Ac-DC power converter

Abstract

To reduce and remove an AC ripple.SOLUTION: An AC-DC power converter (100) comprises: a rectification circuit (101); a power factor correction boost converter circuit (103); a switch mode power supply output stage (105); and a buck and / or boost converter (107). In the buck and / or boost converter (107), a first voltage input terminal (108) is connected to a first boosted DC voltage (104) or a secondary side of a transformer (106), a second input voltage terminal (109) is connected to a second DC voltage (111), the second DC voltage (111) is higher than a voltage on the first voltage input terminal (108) within a predefined voltage range, the buck and / or boost converter (107) is operated by using a pulse width modulation to generate an output DC voltage (122) in which an AC ripple is reduced or removed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an AC-DC power converter with improvements related to reducing or eliminating AC ripple. The present disclosure further relates to a method of converting an input AC voltage to an output DC voltage.

Background Art

[0002] An AC-DC power converter is a device that converts alternating current (AC) to direct current (DC). AC-DC power converters are important for the operation of many electronic devices. An AC-DC power converter may include, for example, a rectifier, a switch-mode power supply, and stages with converters for stepping up or stepping down the voltage.

[0003] An AC-DC power converter may generally include a first rectification stage for removing the negative half-cycle of the incoming original AC voltage. The voltage after the rectification stage may thus generally be a voltage in which the negative 1 / 2 of the AC waveform has been converted to the positive 1 / 2. In the case of a 50 Hz mains voltage, the rectified voltage will thus generally have a frequency of about 100 Hz but will have only positive voltages.

[0004] The rectified voltage may then be further converted, for example, using a boost converter or other types of switch-mode power supplies. The resulting DC voltage of such further conversion will still have some ripple or variation in its magnitude caused by the original AC voltage. Reducing or eliminating such ripple on the converted DC voltage is essential to ensure the stability and reliability of the electronic devices powered by the converted DC voltage.

[0005] To reduce ripple, the load side may be accompanied by a filter, such as a capacitor-based filter, that can be used to smooth the voltage fluctuations. The larger the capacitance value of the capacitor, the better it can filter out the ripple. However, the filtering process to reduce ripple may cause a significant efficiency loss in the power converter. The result is not only that energy is lost, but also that the lost energy is converted into heat, which can have a negative impact on the converter or other components. Therefore, it is beneficial to be able to reduce the losses in the power converter caused by the ripple on the DC voltage.

[0006] Japanese Patent Application Laid-Open No. 2000-125547 discloses a circuit for reducing the ripple component in the DC voltage from the rectifying and smoothing circuit of a DC converter. A DC voltage containing a ripple voltage with a phase opposite to that of the ripple voltage contained in the DC voltage output from the second rectifying and smoothing circuit is output from the chopper circuit via a capacitor, and the DC voltage is added to the DC voltage output from the first rectifying and smoothing circuit via the capacitor.

[0007] U.S. Patent Application Publication No. 2022 / 418070 (A1) discloses an apparatus having a power supply circuit connected to a light-emitting diode (LED) driving circuit, a filter circuit, and a feedback circuit in a display device. The power supply circuit includes a fixed voltage power supply element and a variable voltage power supply element. The topology includes one or more buck circuits.

[0008] CN111901932A also discloses a power supply circuit connected to a light-emitting diode (LED) driving circuit, a filter circuit, and a feedback circuit in a display device. The power supply circuit includes a fixed voltage power supply element and a variable voltage power supply element. The topology includes one or more buck circuits.

Prior Art Documents

Patent Documents

[0009] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2000-125547 [Patent Document 2] U.S. Patent Application No. 2022 / 418070 (A1) [Patent Document 3] CN111901932A [Summary of the Invention]

[0010] The present disclosure relates to an AC-DC power converter with improved reduction or removal of ripple on a DC voltage.

[0011] According to a first embodiment, the present disclosure provides: A rectifier circuit configured to convert an input AC voltage into a rectified AC voltage; A power factor correction boost converter circuit configured to convert the rectified AC voltage into a first boosted DC voltage, wherein the first boosted DC voltage includes an AC ripple; A switch-mode power supply output stage including a converter; A buck and / or boost converter having two input voltage terminals, wherein a first voltage input terminal is connected to the first boosted DC voltage, a second input voltage terminal is connected to a second DC voltage, the second DC voltage is higher than the voltage on the first voltage input terminal within a predefined voltage range, and the buck and / or boost converter is configured to operate using pulse width modulation to generate an output DC voltage with reduced or removed AC ripple, and the output DC voltage is forwarded to the switch-mode power supply output stage; An AC-DC power converter comprising:

[0012] Buck converters have conventionally been used to step down voltage levels in various applications. In the AC-DC power converter of the present disclosure, that is not the intention. Instead, the AC-DC converter is configured to provide a second DC voltage that is slightly higher than the voltage on the first voltage input terminal. The output DC voltage from the buck converter is the voltage level between the voltage levels on the first voltage input terminal and the second input terminal (i.e., between the magnitudes or amplitudes of the voltages), i.e., a voltage slightly higher than the voltage on the first voltage input. One reason for adding the slightly higher voltage and a buck and / or boost converter is that it presents an efficient way to reduce or remove ripple over a limited voltage range. When a boost converter is used, the output DC voltage from the boost converter can instead be slightly higher than the voltage on the second input terminal. There are several variations of buck converters and boost converters, including combinations that may be referred to as buck-boost converters. The AC-DC power converter of the present disclosure can use any suitable variation of a buck and / or boost converter to generate an output DC voltage with reduced or removed AC ripple. For example, the buck and / or boost converter can be a synchronous buck converter, or a buck converter with diode rectification. Alternatively, or in combination, the buck and / or boost converter can be a synchronous boost converter, or a boost converter with diode rectification.

[0013] The buck and / or boost converter has two input voltage terminals. The first voltage input terminal can be connected to a first boosted DC voltage. To explain the operation of AC-DC power, a first exemplary and non-limiting example is provided in FIG. 1. When the input AC voltage is, for example, a mains AC voltage of 220V or 240V, the first boosted DC voltage can be a DC voltage in the range of 300 - 500V with an AC ripple, for example, about 400V. When the second input voltage terminal of the buck and / or boost converter is connected to a second DC voltage that is slightly higher than the voltage on the first voltage input terminal within a predefined voltage range, for example, 5 - 50V higher than the first boosted DC voltage, the buck and / or boost converter will essentially reduce or remove the ripple depending on the nature of how the buck and / or boost converter operates, and the buck and / or boost converter will reduce or remove the ripple over a limited voltage, i.e., the difference between the first voltage input terminal and the second voltage input terminal of the buck and / or boost converter. The additional power loss of the added buck and / or boost converter can be significantly lower compared to using a filter to reduce the ripple on the output DC signal on the load side.

[0014] As described above, the AC-DC power converter can include a switched-mode power supply output stage with a converter. The switched-mode power supply output stage can be configured to step down the voltage level from the buck and / or boost converter, which is on the order of 300 - 500V and can be slightly more by an additional 5 - 50V on the second input voltage terminal of the buck converter, to an output voltage level used by an electronic device, which can be on the order of 40 - 60V.

[0015] The present disclosure further relates to a method of converting an input AC voltage to an output DC voltage, the method comprising - a rectifier circuit configured to convert the input AC voltage to a rectified AC voltage, - A power factor correction boost converter circuit configured to convert a rectified AC voltage into a first boosted DC voltage, wherein the first boosted DC voltage comprises an AC ripple, the power factor correction boost converter circuit; - A switch mode power supply output stage comprising a converter; - A buck and / or boost converter having two input voltage terminals, wherein a first voltage input terminal is connected to the first boosted DC voltage, a second input voltage terminal is connected to a second DC voltage, the second DC voltage is higher than the voltage on the first voltage input terminal within a predefined voltage range, and the output DC voltage of the buck and / or boost converter is forwarded to the switch mode power supply output stage, the buck and / or boost converter; Providing an AC-DC power converter comprising; Operating the AC-DC power converter by adjusting the switching of one or more switches in the buck and / or boost converter to generate an output DC voltage with reduced or removed AC ripple; Including.

[0016] Those skilled in the art will recognize that the method of the present disclosure for converting an input AC voltage into an output DC voltage can be implemented using any embodiment of the AC-DC power converter of the present disclosure, and vice versa.

[0017] Various embodiments will be described below with reference to the drawings. The drawings are examples of embodiments and are intended to show some of the features of the AC-DC power converter of the present disclosure.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

[0019] The present disclosure relates to an AC-DC power converter.

[0020] The AC-DC power converter includes a rectifier circuit configured to convert an input AC voltage to a rectified AC voltage. A power factor correction (PFC) boost converter circuit converts the rectified AC voltage to a first boosted DC voltage. The first boosted DC voltage may be higher and more constant than the rectified AC voltage, but may still include an AC ripple. The PFC boost converter improves the power factor of the load. The PFC boost converter is a converter that shapes the current to be in phase with the voltage while increasing the voltage of the input voltage. The PFC boost converter operates by switching a semiconductor switch, such as a MOSFET, on and off. The control circuit may be configured to regulate the switching of the semiconductor switch. Energy is stored in an inductor and transferred to a capacitor. An example of the PFC boost converter 103 is shown in FIG. 1. Those skilled in the art are generally familiar with PFC boost converters and will be able to implement suitable variations of the PFC boost converter.

[0021] An AC-DC power converter may further include a switched-mode power supply output stage having a converter. The switched-mode power supply generally operates by using a semiconductor switch such as a MOSFET to switch a DC voltage on and off. The DC voltage is switched on and off using a pulse-width modulation signal. The switched DC voltage is then passed through the converter. High-frequency switching enables efficient energy transfer through the converter. The AC-DC power of the present disclosure may include a control circuit configured to regulate the switching of the semiconductor switch. The role of the switched-mode power supply is to convert the voltage level from a PFC boost converter to different levels. As an example, the voltage from the PFC boost converter may be in the range of 300 to 500 V, for example, about 400 V, but the voltage required for the load may be lower, such as in the range of 40 to 70 V. The switched-mode power supply output stage has the advantage that it can provide electrical insulation between the input and output of the power converter. The insulation is achieved because the primary side of the converter is electrically separated from the secondary side. An example of the switched-mode power supply output stage 105 is shown in FIG. 1. Those skilled in the art generally have a good understanding of switched-mode power supplies and will be able to implement variations of the switched-mode power supply output stage.

[0022] The AC-DC power converter further includes a buck and / or boost converter having two input voltage terminals. According to a first embodiment, the first voltage input terminal is connected to a first boosted DC voltage, i.e., the boosted voltage from a PFC boost converter, which may be on the order of 300 to 500 V. The second input voltage terminal is connected to a second DC voltage, which is higher than the voltage on the first voltage input terminal within a predefined voltage range.

[0023] When the buck and / or boost converter is a synchronous buck converter, the synchronous buck converter may include a first switch, a second switch, an inductor, and a smoothing capacitor. The first switch may be connected between a first voltage input terminal and a common node, the second switch may be connected between a second input voltage terminal and the common node, the inductor is connected between the common node and the output DC voltage, and the smoothing capacitor is connected between the output DC voltage and a reference or 0V terminal. The AC-DC power converter may further include a control circuit configured to alternately turn on and off the first switch and the second switch. When the buck and / or boost converter is a buck converter having diode rectification or a boost converter having diode rectification, the control circuit may be configured to alternately turn on and off a single switch in the converter. FIG. 1 shows an example of a synchronous buck converter 107. In this example, the synchronous buck converter 107 includes a first switch 112, a second switch 113, an inductor 114, and a smoothing capacitor 115. The first switch may be connected between a first voltage input terminal and a common node, the second switch may be connected between a second input voltage terminal and the common node, the inductor is connected between the common node and the output DC voltage, and the smoothing capacitor is connected between the output DC voltage and a reference or 0V terminal. The AC-DC power converter may include a control circuit configured to alternately turn on and off the first switch and the second switch. A buck converter such as a synchronous buck converter is generally a converter for stepping down a voltage from a higher voltage to a lower voltage. In the AC-DC power converter of the present disclosure, the operation of the buck converter can be used to remove an AC ripple on a first boosted DC voltage. The output DC voltage is stabilized by the switching of the buck converter. One advantage is that removal can be performed over a limited voltage, i.e., the difference between the first voltage input terminal and the second voltage input terminal of the buck converter.

[0024] Alternatively, the buck and / or boost converter can be a boost converter, such as a boost converter having diode rectification or a synchronous boost converter. FIG. 4 shows an example of the AC-DC power converter 100 of the present disclosure using the boost converter 107. In this example, the boost converter 107 is a boost converter having diode rectification, including a first switch 112, an inductor 114, and a smoothing capacitor 115. The first switch can be connected between the first voltage input terminal and the common node, and the inductor 114 can be connected between the second voltage input and the common node. The output DC voltage and the smoothing capacitor 115 can be connected to the common node. It should be understood that the second DC voltage can be provided by the converter 106, such as from the primary side of the converter 106 or from the secondary side of the converter 106, or from the PFC boost converter circuit 103.

[0025] For example, if the first boosted DC voltage from the PFC boost converter is in the range of 300 to 500 V and the second DC voltage is higher, such as 5 to 50 V, the output DC voltage will have a DC voltage level between the voltage on the first voltage input terminal and the voltage on the second voltage input terminal. For example, if the first boosted DC voltage from the PFC boost converter is 400 V and the second DC voltage is 430 V, in the case of a buck converter, the output DC voltage will be somewhere between 400 V and 430 V depending on how the first switch and the second switch are switched. In the case of a boost converter, the output DC voltage will be slightly higher than the second DC voltage. The output DC voltage is a voltage that is useful for passing on the switch mode power supply output and is ripple-free.

[0026] There are several options for obtaining a second DC voltage that is valid for both the buck converter embodiment and the boost converter embodiment. The second input voltage terminal can be connected to a node or connection point in the converter in the switch mode power supply output stage to provide the second DC voltage to the buck and / or boost converter. This can involve having an additional winding on the primary side of the converter in the switch mode power supply output stage. An example of this is shown in FIG. 1. A further possibility is to obtain this from the PFC boost converter, for example, obtaining a slightly converted voltage from the coil of the inductor in the PFC boost converter. The second input voltage terminal can thus be connected to a node or connection point in the PFC boost converter. An example of this is shown in FIG. 3. In the figure, the second input voltage terminal 109 is connected to the supplementary winding of the PFC inductor in the PFC boost converter circuit 103. The connection of the first voltage input terminal and the second voltage input terminal is also possible in the case of the boost converter.

[0027] The voltage on the secondary side of the converter in the switch mode power supply output stage is generally lower than the first boosted DC voltage from the PFC boost converter. As an example, the voltage from the PFC boost converter can be in the range of 300 - 500V, but the voltage required for the load can be lower, such as in the range of 40 - 70V.

[0028] The operation of the buck and / or boost converter can be based on pulse width modulation to generate an output DC voltage having a DC voltage level between the voltage on the first voltage input terminal and the voltage on the second input terminal, with the AC ripple reduced or removed. The AC-DC power converter can include a control circuit configured to apply pulse width modulation to the buck and / or boost converter. The control circuit senses the output DC voltage and continuously adjusts the buck and / or boost converter to provide a desired output DC voltage. By adjusting the width of the pulses, the output DC voltage can be regulated. Those skilled in the art will generally be familiar with such operation. For example, the control circuit can use a target voltage that is the desired output voltage. The control circuit can then adjust the switching of the first switch and the second switch to regulate the output voltage. High-speed switching of the switches, inductors, and smoothing capacitors can provide a relatively stable DC output voltage.

[0029] The operation of the switch mode power supply output stage is similar to that of the buck and / or boost converter. The switch mode power supply output stage can include one or more actively controlled switching elements, such as the high-side switch 124 and the low-side switch 125 for controlling the flow of current on the primary side of the converter, as shown in the example of FIG. 1. Preferably, the actively controlled switching elements are controlled by pulse width modulation or a fixed duty cycle. The control circuit can be configured to control the switching of the switching elements. Those skilled in the art will generally be familiar with such operation.

[0030] On the secondary side of the switch mode power supply output stage, there can be an output rectifier circuit connected to the secondary side of the converter. Since the power conversion on the switch mode power supply is a variation of AC-DC conversion, the role of the output rectifier circuit is to convert the AC voltage to a DC voltage. This is typically implemented as several diodes arranged in a specific configuration.

[0031] The example of FIG. 1 showing an example of the first embodiment of the AC-DC power converter 100 includes several waveforms showing how the AC ripple is removed. Note that FIG. 1 includes several subsystems, such as a rectifier circuit 101, a PFC boost converter circuit 103, a synchronous buck converter 107, a switched-mode power supply output stage 105, and an output rectifier circuit 121. As will be appreciated by those skilled in the art, each of the subsystems can be implemented in various ways. For example, a particular implementation of the synchronous buck converter 107, which is a subsystem for reducing or removing the AC ripple, does not necessarily require the exact implementation of other subsystems, such as the rectifier circuit 101 in FIG. 1.

[0032] In the example of FIG. 1, the input AC voltage can be the main line AC voltage. The waveform of the input AC voltage is not included in the figure but can be, for example, a sine wave. The voltage after the rectification stage can be a voltage in which the negative 1 / 2 of the AC waveform is converted to the positive 1 / 2. In FIG. 1, the rectified AC voltage 126 is accompanied by a diagram of the general waveform of such a voltage. The next stage in the AC-DC converter 100 is the PFC boost converter circuit 103 that creates the first boosted DC voltage 104. The first boosted DC voltage 104 has a voltage higher than the input voltage but still has a low-frequency AC ripple as shown in FIG. 1. The first boosted DC voltage 104 can be used as the input voltage on the first voltage input terminal 108 of the synchronous buck converter 107. Because the converter 106 has a secondary winding 119 on the primary side that has a second DC voltage 111 slightly higher than the voltage on the first voltage input terminal 108. There can be other options for generating or obtaining a slightly higher voltage. In the example of FIG. 1, the second DC voltage 111 also has a low-frequency AC ripple, but this is not necessary. The second DC voltage 111 is provided to the second voltage input terminal 109. The output of the synchronous buck converter 107 is an output DC voltage 122 without an AC ripple as shown in FIG. 1. The output DC voltage 122 is then forwarded to the switch-mode power supply output stage 105 and more specifically to the high-side switch 124. It can be seen that the outputs of the switch-mode power supply output stage 105 and the output rectifier circuit are also voltages without ripple.

[0033] More generally, the possible voltage levels of the various voltages in the AC-DC power converter of the present disclosure will be apparent to those skilled in the art who are familiar with the operation and functions of the different parts of the AC-DC power converter. According to one embodiment, the input AC voltage is in the range of 100 to 240V with a frequency in the range of 50 to 60Hz, and the AC ripple in the first boosted DC voltage is a low-frequency AC ripple having a frequency in the range of 100 to 120Hz. The first boosted voltage, which is higher than the input AC voltage, can be in the range of 300 to 500V, such as about 400V. The second DC voltage to the buck and / or boost converter needs to be slightly higher than the first DC voltage. For example, the second DC voltage can be 5 to 50V higher than the first boosted DC voltage.

[0034] The first voltage input terminal can preferably be connected to the secondary side of the converter via one or more rectifier components, and the secondary side of the converter provides a voltage on the first voltage input terminal in the range of 40 to 70V, and the second DC voltage is 5 to 20V higher than the voltage on the first voltage input terminal. This embodiment is shown in FIG. 2.

[0035] More generally, the buck converter can be configured to operate over a reduced voltage span compared to the voltage on the first voltage input terminal, such as a voltage span less than 20% of the voltage on the first voltage input terminal.

[0036] FIG. 5 shows an example of a flowchart of method 200 of the present disclosure for converting an input AC voltage to an output DC voltage. The method in FIG. 5 includes a rectifier circuit configured to convert the input AC voltage to a rectified AC voltage, a power factor correction boost converter circuit configured to convert the rectified AC voltage to a first boosted DC voltage, wherein the first boosted DC voltage includes an AC ripple, a switch mode power supply output stage including a converter, and a buck and / or boost converter having two input voltage terminals, wherein the first voltage input terminal is connected to the first boosted DC voltage or the first voltage input terminal is connected to the secondary side of the converter and the second input voltage terminal is connected to a second DC voltage, and providing an AC-DC power converter including the buck and / or boost converter (201); operating the AC-DC power converter by adjusting the switching of one or more switches in the buck and / or boost converter to switch between the voltage on the first voltage input terminal and the second DC voltage, thereby generating an output DC voltage having a DC voltage level between the voltage on the first voltage input terminal and the second DC voltage with the AC ripple reduced or removed (202).

[0037] The AC-DC converter of the present disclosure may include a control circuit for controlling different voltage levels and generating pulses for controlling the PFC boost converter circuit and / or the switch mode power supply output stage and / or the buck and / or boost converter. The control circuit may be part of the AC-DC converter itself or a separate part of the system. The control circuit may be or include a processing circuit, such as a single processor or a processor in a multi-core / multi-processor system.

[0038] The AC-DC power converter of the present disclosure can be used in various applications, such as, for example, as part of a charger for an electronic device, or in a power supply device such as a midspan that enables an existing network to support Power over Ethernet (PoE), or as part of a built-in AC-DC power converter in an electronic device, and the like.

Description of Reference Numerals

[0039] 100 AC-DC power converter 101 Rectifier circuit 102 Input AC voltage 103 PFC boost converter circuit 104 First boosted DC voltage 105 Switching mode power supply output stage 106 Converter 107 Buck / boost converter 108 First voltage input terminal 109 Second voltage input terminal 110 First DC voltage 111 Second DC voltage 112 First switch 113 Second switch 114 Inductor 115 Smoothing capacitor 116 Control circuit 117 Primary winding primary side 118 Primary winding secondary side 119 Secondary winding primary side 120 Secondary winding secondary side 121 Output rectifier circuit 122 Output DC voltage 123 Rectifier diode 124 High-side switch 125 Low-side switch 126 Rectified AC voltage

Claims

1. A rectifier circuit configured to convert an input AC voltage into a rectified AC voltage, A power factor correction boost converter circuit configured to convert the rectified AC voltage into a first boosted DC voltage, wherein the first boosted DC voltage has an AC ripple, the power factor correction boost converter circuit, A switch mode power supply output stage comprising a converter, A buck and / or boost converter having two input voltage terminals, A first voltage input terminal is connected to the first boosted DC voltage, A second input voltage terminal is connected to a second DC voltage, the second DC voltage being higher than the voltage on the first voltage input terminal within a predefined voltage range, and the buck and / or boost converter is configured to be operated using pulse width modulation to generate an output DC voltage with reduced or removed AC ripple, and the output DC voltage is forwarded to the switch mode power supply output stage, A buck and / or boost converter and An AC-DC power converter comprising.

2. The AC-DC power converter according to claim 1, wherein the second input voltage terminal is connected to a node or connection point in the converter for providing the second DC voltage to the buck and / or boost converter.

3. The AC-DC power converter according to claim 1, wherein the switch mode power supply output stage comprises one or more actively controlled switching elements for controlling the flow of current on the primary side of the converter, and preferably, the one or more actively controlled switching elements are controlled by pulse width modulation or a fixed duty cycle.

4. The AC-DC power converter according to claim 1, further comprising an output rectifier circuit connected to the secondary side of the converter.

5. The AC-DC power converter according to claim 1, wherein the second input voltage terminal is connected to a node or connection point in the power factor correction boost converter circuit.

6. The AC-DC power converter according to claim 1, further comprising a control circuit configured to apply pulse width modulation to the buck and / or boost converter, wherein the control circuit detects the output DC voltage and continuously adjusts the buck and / or boost converter to provide a desired output DC voltage.

7. The AC-DC power converter according to claim 1, wherein the buck and / or boost converter is a buck converter comprising a first switch, a second switch, an inductor, and a smoothing capacitor, or a boost converter comprising a first switch, a second switch, an inductor, and a smoothing capacitor.

8. The AC-DC power converter according to claim 7, wherein the first switch is connected between the first voltage input terminal and a common node, the second switch is connected between the second input voltage terminal and the common node, the inductor is connected between the common node and the output DC voltage, and the smoothing capacitor is connected between the output DC voltage and one of the first voltage input terminal, the second input voltage terminal, or a reference or 0V terminal.

9. The AC-DC power converter according to claim 7, further comprising a control circuit configured to alternately turn on and off the first switch and the second switch.

10. The AC-DC power converter according to claim 1, wherein the input AC voltage is in the range of 100 to 240V having a frequency in the range of 50 to 60Hz, and the AC ripple in the first boosted DC voltage is a low-frequency AC ripple having a frequency in the range of 100 to 120Hz.

11. The AC-DC power converter according to claim 1, wherein the first boosted DC voltage is in the range of 300 to 500V, and the second DC voltage is 5 to 50V higher than the first boosted DC voltage.

12. The AC-DC power converter according to claim 1, wherein the first voltage input terminal is preferably connected to the secondary side of the converter via one or more rectifier components, the secondary side of the converter provides a voltage on the first voltage input terminal in the range of 40 to 70V, and the second DC voltage is 5 to 20V higher than the voltage on the first voltage input terminal.

13. The AC-DC power converter according to claim 1, wherein the buck and / or boost converter operates over a reduced voltage span as compared to the voltage on the first voltage input terminal, such as a voltage span less than 20% of the voltage on the first voltage input terminal.

14. A method of converting an input AC voltage to an output DC voltage, the method comprising: - a rectifier circuit configured to convert the input AC voltage to a rectified AC voltage; - a power factor correction boost converter circuit configured to convert the rectified AC voltage to a first boosted DC voltage, wherein the first boosted DC voltage comprises an AC ripple; - a switched-mode power supply output stage comprising a converter; - a buck and / or boost converter having two input voltage terminals, wherein a first voltage input terminal is connected to the first boosted DC voltage, a second input voltage terminal is connected to a second DC voltage, the second DC voltage is higher than the voltage on the first voltage input terminal within a predefined voltage range, and the output DC voltage of the buck and / or boost converter is forwarded to the switched-mode power supply output stage; providing an AC-DC power converter comprising; operating the AC-DC power converter by adjusting the switching of one or more switches in the buck and / or boost converter to generate the output DC voltage with reduced or removed AC ripple; A method of converting an input AC voltage to an output DC voltage, comprising.

15. The method of converting an input AC voltage to an output DC voltage according to claim 14, wherein the AC-DC power converter is the AC-DC power converter according to claim 1.

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