GaN-based switch-mode power supply with planar transformer

Abstract

A switch-mode power supply is provided. The power supply includes a flyback converter with GaN-based power semiconductor transistors and a planar transformer. The planar transformer includes a magnetic core and primary and secondary planar coil windings. The magnetic core has an upper core and a lower core configured to receive the primary and secondary planar coil windings. The lower core has at least three protrusions, including two peripheral protrusions and a central protrusion surrounded by the primary and secondary planar coil windings. The central protrusion and the two peripheral protrusions have the same height, such that when the two peripheral protrusions contact the upper core, there is no air gap between the central protrusion of the lower core and the upper core. The central protrusion is made of iron powder, and the two peripheral protrusions are made of a ferrite material.

Description

Technical Field

[0001] This invention generally relates to GaN-based switch-mode power supplies. More specifically, this invention relates to GaN-based switch-mode power supplies with planar transformers exhibiting improved electrical and magnetic properties. Background Technology

[0002] Switch-mode power supplies are increasingly used in AC-to-DC power converters and battery charging applications (mobile electronics, electric vehicles). Switch-mode power supplies switch between fully on and fully off states with minimal time spent during the transition, reducing energy loss. Switching can occur at high frequencies reaching several MHz; therefore, smaller transformers and other components (e.g., capacitors, inductors) can be used, allowing for a smaller overall footprint for the power supply and power converter.

[0003] One technique for reducing the size of the transformer in a switch-mode power supply is the use of a planar transformer. In a planar transformer, the transformer coil is typically deposited on a substrate using printed circuit technology. The coil is configured to surround a magnetic core to increase the level of magnetic flux. For some types of switch-mode power supplies, a gapped core is used to avoid inductance saturation. However, the air gap can cause leakage flux lines to pass through the transformer coil, resulting in eddy current losses and reduced system efficiency. Therefore, this technique requires an improved GaN-based switch-mode power supply with an improved planar transformer possessing improved magnetic and electrical properties. Summary of the Invention

[0004] According to one aspect of this disclosure, a switch-mode power supply is provided. The power supply includes a flyback converter having a GaN-based power semiconductor transistor and a planar transformer. The planar transformer includes a magnetic core and primary and secondary planar coil windings. The magnetic core has an upper core and a lower core configured to receive the primary and secondary planar coil windings. The lower core has at least three protrusions, including two peripheral protrusions and a central protrusion surrounded by the primary and secondary planar coil windings. The central protrusion and the two peripheral protrusions have the same height, such that when the two peripheral protrusions contact the upper core, there is no air gap between the central protrusion of the lower core and the upper core. The central protrusion is made of iron powder, and the two peripheral protrusions are made of a ferrite material.

[0005] By using iron powder to create the central protrusion of the magnetic core, the air gap between the upper and lower cores is eliminated, thus avoiding inductance saturation. This eliminates leakage flux lines and improves system efficiency. Attached Figure Description

[0006] Figure 1A switch-mode power supply with a flyback converter according to one embodiment is described;

[0007] Figure 2 It is possible Figure 1 A cross-sectional side view of a planar transformer used in a power supply unit;

[0008] Figure 3 yes Figure 2 A perspective view of a planar transformer;

[0009] Figure 4 A switch-mode power supply with an active clamp flyback converter is described according to one embodiment. Detailed Implementation

[0010] In the following description, preferred embodiments of this disclosure are set forth as illustrative rather than limiting examples. Specific details may be omitted so as not to obscure the disclosure; however, this disclosure is prepared to enable those skilled in the art to practice the teachings herein without engaging in undue experimentation.

[0011] Please refer to the individual figures for details. Figure 1 This is a switch-mode power supply 10 according to one embodiment, including a flyback converter configuration. The power supply 10 includes a GaN-based power semiconductor transistor 110, which acts as the main switch for the circuit. The transistor 110 is switched on and off at extremely high frequencies (up to the megahertz range). When the GaN-based switching transistor 110 is in the "on" state, it conducts current; therefore, the voltage drop across the transistor 110 is at its minimum. In the "off" state, no current flows through the transistor 110. This switching forms a high-frequency AC medium. When the switch-mode power supply is used as an AC-to-DC converter, the AC is rectified to produce the desired DC output. Alternatively, a DC input can be used, and the output DC can be gradually increased or decreased.

[0012] Figure 1 The switch-mode power supply features a flyback converter configuration. A flyback converter is a type of buck-boost converter that can produce an output voltage greater than or less than the input voltage depending on the duty cycle. The flyback converter configuration includes a clamping circuit for shifting the input voltage supplied to the transformer. The clamping circuit may include: a clamping capacitor 137, one end of which is electrically connected to the input voltage supply; a resistor 138 connected in parallel to the clamping capacitor 137; and a clamping diode 135, the cathode of which is electrically connected to the other end of the clamping capacitor 137 and the anode of which is electrically connected to the primary winding.

[0013] When the GaN-based switching transistor 110 is closed / closed, the primary coil 190 of the transformer 100 (as shown in the image) Figure 2(As shown) directly connected to the input voltage source 107. The primary current and magnetic flux in the transformer increase. Therefore, energy is stored in the transformer 100. The induced voltage in the secondary coil 192 will be negative. The capacitor 120 supplies energy to the output load 130. When the GaN-based switching transistor is turned on / off, the primary current and magnetic flux decrease. The secondary voltage is positive, and current flows from the transformer 100 and recharges the capacitor 120.

[0014] To increase the efficiency of the switch-mode power supply 10, Figure 2 The transformer. Figure 2 In transformers, the magnetic flux lines are shaped by the configuration of the core, as discussed in further detail below. The magnetic flux lines are avoided from the primary and secondary coils so that when the magnetic flux lines pass through the coils (e.g., Figure 3 (As seen in A) Reduces losses in the primary and secondary coils. Transformer 100 includes a magnetic core comprising an upper core 150 and a lower core 160. The lower core includes three protrusions: two peripheral protrusions 170 and a central protrusion 180. The central protrusion and the two peripheral protrusions 170 have the same height, such that when the two peripheral protrusions contact the upper core 172, there is no air gap between the central protrusion of the lower core 180 and the upper core.

[0015] In some embodiments, the central protrusion 180 is made of iron powder, and the two peripheral protrusions 170 are made of ferrite material.

[0016] Surrounding the central protrusion 180 are a primary planar coil 190 and a secondary planar coil 192. Planar coils 190 and 192 can be deposited on, for example, a printed circuit board 196 using printed circuit technology. Figure 3 Metal lines (e.g., copper, nickel) on substrates such as (as shown) or polymer substrates. However, any technique can be used to form planar metal coils 190 and 192. Figure 2 In the configuration shown, the primary coil 190 is surrounded by the secondary coil 192 on both the upper and lower sides; other arrangements may also be used. Alternative arrangements include alternating primary and secondary coils, or one or more primary coils positioned adjacent to one or more secondary coils. Each element 190 and 192 may be part of a group of side-by-side coils arranged in a planar spiral configuration, such as... Figure 3 It can be seen more clearly in the middle.

[0017] Figure 3 It has a primary coil 190 disposed on a substrate 196. Figure 3 (invisible in the middle) and secondary coil 192 Figure 2A perspective view of a planar transformer. Each coil is arranged in a helical configuration around a central protrusion of 180 degrees, such that multiple metal wires are arranged coplanarly in each of the primary and secondary coil layers. It should be noted that, depending on the selected number of windings, [the following can be achieved / adjusted]. Figure 3 It uses more or fewer primary and secondary coil layers. Other optional layers (not shown) may provide shielding or insulation or other electrical components.

[0018] Figure 4 This is a switch-mode power supply 20 comprising an active clamp flyback converter configuration according to another embodiment of the present invention. The power supply having the active clamp flyback converter 20 differs from... Figure 1 The power supply with flyback converter 10 is characterized in that a switch 212 (which may be a GaN-based power semiconductor transistor) replaces the clamping diode 135. Figure 4 In the active clamped flyback converter, the energy from the leakage inductance of transformer 200 is reused and supplied to load 230. This increases the efficiency of the switch-mode power supply 210. Capacitor 220 alternately stores energy from transformer 200 and supplies energy to output load 230, as described above. Figure 1 In the embodiments described above.

[0019] exist Figure 4 In a power supply with an active clamped flyback converter, the peak voltage across the main switch 215 (a GaN-based transistor) can be reduced; therefore, on-resistance and conduction losses can be reduced. Figure 4 Electromagnetic interference in the circuit is also reduced.

[0020] Industrial applicability:

[0021] The switch-mode power supply of the present invention can be used in AC-DC converters, DC-DC converters, battery chargers for electronic devices (e.g., mobile phones) and battery chargers for electric vehicles.

[0022] While this disclosure has been described and illustrated with reference to specific embodiments thereof, such descriptions and illustrations are not limiting. Those skilled in the art will understand that various changes and equivalents may be made without departing from the true spirit and scope of this disclosure as defined by the appended claims. Illustrations may not be drawn to scale. Differences may exist between artistic representations in this disclosure and actual equipment due to manufacturing processes and tolerances. Other embodiments not specifically described may exist in this disclosure. The description and drawings should be considered illustrative rather than limiting. Modifications may be made to suit particular circumstances, materials, compositions, methods, or processes to the objectives, spirit, and scope of this disclosure. All such modifications are intended to fall within the scope of the appended claims. While the methods disclosed herein have been described with reference to specific operations performed in a particular order, it should be understood that these operations may be combined, subdivided, or reordered to form equivalent methods without departing from the teachings of this disclosure. Therefore, the order and grouping of operations are not limiting unless specifically indicated herein.

[0023] As used herein, the terms “approximately,” “substantially,” “generally,” and “about” are used to describe and explain small variations. When used in conjunction with an event or situation, the terms can refer to the exact occurrence of the event or situation as well as the approximate occurrence of the event or situation. As used herein with respect to a given value or range, the term “about” generally means within ±10%, ±5%, ±1%, or ±0.5% of the given value or range. The range can be indicated herein as from one endpoint to another or between two endpoints. Unless otherwise specified, all ranges disclosed in this disclosure include endpoints. The term “generally coplanar” can refer to two surfaces located within a few micrometers (μm) along the same plane, for example, within 10 μm, 5 μm, 1 μm, or 0.5 μm along the same plane. When referring to the same numerical value or characteristic, the term can refer to a value within ±10%, ±5%, ±1%, or ±0.5% of the average value.

Claims

1. A switch-mode power supply, characterized in that, include: A flyback converter, comprising: GaN-based power semiconductor transistors; A planar transformer, which includes a magnetic core and primary and secondary planar coil windings; in: The magnetic core includes an upper core and a lower core configured to receive the primary and secondary planar coil windings; The lower core has at least three protrusions, including two peripheral protrusions and a central protrusion surrounded by the primary and secondary planar coil windings; The central protrusion and the two peripheral protrusions have the same height, such that when the two peripheral protrusions contact the upper core, there is no air gap between the central protrusion of the lower core and the upper core; The central protrusion is made of iron powder, and the two peripheral protrusions are made of ferrite material; The primary planar coil winding is surrounded by a secondary coil winding on the upper and lower sides; The flyback converter further includes a primary switch electrically coupled to the primary planar coil winding and switched to allow or block current flow through the primary planar coil winding.

2. The switch-mode power supply according to claim 1, characterized in that, The primary and secondary planar coil windings are mounted on one or more planar substrates.

3. The switch-mode power supply according to claim 2, characterized in that, The one or more planar substrates contain one or more printed circuit boards.

4. The switch-mode power supply according to claim 1, characterized in that, The flyback converter further includes a clamping circuit for shifting the input voltage supplied to the transformer.

5. The switch-mode power supply according to claim 1, characterized in that, The flyback converter further includes an output capacitor for storing power from the transformer in the off state.

6. The switch-mode power supply according to claim 1, characterized in that, The flyback converter further includes a synchronous rectifier electrically coupled to the secondary planar coil winding and switched to allow or block current flow through the secondary planar coil winding.

7. A charger for an electronic device, characterized in that, Includes the switch-mode power supply according to claim 1; The primary planar coil winding is surrounded by a secondary coil winding on the upper and lower sides; the flyback converter further includes a primary switch electrically coupled to the primary planar coil winding and switched to allow or block current flow through the primary planar coil winding.

8. The electronic device charger according to claim 7, characterized in that, The primary and secondary planar coil windings are mounted on one or more planar substrates.

9. The electronic device charger according to claim 8, characterized in that, The one or more planar substrates contain one or more printed circuit boards.

10. The electronic device charger according to claim 7, characterized in that, The flyback converter further includes a clamping circuit for shifting the input voltage supplied to the transformer.

11. The electronic device charger according to claim 7, characterized in that, The flyback converter further includes an output capacitor for storing power from the transformer in the off state.

12. The electronic device charger according to claim 7, characterized in that, The flyback converter further includes a synchronous rectifier electrically coupled to the secondary planar coil winding and switched to allow or block current flow through the secondary planar coil winding.

13. An AC-to-DC converter, characterized in that, Includes the switch-mode power supply according to claim 1; The primary planar coil winding is surrounded by a secondary coil winding on the upper and lower sides; The flyback converter further includes a primary switch electrically coupled to the primary planar coil winding and switched to allow or block current flow through the primary planar coil winding.

14. The AC-to-DC converter according to claim 13, characterized in that, The primary and secondary planar coil windings are mounted on one or more planar substrates.

15. The AC-to-DC converter according to claim 14, characterized in that, The one or more planar substrates contain one or more printed circuit boards.

16. The AC-to-DC converter according to claim 13, characterized in that, The flyback converter further includes a clamping circuit for shifting the input voltage supplied to the transformer.

17. The AC-to-DC converter according to claim 13, characterized in that, The flyback converter further includes an output capacitor for storing power from the transformer in the off state.

18. The AC-to-DC converter according to claim 13, characterized in that, The flyback converter further includes a synchronous rectifier electrically coupled to the secondary planar coil winding and switched to allow or block current flow through the secondary planar coil winding.

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