LLC resonant converter

Abstract

The utility model relates to the technical field of converters, in particular to an LLC resonant converter which comprises a square wave generator, a resonant network and a rectification network which are connected in series, the resonant network comprises an inductor Lm, a transformer primary leakage inductor Llkp and a transformer secondary leakage inductor Llks, one end of the inductor Lm is electrically connected with the square wave generator through the transformer primary leakage inductor Llkp, and the other end of the inductor Lm is electrically connected with the rectification network through the transformer secondary leakage inductor Llks. The resonance network is electrically connected with the rectification network through the transformer secondary leakage inductor Llks. The primary leakage inductance Llkp of the transformer and the secondary leakage inductance Llks of the transformer respectively represent the primary leakage inductance and the secondary leakage inductance of the transformer, the excitation inductance is relatively small, the rectification network can be designed into a full-bridge structure with a capacitance output filter, the switching loss is reduced to a certain extent, high frequency is realized conveniently, and the efficiency and the power density are improved.

Description

Technical Field

[0001] The utility model relates to an LLC resonant converter, in particular to an LLC resonant converter, and belongs to the technical field of converters. Background Art

[0002] To address the limitations of traditional resonant converters, LLC resonant converters have many advantages over conventional resonators. First, it can adjust the output over a wide range of input and load variations with relatively small switching frequency changes. Second, it can achieve zero voltage switching (ZVS) over the entire operating range. Finally, all parasitic elements, including the junction capacitance of all semiconductor devices and the leakage inductance and magnetizing inductance of the transformer, are used to achieve ZVS.

[0003] In the design of power converters, the requirements for increasing power density and reducing design size are becoming increasingly higher. Designers are urgently required to increase the switching frequency. The use of high-frequency operation will greatly reduce the size of passive components, but the existing switching losses have an adverse effect on high-frequency operation. In order to reduce switching losses and make high-frequency operation normal, resonant switching technology is proposed. Utility Model Content

[0004] The purpose of the utility model is to provide an LLC resonant converter, a transformer primary leakage inductance L lkp and transformer secondary leakage inductance E lks They represent the leakage inductance of the primary and secondary of the transformer respectively. The magnetizing inductance is relatively small. The rectifier network can be designed as a full-bridge structure with a capacitor output filter, which reduces the switching loss to a certain extent, facilitates the realization of high frequency, and improves the efficiency and power density.

[0005] In order to achieve the above-mentioned purpose, the main technical solutions adopted by the utility model include:

[0006] An LLC resonant converter comprises a square wave generator, a resonant network and a rectifier network connected in series, wherein the resonant network comprises an inductor L m , Transformer primary leakage inductance L lkp and transformer secondary leakage inductance L lks , the inductance L m One end of the transformer passes through the primary leakage inductance L lkp The resonant network is electrically connected to the square wave generator through the secondary leakage inductance E of the transformer. lks The rectifier network is electrically connected to the rectifier network.

[0007] Preferably, the square wave generator is provided with an alternating drive switch Q1 and an alternating drive switch Q2 in series, and the primary leakage inductance L of the transformer lkp The switch is electrically connected between the alternately driven switch Q1 and the alternately driven switch Q2.

[0008] Preferably, the bottom of the alternating drive switch Q2 is connected to the inductor L via the capacitor Cr. m Electrical connection.

[0009] Preferably, the rectifier network is provided with a diode VD1 and a diode VD3 arranged in series, and a diode VD2 and a diode VD4 arranged in series;

[0010] The diode VD1 and the diode VD3 are connected in series and then connected in parallel with the diode VD2 and the diode VD4.

[0011] Preferably, a capacitor Cn is connected in parallel to one side of the diode VD4, and a resistor R0 is connected in parallel to one side of the capacitor Cn.

[0012] Preferably, the output current of the rectifier network is I0, then the average value of I0 is In, and the formula is:

[0013]

[0014] Then

[0015] V RI =+V0 if sin(ωt)>0;

[0016] V RI =+V0 if sin(ωt)>0;

[0017] Where V0 is the output voltage, ω is the angular frequency, t is the time, V RI is the voltage change;

[0018] Then V RI The calculation formula is:

[0019]

[0020] Preferably, the I n The impedance calculation formula is:

[0021]

[0022] Preferably, considering the turns ratio of the transformer, the equivalent load impedance of the primary side of the transformer is:

[0023]

[0024] The utility model has at least the following beneficial effects:

[0025] Transformer primary leakage inductance L lkp and transformer secondary leakage inductance L lksThey represent the leakage inductance of the primary and secondary of the transformer respectively. The magnetizing inductance is relatively small. The rectifier network can be designed as a full-bridge structure with a capacitor output filter, which reduces the switching loss to a certain extent, facilitates the realization of high frequency, and improves the efficiency and power density. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0027] Figure 1 This is a principle structure diagram of the utility model;

[0028] Figure 2 This is a circuit diagram of the utility model.

[0029] In the figure, 1. Square wave generator; 2. Resonant network; 3. Rectification network. DETAILED DESCRIPTION

[0030] The following will describe the implementation methods of the present application in detail with the help of accompanying drawings and examples, so that the implementation process of how the present application uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0031] like Figure 1-Figure 2 As shown, the LLC resonant converter provided in this embodiment, the LLC resonant converter provided in this embodiment, in order to solve the limitations of traditional resonant converters, compared with conventional resonators, the LLC resonant converter has many advantages. First, it can adjust the output when the input and load change in a wide range, and the switching frequency changes relatively little. Second, it can achieve zero voltage switching ZVS in the entire operating range. Finally, all parasitic elements, including the junction capacitance of all semiconductor devices and the leakage inductance and excitation inductance of the transformer, are used to achieve ZVS. The present invention includes a square wave generator 1, a resonant network 2 and a rectifier network 3 connected in series. The resonant network 2 includes an inductor L m , Transformer primary leakage inductance L lkp and transformer secondary leakage inductance L lks , inductance L m One end of the transformer passes through the primary leakage inductance L lkp Electrically connected to the square wave generator 1, the resonant network 2 is connected to the secondary leakage inductance L of the transformer. lks Electrically connected to the rectifier network 3, the inductor L m is the transformer excitation inductance, the transformer primary leakage inductance L lkp and transformer secondary leakage inductance L lksRespectively represent the leakage inductance of the primary and secondary of the transformer. The working principle of the LLC resonant converter is similar to that of the traditional LC series resonant converter. The only difference is that the magnetizing inductance is relatively small, so the inductance L m + Transformer primary leakage inductance L lkp The resonance between the capacitor Cr will affect the operation of the converter. Due to the small magnetizing inductance, there is a considerable magnetizing current L m ;

[0032] The resonant network 2 includes a capacitor, the leakage inductance and the magnetizing inductance of the transformer. The resonant network 2 can filter out high-order harmonic currents. Therefore, even if a square wave voltage is applied to the resonant network, substantially only a sinusoidal current is allowed to flow through the resonant network. The current Ip lags behind the voltage applied to the resonant network, which allows zero voltage turn-on of the MOSFET.

[0033] The rectifier network can be designed as a full-bridge structure with a capacitor output filter, which reduces switching losses to a certain extent, facilitates the realization of high frequency, and improves efficiency and power density.

[0034] Further, such as Figure 1 As shown, the square wave generator 1 is provided with an alternating drive switch Q1 and an alternating drive switch Q2 in series, and the primary leakage inductance L of the transformer lkp Electrically connected between the alternate drive switch Q1 and the alternate drive switch Q2, the square wave generator 1 alternately drives the switch Q1 and the alternate drive switch Q2 at a 50% duty cycle each time it switches to generate a square wave voltage Vd, and the square wave generator stage is a full bridge type;

[0035] The bottom of the alternately driven switch Q2 is connected through the capacitor Cr and the inductor L m Electrically connected, the rectifier network 3 is provided with a diode VD1 and a diode VD3 arranged in series, and a diode VD2 and a diode VD4 arranged in series. The diode VD1 and the diode VD3 are connected in series and then connected in parallel with the diode VD2 and the diode VD4. A capacitor Cn is arranged in parallel on one side of the diode VD4, and a resistor R0 is arranged in parallel on one side of the capacitor Cn. The rectifier network 3 adjusts the alternating current through multiple rectifier diodes and capacitors and outputs a direct current voltage. The rectifier network can be designed as a full-bridge structure with a capacitor output filter, which reduces switching losses to a certain extent, facilitates the realization of high frequency, and improves efficiency and power density.

[0036] Furthermore, the output current of the rectifier network 3 is I0, and the average value of I0 is In, and the formula is:

[0037]

[0038] Then

[0039] V RI=+V0 if sin(ωt)>0;

[0040] V RI =+V0 if sin(ωt)>0;

[0041] Where V0 is the output voltage, ω is the angular frequency, t is the time, V RI is the voltage change;

[0042] Then V RI The calculation formula is:

[0043]

[0044] I n The impedance calculation formula is:

[0045]

[0046] Considering the turns ratio of the transformer, the equivalent load impedance of the transformer primary is:

[0047]

[0048] The filtering function of the resonant network 2 can be used to obtain the voltage gain of the resonator using the classic fundamental approximation principle. It is assumed that only the fundamental of the square wave voltage input to the resonant network contributes to the power transfer to the output. Since the secondary rectifier circuit acts as an impedance transformer, the equivalent load resistance is different from the actual load resistance. The primary circuit is replaced by a sinusoidal current source In and a square wave voltage V RI , as the rectifier input voltage, is used to obtain a larger gain effect.

[0049] like Figure 1-Figure 2 As shown, the principle of the LLC resonant converter provided in this embodiment is as follows:

[0050] The present invention comprises a square wave generator 1, a resonant network 2 and a rectifier network 3 connected in series, wherein the resonant network 2 comprises an inductor L m , Transformer primary leakage inductance L lkp and transformer secondary leakage inductance L lks , inductance L m One end of the transformer passes through the primary leakage inductance L lkp Electrically connected to the square wave generator 1, the resonant network 2 is connected to the secondary leakage inductance L of the transformer. lks Electrically connected to the rectifier network 3, the inductor L m is the transformer excitation inductance, the transformer primary leakage inductance L lkp and transformer secondary leakage inductance L lksRespectively represent the leakage inductance of the primary and secondary of the transformer. The working principle of the LLC resonant converter is similar to that of the traditional LC series resonant converter. The only difference is that the magnetizing inductance is relatively small, so the inductance L m + Transformer primary leakage inductance L lkp The resonance between the capacitor Cr will affect the operation of the converter. Due to the small magnetizing inductance, there is a considerable magnetizing current L m ;

[0051] The resonant network 2 includes a capacitor, the leakage inductance and the magnetizing inductance of the transformer. The resonant network 2 can filter out high-order harmonic currents. Therefore, even if a square wave voltage is applied to the resonant network, substantially only a sinusoidal current is allowed to flow through the resonant network. The current Ip lags behind the voltage applied to the resonant network, which allows zero voltage turn-on of the MOSFET.

[0052] The rectifier network can be designed as a full-bridge structure with a capacitor output filter, which reduces switching losses to a certain extent, facilitates the realization of high frequency, and improves efficiency and power density.

[0053] For example, certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different terms to refer to the same component. This specification and claims do not use differences in names as a way to distinguish components, but use differences in the functions of components as the criteria for distinction. For example, "including" mentioned throughout the specification and claims is an open term, so it should be interpreted as "including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve technical problems within a certain error range and basically achieve technical effects.

[0054] It should be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a product or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such product or system. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the product or system including the elements.

[0055] The above description shows and describes several preferred embodiments of the utility model, but as mentioned above, it should be understood that the utility model is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the utility model concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art do not deviate from the spirit and scope of the utility model, and should be within the scope of protection of the claims attached to the utility model.

Claims

1. An LLC resonant converter, comprising a square wave generator (1), a resonant network (2) and a rectifier network (3) connected in series, characterized in that: The resonant network (2) includes an inductor L m , Transformer primary leakage inductance L lkp and transformer secondary leakage inductance L lks , the inductance L m One end of the transformer passes through the primary leakage inductance L lkp The resonant network (2) is electrically connected to the square wave generator (1), and the resonant network (2) is electrically connected to the square wave generator (1) through the secondary leakage inductance L of the transformer. lks Electrically connected to the rectification network (3).

2. The LLC resonant converter according to claim 1, characterized in that: The square wave generator (1) is provided with an alternating drive switch Q1 and an alternating drive switch Q2 in series, and the transformer primary leakage inductance L lkp The switch is electrically connected between the alternately driven switch Q1 and the alternately driven switch Q2.

3. An LLC resonant converter according to claim 2, characterized in that: The bottom of the alternating drive switch Q2 is connected to the inductor L through the capacitor Cr. m Electrical connection.

4. The LLC resonant converter according to claim 1, characterized in that: The rectifier network (3) is provided with a diode VD1 and a diode VD3 arranged in series, and a diode VD2 and a diode VD4 arranged in series; The diode VD1 and the diode VD3 are connected in series and then connected in parallel with the diode VD2 and the diode VD4.

5. The LLC resonant converter according to claim 4, characterized in that: A capacitor Cn is connected in parallel to one side of the diode VD4 , and a resistor R0 is connected in parallel to one side of the capacitor Cn.

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