PATENT DOCUMENT

Publication Number: US-9831672-B2
Application Number: US-201514733186-A
Country: US
Kind Code: B2

Title: Power delivery in a multiple-output system

Abstract:
The disclosed embodiments provide a system that operates a power supply. During operation, the system disposes a first switching mechanism between a first output of a first power converter and two or more loads. Next, the system obtains two or more error signals for the two or more loads, wherein each error signal from the two or more error signals represents a difference between a load voltage of a load from the two or more loads and a first reference voltage for the load from a first set of reference voltages for driving the two or more loads using the first power converter. The system then uses the first switching mechanism to couple the load with a largest error signal from the two or more error signals to the first output.

Claims:
What is claimed is: 
     
       1. A method for operating a power supply, comprising:
 obtaining two or more error signals for two or more loads coupled to a first output of a first power converter via a first switching mechanism, wherein each error signal from the two or more error signals represents a difference between a load voltage of a load from the two or more loads and a first reference voltage for the load from a first set of reference voltages for driving the two or more loads using the first power converter; and 
 using the first switching mechanism to couple the load with a largest error signal from the two or more error signals to the first output. 
 
     
     
       2. The method of  claim 1 , further comprising:
 generating a control signal for controlling an output current of the first power converter using at least one of:
 a largest value of a half-wave-rectified error signal from the two or more error signals; 
 a sum of positive error signals from the two or more error signals; and 
 an on-duration of a logical disjunction signal generated from the two or more error signals. 
 
 
     
     
       3. The method of  claim 2 , wherein the output current is proportional to the control signal. 
     
     
       4. The method of  claim 1 , further comprising:
 uncoupling the first power converter from the two or more loads upon detecting a higher load voltage for each load from the two or more loads than the first reference voltage for driving the load from the two or more loads. 
 
     
     
       5. The method of  claim 1 , further comprising:
 upon detecting a lower load voltage of the load than a second reference voltage for the load from a second set of reference voltages for driving the two or more loads using a second power converter, engaging the second power converter to supplement the lower load voltage with an output voltage from a second output of the second power converter. 
 
     
     
       6. The method of  claim 5 , further comprising:
 using a second switching mechanism disposed between the second output and the two or more loads to couple the load with the largest error signal to the second output. 
 
     
     
       7. The method of  claim 6 ,
 wherein the first power converter has a higher efficiency than the second power converter, and 
 wherein the second power converter has a higher power than the first power converter. 
 
     
     
       8. The method of  claim 7 ,
 wherein a first switching frequency is used by the first switching mechanism to couple the load with the largest error signal to the first output, and 
 wherein a second switching frequency that is higher than the first switching frequency is used by the second switching mechanism to couple the load with the largest error signal to the second output. 
 
     
     
       9. The method of  claim 7 , wherein the first reference voltage for the load is higher than the second reference voltage for the load. 
     
     
       10. The method of  claim 1 , wherein the two or more error signals comprise two or more request signals obtained from two or more comparators. 
     
     
       11. The method of  claim 10 , wherein using the first switching mechanism to couple the load with the largest error signal to the first output comprises:
 coupling the first output to the load associated with a comparator from the two or more comparators that first asserts a request signal representing a lower load voltage for the load than the reference voltage for the load; and 
 maintaining coupling of the first output to the load for a minimum pre-specified time. 
 
     
     
       12. A power supply, comprising:
 a first power converter with a first output; 
 a first switching mechanism disposed between the first output and two or more loads; and 
 a control circuit configured to:
 obtain two or more error signals for the two or more loads, wherein each error signal from the two or more error signals represents a difference between a load voltage of a load from the two or more loads and a first reference voltage for the load from a first set of reference voltages for driving the two or more loads using the first power converter; and 
 use the first switching mechanism to couple the load with a largest error signal from the two or more error signals to the first output. 
 
 
     
     
       13. The power supply of  claim 12 , further comprising:
 a second power converter with a second output for driving at least one of the two or more loads, 
 wherein upon detecting a lower load voltage of the load than a second reference voltage for the load from a second set of reference voltages for driving the two or more loads using the second power converter, the control circuit is further configured to engage the second power converter to supplement the lower load voltage with an output voltage from the second output. 
 
     
     
       14. The power supply of  claim 13 , further comprising:
 a second switching mechanism disposed between the second output and the two or more loads, 
 wherein the control circuit is further configured to use the second switching mechanism to couple the load with the largest error signal to the second output. 
 
     
     
       15. The power supply of  claim 14 , wherein the control circuit comprises:
 a first sub-circuit configured to control the first power converter and the first switching mechanism; and 
 a second sub-circuit configured to control the second power converter and the second switching mechanism. 
 
     
     
       16. The power supply of  claim 13 ,
 wherein the first power converter has a higher efficiency than the second power converter, and 
 wherein the second power converter has a higher power than the first power converter. 
 
     
     
       17. The power supply of  claim 13 , wherein the first reference voltage for the load is higher than the second reference voltage for the load. 
     
     
       18. The power supply of  claim 12 , wherein the control circuit is further configured to:
 generate a control signal for controlling an output current of the first power converter using at least one of:
 a largest value of a half-wave-rectified error signal from the two or more error signals; 
 a sum of positive error signals from the two or more error signals; and 
 an on-duration of a logical disjunction signal generated from the two or more error signals. 
 
 
     
     
       19. The power supply of  claim 18 , wherein the output current is proportional to the control signal. 
     
     
       20. The power supply of  claim 12 , wherein the two or more error signals comprise two or more request signals obtained from two or more comparators. 
     
     
       21. A portable electronic device, comprising:
 a set of components; and 
 a power supply configured to supply power to the components, wherein the power supply comprises:
 a first power converter with a first output; 
 a first switching mechanism disposed between the first output and two or more loads; and 
 a control circuit configured to:
 obtain two or more error signals for the two or more loads, wherein each error signal from the two or more error signals represents a difference between a load voltage of a load from the two or more loads and a first reference voltage for the load from a first set of reference voltages for driving the two or more loads using the first power converter; and 
 use the first switching mechanism to couple the load with a largest error signal from the two or more error signals to the first output. 
 
 
 
     
     
       22. The portable electronic device of  claim 21 , wherein the power supply further comprises:
 a second power converter with a second output for driving at least one of the two or more loads, 
 wherein upon detecting a lower load voltage of the load than a second reference voltage for the load from a second set of reference voltages for driving the two or more loads using the second power converter, the control circuit is further configured to engage the second power converter to supplement the lower load voltage with an output voltage from the second output. 
 
     
     
       23. The portable electronic device of  claim 22 , wherein the power supply further comprises:
 a second switching mechanism disposed between the second output and the two or more loads, 
 wherein the control circuit is further configured to use the second switching mechanism to couple the load with the largest error signal to the second output. 
 
     
     
       24. The portable electronic device of  claim 22 , wherein the control circuit is further configured to: 
       upon detecting an increase above a threshold in a power state of a load in the two or more loads, generating a control signal to couple all of the first and second power converters to all of the two or more loads through the first and second switching mechanisms.

Description:
RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 62/009,099, entitled “Power Delivery in a Multiple-Output System,” by inventor Louis Luh, filed 6 Jun. 2014, which is hereby incorporated by reference. 
     This application claims the benefit of U.S. Provisional Application No. 62/042,608, entitled “Power Delivery in a Multiple-Output System,” by inventor Louis Luh, filed 27 Aug. 2014, which is hereby incorporated by reference. 
     The subject matter of this application is related to the subject matter in a non-provisional application by inventors Louis Luh, William C. Athas and Heather R. Sullens filed on the same day as the instant application, entitled “Reconfigurable Multiple-Output Power-Delivery System,” having Ser. No. 14/733,211, and filing date 8 Jun. 2015. 
    
    
     BACKGROUND 
     Field 
     The disclosed embodiments relate to power-delivery systems. More specifically, the disclosed embodiments relate to power delivery in multiple-output systems. 
     Related Art 
     Often, power supplies for electronic devices such as smartphones, tablet computers, laptop computers, and desktop computers are designed to efficiently supply a wide range of power levels for a time-varying load such as a central processing unit (CPU) or graphics processing unit (GPU). However, power supplies designed to work equally well over such a wide range of power demands are typically not as efficient as power supplies optimized to supply power over a narrow range of loads. Additionally, although the control logic for a power supply that can deliver power over a wide range of power demands may be stable at a constant power level, transitioning between output power levels may cause decreased accuracy in the regulated output voltage. 
     Hence, the use of power supplies may be facilitated by improvements related to their design and configuration. 
     SUMMARY 
     The disclosed embodiments provide a system that operates a power supply. During operation, the system disposes a first switching mechanism between a first output of a first power converter and two or more loads. Next, the system obtains two or more error signals for the two or more loads, wherein each error signal from the two or more error signals represents a difference between a load voltage of a load from the two or more loads and a first reference voltage for the load from a first set of reference voltages for driving the two or more loads using the first power converter. The system then uses the first switching mechanism to couple the load with a largest error signal from the two or more error signals to the first output. 
     In some embodiments, the system also generates a control signal for controlling an output current of the first power converter using a largest value of a half-wave-rectified error signal from the two or more error signals, a sum of positive error signals from the two or more error signals, and/or an on-duration of a logical disjunction signal generated from the two or more error signals. 
     In some embodiments, the output current is proportional to the control signal. 
     In some embodiments, the two or more error signals comprise two or more request signals obtained using two or more comparators. 
     In some embodiments, using the first switching mechanism to couple the load with the largest error signal to the first output comprises coupling the first output to the load associated with a comparator from the two or more comparators that first asserts a request signal representing a lower load voltage for the load than the reference voltage for the load, and maintaining coupling of the first output to the load for a minimum pre-specified time. 
     In some embodiments, the system also uncouples the first power converter from the two or more loads upon detecting a higher load voltage for each load from the two or more loads than the first reference voltage for driving the load from the two or more loads. 
     In some embodiments, the system also provides a second power converter with a second output for driving at least one of the two or more loads. Upon detecting a lower load voltage of the load than a second reference voltage for the load from a second set of reference voltages for driving the two or more loads using the second power converter, the system engages the second power converter to supplement the lower load voltage with an output voltage from the second output. 
     In some embodiments, the system also disposes a second switching mechanism between the second output and the two or more loads, and uses the second switching mechanism to couple the load with the largest error signal to the second output. 
     In some embodiments, the first power converter has a higher efficiency than the second power converter, and the second power converter has a higher power than the first power converter. 
     In some embodiments, a first switching frequency is used by the first switching mechanism to couple the load with the largest error signal to the first output, and a second switching frequency that is higher than the first switching frequency is used by the second switching mechanism to couple the load with the largest error signal to the second output. 
     In some embodiments, the first reference voltage for driving the load using the first power converter is higher than the second reference voltage for driving the load using the second power converter. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1A  shows a power supply in accordance with the disclosed embodiments. 
         FIG. 1B  shows a power supply in accordance with the disclosed embodiments. 
         FIG. 2A  shows a system for supplying power to components of a portable electronic device in accordance with the disclosed embodiments. 
         FIG. 2B  shows an exemplary voltage-based control circuit in accordance with the disclosed embodiments. 
         FIG. 2C  shows an exemplary voltage-based control circuit in accordance with the disclosed embodiments. 
         FIG. 2D  shows an exemplary voltage-based control circuit in accordance with the disclosed embodiments. 
         FIG. 2E  shows a state diagram for a finite state machine in a control circuit in accordance with the disclosed embodiments. 
         FIG. 3A  shows a system for supplying power to components of a portable electronic device in accordance with the disclosed embodiments. 
         FIG. 3B  shows a control circuit in accordance with the disclosed embodiments. 
         FIG. 4A  shows an exemplary power-delivery system in accordance with the disclosed embodiments. 
         FIG. 4B  shows an exemplary control circuit in accordance with the disclosed embodiments. 
         FIG. 5A  shows a power-delivery system in accordance with the disclosed embodiments. 
         FIG. 5B  shows a power-delivery system in accordance with the disclosed embodiments. 
         FIG. 5C  shows a power-delivery system in accordance with the disclosed embodiments. 
         FIG. 5D  shows a power-delivery system in accordance with the disclosed embodiments. 
         FIG. 6  shows a flowchart illustrating the process of operating a power supply in accordance with the disclosed embodiments. 
         FIG. 7A  shows a power-delivery system in accordance with the disclosed embodiments. 
         FIG. 7B  shows a power-delivery system in accordance with the disclosed embodiments. 
         FIG. 8A  shows a power-delivery system in accordance with the disclosed embodiments. 
         FIG. 8B  shows a power-delivery system in accordance with the disclosed embodiments. 
         FIG. 9  shows a flowchart illustrating the process of operating a power supply in accordance with the disclosed embodiments. 
         FIG. 10A  shows a flowchart illustrating the process of operating a power supply in accordance with the disclosed embodiments. 
         FIG. 10B  shows a flowchart illustrating the process of operating a power supply in accordance with the disclosed embodiments. 
         FIG. 11  shows a portable electronic device in accordance with the disclosed embodiments. 
     
    
    
     In the figures, like reference numerals refer to the same figure elements. 
     DETAILED DESCRIPTION 
     The following description is presented to enable any person skilled in the art to make and use the embodiments, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present disclosure. Thus, the present invention is not limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein. 
     The data structures and code described in this detailed description are typically stored on a computer-readable storage medium, which may be any device or medium that can store code and/or data for use by a computer system. The computer-readable storage medium includes, but is not limited to, volatile memory, non-volatile memory, magnetic and optical storage devices such as disk drives, magnetic tape, CDs (compact discs), DVDs (digital versatile discs or digital video discs), or other media capable of storing code and/or data now known or later developed. 
     The methods and processes described in the detailed description section can be embodied as code and/or data, which can be stored in a computer-readable storage medium as described above. When a computer system reads and executes the code and/or data stored on the computer-readable storage medium, the computer system performs the methods and processes embodied as data structures and code and stored within the computer-readable storage medium. 
     Furthermore, methods and processes described herein can be included in hardware modules or apparatus. These modules or apparatus may include, but are not limited to, an application-specific integrated circuit (ASIC) chip, a field-programmable gate array (FPGA), a dedicated or shared processor that executes a particular software module or a piece of code at a particular time, and/or other programmable-logic devices now known or later developed. When the hardware modules or apparatus are activated, they perform the methods and processes included within them. 
     The disclosed embodiments provide a power supply for an electronic device. As shown in  FIG. 1A , the power supply  100  includes a power source  110  and one or more power converters  120 . Power converters  120  may obtain an input voltage or current from power source  110  and convert the input voltage or current into a number of output voltages or currents for use by a number of loads  122 - 128  in the electronic device. For example, power converters  120  may convert direct current (DC) power from a power adapter acting as power source  110  into low-voltage direct current (DC) that is used to charge a battery and/or power components of a portable electronic device such as a mobile phone, laptop computer, portable media player, and/or tablet computer. When multiple DC power sources are present (e.g., from a power adapter and an external battery), current may be supplied from either or both power sources depending on a number of factors, such as available current from the power adapter. In another example, power source  110  may further include the battery or battery pack in the portable electronic device, such as a lithium-ion and/or lithium-polymer battery pack. Thus, power converters  120  may include buck converters, boost converters, buck-boost converters, single-ended primary-inductor converters (SEPICs), Ćuk converters, and/or class-E DC/DC converters. Power converters  120 —may also be configured to convert from alternating current (AC) power to DC power, AC to AC, DC to DC, and DC to AC depending on the types of power provided by power source  110  and/or used by loads  122 - 128 . 
     In one or more embodiments, power supply  100  delivers power to multiple independent loads (e.g., loads  122 - 128 ) in a portable electronic device such as a laptop computer, tablet computer, mobile phone, personal digital assistant (PDA), portable media player, and/or digital camera. Each load may include one or more components, which are powered separately from the component(s) in other loads of the portable electronic device. For example, loads  122 - 128  may include the central processing unit (CPU), graphics-processing unit (GPU), memory, integrated circuits, radio, ports, and/or other components in the portable electronic device. The components may be grouped into different loads  122 - 128  based on the voltage, current, and/or power requirements or consumption of the components. 
     In other words, power supply  100  may include functionality to deliver power to a multiple-output system (e.g., for driving multiple loads  122 - 128 ) using one or more power converters  120 . More generally, as shown in  FIG. 1B , power converters  120  may be coupled to multiple loads  124 - 126  through a switching assembly  130  containing one or more switches. As discussed below, loads  124 - 126  may be individually coupled to one or more power converters  120 , or multiple power converters  120  may be combined into a single output that is used to power multiple loads  124 - 126 . Each load may be coupled to a feedback unit (e.g., feedback units  134 - 136 ) that monitors the current, voltage, and/or other aspects of the load. The monitored information may be provided by feedback units  134 - 136  as feedback signals to a control unit  140  that operates power converters  120  and switching assembly  130  based at least in part on the feedback signals. 
     As shown in  FIG. 2A , an input voltage (e.g., “V IN ”) is supplied from a power source  200  such as a battery for a portable electronic device and/or a power adapter. The input voltage may be converted into two load voltages (e.g., “V DD1 ” and “V DD2 ”) for driving two loads  206 - 208  respectively using a control circuit  202 , a voltage regulator  204  and/or other type of power converter, and a switching mechanism  210 . Consequently, the circuit of  FIG. 2A  may provide a single-input, multiple-output (SIMO) power supply with one input voltage and two output and/or load voltages. 
     More specifically, an input of voltage regulator  204  is coupled to the input voltage, and loads  206 - 208  are alternately coupled to an output (e.g., “p_out”) of voltage regulator  204  via switching mechanism  210 . Control circuit  202  may generate a switching signal (e.g., “SW”) that controls switching mechanism  210  to switch the output of voltage regulator  204  to either load  206 - 208 , depending on the power consumption of loads  206 - 208 . For example, control circuit  202  may use the load voltages of loads  206 - 208  as feedback voltages (e.g., “V FB1 ” and “V FB2 ”) that are supplied as feedback signals for controlling switching mechanism  210 . Control circuit  202  may further use the load voltages to generate a first control signal (e.g., “EN”) to turn voltage regulator  204  on or off and a second control signal (e.g., “Ctrl”) to control the output current of voltage regulator  204 . In some instances, switching mechanism  210  may be configured to connect the output of voltage regulator  204  to both loads  206 - 208  at the same time in a “tied” configuration, as discussed in further detail below with respect to  FIGS. 8A-8B . 
     As shown in  FIG. 2B , an exemplary implementation of control circuit  202  that is compatible with the power-delivery system of  FIG. 2A  may include two error amplifiers  212 - 214  that generate two error signals such as error voltages (e.g., “V ERR1 ” and “V ERR2 ”) from the feedback voltages of loads  206 - 208  and two reference voltages (e.g., “V REF1 ” and “V REF2 ”), respectively. Each reference voltage may represent a target value for the feedback voltage of the corresponding load  206 - 208 . In turn, each error signal may represent the difference between the reference voltage and the load voltage of the load. For example, the error signal may be calculated by subtracting the feedback voltage of the load from the reference voltage for the load. As a result, the error signal may be negative when the load voltage is higher than the reference voltage and positive when the load voltage is lower than the reference voltage. Alternatively, error signals may be generated from reference and/or load currents instead of voltages. 
     Moreover, the gains of error amplifiers  212 - 214  may be selected to be different to increase the sensitivity to error of one load over that of the other load. For example, error amplifier  212  may have a higher gain than error amplifier  214  to prioritize driving of the load associated with the error signal from error amplifier  212  (i.e., load  206 ) over driving of the load associated with the error signal from error amplifier  214  (i.e., load  208 ). 
     The error signals from error amplifiers  212 - 214  may be provided to three comparators  216 - 220  in control circuit  202 . Comparator  220  may determine which error signal is larger, comparator  216  may determine if the error signal from error amplifier  212  is positive, and comparator  218  may determine if the error signal from error amplifier  214  is positive. A positive value for a given error signal may indicate that the load voltage of the corresponding load is lower than its reference voltage. The outputs of comparators  216 - 220  are then provided as inputs to two AND gates  222 - 224  and/or an OR gate  226 . 
     OR gate  226  is coupled to the outputs of comparators  216 - 218  and generates the control signal (e.g., “EN”) for turning voltage regulator  204  on if either error signal is positive. If both error signals are negative (e.g., if each load has a higher load voltage than the corresponding reference voltage), OR gate  226  may use the control signal to turn voltage regulator  204  off. 
     AND gates  222 - 224  are coupled to the output of comparator  220 , AND gate  222  is coupled to the output of comparator  216 , and AND gate  224  is coupled to the output comparator  218 . AND gates  222 - 224  may use the outputs of comparators  216 - 220  to generate switch control signals (e.g., “SW 1 _ON,” “SW 2 _ON”) for operating switches (e.g., “SW 1 ,” “SW 2 ”) coupled to the outputs of error amplifiers  212 - 214 , respectively. In turn, the switches may couple one of the error signals to the control signal (e.g., “Ctrl”) for controlling the output current of voltage regulator  204 . In other words, AND gates  222 - 224  may provide an analog multiplexer that selects one of the two error signals to pass to voltage regulator  204  for controlling the output of voltage regulator  204 . The switch control signals may also be used to control switching mechanism  210 . For example, the “SW 1 _ON” signal may be used as the “SW” signal in  FIG. 2A  that controls switching mechanism  210  so that switching mechanism  210  couples voltage regulator  204  to load  206  when switch SW 1  is closed and to load  208  when switch SW 1  is open. Conversely, the switch control signals for the “SW 1 ” and “SW 2 ” switches in control circuit  202  may be generated separately from the “SW” signal for controlling switching mechanism  210 . 
     Another control scheme for generating the control signal (e.g., “Ctrl”) is shown in  FIG. 2C . In  FIG. 2C , the control signal may be generated as the sum of two half-wave-rectified error voltages from two rectifiers  230 - 232 . That is, rectifiers  230 - 232  may rectify the error voltages from error amplifiers  212 - 214 , respectively, by outputting the positive portions of the error voltages and setting the negative portions to 0. A positive error voltage may indicate a feedback voltage that is lower than the corresponding reference voltage, while a negative error voltage that is negative may represent a feedback voltage that is higher than the corresponding reference voltage. Thus, the positive error voltage may be reduced by supplying power from voltage regulator  204  to the corresponding load, while the negative error voltage may be reduced by reducing or removing the supply of power from voltage regulator  204  to the corresponding load. The rectified error voltages may then be summed by a voltage-summation circuit  234  as the control signal. 
     The control signal (e.g., “Ctrl”) may be used to control the pulse-width modulation (PWM) of a switching waveform for controlling a switching voltage regulator  204  and/or as a peak current control for peak current-mode control of voltage regulator  204 . For example, the control signal may provide the largest value of the half-wave-rectified error voltages (e.g., the error voltage with a positive value) to voltage regulator  204  so that voltage regulator  204  generates an output current that is proportional to the largest error signal. 
     To reduce the operating power of the regulator, the control circuit  202  may be implemented without error amplifiers, as shown in  FIG. 2D . Comparators  216  and  218  may compare the feedback signals (e.g., “V FB1 ” and “V FB2 ”) representing the load voltages of loads  206 - 208  with the corresponding reference voltages (e.g., “V REF1 ” and “V REF2 ”) to generate request signals corresponding to error signals. The outputs of comparators  216 - 218  (e.g., the request signals) are provided to OR gate  226  to generate a logical disjunction signal that acts as control signals (e.g., “Ctrl” and “EN”) for enabling voltage regulator  204  and controlling the output current of voltage regulator  204 . Voltage regulator  204  may use the continuous-on duration of the logical disjunction signal to control the PWM, the peak current, and/or the current slope of voltage regulator  204 . 
     The switching control for switching mechanism  210  may additionally be implemented as a first-come, first-served switching control using a finite state machine  236  in control circuit  202 . The operation of finite state machine  236  is shown in  FIG. 2E . Finite state machine  236  may include a first step (e.g., “STEP  1 ”), in which finite state machine  236  is in an initialization state  240  (e.g., “INIT”), and switching mechanism  210  couples the output of voltage regulator  204  to either of the loads  206 - 208 . 
     Finite state machine  236  may also include a second step (e.g., “STEP  2 ”) that allows a first of comparators  216 - 218  to assert a positive output (e.g., indicating that the load voltage of the corresponding load is lower than the reference voltage for the load) to cause switching mechanism  210  to couple to the corresponding load  206 - 208  for a minimum pre-specified time X (e.g., a number of microseconds). If comparator  216  asserts first without comparator  218  simultaneously asserting (e.g., “Comp  216 =1, Comp  218  !=1”), finite state machine  236  may enter state  242  (e.g., “HOLD  1 ”), which generates a control signal (e.g., “SW 1 _ON=1”) that causes switching mechanism  210  to couple the output of voltage regulator  204  to load  206 . If comparator  218  asserts first (e.g., “Comp  218 =1”) with or without comparator  216  simultaneously asserting, finite state machine  236  may enter state  244  (e.g., “HOLD  2 ”), which generates a control signal (e.g., “SW 2 _ON=1”) that causes switching mechanism  210  to couple the output of voltage regulator  204  to load  208 . As a result, finite state machine  236  may enter state  242  only when comparator  216  asserts first and state  244  both when comparator  218  asserts first and both comparators  216 - 218  assert at the same time. During the time interval X, no switching is allowed and comparator  206 - 208  signals are ignored. 
     Finite state machine  236  may include a third step (e.g., “STEP  3 ”) that occurs after the time interval X has elapsed. In the third step, switching mechanism  210  may remain in the same configuration until the corresponding comparator  216 - 218  is de-asserted and the other comparator is asserted. To this end, finite state machine  236  may enter a state  246 - 248  (e.g., “ACTIVE  1 ” or “ACTIVE  2 ”) that maintains the configuration of switching mechanism  210 . That is, finite state machine  236  may remain in state  246  while comparator  216  is asserted and comparator  218  is de-asserted (e.g., “Comp  216  !=0, Comp  218  !=1). Similarly, finite state machine  236  may remain in state  238  while comparator  218  is asserted and comparator  216  is de-asserted (e.g., “Comp  216  !=1, Comp  218  !=0). If the comparator associated with the state (e.g., state  246  or  248 ) de-asserts and the other comparator has a positive output, finite state machine  236  may go back to the second step and enter a state (e.g., state  242  or  244 ) that configures switching mechanism  210  to couple the output of voltage regulator  204  to the other load. For example, finite state machine  236  may remain in state  248  while comparator  218  is asserted and comparator  216  is de-asserted. When comparator  216  asserts and comparator  218  de-asserts, finite state machine  236  may transition to state  242 . If both comparators are de-asserted, both finite state machine  236  and switching mechanism  210  may remain the same state and/or configuration until one comparator  216 - 218  has a positive output and triggers a switch back to a state in the second step. 
     The error signals may further be used by control circuit  202  to couple loads  206 - 208  to voltage regulator  204 . In particular, control circuit  202  may use switching mechanism  210  to couple the load with the largest error signal to the output of voltage regulator  204 , thereby allowing the load to be driven by the output. As the coupled load is driven by the output according to the error signal for the coupled load, the load voltage of the other load may fall until the other load has a larger error signal than the coupled load. Control circuit  202  may then use switching mechanism  210  to couple the other load to the output of voltage regulator  204  and provide the error signal of the other load to voltage regulator  204  so that voltage regulator  204  generates an appropriate output current for driving the other load. 
     Consequently, implementations of control circuit  202  in  FIGS. 2B-2D  may continuously switch between driving loads  206 - 208  using voltage regulator  204  and switching mechanism  210 . As one load “charges” up using the output of voltage regulator  204 , the load voltage of the other load drops until the error signal of the other load is larger, causing control circuit  202  to switch to charging the other load with the output of voltage regulator  204 . Control circuit  202  may thus use feedback loops, switching mechanism  210 , and a single voltage regulator  204  to regulate the load voltages of loads  206 - 208  to be at the corresponding reference voltages for loads  206 - 208 . 
     Such power-delivery techniques may also be applied to multiple-input, multiple-output (MIMO) systems. As shown in  FIG. 3A , an input voltage (e.g., “V IN ”) is supplied from a power source  300  and converted into two load voltages (e.g., “V DD1 ” and “V DD2 ”) for driving two loads  308 - 310  using a control circuit  302 , two voltage regulators  304 - 306 , and two switching mechanisms  312 - 314 . The power supply of  FIG. 3A  may thus be a 2-in 2-out MIMO system. 
     In particular, the inputs of voltage regulators  304 - 306  are coupled to the input voltage, and loads  308 - 310  are selectively coupled to an output (e.g., “p_out 1 ”) of voltage regulator  304  using switching mechanism  312  and an output (e.g., “p_out 2 ”) of voltage regulator  306  using switching mechanism  314 . At any given moment, voltage regulators  304 - 306  may be connected to the same load or to different loads. Although the power-delivery system of  FIG. 3A  is illustrated with voltage regulators  304 - 306 , those skilled in the art will appreciate that the power-delivery system may utilize any suitable power converters, such as the power converters discussed above. 
     As with control circuit  202  of  FIGS. 2A-2B , control circuit  302  may use switching mechanisms  312 - 314  to switch the outputs of voltage regulators  304 - 306  to either load  308 - 310 , depending on the power consumption of loads  308 - 310 . For example, control circuit  302  may use the load voltages of loads  308 - 310  as feedback voltages (e.g., “V FB1 ” and “V FB2 ”) for: controlling switching mechanisms  312 - 314 , generating a first set of control signals (e.g., “EN 1 ,” “EN 2 ”) for turning voltage regulators  304 - 306  on or off, and generating a second set of control signals (e.g., “Ctrl 1 ,” “Ctrl 2 ”) for controlling the output currents of voltage regulators  304 - 306 . Each control signal may be used to control the operation and/or output of the corresponding voltage regulator. For example, “EN 1 ” may be used to turn voltage regulator  304  on and off, “Ctrl 1 ” may be used to control the output current of voltage regulator  304 , “EN 2 ” may be used to turn voltage regulator  306  on and off, and “Ctrl 2 ” may be used to control the output current of voltage regulator  306 . 
     In one or more embodiments, voltage regulators  304 - 306  include a higher-efficiency, lower-power regulator and a higher-power, lower-efficiency regulator. To facilitate efficient operation of the power supply, the higher-efficiency regulator may be used as a primary voltage regulator for driving loads  308 - 310 , and the higher-power regulator may be turned on only when more power than the higher-efficiency regulator can deliver is required by one or both loads  308 - 310 . 
     As shown in  FIG. 3B , one example of control circuit  302  suitable for use in the system of  FIG. 3A  includes two sub-circuits  320 - 322 , with each sub-circuit used to independently control a different voltage regulator  304 - 306  and switching mechanism  312 - 314  coupled to the voltage regulator. Each sub-circuit  320 - 322  may include the components of various examples of control circuit  202  in  FIGS. 2A-2D . Each sub-circuit may generate error signals based on a comparison of feedback voltages and corresponding reference voltages (e.g., using error amplifiers as discussed with respect to  FIGS. 2B-2D ). For example, sub-circuits  320 - 322  may each include two error amplifiers that generate error signals (e.g., error voltages) for loads  308 - 310  from the load and/or feedback voltages of loads  308 - 310  (e.g., “V FB1 ” and “V FB2 ”) and reference voltages (e.g., “V REF1 ,” “V REF2 ,” “V REF1 +x,” “V REF2 +x”) for driving the loads using each voltage regulator  304 - 306 . Each sub-circuit  320 - 322  may also include three comparators that identify the larger error signal from loads  308 - 310  and indicate whether the load voltages of loads  308 - 310  are lower than their reference voltages. Finally, each sub-circuit  320 - 322  may include an OR gate that generates a control signal (e.g., “EN 1 ,” “EN 2 ”) for turning the corresponding voltage regulator  304 - 306  on and off, as well as two AND gates that generate switch control signals (e.g., “SW 1 _ 1 ,” “SW 1 _ 2 ,” “SW 2 _ 1 ,” “SW 2 _ 2 ”) for operating switches that couple the larger error signal to a control signal (e.g., “Ctrl 1 ,” “Ctrl 2 ”) for controlling the output current of the voltage regulator. 
     Each of sub-circuits  320 - 322  may additionally use the error signals and switching mechanisms  312 - 314  to couple the load with the largest error signal to the voltage regulators corresponding to the sub-circuit. Consequently, sub-circuits  320 - 322  may each be a SIMO control circuit that is included in control circuit  302  to enable control of a MIMO power-delivery system. 
     In addition, the reference voltages used with sub-circuit  320  (e.g., “V REF1 +x,” “V REF2 +x”) may be higher than the reference voltages used with sub-circuit  322  (e.g., “V REF1 ,” “V REF2 ”). For example, the reference voltages used with sub-circuit  320  may be a predetermined amount (e.g. 10 mV) higher than the reference voltages used with sub-circuit  322 . By setting higher reference voltages for use by sub-circuit  320 , control circuit  302  may increase the use of the voltage regulator (e.g., a higher-efficiency, lower-power regulator) controlled by sub-circuit  320  over the use of the voltage regulator (e.g., a higher-power, lower-efficiency regulator) controlled by sub-circuit  322  in driving loads  308 - 310 . 
     More specifically, the higher reference voltages used by sub-circuit  322  may allow a higher-efficiency voltage regulator controlled by sub-circuit  320  to be used in driving loads  308 - 310  by outputting voltages to loads  308 - 310  that are regulated to be at the higher reference voltages. Since the higher reference voltages are above the reference voltages of sub-circuit  322 , sub-circuit  322  may generate a control signal (e.g., “EN 2 ”) that turns off a higher-power voltage regulator controlled by sub-circuit  322 . However, when one or both loads  308 - 310  draw power at a level above the power limit of the higher-efficiency voltage regulator controlled by sub-circuit  320 , the power demands of the load(s) may exceed the power limit of the higher-efficiency voltage converter, causing the load voltage(s) of the load(s) to decrease. Once the load voltage(s) decrease to at or below the reference voltage(s) of sub-circuit  322 , sub-circuit  322  may engage (e.g., turn on) the higher-power voltage regulator and use an output voltage from the output of the higher-power voltage regulator to supplement the lowered load voltage(s). When the higher-power voltage regulator is not used to supplement the load voltage(s), the higher-power voltage regulator may be placed in a power savings standby mode. 
     The efficiency and/or transient response of the power-delivery system may further be improved by using different maximum switching frequencies to drive loads  308 - 310 . For example, sub-circuit  320  may use a first maximum switching frequency (e.g., 400 KHz) to couple the load with the largest error signal to the output of the higher-efficiency regulator, while sub-circuit  322  may use a second maximum switching frequency that is higher than the first switching frequency (e.g., 2 MHz) to couple the load with the largest error signal to the output of the higher-power regulator. The maximum switching frequency of each sub-circuit may be limited using a clock signal and/or a minimum dwell time (e.g., time interval X in finite state machine  236  of  FIGS. 2D-2E ). The lower maximum switching frequency of sub-circuit  320  may improve the efficiency of the higher-efficiency regulator, while the higher maximum switching frequency of sub-circuit  322  may improve the transient response of the higher-power regulator. Alternatively, the operation of sub-circuits  320 - 322 , components within sub-circuits  320 - 322 , and/or switching mechanisms  312 - 314  may be asynchronous. 
       FIG. 4A  shows an exemplary power-delivery system in accordance with the disclosed embodiments. More specifically,  FIG. 4A  shows a 2-in 4-out MIMO power-delivery system with a set of simulation settings. Similarly,  FIG. 4B  shows a control circuit for the simulated MIMO power-delivery system of  FIG. 4A . 
     The MIMO power-delivery system of  FIG. 4A  includes two buck converters  402 - 404  and load voltages  406 - 412  of four different loads (e.g., “Load 1 ,” “Load 2 ,” “Load 3 ,” “Load 4 ”). One buck converter  404  is a high-efficiency converter for regulating power (e.g., maintaining load voltages) during normal and/or light-load conditions, and the other buck converter  402  is a high-power converter for driving high loads and/or transient conditions. An input voltage is supplied to buck converters  402 - 404  from a power source  414  such as a battery pack. 
     Converter  402  may be coupled to the loads using a switching mechanism  416 , and converter  404  may be coupled to the loads using a separate switching mechanism  418 . Reference voltages for driving the “Load 1 ,” “Load 2 ,” “Load 3 ,” and “Load 4 ” loads using the high-power converter  402  may be set to 5V, 12V, 3.3V, and 1V, respectively, in switching mechanism  416 . Reference voltages for driving the “Load 1 ,” “Load 2 ,” “Load 3 ,” and “Load 4 ” loads using the high-efficiency converter  404  may be set to slightly higher values of 5.01V, 12.01V, 3.31V, and 1.01V, respectively, in switching mechanism  418 . Both buck converters  402 - 404  may be controlled using constant on-time peak current control. The high-efficiency converter  404  may have an inductor  422  with an inductance of 2.2 uH, a peak output current of 1 A, and a switching speed of 400 KHz provided by a clock  426 . The high-power converter  402  may have an inductor  420  with an inductance of 200 nH, a peak output current of 10 A, and a switching speed of 2 MHz provided by a separate clock  424 . The reference voltage used with the high-efficiency converter  404  may be 10 mV higher than the reference voltage used with the high-power converter  402 . 
     Alternative configurations of inputs and outputs in the power-delivery system are shown in  FIGS. 5A-5D . In particular,  FIG. 5A  shows three power converters coupled to two loads  508 - 510 . One or more high-efficiency converters  506  may be selectively coupled to one or both loads  508 - 510  using a switching assembly  512 , and a dedicated high-power converter  502 - 504  is coupled to each load  508 - 510 . 
     The shared high-efficiency converters  506  may be switched or shared between the two loads  508 - 510  based on the power demands of loads  508 - 510 . For example, switching assembly  512  may couple a single high-efficiency converter to the load from loads  508 - 510  with the highest need, which may be represented by the difference between the reference voltage for driving the load using high-efficiency converter  506  and a load voltage of the load. If the power-delivery system includes multiple high-efficiency converters  506 , switching assembly  512  may divide high-efficiency converters  506  between loads  508 - 510  depending on need by, for example, allocating more converters to the load with the higher demand. High-power converters  502 - 504  may also be associated with a higher activation threshold than high-efficiency converters  506  to facilitate efficient operation of the power supply. For example, the reference voltages of high-efficiency converters  506  may be slightly higher than the reference voltages of high-power converters  502 - 504  to enable use of high-efficiency converters  506  during normal, light-load conditions. Each high-power converter  502 - 504  may then be engaged and used to supplement the output of high-efficiency converter  506  once the power demands of the corresponding load cause the load voltage of the load to drop below the reference voltage of the high-power converter. 
       FIG. 5B  also shows three power converters coupled to two loads  520 - 522 . In the configuration of  FIG. 5B , a dedicated high-efficiency converter  514 - 516  is coupled to each load  520 - 522 , and one or more high-power converters  518  are shared by loads  520 - 522  using a switching assembly  524 . As with switching assembly  512  of  FIG. 5A , switching assembly  524  may divide multiple high-power converters  518  between loads  520 - 522  depending on need, or switching assembly  524  may allocate a single high-power converter to the load with the higher demand. High-power converter  518  may be used to drive one or both loads  520 - 522  only when the power demands of the load(s) exceed the power limits of the corresponding dedicated high-efficiency converter(s) and cause the load voltage(s) of the load(s) to drop below the reference voltage of high-power converter  518 . 
       FIG. 5C  shows a number of power converters  526 - 528  and two loads  530 - 532 . One power converter  526  is a dedicated power converter that is directly coupled to a first load  530 , while one or more additional power converter  528  are shared between the first load and a second load  532  using a switching assembly  534  according to the needs of loads  530 - 532 . 
       FIG. 5D  shows a number of power converters and two loads  542 - 544 . One or more high-power converters  536  and one or more high-efficiency converters  538  are shared by both loads using two switching assemblies  546 - 548 , and a third dedicated power converter  540  is coupled directly to the second load  544 . 
       FIG. 6  shows a flowchart illustrating the process of operating a power supply in accordance with the disclosed embodiments. In one or more embodiments, one or more of the steps may be omitted, repeated, and/or performed in a different order. Accordingly, the specific arrangement of steps shown in  FIG. 6  should not be construed as limiting the scope of the embodiments. 
     Initially, two or more error signals for two or more loads coupled to the output(s) of one or more power converters via one or more switching mechanisms are obtained (operation  602 ). For example, the switching mechanisms may be disposed between the outputs of one or more voltage regulator and the loads. As a result, the voltage regulator(s) may be controlled in a group so that all voltage regulators in the group are coupled to a given load at the same time. 
     The error signals may be provided by two or more error amplifiers and/or comparators. Each error signal may be an error voltage that represents the difference between a reference voltage for driving a load from the two or more loads using a voltage regulator and a load voltage of the load. For example, the error signal may include an analog error voltage generated by an error amplifier and/or a digital request signal generated by a comparator. As a result, a reference voltage may be set for each load and each voltage regulator that may be used to drive the load. Each reference voltage may represent a constant target regulated output voltage of the corresponding load. The error signal may thus be positive if the load voltage is lower than the reference voltage and negative if the load voltage is higher than the reference voltage. 
     Next, the error signals may be used to determine if the load voltages are higher than the corresponding reference voltages (operation  604 ) for each power converter or group of power converters that are collectively coupled to one of the loads. If all load voltages are higher than their corresponding reference voltages, the power converter(s) that can be selectively coupled to the loads are turned off (operation  606 ). For example, a high-power voltage regulator may be turned off if the load voltages of the corresponding loads are regulated to be at the reference voltage(s) of a high-efficiency voltage regulator, which is higher than the reference voltage(s) of the high-power voltage regulator. 
     If one or more load voltages are lower than the corresponding reference voltages, one or more switching mechanism(s) may be used to couple the load with the largest error signal to one or more outputs of one or more power converters (operation  608 ). For example, an output of a voltage regulator may be coupled to the load associated with a comparator that first signals a request signal representing a lower load voltage for the load than the reference voltage for the load. Coupling of the output to the load may also be maintained for a minimum pre-specified time. Such coupling of the output to the load may continue until the comparator no longer asserts a lower load voltage for the reference voltage and another comparator associated with the voltage regulator signals a separate request signal representing a lower load voltage for the load associated with the comparator than the load&#39;s reference voltage. 
     Alternatively, no switching mechanism may be required to couple the load to an output of a power converter (e.g., a dedicated voltage regulator) if the load is connected directly to the output. In addition, a control signal for controlling an output current of each coupled power converter may be generated (operation  610 ). The control signal may be generated using the largest value of a half-wave-rectified error signal (e.g., the positive portion of the error signal) from the two or more error signals, the sum of positive error signals, and/or an on-duration of a logical disjunction signal generated from the error signals. In addition, the output current may be generated by each coupled power converter to be proportional to the corresponding control signal. 
     The loads may continue to be driven (operation  612 ) using the switching mechanism(s) and power converter(s). If the loads are to be driven, error signals for the loads are periodically and/or continuously obtained (operation  604 ) and used to operate the power converter(s) and/or couple the power converter(s) to the loads (operations  604 - 610 ). The operations in the flowchart of  FIG. 6  may also be repeated for each group of commonly controlled power converters, such as groups of one or more power converters coupled to individual sub-circuits (e.g., sub-circuits  320 - 322  of  FIG. 3B ) of a control circuit (e.g., control circuit  302  of  FIGS. 3A-3B ) in the power supply. Voltages and currents may continue to be supplied to the loads by the power converter(s) until the power supply is no longer used to drive the loads. 
     In one or more embodiments, a MIMO power-delivery system such as the power-delivery systems of  FIGS. 3A, 4A, and 5A-5D  may be configured through a software-based control apparatus. As shown in  FIG. 7A , the outputs of a number of power converters  702 - 710  may be coupled to two or more loads  714 - 716  through a switching assembly  712  comprising one or more switching mechanisms. A control apparatus  718  (which may be executing within a load, e.g., load  714 ) may be used to generate control signals for switching assembly  712  so that power converters  702 - 710  are coupled to loads  714 - 716  through switching assembly  712  in various configurations. For example, control apparatus  718  may be a software component that executes within an operating system and/or system microcontroller (SMC) of a portable electronic device. The software component may monitor conditions in loads  714 - 716  and generate control signals for controlling an actively controlled switching assembly  712  that includes switching mechanisms such as power metal-oxide-semiconductor field-effect transistors (MOSFETs). 
     More specifically, the output of one or more power converters (e.g., power converter  702 ) may be coupled directly to load  714 , and the output of one or more power converters (e.g., power converter  710 ) may be coupled directly to load  716 . Power converters  704 - 708  may individually be coupled to either load  714 - 716  through switching assembly  712  that are controlled by control apparatus  718 . 
     In some instances, control apparatus  718  may be used to configure the delivery of power from power converters  702 - 710  to loads  714 - 716  that are capable of drawing, in aggregate, power that exceeds the power-output capabilities of power converters  702 - 710 . For example, power converters  702 - 710  may each be 3 W step-down buck regulators in a space-limited portable electronic device, while each load  714 - 716  in the portable electronic device may draw up to 10 W of power. Thus, the maximum power that can be drawn by both loads  714 - 716  is 20 W, which exceeds the maximum of 15 W that can be delivered by power converters  702 - 710 . 
     In these instances, the total amount of power drawn by both loads  714 - 716  may be limited to the maximum that can be supplied by power converters  702 - 710 . Continuing with the above example, loads  714 - 716  may be prevented from drawing the maximum 10 W of power at the same time because power converters  702 - 710  cannot supply 20 W of power to loads  714 - 716 . 
     In one or more embodiments, control apparatus  718  may manage the delivery of power from power converters  702 - 710  to loads  714 - 716  based on discrete, pre-defined power states of loads  714 - 716 . The power states may be represented by different power supply voltage and clock frequency combinations in the portable electronic device. For example, the power states of one or both loads  714 - 716  may be represented by monotonically increasing numbers from 0 to N with increasing power demands (e.g., power supply voltage VDD and clock frequency F CLK ). The power state represented by 0 may be the lowest power state, which is used during idle periods in the portable electronic device. The power state represented by N may be the highest power state, which is used to maximize computing power on the portable electronic device. Power states represented by 1 through N-1 may be selected based on the computing demands of applications and/or components on the portable electronic device. 
     Since the power demand of loads  714 - 716  may be directly related to the power states of loads  714 - 716 , control apparatus  718  may dynamically configure the coupling of power converters  702 - 710  to loads  714 - 716  based on the power states. In general, control apparatus  718  may configure the coupling of at least one power converter and up to four power converters to each load  714 - 716 , with more power converters assigned to the load with the higher power state. For example, an operating system on the portable electronic device may determine the power states of loads  714 - 716  and execute control apparatus  718  to generate control signals for configuring the power-delivery system based on the power states and/or a power-delivery policy for the portable electronic device. 
     Using the exemplary monotonically increasing power states of 0 through 9, control apparatus  718  may configure the coupling of loads  714 - 716  to power converters  702 - 710  through switching assembly  712  using the following exemplary power-delivery policy:
         1. If the power state of a first load increases from less than 2 to 2 or 3 and the power state of the second load is lower than 6, the first load will be coupled to two power converters if the first load is currently coupled to only one power converter.   2. If the power state of the first load increases from less than 4 to 4 or 5 and the power state of the second load is lower than 4, the first load will be coupled to three power converters if the first load is currently coupled to fewer than three power converters.   3. If the power state of the first load increases from less than 6 to 6 or 7 and the power state of the second load is lower than 2, the first load will be coupled to four power converters if the first load is currently coupled to fewer than four power converters.
 
The power-delivery policy may thus specify an increase in the number of power converters coupled to a given load when the power state of the load increases above a first threshold and/or the power state of the other load remains below a second threshold. On the other hand, if an increase in the power state of the load does not exceed the first threshold, the power-delivery policy may maintain an existing configuration of the coupling of loads  714 - 716  to power converters  702 - 710  through switching assembly  712  to avert unnecessary power dissipation associated with reconfiguring switching assembly  712 .
       

     Those skilled in the art will appreciate that the exemplary power-delivery policy described above may be used to couple loads  714 - 716  to power converters  702 - 710  as long as the maximum power demand from both loads does not exceed the 15 W that can be supplied by all five power converters  702 - 710 . If the power demanded by loads  714 - 716  exceeds the maximum that can be generated by power converters  702 - 710 , one or both loads may experience voltage droops, current surges, and/or power overages. 
     As shown in  FIG. 7B , the desired power states and/or power demands of loads  714 - 716  may be monitored by a number of digital-to-analog converters (DACs)  724 - 726  and comparators  720 - 722  that are added to the power-delivery system of  FIG. 7A . Comparator  720  may compare the load voltage of load  714  with a reference voltage for driving load  714  from DAC  724  to detect a droop in the load voltage of load  714 . Similarly, comparator  722  may compare the load voltage of load  716  with a reference voltage for driving load  716  from DAC  726  to detect a droop in the load voltage of load  716 . 
     Control apparatus  718  may monitor the voltage droops of loads  714 - 716  from comparators  720 - 722  and generate control signals for controlling switching assembly  712  and/or the power states of loads  714 - 716  based on the monitored voltage droopss, current surges, and/or power overages. If the load voltage of a first load is lower than the corresponding reference voltage by more than a given amount (e.g., 50 mV), control apparatus  718  may generate a control signal to change a coupling of one or more additional power converters from a second load to the first load. Control apparatus  718  may also reduce a power state of the first load, in lieu of or in addition to diverting the additional power converters from the second load to the first load. 
     For example, control apparatus  718  may divert power converters from the second load to the first load if a voltage droop on the first load is detected and the first load has a higher priority than the second load. If the second load subsequently experiences voltage droop, control apparatus  718  may reduce the power state of the second load until the voltage droop on the second load is no longer detected. 
     In another example, both loads  714 - 716  may experience voltage droop if the power states of loads  714 - 716  are higher than can be accommodated by the subsets of power converters  702 - 710  coupled to loads  714 - 716 . To manage such voltage droops, current surges, and/or power overages, control apparatus  718  may reduce the power states of both loads  714 - 716  until the voltage droop is no longer detected on both loads  714 - 716 . Alternatively, control apparatus  718  may prioritize the driving of a first load over a second load by increasing the number of power converters coupled to the first load and reducing the power state of the second load until the voltage droop is no longer detected on both loads  714 - 716 . Such prioritization may occur when the power demands of one load must be met to satisfy certain system needs, such as powering of critical system components in the load. Finally, control apparatus  718  may reduce the power states of both loads  714 - 716  while diverting one or more power converters from one load to another until the voltage droop is no longer detected on both loads  714 - 716 . 
     The MIMO power-delivery systems described above may further be configured to operate in a “tied” configuration that combines multiple power converters into a single output that is used to power multiple loads in a portable electronic device. As shown in  FIG. 8A , the outputs of a number of power converters  802 - 806  may be coupled to two or more loads  814 - 816  through a switching assembly  812 . A software and/or hardware control apparatus  818  executing within load  814  may be used to generate control signals for switching assembly  812  to configure the coupling of power converters  802 - 806  to loads  814 - 816  through switching assembly  812 . 
     In particular, the output of power converter  802  may be coupled directly to load  814 , and the output of power converter  806  may be coupled directly to load  816 . Switching assembly  812  may include two switches  808 - 810  that collectively couple the output of power converter  804  to one or both loads  814 - 816 . For example, switch  808  may be closed to couple power converter  804  to load  814 , switch  810  may be closed to couple power converter  804  to load  816 , and both switches  808 - 810  may be closed to couple all power converters  802 - 806  to both loads  814 - 816 . 
     An alternative implementation of the “tied” configuration may be provided by the MIMO power-delivery system of  FIG. 8B . As with the power-delivery system of  FIG. 8A , the power-delivery system of  FIG. 8B  includes three power converters  802 - 806  that can be coupled to two loads  814 - 816 . The output of power converter  802  may be coupled directly to load  814 , and the output of power converter  806  may be coupled directly to load  816 . Switching assembly  812  include a first switch  820  that couples the output of power converter  804  to either load  814 - 816 , as well as a second switch  822  that can be closed to “tie” the output of all power converters  802 - 806  to both loads  814 - 816 , independently of the state of switch  820 . Control apparatus  818  includes a switch control  824  that generates a control signal for switch  820  and a tie control  826  that generates a control signal for switch  822 . 
     During power-state-based control of the power-delivery system, control apparatus  818  may monitor the power demand of each load  814 - 816  to determine the configuration of the power-delivery system. When the power state of each load  814 - 816  is below a pre-specified threshold, control apparatus  818  may configure switching assembly  812  to power loads  814 - 816  separately. When the power state of either load exceeds the corresponding threshold, control apparatus  818  may operate the power-delivery system in the “tied” configuration so that the outputs of all power converters  802 - 806  are tied to the inputs of both loads  814 - 816 . The “tied” configuration may increase the peak current supplied to multiple loads when one of the loads demands higher current than can be supplied by the corresponding dedicated power converter(s). 
     For example, load  814  may be associated with a first numeric threshold M, and load  816  may be associated with a second numeric threshold N, which may be the same or different from M. When the power states of loads  814 - 816  are lower than M and N, respectively, control apparatus  818  may generate control signals for switching assembly  812  so that each load  814 - 816  is powered separately by the corresponding dedicated power converter  802  and  806 . When the power state of load  814  is greater than M and/or the power state of load  816  is greater than N, the power supply voltage of the higher power state is selected, and switching assembly  812  are configured by control apparatus  818  to tie all outputs of power converters  802 - 806  to all inputs of loads  814 - 816 . 
     Thus, the power-delivery system in the “tied” configuration effectively becomes a single-output power supply that is connected to all loads  814 - 816 . In the “tied” configuration, loads  814 - 816  may share power at finer levels of granularity than discrete power levels of individual power converters. For example, three 1 W converters that may be split between loads  814 - 816  in a 2-1 configuration may be shared by loads  814 - 816  so that each load receives 1.5 W or one load receives 1.2 W and the other load receives 1.8 W. Such sharing of combined power by multiple loads  814 - 816  may be based on the power draw and/or demand of each load. 
     The “tied” configuration may also be applied to the MIMO power-delivery systems described above that continuously switch between driving loads based on error signals of the loads. Using the power-delivery system of  FIG. 5A  as an example, if the power state of one or both loads  508 - 510  exceeds the power-delivery capabilities of the corresponding dedicated regulators  502  and  504 , the outputs of all three regulators  502 - 506  may be tied to supply power to both loads  508 - 510 . When the power consumed by both loads  508 - 510  drops below the maximum power that can be supplied by the corresponding dedicated regulators  502  and  504 , the power-delivery system may revert to coupling high-efficiency regulator  506  to the load from loads  508 - 510  with the largest error signal. 
     Those skilled in the art will appreciate that the power-delivery systems of  FIGS. 7A-7B and 8A-8B  may be adapted to different types, numbers, and configurations of power converters (e.g., power converters  702 - 710  and  802 - 806 ), loads (e.g., loads  714 - 716  and  814 - 816 ), and switching mechanisms (e.g., switching assemblies  712  and  812  and switches  808 - 810  and  820 - 822 ). For example, different combinations of high-efficiency converter, high-power converters, and/or other types of power converters may be coupled to different numbers or types of loads in various shared and/or dedicated configurations to optimize for power delivery in a portable electronic device. Similarly, the types of power converters and/or components in the power converters may be selected to accommodate different sizes and/or power states of loads in the portable electronic device. Moreover, switches in switching assembly  712  and  812  may be selected and/or configured to couple the power converters to the loads in different ways. Control apparatuses  718  and  818  may further be implemented using hardware and/or software components to couple the power converters to the loads through various types and arrangements of switching assemblies  712  and  812 . Finally, the power-delivery policy used by control apparatus  718  to configure the power-delivery system may be tailored to the power states of the loads, the power output of the power converters, the number of loads, and/or the number of power converters. 
       FIG. 9  shows a flowchart illustrating the process of operating a power supply in accordance with the disclosed embodiments. In one or more embodiments, one or more of the steps may be omitted, repeated, and/or performed in a different order. Accordingly, the specific arrangement of steps shown in  FIG. 9  should not be construed as limiting the scope of the embodiments. 
     Initially, a power-delivery policy for the power supply and power states of two or more loads coupled to two or more voltage regulators in the power supply are obtained (operation  902 ). The power-delivery policy may be tailored to the types and numbers of loads and/or power converters in a portable electronic device, as well as the power consumption and/or power states of the loads. For example, the power-delivery policy may specify the configuring of the loads and/or the coupling of the loads to the power converters based on the power consumption associated with discrete power states of the loads, the maximum power that can be supplied by the power converters, and/or the maximum power that can be drawn from the loads. 
     Next, one or more control signals for the loads and/or a set of switching mechanisms that couple the loads to the outputs of the power converters is generated based on the power-delivery policy, power states, and/or voltage droops. More specifically, the control signals may be used to couple the loads to the outputs of the power converters through the switching mechanisms based on an increase above a first threshold in the power state of a first load (operation  904 ). For example, the power state of the first load may increase from a given range of numbers to a higher range of numbers that is represented by the first threshold. In turn, the power consumption of the first load may increase from a first voltage associated with the lower power state that is below the first threshold to a second voltage associated with the higher power state that is above the first threshold. 
     When an increase in the power state of the first load falls below the first threshold, the existing configuration of the coupling of the loads to the power converters through the switching mechanisms is maintained (operation  906 ). For example, the first threshold may represent a limit to the power that can be outputted by power converters that are already coupled to the first load. As a result, a power state of the first load that remains below the first threshold may indicate that the increased power consumption of the first load can be accommodated by the power converters coupled to the first load. In turn, the configuration of the switching mechanisms may be maintained to avert power consumption associated with unnecessarily moving the switching mechanisms into a new configuration. 
     When the power state of the first load increases above the threshold, the coupling of the power converters to the loads may be managed based on the power state of a second load and a second threshold (operation  908 ). As with the first threshold, the second threshold may represent a limit to the power that can be outputted by power converters that are coupled to the second load. The first and second thresholds may thus be combined to manage the delivery of limited power from the power converters to loads that can demand more power than can be outputted by the power converters. 
     If the power state of the second load is below the second threshold, a control signal is generated to increase the number of power converters coupled to the first load (operation  910 ). For example, the control signal may configure the switching mechanisms to couple one or more additional power converters to the first load to accommodate the added power consumption associated with the increased power state. Because the power state of the second load is below the second threshold, the second load may not be impacted by the coupling of the additional power converters to the first load. 
     If the power state of the second load is above the second threshold, the existing configuration of the coupling of the loads to the power converters through the switching mechanisms is maintained (operation  906 ). For example, a power state of the second load above the second threshold may represent a power consumption of the second load that cannot accommodate the coupling of additional power converters to the first load. As a result, the existing configuration of the switching mechanisms may be maintained because reconfiguring the switching mechanisms increases the power consumption of the power supply and without alleviating the power demands of both loads. 
     An increase in the power state of one or more loads to a point that cannot be accommodated by the power converters in the power supply may result in an excessive voltage droop on the load(s) (operation  912 ) that is optionally monitored to detect excess power demand in the load(s). For example, an increase in the power state of a load that is not accommodated by coupling additional power converters to the load (e.g., due to the use of the power converters by other loads) may produce a voltage droop on the load as the load demands more power than can be produced by power converters coupled to the load. If no voltage droop is found in any of the loads, the loads may continue to be driven (operation  916 ) based on the power states of the loads and thresholds associated with the power states (operations  902 - 910 ). 
     If an excessive voltage droop on a load is detected, a control signal is optionally generated to change the coupling of one or more additional power converters from another load to the load and/or reduce the power state of the load (operation  914 ). For example, if the total power drawn by the loads is detected to exceed the maximum power that can be supplied by the power converters, the power state of one or more loads may be reduced until the total power drawn can be accommodated by the power converters. One or more power converters may also be diverted from a first load to a second load if the power state of the second load has increased and/or the power state of the first load can be lowered until the first load no longer requires the power converter(s). 
     The loads may continue to be driven (operation  916 ) using the switching mechanism(s) and power converter(s). If the loads are to be driven, the power-delivery policy, power states, and voltage droops are obtained (operation  902 ) and used to generate control signals that configure the delivery of power from the power converters to the loads and/or the consumption of power by the loads (operations  904 - 914 ). Power delivery to the loads through the power converters and switching mechanisms may continue until the power supply is no longer used to drive the loads. 
       FIGS. 10A-10B  shows a flowchart illustrating the process of operating a power supply in accordance with the disclosed embodiments. More specifically,  FIG. 10A  shows the operation of a power supply with shared and dedicated power converters, and  FIG. 10B  shows an exemplary operation of the power supply with two loads “Load 0 ” and “Load 1 ” and three power converters “VR 0 ,” “VR 1 ,” and “VR 2 .” Power converter  802  may be represented by “VR 0 ,” power converter  806  may be represented by “VR 1 ,” and power converter  804  may be represented by “VR 2 .” Load  814  may be represented by “Load 0 ,” and load  816  may be represented by “Load 1 .” The power supply of  FIG. 10B  may include the configuration of  FIG. 8A or 8B , in which power converter  804  is shared between two loads  814 - 816  and each load  814 - 816  is coupled directly to its own dedicated power converter  802  and  806 . In one or more embodiments, one or more of the steps may be omitted, repeated, and/or performed in a different order. Accordingly, the specific arrangement of steps shown in  FIGS. 10A-1B  should not be construed as limiting the scope of the embodiments. 
     Initially, a shared power converter is coupled to one of two loads (operation  1002 ). In  FIG. 10B , the shared power converter “VR 2 ” may be coupled to “Load 0 ” in step  1018  or to “Load 1 ” in Step  1020 . Next, the power supply may be operated based on a comparison of the power state of the load coupled to the shared power converter to a threshold associated with a tied configuration (operation  1004 ) in the power supply. Each load may be associated with a numeric and/or other threshold that represents the highest power state that can be accommodated by one or more dedicated power converters for the load and the shared power converter. 
     In other words, if the power drawn by the load is represented by “Load_x,” the maximum power that can be supplied by the dedicated power converter for the load is “VR_x,” and the maximum power that can be supplied by the shared power converter is “VR_shared,” the threshold may be expressed by the following:
 
Load_ x&gt;VR _ x+VR _shared
 
As shown in  FIG. 10B , the threshold associated with the tied configuration may be represented by steps  1022 - 1024 , which follow steps  1018 - 1020 , respectively.
 
     When the power state of the load exceeds the threshold, a control signal is generated to couple all power converters to all loads through the switching mechanisms (operation  1006 ) in a tied configuration. In  FIG. 10B , the tied configuration is represented by step  1026  (e.g., “Tied Mode”). For example, a power supply voltage associated with the highest power state among the loads is selected as the output voltage of the power converters, which is then used to power all loads coupled to the power supply. In other words, the tied configuration may be used to effectively combine the outputs of the power converters into a single output that is used to supply power to all of the loads. 
     The tied configuration may also be triggered when the power states of both loads are above the maximum power that can be supplied by the corresponding dedicated power converters (operation  1008 ). For example, if the power drawn by the two loads is represented by “Load_x” and “Load_y,” respectively, and the maximum power that can be supplied by the corresponding dedicated power converters is represented by “VR_x” and “VR_y,” respectively, the tied configuration may be triggered when the following expression is met:
 
Load_ x&gt;VR _ x  AND Load_ y&gt;VR _y
 
If neither of the above conditions in operations  1004  or  1008  is met, the power supply is not operated in the tied configuration. The condition associated with the power states of both loads exceeding the maximum power that can be supplied by the corresponding dedicated converters is shown in steps  1028 - 1034  in  FIG. 10B .
 
     After the power supply enters the tied configuration (operation  1006 ), the power supply may be kept in the tied configuration until the power state of one load falls below the threshold associated with the tied configuration and the power state of the other load falls below the maximum power that can be delivered by the corresponding dedicated power converter (operation  1012 ). Using the above representations of power drawn by the loads and the maximum power that can be supplied by the power converters, the power supply may exit the tied configuration when the following expression is met:
 
(Load_ x&lt;VR _ x+VR _shared AND Load_ y&lt;VR _ y )
 
OR
 
(Load_ y&lt;VR _ y+VR _shared AND Load_ x&lt;VR _ x )
 
Thresholds that trigger the exit of the power supply from the tied configuration are shown in steps  1036 - 1038  of  FIG. 10B .
 
     To exit the tied configuration, the shared power converter may be coupled to the load with the higher power requirement (operation  1014 ). For example, the shared power converter may be coupled to the load with the power state that falls below the threshold associated with the tied configuration but not below the maximum power that can be delivered by the corresponding dedicated power converter. On the other hand, if the power states of both loads fall below the maximum power that can be supplied by the corresponding dedicated power converters, the shared power converter may be coupled to the load with the power requirement that is closer to the maximum power of the corresponding dedicated power converter. As shown in  FIG. 10B , step  1018  is performed when the condition of step  1036  is met, and step  1020  is performed when the condition of step  1038  is met. 
     If the power supply is not operated in the tied configuration (e.g., if neither of the conditions in operations  1004  or  1008  is met), the shared power converter may continue to be coupled to the existing load (operation  1002 ) until the power state of the load falls below the maximum power of the corresponding dedicated power converter and the power state of the other load increases above the maximum power of the other corresponding dedicated power converter (operation  1010 ). For example, the power requirements of the existing load may be met by the dedicated power converter for the load, while the current drawn by the other load may be higher than the current that can be delivered by one or more other dedicated power converters for the other load. 
     In turn, the condition of operation  1010  may be detected as a voltage droop on the other load. Using the above representations of power drawn by the loads and the maximum power that can be supplied by the power converters, the power state of the existing load “x” may fall below the maximum power of the corresponding dedicated power converter and the power state of the other load “y” may increase above the maximum power of the other corresponding dedicated power converter when the following expression is met:
 
Load_ x&lt;VR _ x  AND Load_ y&gt;VR _ y  
 
The condition of operation  1010  in  FIG. 10A  may be expressed using steps  1040 - 1046  in  FIG. 10B .
 
     When the power state of the load falls below the maximum power of the corresponding dedicated power converter and the power state of the other load increases above the maximum power of the other corresponding dedicated power converter, the shared power converter is coupled to the load with the higher power requirement (operation  1014 ). Put another way, the coupling of the shared power converter is changed from the load in operation  1002  to the other load in operation  1014  to meet the power requirements of the other load when the condition in operation  1010  is met. In  FIG. 10B , step  1018  is performed if the conditions in steps  1044 - 1046  are both true, and step  1020  is performed if the conditions in steps  1040 - 1042  are both true. 
     The loads may continue to be driven (operation  1016 ) using the switching mechanism(s) and power converters. If the loads are to be driven, the shared power converter may be coupled to either load or coupled to both loads in the tied configuration based on the power states of the loads (operations  1004 - 1014 ). Power delivery to the loads through the power converters and switching mechanisms may continue until the power supply is no longer used to drive the loads. 
     The above-described power-delivery system can generally be used in any type of electronic device. For example,  FIG. 11  illustrates a portable electronic device  1100  which includes a processor  1102 , a memory  1104  and a display  1108 , which are all powered by a power supply  1106 . Portable electronic device  1100  may correspond to a laptop computer, tablet computer, mobile phone, PDA, portable media player, digital camera, and/or other type of battery-powered electronic device. Power supply  1106  may include one or more power converters and one or more switching mechanisms disposed between the output(s) of the power converter(s) and two or more loads. Power supply  1106  may also include a control circuit that obtains two or more error signals for the loads and uses the switching mechanism(s) to couple the load with a largest error signal from the two or more error signals to the output(s). The control circuit may also use the absolute value of the largest error signal to control the output current(s) of the power converter(s). 
     Portable electronic device  1100  may also include a software-based control apparatus that obtains power states and voltage droops of the loads and a power-delivery policy for power supply  1106 . Next, the control apparatus may generate one or more control signals for the set of switching mechanisms to configure a coupling of the loads to two or more power converters in power supply  1106  through a set of switching mechanisms based on the power states, voltage droops, and/or power-delivery policy. 
     The foregoing descriptions of various embodiments have been presented only for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the forms disclosed. Accordingly, many modifications and variations will be apparent to practitioners skilled in the art. Additionally, the above disclosure is not intended to limit the present invention.

Metadata:
Filing Date: 20150608
Publication Date: 20171128
Grant Date: 20171128
Priority Date: 20140606
Inventors: LUH LOUIS
ATHAS WILLIAM C.
SULLENS HEATHER R.
Assignee: APPLE INC
CPC Classifications: [{"code": "H02J2207/20", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F11/3058", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J3/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F11/3058", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F11/3058", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J3/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/0063", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/26", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/0065", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J2007/0067", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J1/14", "inventive": true, "first": true, "tree": "[]"}, {"code": "Y10T307/406", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J1/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/0063", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/00712", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/26", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J7/00712", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J7/0063", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J2207/20", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/26", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 54540164