US-12626851-B2 - High frequency integrated planar magnetics for a bidirectional AC to DC CLLC resonant converter

US12626851B2US 12626851 B2US12626851 B2US 12626851B2US-12626851-B2

Abstract

A transformer for a power converter, comprising: a first auxiliary subcore, a central subcore, and a second auxiliary subcore, each respective subcore comprising a lower plate, at least one pair of central spacers, and an upper plate, the lower plate, at least one pair of central spacers, and the upper plate of each subcore, being respectively separated by a gap; the first auxiliary subcore and the central subcore being separated by a gap; the second auxiliary subcore and the central subcore being separated by a gap; a primary coil, encircling a first spacer of the first auxiliary subcore and a first spacer of the central subcore; and a secondary coil, encircling a second spacer of the second auxiliary subcore and a second spacer of the central subcore.

Inventors

Sunil Dube
Kalyan Yenduri
Pritam Das

Assignees

THE RESEARCH FOUNDATION FOR THE STATE UNIVERSITY OF NEW YORK

Dates

Publication Date: 20260512
Application Date: 20220701

Claims (20)

1 . A transformer for a power converter, comprising: a central subcore comprising: a central subcore lower plate, a central subcore upper plate, and first and second magnetically permeable central subcore spacers disposed between the lower plate and the upper plate, wherein: the lower plate is separated from the first and second magnetically permeable central subcore spacers by first flux decoupling gaps, and the upper plate is separated from the first and second magnetically permeable central subcore spacers by second flux decoupling gaps; a first auxiliary subcore comprising: a first auxiliary subcore lower plate, a first auxiliary subcore upper plate, and at least one first magnetically permeable auxiliary subcore spacer disposed therebetween and separated by at least one third flux decoupling gap; a second auxiliary subcore comprising: a second auxiliary subcore lower plate, a second auxiliary subcore upper plate, and at least one second magnetically permeable auxiliary subcore spacer disposed between the second auxiliary subcore lower plate and the second auxiliary subcore upper plate, and being separated by at least one fourth flux decoupling gap; a fifth flux decoupling gap separating the first auxiliary subcore and the central subcore; a sixth flux decoupling gap separating the second auxiliary subcore and the central subcore; a primary coil, encircling the first magnetically permeable auxiliary subcore spacer and the first magnetically permeable central subcore spacer; and a secondary coil, encircling the second magnetically permeable auxiliary subcore spacer and the second magnetically permeable central subcore spacer, wherein the primary coil and the secondary coil have a different number of turns.
2 . The transformer according to claim 1 , wherein the primary coil and the secondary coil are each configured to produce a central magnetic field having an axis intersecting the lower plate and the upper plate of the central subcore.
3 . The transformer according to claim 2 , wherein the magnetically permeable central subcore spacer, the first magnetically permeable auxiliary subcore spacer, and second magnetically permeable auxiliary subcore spacer each comprise at least one seventh flux decoupling gap along the axis.
4 . The transformer according to claim 2 , wherein at least one of the first and second magnetically permeable central subcore spacers, the first magnetically permeable auxiliary subcore spacer, and second magnetically permeable auxiliary subcore spacer is split along the axis by at least two eighth flux decoupling gaps.
5 . The transformer according to claim 2 , wherein each of the first and second magnetically permeable central subcore spacers is split along the axis by at least one ninth flux decoupling gap.
6 . The transformer according to claim 2 , wherein each of the first and second magnetically permeable central subcore spacers, the first magnetically permeable auxiliary subcore spacer, and second magnetically permeable auxiliary subcore spacer is split along the axis by a common number of flux decoupling gaps.
7 . The transformer according to claim 1 , wherein: the fifth flux decoupling gap separating the first auxiliary subcore and the central subcore is configured to decouple a magnetic flux therebetween; the sixth flux decoupling gap separating the second auxiliary subcore and the central subcore is configured to decouple a magnetic flux therebetween; the first auxiliary subcore is configured to provide a reluctance path to a flow of leakage flux to achieve a value of a primary-side inductance; the second auxiliary subcore is configured to provide a value of a secondary-side inductance; and the center subcore carries a flux to meet a magnetizing inductance to transfer power between the primary side to the secondary side, wherein the first auxiliary subcore and the second auxiliary subcore have different dimensions.
8 . The transformer according to claim 1 , wherein the primary coil an the secondary coil are printed circuit planar coils.
9 . A multicore transformer, comprising: a first auxiliary subcore comprising a first magnetically permeable material spacer and including a first upper plate, a first lower plate, a first upper flux decoupling gap disposed between the first upper plate and the first magnetically permeable material spacer, and a first lower flux decoupling gap disposed between the first lower plate and the first magnetically permeable material spacer; a second auxiliary subcore comprising a second magnetically permeable material spacer and including a second upper plate, a second lower plate, a second upper flux decoupling gap disposed between the second upper plate and the second magnetically permeable material spacer, and a second lower flux decoupling gap disposed between the second lower plate and the second magnetically permeable material spacer; a central subcore comprising a pair of third magnetically permeable material spacers and including a third upper plate, a third lower plate, a third upper flux decoupling gap disposed between the third upper plate and the pair of third magnetically permeable material spacers, and a third lower flux decoupling gap disposed between the third lower plate and the pair of third magnetically permeable material spacers; a first flux decoupling gap, separating the first magnetically permeable spacer of the first auxiliary subcore and a first of the pair of third magnetically permeable material spacers of the central subcore, configured to decouple a first auxiliary subcore flux and a central subcore flux; a second flux decoupling gap, separating the magnetically permeable spacer of the second auxiliary subcore and a second of the pair of third magnetically permeable material spacers of the central subcore, configured to decouple a second auxiliary subcore flux and the central subcore flux; the first auxiliary subcore and the second auxiliary subcore being separated by the central subcore; a primary coil of a primary side, encircling the first magnetically permeable material spacer of the first auxiliary subcore and the first of the pair of third magnetically permeable material spacers of the central subcore; and a secondary coil of a secondary side, encircling the second magnetically permeable material spacer of the second auxiliary subcore and the second of the pair of third magnetically permeable material spacers of the central subcore, wherein: the primary coil and the secondary coil have different numbers of turns, the first auxiliary subcore provides a reluctance path to a flow of leakage flux to achieve a primary side resonant inductance, the second auxiliary subcore provides a reluctance path to a flow of leakage flux to achieve a secondary side resonant inductance, and the central subcore carries a main flux to meet a magnetizing inductance of the multicore transformer, such that the primary side resonant inductance is defined independently of the secondary side resonant inductance.
10 . A system for inductively transferring power, comprising: a multicore transformer comprising a first auxiliary subcore, a central subcore, and a second auxiliary subcore, the first auxiliary subcore comprising: a first auxiliary magnetically permeable material portion, a first auxiliary top plate, a first auxiliary bottom plate, a first auxiliary top plate flux decoupling gap between the first auxiliary top plate and the first auxiliary magnetically permeable material portion, and a first auxiliary bottom plate flux decoupling gap between the first auxiliary bottom plate and the first auxiliary magnetically permeable material portion; the second auxiliary subcore comprising: a second auxiliary magnetically permeable material portion, a second auxiliary top plate, a second auxiliary bottom plate, a second auxiliary top plate flux decoupling gap between the second auxiliary top plate and the second auxiliary magnetically permeable material portion, and a second auxiliary bottom plate flux decoupling gap between the second auxiliary bottom plate and the second auxiliary magnetically permeable material portion; the central subcore comprising: a pair of central magnetically permeable material portions, a central top plate, a central bottom plate, a central top plate flux decoupling gap between the central top plate and the pair of central magnetically permeable material portions, and a central bottom plate flux decoupling gap between the central bottom plate and the pair of central magnetically permeable material portions; the first auxiliary subcore being separated from the central subcore by a first flux decoupling gap; the central subcore being separated from the second auxiliary subcore by a second flux decoupling gap; a primary coil encircling a magnetically permeable material portion of the first auxiliary subcore and a first of the pair of central magnetically permeable material portions; and a secondary coil encircling a magnetically permeable material portion of the second auxiliary subcore and a second of the pair of central magnetically permeable material portions, the primary coil and the secondary coil each having a different number of turns; wherein the primary coil is configured to be excited to supply a magnetizing flux of the multicore transformer at an excitation frequency; and wherein the secondary coil is configured to receive the magnetizing flux to thereby generate an electrical current in the secondary coil at the excitation frequency, wherein the first auxiliary subcore is configured to provide a reluctance path to a flow of leakage flux to achieve a primary side resonant inductance, wherein the second auxiliary subcore is configured to provide a reluctance path to a flow of leakage flux to achieve a secondary side resonant inductance, and wherein the central subcore is configured to carry a main flux to meet a magnetizing inductance of the multicore transformer, such that the primary side resonant inductance is defined independently of the secondary side resonant inductance.
11 . The system according to claim 10 , wherein the primary coil and the secondary coil are each configured to produce a central magnetic field having an axis intersecting the lower plate and the upper plate of the central subcore.
12 . The system according to claim 11 , wherein each of the first auxiliary magnetically permeable material portion, the second auxiliary magnetically permeable material portion, and the pair of central magnetically permeable material portions is split along the axis by at least one flux decoupling gap parallel to at least one of the central top plate and the central bottom plate.
13 . The system according to claim 11 , wherein at least one of the first auxiliary magnetically permeable material portion, a first of the pair of central magnetically permeable material portions, a second of the pair of central magnetically permeable material portions, and the second auxiliary magnetically permeable material portion is split along the axis by at least two flux decoupling gaps parallel to at least one of the central top plate and the central bottom plate.
14 . The system according to claim 11 , wherein each of the pair of central magnetically permeable material portions is split along the axis by at least one flux decoupling gap parallel to at least one of the central top plate and the central bottom plate.
15 . The system according to claim 11 , wherein each of the first auxiliary magnetically permeable material portion, the second auxiliary magnetically permeable material portion, and the pair of central magnetically permeable material portions is split along the axis by a plurality of flux decoupling gaps parallel to at least one of the lower plate and the upper plate, and each subcore has the same number of flux decoupling gaps parallel to at least one of the central top plate and the central bottom plate.
16 . The system according to claim 10 , wherein: the first auxiliary subcore, the central subcore, and the second auxiliary subcore are configured with a respective flux decoupling gap between the first auxiliary subcore and the central subcore, and the central core and the second auxiliary subcore, so that magnetic flux linking adjacent subcores is decoupled; the first auxiliary subcore and the second auxiliary subcore have different designs; the second auxiliary subcore is configured to provide a desired value of a secondary-side inductance; and the center subcore is configured to carry a main flux to meet a magnetizing inductance to transfer power between the first side to the second side.
17 . The system according to claim 10 , wherein: the first flux decoupling gap separating the first auxiliary subcore and the central subcore is an air gap configured to decouple a magnetic flux therebetween; and the second flux decoupling gap separating the second auxiliary subcore and the central subcore is an air gap configured to decouple a magnetic flux therebetween.
18 . The system according to claim 10 , wherein the primary coil and the secondary coil are each a planar coil.
19 . The system according to claim 10 , wherein at least a size, shape, and flux decoupling gap configuration of the first auxiliary subcore, the central subcore, and the second auxiliary subcore are optimized to meet at least a defined magnetizing inductance, a defined primary side resonant inductance, a defined secondary side resonant inductance, and a required power transfer capability.
20 . The system according to claim 10 , wherein: the first auxiliary subcore defines a first magnetically coupled path; the second auxiliary subcore defines a second magnetically coupled path; the central subcore defines a third magnetically coupled path; the first magnetically coupled path, the second magnetically coupled path, and the third magnetically coupled path being sufficiently spaced to be respectively magnetically decoupled; the primary coil is a planar primary coil, surrounding the magnetically permeable portion of the first auxiliary subcore and one of the first set of segmented magnetically permeable spacers and the third set of magnetically permeable segmented spacers, such that a magnetizing flux is induced in the third set of magnetically permeable segmented spacers to meet a magnetizing inductance of the multicore transformer and a first leakage flux is induced in the first set of magnetically permeable segmented spacers to provide a reluctance path to a flow of leakage flux to achieve a primary side resonant inductance; and the secondary coil is a planar secondary coil, surrounding the second set of segmented magnetically permeable spacers and the fourth set of magnetically permeable segmented spacers, such that the magnetizing flux in the fourth set of magnetically permeable segmented spacers is coupled to the planar secondary coil, and a second leakage flux is induced in the second set of magnetically permeable segmented spacers to provide a reluctance path to a flow of leakage flux to achieve a secondary side resonant inductance.

Description

CROSS REFERENCE TO RELATED APPLICATIONS The present application is a non-provisional of, and claims benefit of priority from, U.S. Provisional Patent Application No. 63/203,015, filed Jul. 4, 2021, the entirety of which is expressly incorporated herein by reference. STATEMENT OF GOVERNMENT RIGHTS This invention was made with support of the New York State Energy Research and Development Authority (NYSERDA) under Agreement Number 138104 and NYSERDA may have rights in the invention. FIELD OF THE INVENTION The present invention relates to the field of CLLC resonant converters, and more particularly to a bidirectional AC to DC CLLC resonant converter employing planar magnetics. BACKGROUND OF THE INVENTION Citation or identification of any reference herein, in any section of this application, shall not be construed as an admission that such reference is available as prior art to the present application. The disclosures of each reference disclosed herein, whether U.S. or foreign patent literature, or non-patent literature, are hereby incorporated by reference in their entirety in this application, and shall be treated as if the entirety thereof forms a part of this application. Such references are provided for their disclosure of technologies to enable practice of the present invention, to provide basis for claim language, to make clear applicant's possession of the invention with respect to the various aggregates, combinations, and subcombinations of the respective disclosures or portions thereof (within a particular reference or across multiple references). The citation of references is intended to be part of the disclosure of the invention, and not merely supplementary background information. The incorporation by reference does not extend to teachings which are inconsistent with the invention as expressly described herein, and is evidence of a proper interpretation by persons of ordinary skill in the art of the terms, phrase and concepts discussed herein, without being limiting as the sole interpretation available. In Electric Vehicles (EVs) and forklift battery chargers, there is a great demand for high power density and efficient bidirectional AC to DC power electronics converter, to facility use of electrical power and thereby alleviate the fuel consumption. In these applications, the power converter is connected to the grid and the battery is connected to the DC output of the converter with a high-voltage DC link connecting the AC to DC converter and the DC to DC converter. Commonly, the DC link voltage goes to >700V and DC output voltage typically varies from 25V-55V for a nominal 48V lead-acid battery following the State of Charge (SOC) of the battery. Therefore, inherently the converter requires a high step down voltage conversion. A CLLC resonant converter is the best suited for this kind of application. In this resonant converter, the magnetic elements (i.e., inductors and transformers) are integral part of the system. A reduced volume, and efficient magnetic design are desired to achieve high power density, and high efficiency resonant power converter respectively. To achieve these essential requirements, a planar magnetic structure operating at hundreds of kilohertz frequency with interleaving windings layout has been well studied. The planar transformers have a low height. Nevertheless, all these magnetic arrangements are limited to certain design specifications (i.e., turns ratio, resonant inductance, voltage, and current levels). Theoretically, in a CLLC bidirectional resonant converter, the magnetic part consists of the resonant inductor and the high frequency (HF) transformer. This converter is designed to have a soft switching across the semiconductor devices (i.e., MOSFETs, GaN) to reduce the switching loss. The series combination of capacitor and inductors on each side of the HF (e.g., 100 kHz operating frequency) transformer, along with the parallel magnetizing inductance of the transformer, form the CLLC resonant tank used for bidirectional energy transfer in the converter as shown in FIG. 1. In a transformer, there exists leakage inductance on both primary and secondary windings, due to the non-coupled portion of the magnetic flux, which can be utilized to form the series inductors on the two sides of the transformer by use of non-conventional core shapes requiring special manufacturing processes. To integrate substantial value of the series inductors, the leakage flux has to be increased. On the other hand, increased leakage flux can affect the EMI and the HF AC losses in the windings, especially when the rate of change of voltage (i.e., dv/dt) is very high (e.g., 1 kV/10 μS). CN107818865B discloses a high frequency center tap flat surface transformer for use in a LLC half bridge resonant converter, using eight layers of structure. Magnetic cores are spaced vertically by prepreg sheets on which the windings are fabricated. FR3019933A1 discloses a transformer with core elements separated b