 1 to 19Ω, C with ζ>0.7​sn The designed area is as Figure 7 shown. The shaded area is the range of RC values, and the damping ratio of all solutions of D(s)=0 is greater than 0.7, which can well suppress oscillations. Using the same method, when R sn takes other different values at different damping ratios, the corresponding C sn area can also be obtained. Figure 3 The R-C diagram of different damping ratios finally obtained is shown in the figure. The abscissa represents the absorption resistance R, the ordinate represents the absorption capacitance C, the lines represent the same damping gradient, and the gradients of different stripes represent different oscillation suppression effects in the RC plane. The specified area with damping ratio ζ>1 is the non-oscillation area.

[0087] The specific method for minimizing the power consumption of the absorption circuit provided in the embodiment of the present application is as follows:

[0088] The losses during the turn-off process are mainly divided into two parts: the switching loss on the GaN transistor and the loss on the absorption resistance (R sn ).

[0089] The switching loss of the GaN transistor is defined as

[0090]

[0091] where 0 and t1 represent the initial time and the end time of transistor turn-on respectively, and t2 and t3 represent the turn-off time respectively.

[0092] Assuming that the oscillation is suppressed, the loss expressions related to the resistance value of the absorption circuit in two cases are derived.

[0093] That is, in the first resistance value mode in the embodiment of the present application, the resistance value of the absorption circuit is small, and the waveform of the absorption circuit current is shown in Figure 8(a). It can be divided into three stages in each switching cycle, and its expression is as follows:

[0094] The first stage,

[0095]

[0096] where t = 0 represents the instant when the transistor is turned off;

[0097] The second stage,

[0098]

[0099] The third stage (turn-on process),

[0100]

[0101] where t' = 0 represents the instant when the transistor is turned on. The loss of the absorption circuit with a small resistance is derived:

[0102]

[0103]

[0104]

[0105] In the second resistance value mode in the embodiments of the present application, that is, the resistance value of the absorption circuit is relatively large, and the waveform of the current in the absorption circuit is shown in FIG. 8(b). In each switching cycle, it can also be divided into three stages.

[0106] In the first stage, the expression of i sn is the same as (14);

[0107] In the second stage,

[0108]

[0109] In the third stage, when the transistor is turned on, the expression is the same as (16). It is deduced that the loss of the absorption circuit with a large resistance is expressed as:

[0110] E sn (i sn )≈C sn V DC 2 (19)

[0111] It can be inferred from (17) and (19) that the influence of the capacitor C sn on the loss of the absorption circuit is greater than that of the resistor R sn , and the power consumption in the absorption circuit is proportional to the capacitor. Therefore, in order to reduce the absorption loss, it is required that the capacitor be as small as possible, and the optimal value of C sn is the value at the bottom of the non-oscillation region in the RC diagram.

[0112] (3) Simulation and experimental verification

[0113] The present invention verifies the above analysis through simulation, and the step response of the high-frequency equivalent circuit model is used to simulate the voltage oscillation effect during the turn-off process.

[0114] First, the oscillation damping effects with and without the RC absorption circuit are compared. FIGS. 9(a) and (b) show the time-domain waveforms and frequency-domain spectra of the drain-source voltage waveforms. It can be seen from the comparison that the oscillation of VDS is significantly reduced in the case of having the RC absorption circuit, and the results show that the designed RC absorption circuit can effectively suppress the switching oscillation.

[0115] Next, the oscillation suppression effects when the RC absorption value falls inside and outside the non-oscillation region are compared, Figure 10 and the oscillation suppression effects of the switching waveforms in the time domain are compared. When R snLess than the value at point A (C sn = 2 nF, R sn = 9 Ω), as in Figure 3 at point B (C sn = 2 nF, R sn = 2 Ω), the peak voltage and oscillation will be greater than at point A; when R sn is greater than this value, as in Figure 3 at point C (C sn = 2 nF, R sn = 30 Ω), both the peak voltage and oscillation are greater than at point A. Although point D (C sn = 0.2 nF, R sn = 9 Ω) in the RC diagram has the same R sn as point A, its C sn is much smaller, and the peak voltage and oscillation at point D are larger than at point A. Point E (C sn = 4 nF, R sn = 9 Ω) is in the non-oscillating region, but with a larger capacitance. Although it can suppress oscillation, it will cause more power loss. The simulation results show that the R sn and C sn at point A effectively suppress oscillation.

[0116] To verify the theoretical analysis, the present invention conducted a double-pulse test experiment on a half-bridge circuit based on Cascode-type GaN, and the experimental setup is as shown in Figure 11 . The device under test is a TP65H035WS (650V Cascode-type GaN device) produced by Transphorm, the gate driver is a Si8273AB-IS1 produced by Silicon Lab, the current shunt is 0.1 Ω SSDN-414 with a bandwidth of 2 GHz, and the voltage probe is a TPP1000 with a bandwidth of 1 GHz.

[0117] Figure 12 The experimental results with and without an RC buffer circuit are shown. It can be observed that when an RC buffer circuit is used, the oscillation of Vds is significantly suppressed. The same as the simulation results, the designed RC absorption circuit can effectively suppress switching oscillation.

[0118] From Figure 13 are the comparison results of the oscillation suppression effects inside and outside the RC design region. Oscillation can be effectively suppressed in the region near point A (C sn = 2 nF, R sn = 9 Ω). However, whether R sn is smaller (point B, C sn = 2 nF, R sn = 2 Ω) or larger (point C, C sn = 2 nF, R sn= 30 Ω) or C sn Smaller (point D, C sn = 0.2 nF, R sn = 9 Ω), they all have a longer oscillation time; point E with a large absorption capacitance (C sn = 4 nF, R sn = 9 Ω) can also achieve a good damping effect, but it will generate more power losses.

[0119] The present invention also experimentally explored the influence of RC values on the power losses of GaN transistors and absorption circuits. Figure 14 (a) shows the comparison of the test results of the power losses of GaN transistors with different RC values under different inductor currents. It can be seen from the figure that using the recommended RC values (point A, C sn = 2 nF, R sn = 9 Ω), the switching losses are similar to or even smaller than those at points B, C, and D outside the region, and its oscillation suppression effect reaches the best. Compared with condition F (without an RC buffer circuit), the switching energy at point A is only 5 μJ higher. Therefore, it can be confirmed that the added RC buffer circuit will not bring too much additional switching loss to the GaN transistor. Figure 14 (b) is the comparison of the test results of the power losses of buffer resistors with different RC values under different inductor currents. The results show that although the power losses at points B and D are relatively small, the voltage oscillations at these two points are more severe; points A and E are in the non-oscillation region, but the loss at point A is much smaller than that at point E. This result verifies the above theoretical analysis, and the optimal values of the absorption circuit parameters are located at the bottom of the RC non-oscillation region in the figure.

[0120] In summary, the present invention proposes a method for optimizing the parameters of an RC absorption circuit for a bridge converter based on a Cascode-type GaN device. For the high-frequency equivalent circuit model of the switching oscillation of a bridge converter based on a Cascode-type GaN device, an RC-map is generated to reflect the circuit stability; then, the influence of the RC absorption circuit on the switching loss of the transistor and the power loss of the absorption resistor is studied, and a method for calculating the minimum power loss is proposed to obtain the optimal combination of R sn and C sn .

[0121] In the embodiments of the present invention, simulation is performed according to a preset high-frequency equivalent circuit through a preset damping value gradient to generate an absorption circuit parameter mapping diagram; a target area is determined according to the absorption circuit parameter mapping diagram; the minimum power consumption of the preset high-frequency equivalent circuit is calculated according to the target area to obtain target absorption circuit parameters. That is to say, the embodiments of the present invention can quantitatively determine the optimal RC parameters of the absorption circuit of the bridge converter based on the Cascode GaN device, and then can obtain the optimal voltage oscillation suppression effect, and can minimize the power loss of the power tube and the absorption circuit, so as to achieve the technical effect of improving the efficiency of the converter.

[0122] According to one aspect of the embodiments of the present invention, a device for obtaining absorption circuit parameters of a bridge converter is provided. Figure 15 The following is a schematic diagram of a device for obtaining absorption circuit parameters of a bridge converter provided by the embodiments of the present invention, including: a simulation module 1502, configured to perform simulation according to a preset high-frequency equivalent circuit through a preset damping value gradient to generate an absorption circuit parameter mapping diagram; a region determination module 1504, configured to determine a target region according to the absorption circuit parameter mapping diagram; an acquisition module 1506, configured to calculate the minimum power consumption of the preset high-frequency equivalent circuit according to the target region to obtain target absorption circuit parameters.

[0123] Optionally, the absorption circuit parameter mapping diagram is used to indicate the stability of the resistance and capacitance in the absorption circuit parameters. Among them, the horizontal axis of the absorption circuit parameter mapping diagram represents the absorption resistance, the vertical axis represents the absorption capacitance, and the specified region with a damping ratio ζ>1 is the non-oscillation region.

[0124] Optionally, the simulation module 1502 includes: a damping value determination unit, configured to determine the damping value of each resistance and capacitance in the absorption circuit by using the root locus analysis method; an acquisition unit, configured to quantitatively obtain the damping change rule by using the gradient field according to the damping value of each resistance and capacitance to obtain the values of the resistance and capacitance of each oscillation suppression gradient; a simulation unit, configured to obtain the absorption circuit parameter mapping diagram according to the distribution of the values of the resistance and capacitance of each oscillation suppression gradient.

[0125] Further, optionally, the acquisition module 1506 includes: a first acquisition unit, configured to calculate the power consumption according to the turn-off process, the off-state process, and the turn-on process of the preset high-frequency equivalent circuit respectively, and calculate the power consumption according to the first resistance value mode and the second resistance value mode to obtain the minimum power consumption of the preset high-frequency equivalent circuit; a second acquisition unit, configured to obtain the target absorption circuit parameters according to the minimum power consumption.

[0126] Optionally, calculating the power consumption according to the first resistance value mode includes:

[0127]

[0128] Among them, Esn For the power consumption of sn in the preset high-frequency equivalent circuit, R sn is the resistance of sn in the preset high-frequency equivalent circuit, i sn is the current of sn in the preset high-frequency equivalent circuit, V DC is the power supply voltage, C eq is the capacitance of eq in the preset high-frequency equivalent circuit, C sn is the capacitance of sn in the preset high-frequency equivalent circuit.

[0129] Optionally, the power consumption calculation according to the second resistance mode includes:

[0130]

[0131] wherein, E sn For the power consumption of sn in the preset high-frequency equivalent circuit, R sn is the resistance of sn in the preset high-frequency equivalent circuit, i sn is the current of sn in the preset high-frequency equivalent circuit, V DC is the power supply voltage, C eq is the capacitance of eq in the preset high-frequency equivalent circuit, C sn is the capacitance of sn in the preset high-frequency equivalent circuit.

[0132] According to one aspect of the embodiments of the present invention, a circuit is provided, as Figure 4 shown, applied to the preset high-frequency equivalent circuit in the above method, including: a power supply, a first resistor set, a first inductor set and a first capacitor connected in series, a specific inductor is connected in parallel to the output end of the first resistor in the first resistor set, the output end of the specific inductor is connected to the input end of a target resistor, the output end of the target resistor is connected to the input end of a target capacitor, and the output end of the target capacitor is connected to the output end of the first capacitor.

[0133] Specifically, as Figure 4 shown, the power supply is denoted as v(t), the first resistor set includes: R ESR , R DS(on) (i.e., the first resistor in the first resistor set in the embodiments of the present application), R eq , R sens and R loop , the first inductor set includes: L loop and L D , the first capacitor is denoted as C eq , wherein, the positive pole of v(t) is connected to the input end of R ESR , the output end of R ESR is connected to the input end of L loop , the output end of L loop is connected to the input end of R DS(on) , the output end of R DS(on)The output terminal is also connected to L in the first inductor set D The input terminal of is connected, and the output terminal of L D is connected to the input terminal of R eq The output terminal of R eq is connected to the input terminal of C eq The output terminal of C eq is connected to the resistor R sens and R loop in series, and the output terminal of R loop is connected to the negative pole of the power supply v(t); wherein, the output terminal of R DS(on) is connected to the input terminal of a specific inductor L sn and intersects at point D, that is, the input terminal of the specific inductor L sn is connected in parallel, and the output terminal of L sn is connected to the input terminal of the target resistor R sn The output terminal of R sn is connected to the input terminal of the target capacitor C sn The output terminal of C sn is connected in parallel with the output terminal of the first capacitor C eq and intersects at point S.

[0134] The above is only a preferred embodiment of the present invention and is not used to limit the protection scope of the present invention.

Claims

1. A method for obtaining the parameters of the absorption circuit of a bridge converter, characterized in that, Including: Simulating according to a preset high-frequency equivalent circuit through a preset damping value gradient to generate an absorption circuit parameter mapping diagram; Determining a target area according to the absorption circuit parameter mapping diagram; Calculating the minimum power consumption of the preset high-frequency equivalent circuit according to the target area to obtain target absorption circuit parameters; including: Calculating the power consumption respectively according to the turn-off process, off-state process and turn-on process of the preset high-frequency equivalent circuit, and calculating the power consumption according to the first resistance mode and the second resistance mode to obtain the minimum power consumption of the preset high-frequency equivalent circuit; Obtaining the target absorption circuit parameters according to the minimum power consumption.

2. The method according to claim 1, wherein The absorption circuit parameter mapping diagram is used to indicate the stability of the resistance and capacitance in the absorption circuit parameters. Among them, the horizontal axis of the absorption circuit parameter mapping diagram represents the absorption resistance, the vertical axis represents the absorption capacitance, and the specified area with a damping ratio ζ > 1 is the non-oscillation area.

3. The method according to claim 1 or 2, characterized in that, The simulating according to a preset high-frequency equivalent circuit through a preset damping value gradient to generate an absorption circuit parameter mapping diagram includes: Using the root locus analysis method to determine the damping value under the values of each resistance and capacitance in the absorption circuit; Quantitatively obtaining the damping change law according to the damping values under the values of each resistance and capacitance by using the gradient field to obtain the values of the resistance and capacitance of each oscillation suppression gradient; Obtaining the absorption circuit parameter mapping diagram according to the distribution of the values of the resistance and capacitance of each oscillation suppression gradient.

4. The method according to claim 1, wherein Calculating the power consumption according to the first resistance mode includes: ， Among them, E sn is the power consumption of sn in the preset high-frequency equivalent circuit, R sn is the resistance of sn in the preset high-frequency equivalent circuit, i sn is the current of sn in the preset high-frequency equivalent circuit, V DC is the power supply voltage, C eq is the capacitance of eq in the preset high-frequency equivalent circuit, C sn is the capacitance of sn in the preset high-frequency equivalent circuit.

5. The method according to claim 1, wherein Calculating the power consumption according to the second resistance mode includes: ， Among them, E sn is the power consumption of sn in the preset high-frequency equivalent circuit, R sn is the resistance of sn in the preset high-frequency equivalent circuit, i sn is the current of sn in the preset high-frequency equivalent circuit, V DC is the power supply voltage, C eq is the capacitance of eq in the preset high-frequency equivalent circuit, C sn is the capacitance of sn in the preset high-frequency equivalent circuit.

6. A device for obtaining the parameters of the absorption circuit of a bridge converter, characterized in that, Including: A simulation module for simulating according to a preset high-frequency equivalent circuit through a preset damping value gradient to generate an absorption circuit parameter mapping diagram; An area determination module for determining a target area according to the absorption circuit parameter mapping diagram; An acquisition module for calculating the minimum power consumption of the preset high-frequency equivalent circuit according to the target area to obtain target absorption circuit parameters; The acquisition module includes: A first acquisition unit for calculating the power consumption respectively according to the turn-off process, off-state process and turn-on process of the preset high-frequency equivalent circuit, and calculating the power consumption according to the first resistance mode and the second resistance mode to obtain the minimum power consumption of the preset high-frequency equivalent circuit; A second acquisition unit for obtaining the target absorption circuit parameters according to the minimum power consumption.

7. The device according to claim 6, characterized in that, The simulation module includes: A damping value determination unit for using the root locus analysis method to determine the damping value under the values of each resistance and capacitance in the absorption circuit; An acquisition unit for quantitatively obtaining the damping change law according to the damping values under the values of each resistance and capacitance by using the gradient field to obtain the values of the resistance and capacitance of each oscillation suppression gradient; A simulation unit for obtaining the absorption circuit parameter mapping diagram according to the distribution of the values of the resistance and capacitance of each oscillation suppression gradient.

8. A circuit, characterized in that, Applied to the preset high-frequency equivalent circuit in the method according to any one of claims 1 to 5, including: A power supply, a first resistor set, a first inductor set, and a first capacitor are connected in series. The inductor is connected in parallel to the output terminal of the first resistor in the first resistor set. The output terminal of the inductor is connected to the input terminal of a target resistor. The output terminal of the target resistor is connected to the input terminal of a target capacitor. The output terminal of the target capacitor is connected to the output terminal of the first capacitor.

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