Patent Application
20120194150
Embodiments of the invention relate generally to battery operation control, and more particularly to the control of regulated power in a portable communication device.
With recent advances in a wide variety of mobile portable communication standards, there is an increased demand for wider usage of battery voltage in a mobile communication transmitter system in order to elongate the device operation time. In current battery-powered mobile communication transmitter devices, functional operation is guaranteed up to a certain point of battery voltage, below which the operational function is not even specified, or degraded performance is permitted until the operation is disrupted due to a malfunction of internal blocks such as a low drop out (LDO) regulator or other regulator. During a period of low-battery voltage operation, it is difficult to predict remaining operation time and likewise difficult to control the efficiency of device operation up to a point of certain battery voltage where even degraded performance operation is sustainable. In other words, the low-battery voltage region has been wasted; indeed, manufacturers do not design the internal functional circuit blocks to operate in the low-battery voltage region because of the randomness of regulated voltages that are powering the internal sub-blocks.
However, as increasing the usage time of electronic portable devices becomes more important, it may be necessary to control the region of low-battery voltage more accurately and efficiently. Thus, there is an opportunity for systems and methods for low-battery operation control in portable communication devices.
In order to increase the efficiency of LDO designs for mobile communication devices, these designs may keep the output voltage of the LDO as high as possible during normal operation. However, as the battery voltage drops and gets close to the regulated voltage, the LDO driver block may start to drive the block output that is a gate voltage of the Power PMOS (p-channel metal-oxide-semiconductor) transistor as low as possible to maintain the LDO output voltage at a regulated voltage while driving Power PMOS transistor drain voltage up to a regulated voltage close to the battery voltage. This region of operation may be called the “Deep triode region operation”. Because the Power PMOS transistor is placed in the loop of LDO regulator, the characteristic of the Power PMOS transistor in the deep triode region significantly affects the characteristic of LDO regulator itself. The affected performance factors may be bandwidth and stability, and because of these degraded performance criteria, the performance under a certain voltage level of battery may not be guaranteed or even used, resulting in a shorter operation time for mobile communication devices. Accordingly, embodiments of the invention may provide systems and methods operable to variably change the output voltage of LDO regulator in such a way of keeping the Power PMOS transistor from operating in the deep triode region in order to lengthen the operation time of mobile communication devices in a more predicable manner.
In an example embodiment of the invention, there is a low-dropout (LDO) voltage regulator for a portable device. The LDO voltage regulator may include a first amplifier that receives a battery voltage from a battery source and generates a first output voltage; a second amplifier that receives the first output voltage of the first amplifier from the first amplifier, and outputs a control voltage; and a power management circuit that receives the control voltage and provides a regulated voltage based upon the control voltage. When the battery voltage is above a threshold voltage, the control voltage may remain substantially constant, thereby resulting in the regulated voltage being substantially constant. When the battery voltage drops below the threshold voltage, the control voltage may drop proportionally from the substantially constant regulated voltage, thereby resulting in a proportional drop in the regulated voltage from the substantially constant regulated voltage.
According to another example embodiment, there is a voltage regulator for a portable device. The voltage regulator may include a comparator having first and second inputs and generating a control voltage, the first input receiving a battery voltage from a battery source, the second input receiving a fixed voltage independent from the battery voltage, and a power management circuit that receives the control voltage and provides a regulated voltage based upon the control voltage. When the received battery voltage is above the fixed voltage, the control voltage may be provided at a high constant voltage, thereby resulting in the regulated voltage being at a first voltage. When the battery voltage is below the fixed voltage, the control voltage may be provided at a low constant voltage, thereby resulting in the regulated voltage being at a second voltage less than the first voltage.
Having thus described the invention in general terms, reference will be made now to the accompanying drawings, which are not necessarily drawn to scale, and wherein:
Example embodiments of the invention will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all, embodiments of the invention are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.
Embodiments of the invention may provide systems and methods for low-battery operation control in portable communication devices such as cellular phones, Blackberries, iPhones, tablet/laptop/netbook computers, and the like. The systems and methods may provide accurate control of regulated power in low-battery voltage situations to enable one or more of (1) predictable performance in low-battery voltage situations, (2) longer communication time with the given battery specification, and/or (3) efficiency enhancement at low-battery voltage operation.
Turning now to
The output from the output port of the first amplifier 105 can be connected to a first port of resistor 135 (R3), and the second port of the resistor 135 (R3) can be connected to the positive input port of the second amplifier 110. In addition, the second port of resistor 135 (R3) can also be connected to the negative input port of the first amplifier 105. As such, the output of the first amplifier is provided to the positive input port of the second amplifier 110, and fed back to the negative input port of the first amplifier 105, via resistor 135 (R3). A resistor 140 (R4) can be connected between (i) the node commonly connecting the negative input port of the first amplifier 105, the second port of resistor 135 (R3), and the positive input port of the second amplifier 110, and (ii) ground (GND), in order to further adjust the amount of voltage/current provided to the negative input port of the first amplifier 105 and the positive input port of the second amplifier 110. The output from the second amplifier 110 may be fed back to the negative input port of the second amplifier 110.
A series of resistors 145 (R5) and 150 (R6) can be connected between the output of the second amplifier 110 and ground, and a node between resistors 145 (R5) and 150 (R6) can be used to provide the control voltage 155, according to an example embodiment of the invention. The value of resistors 145 (R5) and 150 (R6) can be selected in order to ensure that the control voltage 155 is in the appropriate dynamic range for input to an example power management circuit such as an LDO/regulator. As will be described in further detail with respect to
The operation of the example control voltage generator 100 of
Therefore, as shown in
Turning now to
Still referring to
The operation of the example control voltage generator 200 of
Therefore, as shown in
In addition, the output of the amplifier 310 may be connected to a gate of a power PMOS transistor 315. The source of the power PMOS transistor 315 may be connected to battery voltage 325. It will be appreciated that if the control voltage generators of
In an example embodiment, the internal circuit block 320 may include a complementary-metal-oxide-semiconductor (CMOS) power amplifier, perhaps in accordance with a mobile receiver or transmitter (e.g., a cellular application). In a CMOS mobile transmitter, for various reasons such as device protection and stable operation, the internal circuit block 320 may be powered by the power management circuit 300 (e.g., via the power PMOS transistor 315) at a cost of power efficiency. However, due to the voltage drop throughout the power management circuitry, including that associated with the control voltage generator, that is unavoidable, a certain amount of power is lost at the final power PMOS transistor 315. In order to minimize the power loss and maximize power efficiency of the system, the output voltage from the power management circuit 300 acting as an LDO/regulator may normally be set to the highest possible value somewhere below the battery voltage 325 even at the lowest possible battery voltage situation (e.g., as the name “Low Drop Out” (LDO) implies). From this mechanism of setting the lowest possible voltage of the battery, mobile communication device manufacturers may specify the minimum battery voltage for functional operation of the devices in the internal circuit block 320. In the voltage range below the minimum battery voltage, the functional operation may not be guaranteed.
It will be appreciated that the output of the power management circuit cannot be set to the battery voltage 325, according to an example embodiment of the invention. In particular, in order for the power PMOS transistor 315 employed in the power management circuit to work in saturation, the condition must be satisfied such that the voltage between the source and the drain must be greater than the value of the gate-to-source voltage (Vgs) minus the threshold voltage (VTH) of the power PMOS transistor 315. However, to maximize the efficiency of the system, it may be unavoidable to operate the power PMOS transistor 315 in the triode region where the power PMOS transistor 315 itself works more like in linear operation. Even if the power PMOS transistor 315 goes into a triode region, most of performance criteria, including bandwidth and stability of a power management circuit 300 acting as an LDO or regulator, may be sustained. However, this maintained performance may be disrupted when the power PMOS transistor 315 goes into a deep triode operation region in which the source voltage driven by LDO/regulator driver (i.e., amplifier 310) is forced to be higher than or very close to the battery voltage 325 available at the moment.
It will be appreciated that when the battery voltage drops to the point of operation where the drain voltage (the LDO regulator output of amplifier 310) becomes very close or higher than the battery voltage, the drain-to-source voltage difference Vds of Power PMOS transistor 315 becomes smaller while the gate-to-source voltage difference Vgs of Power PMOS transistor 315 becomes larger (this region of operation of transistor 315 may be called “Deep triode region” and the Power PMOS transistor 315 loses its saturated characteristic and operates more like a resistor with linear relationship between the voltage and the current). When the Power PMOS transistor 315 is being operated in the region of deep triode, the gain through the Power PMOS transistor 315 drops significantly and it may lose its capability of keeping stable operation over various environmental factors such as temperature and battery voltage.
To keep the power PMOS transistor 315 from being operated in the deep triode region, the control voltage generators illustrated in
Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
