Gate driver, gradient driver system, and method for manufacturing driver power supply

Abstract

The present invention provides a gate driver circuit. The gate driver circuit includes an isolated gate driver power supply circuit. The isolated gate driver power supply circuit includes a coreless transformer and a resonant converter coupled to the coreless transformer. Also provided are a method for manufacturing the isolated gate driver power supply circuit for the gate driver circuit and a gradient driver system for a magnetic resonance imaging (MRI) system.

Description

Technical Field

[0001] The subject matter disclosed herein relates to gate drivers, and more particularly to gate drivers for magnetic resonance imaging systems, gradient driver systems, and methods of fabricating isolated gate driver power supply circuits for gate driver circuits. Background Art

[0002] Typically, a magnetic resonance imaging (MRI) system includes multiple subsystems located throughout different rooms of a medical facility (e.g., equipment room, scanning room, control room, etc.). Some of these subsystems include circuits that utilize ferrite / magnetic components that, if present in the scanning room, can interfere with the magnetic field in the scanning room. However, there is a trend to reduce the footprint of MRI systems and to move some of these components into the scanning room. Summary of the Invention

[0003] The following summarizes certain embodiments commensurate with the scope of the originally claimed subject matter. These embodiments are not intended to limit the scope of the claimed subject matter, but rather, these embodiments are intended merely to provide an overview of possible forms of the disclosure. Indeed, the disclosed technology may encompass a variety of forms that may be similar or different from the embodiments set forth below.

[0004] According to a first embodiment, a gate driver circuit is provided. The gate driver circuit includes an isolated gate driver power supply circuit. The isolated gate driver power supply circuit includes a coreless transformer and a resonant converter coupled to the coreless transformer.

[0005] According to a second embodiment, a gradient driver system for a magnetic resonance imaging system is provided. The gradient driver system includes a gate driver circuit. The gate driver circuit includes an isolated gate driver power supply circuit. The isolated gate driver power supply circuit includes an air-core transformer having a plurality of magnetically coupled windings. The isolated gate driver power supply circuit also includes a resonant converter coupled to the air-core transformer. The resonant converter is configured to compensate for leakage inductance of the air-core transformer.

[0006] According to a third embodiment, a method for manufacturing an isolated gate driver power supply circuit for a gate driver circuit is provided. The method includes coupling a coreless transformer to a resonant converter, wherein the coreless transformer includes a primary winding and a secondary resistor coupled via an interconnect. The method also includes coupling a power supply to the coreless transformer. The method also includes coupling a rectifier to the resonant converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] These and other features, aspects, and advantages of the present invention will be better understood when the following detailed description is read with reference to the accompanying drawings, in which like characters represent like parts throughout, and in which:

[0008] Figure 1 is a schematic diagram of an embodiment of a gradient driver system, wherein a gate driver is disposed within a scanning chamber;

[0009] Figure 2 yes Figure 1 A block diagram of an embodiment of a gate driver in FIG.

[0010] Figure 3 yes Figure 2 A schematic diagram of an embodiment of an isolated power supply;

[0011] Figure 4 is a schematic diagram of an embodiment of an air core transformer;

[0012] Figure 5 is a schematic diagram of an embodiment of a circuit model and an analytical model for an air-core transformer having resonance;

[0013] Figure 6 is used for Figure 5 Graphical representation of the gain curve and input impedance curve of the air core transformer;

[0014] Figure 7 is a schematic diagram of an air-core transformer having three windings and a modeled embodiment;

[0015] Figure 8 It is resonant Figure 7 A schematic diagram of an embodiment of an air core transformer;

[0016] Figure 9 is a schematic diagram of an embodiment of a rectifier (e.g., a full-bridge rectifier) ​​for an isolated power supply;

[0017] Figure 10 is a schematic diagram of an embodiment of a rectifier (e.g., a half-bridge rectifier) ​​for an isolated power supply;

[0018] Figure 11 is a schematic diagram of an embodiment of a rectifier (e.g., a center-tapped rectifier) ​​for an isolated power supply;

[0019] Figure 12 is a schematic diagram of an embodiment of a rectifier (e.g., two full-bridge rectifiers coupled to respective windings) for an isolated power supply;

[0020] Figure 13 is a schematic diagram of an embodiment of an isolated gate driver power supply;

[0021] Figure 14 is a graphical representation of the gate voltage versus load for the isolated gate driver power supply;

[0022] Figure 15is a schematic diagram of an embodiment of an air core transformer in which windings (e.g., spirals) are integrated into a printed circuit board;

[0023] Figure 16 is a schematic diagram of an embodiment of an air core transformer in which the windings (e.g., spirals) and interconnections are integrated into a printed circuit board;

[0024] Figure 17 is a schematic diagram of an embodiment of an air core transformer in which the windings (e.g., spiral shape) are integrated into a printed circuit board;

[0025] Figure 18 is a schematic diagram of an embodiment of an air core transformer having cylindrical windings (e.g., having interconnected windings or wires that do not cross);

[0026] Figure 19 is a schematic diagram of an embodiment of an air core transformer having cylindrical windings (e.g., having interdigitated interconnected windings or wires);

[0027] Figure 20 is a schematic diagram of an embodiment of an air core transformer having cylindrical windings (e.g., with spacers for securing interconnecting windings or wires);

[0028] Figure 21 is a schematic diagram of an embodiment of an air core transformer soldered to a printed circuit board (eg, with interconnecting windings or wires integrated into the printed circuit board). DETAILED DESCRIPTION

[0029] One or more specific embodiments of the present disclosure will be described below. In order to provide a concise description of these embodiments, all features of the actual implementation may not be described in the specification. It should be understood that in the development of any such actual implementation (as in any engineering or design project), multiple implementation-specific decisions must be made to achieve the developer's specific goals (such as meeting system-related and business-related constraints), and these specific goals may vary from one implementation to another. In addition, it should be understood that such research and development work may be complex and time-consuming, but will be a routine design, production, and manufacturing task for those of ordinary skill in the art who benefit from the present disclosure.

[0030] When introducing elements of various embodiments of the present disclosure, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the elements described. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0031] The present disclosure relates to a gate driver (e.g., as part of a gradient driver system) that can be reliably and safely used in a scanning room of a magnetic resonance imaging (MRI) system without compromising image quality. The gate driver includes an isolated gate driver power supply circuit that includes a coreless transformer (e.g., an air-core transformer). Thus, the gate driver does not include any ferromagnetic material and is compatible with MRI functional frequencies. In certain embodiments, the coreless transformer includes concentrically arranged primary and secondary windings to provide acceptable magnetic coupling, sufficient insulation, and minimal sensitivity to switching voltage change rate (dv / dt). In certain embodiments, the isolated gate driver power supply circuit may include a resonant converter coupled to the coreless transformer to compensate for leakage inductance and generate a load-independent output voltage. Due to soft switching and resonant operation with stable and synchronized operation, the isolated gate driver power supply circuit can more effectively reduce conducted and radiated interference. Overall, the gate driver provides high power efficiency and load insensitivity at a relatively low cost.

[0032] Figure 1 FIG. 1 is a schematic diagram of an embodiment of a gradient driver (e.g., gradient amplifier) ​​system 10, wherein gate drivers 12 are disposed within a scanning room 14. The gradient driver system 10 includes a controller or control board 16 coupled to a plurality of gate drivers 12 via an interface board 18. The gate drivers 12 are electronic circuits that couple control electronics (e.g., controller 16) to power semiconductor devices to implement control functions (such as turning the power devices on and off). As described in more detail below, each gate driver 12 includes an isolated gate power supply comprising a coreless transformer (e.g., an air-core transformer). The gate drivers 12 are coupled to a power stage 20. The power stage 20 includes power semiconductor devices (e.g., metal-oxide-semiconductor field-effect transistors (MOSFETs), insulated-gate bipolar transistors (IGBTs), or other semiconductor power devices). The number of gate drivers 12 coupled to the power stage 20 to control the switching of the semiconductor power devices can vary. Additionally, a direct current (DC) power supply 22 is coupled to the power stage 20. The power stage 20 is coupled to a filter (e.g., a power supply filter) that filters the power line to remove ripple signals. As depicted, the gate driver 12, along with the power stage 20 and filter 26, due to its structure, are located within the scanning room 14. The gate driver 12 is configured to be reliably and safely utilized in the presence of high magnetic fields within the scanning room.

[0033] Figure 2 yes Figure 11 is a block diagram of an embodiment of a gate driver 12 (or gate driver board). The gate driver 12 includes control logic 28, 30 coupled to drivers 32, 34 for controlling the upper and lower gates of the upper and lower power semiconductor devices, respectively, to turn the devices on and off. The control logic 28, 30 is coupled to fiber optics 36, 38, respectively. The gate driver 12 also includes an isolated power supply (e.g., an isolated gate power supply) that provides voltage levels (e.g., secondary voltages) and power to the control logic to drive (e.g., charge and discharge) the gates of the power semiconductor devices. Power supplies 40, 42 are high voltage isolated to prevent short circuits in the power stages. As depicted, the gate driver 12 may include sensors 44 (e.g., temperature sensors, VBUS sensors, etc.) and provide feedback to the controller 16 via fiber optics, isolated lines, differential lines, or other means.

[0034] Figure 3 yes Figure 2 Schematic diagrams of embodiments of isolated power supplies 40, 42 are shown. As depicted, each isolated power supply 40, 42 includes a coreless transformer 46 (e.g., an air-core transformer) lacking ferromagnetic material, comprising a first coil 48 (e.g., a primary radio frequency (RF) coil) magnetically coupled (e.g., inductively coupled) to a second coil 50 (e.g., a secondary RF coil). In certain embodiments, transformer 46 may include a varying number of windings or coils. As disclosed below, coils 48, 50 may be arranged concentrically to provide acceptable magnetic coupling, sufficient isolation, and minimal sensitivity to switching voltage change rates (dv / dt). As depicted, transformer 46 (particularly coil 48) is coupled to an oscillator 52 and a power amplifier 54. Oscillator 52 converts power from DC to AC. Power amplifier 54 amplifies the power provided to a load. As depicted, transformer 46 is coupled to a rectifier 56 and additional circuitry 58. Rectifier 56 converts AC to DC.

[0035] Figure 4 is a schematic diagram of an embodiment of an air core transformer 46. As depicted, coils 48, 50 (e.g., litz wire) are wound around a single body 60 (e.g., a plastic bobbin) and magnetically coupled together. In some embodiments, coils 48, 50 may be wound around separate bodies and then coupled together. Coils 48, 50 are arranged in a concentric arrangement, with a portion of coil 48 disposed within coil 50. The concentric arrangement improves coupling between coils 48, 50. Two different layers of coils 48, 50 are disposed on ends 60, 62 of body 60. The number of turns of each of coils 48, 50 can vary. As depicted, an insulating layer 64 of varying thickness is disposed between coils 48, 50. Insulating layer 64 may include insulating paper 66 and insulating film 68 (e.g., a polyimide film).

[0036] In order to reduce the effect of leakage inductance on load regulation, the transformer 46 is provided with resonance. Figure 5 is a schematic diagram of an embodiment of a circuit model 70 and an analytical model 72 having a resonant air core transformer 76. As depicted, L a and L p , respectively, represent the first coil 48 and the second coil 50. As depicted, the transformer 76 is coupled to a resonant converter 78 (e.g., a resonant inverter). In particular, the resonant converter 78 includes respective capacitors 80, 82 coupled in series with the coils 48, 50. For example, the capacitors 80 (C1 and C2) are connected to the resonant converter 78. p ) is coupled in series with coil 48, and capacitor 82 (C2 and C s ) is coupled in series with coil 50. Capacitors 80, 82 compensate for leakage inductance. Transformer 76 is coupled to AC power source 84. Models 70, 72 represent the resistance of coils 48, 50 as R1 and R2 for coil 48, respectively. p and R2 and R for coil 50 s .

[0037] Additionally, the resonant converter 82 tunes the transformer 76 to operate at a frequency where the output is a fixed voltage with no load (indicated by numeral 84). In other words, the transformer 76 is insensitive to the output voltage (e.g., it does affect the voltage gain). For example, for the voltage gain (G) of the transformer in the models 70, 72 shown in Equation 1, v ), it is desirable to make the difference in switching frequency Δ(ω) equal to 0 (i.e., not affecting the voltage gain):

[0038]

[0039] in

[0040] Δ(ω)=ω 4 ·L p ·C p ·L s ·C s ·(k ps 2 -1)+ω 2 ·(L p ·C p +L s ·C s )-1 (2)

[0041] Z p (ω)=R p +i·X p ω (3)

[0042] and

[0043]

[0044] The equation for determining the frequencies ωL and ωH to achieve Δ(ω)=0 is:

[0045]

[0046] as well as

[0047]

[0048] In the above equation, M ps represents the mutual inductance between coils 48 and 50, L p and L s represents the respective inductances of coils 48 and 50, C p and C s represents the respective capacitances of coils 48 and 50, R ac Represents the total resistance, R p (ω) represents the resistance of the coil 48, Xp represents the reactance at a given frequency, and Z p (ω) represents the impedance at a given frequency, and k ps represents the coupling coefficient between the coils 48 and 50. Figure 6 It shows how a fixed frequency (eg, a resonant frequency) is selected for the resonant converter 78 to tune the transformer 76 . Figure 6 yes Figure 5 A graphical representation of the gain curve 88 and input impedance curve 90 of the air core transformer 76. The resonant frequency 92 (in this case f_H, where f_H = ω) is selected at a frequency where the gain curves converge so that the output is a fixed voltage to the load. H / 2π). As described above, operating at the resonant frequency 92, the transformer 70 (and the isolated gate driver power supply) will have an output voltage that is insensitive to load variations. This enables the gate driver power supply, along with the resonant transformer 76, to utilize zero voltage switching and therefore soft switching to minimize switching losses and reduce conducted and radiated interference to the MRI system while providing stable and synchronized operation. Any variations in voltage can be compensated via a linear regulator.

[0049] In certain embodiments, an air core transformer may include more than two windings or coils. Figure 7 is a schematic diagram of an air-core transformer 94 having three windings and its modeling. Figure 7 A transformer 94, an inductance matrix 93, and a model 95 of the transformer 94 are depicted. In particular, the transformer 94 includes a primary winding or coil 96, a secondary winding or coil 98, and a tertiary winding or coil 100. The respective inductances for and between the coils 96, 98, 100 are represented by L 11 , L 12 , L13 , L 22 , L 23 and L 33 The leakage inductances of coils 96, 98, and 100 are represented by L l1 , L l2 and L l3 The magnetizing inductance of coil 96 is represented by L m1 The coupling coefficient between the coils is represented by K 12 , K 13 and K 23 In other embodiments, transformer 94 may include a different number of coils or windings.

[0050] As mentioned above, air core transformers may include resonances. Figure 8 It is resonant Figure 7 Schematic diagram of an air-core transformer 94. As depicted, the transformer 94 is coupled to a resonant converter 102 (e.g., a resonant inverter). In particular, the resonant converter 102 includes respective capacitors 104, 106, 108 coupled in series with the coils 96, 98, 100. For example, capacitor 104 (C1) is coupled in series with the coil 96, capacitor 106 (C2) is coupled in series with the coil 98, and capacitor 108 (C3) is coupled in series with the coil 100. Capacitors 104, 106, 108 compensate for leakage inductance. In addition, the resonant converter 102 tunes the transformer 94 to operate at a frequency at which the output is a fixed voltage with no load. This enables the gate driver power supply, along with the resonant transformer 94, to utilize zero voltage switching and, therefore, soft switching to minimize switching losses and reduce conducted and radiated interference to the MRI system, while providing stable and synchronized operation.

[0051] Figure 2 The isolated power supplies 40 , 42 may also each include a rectifier for converting AC to DC and outputting power from the power supplies 40 , 42 . Figures 9 to 12 is a schematic diagram of a rectifier. Figure 9 、 Figure 10 and Figure 11 A full-bridge rectifier 110, a half-bridge rectifier 112, and a center-tapped rectifier 114 are shown coupled to a coil or winding 116 (e.g., a secondary winding) of an air-core transformer. As depicted, winding 116 is coupled in series with a capacitor 118 (C2) of a resonant converter. Rectifiers 110, 112, 114 are coupled to an equivalent load resistance 120 (R_ld). Figure 12 Respective full bridge rectifiers 110, 122 are shown coupled to respective coils or windings of an air core transformer. For example, winding 116 (e.g., a secondary winding) is coupled to full bridge rectifier 110 and winding 124 (e.g., a tertiary winding) is coupled to full bridge rectifier 122. Figure 12, windings 116, 124 are each coupled in series with capacitors 118, 126 of the resonant converter. As depicted, rectifiers 116, 122 are coupled to an equivalent load resistance 120 (R_ld).

[0052] Figure 13 FIG2 is a schematic diagram of an embodiment of an isolated gate driver power supply 128 for a gate driver. The isolated gate driver power supply 128 includes an air-core transformer 130 coupled to a resonant converter 132 (e.g., a resonant inverter). Specifically, the air-core transformer includes three coils or windings 96, 98, and 100 coupled in series with capacitors 104 (C1), 106 (C2), and 108 (C3), respectively, of the resonant converter 132. The windings 96, 98, and 100 serve as the primary, secondary, and tertiary windings, respectively. As described above, the resonant converter 132 provides tuning for the transformer 130 to compensate for leakage inductance. A full-bridge circuit 134 is coupled to the transformer 130 and provides AC power to the transformer 130. Full-bridge rectifiers 110 and 122 are coupled to the windings 98 and 100, respectively. The rectifiers 110 and 122 convert the AC current to DC and provide power to a load 136.

[0053] Figure 14 is an isolated gate driver power supply (e.g. Figure 13 1 . An x-axis 140 and a y-axis 142 represent load and gate voltage, respectively. The graphical representation 138 illustrates that when the load is increased, the gate voltage output of the isolated gate driver power supply remains relatively consistent (e.g., at an efficiency of 80% or greater), as shown by curve 144. In other words, as the load increases, the voltage drop across the isolated gate driver power supply is minimal.

[0054] As described above, with the utilization of air core transformers, it is desirable to increase the coupling coefficient while reducing the capacitive coupling between the primary and secondary windings. Figures 15 to 21 Alternative embodiments are provided for both increasing the coupling coefficient and reducing the capacitive coupling.These embodiments disclose different techniques for fixing the interconnecting winding position between the primary winding (eg, primary side) and the secondary winding (eg, secondary side) of a transformer.

[0055] In certain embodiments, the components of the gate driver can be easily integrated into a printed circuit board (PCB). Figure 15 and Figure 16 1 is a schematic diagram of a primary side 146 and a secondary side 150 of an air core transformer 148 integrated (eg, printed) into or on a PCB 152, wherein the primary side 146 and the secondary side 150 include spiral windings. Figure 15 As depicted in FIG, the interconnecting winding 154 linking the primary side 146 and the secondary side 150 is separate from the PCB 152. Figure 16As depicted in , interconnecting windings 154 are integrated (eg, printed) into PCB 152 and crossed to increase coupling between the windings. Figure 17 1 is a schematic diagram of an air core transformer 148, wherein the windings of the primary side 146 and the secondary side 150 (eg, having a toroidal shape) are integrated into a PCB 152. Figure 17 As depicted, the interconnect winding 154 is separate from the PCB 152.

[0056] Figures 18 to 21 is a schematic diagram of a primary side 146 and a secondary side 150 having cylindrical windings. The cylindrical windings of the primary side 146 and the secondary side 150 may be arranged around a plastic bobbin or any other structure that does not include ferromagnetic material. Figure 18 As depicted, the interconnected windings 154 disposed around the primary side 146 and the secondary side 150 do not cross. Figure 19 As depicted in FIG, the interconnecting windings 154 are crossed to increase coupling between the cylindrical windings. In certain embodiments, as Figure 20 As depicted in FIG, spacers 156 may be used to secure the position of the interconnected windings relative to the cylindrical windings. In certain embodiments, such as Figure 21 As depicted in , the primary side 146 and the secondary side 150 may be soldered to a PCB 152 , while the interconnecting windings 154 (eg, crossed interconnecting windings) are integrated into or onto the PCB 152 .

[0057] Technical effects of the disclosed embodiments include providing a gate driver that can be reliably and safely used in a scanning room of a magnetic resonance imaging (MRI) system without affecting image quality. The gate driver includes an isolated gate driver power supply circuit that includes a coreless transformer (e.g., an air core transformer). In certain embodiments, the isolated gate driver power supply circuit may include a resonant converter coupled to the coreless transformer to compensate for leakage inductance. Additionally, the resonant converter tunes the transformer to enable the isolated gate driver power supply circuit to generate an output that is independent of the load. Due to soft switching and resonant operation with stable and synchronized operation, the isolated gate driver power supply circuit can more effectively reduce conducted interference and radiated interference. Overall, the gate driver provides high power efficiency and load insensitivity at a lower cost.

[0058] This written description uses examples, including the best mode, to disclose the invention and also to enable any person skilled in the art to practice the invention, including making and using any device or system and performing any incorporated method. The patentable scope of the invention is defined by the claims and may include other examples that occur to those skilled in the art. If such other examples have structural elements that do not differ from the literal language of the claims or include equivalent structural elements that are insubstantially different from the literal language of the claims, such other examples are intended to be within the scope of the claims.

Claims

1. A gate driver circuit comprising: Isolated gate driver power supply circuit, including: a coreless transformer comprising a primary winding and a secondary winding, wherein the primary winding and the secondary winding are linked by an interconnecting winding; and A resonant converter is coupled to the coreless transformer.

2. The gate driver circuit according to claim 1, wherein: The primary winding and the secondary winding are magnetically coupled together.

3. The gate driver circuit according to claim 1, wherein: The primary winding and the secondary winding are arranged concentrically relative to each other.

4. The gate driver circuit according to claim 3, wherein: The resonant converter includes a plurality of capacitors, and the plurality of capacitors includes a first capacitor and a second capacitor, the first capacitor and the second capacitor being coupled in series to the primary winding and the secondary winding, respectively.

5. The gate driver circuit according to claim 4, wherein: The resonant converter is configured to compensate for leakage inductance of the coreless transformer.

6. The gate driver circuit according to claim 5, wherein: The resonant converter is configured to enable the isolated gate driver power supply circuit to generate an output voltage that is independent of the load.

7. The gate driver circuit according to claim 6, wherein: The resonant converter is configured to achieve zero voltage switching through the isolated gate driver power supply circuit.

8. The gate driver circuit according to claim 1, wherein: The gate driver circuit is configured to be disposed within and used in a scanning room having a magnetic resonance imaging system.

9. The gate driver circuit according to claim 1, wherein: The isolated gate driver power supply circuit includes a power supply configured to provide power to the isolated gate driver power supply circuit and a rectifier configured to provide a power output from the isolated gate driver power supply.

10. A gradient driver system for a magnetic resonance imaging (MRI) system, comprising: Gate driver circuit, including: Isolated gate driver power supply circuit, including: an air core transformer comprising a primary winding and a secondary winding, wherein the primary winding and the secondary winding are linked by an interconnecting winding; and A resonant converter is coupled to the air-core transformer, wherein the resonant converter is configured to compensate for a leakage inductance of the air-core transformer.

11. The gradient drive system according to claim 10, characterized in that The primary winding and the secondary winding are magnetically coupled together.

12. The gradient drive system according to claim 11, characterized in that The primary winding and the secondary winding are arranged concentrically relative to each other.

13. The gradient drive system according to claim 12, characterized in that The resonant converter includes a plurality of capacitors, and the plurality of capacitors includes a first capacitor and a second capacitor, the first capacitor and the second capacitor being coupled in series to the primary winding and the secondary winding, respectively.

14. The gradient drive system according to claim 13, wherein: The resonant converter is configured to enable the isolated gate driver power supply circuit to generate an output voltage that is independent of the load.

15. The gradient drive system according to claim 10, wherein: The gate driver circuit is configured to be disposed within a scanning room having the MRI system and to be used within the scanning room.

16. The gradient drive system according to claim 10, wherein: The isolated gate driver power supply circuit includes a power supply configured to provide power to the isolated gate driver power supply circuit and a rectifier providing a power output from the isolated gate driver power supply.

17. A method of manufacturing an isolated gate driver power supply circuit for a gate driver circuit, comprising: coupling a coreless transformer to the resonant converter, wherein the coreless transformer includes a primary winding and a secondary winding, the primary winding and the secondary winding being linked by an interconnecting winding; coupling a power source to the coreless transformer; and A rectifier is coupled to the resonant converter.

18. The method according to claim 17, characterized in that The resonant converter includes a first capacitor and a second capacitor, and coupling the coreless transformer to the resonant converter includes coupling the first capacitor and the second capacitor in series to the primary winding and the secondary winding, respectively.

Images