BRPI0407728B1 - BATTERY CHARGING CIRCUIT, METHOD AND SYSTEM FOR CHARGING RECHARGEABLE BATTERY FOR PORTABLE DEVICE USING ENERGY PROVIDED BY UNIVERSAL SERIAL (USB) - Google Patents

Description

BATTERY CHARGING CIRCUIT, METHOD AND SYSTEM FOR CHARGING A RECHARGEABLE BATTERY FOR A LAPTOP DEVICE SUPPLIED BY A UNIVERSAL SERIAL BUS (USB) DOOR Technical Field: This invention generally relates to more specifically, battery chargers to a method and apparatus for charging the battery in a portable communication device from a variety of power sources, including limited capacity sources such as the integral power node of a computer data bus. One such computer data bus would be a Universal Serial Bus (USB) port.

Technology History;

With the current revolution in computing and information, portable electronic devices such as mobile phones, personal digital assistants (PDAs), digital radio call devices, and wireless electronic correspondence devices are becoming quite common. These portable devices are typically powered by internal batteries that need to be recharged periodically by an external power source using a battery charger. Battery chargers typically receive power from a standard AC outlet and convert AC power to a low DC voltage to recharge the battery.

The battery chargers of these portable devices also generally employ a "battery charge controller" to manage battery charging. These battery charge controllers offer features such as: - regulating voltage and current levels for the rechargeable battery; - provide status signals to the main processor of the handheld device; or operate one or more status LEDs; - provide protection circuits such as overcurrent, undervoltage, reverse polarity, and over temperature protection; and ' . - de-energize when the charging source has been removed to minimize battery drain.

Lithium ion batteries, for example, need to be charged according to a relatively narrow algorithm so that they can be fully charged, charged and recharged many times, and safely operated. This load algorithm usually proceeds as follows: 1. In the first stage, any severe undervoltage or deep discharge condition is faced. During this preload stage, the battery voltage is gently brought from a very low or dead state, usually at a rate of 1/10 of the regular charge current; 2. The battery is then charged at a constant current level until the voltage across the battery reaches the design level (say 4.2 VDC). At this point the battery will be only 40 to 70% of full capacity; and then 3. the battery charge remains at a constant voltage level (again, say 4.2 VDC) until it is fully charged. In this mode, the current drawn by the battery will fall over time. When the current charge has fallen to 10% of the initial charge rate or some other limit determined by the battery manufacturer, the charge is interrupted. Charging must stop at this point as dripping charge is not acceptable for lithium batteries; an overload will damage the cells, possibly galvanizing the lithium metal and making it dangerous.

Thus, lithium batteries are almost invariably used with controllers. Battery Charges Designed for Your Particular Charging Parameters Unfortunately, most battery charge controllers are designed to draw from a high capacity power source with a stable voltage that will not sink appreciably under current demands. This is a problem when trying to use a limited capacity power source. Some computer data buses, such as Universal Serial Bus (USB) buses, can be used to power external devices, but although these power sources are very convenient, they have limited capacity. Most personal computers (PCs) and laptop computers available today are equipped with one or more USB ports as standard components. USB ports are designed to support data communication at speeds of 12 megabits and 1.5 megabits per second, support PnP (Plug and Play) installation software, and support hot plugging (ie devices can be plugged in and unplugged while PC is on). Thus, USB ports are often used as interfaces to connect keyboards, mice, game controllers, printers and scanners to PCs.

In addition, USB ports are operated to provide limited power to connected external devices. The standard USB specification requires "high power" USB ports to be operated to provide 4.75-5.25 VDC supply voltage and at least 500mA (often referred to as "live units"). The specification for "low power" USB ports requires a supply voltage of 4.40-5.25 VDC and 100mA current (referred to as "one unit").

USB ports seem to be a very logical choice as a power source for portable devices for a number of reasons. For starters, USB ports provide a low DC voltage supply that is often very close to, or just above, the voltage of the battery being charged (many portable devices have battery voltages in the range 2.5 to 4.5 VCC). Also, many portable devices may be operated to upload and download data or software to and from a personal computer or a laptop computer (often referred to as "synchronization"). Thus, many portable devices are provided with docking cradles as shown in the system diagram of Figure 1. This is a very simple system as the docking cradle 10 is connected to a USB port 12 of a personal computer (PC). 14, via a simple USB cable and connectors 16. The portable device 18 only needs to be attached to the docking cradle 10 and an electronic connection to the PC 14 is made.

If the USB 12 port has enough power, it makes much more sense to use the USB 12 port to provide charging power for portable device 18 rather than using a separate AC charger. For example: 1. a USB power source will have less electrical noise than the AC charger unless the AC charger incorporates large capacitors or DC inductors; 2. The AC charger requires either a heavy-duty transformer or a power supply with expensive switches, none of which would be required if USB power were used, · 3. In implementing the USB power supply, the cable and connectors 16 used to connect PC docking cradle 14 could be used to carry both power and data so that no additional physical components would be required. In contrast, an AC power source would have to be provided as a separate physical component of a USB data cable; and 4. there are no universal standards for AC power sources; A given AC power source may display 120VAC or 240VAC as input, and may provide 3, 4,5, 6, 7,5 or 9VDC output, with one of a large number of different connectors and possible polarities. The traveler who forgets his AC power supply at home may not be able to find a suitable replacement.

In contrast, the USB standard is widely accepted, so the traveler whose mobile device is equipped with a USB connector will have a much better chance of finding a charging source.

Thus, it would be clearly desirable to use USB power to charge portable devices. Unfortunately, however, as noted above, USB ports can only provide limited power. The problem is clear when considering the block diagram of Figure 2. In this scenario, the handheld 18 and the battery charge controller 20 are connected to the USB port 12 in parallel, as under load conditions the control switch 22 will be so that portable device 18 pulls power from USB port 12. When battery 24 is fully charged by battery charge controller 20 and power from USB port 12 is removed, control switch 22 is then triggered so that portable device 18 draws power from battery 24. This type of circuit may work in some circumstances, but it is not acceptable when the power source has limited capacity.

If we try to power both the portable device 18 and the battery charge controller 20 simultaneously from the USB 12 card, it is very likely that an excessively large charge would be placed on the USB 12 card. Overcharging the USB 12 card could result in an undervoltage or condition. low current that could result in a number of undesirable problems such as: battery 24 not being properly charged or permanently damaged, or handheld 18 operating erratically or damaged.

As an alternative, the battery 24 and the portable device 18 could be arranged as shown in Figure 3, so that they are both powered by the battery charge controller 20. Although this design would reduce the total energy drawn by the portable device 18 and battery 24 together, there are a number of other issues: 1. Most importantly, there is still no control over the total power that is pulled from the USB port 12; 2. the power drawn by the portable device 18 could disrupt the protection and carefully designed charging mechanisms of the battery charge controller 26; 3. Portable device-18 and battery 24 compete arbitrarily for the available power, so that they may adversely affect each other's operation. If the available voltage drops too low, or if insufficient current is available, either device may operate erratically or fail at all; 4. If the battery 24 is in a deep discharge state when the power is turned on, the voltage to the portable device 18 will be lowered to the level of the deep discharged battery. Typically, portable devices 18 will not operate at such low voltage level; and 5. the current that needs to be supplied to battery 24 and handheld 18 needs to be dissipated by the battery charge controller 20 or an external semiconductor in some way. As more power is dissipated, the larger the battery charge controller 20 (or the external semiconductor driven by the battery charge controller 20) will need to be. Generally, the ability of the semiconductor to dissipate energy varies with its surface area; thus, if the energy dissipation is doubled, the semiconductor must increase the surface area by four.

New and dedicated battery charge controllers could be developed that are designed to operate with a USB power source and portable device 18, but that would be an expensive and complicated solution. Each battery charge controller would have to be designed to fit a particular pair of a portable device 18 and a battery 24, as it would have to take into account the power consumption requirements of both components.

Therefore, there is a need for a method and apparatus that allows a standard computer data bus such as USB ports to simultaneously power portable devices 18 and their associated battery charging circuits 20 without having to design new battery charge controllers. very specific applications. This design needs to be provided with consideration for the tight operating parameters of the battery charging circuits, the limited physical board area of portable devices, and the reliability and complexity of the design.

Disclosure of the Invention; It is therefore an object of the invention to provide a novel method and apparatus that enables standard battery charge controllers to be provided from standard computer data ports and other power sources that obviates or mitigates at least one of the disadvantages of technology. previous.

One aspect of the invention is broadly defined as a battery charge circuit comprising: a semiconductor switch having an output connected to a rechargeable battery; a battery charge controller for receiving power from an external source, and providing output power for a portable device and the semiconductor switch input, the battery charge controller output current being controllable; and a voltage sensing circuit for: measuring the voltage drop across the battery charge controller; and responding to voltage drop through the battery charge controller by modulating the semiconductor switch to reduce the amount of current supplied to the rechargeable battery when the voltage drop is too large; where the total power dissipated by the battery charge controller is controlled, the handheld device receiving the power it needs to operate and the rechargeable battery receiving any additional power available.

Another aspect of the invention is defined as a battery charger circuit comprising: a battery charge controller connected to the external power supply and energizing the battery and a portable device, and having a maximum current parameter; and a regulator circuit for sensing voltage drop across the battery charge controller, and modulating the battery current to keep the power dissipated by the battery charge controller below a predetermined level.

A further aspect of the invention is defined as a method for charging a battery of a portable device through an external power source, the method comprising the steps of: connecting the input of a battery charge controller to the external power source; connect the battery charge controller output in parallel to the handheld device and the input of a semiconductor switch; connect the output of the semiconductor switch to the battery; control the current output of the battery charge controller; measure the voltage drop through the battery charge controller; and responding to the voltage drop across the battery charge controller by modulating the semiconductor switch to reduce the amount of current supplied to the rechargeable battery when the voltage drop is too large; wherein the total energy dissipated by the battery charge controller is controlled, the portable device receiving the power it needs to operate and the rechargeable battery receiving any additional available energy.

Another aspect of the invention is defined as a power supply circuit comprising: means for measuring voltage drop across a battery charge controller that supplies power to a portable device and the input of a parallel semiconductor switch; means for controlling the current output of the battery charge controller; and means for responding to voltage drop across the battery charge controller by modulating the semiconductor switch to reduce the amount of current supplied to the rechargeable battery when the voltage drop is too large; where the total power dissipated by the battery charge controller is controlled, the handheld device receiving the power it needs to operate and the rechargeable battery receiving any additional power available.

Brief Description of the Drawings;

These and other features of the invention will become more apparent from the following description with reference to the accompanying drawings in which: Figure 1 shows a physical arrangement of a personal computer connected to a portable electronic device in a manner known in the art. technology. Figure 2 shows an electrical block diagram of a battery charging circuit and the portable device being powered in parallel. Figure 3 presents a diagram of electrical blocks of a battery and the portable device both being powered by a battery charge controller. Figure 4 presents an electrical schematic diagram of a battery charge circuit in a broad version of the invention. Figure 5 shows a time diagram of the voltage, current and power curves for charging a lithium ion battery in one embodiment of the invention. Figure 6 presents an electrical schematic diagram of a battery charge circuit in a simple embodiment of the invention.

Figures 7A, 7B and 7C show an electrical schematic diagram of a battery charger circuit in a comprehensive version of the invention. Figure 8 shows a flowchart of a method of operating the battery charge circuit in an environment of the invention.

Best Mode for Carrying Out the Invention: As explained above, 'there is currently no effective design capable of powering both a portable device 18 and a rechargeable battery 24 from a limited capacity power source.

A circuit that overcomes a number of problems in technology is presented as a block diagram in Figure 4. This Figure shows a battery charge circuit built around a standard battery charge controller 20. In this embodiment of the invention, the controller Battery charge 20 is powered from an external source (Vaus) and powers a portable device 18 and rechargeable battery or batteries 24 in parallel, but power to battery 24 is via a semiconductor switch Q1. Current flow control via semiconductor switch Al is modulated by a voltage sensing circuit 30 which measures the voltage drop across battery charge controller 20 and reduces current flow through semiconductor switch Al to battery 24 when the voltage drop is too big. The voltage sensing circuit 30 allows the total power consumption of the circuit to be inferred since the current output of the battery charge controller 20 is controllable, and the energy is the product of the voltage drop and current. Most battery charge controllers known in the art are provided with some kind of maximum current control. In the exemplary versions hereinafter described, for example, the maximum current output of the battery charge controller 20 is simply fixed via an external resistor R1, although of course the current output could also be controlled in many other ways {e.g. being programmable, application specific, or fixed via some form of analog or digital input signal).

Also in the embodiments described hereinafter, the voltage sensing circuit 30 is itself supplied via an operational amp (op amp). Thus, the voltage drop across the battery charge controller 20 could simply be measured by comparing the voltage at the input and output of the battery charge controller 20, as shown in Figure 4. Alternatively, an input to the operational amplifier could be taken from the output of the battery charge controller 20, while the other could be some voltage, reference VEEF; either emulating the Vaus input to the battery charge controller 20 or being scaled in some way.

Thus, by monitoring the voltage drop through the battery charge controller 20 and knowing the maximum current it can supply, the total energy is known. Using this information to modulate power for battery 24, the total energy dissipated by battery charge controller 20 can be controlled.

Also, as this circuit modulates the power available for battery 24, this circuit can be designed to ensure that portable device 18 receives the power it needs for operation, while rechargeable battery 24 only receives power when additional capacity is available. . The total power consumed may therefore be modulated to remain within the available power limits of the USB 12 port, and within the power range that the battery charge controller 20 is capable of dissipating. This allows battery charge controllers 20 to be used "off the shelf" rather than having to design new and larger battery charge controllers 20 that can dissipate enough power to provide both portable device 18 and battery 24. It also allows the battery charge controller 20 or an external trigger element is kept physically small.

With this power modulation mechanism, there is no more competition for power between portable device 18 and battery 24. Battery 24 receives power only if more power is available than portable device 18 needs. This may seem inconsistent with battery charging requirements such as lithium cells, but circuit parameters can easily be designed to accommodate them.

As noted above, battery charge controllers are typically designed to suit a particular battery or battery family. For example, lithium batteries are charged in three phases: 1. resolve deep discharge conditions; 2. constant current charging until the battery reaches a certain voltage level; and then 3. constant voltage charging until the charge current drops to a certain extent.

During the initial treatment of deep discharge conditions, comparatively little current is supplied to the battery (typically 1/10 of the charge current). The circuit of the invention, therefore, is designed so that the battery will rarely have denied this very modest power demand. The constant current charge phase draws the most energy, but lithium cells do not suffer if the charge current is modulated or cycled during this phase. So it is this phase that. is further altered by the circuit of the invention. If portable device 18 is used a lot during this phase, the only negative impact will be that charging the battery 24 takes much longer.

During the constant charging phase of the voltage, the maximum current is less than that of the constant current phase and drops continuously as the battery 24 becomes fully charged. More importantly, the battery voltage 24 remains at a constant and maximum level during this phase, so the total energy dissipated by the battery charge controller 20 will be lower during the constant voltage phase than it was during the power phase. constant current. '.

As will be described in greater detail hereinafter, the voltage sensing circuit 30 is designed to saturate the semiconductor switch Q1 when the full charge voltage level is reached (that is, the semiconductor switch Al does not limit current flow at all in this Score). The change in energy dissipation over time is shown in Figure 5. Four curves are shown in this Figure: battery voltage 24, labeled VBat, charge current, called Icharge, voltage drop across battery charge controller 20. , labeled VDR0P, and the total energy dissipated, labeled PBCC. Note that VDROp varies inversely with VBat, so that the energy dissipated by battery charge controller 20 is the product of Ichange and Vdrop. Clearly, during the conditioning phase, the voltage of battery VBAt is low, so that VDE0P will be high. However, Icharge is also low during this phase (about 1/10 of Imaxcharge, the maximum load current so that the total dissipated energy is modest).

During the constant current phase, the charge current rises to Imaxcharge / tinas the battery voltage, VBat; it drops as the battery becomes charged, so that the energy dissipated by the battery charge controller 20 drops during this phase.

With the beginning of the constant voltage phase, the battery voltage has reached its fully charged level, VF (so that VDROp is at its minimum.) As Icharge drops over the course of this phase, the dissipated energy also continues to rise. fall (note again that the dissipated energy is the product of Icharge and VDR0P).

Clearly, then, the highest energy level is pulled during the constant current phase. As noted above, charging of battery 24 can be safely cycled during this phase, so that current restriction to battery 24 during this phase is permitted.

This circuit also allows the user to start up their portable device 18 very quickly as it isolates battery 24 from portable device 18. If battery 24 and portable device 18 were connected when battery charge controller 20 attempted to condition a battery deep discharge 24, the voltage on the portable device 18 would be pulled to the level of the deep discharge battery 24. Typically this would be too low for proper operation of the portable device 18. With the circuit of the invention, the battery 24 and the device portable 18 are isolated by Ql. Even if battery 24 is in a deep discharge state, portable device 18 will still receive a voltage that is high enough for proper operation. The time for the portable device 18 to start, therefore, is only limited by the activation time of the battery charge controller 20 itself. Typical data for this activation is from 1 ms to 4 ms, although this may vary from a battery controller. battery charge 20 to another.

Thus, the use of the circuitry in Figure 4 allows computer data buses and similar limited capacity power sources to supply power to portable devices and simultaneously discharged batteries.

A number of different versions of the invention will now be described. Each version uses a very small number of simple and reliable components. Thus, as a whole, the invention provides an effective solution that is inexpensive, reliable and consumes a minimum of card space on a portable device.

Basic implementation; Figure 6 shows an electrical schematic diagram of a charge circuit employing four main components: an NCP1800 battery charge controller, a Q2 semiconductor, which serves as an external driver for the battery charge controller 50, an operational amplifier. 52, and a silicon oxide metal oxide Silicon field effect transistor (MOSFET) Q3, which controls the current for the rechargeable battery 24. The NCP1800 50 battery charge controller is a battery charge controller lithium ions from a single standard cell as is known in technology. The maximum current this device will supply is regulated by the resistance between the ISEL pin and ground. In this case, three resistors R2, R3 and R4 are used to set the maximum current levels for different operating conditions. The default condition is that only 100 mA is available (low power USB), which sets the value for resistor R2. If it is detected that the device is plugged into a high-power USB source, then the MOSFET Q4 portal will be energized, and the resistance between ISEL and ground will be fixed by the resistance of R2 and R3 in parallel.

Similarly, if it is detected that the power source for the circuit has even more power available (an AC outlet or car adapter, for example), then MOSFET Q5 will be energized so that the resistance between ISEL and ground will be fixed. by the resistance of R2 and R4 in parallel, the circuit of Figure 6 will typically be included in the portable device 18 itself, or in a docking cradle 10, so it must also be operated with such larger capacity power sources.

NCP1800 50 Battery Charge Controller manufacturer's application notes are available that will assist the designer in establishing specific parameters and values for resistors R2, R3 and R4 and driver transistor Q2. The voltage sensing portion of this circuit is provided by operational amplifier 52, together with resistors R5 and R6, and capacitor Cl. This circuit monitors the voltage at the collector level of Q2 (via voltage divider R5 and R6), and compares it to a reference level (in this case, VREF = 3.3 V). If the voltage on the collecting side of Q2 drops, then the voltage drop across Q2 rises and the energy it needs to dissipate rises. To reduce the energy that needs to be dissipated, Operational Amplifier 52 limits the current through Q3, increasing the resistance of the drain source.

Note that VKef may simply be supplied with VBUS and a voltage regulator. VRef is used as an input to operational amplifier 52 instead of VBUs because the regulator will supply it with a constant output voltage, while VBUS has a wide range making the design more difficult. The resistor values R5 and R6 are established simply by the need to scale the VBus value to the VREF value.

Also, note that capacitor Cl is included in the circuit to smooth out fluctuations and to prevent oscillation.

As described above, this circuit allows portable device 18 to draw power through Q2 without causing the combined withdrawals of portable device 18 and battery 24 to exceed Q2's power capacity. As portable device 18 draws power, the voltage on the collecting side of Q2 drops and the current through Q3 is decreased in linear mode. Power dissipation needs to be designed for the worst case scenario. For example, if the maximum design parameters are as follows: - up to 0.85 A is available; - an input voltage could be as high as 6 V; and - Battery 24 preloading is complete at 3.0 V (ie where the highest current charge is delivered to the battery, as shown in Figure 5); then (6V - 3Vj * 0.85A = 2.58W of power that would be dissipated by the external drive element Q2 (note that on circuits not using such an element, all this power would be dissipated by the battery charge controller 50). external drive element Q2 needs to dissipate heat generated by the current flowing through it.The more energy is dissipated, the larger the physical dimension of this bypass element must be, generally, the surface area that the device requires, rises with the squared energy to be dissipated ie if power is doubled, a transistor with four times the surface area is required Transistor dimensions are standardized so that the preferred version of this circuit is designed to employ SOT-23 packages (or superSOT-6), which are capable of dissipating up to 1.6 W. The next size is SOT-223, which is considerably larger with twice the power dissipation.

As noted above, the decrease in power for battery 24 is such that the current always meets the needs of the portable device 18 and any current left over (difference between the input current and the current for the portable device 18). delivered to battery 24, for example, assuming the circuit is connected to a high-power USB port (500 mA is available) and a portable device 18 such as a portable Blackberry ™ handheld device. When the Blackberry goes to sleep, it can only display 0.3 mA -0.7 mA so that the available current jump (499.3 mA - 499.7 mA) can be supplied to battery 24. When the Blackberry wakes up , which he does periodically to do cleaning work, he pulls say 30 mA - 70 mA, depending on what he does. At this point, battery 24 receives 430 mA - 470 mA. The analysis occurs when the Blackberry must receive or transmit some data, or perform some other task. In each case, the power for battery 24 is dynamically self-adjusting.

When limited power is available, it is also desirable to cut the high power consuming components while preserving power for the processor only. This is easily accomplished by connecting only the processor and memory of portable device 18 to Q2 as shown in Figure 6, and connecting other high power consumers to the battery side of Q3. ' As a result, if we are operating with a limited current source (such as 100 mA low power USB) and an over current component such as a vibrator (typically 120 mA) or a backlight (typically 150 mA) is turned on, The output voltage of Q2 would start to fall, causing Q3 to increase its resistance Rds and preserve the current needed by the processor.

Comprehensive Implementation »The design shown in Figures 7A through 7C uses the same basic circuit as that of Figure 6, but adds several elements that provide other advantages. These advantages include the following: - the battery can be charged with an input voltage just above battery level; starting the portable device 18 when the battery is dead or not present is different from that of Figure 6; - handling of external power supply input problems is improved; and - contrary to the battery charge controller manufacturer's instructions used in this implementation, the VCC and IN pins are powered separately to prevent back voltage leakage and potential stalling problems in the battery charge controller.

Specific design parameters for this version of the invention can be summarized as follows: 1. constant current, constant voltage charge capacity (as required for charging lithium ion batteries); 2. current selection for 100 mA, 500 mA and 750 mA power sources; 3. operation of the portable device 18 when the rechargeable battery 24 is low, dead or not present; 4. starting and operating portable device 18 within less than 100 mS in cases where battery 24 is not present or dead; 5. compliance with USB suspended mode of operation (system should pull less than 500 uA); 6. overvoltage protection above 5.8V for D + line pull resistor; 7. short circuit protection at the battery connector; 8. Allow charging with input voltage as low as portable device 18 needs for safe operation; 9. voltage in the range 3.3 V - 3.6 V for the D + line pull resistor; 10. provide means of connecting and disconnecting the voltage to the pull resistor on the D + line; 11. battery presence indication; and 12. provide the battery charge controller status. The general description of this comprehensive implementation of the invention follows: The circuit of Figures 7A-7C centers around a Texas Instruments bq24020 lithium-ion battery charge controller labeled U909 in Figure 7C. This battery charge controller provides the constant current and constant voltage modes required to charge lithium ion cells, and supports externally programmable current limits: its UVLO (undervoltage locking limit) is provided by the PFVPFO comparator (U808). (Texas Instruments TPS3103E15) with reference, and its limit is set by the VBUS input resistor splitters. U908 is also used to ensure U909 initial pull-off operation with a minimum of 100 mS. This provides a means to enumerate when operating on low / dead battery or without battery. Overvoltage protection (OVP) is provided by the U912 which is set to -5.8 V. The charging situation is provided by the U909 battery charge controller, which indicates whether or not the controller is delivering current to the system. The voltage for the D + pull resistor is provided by the U901 (a low voltage drop regulator, Toko TK71733SCL) is the switching capacity through Q907. The same voltage is also used to power components that are used only when external power is available through VBUS (U906, U9Q5, etc.).

A U905 comparator (LMC711A) and MOSFET Q908 are used to increase system voltage when operating on a low / dead battery or without the battery. This closed loop also "drowns" the current to the system under no battery, and low battery conditions. This is because when the L_BAT voltage drops (due to system load), U905 acts to turn off Q908, directing more current to the system (taken from the battery). The U907 comparator provides the battery presence status indicator. Battery connector short circuit protection is "NANDED" (U908) with charger enable functionality, thus automatically disabling the U909 battery charge controller when a short is present. The U909 Battery Charge Controller automatically restarts charging if the battery voltage drops below an internal limit, and automatically enters sleep mode when the VCC supply is removed.

Theory of Operation: Note that the circuit inputs and outputs in Figures 7A-7C can be summarized as follows: Signal Correction Description Power input for P / a device source, used for VBUS power (USB or battery charge). or the charger) device operation Enables / disables the charger and delivers current to the CHRG_EN Control Signal system; Reset state: HIZ system (pull resistor makes RST = LOW, charger is OFF Activates control signal current limit CHRG_A 450 mA for charger; from system reset state; LOW Activates control signal current limit CHRG_B 750 mA for charger: from system Refixing state: LOW Control signal goes HIGH every time VBUS

USB_CD

System status is above -2.1 V Control signal status indicator CHRG_FLG charger: system state refixing: LOW Main power source For battery for rechargeable battery;

Rechargeable VBAT reset state: Battery voltage value For Provides power to the L_BAT system device; Reset state: Portable VBUS battery voltage level, the input voltage, is displayed via Q904a to the USB input pin of the U909 battery charge controller. Q904 is used for OVP and is controlled by U912 (3.0 V under National Semiconductor voltage detector, LMS33460, whose input voltage is supplied through resistor divider R937 and R925 + R926) * (R925 + R926) < 3.0 V, which provides OVP above -5.8 V.

Although the USB port for the U909 battery charge controller is present, the 100 mA and 500 mA current limit could be selected via CHRGJB (CHRG_B = LOW provides 100 mA, and CHRG_B = HIGH provides 500 mA). Resistor R941 sets the default LOW logic level for the U909 input ISET2, thus allowing a predefined current limit of 100 mA. This is important and makes the system fit the USB specification when operating on low / dead battery or without the battery. The USB device is limited to 100 mA operation until the device enumerates to 500 mA (if the host USB supports it). The resistor R940 provides a predefined portal LOW input level of Q905a, which keeps it out of saturation (OFF) while in refixing mode and therefore sets the portal voltage of Q904b to its source level (at VBUS voltage) that does not allow VBUS to be present at the AC input of the U909 battery charge controller. The resistors R932 and R936 are pull resistors for Q904. The 750 mA load current (used for non-USB power sources) could be selected by setting CHRG_A = HIGH, which sets Q905a to saturation (ON) and in turn also puts Q904b to saturation (ON), showing the VBUS voltage at the AC input of the battery charge controller U909. Since the AC input for the U9Q9 provides override over the USB input (if the AC input voltage exceeds 1.5 load of the input-output path is preset to the AC input) the load current is now programmed by the resistor value. R936. The C925 capacitor is used to prevent Q904b from being conductive because of its parasitic portal-to-drain capacitance (portal-to-drain capacitance would carry the portal if pulled to its source at the time of RC) during rapid responses. VBUS voltage transients, and allows the portal to quickly load to VBUS level while keeping the Q904b in saturation. Resistor R935 is used to limit the discharge current of C925 so that Q905a does not exceed its specified limits. R933 is a pull resistor that prevents the AC input to the U909 battery charge controller from floating. C926 and C927 are input bypass capacitors. It is important to keep the total input capacitance below 10 uF to comply with the USB input current specification. The total current that the system draws from VBUS should not exceed 500 uA when in sleep mode. This is essentially done by the very low operating current of the U909 battery charge controller (typically <100 uA) in the OFF operating mode. Q905b is used to disable the LBAT voltage booster when the U909 battery charge controller is not delivering any current to battery 24 and / or handheld 18. It does this by shorting the U905 positive input that makes its output. to trigger Q908 at saturation (ON). U906b is used as a inverter of the CHRG_FLG flag, simply to make it compatible with software and the hardware of the rest of the system. R931 is a pull resistor for CHRG_FLG to open the drain outlet. The supervisor processor U908 has dual functionality. Its PFI input level is set by the divider resistor R937 + R925 and R926 so that it matches internal reference U908 when the VBUS drops to 3.3 V (or the LBAT voltage value set by the U905 and Q908 when operating at low / dead battery or without battery), causing the open drain outlet (PFO) to go to GND. This would force the positive input node from U905 to go to GND and set Q908 to saturation (ON). This circuit set creates an Under Voltage Lockout (UVLO) limit for the L-BAT boost circuit. This is important as the U909 can operate down to 2.5 V, causing its situation flag to indicate current delivery to the system although it does not actually (battery 24 internally disconnects below 2.5 V ). This condition would cause the system to reset (for battery voltage levels below the preset minimum LBAT value) as the U905 / Q908 would attempt to keep the LBAT voltage at the preset value by disconnecting battery 24 and finding that the charge controller of the U909 battery is delivering enough current. The second feature of the U908 is the starter overlay on the U909-CE input pin, which provides power to the system to a minimum of 100 mS to properly start and enumerate on the USB-BUS. This is done by keeping its GET RESET open drain output before the VBUS reaches 2.5 V and then 100 mS thereafter. This keeps the U909 battery charge controller activated during this time. U906a provides CHRG_EN NAND functionality and presence of short in the battery connector. A shortened battery disables the U909 battery charge controller in hardware. By having the voltage on the VBAT, the CHRGJ2N control line could enable or disable the U908 battery charge controller (CHRG_EN = HIGH would activate the U909 battery charge controller by pulling down the U908 MR input pin). R921 provides battery isolation and U906a input so that the current drain is limited to a maximum of 42 uA although the U906 creates HIP (high impedance} inputs and outputs when power is not present in your VCC. LOW preset input level to U906a during host processor resetting R920 is the pull resistor for CHRG_FLG making it valid only for as long as the U909 battery charge controller is activated U907 produces the battery presence indicator when monitoring the battery BAT_ID input. Its output would be at HIGH logic level any time the BAT_ID resistor is present and its pull is provided by the BAT_CHK signal. The U9Q1 Low Drop Voltage Regulator (ΤΟΚΟ TK71733SCL) provides a supply of 3 , 3 V set for USB data line pull resistors, as well as 3.3 V supply for various components in the charger circuit and as an indicator that a external is attached (EXT_PWR_CD). U901 has reverse concealment and overcurrent protection, built-in thermal shutdown and short circuit protection. U901 supplies power to U906, U908 and U905 as well as 3.3 V voltage to the pull resistor. It is also used to provide indication of the presence of VBUS for the system (EXT + PWR_CD). R904 is used to limit the current at the system input pin. C915 is an input bypass capacitor and C922 is the output filtering capacitor. C910 is used to filter out RF noise that enters the RF circuit, and C912 is the deviation capacitor for internal reference. Q907 is used to switch the USB_VPU voltage and allow smooth enumeration on the USB bus. R909 provides the default OFF condition for P-FET and R905 provides the quick discharge of the USB_SFTCN control line (during RST or suspended initiation without battery). U904 supplies supply voltage to the USB transceiver insert (this is a standard voltage regulator as known in technology). It is activated when VBUS is present #e. Automatically turns off the power when VBUS goes to OFF. C921 and CO13 are output filter capacitors. U904 can optionally be removed to save cost; R942 must then be populated to supply power to the USB transceiver insert. U904 should only be necessary if the transceiver insert does not meet the USB suspension current requirements (and our device can wake up from the suspension by looking only at the D + / D- line responses). U905 and Q908 are essentially used to keep L_BAT = VBAT when VBUS is not present, and to keep L_BAT at least 3.6 V when VBUS is present (while the charger is delivering current to the system) and the battery voltage is below 3.6 V. It is also used to subdivide the total energy dissipation in two (between the battery charge controller and Q908 main pass element) to allow higher charge currents at all battery voltage levels. .

Another important feature of this circuit is to allow proper USB enumeration when the battery is low / dead or not present, by allowing the system to wake up within 15 mS when the battery is not present or dead. Once the U909 delivers all programmed current, U905 / Q908 will keep the minimum pre-programmed voltage at L_BAT (3.5 V in our case) when varying the Q908 drain-to-source resistance. The positive input of U905 is used as a reference and is fixed by R934 and R913. C924 allows a slow upward LBAT ramp, so that the U909 battery charge controller can deliver the full programmed current until Q908 prompts the voltage to increase by L_BAT (if required). Resistor splitters R916 and R915 are used to set the 'minimum voltage1' to L_BAT, while the R914 provides a portal pull pull resistor for Q908. U907 provides the system with indication of the presence of the battery. R927 and R929 are used for fix the reference and R928 is the pull resistor to open the drain outlet of U907.BAT_ID is then displayed its negative input and NO_BAT_N is fixed accordingly.

Preferred values for the components in this circuit are as shown in Figures 7A-7C. Of course, these values will vary with the application and design parameters.

Software Versions: Instead of using only electronic hardware as shown above, the invention may also be implemented using a combination of hardware and software components, including programmable devices such as digital signal processors (DSPs), microcontrollers, portal meshes. field programmable (FPGAs), application specific integrated circuits (ASICs) and the like. Such a version could be implemented as shown in the flowchart of Figure 8.

Like the versions described above, this method could be used to charge any rechargeable battery in a portable or similar electronic device. Any external power source could be used, although the invention is most useful with limited capacity power sources.

As shown in Figure 8, the method of the invention begins at step 90 by connecting the input of a battery charge controller 20 to the external power source, preferably via a USB cable and connectors 16, and a cradle 10 for holding. the portable device 18. The output of the battery charge controller 20 is connected in parallel to the portable device 18 and the input of semiconductor switch Q1 according to step 82, and the output of said semiconductor switch Al is connected to the battery. rechargeable 24 according to step 94. Next, the current output of the battery charge controller 20 is somehow controlled in step 96. As noted above, this can be done in many ways, for example, A digital-to-analog converter (DAC) output from a microcontroller could be used to send an appropriate signal to the battery charge controller's current control input. through the battery charge controller 20 is then measured in step 98. This task could also be done in many ways. For example, many microcontrollers supplied with integral ADCs (analog-to-digital converters) that could be used to perform this function.

Since this current is controlled in step 96, and the voltage drop across the battery charge controller 20 is measured in step 98, this methodology can deduce what the power dissipation is for the battery charge controller 20. The invention is therefore capable of controlling power dissipation by modulating the semiconductor switch Q1 in response to the voltage drop across the battery charge controller 20 in step 100, reducing the amount of current supplied to the rechargeable battery 24 when the voltage drop occurs. voltage is too big.

In this way the total power dissipated by the battery charge controller 20 is controlled; portable device 18 receives the power it needs to operate and rechargeable battery 24 receives any additional power available; The balance of the software code required to perform this algorithm would be simple for one skilled in the art.

The method steps of the invention may be incorporated into executable machine code sets stored in a variety of formats such as object code or source code, integrated with code from other programs, implemented as subroutines, by external program calls or by other techniques. as it is known in technology.

Even hardware versions of the invention could be encoded in software form like the hardware development languages (HDL code) used to make integrated circuits. This HDL or similar code could be stored on any electronic media such as computer diskettes, CD-ROMs, Random Access Memory (RAM) and read-only memory (ROM). Also, electronic signals representing this software code may also be transmitted over a communication network. ■ · Options and Alternatives;

Although particular versions of the present invention have been shown and described, it is clear that changes and modifications may be made to such versions without departing from the true scope and spirit of the invention. For example: 1. The circuit of the invention could be used with any type of power source, including: conventional AC power sources (often referred to as "sockets"), computer data buses such as USB ports, battery batteries. external, laptop power sources, and DC outputs in automobiles or aircraft; 2, Any kind of electrical appliance could be charged with such circuit including portable laptop computers, personal digital assistants (PDAs), mobile phones, wireless and radio call correspondence devices; and 3. Any type of rechargeable battery could be used, including single or multiple lithium ion, nickel cadmium cells or other cell types.

Again, such implementations would be clear to one skilled in the technology of the teachings herein, and not subtracted from the invention.

Industrial Applicability: The present invention provides a method and apparatus for charging a battery in a portable communication device from a variety of power sources.

Claims (21)

1. Battery charging circuit, comprising: a battery charge controller (20) configured to receive power from an external universal serial bus (USB) port (12), and supply output power to a portable device (18). ) and a rechargeable battery (24); the battery charge controller being further configured to limit the output power such that the portable device and rechargeable battery cannot pull more than a predetermined maximum available current from the USB port; and a voltage sensing circuit (30) configured to measure the voltage drop across the battery charge controller, and to respond to the voltage drop across the battery charge controller, characterized in that it controls a quantity of current supplied to the battery. The rechargeable battery is such that the portable device receives a predetermined amount of power required to operate and the rechargeable battery receives the remaining available power from the battery charge controller. Battery charging circuit according to Claim 1, characterized in that it further comprises: an external driver semiconductor controlled by the battery charge controller (20) and operated to supply supply current from the USB port (12) to the portable device (18) and the rechargeable battery (24), wherein the supply current passes through the external drive semiconductor rather than through the battery charge controller. Battery charging circuit according to claim 2, characterized in that the voltage sensing circuit (30) includes an operational amplifier. Battery charging circuit according to claim 3, characterized in that the voltage sensing circuit (30) comprises: an operational amplifier configured to compare a voltage signal from the battery charge controller (20) to a reference voltage signal, and further configured to respond to a voltage difference where the voltage signal is less than the reference voltage by reducing the current to the rechargeable battery (24). Battery charging circuit according to claim 3, characterized in that the voltage sensing circuit (30) includes an operational amplifier for comparing the voltage at the output of the battery charge controller (20) with a voltage of reference. Battery charging circuit according to Claim 2, characterized in that the low-energy critical components of the portable device (18) are fed from the battery charge controller (20) and the non-critical high-voltage components. power of said portable device is fed from the rechargeable battery (24). Battery charging circuit according to Claim 6, characterized in that the low-energy critical components include at least one between a memory and a microprocessor. Battery charging circuit according to claim 6, characterized in that the non-critical high energy components include at least one between a background light system and a vibrator. Battery charging circuit according to claim 2, characterized in that the external driving semiconductor includes a transistor. Battery charging circuit according to Claim 4, characterized in that the operational amplifier circuit further includes a voltage divider for scaling down the battery charge controller voltage signal and the battery voltage signal. be scaled down proportionally. Battery charging circuit according to claim 2, characterized in that the predetermined maximum current that can be pulled from said battery charge controller (20) is limited by an external resistance in the ground. A battery charging circuit according to claim 1, further comprising: a semiconductor switch coupled between the battery charge controller (20) and the rechargeable battery (24), the semiconductor switch being controlled by the voltage sensing circuit to limit the amount of current supplied to the rechargeable battery (24). Battery charging circuit according to Claim 1, characterized in that the battery charge controller (20) can be configured to set the predetermined maximum current depending on the current limits of the USB port (12). Battery charging circuit according to Claim 13, characterized in that the available predetermined maximum current of the USB port (12) may be set to about 100 mA for a low-power USB port and may be fixed to about 500 mA for a high power USB port. Battery charging circuit according to Claim 1, characterized in that the battery charging controller (20) is further configured to receive power from a non-USB source. Battery charging circuit according to claim 15, characterized in that the battery charge controller (20) may be configured to fix the predetermined maximum current depending on whether power is received from the USB port (12). or non-USB source. Battery charging circuit according to Claim 15, characterized in that the non-USB source is an AC plug-in adapter. Battery charging circuit according to Claim 15, characterized in that the non-USB source is a DC / AC adapter for use with a car. Battery charging circuit according to claim 15, characterized in that the battery charge controller (20) may be configured to set the predetermined maximum current to one of a plurality of current limits depending on whether Power is received from a low-power USB port, a high-power USB port, or a non-USB source. A method for charging a rechargeable battery (24) to a portable device (18) using power supplied by a universal serial bus (USB) port (12), comprising: receiving power from the USB port; provide the power received for the rechargeable battery and the portable device, where the power supplied is limited such that the rechargeable battery and the portable device may not pull more than a predetermined maximum amount of current available from the USB port; measure using voltage sensing circuit, the voltage drop across a circuit used to provide the received power for the rechargeable battery and the portable device; and further comprising controlling the amount of current supplied to the rechargeable battery as a function of the measured voltage drop such that the portable device receives a predetermined amount of the received energy required to operate and the rechargeable battery receives the remainder of the received energy. . A system for charging a rechargeable battery (24) to a portable device (18) using power supplied by a universal serial bus (USB) port (12), comprising: means for receiving power from the USB port; means for providing the received power to the rechargeable battery and the portable device, wherein the supplied power is limited such that the rechargeable battery and the portable device may not pull more than a predetermined maximum amount of current available from the USB port; means for measuring, using a voltage sensing circuit, a voltage drop across a circuit used to provide the received power for the rechargeable battery and the portable device; and further comprising means for controlling the amount of current supplied to the rechargeable battery as a function of the measured voltage drop; such that the portable device receives a predetermined amount of the received energy required to operate and the rechargeable battery receives the remainder of the received energy.