Device for inductive charging of portable devices in vehicles

Abstract

A recharging system for portable devices (12), comprising: a base unit (10) generating an electromagnetic field; a portable device (12) comprising a rechargeable battery (14) inductively charged by the electromagnetic field; and spacers (38) disposed between the portable device (12) and the base unit (10), the spacers (38) supporting the portable device (12) and maintaining an air gap (40) between the base unit (10) and the portable device (12); characterized in that the spacers maintain an air gap (40) of 2 mm between the base unit (10) and the portable device (12).

Description

BACKGROUND OF THE INVENTION

[0001] One embodiment relates to a recharging system for portable devices according to the preamble of claim 1, as is known from JP H11-98 705 A.

[0002] A comparable recharging system is also disclosed in US 2011 0 084 657 A1 and US 2011 0 050 164 A1.

[0003] Portable electronic devices, such as mobile phones, are powered by battery packs that require recharging. While such portable devices are known to utilize contact terminals to transfer electrical energy between an external power source (e.g., a wall outlet) and the portable electronic device, contactless charging utilizes inductive charging to recharge portable devices without the electrically coupling contact terminals to transfer electrical energy to the portable electronic device. Examples of such portable devices include cordless telephones, electronic toothbrushes, and other electronic convenience devices. An inductive charging system typically includes a base charging unit that includes an inductive coil for generating an electromagnetic field.The inductive coil of the base charging unit induces an electrical charge in an inductive coil in the portable electrical device. The induced electrical charge is converted into a direct current to recharge the battery.

[0004] Electrical devices such as mobile phones have a self-protection mode in which the device enters a safe charging mode when the temperature of the mobile phone exceeds a predetermined temperature. The safe charging mode requires only a trickle charge to charge electrical energy into the battery. This prevents damage to the battery as well as the electronic components of the mobile phone. The ambient temperature of an environment such as a room in a house or building does not typically cause the mobile phone to enter a safe charging mode; however, charging environments such as a vehicle have higher ambient temperatures, particularly if the vehicle is exposed to sunlight. In such an environment, the vehicle interior temperature can fluctuate from 70°C to -20°C.This condition, combined with heat generation from the primary base station, can cause the mobile phone battery temperature to rise above the predetermined temperature threshold and enter safe charging mode. The mobile phone's inability to charge at the expected rate is annoying and inconvenient for the user. SUMMARY OF THE INVENTION

[0005] An advantage of the embodiments described herein is the improved charging of a rechargeable battery for a portable device, wherein inductive charging is used to charge the battery. Spacers are disposed between a power mat surface comprising the base charging unit and the portable device. The spacers, in addition to supporting the portable device, maintain a respective 2 mm separation between the base charging unit and the portable device, allowing airflow along the recharging surface of the portable device. The airflow helps maintain a temperature of the battery below a threshold temperature, which, when exceeded, causes the phone to enter a safe charging mode and then only a trickle charge is applied to the rechargeable battery, thereby avoiding damage to the rechargeable battery.This reduces the recharging time for the portable device's battery.

[0006] One embodiment contemplates a recharging system for portable devices. The recharging system for portable devices includes a base unit that generates an electromagnetic field. A portable device includes a rechargeable battery that is inductively charged by the electromagnetic field. Spacers are disposed between the portable device and the base unit. The spacers support the portable device and maintain an air gap between the base unit and the portable device. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a diagrammatic view of a basic charging system. Fig. 2 is an inductive charging system for charging the portable device. Fig. 3 is a side view of an induction charging system without a heat dissipation feature. Fig. 4 is a side view of an induction charging system with a heat dissipation feature. Fig. Figure 5 is a graph of temperature versus charging time. Fig. 6 is a graph of charging current versus charging time. DETAILED DESCRIPTION

[0007] Fig. Figure 1 illustrates a base charging unit 10 for inductively recharging a portable device 12, such as a mobile phone, which is a communication device carried by a user for both transmitting and receiving wireless communication signals. It should be understood that the portable device may be any device that utilizes a rechargeable battery and can be recharged using an inductive charging method. The portable device 12 includes a rechargeable battery 14 that powers the portable device 12.

[0008] The rechargeable battery 14 is enclosed in a housing 16 for concealment and protection from external elements and is typically removable from the portable device 12. The rechargeable battery 14 is recharged via inductive charging from the base charging unit 10 while attached to the portable device 12. As shown in Fig. 1, the portable device does not require a docking station; rather, the portable device 12 only requires that the device be located within a respective range of the charging unit 10 to receive an electromagnetic field of sufficient strength to inductively recharge the rechargeable battery 14. However, due to the alignment between the transmitting inductive coils and the receiving inductive coils, a docking station can be used to orient the device in a direction for optimal reception of the generated electromagnetic field, if necessary.

[0009] Fig. Figure 2 is a block diagram of the inductive charging system for charging the portable device 12. The base charging unit 10 includes an external power source 18, a primary control circuit 20, and a primary inductive coil 22. The external power source 18 receives power from a power generation device (e.g., an alternator) or a power storage device (e.g., a battery) in the vehicle. If the supplied power comes from a power storage device, such as a battery, then the external power source may include electrical circuitry capable of converting the supplied power into a respective alternating current (AC). The primary control circuit 20 regulates power generated at the primary inductive coil 22.

[0010] The portable device includes a secondary inductive coil 24, a secondary control circuit 26, and a rechargeable battery 14. The secondary inductive coil 24 and the secondary control circuit 26 may be enclosed within the housing 16, which protects the rechargeable battery 14 from external elements. The secondary control circuit 26 includes electronic circuitry for rectifying an induced AC voltage generated across the secondary inductive coil 24 to recharge the rechargeable battery 14. The secondary control circuit 26 may include a controller or microprocessor for controlling both the amount and rate of charge delivered to the rechargeable battery 14. The primary control circuit 20 applies a voltage waveform having a respective voltage and frequency to the primary inductive coil 22 to energize the primary inductive coil 22.

[0011] The rechargeable battery 14 of the portable device 12 is affected by the heat generation of the base charging unit 10 during recharging. As shown in Fig. 1, the base charging unit 10 includes a power mat surface 36. The power mat surface 36 includes a surface for supporting the portable device 12. The power source and primary control circuitry / coils are disposed beneath the surface of the power mat. The power mat surface 36 preferably includes a rubberized surface that prevents the portable device 12 from sliding around while the vehicle is in motion, and therefore, the power mat can accommodate various types of devices having different shapes and sizes. Furthermore, the power mat surface must also not inhibit the flow of the electromagnetic field generated by the primary inductive coil to the portable device 12.It is understood that the power mat surface is not limited to a rubberized surface, but may comprise other materials suitable for maintaining the portable telephone in a recharging position and allowing the flow of the electromagnetic field from the primary inductive coil to the rechargeable battery of the portable device.

[0012] As previously described, both the temperature of the portable device and the ambient room temperature affect the recharging of the portable device's battery. If the battery temperature of the portable device exceeds a predetermined temperature (e.g., 47°C), the portable device enters a self-protection mode. In self-protection mode, the charging current is regulated according to the battery temperature. Therefore, when switching to self-protection mode, only a trickle charge is applied to the rechargeable battery (e.g., milliamperes). This significantly increases the charging time for the portable phone's rechargeable battery.

[0013] Fig. Figure 3 illustrates a side view of the components of the induction charging system without a heat dissipation feature. The portable device 12 is disposed on a power mat surface 36 of the base charging unit 10. The base charging unit 10 can be integrated into various interior trim elements of the vehicle, including, but not limited to, an armrest, a center console, a storage compartment, or another dedicated surface. The secondary control circuit and the coil are shown cooperating at 30.

[0014] At 32, the base charging unit 10, which supports the portable device 12 and includes the primary control circuit and the coil, is shown cooperating. As shown in Fig. 3, an outer surface 34 of the portable device 12 rests against the power mat surface 36 of the base charging unit 16. The contacting surface of the portable device 12 (such as in the scenario of a mobile phone) comprises an elongated flat surface, with the majority of this flat surface in contact with the flat power mat surface 36. This prevents airflow between the power mat surface 36 and the outer surface 34. Due to the heat generated by the induced electromagnetic field between the portable device 12 and the base charging unit 10, in addition to the ambient temperature of the room (particularly a motor vehicle on a sunny and hot day), the temperature of the rechargeable battery rises significantly because heat cannot be easily dissipated between the contacting surfaces.

[0015] Fig. Figure 4 shows a side view of the induction charging system with the heat dissipation feature. The portable device 12 is shown disposed against a power mat surface 36 of the base charging unit 10. The power mat includes spacers 38 for creating an air gap 40 between the surface of the power mat 36 and the surface of the portable device 12. The spacers 38 may comprise any shape and configuration that creates an air gap 40 between the outer surface of the portable device 34 and the power mat surface 36 to allow heat to dissipate therebetween. The space creating the air gap 40 between surfaces 34 and 36 may be approximately 2 mm. A dimension greater than 2 mm may cause a reduction in the strength of the induced electromagnetic field received at the rechargeable battery. Alternatively, the space may be less than 2 mm; however, as the space decreases below 2 mm, the efficiency of heat dissipation decreases.

[0016] The spacers 38 may comprise any configuration or shape that provides separation while allowing airflow. For example, troughs, ribs, pins, posts, spheres, squares, or any other shape or configuration that supports the portable device 12 and maintains the distance between the portable device 12 and the outer surface 36 of the power mat. Furthermore, the number of spacers and the spacing of the spacers can be optimized for different types of equipment that utilize the power mat for battery recharging. Factors used in the optimization may include, but are not limited to, the support of the portable device 12 on the power mat and the configuration of the spacers 38 for airflow efficiency for heat dissipation. For example, a predetermined number of pins (e.g.,4) aligned in a square, triangular, rectangular, polygonal or non-linear configuration.

[0017] Preferably, the spacers 38 are integrated with the power mat during formation; however, it is understood that the spacers may be a separately formed component, either sitting on or coupled to the outer surface 36 of the power mat. Furthermore, the material composition of the spacers 38 is preferably the same as that of the power mat. Alternatively, the material composition of the spacers 38 may be different from the material composition of the power mat, such as a material that prevents or minimizes the conduction of heat stored in the power mat to the contacting outer surface of the portable device.

[0018] Fig. Figure 5 is a graph showing the battery temperature over time during a battery recharge cycle. The graph shown here illustrates a vehicle exposed to hot sun for one hour, followed by a 1.50-hour city drive. Threshold 42 indicates the temperature threshold (>47°C) at which a portable device would enter self-protection mode. As shown in the graph, using the configuration without the spacers, represented by line 44, the temperature of the rechargeable battery exceeds the temperature threshold at approximately 45 minutes of charging.

[0019] Fig. Figure 6 is a graph showing a charging current over time. Referring to line 46 in Fig. 6, approximately 45 minutes after charging is initiated and the predetermined temperature threshold is exceeded, the self-protection mode is activated, and the charging current decreases to a maintenance charge. As a result, the state of charge (SOC) of the rechargeable battery only increased by 20% during this interval. It should also be noted that approximately 80 minutes after charging is initiated, the rechargeable battery cools down and the temperature of the rechargeable battery drops below the predetermined temperature threshold. When the battery temperature drops below the predetermined temperature threshold, a full charge is initiated. However, the battery temperature rises rapidly due to the heat generated by the inductive charging, and after the battery temperature exceeds the predetermined temperature threshold, the self-protection mode is activated. The current charging cycle is repeatedly switched on and off, as shown in Fig. 6 shown by the line 46.

[0020] With further reference to Fig. 5, the temperature of the rechargeable battery never exceeds the temperature threshold using the configuration with the spacers, as shown by line 48. A significantly lower stable temperature between 35°C and 40°C is maintained. Fig. 6 and especially line 50 illustrates the charging of the rechargeable battery. As shown in Fig.As shown in Figure 6, a full charge is maintained throughout the charging process and is completed within 90 minutes without entering self-protection mode. As a result, the spacers create a 2 mm air gap between the portable device and the base charging unit to provide cooling of the portable device through natural convection. The air gap spacing between the portable device and the power mat can be increased; however, the charging current induced in the rechargeable battery decreases, thereby increasing the time required to fully charge the rechargeable battery. Alternatively, decreasing the air gap spacing between the portable device and the power mat decreases; however, the battery temperature increases, thereby increasing the likelihood of self-protection mode activation.

Claims

[1] A recharging system for portable devices (12), comprising: a base unit (10) that generates an electromagnetic field; a portable device (12) comprising a rechargeable battery (14) inductively charged by the electromagnetic field; and spacers (38) disposed between the portable device (12) and the base unit (10), the spacers (38) supporting the portable device (12) and maintaining an air gap (40) between the base unit (10) and the portable device (12); characterized by , that the spacers maintain an air gap (40) of 2 mm between the base unit (10) and the portable device (12). [2] The portable device recharging system (12) of claim 1, further comprising a power mat including a power mat surface (36), wherein the base unit (10) is integrated into the power mat. [3] A recharging system for a portable device (12) according to claim 2, wherein the spacers (38) are integrated as part of the power mat, the spacers (38) and the power mat comprising a same material composition. [4] The portable device recharging system (12) of claim 2, wherein the spacers (38) are formed separately from the power mat. [5] The portable device recharging system (12) of claim 2, wherein a material composition of the spacers (38) is selected to minimize thermal conduction of heat stored in the power mat to a contacting outer surface of the portable device (12). [6] The portable device recharging system (12) of claim 1, wherein a configuration of the spacers (38) on the power mat surface (36) is selected to maximize airflow between the power mat surface (36) and the portable device (12). [7] The portable device recharging system (12) of claim 1, wherein a number of spacers (38) on the power mat surface (36) are selected to maximize airflow between the power mat surface (36) and the portable device (12). [8] The portable device recharging system (12) of claim 1, wherein one form of the spacers (38) comprises pins.

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