Power converter and system and method for supplying power
By adopting a dual primary side circuit and a single controller design that switches simultaneously in a bidirectional power converter, the complexity of providing power to a bidirectional power converter controller is solved, and the effect of simplified control and hardware reduction is achieved.
Patent Information
- Application Number
- CN202510135968.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-02-09
- Filing Date
- 2025-02-07
- Publication Date
- 2025-08-12
AI Technical Summary
In the prior art, when powering a controller of a bidirectional power converter is provided, two independent power converters are required, resulting in increased control complexity.
A power converter with two primary side circuits is employed, wherein the switch is configured to switch simultaneously and controlled by a controller to generate an output voltage.
Simplifies the control circuit, reduces control complexity, and reduces the hardware requirements of the system.
Smart Images
Figure CN120474342A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to power converters and systems and methods for powering power. Background Art
[0002] A power converter is a device that converts input electrical power into output electrical power. For example, a power converter can convert an input voltage into an output voltage. The output voltage can have a predefined amplitude suitable for a specific application.
[0003] In some applications, a power converter is also used in a system to provide power to a controller of another power converter. For example, a supply voltage for the controller can be generated based on the input voltage of the other power converter.
[0004] Some power converters can be bidirectional, where each side of the power converter can be used as either an input or an output. In this case, providing power to the controller of such a power converter can be a challenge, as the input voltage can be provided on either side. Summary of the Invention
[0005] According to one embodiment, a power converter is provided, comprising: a first primary side circuit including a first input terminal configured to receive a first input voltage, a first primary side winding of a transformer, and a first switch (Q1) coupled between the first input terminal and the first primary side winding; a second primary side circuit including a second input terminal configured to receive a second input voltage, a second primary side winding of the transformer, and a second switch (Q2) coupled between the second input terminal and the second primary side winding; and a secondary side winding of the transformer coupled to an output terminal of the power converter, wherein the first switch (Q1) and the second switch (Q2) are configured to be switched simultaneously.
[0006] For example, a controller may be provided that is configured to switch the first switch (Q1) and the second switch (Q2) simultaneously.
[0007] According to another embodiment, a system is provided, comprising: a bidirectional power converter having a first end and a second end, wherein the bidirectional power converter is configured to selectively generate a second voltage at the second end based on a first voltage at the first end, or to generate the first voltage at the first end based on the second voltage at the second end, a bidirectional power converter controller configured to control the bidirectional power converter, and a power converter according to the above, wherein the first input end of the power converter is coupled to the first end, the second input end of the power converter is coupled to the second end, and the output end of the power converter is coupled to a power supply end of the bidirectional power converter controller.
[0008] According to another embodiment, a method is provided, comprising providing a power converter according to above, and simultaneously operating a first switch (Q1) and a second switch (Q2) of the power converter to generate an output voltage at an output terminal of the power converter.
[0009] The above summary merely provides a brief overview of some embodiments and should not be considered limiting in any way, as other embodiments may include features that differ from those described above. BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Figure 1 is a circuit diagram of a power converter according to one embodiment.
[0011] Figure 2 is used for Figure 1 Schematic diagram of the power converter controller.
[0012] Figure 3 Show Figure 1 Power converters and Figure 2 Example signals for the controller.
[0013] Figure 4 is a block diagram of a system according to one embodiment.
[0014] Figure 5A and 5B is a circuit diagram illustrating power supply of a controller of a power converter according to an embodiment.
[0015] Figure 6A 、 Figure 6B 、 Figure 6C and 6D A circuit diagram illustrating a controller for initially provisioning a power converter according to some embodiments is shown.
[0016] Figure 7A and 7B is a circuit diagram illustrating the generation of a current sensing signal according to some embodiments.
[0017] Figure 8 is a flow chart illustrating a method according to one embodiment. DETAILED DESCRIPTION
[0018] Various embodiments will be described below with reference to the accompanying drawings, which are not to be considered limiting.
[0019] The embodiments described below relate to a power converter that can receive two different input voltages to generate an output voltage. Figure 1In the embodiment of FIG. 1 , the power converter shown can receive the first input voltage Up, the second input voltage Us, or both the first input voltage Up and the second input voltage Us to generate the output voltage Vo. In other words, when Figure 1 When the power converter is operated to generate the output voltage Vo, both the first input voltage Up and the second input voltage Us may exist, or only one of the first input voltage Up or the second input voltage Us may exist.
[0020] The first input voltage Up is shown as being generated by a voltage source 10, while the second input voltage Us is shown as being generated by a voltage source 11. The voltage sources 10, 11 may represent any type of circuit that provides the respective voltages. Figure 4 To explain further, the input voltages Up and Us may be voltages on two different sides of the bidirectional power converter.
[0021] The first input voltage Up is received by the first primary side circuit, which includes a resistor 12, a diode D1, a first primary side winding 14A of a transformer 14 and a first switch Q1. Figure 1 In the embodiments of the present invention, the first primary side circuit is implemented as a field effect transistor switch with a body diode. The resistor 12 may be an explicitly provided resistor, may represent the internal resistance of other circuit elements (such as the electrical connections shown), or may be omitted. In addition, the inductor Lm is explicitly shown, which in many flyback converter implementations is implemented by an air gap in the core of the transformer 14 and is the main inductor for storing energy in the first primary side circuit. Since this inductor Lm is typically implemented in the transformer 14 (for example, by providing an air gap), it will not be explicitly shown in the embodiments discussed further below. In order to measure the current Isense1 in the first primary side circuit, a current measuring device Am1 is provided. For the current measurement, any conventional technique can be used, such as measuring the voltage drop across a low ohmic resistor, using inductive measurement or using magnetoresistance measurement to capture the magnetic field generated by the current, the latter two providing galvanic isolation for the measurement, which may be desirable in some embodiments.
[0022] The second input voltage Us is supplied to a second primary-side circuit, which includes a resistor 13, a diode D2, a second primary winding 14B of the transformer 14, a second switch Q2, and an inductor Lm1. Furthermore, a current measuring device Am2 is provided for measuring a current Isense2 in the second primary-side circuit. The second primary-side circuit can be implemented correspondingly to the first primary-side circuit, and the description of the various elements used for the first primary-side circuit also applies to the corresponding elements of the second primary-side circuit.
[0023] also, Figure 1The power converter includes a secondary side circuit including a secondary side winding 14C of a transformer 14, an output capacitor 15 providing an output voltage Vo across its terminals, and an output resistor 16 representing a load receiving the output voltage Vo. On the secondary side, a voltage sensor 17 can capture the output voltage Vo and output the measured Vo at a terminal 18. The measured output voltage Vo can be used to control Figure 1 The power converter is used to adjust the output voltage Vo to the target output voltage. Figure 1 A single secondary-side circuit is shown in FIG, but in other embodiments, multiple secondary-side circuits may be provided to provide multiple output voltages.
[0024] Figure 1 The power converter is essentially a flyback converter, but it has two primary side circuits. Figure 1 In an embodiment, the switch Q1 of the first primary side circuit and the switch Q2 of the second primary side circuit are configured to operate simultaneously (ie, to be turned on and off substantially at the same time), for example, Figure 1 As shown, the controller is configured to receive the same control signal pwm. In an embodiment, the controller generates the control signal pwm based on feedback of the indicative output signal Vo from the secondary side circuit and based on the currents Isense1 and Isense2. Figure 2 Shown for Figure 1 An example implementation of a controller for a power converter.
[0025] Figure 2 The controller shown in receives the output signal Vo or any indication thereof (for example, if the controller is set on the primary side, it is indicated by an optocoupler) and subtracts the output signal Vo from the reference voltage Vref provided in block 20. The reference voltage Vref is the voltage to be output by the power converter. One or more proportional / integral (PI) controllers 22 process the output of the subtractor 20 to generate a reference value Iref. Other types of controllers can also be used instead of the PI controller 22, such as a type I compensator, a type II compensator or a type III compensator. In addition, the maximum value of Isense1 and Isense2 is formed by block 24 to generate the value Isense. Isense and Iref are processed by the current controller 23 to generate the signal pwm that controls the switches Q1 and Q2. In addition to processing the two measured currents Isense1, Isense2 from the two primary side circuits, the controller can basically operate like any conventional flyback controller, and except Figure 2In addition to the peak current control shown, other conventional flyback controller schemes can be used. For example, the power converter can be implemented as a quasi-resonant flyback converter and the corresponding control scheme can be used. For driving switches Q1 and Q2, in the case of transistors, gate drivers can be used to drive the switches according to the signal pwm. If the ground referenced by the controller is different from the ground of the switch to be driven (for example, if the controller is located in Figure 1 The gate driver may include galvanic isolation (e.g., via a transformer) if the gate driver is on the secondary side of the power converter.
[0026] Figure 3 Figure 1 shows the analog example signals of Isense1, Isense2, Isense and pwm in the example operation. Here, only the current Isense1 flows, while Isense2 is zero. In general, although the two switches Q1 and Q2 are controlled together, in Figure 1 In the embodiment, current will flow only in one primary-side circuit, depending on the ratio R = Up / Us between the first input voltage Up and the second input voltage Us, and the turns ratio RT between the primary-side windings 14A and 14B. Assuming RT = 1 (equal turns in windings 14A and 14B), if Up > Us (R > 1), diode D1 will conduct, and voltage Up will be mirrored to the second primary-side winding via transformer 14, causing diode D2 to block. Conversely, if Us > Up (R < 1), diode D2 will conduct, and diode D1 will block. In the first case (Up > Us), power is supplied to the secondary-side circuit and the output voltage Vo via the first primary-side circuit, i.e., supplied by the first input voltage Up. Conversely, in the second case, the output voltage is supplied by the second input voltage Us. If RT ≠ 1, this is modified by the turns ratio; for example, the ratio R, which determines whether power is supplied from the first or second primary-side circuit, is equal to (Up / Us) * RT.
[0027] For example, in Figure 3 In the simulation results, the input voltage Up is higher than the input voltage Us, so Isense1 can flow, but Isense2 cannot flow. If the input voltage Up is equal to the input voltage Us and RT = 1 (or, more generally, when the above ratio R = 1), power is supplied to the secondary side from both the first primary side circuit and the second primary side circuit.
[0028] Figure 1 The power converter can be used, for example, to power a controller of a bidirectional power converter (hereinafter referred to as a bidirectional power converter controller). This is just one example, and the power converter can also be used to power other components (such as a fan or a relay) instead or in addition. Figure 4 The corresponding system is shown. Figure 4 The system includes a bidirectional DC / DC converter 40 as a bidirectional power converter that converts between a first voltage Up relative to a ground GND_P and a second voltage Us relative to a corresponding ground GND_S. In other words, Up or Us can be used as an input voltage and converted to the corresponding other voltage by the bidirectional DC / DC power converter 40. The bidirectional DC / DC power converter 40 is controlled by a bidirectional power converter controller 42, which can, for example, control gate drivers 41A and 41B that drive switches of the bidirectional DC / DC power converter 40. The bidirectional DC / DC power converter 40 can be implemented in any conventional manner.
[0029] According to one embodiment, the bidirectional power converter controller 42 is powered by a power converter 43, e.g. Figure 1 The power converter shown in FIG. 1 , wherein an output voltage Vo is generated based on a first input voltage Up or a second input voltage Us, Figure 4 In the example of , this voltage Vo is then supplied to the bidirectional power converter controller 43. In conventional solutions, two power converters are required to supply power to the bidirectional power converter controller 42. In such conventional solutions, when the bidirectional converter operates in a first direction (e.g. Up->Us), a first power converter is required to supply power to the bidirectional power converter controller, wherein the first power converter is supplied by the same input voltage Up, and when the bidirectional converter operates in a second direction (e.g. Us->Up), a second power converter is required to supply power to the bidirectional power converter controller, wherein the second power converter is supplied by the same input voltage Us. In contrast, in Figure 1 In the embodiment of FIG. 5 , only a single power converter with two primary side circuits is required.
[0030] In addition, due to Figure 1 In the power converter, switches Q1 and Q2 are controlled simultaneously, eliminating the need for separate control circuits for the two power converters. For the power converter according to the embodiments discussed herein, only one control loop is required to generate a single control signal PWM for the power converter, reducing the complexity of power converter control.
[0031] Next, describe Figure 1 and Figure 2 Although these implementation details show a specific circuit implementation, other implementations may also be used.
[0032] Figure 5A and 5B show to Figure 1 An example of a controller 52 powered by a power converter, such as Figure 2It should be noted that the controller 52 should not be used with Figure 4 The controller 42 in the is confused. Figure 4 The bidirectional power converter controller 42 controls Figure 4 The bidirectional DC / DC power converter 40 is Figure 2 The controller shown controls Figure 1 power converters or e.g. Figure 4 power converter 43.
[0033] exist Figure 5A and Figure 5B In the example of FIG. 5 , the controller 52 for the power converter 50A or 50B is powered by the auxiliary winding of the transformer 14, which substantially corresponds to Figure 1 power converter. Figure 5A and 5B In FIG. 5 , an auxiliary winding 51 is provided on the primary side of the transformer 14 and is coupled to a diode D4, a resistor R1 and a capacitor C1 to form a loop as shown. In each case, the supply voltage of the controller is provided at the capacitor C1.
[0034] Figure 5A An example is shown in which the controller 52 is provided on the output side with respect to the output ground DGND. An auxiliary winding 51A is provided on the secondary side of the transformer 14 and is coupled in a loop with a diode D4, a resistor R1, and a capacitor C1 as shown. The power supply voltage of the controller 52 relative to the output ground DGND is provided at the capacitor C1. The controller 52 can be as follows: Figure 2 The implementation is shown, and receives Isense1, Isense2 and Vo to generate a control signal pwm for the first and second switches Q1, Q2.
[0035] In this case, the current measurement of Isense1 and Isense2 can be performed using galvanic isolation from the primary side. Figure 5A In the example, transformers T2 and T3 are used, with Isense1 and Isense2 tapped on the secondary side. GND_P represents the ground for the first primary-side circuit, and GND_S represents the ground for the second primary-side circuit. Galvanic isolation for this current measurement is not required when the input and output are referenced to the same ground.
[0036] exist Figure 5B In this case, the controller is provided on the primary side with reference to the ground GND_P of the first primary side circuit. In this case, the auxiliary winding 51B is provided on the primary side of the transformer 14, Figure 5ASimilarly, the auxiliary winding 51A is coupled to the circuit with diode D4, resistor R1, and capacitor C1, as shown. Controller 52 is powered by the voltage across capacitor 51 relative to GND_P. In this case, a simple measuring resistor R2 can be used to measure Isense1, while a transformer is still used for Isense2, where the secondary winding is referenced to GND_P.
[0037] It should be noted that in other embodiments, Figure 1 The power converters or controllers of power converters 50A, 50B may be powered by some other power source in the respective system.
[0038] When power is supplied to the controller via auxiliary winding 51A or 51B, the power converter must operate to provide power to the controller. In order for the power converter to operate, the controller requires power to control the power converter accordingly. Therefore, the circuit including auxiliary winding 51A or 51B provides power after startup. An additional startup circuit may be provided to provide isolated power to the controller during startup. Figures 6A to 6D An example of such an isolated power supply is shown.
[0039] Figure 6A and 6B An example of a power supply circuit for generating output power at a corresponding output capacitor C5 is shown, wherein Figure 6A and Figure 6B The embodiments differ in the rectification provided on the secondary side. The corresponding transformer T1 provides galvanic isolation. The power circuit is controlled by a control chip 60. The control chip 60 is a timing chip configured to generate a control signal pwm having a desired frequency.
[0040] Figure 6A and 6B The power supply circuit relies on the input voltage Up as input power. Figure 4 In the case of the bidirectional power converter system shown, there may be an input voltage Up or an input voltage Us at startup. In this case, as Figure 6C and 6D As shown, for start-up, a power supply circuit can be provided which can operate at both input voltages Us and Up.
[0041] Figure 6C An example is shown where GND_P with reference to input voltage Up provides a power converter (similar to Figure 5B In this case, the input voltage Up does not need to be isolated, but for the input voltage Us, the following Figure 6A Or the circuit shown in 6B is used as the power supply circuit. The two parts are then matched so that their outputs are added together. Figure 6DShows the case where a power supply controller is provided on the output side (similar to Figure 5A In this case, you can Figure 5A power supply combination), where both input voltages Up and Us are provided as follows Figure 6A and 6B The circuit shown. Figure 6C In the case of Figure 6D In this case, the controller will be powered by the higher of the voltages at capacitors C5 and C10. Note that Figures 6A to 6D The circuit is designed to be powered at startup while still under light load conditions, and later in operation, it can be powered through the auxiliary winding, as shown in the reference Figure 5A and 5B As stated.
[0042] Figure 7A and 7B Two example circuits showing how to add the signals Isense1 and Isense2 to arrive at the signal Isense. When the controller is in the first primary side circuit referenced to GND_P, it can be used Figure 7A In this case, the signal Isense2 is provided via a diode, and the signal Isense1 is directly provided to generate Isense. Figure 7B An example is shown where the controller is on the secondary side, where both Isense1 and Isense2 are tapped using galvanic isolation, as shown in Figure 5A Other circuits can also be used to generate Isense.
[0043] Figure 8 is a flow chart of a method according to one embodiment.
[0044] At 1000, the method includes providing a power converter, such as Figure 1 As shown, the power converter has a first primary side circuit and a second switch (Q2) in the second primary side circuit. At 1001, the method includes operating the first switch (Q1) and the second switch (Q2) simultaneously, as described above for Figure 1 The power converter is described.
[0045] Some embodiments are defined by the following examples:
[0046] Example 1. A power converter comprising:
[0047] a first primary-side circuit including a first input terminal configured to receive a first input voltage, a first primary-side winding of a transformer, and a first switch coupled between the first input terminal and the first primary-side winding,
[0048] a second primary-side circuit including a second input terminal configured to receive a second input voltage, a second primary-side winding of the transformer, and a second switch coupled between the second input terminal and the second primary-side winding, and
[0049] The secondary winding of the transformer, which is coupled to the output of the power converter,
[0050] The first switch and the second switch are configured to be switched simultaneously.
[0051] Example 2. The power converter of Example 1,
[0052] The first primary side circuit includes a first diode coupled between the first input terminal and the first primary side winding, and the second primary side circuit includes a second diode coupled between the second input terminal and the second primary side winding.
[0053] Example 3. The power converter of Example 1 or 2,
[0054] Also included is a controller configured to switch the first switch and the second switch simultaneously.
[0055] Example 4. The power converter of Example 3, further comprising:
[0056] a first current sensor configured to measure a first current in the first primary side circuit,
[0057] a second current sensor configured to measure a second current in the second primary side circuit,
[0058] The controller is configured to control the first switch and the second switch based on the first current and the second current.
[0059] Example 5. The power converter of Example 4, wherein at least one of the first current sensor or the second current sensor comprises galvanic isolation.
[0060] Example 6. The power converter of Example 4 or 5, wherein the controller is configured to control the first switch and the second switch further based on a voltage at an output of the power converter.
[0061] Example 7. The power converter of any one of Examples 3 to 6 further includes an auxiliary winding of the transformer, the auxiliary winding being disposed at one of the primary side of the transformer or the secondary side of the transformer, wherein the auxiliary winding is coupled to a power input terminal of the controller.
[0062] Example 8. The power converter of any one of Examples 3 to 7 further includes a startup power circuit configured to supply power to the controller based on one of the first input voltage or the second input voltage at startup.
[0063] Example 9. The power converter of Example 8, wherein the startup power circuit includes galvanic isolation.
[0064] Example 10. The power converter of Example 8 or 9, wherein the startup power circuit is configured to supply power to the controller at startup based on the higher of the first input voltage and the second input voltage.
[0065] Example 11. The power converter of any one of Embodiments 3 to 10, wherein the power converter is configured to drive the first switch and / or the second switch via galvanic isolation.
[0066] Example 12. A system comprising:
[0067] A bidirectional power converter having a first terminal and a second terminal, wherein the bidirectional power converter is configured to selectively generate a second voltage at the second terminal based on a first voltage at the first terminal, or to generate a first voltage at the first terminal based on a second voltage at the second terminal,
[0068] a bidirectional power converter controller configured to control the bidirectional power converter,
[0069] The power converter according to any one of claims 1 to 11, wherein the first input terminal of the power converter is coupled to the first terminal, the second input terminal of the power converter is coupled to the second terminal, and the output terminal of the power converter is coupled to the power supply terminal of the bidirectional power converter controller.
[0070] Example 13. A method comprising:
[0071] There is provided a power converter according to any one of claims 1 to 11, and
[0072] The first switch and the second switch are operated simultaneously to generate an output voltage at an output terminal of the power converter.
[0073] Although specific embodiments have been illustrated and described herein, those skilled in the art will recognize that various alternative and / or equivalent embodiments may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. The present disclosure is intended to cover any modifications or variations of the specific embodiments discussed herein. Accordingly, the present invention is limited only by the claims and their equivalents.
Claims
1. A power converter (43, 50A, 50B), comprising: A first primary side circuit includes a first input terminal configured to receive a first input voltage (Up), a first primary side winding (14A) of a transformer (14), and a first switch (Q1) coupled between the first input terminal and the first primary side winding (14A). a second primary-side circuit comprising a second input terminal configured to receive a second input voltage (Us), a second primary-side winding (14B) of the transformer (14), and a second switch (Q2) coupled between the second input terminal and the second primary-side winding (14B); and a secondary winding (14C) of the transformer (14), coupled to an output terminal (18) of the power converter (43, 50A, 50B), The first switch (Q1) and the second switch (Q2) are configured to be switched simultaneously.
2. The power converter (43, 50A, 50B) according to claim 1, The first primary side circuit includes a first diode (D1) coupled between the first input terminal and the first primary side winding (14A), and the second primary side circuit includes a second diode (D2) coupled between the second input terminal and the second primary side winding (14B).
3. The power converter (43, 50A, 50B) of claim 1 or 2, further comprising a controller (52) configured to switch the first switch (Q1) and the second switch (Q2) simultaneously.
4. The power converter (43, 50A, 50B) according to claim 3, further comprising: a first current sensor (Am1) configured to measure a first current (Isense1) in the first primary-side circuit, a second current sensor (Am2) configured to measure a second current (Isense2) in the second primary-side circuit, The controller (70) is configured to control the first switch (Q1) and the second switch (Q2) based on the first current (Isense1) and the second current (Isense2).
5. The power converter (43, 50A, 50B) of claim 4, wherein at least one of the first current sensor or the second current sensor comprises galvanic isolation.
6. The power converter (43, 50A, 50B) of claim 4 or 5, wherein the controller (70) is configured to control the first switch (Q1) and the second switch (Q2) further based on a voltage at the output terminal (18) of the power converter (43, 50A, 50HB).
7. The power converter (43, 50A, 50B) according to any one of claims 3 to 6, further comprising an auxiliary winding (51) of the transformer (14), the auxiliary winding being arranged at one of the primary side of the transformer (14) or the secondary side of the transformer (14), wherein the auxiliary winding is coupled to a power supply input terminal of the controller (70).
8. The power converter (43, 50A, 50B) according to any one of claims 3 to 7, further comprising a startup power supply circuit configured to supply power to the controller (70) based on one of the first input voltage or the second input voltage at startup.
9. The power converter (43, 50A, 50B) of claim 8, wherein the startup power circuit includes galvanic isolation.
10. The power converter (43, 50A, 50B) of claim 8 or 9, wherein the startup power circuit is configured to supply power to the controller (70) based on the higher of the first input voltage and the second input voltage at startup.
11. The power converter (43, 50A, 50B) according to any one of claims 3 to 10, wherein the power converter (43, 50A, 50B) is configured to drive the first switch (Q1) and / or the second switch (Q2) via galvanic isolation.
12. A system for supplying power, comprising: A bidirectional power converter (40) having a first terminal and a second terminal, wherein the bidirectional power converter (40) is configured to selectively generate a second voltage at the second terminal based on a first voltage at the first terminal, or to generate a first voltage at the first terminal based on the second voltage at the second terminal, a bidirectional power converter controller (42) configured to control the bidirectional power converter, A power converter (43, 50A, 50B) according to any one of claims 1 to 11, wherein the first input terminal of the power converter (43, 50A, 50B) is coupled to the first terminal, the second input terminal of the power converter (43, 50A, 50B) is coupled to the second terminal, and the output terminal (18) of the power converter (43, 50A, 50B) is coupled to the power supply terminal of the bidirectional power converter controller.
13. A method for supplying power, comprising: There is provided a power converter (43, 50A, 50B) according to any one of claims 1 to 11, and The first switch (Q1) and the second switch (Q2) are operated simultaneously to generate an output voltage at an output terminal of the power converter (43, 50A, 50B).