WO2023272738A1

WO2023272738A1 - Coreless power transformer and isolating power source

Info

Publication number: WO2023272738A1
Application number: PCT/CN2021/104364
Authority: WO
Inventors: Huan SHI; Wei Liu; Yongfei QU
Original assignee: Abb Schweiz Ag
Priority date: 2021-07-02
Filing date: 2021-07-02
Publication date: 2023-01-05
Also published as: CN117063252A

Abstract

A coreless power transformer (100) comprises: a primary winding comprising a first planar coil (201) arranged on a PCB layer (101) and a second planar coil (202) arranged on a PCB layer (102), and configured to receive power from a power supply; and a secondary winding comprising a third planar coil (203) arranged on a PCB layer (103) and a fourth planar coil (204) arranged on a PCB layer (104), and configured to receive the power from the primary winding and provide the power to a load, wherein the PCB layer (101), the PCB layer (102), the PCB layer (103) and the PCB layer (104) are substantially parallel to each other.

Description

CORELESS POWER TRANSFORMER AND ISOLATING POWER SOURCE

FIELD

Embodiments of the present disclosure generally relate to the field of power transformers, and more particularly, to a coreless power transformer and an isolating power source.

BACKGROUND

A planar transformer is typically used in small-scale equipment with a low-power isolation power supply to deliver power. The low-power isolation power supply includes a small isolated power supply, a DCS equipment power supply, and the like. A conventional planar transformer usually comprises a magnetic core to increase an energy delivering efficiency. However, the magnetic core increases a cost of the planar transformer. Moreover, the magnetic core needs to be mounted at a place where the planar transformer is mounted, for example, on a PCB, which increases the cost of manufacturing the PCB. Thus, there is a need to reduce the cost of the planar transformer while satisfying a power level of the low-power isolation power supply.

SUMMARY

In view of the foregoing problems, various example embodiments of the present disclosure provide a coreless power transformer and an isolating power source to reduce the cost of the power transformer while satisfying the power level of the low-power isolation power supply.

In a first aspect of the present disclosure, example embodiments of the present disclosure provide a coreless power transformer for delivering power. The coreless power transformer comprises a primary winding comprising a first coreless planar coil arranged on a PCB layer 1 and a second coreless planar coil arranged on a PCB layer 2, and configured to receive power from a power supply; and a secondary winding comprising a third coreless planar coil arranged on a PCB layer 3 and a fourth coreless planar coil arranged on a PCB layer 4, and configured to receive the power from the primary winding and provide the power to a load, wherein the PCB layer 1, the PCB layer 2, the PCB layer 3 and the PCB layer 4 are substantially parallel to each other. With these embodiments, only four layers of PCBs and corresponding planar coils are used in the coreless power transformer to satisfy the power level of the low-power isolation power supply, which reduces the cost of the coreless power transformer.

In some embodiments, the PCB layer 1 and the PCB layer 2 are sandwiched between the PCB layer 3 and the PCB layer 4. With these embodiments, a coupling coefficient between the primary winding and the secondary winding of the coreless power transformer can be improved.

In some embodiments, the PCB layer 1, the PCB layer 2, the PCB layer 3 and the PCB layer 4 are arranged at equal intervals. With these embodiments, an energy delivering efficiency of the coreless power transformer can be improved.

In some embodiments, a distance between adjacent ones of the PCB layer 1, the PCB layer 2, the PCB layer 3 and the PCB layer 4 is 0.3mm. With these embodiments, the energy delivering efficiency of the coreless power transformer can be maximized when an output voltage of the coreless power transformer is 24V and an output current of the coreless power transformer is 25mA.

In some embodiments, a turn ratio between the primary winding and the secondary winding is 1. With these embodiments, the output voltage of the coreless power transformer can achieve a desired value while setting an inductance of the primary winding at a relatively high value.

In some embodiments, each of the first coreless planar coil, the second coreless planar coil, the third coreless planar coil and the fourth coreless planar coil comprises: a coil body arranged on the respective PCB and configured to produce an alternating magnetic field for delivering the power; and a metal ring arranged around the coil body and configured to produce a magnetic field having a direction opposite to the alternating magnetic field produced by the coil body. With these embodiments, the magnetic flux outside the coreless planar coil will be largely reduced and the magnetic flux inside the coreless planar coil will be maintained, thereby reducing the crosstalk and improving the efficiency of the coreless planar coil.

In some embodiments, a wire width of the coil body can be 12 mil, and a wire spacing of the coil body can be 5 mil. With these embodiments, a proximity effect and a skin effect of the coil body can be reduced.

In some embodiments, each of the primary winding and the secondary winding comprises at least one additional coreless planar coil arranged on at least one additional PCB, and the least one additional PCB is substantially parallel to the PCB layer 1, the PCB layer 2, the PCB layer 3 and the PCB layer 4. With these embodiments, the power level of the coreless power transformer can be further improved.

In a second aspect of the present disclosure, example embodiments of the present disclosure provide an isolating power source. The isolating power source comprises a primary circuit coupled to a power supply and configured to adjust a voltage of the power supply; a coreless power transformer according to the first aspect of the present disclosure, wherein the primary winding of the coreless power transformer is coupled to the primary circuit to receive the adjusted voltage; and a secondary circuit coupled to the secondary winding of the coreless power transformer and configured to output one or more voltages. Since the isolating power source comprises the coreless power transformer according to the first aspect of the present disclosure, the isolating power source may provide the same advantages.

In some embodiments, the isolating power source further comprises a feedback circuit coupled to the primary winding of the coreless power transformer and the primary circuit, and configured to provide a feedback voltage to the primary circuit based on the adjusted voltage. With these embodiments, the feedback voltage may be set to a low value, such that an exciting current of the primary winding can be reduced, thereby reducing the power loss of the isolating power source.

In some embodiments, the feedback circuit comprises a first capacitor.

In some embodiments, the isolating power source further comprises a compensation circuit coupled between the secondary winding of the coreless power transformer and the secondary circuit, and configured to compensate a voltage drop in the primary circuit and the coreless power transformer. With these embodiments, a voltage drop on the internal resistance of the windings and primary circuit can be compensated.

In some embodiments, the compensation circuit comprises a second capacitor and a first diode; a first terminal of the second capacitor is coupled to a first terminal of the secondary winding of the coreless power transformer, and a second terminal of the second capacitor is coupled to the secondary circuit; and a cathode of the first diode is coupled to the second terminal of the second capacitor, and an anode of the first diode is coupled to a second terminal of the secondary winding of the coreless power transformer.

In some embodiments, the primary circuit comprises a first MOSFET, a second MOSFET and a PWM controller; a drain of the first MOSFET is coupled to the power supply, a source of the first MOSFET is coupled to a first terminal of the primary winding of the coreless power transformer, and a gate of the first MOSFET is coupled to the PWM controller; a drain of the second MOSFET is coupled to the source of the first MOSFET, a source of the second MOSFET is coupled to ground, and a gate of the second MOSFET is coupled to the PWM controller; and the PWM controller is configured to control duty cycles of the first MOSFET and the second MOSFET to output the adjusted voltage at different predetermined levels.

In some embodiments, the secondary circuit comprises a third capacitor, a fourth capacitor, a second diode and a third diode; an anode of the second diode is coupled to a first terminal of the secondary winding of the coreless power transformer, a cathode of the second diode is coupled to a first terminal of the third capacitor to output a first output voltage, and a second terminal of the third capacitor is coupled to a second terminal of the secondary winding; and a cathode of the third diode is coupled to the first terminal of the secondary winding, an anode of the third diode is coupled to a first terminal of the fourth capacitor, a second terminal of the fourth capacitor is coupled to the second terminal of the secondary winding to output a second output voltage. With these embodiments, the two output voltages can be achieved by using only one secondary winding, thereby reducing the cost of the coreless power transformer.

It is to be understood that the Summary section is not intended to identify key or essential features of embodiments of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure. Other features of the present disclosure will become easily comprehensible through the following description.

DESCRIPTION OF DRAWINGS

Through the following detailed descriptions with reference to the accompanying drawings, the above and other objectives, features and advantages of the example embodiments disclosed herein will become more comprehensible. In the drawings, several example embodiments disclosed herein will be illustrated in examples and in a non-limiting manner, wherein:

FIG. 1 is a schematic view illustrating a coreless power transformer in accordance with an embodiment of the present disclosure;

FIG. 2 is a cross-section view of a coreless power transformer including four layers of PCBs in accordance with an embodiment of the present disclosure;

FIG. 3 is a schematic view illustrating a coreless planar coil in accordance with an embodiment of the present disclosure; and

FIG. 4 is a schematic circuit diagram of an isolating power source in accordance with an embodiment of the present disclosure.

Throughout the drawings, the same or similar reference symbols are used to indicate the same or similar elements.

DETAILED DESCRIPTION OF EMBODIMETNS

Principles of the present disclosure will now be described with reference to several example embodiments shown in the drawings. Though example embodiments of the present disclosure are illustrated in the drawings, it is to be understood that the embodiments are described only to facilitate those skilled in the art to better understand and thereby implement the present disclosure, rather than to limit the scope of the disclosure in any manner.

The term “comprises” or “includes” and its variants are to be read as open terms that mean “includes, but is not limited to. ” The term “or” is to be read as “and/or” unless the context clearly indicates otherwise. The term “based on” is to be read as “based at least in part on. ” The term “being operable to” is to mean a function, an action, a motion or a state that can be achieved by an operation induced by a user or an external mechanism. The term “one embodiment” and “an embodiment” are to be read as “at least one embodiment. ” The term “another embodiment” is to be read as “at least one other embodiment. ” The terms “first, ” “second, ” and the like may refer to different or same objects. Other definitions, explicit and implicit, may be included below. A definition of a term is consistent throughout the description unless the context clearly indicates otherwise.

According to embodiments of the present disclosure, the cost of the power transformer is reduced by using coreless planar coils, while the output energy level of the power transformer satisfies the power level of the low-power isolation power supply by making full use of available resources, for example, the PCB area. The above idea may be implemented in various manners, as will be described in detail in the following paragraphs.

Hereinafter, the principles of the coreless power transformer in accordance with embodiments of the present disclosure will be described in detail with reference to FIGS. 1-3. Referring to FIG. 1 first. FIG. 1 is a schematic view illustrating a coreless power transformer in accordance with an embodiment of the present disclosure.

As shown in FIG. 1, the coreless power transformer 100 comprises four layers of

PCBs

101, 102, 103, 104. The PCB layer 101, the PCB layer 102, the PCB layer 103 and the PCB layer 104 are substantially parallel to each other. A first planar coil 201 is arranged on the PCB layer 101, a second planar coil 202 is arranged on the PCB layer 102, a third planar coil 203 is arranged on the PCB layer 103, and a fourth planar coil 204 is arranged on the PCB layer 104. A primary winding of the coreless power transformer 100 comprises two of the first planar coil 201, the second planar coil 202, the third planar coil 203 and the fourth planar coil 204, and a secondary winding of the coreless power transformer 100 comprises the other two of the first planar coil 201, the second planar coil 202, the third planar coil 203 and the fourth planar coil 204.

By using coreless planar coils, the cost of the power transformer is reduced. Meanwhile, by making full use of the four layers of PCBs, the output energy level of the power transformer can meet the need of the low-power isolation power supply, for example, a DCS equipment power supply.

In some embodiments, each of the primary winding and the secondary winding comprises at least one additional coreless planar coil arranged on at least one additional PCB, and the least one additional PCB is substantially parallel to the PCB layer 101, the PCB layer 102, the PCB layer 103 and the PCB layer 104.

In some embodiments, as shown in FIG. 1, the primary winding comprises the first planar coil 201 and the second planar coil 202, and the secondary winding comprises the third planar coil 203 and the fourth planar coil 204. The first planar coil 101 and the second planar coil 102 are sandwiched between the third planar coil 103 and the fourth planar coil 104. With such an arrangement, magnetic lines of force generated by the primary winding can largely travel through the secondary winding, thereby the coupling coefficient between the primary winding and the secondary winding can be maximized.

In other embodiments, the primary winding and the secondary winding can be arranged in other arrangements. For example, the primary winding can comprise the third planar coil 203 and the first planar coil 201, and the secondary winding can comprise the second planar coil 202 and the fourth planar coil 204. The scope of the present disclosure is not intended to be limited in this respect.

Now referring to FIG. 2. FIG. 2 is a cross-section view of a coreless power transformer including four layers of PCBs in accordance with an embodiment of the present disclosure. As shown in FIG. 2, substrates 105 are provided between the PCBs to support the PCBs. The magnetic lines of force can travel through the substrates 105. The thickness of the substrates 105 decides distances d1, d2 and d3 between adjacent ones of the PCB layer 101, the PCB layer 102, the PCB layer 103 and the PCB layer 104.

The distances d1, d2 and d3 will influence the power loss and energy delivering efficiency of the coreless power transformer. If the distances d1, d2 and d3 are too small, the power loss of the coreless power transformer will be large due to the proximity effect. On the other hand, if the distances d1, d2 and d3 are too large, the coupling coefficient between the planar coils will be small, resulting in a reduced energy delivering efficiency.

In some embodiments, as shown in FIG. 2, the PCB layer 101, the PCB layer 102, the PCB layer 103 and the PCB layer 104 are arranged at equal intervals. That is, d1=d2=d3. With such an arrangement, the energy delivering efficiency of the coreless power transformer 100 can be improved and the power loss of the coreless power transformer will be small. In an embodiment where an output voltage of the coreless power transformer is 24V and an output current of the coreless power transformer is 25mA, when d1=d2=d3=0.3mm, the energy delivering efficiency of the coreless power transformer can be maximized. In other embodiments, the distances d1, d2, d3 can be different from each other. The scope of the present disclosure is not intended to be limited in this respect.

Compared with a planar coil with a magnetic core, an inductance of the coreless planar coil is relatively small. Besides, because of a restriction of the area of the PCB, the coreless planar coil cannot occupy too many areas of the PCB. Thereby, an inductance of the primary winding of the coreless power transformer is smaller than that of a power transformer using planar coils with the magnetic core. As a result, an exciting current of the primary winding of the coreless power transformer must be larger than that of the power transformer using planar coils with the magnetic core to achieve the same output energy level, thereby resulting in a larger power loss. To reduce the power loss, the inductance of the primary winding should be as large as possible within the restriction of the area of the PCB.

In some embodiments, a turn ratio between the primary winding and the secondary winding is 1. With such an arrangement, the inductance of the primary winding can be set at a relatively high value, while the output voltage of the coreless power transformer can satisfy the need of the output.

Now referring to FIG. 3. FIG. 3 is a schematic view illustrating a coreless planar coil in accordance with an embodiment of the present disclosure. As shown in FIG. 3, the coreless planar coil 201 comprises a coil body 205. The coil body 205 is arranged in a PCB and is used to receive power from a power source, and generate an alternating magnetic field to deliver the power.

In some embodiments, the turn number of the coil body 205 is 48. In other embodiments, the turn number of the coil body 205 can be other numbers, for example, 44, 46, 50, 52, and so on. The scope of the present disclosure is not intended to be limited in this respect.

Due to the proximity effect and skin effect, the working frequency of the coreless planar coil 201 is limited, and a wire width W of the coil body 205 and a wire spacing S of the coil body 205 are also limited to reduce the power loss. In some embodiments, the wire width W is 12 mil, and the wire spacing S is 5 mil. In other embodiments, the wire width W and the wire spacing S can be other values. The scope of the present disclosure is not intended to be limited in this respect.

In some embodiments, as shown in FIG. 3, the coreless planar coil 201 further comprises a metal ring 206. The metal ring 206 is arranged around the coil body 205, and is used to produce a magnetic field having a direction opposite to the alternating magnetic field produced by the coil body 205. By reducing the distribution of magnetic field outside the metal ring 206, the magnetic field generated by the coil body 205 is concentrated inside the metal ring 206, and the amplitude of the magnetic field is decreased. As a result, the influence of the alternating magnetic field on nearby electronic systems is reduced, and the influence of the alternating magnetic field on the electronic systems parallel to the coreless planar coil 201 is also reduced, and thus the reliability of the systems is improved.

Hereinafter, the principles of an isolating power source will be described in detail with reference to FIG. 4. FIG. 4 is a schematic circuit diagram of an isolating power source in accordance with an embodiment of the present disclosure. As shown in FIG. 4, the isolating power source 300 generally includes a primary circuit 301, a coreless power transformer 100 according to embodiments of the present disclosure, and a secondary circuit 304.

The primary circuit 301 is coupled to a power supply and configured to adjust a voltage Vin of the power supply. As shown in FIG. 4, the primary circuit 301 comprises a first MOSFET S1, a second MOSFET S2 and a PWM controller T. A drain of the first MOSFET S1 is coupled to the power supply, a source of the first MOSFET S1 is coupled to a first terminal of the primary winding of the coreless power transformer 100, and a gate of the first MOSFET S1 is coupled to the PWM controller T. A drain of the second MOSFET S2 is coupled to the source of the first MOSFET S1, a source of the second MOSFET S2 is coupled to ground, and a gate of the second MOSFET S2 is coupled to the PWM controller T. The PWM controller T is configured to control duty cycles of the first MOSFET S1 and the second MOSFET S2 to output the adjusted voltage at different predetermined levels.

The coreless power transformer 100 is coupled between the primary circuit 301 and the secondary circuit 304, and used to isolate the primary circuit 301 and the secondary circuit 304.

The secondary circuit 304 is coupled to the secondary winding of the coreless power transformer 100 and configured to output one or more voltages. As shown in FIG. 4, the secondary circuit 304 comprises a third capacitor C3, a fourth capacitor C4, a second diode D2 and a third diode D3. An anode of the second diode D2 is coupled to a first terminal of the secondary winding of the coreless power transformer 100, a cathode of the second diode D2 is coupled to a first terminal of the third capacitor C3 to output a first output voltage Vo1, for example, 24V, and a second terminal of the third capacitor C3 is coupled to a second terminal of the secondary winding. A cathode of the third diode D3 is coupled to the first terminal of the secondary winding, an anode of the third diode D3 is coupled to a first terminal of the fourth capacitor C4, a second terminal of the fourth capacitor C4 is coupled to the second terminal of the secondary winding to output a second output voltage Vo2, for example, 3.7V. In other embodiments, the secondary circuit 304 can output the voltage of other values. The scope of the present disclosure is not intended to be limited in this respect.

In some embodiments, as shown in FIG. 4, the isolating power source 300 further comprises a feedback circuit 302 coupled to the primary winding of the coreless power transformer 100 and the primary circuit 301. The feedback circuit 302 is configured to provide a feedback voltage to the primary circuit 301 based on the adjusted voltage. In some embodiments, the feedback circuit 302 comprises a first capacitor C1. In other embodiments, the feedback circuit 302 can comprises other components. The scope of the present disclosure is not intended to be limited in this respect.

In some embodiments, as shown in FIG. 4, the isolating power source 300 further comprises a compensation circuit 305 coupled between the secondary winding of the coreless power transformer 100 and the secondary circuit 304. The compensation circuit 305 is configured to compensate a voltage drop in the primary circuit 301 and the coreless power transformer 100.

In some embodiments, as shown in FIG. 4, the compensation circuit 305 comprises a second capacitor C2 and a first diode D1. A first terminal of the second capacitor C2 is coupled to a first terminal of the secondary winding of the coreless power transformer 100, and a second terminal of the second capacitor C2 is coupled to the secondary circuit 304. A cathode of the first diode D1 is coupled to the second terminal of the second capacitor C2, and an anode of the first diode D1 is coupled to a second terminal of the secondary winding of the coreless power transformer 100. In other embodiments, the compensation circuit 305 can comprises other components. The scope of the present disclosure is not intended to be limited in this respect.

Hereinafter, a working process of the isolating power source 300 will be described. First, when the first MOSFET S1 is turned on and the second MOSFET S2 is turned off, the voltage Vin is applied to the primary winding, the voltage at point 1 is higher than the voltage at point 2 at this time. Correspondingly, the voltage at point 3 is higher than the voltage at point 4, and the secondary winding outputs a first output voltage that is equal to the voltage Vin, because the turn ratio of the primary winding and the secondary winding is 1. As a result, the first output voltage Vo1 equals to the voltage Vin.

Next, when the first MOSFET S1 is turned off and the second MOSFET S2 is turned on, the voltage at point 2 is higher than the voltage at point 1. Correspondingly, the voltage at point 4 is higher than the voltage at point 3, and the secondary winding outputs a second output voltage V _FB that is equal to a voltage at point FB. As a result, the second output voltage Vo2 equals to the V _FB. Meanwhile, the capacitor C2 is charged through the diode D1. The voltage across the capacitor C2 can compensate a voltage drop in the primary circuit 301 and the coreless power transformer 100 when outputting the first output voltage Vo1.

Meanwhile, by setting the feedback voltage V _FB at a low value, the exciting current of the primary winding can be reduced, thereby the power loss can be reduced.

While several inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the inventive embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure.

Claims

A coreless power transformer (100) for delivering power, comprising:

a primary winding comprising a first coreless planar coil (201) arranged on a PCB layer 1 (101) and a second coreless planar coil (202) arranged on a PCB layer 2 (102) , and configured to receive power from a power supply; and

a secondary winding comprising a third coreless planar coil (203) arranged on a PCB layer 3 (103) and a fourth coreless planar coil (204) arranged on a PCB layer 4 (104) , and configured to receive the power from the primary winding and provide the power to a load,

wherein the PCB layer 1 (101) , the PCB layer 2 (102) , the PCB layer 3 (103) and the PCB layer 4 (104) are substantially parallel to each other.
The coreless power transformer (100) according to claim 1, wherein the PCB layer 1 (101) and the PCB layer 2 (102) are sandwiched between the PCB layer 3 (103) and the PCB layer 4 (104) .
The coreless power transformer (100) according to claim 1, wherein the PCB layer 1 (101) , the PCB layer 2 (102) , the PCB layer 3 (103) and the PCB layer 4 (104) are arranged at equal intervals.
The coreless power transformer (100) according to claim 3, wherein a distance between adjacent ones of the PCB layer 1 (101) , the PCB layer 2 (102) , the PCB layer 3 (103) and the PCB layer 4 (104) is 0.3mm.
The coreless power transformer (100) according to claim 1, wherein a turn ratio between the primary winding and the secondary winding is 1.
The coreless power transformer (100) according to claim 1, wherein each of the first coreless planar coil (201) , the second coreless planar coil (202) , the third coreless planar coil (203) and the fourth coreless planar coil (204) comprises:

a coil body (205) arranged on the respective PCB and configured to produce an alternating magnetic field for delivering the power; and

a metal ring (206) arranged around the coil body (205) and configured to produce a magnetic field having a direction opposite to the alternating magnetic field produced by the coil body (205) .
The coreless power transformer (100) according to claim 6, wherein a wire width (W) of the coil body (205) is 12 mil, and a wire spacing (S) of the coil body (205) is 5 mil.
The coreless power transformer (100) according to claim 1, wherein each of the primary winding and the secondary winding comprises at least one additional coreless planar coil arranged on at least one additional PCB, and the least one additional PCB is substantially parallel to the PCB layer 1 (101) , the PCB layer 2 (102) , the PCB layer 3 (103) and the PCB layer 4 (104) .
An isolating power source (300) , comprising:

a primary circuit (301) coupled to a power supply and configured to adjust a voltage of the power supply;

a coreless power transformer (100) according to any of claims 1-8, wherein the primary winding of the coreless power transformer (100) is coupled to the primary circuit (301) to receive the adjusted voltage; and

a secondary circuit (304) coupled to the secondary winding of the coreless power transformer (100) and configured to output one or more voltages.
The isolating power source (300) according to claim 9, further comprising:

a feedback circuit (302) coupled to the primary winding of the coreless power transformer (100) and the primary circuit (301) , and configured to provide a feedback voltage to the primary circuit (301) based on the adjusted voltage.
The isolating power source (300) according to claim 10, wherein the feedback circuit (302) comprises a first capacitor (C1) .
The isolating power source (300) according to claim 9, further comprising:

a compensation circuit (305) coupled between the secondary winding of the coreless power transformer (100) and the secondary circuit (304) , and configured to compensate a voltage drop in the primary circuit (301) and the coreless power transformer (100) .
The isolating power source (300) according to claim 12, wherein the compensation circuit (305) comprises a second capacitor (C2) and a first diode (D1) ;

a first terminal of the second capacitor (C2) is coupled to a first terminal of the secondary winding of the coreless power transformer (100) , and a second terminal of the second capacitor (C2) is coupled to the secondary circuit (304) ; and

a cathode of the first diode (D1) is coupled to the second terminal of the second capacitor (C2) , and an anode of the first diode (D1) is coupled to a second terminal of the secondary winding of the coreless power transformer (100) .
The isolating power source (300) according to claim 9, wherein the primary circuit (301) comprises a first MOSFET (S1) , a second MOSFET (S2) and a PWM controller (T) ;

a drain of the first MOSFET (S1) is coupled to the power supply, a source of the first MOSFET (S1) is coupled to a first terminal of the primary winding of the coreless power transformer (100) , and a gate of the first MOSFET (S1) is coupled to the PWM controller (T) ;

a drain of the second MOSFET (S2) is coupled to the source of the first MOSFET (S1) , a source of the second MOSFET (S2) is coupled to ground, and a gate of the second MOSFET (S2) is coupled to the PWM controller (T) ; and

the PWM controller (T) is configured to control duty cycles of the first MOSFET (S1) and the second MOSFET (S2) to output the adjusted voltage at different predetermined levels.
The isolating power source (300) according to claim 9, wherein the secondary circuit (304) comprises a third capacitor (C3) , a fourth capacitor (C4) , a second diode (D2) and a third diode (D3) ;

an anode of the second diode (D2) is coupled to a first terminal of the secondary winding of the coreless power transformer (100) , a cathode of the second diode (D2) is coupled to a first terminal of the third capacitor (C3) to output a first output voltage (Vo1) , and a second terminal of the third capacitor (C3) is coupled to a second terminal of the secondary winding; and

a cathode of the third diode (D3) is coupled to the first terminal of the secondary winding, an anode of the third diode (D3) is coupled to a first terminal of the fourth capacitor (C4) , a second terminal of the fourth capacitor (C4) is coupled to the second terminal of the secondary winding to output a second output voltage (Vo2) .