ZVS condition optimization and adaptive dead-time control method for LCC resonant converter

Abstract

The application relates to a ZVS condition optimization and adaptive dead-time control method of an LCC resonant converter, which comprises the following steps: establishing a dead-time model of the LCC resonant converter; sampling and preprocessing a resonant current in the LCC resonant converter; inputting switch parameters of the LCC resonant converter and the preprocessed resonant current into the dead-time model to output ZVS realization discrimination results and minimum dead-time prediction results required for realizing ZVS; and according to the output results of the dead-time model, corresponding ZVS condition optimization or adaptive dead-time control of the LCC resonant converter is carried out. Compared with the prior art, the application can conveniently, quickly and accurately discriminate whether the switch element in the LCC resonant converter can realize zero-voltage switching, and can predict the minimum dead-time required for realizing zero-voltage switching, so as to optimize the ZVS condition and realize adaptive dead-time control, and avoid problems such as increased loss, reduced efficiency, aggravated EMI and reduced performance of the converter caused by unreasonable setting of the dead-time.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a method for ZVS condition optimization and adaptive dead-time control of an LCC resonant converter. Background Technology

[0002] The LCC resonant converter is a high-efficiency, low-voltage, high-frequency DC-DC converter. Its main working principle is to use a resonant network to realize the conversion of DC voltage. The working topology of the LCC resonant converter mainly consists of inductors, capacitors and transistors. Among them, the inductors and capacitors form a resonant network, and the transistors control the switching of the resonant network to realize energy transfer.

[0003] The LCC resonant converter combines the characteristics of a two-element series resonant converter and a parallel resonant converter, possessing excellent voltage gain characteristics and resistance to open-circuit and short-circuit loads. The LCC resonant converter also exhibits good parasitic parameter absorption capability; the leakage inductance and parasitic capacitance of its high-frequency transformer can both be considered as resonant parameters or as part of the resonant parameters. This feature has led to the widespread application of LCC resonant converters in high-voltage, high-power power supply applications.

[0004] In existing technologies, most LCC resonant converters employ zero-point switching of both input current and output voltage for control, achieving zero-point switching, reducing energy loss, and thus improving conversion efficiency. Current modeling of LCC resonant converters mainly focuses on steady-state and small-signal modeling. Dead time is typically used to prevent shoot-through of the upper and lower switching devices in the half-bridge arms of the inverter circuit. The choice of dead time not only affects the efficiency of the LCC resonant converter but also determines whether zero-voltage turn-on of the switching devices can be achieved. However, in practical applications, to avoid arm shoot-through and ensure zero-voltage turn-on, excessively large dead times are often set. This not only increases converter losses, reduces conversion efficiency, and exacerbates EMI (Electromagnetic Interference) problems but also hinders adaptive dead-time control of the LCC resonant converter, limiting further performance improvements. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art by providing a method for optimizing the ZVS (Zero Voltage Switch) conditions and adaptive dead-time control of an LCC resonant converter. By accurately estimating the ZVS conditions and the corresponding minimum dead time of the LCC resonant converter, the ZVS conditions of the LCC resonant converter can be optimized and adaptive dead-time control can be achieved, avoiding a series of problems caused by setting an excessively large dead time.

[0006] The objective of this invention can be achieved through the following technical solution: a method for ZVS condition optimization and adaptive dead-time control of an LCC resonant converter, comprising the following steps:

[0007] S1. Establish a dead time model for the LCC resonant converter to determine whether the LCC resonator can achieve ZVS and predict the minimum dead time required to achieve ZVS.

[0008] S2. Sample the resonant current in the LCC resonant converter and perform preprocessing;

[0009] S3. Input the switching device parameters of the LCC resonant converter and the preprocessed resonant current into the dead time model, and output the ZVS realization discrimination result and the minimum dead time prediction result required to realize ZVS.

[0010] S4. Based on the results output in step S3, perform ZVS condition optimization or adaptive dead-time control on the LCC resonant converter.

[0011] Furthermore, the specific process of establishing the dead-time model of the LCC resonant converter in step S1 is as follows:

[0012] S11. Based on the steady-state operating point of the LCC resonant converter, the state of each element in the LCC resonant converter during the dead time is obtained.

[0013] S12. Based on the state of each component in the LCC resonant converter during the dead time, the dead time model of the LCC resonant converter is established by using the Laplace transform.

[0014] Furthermore, the realization of ZVS specifically refers to the drain-source voltage V of the switching devices in the inverter circuit of the LCC resonant converter. ds It drops to zero before the switching device is turned on;

[0015] The minimum dead time required to achieve ZVS specifically refers to meeting the drain-source voltage V of the switching device. ds From the bus voltage V dc The minimum time required to reduce to zero.

[0016] Furthermore, step S2 specifically employs a multi-order polynomial fitting algorithm to preprocess the resonant current.

[0017] Furthermore, the specific process of step S2 is as follows: fitting the resonant current using a multi-order polynomial function.

[0018] Furthermore, the switching device parameters of the LCC resonant converter in step S3 include the drain-source voltage V of the switching device. ds Resonant inductor voltage VLr Resonant inductor L r and the output capacitor C of the switching device oss .

[0019] Furthermore, in step S3, the dead-time model is specifically based on the ZVS discriminant formula to output the ZVS discriminant result. The ZVS discriminant formula is as follows:

[0020]

[0021] Among them, I LrM3 V is the current in the resonant inductor at the moment of entering the dead time. LrM3 The voltage of the resonant inductor at the moment of entering the dead time;

[0022] If Δ > 0, output "Yes" for the ZVS implementation judgment result; otherwise, output "No" for the ZVS implementation judgment result.

[0023] Furthermore, in step S3, the dead time model is specifically calculated based on the following formula to obtain the minimum dead time prediction result required to achieve ZVS:

[0024]

[0025] Among them, t d To implement the minimum dead time for ZVS when the discrimination result is "yes".

[0026] Furthermore, in step S4, if the ZVS determination result is "no", the ZVS condition of the LCC resonant converter is optimized by adjusting the switching device parameters of the LCC resonant converter.

[0027] Furthermore, in step S4, if the ZVS implementation judgment result is "yes" and the minimum dead time prediction result required to implement ZVS is obtained, then adaptive dead time control is performed on the LCC resonant converter according to the minimum dead time prediction result.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] I. This invention establishes an s-domain dead-time model for an LCC resonant converter. By inputting the switching device parameters and pre-processed resonant current of the LCC resonant converter into this dead-time model, the ZVS (Zero-Voltage-Side Response) determination result and the predicted minimum dead-time required to achieve ZVS can be output. Based on the output results, the ZVS conditions of the LCC resonant converter can be optimized, and adaptive dead-time control can be achieved. This not only ensures that the LCC resonant converter achieves ZVS but also provides the minimum dead-time required to achieve ZVS. This solves the problems of existing technologies that, in order to achieve ZVS in LCC resonant converters, can only reserve a large phase angle and set an unreasonable dead time, leading to reduced converter performance, increased losses, reduced conversion efficiency, and aggravated EMI.

[0030] Second, this invention analyzes the steady-state operating point of the LCC resonant converter to obtain the state of each component in the LCC resonant converter during the dead time. Then, it uses Laplace transform to establish a dead time model of the LCC resonant converter. The input variables of this dead time model include the initial value of each component entering the dead time and the resonant parameters. Combined with the corresponding ZVS implementation discriminant formula and minimum dead time calculation formula, the accuracy of the dead time model output results is ensured.

[0031] Third, based on the output of the dead-time model, if the ZVS realization result is "no", the switching device parameters of the LCC resonant converter are adjusted to optimize the ZVS condition of the LCC resonant converter; if the ZVS realization result is "yes" and the minimum dead time prediction result required to realize ZVS is obtained, adaptive dead-time control of the LCC resonant converter is performed according to the minimum dead-time prediction result. This can effectively and specifically improve the performance of the LCC resonant converter. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the method flow of the present invention;

[0033] Figure 2 This is a schematic diagram illustrating the application process of an example.

[0034] Figure 3 This is a schematic diagram of the circuit topology of the LCC resonant converter in the embodiment;

[0035] Figure 4 This is a schematic diagram of the equivalent circuit of the s-domain dead-time model in the embodiment. Detailed Implementation

[0036] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0037] Example

[0038] like Figure 1 As shown, a method for ZVS condition optimization and adaptive dead-time control of an LCC resonant converter includes the following steps:

[0039] S1. Establish a dead time model for the LCC resonant converter to determine whether the LCC resonator can achieve ZVS and predict the minimum dead time required to achieve ZVS.

[0040] S2. Sample the resonant current in the LCC resonant converter and perform preprocessing;

[0041] S3. Input the switching device parameters of the LCC resonant converter and the preprocessed resonant current into the dead time model, and output the ZVS realization discrimination result and the minimum dead time prediction result required to realize ZVS.

[0042] S4. Based on the results output in step S3, perform ZVS condition optimization or adaptive dead-time control on the LCC resonant converter.

[0043] This embodiment applies the above-described technical solution, such as Figure 2 As shown, the specific process includes:

[0044] I. By analyzing the steady-state operating point of the LCC resonant converter, the state of each component in the LCC resonant converter during the dead time is obtained. A dead-time model of the LCC resonant converter is established using the Laplace transform. The topology of the LCC resonant converter is as follows: Figure 3 The series resonant capacitor C of the LCC resonant converter is shown. r and parallel resonant capacitor C p Much larger than the output capacitance C of the switching device oss The equivalent circuit of the s-domain dead-time model is as follows: Figure 4 As shown.

[0045] II. To verify the effectiveness of the dead-time model, simulation tests were conducted in simulation software: Based on the voltage variation range of the switching devices, the dead-time model established in the s-domain was solved through simulation to obtain the ZVS condition of the LCC resonant converter and the minimum dead time to achieve the ZVS condition. Here, ZVS refers to the drain-source voltage Vd of the switching devices in the full-bridge (half-bridge) inverter circuit of the LCC resonant converter. ds The dead time drops to zero before the switching device is turned on; the minimum dead time is exactly the time required to satisfy the drain-source voltage V of the switching device. ds From the bus voltage V dc The time required to reduce to zero.

[0046] Third, sample the resonant current in the LCC resonant converter and preprocess it using a multi-order polynomial fitting algorithm. That is, the resonant current is described by a multi-order polynomial function. According to the Taylor expansion, the polynomial can fit any function.

[0047] IV. Using the pre-treated resonant current I Lr Combined with the drain-source voltage V of the switching device ds Resonant inductor voltage V Lr Resonant inductor L r and the output capacitor C of the switching device oss As input to the dead-time model, it is determined whether the switching elements in the LCC resonant converter can achieve zero-voltage switching. If ZVS can be achieved, the minimum dead time required to achieve zero-voltage switching is further predicted and estimated.

[0048] The discriminant formula for the ZVS condition is:

[0049]

[0050] Minimum dead time t d for:

[0051]

[0052] In the formula, I LrM3 V is the current in the resonant inductor at the moment of entering the dead time. LrM3 The voltage of the resonant inductor at the moment of entering the dead time; if Δ>0, the ZVS judgment result is output as "yes", otherwise the ZVS judgment result is output as "no"; t d This refers to the minimum dead time when the ZVS implementation determines the result as "yes".

[0053] 5. If the ZVS determination result is "no", then the ZVS condition of the LCC resonant converter is optimized by adjusting the switching device parameters of the LCC resonant converter.

[0054] If the ZVS implementation result is "yes" and the minimum dead time prediction result required to implement ZVS is obtained, then adaptive dead time control is performed on the LCC resonant converter based on the minimum dead time prediction result.

[0055] To verify the effectiveness of this technical solution, this embodiment conducts corresponding simulation tests under different operating conditions in the SIMetrix simulation software. The simulation results are compared with the actual results, as shown in Table 1. This demonstrates that the technical solution can accurately determine whether the switching elements in the LCC resonant converter can achieve zero-voltage switching and accurately predict the minimum dead time required to achieve zero-voltage switching.

[0056] Table 1

[0057] ZVS conditions Satisfies, Δ>0 Satisfies, Δ>0 Satisfies, Δ>0 Satisfies, Δ>0 Satisfies, Δ>0 Dead zone estimation 31.30ns 36.68ns 42.84ns 51.50ns 64.60ns Simulation results 31.66ns 38.00ns 44.95ns 52.12ns 65.77ns

[0058] In summary, this technical solution models the ZVS process of an LCC resonant converter, obtaining a dead-time model for determining whether the LCC resonator can achieve ZVS and predicting the minimum dead time required to achieve ZVS. The variables of this model include the initial values ​​of the dead time of each component and the resonant parameters. Using this model, it is possible to conveniently, quickly, and accurately determine whether the switching elements in the LCC resonant converter can achieve zero-voltage switching and predict the minimum dead time required to achieve zero-voltage switching. This can be used to optimize the ZVS condition of the LCC resonant converter and for adaptive dead-time control. It can solve the problems of additional losses or even loss of ZVS conditions caused by unreasonable estimation of dead time in engineering. It also solves the problems of rough estimation of dead time in the prior art, which may lead to failure to meet the zero-voltage switching condition and greater reverse conduction losses of switching devices. It significantly improves the adverse phenomena of increased converter losses, reduced efficiency, and aggravated EMI problems caused by setting too large a dead time to avoid bridge arm shoot-through in practical applications of LCC resonant converters.

Claims

1. A method for ZVS condition optimization and adaptive dead-time control of an LCC resonant converter, characterized in that, Includes the following steps: S1. Establish a dead time model for the LCC resonant converter to determine whether the LCC resonator can achieve ZVS and predict the minimum dead time required to achieve ZVS. The specific process of establishing the dead-time model of the LCC resonant converter is as follows: S11. Based on the steady-state operating point of the LCC resonant converter, the state of each element in the LCC resonant converter during the dead time is obtained. S12. Based on the state of each component in the LCC resonant converter during the dead time, the dead time model of the LCC resonant converter is established using the Laplace transform method. The aforementioned ZVS specifically refers to the drain-source voltage V of the switching devices in the inverter circuit of the LCC resonant converter. ds It drops to zero before the switching device is turned on; The minimum dead time required to achieve ZVS specifically refers to meeting the drain-source voltage V of the switching device. ds From the bus voltage V dc The minimum time required to reduce to zero; S2. Sample the resonant current in the LCC resonant converter and perform preprocessing; S3. Input the switching device parameters of the LCC resonant converter and the preprocessed resonant current into the dead time model, and output the ZVS realization discrimination result and the minimum dead time prediction result required to realize ZVS. S4. Based on the results output in step S3, perform ZVS condition optimization or adaptive dead-time control on the LCC resonant converter.

2. The ZVS condition optimization and adaptive dead-time control method for an LCC resonant converter according to claim 1, characterized in that, Step S2 specifically employs a multi-order polynomial fitting algorithm to preprocess the resonant current.

3. The ZVS condition optimization and adaptive dead-time control method for an LCC resonant converter according to claim 2, characterized in that, The specific process of step S2 is as follows: the resonant current is fitted using a multi-order polynomial.

4. The ZVS condition optimization and adaptive dead-time control method for an LCC resonant converter according to claim 1, characterized in that, In step S3, the switching device parameters of the LCC resonant converter include the drain-source voltage V of the switching device. ds Resonant inductor voltage V Lr Resonant inductor L r and the output capacitor C of the switching device oss .

5. The ZVS condition optimization and adaptive dead-time control method for an LCC resonant converter according to claim 4, characterized in that, In step S3, the dead-time model is specifically based on the ZVS discriminant formula to output the ZVS discriminant result. The ZVS discriminant formula is as follows: in, The current in the resonant inductor at the moment of entering the dead time. The voltage of the resonant inductor at the moment of entering the dead time; If satisfied If the condition is met, the ZVS implementation result will be output as "Yes"; otherwise, the ZVS implementation result will be output as "No".

6. The ZVS condition optimization and adaptive dead-time control method for an LCC resonant converter according to claim 5, characterized in that, In step S3, the dead time model is specifically calculated based on the following formula to obtain the minimum dead time prediction result required to achieve ZVS: in, I Lr This is the resonant current after pretreatment. To implement the minimum dead time for ZVS when the discrimination result is "yes".

7. The ZVS condition optimization and adaptive dead-time control method for an LCC resonant converter according to claim 5, characterized in that, In step S4, if the ZVS determination result is "no", the ZVS condition of the LCC resonant converter is optimized by adjusting the switching device parameters of the LCC resonant converter.

8. The ZVS condition optimization and adaptive dead-time control method for an LCC resonant converter according to claim 5, characterized in that, In step S4, if the ZVS implementation judgment result is "yes" and the minimum dead time prediction result required to implement ZVS is obtained, then adaptive dead time control is performed on the LCC resonant converter according to the minimum dead time prediction result.

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