BACKGROUND The present invention, in some embodiments thereof, relates to a power converter, and more specifically, but not exclusively, to a power converter for an on-board charger of an electric vehicle.

Vehicle electrification is being promoted by many local and national governments in response to the urgent need for reducing fossil fuel consumption and emissions of carbon dioxide and other greenhouse gases and harmful particulates from the transportation sector. To help accelerate the acceptance of electric vehicles, low-cost on-board chargers are highly desirable. In addition, chargers with bidirectional power flow capability can enhance the functionality and value of the vehicles by providing additional capabilities.

An ideal on-board charger should have high power density and high efficiency in order to have the highest energy utilization and facilitate packaging. One of the most important requirements of the on-board charger is efficiency. Currently, known on-board chargers can achieve efficiency of no more than 96.5%.

A solution commonly used in the market is single stage power conversion. Single stage power conversion means that one converter implements both the function of power factor correction and DC/DC conversion. The control and driver for single stage power conversion apparatuses are complicated. Another solution is a two-stage power conversion, where the power factor correction and DC/DC conversion work separately. The main issue with this approach is that the power needs to be converted two times, which requires narrow output voltage range and reduced system efficiency.

SUMMARY

It is an object of the present invention to provide a new topology of a 1.5 stage variable gain partial control power converter and its control method, with high efficiency. The expected peak efficiency is 98%. The output voltage is partially controlled, and the portion of the output voltage that is partially controlled can be configured as different output voltage. This function allows for a very high range of output power. It is another object of the present invention to provide a method for power conversion that provides a high range of output power at high efficiency.

The foregoing and other objects are achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

Unless otherwise defined, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

According to a first aspect, a power converter comprises an input power source, a transformer isolated open loop converter comprising at least one primary winding and a plurality of secondary windings, and a plurality of DC/DC closed loop converters, wherein an input of each of the DC/DC closed loop converters is connected to an output of a respective secondary winding. Each of the plurality of DC/DC closed loop converters is switchable between a straight-through operating state and a closed-loop operating state. An output voltage of two or more DC/DC closed loop converters is connected in series to determine an output voltage of the power converter. The output voltage of the power converter is controllable based on whether each of the plurality of DC/DC closed loop converters is in the straight through operating state or the closed loop operating state. An advantage of this topology is that the full range of load efficiency is high, and most of the power is converted by the open loop topology and the closed-loop converter in the through state. The closed loop control topology converts only a small portion of the power, and the closed- loop topology with a straight-through state has a high power density. By increasing the proportion of the output power in the through state, the power converter achieves high efficiency and a high range of output power.

In another possible implementation of the power converter according to the first aspect, the plurality of DC/DC closed loop converters comprises at least one voltage step down converter. Advantageously, the voltage step down converter may be used to step down the voltage from a high voltage input to a lower voltage required by an electric vehicle battery.

In another possible implantation of the power converter according to the first aspect, at least 90% of the output voltage derives from a DC/DC closed loop converter in a straight-through operating state. Advantageously, deriving a large percentage of the output with a converter in the straight-through operating state promotes efficiency of the conversion.

In another possible implementation of the power converter according to the first aspect, at least 98% of the output voltage derives from a DC/DC closed loop converter in the straight-through operating state when the output voltage of the power converter is 380 V dc. Advantageously, the power converter may be configured to achieve this maximum efficiency at a voltage commonly used for on-board chargers of electric vehicles.

In another possible implementation of the power converter according to the first aspect, an electric vehicle with an on-board charger incorporates the power converter. Advantageously, the on-board charger may be used to power a battery of an electric vehicle.

According to a second aspect, a power converter comprises an input power source, and a plurality of DC/DC closed loop converters connected in series to the input power source. Each of the plurality of DC/DC closed loop converters is switchable between a straight-through operating state and a closed-loop operating state. A transformer isolated open loop converter comprises a plurality of primary windings and at least one secondary winding. An output of each of the plurality of DC/DC closed loop converters is connected to a respective primary winding and bridged into a bridge circuit. An output voltage of the transformer isolated open-loop converter defines an output voltage of the power converter. The output voltage of the power converter is controllable based on whether each of the plurality of DC/DC closed loop converters is in the straight through operating state or the closed loop operating state. An advantage of this topology is that the full range of load efficiency is high, and most of the power is converted by the open loop topology and the closed-loop converter in the through state. The closed loop control topology converts only a small portion of the power, and the closed-loop topology with a straight-through state has a high power density. By increasing the proportion of the output power in the through state, the power converter achieves high efficiency and a high range of output power.

In another possible implementation of the power converter according to the second aspect, the plurality of DC/DC closed loop converters comprises two DC/DC closed loop converters and the plurality of primary windings comprises two primary windings. Advantageously, the use of exactly two closed loop converters and two primary windings within the topology of the power converter allows for high efficiency power conversion with a minimum of required space and a minimum of power losses.

In another possible implementation of the power converter according to the second aspect, the plurality of DC/DC closed loop converters comprises at least one voltage step down converter. Advantageously, the voltage step down converter may be used to step down the voltage from a high voltage input to a lower voltage required by an electric vehicle battery.

In another possible implementation of the power converter according to the second aspect, an input voltage of the input power source is between 40 and 60 V dc, the output voltage of the power converter is between 0.6 and 1.1 V dc, and the output current of the power converter is 300 A. These values provide one exemplary embodiment for the delivery of power to an output of the power converter.

In another possible implementation of the power converter according to the second aspect, at least 90% of the output voltage derives from a DC/DC closed loop converter in a straight- through operating state. Advantageously, deriving a large percentage of the output with a converter in the straight-through operating state promotes efficiency of the conversion.

According to a third aspect, a method of converting power comprises inputting power into a power converter comprising a transformer isolated open loop converter and a plurality of DC/DC closed loop converters. Either (i) the transformer isolated open loop converter comprises at least one primary winding and a plurality of secondary windings, and an input of each of the plurality of DC/DC closed loop converters is connected to an output of a respective secondary winding; or (ii) the plurality of DC/DC closed loop converters is connected in series to an input power source, the transformer isolated open loop converter comprises a plurality of primary windings and at least one secondary winding, and an output of each of the plurality of DC/DC closed loop converters is connected to a respective primary winding. The method further comprises setting at least one of the plurality of DC/DC closed loop converters in the straight through operating state and at least one of the plurality of DC/DC closed loop converters in the closed- loop operating state, so that the power converter will output power in accordance with a predetermined output voltage. The method further comprises transmitting power through the transformer isolated open loop converter and plurality of DC/DC closed loop converters; bridging the power output from the plurality of DC/DC closed loop converters; and outputting converted power from the power converter.

An advantage of the disclosed method is that the full range of load efficiency is high. Most of the power is converted by the open loop topology and the closed-loop converter in the through state. The closed loop control topology converts only a small portion of the power, and the closed- loop topology with a straight-through state has a high power density. By increasing the proportion of the output power in the through state, the method achieves high efficiency and a high range of output power.

In another possible implementation of the method according to the third aspect, the plurality of DC/DC closed loop converters comprise at least one voltage step down converter. Advantageously, the voltage step down converter may be used to step down the voltage from a high voltage input to a lower voltage required by an electric vehicle battery.

In another possible implementation of the method according to the third aspect, the outputting step comprises outputting a voltage of between 0 and 500 volts. Advantageously, the method may be used to output specific voltages as required by any particular battery of an electric vehicle.

In another possible implementation of the method according to the third aspect, the method further comprises transmitting at least 90% of the outputted converted power through a DC/DC closed loop converter in the straight through operating state. Advantageously, deriving a large percentage of the output with a converter in the straight-through operating state promotes efficiency of the conversion.

In another possible implementation of the method according to the third aspect, the method further comprises achieving a straight-through power ratio of at least 98% when the output voltage of the power converter is 380 V dc. Advantageously, the method achieves this maximum efficiency at a voltage commonly used for on-board chargers of electric vehicles.

Other systems, methods, features, and advantages of the present disclosure will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present disclosure, and be protected by the accompanying claims. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the invention. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the invention may be practiced.

In the drawings:

FIG. 1 is a schematic block diagram of a power converter according to embodiments of the invention;

FIG. 2 is a more detailed block diagram of the power converter of FIG. 1;

FIG. 3 is a chart depicting a power output function of the high power converter of FIG. 1; FIG. 4 is a chart depicting a mode switching scheme of the power converter of FIG. 1; FIG. 5 is a chart depicting the straight through power ratio of the power converter of

FIG. 1;

FIG. 6 is a chart comparing the efficiency of the power converter of FIG. 1 with the efficiency of a prior art CLLC topology;

FIG. 7 is a schematic block diagram of a second embodiment of a power converter, according to embodiments of the invention;

FIG. 8 is a more detailed block diagram of the power converter of FIG. 7; and

FIG. 9 is a chart depicting the mode switching scheme of the high efficiency converter of FIG. 7; and

FIG. 10 is a schematic diagram showing the power converter of embodiments of the invention installed within an on-board charger of an electric vehicle. DETAIFED DESCRIPTION

The present invention, in some embodiments thereof, relates to a power converter, and more specifically, but not exclusively, to a power converter for an on-board charger of an electric vehicle.

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details of construction and the arrangement of the components and/or methods set forth in the following description and/or illustrated in the drawings and/or the Examples. The invention is capable of other embodiments or of being practiced or carried out in various ways.

Referring to FIG. 1, a schematic block diagram of power converter 100 is disclosed. Power converter 100 is a 1.5 stage variable gain power converter. As used in this disclosure, the term“1.5 stage” refers to a topology in which all of the input power is converted through a first power conversion stage, but only a portion of the power is converted through a second power conversion stage.

In the embodiment of FIG. 1, power is input from input power source 101 to transformer isolated open loop converter 104. A capacitor Cl at input power source 101 may regulate the power entering the transformer isolated open loop converter 104 to limit the effects of random fluctuations.

Input power source 101 is a source of DC power. In cases in which the power converter utilizes AC power (e.g., standard wall power), the power converter 100 may also comprise rectification circuitry (not shown) for converting the AC input voltage and current into DC form. The input converter may also comprise power-factor-correcting circuitry (also not shown).

Transformer isolated open loop converter 104 consists of a primary winding 106 and a plurality of secondary windings 108a-n. In the illustrated embodiment, there are a plurality of primary windings 106 as well. In such embodiments, the primary windings 106 deliver power at the same voltage and are functionally equivalent. By contrast, secondary windings 108a-n differ in their output voltages, as will be discussed further herein.

As used in the pending disclosure, the notation [reference numeral] a-n indicates that there may be up to an infinite number of identical elements connected in parallel. In theory, the number of identical elements may be bounded only by considerations of size. Increasing the number of elements may promote the ability of the power converter 100 to regulate an output voltage at maximum efficiency. In the illustrated embodiments, there are two identical elements, denoted by the notation [reference numeralja and [reference numeral]!). As will be discussed further herein, power converter 100 converts at high efficiency even with only two such identical elements.

After the power is converted through the transformer isolated open loop converter, the rectified voltage is passed through closed loop topology 112. Closed loop topology 112 comprises a plurality of DC/DC closed loop converters 114a-n. An input of each of the DC/DC closed loop converters 114 is connected to an output of a respective secondary winding 108.

Each of the DC/DC closed loop converters 114 of the closed loop topology 112 can be switched between a straight-through operating state and a closed-loop operating state. In the straight-through operating state, the switches of the closed-loop converter 114 (not shown in FIG. 1) are configured so that power passes directly through closed loop converter 114 without being modified. In the closed-loop state, the power is controlled according to the configuration of the switches in order to achieve a desired voltage. For example, the DC/DC closed loop converter 114 may be a voltage step down converter, and the output voltage may be regulated in accordance with the duty cycle of the voltage step down converter. A voltage step down converter may also be referred to as a buck converter. Alternatively, the DC/DC closed loop converter may be of any other configuration known to those of skill in the art, such as a forward converter, a flyback converter, a push-pull converter, a boost converter, or a buck-boost converter.

Power is distributed between the DC/DC closed loop converters 114 in such a way that most of the power is converted by the transformer isolated open loop converter 104 and the DC/DC closed loop converter 114 when it is in the straight-through state. The closed-loop control topology converts only a small portion of the power. The closed-loop topology with a straight-through state has a high power density. Following processing of the power through the closed loop topology 112, the output power is connected in series and delivered to the load (represented schematically by trace 117 with capacitor 118).

FIG. 2 depicts a circuit diagram of power converter 100. As depicted in FIG. 2, capacitor Cl is situated at the input 101. Transformer isolated open loop converter 104 may include open- loop FFC topology 102. The open-loop FFC topology 102 includes transistors Ql, Q2, Q3, and Q4, as well as capacitor C3. In the illustrated embodiments, each of the transistors is depicted as an n-channel MOSFET (metal-oxide semiconductor field effect transistor). Fow-voltage MOSFETs may be used in order to minimize conduction losses. The transistors are each configurable between an off state, in which current does not flow through the transistors, and an on state, in which current proceeds through the transistors to the primary winding 106. Open loop LLC topology 102 always works at the resonance point.

Transformer isolated open loop converter 104 has three windings, primary winding 106 (also labeled Nl) and secondary windings 108a and 108b (also labeled N2 and N3). The output voltage of the two secondary windings N2, N3 is then bridged and rectified with transistors Q5- Q12. Transistors Q5-Q12 are also depicted as n-channel MOSFETs. The output voltage is then connected to two buck circuits 114a, 114b. Buck circuits 114a, 114b may also be referred to as voltage step down circuits. Capacitors C4 and C5 are situated between transistors Q5-Q12 and buck circuits 114.

Transistors Q1-Q4, Q5-Q8, and Q9-Q12 are the main switching devices of the open loop LLC converter 104. The switching frequency is fixed and is equal to the resonant frequency of the open loop LLC converter 104. The duty cycle for the open loop LLC converter 104 is fixed at approximately 50%. The switching frequency and duty cycle for transistors Q1-Q12 remains the same regardless of changes in input and output voltage.

Each buck circuit 114 includes two transistors Q13 and Q14 or Q15 and Q16, inductor LI or L2, and capacitor C6 or C7. The transistors serve as switches. When the buck circuit 1 14 is in a straight-through operating state, transistors Q13 and Q14, and transistors Q15 and Q16, are configured in a through state, in which one of the paired transistors is always in an on state, while the other is always in an off state. By contrast, when buck circuit 114 is in a closed loop operating state, the transistors Q13 and Q14, and Q15 and Q16 are in a switching state, and switch on and off in accordance with closed loop control feedback from the output of the buck circuit 114.

Advantageously, configuring a plurality of buck circuits 114 in this fashion helps minimize power losses. The switching of a buck circuit in a closed loop control state causes loss of energy due to various factors, such as switching loss and conduction loss. Switching loss refers to losses while the transistors Q13 and Q14, or Q15 and Q16, are transitioning from an off state to a fully on state. Conduction loss refers to voltage drop due to the functioning of the transistors Q13-Q16 themselves, when they are in the on position. In addition, inductors LI, L2 work in a large ripple current state, which has great AC loss and core loss. When a voltage step down converter 114 is in the through state, by contrast, switching loss is zero, and only one device’s conduction loss exists. In addition, the inductance also works in a no ripple current state, and therefore does not have AC loss and core loss.

The output voltage of each of the buck circuits 114 is then connected in series and delivered to the load (not shown). The load may be a battery for an electric vehicle, for example.

The basic principle of operation of power converter 100 is thus based on a quasi-parallel architecture scheme, adding a closed-loop topology with straight-through and closed-loop state switching functions, increasing the function of changing the gain of the output through-state voltage, and increasing the proportion of the output power of the through state.

The turns ratio of the transformer isolated open loop converter 104 may be set according to the desired input and output voltages, in order to maximize the amount of voltage that is converted in the straight-through state. In one example, the turns ratio of the N1 :N2:N3 windings is 8:4:7.

FIG. 3 depicts an exemplary output function of the power converter 100, according to some embodiments. The output voltage and current are inversely correlated, so that the total power output remains constant. In the illustrated embodiment, the maximum total power, represented by downwardly sloping line 120, is 6600 W. For example, the output may be set at 275 volts, at a current of 24A. The output may also be set at 490 volts, or at 240 volts, with corresponding changes in the current. These values are merely exemplary, and other voltage and current combinations may be employed.

FIG. 4 illustrates the mode switching scheme of the power converter 100, according to some embodiments. In the example of FIG. 4, the power converter 100 is set up as in FIG. 2, with one primary winding 106 or N1 and two secondary windings 108a, 108b (N2 and N3). In this example, as discussed above, the turns ratio of N1 :N2:N3 is 8:4:7. Thus, when the input voltage is 380 V dc, the output voltage at N2 is 190 Vdc, and the output voltage at N3 is 332.5 V dc. The output voltage of the power converter 100 is represented by line 122. When the desired output voltage is in region 124 (i.e., below 380 V dc), voltage step down converter 114a associated with secondary winding N2 is configured in the straight-through state, and the voltage step down converter 114b associated with secondary winding N3 is in closed loop control and regulates the output voltage. In this way, more of the output voltage is comprised of voltage passing through the straight-through state at 190V. When the desired output voltage is in region 126 (i.e., above 380 V dc), the voltage step down converter 114b associated with secondary winding N3 is configured in the straight through state, and the voltage step down converter 114a associated with secondary winding N2 is in the closed loop control state to regulate the output voltage. In this way, more of the output voltage is comprised of voltage passing through the straight-through state at 332.5 V.

FIG. 4 depicts the straight-through power ratio (indicated by line 130) of the power converter 100 as a function of the output voltage, for the example provided of a turns ratio of 8:4:7. The straight-through power ratio is the percentage of the power that is delivered through a voltage step down converter 114 in a straight-through power state as opposed to a closed-loop power state. As can be seen, when the output voltage is around 380 V dc, the transmission power ration of the rated point is 90%.

FIG. 5 depicts the efficiency of the topology of power converter 100, as a function of output voltage. Solid line 132 represents the efficiency of power converter 100, whereas dashed line 134 represents the efficiency of a power converter functioning with a CLLC topology known in the art. As can be seen, the efficiency of power converter 100 exceeds the efficiency of a prior art CLLC power converter at all output voltages, and exceeds 98% for an output voltage of 380 V.

In an alternative embodiment, rather than operating only one buck circuit 114 in closed loop mode, both buck circuits 114 may be operated simultaneously. While operating both buck circuits 114 simultaneously causes more power loss, as discussed above, the range of possible output voltages may be wider. For example, the output voltage of power converter 100 may range from 0 to 500V. This flexibility is advantageous for devices that require a wider output voltage range.

A second embodiment of a power converter 200 is depicted in FIGS. 7-9. Power converter 200 has many similar features to power converter 100, and accordingly like features will be designated with like reference numerals, except that they will be preceded by the numeral“2” rather than the numeral“1

FIG. 7 is a schematic block diagram of a second embodiment 200 of a power converter, according to embodiments of the invention. Power converter 200 is similar to power converter 100 in many respects. A key difference is that input power is first converted through closed loop topology 212, with the plurality of DC/DC closed loop converters 214a-n, and then converted through transformer isolated open loop converter 204, rather than vice versa as in power converter 100. As seen in FIG. 7, power is input to converter 200 at input 201. Capacitor 209 is situated at input 200. The power is then conducted to closed loop topology 212, which consists of a plurality of DC/DC closed loop converters 214a-n. The input voltage of the DC/DC converters is connected in series (through capacitors 210a-n) but the output voltages of the DC/DC converters are separated.

Transformer isolated open loop winding 204 consists of a plurality of primary windings 206a-n, one for each DC/DC closed loop converter 214. The input voltage of each primary winding 206 is the output voltage of its corresponding DC/DC converter 214. Transformer isolated open loop winding 204 further includes a secondary winding 208. In the illustrated embodiment, there are a plurality of secondary windings as well. In such embodiments, the secondary windings all deliver power at the same voltage, and are thus functionally equivalent. After the voltage is transformed in the transformer isolated open loop winding, it is delivered to the load (not shown), e.g., an integrated circuit. The output voltage is connected to capacitor 218.

As in the embodiment of FIG. 1, the DC/DC closed loop converters 214a-n may work in a direct conduction state or in a closed loop switching state. The closed loop converters may be switched according to the input voltage and the desired output voltage. The switching scheme of the closed loop converters 214 may be configured so that most of the power is handled by the open loop topology 204 and the closed loop converter 214 in a through state. The closed- loop control topology only takes a small part of the power, and the closed- loop topology with a straight-through state has a high power density.

The basic principle of operation of power converter 200 is thus based on a quasi-parallel architecture scheme, adding a closed-loop topology with straight-through and closed-loop state switching functions, increasing the function of changing the gain of the output through-state voltage, and increasing the proportion of the output power of the through-state.

FIG. 8 is a more detailed block diagram of the power converter 200 of FIG. 7. In the illustrated embodiment, closed loop DC/DC converter 214a has a topology including capacitor Cl, inductor LI, and transistors Q1 and Q2. DC/DC converter 214b has a topology including capacitor C2, inductor L2, and transistors Q3, Q4, Q5, and Q6. The input voltage of DC/DC converters 214a and 214b is in series, and the output voltages are independent of each other. As discussed in connection with power converter 100, each of the DC/DC converters 214 may work in a straight through state or in a closed-loop mode. Alternatively, both of the DC/DC converters may be operated in the closed loop mode, to provide greater range in output voltage.

The output voltages are then transferred to the transformer isolated open loop winding 204 via open loop LLC topology 202a and 202b, which together form a bridge circuit. The open loop LLC topology consists of, respectively, capacitor C3 and transistors Q7-Q10, and capacitor C4 and transistors Q11-Q14. Open loop LLC topology 202 always works at the resonance point, similar to open loop LLC topology 102. The output voltages of DC/DC converters 214a and 214b are used as the input voltage of the bridge circuit 215 of the two windings N2, N3, also referred to as 206a and 206b, of the primary side of the transformer isolated open loop winding 204.

The transformer isolated open loop winding 204 has two primary windings 206a and 206b, and one primary winding 208, also referred to as Nl . The transformer isolated open loop winding 204 functions as an open loop LLC converter with isolation. The output voltage from transformer isolated open loop topology 204 proceeds through an output topology including transistors Q15- Q18, capacitor C5, and capacitor 218.

FIG. 9 is a chart depicting the mode switching scheme of power converter 200 of FIG. 7. In the example of FIG. 9, the turns ratio of the primary and secondary windings (N2:N3:N1) is 44:24: 1. In one such embodiment, the input voltage is between 40 and 60 Volts DC, the output voltage range is 0.6V to 1.1 V dc, and the output current is around 300 A. Advantageously, voltages at this range may be suitable for providing power to integrated circuits at high efficiency.

FIG. 9 provides the straight-through power ratio as a function of input voltage (x axis, between 40 and 60 V dc) depending on whether the desired output voltage is 1.1 V (solid line 240); 1.0 V (dashed line 242), or 0.6 V (dot-dash line 244, which is obscured in part by solid line 240). The straight-through power ratio is at or above 90% at an input voltage of 52 V, for an output voltage of 1.1 V; and at an input voltage of 49 V, for an output voltage of 1.0 V.

FIG. 10 schematically depicts power converter 100, 200 within an on-board charger 310 of electric vehicle 300. While only one power converter 100, 200 is depicted, it is possible to parallelize converters 100, 200 in order to obtain more power. The power density of power converter 100, 200 may be higher than 50 kW/dm ³ . Advantageously, the power converters 100 may be suitable for a very wide input and output voltage range, and may deliver a high power density at comparatively low cost. The descriptions of the various embodiments of the present invention have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

It is expected that during the life of a patent maturing from this application many relevant converters, transformers, on-board chargers, and electric vehicles will be developed and the scope of the terms converter, transformer, on-board charger, or electric vehicle is intended to include all such new technologies a priori.

As used herein the term“about” refers to ± 10 %.

The terms "comprises", "comprising", "includes", "including", “having” and their conjugates mean "including but not limited to". This term encompasses the terms "consisting of' and "consisting essentially of'.

The phrase "consisting essentially of' means that the composition or method may include additional ingredients and/or steps, but only if the additional ingredients and/or steps do not materially alter the basic and novel characteristics of the claimed composition or method.

As used herein, the singular form "a", "an" and "the" include plural references unless the context clearly dictates otherwise. For example, the term "a compound" or "at least one compound" may include a plurality of compounds, including mixtures thereof.

The word“exemplary” is used herein to mean“serving as an example, instance or illustration”. Any embodiment described as“exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments and/or to exclude the incorporation of features from other embodiments.

The word“optionally” is used herein to mean“is provided in some embodiments and not provided in other embodiments”. Any particular embodiment of the invention may include a plurality of“optional” features unless such features conflict. Throughout this application, various embodiments of this invention may be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

Whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range. The phrases“ranging/ranges between” a first indicate number and a second indicate number and“ranging/ranges from” a first indicate number “to” a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numerals therebetween.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. To the extent that section headings are used, they should not be construed as necessarily limiting.