TW202412449A - Power converter - Google Patents

Abstract

A power converter includes a primary-side rectifying/filtering circuit, an AC-DC converter, a DC/DC converter, a primary-side controller, a secondary-side rectification controller, and a secondary-side feedback controller. The primary-side rectifying/filtering circuit receives an input voltage, and rectifies and filters the input voltage into an adjusted input voltage. The AC-DC converter receives the adjusted input voltage. The primary-side controller provides a first control signal to control the AC-DC converter to convert the adjusted input voltage into a DC input voltage, and provides a second control signal to control the DC-DC converter. The secondary-side rectification controller provides a third control signal to control the DC-DC converter to convert the DC input voltage into a conversion voltage to supply power to a load based on a gain condition. The secondary-side feedback controller receives a power demand signal provided by the load to control the primary-side controller and the secondary-side rectification controller.

Description

Power Converter

The present invention relates to a power converter, and more particularly to a power converter that can be operated in a half-bridge or full-bridge circuit topology to provide multiple sets of output voltages of different magnitudes.

When the power is greater than 100 watts, power products usually choose the PFC+LLC topology. The main reason is that LLC has the characteristic of zero-voltage switching, which allows power products to operate at a higher frequency, thereby shrinking the magnetic components and reducing the size of the product.

The structure of PFC as the first stage and LLC as the second stage is a very common power supply design structure. However, in response to the continuous advancement of technology, the voltages required for 3C products are different, and therefore power product specifications with different output voltages have become more and more popular. However, since the LLC's best operating point for efficiency is the resonant frequency point, a stable input voltage and a stable output voltage must be maintained at this resonant frequency point, so LLC is usually not the best solution under a single output voltage.

Therefore, how to design a power converter to solve the problems and technical bottlenecks existing in the prior art is an important topic studied by the inventors of this case.

The purpose of the present invention is to provide a power converter to solve the problems of the prior art.

To achieve the above-mentioned purpose, the power converter proposed by the present invention includes a primary-side rectifying and filtering circuit, an AC-to-DC converter, a DC-to-DC converter, a primary-side controller, a secondary-side rectifying controller, and a secondary-side feedback controller. The primary-side rectifying and filtering circuit receives an input voltage, and rectifies and filters the input voltage to output an adjusted input voltage. The AC-to-DC converter is coupled to the primary-side rectifying and filtering circuit, and receives the adjusted input voltage. The DC-to-DC converter is coupled to the AC-to-DC converter. The primary-side controller is coupled to the AC-to-DC converter and the DC-to-DC converter, provides a first control signal to control the AC-to-DC converter to convert the adjusted input voltage into a DC input voltage, and provides a second control signal to control the DC-to-DC converter. The secondary-side rectifier controller is coupled to the DC-to-DC converter, and provides a third control signal to control the DC-to-DC converter to convert the DC input voltage into a conversion voltage based on a gain condition to supply power to the load. The secondary-side feedback controller is coupled to the primary-side controller and the secondary-side rectifier controller, and the secondary-side feedback controller receives a load power supply demand signal provided by the load to control the operation of the primary-side controller and the secondary-side rectifier controller.

In one embodiment, the secondary-side feedback controller provides a feedback control signal including an AC/DC feedback control signal and a DC/DC feedback control signal to the primary-side controller, and provides a rectification control signal to the secondary-side rectification controller. The primary-side controller controls the AC/DC converter according to the AC/DC feedback control signal, controls the DC/DC converter according to the DC/DC feedback control signal, and controls the secondary-side rectification controller and adjusts the gain condition according to the rectification control signal.

In one embodiment, the DC-to-DC converter includes a primary-side isolation circuit and a secondary-side isolation circuit. The primary-side isolation circuit is coupled to the AC-to-DC converter and the primary-side controller to receive a second control signal and a DC input voltage. The secondary-side isolation circuit is coupled to the secondary-side rectifier controller to isolate and convert the DC input voltage.

In one embodiment, the primary side isolation circuit includes a bridge switching circuit and a resonant circuit, and the secondary side isolation circuit includes a bridge synchronous rectification circuit and a buck conversion circuit.

In one embodiment, the bridge switching circuit includes an upper switch and a lower switch. The first end of the upper switch is coupled to the AC-DC converter. The first end of the lower switch is coupled to the second end of the upper switch and the resonant circuit. The primary side controller provides a second control signal to control the upper switch and the lower switch.

In one embodiment, the bridge synchronous rectification circuit includes a first switch, a second switch, a third switch, a fourth switch, a first resonant inductor, and a second resonant inductor. The first end of the second switch is coupled to the second end of the first switch. The first end of the third switch is coupled to the first end of the first switch and the buck conversion circuit. The first end of the fourth switch is coupled to the second end of the third switch. The first end of the first resonant inductor is coupled between the second end of the first switch and the first end of the second switch. The first end of the second resonant inductor is coupled to the second end of the first resonant inductor, and the second end of the second resonant inductor is coupled between the second end of the third switch and the first end of the fourth switch. The secondary side rectification controller provides a third control signal to control the first switch, the second switch, the third switch, and the fourth switch.

In one embodiment, the bridge synchronous rectification circuit further includes a first capacitor and a second capacitor. The first end of the first capacitor is coupled to the third switch. The first end of the second capacitor is coupled to the second end of the first capacitor, and the second end of the second capacitor is coupled to the fourth switch.

In one embodiment, the buck converter circuit includes a fifth switch, a sixth switch, a diode, an inductor, and a capacitor. The first end of the fifth switch is coupled to the first end of the third switch. The first end of the sixth switch is coupled between the second end of the first resonant inductor and the first end of the second resonant inductor, and the second end of the sixth switch is coupled to the second end of the fifth switch. The cathode of the diode is coupled to the second end of the fifth switch and the second end of the sixth switch. The first end of the inductor is coupled to the cathode of the diode. The first end of the capacitor is coupled to the second end of the inductor, and the second end of the capacitor is coupled to the anode of the diode and the second end of the fourth switch.

In one embodiment, when the conversion voltage is the first voltage, the first switch and the third switch are turned off, and the second switch and the fourth switch are switched on to excite the first resonant inductor or the second resonant inductor.

In one embodiment, when the second switch is turned on, a first magnetic excitation path is formed, including the second switch, the first resonant inductor, and the buck-type conversion circuit, and the first resonant inductor is excited. When the fourth switch is turned on, a second magnetic excitation path is formed, including the fourth switch, the second resonant inductor, and the buck-type conversion circuit, and the second resonant inductor is excited.

In one embodiment, when the conversion voltage is the first voltage, the second switch and the fourth switch are turned off, and the first switch and the third switch are switched on to excite the first resonant inductor or the second resonant inductor.

In one embodiment, when the first switch is turned on, a third magnetic excitation path is formed, including the first switch, the first resonant inductor and the buck-type conversion circuit, and the first resonant inductor is excited. When the third switch is turned on, a fourth magnetic excitation path is formed, including the third switch, the second resonant inductor and the buck-type conversion circuit, and the second resonant inductor is excited.

In one embodiment, when the conversion voltage is the second voltage, the first switch and the fourth switch are turned on and off at the same time, the second switch and the third switch are turned on and off at the same time, and the first switch and the second switch are switched on and off to excite the first resonant inductor and the second resonant inductor.

In one embodiment, when the first switch and the fourth switch are turned on at the same time, a first magnetic excitation path is formed, including the first switch, the first resonant inductor, the second resonant inductor, the fourth switch, and the buck converter circuit. When the second switch and the third switch are turned on at the same time, a second magnetic excitation path is formed, including the second switch, the first resonant inductor, the second resonant inductor, the third switch, and the buck converter circuit.

In one embodiment, when the conversion voltage is less than the first voltage, the fifth switch and the sixth switch conduct the buck conversion circuit.

In one embodiment, when the conversion voltage is less than the second voltage, the fifth switch and the sixth switch conduct the buck conversion circuit.

In one embodiment, a buck converter circuit is used to convert the conversion voltage into a DC output voltage.

In one embodiment, the conversion voltage is stepped down into a DC output voltage of different voltage magnitudes by controlling the duty cycle of the fifth switch or the duty cycle of the sixth switch.

The proposed power converter can be operated in a half-bridge or full-bridge circuit topology to flexibly provide multiple sets of output voltages of different magnitudes.

In order to further understand the technology, means and effects adopted by the present invention to achieve the intended purpose, please refer to the following detailed description and drawings of the present invention. It is believed that the purpose, features and characteristics of the present invention can be understood in depth and in detail. However, the attached drawings are only provided for reference and explanation, and are not used to limit the present invention.

The technical content and detailed description of the present invention are described as follows with reference to the accompanying drawings.

Please refer to FIG. 1 and FIG. 2, which are respectively the block diagram and detailed block diagram of the power converter of the present invention. The power converter with buck-boost conversion includes a primary-side rectifying and filtering circuit 1, an AC-to-DC converter 2, a DC-to-DC converter 3, a primary-side controller 4, a secondary-side rectifying controller 5, and a secondary-side feedback controller 6.

The primary-side rectifying and filtering circuit 1 receives the input voltage V _IN , and rectifies and filters the input voltage V _IN to output the regulated input voltage V _INRF . Specifically, the primary-side rectifying and filtering circuit 1 comprises a primary-side rectifying circuit and a primary-side filtering circuit (not shown). The primary-side rectifying circuit is used to rectify the input voltage V _IN . The primary-side filtering circuit is used to filter the rectified input voltage to output the regulated input voltage V _INRF to the AC-DC converter 2 .

The AC-to-DC converter 2 is coupled to the primary-side rectifying and filtering circuit 1 , and receives the regulated input voltage V _INRF outputted by the primary-side rectifying and filtering circuit 1 .

The DC-to-DC converter 3 is coupled to the AC-to-DC converter 2. Specifically, as shown in FIG. 3 and FIG. 4, they are circuit diagrams of the DC-to-DC converter of the present invention. The DC-to-DC converter 3 includes a primary-side isolation circuit 31 and a secondary-side isolation circuit 32. The primary-side isolation circuit 31 is coupled to the AC-to-DC converter 2 and the primary-side controller 4 to receive the second control signal _SC2 and the DC input voltage V _INDC provided by the primary-side controller 4. The secondary-side isolation circuit 32 is coupled to the secondary-side rectifier controller 5 to isolate and convert the DC input voltage V _INDC .

The primary-side isolation circuit 31 includes a bridge switching circuit 311 and a resonant circuit 312. The bridge switching circuit 311 includes an upper switch _QH and a lower switch _QL . A first end of the upper switch _QH is coupled to the AC-DC converter 2. A first end of the lower switch _QL is coupled to a second end of the upper switch _QH and the resonant circuit 312. The primary-side controller 4 provides a second control signal _SC2 to control the upper switch _QH and the lower switch _QL .

The secondary-side isolation circuit 32 includes a bridge-type synchronous rectification circuit 321 and a buck-type conversion circuit 322. The bridge-type synchronous rectification circuit 321 includes a first switch Q1, a second switch Q2, a third switch Q3, a fourth switch Q4, a first resonant inductor L1, and a second resonant inductor L2. The first end of the second switch Q2 is coupled to the second end of the first switch Q1. The first end of the third switch Q3 is coupled to the first end of the first switch Q1 and the buck-type conversion circuit 322. The first end of the fourth switch Q4 is coupled to the second end of the third switch Q3. The first end of the first resonant inductor is coupled between the second end of the first switch Q1 and the first end of the second switch Q2. The first end of the second resonant inductor L2 is coupled to the second end of the first resonant inductor L1, and the second end of the second resonant inductor L2 is coupled between the second end of the third switch Q3 and the first end of the fourth switch Q4. The secondary-side rectifier controller 5 provides a third control signal _SC3 to control the first switch Q1, the second switch Q2, the third switch Q3 and the fourth switch Q4.

The bridge synchronous rectification circuit 321 further includes a first capacitor C1 and a second capacitor C2. A first end of the first capacitor C1 is coupled to the third switch Q3. A first end of the second capacitor C2 is coupled to the second end of the first capacitor C1, and a second end of the second capacitor C2 is coupled to the fourth switch Q4.

The buck converter circuit 322 is used to convert the conversion voltage V _CON into a DC output voltage V _OUTDC . The buck converter circuit 322 includes a fifth switch Q5, a sixth switch Q6, a diode D, an inductor L, and a capacitor C. The first end of the fifth switch Q5 is coupled to the first end of the third switch Q3. The first end of the sixth switch Q6 is coupled between the second end of the first resonant inductor L1 and the first end of the second resonant inductor L2, and the second end of the sixth switch Q6 is coupled to the second end of the fifth switch Q5. The cathode of the diode D is coupled to the second end of the fifth switch Q5 and the second end of the sixth switch Q6. The first end of the inductor L is coupled to the cathode of the diode D. The first end of the capacitor C is coupled to the second end of the inductor L, and the second end of the capacitor C is coupled to the anode of the diode D and the second end of the fourth switch Q4. In one embodiment, the sixth switch Q6 can be implemented by back-to-back semiconductor elements, but this is not intended to limit the present invention.

The primary-side controller 4 is coupled to the AC-DC converter 2 and the DC-DC converter 3 , provides a first control signal S _C1 to control the AC-DC converter 2 to convert and adjust the input voltage V _INRF into a DC input voltage V _INDC , and provides a second control signal S _C2 to control the DC-DC converter 3 .

The secondary-side rectifier controller 5 is coupled to the DC-DC converter 3 and provides a third control signal _SC3 to control the DC-DC converter 3 to convert the DC input voltage V _INDC into a conversion voltage V _CON based on a gain condition to supply power to the load 7 .

The secondary-side feedback controller 6 is coupled to the primary-side controller 4 and the secondary-side rectifier controller 5. The secondary-side feedback controller 6 receives a load power demand signal S _LP provided by the load 7 to control the operations of the primary-side controller 4 and the secondary-side rectifier controller 5. Specifically, the secondary-side feedback controller 6 provides a feedback control signal including an AC/DC feedback control signal S _CAD and a DC/DC feedback control signal S _CDD to the primary-side controller 4, and provides a rectifier control signal S _CSR to the secondary-side rectifier controller 5.

The primary-side controller 4 controls the AC-DC converter 2 according to the AC-DC feedback control signal S _CAD , controls the DC-DC converter 3 according to the DC-DC feedback control signal S _CDD , and controls the secondary-side rectifier controller 5 and adjusts the gain condition according to the rectifier control signal S _CSR .

When the bridge synchronous rectification circuit 321 is in half-bridge operation, the conversion voltage V _CON is a first voltage, such as but not limited to 20 volts, and the third control signal _SC3 controls the first switch Q1 and the third switch Q3 to be turned off, and controls the second switch Q2 and the fourth switch Q4 to be switched on and off, thereby exciting the first resonant inductor L1 or the second resonant inductor L2. In this embodiment, when the second switch Q2 is turned on, a first magnetic excitation path is formed, including the second switch Q2, the first resonant inductor L1, and the buck-type conversion circuit 322, so that the first resonant inductor L1 is excited. When the fourth switch Q4 is turned on, a second magnetic excitation path is formed, including the fourth switch Q4, the second resonant inductor L2, and the buck-type conversion circuit 322, so that the second resonant inductor L2 is excited.

The symmetrical circuit operation is that when the conversion voltage V _CON is the first voltage, the third control signal _SC3 controls the second switch Q2 and the fourth switch Q4 to be turned off, and controls the first switch Q1 and the third switch Q3 to be switched on and off, thereby exciting the second resonant inductor L2. In this embodiment, when the first switch Q1 is turned on, a third magnetic excitation path is formed, including the first switch Q1, the first resonant inductor L1, and the buck-type conversion circuit 322, thereby exciting the first resonant inductor L1. When the third switch Q3 is turned on, a fourth magnetic excitation path is formed, including the third switch Q3, the second resonant inductor L2, and the buck-type conversion circuit 322, thereby exciting the second resonant inductor L2.

When the conversion voltage V _CON is less than the first voltage (i.e., less than 20V), the fifth switch Q5 and the sixth switch Q6 turn on the buck conversion circuit 322. Specifically, by controlling the duty cycle of the fifth switch Q5 or the duty cycle of the sixth switch Q6, the conversion voltage V _CON is stepped down into DC output voltages V _OUTDC of different voltages to provide multiple sets of output voltages of different magnitudes.

When the bridge synchronous rectification circuit 321 is in full bridge operation, the conversion voltage V _CON is a second voltage, such as but not limited to 48V or 36V, and the third control signal _SC3 controls the first switch Q1 and the fourth switch Q4 to be turned on and off at the same time, and controls the second switch Q2 and the third switch Q3 to be turned on and off at the same time, and controls the first switch Q1 and the second switch Q2 to be switched on and off to excite the first resonant inductor L1 and the second resonant inductor L2. Specifically, when the first switch Q1 and the fourth switch Q4 are turned on at the same time, the first magnetic excitation path includes the first switch Q1, the first resonant inductor L1, the second resonant inductor L2, the fourth switch Q4 and the buck conversion circuit 322, so the first resonant inductor L1 and the second resonant inductor L2 are excited at the same time. When the second switch Q2 and the third switch Q3 are turned on at the same time, the second magnetic excitation path includes the second switch Q2, the first resonant inductor L1, the second resonant inductor L2, the third switch Q3 and the buck converter circuit 322, so the first resonant inductor L1 and the second resonant inductor L2 are excited at the same time.

When the conversion voltage V _CON is less than the second voltage (i.e., less than 48V or 36V), the fifth switch Q5 and the sixth switch Q6 turn on the buck conversion circuit 322. By controlling the duty cycle of the fifth switch Q5 or the duty cycle of the sixth switch Q6, the conversion voltage V _CON is stepped down into DC output voltages V _OUTDC of different voltages to provide multiple sets of output voltages of different magnitudes.

The power converter proposed by the present invention can be operated in a half-bridge or full-bridge circuit topology to flexibly provide multiple sets of output voltages of different magnitudes.

The above description is only a detailed description and drawings of the preferred specific embodiments of the present invention, but the features of the present invention are not limited thereto, and are not used to limit the present invention. The entire scope of the present invention shall be subject to the following patent application scope. All embodiments that conform to the spirit of the patent application scope of the present invention and its similar variations shall be included in the scope of the present invention. Any changes or modifications that can be easily thought of by anyone familiar with the art within the field of the present invention can be covered by the following patent scope of this case.

1: Primary side rectifier filter circuit 2: AC to DC converter 3: DC to DC converter 4: Primary side controller 5: Secondary side rectifier controller 6: Secondary side feedback controller 7: Load 31: Primary side isolation circuit 32: Secondary side isolation circuit 311: Bridge switching circuit 312: Resonance circuit 321: Bridge synchronous rectifier circuit 322: Buck converter circuit Q _H : Upper switch Q _L : Lower switch Q1: First switch Q2: Second switch Q3: Third switch Q4: Fourth switch Q5: Fifth switch Q6: Sixth switch L1: First resonant inductor L2: Second resonant inductor C1: First capacitor C2: Second capacitor D: Diode L: Inductor C: Capacitor V _IN : Input voltage V _INRF : Adjust input voltage V _INDC : DC input voltage V _CON : Conversion voltage V _OUTDC : DC output voltage S _C1 : First control signal S _C2 : Second control signal S _C3 : Third control signal S _LP : Load power demand signal S _CSR : Rectification control signal S _CAD : AC/DC feedback control signal S _CDD : DC/DC feedback control signal

FIG1 is a block diagram of the power converter of the present invention.

FIG. 2 is a detailed block diagram of the power converter of the present invention.

FIG. 3 and FIG. 4 are circuit diagrams of the DC-to-DC converter of the present invention.

1: Primary side rectification and filtering circuit

2: AC to DC converter

3: DC to DC converter

4: Primary side controller

5: Secondary side rectifier controller

6: Secondary side feedback controller

7: Load

V _IN : Input voltage

V _INRF : Adjust input voltage

V _INDC : DC input voltage

V _OUTDC : DC output voltage

S _C1 : First control signal

S _C2 : Second control signal

S _C3 : The third control signal

S _LP : Load power demand signal

S _CSR : Rectification control signal

S _CAD : AC/DC feedback control signal

S _CDD : DC feedback control signal

Claims (18)

A power converter includes: a primary-side rectifying and filtering circuit, receiving an input voltage, rectifying and filtering the input voltage to output an adjusted input voltage; an AC-to-DC converter, coupled to the primary-side rectifying and filtering circuit, and receiving the adjusted input voltage; a DC-to-DC converter, coupled to the AC-to-DC converter; a primary-side controller, coupled to the AC-to-DC converter and the DC-to-DC converter, providing a first control signal to control the AC-to-DC converter to convert the adjusted input voltage into a DC input voltage, and providing a second control signal to control the DC-to-DC converter; A secondary-side rectifier controller is coupled to the DC-DC converter and provides a third control signal to control the DC-DC converter to convert the DC input voltage into a conversion voltage based on a gain condition to supply power to a load; and A secondary-side feedback controller is coupled to the primary-side controller and the secondary-side rectifier controller. The secondary-side feedback controller receives a load power supply demand signal provided by the load to control the operation of the primary-side controller and the secondary-side rectifier controller. A power converter as described in claim 1, wherein the secondary-side feedback controller provides a feedback control signal including an AC/DC feedback control signal and a DC feedback control signal to the primary-side controller, and provides a rectification control signal to the secondary-side rectification controller; wherein the primary-side controller controls the AC/DC converter according to the AC/DC feedback control signal, controls the DC/DC converter according to the DC feedback control signal, and controls the secondary-side rectification controller and adjusts the gain condition according to the rectification control signal. A power converter as described in claim 1, wherein the DC-to-DC converter comprises: a primary-side isolation circuit coupled to the AC-to-DC converter and the primary-side controller for receiving the second control signal and the DC input voltage; and a secondary-side isolation circuit coupled to the secondary-side rectifier controller for isolating and converting the DC input voltage. A power converter as described in claim 3, wherein the primary-side isolation circuit includes a bridge switching circuit and a resonance circuit; and the secondary-side isolation circuit includes a bridge synchronous rectification circuit and a buck conversion circuit. A power converter as described in claim 4, wherein the bridge switching circuit comprises: an upper switch, a first end of the upper switch is coupled to the AC-DC converter; and a lower switch, a first end of the lower switch is coupled to a second end of the upper switch and the resonant circuit. wherein the primary-side controller provides the second control signal to control the upper switch and the lower switch. A power converter as described in claim 4, wherein the bridge synchronous rectification circuit comprises: a first switch; a second switch, a first end of the second switch coupled to a second end of the first switch; a third switch, a first end of the third switch coupled to a first end of the first switch and the buck conversion circuit; a fourth switch, a first end of the fourth switch coupled to a second end of the third switch; a first resonant inductor, a first end of the first resonant inductor coupled between the second end of the first switch and the first end of the second switch; and a second resonant inductor, a first end of the second resonant inductor coupled to the second end of the first resonant inductor, a second end of the second resonant inductor coupled between the second end of the third switch and the first end of the fourth switch; The secondary-side rectifier controller provides the third control signal to control the first switch, the second switch, the third switch and the fourth switch. A power converter as described in claim 6, wherein the bridge synchronous rectification circuit further comprises: a first capacitor, a first end of which is coupled to the third switch; and a second capacitor, a first end of which is coupled to a second end of the first capacitor, and a second end of which is coupled to the fourth switch. A power converter as described in claim 6, wherein the step-down conversion circuit comprises: a fifth switch, a first end of the fifth switch coupled to the first end of the third switch; a sixth switch, a first end of the sixth switch coupled between the second end of the first resonant inductor and the first end of the second resonant inductor, and a second end of the sixth switch coupled to a second end of the fifth switch; a diode, a cathode of the diode coupled to the second end of the fifth switch and the second end of the sixth switch; an inductor, a first end of the inductor coupled to the cathode of the diode; and a capacitor, a first end of the capacitor coupled to a second end of the inductor, and a second end of the capacitor coupled to an anode of the diode and a second end of the fourth switch. A power converter as described in claim 6, wherein when the conversion voltage is a first voltage, the first switch and the third switch are turned off, and the second switch and the fourth switch are switched on to excite the first resonant inductor or the second resonant inductor. A power converter as described in claim 9, wherein when the second switch is turned on, a first magnetic excitation path is formed including the second switch, the first resonant inductor and the buck-type conversion circuit, and the first resonant inductor is excited; when the fourth switch is turned on, a second magnetic excitation path is formed including the fourth switch, the second resonant inductor and the buck-type conversion circuit, and the second resonant inductor is excited. A power converter as described in claim 6, wherein when the conversion voltage is a first voltage, the second switch and the fourth switch are turned off, and the first switch and the third switch are switched on to excite the first resonant inductor or the second resonant inductor. A power converter as described in claim 11, wherein when the first switch is turned on, a third magnetic excitation path is formed including the first switch, the first resonant inductor and the buck-type conversion circuit, and the first resonant inductor is excited; when the third switch is turned on, a fourth magnetic excitation path is formed including the third switch, the second resonant inductor and the buck-type conversion circuit, and the second resonant inductor is excited. A power converter as described in claim 6, wherein when the conversion voltage is a second voltage, the first switch and the fourth switch are turned on and off at the same time, the second switch and the third switch are turned on and off at the same time, and the first switch and the second switch are switched on alternately to excite the first resonant inductor and the second resonant inductor. A power converter as described in claim 12, wherein when the first switch and the fourth switch are turned on at the same time, a first magnetic excitation path is formed including the first switch, the first resonant inductor, the second resonant inductor, the fourth switch and the buck-type conversion circuit; when the second switch and the third switch are turned on at the same time, a second magnetic excitation path is formed including the second switch, the first resonant inductor, the second resonant inductor, the third switch and the buck-type conversion circuit. A power converter as described in claim 9, wherein when the conversion voltage is less than the first voltage, the fifth switch and the sixth switch turn on the step-down conversion circuit. A power converter as described in claim 13, wherein when the conversion voltage is less than the second voltage, the fifth switch and the sixth switch turn on the step-down conversion circuit. A power converter as described in claim 6, wherein the step-down conversion circuit is used to convert the conversion voltage into a DC output voltage. A power converter as described in claim 17, wherein the conversion voltage is stepped down to the DC output voltage of different voltage magnitude by controlling a duty cycle of the fifth switch or a duty cycle of the sixth switch.

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