Autonomous adapter pass through mode for buck-boost battery charger

According to certain aspects, the present embodiments are related to systems and methods providing an autonomous adapter pass through mode in a battery charger. For example, when an adapter is connected to the battery charger, but the system is idling, embodiments allow for power from the adapter to be directly coupled to the battery charger output, and main switching to be stopped, thereby dramatically reducing battery charger current consumption. These and other embodiments provide various circuitry and techniques to ensure that the battery is protected in this mode. According to further aspects, the present embodiments provide for the charger itself to autonomously enter and exit the adapter pass through mode, thereby eliminating the need for excessive processing overhead in components external to the battery charger.

TECHNICAL FIELD

The present embodiments are directed generally toward battery charging, and more particularly to an autonomous adapter pass through mode for buck-boost chargers.

BACKGROUND

Battery chargers, in particular battery chargers for mobile computing devices, are evolving beyond just being responsible for charging a battery when a power adapter is connected. For example, conventional mobile computing devices such as laptop or notebook computers include a dedicated and typically proprietary plug-in port for a power adapter. When the adapter is plugged in to this dedicated port, the battery charger is responsible for charging the battery using the adapter voltage specified by the manufacturer of the mobile computing device. Relatedly, most conventional mobile computing devices also include standardized interfaces such as Universal Serial Bus (USB) ports. When an external device is plugged into such a USB port, the mobile computing device can exchange data with the external device using the well-known USB protocol. Moreover, the USB standard allows the connected external device (e.g. a smartphone with a micro USB port) to receive power from the mobile computing device via the mobile computing device's USB interface, for example to charge the external device's own battery. Accordingly, conventional battery chargers are further responsible for allowing power to be supplied from the battery to the external device, including from the mobile computing device's own battery when a power adapter is not connected.

Recently, some mobile computing device manufacturers have moved toward replacing the typically separate and proprietary power adapter port with USB ports supporting the newer USB Type C (USB-C) or USB Power Delivery (USB PD) protocols. USB-C supports bi-directional power flow at a much higher level than previous versions of the USB interface (e.g. 5V). Starting from a default 5V voltage, the USB-C port controller is capable of negotiating with the plugged-in device to raise the port voltage to 12V, 20V, or another mutually agreed on voltage, at a mutually agreed current level. The maximum power a USB-C port can deliver is 20V at 5 A current, which is 100 W of power—more than adequate to charge a computer, especially since most 15-inch Ultrabooks require just around 60 W of power.

Conventional battery chargers will need to change when mobile system manufacturers transition to using power adapters that connect to the USB-C port. The battery charger must be capable of charging a battery for a mobile computing device (e.g. an Ultrabook having a 1-, 2-, 3- or 4-cell battery stack) with power from a USB-C adapter having a 5V-20V range. Future battery chargers will also need to accommodate the need to supply power to external electronic devices such as tablets, smartphones, power banks and more that connect to the mobile computing device via the USB-C port. There are many challenges that need to be overcome to accomplish this requirement, such as challenges arising when an adapter is connected to the USB-C port, but the system is idling.

SUMMARY

According to certain aspects, the present embodiments are related to systems and methods providing an autonomous adapter pass through mode in a battery charger. For example, when an adapter is connected to the battery charger, but the system is idling, embodiments allow for power from the adapter to be directly coupled to the battery charger output, and main switching to be stopped, thereby dramatically reducing battery charger current consumption. These and other embodiments provide various circuitry and techniques to ensure that the battery is protected in this mode. According to further aspects, the present embodiments provide for the charger itself to autonomously enter and exit the adapter pass through mode, thereby eliminating the need for excessive processing overhead in components external to the battery charger.

DETAILED DESCRIPTION

The present embodiments will now be described in detail with reference to the drawings, which are provided as illustrative examples of the embodiments so as to enable those skilled in the art to practice the embodiments and alternatives apparent to those skilled in the art. Notably, the figures and examples below are not meant to limit the scope of the present embodiments to a single embodiment, but other embodiments are possible by way of interchange of some or all of the described or illustrated elements. Moreover, where certain elements of the present embodiments can be partially or fully implemented using known components, only those portions of such known components that are necessary for an understanding of the present embodiments will be described, and detailed descriptions of other portions of such known components will be omitted so as not to obscure the present embodiments. Embodiments described as being implemented in software should not be limited thereto, but can include embodiments implemented in hardware, or combinations of software and hardware, and vice-versa, as will be apparent to those skilled in the art, unless otherwise specified herein. In the present specification, an embodiment showing a singular component should not be considered limiting; rather, the present disclosure is intended to encompass other embodiments including a plurality of the same component, and vice-versa, unless explicitly stated otherwise herein. Moreover, applicants do not intend for any term in the specification or claims to be ascribed an uncommon or special meaning unless explicitly set forth as such. Further, the present embodiments encompass present and future known equivalents to the known components referred to herein by way of illustration.

According to certain general aspects, the present embodiments relate to methods and apparatuses for operating a battery charger in computing systems having certain system load requirements, battery configurations and external device power supply support. According to further aspects, when an adapter is connected to the battery charger, but the system is idling, embodiments allow for power from the adapter to be directly coupled to the battery charger output, and main switching to be stopped, thereby dramatically reducing battery charger current consumption. These and other embodiments provide various circuitry and techniques to ensure that the battery is protected in this mode.

FIG. 1is a block diagram illustrating aspects of an example system100incorporating the present embodiments. System100is a computing device such as a notebook computer (e.g. MacBook, Ultrabook, etc.), laptop computer, pad or tablet computer (iPad, Surface, etc.), etc., a power bank, a USB-C interface platform, or any system using a battery with sensitivity to the supply rail. In these and other embodiments, system100includes a load116, such as a CPU running a conventional operating system such as Windows or Apple OS, and can be an x86 processor from Intel, AMD or other manufacturers, as well as other processors made by Freescale, Qualcomm, DSPs, GPUs, etc. It should be apparent that system100can include many other components not shown such as solid state and other disk drives, memories, peripherals, displays, user interface components, etc. According to certain aspects, a system100in which the present embodiments can find particularly useful application has operational power needs that can exceed the power limits of technologies such as USB-A, for example over 60 watts. However, the present embodiments are not limited to applications in such systems.

As shown, system100includes a battery104and a battery charger102. In embodiments, charger102is a buck-boost narrow output voltage DC (NVDC) charger. According to certain general aspects, during normal operation of system100, when a power adapter is plugged into port106, battery charger102is configured to charge battery104. Preferably, in addition to charging battery104, battery charger102is further adapted to convert the power from the adapter to a voltage suitable for supplying to components of the system100, including load116(e.g., in a buck mode, a boost mode, or a buck-boost mode as is known in the art). According to certain other general aspects, when a power adapter is not plugged into port106, battery charger102is configured to manage the supply of power to the load116and/or a peripheral device connected to port106from battery104(e.g., in a buck mode, a boost mode, or a buck-boost mode as is known in the art). Further details of battery charger102according to the present embodiments will be provided below.

In notebook computer (e.g. Ultrabook) and other embodiments of system100, battery104can be a rechargeable 1S/2S/3S/4S (i.e. 1 cell, 2 cell, 3 cell, or 4 cell stack) Lithium-ion (Li-ion) battery. In these and other embodiments, port106can be a Universal Serial Bus (USB) port, such as a USB Type C (USB-C) port or a USB Power Delivery (USB PD) port. Although not shown inFIG. 1, switches between port106and charger102can also be provided for controllably coupling power from an adapter connected to port106to charger102, or alternatively providing system power to charger102and/or port106. Such switches can also include or be implemented by active devices such as back-to-back FETs.

As further shown, example system100in which the present embodiments can find useful applications includes a Type C port controller (TCPC)112and an embedded controller (EC)114. TCPC112includes functionality for detecting the type of USB device connected to port116, controlling switches associated with connecting port106to system100, and for communicating port status to EC114(e.g. via an I2C interface). EC114is generally responsible for managing power configurations of system100(e.g. depending on whether a power adapter is connected or not connected to port106as communicated to EC114from TCPC112, etc.), receiving battery status from battery104, and for communicating battery charging and other operational control information to charger102(e.g. via SMbus interface), as will become more apparent from the descriptions below.

According to certain aspects, the present applicant recognizes various problems afflicting conventional battery chargers such as that shown inFIG. 1, and/or adapters incorporating voltage regulators or converters. One problematic scenario is when the charger is plugged into an adapter, but not charging, but idling (i.e. VSYS is up). Certain industry and customer standards such as the EUP Lot7 and Energy Star requirements are toughest at the idle state, requiring less than 300 mW dissipated from the entire system, for example. Meanwhile, in order to pass an adapter voltage of 5V to an output load of 20V, VSYS must be maintained greater than the battery voltage VBAT to prevent battery current from flowing back into the adapter. The battery must also be protected from excessive voltage or discharge. Another problem to consider is thermal issues (although such issues are typically easier to handle). Finally, charger102should preferably be able to manage the idle state in an autonomous manner; i.e., EC114should not be required to monitor the idle state for customer ease of use.

To address these issues, some conventional products have a pass through mode from adapter to load, but they do not monitor anything to automatically exit this mode. Moreover, these products are typically not battery chargers but buck-boost bi-directional regulators. In other attempts, some conventional buck regulators go into a 100% duty cycle mode and exit based on input/output voltage. Some regulators transition from buck to boost modes with a pass through instead of a buck-boost phase (i.e., regulation voltage is not as tight). None of these attempted solutions are fully satisfactory.

According to certain aspects, the present embodiments address these and other issues by incorporating autonomous adapter pass-through mode functionality in a buck-boost charger. According to further aspects, the present embodiments can monitor key parameters to independently enter and exit the pass-through mode while keeping the system within safe operation. For example, one important object that is satisfied in embodiments is that the battery is always protected.

FIG. 2is a schematic diagram of an example implementation of the present embodiments using an integrated circuit202.

The example charger102in these embodiments includes a plurality of power switching transistors including a field-effect transistor (FET) Q1, having its drain coupled to node204and its source coupled an intermediate node206. Another FET Q2has its drain coupled to node206and its source coupled to GND. The charger102includes an inductor L1coupled between node206and the node208. The example charger102in these embodiments further includes FET Q4, having its drain coupled to output node210and its source coupled an intermediate node208. Another FET Q3has its drain coupled to node208and its source coupled to GND. As shown, output node210provides a system voltage VSYS to a system load116such as a CPU (not shown).

Charger102in this example further includes a battery current sense resistor Rs2coupled between output node210and an intermediate node212. Another FET214has its source coupled to node212and its drain coupled to the rechargeable battery104developing the battery voltage VBAT. The gate of FET212is coupled to the IC202for controlling charge and discharge of the rechargeable battery104. For example, when the power adapter is not connected, the FET214may be turned fully on to provided power to the system load via VSYS. When the power adapter is connected, the FET214may be controlled in a linear manner to control charging of the rechargeable battery104.

The FETs Q1, Q2, Q3, Q4and214are shown implemented using N-channel MOSFETs, although other types of switching devices are contemplated, such as P-channel devices, other similar forms (e.g., FETs, MOS devices, etc.), bipolar junction transistor (BJTs) and the like, insulated-gate bipolar transistors (IGBTs) and the like, etc.

As shown, IC202according to the present embodiments includes normal module222and a pass-through mode (PTM) module224that respectively control operation of transistors Q1, Q2, Q3and Q4via output connections to the gates thereof during a normal mode and during a pass-through mode. Modules222and224are shown separately for ease of illustration but can include common circuitry, including circuitry also shared by modules for controlling other operations of system100by IC202. Additionally and relatedly, although the present descriptions will focus on IC202operating when an adapter is connected to port106, it should be apparent that IC202can include additional functionality for operating in other modes, such as when a power adapter is not connected to port106and battery104is supplying power to the load. The details of such additional functionality and/or circuitry will be omitted here for sake of clarity of the present embodiments.

Module222operates FETs Q1, Q2, Q3, Q4and214in a buck mode, a boost mode, or a buck-boost mode to regulate the output voltage VSYS to a narrow DC range for stable system bus voltage. Module222can operate when system is provided from the adapter, battery, or a combination of both (e.g., with only the battery104connected, with only an adapter connected to port106, or a combination of both). As such, in embodiments, module222is configured to operate in a variety of power and load conditions, such as battery104configurations of 2-, 3- or 4-cell Li-ion batteries, input voltages having a range of 3.2 V to 23.4 V, and system output voltages VSYS having a range of 2.4 V to 18.304 V. Various known techniques can be used to implement module222, and so further details thereof will be omitted here for sake of clarity of the invention.

Module224implements PTM operations to regulate the output voltage VSYS when both an adapter and a battery are connected (as well as various other conditions), according to aspects of the present embodiments and as will be described in more detail below. Module226determines and manages autonomous PTM mode entry and exit conditions (i.e., the determination and selection of operation of module224in place of operation of module222is managed entirely within IC202) as will also be described in more detail below. It should be appreciated that IC202can include additional modules for controlling operations according to other system requirements, as well as other components. However, details of such additional modules and components will be omitted here for sake of clarity of the present embodiments.

FIG. 3is a diagram illustrating an example implementation of Normal mode module222and PTM module224according to embodiments.

As shown in this example implementation, modules222and224share much the same circuitry. More particularly, as shown inFIG. 3, for both normal mode and PTM mode, there are four control loops: system voltage loop302, charge current loop304, adapter current loop306and input voltage loop308. As further shown, each loop has its own DAC and feedback, which produce corresponding voltages that are provided to an error amplifier.

During normal mode, the amplified error from each loop comprise the difference between the feedback voltage and the DAC voltage. The loop selector310receives and compares the four amplified loop errors, and picks the loop with highest error (or the highest error above a minimum threshold error voltage) as the regulation loop in control. Depending on the loop selected by loop selector320, modulator312produces a PWM modulated signal using the loop errors from the selected one of loops302,204,306,308. PWM driver312operates FETs Q1, Q2, Q3, Q4based on PWM modulated signal from modulator312.

More particularly, as shown in the example ofFIG. 3, when loop302is selected by loop selector320, modulator312acts to regulate the output voltage VSYS to a reference voltage specified by CV_DAC. When loop304is selected, modulator312acts to regulate the voltage corresponding to the battery current across Rs2to a reference voltage specified by I_BAT_DAC. When loop306is selected, modulator312acts to regulate the voltage corresponding to the battery current across Rs1to a reference voltage specified by I_AC_DAC. When loop308is selected, modulator312acts to regulate the adapter voltage VIN to a reference voltage specified by VIN_DAC.

In general, during PTM, the loop selector320is disabled and power from the adapter coupled to port106is provided directly to the load116, which dramatically decreases the amount of power consumed by charger102. To do this, PWM driver314turns on Q1and Q4and turns off Q2and Q3. In embodiments, however, rather than completely stopping the switching of Q1, Q2, Q3and Q4as performed in normal mode (e.g. to maintain a regulated voltage VSYS at the output), entry/exit module226activates a timer in modulator312that, when it expires due to no switching cycles, forces one quick cycle of the gates to Q2and Q3so as to refresh the gate voltage.

Likewise, during PTM, entry/exit module226receives the outputs from loops302,304,306and308to control PTM mode entry/exit as will be described in more detail below. It should be noted that, although the same DACs can be used, the DAC settings might be different in PTM than in normal mode.

FIG. 4is a logic block diagram illustrating an example implementation of autonomous PTM entry/exit module226according to embodiments.

As shown inFIG. 4, a flip-flop402latches on its Q output indicating entry into PTM mode based on a set input from AND gate404, and turns off the Q output indicating an exit from PTM mode based on a reset input from OR gate406.

As further shown in this example, AND gate404has four inputs, which all need to be set “on” in order for the output of AND gate404to be turned “on”, and thus for flip-flop402to indicate entry into PTM mode. One input is a PTM Request control bit. In embodiments, this is set to “on” based on an input to charger102from EC114, via an SMBus for example. Another input is BGATE_OFF, which when in the “on” state, indicates that the BFET214connected to battery104is turned off, thereby protecting the battery during PTM mode. A third input is ENCHG=0, which when “on”, indicates that charging of battery104by charger102is completely disabled. A fourth input is VIN=VOUT, which is set to “on” when the charger102determines that the input voltage VADP from the adapter at port106is substantially equal to the output voltage VSYS on the output of charger102. For example, module224and/or226can include circuitry for controlling modulator312to ramp the output voltage VOUT/VSYS toward the value of the input voltage VIN/VADP, and these voltage values can be compared via loops302and308.

Returning to the example ofFIG. 4, OR gate406has seven inputs, any one of which, when set “on,” will cause the output of OR gate406to be turned “on”, and thus for flip-flop402to indicate exit from PTM mode. A first input ADPOV is set to “on” when charger102determines that the adapter voltage exceeds an over-voltage value. For example, as shown inFIG. 4, this happens when the input voltage VIN from the adapter (after being divided by 12 in this example) falls below a reference value (either 1.92V or 1.4V in this example) as detected by comparator408in module226. A second input BATDC is set to “on” when charger102determines that IDCGT has reached 300 mA. This provides a margin to prevent the battery BFET214to be turned back on until VSYS is about equal to VBAT to prevent damage to the BFET. A third input ACLIM is set to on when charger102determines that IGTCBC is on, which indicates that the adapter current has reached a limit. A fourth input is set to “on” when the adapter voltage value AVSEL indicates that VIN has fallen below a brownout threshold voltage.

A fifth input to OR gate406is when the input voltage VIN has fallen substantially below the output voltage VOUT, which can be detected by comparing VIN to a voltage reference from a DAC, for example. A sixth input is set to “on” when a CC register bit has been set to a non-zero value, indicating that the battery needs to be charged. A seventh input is set to “on” when any one of a number of optional fault conditions are detected by charger102, such as an output overcurrent fault WOC, a power-on reset fault POR and an over-temperature fault OT.

FIG. 5is a flowchart illustrating an example methodology for implementing an autonomous adapter PTM according to embodiments.

For illustration,FIG. 5shows charger102operating in a normal (i.e. non-PTM) mode in block S502. In the example ofFIG. 2, this can include normal mode222controlling the switching of FETs Q1, Q2, Q3and Q4to provide a regulated output to load116as described above, including when an adapter is attached to port106or not attached, and whether or not battery104is being charged.

Block S504represents a condition where a transition to PTM mode from normal mode is indicated. For example, EC114can request that charger102transition to PTM mode by signaling that PTM is enabled (e.g. by setting an appropriate bit or sending an appropriate SMBus signal). It should be appreciated that EC114(either alone or with interaction with charger102while module222is still active) can also simultaneously or previously perform a number of PTM mode set-up operations. This can include, for example, performing certain operations to ensure BFET214is tuned off and to otherwise protect battery104. EC114can do this by writing certain values to registers via SMBus, such as writing CC=0 A and IDM Disable (e.g. Control1, bit6). EC114can also perform certain operations to cause VSYS and/or VIN/VADP to ramp towards the same voltage value. In connection with VSYS, EC114can direct charger102to regulate VSYS to a certain target voltage (e.g. via SMbus). Additionally or alternatively, in connection with VIN/VADP, EC114can cause TCPC112to negotiate the same target voltage with the adapter via port106and USB-C protocols. In embodiments, EC114can also perform certain operations to prevent battery current from flowing back to the adapter, such as by writing the VBAT voltage level to VINREG in charger102via SMBus.

In response to the indication that PTM mode is requested in S504, charger102autonomously performs certain operations to transition into PTM mode in block S506. Referring toFIG. 4, this block can include module226monitoring several conditions before causing flip-flop402to latch the PTM status (e.g. Q output is “On”) and to thereby activate PTM module224and turn off the main switching performed by module222. Importantly, module226monitors VSYS/VOUT to determine when/whether it has reached the level of VADP/VIN. In the example ofFIG. 4, several other PTM mode entry conditions are verified, including determining whether the BGATE214is turned off, and whether charging has been disabled.

Once latched, PTM mode operation of charger102is commenced in block S508. This block includes the operation of PTM module224, for example as described in connection withFIG. 3.

The present embodiments allow for PTM mode to be exited either autonomously or by an external request, such as from EC114. The example methodology shown inFIG. 5illustrates the former. More particularly, as shown inFIG. 5, as described in more detail in connection withFIG. 4, block S510includes PTM entry/exit module226monitoring certain conditions, any one of which can cause PTM mode to be exited. For example, these conditions include an adapter overvoltage condition (ADPOV), a battery discharge condition, an adapter overcurrent condition (ACLIM), an input voltage brownout condition, an input/output voltage mismatch condition, a need for battery charging, and other fault conditions.

As further shown in the example ofFIG. 5, when PTM mode exit is detected in block S510, charger102can perform a number of additional autonomous exit operations in block S512. For example, in the case of ADPOV, charger102can perform a restart operation, turn off the ASGATE, and perform similar operations as in any other ADPOV condition. In the case of battery discharge, since IDM has been disabled, BGATE214will still stay OFF. Nevertheless, charger102can provide a margin for transients since VADP should be way above the battery voltage VBAT. So charger102will not allow BFET214to be turned back on until VSYS and VBAT are about the same so as to prevent damage to BFE214. In any of these or other exit conditions, operation returns to block S502, and main switching resumes, for example as performed by normal mode operating module222.

As set forth above, although not shown inFIG. 5, PTM mode exit can be controlled by an external entity, such as by EC114using SMBus signals to charger102. This can include performing operations to ensure that PTM module224is deactivated and a return to switching as controlled by module222is resumed. For example, EC114can write SMBus PTM Disable bit and write a non-zero value to CC register via SMBus CC=non-zero (CC register). EC114(alone or in interaction with charger102) further preferably monitors VSYS before BFET214is allowed to turn on or else the battery will see an excessive voltage/current spike. This can be handled internal using comparators and ideal diode mode logic. Finally, EC114can optionally write various SMBus target values such as IDM, VINREG and ACLIM.

It should be noted that the Autonomous PTM mode of the present embodiments can be set-and-forget by customers and so overhead processing to monitor and protect the system or the battery is not needed. As such, buck-boost chargers with Autonomous PTM could replace all existing buck-boost chargers.

Although not described in detail herein, in an additional or alternative embodiment, for low power needs, a low ohm switch can short the adapter to VSYS. It could even be put into an LDO mode to provide some OCP and OV protection. The same fault conditions could be used to exit this mode.

Although the present embodiments have been particularly described with reference to preferred examples thereof, it should be readily apparent to those of ordinary skill in the art that changes and modifications in the form and details may be made without departing from the spirit and scope of the present disclosure. It is intended that the appended claims encompass such changes and modifications.