LLC resonant power converter with variable turns ratio

Abstract

The application discloses an LLC resonant power converter with variable turns ratio, comprising: a switching circuit electrically coupled to an input DC voltage, for converting the DC voltage into a switching signal; a resonant tank electrically coupled to the switching circuit, the resonant tank is composed of a resonant inductor, an excitation inductor and a resonant capacitor, for receiving the switching signal to provide a primary side current; a transformer circuit electrically coupled to the resonant tank, the transformer circuit includes a plurality of discrete transformers, each transformer has a primary side winding and a secondary side winding, wherein the primary side winding of each transformer has different turns, and can be dynamically selected in series or parallel with the primary side winding of other transformers to form a dynamically changing equivalent primary side winding, so that the turns ratio in the transformer circuit can be dynamically changed accordingly.

Description

Technical Field

[0001] This invention relates to the technical field of LLC resonant power converters, and more specifically to an LLC resonant power converter with a variable turns ratio. Background Technology

[0002] In traditional switched power supplies, magnetic components are typically used for filtering, energy storage, and transmission. The higher the operating frequency of the switching component, the smaller the size of the magnetic component can be, making it easier to achieve miniaturization, weight reduction, and cost reduction of the power supply. However, increasing the switching frequency correspondingly increases the switching losses of the switching component, hence the development of soft-switching technology. To achieve ideal soft switching, the best scenario is to make the switch (switching component) turn off and on when both voltage and current are zero (zero-voltage switching, ZVS; zero-current switching, ZCS), thus truly eliminating losses. To achieve this goal, resonant technology must be employed.

[0003] According to circuit principles, an inductor and capacitor connected in series or in parallel can form a resonant circuit, causing the current in the circuit to change sinusoidally when the power supply is DC. Since the current or voltage changes sinusoidally, there is a zero-crossing point. If the switching component is turned on or off at this point, the resulting loss is zero.

[0004] An LLC resonant power converter is a resonant inverter with three reactive elements. The DC input voltage is converted to a square wave via a switch network configured as a half-bridge or full-bridge to feed into the LLC resonant tank, effectively filtering harmonics and providing a sinusoidal voltage and current waveform. This, in turn, powers a transformer that provides voltage scaling and primary-secondary isolation. The converter's power flow is controlled by modulating the square wave frequency relative to the resonant tank circuit. In an LLC resonant power converter, all semiconductor switches are soft-switching or zero-voltage switching (ZVS) when the primary MOSFETs are on, and the secondary rectifiers are zero-current switching (ZCS) when on and off, resulting in low electromagnetic emission levels. Furthermore, it enables a high degree of integration of magnetic components, thereby allowing the design of converters with higher efficiency and power density.

[0005] An LLC resonant power converter is a topology of a series resonant converter that provides an output voltage signal isolated from the input signal. An LLC resonant power converter includes a series resonant circuit with the primary winding of a transformer. A switching circuit alternately couples the switching node of the resonant circuit or energy storage circuit to a positive power node and a ground node to provide an AC resonant current flowing through the primary winding of the transformer. Secondary circuitry (e.g., a rectifier) ​​provides the output voltage to drive the load. This secondary circuitry may include a synchronous rectifier switch or a diode rectifier. The primary-side switching circuitry can be regulated to regulate the output voltage. LLC resonant converters offer high efficiency and high power density, and can provide zero-voltage switching and low shutdown current for the primary-side switching over a fairly wide load range. These advantages make LLC resonant power converters suitable for a variety of applications, such as high-performance servers and telecommunications applications.

[0006] As mentioned earlier, when the primary-side switching frequency is below the resonant frequency, the primary side can be switched off with zero current. This helps improve voltage gain capability without reducing efficiency in applications with hold-up time requirements. Operating at high switching frequencies can reduce the size of magnetic components and capacitors in LLC resonant power converters. However, this increases switching-related losses and magnetic component losses, leading to inefficiency. Due to core and winding losses, especially at high switching frequencies, the magnetic components used in LLC resonant power converters remain a limitation to improving converter efficiency. Further improvements are needed to support higher efficiency and power density in LLC resonant power converters.

[0007] The magnetic components of an LLC resonant power converter can change the parameters of the resonant tank by altering the series and parallel connections of the windings on the circuit board. However, the range of fine-tuning is limited. In conjunction with external series and parallel inductor and capacitor components, the parameters can be changed more significantly. The development trend of LLC resonant power converters is to increase the range of resonant tank parameter adjustment to meet the increasingly wider output voltage and current requirements.

[0008] Therefore, there is an urgent need to improve the power density and output voltage and current range of LLC resonant power converters by introducing variable turns ratio transformer windings and changing resonant slot parameters, in order to address the shortcomings of existing LLC resonant power converters. Summary of the Invention

[0009] In view of this, to solve the above problems, the present invention proposes an LLC resonant power converter with a variable turns ratio, comprising: a switching circuit electrically coupled to an input DC voltage to convert the DC voltage into a switching signal; a resonant tank electrically coupled to the switching circuit, the resonant tank being composed of a resonant inductor, a magnetizing inductor, and a resonant capacitor, used to receive the switching signal to provide primary-side current; and a transformer circuit electrically coupled to the resonant tank, the transformer circuit comprising multiple discrete transformers, each transformer having a primary winding and a secondary winding, wherein the primary winding of individual transformers has a different number of turns, which can be dynamically selected to be electrically coupled to or isolated from the resonant tank. Furthermore, it can be dynamically selected to be connected in series or in parallel with the primary windings of other transformers to form a dynamically changing equivalent primary winding; wherein, the number of turns in the secondary winding of each transformer is fixed and the same, so that the turns ratio in the transformer circuit can be dynamically changed accordingly; and a rectifier and filter circuit is coupled to the transformer circuit to rectify and filter the secondary current output from the secondary winding of the transformer circuit to provide an output voltage; wherein, one end of the resonant inductor is electrically coupled to the switching circuit, and the other end is connected in series with the equivalent primary winding; the magnetizing inductor is connected in series with the resonant inductor, one end of the resonant capacitor is connected in series with the magnetizing inductor, and the other end is electrically coupled to the switching circuit; the magnetizing inductor is connected in parallel with the equivalent primary winding.

[0010] In one embodiment, the aforementioned equivalent primary winding that forms a dynamic change is achieved by dynamically adjusting the series and parallel connection of the primary winding through a configuration of multiple switches.

[0011] In one embodiment, the aforementioned multiple switches are various types of switches such as transistor switching assemblies and relays.

[0012] In one embodiment, the resonant inductor, the magnetizing inductor, and the turns ratio can all be dynamically adjusted by a combination of these switches.

[0013] In one embodiment, both the primary winding and the secondary winding are disposed on a multilayer printed circuit board to effectively reduce stray characteristics caused by the winding.

[0014] In one embodiment, the aforementioned LLC resonant power converter with variable turns ratio further includes an adjustable capacitor disposed in a multilayer printed circuit board, which is integrated with the primary winding and secondary winding of the transformer to form an additional resonant capacitor.

[0015] In one embodiment, the adjustable capacitor is formed by fabricating metal plates with fixed area and size at the same position on each layer of a multilayer printed circuit board in a selected area. Multiple metal plates and multiple dielectric layers between them can be combined to form a capacitor and integrated with the windings of a transformer to form the additional resonant capacitor.

[0016] In one embodiment, the additional resonant capacitor described above can change the resonant capacitance value of the resonant slot of the LLC resonant power converter by adjusting the distance between the capacitor plates and changing the configuration of the positive and negative terminals of the capacitor plates.

[0017] In one embodiment, the additional resonant capacitor can be connected in parallel, in series, or completely isolated from the resonant capacitor by configuring multiple switches between the additional resonant capacitor and the transformer windings.

[0018] In one embodiment, the aforementioned multiple switch configuration is achieved by an external controller of an electrically coupled LLC resonant power converter. Based on the output voltage feedback and output current feedback received by the external controller, the controller outputs corresponding resonant capacitor adjustment signals and turns ratio adjustment signals to the resonant tank and transformer, respectively. This dynamically adjusts the size of the resonant capacitor and the turns ratio of the transformer, thereby achieving the purpose of adjusting the range of output voltage and output current of the LLC resonant power converter. Attached Figure Description

[0019] The components, features, and advantages of the present invention can be understood through the detailed description of the preferred embodiments outlined in the specification and the accompanying drawings:

[0020] Figure 1This diagram shows a schematic of the circuit architecture of an LLC resonant power converter in the prior art.

[0021] Figure 2 This diagram shows a circuit schematic of a variable turns ratio transformer winding in an LLC resonant power converter according to an embodiment of the present invention.

[0022] Figure 3 This diagram illustrates how an adjustable capacitor is fabricated using a multilayer printed circuit board (PCB) in an LLC resonant power converter according to an embodiment of the present invention.

[0023] Figure 4(A) shows a schematic diagram of the circuit architecture of an LLC resonant power converter according to an embodiment of the present invention.

[0024] Figures 4(B)-4(E) Schematic diagrams of various embodiments of the resonant slot transformer circuit block proposed according to the present invention are shown respectively.

[0025] Figure 5 The gain curve M(f) of the LLC resonant power converter, as shown in an embodiment of the present invention, is illustrated. s (K,Q) and operating frequency f s The relationship diagram.

[0026] Figure 6 This diagram shows a circuit block diagram and related operation control flow of an LLC resonant power converter according to an embodiment of the present invention.

[0027] Explanation of key component symbols:

[0028] Half-bridge switching circuit 101

[0029] Resonant slot 103

[0030] Transformer 104

[0031] 105 Rectifier and filter circuit

[0032] 401 Full-bridge switching circuit

[0033] Resonant slot 403

[0034] Transformer circuit 404

[0035] 405 rectifier filter circuit

[0036] Resonant Slot Transformer Circuit Block 403-1

[0037] Curves 501, 503, 511 and 513

[0038] 601 Full-bridge / Half-bridge Switching Circuit

[0039] 603 Resonant Slot and Transformer Circuit

[0040] 605 rectifier filter circuit

[0041] External control circuit 607 Detailed Implementation

[0042] Some preferred embodiments of the invention will now be described in more detail. However, it should be understood that the preferred embodiments of the invention are provided for illustrative purposes and not for limiting the invention. Furthermore, the invention may be practiced in a wide range of other embodiments besides those explicitly described, and the scope of the invention is not expressly limited unless specified in the appended claims.

[0043] As previously described in the background section, the magnetic components of an LLC resonant power converter can change the parameters of the resonant tank by altering the series and parallel connections of the windings on the circuit board. However, the range of fine-tuning is limited. In conjunction with external series and parallel inductor and capacitor components, the parameters can be changed more significantly. The development trend of LLC resonant power converters is to increase the range of resonant tank parameter adjustment to meet the increasingly wider output voltage and current requirements.

[0044] Figure 1 This is a schematic diagram of the circuit architecture of an existing LLC resonant power converter, employing a half-bridge LLC resonant power converter with a discrete transformer core integrated with synchronous rectification. The LLC resonant power converter is used to convert the DC input voltage V... in Converted to DC output voltage V o To provide load R L The system includes a half-bridge switching circuit 101, a resonant tank 103, a transformer 104, and a rectifier-filter circuit 105. The switching circuit 101 is used to control the DC voltage V. in The input. The resonant slot 103 is coupled to the switching circuit 101, which includes a resonant inductor L connected in series. r Magnetizing inductance L m and resonant capacitor C r The transformer 104 is coupled to the resonant slot 103 and includes a magnetic core, a primary (main and secondary) winding, and a secondary winding. The secondary winding is rectified by a center tap and rectified by a rectifier switch.

[0045] During the operation of the LLC resonant power converter, the output node of the half-bridge switching circuit 101 is alternately turned on due to the periodic switching of the switching switch, generating a periodically changing switching signal. When the signal is input to the resonant slot 103, the magnetizing inductor L... m The voltage and back electromotive force are repeatedly generated by the excitation, due to the resonant inductance L of the primary winding of transformer 104 and resonant slot 103. rand resonant capacitor C r Series connection with magnetizing inductor L m The parallel connection creates a primary current in the circuit that varies sinusoidally, while the secondary winding of transformer 104 continuously generates a periodically changing current. This current is rectified and filtered by rectifier and filter circuit 105, converting it into a DC current output to provide a DC output voltage V. o Give load R L Basically, once the circuit topology of an LLC resonant power converter is determined, its resonant tank parameters are fixed and cannot be adjusted for different operating conditions. That is, the range of its output voltage and output current cannot be adjusted according to operational needs.

[0046] To improve the power density and increase the output voltage and current range of LLC resonant power converters, this invention proposes to improve the power density and output voltage and current range by introducing a variable turns ratio transformer winding and changing the resonant slot parameters, thereby addressing the shortcomings of existing LLC resonant power converters.

[0047] The technical means proposed in this invention is to reduce the stray characteristics of the magnetic components by introducing a variable turns ratio transformer winding on the printed circuit board (PCB), thereby changing the resonant slot parameters of the LLC resonant power converter to obtain a larger output voltage and output current range and improve the power density of the LLC resonant power converter, so that the LLC resonant power converter can effectively operate in the range of switching operating frequencies above Mega Hz.

[0048] To reduce the size of magnetic components, flux cancellation technology is typically used to configure the magnetic components and windings. Designing the windings on a printed circuit board (PCB) effectively reduces stray characteristics caused by the windings. Because the windings are designed on the PCB, a 0.5-turn characteristic can be designed based on the PCB's routing configuration. Therefore, by connecting the windings in series and parallel, a transformer with a finely adjustable turns ratio N can be achieved, while simultaneously controlling resonant slot parameters, such as the transformer's magnetizing inductance L. m and resonant inductance (leakage inductance) L r It will also change.

[0049] To achieve planarization and integration of LLC resonant power converters, discrete transformers (a collection of multiple transformers) can flexibly change the series and parallel connection relationship of the primary and secondary windings in practical applications, and adjust the required turns ratio, so that LLC resonant power converters can meet increasingly wider output voltage and current requirements.

[0050] Figure 2This diagram shows a circuit schematic of the variable turns ratio transformer winding in the LLC resonant power converter of the present invention. In the embodiment shown in the diagram, there are four sets of transformers (T1, T2, T3, T4), which are discrete transformers and can be configured discretely. Since the transformer windings are designed on a printed circuit board, a 0.5-turn characteristic can be designed according to the routing design on the printed circuit board. The secondary windings of all transformers are designed with 1 turn; the primary winding of transformer T1 is designed with 4 turns, the primary winding of transformer T2 is designed with 4 turns, the primary winding of transformer T3 is designed with 4.5 turns, and the primary winding of transformer T4 is designed with 3.5 turns. According to this design, the series and parallel connection of the transformer windings can be adjusted by switches, such as transistor switching components, relays, and other types of switches, dynamically changing the resonant inductance L. r Magnetizing inductance L m The ratio of turns to N.

[0051] In one embodiment, the series-parallel connection of the windings can be achieved by configuring multiple switches between the windings.

[0052] In one embodiment, when multiple switching operations are used to connect the primary windings of transformers T1 and T2 in series, the number of turns of each primary winding is N. p1 =4 and N p2 =4, the combined number of turns of the primary winding is 8 turns, and the turns ratio of the transformer is 8:1.

[0053] In one embodiment, when multiple switching operations are performed between the windings to connect the primary windings of transformers T1 and T3 in series, the number of turns of each primary winding is N. p1 =4 and N p3 =4.5, the combined number of turns of the primary winding is 8.5 turns, and the turns ratio of the transformer is 8.5:1.

[0054] Similarly, when multiple switching operations are used to connect the primary windings of transformers T1 and T4 in series, the number of turns of each primary winding is N. p1 =4 and N p3 =3.5, the combined number of turns of the primary winding is 7.5 turns, and the turns ratio of the transformer is 7.5:1.

[0055] The examples above only illustrate different turns ratios achieved by using two of the four transformers in different series combinations. The number of transformers can be increased or decreased according to actual needs. Similarly, depending on the application, three of the four transformers can be used in different series combinations; or two of the four transformers can be used in different parallel combinations; or a series-parallel combination can be used. Numerous combinations are not listed here; the above are merely illustrative and not intended to limit the scope of the claims of this invention.

[0056] According to the concept of this invention, in order to increase the output voltage and output current range, in addition to dynamically changing the resonant inductance L in the manner described above... r Magnetizing inductance L m Besides using the turns ratio to achieve the desired effect, based on the transformer winding fabrication on the PCB, the resonant slot parameter C can also be changed by integrating the capacitors on the circuit board. r For detailed implementation instructions, please refer to [link / reference]. Figure 3 .

[0057] Discrete transformers typically use four-layer PCBs to fabricate their winding wiring; the primary winding wiring is fabricated on the second (Layer 2) and third (Layer 3) layers, while the secondary winding wiring is fabricated on the first (Layer 1) and fourth (Layer 4) layers.

[0058] Figure 3 This diagram illustrates how an adjustable capacitor is fabricated using a multilayer printed circuit board (PCB) in the LLC resonant power converter of this invention. Figure 3 As shown, using a four-layer PCB as an example, metal plates with fixed areas and dimensions are fabricated at the same locations on each layer within a selected area of ​​the PCB. The diagram shows a cross-sectional view. For simplicity, only the metal plates (as capacitor plates) are shown in the diagram; the dielectric layers (e.g., fiberglass boards) between the metal plates are not shown. These multiple metal plates and the multiple dielectric layers between them can be combined to form a capacitor, and integrated with the windings of the transformer fabricated in the PCB to form an additional resonant capacitor C. r '.

[0059] In one embodiment, reference is made to Figure 3 When metal plate electrodes 1 and 2 are selected as the positive and negative terminals of the capacitor, the capacitance is two units; when metal plate electrodes 1 and 3 are selected as the positive and negative terminals, the capacitance is one unit; when metal plate electrodes 1 and 3 are selected as the positive terminal and metal plate electrodes 2 and 4 are selected as the negative terminal, the capacitance is four units. By adjusting the distance between the capacitor plates and changing the configuration of the positive and negative terminals, the resonant capacitance C of the resonant slot of the LLC resonant power converter can be changed. r .

[0060] The examples above, using only a four-layer PCB as an example, demonstrate that the additional resonant capacitor formed by integrating the transformer windings fabricated within the PCB can be easily extended to PCBs with other layer counts. Furthermore, the additional resonant capacitor C formed by integrating the transformer windings fabricated within the PCB... r The resonant capacitor C of the original LLC resonant power converter can be achieved by configuring multiple switches between the windings. r Parallel, series, or completely isolated.

[0061] Figure 4(A) shows a schematic diagram of the circuit architecture of an LLC resonant power converter according to one embodiment of the present invention. As shown in Figure 4(A), the LLC resonant power converter of the present invention converts the input voltage V... in Converted to output voltage V o The system provides power to the load and includes a full-bridge switching circuit 401, a resonant tank 403, transformers (T1, T2, T3, T4), a rectifier and filter circuit 405, and a control circuit (not shown). Figure 4(A) shows a full-bridge switching circuit as an example, but it is not limited to this and may also include a half-bridge switching circuit. The rectifier and filter circuit 405 has a rectifier and filter circuit 405 connected to the transformers (T1, T2, T3, T4) (containing multiple sets of center-tapped secondary windings, each center-tapped secondary winding including positive and negative half-cycle windings, each positive and negative half-cycle winding connected in series with a rectifier switch and a capacitor for rectification and filtering of the positive and negative half-cycles). The full-bridge switching circuit 401 includes switching switches Q1, Q2, Q3, and Q4, wherein, in the positive half-cycle operation mode, the primary side upper bridge switch Q1 and the primary side lower bridge switch Q4 are turned on, the primary side upper bridge switch Q3 and the primary side lower bridge switch Q2 are turned off, and the current flows through L. r The primary windings of transformers T1 and T2, and L connected in parallel with the primary windings of transformers T1 and T2. m And C r The upper half-cycle of the secondary winding coupled to each other is rectified and filtered to generate the output voltage V. o To provide load R L In the negative half-cycle operation mode, primary side upper bridge switch Q3 and primary side lower bridge switch Q2 are turned on, while primary side upper bridge switch Q1 and primary side lower bridge switch Q4 are turned off, and current flows through L. r The primary windings of transformers T1 and T2, and L connected in parallel with the primary windings of transformers T1 and T2. m And C r The lower half-cycle windings of the respective coupled secondary windings are rectified and filtered to generate the output voltage V. o To provide load R L use.

[0062] According to the concept of the present invention and Figure 2-3 As illustrated in Figure 4(A), the resonant slot 403 coupled to the transformer circuit 404 in the LLC resonant power converter circuit can have different variations in design; taking Figure 4(A) as an example, it shows that the primary windings of transformers T1 and T2 are connected in series, while transformers T3 and T4 are disconnected.

[0063] Figure 4(B) shows the resonant slot transformer circuit block 403-1 (the primary windings of transformers T1 and T3 in resonant slot 403 and transformer circuit 404 are connected in series, while transformers T2 and T4 are disconnected).

[0064] Figure 4(C) shows the resonant slot transformer circuit block 403-1 (the primary windings of transformers T1 and T4 in resonant slot 403 and transformer circuit 404 are connected in series, while transformers T2 and T3 are disconnected).

[0065] Figure 4(D) shows the circuit block 403-1 (resonant slot 403 and transformer circuit 404), where the primary windings of transformers T1 and T2 are connected in parallel, and transformers T3 and T4 are connected in series.

[0066] The above are as follows Figures 4(A)-4(D) The transformer winding with varying turns ratio can be dynamically adjusted / controlled by appropriately configuring multiple switches between the transformer windings, resulting in different series and parallel combinations of windings between multiple transformers T1-T4. An external controller can then control the individual switches to turn on or off based on the actual output voltage / current requirements, thereby achieving the purpose of dynamically adjusting / controlling the transformer's turns ratio N.

[0067] Figure 4(E) shows that in circuit block 403-1 (resonant tank 403 and transformer circuit 404), the primary windings of transformers T1 and T2 are connected in series, transformers T3 and T4 are disconnected, and the resonant tank 403 is connected to a switch S. c Coupling with an additional resonant capacitor C r The coupling method can be shown in the diagram with the original resonant capacitor C. r Parallel or series connection. Similarly, an additional resonant capacitor C. r 'With the original resonant capacitor C r The coupling method can also be used to dynamically adjust / control the resonant capacitor C by controlling the conduction or cutoff of individual switches through an external controller based on the actual output voltage / current requirements. r The purpose of size.

[0068] In one embodiment, the additional resonant capacitor C rIt utilizes a multilayer printed circuit board (PCB) to fabricate an adjustable capacitor and integrates it with the windings of the transformer fabricated in the PCB.

[0069] pass Figure 2 -4 indicates that this invention can be based on the actual output voltage V o / Current I o The requirement is to dynamically change or adjust the turns ratio N of the transformer and the resonant capacitor C in the LLC resonant power converter. r Size.

[0070] The voltage gain of the LLC resonant power converter is expressed by equation (1), if L r L m C r If both I and N are fixed values, then the gain value is determined by the output current I. o Output voltage V o and operating frequency f s Decision, when I o V o To achieve the target value, change f s Obtain the desired gain value.

[0071]

[0072] Where K = L r / L m (Inductance ratio); (Quality Factor); (Resonant frequency); N is the turns ratio of the transformer.

[0073] This invention changes the turns ratio N by adjusting the series and parallel connections of the transformer windings. When the windings are adjusted, in addition to the change in the turns ratio, L... m L r And so it changed, C r The distance between the capacitor plates on the printed circuit board can be adjusted. When the resonant groove parameters are fixed, I... o V o Changing the Q value will change the Q value; the gain curve M(f) can be plotted based on the change in Q value. s (K,Q) and operating frequency f s The relationship diagram.

[0074] like Figure 5As shown, when the Q value changes from Q_1 to Q_2, the gain value changes from more than 1.5 to less than 1.5 (that is, the gain changes from curve 501 to curve 503), and the power converter cannot operate. If the turns ratio N is changed, the K value changes to K1, and the Q value also changes accordingly. Under the K1 parameter, the Q value changes from Q_3 to Q_4 to obtain the corresponding Q_3 and Q_4 gain values ​​(curves 511 and 513). The Q_4 gain value under the K1 parameter is greater than 1.5, which can meet the gain requirement.

[0075] Generally speaking, even if changing the series-parallel connection method of the windings does not significantly change the value of K, changing the turns ratio N will have a considerable impact on the change in the value of Q. In addition, changing the resonant capacitor C r The resonant frequency f can be changed r1 And the Q value. Therefore, by changing the turns ratio N and the resonant capacitance C r The range of output voltage can be changed significantly; this conclusion can be drawn from... Figure 5 The changes in the output voltage gain curves 511 and 513 are obtained from this.

[0076] Figure 6 This diagram shows the circuit block diagram and related operation control flow of the LLC resonant power converter. The LLC resonant power converter is used to convert the input DC voltage V in Converted to DC output voltage V o This circuit, designed to supply power to a load, includes a full-bridge / half-bridge switching circuit 601, a resonant tank and transformer circuit 603, a rectifier and filter circuit 605, and an external control circuit 607. The full-bridge / half-bridge switching circuit 601, controlled by the external control circuit 607, switches the upper or lower bridge switch to either side of the circuit. This allows the circuit to input a periodically varying switching signal to the resonant tank and transformer circuit 603, causing the current in the circuit to change sinusoidally. The rectifier and filter circuit 605, coupled to the secondary winding of the resonant tank and transformer 603, then rectifies and filters the current in the secondary winding, generating a DC current I. o And output DC voltage V o To be provided for use by the load.

[0077] The resonant tank and transformer functional block 603 includes a resonant tank (including a series-connected resonant inductor L) coupled to a full-bridge / half-bridge switching circuit 601. r Magnetizing inductance L m and resonant capacitor C rThe LLC resonant power converter includes a transformer (containing a magnetic core, primary (main and secondary) windings, and secondary windings) coupled to the resonant slot. The secondary windings of the transformer are coupled to a rectifier and filter circuit 605 (rectified via a rectifier switch). During operation of the LLC resonant power converter, the rectifier and filter circuit 605 rectifies and filters the input secondary signal (current or voltage) to convert it into DC output, providing a DC output voltage V. o The external control circuit 607 is coupled to the aforementioned full-bridge / half-bridge switching circuit 601, resonant tank and transformer 603, and rectifier-filter circuit 605. The external control circuit 607 receives output voltage feedback, output current feedback, and external communication signals (to confirm output voltage) from the LLC resonant power converter. Based on these feedbacks, it outputs switching signals to control the on / off state of the upper or lower bridge switching switch in the full-bridge / half-bridge circuit 601. Furthermore, based on the received output voltage and current feedback, it outputs corresponding resonant capacitor adjustment signals and turns ratio adjustment signals to the resonant tank and transformer, thereby dynamically adjusting the resonant capacitor C. r The size and turns ratio N of the transformer are adjusted to control the range of its output voltage and current.

[0078] In a preferred embodiment, the external control circuit 607 may be a microprocessor, a microcontroller (MCU), a digital signal processor (DSP), or a computing device with similar functions.

[0079] Basically, once the circuit topology of the LLC resonant power converter is determined, its resonant slot parameter L... r L m and C r It has been determined that it cannot be adjusted for different operating scenarios. That is, it cannot adjust the range of its output voltage and output current according to operational needs. While existing variable resonant slot LLC power converters can change the resonant slot parameters, the adjustment range is relatively small when changing the resonant slot by connecting windings in series and parallel.

[0080] This invention further designs individual transformer windings to be unequal, allowing the turns ratio to change when the windings are connected in series and parallel, thereby increasing the adjustment range of the resonant slot and eliminating the need for the power converter to change the external L. r L m and C r This will achieve the goal of widening the voltage and current range.

[0081] According to the concept of the present invention, in another embodiment, the individual transformer windings are designed to be unequal, for example, the number of turns of the primary winding is fixed, while the number of turns of the secondary winding is changed, so that the turns ratio is changed when the windings are connected in series and parallel.

[0082] In other words, according to the concept of the present invention, the primary winding and one of the secondary windings of an individual transformer have different numbers of turns, and can be dynamically selected to be electrically coupled or isolated from the resonant slot, and can be dynamically selected to be connected in series or in parallel with the primary windings of other transformers to form a dynamically changing equivalent primary winding; the number of turns of the secondary winding and one of the primary windings of each transformer is fixed and the same, so that the turns ratio in the transformer circuit can be dynamically changed accordingly.

[0083] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention and its benefits have been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications can still be made to the embodiments described above, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to depart from the scope of the claims of the present invention.

Claims

1. An LLC resonant power converter with a variable turns ratio, characterized in that, Include: A switching circuit is electrically coupled to an input DC voltage to convert the DC voltage into a switching signal; A resonant slot is electrically coupled to the switching circuit. The resonant slot consists of a resonant inductor, a magnetizing inductor, and a resonant capacitor, and is used to receive the switching signal to provide primary side current. A transformer circuit is electrically coupled to the resonant slot. This transformer circuit comprises multiple discrete transformers, each having a primary winding and a secondary winding. Among them, the primary winding and one of the secondary windings of individual transformers have different numbers of turns, and can be dynamically selected to be electrically coupled or isolated from the resonant slot, and can be dynamically selected to be connected in series or in parallel with the primary windings of other transformers to form a dynamically changing equivalent primary winding. In this system, the number of turns in one of the primary and secondary windings of each transformer is fixed and identical, allowing the turns ratio in the transformer circuit to be dynamically changed accordingly; and A rectifier and filter circuit is coupled to the transformer circuit to rectify and filter the secondary current output from the secondary winding of the transformer circuit in order to provide an output voltage. One end of the resonant inductor is electrically coupled to the switching circuit, and the other end is connected in series with the equivalent primary winding. The magnetizing inductor is connected in series with the resonant inductor, and one end of the resonant capacitor is connected in series with the magnetizing inductor, while the other end is electrically coupled to the switching circuit. The magnetizing inductor is connected in parallel with the equivalent primary winding.

2. The LLC resonant power converter with variable turns ratio according to claim 1, characterized in that, The formation of the dynamically changing equivalent primary winding is achieved by dynamically adjusting the series and parallel connection of the primary winding through multiple switch configurations.

3. The LLC resonant power converter with variable turns ratio according to claim 2, characterized in that, This switch includes various types of transistor switching assemblies and relay switches.

4. The LLC resonant power converter with variable turns ratio according to claim 3, characterized in that, The resonant inductor, the magnetizing inductor, and the turns ratio can all be dynamically adjusted through a combination of these switches.

5. The LLC resonant power converter with variable turns ratio according to claim 1, characterized in that, Both the primary winding and the secondary winding are mounted on a multilayer printed circuit board.

6. The LLC resonant power converter with variable turns ratio according to claim 5, characterized in that, It also includes an adjustable capacitor disposed in the multilayer printed circuit board, which is integrated with the primary winding and the secondary winding of the transformer to form an additional resonant capacitor.

7. The LLC resonant power converter with variable turns ratio according to claim 6, characterized in that, In this adjustable capacitor, metal plates with fixed area and size are fabricated at the same position on each layer of the multilayer printed circuit board in a selected area. Multiple metal plates and multiple dielectric layers in between are combined to form a capacitor, and integrated with the windings of the transformer to form the aforementioned additional resonant capacitor.

8. The LLC resonant power converter with variable turns ratio according to claim 7, characterized in that, The additional resonant capacitor is used to change the resonant capacitance value of the resonant slot of the LLC resonant power converter by adjusting the distance between the capacitor plates and changing the configuration of the positive and negative terminals of the capacitor plates.

9. The LLC resonant power converter with variable turns ratio according to claim 8, characterized in that, The additional resonant capacitor can be connected in parallel, in series, or completely isolated from the transformer winding by configuring multiple switches between the additional resonant capacitor and the transformer winding.

10. The LLC resonant power converter with variable turns ratio according to claim 4, characterized in that, Multiple of these switches are configured to be electrically coupled to an external controller of the LLC resonant power converter. Based on the output voltage feedback and output current feedback received by the external controller, the external controller outputs corresponding resonant capacitor adjustment signals and turns ratio adjustment signals to the resonant tank and the transformer, respectively, thereby dynamically adjusting the size of the resonant capacitor and the turns ratio of the transformer to adjust the range of the output voltage and output current of the LLC resonant power converter.

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