AC power output to reduce corrosion

Abstract

Electric fields that can lead to corrosion of contacts can be compensated for by embodiments of the present invention. For example, voltage waveforms at the contacts can be designed to have an average value of zero volts and thus generate no electric field overall. Galvanic voltages generated by the different metals used in a contact and a housing can generate an electric field, and currents caused by the galvanic electric field can be blocked by capacitive coupling of the contacts to their respective circuits.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 541,726, entitled "AC POWER OUTPUT TO REDUCE CORROSION," filed September 29, 2023, and U.S. Patent Application No. 18 / 896,299, entitled "AC POWER OUTPUT TO REDUCE CORROSION," filed September 25, 2024, which are incorporated herein by reference. BACKGROUND

[0002] In recent years, the amount of data transferred between electronic devices has increased dramatically. Large amounts of audio, streaming video, text, and other types of data content are now regularly transferred between desktop computers and portable computers, media devices, portable media devices, displays, storage devices, and other types of electronic devices.

[0003] Power and data can be provided from one electronic device to another via cables that may include one or more wire conductors, fiber optic cables, or other conductors. Connector inserts may be disposed at each end of these cables and plug into connector receptacles in the communicating or power-transmitting electronic device. Contacts in or on a connector insert can form electrical connections with corresponding contacts in a connector receptacle. Other devices may have contacts on a surface of a device. Paths for power and data can be formed when devices are attached to or positioned side by side and corresponding contacts are electrically connected.

[0004] These various contacts in connector inserts, receptacles, or on the surface of a device can be exposed to the local environment. These contacts can come into contact with liquid, moisture, or other harmful contaminants. For example, liquids can be spilled onto these contacts, or a device can be placed in a position where its contacts are immersed in a pool of liquid. Users can swim or exercise while wearing or holding an electrical device. These activities can position the contacts for the electronic devices where they come into contact with various contaminants.

[0005] These fluids or other contaminants can corrode and damage the contacts. This corrosion can be greatly exacerbated by the presence of an electric field, such as when a constant or DC voltage is applied to a contact. This can make power contacts particularly susceptible to corrosion.

[0006] Therefore, methods, structures and devices are needed that are capable of transferring power across device contacts while minimizing their corrosion. SUMMARY

[0007] Accordingly, embodiments of the present invention may provide methods, structures, and devices capable of delivering power across a pair of power contacts while minimizing corrosion thereof. An exemplary embodiment of the present invention may provide methods, structures, and devices capable of delivering power across a pair of power contacts while minimizing corrosion by delivering power using a differential AC voltage having an average voltage of (or near) zero volts. This and other embodiments of the present invention may prevent current flow that may result from galvanic stresses by capacitively coupling the power contacts to circuits in an electronic device.

[0008] Contacts on electronic devices can be exposed to corrosive materials and liquids. These corrosive materials and liquids can cause corrosion of the contacts, thereby releasing ions from the contacts. In the presence of a direct electric field, the corrosion and release of ions can be accelerated. By applying an alternating electric field, the net corrosion of the contacts can be reduced. By applying an alternating electric field with a voltage whose average value is zero volts or nearly zero volts, the migration of ions out of a contact can be at least approximately equal to the migration of ions into the contact. This symmetrical migration can reduce contact corrosion.The effectiveness of this solution can be reduced by galvanic voltages that may exist between a first metal forming a contact and a second metal forming a housing or enclosure for the electronic device. This galvanic voltage can create an electric field that can also cause corrosion. A galvanic voltage can allow current to flow through a contact and through circuits in the electronic device, to the housing or enclosure, which can be grounded. The electron flow of this current can offset the migration of ions into a liquid. This current can be interrupted by capacitive coupling of the current contacts to circuits in an electronic device.That is, the capacitor can act as a direct current (DC) blocker, which can block the DC component of the current caused by the galvanic voltage, thereby further reducing the corrosion of the power contacts.

[0009] Various contact structures may be used in these and other embodiments of the present invention. First contacts on a first device may be connected to second contacts on a second device. The first contacts may be spring-loaded to provide a contact force, while the second contacts may be attached to a device enclosure and acted upon by the contact force of the first contacts. The first contacts may be loaded by a pair of canted-coil springs. The canted-coil springs may be arranged in a housing such that their central axis is orthogonal to a mating direction of the first contact. When the first device and the second device are connected, the first contact may be forced in one direction into the first device.The first contact can press a plate and a retainer into the canted coil springs, thereby compressing or flattening the diameter of the canted coil springs. The deformed canted coil springs can then exert a deflection force on the second contact. When the first and second devices are separated, the canted coil springs can return to their original shape and push the first contact away from the first device. The movement of the first contact can be limited by attaching the first contact and pins to the retainer, with the pins able to move in corresponding slots in a housing in the first device. The canted coil springs can be held in position using one or more pins passing through the central axis of the canted coil springs.

[0010] In these and other embodiments of the present invention, the first contacts may be loaded by a single canted coil spring. The canted coil spring may be disposed in a housing such that its central axis is orthogonal to a mating direction of the first contact. When the first device and the second device are connected, the first contact may be pushed in one direction into the first device. The first contact may push a plate and a retainer into the canted coil spring, thereby compressing or flattening the diameter of the canted coil spring. The deformed canted coil springs may then exert a deflection force on the second contact. When the first and second devices are separated, the canted coil spring may return to its original shape and push the first contact away from the first device.The movement of the first contact can be limited by attaching a pin to the support, which pin can move within a slot in a housing in the first device. The canted coil spring can be held in position by means of a number of blades attached to a frame.

[0011] In these and other embodiments of the present invention, the first contacts may be preloaded by one or more stacks of Belleville washers. The Belleville washers may be placed back-to-back and then stacked. To limit the movement of the Belleville washers, the stack may be placed on an alignment pin. When the first device and the second device are connected, the first contact may be pushed in one direction into the first device. The first contact may push a plate into the Belleville washers. As the plate is pushed into the Belleville washers stack, the Belleville washers may be compressed, thereby reducing the length of the Belleville washers stack. The Belleville washers may have the same or different thicknesses so that the Belleville washers provide at least a reasonably constant force throughout the deflection of the first contact.When the first and second devices are separated, the Belleville springs can return to their original shape and push the first contact away from the first device. The first contact and the plate can be attached to a bracket. The movement of the first contact can be limited by attaching a pin to the bracket, which can move within a slot in a housing in the first device.

[0012] In these and other embodiments of the present invention, the second contacts may be mounted in the second device, and a first contact may exert a force against a second contact. The second contact may be carried by a housing sealed to a casing or enclosure of the second device by a gasket. The contact and housing may be attached to a power cord with a pressure-sensitive or other adhesive. The power cord may be held in place by a shroud. The shroud may be attached to the power cord with a pressure-sensitive or other adhesive. The shroud may be attached to the casing or enclosure of the second device.

[0013] Various circuits may be used to transfer power in these and other embodiments of the present invention. These circuits may be used to transfer power from the first device to the second device and from the second device to the first device, or alternatively, power may be transferred bidirectionally, or back and forth, between the first and second devices. For example, the first device may be powered by a charging device or an AC adapter. While the first device is being powered, the second device may be connected to the first device. This allows the first device to supply power to the second device. During device operation, the second device may supply power back to the first device.During device operation, the first device may continue to supply power to the second device as needed.

[0014] These circuits may be the same or substantially similar in the first and second devices. In these and other embodiments of the present invention, the first device and the second device may have differences, for example, if the power transfers between the first and second devices are unidirectional or one-sided.

[0015] This and other embodiments of the present invention may provide a power transfer circuit including a battery. A first power transfer circuit may be housed in the first device, while a second power transfer circuit may be housed in the second device. The battery may be connected to electrical circuits in the first device. The battery may be connected to a switch that can be opened when the first device is disconnected from the second device and closed when power is transferred. The switch, in turn, may be connected to a buck-boost circuit, which, in turn, may be connected to an inverter / rectifier circuit. The inverter / rectifier circuit may provide capacitively coupled output signals to a pair of first contacts.The capacitively coupled output signals can be received from the pair of first contacts by a pair of second contacts of the second device. A rectifier / inverter circuit, which can be the same as or similar to the inverter / rectifier circuit of the first device, can receive the output signals and provide an output to a buck-boost circuit, which can be the same as or similar to the buck-boost circuit in the first electronic device. The buck-boost circuit can be coupled to a battery and internal circuitry of the second device via a switch.

[0016] Power can be transferred from the first device to the second device. In the first power transfer circuit, the switch can connect the battery to the buck-boost circuit. The buck-boost circuit can act as a boost converter to increase the battery voltage and provide a high and low voltage to the inverter / rectifier circuit. The inverter / rectifier circuit can operate as an inverter to provide a differential output signal. The differential output signal can be capacitively coupled to a pair of first contacts of the first device.

[0017] The differential output signal can be received by a pair of second contacts of the second device. The differential output signal can be capacitively coupled to the rectifier / inverter circuit, which can convert the differential output signal into a high voltage and a low voltage. The high voltage and the low voltage can be down-converted by the buck-boost circuit, which can provide power to charge the battery of the second device via the switch. While power is described as being transferred from the first device to the second device, power can also be transferred from the second device to the first device.

[0018] Various differential output signals can be provided by inverter circuits consistent with embodiments of the present invention. For example, anti-phase (or 180-degree out-of-phase) sine waves can be provided at pairs of first contacts or pairs of second contacts. Anti-phase square waves can be provided at pairs of first contacts or pairs of second contacts. Anti-phase square waves that have been filtered to remove high-frequency components can be provided at pairs of first contacts or pairs of second contacts. Bandwidth-limited and anti-phase square waves can be provided at pairs of first contacts or pairs of second contacts. Other differential waveforms can be provided at pairs of first contacts or pairs of second contacts.

[0019] The frequency of the differential output signals can be varied. The amplitude of the differential output signals can be varied. These parameters can be varied when the various conditions for the pairs of first contacts or the pairs of second contacts vary. For example, if liquid is detected at one or more contacts, the frequency, the amplitude, or both for the differential output signals can be varied. Under certain circumstances, the differential output signals can be interrupted.

[0020] The first contacts in the first device may be capacitively coupled to the first power transfer circuit in the first device, and the second contacts in the second device may be capacitively coupled to the second power transfer circuit in the second device. The presence of capacitors used for this AC or capacitive coupling may interrupt DC current paths between the first contacts, second contacts, an enclosure for the first device, and an enclosure for the second device.

[0021] For example, a liquid or fluid may be located over some or all of the first contacts, second contacts, an enclosure for the first device, and an enclosure for the second device. As part of an electrochemical corrosion process, the liquid may cause corrosion of one or more of the first contacts, second contacts, the enclosure for the first device, or the enclosure for the second device, thereby releasing ions from the structures into the liquid. The transfer of the ions into the liquid may be part of a loop involving a galvanic potential that stimulates electron migration from a contact through circuitry in either the first or second device and then to a grounded housing or enclosure.The input coupling capacitors can block the DC component of this current, thereby breaking the loop and slowing the flow of ions out of the contact and into the liquid.

[0022] In short, the presence of an electric field can cause ions to migrate from a contact into a liquid. This process can lead to corrosion of the contact. Consequently, electric fields can be compensated for by embodiments of the present invention. For example, voltage waveforms at the contacts can be designed to have an average value of zero volts, thus generating no overall electric field. Also, galvanic voltages generated by the dissimilar metals used by a contact and a housing can generate an electric field, but currents caused by the galvanic electric field can be blocked by capacitive coupling of the contacts to their corresponding circuits.

[0023] Data may be transferred between the first device and the second device in various ways. The amplitude of the differential output signal may be modulated with data. The phase of the differential output signal may be modulated with data. The frequency of the differential output signal may be modulated with data. These modulations may be applied by a power and data transmitting device and restored by a power and data receiving device. In these and other embodiments of the present invention, a power transmitting device may provide a differential output signal. A power receiving device may be a data transmitting device and modulate a load detected by the power transmitting device. The load may be modulated by data that the power receiving device sends back to the power transmitting device.The power transmission device can also be the data reception device and restore the data.

[0024] These and other embodiments of the present invention may include additional features that can help prevent or reduce corrosion. For example, electrical impedance spectrography circuits may be incorporated. These circuits may apply a voltage waveform to one or more contacts of a device. A resulting voltage, a resulting current, or both may be measured. A resulting current may indicate that current is flowing through a fluid. A phase shift between the applied voltage waveform and the resulting current or voltage may indicate the amount or type of fluid. To prevent a corrosion path, coupling capacitors may be inserted between the contacts and the electrical impedance spectrography circuits.

[0025] Embodiments of the present invention may provide power transfer circuits and devices that may be located in various types of devices, such as portable computing devices, tablet computers, desktop computers, laptops, all-in-one computers, wearable computing devices, mobile phones, smartphones, media phones, storage devices, portable media players, navigation systems, monitors, video transmission systems, power supplies, adapters, remote control devices, charging devices, and other devices.

[0026] The first device and the second device may be different types of devices. While the first and second devices may be connected via a cable, they are often connected directly to each other. For example, the first device may be an audio device such as headphones or earbuds, while the second device may be a case for carrying and charging the audio device, or the second device may be an audio device such as headphones or earbuds, while the first device may be a case for carrying and charging the audio device. The first device may be a tablet computer, while the second device may be a case and a keyboard, or the second device may be a tablet computer, while the first device may be a case and a keyboard.The first device may be a watch, while the second may be a watchband, or the second device may be a watch, while the first device may be a watchband. The first device and the second device may be other types of devices that can be connected to each other by directly connecting them.

[0027] Various embodiments of the present invention may incorporate one or more of these and the other features described herein. A better understanding of the nature and advantages of the present invention may be obtained by reference to the following detailed description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 illustrates an electronic system according to an embodiment of the present invention; Fig. 2 illustrates a spring-loaded contact assembly according to an embodiment of the present invention; Fig. 3 illustrates a spring-loaded contact assembly according to an embodiment of the present invention; Fig. 4 is an exploded view of the contact assembly of Fig. 3; Fig. 5 illustrates a force-deflection curve for a first contact according to an embodiment of the present invention; Fig. 6 illustrates a variation of a spring-loaded contact assembly according to an embodiment of the present invention; Fig. 7 is an exploded view of the contact assembly of Fig. 6; Fig. 8 is a cross-sectional view of a second contact assembly according to an embodiment of the present invention; Fig. 9 is an exploded view of the contact assembly of Fig. 8; Fig. 10 is a block diagram of a charging system for the electronic system of Fig. 1 according to an embodiment of the present invention; Fig. 11 is a circuit diagram of a contact interface of the electronic system of Fig. 1 according to an embodiment of the present invention; Fig. 12 is a simplified circuit diagram of a portion of a power circuit according to an embodiment of the present invention; Fig. 13 is an alternative simplified circuit diagram of a portion of a power circuit according to an embodiment of the present invention; Fig. 14 is a simplified circuit diagram of portions of two power circuits transferring power in accordance with an embodiment of the present invention; Fig. 15 to Fig. 17 illustrate contact assemblies according to an embodiment of the present invention; Fig. 18A to Fig. 18D illustrate profiles of contact assemblies according to an embodiment of the present invention; Fig. 19 illustrates contact assemblies for a contact interface according to an embodiment of the present invention; Fig. 20 illustrates further details of a contact assembly according to an embodiment of the present invention; Fig. 21 illustrates contact assemblies for a contact interface according to an embodiment of the present invention; Fig. 22 is a side sectional view of a contact assembly according to an embodiment of the present invention; Fig. 23 illustrates galvanic corrosion paths in electronic devices according to embodiments of the present invention; Fig. 24 illustrates optional DC charging in electronic devices according to an embodiment of the present invention; Fig. 25 illustrates an AC waveform for power transfers according to an embodiment of the present invention; Fig. 26 illustrates a charging path through an electronic system according to an embodiment of the present invention; Fig. 27 illustrates another charging path through an electronic system according to an embodiment of the present invention; Fig. 28 illustrates another charging path through an electronic system according to an embodiment of the present invention; Fig. 29 illustrates data that may be used by a method for determining a type of material used for a contact according to an embodiment of the present invention; and Fig. 30 illustrates a method for optimizing a charging waveform according to an embodiment of the present invention. DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0028] Fig. Figure 1 illustrates an electronic system according to an embodiment of the present invention. This figure, like the other included figures, is shown for illustrative purposes and does not limit the possible embodiments of the present invention or the claims.

[0029] In this example, the electronic system 10 may include a first device 100 that may be connected to the second device 200 to share data, power, or both. The first contact 110, the first contact 112, and the first contact 114 (collectively, first contacts 110) on the first device 100 may be electrically connected to the second contact 210, the second contact 212, and the second contact 214 (collectively, second contacts 210) on the second device 200. First contacts 110 on the first device 100 may be electrically connected to second contacts 210 on the second device 200 using a cable (not shown). In other embodiments of the present invention, first contacts 110 on the first device 100 may be directly and electrically connected to second contacts 210 on the second device 200.In various embodiments of the present invention, the first contacts 110 and the second contacts 210 may be power contacts or other types of contacts. Examples of embodiments of the present invention in which the first contact 110, the first contact 112, the second contact 210, and the second contact 212 are power contacts are shown in the following figures. The first contact 114 and the second contact 214 may be ground contacts, data or signal contacts, or other types of contacts.

[0030] Embodiments of the present invention may transfer power from a first device 100 to a second device 200 by providing an alternating differential voltage having an average value of or near zero volts across the first contact 110 and the first contact 112. By providing an alternating differential voltage having an average value of or near zero volts across the second contact 210 and the second contact 212, power may be transferred from a second device 200 to a first device 100. This may result in reduced or low ion migration into the contact, thereby reducing corrosion of the first contacts 110 and the second contacts 210 when the power contact of the device is exposed to contaminants.First contacts 110 may be capacitively coupled to power transfer circuit 120, and second contacts 210 may be capacitively coupled to power transfer circuit 220. The capacitive coupling may eliminate or reduce currents generated by galvanic voltages between dissimilar metals used for the first contacts 110, the second contacts 210, and the enclosure or housing for the first device 100 and the second device 200.

[0031] First contacts 110 may be coupled to power transfer circuitry 120 in a first device 100. Power transfer circuitry 120 may supply power to or receive power from battery 190. Second contacts 210 may be coupled to power transfer circuitry 220 in a second device 200. Power transfer circuitry 220 may supply power to or receive power from battery 290.

[0032] A first device 100 and a second device 200 may be different types of devices. While a first device 100 and a second device 200 may be connected via a cable, they are often connected directly to each other. For example, a first device 100 may be an audio device such as headphones or earbuds, while a second device 200 may be a case for carrying and charging the audio device, or a second device 200 may be an audio device such as headphones or earbuds, while a first device 100 may be a case for carrying and charging the audio device. A first device 100 may be a tablet computer, while a second device 200 may be a case and keyboard, or a second device 200 may be a tablet computer, while a first device 100 may be a case and keyboard.A first device 100 may be a watch, while a second device 200 may be a watchband, or a second device 200 may be a watch, while a first device 100 may be a watchband. A first device 100 and a second device 200 may be other types of devices that can be connected to each other by directly connecting them.

[0033] First contacts 110 may be spring-loaded contacts that can be connected to fixed second contacts 210. First contacts 110 may be spring-loaded, so they exert a force on the second contacts 210 to provide a good electrical connection. Examples of first contacts are shown in the following figures.

[0034] Fig. Figure 2 illustrates a spring-loaded contact assembly according to an embodiment of the present invention. A first contact assembly 20 may include a first contact 110. A first contact 110 may be biased by a pair of canted coil springs 130. The canted coil springs 130 may be arranged in the housing 150 such that the central axes of the canted coil springs 130 are orthogonal to a terminal direction of the first contact 110. When a first device 100 and the second device 200 (both in Fig. 1), the first contact 110 may be pushed in one direction into the first device 100. A first contact 110 may push plate 170 and retainer 160 into the canted coil springs 130, thereby compressing or flattening the canted coil springs 130 in the direction of their diameter. When a first device 100 and a second device 200 are separated, a canted coil spring 130 may return to its original shape and push a first contact 110, plate 170, and retainer 160 away from a first device 100. The movement of the first contact 110 may be limited by securing the first contact and pins 162 to retainer 160, where pins 162 can move in slots 152 in housing 150 in a first device 100. The canted coil springs 130 may be held in position by one or more pins 140 extending through the central axis of the canted coil spring 130.Wire 180 may connect the first contact 110 to a coupling capacitor such as the coupling capacitor C1 in . Fig. 11 pair.

[0035] Fig. 3 illustrates a spring-loaded contact assembly according to an embodiment of the present invention. In these and other embodiments of the present invention, a first contact 110 may be biased by a single canted coil spring 230. A first contact assembly 30 may include a canted coil spring 230. A canted coil spring 230 may be arranged in housing 250 such that its central axes are orthogonal to a connection direction of a first contact 110. When a first device 100 and a second device 200 (both in Fig. 1), the first contact 110 may be pushed in one direction into the first device 100. A first contact 110 may push plate 270 and retainer 260 into a canted coil spring 230, thereby compressing or flattening the canted coil spring 230 in the direction of its diameter. When a first device 100 and a second device 200 are separated, a canted coil spring 230 may return to its original shape and push a first contact 110, plate 270, and retainer 260 away from a first device 100. The movement of the first contact 110 may be limited by attaching a first contact 110 and pins 262 to retainer 260, with pins 262 movable within slots 252 in housing 250 in a first device 100. A canted coil spring 130 can be held in position by means of a number of vanes 242 attached to the frame 240.Wire 280 may connect the first contact 110 to a coupling capacitor such as the coupling capacitor C1 in . Fig. 11 pair.

[0036] Fig. 4 is an exploded view of the contact assembly of Fig. 3. A first contact assembly 30 may include a canted coil spring 230. A canted coil spring 230 may be held in place by louvers 242 extending from the frame 240. Plate 270 may further confine the canted coil springs 230. Plate 270 may be attached to the underside of holder 260. Holder 620 may hold a first contact 110 in slot 264. Plate 270 may be attached to an underside of holder 260. Wire 280 may conduct voltages and currents from a first contact 110 to the power transfer circuit 120 in a first device 100. Holder 260 may slide through a region defined by pins 262 in slots 252 in housing 250 (in Fig. 3). When a first device 100 and the second device 200 (both in Fig. 1), the first contact 110 can be pushed in one direction into the first device 100. A first contact 110 can push plate 170 and retainer 160 into canted coil springs 130, thereby compressing or flattening canted coil springs 130 in the direction of their diameter. When a first device 100 and a second device 200 are separated, a canted coil spring 130 can return to its original shape and push plate 270, retainer 260, and a first contact 110 away from a first device 100.

[0037] Fig. Figure 5 illustrates a force-deformation curve according to an embodiment of the present invention. Diagram 500 illustrates a force-deformation curve 530, which is defined as the force-deformation curve 530 applied by a first contact 110 (in Fig. 1) is plotted as a function of the deflection 520 of the first contact. When a first device and a second device are connected, a first contact 110 may be deflected by an amount that may be in the range 540. The deflection may vary in the range due to manufacturing tolerances in forming a first device 100, a second device 200, first contacts 110, second contacts 210, as well as the manner in which they are connected. Therefore, it may be desirable for the contact force to be independent of the displacement. That is, it may be desirable for the force-deflection curve 530 to be relatively flat, at least in the region 540. This can be achieved by using the canted coil springs 130 and the canted coil springs 230 in the examples of Fig. 2 and Fig. 3. The force-deformation curve 530 can be brought into a flat section in region 540 by using other structures. An example is shown in the following figures.

[0038] Fig. Figure 6 illustrates a variant of a spring-loaded contact assembly according to an embodiment of the present invention. In contact assembly 30, first contacts 110 can be preloaded by one or more stacks of disc springs 630. Disc springs 630 can be placed back-to-back and subsequently stacked.

[0039] The stack of disc springs 630 can be arranged on the alignment pin 644 to limit the movement of the disc springs 630. When a first device 100 and a second device 200 (both in Fig. 1), the first contact 110 may be pushed in one direction into the first device 100. A first contact 110 may push plate 670 into disc springs 630. As plate 270 is pushed into the stack of disc springs 630, the disc springs 630 may begin to compress, thereby reducing the length of the stack of disc springs 630. Disc springs 630 may have the same or different thicknesses so that the disc springs 630 can provide at least a somewhat constant force throughout the deflection of the first contact 110. When a first device 100 and a second device 200 are separated, disc springs 630 may resume their original shape and push a first contact 110, holder 660, and plate 670 away from a first device 100.Wire 680 can conduct voltages and currents from a first contact 110 to power transfer circuitry 120 in a first device 100 (all in . Fig. 1). An insulation 682 may be provided around wire 680.

[0040] Fig. 7 is an exploded view of the contact assembly of Fig. 6. Stacks of disc springs 630 can be arranged on alignment pins 644 in contact assembly 30. Disc springs 630 can be held between frame 640 and plate 670. Blades 642 can extend from frame 640. Wire 680 can conduct voltages and currents from a first contact 110 to power transfer circuit 120 in a first device 100 (all in Fig. 1). Holder 660 can hold pins 662 (in Fig. 6), a first contact 110 and plate 670. Holder 660 can move over a range defined by pins 662 in openings (not shown) in housing 650.

[0041] Fig. Figure 8 is a cross-section of a second contact assembly according to an embodiment of the present invention. In these and other embodiments of the present invention, second contacts 210 in a second contact assembly 80 may be incorporated in a second device 200 (in Fig. 1) and a first contact 110 may exert a force against a second contact 210. A second contact 210 may be supported by housing 810, which is sealed to housing or enclosure 890 of a second device 200 by a gasket 820. A second contact 210 may be attached to a flexible circuit board 830 with a pressure-sensitive adhesive 840 or other adhesive. A flexible circuit board 830 may be held in place by a shroud 850. Shroud 850 may be attached to a flexible circuit board 830 with a pressure-sensitive adhesive 860 or other adhesive. Shroud 850 may be attached to the housing or enclosure 890 of a second device 200 by fasteners 892.

[0042] Fig. 9 is an exploded view of the contact assembly of Fig. 8. A second contact 210 in a second contact assembly 80 may be carried by housing 810. Housing 810 may be connected to housing or enclosure 890 (in Fig. 8) of a second device 200 (in Fig. 2). A second contact 210 may make contact with pad 832 on a flexible circuit board 830. A flexible circuit board 830 may include pad 834, which may be connected to pad 832 to provide electrical connection to power transfer circuitry 220 (in Fig. 1) in a second device 200. Housing 810 may be attached to a flexible circuit board 830 with a pressure-sensitive adhesive 840 or other adhesive. A flexible circuit board 830 may be held in place by a shroud 850. Shroud 850 may be attached to a flexible circuit board 830 with a pressure-sensitive adhesive 860 or other adhesive. Shroud 850 may be attached to the housing or enclosure 890 of a second device 200 by passing fasteners 892 through openings 852 and inserting the fasteners 892 into corresponding holes in the housing or enclosure 890 of a second device 200.

[0043] Various circuits may be used to transfer power in these and other embodiments of the present invention. These circuits may be used to transfer power from the first device to the second device and from the second device to the first device, or alternatively, power may be transferred bidirectionally, or back and forth, between the first and second devices. For example, the first device may be powered by a charging device or an AC adapter. While the first device is being powered, the second device may be connected to the first device. This allows the first device to supply power to the second device. During device operation, the second device may supply power back to the first device.During device operation, the first device may continue to supply power to the second device as needed.

[0044] These circuits may be the same or substantially similar in the first and second devices. In these and other embodiments of the present invention, the first device and the second device may differ, for example, if the power transfers between the first and second devices are unidirectional or one-sided. Examples are illustrated in the following figures.

[0045] Fig. 10 is a block diagram of a charging system for the electronic system of Fig. 1 according to an embodiment of the present invention. A first power transmission circuit 120 may be incorporated in a first device 100 ( Fig. 1), while a second power transmission circuit 220 may be housed in a second device 200 ( Fig. 1). A first power transfer circuit 120 may share power with a second power transfer circuit 220. For example, power transfer circuit 120 may transfer power to a second power transfer circuit 220. Battery 190 may be connected to switch 1010, which may be opened when a first device is disconnected from a second device 200 and closed when power is transferred. Switch 1010, in turn, may be connected to a buck-boost circuit 1020, which may be connected to an inverter / rectifier circuit 1030. Inverter / rectifier circuit 1030 may provide capacitively coupled output signals via capacitors C1 and C2 to a pair of first contacts, including a first contact 110 and a first contact 112.The capacitively coupled output signals may be received from the pair of first contacts 110 by a pair of second contacts 210, including second contact 210 and second contact 212 of a second device. The signals at a second contact 210 and at a second contact 212 may be capacitively coupled to rectifier / inverter circuit 1040 via capacitors C3 and C4. Rectifier / inverter circuit 1040, which may be the same as or similar to inverter / rectifier circuit 1030 of a first power transfer circuit 120, may provide an output to buck-boost circuit 1050, which may be the same as or similar to buck-boost circuit 1020 in a first power transfer circuit 120. Buck-boost circuit 1050 may be connected to battery 290 and internal circuitry of a second device 200 via switch 1060.

[0046] Power may be transferred from a first device 100 to a second device 200. In a first power transfer circuit 120, switch 1010 may connect battery 190 to buck-boost circuit 1020. Buck-boost circuit 1020 may act as a boost converter to increase the voltage of battery 190 and provide a high and a low voltage to inverter / rectifier circuit 1030. Inverter / rectifier circuit 1030 may operate as an inverter to provide a differential output signal. The differential output signal may be capacitively coupled to a first contact 110 via capacitor C1 and to a first contact 112 via capacitor C2.

[0047] The differential output signal may be received by a second contact 210 and by a second contact 212 of a second device 200. The differential output signal may be capacitively coupled via capacitors C3 and C4 to rectifier / inverter circuit 1040, which may convert the differential output signal into a high voltage and a low voltage. The high voltage and a low voltage may be down-converted by buck-boost circuit 1050, which may provide power to charge battery 290 of a second device 200 via switch 1060. While power is described as being transferred from the first device 100 to a second device 200, power may also be transferred from a second device 200 to a first device 100.

[0048] Various differential output signals may be provided by the inverters of inverter / rectifier circuit 1030 and rectifier / inverter circuit 1040, in accordance with embodiments of the present invention. For example, anti-phase (or 180 degrees out of phase with each other) sine waves may be provided at pairs of first contacts or pairs of second contacts. Anti-phase square waves may be provided at pairs of first contacts or pairs of second contacts. Anti-phase square waves that have been filtered to remove high-frequency components may be provided at pairs of first contacts or pairs of second contacts. Bandwidth-limited and anti-phase square waves may be provided at pairs of first contacts or pairs of second contacts. Other differential waveforms may be provided at pairs of first contacts or pairs of second contacts.

[0049] The frequency of the differential output signals can be varied. The amplitude of the differential output signals can be varied. These parameters can be varied when the various conditions for the pairs of first contacts or the pairs of second contacts vary. For example, if liquid is detected at one or more contacts, the frequency, the amplitude, or both for the differential output signals can be varied. Under certain circumstances, the differential output signals can be interrupted.

[0050] Data can be transferred between a first device 100 and a second device 200 in several ways. The amplitude of the differential output signal can be modulated with data. The phase of the differential output signal can be modulated with data. The frequency of the differential output signal can be modulated with data. These modulations can be applied by a power and data transmitting device and restored by a power and data receiving device. In these and other embodiments of the present invention, a power transmitting device can provide a differential output signal. A power receiving device can be a data transmitting device and modulate a load detected by the power transmitting device. The load can be modulated by data that the power receiving device sends back to the power transmitting device.The power transmission device may also simultaneously be the data reception device and recover the data. Instead of using a differential output signal, data may be transmitted via a first contact 114 of a first device 100 and a second contact 214 of a second device 200 (all shown in FIG. Fig. 1 shown).

[0051] A first contact 110 and a first contact 112 in a first device 100 may be capacitively coupled to a first power transfer circuit 120 in a first device 100 using capacitors C1 and C2, and a second contact 210 and a second contact 212 in a second device 200 may be capacitively coupled to a second power transfer circuit 220 in a second device 200 using capacitors C3 and C4. The presence of the capacitors used for this AC or capacitive coupling may provide DC current paths between a first contact 110, a second contact 210, a device housing 1110 (in Fig. 11) for a first device 100 and a device enclosure 1120 (in Fig. 11) for a second device 200.

[0052] For example, a fluid or liquid may be present over some or all of the first contacts 110, the second contacts 210, the device enclosure 1110 for a first device 100, and the device enclosure 1120 for a second device 200. As part of an electrochemical corrosion process, the liquid may cause corrosion and cause ions to leak from one or more of the first contact 110, the second contact 210, the device enclosure 1110 for a first device 100, and the device enclosure 1120 for a second device 200 and enter the liquid. The transfer of ions from a contact into the liquid may be part of a loop that includes a current flowing from the contact through circuits in the first device or the second device and then to ground.The input coupling capacitors can block the DC component of this current, thereby breaking the loop and slowing the flow of ions out of the contact and into the liquid. Further details are shown in the following figures.

[0053] Fig. 11 is a circuit diagram of a contact interface of the electronic system of Fig. 1 according to an embodiment of the present invention. A first contact 110 may be coupled to electrostatic discharge diodes D1. Electrostatic discharge diodes D1 may be high-impedance, low-leakage diodes. A first contact 110 may be coupled to capacitor C1, which in turn may be coupled to inductor L1. Inductor L1 may be included to reduce a current surge through capacitor C1 when a first power transfer circuit 120 supplies power to a second power transfer circuit 220. Capacitor C1 may be chosen large enough to provide a low impedance to the differential output signals, yet small enough to be physically meaningful. Inductor L1 may be chosen such that the tuned frequency of inductor L1 and capacitor C1 has a period shorter than the period of the differential output signals.

[0054] A liquid or fluid may be present on one or more of first contact 110, first contact 112, device enclosure 1110, second contact 210, second contact 212, and device enclosure 1120. As part of an electrochemical corrosion process, the liquid may cause corrosion and result in ions leaking from one or more of first contacts 110, second contacts 210, device enclosure 1110, and device enclosure 1210 and entering the liquid. The transfer of ions may be enabled by a current flowing from one of first contacts 110 or second contacts 210 through circuitry in either first device 100 or second device 200 and then to device enclosure 1110 or device enclosure 1120, which may be grounded.This current flow may be driven by galvanic voltages that may occur, for example, between first contacts 110 and device enclosure 1110. For example, first contacts may be coated with gold or another conductive material, while device enclosure 1110 may be made of steel, aluminum, or another material. These different materials may create a galvanic voltage between first contacts 110 and device enclosure 1110. Input coupling capacitors C1 and C2 may block the DC component of this current from one of the first contacts 110 to device enclosure 1110. Input coupling capacitors C3 and C4 may block the DC component of a current from one of the second contacts 210 to device enclosure 1120.

[0055] In this example, capacitor C2 may be coupled to a first contact 112, electrostatic discharge diodes D2, and inductor L2. Inductor L1 and inductor L2 may be coupled to inverter / rectifier circuit 1030. Diodes D1 and D2 may be the same or similar. Inductors L1 and L2 may be the same or similar. Coupling capacitor C3 may be coupled to a second contact 210, electrostatic discharge diodes D3, and inductor L3. Diodes D1 and D3 may be the same or similar. Inductors L1 and L3 may be the same or similar. Coupling capacitor C4 may be coupled to a second contact 212, electrostatic discharge diodes D4, and inductor L4. Diodes D1 and D4 may be the same or similar. Inductors L1 and L4 may be the same or similar. Inductor L3 and inductor L4 can be coupled with rectifier / inverter circuit 1040.Stray impedances between first contacts 110, second contacts 210, device enclosure 1110 for a first device 100, and device enclosure 1120 for a second device 200 can be modeled as resistors R1 through R7. Capacitor C1, capacitor C2, capacitor C3, and capacitor C4 can be the same or similar.

[0056] Various circuits can be used to implement power transfer circuit 120 and power transfer circuit 220. Examples are shown in the following figures.

[0057] Fig. 12 is a simplified circuit diagram of a portion of a power circuit according to an embodiment of the present invention. In this example, switch 1010 (and switch 1060) may be implemented using transistor P1. Transistor P1 may connect battery 190 (or battery 290) to buck-boost circuit 1020 (or buck-boost circuit 1050). Transistor P1 is shown as a P-MOS transistor, although transistor P1 may be implemented in other ways, such as an N-MOS transistor, two transistors in parallel with a resistor in series with one of them, or other devices or circuits. Buck-boost circuit 1020 (and buck-boost circuit 1050) may be implemented using a single-input multiple-output (SIMO) architecture including inductor L1, transistor N1, transistor N2, transistor N3, and transistor N4.Buck-boost circuit 1020 (or buck-boost circuit 1050) may be coupled to inverter / rectifier circuit 1030 (or rectifier / inverter circuit 1040). Buck-boost circuit 1020 (and buck-boost circuit 1050) may have a full-bridge architecture that may include transistor N5, transistor N6, transistor N7, and transistor N8.

[0058] Fig. 13 is an alternative simplified circuit diagram of a portion of a power circuit according to an embodiment of the present invention. In these and other embodiments of the present invention, such as the Fig. 12, switch 1010 (and switch 1060) can be replaced with a circuit (not shown) that is a voltage and current limiter when receiving power and a current limiter when transmitting data. Buck-boost circuit 1020 (and buck-boost circuit 1050) can be implemented using a SEPIC Cuk DC / DC converter that includes three inductors: inductor L1, inductor L2, and inductor L3. Transistor P1, transistor N1, and transistor N2 can be included along with capacitor C1, capacitor C2, capacitor C3, capacitor C4, and capacitor C5. Buck-boost circuit 1020 (and buck-boost circuit 1050) can again have a full-bridge architecture that can include transistor N5, transistor N6, transistor N7, and transistor N8.

[0059] These and other embodiments of the present invention may include additional features that can help prevent or reduce corrosion. For example, electrical impedance spectrography circuits may be incorporated. These circuits may apply a voltage waveform to one or more contacts of a device. A resulting voltage, a resulting current, or both may be measured. A resulting current may indicate that current is flowing through a fluid. A phase shift between the applied voltage waveform and the resulting current or voltage may indicate the amount or type of fluid. To prevent a corrosion path, coupling capacitors may be inserted between the contacts and the electrical impedance spectrography circuits. An example is shown in the following figure.

[0060] Fig. Figure 14 is a simplified circuit diagram of portions of two power circuits transferring power according to an embodiment of the present invention. Inverter / rectifier circuit 1030 may act as an inverter and provide a differential output signal to the first contacts 110 via switch 1420 and coupling capacitors 1430. Coupling capacitors 1430 may include capacitors C1 and C2 from the contact interface of Fig. 11. Second contacts 210 can receive the differential output signals and provide them to rectifier / inverter circuit 1040, which can act as a rectifier and provide a high voltage and a low voltage to a power factor correction regulator 1450. Power factor correction regulator 1450 can provide an output to power management regulator 1460, which can charge battery pack 290. Power management regulator 1460 can control the voltage and current that occur at battery pack 290 during charging. This path can be reversed so that a second device 200 can charge a first device 100.

[0061] An electrochemical impedance spectroscopy (EIS) circuit 1470 may be included. The EIS circuit 1470 may provide a voltage waveform or a current waveform, although in this example, a voltage waveform may be provided. The voltage waveform may be a sine wave, square wave, or other voltage waveform. The EIS circuit 1470 may be coupled to first contacts 110 via coupling capacitors 1430. When liquid is present at one or more first contacts 110, a current or voltage may be detected using the EIS circuit 1470. The current, voltage, or both may indicate a change in capacitance and resistance occurring at the first contacts 110.EIS circuit 1470 can detect the magnitude of this current and voltage, as well as any phase shift relative to the applied voltage, and use this to determine a change in capacitance and resistance at first contacts 110. From the changes in capacitance and resistance, the presence of liquid and information about the type of liquid can be determined. Further details can be found in U.S. Patent No. 11,658,443, entitled LIQUID DETECTION AND CORROSION MITIGATION, issued May 23, 2023, which is incorporated by reference. Sources Source 1 and Source 2 can be used as the voltage signal in EIS circuit 1470.

[0062] Other types of circuitry may be included in or connected to power transfer circuit 120 and / or power transfer circuit 220. For example, connection detection may be used to disconnect battery 190 or battery 290 when the opposing device is not connected. This connection detection may include occasionally sending a voltage ping to first contacts 110. This voltage ping should be of a type where the average value of the ping or the average value of a series of pings should be zero volts.

[0063] Fig. 15 to Fig. 17 illustrate contact assemblies according to an embodiment of the present invention. In Fig. 15, the contact assembly 1500 may enclose the contact 110 and the housing 1530. Insulation 1520 may form a seal between the contact 110 and the housing 1530 to prevent leakage into the interior of the device with the contact assembly 1500.

[0064] The contact 110 may be formed from a mass or substrate 1510. An optional plating layer 1512 may be formed on a bottom or inner surface of the contact 110. Other optional platings may be formed along the sides of the mass or substrate 1510. The mass or substrate 1510 may be made of stainless steel, titanium, tantalum, Inconel, nickel-aluminum bronze, copper, a copper alloy, or another material. Using these materials can provide contacts that are easy to manufacture and save valuable resources compared to contacts that may use exotic materials. These materials can provide good durability and corrosion resistance. The optional plating layer 1512 may be made of gold or another conductive material; for example, the optional plating layer 1512 may be gold flash.The optional plating layer 1512 may form a surface that is solderable to a flexible circuit board or other suitable substrate.

[0065] In these and other embodiments of the present invention, the voltage waveforms conducted by contacts 110 may be AC ​​waveforms. Thus, a majority of the current through contacts 110 may be conducted across the surface of contacts 110. Accordingly, embodiments of the present invention may provide plating on some or all sides 1514 of the mass or substrate 1510. This plating may be gold, diamond-like carbon (formed to be conductive), titanium nitride, tin-silver, nickel-gold, or another material. In these and other embodiments of the present invention, this plating may extend along a top surface and some or all sides of the mass or substrate 1510. An example is shown in the following figure.

[0066] In Fig. 16, the contact assembly 1600 may include the contact 110, the housing 1530, and the insulation 1520, which may form a seal between the contact 110 and the housing 1530. The contact 110 may include the ground or substrate 1510 and the optional plating layer 1512, which may be plated with the cap layer 1610. The cap layer 1610 may be made of diamond-like carbon (which has been formed to be conductive), tin, tin-silver, nickel-gold, or another material.

[0067] In Fig. 17, the contact assembly 1700 may include the contact 110, the housing 1530, and the insulation 1520, which may form a seal between the contact 110 and the housing 1530. The contact 110 may include the ground or substrate 1510, the optional plating layer 1512 and the cap layer 1610, and the interlayer 1710. The additional interlayer 1710 reduces the need for the ground or substrate 1510 to conduct the AC waveforms. This may enable the use of less conductive or non-conductive materials such as plastic, ceramic, ceramic plastics, aluminum, stainless steel, or other materials than the ground or substrate 1510. The interlayer 1710 may be made of gold, copper, nickel, or a combination of these or other conductive metals.The currents generated by the AC waveforms received by contacts 110 can be conducted due to skin effects near the surface of contacts 110. Accordingly, the intermediate layer can be relatively thin, for example, 10 to 100 micrometers, depending on the desired frequency range for the AC waveforms. This thickness can enable good conductivity for the AC waveforms.

[0068] The materials and various layers that comprise contacts 110 can provide at least three functions. They can provide an interface function for connecting to another contact, they can provide a conductivity function for transmitting a charging AC waveform, and they can provide a mechanical function that provides structure for the contact. Fig. 15, the mass or substrate 1510 may provide a permanent interface for connection to contacts on a second device. The conductivity of the mass or substrate 1510 may be improved by adding the optional plating layer 1512 to the bottom and sides of the mass or substrate 1510. The mass or substrate 1510 may provide a mechanical function. Fig. 16, the interface function can be improved by adding the cover layer 1610. The cover layer 1610 can provide a surface that has improved hardness and corrosion resistance. In Fig. 17, the addition of the intermediate layer 1710 offers the opportunity to enhance the conductivity function of the contact 110 by including a layer of conductive material. Again, the addition of the intermediate layer 1710 can eliminate the need to provide conductivity with the ground or substrate 1510. This allows the ground or substrate 1510 to be composed of a low-conductivity or non-conductivity material.

[0069] These functions can be distributed among these layers in different ways in various embodiments of the present invention. Fig. 16, for example, the cap layer 1610 may have a lower conductivity, while the bulk or substrate 1510 may have a higher conductivity. In these and other embodiments of the present invention, more than two layers may be plated or otherwise formed over the bulk or substrate 1510.

[0070] By using AC waveforms, the skin effect can be exploited. That is, the skin effect can allow the conductivity of the cap layer 1610 and the intermediate layer 1710 to be sufficient for charge conduction. Such dependence on the cap layer 1610 and the intermediate layer 1710 may not be possible when transferring power using conventional DC voltages and currents.

[0071] Unfortunately, the use of these plating layers can promote corrosion of these contacts 110. When a connection is made using a contact 110, the plating layers (such as the cap layer 1610 and the intermediate layer 1710) and the substrate (such as the ground or substrate 1510) can be damaged, for example, by scratches. A galvanic voltage can then develop across the scratch. The presence of an electrolyte can then lead to corrosion of the contact 110.

[0072] Embodiments of the present invention may include various features to reduce galvanic corrosion that may be caused by a scratch on contact 110. For example, the plating and substrate materials may be selected to reduce galvanic stresses. For example, the plating of the contacts may be plated with gold, which has a galvanic stress range of 0.07 to 0.2 V, while the ground or substrate may be titanium, which has a galvanic stress range of -0.12 to 0.04 V. Alternatively, the ground or substrate may be made of a non-conductive material such as ceramic, plastic, or a combination of these or other materials.

[0073] In addition to reducing galvanic stresses at a scratch, embodiments of the present invention may include contact assemblies that can minimize the possibility of such scratches and other types of damage occurring. Examples are illustrated in the following figure.

[0074] Fig. 18A to Fig. 18D illustrate profiles of contact assemblies according to an embodiment of the present invention. In Fig. 18A, a first device may include a contact assembly 1810, which may include a contact 1812 surrounded by adjacent insulation 1814 and a housing 1816. A second device may include a contact assembly 1820, which may include a contact 1822 surrounded by adjacent insulation 1824 and a housing 1826. In this example, the contact 1812, the insulation 1814, and the housing 1816 are flush with each other, while the contact 1822 and the insulation 1824 are flush with each other and can move relative to the housing 1826.

[0075] Contact 1822 and insulation 1824 can move relative to housing 1826 so that contact 1822 can engage contact 1812. Contact assembly 1820 can be connected to contact assembly 1810 in a contact direction that is orthogonal or normal to a surface of contact 1822. Alternatively, contact assembly 1820 can slide laterally over contact assembly 1810 (or contact assembly 1810 can slide laterally over contact assembly 1820) until contact 1822 is aligned with contact 1812, after which contact 1822 and insulation 1824 can move toward contact assembly 1810 so that contact 1822 is connected to contact 1812.

[0076] When contact assembly 1810 and contact assembly 1820 engage in the normal direction, contact 1812 and contact 1822 may be slightly damaged. However, when contact assembly 1820 moves laterally over contact assembly 1810 (or contact assembly 1810 slides laterally over contact assembly 1820), contact 1822 may interact with housing 1816 and contact 1812 and become damaged. Likewise, contact 1812 may interact with housing 1826 and become damaged. This damage may result in scratches. These scratches may expose galvanic connections and galvanic stresses between the various plating layers and substrates of contacts 1812 and 1822. These galvanic stresses, in the presence of an electrolyte, may cause corrosion to the surfaces of contacts 1812 and 1822.

[0077] In Fig. 18B, a first device may include a contact assembly 1830, which may include a contact 1832 surrounded by adjacent insulation 1834 and a housing 1836. A second device may include a contact assembly 1840, which may include a contact 1842 surrounded by adjacent insulation 1844 and a housing 1846. In this example, the contact 1832, the insulation 1834, and the housing 1836 are flush with each other, while the contact 1842 may include an extension 1848 that protrudes beyond the insulation 1844. The contact 1842 and the insulation 1844 may move relative to the housing 1846.

[0078] Contact 1842 and insulation 1844 can move relative to housing 1846 so that contact 1842 can engage contact 1832. Contact assembly 1840 can be connected to contact assembly 1830 in a contact direction that is orthogonal or normal to a surface of contact 1842. Alternatively, contact assembly 1840 can slide laterally over contact assembly 1830 until contact 1842 is aligned with contact 1832, after which contact 1842 and insulation 1844 can move toward contact assembly 1830 so that contact 1842 is connected to contact 1832.

[0079] When contact assembly 1830 and contact assembly 1840 engage in the normal direction, contact 1832 and contact 1842 may be slightly damaged. However, when contact assembly 1840 moves laterally over contact assembly 1830 (or contact assembly 1830 slides laterally over contact assembly 1840), extension 1848 of contact 1842 may interact with housing 1836 and contact 1832 and become damaged. Likewise, contact 1832 may interact with housing 1846 and become damaged. This damage may result in scratches. These scratches may expose galvanic connections and galvanic stresses between the various plating layers and substrates of contacts 1832 and 1842. These galvanic stresses, in the presence of an electrolyte, may cause corrosion to the surfaces of contacts 1832 and 1842.

[0080] In Fig. 18C, a first device may include a contact assembly 1850, which may include a contact 1852 surrounded by adjacent insulation 1854 and a housing 1856. A second device may include a contact assembly 1860, which may include a contact 1862 surrounded by adjacent insulation 1864 and a housing 1866. In this example, the contact 1852 may be recessed from the housing 1856, while the insulation 1854 may be further recessed from the housing 1856. The contact 1862 may include an extension 1868 that extends beyond the housing 1866, while the insulation 1864 may include an extension 1869 that extends beyond both the housing 1866 and the contact 1862. The contact 1862 and the insulation 1864 can move relative to the housing 1866.

[0081] Contact 1862 and insulation 1864 can move relative to housing 1866 so that contact 1862 can engage contact 1852. Contact assembly 1860 can be connected to contact assembly 1850 in a contact direction that is orthogonal or normal to a surface of contact 1862. Alternatively, contact assembly 1860 can slide laterally over contact assembly 1850 until contact 1862 is aligned with contact 1852, whereupon contact 1862 and insulation 1864 move toward contact assembly 1850 so that contact 1862 is connected to contact 1852.

[0082] When contact assembly 1850 and contact assembly 1860 engage in the normal direction, contact 1852 and contact 1862 may be slightly damaged. If contact assembly 1860 moves laterally over contact assembly 1850 (or contact assembly 1850 slides laterally over contact assembly 1860), extension 1858 of contact 1852 may interact with extension 1869 of insulation 1864, possibly causing no significant damage. Extension 1868 of contact 1862 may be protected by extension 1869 of insulation 1864, thereby reducing damage to contact 1862.

[0083] In Fig. 18D, a first device may include a contact assembly 1870, which may include a contact 1872 surrounded by adjacent insulation 1874 and housing 1876. A second device may include a contact assembly 1880, which may include a contact 1882 surrounded by adjacent insulation 1884 and housing 1886. In this example, contact 1872 may be recessed from housing 1876, while insulation 1874 may be further recessed from housing 1876. Contact 1882 may be flush with insulation 1884, both of which may be recessed from housing 1886. Contact 1882 and insulation 1884 may move relative to housing 1886.

[0084] The contact 1882 and insulation 1884 can move relative to the housing 1886 so that contact 1882 can engage contact 1872. The contact assembly 1880 can be connected to the contact assembly 1870 in a contact direction that is orthogonal or normal to a surface of the contact 1882. Alternatively, the contact assembly 1880 can slide laterally over the contact assembly 1870 until the contact 1882 is aligned with the contact 1872, after which the contact 1882 and insulation 1884 move toward the contact assembly 1870 so that the contact 1882 is connected to the contact 1872. This movement can be facilitated by the magnets 1879 in the contact assembly 1870 and the magnets 1889 in the contact assembly 1880.

[0085] When contact assembly 1870 and contact assembly 1880 engage in the normal direction, contact 1872 and contact 1882 may be slightly damaged. If contact assembly 1880 moves laterally over contact assembly 1870 (or contact assembly 1870 slides laterally over contact assembly 1880), extension 1878 of contact 1872 may not interact with contact assembly 1880 and thus may not be damaged. Contact 1882 may be recessed and protected by insulation 1884, preventing damage.

[0086] Fig. 19 illustrates contact assemblies for a contact interface according to an embodiment of the present invention. A first electronic device 1902 and a second electronic device 1904 may form an electronic system 1900. The first electronic device 1902 may include a contact assembly including the contact 1910 supported by the insulation 1930. The contact 1910 and the insulation 1930 may be located in a recess 1942 in the enclosure 1940 of the first electronic device 1902.

[0087] The second electronic device 1904 may include a contact assembly including a contact 1950 supported by an insulation 1960. The contact 1950 and the insulation 1960 may be located in the opening 1972 of the enclosure 1970 of the second electronic device 1904. The contact 1950 and the insulation 1960 may move to be positioned in the recess 1942 of the enclosure 1940 of the first electronic device 1902 when the contact 1910 of the first electronic device is connected to the contact 1950 of the second electronic device 1904.

[0088] Fig. Figure 20 illustrates further details of a contact assembly according to an embodiment of the present invention. The contact assembly 2000 may include two contacts 1950, each supported by an insulation 1960. The insulation 1960 may be supported by the carrier 2010. The carrier 2010 may be driven by springs 2030 such that the contacts 1950 may engage the contacts 1910 (as shown in Fig. 19). The carrier 2010 can be pressed in by the alignment portion 2020. The alignment portion 2020 can be aligned with a recess in the first electronic device 1902 (as shown in Fig. 19) so that the springs 2030 can urge the contacts 1950 into engagement with the contacts 1910.

[0089] Fig. Figure 21 illustrates contact assemblies for a contact interface according to an embodiment of the present invention. A first electronic device 2102 and a second electronic device 2104 may form an electronic system 2100. The first electronic device 2102 may include a contact assembly including a contact 2110 supported by an insulation 2130. The contact 2110 and the insulation 2130 may be located in a recess 2142 in the enclosure 2140 of the first electronic device 2102.

[0090] The second electronic device 2104 may include a contact assembly including a contact 2150 supported by an insulation 2160. The contact 2150 and the insulation 2160 may be located in the opening 2172 of the enclosure 2170 of the second electronic device 2104. The contact 2150 and the insulation 2160 may move to be positioned in the recess 2142 of the enclosure 2140 of the first electronic device 2102 when the contact 1910 of the first electronic device is connected to the contact 1950 of the second electronic device 1904.

[0091] The contact 2150 may include two contacting portions separated by an insulation portion 2162. The insulation portion 2162 may be a surface that may be subjected to wear to protect the exposed areas of the contact 2150. Similar to the extensions 1869 of the insulation 1864 (as shown in Fig. 18C), the insulation portion 2162 may engage the enclosure 2140 and the contact 2110 of the first electronic device 2102 as the first electronic device 2102 and the second electronic device 2104 move laterally over each other during mating.

[0092] Fig. 22 is a side sectional view of a contact assembly according to an embodiment of the present invention. The contact assembly 2200 may include the contact 2150, which may be supported by the insulation 2160. The contact 2150 and the insulation 2160 may be positioned in the opening 2172 of the enclosure 2170. The enclosure 2170 may be located over the housing 2230. The housing 2230 may include a hole 2232 for the spring 2210. The spring 2210 may be compressed when the first electronic device 2102 and the second electronic device 2104 (both in Fig. 21) during connection. The spring 2210 can press the contact 2150 into the contact 2110 when the contact 2150 and the insulation 2160 are aligned with the recess 2142 of the enclosure 2140 (both in Fig. 21). The signals received and provided at contact 2150 may be conducted through conductor 2220. Conductor 2220 may be insulated with insulation 2222.

[0093] Embodiments of the present invention may incorporate various features to limit or reduce galvanic corrosion of contacts in electronic devices. For example, the materials used for the contacts and the housing may be selected to avoid differences in galvanic voltages. Other DC voltages, such as DC offsets in the AC waveforms used for power transmission, may be avoided or adjusted to cancel galvanic voltages between the materials used. DC conduction paths may also be blocked to limit electrochemical reactions that can lead to corrosion. Examples are illustrated in the following figures.

[0094] Fig. Figure 23 illustrates galvanic corrosion paths in electronic devices according to embodiments of the present invention. Electronic system 2300 may include a first electronic device 2302 and a second electronic device 2304. First electronic device 2302 may provide AC power via capacitor C1 and capacitor C2 and contacts 2310. Contacts 2310 may be insulated by insulation 2320 and supported by housing 2330.

[0095] In this example, ion paths may exist between contacts 2310 and housing 2330. For example, ion path 2380 may exist between contacts 2310. Ion paths 2385 may exist between each contact 2310 and housing 2330. The AC nature of the waveforms delivered to contacts 2310 may change rapidly enough to limit any electrochemical reactions. However, the presence of DC currents, whether due to a galvanic voltage, an offset in the AC waveforms, or otherwise, may cause electrochemical reactions that could lead to corrosion.

[0096] Accordingly, as above in Fig. As shown in Figure 10, the DC blocking capacitor C1 and the blocking capacitor C2 can be arranged in series between the internal circuits of the first electronic device 2302 and the contacts 2310. Capacitor C1 and capacitor C2 can block DC currents that could otherwise lead to electrochemical reactions that could cause corrosion.

[0097] These and other embodiments of the present invention can further limit corrosion by further reducing the electric fields between contacts 2310 and housing 2330. For example, the materials for contacts 2310, including the plating and housing materials 2330, can be selected to reduce galvanic stresses. For example, contacts 2310 can be plated with gold, which has a galvanic stress range of 0.07 to 0.2 V, while the housing can be made of titanium, which has a galvanic stress range of -0.12 to 0.04 V.

[0098] These and other embodiments of the present invention may further reduce galvanic voltage differences by selecting a non-conductive material for a housing. For example, the second electronic device 2304 may include contacts 2340 supported by the housing 2360. The contacts 2340 may be metallic regions formed or plated on the housing 2360. The housing 2360 may be made of a non-conductive material, such as plastic, ceramic, or a combination of these or other materials.

[0099] Choosing a non-conductive material for housing 2360 can reduce the ion paths to path 2380, located between contacts 2340. As a result, only one capacitor, depicted here as capacitor C3, may be required to block the DC current flowing through path 2380. The use of the single capacitor may be more likely in a power-receiving device, where asymmetries caused by the absence of a second capacitor in a power-delivering device are not relevant.

[0100] In these and other embodiments of the present invention, it may be desirable for the capacitors used, such as capacitor C1, capacitor C2, and capacitor C3, to fail in the open state to prevent the formation of a DC current path. Accordingly, open-state "Y" capacitors may be used as capacitors C1, C2, and C3.

[0101] Electrolytes are not always present in these and other types of electronic systems. Often, the contacts 2310 or other contacts are dry and free of liquids or other electrolytes. In such a case, power can be saved by transmitting direct current. For example, the inverter / rectifier circuit 1030 and the inverter / rectifier circuit 1040 (both in Fig. 10). An example is shown in the following figure.

[0102] Fig. Figure 24 illustrates optional DC charging in electronic devices according to embodiments of the present invention. The electronic system 2400 may include a first electronic device 2402 and a second electronic device 2404. In the first electronic device 2402, the contacts 2410 may be insulated by insulation 2420 and supported by a housing 2430. In the second electronic device 2404, the contacts 2440 may be supported by the non-conductive housing 2460 or may be plated thereon.

[0103] The first electronic device 2402 can provide AC power via capacitor C1 and capacitor C2 and contacts 2410. The first electronic device 2402 can provide DC power via the closed switch S1, which can bypass capacitor C1, and via the closed switch S2, which can bypass capacitor C2, thus connecting contacts 2410 to the DC source. Similarly, the second electronic device 2404 can receive power via capacitor C3 and can receive DC power by bypassing capacitor C3 with switch S3.

[0104] It may be desirable for switch S1, switch S2, and switch S3 to have a very high open impedance to prevent DC leakage in the presence of electrolyte at contacts 2410 and contacts 2440. Accordingly, embodiments of the present invention may utilize micro-relays, micro-mechanical switches, or other types of switches. It should also be noted that many of the design considerations described herein may not provide a contact optimized for transmitting DC power, and further compromises must be made.

[0105] Switch S1, switch S2, and switch S3 may each be controlled by a first electronic device 2402 or by the second electronic device 2404. Switch S1 and switch S2 may be controlled by the first electronic device 2402, while switch S3 may be controlled by the second electronic device 2404, or these switches may be controlled by other circuits. For example, the first electronic device 2402 may determine that contacts 2410 and contacts 2440 are not in contact with electrolyte and may close switch S1, switch S2, and switch S3 before dissipating DC power.The second electronic device 2404 may determine that the contacts 2410 and the contacts 2440 are not exposed to electrolyte and may close the switch S1, the switch S2, and the switch S3 before requesting DC power from the first electronic device 2402.

[0106] Embodiments of the present invention may, in turn, take measures to reduce or cancel DC electric fields or DC voltages at contacts of electronic devices. These measures may reduce galvanic voltages as described above. They may also reduce the DC offsets of the AC waveforms used in data transmission. They may also include the use of a DC offset of the AC waveforms to cancel residual galvanic voltages. They may also include the use of a DC offset of the AC waveforms that have been empirically or otherwise determined to provide lower corrosion. An example of such a waveform is illustrated in the following figure.

[0107] Fig. 25 illustrates a differential AC waveform for power transmissions according to an embodiment of the present invention. Waveform 2500 may have a low voltage V2, a high voltage V1, and a medium voltage V0. Waveform 2500 may have a rise time from V0 to V1 from Tr1 and remain at V1 for a time T1. Waveform 2500 may have a fall time from V1 to V0 from Tf1 and a fall time from V0 to V2 from Tf2. Waveform 2500 may remain at V2 for a time T2. Waveform 2500 may have a rise time from V2 to V0 from Tr2. Waveform 2500 may have a positive pulse width of Tp1 and a negative pulse width of Tp2. Filtering may be used to reduce the harmonic content of AC waveform 2500.

[0108] Some or all of these rise times, fall times, high and low levels, and other parameters can be adjusted. For example, the average voltage V0 can be varied. The average voltage V0 can be adjusted to be near zero to reduce the DC voltages generated by the differential AC waveform 2500. The average voltage V0 can instead be adjusted to a level that cancels or compensates for any galvanic voltage present at the power-transmitting contacts. The average voltage V0 can instead be adjusted to a level that has been determined, empirically or otherwise, to provide less corrosion at the power-transmitting contacts. An example of circuits and methods that can be used is shown in the figure below.

[0109] Fig. Figure 26 illustrates a charging path through an electronic system according to an embodiment of the present invention. In this example, a first electronic device 2602 may provide power to a second electronic device 2604 in the electronic system 2600. The DC / DC converter 2610 may receive a DC input voltage DCIN, which may be a battery voltage or another voltage. The DC / DC converter 2610 may supply the high voltage V1 and the low voltage V2 (as shown in Fig. 25) for the AC waveforms provided by the inverter 2620 in the first electronic device 2602 to the rectifier 2630 in the second electronic device 2604. The rectifier 2630 may provide an output for the DC / DC converter 2640, which may provide an output voltage DCOUT.

[0110] In this example, the voltages V1 and V2 can be programmable. The voltages V1 and V2 can be programmed so that the average voltage V0 (as in Fig. 25) is close to zero to reduce any DC voltages generated by the differential AC waveform 2500. V1 and V2 can instead be programmed to adjust the average voltage V0 to a level that cancels or compensates for any galvanic voltage present at the power-transmitting contacts. V1 and V2 can instead be programmed to provide an average voltage V0 that has been determined, empirically or otherwise, to minimize corrosion.

[0111] In this example, voltage V1 and voltage V2 may be provided in an open loop. In these and other embodiments of the present invention, voltage V1 and voltage V2 may be provided in a closed loop. Examples are illustrated in the following figures.

[0112] Fig. Figure 27 illustrates another charging path through an electronic system according to an embodiment of the present invention. In this example, a first electronic device 2602 may provide power to a second electronic device 2604 in the electronic system 2600. The DC / DC converter 2610 may receive a DC input voltage DCIN, which may be a battery voltage or another voltage. The DC / DC converter 2610 may supply the high voltage V1 and the low voltage V2 (as shown in Fig. 25) for the AC waveforms provided by the inverter 2620 in the first electronic device 2602 to the rectifier 2630 in the second electronic device 2604. The rectifier 2630 may provide an output for the DC / DC converter 2640, which may provide an output voltage DCOUT.

[0113] In this example, the voltage V1 and the voltage V2 may be adjusted by a feedback path including the correction circuit 2710 in the first electronic device 2602. The voltage V1 and the voltage V2 at the power-transmitting contacts of the inverter 2620 may be sensed and provided to the correction circuit 2710. The voltages V1 and V2 may be adjusted by the correction circuit 2710 such that the average voltage V0 (as in Fig. 25) is close to zero to reduce any DC voltages generated by the differential AC waveform 2500. V1 and V2 may instead be adjusted by the correction circuit 2710 so that the average voltage V0 can be adjusted to a level that cancels or compensates for any galvanic voltage present at the power-transmitting contacts. V1 and V2 may instead be adjusted by the correction circuit 2710 to provide an average voltage V0 that has been empirically or otherwise determined to minimize corrosion. The correction circuit 2710 may be used to integrate the positive and negative pulses of the waveform 2500 to adjust the average voltage V0.

[0114] Fig. Figure 28 illustrates another charging path through an electronic system according to an embodiment of the present invention. In this example, a first electronic device 2602 may provide power to a second electronic device 2604 in the electronic system 2600. The DC / DC converter 2610 may receive a DC input voltage DCIN, which may be a battery voltage or another voltage. The DC / DC converter 2610 may convert the high voltage V1 and the low voltage V2 (as shown in Fig. 25) for the AC waveforms provided by the inverter 2620 in the first electronic device 2602 to the rectifier 2630 in the second electronic device 2604.

[0115] The rectifier 2630 can provide an output for the DC / DC converter 2640, which can provide an output voltage DCOUT.

[0116] In this example, the voltage V1 and the voltage V2 may be adjusted by a feedback path including the reception detection circuit 2810 in the second electronic device 2604 and the adjustment circuit 2820 in the first electronic device 2602. This may be done in several ways. In one example, the voltage V1 and the voltage V2 at the power-receiving contacts of the rectifier 2630 may be detected by the reception detection circuit 2810. This information may be passed to the adjustment circuit 2820. The voltages V1 and V2 may be adjusted by the adjustment circuit 2820 such that the average voltage V0 (as in Fig. 25) is close to zero to reduce any DC voltages generated by the differential AC waveform 2500 (in Fig. 25). In another example, the receive detection circuit 2810 may determine an adjustment to be made and provide this information to the adjustment circuit 2820. V1 and V2 may instead be adjusted by the adjustment circuit 2820 such that the average voltage V0 can be adjusted to a level that cancels or compensates for a galvanic voltage present at the power-transmitting contacts. V1 and V2 may instead be adjusted by the adjustment circuit 2820 to provide an average voltage V0 that has been empirically or otherwise determined to minimize corrosion. The receive detection circuit 2810 may communicate with the adjustment circuit 2820 across the power-transmitting contacts by sending an AC signal at a different frequency than the AC waveform 2500.The reception detection circuit 2810 may communicate with the matching circuit 2820 via another wired, wireless, or other type of communication channel.

[0117] In these and other embodiments of the present invention, known patterns, which may be referred to as training patterns, may be provided by the first electronic device 2602 to the second electronic device 2604. These known patterns may be used by the reception detection circuit 2810 in the second electronic device 2604 and the adaptation circuit 2820 in the first electronic device 2602 to adapt the AC waveform provided by the first electronic device 2602 to the second electronic device 2604.

[0118] Data may be transmitted between the first electronic device 2602 and the second electronic device 2604 using the AC waveforms. The frequency, phase, amplitude, or other property of the AC waveform may be modulated to convey data. Other signals at different frequencies may be combined with the AC waveform using a diplexer, common-mode choke, or other circuitry. Data may be transmitted in the same direction as power, or power and data may be transmitted in different directions.

[0119] Various aspects of the 2500 differential AC waveform can be varied or adjusted depending on the contact materials, the housing materials, the presence or absence of electrolytes, and the types of electrolytes present. An example method for determining the type of material used in a contact is shown in the following figure.

[0120] Fig. Figure 29 illustrates data that can be used by a method for determining a type of material used for a contact according to an embodiment of the present invention. In this example, electrochemical impedance spectroscopy (EIS) curves for various materials in the absence of electrolyte are generated in advance. An electronic device can take similar measurements shortly after the connection between two electronic devices, when the absence of electrolyte is likely. These measurements can be taken at these and other times at which the absence of electrolyte has been determined.

[0121] The EIS curve measured by the electronic device may reflect the parallel combination of a contact on the measuring device and a contact of a connected device. The contact on the device may be known and stored during manufacturing. Using the measured EIS curve and the known material of the measuring device, the contribution of the parallel connected device contact to the EIS curve can be extrapolated. The extrapolated EIS curve of the connected device contact can be compared to pre-measured curves, such as those in this figure. From this, the material for the contact of the connected device can be determined. This and other embodiments of the present invention may not produce complete curves. Instead, data points at a few specific frequencies may be used.

[0122] Fig. Figure 30 illustrates a method for optimizing a charging waveform according to an embodiment of the present invention. In operation 3010 of method 3000, when a connection is established, a first device may determine the contact material of a second device using EIS. Such a method is described in Fig.29 above. Instead of using EIS, the first device may obtain information about the contact material directly from the second device in operation 3020. The first device may collect additional information during use. This information may include environmental information and other information. For example, the first device may receive EIS updates, depth information, and other information from other sensors in operation 3030. An optimized charging waveform may be determined in operation 3040. This charging waveform may be provided to the contacts of the first device for reception by the contacts of the second device in operation 3050.

[0123] Embodiments of the present invention may provide power delivery circuits and devices that may be located in various types of devices, such as portable computing devices, tablet computers, desktop computers, laptops, all-in-one computers, wearable computing devices, mobile phones, smartphones, media phones, storage devices, portable media players, navigation systems, monitors, video transmission systems, power supplies, adapters, remote control devices, charging devices, and other devices.

[0124] Reference symbols are used consistently in the various figures.

[0125] It goes without saying that when using personal data, data protection policies and practices should be followed that are generally accepted and that meet or exceed industry-specific or regulatory requirements to protect user privacy. In particular, personal data should be managed and handled in a manner that minimizes the risk of accidental or unauthorized access or use, and the nature of the authorized use should be clearly communicated to users.

[0126] The foregoing description of the embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and many modifications and variations are possible in light of the above teachings. The embodiments were chosen and described in order to explain as fully as possible the principles of the invention and its practical applications, and thereby to enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is therefore to be understood that the invention is intended to cover all modifications and equivalents within the scope of the following claims. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 63 / 541,726

[0001] US 18 / 896,299

[0001] US 11,658,443

[0061]

Claims

[1] A method of supplying power from a first electronic device to a second electronic device, the method comprising: with the first electronic device, determining one or more environmental parameters; Using the one or more environmental parameters to optimize an AC charging waveform; and Providing the optimized AC charging waveform to the second electronic device. [2] The method of claim 1, wherein the one or more environmental parameters comprise the presence of an electrolyte. [3] The method of claim 2, wherein the AC charging waveform is optimized in part by adjusting an average value of the AC charging waveform to compensate for a galvanic voltage of the first electronic device. [4] The method of claim 3, wherein the AC charging waveform comprises one of two bandwidth-limited anti-phase square waves, two anti-phase square waves, and two anti-phase sine waves. [5] Power transmission circuit comprising: a battery; a switch that is linked to the battery; a buck-boost circuit coupled to the switch; an inverter / rectifier circuit coupled to the buck-boost circuit; a first capacitor coupled to a first output of the inverter / rectifier circuit; and a second capacitor coupled to a second output of the inverter / rectifier circuit; a first contact coupled to the first capacitor; and a second contact coupled to the second capacitor. [6] The power transfer circuit of claim 5, wherein the first contact and the second contact are spring-loaded contacts. [7] The power transfer circuit of claim 6, wherein the first contact and the second contact each comprise a canted coil spring. [8] The power transfer circuit of claim 6, wherein the first contact and the second contact each comprise a stack of Belleville washers. [9] The power transmission circuit of claim 6, wherein the first contact and the second contact each comprise two stacks of disc springs. [10] The power transmission circuit according to claim 5, wherein the first contact and the second contact are fixed contacts. [11] The power transfer circuit of claim 5, wherein the switch is configured to disconnect the battery from the buck-boost circuit when the power transfer circuit is not transmitting or receiving power. [12] The power transfer circuit of claim 11, wherein the buck-boost circuit increases the voltage from the battery and provides a high voltage and a low voltage when the power transfer circuit transfers power. [13] The power transfer circuit of claim 12, wherein the buck-boost circuit decreases a voltage from the inverter / rectifier and provides a charging voltage for the battery when the power transfer circuit receives power. [14] The power transfer circuit of claim 13, wherein the inverter / rectifier circuit converts the high voltage and the low voltage from the buck-boost circuit into a differential output signal when the power transfer circuit transfers power. [15] The power transfer circuit of claim 14, wherein the inverter / rectifier circuit rectifies a differential output signal when the power transfer circuit receives power. [16] The power transfer circuit of claim 15, wherein the differential output signal comprises two antiphase sine waves. [17] The power transfer circuit of claim 15, wherein the differential output signal comprises two antiphase square waves. [18] The power transfer circuit of claim 15, wherein the differential output signal comprises two bandwidth-limited antiphase square waves. [19] Power transmission circuit for generating a differential output signal, the power transmission circuit comprising: a first capacitor coupled to receive a first side of the differential output signal; a second capacitor coupled to receive a second side of the differential output signal; a first contact coupled to the first capacitor; and a second contact coupled to the second capacitor. [20] The power transfer circuit of claim 19, wherein the differential output signal comprises one of two bandwidth-limited anti-phase square waves, two anti-phase square waves, or two anti-phase sine waves.

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