Patent Application
20110148385
Many direct current (DC) powered devices require a regulated DC power supply at a particular voltage or set of voltages for operation. Power sources such as alternating current (AC) line power or DC battery power, however, may not provide power that is sufficiently regulated for direct use by sensitive electronics. Moreover, many electronics operate at power levels different than those provided by the power sources.
To remedy this situation, voltage regulators can be used to convert power from a power source into regulated power of the proper voltage for a particular electronic device. In certain examples, a voltage regulator can be incorporated into a powered device, or can be a separate unit between the powered device and the power source. Many modern electronic devices use multiple voltage regulators to provide power at different levels for use by various components throughout the device.
A linear voltage regulator is one type of voltage regulator. Linear voltage regulators (also referred to herein as “linear regulators”) can be used to convert a range of voltages above a desired voltage into the desired voltage, such as by passing the voltage through an active device (e.g. transistor) and burning off the “unwanted” voltage as heat. Although linear regulators can regulate output voltages with specificity and low ripple, linear regulators can have relatively low bandwidth compared to other voltage regulators.
Charge pumps are another mechanism used to convert an input voltage of a first level into an output voltage of a second level. Charge pumps can be used to generate an output voltage of a level that is increase or decrease an input voltage.
This document discusses, among other things, a device for providing a DC output voltage, including a first output voltage and a second output voltage, from an input voltage. In an example, the device can be configured to operate in a first configuration when the input voltage is below a threshold voltage and in a second configuration when the input voltage is above the threshold voltage. In the first configuration, a first voltage regulator can provide the first output voltage and a charge pump can provide the second output voltage. The charge pump can be configured to operate in a two-state mode to provide the second output voltage from the first output voltage. In the second configuration, the charge pump can be configured to operate in a three-state mode to provide both the first output voltage and the second output voltage.
This overview is intended to provide an overview of subject matter of the present patent application. It is not intended to provide an exclusive or exhaustive explanation of the invention. The detailed description is included to provide further information about the present patent application.
In the drawings, which are not necessarily drawn to scale, like numerals may describe similar components in different views. Like numerals having different letter suffixes may represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.
The present inventors have recognized, among other things, that the flexibility and simplicity of a linear regulator can be combined with an efficient and inexpensive, but in certain examples less flexible, charge pump to create a hybrid voltage regulator that can efficiently and inexpensively convert an input voltage into an output voltage. In certain examples, during generation of an output voltage, a less efficient linear regulator can be bypassed by a more efficient charge pump. In an example, the efficiency of a linear regulator can be based on a voltage drop between the input voltage and the output voltage. Accordingly, in certain examples, the linear voltage regulator can be bypassed when an input voltage is at a high voltage level relative to the output voltage.
In certain examples, when the difference between the input voltage and the output voltage is large, the output voltage can be provided by a charge pump, and when the difference between the input voltage and the output voltage is small, the output voltage can be provided by the linear regulator. A threshold voltage can be selected to determine when to provide the output voltage with the charge pump and when to provide the output voltage with the linear regulator. Additionally, in certain examples, a second linear regulator can be included. The second linear regulator can generate a stable input voltage for use by charge pump when the charge pump is generating the output voltage.
In certain examples, the circuit 100 of
The voltage regulator 102 can be coupled between a switching device 112 and the first output voltage 106. The voltage regulator 102 can also be coupled to a ground 101. In certain examples, the voltage regulator 102 can include a linear regulator. For instance, a linear regulator can be used to convert a higher input DC voltage 108 (e.g. +3.5 V) into a lower first output DC voltage 106 (e.g. +1.7 V). A linear regulator can also be used to half-wave rectify an AC input voltage 108 that has a higher magnitude than the first DC output voltage 106. In certain examples, the voltage regulator 104 can include a switching regulator.
In operation, the voltage regulator 102 can be used to provide the first output voltage 106 during certain conditions and the charge pump 104 can be used to provide the first output voltage 106 during other conditions. Whether the voltage regulator 102 or the charge pump 104 can provide the first output voltage 106 can be based on the difference between the input voltage 108 and the first output voltage 106. In certain examples the charge pump 104 can be used to provide the first output voltage 106 when the difference between the input voltage 108 and the first output voltage 106 is large. When the difference between the input voltage 108 and the first output voltage 106 is small, the voltage regulator 102 can be used to provide the first output voltage 106. Utilizing both the voltage regulator 106 and the charge pump 108 can enable the circuit 100 of
In an example, a threshold voltage can be used to determine whether the voltage regulator 102 or the charge pump 104 can be used to generate the first output voltage 106. To control whether the first output voltage 106 can be provided by voltage regulator 102 or charge pump 104, the circuit 100 of
As referred to herein, the circuit 100 of
In an example, the actual difference between the input voltage 108 and the output voltage 106 does not need to be determined. Accordingly, in certain examples, the threshold voltage can be compared directly to the input voltage 105. When the input voltage 108 is less than the threshold voltage, the circuit 100 of
In an example, the threshold voltage can be compared to a difference between the input voltage 102 and the first output voltage 106. When the difference between the input voltage 108 and the first output voltage 106 is less than the threshold voltage the circuit 100 of
In an example, the controller 112 can compare the input voltage 108 to the threshold voltage to determine when to switch between the voltage regulator 102 and the charge pump 104. In other examples, however, the controller 112 can compare the threshold voltage to a difference between the input voltage 108 and the first output voltage 106 to determine when to switch the switching device 112.
In an example, the charge pump 108 can provide the second output voltage 107 regardless of whether the voltage regulator 102 or the charge pump 108 provided the first output voltage 106. The charge pump 108 can be coupled to the switching device 112, the first output voltage 106, the second output voltage 107, and ground 101.
In an example, the charge pump 104 can be configured to generate the second output voltage 107 using the first output voltage 106 generated by the voltage regulator 102. Thus, when the circuit 100 of
When the circuit 100 of
Referring back to
In addition to being coupled in the first state 302 for approximately the same length of time as the second state 304, in an example, the flying capacitor 202 is also coupled in the third state 306 for approximately the same length of time as the first state 302 or the second state 304. In an example, the flying capacitor 202 can be coupled in the first state 302, in the second state 304, and in the third state 306 for approximately the same lengths of time. In an example, the first output voltage 106 can be approximately half of the input voltage 108, and the second output voltage 107 can be the complement of the first output voltage 106. In other examples, the flying capacitor 202 can be coupled in one or more of the first state 302, the second state 304, or the third state 306 of the three-state mode for different amounts of time, depending on desired output voltages or one or more other factors.
In an example, the three-state mode can be explained mathematically. With a rapidly switching capacitor (e.g. the flying capacitor 202), the voltage across the capacitor should be constant across each state. Thus, with the flying capacitor 202 coupled in each of the three states of
Additionally, in certain examples, the charge pump 104 can include variable state timing, such that charge pump 104 can provide stable voltages for the first output voltage 106 and the second output voltage 107 from a range of input voltages. For example, when the input voltage 108 is higher, the charge pump 104 can be coupled in the third state 306 for a shorter amount of time than when the input voltage 108 is lower. Thus, less charge can build up in the flying capacitor 202 and, in turn, less voltage can be transferred to the output voltages 106, 107. Similar to that discussed above with respect to
In the examples shown in
Similar to that described in circuit 100 of
In converting the input voltage 408 to the intermediate voltage 416, the second voltage regulator 414 can generate a stable voltage for the intermediate voltage 416 from the variable input voltage 408. The second voltage regulator 414, therefore, can help reduce the complexity of the charge pump 404, because the charge pump 404 can generate the first output voltage 406 and the second output voltage 408 from a single stable voltage. Accordingly, in an example, the charge pump 404 can be configured to generate output voltages 106, 107 from a single input voltage level. In certain examples, however, the charge pump 404 can be configured to adjust for variable input voltages.
In operation, the switching device 412 can couple the intermediate voltage 416 to either the voltage regulator 402 (the first configuration of the circuit 400) or the charge pump 404 (the second configuration of the circuit 400). In certain examples, the controller 410 can control the switching device 412 based on a comparison of a threshold voltage similar to that described with respect to the circuit 100 of
In the first configuration, the switching device 412 can be set to couple the intermediate voltage 408 to the first voltage regulator 402. The voltage regulator 402 can convert the intermediate voltage 408 into the first output voltage 406. The controller 410, along with setting the switching device 412, can be configured to couple the intermediate voltage 408 to the first voltage regulator 402, or can set the charge pump 404 in a two-state mode. In the two-state mode, the charge pump 404 can generate the second output voltage 407 from the first output voltage 406.
In the second configuration, the switching device 412 can be set to couple the intermediate voltage 408 to the charge pump 404. The controller 410, along with setting the switching device 412 to couple the intermediate voltage 408 to the charge pump 404, can also set the charge pump 404 in a three-state mode. The charge pump 404 can convert the intermediate voltage into the first output voltage 406 and the second output voltage 407.
In certain examples, the first and second output voltage 406, 407 can include regulated voltages. Accordingly, the controller 410 can determine when to switch the switching device 412 based on the input voltage 408. In other examples, however, the controller 410 can determine when to switch the switching device 412 based on a difference between the input voltage 408 and the first output voltage 408.
In an example, the controller 410 can use a threshold voltage to determine when to switch the switching device 412. In an example, the threshold voltage can include a difference between the input voltage 408 and the first output voltage 406. When the difference is less than the threshold voltage the circuit 400 can be set in the first configuration. When the difference between the input voltage 408 and the first output voltage 406 is greater than the threshold voltage, the circuit 400 can be set in the second configuration. In certain examples, the first output voltage 406 can be regulated. When the first output voltage 406 is regulated, the threshold voltage can be compared directly to the input voltage 408 because the first output voltage 406 does not change substantially. In certain examples, therefore, when the input voltage 408 is less than the threshold voltage, the controller 410 can set the circuit 400 in a first configuration. When the input voltage 408 is greater than the threshold voltage, the controller 410 can set the circuit 400 in the second configuration.
In an example, the threshold voltage can be selected such that the second voltage regulator 414 is high enough that the second voltage regulator 414 can provide an intermediate voltage 416 that is double the desired first output voltage 406. For example, if the desired output voltage is 1.7 volts, the intermediate voltage can be set at double 1.7 V=3.4 volts. Thus, the threshold voltage level can be set to slightly higher than 3.4 volts to account for the voltage drop across second voltage regulator 414. The determination of the threshold voltage can also be applied when the threshold voltage is the difference between the input voltage 408 and the first output voltage 406.
In an example, the threshold voltage can be selected based on the drop out voltage of the second voltage regulator 414. For instance, the threshold can be set at the lowest input voltage 408 that the second voltage regulator 414 can convert into a sufficient intermediate voltage 416 for the charge pump 104. In an example, a sufficient intermediate voltage 416 for the charge pump 404 can include an intermediate voltage 416 that is double the first output voltage 406. Thus, in this example the threshold can be set at double the first output voltage 106 plus the minimum drop-out of the second voltage regulator 414. Accordingly, in certain examples, when the input voltage 408 drops below this threshold, the second voltage regulator 414 can no longer provide a sufficient intermediate voltage 416 for the charge pump 404. The controller 410, therefore, can set the switching device 412 to couple the intermediate voltage 416 to the first linear regulator 402. In addition, when the input voltage 408 drops below the level that the second linear regulator 414 can effectively provide the desired regulated intermediate voltage 416 (due to the required drop-out of second linear regulator 414), the second linear regulator 414 can enter a drop-out region. In the drop-out region, the second linear regulator 414 can function as a pass through device that simply passes through the input voltage 402 to the intermediate voltage 416 with minimal voltage loss.
Although in the examples described above, a single controller 410 is described to control the switching device 412 and the charge pump 404, in other examples, individual controllers can be used.
The three-state mode and two-state mode of the charge pump 404 can operate substantially as that described above with respect to
The present inventors have recognized that the circuits and methods described above can be used to combine the advantages of a linear regulator and a charge pump, while avoiding the disadvantages of each. For example, linear regulators can be less efficient when there is a large voltage drop across the linear regulator. Therefore, when there is a large voltage drop across the linear regulator, a charge pump can be used to provide the output voltage. The charge pump can provide the output voltage with high efficiency when there is a large drop across the charge pump. In certain examples, however, a complex charge pump circuit may be required in order to deal with varying input voltages. In an example, therefore, a second linear regulator can be provided to regulate the input voltage for the charge pump. Even with the second linear regulator, however, the efficiency of the circuit can be held high as a majority of the voltage drop between the input voltage and the output voltage is handled by the charge pump. The voltage drop across the second linear regulator, therefore, can be kept lower to improve the efficiency of the second linear regulator.
The present inventors have recognized that the circuits or examples described above can be particularly efficient in generating a regulated, step-down voltage from a battery. As an example, a typical lithium ion battery has discharge curves as shown in the graph 500 of
The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention can be practiced. These embodiments are also referred to herein as “examples.” Such examples can include elements in addition to those shown and described. However, the present inventor also contemplates examples in which only those elements shown and described are provided.
All publications, patents, and patent documents referred to in this document are incorporated by reference herein in their entirety, as though individually incorporated by reference. In the event of inconsistent usages between this document and those documents so incorporated by reference, the usage in the incorporated reference(s) should be considered supplementary to that of this document; for irreconcilable inconsistencies, the usage in this document controls.
In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of “at least one” or “one or more.” In this document, the term “or” is used to refer to a nonexclusive or, such that “A or B” includes “A but not B,” “B but not A,” and “A and B,” unless otherwise indicated. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, a system, device, article, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects.
As used herein the terms “higher”, “greater”, “lower” and “less” with regards to voltage levels relate to the absolute value of a voltage relative to a ground voltage. For example, a +3 voltage is greater than a +2 voltage and a −3 voltage is greater than a −2 voltage.
Method examples described herein can be machine or computer-implemented at least in part. Some examples can include a computer-readable medium or machine-readable medium encoded with instructions operable to configure an electronic device to perform methods as described in the above examples. An implementation of such methods can include code, such as microcode, assembly language code, a higher-level language code, or the like. Such code can include computer readable instructions for performing various methods. The code may form portions of computer program products. Further, the code may be tangibly stored on one or more volatile or non-volatile computer-readable media during execution or at other times. These computer-readable media may include, but are not limited to, hard disks, removable magnetic disks, removable optical disks (e.g., compact disks and digital video disks), magnetic cassettes, memory cards or sticks, random access memories (RAMs), read only memories (ROMs), and the like.
The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description. The Abstract is provided to comply with 37 C.F.R. §1.72(b), to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.
