AC-DC power converter

Abstract

The present disclosure relates to an AC-DC power converter comprising: a rectification 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 to a first boosted DC voltage, the first boosted DC voltage comprising an AC ripple; comprising a transformer; a step-down and / or step-up converter having two input voltage terminals, the first voltage input terminal being connected to the first step-up DC voltage or the secondary side of the transformer, the second input voltage terminal being connected to a second DC voltage, the second DC voltage being higher in a predefined voltage range than the voltage at the first voltage input terminal, the buck and / or boost converter is configured to operate using pulse width modulation to produce an output DC voltage with reduced or eliminated AC ripple. The disclosure also relates to a method of converting an input AC voltage into an output DC voltage.

Description

Technical Field

[0001] The present disclosure relates to an alternating current - direct current (AC - DC) power converter having improvements related to reducing or eliminating AC ripple. The present disclosure also relates to a method of converting an input AC voltage to an output DC voltage. Background Art

[0002] An alternating current - direct current (AC - DC) power converter is a device that converts alternating current (AC) into direct current (DC). AC - DC power converters are crucial for the operation of many electronic devices. AC - DC power converters can involve, for example, rectifiers, switched - mode power supplies, and stages that include transformers for boosting or bucking.

[0003] An AC - DC power converter typically can include a first rectification stage for eliminating the negative half - cycles of the input raw AC voltage. Thus, the voltage after the rectification stage is typically a voltage in which the negative half - part of the AC waveform has been converted to the positive half - part. Thus, for a 50 Hz supply voltage, the rectified voltage typically will have a frequency of about 100 Hz but only positive voltages.

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

[0005] To reduce ripple, the load side can involve filters, for example, capacitor - based filters, which can be used to smooth voltage variations. The larger the capacitance value of the capacitor, the better it can filter ripple. However, filtering to reduce ripple can lead to a significant efficiency loss in the power converter. The result is not only an energy loss, but the lost energy is also converted into heat, which can affect the converter or other components in a negative way. Thus, it would be beneficial to be able to reduce the losses in the power converter caused by ripple on the DC voltage.

[0006] JP 2000 125547A discloses a circuit for reducing the ripple component in a DC voltage from a rectifying and smoothing circuit of a DC converter. A DC voltage containing a ripple voltage having 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 a chopper circuit through a capacitor, and is added to the DC voltage output from the first rectifying and smoothing circuit through a capacitor.

[0007] US2022 / 418070 A1 discloses a device with a power supply circuit, which is connected to a light-emitting diode (LED) driving circuit, a filtering 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] CN 111 901 932A also discloses a power supply circuit, which is connected to a light-emitting diode (LED) driving circuit, a filtering 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. SUMMARY OF THE INVENTION

[0009] The present disclosure relates to an AC-DC power converter with improved built-in reduction or elimination of ripples on a DC voltage.

[0010] According to a first embodiment, the present disclosure relates to an AC-DC power converter, comprising:

[0011] a rectifying circuit configured to convert an input AC voltage into a rectified AC voltage;

[0012] 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;

[0013] a switched-mode power supply output stage including a transformer;

[0014] 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, and wherein a second input voltage terminal is connected to a second DC voltage, wherein the second DC voltage is higher than the voltage on the first voltage input terminal within a predefined voltage range, wherein the buck and / or boost converter is configured to use pulse width modulation operation to generate an output DC voltage with reduced or eliminated AC ripple, and wherein the output DC voltage is forwarded to the switched-mode power supply output stage.

[0015] Buck converters are commonly used to reduce the voltage level in various applications. In the AC-DC power converter of the present disclosure, the intention is not to reduce the DC voltage. 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 of 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., slightly higher than the voltage on the first voltage input. One reason for increasing the slightly higher voltage of the buck and / or boost converter is that it provides an effective way to reduce or eliminate ripple within a limited voltage range. In the case of using a boost converter, the output DC voltage from the boost converter can instead be slightly higher than the voltage on the second input terminal. There are many variants of buck converters and boost converters, including combinations, sometimes referred to as buck-boost converters. The AC-DC power converter of the present disclosure can use any suitable variant of the buck and / or boost converter to produce an output DC voltage with reduced or eliminated 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.

[0016] The buck and / or boost converter has two input voltage terminals. The first voltage input terminal can be connected to the first boost DC voltage. To explain the operation of the AC-DC power, a first illustrative and non-limiting example is provided in Figure 1 . If the input AC voltage is a mains AC voltage such as 220V or 240V, then the first boost DC voltage can be a DC voltage with AC ripple in the range of 300 - 500V, for example, approximately 400V. Then if the second input voltage terminal of the buck and / or boost converter is connected to a second DC voltage (which is slightly higher than the voltage on the first voltage input terminal within a predefined voltage range of, for example, 5 - 50V higher than the first boost DC voltage), then due to the nature of how the buck and / or boost converter operates, the buck and / or boost converter will inherently reduce or eliminate the ripple, and it will do so at 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). Compared to using a filter to reduce the ripple on the output DC signal on the load side, the power loss of the increased buck and / or boost converter is much lower.

[0017] As described above, the AC-DC power converter may include a switched-mode power supply output stage that includes a transformer. The switched-mode power supply output stage may be configured to reduce the voltage level from a buck and / or boost converter (which may be on the order of 300 - 500V as described above, and slightly more due to an additional 5 - 50V on the second input voltage terminal of the buck converter) to an output voltage level used by the electronic device (which may be on the order of 40 - 60V for example).

[0018] The present disclosure also relates to a method of converting an input AC voltage to an output DC voltage, the method comprising the steps of:

[0019] Providing an AC-DC power converter, the AC-DC power converter comprising:

[0020] A rectifier circuit configured to convert the input AC voltage to a rectified AC voltage;

[0021] 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;

[0022] A switched-mode power supply output stage including a transformer; and

[0023] 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, and wherein a second input voltage terminal is connected to a second DC voltage, wherein the second DC voltage is higher than the voltage on the first voltage input terminal within a predefined voltage range, and wherein the output DC voltage of the buck and / or boost converter is forwarded to the switched-mode power supply output stage,

[0024] Operating the AC-DC power converter by adjusting the switching of one or more switches in the buck and / or boost converter to produce an output DC voltage having reduced or eliminated AC ripple.

[0025] Those skilled in the art will recognize that the method of converting an input AC voltage to an output DC voltage of the present disclosure may be performed using any embodiment of the AC-DC power converter of the present disclosure, and vice versa. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Various embodiments are described below with reference to the accompanying drawings. The drawings are examples of the embodiments and are intended to illustrate some features of the AC-DC power converter of the present disclosure.

[0027] Figure 1 An example of a first embodiment of an AC-DC power converter is shown.

[0028] Figure 2Shows an example of an AC-DC power converter not covered by the claims.

[0029] Figure 3 Shows an example of a third embodiment of an AC-DC power converter.

[0030] Figure 4 Shows an example of a fourth embodiment of an AC-DC power converter.

[0031] Figure 5 Shows an example of a flowchart of a method of the present disclosure for converting an input AC voltage to an output DC voltage. Detailed Description

[0032] The present disclosure relates to an AC-DC (alternating current - direct current) power converter.

[0033] The AC-DC power converter includes a rectification circuit configured to convert an input AC voltage into a rectified AC voltage. A power factor correction (PFC) boost converter circuit converts the rectified AC voltage into a first boosted DC voltage. The first boosted DC voltage can be higher and more constant than the rectified AC voltage, but may still contain AC ripple. The PFC boost converter improves the power factor of the load. The PFC boost converter is a converter that increases the voltage of the input voltage and at the same time makes the current consistent with the voltage. The PFC boost converter works by turning on and off semiconductor switches (e.g., MOSFETs). A control circuit can be configured to regulate the switching of the semiconductor switches. Energy is stored in an inductor and transferred to a capacitor. An example of the PFC boost converter 103 is Figure 1 shown. Those skilled in the art will generally be familiar with PFC boost converters and will be able to implement suitable variants of the PFC boost converter.

[0034] The AC-DC power converter may further include a switched-mode power supply output stage including a transformer. The switched-mode power supply works by turning on and off a DC voltage, typically using semiconductor switches (such as MOSFETs). The DC voltage is turned on and off using a pulse width modulation signal. The switched DC voltage then passes through the transformer. High-frequency switching allows for efficient energy transfer through the transformer. The AC-DC power of the present disclosure may include a control circuit configured to regulate the switching of the semiconductor switches. The role of the switched-mode power supply is to convert the voltage level from the PFC boost converter to a different level. As an example, the voltage from the PFC boost converter may be in the range of 300 - 500V, for example, about 400V, while the voltage required by the load may be lower, for example, in the range of 40 - 70V. The switched-mode power supply output stage has the advantage that it can provide electrical isolation between the input and output of the power converter. The isolation is achieved because the primary side and the secondary side of the transformer are electrically separated.Figure 1 An example of a switched-mode power supply output stage 105 is shown. Those skilled in the art will generally be familiar with switched-mode power supplies and will be able to implement variants of the switched-mode power supply output stage.

[0035] 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 the PFC boost converter, which can be on the order of 300 - 500V. The second input voltage terminal is connected to a second DC voltage that is higher than the voltage on the first voltage input terminal within a predetermined voltage range.

[0036] In the case where 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 the first voltage input terminal and a common node, and the second switch is connected between the second input voltage terminal and the common node, wherein the inductor is connected between the common node and the output DC voltage, and wherein 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. In the case where the buck and / or boost converter is a buck converter with diode rectification or a boost converter with diode rectification, the control circuit may be configured to alternately turn on and off a single switch in the converter. Figure 1 An example of a synchronous buck converter 107 is shown. 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 the first voltage input terminal and a common node, and the second switch may be connected between the second input voltage terminal and the common node, wherein the inductor is connected between the common node and the output DC voltage, and wherein 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 (e.g., a synchronous buck converter) is generally a converter that steps down the 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 the AC ripple on the first boosted DC voltage. The output DC voltage is stabilized by the switching of the buck converter. One advantage is that the elimination can be accomplished at a limited voltage (i.e., the difference between the first voltage input terminal and the second voltage input terminal of the buck converter).

[0037] Alternatively, the buck and / or boost converter can be a boost converter, such as a boost converter with diode rectification or a synchronous boost converter. Figure 4 An example of an AC-DC power converter 100 using a boost converter 107 of the present disclosure is shown. In this example, the boost converter 107 is a boost converter with diode rectification, including a first switch 112, an inductor 114, and a smoothing capacitor 115. The first switch can be connected between a first voltage input terminal and a common node, and the inductor 114 can be connected between a second voltage input terminal and the common node. The output DC voltage, as well as the smoothing capacitor 115, can be connected to the common node. It can be understood that the second DC voltage can be provided by the transformer 106, for example, from the primary side of the transformer 106 or from the secondary side of the transformer 106, or from the PFC boost converter circuit 103.

[0038] For example, if the first boosted DC voltage from the PFC boost converter is in the range of 300 - 500V and the second DC voltage is 5 - 50V higher, the output DC voltage will have a DC voltage level between the voltages on the first voltage input terminal and the second voltage input terminal. For example, if the first boosted DC voltage from the PFC boost converter is 400V and the second DC voltage is 430V, in the case of a buck converter, the output DC voltage will depend on how the first switch and the second switch are switched and will be a voltage between 400V and 430V. 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 useful ripple-free voltage to be delivered to the switched-mode power supply output.

[0039] There are several ways to obtain the second DC voltage, which are effective 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 transformer of the switched-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 transformer in the switched-mode power supply output stage. Figure 1 An example of this is shown. Another possibility is to obtain it from the PFC boost converter, for example, obtaining a slightly converted voltage from the coil of the inductor in the PFC boost converter. Thus, the second input voltage terminal can be connected to a node or connection point in the PFC boost converter. Figure 3 An example of this is shown. 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 for the boost converter.

[0040] The voltage on the secondary side of the transformer in the switched - mode power supply output stage is typically 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, while the voltage required by the load may be lower, for example, in the range of 40 - 70V.

[0041] 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 reduced or eliminated AC ripple. The AC - DC power converter can include a control circuit configured to apply pulse - width modulation to the buck and / or boost converter, where the control circuit detects the output DC voltage and continuously adjusts the buck and / or boost converter to provide the desired output DC voltage. By adjusting the width of the pulses, the output DC voltage can be adjusted. This operation is generally familiar to those skilled in the art. For example, the control circuit can use a target voltage, i.e., the desired output voltage. Then, the control circuit can adjust the switching of the first switch and the second switch to adjust the output voltage. The rapid switching of the switches, along with the inductor and the smoothing capacitor, can provide a relatively stable DC output voltage.

[0042] The operation of the switched - mode power supply output stage is similar to that of the buck and / or boost converter. The switched - mode power supply output stage can include one or more actively - controlled switch elements. For example, as Figure 1 shown in the example of the high - side switch 124 and the low - side switch 125 are used to control the current on the primary side of the transformer. Preferably, the actively - controlled switch elements are controlled by pulse - width modulation or a fixed duty cycle. The control circuit can be configured to control the switching of the switch elements. This operation is generally familiar to those skilled in the art.

[0043] On the secondary side of the switched - mode power supply output stage can be an output rectification circuit connected to the secondary side of the transformer. Since the power conversion on the switched - mode power supply is a variant of AC - DC conversion, the role of the output rectification circuit is to convert the AC voltage to a DC voltage. This is typically achieved as a plurality of diodes arranged in a specific configuration.

[0044] Figure 1 The example (which shows an example of the first embodiment of the AC - DC power converter 100) includes a plurality of waveforms showing how to eliminate AC ripple. It should be noted that Figure 1It includes multiple subsystems. For example, 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 those skilled in the art will recognize, each subsystem can be implemented in various ways. For example, a specific implementation of the synchronous buck converter 107 as a subsystem for reducing or eliminating AC ripple does not necessarily need to precisely implement other subsystems, such as Figure 1 the rectifier circuit 101 in

[0045] In Figure 1 the example of , the input AC voltage can be a power supply AC voltage. The waveform of the input AC voltage is not shown 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 half of the AC waveform has been converted to the positive half. In Figure 1 the rectified AC voltage 126 is accompanied by an illustration of a typical waveform of such voltage. The next stage of the AC-DC converter 100 is the PFC boost converter circuit 103, which generates a first boosted DC voltage 104. The first boosted DC voltage 104 has a higher voltage than the input voltage but still contains low-frequency AC ripple, as shown in Figure 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. To have a second DC voltage 111 that is slightly higher than the voltage on the first voltage input terminal 108, a secondary winding 119 is used on the primary side of the transformer 106. There may be other ways to generate or obtain a slightly higher voltage. In Figure 1 the example of , the second DC voltage 111 also has low-frequency AC ripple, but this is not necessary. The second DC voltage 111 is supplied to the second voltage input terminal 109. The output of the synchronous buck converter 107 is an output DC voltage 122 without any AC ripple, as shown in Figure 1 . Then the output DC voltage 122 is forwarded to the switched-mode power supply output stage 105, more specifically to the high-side switch 124. It can be seen that the outputs of the switched-mode power supply output stage 105 and the output rectifier circuit are also ripple-free voltages.

[0046] More generally, the possible voltage levels of the various voltages in the AC-DC power converter of the present disclosure will be clear to those skilled in the art who are familiar with the operation and function of the different parts of an AC-DC power converter. According to one embodiment, the input AC voltage is in the range of 100 - 240V and the frequency is in the range of 50 - 60Hz, wherein the AC ripple in the first boosted DC voltage is a low-frequency AC ripple with a frequency in the range of 100 - 120Hz. The first boosted voltage (which is higher than the input AC voltage) can be in the range of 300 - 500V, for example, about 400V. The second DC voltage of 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 - 50V higher than the first boosted DC voltage.

[0047] The first voltage input terminal can preferably be connected to the secondary side of the transformer through one or more rectifier components, wherein the secondary side of the transformer provides a voltage in the range of 40 - 70V at the first voltage input terminal, and wherein the second DC voltage is 5 - 20V higher than the voltage at the first voltage input terminal. This embodiment is shown in Figure 2 More generally, the buck converter can be configured to operate over a reduced voltage span, for example, a voltage span less than 20% of the voltage at the first voltage input terminal, compared to the voltage at the first voltage input terminal.

[0048] Figure 5 An example of a flowchart of a method 200 for converting an input AC voltage to an output DC voltage according to the present disclosure is shown. Figure 5 The method in

[0049] The AC-DC converter of the present disclosure may include a control circuit to control different voltage levels and generate pulses to control the PFC boost converter circuit and / or the switched-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, e.g., a single processor or a processor in a multi-core / multi-processor system.

[0050] The AC-DC power converter of the present disclosure can be used in various applications, including, for example, as part of a charger for an electronic device, or as a power supply device (e.g., a midspan device) to enable an existing network to support Power over Ethernet (PoE), or as part of an AC-DC power converter built into an electronic device.

[0051] Element list in the figure

[0052] 100 - AC-DC Power Converter

[0053] 101 - Rectifier Circuit

[0054] 102 - Input AC Voltage

[0055] 103 - PFC Boost Converter Circuit

[0056] 104 - First Boost DC Voltage

[0057] 105 - Switched-Mode Power Supply Output Stage

[0058] 106 - Transformer

[0059] 107 - Buck / Boost Converter

[0060] 108 - First Voltage Input Terminal

[0061] 109 - Second Voltage Input Terminal

[0062] 110 - First DC Voltage

[0063] 111 - Second DC Voltage

[0064] 112 - First Switch

[0065] 113 - Second Switch

[0066] 114 - Inductor

[0067] 115 - Smoothing Capacitor

[0068] 116 - Control Circuit

[0069] 117 - Primary Winding Primary Side

[0070] 118 - Primary Winding Secondary Side

[0071] 119 - Primary side of secondary winding

[0072] 120 - Secondary side of secondary winding

[0073] 121 - Output rectifying circuit

[0074] 122 - Output DC voltage

[0075] 123 - Rectifying diode

[0076] 124 - High - level switch

[0077] 125 - Low - level switch

[0078] 126 - Rectified AC voltage.

Claims

1. An AC-DC power converter, comprising: 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 transformer; Buck and / or boost converters with two input voltage terminals, wherein the first voltage input terminal is connected to the first boosted DC voltage, and the second voltage input terminal is connected to the second DC voltage, wherein the second DC voltage is higher than the voltage on the first voltage input terminal within a predefined voltage range, wherein the buck and / or boost converter is configured to operate using pulse width modulation to generate an output DC voltage with reduced or eliminated AC ripple, and wherein the output DC voltage is forwarded to the switch mode power supply output stage.

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 transformer to provide 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 current on the primary side of the transformer, preferably, wherein 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 of claim 1, further comprising an output rectifier circuit connected to a secondary side of the transformer.

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 of 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 including a first switch, a second switch, an inductor and a smoothing capacitor, or a boost converter including 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, and the second switch is connected between the second input voltage terminal and the common node, wherein the inductor is connected between the common node and the output DC voltage, and wherein the smoothing capacitor is connected between the output DC voltage and one of the first voltage input terminal and the second input voltage terminal or a reference or 0V terminal. 9 . The AC-DC power converter of 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 100-240V and the frequency is in the range of 50-60Hz, and wherein the AC ripple in the first boosted DC voltage is a low frequency AC ripple in the range of 100-120Hz.

11. The AC-DC power converter according to claim 1, wherein: The first boosted DC voltage is in the range of 300-500V, and wherein the second DC voltage is 5-50V 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 transformer via one or more rectifier components, wherein the secondary side of the transformer provides a voltage in the range of 40-70V at the first voltage input terminal, and wherein the second DC voltage is 5-20V higher than the voltage at 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 voltage range that is reduced compared to the voltage at the first voltage input terminal, for example over a voltage range that is less than 20% of the voltage at the first voltage input terminal.

14. A method for converting an input AC voltage into an output DC voltage, the method comprising the following steps: An AC-DC power converter is provided, the AC-DC power converter comprising: 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 transformer; and 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, and wherein a second input voltage terminal is connected to a second DC voltage, wherein the second DC voltage is higher than the voltage at the first voltage input terminal within a predefined voltage range, and wherein an output DC voltage of the buck and / or boost converter is forwarded to the switch-mode supply output stage; The AC-DC power converter is operated to generate the output DC voltage with reduced or eliminated AC ripple by regulating the switching of one or more switches in the buck and / or boost converter.

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

Images