Abstract:
In one embodiment, an electronic system comprises one or more power circuits configured to receive a first voltage from an external power source and produce a second voltage to one or more electronic components of the electronic system, and a power management circuit configured to determine one or more output currents of the one or more power circuits, wherein the power management circuit causes the external power source to change the first voltage based on at least one output current of at least one power circuit to reduce power loss of the at least one power circuit.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional App. No. 61/907,304 filed Nov. 21, 2013, the content of which is incorporated herein by reference in its entirety for all purposes. 
    
    
     BACKGROUND 
     The present disclosure relates to electronic circuits and methods, and in particular, to circuits and methods for adjusting power supply voltages. 
     Unless otherwise indicated herein, the approaches described in this section are not admitted to be prior art by inclusion in this section. 
     Reducing thermals and power dissipation is a big challenge in battery powered and non-battery power electronic devices. For example, most battery charger integrated circuits (ICs) operate at a constant input voltage. However, the efficiency is not constant over the entire battery voltage range. This results in non-optimal efficiency. 
     In particular, when an electronic device is charging its battery from a wall adapter, CPU intensive, graphics intensive, and modem (wireless) intensive workloads may cause worst case thermal conditions, which can increase skin temperature of the device making the device unusable to a user and possibly even causing damage to the device. 
     High power consumption trends of current devices also cut across other physical limitations, such as form factor limits on the connector size, which reduces the current limit of the cables used to connect devices to external power supplies, for example. 
     SUMMARY 
     The present disclosure relates to adjusting power supply voltages. In one embodiment, changes to a voltage from an external power source is requested by an electronic device based on operating conditions of one or more power circuits in the electronic device. 
     In one embodiment, the present disclosure includes an electronic system comprising one or more power circuits configured to receive a first voltage from an external power source and produce a second voltage to one or more electronic components of the electronic system, and a power management circuit configured to determine one or more output currents of the one or more power circuits, wherein the power management circuit causes the external power source to change the first voltage based on at least one output current of at least one power circuit to reduce power loss of the at least one power circuit. 
     In one embodiment, the power management circuit determines whether the one or more output currents of the one or more power circuits are outside a target range and causes the external power source to change the first voltage until one or more output currents of the one or more power circuits are inside the target range responsive to the output currents being outside the target range. 
     In one embodiment, the power management circuit determines whether a change of operating conditions of the electronic system is occurring, and responsive to no detected change, suspends causing the external power source to change the first voltage. 
     In one embodiment, one of the one or more power circuits is a switching regulator configured to charge a battery, and wherein the at least one output current is a charge current into the battery, wherein the power management circuit causes the external power source to increase the first voltage until the charge current into the battery meets a set charge current. 
     In one embodiment, the one or more power circuits comprise at least one switching regulator. 
     In one embodiment, the power management circuit is configured to poll the one or more electronic components to determine the electronic component that draws the highest power, and further configured to determine whether said electronic component that draws the highest power is a low voltage component, and to cause the external power source to increase the first voltage if the highest power electronic component is not a low voltage component, and to decrease the first voltage if the highest power electronic component is a low voltage component. 
     In one embodiment, the power management circuit is further configured to cause the external power source to change the first voltage in order to minimize overall voltage conversion loss of the one or more power circuits based on input information of acceptable input voltage ranges, power loss estimations for the acceptable input voltage ranges, and output currents of the one or more power circuits. 
     In another embodiment, the present disclosure includes a method comprising receiving a first voltage in one or more power circuits of an electronic system from an external power source to provide a second voltage to one or more electronic components of the electronic system, determining an operating condition of the one or more power circuits, and generating signals from the electronic system to the external power source to change the first voltage responsive to the determined operating condition. 
     In one embodiment, the operating condition is power drawn by one or more power circuits. Generating the signals from the electronic system to the external power source to change the first voltage is to reduce power loss in the electronic system. 
     In one embodiment, the method further comprises determining whether the second voltage to one or more electronic components are outside a target range, and generating the signals from the electronic system to the external power source to change the first voltage responsive to the second voltage to one or more electronic components being outside the target range. 
     In one embodiment, one of the one or more power circuits is a switching regulator configured to charge a battery. At least one charge current into the battery is associated with the second voltage associated with the switching regulator. The method further comprises generating the signals from the electronic system to the external power source to increase the first voltage until the charge current into the battery meets a set charge current. 
     In one embodiment, the method further comprises polling the one or more electronic components to determine the electronic component that draws the highest power, and determining whether said electronic component that draws the highest power is a low voltage component. Generating the signals from the electronic system to the external power source further comprises generating the signals from the electronic system to the external power source to increase the first voltage responsive to said electronic component not being a low voltage component and to decrease the first voltage responsive to said electronic component being a low voltage component. 
     In one embodiment, the one or more power circuits comprise at least one switching regulator. 
     In one embodiment, the present disclosure includes a method comprises determining an optimal voltage of an external power source in order to minimize overall voltage conversion loss on a plurality of power circuits inside a computing system based on input information of acceptable input voltage ranges, power loss estimations for the acceptable input voltage ranges, and output currents of the plurality of power circuits. 
     In one embodiment, the one or more power circuits comprise at least one voltage regulator. 
     In one embodiment, the method further comprises assigning priority to one power circuit based on an operating condition of the power circuit, and determining the optimal voltage further based on the assigned priority. 
     In one embodiment, one power circuit is a battery charger and the operating condition is charging of a battery. 
     In one example embodiment, an input voltage may be specified based on a battery voltage and current (input or output) in a battery charger to obtain high efficiency operation. In other embodiments, an input voltage may be specified to reduce overall power dissipation and heat generation to reduce skin temperature and other temperatures in the system. When some components of the electronic device enter high power states, such component&#39;s requirements may be factored into a determination of a requested input voltage to optimize overall system efficiency. 
     In one example embodiment, a high voltage dedicated charge port (HVDCP), for example, produces a voltage to a battery charger integrated circuit or system load based on a high efficiency point tracking algorithm. 
     In another embodiment, the present disclosure includes a software algorithm. For example, the software algorithm may perform a method comprising determining an optimal voltage of an external power source in order to minimize overall voltage conversion loss on a plurality of voltage regulators inside a computing system based on input information of acceptable input voltage ranges, power loss estimations for the acceptable input voltage ranges, and output currents of the plurality of voltage regulators. 
     In one embodiment, multiple power circuits (e.g., regulators) may report output voltage and output current for processing by an algorithm. The algorithm may determine an acceptable range for each power circuit (e.g., using stored upper voltages and lower bounds based on the reported output voltage and a stored margin). The acceptable ranges and output currents and/or voltages of each regulator may be used to maximize combined conversion efficiency of the power circuits by setting an external voltage from an external power source. 
     In another embodiment, additional voltage margin from the external power source can be dynamically adjusted based on the total system current loading and IR drop from the external power source to the computing system. 
     In one embodiment, input information about each internal voltage regulator may be maintained by a centralized controller or maintained by each voltage regulator, for example, and ‘voted’ (reported) from each voltage regulator to a centralized controller for the voltage range and preferred voltage in order to determine the optimal voltage of external power source meeting the range constraints and minimizing the conversion loss inside the computing system. 
     In one embodiment, an electronic device includes a switch mode battery charger (SMBC), switch mode power supplies (SMPSs), and one or more boost SMPSs. Each power circuit may report an ‘acceptable input voltage range’ and a ‘power loss estimation’ for the voltage range at the current load (e.g., V_range_SMBC, P_loss_SMBC (V_range_SMBC, I_SMBC_output), V_range_SMPS, P_loss_SMPS (V_range_SMPS, I_SMPS_output), V_range_Boost, P_loss_Boost (V_range_Boost, I_Boost_output)). 
     In one embodiment, the electronic device may measure and report the adapter current. 
     In one embodiment, a main power management integrated circuit (PMIC) may decide an optimal target adapter output voltage and send the request to the external power source so that the voltage from the external power source is within all acceptable ranges, minimizes the power loss of SMBC+SMPSs+Boost SMPS within the ranges, and is higher than: (current system power+guard band)/max connector current limit. In response to signals from a main PMIC, the external power source may change the adapter output voltage to the target that the main PMIC requested, for example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a block diagram of a dynamic voltage adjust system according to one embodiment. 
         FIG. 2  illustrates a method for dynamic voltage adjust according to one embodiment. 
         FIG. 3  illustrates dynamic voltage adjust of a battery charger circuit according to one embodiment. 
         FIG. 4  illustrates a method for dynamic voltage adjust including a battery charger circuit according to one embodiment. 
         FIG. 5  shows an example of dynamic voltage adjust according to another embodiment. 
         FIG. 6  shows another example of dynamic voltage adjust according to another embodiment. 
         FIG. 7  shows another example of dynamic voltage adjust according to another embodiment. 
         FIG. 8  illustrates a method for dynamic voltage adjust for polling according to one embodiment. 
         FIG. 9  illustrates a block diagram of a dynamic voltage adjust system according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure pertains to adjusting voltage provided to a system to improve system performance. In the following description, for purposes of explanation, numerous examples and specific details are set forth in order to provide a thorough understanding of the present disclosure. It will be evident, however, to one skilled in the art that the present disclosure as expressed in the claims may include some or all of the features in these examples alone or in combination with other features described below, and may further include modifications and equivalents of the features and concepts described herein. 
       FIG. 1  illustrates a block diagram of a dynamic voltage adjust system  100  according to one embodiment.  FIG. 1  shows an electronic device  101  coupled to an external power source  102 . External power source  102  provides a voltage Vin (also referred to herein as VBUS) and current to electronic device  101 . Electronic device  101  may include one or more power circuits (e.g., power circuits  111 ,  112 , and  113 ) that receive the voltage VBUS from external power source  102  and provide voltage and current to one or more electronic components (e.g., electronic components  121 ,  122  and  123 ), such as processors, wireless transceivers, display circuits (e.g., backlights), or battery chargers, for example. In this example, external power source  102  is coupled to electronic device  101  via a cable  160  that is attached using connectors  161  and  162 . Cable  160  may include wires for voltage Vin and ground, as well as one or more data wires for communicating information between electronic device  101  and external power source  102 . 
     External power source  102  may be a universal serial bus (USB) host, a USB hub, or a wall adapter that plugs into a power outlet and converts AC power to DC power, for example. One example wall adapter that may be used in certain embodiments is a high voltage dedicated charge port (HVDCP). Embodiments using HVDCP may adjust the externally supplied voltage, for example. In the case where the power circuit is a battery charger and the electronic component is a battery, and depending on the battery voltage, the input voltage from the external power source  102  can be adjusted so that charging and system load is always operating at a high (or even maximum) efficiency. External power source  102 , such as an HVDCP, may include a voltage control component  103  that may change the voltage Vin to different levels, for example, in response to signals received over cable  160  from a communication circuit  150  in electronic device  101 . 
     In this example, voltage Vin from external power source  102  is coupled to power circuit  111 . Power circuit  111  receives voltage Vin and produces an output voltage Vdd 1  to electronic components  121 . Power circuit  111  may send and/or receive signals to and/or from a power management circuit  110 . Power management circuit  110  may configure power circuit  111  for operation, such as configuring the voltage Vdd 1  or current outputs, for example. In some applications, an output of one power circuit may be provided as an input to another power circuit. For example, the voltage Vdd 1  from power circuit  111  may be provided as an input to power circuit  112 . Power circuit  112  may generate another output voltage Vdd 2  to electronic components  122 . Similarly, power circuit  112  may send and/or receive signals to and/or from a power management circuit  110 . Power management circuit  110  may configure power circuit  112  for operation, such as configuring the voltage Vdd 2  or current outputs, for example. Finally, in this example, another power circuit  113  receives voltage Vin and produces an output voltage Vdd 3  to electronic components  123 . Power circuit  113  may send and/or receive signals to and/or from a power management circuit  110 . Power management circuit  110  may configure power circuit  113  for operation, such as configuring the voltage Vdd 3  or current outputs, for example. In some examples implementations, power management circuit  110  may be a power management integrated circuit (PMIC) including one or more power circuits, while other example implementations may have distinct power circuits separate from the PMIC (e.g., some battery charger applications). Additionally, in some embodiments, one or more power circuits  111 ,  112 , and/or  113  may be switching regulators, for example, and others may be low dropout regulators (LDOs). 
     Features and advantages of the present disclosure may include adjusting the voltage Vin from external power supply  102  to improve the efficiency of one power circuit  111 ,  112 ,  113  or even multiple power circuits  111 ,  112 ,  113  operating together. In one embodiment, one of the power circuits  111 ,  112 ,  113  may be a battery charger, for example, charging a battery using a particular charge current. If the voltage Vin from the external power source is too low, the full amount of desired charge current may not be available from power circuit  111 ,  112 ,  113 . Thus, the electronic device  101  may send signals to external power source  102  (e.g., via communication circuit  150 ) to increase the voltage Vin so that power circuit  111 ,  112 ,  113  may provide the desired value of charge current. More generally, given the current loads of one or more power circuits  111 ,  112 ,  113  in electronic device  101 , the voltage received from external power source  102  may be changed to optimize the efficiency and performance of power circuits  111 ,  112 ,  113 . In one example embodiment described in more detail below, multiple power circuit operating conditions may be analyzed by the power management circuit to determine if an increase or decrease in the external power supply voltage Vin would result in improved efficiency. 
       FIG. 2  illustrates a method  200  for dynamic voltage adjust according to one embodiment. At  201 , one or more power circuit output currents may be determined For example, an output current of a battery charger may be sensed as described in more detail below. Based on the operation of power circuits  111 ,  112 ,  113 , the voltage from an external power source may be changed at  202  to improve the efficiency of power circuits  111 ,  112 ,  113 , for example. At  203 , an output current check may be conducted. For example, a battery charger circuit may perform a check to determine if the magnitude of a charge current into a battery is equal to a set (or target) charge current value. If the current does not meet a target, then the system may loop back to  202  from  203 , and in the battery charger case increase the voltage from the external power source. Similarly, if the output current check meets the target and does not cause a further change in the power supply voltage Vin, then a change in operating conditions at  204  may cause the system to loop back to  201  and determine the power circuit output currents and adjust the power source voltage as described above. The system may hold the power source voltage Vin at  205  until a change in operating conditions, for example. 
       FIG. 3  illustrates dynamic voltage adjust of a battery charger circuit according to one embodiment.  FIG. 3  shows an example where a battery charger receives a voltage, VBUS, from an external power source and couples voltage and current to a battery  350  to charge the battery, for example. In this example, the power circuit is a switching regulator  301 , and VBUS is greater than that voltage provided to the battery  350 . Accordingly, switching regulator  301  is a step down (or “Buck”) DC-DC converter. Switching regulator  301  may be configured to produce a set amount of current into battery  350  to charge the battery (e.g., current Ichg), and may include a feedback loop (not shown) to sense output current and configure the switching regulator  301  to produce the desired charge current. For example, in one embodiment, the switching regulator  301  may be configured to generate charge current Ichg=3 A. 
     Initially, VBUS is configured to a low setting. For example, if the external power source is a programmable adapter or USB source, the initial voltage on VBUS may be 5v. However, the external power source may have a maximum output current (Imax), where the total output power available from the external power source is Imax*VBUS. If Imax is too low, the external power source may not be able to provide enough power to switching regulator  301  to allow the switching regulator to generate the set amount of charge current. Thus, some example embodiments may sense output current (e.g., Ichg) and compare the actual output current to the desired (or expected) output current. Current sensing may be performed with a series resistor  302  (as shown in  FIG. 3 ) or using a sense FET (i.e., a small FET configured to detect current through the regulator), for example. In this example, sense resistor  302  detects charge current Ichg using amplifier  303 . The output of amplifier  303  is provided to comparator  304 , which compares the detected current to the set (or target) charge current value. Additionally, the circuit may optionally include an analog-to-digital converter  320  to detect the voltage from the external device at the input of the switching regulator  301  to determine the voltage on VBUS. If the detected charge current is below the target charge current, the comparator output may trigger communication circuit  310  to communicate with the external power source to increase the voltage on VBUS. In this example, communication between an electronic device and external power source may be over a two wire interface, which in this case is are the D+ and D− data lines of a USB connection. In response to the signals on D+/D− from communication circuit  310 , the external power source may incrementally increase the voltage on VBUS until the detected charge current is equal to the target charge current. 
       FIG. 4  illustrates a method  400  for dynamic voltage adjust including a battery charger circuit according to one embodiment. At  401 , a battery charger may be enabled. At  402 , the external voltage may be set to a low value (e.g., a minimum value of available values). At  403 , the current limit of the external power source may be determined to determine maximum output current available from the external power source. At  404 , a charge current (Ichg) is set. In one embodiment, charge current may be programmed digitally, for example, to one of a plurality of available values. At  405 , the charge current into a battery is detected. If the detected charge current (Isense) is less than the set charge current (Ichg) at  406 , then the electronic device may signal the external power source to increase the voltage. The external voltage may be increased (e.g., to the next available value above the current value) at  407 . If set charge current Ichg is equal to sense current Isense, then the process may stop at  408 . The external power source may maintain the voltage on VBUS until circuit operating conditions change and the process may be repeated under different conditions, for example. 
       FIG. 5  shows an example of dynamic voltage adjust according to another embodiment. In the example illustrated by  FIG. 5 , information from multiple different power circuits are combined to determine the voltage provided by an external power source. In this example, a main PMIC may include a switched mode battery charger (SMBC) power circuit for charging a battery, and one or more switch mode power supplies (SMPS) and LDOs to provide voltage and current to an application processor, for example. Additionally, the SMBC provides voltage and current to a secondary SMPS and LDOs to provide voltage and current to a modem (e.g., one or more transceivers), for example, and voltage and current to a SMPS for increasing (boosting) the voltage for an LCD backlight, for example. 
     In this example, changing the system input voltage may minimize the losses and heat generation caused by the SMBC and SMPCs, for example. Additionally, if the system total current is approaching the connector current limit, an increase in the external power source voltage allows more power into the system (e.g., at lower current), for example. 
     Each regulator may report, for example in response to polling, an acceptable input range and power loss estimation for the voltage range at the current load current. For example, in one embodiment, each regulator may measure output voltage and output current and send this information to a PMIC. The measured output voltage of each regulator may be used to determine an acceptable range of input voltages. For instances, an upper bound of an acceptable input voltage range may be a prestored value corresponding to maximum input voltage for the particular regulator beyond which damage to the regulator may occur. The lower bound may be determined by combining the reported output voltage with a prestored margin (e.g., an amount that the input voltage must be greater than the output voltage for the particular regulator to operate). One or more conversion efficiencies may be stored as a lookup table or encoded as an equation, for example. Accordingly, an algorithm may determine an external power source voltage to achieve a maximum combined efficiency of the combined power circuits based on operating conditions of the individual power circuits (e.g., output voltage and output current of each regulator). In various embodiments, an algorithm for receiving information from multiple regulators and determining a new output voltage from an external power source to improve system efficiency may be implemented as software or firmware on a PMIC or as software on a processor (e.g., a PMIC driver) and stored on a non-transitory computer readable medium such as a volatile or non-volatile memory, for example. SMBC may report an ‘acceptable input voltage range’ (V_range_SMBC) and a ‘power loss estimation’ (P_loss_SMBC(V_range_SMBC, I_SMBC_output)) for the voltage range at the current load. SMPS may report an ‘acceptable input voltage range’ (V_range_SMPS) and a ‘power loss estimation’ (P_loss_SMPS (V_range_SMPS, I_SMPS_output)) for the voltage range at the current load. Discrete boost SMPS may report an ‘acceptable input voltage range’ (V_range_Boost) and a ‘power loss estimation’ (P_loss_Boost (V_range_Boost, I_Boost_output)) for the voltage range at the current load, 
     Additionally, the adapter current into the system from the external power source may be measured and reported to the PMIC. The main PMIC may decide the optimal target external power source voltage and send the request to the external power source (e.g., USB or adapter). The PMIC may determine the external source type (e.g., USB type or adapter type) and signal the external source for voltages that the external source is capable of producing. An algorithm in the PMIC may minimize power loss of the SMBC, SMPSs, and Boost SMPS within the voltage ranges available from the particular external power source, for example. In one embodiment, the external source voltage may be advantageously higher than the current system power plus a guardband divided by the maximum connector current limit, for example. Changing conditions, such as modem (wireless) activity, application processor (e.g., ARM, graphics processors, etc. . . . ) activity, battery charging, etc. . . . may cause the system to signal the external power source to change the external voltage supplied to the system, for example. Benefits of these techniques may include lower temperatures while battery charging, more thermal budget for CPU and graphics intensive workloads. Additionally, faster battery charging may be achieved because there is better thermal room for the SMBC. Further, improved efficiencies and thermal performance may result in reduced form factor, thinner designs, and allow the use of a standard USB connector that may have current limitations, for example. Embodiments of the present invention may be implemented using High Voltage Dedicated Charge Ports (HVDCP) wall adapters, for example, and USB cables with no change required in compatible USB systems in some embodiments, for example. 
       FIG. 6  shows another example of dynamic voltage adjust according to another embodiment. In  FIG. 6 , acceptable voltage ranges  602 - 1 ,  602 - 2 , and  602 - 3  and power losses  604 - 1 ,  604 - 2 , and  604 - 3  are shown for a condition where the electronic device operating condition is where the battery is charging, a video conference is being conducted, the battery is almost empty (e.g., battery voltage approximately 3.0 V), and the liquid crystal display (LCD), respectively, is set to medium brightness. As illustrated, the battery charger conversion loss  604 - 1  and processor/modem SMPS conversion loss  604 - 2  increases with increasing input voltage, but the conversion loss  604 - 3  for the booster decreases with increasing voltage. Accordingly, a system optimum, as shown by arrow  606 , may occur between about 3 and 3.7 volts as shown at the boundary of an acceptable system voltage range  602 - 4  for the externally supplied voltage (the range of external voltages that may be supplied to the system) and have a total conversion loss  604 - 4  in the range  602 - 4 . In some embodiments, the battery charging is given priority over video conferencing, and thus the associated power circuit for battery charging is given priority over the associated power circuit for video conferencing. Therefore, the total conversion loss  604 - 4  becomes the same as or substantially the same as the conversion loss  604 - 1  for the battery charging. The method for the dynamic voltage adjust of  FIG. 6  can be implement by the method of  FIG. 8 , for example. 
       FIG. 7  shows another example of dynamic voltage adjust according to another embodiment. In this example, the operating conditions are web browsing is occurring, the battery is full (e.g., battery voltage approximately 4.35 V), and the battery charger is turned off, and the LCD is at maximum brightness. As illustrated, the battery charger conversion loss  704 - 1  is shown as the zero line in the acceptable voltage range  702 - 1  and can be ignored. Processor/modem SMPS conversion loss  704 - 2  increases (although at a lower rate than in  FIG. 6 ) with increasing input voltage in the acceptable voltage range  702 - 2 , but the conversion loss  704 - 3  for the booster decreases (although at a higher rate than in  FIG. 6 ) with increasing voltage in the acceptable voltage range  702 - 3 . In this example, the system optimum, as shown by arrow  706 , may occur at the other boundary of the acceptable system voltage range  702 - 4  around 9.5 V, for example. The method for the dynamic voltage adjust of  FIG. 7  can be implement by the method of  FIG. 8 , for example. 
       FIG. 8  illustrates a method  800  for dynamic voltage adjust according to one embodiment.  FIG. 9  illustrates a block diagram of a dynamic voltage adjust system  900  according to one embodiment. Dynamic voltage adjust system  900  is an illustrative example of dynamic voltage adjust system  100  in which electronic components  121  is a battery charger, electronics components  122  is a processor and electronics components  123  is an LCD backlight. Further, the voltage Vdd 1  is also applied to power circuit  113 . In this example, the input voltage Vin is 5-9 V. Power circuit  111  steps down the voltage, for example, by using a buck converter, to a range of 3-5 V. Power circuit  111  provides the voltage to the power circuits  112  and  113 . Power circuit  112  steps down the voltage to a range of 0.5-3 V, and power circuit  113  steps up the voltage to a range of 24.8-33.3 V. 
     Referring to  FIG. 8 , at  802 , input voltage Vin is applied to electronic device  101 . At  804 , power management circuit  110  determines whether charging is enabled. If charging is enabled, at  806 , power management circuit  110  executes a charging method, such as method  400  (see  FIG. 4 ). In some embodiments, the charging is given priority over other power circuits, and thus the method  400  is executed. Otherwise, if, at  804 , charging is not enabled, power management circuit  110  begins a polling algorithm. At  810 , power management circuit  110  determines which electronic component  122 ,  123  will require the highest power. At  812 , power management circuit  110  determines if the electronic component  122 ,  123  that will require the highest power is a low voltage component. In the example of  FIGS. 7 and 9 , electronic components  123  (the LCD backlight) has the highest power draw. If the electronic component is a low voltage component, at  814 , power management circuit  110  reduces the system voltage by reducing the input voltage Vin, and ensures that sufficient power is available from the input voltage Vin, and returns to determining the component at  810 . Otherwise, if, at  812 , the electronic component is not a low voltage component, at  816 , power management circuit  110  increases the system voltage by increasing the input voltage Vin, and ensures that sufficient power is available from the input voltage Vin, and returns to determining the component at  810 . In this example, the LCD backlight is not a low voltage component, thus, power management circuit  110  increases the input voltage Vin from external power source  102 . In this example, the input voltage Vin is increased to the upper end of the range to be close to 9 V. This improves the efficiency because the voltage boost by power circuit  113  is from 9 V rather than a lower voltage such as 5 V. In another example, if the high power drawing component was the processor, which was also the low voltage component. The input voltage Vin would be reduced to the lower end of the range so that the step down in voltage for the processor is from 5 V to 0.5-3 V rather than stepping down from 9 V. 
     The above description illustrates various embodiments of the present disclosure along with examples of how aspects of the particular embodiments may be implemented. The above examples should not be deemed to be the only embodiments, and are presented to illustrate the flexibility and advantages of the particular embodiments as defined by the following claims. Based on the above disclosure and the following claims, other arrangements, embodiments, implementations and equivalents may be employed without departing from the scope of the present disclosure as defined by the claims.