Ac power supply for reducing corrosion

Abstract

To provide an AC power supply method and a power transmission circuit to reduce corrosion.SOLUTION: In a system that compensates electric fields that can cause corrosion at contact points, a voltage waveform at the contact points has 0 volt average and therefore 0 net electric field. The galvanic voltage generated by the dissimilar metals used at the contact points and a housing can create an electric field, and the current induced by the galvanic field can be blocked by capacitively coupling the contact points to their corresponding circuits.SELECTED DRAWING: None

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 63 / 541,726, filed September 29, 2023, for "AC Power Supply for Reducing Corrosion," and U.S. Non-Provisional Patent Application No. 18 / 896,299, filed September 25, 2024, for "AC Power Supply for Reducing Corrosion," which are hereby incorporated by reference in their entireties for all purposes. [Background technology]

[0002] The amount of data being transferred between electronic devices has increased significantly over the last few years. Large amounts of audio, streaming video, text, and other types of data content are now regularly transferred between desktop and portable computers, media devices, handheld 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, which may include one or more wire conductors, fiber optic cables, or other conductors. Connector inserts can be placed on each end of these cables and can be inserted into connector receptacles of the communication or power transmitting electronic device. Contacts in or on the connector inserts can form electrical connections with corresponding contacts in the connector receptacle. Other devices can have contacts on a surface of the device. Paths for power and data can be formed when the devices are mounted or placed adjacent to one another and corresponding contacts are electrically connected to one another.

[0004] These various contacts in the connector insert, connector receptacle, or on the surface of the device may be exposed to the local environment. These contacts may encounter liquid, moisture, or other harmful contaminants. For example, liquid may be spilled on these contacts, or the device may be placed such that its contacts land in a puddle of liquid. A user may swim or exercise while wearing or holding an electrical device. These activities may place the contacts of the electronic device in positions where they encounter various contaminants.

[0005] These liquids 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 the contacts. As a result, power contacts can be particularly susceptible to corrosion.

[0006] Therefore, what is needed is a method, structure, and apparatus that can deliver power through device contacts while minimizing erosion of the device contacts. Summary of the Invention

[0007] Thus, embodiments of the present invention can provide methods, structures, and apparatus that can provide power through a pair of power contacts while minimizing corrosion. Exemplary embodiments of the present invention can provide methods, structures, and apparatus that can provide power through a pair of power contacts while minimizing corrosion by providing power using a differential AC voltage having an average voltage of 0 volts (or close to zero volts). These and other embodiments of the present invention can prevent the flow of current that can result from galvanic voltages by capacitively coupling the power contacts to circuitry within the electronic device.

[0008] Contacts on electronic devices may be exposed to corrosive materials and fluids. These corrosive materials and fluids may induce corrosion of the contacts, thereby releasing ions from the contacts. In the presence of a DC electric field, the corrosion and release of ions may be accelerated. By applying an AC electric field, the net corrosion of the contacts may be reduced. By applying an AC electric field having a voltage with an average value at or near 0 volts, the movement of ions away from the contacts may be at least approximately equal to the movement of ions into the contacts. This symmetrical movement may reduce the corrosion of the contacts. This effect may be reduced by a galvanic voltage that may exist between a first metal forming the contacts and a second metal forming the housing or enclosure of the electronic device. This galvanic voltage may create an electric field that may also cause corrosion. The galvanic voltage may provide a flow of current through the contacts, through a circuit in the electronic device, and into the housing or enclosure, which may be grounded. The electron flow of this current may balance the movement of ions in the liquid. This current may be interrupted by capacitively coupling the power contacts to the circuit in the electronic device. That is, the capacitor can act as a direct current (DC) block, blocking the DC component of the current induced by the galvanic voltage, further reducing the erosion of the power contacts.

[0009] In these and other embodiments of the invention, various contact structures can be used. A first contact on a first device can be mated with a second contact on a second device. The first contact can be spring biased to provide a contact force, and the second contact can be secured to the device enclosure and acted upon by the contact force of the first contact. The first contact can be biased by a pair of canted coil springs. The canted coil spring can be disposed within the housing such that its central axis is perpendicular to the connection direction of the first contact. When the first and second devices are mated, the first contact can be forced in a direction into the first device. The first contact can force the plate and holder into the canted coil spring, thereby crushing or flattening the diameter of the canted coil spring. The distorted canted coil spring can provide a deflection force to the second contact. When the first and second devices are disconnected, the canted coil spring can return to its original shape, forcing the first contact away from the first device. The movement of the first contact can be restricted by mounting the first contact and a pin in a holder, and the pin can move within a corresponding slot in a housing in the first device. The canted coil spring can be held in place using one or more pins positioned through a central axis of the canted coil spring.

[0010] In these and other embodiments of the invention, the first contact can be biased by a single canted coil spring. The canted coil spring can be positioned in the housing with its central axis perpendicular to the connection direction of the first contact. When the first and second devices are mated, the first contact can be forced in a direction into the first device. The first contact can force the plate and holder into the canted coil spring, thereby crushing or flattening the diameter of the canted coil spring. The distorted canted coil spring can provide a deflection force to the second contact. When the first and second devices are disconnected, the canted coil spring can return to its original shape, pushing the first contact away from the first device. The movement of the first contact can be limited by attaching a pin to the holder, and the pin can move in a slot in the housing in the first device. The canted coil spring can be held in place using a number of slats attached to a frame.

[0011] In these and other embodiments of the invention, the first contact may be biased by one or more stacks of Belleville washers. The Belleville washers may be placed back-to-back and then stacked. The stacks may be placed on alignment pins to limit movement of the Belleville washers. When the first and second devices are mated, the first contact may be forced in a direction into the first device. The first contact may force the plate into the Belleville washers. When the plate is forced into the stack of Belleville washers, the Belleville washers may compress, thereby reducing the length of the stack of Belleville washers. The Belleville washers may have the same or different thicknesses such that the Belleville washers provide at least some constant force over the deflection of the first contact. When the first and second devices are disconnected, the Belleville washers may return to their original shape, pushing the first contact away from the first device. The first contact and the plate may be attached to a holder. Movement of the first contact can be restricted by mounting a pin on a holder, with the pin capable of moving within a slot in a housing in the first device.

[0012] In these and other embodiments of the invention, the second contact may be secured within the second device and the first contact may provide a force against the second contact. The second contact may be supported by a housing that is sealed to a housing or enclosure of the second device by a sealing ring. The contact and housing may be attached to the flex using a pressure sensitive adhesive or other adhesive. The flex may be held in place by a cowling. The cowling may be attached to the flex using a pressure sensitive adhesive or other adhesive. The cowling may be secured to a housing or enclosure of the second device.

[0013] In these and other embodiments of the invention, various circuits can be used to transfer power. These circuits can be used to transfer power from a first device to a second device, from a second device to the first device, or power can be transferred bidirectionally or back and forth between the first device and the second device. For example, the first device can receive power from a charger or power adapter. While the first device is powered, the second device can connect to the first device. This can allow the first device to provide power to the second device. During device operation, the second device can provide power back to the first device. During device operation, the first device can continue to provide power to the second device as needed.

[0014] These power circuits can be the same or substantially similar in the first device and the second device. In these and other embodiments of the invention, the first device and the second device can have differences, for example, where the transmission of power between the first device and the second device is unidirectional or one-way.

[0015] These and other embodiments of the invention may provide a power transmission circuit having a battery. The first power transmission circuit may be housed in a first device and the second power transmission circuit may be housed in a second device. The battery may be connected to a power circuit in the first device. The battery may be connected to a switch, which may be open when the first device is disconnected from the second device and may be closed when power is being transmitted. The switch may then be connected to a boost / buck circuit, which may be connected to an inverter / rectifier circuit. The inverter / rectifier circuit may provide a capacitively coupled output signal to a pair of first contacts. The capacitively coupled output signal may be received from the pair of first contacts by a pair of second contacts of the second device. The rectifier / inverter circuit may receive the output signal from the inverter / rectifier circuit of the first device and provide an output to a buck / boost circuit, which may be the same as or similar to the boost / buck circuit in the first electronic device. The buck / boost circuit may be coupled to a battery and internal circuitry of the second device through a switch.

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

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

[0018] Various output differential signals can be provided by the inverter circuit according to the embodiments of the present invention. For example, an anti-phase (or 180° out of phase) sine wave can be provided to the first pair of contacts or the second pair of contacts. An anti-phase square wave can be provided to the first pair of contacts or the second pair of contacts. An anti-phase square wave that is filtered to remove high frequency components can be provided to the first pair of contacts or the second pair of contacts. A bandwidth limited anti-phase square wave can be provided to the first pair of contacts or the second pair of contacts. Other differential waveforms can be provided on the first pair of contacts or the second pair of contacts.

[0019] The frequency of the differential output signal may be varied. The amplitude of the differential output signal may be varied. These parameters may be varied as various conditions on the first pair of contacts or the second pair of contacts change. For example, if liquid is detected on one or more of the contacts, the frequency, the amplitude, or both may be changed for the differential output signal. The differential output signal may be interrupted under several conditions.

[0020] A first contact in the first device may be capacitively coupled to a first power transmission circuit in the first device, and a second contact in the second device may be capacitively coupled to a second power transmission circuit in the second device. The presence of a capacitor used for this AC or capacitive coupling may interrupt a DC current path between the first contact, the second contact, the enclosure for the first device, and the enclosure for the second device.

[0021] For example, the liquid or fluid may be on some or all of the first contact, the second contact, the enclosure for the first device, and the enclosure for the second device. As part of the electrochemical corrosion process, the fluid may induce corrosion of one or more of the first contact, the second contact, the enclosure for the first device, or the enclosure for the second device, thus releasing ions from the structure into the fluid. The movement of ions into the fluid may be part of a loop that includes a galvanic voltage that induces electron movement from the contact through the circuit of either the first device or the second device, and then to the grounded housing or enclosure. The input coupling capacitor may block the DC component of this current, thereby breaking the loop and slowing the flow of ions out of the contact and into the fluid.

[0022] In short, the presence of an electric field can move ions from the contacts to the liquid. This process can corrode the contacts. Therefore, the electric field can be compensated for by embodiments of the present invention. For example, the voltage waveform at the contacts can have 0 volts average and therefore 0 net electric field. Also, the galvanic voltages generated by the dissimilar metals used by the contacts and the housing can generate an electric field, but the current induced by the galvanic field can be blocked by capacitively coupling the contacts to their corresponding circuits.

[0023] Data may be transferred between the first and second devices in a variety of ways. The amplitude of the differential output signal may be modulated with the data. The phase of the differential output signal may be modulated with the data. The frequency of the differential output signal may be modulated with the data. These modulations may be applied by the power and data transmitting device and recovered by the power and data receiving device. In these and other embodiments of the invention, the power transmitting device may provide a differential output signal. The power receiving device may be a data transmitting device and may modulate a load seen by the power transmitting device. The load may be modulated by data that the power receiving device transmits back to the power transmitting device. The power transmitting device may be a data receiving device and may recover the data.

[0024] These and other embodiments of the invention can include additional features that can help prevent or reduce corrosion. For example, electrical impedance spectroscopy circuitry can be included. These circuits can provide a voltage waveform to one or more contacts of the device. The resulting voltage, the resulting current, or both can be measured. The resulting current can indicate that current is flowing through the liquid. A phase shift between the applied voltage waveform and the resulting current or resulting voltage can indicate the amount of liquid type. Coupling capacitors can be inserted between the contacts and the electrical impedance spectroscopy circuitry to prevent corrosion paths.

[0025] Embodiments of the present invention may provide power transmission circuits and apparatus that may be located within 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, power supplies, video distribution systems, adapters, remote control devices, chargers, and other devices.

[0026] The first device and the second device can be various types of devices. Although the first device and the second device can be connected via a cable, they are often mated directly together. For example, the first device can be an audio device such as headphones or earphones, and the second device can be a case for carrying and charging the audio device, or the second device can be an audio device such as headphones or earphones, and the first device can be a case for carrying and charging the audio device. The first device can be a tablet computer, and the second device can be a case and a keyboard, or the second device can be a tablet computer, and the first device can be a case and a keyboard. The first device can be a watch, and the second device can be a watch band, or the second device can be a watch, and the first device can be a watch band. The first device and the second device can be other types of devices that can be connected to each other by mating directly.

[0027] Various embodiments of the present invention may incorporate one or more of these and other features described herein. A better understanding of the nature and advantages of the present invention can be obtained by reference to the following detailed description and the accompanying drawings. [Brief description of the drawings]

[0028] [Figure 1] FIG. 1 illustrates an electronic system according to one embodiment of the present invention.

[0029] [Diagram 2] 1 illustrates a spring biased contact assembly according to one embodiment of the present invention.

[0030] [Diagram 3] 1 illustrates a spring biased contact assembly according to one embodiment of the present invention.

[0031] [Figure 4] FIG. 4 is an exploded view of the contact assembly of FIG. 3.

[0032] [Diagram 5] 4 illustrates a force-deflection curve of a first contact according to one embodiment of the present invention.

[0033] [Figure 6] 1 illustrates a variation of a spring-loaded contact assembly according to an embodiment of the present invention.

[0034] [Figure 7] FIG. 7 is an exploded view of the contact assembly of FIG. 6.

[0035] [Figure 8] FIG. 2 is a cross-sectional view of a second contact assembly according to one embodiment of the present invention.

[0036] [Figure 9] FIG. 9 is an exploded view of the contact assembly of FIG. 8.

[0037] [Figure 10] FIG. 2 is a block diagram of a charging system for the electronic system of FIG. 1 according to one embodiment of the present invention.

[0038] [Figure 11] FIG. 2 is a circuit diagram of a contact interface for the electronic system of FIG. 1 in accordance with one embodiment of the present invention.

[0039] [Figure 12] 2 is a simplified circuit diagram of a portion of a power system circuit according to one embodiment of the present invention;

[0040] [Figure 13] FIG. 2 is an alternative simplified circuit diagram of a portion of a power system circuit in accordance with one embodiment of the present invention.

[0041] [Figure 14]FIG. 2 is a simplified circuit diagram of a portion of two power system circuits transferring power, according to one embodiment of the present invention.

[0042] [Figure 15] 1 illustrates a contact assembly according to one embodiment of the present invention. [Figure 16] 1 illustrates a contact assembly according to one embodiment of the present invention. [Figure 17] 1 illustrates a contact assembly according to one embodiment of the present invention.

[0043] [Figure 18A] 1 illustrates a profile of a contact assembly according to one embodiment of the present invention. [Figure 18B] 1 illustrates a profile of a contact assembly according to one embodiment of the present invention. [Figure 18C] 1 illustrates a profile of a contact assembly according to one embodiment of the present invention. [Figure 18D] 1 illustrates a profile of a contact assembly according to one embodiment of the present invention.

[0044] [Figure 19] 1 illustrates a contact assembly for a contact interface according to one embodiment of the present invention.

[0045] [Figure 20] 4 shows further details of a contact assembly according to one embodiment of the present invention.

[0046] [Figure 21] 1 illustrates a contact assembly for a contact interface according to one embodiment of the present invention.

[0047] [Figure 22] 1 illustrates a cutaway side view of a contact assembly according to one embodiment of the present invention.

[0048] [Figure 23] 1 illustrates galvanic corrosion paths in an electronic device according to an embodiment of the present invention.

[0049] [Figure 24] 1 illustrates optional DC charging in an electronic device according to one embodiment of the present invention.

[0050] [Diagram 25] 1 illustrates an AC waveform for power transfer according to one embodiment of the present invention.

[0051] [Figure 26] 1 illustrates a charging path through an electronic system according to one embodiment of the present invention.

[0052] [Figure 27] 1 illustrates a charging path through an electronic system according to one embodiment of the present invention.

[0053] [Figure 28] 1 illustrates a charging path through an electronic system according to one embodiment of the present invention.

[0054] [Figure 29] 4 illustrates data that may be used by a method for determining the type of material used in a contact, according to one embodiment of the present invention.

[0055] [Diagram 30] 1 illustrates a method for optimizing a charging waveform according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0056] Figure 1 illustrates an electronic system according to one embodiment of the present invention. This figure, as well as the other figures included herein, are provided for illustrative purposes and are not intended to limit any of the possible embodiments of the invention or the scope of the claims.

[0057] In this example, the electronic system 10 may include a first device 100 that may be connected to a second device 200 to share data, power, or both. A first contact 110, a first contact 112, and a first contact 114 (collectively, the first contacts 110) on the first device 100 may be electrically connected to a second contact 210, a second contact 212, and a second contact 214 (collectively, the second contacts 210) on the second device 200. The first contact 110 on the first device 100 may be electrically connected to the second contact 210 on the second device 200 using a cable (not shown). In other embodiments of the invention, the first contact 110 of the first device 100 may be directly and electrically connected to the second contact 210 of the second device 200. In various embodiments of the invention, the first contact 110 and the second contact 210 may be power contacts or other types of contacts. An example of an embodiment of the present invention is shown in the following figure where first contact 110, first contact 112, second contact 210, and second contact 212 are power contacts. First contact 114 and second contact 214 can be ground contacts, data or signal contacts, or other types of contacts.

[0058] An embodiment of the present invention can transfer power from the first device 100 to the second device 200 by providing an AC differential voltage having an average value at or near 0 volts at the first contact 110 and the first contact 112. Power can be transferred from the second device 200 to the first device 100 by providing an AC differential voltage having an average value at or near 0 volts at the second contact 210 and the second contact 212. This can provide a reduced or low level of ion migration to the contacts, thereby reducing corrosion of the first contact 110 and the second contact 210 when the device power contacts are exposed to contaminants. The first contact 110 can be capacitively coupled to the power transfer circuit 120 and the second contact 210 can be capacitively coupled to the power transfer circuit 220. Capacitive coupling can eliminate or reduce currents generated by galvanic voltages between dissimilar metals used in the first contact 110, the second contact 210, and the enclosures or housings of the first device 100 and the second device 200.

[0059] The first contacts 110 may be coupled to a power transmission circuit 120 in the first device 100. The power transmission circuit 120 may supply power to or draw power from a battery 190. The second contacts 210 may be coupled to a power transmission circuit 220 in the second device 200. The power transmission circuit 220 may supply power to or draw power from a battery 290.

[0060] The first device 100 and the second device 200 can be various types of devices. The first device 100 and the second device 200 can be connected via a cable, but they are often directly mated to each other. For example, the first device 100 can be an audio device such as headphones or earphones, and the second device 200 can be a case for carrying and charging the audio device, or the second device 200 can be an audio device such as headphones or earphones, and the first device 100 can be a case for carrying and charging the audio device. The first device 100 can be a tablet computer, and the second device 200 can be a case and a keyboard, or the second device 200 can be a tablet computer, and the first device 100 can be a case and a keyboard. The first device 100 can be a watch and the second device 200 can be a watch band, or the second device 200 can be a watch and the first device 100 can be a watch band. The first device 100 and the second device 200 may be other types of devices capable of connecting to each other by direct mating.

[0061] The first contact 110 can be a spring-loaded contact that can mate with a fixed second contact 210. The first contact 110 can be spring-loaded to provide a force against the second contact 210 to provide a good electrical connection. Examples of first contacts are shown in the following figures.

[0062] FIG. 2 illustrates a spring-loaded contact assembly according to an embodiment of the present invention. The first contact assembly 20 can include a first contact 110. The first contact 110 can be loaded by a pair of canted coil springs 130. The canted coil springs 130 can be disposed within a housing 150 such that a central axis of the canted coil springs 130 is perpendicular to a connection direction of the first contact 110. When the first device 100 and the second device 200 (both shown in FIG. 1 ) are mated, the first contact 110 can be pressed in a direction into the first device 100. The first contact 110 can press the plate 170 and the holder 160 into the canted coil springs 130, thereby crushing or flattening the canted coil springs 130 in the direction of their diameter. When the first device 100 and the second device 200 are disconnected, the canted coil spring 130 can return to its original shape and push the first contact 110, the plate 170, and the holder 160 away from the first device 100. The movement of the first contact 110 can be restricted by attaching the first contact and a pin 162 to the holder 160, which can move within a slot 152 in the housing 150 of the first device 100. The canted coil spring 130 can be held in place using one or more pins 140 disposed through a central axis of the canted coil spring 130. A wire 180 can couple the first contact 110 to a coupling capacitor, such as the coupling capacitor C1 of FIG. 11.

[0063] FIG. 3 illustrates a spring-biased contact assembly according to one embodiment of the present invention. In these and other embodiments of the present invention, the first contact 110 can be biased by a single canted coil spring 230. The first contact assembly 30 can include the canted coil spring 230. The canted coil spring 230 can be disposed within the housing 250 such that its central axis is perpendicular to the connection direction of the first contact 110. When the first device 100 and the second device 200 (both shown in FIG. 1 ) are mated, the first contact 110 can be pushed in a direction into the first device 100. The first contact 110 can push the plate 270 and the holder 260 into the canted coil spring 230, thereby crushing or flattening the canted coil spring 230 in its diameter. When the first device 100 and the second device 200 are disconnected, the canted coil spring 230 can return to its original shape and push the first contact 110, the plate 270, and the holder 260 away from the first device 100. The movement of the first contact 110 can be restricted by attaching the first contact 110 and a pin 262 to the holder 260, and the pin 262 can move within a slot 252 in a housing 250 in the first device 100. The canted coil spring 130 can be held in place using a number of slats 242 attached to a frame 240. A wire 280 can couple the first contact 110 to a coupling capacitor, such as the coupling capacitor C1 of FIG.

[0064] FIG. 4 is an exploded view of the contact assembly of FIG. 3. The first contact assembly 30 can include a canted coil spring 230. The canted coil spring 230 can be held in place by slats 242 extending from a frame 240. A plate 270 can further confine the canted coil spring 230. The plate 270 can be attached to the bottom of the holder 260. The holder 620 can hold the first contact 110 in the slot 264. The plate 270 can be attached to the underside of the holder 260. A wire 280 can transmit voltage and current from the first contact 110 to the power transmission circuit 120 in the first device 100. The holder 260 can slide through a range defined by a pin 262 in a slot 252 in a housing 250 (shown in FIG. 3). When the first device 100 and the second device 200 (both shown in FIG. 1 ) are mated, the first contact 110 can be forced in a direction into the first device 100. The first contact 110 can force the plate 170 and holder 160 into the canted coil spring 130, thereby crushing or flattening the canted coil spring 130 in its diameter. When the first device 100 and the second device 200 are disconnected, the canted coil spring 130 can return to its original shape, pushing the plate 270, holder 260, and first contact 110 away from the first device 100.

[0065] FIG. 5 illustrates a force-deflection curve of a first contact according to an embodiment of the present invention. The graph 500 illustrates a force-deflection curve 530 that plots the contact force 510 provided by the first contact 110 (shown in FIG. 1) as a function of the deflection 520 of the first contact. When the first device and the second device are mated, the first contact 110 can deflect by an amount that can be within a range 540. The deflection can vary within a range due to manufacturing tolerances in the formation of the first device 100, the second device 200, the first contact 110, the second contact 210, and the manner in which they are mated. Thus, it may be desirable for the contact force to be independent as a function of displacement. That is, it may be desirable for the force-deflection curve 530 to be at least relatively flat in the range 540. This can be achieved using the canted coil spring 130 and the canted coil spring 230 in the examples of FIGS. 2 and 3. The force-deflection curve 530 can use other structures to provide a flat portion in the range 540. Examples are shown in the following figures.

[0066] FIG. 6 illustrates a variation of a spring-loaded contact assembly according to an embodiment of the present invention. In the contact assembly 30, the first contact 110 may be loaded by one or more stacks of Belleville washers 630. The Belleville washers 630 may be placed back-to-back and then stacked. The stack of Belleville washers 630 may be placed on alignment pins 644 to limit the movement of the Belleville washers 630. When the first device 100 and the second device 200 (both shown in FIG. 1) are mated, the first contact 110 may be pushed in a direction into the first device 100. The first contact 110 may push the plate 670 into the Belleville washers 630. When the plate 270 is pushed into the stack of Belleville washers 630, the Belleville washers 630 begin to compress, thereby reducing the length of the stack of Belleville washers 630. The Belleville washers 630 can have the same or different thicknesses such that the Belleville washers 630 can provide at least a somewhat constant force across the deflection of the first contact 110. When the first device 100 and the second device 200 are disconnected, the Belleville washers 630 can return to their original shape and push the first contact 110, the holder 660, and the plate 670 away from the first device 100. The wires 680 can carry voltage and current from the first contact 110 to the power transmission circuitry 120 in the first device 100 (all shown in FIG. 1). An insulator 682 can be provided around the wires 680.

[0067] FIG. 7 is an exploded view of the contact assembly of FIG. 6. A stack of Belleville washers 630 can be placed on alignment pins 644 in the contact assembly 30. The Belleville washers 630 can be held between a frame 640 and a plate 670. Slats 642 can extend from the frame 640. Wires 680 can transmit voltage and current from the first contacts 110 to the power transmission circuitry 120 in the first device 100 (all shown in FIG. 1). A holder 660 can support the pins 662 (shown in FIG. 6), the first contacts 110, and the plate 670. The holder 660 can move throughout a range defined by the pins 662 in an opening (not shown) in the housing 650.

[0068] FIG. 8 is a cross-sectional view of a second contact assembly according to an embodiment of the invention. In these and other embodiments of the invention, the second contact 210 in the second contact assembly 80 can be secured within the second device 200 (shown in FIG. 1 ) and the first contact 110 can provide a force against the second contact 210. The second contact 210 can be supported by a housing 810 that is sealed to a housing or enclosure 890 of the second device 200 by a sealing ring 820. The second contact 210 can be attached to a flexible circuit board 830 using a pressure sensitive adhesive 840 or other adhesive. The flexible circuit board 830 can be held in place by a cowling 850. The cowling 850 can be attached to the flexible circuit board 830 using a pressure sensitive adhesive 860 or other adhesive. The cowling 850 can be secured to the housing or enclosure 890 of the second device 200 by a fastener 892.

[0069] FIG. 9 is an exploded view of the contact assembly of FIG. 8. The second contacts 210 of the second contact assembly 80 may be supported by a housing 810. The housing 810 may be sealed to a housing or enclosure 890 (shown in FIG. 8) of the second device 200 (shown in FIG. 2) by a sealing ring 820. The second contacts 210 may contact pads 832 on a flexible circuit board 830. The flexible circuit board 830 may include pads 834 that may be connected to the pads 832 for electrically connecting to the power transmission circuit 220 (shown in FIG. 1) in the second device 200. The housing 810 may be attached to the flexible circuit board 830 using a pressure sensitive adhesive 840 or other adhesive. The flexible circuit board 830 may be held in place by a cowling 850. The cowling 850 may be attached to the flexible circuit board 830 using a pressure sensitive adhesive 860 or other adhesive. The cowling 850 can be secured to the housing or enclosure 890 of the second device 200 by passing fasteners 892 through the openings 852 and inserting the fasteners 892 into corresponding holes in the housing or enclosure 890 of the second device 200.

[0070] In these and other embodiments of the invention, various circuits can be used to transfer power. These circuits can be used to transfer power from a first device to a second device, from a second device to the first device, or power can be transferred bidirectionally or back and forth between the first device and the second device. For example, the first device can receive power from a charger or power adapter. While the first device is powered, the second device can connect to the first device. This can allow the first device to provide power to the second device. During device operation, the second device can provide power back to the first device. During device operation, the first device can continue to provide power to the second device as needed.

[0071] These power circuits may be the same or substantially similar in the first device and the second device. In these and other embodiments of the present invention, the first device and the second device may have differences, for example, where the transmission of power between the first device and the second device is unidirectional or one-way. An example is shown in the following figure.

[0072] 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. The first power transmission circuit 120 can be housed in the first device 100 (shown in FIG. 1 ), and the second power transmission circuit 220 can be housed in the second device 200 (shown in FIG. 1 ). The first power transmission circuit 120 can share power with the second power transmission circuit 220. For example, the power transmission circuit 120 can transmit power to the second power transmission circuit 220. The battery 190 can be connected to a switch 1010, which can be open when the first device is disconnected from the second device 200 and can be closed when power is being transferred. The switch 1010 can then be connected to a boost / buck circuit 1020, which can be connected to an inverter / rectifier circuit 1030. The inverter / rectifier circuit 1030 may provide a capacitively coupled output signal via capacitors C1 and C2 to a pair of first contacts including the first contact 110 and the first contact 112. The capacitively coupled output signal may be received from the pair of first contacts 110 by a pair of second contacts 210 including the second contact 210 and the second contact 212 of the second device. The signals on the second contact 210 and the second contact 212 may be capacitively coupled to the rectifier / inverter circuit 1040 via capacitors C3 and C4. The rectifier / inverter circuit 1040 may be the same as or similar to the inverter / rectifier circuit 1030 of the first power transmission circuit 120 and may provide an output to a buck / boost circuit 1050, which may be the same as or similar to the boost / buck circuit 1020 in the first power transmission circuit 120. The buck / boost circuit 1050 may be coupled to the battery 290 and the internal circuitry of the second device 200 via a switch 1060 .

[0073] Power may be transferred from the first device 100 to the second device 200. In the first power transfer circuit 120, a switch 1010 may connect a battery 190 to a boost / buck circuit 1020. The boost / buck circuit 1020 may act as a boost to increase the voltage from the battery 190 and provide a high voltage and a low voltage to an inverter / rectifier circuit 1030. The inverter / rectifier circuit 1030 may operate as an inverter to provide a differential output signal. The differential output signal may be capacitively coupled to the first contact 110 via a capacitor C1 and to the first contact 112 via a capacitor C2.

[0074] The differential output signal may be received by the second contact 210 and the second contact 212 of the second device 200. The differential output signal may be capacitively coupled to the rectifier / inverter circuit 1040 via capacitors C3 and C4, which may convert the differential output signal to a high voltage and a low voltage. The high voltage and the low voltage may be stepped down by the buck / boost circuit 1050, which may provide power through a switch 1060 to charge the battery 290 of the second device 200. Although power is described as being transmitted from the first device 100 to the second device 200, power may also be transmitted from the second device 200 to the first device 100.

[0075] Various output differential signals may be provided by the inverters of the inverter / rectifier circuit 1030 and the rectifier / inverter circuit 1040 according to embodiments of the present invention. For example, sine waves in antiphase (or 180° out of phase with each other) may be provided to the first pair of contacts or the second pair of contacts. Square waves in antiphase may be provided to the first pair of contacts or the second pair of contacts. Square waves in antiphase that are filtered to remove high frequency components may be provided to the first pair of contacts or the second pair of contacts. Square waves in antiphase that are bandwidth limited may be provided to the first pair of contacts or the second pair of contacts. Other differential waveforms may be provided on the first pair of contacts or the second pair of contacts.

[0076] The frequency of the differential output signal may be varied. The amplitude of the differential output signal may be varied. These parameters may be varied as various conditions on the first pair of contacts or the second pair of contacts change. For example, if liquid is detected on one or more of the contacts, the frequency, the amplitude, or both may be changed for the differential output signal. The differential output signal may be interrupted under several conditions.

[0077] Data can be transferred between the first device 100 and the second device 200 in a variety of 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 the power and data transmitting device and recovered by the power and data receiving device. In these and other embodiments of the invention, the power transmitting device can provide a differential output signal. The power receiving device can be a data transmitting device and can modulate a load seen by the power transmitting device. The load can be modulated by data that the power receiving device transmits back to the power transmitting device. The power transmitting device can be a data receiving device and can recover the data. Instead of using a differential output signal, data can be transmitted using the first contact 114 of the first device 100 and the second contact 214 of the second device 200 (all shown in FIG. 1).

[0078] The first contact 110 and the first contact 112 in the first device 100 may be capacitively coupled to the first power transmission circuit 120 in the first device 100 using capacitors C1 and C2, and the second contact 210 and the second contact 212 in the second device 200 may be capacitively coupled to the second power transmission circuit 220 in the second device 200 using capacitors C3 and C4. The presence of the capacitors used for this AC or capacitive coupling may interrupt DC current paths between the first contact 110, the second contact 210, the device enclosure 1110 for the first device 100 (shown in FIG. 11 ), and the device enclosure 1120 for the second device 200 (shown in FIG. 11 ).

[0079] For example, the fluid or liquid may be on some or all of the first contact 110, the second contact 210, the device enclosure 1110 for the first device 100, and the device enclosure 1120 for the second device 200. As part of the electrochemical corrosion process, the fluid may cause corrosion and induce ions to migrate into the fluid of one or more of the first contact 110, the second contact 210, the device enclosure 1110 for the first device 100, and the device enclosure 1120 for the second device 200. The migration of ions from the contact to the fluid may be part of a loop that includes a current traveling from the contact through the circuitry of either the first device or the second device to ground. The input coupling capacitor may block the DC component of this current, thereby breaking the loop and slowing the flow of ions out of the contact and into the fluid. Further details are shown in the following figures.

[0080] FIG. 11 is a circuit diagram of a contact interface for the electronic system of FIG. 1 according to an embodiment of the present invention. The first contact 110 can be coupled to an electrostatic discharge diode D1. The electrostatic discharge diode D1 can be a high impedance, low leakage diode. The first contact 110 can be coupled to a capacitor C1, which can be coupled to an inductor L1. The inductor L1 can be included to reduce a sudden increase in current through the capacitor C1 when the first power transmission circuit 120 supplies power to the second power transmission circuit 220. The capacitor C1 can be selected to be large enough to provide a low impedance to the differential output signal, but small enough to be physically reasonable. The inductor L1 can be selected so that the tuning frequency of the inductor L1 and the capacitor C1 has a period that is shorter than the period of the differential output signal.

[0081] A liquid or fluid may be present on one or more of the first contact 110, the first contact 112, the device enclosure 1110, the second contact 210, the second contact 212, and the device enclosure 1120. As part of the electrochemical corrosion process, the fluid may cause corrosion and induce ions to migrate out of one or more of the first contact 110, the second contact 210, the device enclosure 1110, and the device enclosure 1210 and into the fluid. The migration of ions may be driven by a current flowing from one of the first contact 110 or the second contact 210, through the circuitry of either the first device 100 or the second device 200, and then to one of the device enclosure 1110 or the device enclosure 1120, which may be grounded. This current flow may be driven by a galvanic voltage that may appear between the first contact 110 and the device enclosure 1110, for example. For example, the first contacts can be plated with gold or other conductive material, and the device enclosure 1110 can be steel, aluminum, or other material. These dissimilar materials can form a galvanic voltage between the first contacts 110 and the device enclosure 1110. Input coupling capacitors C1 and C2 can block the DC component of this current from one of the first contacts 110 to the device enclosure 1110. Input coupling capacitors C3 and C4 can block the DC component of the current from one of the second contacts 210 to the device enclosure 1120.

[0082] In this example, the capacitor C2 may be coupled to the first junction 112, the electrostatic discharge diode D2, and the inductor L2. The inductor L1 and the inductor L2 may be coupled to the inverter / rectifier circuit 1030. The diodes D1 and D2 may be the same or similar. The inductors L1 and L2 may be the same or similar. The coupling capacitor C3 may be coupled to the second junction 210, the electrostatic discharge diode D3, and the inductor L3. The diodes D1 and D3 may be the same or similar. The inductors L1 and L3 may be the same or similar. The coupling capacitor C4 may be coupled to the second junction 212, the electrostatic discharge diode D4, and the inductor L4. The diodes D1 and D4 may be the same or similar. The inductors L1 and L4 may be the same or similar. The inductor L3 and the inductor L4 may be coupled to the rectifier / inverter circuit 1040. Stray impedances between the first contact 110, the second contact 210, the device enclosure 1110 of the first device 100, and the device enclosure 1120 of the second device 200 can be modeled as resistors R1-R7. Capacitor C1, capacitor C2, capacitor C3, and capacitor C4 can be the same or similar.

[0083] Various circuits can be used to implement power delivery circuitry 120 and power delivery circuitry 220. Examples are shown in the following figures.

[0084] 12 is a simplified circuit diagram of a portion of a power system circuit according to an embodiment of the present invention. In this example, the switch 1010 (and the switch 1060) may be implemented using a transistor P1. The transistor P1 may connect the battery 190 (or the battery 290) to the boost / buck circuit 1020 (or the buck / boost circuit 1050). Although the transistor P1 is shown as a P-MOS transistor, the transistor P1 may be implemented in various ways, for example, by an N-MOS transistor, by two parallel transistors with a resistor in series with one of the two, or by other devices or circuits. The boost / buck circuit 1020 (and the buck / boost circuit 1050) may be implemented using a single-input multiple-output (SIMO) type architecture including an inductor L1, a transistor N1, a transistor N2, a transistor N3, and a transistor N4. The boost / buck circuit 1020 (or the buck / boost circuit 1050) may be coupled to the inverter / rectifier circuit 1030 (or the rectifier / inverter circuit 1040). The boost / buck circuit 1020 (and the buck / boost circuit 1050) may have a full-bridge architecture that may include transistor N5, transistor N6, transistor N7, and transistor N8.

[0085] FIG. 13 is an alternative simplified circuit diagram of a portion of a power system circuit according to an embodiment of the present invention. In these and other embodiments of the present invention as shown in FIG. 12, the 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. The boost / buck 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. The boost / buck 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.

[0086] These and other embodiments of the invention can include additional features that can help prevent or reduce corrosion. For example, electrical impedance spectroscopy circuitry can be included. These circuits can provide a voltage waveform to one or more contacts of the device. The resulting voltage, the resulting current, or both can be measured. The resulting current can indicate that current is flowing through the liquid. A phase shift between the applied voltage waveform and the resulting current or resulting voltage can indicate the amount of liquid type. To prevent corrosion paths, a coupling capacitor can be inserted between the contacts and the electrical impedance spectroscopy circuitry. An example is shown in the following figure.

[0087] FIG. 14 is a simplified circuit diagram of a portion of two power system circuits transferring power, according to an embodiment of the present invention. The inverter / rectifier circuit 1030 can act as an inverter and provide a differential output signal to the first contact 110 via a switch 1420 and a coupling capacitor 1430. The coupling capacitor 1430 can include capacitors C1 and C2 from the contact interface of FIG. 11. The second contact 210 can receive the differential output signal and provide it to the rectifier / inverter circuit 1040, which can act as a rectifier and provide high and low voltages to the power factor correction controller 1450. The power factor correction controller 1450 can pass an output to a power management controller 1460, which can charge the battery 290. The power management controller 1460 can control the voltage and current seen by the battery 290 during charging. This path can be reversed if the second device 200 is able to charge the first device 100 .

[0088] An electrochemical impedance spectroscopy (EIS) circuit 1470 can be included. The EIS circuit 1470 can provide a voltage waveform or a current waveform, and in this example, a voltage waveform. The voltage waveform can be a sine wave, a square wave, or other voltage waveform. The EIS circuit 1470 can be coupled to the first contacts 110 via a coupling capacitor 1430. If liquid is present at one or more of the first contacts 110, the EIS circuit 1470 can be used to detect a current or a voltage. The current, voltage, or both can indicate a change in capacitance and resistance seen at the first contacts 110. The EIS circuit 1470 can detect the magnitude of this current and voltage, as well as any phase shift compared to the applied voltage, and can then determine the change in capacitance and resistance seen at the first contacts 110. From the change in capacitance and resistance, information about the presence of liquid and the type of liquid present can be determined. Further details on this can be found in U.S. Patent No. 1,1658,443, entitled "LIQUID DETECTION AND CORROSION MITIGATION," issued May 23, 2023, which is incorporated by reference. Source 1 and Source 2 can be used as voltage signals in EIS circuit 1470.

[0089] Other types of circuitry may be included in or associated with either or both of power transmission circuitry 120 and power transmission circuitry 220. For example, connection detection may be used to disconnect battery 190 or battery 290 when the opposing device is not mated. This connection detection may include sending an occasional voltage ping at first contact 110. This voltage ping should be of such a nature that the average value of the ping, or the average value of a set of pings, should be 0 volts.

[0090] 15-17 show a contact assembly according to one embodiment of the present invention. In FIG. 15, contact assembly 1500 can include contacts 110 and a housing 1530. Insulator 1520 can form a seal between contacts 110 and housing 1530 to prevent leakage into the interior of a device incorporating contact assembly 1500.

[0091] The contact 110 can be formed from a bulk or substrate 1510. An optional plating layer 1512 can be formed on the bottom or inner surface of the contact 110. Other optional plating can be formed along the sides of the bulk or substrate 1510. The bulk or substrate 1510 can be formed from stainless steel, titanium, tantalum, Inconel, nickel-aluminum bronze, copper, copper alloys, or other materials. The use of these materials can provide contacts that can be easily manufactured and can conserve valuable resources compared to contacts that can use exotic materials. These materials can provide good durability and corrosion resistance. The optional plating layer 1512 can be formed from gold or other conductive materials, for example, the optional plating layer 1512 can be a gold flash. The optional plating layer 1512 can form a surface that can be soldered to a flexible circuit board or other suitable substrate.

[0092] In these and other embodiments of the invention, the voltage waveform transmitted by the contact 110 may be an AC waveform. Thus, much of the current through the contact 110 may be transmitted at the surface of the contact 110. Thus, embodiments of the invention may provide plating on some or all of the side 1514 of the bulk or substrate 1510. This plating may be gold, diamond-like carbon (formed to be conductive), titanium nitride, tin-silver, nickel-gold, or other materials. In these and other embodiments of the invention, this plating may extend along some or all of the top and sides of the bulk or substrate 1510. Examples are shown in the following figures.

[0093] 16, the contact assembly 1600 can include a contact 110, a housing 1530, and an insulator 1520 that can form a seal between the contact 110 and the housing 1530. The contact 110 can include a bulk or substrate 1510 and an optional plating layer 1512 that can be plated with a finishing layer 1610. The finishing layer 1610 can be formed from diamond-like carbon (formed to be conductive), tin, tin-silver, nickel-gold, or other materials.

[0094] In FIG. 17, the contact assembly 1700 can include the contact 110, the housing 1530, and the insulator 1520 that can form a seal between the contact 110 and the housing 1530. The contact 110 can include a bulk or substrate 1510, an optional plating layer 1512, and a finishing layer 1610, as well as an intermediate layer 1710. The addition of the intermediate layer 1710 reduces the need for the bulk or substrate 1510 to conduct the AC waveform. This allows for the use of low conductive or non-conductive materials such as plastic, ceramic, ceramic plastic, aluminum, stainless steel, or other materials as the bulk or substrate 1510. The intermediate layer 1710 can be gold, copper, nickel, or combinations thereof, or other conductive metals. Current generated by the AC waveform received by the contact 110 can be conducted near the surface of the contact 110 due to the skin effect. Thus, the intermediate layer can be relatively thin, for example 10 to 100 microns, depending on the desired frequency range of the AC waveform. This thickness can allow for good electrical conductivity for AC waveforms.

[0095] The materials and various layers that make up the contact 110 can provide at least three functions. They can provide an interface function to mate with another contact, can provide a conductive function to transfer the charging AC waveform, and can provide a mechanical function to provide structure for the contact. In FIG. 15, the bulk or substrate 1510 can provide a durable interface to mate with a contact on a second device. The conductivity of the bulk or substrate 1510 can be improved by adding an optional plating layer 1512 to the bottom and sides of the bulk or substrate 1510. The bulk or substrate 1510 can provide a mechanical function. In FIG. 16, the interface function can be improved by the addition of a finish layer 1610. The finish layer 1610 can provide a surface with improved hardness and corrosion resistance. In FIG. 17, the addition of an intermediate layer 1710 provides an opportunity to improve the conductive 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 to the bulk or substrate 1510. This allows the bulk or substrate 1510 to be made of a low or non-conductive material.

[0096] These functions may be allocated between these layers in different ways in different embodiments of the invention. For example, in Figure 16, the finishing layer 1610 may have a lower conductivity and the bulk or substrate 1510 may have a higher conductivity. In these and other embodiments of the invention, more than two layers may be plated or otherwise formed on the bulk or substrate 1510.

[0097] The use of an AC waveform can allow the skin effect to be utilized, i.e., the skin effect can allow the electrical conductivity of the finish layer 1610 and the intermediate layer 1710 to rely on charge conduction. Such reliance on the finish layer 1610 and the intermediate layer 1710 may not be possible when power is transmitted using conventional DC voltages and currents.

[0098] The use of these plating layers can unfortunately promote corrosion of these contacts 110. When a connection is made using the contacts 110, the plating layers (such as the finishing layer 1610 and the intermediate layer 1710) and the substrate (such as the bulk or substrate 1510) can be damaged, for example, leading to scratches. A galvanic voltage can then appear across the scratches. The presence of electrolyte can cause corrosion of the contacts 110.

[0099] Embodiments of the present invention can include various features to reduce galvanic corrosion that may be caused by scratches on the contacts 110. For example, materials for the plating and substrate can be selected to reduce any galvanic voltage. As an example, the plating of the contacts can be gold plated, which has a galvanic voltage range of 0.07 to 0.2 V, and the bulk or substrate can be titanium, which has a galvanic voltage range of -0.12 to 0.04 V. Alternatively, the bulk or substrate can be a non-conductive material such as ceramic, plastic, or a combination of these or other materials.

[0100] In addition to reducing the galvanic voltage at the scratch, embodiments of the present invention can contact assemblies that can minimize the chances of such scratches and other types of damage occurring. Examples are shown in the following figures.

[0101] 18A-18D show profiles of contact assemblies according to one embodiment of the invention. In FIG. 18A, a first device can include a contact assembly 1810 that can include a contact 1812 surrounded by an adjacent insulator 1814 and a housing 1816. A second device can include a contact assembly 1820 that can include a contact 1822 surrounded by an adjacent insulator 1824 and a housing 1826. In this example, the contact 1812, insulator 1814, and housing 1816 are flush with one another, and the contact 1822 and insulator 1824 are flush with one another and can move relative to the housing 1826.

[0102] The contacts 1822 and insulator 1824 can move relative to the housing 1826 so that the contacts 1822 can engage the contacts 1812. The contact assembly 1820 can mate with the contact assembly 1810 in a contact orientation that is orthogonal or perpendicular to the surface of the contacts 1822. Alternatively, the contact assembly 1820 can slide laterally across the contact assembly 1810 (or the contact assembly 1810 can slide laterally across the contact assembly 1820) until the contacts 1822 are aligned with the contacts 1812, at which point the contacts 1822 and insulator 1824 can move toward the contact assembly 1810 so that the contacts 1812 mate with the contacts 1822.

[0103] When the contact assemblies 1810 and 1820 engage in a vertical orientation, the contacts 1812 and 1822 are largely undamaged. However, when the contact assembly 1820 moves laterally across the contact assembly 1810 (or the contact assembly 1810 slides laterally across the contact assembly 1820), the contacts 1822 may interact with and be damaged by the housing 1816 and the contacts 1812. Similarly, the contacts 1812 may interact with and be damaged by the housing 1826. This damage may lead to scratches. These scratches may expose the galvanic connections and galvanic voltages between the various plating layers and substrates of the contacts 1812 and 1822. These galvanic voltages in the presence of electrolyte may cause corrosion at the surfaces of the contacts 1812 and 1822.

[0104] 18B, a first device can include a contact assembly 1830 that can include a contact 1832 surrounded by an adjacent insulator 1834 and a housing 1836. A second device can include a contact assembly 1840 that can include a contact 1842 surrounded by an adjacent insulator 1844 and a housing 1846. In this example, the contact 1832, the insulator 1834, and the housing 1836 are flush with one another, and the contact 1842 can include an extension 1848 that protrudes from the insulator 1844. The contact 1842 and the insulator 1844 can move relative to the housing 1846.

[0105] The contacts 1842 and insulator 1844 can move relative to the housing 1846 so that the contacts 1842 can engage the contacts 1832. The contact assembly 1840 can mate with the contact assembly 1830 in a contact orientation that is orthogonal or perpendicular to the surface of the contacts 1842. Alternatively, the contact assembly 1840 can slide laterally across the contact assembly 1830 until the contacts 1842 are aligned with the contacts 1832, at which point the contacts 1842 and insulator 1844 can move toward the contact assembly 1830 so that the contacts 1842 mate with the contacts 1832.

[0106] When the contact assemblies 1830 and 1840 engage in a vertical orientation, the contacts 1832 and 1842 are largely undamaged. However, as the contact assembly 1840 moves laterally across the contact assembly 1830 (or the contact assembly 1830 slides laterally across the contact assembly 1840), the extensions 1848 of the contacts 1842 may interact with and be damaged by the housing 1836 and the contacts 1832. Similarly, the contacts 1832 may interact with and be damaged by the housing 1846. This damage may lead to scratches. These scratches may expose the galvanic connections and galvanic voltages between the various plating layers and substrates of the contacts 1832 and 1842. These galvanic voltages in the presence of an electrolyte may cause corrosion at the surfaces of the contacts 1832 and 1842.

[0107] 18C, the first device can include a contact assembly 1850 that can include a contact 1852 surrounded by an adjacent insulator 1854 and a housing 1856. The second device can include a contact assembly 1860 that can include a contact 1862 surrounded by an adjacent insulator 1864 and a housing 1866. In this example, the contact 1852 can be recessed relative to the housing 1856 and the insulator 1854 can be further recessed relative to the housing 1856. The contact 1862 can include an extension 1868 that protrudes from the housing 1866 and the insulator 1864 can include an extension 1869 that protrudes from both the housing 1866 and the contact 1862. The contact 1862 and the insulator 1864 can move relative to the housing 1866.

[0108] The contacts 1862 and insulator 1864 can move relative to the housing 1866 so that the contacts 1862 can engage the contacts 1852. The contact assembly 1860 can mate with the contact assembly 1850 in a contact orientation that is orthogonal or perpendicular to the surface of the contacts 1862. Alternatively, the contact assembly 1860 can slide laterally across the contact assembly 1850 until the contacts 1862 are aligned with the contacts 1852, at which point the contacts 1862 and insulator 1864 can move toward the contact assembly 1850 so that the contacts 1862 mate with the contacts 1852.

[0109] When contact assembly 1850 and contact assembly 1860 engage in a vertical orientation, contacts 1852 and 1862 suffer little damage. When contact assembly 1860 moves laterally across contact assembly 1850 (or contact assembly 1850 slides laterally across contact assembly 1860), extension 1858 of contact 1852 can interact with extension 1869 of insulator 1864, which may not cause significant damage. Extension 1868 of contact 1862 can be protected by extension 1869 of insulator 1864, thereby reducing damage to contact 1862.

[0110] 18D, a first device can include a contact assembly 1870 that can include a contact 1872 surrounded by an adjacent insulator 1874 and a housing 1876. A second device can include a contact assembly 1880 that can include a contact 1882 surrounded by an adjacent insulator 1884 and a housing 1886. In this example, the contact 1872 can be recessed relative to the housing 1876 and the insulator 1874 can be further recessed relative to the housing 1876. The contact 1882 can be flush with the insulator 1884 or both can be recessed relative to the housing 1886. The contact 1882 and the insulator 1884 can move relative to the housing 1886.

[0111] The contacts 1882 and insulator 1884 can move relative to the housing 1886 such that the contacts 1882 can engage the contacts 1872. The contact assembly 1880 can mate with the contact assembly 1870 in a contact orientation that is orthogonal or perpendicular to the surface of the contacts 1882. Alternatively, the contact assembly 1880 can slide laterally across the contact assembly 1870 until the contacts 1882 are aligned with the contacts 1872, at which point the contacts 1882 and insulator 1884 can move toward the contact assembly 1870 such that the contacts 1882 mate with the contacts 1872. This movement can be facilitated by magnets 1879 in the contact assembly 1870 and magnets 1889 in the contact assembly 1880.

[0112] When contact assembly 1870 and contact assembly 1880 engage in a vertical orientation, contacts 1872 and contacts 1882 are substantially undamaged. When contact assembly 1880 moves laterally across contact assembly 1870 (or contact assembly 1870 slides laterally across contact assembly 1880), extensions 1878 of contacts 1872 may not interact with contact assembly 1880 and may avoid being damaged. Contact 1882 may be recessed and protected by insulator 1884, thereby avoiding damage.

[0113] 19 illustrates a contact assembly for a contact interface according to one embodiment of the present invention. A first electronic device 1902 and a second electronic device 1904 can form an electronic system 1900. The first electronic device 1902 can include a contact assembly including a contact 1910 supported by an insulator 1930. The contact 1910 and the insulator 1930 can be disposed within a recess 1942 in an enclosure 1940 of the first electronic device 1902.

[0114] The second electronic device 1904 can include a contact assembly including contacts 1950 supported by insulators 1960. The contacts 1950 and insulators 1960 can be disposed within openings 1972 in an enclosure 1970 of the second electronic device 1904. The contacts 1950 and insulators 1960 can move to be disposed within recesses 1942 in the enclosure 1940 of the first electronic device when the contacts 1910 of the first electronic device 1902 mate with the contacts 1950 of the second electronic device 1904.

[0115] 20 shows further details of a contact assembly according to one embodiment of the invention. The contact assembly 2000 can include two contacts 1950, each supported by an insulator 1960. The insulator 1960 can be supported by a beam 2010. The beam 2010 can be driven by a spring 2030 such that the contacts 1950 can engage with the contact 1910 (shown in FIG. 19). The beam 2010 can be pushed down by an alignment portion 2020. The alignment portion 2020 can be aligned with a recess in the first electronic device 1902 (shown in FIG. 19), allowing the spring 2030 to push the contact 1950 into engagement with the contact 1910.

[0116] 21 illustrates a contact assembly for a contact interface according to one embodiment of the present invention. A first electronic device 2102 and a second electronic device 2104 can form an electronic system 2100. The first electronic device 2102 can include a contact assembly including a contact 2110 supported by an insulator 2130. The contact 2110 and the insulator 2130 can be disposed within a recess 2142 in an enclosure 2140 of the first electronic device 2102.

[0117] The second electronic device 2104 can include a contact assembly including contacts 2150 supported by insulators 2160. The contacts 2150 and insulators 2160 can be disposed within openings 2172 in an enclosure 2170 of the second electronic device 2104. The contacts 2150 and insulators 2160 can move to be disposed within recesses 2142 in the enclosure 2140 of the first electronic device when the contacts 1910 of the first electronic device 2102 mate with the contacts 1950 of the second electronic device 1904.

[0118] The contact 2150 can include two contact portions separated by an insulating portion 2162. The insulating portion 2162 can be a surface that can be exposed to wear to protect exposed areas of the contact 2150. Similar to the extension 1869 of the insulator 1864 (shown in FIG. 18C ), the insulating portion 2162 can engage the enclosure 2140 of the first electronic device 2102 and the contact 2110 as the first electronic device 2102 and the second electronic device 2104 move laterally across one another during mating.

[0119] FIG. 22 shows a cutaway side view of a contact assembly according to an embodiment of the present invention. The contact assembly 2200 can include a contact 2150 that can be supported by an insulator 2160. The contact 2150 and the insulator 2160 can be disposed within an opening 2172 in an enclosure 2170. The enclosure 2170 can cover a housing 2230. The housing 2230 can include a hole 2232 for the spring 2210. The spring 2210 can be compressed when the first electronic device 2102 and the second electronic device 2104 (both shown in FIG. 21) move laterally toward each other during mating. When the contact 2150 and the insulator 2160 are aligned with the recess 2142 in the enclosure 2140 (both shown in FIG. 21), the spring 2210 can press the contact 2150 into the contact 2110. Signals received and provided on the contact 2150 can be conveyed by the conductor 2220. The conductors 2220 may be insulated with insulators 2222 .

[0120] Embodiments of the present invention can incorporate various features to limit or reduce galvanic corrosion of contacts of electronic devices. For example, materials used for the contacts and housing can be selected to avoid differences in their galvanic voltages. Other DC voltages, such as DC offsets in AC waveforms used to transmit power, can be avoided or adjusted to cancel galvanic voltages between materials used. DC conduction paths can also be interrupted to limit electrochemical reactions that may lead to corrosion. An example is shown in the following figure.

[0121] 23 illustrates galvanic corrosion pathways in an electronic device according to an embodiment of the present invention. An electronic system 2300 can include a first electronic device 2302 and a second electronic device 2304. The first electronic device 2302 can be supplied with AC power via capacitors C1 and C2 and contacts 2310. The contacts 2310 can be insulated by an insulator 2320 and supported by a housing 2330.

[0122] In this example, an ion path may exist between the contacts 2310 and the housing 2330. For example, an ion path 2380 may exist between the contacts 2310. An ion path 2385 may exist between each contact 2310 and the housing 2330. The AC nature of the waveform delivered on the contacts 2310 may alternate quickly enough to limit any electrochemical reactions. However, the presence of DC current, whether based on galvanic voltage, an offset in the AC waveform, or otherwise, may cause electrochemical reactions that may lead to corrosion.

[0123] 10, DC blocking capacitor C1 and blocking capacitor C2 can be placed in series between the internal circuitry of the first electronic device 2302 and the contact 2310. Capacitor C1 and capacitor C2 can block DC current that could otherwise result in electrochemical reactions that could lead to corrosion.

[0124] These and other embodiments of the invention can further limit corrosion by further reducing the electric field between contacts 2310 and housing 2330. For example, the materials selected for contacts 2310, including any plating and materials for housing 2330, can be selected to reduce any galvanic voltage. As an example, contacts 2310 can be plated with gold, which has a galvanic voltage range of 0.07 to 0.2V, and the housing can be titanium, which has a galvanic voltage range of -0.12 to 0.04V.

[0125] These and other embodiments of the invention can further reduce the galvanic voltage difference by selecting a non-conductive material for the housing. For example, the second electronic device 2304 can include a contact 2340 supported by a housing 2360. The contact 2340 can be a metallic area formed or plated on the housing 2360. The housing 2360 can be a non-conductive material such as plastic, ceramic, or a combination of these or other materials.

[0126] Selection of a non-conductive material for the housing 2360 can reduce the ionic path to the path 2380 between the contacts 2340. As a result, only one capacitor, shown here as capacitor C3, may be required to block the DC current flowing through the path 2380. Using one capacitor is more likely in a powered device, and asymmetries caused by the lack of a second capacitor in the power supply device are not relevant.

[0127] In these and other embodiments of the invention, it may be desirable for the capacitors used, such as capacitor C1, capacitor C2, and capacitor C3, to fail open to prevent DC current paths from being formed. Thus, capacitors C1, C2, and C3 may be Y-capacitors that fail open.

[0128] Electrolytes are not always present in these and other types of electronic systems. Often, contact 2310 or other contacts are dry and free of liquid or other electrolytes. In such situations, power can be conserved by transferring power in a DC manner. For example, inverter / rectifier circuit 1030 and inverter / rectifier circuit 1040 (both shown in FIG. 10) can be bypassed. An example is shown in the following figure.

[0129] 24 illustrates optional DC charging in an electronic device according to an embodiment of the present invention. Electronic system 2400 can include a first electronic device 2402 and a second electronic device 2404. In first electronic device 2402, contacts 2410 can be insulated by insulator 2420 and supported by housing 2430. In second electronic device 2404, contacts 2440 can be supported by or plated on non-conductive housing 2460.

[0130] The first electronic device 2402 can provide AC power via capacitors C1 and C2 and contacts 2310. The first electronic device 2402 can provide DC power through a closed switch S1 that can bypass capacitor C1 and through a closed switch S2 that can bypass capacitor C2, thereby connecting contacts 2410 to a DC supply. Similarly, the second electronic device 2404 can receive power through capacitor C3 and can receive DC power by bypassing capacitor C3 with switch S3.

[0131] It may be desirable for switches S1, S2, and S3 to have very high open impedance to prevent DC leakage in the presence of electrolyte at contacts 2410 and 2440. Thus, embodiments of the invention may use micro-relays, micro-mechanical switches, or other types of switches. Also, note that many of the design considerations described herein may not provide contacts that are optimized for DC power transfer, and further compromises may need to be made.

[0132] Switches S1, S2, and S3 can each be controlled by the first electronic device 2402 or the second electronic device 2404. Switches S1 and S2 can be controlled by the first electronic device 2402 and switch S3 can be controlled by the second electronic device 2404, or the switches can be controlled by other circuits. For example, the first electronic device 2402 can determine that contacts 2410 and 2440 are not exposed to an electrolyte and can close switches S1, S2, and S3 before providing DC power. The second electronic device 2404 can determine that contacts 2410 and 2440 are not exposed to an electrolyte and can close switches S1, S2, and S3 before requesting DC power from the first electronic device 2402.

[0133] Again, embodiments of the present invention may take steps to reduce or cancel out DC fields or voltages at the contacts of electronic devices. These steps may reduce galvanic voltages as described above. They may also include reducing the DC offset of the AC waveforms used in transferring data. They may also include using a DC offset of the AC waveform to cancel out remaining galvanic voltages. They may also involve using a DC offset of an AC waveform that has been found empirically or otherwise to provide reduced corrosion. Examples of such waveforms are shown in the following figures.

[0134] FIG. 25 illustrates an AC waveform for power transfer according to one embodiment of the present invention. Waveform 2500 may have a low voltage V2, a high voltage V1, and an average voltage V0. Waveform 2500 may have a rise time from V0 to V1 of Tr1 and may remain at V1 for a time T1. Waveform 2500 may have a fall time from V1 to V0 of Tf1 and a fall time from V0 to V2 of Tf2. Waveform 2500 may remain at V2 for a time T2. Waveform 2500 may have a rise time from V2 to V0 of 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 amount of harmonics present in AC waveform 2500.

[0135] Some or all of these rise times, fall times, high and low levels, and other parameters may be adjustable. For example, the average voltage V0 may be varied. The average voltage V0 may be adjusted to be closer to zero to reduce any DC voltages generated by the differential AC waveform 2500. Alternatively, the average voltage V0 may be adjusted to a level that cancels or compensates for galvanic voltages present at the power transfer contacts. Alternatively, the average voltage V0 may be adjusted to a level that is known empirically or otherwise to reduce corrosion at the power transfer contacts. Examples of circuits and methods that may be used are shown in the following figures.

[0136] FIG. 26 illustrates a charging path through an electronic system according to one embodiment of the present invention. In this example, a first electronic device 2602 can provide power to a second electronic device 2604 in the electronic system 2600. A DC-DC converter 2610 can receive a DC input voltage DCIN, which can be a battery or other voltage. The DC-DC converter 2610 can set a high voltage V1 and a low voltage V2 (shown in FIG. 25) for an AC waveform provided from an inverter 2620 in the first electronic device 2602 to a rectifier 2630 in the second electronic device 2604. The rectifier 2630 can provide an output to a DC-DC converter 2640, which can provide an output voltage DCOUT.

[0137] In this example, voltages V1 and V2 may be programmable. Voltages V1 and V2 may be programmed such that the average voltage V0 (shown in FIG. 25) is close to zero to reduce any DC voltage produced by differential AC waveform 2500. Alternatively, V1 and V2 may be programmed such that the average voltage V0 may be adjusted to a level that offsets or compensates for galvanic voltages present at the power transfer contacts. V1 and V2 may instead be programmed to provide an average voltage V0 that is empirically or otherwise known to minimize corrosion.

[0138] In this example, voltage V1 and voltage V2 may be provided in an open loop manner. In these and other embodiments of the invention, voltage V1 and voltage V2 may be provided in a closed loop manner. An example is shown in the following figure.

[0139] FIG. 27 illustrates a charging path through an electronic system according to one embodiment of the present invention. In this example, a first electronic device 2602 can provide power to a second electronic device 2604 in the electronic system 2600. A DC-DC converter 2610 can receive a DC input voltage DCIN, which can be a battery or other voltage. The DC-DC converter 2610 can set a high voltage V1 and a low voltage V2 (shown in FIG. 25) for an AC waveform provided from an inverter 2620 in the first electronic device 2602 to a rectifier 2630 in the second electronic device 2604. The rectifier 2630 can provide an output to a DC-DC converter 2640, which can provide an output voltage DCOUT.

[0140] In this example, the voltages V1 and V2 may be adjusted by a feedback path including a correction circuit 2710 in the first electronic device 2602. The voltages V1 and V2 at the power transfer contacts of the inverter 2620 may be detected and provided to the correction circuit 2710. The voltages V1 and V2 may be adjusted by the correction circuit 2710 so that the average voltage V0 (shown in FIG. 25) is close to zero, reducing any DC voltages generated by the differential AC waveform 2500. Alternatively, V1 and V2 may be adjusted by the correction circuit 2710 so that the average voltage V0 may be adjusted to a level that cancels or compensates for the galvanic voltages present at the power transfer contacts. Alternatively, V1 and V2 may be adjusted by the correction circuit 2710 to provide an average voltage V0 that is empirically or otherwise known 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.

[0141] FIG. 28 illustrates a charging path through an electronic system according to one embodiment of the present invention. In this example, a first electronic device 2602 can provide power to a second electronic device 2604 in the electronic system 2600. A DC-DC converter 2610 can receive a DC input voltage DCIN, which can be a battery or other voltage. The DC-DC converter 2610 can set a high voltage V1 and a low voltage V2 (shown in FIG. 25) for an AC waveform provided from an inverter 2620 in the first electronic device 2602 to a rectifier 2630 in the second electronic device 2604. The rectifier 2630 can provide an output to a DC-DC converter 2640, which can provide an output voltage DCOUT.

[0142] In this example, the voltages V1 and V2 may be adjusted by a feedback path that includes the receiver detection circuit 2810 in the second electronic device 2604 and the adjustment circuit 2820 in the first electronic device 2602. This can be done in a variety of ways. In one example, the voltages V1 and V2 at the power receiving contacts of the rectifier 2630 may be detected by the receiver detection circuit 2810. This information may be communicated to the adjustment circuit 2820. The voltages V1 and V2 may be adjusted by the adjustment circuit 2820 such that the average voltage V0 (shown in FIG. 25) is close to zero to reduce any DC voltages generated by the differential AC waveform 2500 (shown in FIG. 25). In another example, the receiver detection circuit 2810 may determine the adjustments to be made and provide that information to the adjustment circuit 2820. Alternatively, V1 and V2 may be adjusted by the adjustment circuit 2820 such that the average voltage V0 may be adjusted to a level that offsets or compensates for the galvanic voltages present at the power transfer contacts. Alternatively, V1 and V2 may be regulated by a regulation circuit 2820 to provide an average voltage V0 that is empirically or otherwise known to minimize corrosion. The receiver and detector circuit 2810 may communicate with the regulation circuit 2820 through the power transfer contacts by transmitting an AC signal at a different frequency compared to the AC waveform 2500. The receiver and detector circuit 2810 may communicate with the regulation circuit 2820 through other wired, wireless, or other types of communication channels.

[0143] In these and other embodiments of the 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 receive and detect circuitry 2810 in the second electronic device 2604 and the conditioning circuitry 2820 in the first electronic device 2602 in conditioning the AC waveform provided by the first electronic device 2602 to the second electronic device 2604.

[0144] Data may be transferred between the first electronic device 2602 and the second electronic device 2604 using an AC waveform. The frequency, phase, amplitude, or other characteristics of the AC waveform may be modulated to convey the data. Other signals at other frequencies may be combined with the AC waveform using diplexers, common mode chokes, or other circuits. The data may be transmitted in the same direction as the direction of power transmission, or power and data may be transmitted in different directions.

[0145] Various aspects of the differential AC waveform 2500 can be modified or adjusted based on the contact material, the housing material, the presence or absence of electrolyte, and the type of electrolyte if any is present. An example of a method for determining the type of material used for the contacts is shown in the following figure.

[0146] 29 illustrates data that may be used by a method for determining the type of material used in a contact, according to an embodiment of the present invention. In this example, electrochemical impedance spectroscopy (EIS) curves are pre-generated for different materials in the absence of electrolyte. The electronic device can perform similar measurements immediately after connection between the two electronic devices, when electrolyte is likely not present. These measurements can be performed at these and other times when it is determined that no electrolyte is present.

[0147] The EIS curve measured by the electronic device can reflect the parallel combination of the contacts in the measurement device and the contacts of the mating device. The contacts in the measurement device can be known and stored during manufacturing. Using the measured EIS curve and the known measurement device material, the contribution to the EIS curve by the parallel mated device contacts can be extrapolated. The extrapolated EIS curve of the mated device contacts can be compared to a previously measured curve such as the one in this figure. From this, the material of the mated device contacts can be determined. These and other embodiments of the invention do not have to generate the entire curve. Instead, data points at a few specific frequencies can be used.

[0148] FIG. 30 illustrates a method of optimizing a charging waveform according to an embodiment of the present invention. In operation 3010 of method 3000, once a connection is made, the first device can use EIS to determine the contact material of the second device. Such a method is outlined in FIG. 29 above. Instead of using EIS, the first device can receive information about the contact material directly from the second device in act 3020. The first device can gather other information during use. This information can include environmental and other information. For example, the first device can receive EIS updates, depth, and other information from other sensors in operation 3030. In operation 3040, an optimized charging waveform can be determined. This charging waveform can be provided to the contacts of the first device for receipt by the contacts of the second device in operation 3050.

[0149] Embodiments of the present invention may provide power transmission circuits and apparatus that may be located within 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, power supplies, video distribution systems, adapters, remote control devices, chargers, and other devices.

[0150] Reference numbers are used consistently herein among the various figures.

[0151] It is understood that use of personally identifiable information should comply with privacy policies and practices generally recognized as meeting or exceeding industry or governmental requirements for maintaining user privacy. In particular, personally identifiable information data should be managed and handled in a manner that minimizes the risk of unintended or unauthorized access or use, and the nature of permitted uses should be clearly indicated to users.

[0152] The above description of the embodiments of the present 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 described, as many modifications and variations are possible in light of the above teachings. The embodiments have been chosen and described to best explain the principles of the invention and its practical application, thereby enabling others skilled in the art to best utilize the invention in various embodiments, and with various modifications as may be suitable for the particular use contemplated. It will therefore be understood that the present invention is intended to cover all modifications and equivalents within the scope of the following claims.

Claims

1. 1. A method of providing power from a first electronic device to a second electronic device, comprising: determining one or more environmental parameters using the first electronic device; using the one or more environmental parameters to optimize an AC charging waveform; providing the optimized AC charging waveform to the second electronic device.

2. The method of claim 1 , wherein the one or more environmental parameters include a presence of an electrolyte.

3. 3. The method of claim 2, wherein the AC charging waveform is optimized in part by adjusting an average of the AC charging waveform to compensate for a galvanic voltage of the first electronic device.

4. 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. 1. A power transmission circuit, comprising: A battery; a switch coupled to the battery; a boost / buck circuit coupled to the switch; an inverter / rectifier circuit coupled to the boost / buck circuit; a first capacitor coupled to a first output of the inverter / rectifier circuit; a second capacitor coupled to a second output of the inverter / rectifier circuit; a first contact coupled to the first capacitor; 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 transfer circuit of claim 6 , wherein the first contact and the second contact each comprise two stacks of Belleville washers.

10. The power transfer circuit of claim 5 , wherein the first contact and the second contact are fixed contacts.

11. 6. The power delivery circuit of claim 5, wherein the switch is configured to disconnect the battery from the boost / buck circuit when the power delivery circuit is not transmitting or receiving power.

12. 12. The power transfer circuit of claim 11, wherein the boost / buck circuit increases a voltage from the battery and provides a high voltage and a low voltage when the power transfer circuit is transferring power.

13. 13. The power transfer circuit of claim 12, wherein the boost / buck circuit reduces a voltage from an inverter / rectifier and provides a charging voltage for the battery when the power transfer circuit is receiving power.

14. 14. The power transfer circuit of claim 13, wherein the inverter / rectifier circuit converts the high voltage and the low voltage from a boost / buck circuit into a differential output signal when the power transfer circuit is transferring power.

15. The power transfer circuit of claim 14 , wherein the inverter / rectifier circuit rectifies a differential output signal when the power transfer circuit is receiving power.

16. The power delivery circuit of claim 15 , wherein the differential output signal comprises two anti-phase sine waves.

17. The power delivery circuit of claim 15 , wherein the differential output signal comprises two anti-phase square waves.

18. The power delivery circuit of claim 15 , wherein the differential output signal comprises two bandwidth limited antiphase square waves.

19. 1. A power delivery circuit for generating a differential output signal, 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; and a first contact coupled to the first capacitor; a second contact coupled to the second capacitor.

20. 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, and two anti-phase sine waves.

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