Auxiliary circuit for zero voltage switching in phase-shifted full-bridge converter

Abstract

An example apparatus can include one or more of a transformer, a primary circuit electrically coupled to the transformer, and a first auxiliary circuit and a second auxiliary circuit, wherein the primary circuit includes a first bridge leg having a first pair of switches and a second bridge leg having a second pair of switches, the first auxiliary circuit is electrically coupled to the first bridge leg of the primary circuit, the second auxiliary circuit is electrically coupled to the second bridge leg of the primary circuit, wherein each auxiliary circuit is configured to store energy when one switch of a respective pair of switches is on and the other switch of the respective pair of switches is off, and provide the stored energy to recharge all attached capacitances in the respective bridge leg when both switches of the respective pair of switches are off.

Description

Background Technology

[0001] Some system constraints can make modern resonant converters less desirable within a system. For example, these constraints might include a very high peak-to-average power ratio or a very wide output voltage range. In these cases, older converter types such as phase-shifted full-bridge converters may offer better solutions. Phase-shifted full-bridge converters are similar to full-bridge DC-DC converters but with added phase-shift control. Phase-shift control enables the converter to achieve "soft switching," thereby reducing switching losses and improving efficiency.

[0002] However, phase-shifted full-bridge converters typically suffer from zero-voltage switching loss during low-power output. Furthermore, for converters with high peak power ratios, the use of large switching semiconductors (common in phase-shifted full-bridge converters) and high voltage ratings results in unacceptably high no-load losses. Related circuits in use have the same fundamental advantages, and in particular, these circuits may experience startup problems and variations in stored charge depending on the converter's regulation state. Summary of the Invention

[0003] One example embodiment provides an apparatus that may include at least one of: a transformer, a primary circuit electrically coupled to the transformer, and a first auxiliary circuit and a second auxiliary circuit, wherein the primary circuit includes a first arm having a first pair of switches and a second arm having a second pair of switches, the first auxiliary circuit being electrically coupled to the first arm of the primary circuit, and the second auxiliary circuit being electrically coupled to the second arm of the primary circuit, wherein each auxiliary circuit is configured to store energy when one switch in the corresponding pair of switches is turned on and the other switch in the corresponding pair of switches is turned off, and to provide the stored energy when both switches in the corresponding pair of switches are turned off, so as to recharge all attached capacitors in the corresponding arm. Attached Figure Description

[0004] Figure 1A This is a schematic diagram illustrating an example of a phase-shifted full-bridge converter according to an exemplary embodiment.

[0005] Figure 1B This is a diagram illustrating the example embodiment from... Figure 1A A schematic diagram of the power signal waveforms of the four switches in a phase-shifted full-bridge converter.

[0006] Figure 2A This is a schematic diagram illustrating an example of an auxiliary circuit for a ZVS phase-shifted full-bridge power converter according to other exemplary embodiments.

[0007] Figure 2BThis is a schematic diagram illustrating the changes in voltage and current over time at different locations within the auxiliary circuit according to an example embodiment. Detailed Implementation

[0008] The example embodiment relates to an auxiliary circuit that can be integrated into the primary circuitry of a ZVS phase-shifted full-bridge converter, such as one commonly used to power loads (e.g., speakers, amplifiers, etc.). Zero-voltage switching (ZVS) is a technique that disconnects the switch when the voltage is zero. It is a "soft-switching" technique that reduces thermal requirements, switching losses, electromagnetic interference (EMI) radiation, etc.

[0009] Traditional ZVS phase-shifted full-bridge converters struggle to achieve zero-voltage switching (ZVS) when there is no voltage across the load. The auxiliary circuitry described in this paper ensures sufficient current in the circuit to achieve ZVS at the main switch, even in the absence of power transmission through the transformer.

[0010] The primary circuit of the ZVS phase-shifted full-bridge converter may include four switches (e.g., Q1, Q2, Q3, and Q4) and four capacitors, each switch coupled to a different corresponding capacitor such that the corresponding capacitor provides inherent capacitance and / or external capacitance in / across the switch. The primary circuit also includes leading and lagging arms coupled to opposite sides of a transformer configured to supply power to the secondary side of the ZVS phase-shifted full-bridge converter.

[0011] According to various embodiments, the auxiliary circuitry may include one or more inductors, one or more diodes, one or more capacitors, etc., which can provide the necessary current of the required polarity to the different switches (e.g., four switches) in the full-bridge power converter to achieve completely zero-voltage switching even during phase-shift periods. This circuitry utilizes the added diodes to generate charge limiting and can allow variations in pulse length and / or phase shift without significantly altering the charge of the auxiliary circuitry. This circuitry provides the ability to operate the phase-shift converter completely unloaded at any output voltage, while still operating with completely zero-voltage switching of all phase-shift bridge arm semiconductors.

[0012] During operation, the effect of the auxiliary circuitry will be canceled out by the transmitted current at some point. Therefore, to achieve complete zero-voltage switching across the entire voltage and load range, the circuit can be supplemented with a controlled transformer magnetizing inductance and / or leakage inductance to close all gaps for all operating points. This circuit enables the design of power supplies with extremely high peak power while maintaining low no-load power consumption and low EMC radiation.

[0013] The auxiliary circuit provides the necessary current of the required polarity to achieve completely zero-voltage switching even during periods without phase shift. The current is controlled by the size of the capacitor in the auxiliary circuit, which limits the amount of charge on the capacitor. The capacitor is charged via an inductor included in the auxiliary circuit, and the energy charged generates a current in the inductor. The sizes of the inductor and capacitor in the auxiliary circuit determine the time required for the circuit to recharge to the new potential. This current is tuned sufficient to overcome the output capacitance of the switch within a reasonable time, and the timing is configured to allow for changes in the state of the auxiliary circuit well before the next switching event occurs.

[0014] The primary circuit of the ZVS phase-shifted full-bridge converter has four switches that can be operated to generate voltage across the transformer. The first arm includes a first pair of switches (i.e., Q1 and Q2), and the second arm includes a second pair of switches (i.e., Q3 and Q4). During operation, the four switches are turned on and off at different times, thereby generating voltage across the transformer, which allows power to be transferred from the primary circuit to the secondary circuit (i.e., the secondary circuit of the load).

[0015] Components within the auxiliary circuitry of each bridge arm (e.g., inductors, capacitors, diodes, etc.) do not participate in the power transfer from the primary to the secondary side. Instead, the components within the auxiliary circuitry hold the current within the circuit. The auxiliary circuitry can continuously supply current to ensure that there is always sufficient current in the system for zero-voltage switching. Due to the auxiliary circuitry, there will be current in the system even when there is no load on the secondary side of the circuit. The auxiliary circuitry can act as both a current sink and a current source to ensure that zero-voltage switching is always possible. Once a capacitor is charged to equal the input voltage, it conducts a diode, allowing current to flow out and preventing further charging and energy storage in the capacitor.

[0016] A standard full-bridge converter implementation typically uses four devices (such as metal-oxide-semiconductor field-effect transistors (MOSFETs)) as switches and one transformer, such as... Figure 1AAs shown in the configuration. To transfer electricity from the primary side of the transformer to the secondary side, a voltage difference must be generated across the primary side. This voltage difference is created by changing which switches are turned on and which are turned off, thus enabling a voltage difference to be formed across the transformer. For example, when switches Q1 and Q4 are turned on approximately simultaneously, while switches Q2 and Q3 are turned off approximately simultaneously, a positive primary voltage is formed. Conversely, when switches Q1 and Q4 are turned off, while switches Q2 and Q3 are turned on, a negative primary voltage is formed. This process can be repeated. For example, switches Q2 and Q3 can then be turned off, and switches Q1 and Q4 can be turned on again. By alternating the simultaneous on / off states of switches Q1 and Q4 and the simultaneous off / on states of switches Q2 and Q3 in a phase-shifting manner at different times, electricity can be driven through the transformer.

[0017] The ZVS phase-shifted full-bridge converter may include logic that controls when switches are turned on and off. For example, this logic could control the switches to allow voltages of two polarities to pass through the transformer. The goal is to maintain a balance between the magnetic flux and the magnetic field. The converter switches in a phase-shifted manner, with both switches being on for half the time. The first pair of switches (leading arms) typically alternates between on and off based on a fixed clock signal. Furthermore, the second pair of switches (lagging arms) turns on and off at different times than the first pair. Simultaneously, auxiliary circuitry allows the switches to be turned on even when the voltage at the switch is zero.

[0018] The auxiliary circuitry, implemented within the primary circuitry, is an independent circuit connected to each corresponding point in the bridge arm. The auxiliary circuitry can operate in a 50% high and 50% low manner. It alternates between high and low charging states of the capacitors. Recharging the capacitors takes a short time due to the presence of inductors. If the system moves the capacitors from zero volts to a specific input voltage, this also takes time. Charge can be transferred through the inductors. The charge required to charge the capacitors is retained in the inductors as magnetic flux. This logic can be used to pre-set how much current (e.g., at least a minimum threshold level) is flowing in the network when switching from high to low or low to high.

[0019] Figure 1A The illustration shows an example of a zero-voltage switching (ZVS) phase-shifted full-bridge converter 100A according to an exemplary embodiment. Figure 1B Illustrated explanation of the example embodiment from Figure 1A The waveforms of the pulse signals from the four switches in the circuit are shown in Figure 100B. (Refer to...) Figure 1A and Figure 1BThe ZVS phase-shifted full-bridge converter 100A described herein provides isolation between the primary circuit 120 and the secondary circuit 130 of the ZVS phase-shifted full-bridge converter 100A via a transformer 125. The primary circuit 120 includes a voltage source 110 as input and four electronic switches (e.g., MOSFETs, insulated-gate bipolar transistors (IGBTs), etc.). The four electronic switches include an upper left switch 121, a lower left switch 122, an upper right switch 123, and a lower right switch 124.

[0020] In this example, transformer 125 can be a high-frequency transformer. It also provides isolation between primary circuit 120 (primary side) and secondary circuit 130 (secondary side) as well as any desired voltage gain. Secondary circuit 130 also includes an inductor 132 for limiting output current ripple and a capacitor 134 for acting as a filter to stabilize the output voltage to load 136 (e.g., an amplifier). To enable power transfer from primary circuit 120 to secondary circuit 130 (and to power load 136), four electronic switches alternate between on and off states.

[0021] In this example, the left arm of the primary circuit 120 includes a first pair of switches (i.e., Q1 and Q2). This first pair of switches is also labeled as upper left switch 121 (Q1) and lower left switch 122 (Q2). To prevent shoot-through, i.e., short-circuiting of the voltage source 110 via upper left switch 121 (Q1) and lower left switch 122 (Q2), upper left switch 121 and lower left switch 122 can be modulated with a 180-degree phase difference, so that upper left switch 121 and lower left switch 122 do not simultaneously "conduct". An example of phase shift for upper left switch 121 (Q1) is shown in... Figure 1B In this example, it is represented as pulse signal 141. Meanwhile, an example of the pulse signal for the lower left switch 122 is shown in... Figure 1B The signal is represented as pulse signal 142.

[0022] The right arm of the primary circuit 120 includes a second pair of switches (i.e., switches Q3 and Q4, etc.). This second pair of switches is also labeled as upper right switch 123 (Q3) and lower right switch 124 (Q4). To prevent shoot-through, upper right switch 123 and lower right switch 124 can be modulated with a 180-degree phase difference (e.g., out of phase, etc.) so that upper right switch 123 (Q3) and lower right switch 124 (Q4) will not be "on" simultaneously. Thus, the pulse shapes of upper right switch 123 (Q3) and lower right switch 124 (Q4) will not be simultaneously on.

[0023] Furthermore, in order to generate voltage on transformer 125, the right and left arms of the primary circuit 120 need to be out of phase relative to each other. To achieve this, the pulse signal of the upper right switch 123 (Q3) is phase-shifted relative to the upper left switch 121 (Q1), as follows: Figure 1BThe example shows pulse signal 143. Similarly, the pulse signal of the lower right switch 124 (Q4) is phase-shifted relative to the lower left switch 122 (Q2), as shown... Figure 1B The example shows pulse signal 144.

[0024] During operation of the primary circuit 120, the primary circuit 120 may include control logic (not shown) to control when and for how long the switches are turned on. When the upper left switch 121 (Q1) and the lower right switch 124 (Q4) are both turned on, and the lower left switch 122 (Q2) and the upper right switch 123 (Q3) are turned off, a positive voltage flows through the transformer, such as... Figure 1B The example shows pulse signal 145. On the other hand, when the upper left switch 121 (Q1) and the upper right switch 123 (Q3) are turned on simultaneously, and the lower left switch 122 (Q2) and the lower right switch 124 (Q4) are turned off, the transformer 125 is short-circuited, resulting in no voltage (zero voltage) across the transformer 125, as shown by pulse signal 145.

[0025] Furthermore, when the lower left switch 122 (Q2) and the upper right switch 123 (Q3) are simultaneously turned on, while the upper left switch 121 (Q1) and the lower right switch 124 (Q4) are turned off, a negative voltage is generated across the transformer 125, such as... Figure 1B The example shows pulse signal 145. The phase-shifting pattern of the switch, which is turned on and off in an alternating and phase-shifting manner, can continue on an iterative basis to generate electricity, which is then transmitted to the secondary circuit 130 via transformer 125.

[0026] Figure 2A The diagram illustrates view 200A of an auxiliary circuit for a ZVS phase-shifted full-bridge power converter according to other example embodiments. (Refer to...) Figure 2A The auxiliary circuitry can be integrated into the primary circuitry of the ZVS phase-shifted full-bridge power converter. In this example, a primary circuitry with four switches is shown: an upper left switch 210, a lower left switch 211, an upper right switch 212, and a lower right switch 213. The primary circuitry also includes a voltage source 202 and a transformer 208. Furthermore, the primary circuitry includes a leading bridge arm output 204 electrically coupled to the right bridge arm of the primary circuitry and a lagging bridge arm output 206 electrically coupled to the left bridge arm of the primary circuitry.

[0027] exist Figure 2A In this example, capacitor 214 is located across the upper left switch 210, capacitor 215 is located across the lower left switch 211, capacitor 216 is located across the upper right switch 212, and capacitor 217 is located across the lower right switch 213. Here, capacitors 214, 215, 216, and 217 store energy, which allows the corresponding upper left switch to turn on when the voltage across the switch is close to zero.

[0028] The components of the auxiliary circuit are electrically coupled between the right and left arms of the primary circuit. In this example, the auxiliary circuit includes a first auxiliary circuit (e.g., inductor 220, diode 224, diode 225, capacitor 222, and capacitor 223) and a second auxiliary circuit (e.g., inductor 230, diode 234, diode 235, capacitor 232, and capacitor 233); however, a combination of these circuits may also be referred to as an auxiliary circuit. The first auxiliary circuit includes the left-side inductor 220, and the second auxiliary circuit includes the right-side inductor. The first auxiliary circuit also includes diode 224 electrically coupled to the left-side inductor 220 and the upper left switch 210, and diode 225 electrically coupled to the left-side inductor 220 and the lower left switch 211. The first auxiliary circuit also includes capacitor 222 located across diode 224 and capacitor 223 located across diode 225.

[0029] In this example, the second auxiliary circuit includes a diode 236 electrically coupled to the right inductor 230 and the upper right switch 212, and a diode 235 electrically coupled to the right inductor 230 and the lower right switch 213. The second auxiliary circuit also includes a capacitor 232 located across the diode 236 and a capacitor 233 located across the diode 235.

[0030] In this example, the cross-sectional area 270 of the first auxiliary circuit depicts a point 240 representing a voltage pulse, a point 250 representing the current on the left inductor 220, and a point 260 representing the voltage relative to capacitors 222 and 223.

[0031] In some embodiments, both arms can operate at a fixed frequency and a fixed duty cycle. This is true in a general sense, but may not be true in all specific cases, nor is it necessarily a necessary condition (i.e., it can be designed to switch the frequency or duty cycle, which may limit the operation of the circuit, but does not mean that the circuit cannot be used). One advantage of the auxiliary circuit in this design is that even when no power is being transferred and the transformer primary voltage is zero, there will be pulses of a relevant length on each arm, which can energize the circuit to operate reliably regardless of the operating point. In contrast, conventional converters (such as full-bridge converters, half-bridge, push-pull, single-switch topologies, etc.) stop generating pulses during no-power periods.

[0032] The stored energy is the charge required to charge the capacitors across diodes 224 and 225. This charge will be converted into current in the left-hand inductor 220. Depending on the size of the components, this process may proceed faster (if the components are small) or slower (if the components are large). The current needs to be high enough for the switching to complete within a reasonable time, and preferably well before the next switching cycle. Even though each arm operates at a fixed frequency and duty cycle, the pulse needs to be longer or shorter to advance the commutation of the arms over time because the phase between the arms changes with the adjustment. Proper design of these components will make the circuit unaffected by these variations, as long as they remain moderate. In this example, the circuit is fully charged at approximately 75% of the pulse, leaving 25% of the pulse available for the adjustment to shorten the pulse without affecting the charging current. Since the final current is clamped, there is practically no limit to how long the pulse can last.

[0033] According to various embodiments, each auxiliary circuit is configured to store energy when one switch in a corresponding pair of switches is turned on and the other switch in a corresponding set of switches is turned off. Furthermore, each auxiliary circuit is configured to provide the stored energy to recharge all attached capacitors in the corresponding bridge arm when both switches in the corresponding pair are turned off. The auxiliary circuit can keep switches (e.g., MOSFETs, etc.) energized, thereby reducing some of their parasitic characteristics, such as inherent nonlinear capacitance. In addition, the auxiliary circuit can reduce electromagnetic interference (EMI), noise, and other problems, as well as power loss at low operating levels where the circuit outputs minimal power.

[0034] Figure 2B Illustrated explanation according to the example embodiment Figure 2A View 200B shows the voltage and current variations over time at different locations in the auxiliary circuit during operation of the ZVS phase-shifted full-bridge converter. (Refer to...) Figure 2B The graph 272 shows the voltage and current changes over time. Here, signal 242 corresponds to the voltage change over time at point 240 of cross-sectional region 270, signal 252 corresponds to the current change over time at point 250 of cross-sectional region 270, and signal 262 corresponds to the voltage change over time at point 260 of cross-sectional region 270.

[0035] At point t1 in curve 272, the current at the inductor is 0, as shown in signal 252. Simultaneously, switch Q2 is turned on, making the voltage at point 240 0V, as shown in signal 242. Due to the previous pulse, the voltage at point 260 is Vs, as shown in signal 262, where Vs refers to the steady-state voltage. As a result, a significant voltage difference exists across the left inductor 220. This voltage will increase the current in the inductor, and simultaneously, capacitors 222 and 223 across diodes 224 and 225, respectively, will carry the same current, thus changing their charge and causing the voltage at point 260 to decrease. As the voltage at point 260 decreases, the voltage across the left inductor 220 decreases, and the current will increase at a decreasing rate over time, as shown in signal 252. As time approaches t2, the voltage across the left inductor 220 will approach 0, and the current will approach steady state.

[0036] At t2 in curve 272, in this example, the left inductor 220 has been charged to a steady-state current level (-As), and the voltages at points 240 and 260 are both zero, as shown in signals 242 and 262. Since the left inductor 220 has charging current, it wants to continue charging capacitors 222 and 223 across diodes 224 and 225, respectively. However, at this point, diode 225 will prevent the voltage at point 260 from becoming negative, and when this happens, diode 225 will take over the current from capacitors 222 and 223 alone. The charging current will now flow through diode 225 and Q2 and can remain constant for a relatively long time. Due to various losses in the system, the current will decay slowly, but for a short period before the next switching cycle, the current will remain almost constant.

[0037] At point t3 in curve 272, the regulating system (not shown) determines it is time to open the lower left switch 211. There is a short period during which both the upper left switch 210 and the lower left switch 211 are open, commonly referred to as the dead time. When the lower left switch 211 is open, current can no longer flow through that path, but instead flows through capacitor 215 across the lower left switch 221. Naturally, without recharging both capacitors 214 and 215, the voltage at point 240 cannot change, and therefore current will be shunt between capacitors 214 and 215. The current distribution between capacitors 214 and 215 will depend on the size of these capacitors.

[0038] If capacitors 214 and 215 are inherent in the semiconductor switch, then it will be highly nonlinear, and the voltage will initially begin to change slowly because the capacitance in the lower left switch 211 is much larger when the voltage across it is small. Then, as the voltage increases, the capacitance decreases, and the voltage changes more rapidly until it begins to approach the supply voltage, at which point the capacitance in the upper left switch 210 increases. The current will be distributed according to the capacitance. If capacitors 214 and 215 are discrete or linear, the current will be distributed more evenly, and the rate of change of voltage will be more constant. The most useful approach is to use a combination of inherently nonlinear capacitors with external linear capacitors, because the inherently nonlinear capacitors help to quickly disconnect the lower left switch 211 before the voltage is established (thus achieving ZVS), while the external linear capacitors slow the transition midway to reduce EMC. As the voltage at point 240 increases (as shown in signal 242), the voltage across the inductor also increases (as shown in signal 252), but now with a different polarity than before. When the voltage changes, the current will begin to change at the same rate as the voltage. This is why the current is already approaching zero voltage when the voltage change is complete.

[0039] At time t4 in curve 272, the regulating system determines that the dead time will end in some way (this could be pre-programmed, fixed, or varying based on the applied current, or sensed by voltage detection). In response, the upper left switch 210 turns on with no voltage across it, thus achieving ZVS. At this point, the current at point 250 has begun to decay, but the voltage across the inductor is now fixed because diode 224 conducts current, keeping the voltage at point 260 at zero volts, while the voltage at point 240 is fixed at the steady-state voltage (Vs). This means that the left inductor 220 will experience a fixed voltage almost equal to the input voltage, but with a different polarity than the current within it. Based on this, the current will move towards 0 at a fixed rate.

[0040] At time t5 in graph 272, the current in the inductor has reached 0A. However, there is still a voltage across the left inductor 220, although diode 222 is no longer conducting. Therefore, nothing maintains the potential at point 260 except for capacitors 214 and 215 across the upper left switch 210 and lower left switch 211. Capacitors 214 and 215 will carry current as they charge. The voltage at point 260 will begin to move from 0V toward the input voltage. Initially, the inductor current is low, so the voltage change is slow, but as the current increases, the rate of voltage change also increases. As the voltage at point 260 increases, the voltage across the left inductor 220 decreases, so the inductor current will stop changing when the voltage at point 260 approaches the input voltage.

[0041] At time t6 in graph 272, when the voltage at point 260 has increased to or slightly above the input voltage, diode 224 will prevent the voltage at point 260 from rising by taking over the current previously flowing through capacitors 222 and 223, respectively, across diodes 224 and 225. At this time, the current in the left inductor 220 has charged to the desired current level, and the voltage across the left inductor 220 is close to 0. The current will decay very slowly, but will remain almost constant for a short period until the next switching cycle. The current at point 250 will now flow through diode 224 and the upper left switch 210.

[0042] At time t7 in graph 272, the control system determines it's time to open the upper left switch 210, and both upper left switch 210 and lower left switch 221 will be off for a short period, also known as the dead time. During this dead time, the current at point 250 can no longer flow through upper left switch 210, so it begins to flow through capacitors 214 and 215, causing charge to accumulate in capacitors 214 and 215. As capacitors 214 and 215 charge, the voltage at point 240 will begin to move towards 0V. The current at each moment will be distributed between capacitors 214 and 215 according to their capacitance, which may be voltage-dependent. Since the voltage will not change immediately if upper left switch 210 is opened quickly enough, the inherently high nonlinear capacitance will help prevent the voltage from building up immediately, so upper left switch 210 is off when there is no voltage across it. As the voltage at point 240 changes, the voltage across the left inductor 220 at point 250 also changes, and the current at point 250 will begin to change towards 0.

[0043] At time t8 in graph 272, the regulating system determines the end of the dead time in some way (this could be pre-programmed, fixed, or varying based on the applied current, or sensed by voltage detection). Here, the lower left switch 211 is turned on when there is no voltage across it, thus achieving ZVS. At this point, the current at point 250 has begun to decay towards 0, but the voltage across the left inductor 220 is now fixed because diode 225 conducts current, maintaining the voltage at point 260 at the input voltage, while the voltage at point 240 is fixed at 0V. This means that the left inductor 220 will experience a fixed voltage almost equal to the input voltage, but with a different polarity than the current within it. Based on this, the current will move towards 0 at a fixed rate.

[0044] At time t9 in graph 272, the current in the left inductor 220 will reach 0A. At this time, there is still a voltage across the left inductor 220, but diode 224 is no longer conducting. Therefore, nothing maintains the potential at point 260 except for capacitors 222 and 223 across diodes 224 and 225. Capacitors 222 and 223 will carry current as they charge. The voltage at point 260 will begin to shift from the input voltage towards 0V.

[0045] It should be readily understood that, as summarized and illustrated herein in the accompanying drawings, the various components of this application can be arranged and designed in a variety of different configurations. Therefore, the detailed description of the embodiments is not intended to limit the scope of the claimed application, but merely represents selected embodiments of the application.

[0046] It will be readily understood by those skilled in the art that the above can be practiced with steps in a different order and / or with hardware components configured differently from the disclosed configuration. Therefore, although this application has been described based on these preferred embodiments, certain modifications, variations, and alternative constructions will be apparent to those skilled in the art.

[0047] While preferred examples of this immediate solution have been described, it should be understood that the described examples are merely illustrative, and the scope of this exemplary solution will be limited only by the appended claims in consideration of all its equivalents and modifications (e.g., protocols, hardware devices, software platforms, etc.).

Claims

1. A phase-shifting full-bridge device, comprising: transformer; Electrically coupled to the primary circuit of the transformer, wherein the primary circuit includes a first bridge arm having a first pair of switches and a second bridge arm having a second pair of switches; as well as A first auxiliary circuit and a second auxiliary circuit, wherein the first auxiliary circuit is electrically coupled to the first bridge arm of the primary circuit, and the second auxiliary circuit is electrically coupled to the second bridge arm of the primary circuit. Each auxiliary circuit is configured to store energy when one switch in a corresponding pair of switches is on and the other switch in the corresponding set of switches is off, and to provide the stored energy to recharge all attached capacitors in the corresponding bridge arm when both switches in the corresponding pair of switches are off.

2. The apparatus according to claim 1, wherein each auxiliary circuit is further configured to reduce the parasitic characteristics of the corresponding pair of switches when the transformer outputs power to the secondary circuit.

3. The apparatus according to claim 1, wherein the first auxiliary circuit includes an inductor coupled to the first pair of switches, a diode coupled to the inductor and a first switch of the first pair of switches, a second diode coupled to the inductor and a second switch of the first pair of switches, a capacitor coupled to the first diode, and a second capacitor coupled to the second diode.

4. The apparatus according to claim 3, wherein the inductor is configured to store energy therein when the first switch is turned on and the second switch is turned off, and to release the stored energy when the first switch in the first pair of switches is turned off and the second switch in the first pair of switches is still turned off.

5. The apparatus according to claim 3, wherein the second auxiliary circuit includes a second inductor coupled to the second pair of switches, a third diode coupled to the second inductor and a first switch in the second pair of switches, a fourth diode coupled to the second inductor and a second switch in the second pair of switches, a third capacitor coupled to the third diode, and a fourth capacitor coupled to the fourth diode.

6. The apparatus according to claim 5, wherein the second inductor is configured to store energy therein when the first switch in the second pair of switches is turned on and the second switch in the second pair of switches is turned off, and to release the stored energy when the first switch in the second pair of switches is turned off and the second switch in the second pair of switches remains off.

7. The apparatus according to claim 1, wherein each auxiliary circuit is integrated into the primary circuit of the phase-shifting full-bridge apparatus.

8. The apparatus according to claim 1 further includes a secondary circuit electrically coupled to the transformer and configured to receive power from the primary circuit via the transformer.

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