Buck converter with dual transformers

Abstract

Systems and apparatus for a voltage converter are described. A circuit may include a plurality of switching elements, a first transformer, and a second transformer. The first transformer may be configured to receive an input voltage at a first voltage level. The first transformer may be further configured to reduce the input voltage based on a state of the plurality of switches to generate an output voltage. The output voltage may be at a second voltage level less than the first voltage level. The second transformer may be connected in parallel with the first transformer. The second transformer may be configured to perform ripple cancellation on the output voltage. The second transformer may be further configured to provide the output voltage to a load operating at a second voltage level.

Description

Technical Field

[0001] This disclosure generally relates to apparatus and devices including a buck converter, wherein the buck converter has a dual transformer configuration. Background Technology

[0002] A buck converter, or step-down converter, is a DC-DC voltage converter that transforms a higher input voltage into a lower output voltage. Buck converters can be used in a variety of applications and power systems to provide a stable power supply with a reduced voltage level. Buck converters may include switching elements such as metal-oxide-semiconductor field-effect transistors (MOSFETs), which can be rapidly turned on and off based on a switching signal. Control signals (e.g., pulse-width modulation (PWM) signals) can be used to control the output voltage by adjusting the duty cycle of the switching signal. Attached Figure Description

[0003] Figure 1 This is a diagram illustrating an example system of a buck converter with dual transformers that can be implemented in one embodiment.

[0004] Figure 2A This is a diagram illustrating a buck converter with dual transformers in one embodiment.

[0005] Figure 2B This illustrates one embodiment. Figure 2A A diagram illustrating the layout of the buck converter.

[0006] Figure 3A This is a diagram illustrating the state of a buck converter with dual transformers in one embodiment.

[0007] Figure 3B This is a diagram illustrating another state of a buck converter with dual transformers in one embodiment.

[0008] Figure 3C This is a diagram illustrating another state of a buck converter with dual transformers in one embodiment.

[0009] Figure 3D This is a diagram illustrating another state of a buck converter with dual transformers in one embodiment.

[0010] Figure 4 This is a diagram illustrating the current waveform generated by implementing a buck converter with dual transformers in one embodiment.

[0011] Figure 5A This is a diagram illustrating another buck converter with dual transformers in one embodiment.

[0012] Figure 5BThis is a diagram illustrating another buck converter with dual transformers in one embodiment.

[0013] Figure 5C This is a diagram illustrating another buck converter with dual transformers in one embodiment.

[0014] Figure 5D This is a diagram illustrating another buck converter with dual transformers in one embodiment.

[0015] Figure 5E This is a diagram illustrating another buck converter with dual transformers in one embodiment.

[0016] Figure 5F This is a diagram illustrating another buck converter with dual transformers in one embodiment.

[0017] Figure 5G This is a diagram illustrating another buck converter with dual transformers in one embodiment.

[0018] Figure 6A This is a diagram illustrating magnetic components with a stacked configuration in a buck converter with dual transformers in one embodiment.

[0019] Figure 6B This is a diagram illustrating a magnetic assembly with integrated dual transformers in a buck converter of one embodiment.

[0020] Figure 7 This is a diagram illustrating an example implementation of a rectifier in one embodiment. Detailed Implementation

[0021] In the following description, numerous specific details are set forth, such as particular structures, components, materials, dimensions, processing steps, and techniques, in order to provide an understanding of various embodiments of this application. However, those skilled in the art will understand that various embodiments of this application can be practiced without these specific details. In other instances, well-known structures or processing steps have not been described in detail to avoid obscuring the application.

[0022] Figure 1 This is a diagram illustrating an example system 100 that can implement a buck converter with dual transformers in one embodiment. System 100 may be part of devices or machines such as motherboards, computers, servers, vehicles, or other computing devices and machines that include loads operating based on a stable voltage output from a power converter. Figure 1In the example shown, system 100 may include power supply 102, controller 104, AC to DC power converter 106 (“AD / DC converter 106”), buck converter 110 and at least one load (e.g., load 114 and load 116).

[0023] Power source 102 can be configured to provide power to various components in system 100 via one or more power converters. Power source 102 can provide alternating current (AC) power to AC / DC converter 106 in the form of a voltage signal labeled AC input 120. AC / DC converter 106 can be a power converter configured to convert AC input 120 into direct current (DC) voltage labeled DC voltage 126. DC voltage 126 can be a voltage signal having a voltage level V1. AC / DC converter 106 can provide DC voltage 126 to at least one load operating at voltage level V1. As an example, AC / DC converter 106 can provide DC voltage 126 to load 116.

[0024] To supply power to other loads operating at a voltage level different from that at voltage level V1, AC / DC converter 106 can supply DC voltage 126 to a DC-DC converter to convert DC voltage 126 to another voltage level. As an example, load 114 operates at voltage level V2, where V2 is less than V1. AC / DC converter 106 can supply DC voltage 126 to buck converter 110. Buck converter 110 can be a DC-DC power converter configured to convert DC voltage 126 to DC voltage 128. DC voltage 128 can be a voltage signal having voltage level V2. Buck converter 110 can supply DC voltage 128 to load 114.

[0025] In one embodiment, the buck converter 110 may include a DC-to-AC inverter 130 (“DC / AC inverter 130”), a buck transformer circuit 132, and an AC-to-DC rectifier 134 (“AC / DC rectifier 134”). The DC / AC inverter 130 may be configured to receive a DC voltage 126 and convert it into an AC voltage, which may be processed by a transformer in the buck transformer circuit 132. The buck transformer circuit 132 may be configured to receive the AC voltage from the DC / AC inverter 130 and generate a stepped-down AC voltage (e.g., a lower voltage level). The AC / DC rectifier 134 may be configured to receive the stepped-down AC voltage and convert it into a DC voltage 128.

[0026] Controller 104 may be a microcontroller configured to generate different control signals for AC / DC converter 106 and buck converter 110. Figure 1 In the example shown, controller 104 can generate and provide a control signal for AC / DC converter 106, which is a PWM signal, denoted as PWM 122. Controller 104 can also generate and provide another control signal for buck converter 110, which is a PWM signal, denoted as PWM 124. PWM 122 can control the duty cycle of the switching signal used to turn the switching elements within AC / DC converter 106 on and off. PWM 124 can control the duty cycle of the switching signal used to turn the switching elements within buck transformer circuit 132 of buck converter 110 on and off.

[0027] In one aspect, a buck converter may include a buck ratio transformer that defines a conversion ratio for converting a higher input voltage to a lower output voltage. The conversion ratio may be defined by the ratio of the primary turns to the secondary turns of the buck ratio transformer. In a buck ratio transformer, the primary turns are greater than the secondary turns. In some aspects, multiple conversion stages may be required to convert input voltages significantly higher than the desired output voltage. For example, to convert a 48-volt (V) DC signal to 3.3V, a first conversion stage using a buck converter with a 4:1 ratio can convert 48V to 12V, and then another converter is needed to convert 12V to 3.3V.

[0028] To reduce power losses caused by this two-stage buck converter, a high-buck converter can be used, replacing two stages with a single conversion stage. Designing and implementing such a high-buck converter can present various challenges. Some solutions for high-buck converters utilize three-phase transformers. However, LLC buck converters can generate large ripple currents, and output voltage regulation becomes difficult. Other solutions encounter challenges such as complex transformer design and / or decreased efficiency with increasing conversion ratio.

[0029] To address the challenges in high-buck converters, buck converter 110 may include a dual-transformer configuration (e.g., having two different transformers). The dual-transformer configuration causes a first transformer (which may be a buck transformer) to perform voltage bucking, and a second transformer (which may be an autotransformer) to perform current multiplication for ripple current cancellation. The separation of the two transformers in buck converter 110 allows the first transformer to be tuned to adjust the buck conversion ratio without affecting the ripple current cancellation performed by the second transformer. The current within the second transformer may be quasi-DC (e.g., DC-dominated with a small AC ripple), which can reduce high-frequency line losses. Therefore, the buck ratio can be significantly increased by tuning the first transformer with minimal impact on efficiency.

[0030] Figure 2AThis is a diagram illustrating a buck converter with dual transformers in one embodiment. Figure 2A The diagram shows a buck converter 200. The buck converter 200 can be... Figure 1 The illustrated embodiment of buck converter 110. Buck converter 200 may include a plurality of switching elements QU_A, QU_B, QM_A, QM_B, QB_A, QB_B. Switching elements QU_A and QU_B may be upper-side or high-side switches, switching elements QM_A and QM_B may be intermediate switches, and switching elements QB_A and QB_B may be lower-side or low-side switches. Switching elements QU_A, QU_B, QM_A, QM_B, QB_A, and QB_B may be MOSFETs. The state (e.g., on or off) of switching elements QU_A, QU_B, QM_A, QM_B, QB_A, and QB_B may be controlled by a control signal provided by a controller (e.g., by...). Figure 1 The controller 104 shown provides PWM 124 control. In one embodiment, if the duty cycle of PWM 124 is greater than or equal to 0.5, zero-voltage switching (ZVS) can be activated for all switching elements QU_A, QU_B, QM_A, QM_B, QB_A, and QB_B.

[0031] The buck converter 200 may also include flying capacitors C1 and C2, a first transformer 210, and a second transformer 220. The high-side switching elements QU_A and QU_B and the intermediate switching elements QM_A and QM_B may be a full-bridge inverter (e.g., Figure 1 The DC / AC inverter 130 in the middle). The first transformer 210 can be Figure 1 The step-down transformer circuit 132 shown. The secondary winding 213, low-side switching elements QB_A, QB_B, and second transformer 220 can form a rectifier (e.g., Figure 1(AC / DC rectifier 134 in the example). The first transformer 210 may be a control transformer including primary windings 211, 212 and secondary winding 213. The turns ratio of the primary windings 211, 212 to the secondary winding 213 may be N:N:1, where N may be a decimal or an integer greater than 1. The primary windings 211, 212 may have the same number of turns. A flying capacitor C1 may be connected between the node between switching elements QU_A and QM_B and the primary winding 212. A flying capacitor C2 may be connected between the node between switching elements QU_B and QM_A and the primary winding 211. The series connection of the flying capacitor C1 with the first transformer 210 and the series connection of the flying capacitor C2 with the second transformer 220 can provide a voltage reduction of up to half (e.g., reducing Vin by 50%). The second transformer 220 may be an autotransformer including one winding, and the second transformer 220 may have a tap at the center point 223, such that the winding of the second transformer 220 can be divided into sections 211 and 222, and sections 211 and 222 may have a 1:1 turns ratio. The 1:1 turns ratio allows the second transformer 220 to operate in a manner similar to a current multiplier.

[0032] The first transformer 210 can be configured to process or operate on AC (e.g., capable of receiving and outputting AC), and the first transformer 210 can be a step-down transformer that provides a voltage reduction. The second transformer 220 can be configured to process or operate on AC (e.g., capable of receiving and outputting AC). The second transformer 220 can be an autotransformer. Due to the nature of an autotransformer, the current inside the second transformer 220 can be quasi-DC (e.g., DC dominant with a small AC ripple). Due to current multiplication, the second transformer 220 can also provide a voltage reduction of up to half (e.g., a 50% reduction). The step-down converter 200 can also include an output inductor L0 and an output capacitor C0. The output inductor L0 and capacitor C0 can form a standard step-down converter for voltage regulation and filtering.

[0033] The buck converter 200 can receive an input voltage (“input voltage V1”) having a first voltage level V1 at the node between switching elements QU_A and QU_B. The buck converter 200 can convert the input voltage V1 to a second voltage level V2 (“output voltage V2”), which can be provided to a load labeled as resistor R0 (“load R0”). The output voltage V2 can range from 0 V to V1. The load R0 can be a load operating at voltage level V2 (e.g., ...). Figure 1(See load 114). To convert the input voltage V1 to the output voltage V2, the first transformer 210 can step down the input voltage V1 to a voltage level V2 that is lower than V1. The first transformer 210 can step down the input voltage V1 by reducing the input voltage V1 based on the turns ratio N:N:1 of the first transformer 210. The second transformer 220 can perform current multiplication to eliminate current ripple in the output voltage V2 and provide the output voltage V2 to the load R0. The voltage gain of the buck converter 200 can be expressed as:

[0034] in, It's V2. V1 is the duty cycle of the control signal PWM 124, and N is the number of turns in the turns ratio N:N:1 of the first transformer 210.

[0035] In one embodiment, the buck converter 200 (and other variations and embodiments discussed herein) can operate in two different modes—resonant mode and PWM mode. In resonant mode, flying capacitors C1 and C2 can resonate with the leakage inductance of the first transformer 210 and the second transformer 220. The resonance between the flying capacitors C1 and C2 and the leakage inductance of the first transformer 210 can generate a sinusoidal or near-sinusoidal current through the switching elements in the buck converter 200. This sinusoidal current can result in reduced body diode conduction, voltage spikes, ringing, and switching losses. In one embodiment, the flying capacitors C1 and C2 can be designed to have a small size to increase the frequency for generating the sinusoidal current. In PWM mode, the voltage across the flying capacitors C1 and C2 can be a quasi-DC voltage, and the current across the second transformer 220 can be a quasi-DC current.

[0036] On one hand, to facilitate connections (e.g., primary winding pin swaps), conventional buck converters allow the primary winding wires to cross each other. If this crossover is located outside the first transformer 210, it must be implemented on a printed circuit board (PCB), requiring interlayer vias and long traces. Crossovers on the PCB can result in high ohmic losses in high-current applications. In the various embodiments shown herein, this crossover is implemented inside the first transformer 210. As an example, the first transformer 210 may allow the primary winding wires 211, 212 to cross at crossover point 215 internally (e.g., inside the first transformer 210). (Refer to...) Figure 2BThe layout 230 of the buck converter 200 allows all components to be mounted on the same side of the PCB (including mounting the first transformer 210 as a separate component). Since the primary windings 211 and 212 cross inside the first transformer 210, the primary windings 211 and 212 do not need to span different layers of the PCB. The layout 230 of the buck converter 200 reduces energy loss by minimizing PCB wiring and vias.

[0037] Figure 3A This is a diagram illustrating the state of a buck converter with dual transformers in one embodiment. Figure 3A The diagram shows a buck converter (e.g., Figure 1 State 300 (110 in Figure 1 or 200 in Figure 2). State 320 can be activated in response to the buck converter's duty cycle being equal to 0.5. In state 300, switching elements QU_A, QM_A, and QB_A are turned on, while QU_B, QM_B, and QB_B are turned off. In state 300, flying capacitor C1 can be charged, and flying capacitor C2 can be discharged. Figure 3A The circuit model 301 for state 300 is also shown. Comparing state 300 with circuit model 301, the input voltage V1 is Vin, the primary winding 211 is P1, the primary winding 212 is P2, the secondary winding 213 is S1, and segments 221 and 222 are segments T2A and T2B, respectively. The current flow direction in state 300 is... Figure 3A The arrows indicate this. In state 300, current can flow from V1 (or Vin) towards node 302 between primary windings 211, 212 (or P1, P2), then towards node 304 between node 302 and secondary winding 213 (or S1), and then towards node 306 at the center tap (e.g., center point 223) of the second transformer 220 between T2A and T2B. This current flow in state 300 can charge flying capacitor C1 and discharge flying capacitor C2.

[0038] Figure 3B This is a diagram illustrating another state of a buck converter with dual transformers in one embodiment. Figure 3B The diagram shows a buck converter (e.g., Figure 1 State 310 (either 110 in Figure 2 or 200 in Figure 2). State 310 can be activated in response to the buck converter's duty cycle being equivalent to 0.5. Note that when the buck converter's duty cycle is 0.5, Figure 3A State 300 and Figure 3BState 310 is a complementary state. In state 320, switching elements QU_B, QM_B, and QB_B are turned on, while QU_A, QM_A, and QB_A are turned off. In state 310, flying capacitor C1 can discharge, and flying capacitor C2 can charge. Figure 3B The circuit model 311 for state 310 is also shown. Comparing state 310 with circuit model 311, the input voltage V1 is Vin, the primary winding 211 is P1, the primary winding 212 is P2, the secondary winding 213 is S1, and segments 221 and 222 are segments T2A and T2B, respectively. The current flow direction in state 310 is... Figure 3B The arrows indicate this. In state 310, current can flow from V1 (or Vin) towards node 312 between the primary windings 211, 212 (or P1, P2), then towards node 314 between node 312 and the secondary winding 213 (or S1), and then towards node 306 at the center tap (e.g., center point 223) of the second transformer 220 between T2A and T2B. The current flow in state 310 can discharge the flying capacitor C1 and charge the flying capacitor C2.

[0039] Figure 3C This is a diagram illustrating another state of a buck converter with dual transformers in one embodiment. Figure 3C The diagram shows a buck converter (e.g., Figure 1 State 320 (132 in Figure 2 or 200 in Figure 2). State 320 can be activated in response to the buck converter's duty cycle being greater than 0.5. In state 320, switching elements QU_A and QU_B are turned on, while QM_A, QM_B, QB_A, and QB_B are turned off. Further, in state 320, flying capacitors C1 and C2 can be charged, and the first transformer 210 can be short-circuited. Figure 3C The circuit model 321 for state 320 is also shown. Comparing state 320 with circuit model 321, the input voltage V1 is Vin, and segments 221 and 222 are segments T2A and T2B, respectively. The current flow direction in state 320 is... Figure 3C As indicated by the arrows. In state 320, current can flow from V1 (or Vin) toward node 306, which is located at the center tap (e.g., center point 223) of the second transformer 220 between T2A and T2B. The current flow in state 320 can charge flying capacitors C1 and C2.

[0040] Figure 3D This is a diagram illustrating another state of a buck converter with dual transformers in one embodiment. Figure 3D The diagram shows a buck converter (e.g., Figure 1State 330 (110 in Figure 2 or 200 in Figure 2). State 330 can be activated in response to the duty cycle of the buck converter being less than 0.5. In state 330, switching elements QB_A and QB_B are turned on, while QU_A, QU_B, QM_A, and QM_B are turned off. Further, in state 330, flying capacitors C1 and C2 can be in an open circuit, and the first transformer 210 can be short-circuited. Figure 3D The circuit model 331 for state 330 is also shown. Comparing state 330 with circuit model 331, segments 221 and 222 are segments T2A and T2B, respectively. The current flow direction in state 330 is... Figure 3D As indicated by the arrow. In state 330, current can flow toward node 306, which is located at the center tap (e.g., center point 223) of the second transformer 220 between T2A and T2B.

[0041] Figure 4 This is a diagram illustrating the current waveform generated by implementing a buck converter with dual transformers in one embodiment. Figure 4 The diagram shows a set of current waveforms 400 that vary with time. Waveform 400 shows the current changing over time with respect to the primary windings 211 and 212 of the first transformer 210 in Figure 2, the secondary winding 213 of the first transformer 210 in Figure 2, and the winding 221 of the second transformer 220. As shown in waveform 400, the currents on the primary windings 211 and 212 of the first transformer 210 can change at the same rate. The current on the second winding 213 can also change with the currents on the primary windings 211 and 212, but in the opposite direction (e.g., when the currents on the primary windings 211 and 212 are positive, the current on the secondary winding 213 is negative, and vice versa). Further, Figure 4 The current on winding 221 of the second transformer shown is similar to a quasi-DC current.

[0042] Figure 5A This is a diagram illustrating another buck converter with dual transformers in one embodiment. Figure 5A The diagram shows a buck converter 500. The buck converter 500 can be... Figure 1 The illustrated embodiment of the buck converter 110. The buck converter 500 can be... Figure 2AA variation of the buck converter 200 is shown. The buck converter 500 may include flying capacitors C1 and C2, a first transformer 210, and a second transformer 220. In the buck converter 500, the flying capacitor C1 may be connected between the node between switching elements QM_A and QB_B and the primary winding 212. Further, in the buck converter 500, the flying capacitor C2 may be connected between the node between switching elements QM_B and QB_A and the primary winding 211. The voltage gain of the buck converter 500 can be expressed as:

[0043] in, It's V2. V1 is the duty cycle of the control signal PWM 124, and N is the number of turns in the turns ratio N:N:1 of the first transformer 210.

[0044] Figure 5B This is a diagram illustrating another buck converter with dual transformers in one embodiment. Figure 5B The diagram shows a buck converter 510. The buck converter 510 can be... Figure 1 The illustrated embodiment of the buck converter 110. The buck converter 510 can be... Figure 2A A variation of the buck converter 200 is shown. Buck converter 510 may include flying capacitors C1 and C2, a first transformer 210, a second transformer 220, and diodes D1 and D2. In buck converter 510, flying capacitor C1 may be connected between the node between switching elements QM_A and QB_B and the primary winding 212. Further, in buck converter 500, flying capacitor C2 may be connected between the node between switching elements QM_B and QB_A and the primary winding 211. The voltage gain of buck converter 500 can be expressed as:

[0045] in, It's V2. V1, D is the duty cycle of the control signal PWM 124, and N is the number of turns in the turns ratio N:N:1 of the first transformer 210. Adding diodes D1 and D2 provides a buffer circuit that prevents overvoltage by clamping the voltage across the low-side switching elements QB_A and QB_B to half of Vin (or half of V1, or 0.5V1).

[0046] Figure 5C This is a diagram illustrating another buck converter with dual transformers in one embodiment. Figure 5C The diagram shows a buck converter 520. The buck converter 520 can be... Figure 1The illustrated embodiment of buck converter 110. Buck converter 520 may be... Figure 2A The illustrated buck converter 200 is a variant. Buck converter 520 may include flying capacitors C1, C2, C3, C4, a first transformer 210, a second transformer 220, and multiple switching elements QU_A, QU_B, QM1_A, QM2_A, QM1_B, QM2_B, QB_A, and QB_B. The switching elements in buck converter 520 may be MOSFETs, and the states of the switching elements may be controlled by a control signal provided by a controller (e.g., by...). Figure 1 The controller 104 shown provides PWM 124 control. In one embodiment, if the PWM 124 has a duty cycle greater than or equal to 0.5, zero-voltage switching (ZVS) can be activated for all switching elements in the buck converter 520.

[0047] In the buck converter 520, flying capacitor C1 can be connected between the node between switching elements QM1_B and QM2_A and the primary winding 212. Flying capacitor C2 can be connected between the node between switching elements QM1_A and QM2_B and the primary winding 211. Flying capacitor C3 can be connected between the node between switching elements QU_A and QM1_B and the primary winding 211. Flying capacitor C4 can be connected between the node between switching elements QU_B and QM1_A and the primary winding 212. The voltage gain of the buck converter 520 can be expressed as:

[0048] in, It's V2. V1, D is the duty cycle of the control signal PWM 124, and N is the number of turns in the N:N:1 turns ratio of the first transformer 210. (Refer to...) Figure 2A , Figure 5A and Figure 5B Buck converter 520 includes eight switching elements, while buck converters 200, 500, and 510 include six switching elements. The additional switching elements in buck converter 520 can provide a higher buck ratio compared to embodiments with six switching elements. Therefore, embodiments with fewer switching elements use fewer components, while embodiments with more switching elements provide a higher buck ratio.

[0049] Figure 5D This is a diagram illustrating another buck converter with dual transformers in one embodiment. Figure 5D The diagram shows a buck converter 530. The buck converter 530 can be... Figure 1 The illustrated embodiment of the buck converter 110. The buck converter 530 can be... Figure 2AA variation of the buck converter 200 shown. The buck converter 530 may include flying capacitors C1, C2, C3, C4, a first transformer 210, a second transformer 220, and multiple switching elements QU_A, QU_B, QM1_A, QM2_A, QM1_B, QM2_B, QB_A, and QB_B.

[0050] In the buck converter 530, a flying capacitor C1 can be connected between the node between switching elements QM1_B and QM2_A and the primary winding 212. A flying capacitor C2 can be connected between the node between switching elements QM1_A and QM2_B and the primary winding 211. A flying capacitor C3 can be connected between the node between switching elements QU_A and QM1_B and section 221 of the second transformer 220. A flying capacitor C4 can be connected between the node between switching elements QU_B and QM1_A and section 222 of the second transformer 220. The voltage gain of the buck converter 520 can be expressed as:

[0051] in, It's V2. V1, D is the duty cycle of the control signal PWM 124, and N is the number of turns in the turns ratio N:N:1 of the first transformer 210. Connecting the flying capacitors C3 and C4 to the second transformer 220 can prevent overvoltage by clamping the voltages of the high-side switching elements QU_A and QU_B and the low-side switching elements QB_A and QB_B to 0.2Vin (or 0.2V1).

[0052] Figure 5E This is a diagram illustrating another buck converter with dual transformers in one embodiment. Figure 5E The diagram shows a buck converter 540. The buck converter 540 can be... Figure 1 The illustrated embodiment of the buck converter 110. The buck converter 540 can be... Figure 2AA variation of the buck converter 200 is shown. The buck converter 540 may include flying capacitors C1 and C2, a first transformer 210, a second transformer 220, and snubber circuits 542 and 544. In the buck converter 540, flying capacitor C1 may be connected between the node between switching elements QU_A and QM_B and the primary winding 212. Flying capacitor C2 may be connected between the node between switching elements QU_B and QM_A and the primary winding 211. Snubber circuit 542 may be connected between the node between switching elements QU_A and QM_A and the source terminal of switching element QB_B. Snubber circuit 544 may be connected between the node between switching elements QU_B and QM_B and the source terminal of switching element QB_A. Adding snubber circuits 542 and 544 can prevent overvoltage by clamping the voltage across the low-side switching elements QB_A and QB_B to half of Vin (or half of V1, or 0.5V1).

[0053] Figure 5F This is a diagram illustrating another buck converter with dual transformers in one embodiment. Figure 5F The diagram shows a buck converter 550. The buck converter 550 can be... Figure 1 The illustrated embodiment of the buck converter 110. The buck converter 550 can be... Figure 2A A variation of the buck converter 200 is shown. The buck converter 550 may include flying capacitors C1 and C2, a first transformer 210, a second transformer 220, and snubber circuits 552 and 554. In the buck converter 550, flying capacitor C1 may be connected between the node between switching elements QU_A and QM_B and the primary winding 212. Flying capacitor C2 may be connected between the node between switching elements QU_B and QM_A and the primary winding 211. Snubber circuit 552 may be connected between the source terminal of switching element QB_B and the gate of switching element QM_A. Snubber circuit 544 may be connected between the source terminal of switching element QB_A and the gate of switching element QM_B. Adding snubber circuits 552 and 554 can prevent overvoltage by clamping the voltage across the low-side switching elements QB_A and QB_B to half of Vin (or half of V1, or 0.5V1).

[0054] Figure 5G This is a diagram illustrating another buck converter with dual transformers in one embodiment. Figure 5G The diagram shows a buck converter 560. The buck converter 560 can be... Figure 1 The illustrated embodiment of the buck converter 110. The buck converter 560 can be... Figure 2AA variation of the buck converter 200 is shown. Buck converter 560 may include flying capacitors C1 and C2, a first transformer 210, a second transformer 220, and k parallel output blocks from block 562-1 to 562-k. In buck converter 560, flying capacitor C1 may be connected between the node between switching elements QU_A and QM_B and the primary winding 212. Flying capacitor C2 may be connected between the node between switching elements QU_B and QM_A and the primary winding 211. Each of the k parallel output blocks may include a copy of secondary winding 213 (including 213-1 to 213-k) and copies of segments 221 and 222 (including 221-1, 222-1 to 221-k, 222-k). The k parallel output blocks can shunt large output currents and reduce ohmic losses in buck converter 560.

[0055] Figure 6A This is a diagram illustrating stacked magnetic components in a buck converter with dual transformers in one embodiment. Figure 6A The diagram shows a magnetic assembly 600 with five input / output (I / O) pins P1, P2, P3, P4, and P5. The magnetic assembly can be part of a buck converter (e.g., one of the buck converters 110, 200, 500, 510, 520, 530, 540, 550, and 560 described herein). The five I / O pins can reduce the PCB layout complexity of the buck converter. The magnetic assembly 600 can have, as shown... Figure 6A The stacking configuration 602 shown is described. The stacking configuration 602 of the magnetic assembly 600 may include a magnetic core composed of a magnetic material 604, wherein the magnetic material 604 may be ferrite or other magnetic materials. Primary windings 211, 212, secondary winding 213, and winding segments 221, 222 may be wound around or surrounded by the magnetic core composed of the magnetic material 604. The magnetic material 604 may also isolate the first transformer 210 from the second transformer 220. This can minimize the coupling factor between the first transformer 210 and the second transformer 220. The stacking configuration 602 can reduce the overall size, simplify PCB layout, and reduce overall cost.

[0056] Figure 6B This is a diagram illustrating a magnetic assembly with integrated dual transformers in a buck converter of one embodiment. Figure 6A The magnetic component 600 can have, for example Figure 6BThe integrated dual transformer configuration 610 shown. The integrated dual transformer configuration 610 of the magnetic assembly 600 may include a first magnetic core composed of magnetic material 604 and a second magnetic core composed of material 612, wherein magnetic materials 604 and 612 may be ferrite or other magnetic materials. Primary windings 211 and 212 and secondary winding 213 may be wound around or surrounded by the first magnetic core composed of magnetic material 604. Winding segments 221 and 222 may be wound around or surrounded by the second magnetic core composed of magnetic material 612. The integrated dual transformer configuration 610 can minimize the coupling factor between the first transformer 210 and the second transformer 220.

[0057] Figure 7 This is a diagram illustrating an example implementation of a rectifier in one embodiment. In one embodiment, the secondary winding 213 of the first transformer 210, the second transformer 220, and the low-side switching elements QB_A and QB_B can form a rectifier 700. The rectifier 700 can be... Figure 1 The embodiment of AC / DC rectifier 134 is shown. Rectifier 700 can be configured to perform output ripple current cancellation, can handle quasi-DC current in the second transformer 220, and can perform current multiplication. Rectifier 700 can also be used in a variety of applications (e.g., Figure 7 The LLC converter 702 shown is illustrated.

[0058] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, the singular forms “a,” “an,” and “the” also include the plural forms unless the context clearly indicates otherwise. It should further be understood that the terms “comprises” and / or “comprising,” when used in this specification, specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0059] All means or steps plus functional elements (if any) in the appended claims are intended to include corresponding structures, materials, actions, and equivalents for performing functions in combination with other claimed elements, as specifically claimed. The description of the invention has been made for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the forms disclosed. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Embodiments have been chosen and described to best illustrate the principles and practical application of the invention, and to enable others skilled in the art to understand the invention, and various suitable modifications to the various embodiments for the particular application considered.

Claims

1. A circuit comprising: Multiple switching elements; The first transformer is configured as follows: Receives an input voltage at the first voltage level; as well as The input voltage is reduced based on the states of the plurality of switches to generate an output voltage, wherein the output voltage is at a second voltage level, the second voltage level being lower than the first voltage level; A second transformer is connected in parallel with the first transformer, and the second transformer is configured as follows: Ripple cancellation is performed on the output voltage; and The output voltage is provided to a load operating at the second voltage level.

2. The circuit according to claim 1, wherein: The first transformer is a step-down transformer; and The second transformer is an autotransformer.

3. The circuit according to claim 1, wherein, The first transformer includes: First primary winding; The second primary winding; and The secondary winding has a turns ratio of N:N:1 between the first winding and the second primary winding and the secondary winding.

4. The circuit according to claim 3, wherein, The ratio of the first voltage level to the second voltage level depends on N and the duty cycle of the switching signal used to control the state of the plurality of switches.

5. The circuit according to claim 1, wherein, The second transformer has a tap at the center point, and the turns ratio of the second transformer is 1:

1.

6. The circuit according to claim 1, wherein, The pin swapping of the two primary windings in the first transformer allows the components of the circuit to be placed on the same layer of the PCB without interlayer routing.

7. A power converter, comprising: An inverter is configured to receive a direct current (DC) voltage and convert the DC voltage into an alternating current (AC) voltage having a first voltage level. The first transformer is configured as follows: Receive the AC voltage from the inverter; as well as The AC voltage is reduced to generate an AC output voltage, wherein the AC output voltage is at a second voltage level, which is lower than the first voltage level; The rectifier includes a second transformer connected in parallel with the first transformer, the rectifier being configured to receive the AC output voltage and convert the AC output voltage into a DC output voltage, and the second transformer being configured to perform ripple cancellation on the DC output voltage.

8. A system comprising: The controller is configured to generate control signals; Power converter, including: An inverter is configured to receive a direct current (DC) voltage and convert the DC voltage into an alternating current (AC) voltage having a first voltage level. The first transformer is configured as follows: Receive the AC voltage from the inverter; and The control signal is used to reduce the AC voltage to generate an AC output voltage, wherein the AC output voltage is at a second voltage level, which is lower than the first voltage level; The rectifier includes a second transformer connected in parallel with the first transformer, the rectifier being configured to receive the AC output voltage and convert the AC output voltage into a DC output voltage, and the second transformer being configured to perform ripple cancellation on the DC output voltage.

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