Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
  • H02J7/0042—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries characterised by the mechanical construction
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
  • H02J7/02—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries for charging batteries from ac mains by converters
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries

Definitions

• the present invention relates to electronic systems and methods for providing electrical power and/or data to one or more electronic or electrically powered devices with a power delivery surface.
• a variety of electronic or electrically powered devices such as toys, game devices, cell phones, laptop computers, cameras, and personal digital assistants, have been developed along with ways for powering them.
• Mobile electronic devices typically include batteries which are rechargeable by connecting them through power cord units, which include transformers and/or power converters, to a power source, such as an electric wall outlet or power grid.
• a non-mobile electronic device is generally one that is powered through a power cord unit and is not intended to be moved during use.
• the power cord unit includes an outlet connector for connecting it to the power source and a battery connector for connecting it to a corresponding battery power receptacle of the battery.
• the outlet and battery connectors are in communication with each other so electrical signals flow between them. In this way, the power source charges the battery through the power cord unit.
• the power cord unit may include a power adapter, transformer, or converter connected to the outlet and battery connectors through AC input and DC output cords, respectively.
• the power adapter adapts an AC input voltage received from the power source through the outlet connector and AC input cord to output a DC voltage through the DC output cord.
• the DC output current flows through the receptacle and is used to charge the battery.
• FIG. 1 is a perspective view of a charging pad, in accordance with the invention, which includes a power delivery support structure and an enabled device to be charged.
• FIG. 2 is an isometric view of the charging pad of FIG. 1, showing an array of alternately positively and negatively charged contact strips.
• FIG. 3 is a bottom plan view of an enabled device of the invention.
• FIG. 4 is a top plan view of a portion of the charging pad of FIG. 1, depicting how several enabled devices are arranged in various orientations for charging on the pad.
• FIG. 5 is a block diagram of the charging system of FIG. 1.
• FIG. 6 is a top plan view of a representative example wireless charging pad of the invention.
• FIG. 7 is a top plan view of several conductive strips of the charging pad of FIG. 1.
• FIG. 8 is a diagram showing the "tetrahedron" arrangement of the four contact points of an enabled device, in accordance with the invention.
• FIG. 9 is a diagram showing the angular orientation of the contact points of the tetrahedron arrangement of FIG. 8.
• FIG. 10 is a bottom plan view of an enabled device of the invention.
• FIG. 11 is a cut-away side view of along line 11-11 of Figure 10.
• FIG. 12 is a bottom plan view of an enabled device showing the approximate location of magnets shown in phantom lines.
• FIG. 13 is a cut-away side view of a mounted magnet along line 13-13 of Figure 12, showing example approximate dimensions of a magnet embedded in the casing of an enabled device.
• FIG. 14 is a schematic diagram of a four- way bridge rectifier, in accordance with the invention.
• FIG. 15 is a schematic diagram of a four-way bridge rectifier, showing the addition of a pass diode.
• FIG. 16 is a schematic diagram of the four- way bridge rectifier of FIG. 14, showing an alternate configuration of the active rectifier.
• FIG. 17 is a schematic diagram of an aftermarket device enablement.
• FIG. 18 is a schematic diagram of a built-in handset enablement.
• FIG. 19 is a schematic diagram of a single leg of a bridge rectifier.
• FIG. 20 is a schematic diagram of a single active rectifier based on an N-channel
• FIG. 21 is a graph showing the transfer function of the control circuit of the present invention.
• FIG. 22 is a schematic diagram of a squelching regulator used to drive the supply voltage to the active rectifier of the present invention.
• FIG. 23 is a schematic diagram of the power conditioning circuit used to receive power from the power delivery surface of the present invention.
• FIG. 24 shows a perspective view of a constellation module of the present invention embedded in a shell-type housing.
• FIG. 25 A is a top view of the constellation module of the present invention, showing example dimensions.
• FIG. 25B is a bottom view of the constellation module of the present invention showing the arrangement of the contact points.
• FIG. 26 is a perspective view of the two halves of a gel case for enclosing the constellation module of the present invention.
• FIG. 27 is a perspective view of a constellation module showing the wireless power connection assembly.
• FIG. 28 is a perspective view of a constellation module showing the gel case and the wireless power assembly.
• FIG. 29A is a cut-away view of an example gel case structure and mounting of the constellation module.
• FIG. 29B is an enlarged cross-section of a portion of the cut-away side view of FIG.
• FIG. 30 is a perspective view of an example power connection assembly, in which the flexible circuit carrier and strain relief are a single unit.
• FIG. 31 is a perspective view of an example connection assembly showing the connection between the flexible circuit carrier and the constellation module.
• FIG. 32 and FIG 33 are schematic diagrams that illustrate example circuits for implementing the control and safety system of the invention.
• FIG. 1 An example charging pad 10 and charging pad-enabled device 20 are shown in Figure 1.
• the charging pad 10 transfers power wirelessly, i.e., without a charging adapter cord, to one or more devices 20 resting on it.
• wireless wireless
• wirelesslessly are used to indicate that charging of the device is achieved without a cord-type electric charging unit or adapter, and in the example, is achieved with through electrical conduction through contacts with selective geometry, as described below.
• Wireless in this context does not mean electromagnetic radiation without electrical conductors.
• the term “enabled” device is used for convenience to mean an electronic or electrically powered device, for example, cell phone, computer, radio, camera, personal digital assistant, digital recorder and playback device, hearing aid, GPS receiver or transmitter, medical instrument, or just about any other portable device, that is equipped with charging contacts and associated electronic circuitry to enable the device to be electrically charged by the power pad 10 component.
• the top surface of charging pad 10 contains an array 12 of contact strips 14, 16 which are energized with low voltage DC so that every other strip, e.g., the strips 14, are positive and the strips 16 in-between the positive strips 14 are negative, as shown in Figure 2.
• On the underside 22 of the enabled device 20 there are four contact points 26 arranged in a "constellation" configuration 24 as shown in Figure 3.
• the contact constellation 24 on the enabled device 20 and the contact strip array 12 on the charging pad 10 form a geometrically complementary pair with the property that electrical power can be transferred from the pad 10 into the device 20 regardless of the position and orientation of each particular device 20 on the pad.
• Several orientations are shown for example in Figure 4 to illustrate this principle, but they are not the only orientations that work.
• the pad voltage is fixed and independent of the devices 20 resting on the pad surface 18.
• Each individual device 20 on the pad 10 is responsible for conditioning the electric power from the pad 10 to power that is appropriate for use.
• This scheme inherently allows for multiple devices 20 of various manufacturers with various power requirements to be charged from the same pad 10.
• each enabled device 20 contains a pickup constellation 24, a rectifier 28, and a power conditioning circuit
• a control and safety system 29 renders the contact array 12 benign and safe to the user.
• the control and safety system 29 energizes the array 12 only when a compliant load is detected.
• the system 29 senses the presence of non-enabled devices such as keys or hands and instantly safely shuts down.
• the control and safety system 29 also has a spark suppression feature.
• a metallic object such as a set of keys
• a spark could cause pitting in the metal, it could be a safety hazard, or it could be startling to a user who might then assume the surface electrodes are dangerous.
• FIGs 32 and 33 illustrate example circuits for implementing the control and safety system 29.
• a spark is the result of very high current.
• the bandwidth of the outer feedback loop is very high, but not high enough to prevent the genesis of a spark during the first few tens of nanoseconds of a short circuit event. Once the spark is initiated and the spark gap floods with ions, the spark becomes easier to sustain. It is important that the circuit prevent even the genesis of the spark.
• This technique uses the inductor Ll in the source lead of the MOSFET Ql .
• the current attempts to rise very rapidly.
• a voltage is induced across the inductor that opposes the gate drive and turns off the MOSFET Ql . This reaction is fast enough to prevent the initial spark genesis, but cannot alone maintain spark suppression.
• Transistor Q5, and associated components R7, R14, R16, and Zl detects when the system has gone into current limit and reports this condition to the microcontroller. The microcontroller responds when appropriate to remove drive from the MOSFET Ql. In this way, an unexpected short results in momentary current limit followed by shutdown.
• Reduced Output Capacitance The first spark suppression technique is to reduce the capacitance being presented across the surface electrodes. Stray capacitance is unavoidable, but also discrete capacitors are not used directly across the surface electrodes. Capacitors store energy, and when shorted, they deliver high current to dissipate the energy quickly. The size of the resulting spark is related to the amount of energy stored in the capacitance.
• a spark is non-linear in the sense that it is easier to sustain a spark than to start one. In other words, the same conditions that sustain a spark may not be sufficient to start a spark. Therefore it is desirable to prevent the initiation of the spark.
• Capacitance in parallel with Rl 9 will act to initiate a spark where a shorting piece of metal bridges across two adjacent contact strips.
• Current Limit Another spark suppression technique is to limit the current in the circuit.
• R2, Ul, Q2, Q3, and Q4 form a high bandwidth current limit circuit. When the current is sufficiently below the current limit, Ul is off and Q4 acts as a switch either supplying or removing drive from the MOSFET Ql . However, when the output current exceeds a predetermined value, Ul begins to conduct acting as an amplifier.
• the collector of UlA drives the current source created by Q4.
• the current source created by Q4 has a high equivalent resistance and so the gain of Ul A is high.
• the collector output is coupled to the gate of MOSFET Ql through a unity gain buffer formed by Q2 and Q3. This feedback loop maintains the output current below a predetermined value.
• Rapid Shutdown A further spark suppression feature is rapid shutdown of the system.
• the microcontroller upon detecting the signal from Q5 indicating current limiting is occurring, can remove drive to Q4, which in turn will remove gate drive from MOSFET Ql .
• Free positioning means that a mobile device can rest anywhere and at any orientation on the charging pad surface and receive full, uninterrupted power. There is no need for the user to orient or position the device in a specific way in order to receive power. [0061]
• the charging system inherently allows many devices of differing power needs to rest on and receive power from the pad at the same time.
• the wireless power technology of the system makes powering and charging a device simple. A user can effortlessly set a device on the pad without any particular thought or effort as to orientation or hook-up to fully power and charge the device.
• the charging system is a universal power interface meaning that different mobile devices can share the same power source. This greatly simplifies the lives of users who typically have several mobile electronic devices, each with their own AC adapter.
• Having a universal power source that is so easy to use results in the system being accessed more frequently. This, in turn, means users experience their batteries being more fully charged. Users can use more power-hungry features of their devices given the more frequent charging that naturally occurs.
• the charging system also eliminates the tangle and clutter of the multitude of wires needed to power and charge the number and variety of devices many users typically have. [0067]
• the charging system eliminates the need for a plethora of AC adapters - one for each mobile device. Instead, just one charging pad can supply the power needs of many mobile devices.
• the charging system is also capable of economically bringing the convenience of wireless power to higher power devices such as laptop computers, lamps, portable televisions, razors, hair care devices, power tools, and many others as well.
• the present invention eliminates the array of separate AC adapters that a typical consumer needs to power and charge all their devices. With the charging pad 10 available, the AC adapters that now come with the purchase of almost every new device, even of the same type, are no longer needed. In a typical home several of these adapters can be found plugged in, but not in use, wasting energy.
• Pads with multiple power handling capabilities exist simultaneously. For example, there may be three power capabilities present throughout the infrastructure: 15 W pads, 65 W pads, and 120W pads.
• many enabled devices such as cell phones, cameras, laptops, medical equipment, power tools, etc., exist covering a broad range of power input needs from IW to 120W.
• All of these different requirements may be transparent to the users. Any number of devices can be placed on and charged by any given pad, provided that the total power requirement does not exceed the rating of the pad. This means, for example, that one can operate his or her laptop computer on a pad while also charging a cell phone and powering an enabled coffee mug on the same pad.
• a device 20 can be enabled to determine the power handling capacity of the pad it is resting on. Power management occurs in three tiers within the specification and may be characterized or keyed by output voltage and/or digital communications, for example:
• Tier 1 power pads may be designed primarily for charging multiple low power hand held devices. Typically these devices consume 2-5 W. In this case, power management is inherent to the surface area of the pad.
• a typical cell phone occupies about 8in 2 of pad area, and consumes about 3 W of power or about 0.38W/in 2 .
• a 15W may have about 38 in 2 of active area, which corresponds to approximately 14.4W of cell phone usage.
• Tier 2 power pads may be designed for one medium device and numerous smaller devices as in a travel application.
• a single laptop could be charged or used along with perhaps a cell phone and music player.
• power management may correspond or be provided by a purposely limited charging surface area, given the assumption that only one laptop or other such larger device can fit in the given area.
• Digital power management is optional but not mandatory in this tier and can be included for product differentiation (good/better/best).
• Tier 3 power pads may be designed for multiple high-power devices. In this case an unknown number of high power devices may be present and the surface area is not likely to limit usage in a predictable way. This would be the case, for example, in a conference room application or coffee shop table situation where one large pad may cover most of the surface area of a table or where multiple power tools of widely varying sizes may be used. In this case, digital power management is recommended.
• a digital communication scheme optionally provides digital power management communications between the pad and each device in tier 2 and tier 3.
• Tier 1 applications offer the most straightforward and cost effective implementations. It is convenient that they also comprise the largest fraction of consumer applications.
• Voltage discrimination is used as a straightforward method of distinguishing the first level of power management. For example, a laptop computer requiring 85W would not need to engage the pad 10 if it did not detect at least 19.5V on the pad. Likewise a 4OW desk lamp could enable only if the pad voltage detected was 19.5V or greater.
• a low power device (less than 5W), on the other hand, can be made to work on a pad 10 from any of the three tiers.
• This method of power management can handle a large number of cases comprising the largest usage model while keeping the system complexity and cost down.
• Digital power management becomes more important for pads 10 that can supply a larger amount of power and/or have a greater area. In this case communications are established between the device and the pad. The device and pad then share information such that devices throttle back or turn off to prevent attempting to draw more power than the pad can supply. Digital power management is beyond the scope of this document and will not be discussed further herein.
• the pad 10 may also employ an LED, power meter, LCD screen, or other type of user display to indicate that an overload condition is present.
• Charging pads 10 provide a surface of conductive strips of specified width and array spacing to mate with the standard pickup or contact geometry, e.g., the constellation shown in
• Figures 3 and 4 see below.
• the overall size and shape of a pad 10 can vary, but the width and spacing of the strips 14, 16 must remain the same in order to deliver power to a particular contact 26 arrangement and size.
• charging pads 10 of many styles and power handling capabilities exist to support an array or variety of mobile devices 20.
• each mobile device 20 uses a pattern of contacts designed to compliment the same basic surface electrode geometry.
• every pad 10 uses identical surface electrode dimensions and geometry. The electrical characteristics of both the surface electrodes and the mobile device enablement ensure the maximum interoperability and predictable fault tolerance across a broad spectrum of applications.
• the dimensions A, B of an active surface may vary depending on the length and number of strips in the particular design. However, for a particular set of pads 10, it is desirable that every charging surface will maintain the same specified width and spacing of the strips in order to interface with a particular constellation pattern and size of contacts 26 used on a group of various mobile devices 20.
• the surface 11 of the charging pad 10 comprises conductive strips 12 arranged parallel to one-another in an array with a specific width and spacing.
• the standard dimensions of the metal strips are as shown in Figure 7.
• the width B of the active area in an example implementation is given by:
• the array spacing used in this example is 0.48125", which is the exact value of the example design.
• the overall surface 11 of the charging pad 10 is preferably smooth and flat or have a gentle curve over all of the strips 14, 16 and intermediate spacings between them to insure that the enabled device 20 seats properly when resting on the surface 11, regardless of where any of the particular contacts 26 may land on the surface 11.
• the performance is more sensitive to ridges or steps rather than an overall smooth curvature of the surface 11. For this reason, it may be desirable to take care that the surface 11 does not have a significant step between the surface of each strip 12 and the surface of the gaps between the strips 12.
• Polished stainless steel strips with a bright nickel plate make good example strips 14, 16.
• the 430 stainless steel is used to ensure high product durability and corrosion resistance.
• the nickel plate ensures reliable electrical contact performance over time as well as a mirror- like finish.
• the 430 stainless steel strips are 0.015" thick to provide adequate conductivity at the rated power of 15 W.
• This metal is also ferromagnetic, and at this thickness allows the magnets 42 ( Figures 12 and 13) in the enablements to pull the device 20 firmly to the surface 11 of the pad 10.
• Other materials may be used to achieve conductivity, contact reliability, and magnetic attraction, as would be known to persons skilled in the art, once they understand the principles of this invention.
• the backing material used in the pad 10 is non- conductive and may take various forms, such as an engineered thermoplastic, for example.
• the contact strips 12 are energized with low voltage DC. Depending on the application, the DC voltage can range in one example from 1 IV to 19.5V. The polarity of the voltage is positive on every other strip 14 and negative on the strips 16 in-between (see Figures 2 and 7). The negative potential is defined as ground (OV), although is not necessarily connected to Earth ground.
• OV ground
• the DC voltage may occasionally be interrupted for a brief period (lO ⁇ s). For this reason, it may be advantageous for the pickup electronics to use a capacitor to store energy during this interval to avoid causing a drop-out in the supply of power to the target device 20.
• the system controller supplies power to the contact strips when appropriate and senses fault conditions.
• the system controller provides the following functions:
• the constellation geometry and the surface contact geometry form a matched pair to provide power transfer at any orientation of the constellation or device 20 with respect to the pad 10.
• the scope of this document will be limited to one such constellation, loosely referred to as the "tetrahedron” for its resemblance to the top plan view of a tetrahedron.
• the "tetrahedron" constellation 24 configuration of contacts 26 is shown in Figure 8.
• charging pads 10 of many styles and power handling capabilities may exist to support an array of mobile devices 20. Any mobile device 20 may be placed on any subject charging pad 10. To facilitate this, each mobile device 20 uses the same size and pattern of contacts 26. (Note that other patterns can be used. Nevertheless, the point remains that all patterns are designed to compliment one standard geometry and dimension of surface electrodes). In addition, each mobile device 20 contains circuitry to appropriately handle a range of input voltages from an array of compliant power delivery surfaces (pads). [0100] Figure 9 shows the relationship of the four contact points comprising the constellation 24. The dimension R in this example is 0.385".
• FIG. 10 An example contact stack of each contact point 26 is shown in Figures 10 and 11.
• a ball bearing 32 is resting in contact with a metal strip 12 of the pad 10.
• the housing 38 of the enabled device 20 is being held to the pad 10 by magnets 42 ( Figures 12 and 13) pulling the printed circuit board 36 to the surface 44 of the metal contact strip 12.
• a backing on or portion of the printed circuit board 36 makes contact with the spring 34 and creates the opposing force pressing the ball 32 onto the surface 44 of the metal contact strip 12.
• the contacts 26 meet the surface 44 at a point or nearly a point. It is also required that the contact 26 does not bridge the distance between strips (e.g., 0.077") to prevent a short circuit between the strips 14, 16.
• the contacts 26 can be spherical, as shown in Figure 11. It has been found that 2mm ball bearings are an excellent choice for their durability and low cost.
• the housing 38 of the device 20 should hold the contact ball 32 so that it protrudes slightly, for example, about 0.020" proud of the bottom surface 46 of the housing 38 when the device 20 is not resting on a charging pad 10. This example protrusion dimension has been found to be sufficient to allow contact in the presence of reasonable debris on the surface of the pad 10.
• the exit hole 48 of the housing 38 should be round and held to a reasonable tolerance so that when the ball bearing 32 is seated, it forms a seal to prevent contaminants from entering the housing 38.
• the contact balls 32 are brought in contact with the surface 46 with conical springs 34.
• the springs 34 carry the current between the ball bearing 32 and the printed circuit board 36.
• the springs 34 are conical to allow them to collapse on themselves to keep the overall stack size as small as possible.
• Nickel plated beryllium-copper is a suitable material for the springs 34, although other electrically conductive materials can also be used. The nickel plating provides excellent contact performance, while the beryllium-copper works well for springs yet is not magnetic (important for assembly when magnets are present).
• the contact pads 50 on the printed circuit board 36 carry the current picked up by the ball 32.
• the spring 34 need not be soldered to the contact pad 50, rather the pad 50 and spring 34 can connect through direct contact. It is recommended that the printed circuit board pads 50 be ENIG plated (Electroless Nickel Immersion Gold) for reliability.
• the contact constellation 24 rest squarely on the pad surface 18.
• the frame holding the contact constellation 24 should be rigid so that it does not distort under the pressure of the presumed magnetic force. Distortion of the material translates to rocking motion of the device 20 depending on the design.
• the contacts 26 may be nickel plated with a layer at least 50 microinches thick. This will provide the good reliability and low contact resistance over the life of the product.
• Spring exertion of a force of a contact 26 on the surface 11 of at least 3oz. is usually sufficient to insure reliable contact performance over the life of the product. Given that there are four contacts 26 in the constellation pattern, this means the total force is 12oz. For small devices, gravity alone may not be sufficient and magnets, for example, the magnets 42, as shown in Figures 12 and 13, may have to be employed.
• the weight of the target device 20 may be sufficient to allow generating at least 3 oz. of force on each contact. If the target device 20 is just over the required 12 oz., then it may be helpful to align the center of the "tetrahedron" with the device's center of gravity to prevent rocking or tipping. [0111] For target devices 20 weighing much more than 12 oz., aligning the center of gravity with the center of the "tetrahedron" is much less important.
• Figure 12 shows a typical application designed to achieve sufficient contact force.
• magnets 42 are employed to augment the contact force to attain the minimum recommended level of 3 oz. per contact ball 32.
• the attractive force of the magnet 42 can also be exploited to stabilize a mobile device 20 in automotive applications. Devices can be made to support their own weight and cling to a vertical surface, such as a refrigerator door, or to a pad 10 mounted with its surface 11 oriented vertically or at any angle from horizontal.
• Note that the exact position of the magnets 42 on the bottom surface 22 of the device 20 is not critical, but the attractive force transmits through the enclosure to create force on the springs 34. It is also desirable that the face in contact with the pad surface 18 does not distort due to the force exerted by the magnets 42.
• the phantom-lined circles indicate example locations of three magnets 42 retained by the plastic cover 52 of the device 20.
• Three neodymium magnets 0.25" in diameter and 0.062" thick can provide the necessary magnetic attraction to the ferromagnetic contact strips 12 of the charging pad 10, although other materials and magnets can be used.
• the cover 52 itself could comprise a composite magnetic material.
• the neodymium magnets used in one embodiment of the invention create a magnetic field that can affect the operation of certain electronic components such as inductors, audio speakers, motors, and magnetic disk drives. Care should be taken to insure that the magnets are separated from such devices, or that the devices are functioning properly in the presence of the magnets.
• Another option is to use more magnets. More magnets will increase the force without increasing the peak field strength. It is the peak field strength that is potentially damaging to such things as credit card magnetic stripes. Most hand-held devices can be easily attached to a refrigerator door with 4 or 5 magnets of the type as shown above.
• the contact points 26 of the constellation 24 come in electrical contact with the parallel contact strips 12 of the charging pad 10.
• the geometries insure that at least one constellation contact point 26 will come in contact with a positive pad contact strip 14, and another constellation contact point 26 will come in contact with a negative pad contact strip 16.
• constellation contact point 26 will be positive, and which will be negative. Further, multiple constellation contacts 26 could come in contact with a given polarity contact strip.
• a four-way bridge rectifier 28 as shown in Figure 14 is used to commutate the constellation contacts appropriately to positive and negative rails. Schottky diodes may be used in the rectifier for good efficiency, but other kinds of diodes can be used.
• Figure 14 also shows a resister R and capacitor C which will be discussed in further detail below.
• the diodes 56 should be sized to adequately handle the rated current over all input voltage conditions. In a typical cell phone application, the maximum input power is approximately 2.5W.
• the control and safety circuit 29 detects enabled devices 20 and activates the charging pad 10.
• the rectifier 28 may need a resistor R across the output of the rectifier 28.
• the value of this resistor may be, for example, about 1OK ohms for good operation.
• the output of the bridge rectifier 28 of Figure 14 may be back- biased by the circuit it is powering. What is meant by this is that when the device 20 is not resting on the charging pad 10, the voltage across resistor R is not zero. [0126] This situation is problematic for two reasons. Firstly, battery current will flow through the 1OK resistor reducing battery life. Secondly, back bias will prevent the start circuit from properly detecting the device 20 on the pad 10.
• the first example is by the addition of a pass diode 54 as shown in Figure 15.
• This simple solution has the disadvantage that the efficiency is degraded by the additional loss of the pass diode 54.
• the additional loss may be on the order of 9OmW.
• the second example technique is shown in Figure 16.
• a separate rectifier is used for compatibility with the start circuitry, yet no additional loss is inserted in the circuit.
• the additional diodes used can be sized for very low current as they are not involved in power transfer.
• the capacitor C2 is required and should be a value of 2.2nF.
• P is the maximum power required by the device, and l ⁇ F/W ⁇ K ⁇ 150 ⁇ F/W.
• a good value for K is about 5 ⁇ F/W corresponding to a maximum droop of about 18OmV.
• a startup delay may be beneficial in each enablement to allow the pad voltage to stabilize at the nominal value before full power is delivered.
• the startup delay may be, for example, 100ms or longer.
• the turn-on delay spec should be met even after a short, for example, three second, loss of power.
• FIG. 17 and 18 represent typical implementations of receivers for picking up power from a pad 10.
• An example aftermarket device enablement schematic generating 5V at IA is shown in Figure 17.
• Tl , T2, T3, and T4 are the contact point connections. The input from the contact points is rectified and filtered before being input into the switching regulator IC.
• Zl, R4, R5, and C3 form the turn-on delay circuit.
• D5 ensures the turn-on delay circuit resets quickly in case the power drops out momentarily.
• Ll 5 DI l, and C6 form the buck output circuit for the LM2734. This implementation assumes the target device operates from 5 V DC at up to IA.
• FIG. 18 An example built-in handset enablement is shown in Figure 18.
• the contact points are connected to the input of a bridge rectifier.
• the handset design-in implementation assumes that the input circuitry of the handset is capable of handling up to 20V DC. If that were not the case, a regulator as shown in the aftermarket device enablement schematic ( Figure 17) could be employed.
• the current requirement is very high.
• a 20V pad 10 is delivering power to a 100 Watt laptop computer.
• the current drawn would be 5 Amps.
• a commercially available Schottkey diode rated at 5A has a forward voltage drop of about 0.55V. At least two such diodes would have to conduct for there to be a closed circuit. In this case, the two diodes dissipate 5.5 W, which is a relatively high loss resulting in possible cooling problems.
• Figure 19 shows a single leg of an example bridge rectifier with two active diode based FET switches and polarity detectors.
• Figure 20 shows an example single active rectifier based on an N-Channel MOSFET.
• UlA and UlB form a difference amplifier comparing the input voltage Vin (the drain of Q2) to ground.
• Each base is tied to diodes U3 to stand off the voltage Vin when the active diode is reverse biased (Vin positive).
• U2A and U2B further amplify the difference signal as a current mirror.
• the output of the difference amplifier is at the collector junction of UlB and U2B.
• the difference amplifier output drives inverting transistor switch Ql which drives the N-Channel MOSFET.
• the overall operation of this example active rectifier is as follows. Positive voltages
• a negative voltage on the input Vin will turn on UlA and turn off UlB.
• the increased current at the collector of UlA will be reflected through the current mirror U2 to the collector of U2B.
• Base drive to Ql will be off, and the voltage at the collector of Ql will be high, turning on MOSFET Q2. Therefore, current will flow through the drain and source ofQ2.
• the active rectifier control circuit performs the function of a high gain amplifier.
• this configuration is ideally suited to drive the MOSFET as an active diode.
• the control circuit monitors the voltage across the MOSFET Drain and Source. If the voltage is positive (for the N-Channel active diode), then gate drive is removed. If the voltage is negative, then full gate drive is commanded. When at zero volts, the gate drive should be off. This prevents a lock-up that can occur if there is a slight offset in the system. If an undesirable offset is present, then the device may stay on with positive voltage. If the device stays on, then it will hold the voltage low, which will maintain the device in a locked condition. [0141] The control circuit has an input imbalance as part of current mirror intrinsic asymmetry. This is taken advantage of to create a unique and simple design topology. The asymmetry of the current mirror is further exaggerated by R2.
• FIG. 20 The schematic of Figure 20 shows a high-side and low-side active diode connected to a single input.
• Figure 22 shows an example squelching regulator that can be used to drive the supply voltage to the active rectifier.
• squelching it is meant that the regulator does not provide a substantial output until the input (rectified voltage) exceeds a threshold.
• An overview of its operation is as follows. When with no input voltage on A,B,C, or D - the bridge rectifier input - the rectified output will be zero. In Figure 22 the rectified output is delineated as
• the intrinsic diode within the MOSFET becomes part of the rectifier.
• the intrinsic diode is in parallel with the active diode. When the voltage NlOV become great enough, the active diode begins to function and the intrinsic diode will not conduct.
• Constellation Module A device (“black box”) containing all the necessary technology to pick up power from a pad and generate a useable, regulated output.
• Module standard unit is a standard unit that can be used in a number of device enablements.
• Enabled Device An electronic unit capable of receiving power from a pad.
• Enablement The components, circuitry, contact points, and mechanical casement to attach to a device and provide power to it as received from a pad.
• Pad The surface and support structure with electrodes upon it and upon which devices rest to receive power.
• Swim lanes The set of electrodes comprising the surface of the pad. This term is more descriptive as the electrodes resemble swim lanes in an Olympic pool.
• Target Device The electronic unit which is selected to be energized by wireless power received from the pad.
• the charging system comprises a pad that transfers power wirelessly to one or more devices resting on it. This is achieved through electrical conduction and the use of geometry.
• An example charging pad and device is shown in Figure 1.
• Figure 23 is a schematic ("Generic DC/DC Adapter Circuit") showing the power conditioning circuit used to receive power from the power delivery surface.
• the four contact points forming a "tetrahedron" shape are connected to the points Tl, T2, T3, and T4.
• the bridge rectifier formed by D1,D2, D5, D7, D6, D9, DlO, and Dl 1, together with resistor R3 and capacitor Cl forms the required turn-on network to alert the system controller, with associated sensing functions described above, that a compliant load is present on the power delivery surface.
• the output of the bridge rectifier flows through Ferrite Bead Rl and is further filtered by C2, R2, and C5.
• An integrated buck switching converter chip is used to regulate the predetermined input voltage to a predetermined output voltage.
• the output voltage is set at 5.0V by R4 and R5.
• a turn-on delay circuit is formed by R7, R6, C4, Zl, and D4. This prevents the regulator from operating until the input voltage has stabilized using the assumption that within 240 ms the input voltage will have stabilized.
• a current limiting circuit comprising R8, R9, RlO, R12, R13, D6, Ql, and U2 is connected to the output to both protect the circuit and to mimic the function that certain mobile devices expect.
• Constellation Module Overview The Constellation Module 64 facilitates rapid enablement of a broad range of small devices.
• Figure 24 shows an example implementation.
• the constellation module 64 is embedded in a "shell"-type housing 102 for a mobile phone.
• the Constellation Module allows technology implementers to design-in charging system pad compatibility with a minimum of effort.
• the Constellation Module makes a "black box” out of the wireless charging system technology, simplifying the interface to just two wires - power and ground.
• the outer dimensions of a useful Constellation Module measure 1.350" X 1.350" X 0.115".
• Example output ratings are as follows:
• the Constellation ModuleTM allows charging system wireless power technology to be implemented in a variety of applications.
• the Constellation Module makes a "black box” out of the wireless power technology, simplifying the interface to just two wires - power and ground.
• the example constellation module 64 shown in Figures 25A-B can be embedded in a "gel" type skin to easily “enable” common wireless devices to be charged by the charging pad of this invention.
• Figure 26 shows the two halves of a gel-type case, consisting of an upper section 60 and a lower section 62.
• the design implementation can be broken into two tasks: 1) the design of an attractive, ergonomic "gel” skin, and T) the design of the connection assembly - the connection between the constellation module 64 and the device 20.
• the focus of this application note will be the task of designing the connection assembly 76.
• Figure 27 shows the wireless power assembly comprising the constellation module 64, flexible circuit carrier 66, flexible circuit 72 (not visible), strain relief 70, and power connector 68. Note that the exact implementation of the connection assembly will vary depending on the specific device being enabled. Nevertheless, Figure 27 helps to illustrate the functions needed in such enablements.
• the solution includes two main components, the gel case, and the wireless power Assembly, which is insert-molded into the gel case.
• insert molding involves the rigid constellation module 64 and semi-rigid connection assembly 76 and requires proper gating to ensure the material does not flow into unwanted areas.
• the gel material should not flow into the connector cavity 78 thereby interfering with the electrical connection to the device.
• the gates should also prevent material entering the cavity 78 from pulling up the flexible circuit board from the carrier or strain relief 70.
• the material should also be blocked from the top and bottom surface of the constellation module 64. Any material on either the top or bottom of the constellation module will interfere with operation and increase the overall thickness of the design.
• the constellation module 64 and the thermoplastic elastomer (TPE) material will chemically bond thereby creating a durable and reliable joint.
• the electrical connection between the constellation module 64 and the power connector 68 is established through traces on a flexible printed circuit 72, also called a flat flexible circuit (FFC).
• FFC flat flexible circuit
• the flexible circuit 72 is laminated to a carrier 66 to provide stability and durability.
• the laminate is insert-molded within the TPE or other "gel" material.
• Some type of strain relief mechanism is required to ensure the reliability of the connection between the flexible circuit carrier 66 and the power connector 68.
• Figure 30 shows an example where the flexible circuit carrier 66 and strain relief 70 are a single unit molded of plastic.
• the strain relief 70 also serves as a gate to prevent material from flowing into the connector 68 during the overmolding process.
• the strain relief 70 relieves the load on the connector 68 from the flexible circuit 72.
• the flexible circuit 72 does not have the ability to mechanically retain or stabilize the connector 68. Any forces acting between the connector 68 and the flexible circuit 72 could result in damage to the electrical connections critical for operation.
• the connection assembly 76 interfaces to the constellation module 64 by plugging into a ZIF connector 74 on the constellation module 64.
• the flexible circuit carrier 66 should come flush to the constellation module housing.
• the flexible circuit 72 should extend further and into the ZIF connector 74.
• the power connector 68 for the target device 20 should protrude as little as possible. Ideally the connector 68 would not protrude from the device it is plugged into further than the thickness of the gel case itself. However, this is not always possible. This requirement may call for a custom connector to be manufactured.

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• Engineering & Computer Science (AREA)
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• Charge And Discharge Circuits For Batteries Or The Like (AREA)

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• 2008
  • 2008-10-30 GB GB1109079A patent/GB2477258A/en not_active Withdrawn
  • 2008-10-30 WO PCT/US2008/081859 patent/WO2010050958A1/en active Application Filing
  • 2008-10-30 CN CN2008801327812A patent/CN102273041A/zh active Pending

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