TW202008701A - Power converter - Google Patents

Abstract

A flyback power converter includes a hybrid clamp circuit and a corresponding power management unit that substantially optimizes the performance of the flyback power converter in its entire line and load ranges. The clamp circuit, which is connected in parallel to a primary winding of the flyback transformer, includes a parallel combination of a capacitor and resistor that is connected in series with a parallel combination of a switch and a diode. By sensing the operating conditions, the power management circuit configures the clamp circuit either as a passive clamp or as an active clamp. In the passive-clamp configuration, the switch is kept turned off. In the active-clamp configuration, the switch operates with pulse-width modulation (PWM) which enables ZVS turn-on of the main switch.

Description

Power converter and its control method

The invention relates to a power management and control method to optimize the performance of a power converter, and in particular to a flyback power converter.

Wide-band-gap semiconductor devices (wide-band-gap semiconductor devices) popularization and the current size of external power supply needs to shrink, such as notebooks, tablets, mobile devices, game consoles and printers (adapters) Or charger, continue to promote the large-scale development and research of high-efficiency and high-power density power conversion technology. In general, the size of a switch mode power supply can be reduced by increasing the switching frequency, because the size of passive components (such as transformers, input and output filters) can be reduced at higher switching frequencies.

As silicon-based components approach their theoretical performance limits, further performance improvement of power supplies becomes more difficult. However, emerging wide bandgap devices (such as gallium nitride-based devices and silicon carbide-based devices) are expected to bring value-added energy efficiency in the future because they have gate charge and output capacitance much lower than silicon counterparts improve. Since the wide bandgap device can operate at a higher switching frequency without reducing efficiency, the size of the power supply can be further reduced.

In low-power applications, flyback prototypes are widely used because of their simplicity and low cost. In order to achieve high efficiency at high switching frequencies, switching losses must be reduced. Various soft-switching technologies can be used to reduce switching losses. These technologies use circuit parasitic components, such as transformer leakage inductance and semiconductor component capacitance, to turn on at a reduced voltage. ) Switch, or turn off the switch at a reduced current. Specifically, under the zero-voltage-switching (ZVS) technology, the loss of the conduction switch is eliminated by turning on the device at a zero voltage; in the zero-current-switching (ZCS) technology Next, by turning off the device at zero current, the wear of closing the switch is eliminated.

An integral part of the flyback power converter is the clamping circuit, which is used to process the energy stored in the leakage inductance of the flyback transformer after the main switch is turned off. In general, the flyback prototype can be implemented in various clamping structures. As shown in FIG. 1a and FIG. 1b, two common clamp structures are RCD clamp and active clamp. In RCD clamping, the energy stored in the leakage inductance of the flyback transformer can be eliminated in the clamp resistor. In active clamping, the energy stored in the leakage inductance can be recycled for the turn-on of the zero-voltage switch (ZVS) of the main switch. In particular, in the RCD clamp structure, the turn-on of the zero-voltage switch (ZVS) of the main switch can only be achieved when the input voltage V _{IN is} lower than the output voltage V _O times N, where N is The coil ratio of the transformer, that is, the ratio of the number of primary coil turns and the number of secondary coil turns. Therefore, due to zero voltage switching (ZVS) and leakage inductance energy recovery, active clamping usually exhibits better performance than RCD clamping under conditions of high load and high input voltage. Conversely, under a low load condition, that is, when the flyback power converter operates in discontinuous-conduction mode (DCM) and the active clamping switch is turned on, the magnetizing inductance of the flyback transformer The resonance between the (magnetizing inductance) and the parasitic capacitance of the circuit has almost disappeared, and the turn-on loss of the switch in active clamping at a low input voltage (that is, V _IN <N*V _O ) is greater than that of the main switch. Reduced losses due to ZVS turn-on. Furthermore, since the energy stored in the leakage inductance of the flyback transformer under a lighter load is almost negligible, RCD clamping is usually performed at a lower load and low input voltage (that is, V _IN <N*V _O ) Shows better performance than active clamping.

Therefore, there is a need for a flyback power converter that can optimize performance over the entire line and load range.

The invention provides a flyback power converter, which has a hybrid clamping circuit and a corresponding power management unit. The hybrid clamping circuit is also a combined circuit with the characteristics of a passive RCD circuit and an active clamping circuit. It substantially optimizes the performance of the flyback power converter in the overall line and load range. According to an embodiment of the invention, the clamping circuit is connected in parallel with the primary coil of the flyback transformer, and it includes a parallel circuit with switches and diodes and a parallel circuit with capacitors and resistors connected in series. By detecting the operating conditions, the power management unit configures the clamping circuit as a passive clamping or an active clamping. In the passive clamping configuration, the switch remains closed. In the active clamping configuration, the switch works under the control of pulse width modulation (PMW), so that the zero-voltage switch (ZVS) of the main switch is turned on. In one embodiment, the power management unit includes an input voltage sensing circuit, an output current sensing circuit, and a circuit that provides an enable/disable signal to control the switch of the clamp circuit.

In order to achieve one, part, or all of the foregoing or other objectives, embodiments of the present invention provide a power converter for receiving an input voltage and providing an output voltage and an output current to a load. It includes: a transformer with a primary coil and a secondary coil, the secondary coil provides the output voltage and the output current to the load; a first switch, coupled to the primary coil, when the first switch is turned on ( turn on), the first switch couples the input voltage to the primary coil; an clamping circuit includes a first and a second parallel circuit and the first and the second parallel circuit are connected in series with each other, wherein the first A parallel circuit includes a second switch and a clamping diode. The second parallel circuit includes a clamping capacitor and a clamping resistor, so that the clamping circuit is closed or opened according to whether the second switch is closed open) to provide an active clamping or a passive clamping; a controller to periodically turn on and turn off the first switch to regulate the output voltage or the output current; and A power management unit is used to enable or disable the switching of the second switch according to the operating conditions of the power converter.

In one embodiment, the power management unit keeps the second switch continuously off for the set of operating conditions.

In one embodiment, the operating condition is determined based on at least one of the input voltage, a current through the first switch, the output voltage, the output current, and a switching frequency. An embodiment further includes a rectifier coupling the secondary coil to the load, wherein the operating condition is determined according to a current through the rectifier.

In one embodiment, the power converter operates in continuous conduction mode, discontinuous conduction mode or a threshold between continuous conduction mode and discontinuous conduction mode.

In one embodiment, the power management unit optimizes at least one of conversion efficiency, component stress, electromagnetic interference performance, and transformer performance.

In an embodiment, the power management unit selects the power converter to operate in the continuous conduction mode, the discontinuous conduction mode, or at least one of the threshold between the continuous conduction mode and the discontinuous conduction mode according to the operating condition.

In one embodiment, the first switch and the second switch will not turn on simultaneously during operation.

In one embodiment, the clamping circuit is coupled in parallel to the primary coil of the transformer.

In one embodiment, the clamping circuit is coupled to the first switch in parallel.

In an embodiment, the first switch is turned on at zero voltage; or when the input voltage is greater than N times the output voltage, the first switch at a voltage is approximately equal to the input voltage and N times The difference between the output voltages turns on, where N is the ratio of the number of primary coil turns to the number of secondary coil turns.

In one embodiment, one of the second switches has a built-in diode as the embedded diode.

In an embodiment, a filter capacitor is further included in parallel with the load, wherein the filter capacitor and the load are coupled to the secondary coil of the transformer. In one embodiment, the filter capacitor and the load are coupled to the secondary coil of the transformer through a rectifying diode. In one embodiment, the filter capacitor and the load are coupled to the secondary coil of the transformer through a third switch. The third switch provides rectification.

In one embodiment, when the second switch is disabled, the first switch turns on when passing a valley voltage of the first switch.

In one embodiment, the second switch turns on when passing a peak voltage of the first switch.

In an embodiment, at least one of the first switch and the second switch includes a gallium nitride (GaN) switch or a silicon carbide (SiC) switch.

In one embodiment, the second switch includes an enhancement mode gallium nitride (GaN) switch. The gallium nitride (GaN) switch carries a reverse current through the reverse conduction of the switch.

The following provides a detailed description in conjunction with the drawings to better understand the present invention.

200, 500, 600, 700 ‧‧‧Flyback power converter

201‧‧‧Transformer

202‧‧‧ (embedded) capacitor C

203‧‧‧(embedded) resistance R

204‧‧‧ (embedded) diode D

205‧‧‧Embedded switch (second switch)

206‧‧‧Main switch (first switch)

207‧‧‧ Output capacitance (C _O )

208‧‧‧Synchronous rectifier switch (third switch)

209‧‧‧Load

220‧‧‧hybrid embedded circuit

260‧‧‧Control table

261‧‧‧Controller

262‧‧‧Power Management Unit

501, 502, 503‧‧‧MOSFET switch

601‧‧‧Diode

EN‧‧‧Enable signal

I _O ‧‧‧ output current

I _SW1 ‧‧‧ Main switch current

I _SW2 , I _SW3 ‧‧‧ current

SW ₁ 、SW ₂ 、SW ₃ ‧‧‧Control signals

V _IN ‧‧‧ input voltage

V _O ‧‧‧ output voltage

V _SW1 ‧‧‧ main switch voltage

V _CTRL , V _GS1 , V _GS2 ‧‧‧ voltage

Figure 1a is a conventional flyback power converter with RCD clamping.

Figure 1b is a conventional flyback power converter with active clamps.

FIG. 2 is a schematic circuit diagram of a flyback power converter 200 with a hybrid clamping circuit 220 according to an embodiment of the invention.

FIG. 3 is a required operation area for output current I _O and input voltage V _IN under active clamping operation and passive clamping operation in an embodiment of the present invention.

FIG. 4 is an input voltage V _IN , an output current I _O , a control signal EN, a switch control signal SW _{1 of the} main switch 206, and a clamp switch 205 under operation points A and B of FIG. 3 in an embodiment of the present invention. The signal conversion diagram of the switch control signal SW ₂ .

FIG. 5 shows that in the flyback power converter 200 of FIG. 2 in one embodiment of the present invention, silicon metal oxide semiconductor field effect transistor (MOSFET) switches 501, 502, and 503 are used to realize the main The implementation circuit 500 of the switch 206, the clamping switch 205 and the synchronous rectification switch 208.

FIG. 6 is an implementation circuit 600 in which an additional diode 601 is provided in the flyback power converter of FIG. 5 to realize a passive clamping structure according to an embodiment of the invention.

FIG. 7 is a schematic circuit diagram of a flyback power converter 700 with a hybrid clamping circuit 720 in another embodiment of the invention.

FIG. 8a is a timing waveform diagram when the flyback power converter 200 is in continuous conduction mode (CCM) under passive clamping operation.

FIG. 8b is a timing waveform diagram of the flyback power converter 200 under the passive clamping operation at the CCM/DCM boundary.

FIG. 8c is a timing waveform diagram of the flyback power converter 200 in a discontinuous conduction mode (DCM) under passive clamping operation.

FIG. 9a is a timing waveform diagram when the flyback power converter 200 uses CCM under active clamping operation.

9b is a timing waveform diagram of the flyback power converter 200 under the active clamping operation at the CCM/DCM boundary.

FIG. 9c is a timing waveform diagram when the flyback power converter 200 uses DCM under active clamping operation.

FIG. 2 is a circuit diagram of a flyback power converter 200 with a hybrid clamping circuit 220 according to an embodiment of the invention. As shown in FIG. 2, the hybrid clamp circuit 220 is connected in parallel to the primary coil of the flyback transformer 201, and it includes a parallel circuit with a capacitor 202 and a resistor 203 connected in series and a switch 205 and a diode 204 Parallel circuit. FIG. 2 also illustrates a control table 260, which includes a controller 261 and a power management unit 262. In particular, the controller 261 and the power management unit 262 can be implemented by hardware, software, or any combination of software and hardware. Generally speaking, hardware implementations include analog and digital circuits, while software implementations include one or more microcontrollers, analog digital signal processors, or both to specify the controller 261 and power management unit 262 Perform operations.

The controller 261 provides control signal for main switch 206 (Control signals) SW _1, a clamp switch control signal 205 of control signal SW ₂ and SW ₃ (if any, for the synchronous rectification switch 208) to regulate Output voltage, output current, or both. In the embodiment shown in FIG. 2, the controller 261 senses the output voltage V _O through the output capacitor 207, the sense output current I _O flowing through the load 209, the sense main switch current I _SW1 , and the sense main switch The voltage V _SW1 and the active clamping enable signal EN provided by the power management unit 262 are used to generate an output control number. However, the controller 261 can also be implemented by sensing variables of other converters. In addition, if only one output variable (eg, output voltage V _O or output current I _O ) is regulated, there is no need to sense unregulated variables.

The power management unit 262 generates the active clamping enable signal EN according to the operating conditions of the flyback power converter 200 to enable the active control of the control signal SW ₂ of the clamping switch 205. In one embodiment of FIG. 2, the operating conditions of the flyback power converter 200 are determined based on the sensed output voltage V _O , output current I _O and input voltage V _IN , where when the output voltage V _O is a fixed value The output current I _O and the input voltage V _IN are also sufficient to determine the operating conditions of the flyback power converter 200. Other variables (such as the current I _SW1 through the main switch, the voltage V _SW1 through the main switch, the current I _SW3 through the secondary coil coupled to the rectifier, and the switching frequency) can also be used to determine the operating conditions of the flyback power converter 200 . As shown in FIG. 2, when the signal EN is LOW, the hybrid clamp circuit 220 is configured as a passive clamp by opening the switch 205 to form a passive clamp operation (passive clamp) operation). Conversely, when the signal EN is HIGH, the hybrid clamping circuit 220 switches the clamp switch 205 at the same frequency as the main switch 206, so that the main switch 206 is turned on under the condition of zero voltage switch (ZVS), configured as An active clamp (active clamp) to constitute an active clamp operation (active clamp operation). During the active clamping operation, the main switch 206 and the clamp switch 205 are not simultaneously turned on at the same time. For example, after the main switch 206 is turned off, the clamp switch 205 is turned on; vice versa.

3 and 4 illustrate the working principle of the hybrid clamp circuit 220. FIG. 3 is a required operation area for output current I _O and input voltage V _IN under PCL and ACL operations (under passive clamping operation and active clamping operation, respectively) in an embodiment of the present invention. In FIG. 3, the boundary between the operation areas PCL and ACL is indicated by a dotted line, which is determined by several better optimization criteria (such as maximum efficiency). For example, when all values of the input voltage V _IN and the output current I _{O of the} flyback power converter 200 correspond to the operation point A shown in FIG. 3, the passive clamping operation is optimal, so that the power management unit 262 Set the signal EN to LOW. Therefore, referring to FIG. 4, at the operating point A, the flyback power converter 200 with the hybrid clamping circuit 220 is in a passive clamping configuration (that is, only the control signal SW _{1 of the} main switch 206 is regulated). Conversely, when all values of the input voltage V _IN and the output current I _{O of the} flyback power converter 200 correspond to the operation point B shown in FIG. 3, the active clamping operation is optimal, so that the power management unit 262 will The signal EN is set to a high state (HIGH). Therefore, with reference to FIG. 4, the flyback power converter 200 with the hybrid clamping circuit 220 is configured under active clamping. In the active clamp configuration, the main switch control signal SW ₁ 206 and 205 of the clamp switch control signal SW ₂ are regulated.

In general, the required operating area under passive clamping operation and active clamping operation can be determined based on the optimization criteria of any design. For example, in addition to conversion efficiency, component stress, electromagnetic interference (EMI) and transformer performance are also optimization criteria. The required operating area can be determined through analysis or experience, for example by calculation, simulation or measurement on the prototype circuit. Whether it is analysis or experience, the required optimization criteria will be evaluated at several operating points under passive clamping operation and under active clamping operation. The boundary between the advantageous passive clamping operation area and the active clamping operation area can then be defined and used in the power management calculation of the power management unit 262. In digital implementation, for example, boundary operating points can be stored in a look-up table to facilitate power management calculations to dynamically test an actual operating point, and then in passive clamping operation and active clamping Choose the best operation between operations.

5 is a schematic diagram of a flyback power converter 200 of FIG. 2 in which an embodiment of the present invention uses silicon metal oxide semiconductor field effect transistor (MOSFET) switches 501, 502 and 503 respectively to realize the main switch 206. An implementation circuit 500 of the clamping switch 205 and the synchronous rectification switch 208. In FIG. 5, a body diode is built in the MOSEFET clamping switch 502 as the diode 204 in the passive clamping structure. However, in the implementation circuit 600 of FIG. 6, an additional diode 601 is connected to the MOSEFET clamping switch 502 to realize a passive clamping structure. In the embodiments of the present invention in FIGS. 2, 5 and 6, as shown in FIG. 7, the hybrid clamping circuit 220 may be connected in parallel to the main switch 206.

In the embodiments of the present invention, a gallium nitride (GaN) switch or a silicon carbide (SiC) switch may also be used for implementation. Specifically, if it is helpful, some or all of the main switch 206, the clamp switch 205, and the synchronous rectification switch 208 in FIG. 2 may also be enhanced-mode or cascode ) Gallium nitride (GaN) high electron mobility transistor (High Electron Mobility Transistor, HEMT), or silicon carbide (SiC) MOSEFET to implement. In one embodiment, when the embedded switch 205 uses an enhanced gallium nitride (GaN) HEMT without a built-in diode, the reverse current of the switch is carried by the reverse conduction of the switch.

According to a control algorithm implemented in the controller 261 in FIG. 2, the power converter 200 with the hybrid clamping circuit 220 can operate in continuous-conduction mode (CCM) or discontinuous-conduction mode (discontinuous-conduction) mode, DCM) or a threshold between continuous conduction mode and discontinuous conduction mode (CCM/DCM). As shown in FIG. 8a, when the hybrid clamp circuit 220 is configured in a passive clamping circuit, the main switch 206 operating in the continuous conduction mode (CCM) is turned on when the voltage V _SW1 =V _IN +NV _O (turn on ), where N is the ratio of the number of primary coil turns to the number of secondary coil turns. The timing waveform diagram of FIG. 8a also illustrates the waveforms of key signals, including (i) a current sensing resistor R _CS (not shown in FIG. 2) connected across the main switch 206 carrying the current I _SW1 The voltage drop increases to the control voltage V _CTRL immediately before the main switch 206 turns off; (ii) the voltage V _GS1 represents the gate-to-source voltage in the main switch 206; and ( iii) The voltage V _GS2 represents the gate-to-source voltage in the clamp switch 205. In FIG. 8b and FIG. 8c, under the critical (CCM/DCM) and discontinuous conduction mode (DCM) between the continuous conduction mode and the discontinuous conduction mode, respectively, the main switch 206 is turned on by valley switching (turns-on). Specifically, as shown in FIG. 8b, the main switch 206 is turned on in the first valley at the threshold (CCM/DCM) between the continuous conduction mode and the discontinuous conduction mode. As shown in FIG. 8c, the main switch 206 turns on in the second valley or a subsequent valley in the discontinuous conduction mode (DCM). In order to achieve valley switching of the main switch 206, the controller 261 in FIG. 2 may include a valley detection circuit and a valley counter circuit.

As shown in FIGS. 9a-9c, when the hybrid clamp circuit 220 is configured in an active clamping circuit, the main switch 206 can be turned on by using a zero voltage switch (ZVS) in three modes of operation (CCM, CCM/DCM, and DCM). In order to realize the ZVS switching of the main switch 206, the controller 261 in FIG. 2 includes a peak detection circuit and a peak counter circuit. As shown in FIG. 9c, the hybrid clamping circuit 220 turns on after a timely peak detection of the voltage V _SW1 .

Whether in passive or active clamping operation, the operating mode is selected to achieve the best performance under a given operating condition. For example, when the power converter 200 is configured in passive clamping operation at high frequencies, because the CCM/DCM provides a zero-voltage switch (ZVS) or a zero-voltage switch (ZVS) adjacent to the main switch 206 and a secondary-side rectifier diode Or zero-current-switching (ZCS) of the synchronous rectifier switch 208, CCM/DCM is the best operating mode under a medium load or full load or under a low input voltage V _IN condition.

Similarly, under light loads, because of possible frequency foldback (that is, corresponding to a smaller load or a larger input voltage, reducing the switching frequency), the DCM mode is generally preferred. Frequency foldback reduces switching losses and improves conversion efficiency.

When the flyback power converter 200 is configured for active clamping operation, the flyback power converter 200 can be selected to operate in continuous conduction mode (CCM), discontinuous conduction mode (DCM), or in a continuous conduction mode according to operating conditions And at least one of the thresholds (CCM/DCM) between discontinuous conduction modes.

Generally speaking, the operation mode optimization for the passive clamping operation or the active clamping operation may be performed in the power management unit 262 or the controller 261, or in both. As a part of the power management unit 262, in addition to the control signal EN, the power management unit 262 also provides additional information (not shown in the figure), such as an operation mode, to the controller 261 to explicitly specify.

The above detailed description is intended to provide specific embodiments of the present invention, but is not limited thereto. Many changes or modifications can still be made within the scope of the disclosure. The following patent application scope illustrates the invention.

200‧‧‧Flyback power converter

201‧‧‧Transformer

202‧‧‧ (embedded) capacitor C

203‧‧‧(embedded) resistance R

204‧‧‧ (embedded) diode D

205‧‧‧Embedded switch (second switch)

206‧‧‧Main switch (first switch)

207‧‧‧ Output capacitance (C _O )

208‧‧‧Synchronous rectifier switch (third switch)

209‧‧‧Load

220‧‧‧hybrid embedded circuit

260‧‧‧Control table

261‧‧‧Controller

262‧‧‧Power Management Unit

Claims (21)

A power converter for receiving an input voltage and providing an output voltage and an output current to a load, including: a transformer, having a primary coil and a secondary coil, the output voltage and the output current from the secondary coil Provided to the load; a first switch coupled to the primary coil, and when the first switch turns on, the first switch couples the input voltage to the primary coil; an embedding circuit includes a first One and a second parallel circuit and the first and the second parallel circuit are connected in series with each other, wherein the first parallel circuit includes a second switch and a clamping diode, the second parallel circuit includes a clamping capacitor and A clamping resistor, so that the clamping circuit provides an active clamping or a passive clamping according to whether the second switch is closed or opened; a controller is turned on periodically ) And turn off the first switch to regulate the output voltage or the output current; and, a power management unit to enable or disable the switching of the second switch according to the operating conditions of the power converter. The power converter as described in item 1 of the patent application range, wherein the power management unit keeps the second switch continuously off for the set of operating conditions. The power converter according to item 1 of the patent application scope, wherein the operating condition is determined according to at least one of the input voltage, a current through the first switch, the output voltage, the output current, and a switching frequency. The power converter as described in item 3 of the patent application scope further includes a rectifier coupling the secondary coil to the load, wherein the operating condition is determined according to a current passing through the rectifier. The power converter according to item 1 of the patent application scope, wherein the power converter operates in a continuous conduction mode, a discontinuous conduction mode, or a threshold between the continuous conduction mode and the discontinuous conduction mode. The power converter as described in item 1 of the patent application scope, wherein the power management unit optimizes at least one of conversion efficiency, component stress, electromagnetic interference performance, and transformer performance. The power converter as described in item 1 of the patent application scope, wherein the power management unit selects the power converter to operate in the continuous conduction mode, the discontinuous conduction mode, or one of the continuous conduction mode and the discontinuous conduction mode according to the operating conditions At least one of the criticality between. The power converter as described in item 1 of the patent application scope, wherein the first switch and the second switch are not turned on simultaneously during operation. The power converter as described in item 1 of the patent application scope, wherein the clamping circuit is coupled in parallel to the primary coil of the transformer. The power converter as described in item 1 of the patent application scope, wherein the clamping circuit is coupled to the first switch in parallel. The power converter as described in item 1 of the patent application scope, wherein the first switch is turned on at zero voltage; or when the input voltage is greater than N times the output voltage, the first switch is turned on The voltage is approximately equal to the difference between the input voltage and N times the output voltage when turned on, where N is the ratio of the number of primary coil turns to the number of secondary coil turns. The power converter as described in item 1 of the patent application scope, wherein one of the second switches has a built-in diode as the embedded diode. The power converter as described in item 1 of the patent application scope further includes a filter capacitor in parallel with the load, wherein the filter capacitor and the load are coupled to the secondary coil of the transformer. The power converter as described in item 13 of the patent application scope, wherein the filter capacitor and the load are coupled to the secondary coil of the transformer through a rectifying diode. The power converter as described in item 13 of the patent application scope, wherein the filter capacitor and the load are coupled to the secondary coil of the transformer through a third switch. The power converter as described in item 15 of the patent application scope, wherein the third switch provides rectification. The power converter as described in item 1 of the patent application scope, wherein when the second switch is disabled, the first switch turns on when passing a valley voltage of the first switch. The power converter as described in item 1 of the patent application scope, wherein the second switch turns on when passing a peak voltage of one of the first switches. The power converter as described in item 1 of the patent application scope, wherein at least one of the first switch and the second switch includes a gallium nitride (GaN) switch or a silicon carbide (SiC) switch. The power converter as described in item 1 of the patent application scope, wherein the second switch includes an enhanced gallium nitride (GaN) switch. A power converter as described in item 20 of the patent application range, wherein the gallium nitride (GaN) switch carries a reverse current through the reverse conduction of the switch.

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