Electronic device with attachment and switching between batteries therefor

ES 2 339 856 T3

DESCRIPTION

Electronic device with accessory and switching between batteries for them.

I. Field of the invention

The present invention relates generally to consumer electronic devices with battery powered pluggable options.

II. Background of the invention

Many battery-powered consumer electronic devices ("host devices") may include plug-in options ("accessories") that may themselves have batteries. An example may be a personal digital assistant (PDA) or camera / camcorder to which a wireless modem card can be connected to transmit data to and from the PDA / camera / camcorder. Under certain circumstances another battery may be required in the accessory because design limitations on the amount of current through the interface between the host and the accessory limit the amount of current that can be supplied to the accessory from the host battery. .

The present invention considers that for reasons of size and cost, it is desirable to minimize the size of the battery especially in the accessory, the electrical load of the combined system being shared between the accessory battery and the host battery. As an example, a code division multiple access (CDMA) wireless modem card accessory that is designed to meet the Compact Flash Interface specification may require more than 800 mA of output power from maximum transmission, but the Compact Flash interface allows the host battery to supply no more than 500 mA through the host-accessory interface. For this reason, another battery must be provided on the card, and it can share the power load with the host's battery.

The following documents discuss the use of cards having associated power supplies: US-A6 011 323, which shows an apparatus and method for providing auxiliary battery conversion in adapters requiring auxiliary batteries; and US-A-5 928 336, which teaches the use of a PC card that can be inserted into a host computer system and can be driven by a built-in battery to function as a standalone apparatus.

However, the present invention critically notes that it can be difficult to link battery power supplies by simply connecting them together. Even though the batteries may be of the same type, the voltages may be different depending on their relative states of discharge and their relative temperatures. Under circumstances of such environmental imbalance, charge from one battery can immediately begin to flow to the other battery, and can flow back through the interface, which could be prohibited by design specifications. On the other hand, if the batteries are separated from each other by, for example, supplying separate parts of the card from each battery, it can be difficult to find a good division in which the maximum currents required from both batteries satisfy design limits.

Also, different circuits can have different and difficult to predict voltage demands. In particular regarding a CDMA card accessory, for example, its power amplifier exhibits an extremely non-linear, approximately exponential, demand for current versus output power. Consequently, due to this wide variation in current demand from the CDMA modem, mainly attributable to the power amplifier, it is not possible to predict the amount of current that the power amplifier will need at any time in relation to the rest of the card. CDMA modem. The result is that a larger accessory battery may be needed than is necessary, causing its capacity to be wasted most of the time. As understood by the present invention, while it is desirable to minimize the size of the accessory battery, it is also desirable to achieve a balance whereby one battery does not always drain before the other battery.

The present invention has considered the problems mentioned above and has provided the following solutions for one or more of these.

In a first aspect, there is provided an electronic system according to appended claim 1.

In a second aspect, there is provided a method according to appended claim 10.

The details of the present invention, both about its structure and its operation, can be better understood with reference to the accompanying drawings, in which the same reference numbers refer to the same parts, and in which:

Brief description of the drawings

Figure 1 is a simplified block diagram of one embodiment of the present invention;

2 339 856 T3 Figure 2 is a block diagram of the combined host / accessory electrical circuits; and Figure 3 is a flow chart of the present logic.

Detailed description of the preferred embodiment

Referring initially to Figure 1, there is shown a system, generally designated 10, that includes a host device 12 such as, but not limited to, a personal digital assistant (PDA) or an imaging device such as a camcorder, etc. System 10 further includes an accessory 14 such as, but not limited to, a wireless modem card, such as for example a CDMA modem card. It should also be understood that a wide range of hosts 12 / accessories 14 is contemplated herein, with the accessory 14 preferably being removably hand-coupled with a rack or other socket 16 of the host device 12, by means known in the art. .

As shown in Figure 1, host device 12 has at least one host battery 18 and logic module 20 that can be accessed by host device processor 12 to execute the logic discussed later. An interface 22 electrically connects host device 12 with accessory 14.

Like host device 12, accessory 14 may include a logic module 24 that can be accessed by a processor within accessory 14 to execute the logic it contains instead of, or in line with, host device 12 executing its module. Logic 20. Logic modules 20, 24 may be implemented in hardware or software, and may be stored on computer-readable media.

Figure 1 shows that accessory 14 includes at least one accessory battery 26. An exemplary non-limiting accessory battery 26 may be a 250 milliamp-hour nominal lithium-ion type battery. A first circuit 28 in accessory 14 is always powered by the accessory's battery when accessory 14 is operating. The first circuit can be, without limitation, a power amplifier in a CDMA modem or other circuit. A second circuit 30, also referred to herein as a shared power circuit, is contained in accessory 14 and is selectively activated by either host battery 18 (on interface 22) or accessory battery 26 as will be described later in more detail.

Before explaining the logic by which it is determined whether to power the shared power circuit 30 using the host battery 18 or the accessory battery 26, reference is made to Figure 2, for an understanding of non-shared circuitry. limitative. As shown, the host battery 18 is used to power loads 32 of the host battery only within the host device 12. A current measuring device 34 may be provided such as, but not limited to, a series resistor of the milli-ohm type that can sample current to the loads 32, for example at 0.5 second intervals, to generate a representative signal. of current to the host's 32 charges alone. The samples can be averaged, if desired, over the last twenty-six (or some other appropriate number) samples.

In contrast, the accessory battery 26 activates loads only of the accessory battery such as the first circuit 28. A current measuring device 36 may be provided to generate a signal representative of the current to the accessory loads 28 only.

Figure 2 further illustrates that shared loads such as the second circuit 30 shown in Figure 1 can be activated by either battery 18, 26, depending on whether a host battery switch 38 or a switch 40 is closed. accessory battery. The following logic determines which switch is closed. A current measuring device 42 may be provided to measure the current absorbed by the loads 30. It should be understood that while three current measurement devices are shown, other current measurement configurations may be used in accordance with the present principles.

Taking into account the above explanation, attention is drawn to the logic flow chart of figure 3. Although the logic is shown in flow format, it should be understood that in a real implementation software, state machines and / or other devices can be used. logical mechanisms.

Starting at decision frame 44, in a preferred non-limiting embodiment it is determined whether a predetermined circuit load is below a threshold. As an example, it can be determined if the total current being supplied from the accessory battery 26 is less than twice the capacity of the battery. As another example, if the accessory is a CDMA modem, it can be determined in decision box 44 whether the receiver is operating above or below a particular power level, eg -94 dBm.

If the threshold is exceeded, the logic proceeds to block 46, where the shared loads 30 are powered by the host battery 18 (for example, by causing the host battery switch 38 to close and the host battery switch to open 40 accessory battery). By contrast, if the threshold is not exceeded, the logic can move to decision box 48 for another test.

ES 2 339 856 T3

In decision box 48, the preferred logic contemplates the determination of the relationship between the remaining capacities of the batteries 18, 26. Specifically, at least one and preferably the three current signals coming from the devices 34, 36, 42 of Current measurements shown in Figure 2 are used to determine which battery should power the shared loads 30. In a non-limiting exemplary embodiment, the determination in decision box 48 is made using the following inequality:

Cc> Hc (A + C / 2) / (B + C / 2), where Cc is the remaining charge capacity of the accessory battery, Hc is the remaining charge capacity of the host battery, A is the current measured by the measuring device 36, B is the current measured by the measuring device 34, and C is the current measured by the measuring device 42.

If the inequality is not met (meaning that the accessory battery 26's capacity is relatively less), the logic passes to block 46 to allow the host battery 18 to power the shared loads 30. Otherwise, if the inequality is satisfied, indicating that the capacity of the accessory battery 26 is relatively high, the logic goes to block 50. At block 50, accessory battery 26 is used to power shared loads 30 (for example, by causing host battery switch 38 to open and accessory battery switch 40 to close) .

While the "Electronic Device with Accessory and Battery Switching Therefor", as shown and described in detail herein, is fully capable of achieving the objectives of the invention described above, it should be understood that this is the presently preferred embodiment. of the present invention and is therefore representative of the subject matter that is widely contemplated by the present invention, that the scope of the present invention fully encompasses other embodiments that may be obvious to those skilled in the art, and that accordingly the scope of the present invention should not be limited except by the appended claims, in which reference to an element specifically, it is not intended to mean “one and only one” unless otherwise stated, but rather “one or more”.