Not applicable
1. Field of Invention
This invention relates to electronic devices, specifically to power management methods for electronic devices.
2. Description of Prior Art
The various embodiments described herein relate to power management of an electronic system. Various techniques are known in the art to reduce power consumption in an electronic system, particularly for devices or systems that are battery powered.
Unfortunately, however, these conventional techniques still waste significant amount of powers. There is a need to develop novel systems and methods that utilize valuable powers more efficiently.
It is therefore an object of the present invention to provide power management methods that utilize powers more efficiently by operating electronic systems or subsystems at minimum possible power supply and yet providing satisfactory functionalities and performances.
In one embodiment, an electronic system is connected to a power supply through a power limiter that limits the maximum power that the electronic device can draw from the power supply. A controller sends a control signal to the power limiter. In response to the signal, the electronic system operates under the maximum power limit. The power limit may be determined during functional tests of the system. The power limit may be progressively adjusted down to a minimum level that the system can still deliver satisfactory functionalities and performances. Performance sensors may be used to monitor the performances of the system or the subsystem.
The inventive concept can be extended to an electronic system comprising multiple subsystems. Each of the subsystems may be connected to a power supply through a power limiter. In one aspect, a centralized controller is used. In another aspect, each of the subsystems has a controller. The electronic subsystems may be integrated in a single chip.
For a more complete understanding of the present invention and its various embodiments, and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings.
The present invention will now be described in detail with references to a few preferred embodiments thereof as illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order not to unnecessarily obscure the present invention.
System 100 further comprises a power supply 104 to provide power for electronic system 102. Power supply 104 may be a DC power supply or an AC power supply. Power supply 104 includes but is not limited to a battery including a rechargeable battery, an output from an AC/DC converter, a solar energy generation system, an outlet connected to an AC power grid and a fuel cell system. Power supply 104 may further include a power processing unit, such as, for example, a voltage regulator.
Electronic system 102 connects to power supply 104 through a power limiter 106. Power limiter 106 sets a limit for maximum power that power supply 104 can deliver to electronic system 102. Power limiter 106 is a programmable unit connected to a controller 108. In one aspect, controller 108 communicates with power limiter 106 through a wired connection (e.g., controller 108 sends control signal 103 to power limiter 106 through a databus). In another aspect, controller 108 communicates with power limiter 106 through a wireless connection. A program may be stored in a file storage system of controller 108. The program may be executed by controller 108 to reduce power consumption of electronic system 102. Controller 108 may comprise a microprocessor or microcontroller. Controller 108 may comprise special purpose processor. Controller 108 may further comprise ASIC and FPGA types of circuits. Controller 108 may comprise hardware, software and firmware.
Electrical power flow 105 flows from power supply 104 to electronic system 102 through power limiter 106 controlled by controller 108.
A voltage regulator 110 is included in electronic system 102. Voltage regulator 110 may be controlled by controller 108. When a power limit is imposed by controller 108 to power limiter 106, voltage regulator 110 generates an appropriate output voltage that is further coupled to performance sensor 112 and to system components 114. Voltage regulator 110 provides bias voltage for performance sensor 112 and system components 114. Controller 108 may include a program to find a suitable bias voltage for operations of electronic system 102. Controller 108 may control voltage regulator 110 to generate an initial output. While adjusting progressively the output of voltage regulator 110 by controller 108, performance indicators of performance sensor 112 are measured by controller 108. The program executed by controller 108 locks-in output voltage of voltage regulator 112 while the performance indicators of performance sensor 112 are optimized. Performance sensor 112 may comprise one or more test circuits and their performances are closely correlated to performances of system components 114. In an exemplary case, performance sensor 112 may have performance indicators reflecting performance of critical path in a digital integrated circuit. Performance sensor 112 may be an oscillator in one aspect. Performance sensor 112 may comprise current sensors for a NMOSFET and a PMOSFET. Measured currents depend on variations of a manufacturing process, such as for example, gate patterning and etching processes. Performance indicators of performance sensor 112 may demonstrate “look-ahead” natures. It means performance sensor 112 may fail one or more performance indicators before system components 114 actually fail.
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In another implementation as shown in
In another implementation as shown in
This known semiconductor circuit theoretically consists of a heating element, integrated in the circuit, and a temperature sensor. The power dissipated in the heating element is measured with the help of an integrated amplifier unit, an amplifier with a positive feedback loop being used, because of which the temperature oscillates around a constant value with small amplitude. In the known circuit the temperature will oscillate in a natural way because of the existence of a finite transfer time of the heating element and the temperature sensor with a high amplifier-factor.
In the embodiment, an exemplary power limiter 800 comprises an incoming DC power 802 that is drawn from power supply 104. If power supply 104 is an AC power source, an AC/DC converter may be added to convert AC power into DC power. DC power 802 is coupled to a first input of DC power modulator 804. In one aspect of the embodiment, block 804 modulates DC power 802 by a PWM signal 816. Output power of block 804, in PWM form, is converted back into DC power by PWM to DC converter 806. One of the outputs of block 806 is coupled to a power sensor 808 that receives a predetermined proportional portion of output power of block 806. Power sensor 808 may comprise a voltage sensor and a current sensor (not shown in
In another aspect of the embodiment, power sensor 808 may draw the predetermined portion of power from block 806 directly (not shown in
The maximum output power of DC power modulator 804 is determined by the reference that sets a level around which the chip's temperature will oscillate. To sustain a higher temperature, the power sensor 808 will need to draw more power proportionally from blocks 806. The reference is determined by controller 818. Controller 818 may determine the reference based upon the determined maximum power from a test result.
It should be noted that the power required to sustain the temperature level, around which the chip's temperature oscillates, also depends on an ambient temperature. At a lower ambient temperature, it requires more power to heat the heating element to maintain the temperature level. At a higher ambient temperature, less power is required. In one aspect of the embodiment, an ambient temperature sensor 820 is used to measure the ambient temperature. The measurement results are sent to controller 818. Ambient temperature may be measured regularly. Temperature sensor 820 may be a sensor external to the integrated circuit or the chip. Temperature sensor 820 may also be a part of the integrated circuit or the chip that will require an appropriate thermal isolation between temperature sensor 812 and temperature sensor 820. Such thermal isolation techniques are known in the art. Ambient temperature sensor 820 may even be integrated with controller 818.
The chip (microstructure) is associated with a thermal capacity. It requires a predetermined amount of power to heat the chip to a predetermined temperature above the ambient temperature. The required temperature difference caused by the heating power is further converted to the reference voltage by controller 818 based on characteristics of temperature sensors 812 and 820. Since power sensor 808 draws a proportional portion of power from block 806, a predetermined relationship between the output power of block 806 and the reference voltage may be established and be stored in a file storage of controller 818.
There may be various ways to integrate components of power limiter 800 at different integration levels. At a minimum level, 810 and 812 are integrated in a single chip or in a single microstructure. All such variations with different levels of integration fall within the scope of inventive concepts of the present invention.
Comparator 814 takes an output of temperature sensor 812 as a first input and a reference generated by controller 818 as a second input. The output of comparator 814 is coupled to a first input of gate 817 which has a second input connected to a clock signal 819. The output (815) of gate 817 in bit stream form is coupled to the second input of DC power modulator 804. The thermal feedback loop is completed. The reference generated by controller 818 sets a level of temperature around which the chip's temperature oscillates and, therefore, sets the output power of block 804 and block 807.
Comparator 814 takes an output of power to voltage converter 826 as a first input and a reference generated by controller 818 as a second input. The output of comparator 814 is coupled to a first input of gate 817 which has a second input connected to a clock signal 819. The output of gate 817 in the bit stream form is coupled to the second input of DC power modulator 804. The output power of block 804 is determined by pulse counts of the bit stream signal in a predetermined time interval. The output voltage of block 826 oscillates around the reference voltage generated by controller 818. The pulse counts of the bit stream signal within a predetermined time interval determine output power of block 804 and block 807.
If several power limiters are employed based upon the thermal feedback loops, thermal isolations are required among the power limiters in order to prevent heat interferences. Therefore, power limiters based upon the thermal feedbacks are more suitable for the applications wherein subsystems are thermally isolated. Power limiters based upon the electrical feedback loop may be employed for subsystems of an integrated circuit, such as, for example, subsystems of a SOC.
While the invention has been disclosed with respect to a limited number of embodiments, numerous modifications and variations will be appreciated by those skilled in the art. Additionally, although the invention has been described particularly with respect to electronic systems with DC power supply, it should be understood that the inventive concepts disclosed herein are also generally applicable to other electronic systems with AC power supply. Furthermore, the present inventive concepts are applicable to any implementation of power limiters. It is intended that all such variations and modifications fall within the scope of the following claims: