Ac / dc power converter

Abstract

An AC / DC power conversion apparatus employs a dual leg topology. A first leg includes a first AHB switching network for receiving AC grid power and generating an AC power source coupled through a series resonant impedance to a first primary winding of a transformer. The first switching network includes two bidirectional switches coupled in series, where each bidirectional switch includes two switching devices coupled in series with opposite polarity. A secondary winding of the transformer is coupled through an SR switching device to an output DC power source. A second leg includes a diode bridge for receiving the AC grid power and generating a DC power source coupled to a second AHB switching network. The second AHB switching network is coupled through a second series resonant impedance to a second primary winding of the transformer. Each of the first and second legs operate alternately and independently.

Description

TECHNICAL FIELD

[0001] Aspects of the disclosed embodiments generally relate to power conversion devices, and more particularly to resonant AC-DC power converters. BACKGROUND

[0002] The increasing processing power and screen size of modern mobile devices results in increased power consumption and a corresponding increase in battery size. Unfortunately, these larger batteries require a long charging time for conventional battery chargers. High-end cell phones are currently equipped with chargers that range in power from 40 to 65 watts. Multi-purpose chargers designed for charging cell phones, laptops, and other types of devices typically provide charging power of 75 watts or more. Regulatory requirements, such as those implemented in certain jurisdictions for chargers with power exceeding 75 watts, add complexity and cost and can reduce the overall efficiency of higher power chargers.

[0003] Current shaping techniques in combination with ACF topologies can reduce the number of components and system cost. However, in these topologies, energy is processed twice, resulting in low system efficiency, which is unacceptable. Combining bridgeless techniques with active half-bridge (AHB) topologies can improve system efficiency, but still requires processing energy twice, limiting system efficiency.

[0004] AHB flyback converters can provide high efficiency and low component stress and show potential for high power density. However, these techniques are limited to lower power applications, such as below 75 watts.

[0005] Therefore, there is a need for improved high output AC / DC power converters that can provide high efficiency and high power density while meeting applicable regulatory requirements. Accordingly, there is a need to provide a device that at least partially addresses the above problems. SUMMARY

[0006] Aspects of the disclosed embodiments relate to an AC / DC power conversion device that employs a dual-leg topology to provide high system efficiency and high power density in a converter capable of providing high output power under wide range of input power and wide range of output power (WIWO) operating conditions. Aspects of the disclosed embodiments provide WIWO power conversion while transforming most of the energy only once. The subject matter of the independent claims is implemented to achieve this object and others. Further advantageous modifications are found in the dependent claims.

[0007] According to a first aspect, the above and further objects and advantages are achieved by a device. In one embodiment, the device comprises a transformer comprising a first primary winding magnetically coupled to a secondary winding and a first series resonant impedance comprising a first resonant inductance, a first resonant capacitance and the first primary winding in series. The device further comprises a first switch network connected between a first AC supply node and a second AC supply node. The first switch network comprises a first bidirectional switch in series with a second bidirectional switch, wherein the first series resonant impedance is parallel to the second bidirectional switch. The device further comprises a rectifier tube switch connected between a first end of the secondary winding and a first DC node, wherein a second end of the secondary winding is connected to a second DC node. The first bidirectional switch comprises a first switching device in series with a second switching device, wherein a source of the first switching device is connected to a source of the second switching device. The second bidirectional switch comprises a third switching device in series with a fourth switching device, wherein a source of the third switching device is connected to a source of the fourth switching device. The resonant DC-DC converter provides an efficient single stage power conversion, while the bidirectional switches provide the ability to disable the switch network, thereby allowing the converter to be disabled and power flow through the converter to be stopped.

[0008] In one possible implementation form of the device, the device further comprises a second primary winding magnetically coupled to the secondary winding and a second series resonant impedance comprising a second resonant inductance, a second resonant capacitance and the second primary winding in series. The device comprises a diode bridge connected between the first AC supply node and the second AC supply node and configured to generate a first DC supply. A second switch network is parallel to the first DC supply, wherein the second switch network comprises a fifth switching device in series with a sixth switching device. The second series resonant impedance is parallel to the sixth switching device. Including a second converter branch allows efficient power conversion over a wider range of AC voltages.

[0009] In a possible implementation form of the apparatus, an AC voltage is connected between the first AC supply node and the second AC supply node. When an amplitude of the AC voltage is greater than a predetermined voltage threshold, the fifth and sixth switching devices are turned off and the first and second bidirectional switches are operated to transfer power from the AC voltage to the first and second DC nodes. When the amplitude of the AC voltage is not greater than the predetermined voltage threshold, the first and second bidirectional switches are turned off and the fifth and sixth switching devices are operated to transfer power from the AC voltage to the first and second DC nodes. Selectively enabling the first converter branch when the input voltage is greater than the voltage threshold and the second converter branch otherwise improves converter efficiency by enabling the most efficient branch when the AC voltage varies.

[0010] In a possible implementation form of the apparatus, the predetermined voltage threshold is greater than a DC output voltage multiplied by a turns ratio between the first primary winding and the secondary winding. Setting the voltage threshold to be greater than the DC output voltage multiplied by the turns ratio enables the more efficient single-stage branch when operating in a step-down mode and the second branch otherwise.

[0011] In a possible implementation form of the apparatus, the first series resonant impedance is in parallel with the first bidirectional switch. This circuit configuration is an equivalent alternative to the aforementioned configuration.

[0012] In a possible implementation form of the apparatus, the second series resonant impedance is in parallel with the fifth switching device. This circuit configuration is an equivalent alternative to the aforementioned configuration.

[0013] In a possible implementation form of the apparatus, the first DC node is a positive DC node and the second DC node is a negative DC node. This circuit configuration is an equivalent alternative to the aforementioned configuration.

[0014] In a possible implementation form of the apparatus, the first DC node is a negative DC node and the second DC node is a positive DC node. This circuit configuration is an equivalent alternative to the aforementioned configuration.

[0015] In a possible implementation form of the apparatus, a bus capacitor is in parallel with the second switching network. Including a bus capacitor improves efficiency of the second branch of the converter.

[0016] In a possible implementation form of the apparatus, an output capacitor is connected between the first and second DC nodes. Including an output capacitor facilitates filtering of output power.

[0017] These and other aspects, implementations, and exemplary embodiments are evident from the following description of the embodiments, reference being made to the accompanying drawings. However, it is to be understood that this description and the drawings are merely intended to illustrate the application; any limitations of the application are to be found in the appended claims. Additional aspects and advantages of the application will be described in the following description, and will be apparent from the description, or can be learned by practice of the application. Moreover, the advantages of the application can be achieved by means of the instrumentalities and combinations particularly pointed out in the appended claims. BRIEF DESCRIPTION OF DRAWINGS

[0018] In the following detailed portion of the specification, the application will be explained in connection with exemplary embodiments illustrated in the drawings, in which like numbering represents like elements:

[0019] Figure 1 A schematic diagram of an exemplary AC / DC power converter device incorporating aspects of the disclosed embodiments is shown;

[0020] Figure 2 A schematic diagram of an exemplary power conversion device incorporating aspects of the disclosed embodiments is shown;

[0021] Figure 3 A working waveform diagram of an exemplary device incorporating aspects of the disclosed embodiments is shown;

[0022] Figure 4 A working waveform diagram of an exemplary device incorporating aspects of the disclosed embodiments is shown;

[0023] Figure 5 A schematic diagram of an exemplary device incorporating aspects of the disclosed embodiments is shown;

[0024] Figure 6 A working waveform diagram of an exemplary device incorporating aspects of the disclosed embodiments is shown;

[0025] Figure 7 A schematic diagram of an exemplary power conversion device incorporating aspects of the disclosed embodiments is shown;

[0026] Figure 8 A schematic diagram of an exemplary power conversion device incorporating aspects of the disclosed embodiments is shown;

[0027] Figure 9 A schematic diagram of an exemplary power conversion device incorporating aspects of the disclosed embodiments is shown;

[0028] Figure 10 A schematic diagram of an exemplary power conversion device incorporating aspects of the disclosed embodiments is shown;

[0029] Figure 11 A schematic diagram of an exemplary power conversion device incorporating aspects of the disclosed embodiments is shown;

[0030] Figure 12 A schematic diagram of an exemplary power conversion device incorporating aspects of the disclosed embodiments is shown;

[0031] Figure 13 A schematic diagram of an exemplary power conversion device incorporating aspects of the disclosed embodiments is shown. DETAILED DESCRIPTION

[0032] Reference is made to Figure 1 , Figure 1 A schematic diagram of a power conversion device 100 is shown. The device 100 provided by the disclosed embodiments relates to an AC / DC power conversion device that employs a dual-leg topology to provide high system efficiency and high power density in a converter capable of providing high output power, for example, greater than seventy-five (75) watts of output power. The device 100 is suitable for use as a charging device for mobile devices, laptops, and other battery powered devices that can benefit from a high efficiency, small form factor charger capable of providing high output power over a wide input and wide output (WIWO) range.

[0033] In the drawings, connections or lines in a circuit diagram that do not cross point 150 are not connected, and connections of lines that cross or intersect point 152 are connected.

[0034] Reference is made to Figure 1 In one embodiment, the device 100 includes a transformer T1 that includes a first primary winding 106 magnetically coupled to a secondary winding 110. A first series resonant impedance Zr1 includes a first resonant inductance Lr1, a first resonant capacitance Cr1, and the first primary winding 106 in series.

[0035] A first switch network 130 is connected between a first AC supply node 122 and a second AC supply node 128. In the illustrated embodiment, the first switch network 130 has a first bidirectional switch 102 in series with a second bidirectional switch 104. The first series resonant impedance Zr1 is in parallel with the second bidirectional switch 104.

[0036] A rectifier diode switch S7 is connected between a first end 138 of the secondary winding 110 and the first DC node 124. A second end 140 of the secondary winding 110 is connected to the second DC node 126.

[0037] The first bidirectional switch 102 includes a first switching device S1 in series with a second switching device S2. A source 114 of the first switching device S1 is connected to a source 116 of the second switching device S2.

[0038] The second bidirectional switch 104 includes a third switch S3 connected in series with the fourth switch S4. The source 118 of the third switch S3 is connected to the source 120 of the fourth switch S4.

[0039] like Figure 1 As shown, the device 100 includes seven switching devices S1, S2, S3, S4, S5, S6, and S7. Each switching device may be a metal-oxide-semiconductor field-effect transistor (MOSFET) having an inherent body diode or anti-parallel diode as shown in the embodiments. Alternatively, to implement each switching device S1, S2, S3, S4, S5, S6, and S7, any suitable type of switching device capable of efficiently switching the required power at the desired switching frequency can be used.

[0040] The first and second switching networks 130 and 134, also referred to as active half-bridge (AHB) type switching networks, are used to transfer power from the AC voltage Vac to the primary winding 142 of transformer T1. As will be discussed further below, each switching network 130 and 134 operates independently, such that only one switching network 130 or 134 transfers power at a time. Therefore, the converter device 100 has two independent power paths, referred to herein as branches. When the first branch is transferring power, the two switching devices S5 and S6 in the second switching network 134 are turned off, and the first switching network 130 is operated to transfer power from the AC voltage Vac to the first primary winding 106 of transformer T1. When the second branch is transferring power, the two bidirectional switches 102 and 104 in the first switching network 130 are turned off, and the second switching network 134 is operated to transfer power from the AC voltage Vac to the second primary winding 108 of transformer T1.

[0041] A first switch network 130 is connected between a first AC power node 122 and a second AC power node 128. The first switch network 130 includes a first bidirectional switch 102 connected in series with a second bidirectional switch 104, forming a central node 112. The central node 112 is located between the first bidirectional switch 102 and the second bidirectional switch 104.

[0042] The first bidirectional switch 102 is formed by a first switching device S1 connected in series with the second switching device S2. Figure 1In the illustrated example embodiment, the switching devices S1, S2 are MOSFETs, which have intrinsic body diodes disposed in parallel with the switching terminals. Thus, each switching device S1, S2 is capable of blocking current in only one direction. By connecting the switching devices S1 and S2 in opposite directions, with the source 114 of the first switching device connected to the source 116 of the second switching device S2, the bidirectional switch 102 can block current or voltage in both directions when both switching devices S1, S2 are off. Similarly, the second bidirectional switch 104 includes two switching devices S3, S4 connected in series in opposite directions, with the source 118 of the third switching device S3 connected to the source 120 of the fourth switching device S4. The first bidirectional switch 102 and the second bidirectional switch 104 form a first half-bridge 130 connected across the input AC voltage Vac.

[0043] As used herein, a switching device (e.g., a MOSFET switching device) is said to be on or open when it is conducting current, and is said to be off or closed when it is not conducting current.

[0044] The example apparatus 100 includes a first series resonant impedance Zr1 in parallel with the second bidirectional switch 104. Alternatively, the first series resonant impedance Zr1 can advantageously be in parallel with the first bidirectional switch 102.

[0045] The first series resonant impedance Zr1 includes a first resonant inductance Lr1 and a first resonant capacitance Cr1 in series with the first winding 106 of the transformer T1. In the illustrated example embodiment, the first resonant inductance Lr1 is coupled between the center node 112 of the first switching network 130 and the first primary winding 106 of the transformer T1, and the first resonant capacitance Cr1 is coupled between the second AC supply node 128 and the first primary winding 106. Alternatively, the three resonant components: the first resonant inductance Lr1, the first resonant capacitance Cr1, and the first primary winding 106, can be connected in any desired order to form the first series resonant impedance Zr1. Figure 1

[0046] The transformer T1 includes the first primary winding 106 disposed on a primary side 142 of the transformer T1 and the secondary winding 110 disposed on a secondary side 144 of the transformer T1. The first primary winding 106 is magnetically coupled to the secondary winding 110. A first turns ratio N1 represents the ratio of the number of turns in the first primary winding 106 to the number of turns in the secondary winding 110.

[0047] ​At the secondary side 144, a rectifier switch S7 is connected between the first end 138 of the secondary winding 110 and the first DC node 124, and the second end 140 of the secondary winding 110 is connected to the second DC node 126. The rectifier switch S7 can operate as a synchronous rectifier to convert the AC power from the secondary winding 110 to DC power delivered to the load 146, which can be connected between the first DC node 124 and the second DC node 126. In one embodiment, the rectifier switch S7 can be connected between the second end 140 of the secondary winding 110 and the second DC node 126.

[0048] As described above, the first branch or first power path delivers power from the AC voltage Vac to the load 146 through the first switch network 130 and the first primary winding 106. This type of active half bridge resonant (AHBR) converter is advantageous when the value of the AC voltage Vac is large. However, if the value of the AC voltage Vac is small, it can not be as advantageous as other converter topologies. Accordingly, the exemplary apparatus 100 includes a second branch to provide improved performance in the event that the value of the AC voltage Vac is small.

[0049] The second branch or power path employs a diode bridge 132 coupled to the first AC supply node 122 and the second AC supply node 128. The diode bridge 132 is used to receive the AC voltage Vac and generate a DC voltage Vdc. The exemplary diode bridge 132 includes four diodes Dl, D2, D3, D4 arranged in a full bridge circuit configuration that is adapted to provide a DC voltage Vdc of the same polarity for either polarity of the AC voltage Vac. Those skilled in the art will readily recognize that any type of rectifier circuit adapted to receive an AC voltage and generate a DC voltage can be advantageously employed without departing from the spirit or scope of the disclosed embodiments. In certain embodiments, a bus capacitor Cbus can be coupled in parallel with the DC voltage Vdc to help smooth the DC voltage Vdc and reduce voltage stress and improve performance of the second switch network.

[0050] The second switch network 134 is connected across or in parallel with the DC voltage Vdc. The second switch network includes a fifth switch device S5 in series with a sixth switch device S6. The central node 136 is formed between the fifth switch device S5 and the sixth switch device S6.

[0051] The second primary winding 108 of the transformer Tl is magnetically coupled to the secondary winding 110. The second primary winding 108 receives power from the second switch network 134 through a second series resonant impedance Zr2. A second turns ratio N2 represents the ratio of the number of turns in the second primary winding 108 to the number of turns in the secondary winding 110.

[0052] The second series resonant impedance Zr2 includes a second resonant inductance Lr2, a second resonant capacitance Cr2, and a second primary winding 108 in series. The magnetizing inductance of the second primary winding 108 combines with the second resonant inductance Lr2 to produce a resonant behavior of the second series resonant impedance Zr2. The second resonant inductance Lr2, the second resonant capacitance Cr2, and the second primary winding 108 can advantageously be in series in any desired order to form the second series resonant impedance Zr2.

[0053] In the exemplary apparatus 100, the second series resonant impedance Zr2 is in parallel with the sixth switching device S6. Alternatively, the second series resonant impedance Zr2 can advantageously be in parallel with the fifth switching device S5.

[0054] The exemplary apparatus 100 provides improved system efficiency by transforming most of the energy only once. In this sense, the exemplary apparatus 100 can be considered a single-stage power converter. The efficiency improvement is achieved in part by including two power branches. The first branch transfers power from the AC voltage Vac to the load 146 through the first switching network 130 and the first primary winding 106. The second branch transfers power from the AC voltage Vac to the load 146 through the diode bridge 132, the second switching network 134, and the second primary winding 108.

[0055] As will be discussed further below, the primary side 142 of the apparatus 100 includes two independent branches, each with its own set of power path components. On the secondary side 144, the two branches share a set of power transfer components. The transformer core is also shared between the two branches. Interference between the two branches is limited by activating only one branch at a time.

[0056] During operation, each of the two branches operates independently and alternately, with only one branch transferring power from the AC input nodes 122, 128 to the DC output nodes 124, 126 at a time. The transition between the two branches is based on the magnitude or absolute value of the AC voltage. As used herein, the magnitude of the AC voltage is equal to the absolute value of the AC voltage |Vac|. When the magnitude of the AC voltage |Vac| is greater than a predetermined voltage threshold Vth (|Vac| > Vth), power is transferred through the first branch. When the magnitude of the AC voltage |Vac| is not greater than the predetermined voltage threshold Vth (|Vac| < Vth), power is transferred through the second branch.

[0057] When power is transferred through the first branch, two switching devices S5 and S6 in the second switching network 134 are turned off, and the first switching network 130 is operated to transfer power from the first and second AC supply nodes 122 and 128 to the first series resonant impedance Zr1. When power is transferred through the second branch, four switches S1, S2, S3, S4 in the first switching network 130 are turned off, and the second switching network 134 is operated to transfer power from the DC voltage Vdc to the second series resonant impedance Zr2.

[0058] The predetermined voltage threshold Vth for selectively activating each branch is determined based on the desired DC output voltage Vo and the turns ratio N1 between the first primary winding 108 and the secondary winding 110 of the transformer T1. The predetermined voltage threshold Vth can be set to be greater than the turns ratio N1 multiplied by the desired output voltage Vo, as shown in equation (1):

[0059] Vth > Vo · N1 (1).

[0060] Figure 2 A schematic diagram of an exemplary power conversion device 200 incorporating aspects of the disclosed embodiments is shown. The device 200 provided by the disclosed embodiments, referred to herein as a first branch, depicts a portion of the exemplary power conversion device 100 for providing a first power path between an AC voltage Vac and a load 146. Figure 2 The depicted device 200 depicts Figure 1 a portion of the depicted device 100, where like reference numerals indicate like elements. Power is transferred through the first branch 200 when the magnitude of the AC voltage |Vac| is greater than the predetermined voltage threshold Vth (|Vac| > Vth).

[0061] The operation of the device 200 is facilitated by separately considering each of two modes of operation of the device 200. The first mode of operation to be considered is when the AC voltage Vac is greater than the voltage threshold Vth; Vac > Vth.

[0062] Figure 3 A plot of waveforms 300 of the exemplary device 200 during the first mode of operation incorporating aspects of the disclosed embodiments is shown. In the plot 300, time is depicted as increasing to the right along the horizontal axis 302, and in each of the plots 306, 308, 310, and 314, magnitude is depicted as increasing upward along the vertical axis 304. The control signals V gs1 , V gs3 of the first switching device S1 and the second switching device S2 are shown in plots 306 and 308, respectively, where a value of one (1) indicates that the corresponding switching device is on, and a value of zero (0) indicates that the corresponding switching device is off. Plot 310 depicts the current I lr1and a first excitation current I of transformer T1 lm1 where line 314 depicts the first excitation current I lm1 of transformer T1 and dashed line 316 depicts the first resonant inductor current I lr1 of transformer T1. Graph 312 depicts the current I M7 .

[0063] During the first mode of operation, the second switch device S2 and the fourth switch device S4 remain on. Diode switch S7 functions as a synchronous rectifier (SR) assembly to convert the voltage of the secondary winding 110 to a DC power supply. The current through the seventh switch device S7 is represented in graph 312 as I M7 .

[0064] The switch networks 130, 134 and the SR assembly S7 all operate at the same switching frequency, which is set to be much higher than the frequency of the AC voltage Vac, for example, two or more orders of magnitude higher. In certain embodiments, the AC voltage Vac can be provided by a local grid power and can have a frequency of about fifty (50) hertz or sixty (60) hertz. Because the switching frequency of the switch devices S1-S7 is much higher than the AC input voltage Vac, the AC voltage Vac can be treated as a constant input voltage V in .

[0065] Referring again to graph 300, it can be seen that, during the time interval between time to and time tl, the first switch device S1 is on and the third switch device S3 is off. During this time interval, the excitation current of the first primary winding 106 of transformer T1 increases, as shown in equation (2):

[0066]

[0067] where V cr1 is the average voltage of the first resonant capacitor Cr1, Lm1 is the value of the magnetization inductance of the first primary winding 106 of transformer T1, I lr1 is the current through the first resonant inductor Lr1, I 0lr1 is the initial current through the first resonant inductor Lr1 at the beginning of the time interval.

[0068] At time tl, the first switch device S1 turns off and the current begins to flow through the body diode of the third switch device S3. At time t2, the third switch device S3 reaches a zero-voltage switching (ZVS) state and turns on. During the time interval between times t2 and t3, the diode switch S7 begins to turn on. Because the voltage V cr1 of the first resonant capacitor divided by the turns ratio N1 is greater than the DC output voltage Vo The first resonant inductor Lr1 and the first resonant capacitor Cr1 form a resonant circuit, in which the current I lr1 From equation (3) we have:

[0069]

[0070] where the value ω is given by equation (4):

[0071]

[0072] The first impedance Z1 is given by equation (5):

[0073]

[0074] The value V crini is the initial voltage of the first resonant capacitor Cr1 before the resonance starts.

[0075] The magnetizing current I lm1 is given by equation (6):

[0076]

[0077] The current I lr1 through the first resonant inductor Lr1 is given by equation (7): lm1 The current difference between the magnetizing current I

[0078] I M7 = (I lm1 -I lr1 ) · N1 (7).

[0079] At time t3, the third switch S3 is turned off, and at time t4, the first switch S1 is turned on. It is important to ensure that the magnetizing current is negative at time t3 to facilitate achieving zero voltage switching (ZVS) of the first switch S1.

[0080] The output voltage Vo during the first mode of operation is given by equation (8):

[0081]

[0082] where D1 is the duty cycle of the first switch S1.

[0083] During the second mode of operation of the first branch, the AC voltage Vac is less than the negative value of the voltage threshold; Vac<-Vth. The first switch S1 and the third switch S3 remain turned on, while the second switch S2 and the fourth switch S4 are operated to regulate the input voltage Vin and the power flow between the first series resonant impedance Zr1. The rectifier switch S7 is used as a synchronous rectifier (SR) component to convert the voltage of the secondary winding 110 into a DC power source.

[0084] Figure 4 A plot 400 of waveforms of the exemplary apparatus 200 during the second mode of operation in conjunction with aspects of the disclosed embodiments is shown. In the plot 400, time increases along the horizontal axis 402 to the right, and in each of the plots 406, 408, 410, and 414, the magnitude increases along the vertical axis 404 upward. The control signals V gs2 , V gs4 S2 and S4 are shown in plots 406 and 408, respectively, where a value of one (1) indicates that the corresponding switch device is on, and a value of zero (0) indicates that the corresponding switch device is off. Plot 410 depicts the current I lr1 through the first resonant inductor Lr1 and the first primary winding 106 first magnetizing current I lm1 , where the solid line 414 depicts the first magnetizing current I lm1 , and the dashed line 416 depicts the first resonant inductor current I lr1 . Plot 412 depicts the current I M7 through the SR component M7.

[0085] Prior to time t6, the magnetizing current I lm1 is negative, and current flows through the body diode of the fourth switch device S4, thereby allowing ZVS while the fourth switch device S4 is on. During the time interval between time t6 and time t7, the fourth switch device S4 is on, and the second switch device S2 is off. The magnetizing current I lm during this period is given by equation (9):

[0086]

[0087] At time t7, the fourth switch device S4 is off, and current begins to flow through the body diode of the second switch device S2, thereby providing ZVS while the second switch device S2 is on.

[0088] During the time interval between time t8 and time t9, the current I lr1 through the first resonant inductor and the magnetizing current I lm1 may be given using equation (10):

[0089]

[0090] where V crini2 is the initial voltage of the first resonant capacitor Cr1 prior to the start of resonance, and I0lr1 is the initial current through the first resonant inductance Lr1.

[0091] The excitation current during this time interval is given by equation (11):

[0092]

[0093] The current difference between the current I lr1 and the excitation current I lm1 is transferred to the secondary side 144 of the transformer as given by equation (7) above. The output voltage Vo is given by equation (12):

[0094]

[0095] where D2 is the duty cycle of the second switching device S2.

[0096] Figure 5 A schematic diagram of an exemplary power conversion apparatus 500 incorporating aspects of the disclosed embodiments is shown. The apparatus 500 provided by the disclosed embodiments, referred to herein as a second branch, depicts a portion of the exemplary power conversion apparatus 100 for providing a second power path between the AC voltage Vac and the load 146. Figure 5 The depicted apparatus 500 depicts Figure 1 a portion of the depicted apparatus 100, where like reference numerals indicate like elements. Power is transferred through the second branch when the magnitude of the AC voltage |Vac| is not greater than a predetermined voltage threshold Vth (|Vac| < Vth).

[0097] The second branch 500 includes a diode bridge 132 for rectifying the AC voltage Vac and producing a DC voltage Vdc. An energy storage capacitor Cbus smooths the DC voltage Vdc, and a second switching network 134 converts the DC voltage Vdc into an AC supply. A second series resonant impedance Zr2 connects the second switching network 134 to the second primary winding 108, and includes a second resonant inductance Lr2 and a second resonant capacitance Cr2, which in addition to participating in resonance, also acts as a blocking capacitance to block DC bias produced by the second switching network 134. On the secondary side of the transformer 144, a rectifier switch S7 acts as an SR assembly to provide a DC supply to the load 146.

[0098] The apparatus 500, also referred to as a second branch, converts energy twice. First, the AC voltage Vac is converted to a DC voltage Vdc by the diode bridge 134 and stored in the energy storage capacitor Cbus. The second energy conversion is performed by the AHBR converter, which includes the second switching network 134, the second series resonant impedance Zr2, and the SR assembly S7. The operation of the second AHBR energy conversion will be described in more detail below.

[0099] Figure 6 A plot 600 of waveforms is shown that illustrate the operation of the exemplary apparatus 500 incorporating aspects of the disclosed embodiments. In the plot 600, time increases along the horizontal axis 602 to the right, and in each of the plots 606, 608, 610, and 614, amplitude increases along the vertical axis 604 upward. The control signals V gs5 gs6 for the fifth and sixth switching devices S5 and S6 are shown in plots 606 and 608, respectively, where a value of one (1) indicates that the corresponding switching device is on, and a value of zero (0) indicates that the corresponding switching device is off. Plot 610 depicts the current I lr2 through the second resonant inductor Lr2 and the second excitation current I lm2 through the second primary winding 108, where the solid line 614 depicts the second excitation current I lm2 and the dashed line 616 depicts the second resonant inductor current I lr2 . Plot 612 depicts the current I M7 through the SR assembly M7.

[0100] Between times t 12 and t 13 , the fifth switching device S5 is on, the sixth switching device S6 is off, and the excitation current of the transformer increases according to equation (14):

[0101]

[0102] where I lr2 is the current through the second resonant inductor Lr2, I lm2 is the excitation current of the second primary winding 110 of the transformer T1, Lm2 is the magnetizing inductance of the second primary winding 110, V cr2 is the average voltage of the second resonant capacitor Cr2, I 0lr2 is the initial current of the second resonant inductor Lr2 at the beginning of time t 12 .

[0103] At time t 13 , the fifth switching device S5 is turned off, and the current begins to flow through the body diode of the sixth switching device S6. This allows the sixth switching device S6 to reach the ZVS state at time t 14 .

[0104] During the time interval between t 14 and t 15 , the average voltage V cr2 of the second resonant capacitor divided by the turns ratio N2 ​greater than the output voltage Vo. This causes the body diode of the rectifier switch S7 to conduct current, thereby inducing resonance in the second series resonant impedance Zr2. The current in the second resonant inductor Lr2 is given by equation (15):

[0105]

[0106] where the value ω is given by equation (16):

[0107]

[0108] The second impedance Z2 is given by equation (17):

[0109]

[0110] where V cr2ini is the initial voltage of the second resonant capacitor prior to the start of resonance, I 1lr2 is the initial inductor current in the second resonant inductor Lr2 at the start of the time interval, and N2 is the turns ratio between the second primary winding 108 and the secondary winding 110.

[0111] The magnetizing current I lm2 in the second primary winding is given by equation (18):

[0112]

[0113] The current I lr2 through the second resonant inductor is given by equation (19): lm2 and the magnetizing current I M7 of the second primary winding 110. The difference between the current I M7 through the rectifier switch S7 is given by equation (19):

[0114] I lm2 = (I lr2 -I 15 ) · N2 (19).

[0115] At time t lm2 , the sixth switch device S6 turns off. Again, it is important that the magnetizing current I 15 is negative at time t 16 to ensure that the fifth switch device S5 experiences ZVS when it turns on at time t lr2 . The output voltage during this time interval is given by equation (20):

[0116]

[0117] where D5 is the duty cycle of the fifth switch device S5.

[0118] Figure 7 A schematic diagram of an exemplary power conversion device 700 incorporating aspects of the disclosed embodiments is shown. The exemplary device 700 is similar to the above-referenced... Figure 1 The exemplary device 100 is described, wherein the same reference numerals denote the same elements. In the exemplary device 100, the polarity of the transformer T1 windings 106, 108, 110 is intentionally omitted. The omission of polarity is to highlight the characteristics of the exemplary device 100, and any suitable polarity of the three transformer windings 106, 108, 110 may be advantageously employed without departing from the spirit or scope of the disclosed embodiments.

[0119] To illustrate this feature, the exemplary device 700 includes polarity markings 702 for three transformer windings 106, 108, and 110. As used herein, the transformer winding polarity is marked by placing a dot at one end of each transformer winding, wherein, as is typical of transformer polarity marking, current flowing into the dot of the primary winding causes a corresponding current to flow out of the dot of the secondary winding. When the two switching networks 130, 132 and the SR component S7 are properly operated, the exemplary power converter device 700 is equivalent to the exemplary device 100 described above.

[0120] Figure 8 A schematic diagram of an exemplary power conversion device 800 incorporating aspects of the disclosed embodiments is shown. The exemplary device 800 is similar to the above-referenced... Figure 1 The exemplary device 100 described herein refers to the same reference numerals denote the same elements. In device 800, as indicated by polarity reference numeral 802, the polarity of the second primary winding 108 is the same as that referenced in the exemplary device 700 described above. Figure 7 The polarities shown are opposite. When the second switching network 134 is properly operated, the exemplary device 800 becomes equivalent to the exemplary device 700 and provides similar power conversion characteristics.

[0121] Figure 9 A schematic diagram of an exemplary power conversion device 900 incorporating aspects of the disclosed embodiments is shown. The exemplary device 800 is similar to the above-referenced... Figure 1 The exemplary device 100 is described, wherein the same reference numerals denote the same elements. In the exemplary device 900, the position of the SR component S8 has been moved compared to the SR component S7 of device 100, wherein the SR component S8 is connected between the second end 140 of the secondary winding 110 and the second DC node 126. The exemplary device 900 is equivalent to the exemplary device 100 and provides equivalent power conversion characteristics when the SR component S8 is properly operated.

[0122] It should be noted that when the SR component S8 is oriented as shown (with its source 902 connected to the secondary winding 110 and its drain connected to the second DC node), the device 900 provides DC power to the load 146 in the same polarity as provided by the device 100 described above. Alternatively, the SR component S8 can have the opposite polarity, with the source 902 connected to the second DC node 126 and the drain connected to the secondary winding 110. When the SR component S8 is connected in this opposite polarity and operated appropriately, the polarity of the DC power delivered to the load 146 will be reversed.

[0123] Figure 10 A schematic diagram of an exemplary power conversion device 1000 incorporating aspects of the disclosed embodiments is shown. The exemplary device 1000 is similar to the exemplary device 100 described above with reference to Figure 1 where like reference numerals indicate like elements. In comparison to the exemplary device 100 described above, the second series resonant impedance Zr2 in the exemplary device 1000 is connected in parallel with the fifth switching device S5. Converting the second series resonant impedance Zr2 from being connected in parallel with the sixth switching device S6 (as shown in the device 100 described above) to being connected in parallel with the fifth switching device S5 results in a power conversion device 1000 that is equivalent to the exemplary device 100.

[0124] Figure 11 A schematic diagram of an exemplary power conversion device 1100 incorporating aspects of the disclosed embodiments is shown. The exemplary device 1100 is similar to the exemplary device 100 described above with reference to Figure 1 where like reference numerals indicate like elements. In comparison to the exemplary device 100 described above, the first series resonant impedance Zr1 in the exemplary device 1100 is connected in parallel with the first bidirectional switch 102. Converting the first series resonant impedance Zr1 from being connected in parallel with the second bidirectional switch 104 (as shown in the device 100 described above) to being connected in parallel with the first bidirectional switch 102 results in a power conversion device 1100 that is equivalent to the exemplary device 100 described above.

[0125] Figure 12 A schematic diagram of an exemplary power conversion device 1200 incorporating aspects of the disclosed embodiments is shown. The exemplary device 1200 is similar to the exemplary device 100 described above with reference to Figure 1The exemplary device 100 is described, where like reference numerals refer to like elements. In contrast to the exemplary device 100 described above, a second series resonant impedance Zr2 in the exemplary device 1200 is in parallel with the fifth switching device S5. In further contrast to the exemplary device 100 described above, a first series resonant impedance Zr1 in the exemplary device 1200 is in parallel with the first bidirectional switch 102. As shown in the exemplary device 1200, changing the parallel of the first series resonant impedance Zr1 and the second series resonant impedance Zr2 results in a power conversion device equivalent to the exemplary device 100 described above, and provides power conversion characteristics equivalent to the exemplary device 100 described above.

[0126] Figure 13 A schematic diagram of an exemplary power conversion device 1300 incorporating aspects of the disclosed embodiments is shown. The exemplary device 1300 is similar to the device 100 described above with reference to FIG. 1, and like reference numerals refer to like elements. In the exemplary device 1300, a second transformer T2 is used to transfer power from the first series resonant impedance Zr1 to the load 146, and a third transformer T3 is used to transfer power from the second series resonant impedance Zr2 to the load 146. Figure 1 The exemplary device 100 is described, where like reference numerals refer to like elements. The exemplary device 1300 employs dual transformers T2, T3 to provide power conversion characteristics similar to the device 100 described above.

[0127] In the exemplary device 1300, the second transformer T2 is used to transfer power from the first series resonant impedance Zr1 to the load 146, and the third transformer T3 is used to transfer power from the second series resonant impedance Zr2 to the load 146. In the exemplary device 1300, the first series resonant impedance Zr1 includes the first winding 1302 of the second transformer T2 in series with the first resonant inductance Lr1 and the first resonant capacitance Cr1. A first end 1310 of the secondary winding 1304 of the second transformer T2 is coupled to the first DC node 124 through the SR switching device S7. A second end 1312 of the secondary winding 1304 of the second transformer T2 is coupled to the second DC node 126.

[0128] The second series resonant impedance Zr2 includes the first winding 1306 of the third transformer T3 in series with the second resonant inductance Lr2 and the second resonant capacitance Cr2. A first end 1314 of the secondary winding 1308 of the third transformer T3 is connected to the second DC node 126. A second end 1316 of the secondary winding 1308 is coupled to the first DC node 124 through the SR switching device S8. The device 1300 provides dual leg power conversion characteristics similar to the device 100 described above.

[0129] The use of the dual leg topology shown in the device 100 provides an AC / DC power conversion device 100 that supports WIWO operation, suitable for many charger applications today. In the device 100, soft switching can be achieved in all modes of operation, and most of the energy is processed only once, resulting in an AC / DC power converter that can operate efficiently. The bridgeless design also helps to improve system efficiency.

[0130] Thus, although there have been shown, described and pointed out fundamental novel features of the application as applied to the exemplary embodiments of the application, it will be understood that various omissions and substitutions and changes in the form and details of devices and methods illustrated, and in their operation, can be made by those skilled in the art without departing from the spirit and scope of the application. Further, it is expressly intended that all combinations of those elements that perform substantially the same function in substantially the same way to achieve the same results are within the scope of the application. Moreover, it should be recognized that structures and / or elements from a disclosure of any form or embodiment of the application can be incorporated in any other form or embodiment of the application, as a general matter of design choice. It is the intention of the inventor to retain all patentable combinations of the many aspects of the application disclosed and claimed herein. Therefore, the application should only be limited by the scope of the appended claims.

Claims

1. A power converter (100), characterized in that, The power converter (100) includes: The transformer (T1) includes a first primary winding (106) magnetically coupled to the secondary winding (110); The first series resonant impedance (Zr1) includes a first resonant inductor (Lr1), a first resonant capacitor (Cr1), and a first primary winding (106) connected in series. A first switching network (130) is connected between a first AC power node (122) and a second AC power node (128). The first switching network (130) includes a first bidirectional switch (102) connected in series with a second bidirectional switch (104), and the first series resonant impedance (Zr1) is connected in parallel with the second bidirectional switch (104). A rectifier switch (S7) is connected between the first end (138) of the secondary winding (110) and the first DC node (124). The second end (140) of the secondary winding (110) is connected to the second DC node (126). The first bidirectional switch (102) includes a first switching device (S1) connected in series with the second switching device (S2), and the source (114) of the first switching device (S1) is connected to the source (116) of the second switching device (S2). The second bidirectional switch (104) includes a third switch (S3) connected in series with the fourth switch (S4), and the source (118) of the third switch (S3) is connected to the source (120) of the fourth switch (S4). The power converter (100) further includes: a second primary winding (108) magnetically coupled to the secondary winding (110); The second series resonant impedance (Zr2) includes the second resonant inductor (Lr2), the second resonant capacitor (Cr2), and the second primary winding (108) connected in series. A diode bridge (132) is connected between the first AC power node (122) and the second AC power node (128) and is used to generate a first DC power supply (Vdc). The second switching network (134) is connected in parallel with the first DC power supply (Vdc), and the second switching network (134) includes a fifth switching device (S5) connected in series with the sixth switching device (S6). The second series resonant impedance (Zr2) is connected in parallel with the sixth switching device (S6); The power converter (100) also includes an AC voltage (Vac) connected between the first AC power node (122) and the second AC power node (128); When the magnitude of the AC voltage (Vac) is greater than a predetermined voltage threshold, the fifth switching device (S5) and the sixth switching device (S6) are turned off, and the first bidirectional switch (102) and the second bidirectional switch (104) are operated to transfer power from the AC voltage (Vac) to the first DC node (124) and the second DC node (126). When the amplitude of the AC voltage (Vac) is not greater than the predetermined voltage threshold, the first bidirectional switch (102) and the second bidirectional switch (104) are turned off, and the fifth switching device (S5) and the sixth switching device (S6) are operated to transfer power from the AC voltage (Vac) to the first DC node (124) and the second DC node (126).

2. The power converter (100) according to claim 1, characterized in that, The predetermined voltage threshold is greater than the DC output voltage multiplied by the turns ratio (N2) between the first primary winding (106) and the secondary winding (110).

3. The power converter (100) according to claim 1, characterized in that, The first series resonant impedance (Zr1) is connected in parallel with the first bidirectional switch (102).

4. The power converter (100) according to claim 1, characterized in that, The second series resonant impedance (Zr2) is connected in parallel with the fifth switching device (S5).

5. The power converter (100) according to claim 1, characterized in that, The first DC node (124) is a positive DC node, and the second DC node (126) is a negative DC node.

6. The power converter (100) according to claim 1, characterized in that, The first DC node (124) is a negative DC node, and the second DC node (126) is a positive DC node.

7. The power converter (100) according to claim 1, characterized in that, The power converter (100) includes a bus capacitor (Cbus) connected in parallel with the second switching network (134).

8. The power converter (100) according to claim 1, characterized in that, The power converter (100) includes an output capacitor (Cout) connected between the first DC node (124) and the second DC node (126).

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