Patent Application
20190041884
The present document relates to the field of power converters. More specifically, the present document relates to modular and configurable power converters capable of dynamically adjusting their maximum output currents.
Typically, a power management integrated circuit PMIC comprises a large number of power converters. These power converters may differ e.g. in terms of power consumption, noise generation, dropout voltages and maximum load currents that they support. However, during the time of designing the PMIC, the specific requirements of the application may not be sufficiently defined and the power converters may not be optimally selected and positioned on the printed circuit board PCB.
For example, a frequently occurring problem is that an output current is needed which exceeds a maximum output current a specific power converter can deliver. In this situation, in order to avoid overloading the specific power converter, one possibility is to connect a second power converter in parallel to provide the required maximum output current. However, when coupling two or more power converters, stability problems may arise. In addition, when coupling two power converters with different gains, only one of both power converters may be effectively regulating whereas the other power converter may be e.g. off by overvoltage or in current limit by under voltage.
Having the possibility of changing the physical location of a particular output of a particular power converter may be desirable. Moreover, it may be advantageous to have a set of connectable power converters such that e.g. a power converter with a low noise input stage or a power converter with a sufficient maximum output current may be implemented at a particular position on the PCB. These configurable positions and properties of power converters are in particular desirable in the field of application-specific standard products (ASSP) have to be adapted to the peculiarities of the application in a pre-operational phase.
The present document addresses the above mentioned technical problems. In particular, the present document addresses the technical problem of providing a method for dynamically changing locations of the outputs of power converters and for dynamically coupling two or more power converters to obtain a variable maximum output current.
According to an aspect, a power converter comprising an error amplifier, a reference current circuit branch and load current circuit branch is presented. The error amplifier is configured to generate an error signal based on a reference value and an output signal at an output of the power converter. The reference current circuit branch comprises a modulation device configured to modulate, based on the error signal, a reference current in the reference current circuit branch. The load current circuit branch comprises a first output transistor configured to adjust, based on the reference current, an output current at the output of the power converter.
The power converter may be e.g. a voltage regulator for regulating an output voltage at the output of the power converter or a current regulator for regulating an output current at the output of the power converter. For example, the power converter may be a linear regulator configured to maintain a steady output voltage such as e.g. a low-dropout LDO regulator.
The error amplifier may form part of an input stage of the power converter. In particular, the error amplifier may form part of the input stage of a feedback loop for regulating the output signal towards the pre-determined reference value. Depending on the type of power converter used, the error amplifier may generate the error signal based on a reference voltage value and an output voltage at the output of the power converter. Alternatively or additionally, the error amplifier may generate the error signal based on a reference current value and an output current at the output of the power converter. In any case, the error amplifier (or differential amplifier) may be configured to determine a difference signal based on the reference value and the output signal, and to generate the error signal as an amplified version of said difference signal. For this purpose, any suitable type of circuit comprising an operational amplifier may be used. For example, the error amplifier may be of an N-type metal-oxide semiconductor MOS, a P-type MOS, or a bipolar junction transistor BJT input differential pair. Specifically, the error amplifier may comprise e.g. a voltage controlled current source VCCS with an appropriately chosen transconductance Gm.
Both the reference current circuit branch and the load current circuit branch may form part of an output stage of the described power converter. For instance, the reference current circuit branch and the load current circuit branch may form parallel electrical paths between a supply voltage and ground. Throughout this document, the term “ground” is meant in its broadest possible sense. In particular, ground is not limited to a reference point with a direct physical connection to earth. Rather, the term “ground” may refer to any reference point to which and from which electrical currents may flow or from which voltages may be measured.
The modulation device may be e.g. any type of field effect transistor FET or BJT.
Similarly, the first output capacitor (also denoted as pass device) may be any type of FET or BJT. Preferably, the first output transistor is configured to adjust the output current such that the output current is an amplified version of the reference current. This may be achieved by (a) providing a reference transistor in series with the modulation device in the reference current circuit branch between the supply voltage and ground, and (b) by connecting the reference transistor and the first output transistor such that both transistors form a first current mirror. To this end, the reference transistor may be a diode-connected transistor and a gate terminal of the reference transistor and a gate terminal of the first output transistor may be biased at the same voltage level. In addition, both the reference transistor and the first output transistor may be of the same type, e.g. of the p-channel MOSFET type.
The above-described structure of the power converter makes it possible to couple two or more power converters on an electronic device in a stable and efficient manner. The idea is to provide a modular concept with identically or at least similarly structured power converters with the above-described components. These power converters may be dynamically (re-)configured to fulfill the requirements of the application. Further, the idea is to configure one power converter acting as a master power converter and configure another power converter acting as a slave power converter using a dedicated configuration unit with a switching matrix. The switching matrix may be configured to connect a gate terminal of the first output transistor of the master power converter with a gate terminal of the first output transistor of the slave power converter. The switching matrix may be configured to connect an output of the error amplifier of the master power converter with an input of the modulation device of the master power converter. At the same time, the switching matrix may be configured to disable the modulation device of the slave power converter. Disabling the modulation device may be achieved e.g. by connecting a gate terminal of a transistor implementing the modulation device with ground. Hence, it becomes possible to connect both outputs of the master power converter and the slave power converter together and to draw an increased maximum output current from the connected outputs while at the same time avoiding stability problems.
In the following description, it is assumed that—without loss of generality—only two power converters are coupled together. However, it is appreciated that the master power converter may be connected to an arbitrary number of slave power converters.
Moreover, the power converter may further comprise a slave current circuit branch with a second output transistor configured to adjust, based on the reference current, a slave current in the slave current circuit branch for controlling an external slave power converter. Still, the reference transistor and the first output transistor may be configured to form the first current mirror. Additionally, the reference transistor and the second output transistor may be connected to form a second current mirror. Again, the reference transistor may be a diode-connected transistor. The gate terminal of the reference transistor, the gate terminal of the first output transistor, and a gate terminal of the second output transistor may be biased at the same voltage level. The reference transistor, the first output transistor and the second output transistor may be of the same type, e.g. of the p-channel MOSFET type.
The slave current circuit branch serves as an additional structure within the power converter to branch off a current (i.e. the slave current) which has a well-known relationship to the actual output current of the power converter. In fact, the ratio of the slave current to the output current may be determined based on the characteristics (such as e.g. the resistance values at the respective operating points) of the first current mirror and the second current mirror. The generated slave current may be advantageously used to control operation of the external slave power converter.
The reference current circuit branch may comprise a master current injection branch for injecting a master current from an external master power converter, wherein the master current injection branch is arranged in parallel to the modulation device. For example, the master current injection branch may extend between ground and a node on the reference current circuit branch located between the modulation device and the reference transistor. The master current injection branch may comprise a third current mirror with an injection transistor and a mirror transistor, wherein the mirror transistor is connected in parallel to the modulation device. The injection transistor may be a diode-connected transistor for injecting the master current. The injection transistor and the mirror transistor may be of the same type, e.g. of the n-channel MOSFET type. For example, the master current may be injected into the drain terminal or the source terminal of the injection transistor in case the latter is implemented using MOSFET technology. At this, the person skilled in the art understands that the master current may not be directly injected into the drain terminal or the source terminal, but may as well be injected into any conducting structures electrically coupled to the drain terminal or to the source terminal.
The master current injection branch serves as an additional structure within the power converter to couple in a current (i.e. the master current) for controlling the power converter from the external master power converter. The master current injection branch in parallel to the modulation device enables substituting the reference current by the master current in case the modulation device is disabled. In other words, as will be described in detail below, a configuration unit may decide that a specific power converter is supposed to act as slave power converter and a switching matrix of this configuration unit may interrupt the propagation of the error signal between the error amplifier and the modulation device of the specific power converter. In the described situation, the switching matrix is configured to establish an electrical connection between a master power converter and the master current injection branch of the power converter such that the injected master current replaces a reference current which would be adjusted by the modulation device during normal operation of the power converter (i.e. when the power converter is not elected to behave as a slave power converter).
The power converter may further comprise an output capacitor coupled between the output of the power converter and ground.
According to another aspect, an electronic device comprising two of the above-described power converters is presented. One of the two power converters is denoted a master power converter, whereas the other power converter is denoted as slave power converter. The reference value applied to the error amplifier of the master power converter may be identical to or different from the reference value applied to the error amplifier of the slave power converter. The electronic device comprises a configuration unit with a switching matrix configured to connect the slave current circuit branch of the master power converter with the master current injection branch of the slave power converter such that the slave current of the master power converter is injected as the master current into the slave power converter.
The switching matrix may be configured to connect an output of the error amplifier of the master power converter with an input of the modulation device of the master power converter, or to connect an output of the error amplifier of the slave power converter with the latter input. On the other hand, the switching matrix may be configured to disconnect the output of the error amplifier of the master power converter from the input of the modulation device of the master power converter, or to disconnect the output of the error amplifier of the slave power converter from the latter input. For example, the switching matrix may be configured to disable the modulation device of the slave power converter (e.g. by connecting the gate terminal of the modulation device to ground) when the output of the error amplifier of the master power converter is connected with the input of the modulation device of the master power converter. Or, the switching matrix may be configured to disable the modulation device of the master power converter e.g. by connecting the gate terminal of the modulation device to ground) if needed.
Moreover, the switching matrix may be configured to disable the master current injection branch of the master power converter (e.g. by connecting a drain terminal or a source terminal of the injection transistor with ground) when the output of the error amplifier of the master power converter is connected with the input of the modulation device of the master power converter. The configuration unit may further comprise one or more registers for programming the switching behavior of the switching matrix and/or for storing the reference values of the error amplifiers.
The electronic device may be e.g. a power management integrated circuit PMIC. More specifically, the electronic device may be an application-specific standard product e.g. where the final application of a complex PMIC is not defined at design time. Those skilled in the art will appreciate that the electronic device may comprise a plurality of power converters comprising respective input stages and output stages. On the one hand, the input stages may comprise respective error amplifiers. On the other hand, the output stages may comprise respective modulation devices and the above-described circuit branches for amplifying reference currents, extracting slave currents and injecting master currents. Hence, the described electronic device enables a dynamic selection of one input stage and connection of the selected input stage with a selected output stage. A user of the electronic device may select the input stage according to the requirements of the application. Further, the user may select an output stage e.g. based on the location of an output terminal the output stage. With the help of the switching matrix, an arbitrary number of output stages may be coupled to this output stage to increase the maximum output current of the combined power converter.
At the same time, a uniform current distribution between output stages may be achieved by dimensioning the output stages accordingly. Particularly, situations are avoided in which only one power converter of two or more coupled power converters carries the entire output current.
According to yet another aspect, a method of operating a power converter is presented. The method comprises generating, by an error amplifier, an error signal based on a reference value and an output signal at an output of the power converter. The method further comprises modulating, by a modulation device, based on the error signal, a reference current in a reference current circuit branch of the power converter. A first output transistor adjusts, based on the reference current, an output current at the output of the power converter. The method may further comprise adjusting, by a second output transistor, based on the reference current, a slave current in a slave current circuit branch for controlling an external slave power converter. Further, the slave current may be injected into the external slave power converter. In particular, the method may further comprise providing a reference transistor in series with the modulation device within the reference current circuit branch, configuring the reference transistor and the first output transistor such that the reference transistor and the first output transistor form a first current mirror; and configuring the reference transistor and the second output transistor such that the reference transistor and the second output transistor form a second current mirror.
In addition, the method may comprise providing within the reference current circuit branch a master current injection branch such that the master current injection branch is arranged in parallel to the modulation device; and injecting a master current from an external master power converter into the master current injection branch.
According to yet another aspect, a method of coupling a master power converter as described in the foregoing description with a slave power converter as described in the foregoing description is presented. The method comprises connecting, using a switching matrix, the slave current circuit branch of the master power converter with the master current injection branch of the slave power converter such that the slave current of the master power converter is injected as the master current into the slave power converter. The method may comprise connecting, using the switching matrix, an output of the error amplifier of the master power converter with an input of the modulation device of the master power converter. Alternatively or additionally, the method may comprise connecting, using the switching matrix, the output of the error amplifier of the slave power converter with the latter input.
According to yet another aspect, a method of coupling a master power converter as described in the foregoing description with a slave power converter as described in the foregoing description is presented. The method comprises connecting, using a switching matrix, a gate terminal of the first output transistor of the master power converter with a gate terminal of the first output transistor of the slave power converter.
It should be noted that the methods and systems including its preferred embodiments as outlined in the present document may be used stand-alone or in combination with the other methods and systems disclosed in this document. In addition, the features outlined in the context of a system are also applicable to a corresponding method. Furthermore, all aspects of the methods and systems outlined in the present document may be arbitrarily combined. In particular, the features of the claims may be combined with one another in an arbitrary manner.
In the present document, the term “couple”, “connect”, “coupled” or “connected” refers to elements being in electrical communication with each other, whether directly connected e.g., via wires, or in some other manner.
The disclosure is explained below in an exemplary manner with reference to the accompanying drawings, wherein:
In the depicted example device 1, the first power converter is elected as master power converter. Consequently, a switching matrix 3 establishes an electrical connection 32 between input stage 11 and the output stage 13 of the first power converter.
The reference current circuit branch of the second power converter further comprises a master current injection branch for injecting a master current from e.g. the first power converter. As illustrated in
It should be noted that at the outputs of both output stages 13, 23, respective output capacitors 41, 42 are connected which may have preferably the same or similar capacitances. If then outputs of the output stages are connected to an external load, the capacitances of the output capacitors 41, 42 add up, providing an almost constant bandwidth behavior.
Finally, it should be noted that the switching matrix 3 may be configured to disable the master current injection branch of the master power converter because it is not needed in the depicted scenario. This may be done e.g. by grounding the gate of the mirror transistor 18 and/or the gate of the injection transistor 19 via electrical connection 33.
This is also illustrated in
It should be noted that the description and drawings merely illustrate the principles of the proposed methods and systems. Those skilled in the art will be able to implement various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. Furthermore, all examples and embodiment outlined in the present document are principally intended expressly to be only for explanatory purposes to help the reader in understanding the principles of the proposed methods and systems. Furthermore, all statements herein providing principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102017213676.6 | Aug 2017 | DE | national |
