Patent Application
20240364281
The present disclosure relates generally to power amplification. In particular, but not by way of limitation, the present disclosure relates to systems, methods and apparatuses for amplifiers with switched preamplifiers and multiple cascoded power amplifying cells.
Amplifiers are integral components in a wide range of electronic systems, serving to increase the power of a signal. They find application in numerous fields, including audio and video broadcasting, wireless communication, and even medical devices. The design and operation of amplifiers can vary greatly depending on the specific requirements of the application, such as the desired gain, frequency range, and power efficiency.
One common type of amplifier is the power amplifier, which is designed to deliver a large amount of power to a load, such as a speaker, antenna, or plasma processing chamber. Power amplifiers are typically classified into different classes (A, B, AB, C, D, etc.) based on their operating principle and efficiency. For instance, Class D amplifiers, also known as switching amplifiers, are known for their high efficiency, but they can see higher distortion than Class A, B, and AB amplifiers. On the other hand, Class H amplifiers are designed to improve efficiency by modulating the supply voltage according to the input signal, but they can be complex to implement.
The Class AB, or push-pull amplifier, uses an output pulled from between a switched connection to a high voltage rail and a switched connection to ground or an opposite polarity high voltage rail (see
Although efforts have been made to improve the AB amplifier, for instance the cascoded FETs and Zener diodes in U.S. Pat. No. 10,511,262 and cascoded FETs in U.S. Pat. Nos. 4,697,155, 10,177,713, and 10,301,587. Such efforts still utilize mostly high-voltage components and thus cannot achieve a significant cost and size reduction. Some Class D amplifiers use feedback to control distortion at higher power, and at least one attempt even disengages feedback at lower powers to seek the best of both non-distorted high power and accuracy at lower powers (see U.S. Pat. No. 11,121,690). Other attempts have sought to bring greater linearity to Class D switching outputs, for instance, by providing multiple pulse-width modulated output levels as seen in U.S. Pat. No. 9,979,354. Japanese Patent No. 6046091 discloses multiple linear amplifiers for different RF protocols.
The cascoded topology seen in
The following presents a simplified summary relating to one or more aspects and/or embodiments disclosed herein. As such, the following summary should not be considered an extensive overview relating to all contemplated aspects and/or embodiments, nor should the following summary be regarded to identify key or critical elements relating to all contemplated aspects and/or embodiments or to delineate the scope associated with any particular aspect and/or embodiment. Accordingly, the following summary has the sole purpose to present certain concepts relating to one or more aspects and/or embodiments relating to the mechanisms disclosed herein in a simplified form to precede the detailed description presented below.
In some aspects, the techniques described herein relate to an amplifier including: a switched preamplifier; and a power amplifier including: a first amplifying cell and a second amplifying cell; wherein the first amplifying cell is coupled between the switched preamplifier and the second amplifying cell.
In some aspects, the techniques described herein relate to a method of operating an amplifier including: receiving a low voltage at a switching preamplifier; controlling rails of the switching preamplifier according to the low voltage; and amplifying an output of the switching preamplifier to a high voltage via two or more low voltage amplifier cells.
In some aspects, the techniques described herein relate to a non-transitory, tangible computer readable storage medium, encoded with processor readable instructions to perform a method for amplification, the method including: controlling a switching preamplifier to apply gain to a low-voltage input signal via Class D amplification, variable power rails, or a blending of the two; and regulating power to two or more amplifying cells connected to an output of the switching preamplifier, the two or more amplifying cells having a switching speed commensurate with a switching speed of the switching preamplifier.
In one aspect, the disclosure describes series-connected amplifiers or variable DC sources that change their voltage concurrently in series. In some aspects, the amplifiers may be configured to provide a high-voltage output signal to a load. This high-voltage output capability may make the amplifiers suitable for applications requiring high voltage outputs, such as, but not limited to, audio amplification or power supply applications. Feedforward connections between amplifiers communicate an input signal upstream and this feedforward network eliminates the need for parallel high-voltage opto-couplers on each cell or stage. Because the cells are arranged in a cascode, and because each amplifier is controlled by voltage from a previous amplifier and also produces a voltage, the system can be referred to as a cascoded high-voltage amplifier or cascoded voltage-controlled-voltage-source high-voltage amplifier.
In one aspect, a cascoded amplifier is disclosed including a series of amplification cells arranged sequentially such that an output of an Nth cell in the chain is provided to an immediately following cell (e.g., both inputs of the immediately following cell) via a resistor network (e.g., two voltage dividers). The input of an Nth cell can be provided to an input of the immediately following cell to provide level shifting of one cell to the next via feedforward links. In other words, each cell's output is coupled to the input of the next two cells. In an embodiment, the resistor networks are selected so that every cell exhibits substantially a common gain, A (such as 2, 4, or 8), and via feedforward biases between adjacent cells, cause equal level shifting from cell to cell, thereby causing a final cell to provide a high-voltage amplified version of the input signal that is N*A times greater than the input signal. While the first cell can have a grounded input, all subsequent cells are floating. The resulting high voltage amplifier achieves N*A amplification without a high-voltage (e.g., greater than 50V) drop across components of the cascoded amplifier and without high-voltage isolation between the cells (e.g., no optoisolators are needed to isolate cells from each other). Said another way, this topology allows high voltage amplification using exclusively low-voltage components.
Some embodiments of the disclosure may be characterized as a high-voltage amplifier. The high-voltage amplifier can be a cascaded high-voltage amplifier in some embodiments. The high-voltage amplifier can include a voltage input, first and second amplifying cells, and an Nth amplifying cell. The voltage input can be configured to receive an input voltage. The first amplifying cell can comprise a first amplifier coupled to the voltage input via a first input and having a first output, and can be configured to amplify the input voltage with a first gain to provide an amplified version of the input voltage at the first output. The second amplifying cell can comprise a second amplifier having a second output and can be configured to amplify the first output by a second gain. The second amplifying cell has a first feedforward connection between the first input of the first amplifier and a first input of the second amplifier. The Nth amplifying cell can comprise an Nth-1 amplifier configured to output a high voltage version of the input voltage, wherein N is a number of amplifying cells, and wherein at least the second and Nth amplifying cells are provided power while being isolated from a grounded source of the power.
Other embodiments of the disclosure may also be characterized as an amplifier comprising a voltage input, a first variable DC source, a second variable DC source, and an Nth variable DC source. The voltage input can be configured to receive an input. The first variable DC source can be coupled to the voltage input and can have a first output. The first variable DC source can have a first gain, and can be configured to amplify the input voltage and to provide an amplified version of the input voltage at the first output. The second variable DC source can be configured to amplify the first output. The Nth variable DC source can be configured to amplify an output of an Nth-1 variable DC source and to output a high-voltage version of the input voltage. N is a number of variable DC sources in the amplifier. Feedforward connections between adjacent ones of the variable DC sources level shift subsequent variable DC sources in response to changes to the input voltage.
Other embodiments of the disclosure can be characterized as a method including receiving a low-voltage signal from a signal source at a first time; powering a chain of N low-voltage amplifiers via voltage regulators that are isolated from a power supply of the voltage regulators; amplifying the low-voltage signal via the chain of low-voltage amplifiers coupled in series to provide a high-voltage output signal to a load, wherein the second through Nth-1 low-voltage amplifiers are floating; receiving a change in the low-voltage signal from the signal source at a second time; and level shifting the low-voltage amplifiers, in response to the change, via feedforward connections between inputs of adjacent ones of the low-voltage amplifiers, to provide a correspondingly changed high-voltage output signal to the load.
According to an aspect of the present disclosure, the amplifier includes a switched preamplifier and a power amplifier. The power amplifier includes a first amplifying cell and a second amplifying cell. There is a feedforward connection between the first amplifying cell and the second amplifying cell, with the first amplifying cell being coupled between the switched preamplifier and the second amplifying cell.
According to other aspects of the present disclosure, the amplifier may include one or more of the following features. The switched preamplifier may have variable rails powering a switching amplifier cell. The switched preamplifier may be a Class D-H amplifier configured to adjust a blending of D and H modes (i.e., a blended D-H amplifier). The first amplifying cell may be coupled to a power regulator that is isolated from a power source. The switched preamplifier may have a voltage input below 50 volts and the power amplifier may have a voltage output above 100 volts or above 500 volts or above 1000 volts. A voltage across either of the first and second amplifying cells may be less than or equal to 50 volts. The feedforward connection may be between an input of the first amplifying cell and an input of the second amplifying cell. Outputs of the first and second amplifying cells may see a common current. The switched preamplifier may include a switched pair output stage. The first and second amplifying cells each may include at least one switch having a switching speed substantially the same or greater than a switching speed of the at least a pair of switches in the switched preamplifier. The amplifier may be configured to receive a low voltage pulsed input and generate a high voltage pulsed output. The amplifier may be configured to receive a low voltage analogue input and generate a high voltage analogue output. A filter may be arranged between a final amplifying cell in the power amplifier and an output of the power amplifier. The switched preamplifier may convert the low voltage analogue input to a pulse-width-modulated signal before providing it to the first amplifying cell. A voltage divider at an input of the second amplifying cell may bias an input of the second amplifying cell with a voltage that is part-way between the input and output of the second amplifying cell. An output of the first amplifying cell may be coupled to an input of the second amplifying cell via an impedance component. The first and second amplifying cells may have a same gain.
According to another aspect of the present disclosure, a method of operating an amplifier includes receiving a low voltage at a variable-amplitude switching preamplifier, amplifying an output of the variable-amplitude switching preamplifier via two or more switching amplifier cells with a feedforward connection therebetween, and providing a high voltage version of the low voltage at an output of the two or more switching amplifier cells.
According to other aspects of the present disclosure, the method may include one or more of the following features. The low voltage may be linear, and the method may further include converting the low voltage to a variable amplitude pulse-width modulated voltage in the variable-amplitude switching preamplifier. The method may further include filtering an output of each of the two or more switching amplifier cells. The method may further include amplifying a pulsed voltage and the two or more switching amplifier cells may be linear.
According to another aspect of the present disclosure, an amplifier includes a switched preamplifier and a power amplifier. The power amplifier includes a first amplifying cell coupled to a second cell. The first amplifying cell is coupled to the preamplifier and is configured to amplify an output of the preamplifier by a first gain. The second cell is coupled to the first amplifying cell and is configured to amplify an output of the first amplifying cell. The second amplifying cell has a first feedforward connection between the first amplifying cell and the second amplifying cell.
According to another aspect of the present disclosure, an amplifier includes a switched preamplifier and a power amplifier. The power amplifier includes a first amplifying cell coupled to a second cell. The first amplifying cell is coupled to the preamplifier and is configured to amplify an output of the preamplifier by a first gain. The second cell is coupled to the first amplifying cell and is configured to amplify an output of the first amplifying cell. The second amplifying cell has a first feedforward connection between the first amplifying cell and the second amplifying cell. The switched preamplifier is a Class D-H amplifier configured to adjust a blending of D and H modes (i.e., a blended D-H amplifier).
According to another aspect of the present disclosure, an amplifier includes a switched preamplifier and a power amplifier. The power amplifier includes a first amplifying cell coupled to a second cell. The first amplifying cell is coupled to the preamplifier and is configured to amplify an output of the preamplifier by a first gain. The second cell is coupled to the first amplifying cell and is configured to amplify an output of the first amplifying cell. The second amplifying cell has a first feedforward connection between the first amplifying cell and the second amplifying cell. The switched preamplifier comprises variable rails.
According to other aspects of the present disclosure, the amplifier may include one or more of the following features. The second amplifying cell may be coupled to a power regulator that is isolated from a power source. The switched preamplifier may have a low voltage input and the power amplifier may have a high voltage output. A voltage across either of the first and second amplifying cells may be less than or equal to 50 volts. The first feedforward connection may be between an input of the first amplifying cell and an input of the second amplifying cell. Outputs of the first and second amplifying cells may see a common current. The switched preamplifier may comprise at least a pair of switches in parallel. The first and second amplifying cells each may comprise at least one switch having a switching speed substantially the same as a switching speed of the at least a pair of switches in the switched preamplifier. The switched preamplifier may comprise variable rails. The switched preamplifier may be a Class D-H amplifier configured to adjust a blending of D and H modes. A voltage divider may bias a first input of the first voltage-controlled voltage source with a voltage that is part-way between the input and output of the voltage source. An output of the first amplifying cell may be coupled to an input of the second amplifying cell via an impedance component.
Various objects and advantages and a more complete understanding of the present disclosure are apparent and more readily appreciated by referring to the following detailed description and to the appended claims when taken in conjunction with the accompanying drawings:
a cascoded power stage comprising two or more linear amplifiers;
Prior to describing the embodiments in detail, it is expedient to define terms as used in this document.
The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.
The flowcharts and block diagrams in the following Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present disclosure. In this regard, some blocks in these flowcharts or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustrations, and combinations of blocks in the block diagrams and/or flowchart illustrations, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
It will be understood that, although the terms first, second, third etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present disclosure.
Spatially relative terms, such as “beneath,” “below,” “lower,” “under,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the amplifier in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” or “under” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary terms “below” and “under” can encompass both an orientation of above and below. The amplifier may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. In addition, it will also be understood that when a layer is referred to as being “between” two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, components, and/or groups but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items, and may be abbreviated as “/”.
Embodiments of the disclosure are described herein with reference to illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of the disclosure. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments of the disclosure should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. Accordingly, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of the disclosure.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and/or the present specification and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
For the purposes of this disclosure, “coupled to” means an electrical path between two nodes, regardless of the impedance of that path and whether current passes through one or more impedance components between the two nodes. For instance, an output of a low-voltage amplifier may be coupled to an input of a next or subsequent or adjacent low-voltage amplifier whether or not this electrical path includes an impedance component such as a resistor.
For the purposes of this disclosure, a voltage-controlled voltage source, can include, but is not limited to, an amplifier, class D amplifier, variable power source or supply, variable DC source, DC-DC converter, signal booster, op amp, differential pair, or symmetrical circuit.
As noted, the low-voltage amplifiers 302, 304, 306, other than the first and last or Nth, are floating. Each low-voltage amplifier 302, 304, 306 is also powered or biased by an earth-referenced power supply. For instance, in
In some embodiments, each low-voltage amplifier 302, 304, 306 can have at least one input that is biased or controlled by an impedance network (having at least two impedance components in
Like the low-voltage amplifiers other than the first and Nth or last, the low-voltage amplifier cells, except the first and Nth or last, are floating. This, along with being isolated from the power supply 340, and the feedforward connections 310, 314, 316, means that the cascoded high-voltage amplifier 300 can respond to changes in input signal using low voltage cells. In other words, the impedance networks and feedforward connections can also use components tailored for low voltage operation or rated up to 50V, which are often off-the-shelf and low-cost components.
Additionally, it should be noted that since the voltage drop across any one low-voltage amplifier 302, 304, 306 or low-voltage amplifier cell 330, 332, 334 is low voltage (i.e., less than or equal to 50V), power dissipation is relatively low and evenly distributed across the cascoded high-voltage amplifier 300. In the case where the chain of cells gets too long in a certain direction, for instance, from a packaging standpoint, the chain can follow a u-shaped or s-shaped path to maintain a compact package. Further, circuit boards can be stacked in order to add even more cells while still maintaining a relatively compact overall high-voltage amplifier package.
The discussion now turns to additional details of the embodiment shown in
A voltage output 322 for the cascoded high-voltage amplifier 300 may or may not be a part of the last or Nth amplifier cell 334, and the voltage output 322 can be configured for coupling to a load 303 such as a speaker's voice coil, a digital circuit on a circuit board, an electrode in a plasma processing chamber, or the rotor or stator of an electrical motor, to name just a few non-limiting examples. In other words, the cascoded high-voltage amplifier 300 can be coupled between a signal source 301, and a load 303. Electrical connections well known to those of skill in the art can be made between (1) the signal source 301 and the cascoded high-voltage amplifier 300, and (2) between the cascoded high-voltage amplifier 300 and the load 303.
A high-voltage signal at the voltage output 322 can be an amplified version of the input signal at the voltage input 320, where a ratio of the output voltage over the input voltage, or the output signal over the input signal, or the signals at the voltage output 322 over that at the voltage input 320, can be called the amplifier gain. The amplifier gain is larger than a gain of any one of the low-voltage amplifier cells 330, 332, 334, and in many cases will be a sum of the gains of each of the low-voltage amplifier cells 330, 332, 334. In other words, a last or Nth low-voltage amplifier cell 334 in the chain, can include an Nth low-voltage amplifier 306 configured to output a high-voltage version of the input voltage.
The low-voltage amplifiers 302, 304, 306, can be, but are not limited to, a variable DC source, class D amplifier, variable power source or supply, voltage-controlled voltage source, DC-DC converter, signal booster, op amp, differential pair, symmetrical circuit, etc. In some cases, the low-voltage amplifiers 302, 304, 306 can be voltage sources, though current and power sources can also be implemented. It should also be understood that the low-voltage amplifiers 302, 304, 306 are not limited in response time, and can therefore provide low-latency signal tracking of pulsed DC, AC, and arbitrary waveforms, to name a few. In some cases, digital amplifiers can be used for the low-voltage amplifiers 302, 304, 306 where higher frequency input signals are used (e.g., greater than 5 MHz). In some cases, the low-voltage amplifiers 302, 304, 306 can be replaced with high-voltage amplifiers, such as those using components rated to greater than 50V. These situations may be seen where an especially large output voltage is desired.
In some cases, the first low-voltage amplifier 302 is different than the remaining low-voltage amplifiers 304, 306 or may not even be an amplifier. For instance, a buffer or other device having a gain of 1 could be used in place of the low-voltage amplifier 302. Said another way, the first amplifying cell 330 has a gain of 1 and subsequent amplifying cells have a gain greater than 1. Similarly, the low-voltage amplifiers 302, 304, 306 may have the same gain, while in other situations different gains may be used. In one embodiment, the second through last or Nth low-voltage amplifier 304, 306 have a gain of 2, while in another embodiment, all of the low-voltage amplifiers 302, 304, 306 have a gain of 2.
Each low-voltage amplifier cell 330, 332, 334 can have an input and an output. The first low-voltage amplifier cell 330 can be configured to amplify the input voltage with a first gain to provide an amplified version of the input voltage at the first output of the first low-voltage amplifier 302, which can be provided to an input of the second low-voltage amplifier cell 332. The second low-voltage amplifier cell 332 can include a second low-voltage amplifier 304 configured to amplify the first output by a second gain. The first low-voltage amplifier cell 330 can include a first feedforward connection 310 between the first input of the first low-voltage amplifier 302 and a first input of the second low-voltage amplifier 304. The first input of the second low-voltage amplifier 304 can be formed by a sum the output of the first low-voltage amplifier 302 and the first feedforward connection 310. For instance, this summing can be performed by a voltage divider comprising impedance components 308 and 326. In an embodiment, the output of the first low-voltage amplifier 302 can be coupled to the first input of the second low-voltage amplifier 304, and the input of the first low-voltage amplifier 302 can be coupled to the first input of the second low-voltage amplifier 304. This coupling can be made via a voltage divider such that the second low-voltage amplifier 304 is at a voltage less than the output of the first low-voltage amplifier 302 but greater than the input of the first low-voltage amplifier 302. Said another way, the output of the first low-voltage amplifier 302 is coupled to the input of the second low-voltage amplifier 304 via an impedance component 308, such that voltage actually drops between an output of one low-voltage amplifier and an input of a next low-voltage amplifier. Thus, while the overall cascoded high-voltage amplifier 300 amplifies the input signal at input voltage 320, voltage actually drops between low-voltage amplifiers.
As noted, the first low-voltage amplifier 302 or low-voltage amplifier cell 330 can be referenced to ground.
Each feedforward connection 310, 314, 316 may pass through an impedance component (e.g., 326, 328) in route to an input of a next low-voltage amplifier. Similarly, each output of a low-voltage amplifier 302, 304, 306 or low-voltage amplifier cell 330, 332, 334 may pass through an impedance component (e.g., 308, 312) in route to the input of the next low-voltage amplifier. Said another way, each low-voltage amplifier except the Nth or last one, can be coupled to a next or next adjacent low-voltage amplifier via an impedance component. The impedance components can include resistors or other resistive devices, though reactive components and components having both resistive and inductive components could also be implemented. In other terms, devices seeing a voltage drop can be implemented as the impedance components so long as they are selected to achieve a desired voltage drop from low-voltage amplifier output to low-voltage amplifier input that achieves a desired gain across a respective low-voltage amplifier cell (i.e., from one low-voltage amplifier output to an output of a next low-voltage amplifier). The impedance components 307, 324, 308, 326, 312, 328 can be part of impedance component networks, one impedance component network for each low-voltage amplifier cell 330, 332, 334 or each low-voltage amplifier 302, 304, 306. In
Isolation, and thus the ability of all but the first and last or Nth low-voltage amplifier cells to be floating, is an important feature that allows the low-voltage amplifier gains to sum and generate a high-voltage output. As noted earlier, the low-voltage amplifier cells 332, 334, except the first low-voltage amplifier cell 330 are each provided with power isolated from a grounded source of the power (e.g., power supply 340). In other words, all but a first low-voltage amplifier cell 330 in the chain is floating and receives power from DC-DC converters that are isolated or include isolation from, the power supply 340. Packaging for the cascoded high-voltage amplifier 300 may also support the isolation boundary, for instance a PCB without any conductive traces that cross the isolation boundary, or a PCB with elongated slits formed therein in a zigzagging pattern may reduce a cross section of the PCT spanning the isolation boundary thereby increasing dielectric resistance at the isolation boundary. In
Further, feedforward connections 310, 314, 316 between adjacent low-voltage amplifier cells 330, 332, 334 level shift the entire chain of low-voltage amplifier cells 330, 332, 334 without high-voltage isolation (such as optoisolators) along the feedforward connections 310, 314, 316. At the same time, isolation, floating cells, and the feedforward connections enable the cascoded high-voltage amplifier 300 is able to avoid or minimize use of high-voltage components and high-voltage isolation for a cooler-running and more compact form factor than is known in the art. What is more, by distributing amplification duties across N low-voltage amplifier cells, this disclosure more evenly achieves spatial distribution of thermal effects thereby avoiding hot spots in the cascoded high-voltage amplifier 300. Further, by removing optoisolators, the disclosure removes delays associated with signals that have to pass through optoisolators, thus making the cascoded high-voltage amplifier 300 more responsive to respond to input signals and transients.
Each low-voltage amplifier cell 330, 332, 334 can be configured to amplify an input voltage to that cell (in the case of all but the first low-voltage amplifying cell, this would be the output of the previous low-voltage amplifier cell). In some cases, all low-voltage amplifier cells 330, 332, 334 can have the same gain, referred to as A. In other cases, different low-voltage amplifier cells 330, 332, 334 may have different gains, for instance the first low-voltage amplifier cell 330 can have a gain B and the remaining low-voltage amplifier cells 332, 334 can have the gain A. The gain A, whether equal to B or not, can equal 2. However, the gain A (and optionally B as well) can be greater than 2 and in some cases can be an exponential of 2 (i.e., 2C, where C is a positive integer), such that A (and optionally B) can equal 2, 4, 8, 16, etc. In some embodiments, the gain A (and optionally B) can equal 2C and be less than a ratio of the output voltage over the input voltage. For instance, where the input voltage is 1V and the output voltage is 500V, C can be any positive integer such that 2C<500/1 (i.e., C is a positive integer less than 9) and hence there could be up to 256 amplifying cells (29). In other words, the first and second gain are equal to 2C and less than the output voltage/the input voltage, where C is a positive integer. Regardless of the gain of each low-voltage amplifier cell 330, 332, 334 or the number N of low-voltage amplifier cells, the serial topology of the low-voltage amplifier cells 330, 332, 334 means that a common current is seen at the output of each low-voltage amplifier 302, 304, 306.
The number N of low-voltage amplifier cells 330, 332, 334 is not limited, but preferably will be equal to a total gain of the cascoded high-voltage amplifier 300 divided by at least a maximum voltage to be seen across any given low-voltage amplifier cell 330, 332, 334. For example, where a 1000V output is desired from a 1V input, and 50V is considered the desired cutoff for each cell to be considered “low voltage”, at least 20 low-voltage amplifier cells would be used. However, in some embodiments, this same topology can apply to situations where some or all of the low-voltage amplifier cells may not be considered low voltage, for instance, where a voltage across each cell is 75V, or 250V, or some other higher valuer above 50V. Such a compromise of the low voltage nature may be worthwhile for higher output voltage embodiments of the cascoded high-voltage amplifier 300.
During steady state operation, both inputs of each op amp 402, 404, 406 are equal or balanced and the gain of each op amp 402, 404, 406 is set via the corresponding resistor network (e.g., 407, 424, 436, 438 for the first op amp 402 and 408, 426, 440, 442 for the second op amp 404). Each resistor network is formed from two voltage dividers, one for each of the op amp inputs. While the feedforward connection 410 of the first low-voltage amplifier cell is ground referenced or referenced to V1, all subsequent feedforward connections such as the second feedforward connection 414 and the Nth feedforward connection 416, are floating.
Where the gain of each op amp 402, 404, 406 is equal, the resistor networks can use the same resistance values. For instance, where a gain of 2 is used, the resistors of the first and second low-voltage amplifier cells can be as follows, where R is an arbitrary resistance: 436, 407, 440, 408=R and 438, 410, 442, and 426=2R. Although this example uses a relationship between resistors of 2R to obtain a gain of 2, other ratios can also be used to achieve other gains. Additionally, the resistor values for the entire resistor network of a low-voltage amplifier cell can be adjusted while maintaining a ratio and thus a gain in order to optimize bandwidth and efficiency. For instance, reducing resistor values gives greater bandwidth but lower efficiency. In one non-limiting example, the resistors 436, 407, 440, 408 can equal 1000 Ohms, while the resistors 438, 410, 442, and 426 can equal 2000 Ohms.
Each op amp 402, 404, 406 can be biased by a DC-DC converter 448, 450, 452, where each of these DC-DC converters 448, 450, 452 are isolated from an earth-referenced power bus 458. For instance, each DC-DC converter 448, 450, 452 can use a transformer to both down convert voltage from the earth-referenced power bus 458 as well as provide isolation from the ‘high-voltage’ side of the isolation boundary (it should be noted that the earth-referenced power bus 458 may also be low voltage). The first earth-referenced power bus 448 may be referenced to voltage V1 (e.g., ground) and thus may not need internal isolation structures such as a transformer. Although a transformer is one means of converting the earth-referenced power bus voltage to a voltage for use within each of the low-voltage amplifier cells, other conversion topologies such as switching converters, etc. can also be used. The first feedforward connection 410 as well as a second input to the first low-voltage amplifier cell are both held to voltage V1, or the same reference voltage as the first DC-DC converter 448. In some cases, V1 is ground, but this is not required. Accordingly, the first low-voltage amplifier cell and the first low-voltage amplifier 402 are not floating, but rather have a fixed reference voltage, V1. The remaining low-voltage amplifier cells and low-voltage amplifiers except the last or Nth are floating. The last or Nth low-voltage amplifier cell and low-voltage amplifier are referenced to a load once coupled thereto.
The second through Nth low-voltage amplifier cells can include an optional bias line between a respective one of the DC-DC converters 450, 452 and a common node (e.g., the common node for the first or second low-voltage amplifier cells is effectively the output of the first low-voltage amplifier 402 and the node preceding the resistance 408). These optional bias lines enable a given DC-DC converter to bias a corresponding low-voltage amplifier relative to the common node preceding that low-voltage amplifier.
In this embodiment, a first two cells and an Nth cell are shown for simplicity, but those of skill in the art will appreciate that any number of two or more low-voltage amplifier cells may be implemented in the cascoded high-voltage amplifier based on the teachings in
Assuming a constant gain A for all of the cells, the output signal can be N*A times larger than the input signal, where N is the number of low-voltage amplifier cells in the cascoded high-voltage amplifier 400.
Although
For the purposes of clarity, one will note that the gain of a low-voltage amplifier cell and the gain of a low-voltage amplifier are different. For instance, the gain of each low-voltage amplifier cell is 2, and the gain of each low-voltage amplifier depends on the low-voltage amplifier in question.
The low-voltage amplifier 904 can be biased by high and low signals from a DC-DC converter 950 that provides isolation from an earth-referenced power bus 958.
The first input 956a can be coupled to the input 957 as well as the first feedforward connection 910 through impedances 908 and 926, respectively. In other words, the first input 956a can be biased by or coupled to an output of the previous low-voltage amplifier cell and an input of the previous low-voltage amplifier cell via the impedances 908 and 926, respectively. Similarly, the second input 956b can be coupled to the output 960 as well as the first feedforward connection 910 through impedances 942 and 940, respectively. In other words, the second input 956b can be biased by or coupled to the output 960 of the low-voltage amplifier cell 932 as part of feedback of the low-voltage amplifier cell 932 that controls balancing of the differential or balanced inputs of the low-voltage amplifier 904.
The low-voltage amplifier cell 932 also includes two feedforward connections, a first 910 and a second 914. The first feedforward connection 910 couples an input of a previous low-voltage amplifier cell to an input of the low-voltage amplifier 904 through the impedance component 926. The second feedforward connection 914 couples the input 958 of the low-voltage amplifier cell 932 to a next low-voltage amplifier cell and in particular to one of two inputs of that next low-voltage amplifier through a respective impedance component of the next low-voltage amplifier cell.
Although not shown, the low-voltage amplifier cell 932 could include a power gain stage at the output, for instance, comprising a switched pair of MOSFETs or other switches, as is well known to those of skill in the art.
Here, one sees the impedance network comprising four distinct impedance components 608, 626, 640, 642 that can be implemented as resistors in one embodiment. The impedances can be selected to control a gain of the low-voltage amplifier cell 632, as defined by a ratio of the output 660 over the input 657. Because of the impedance network, the gain of the low-voltage amplifier cell 632 is different than a gain between input 656a and output 660 (or between input 656b and output 660).
The low-voltage amplifier cell 632 also includes two feedforward connections, a first 610 and a second 614. The first feedforward connection 610 couples an input of a previous low-voltage amplifier cell 632 to a first input 656a of the low-voltage amplifier (i.e., the transistor 662) through the impedance component 662. The second feedforward connection 614 couples the input 657 of the low-voltage amplifier cell 632 to a next low-voltage amplifier cell and in particular to one of the two transistors of that next low-voltage amplifier cell through a respective impedance component thereof.
In some cases, all amplifying cells can have the same gain, referred to as A (i.e., A=B). In other cases, different amplifying cells may have different gains, for instance the first cell can have a gain B and the remaining cells can have a gain A. The gain A, whether equal to B or not, can equal 2. However, the gain A can be greater than 2 and, in some cases, can be an exponential of 2 (i.e., 2C, where C is a positive integer), such that A can equal 2, 4, 8, 16, etc. In some embodiments, the gain A can equal 2C and be less than a ratio of the output voltage over the input voltage. For instance, where the input voltage is 1V and the output voltage is 500V, C can be any positive integer such that 2C<500/1 (i.e., C is a positive integer less than 9) and hence there could be up to 256 amplifying cells (29). Regardless of the gain of each cell or the number of cells N, the serial topology of the amplifying cells means that an output of each low-voltage amplifier in each low-voltage amplifier cell sees a common current. In some embodiments, no more than 50V drops across, or can be measured across, adjacent amplifying cells or across components within a given amplifying cell.
Since applications will often be directed to dynamic low-voltage signals, such as pulsed waveforms, stepped waveforms, and arbitrary waveforms, the method 800 can further include receiving a change in the low-voltage signal from the signal source at a second time (Block 808). In other words, the signal source (e.g., 301 in
The method 800 is applicable to any of the cascoded high-voltage amplifiers described in this disclosure, including, but not limited to, those shown in
Power electronics designers are continuously looking for topologies that can follow higher frequency signals and yet also deliver high power. Class D, or switching amplifiers, typically achieve high speed, but when combined with high power amplification, such as at 1 kV or more, these amplifiers begin to radiate noticeable microwave radiation. The forementioned VCVS power amplifier cells have the ability to operate at high frequencies, yet because of the cell-based topology, no one cell swings between the full high voltage extents. Thus, in theory the VCVS power amplifier can achieve higher rates and higher power without noticeable microwave radiation.
In practice however, the VCVS is a linear device incapable of achieving pure Class D amplifier switching speeds. To better mimic the frequency of a pure switching amplifier, the VCVS can be implemented using high-speed switches such as MOSFETs and can be coupled to a Class D or switching preamplifier as shown in
In order for the power stage to keep pace with the Class D (or Class D-H) preamplifier, the low-voltage amplifier in each cell includes one or more switches having a switching speed substantially the same or greater to that of the switches in the preamplifier. For instance, MOSFETs can be used in the power stage, fast linear switches biased to a switching regime, or fast FJETs with some loss of stability resulting as a compromise to their slightly slower speed. Typically, devices having nano and picosecond switching speeds are effective.
The preamplifier can be a Class D or switching amplifier that converts a low-voltage linear input signal to a PWM signal that is passed to the power stage. A filter, such as an RLC filter, at the output of the power stage, or distributed within the power stage amplifier cells, can smooth the amplified PWM signal to form a linear output. Alternatively, where the amplifier operates on pulsed or other nonlinear signals, the preamplifier can again be a Class D or switching amplifier, but merely amplifies the low voltage pulsed input signal (no PWM conversion is needed), as shown in
In some embodiments, additional linearity of the amplifier output signal can be achieved by adding variable rails to the preamplifier as shown in
The preamplifier also has the ability to swing between pure H and pure D modes of operation as well as to operate in a blended state between these two extremes. For instance,
The performance mode selectors seen in
For a low voltage pulsed input (
The Class D or switching amplifier 2006 can have fixed rails in some embodiments, but as shown has variable rails and thus operates as a Class D-H amplifier or a switching amplifier with variable rails. Performance mode selectors 2010 and 2012 are coupled to op amps 2014 and 2016 receiving the buffered low voltage linear signal at their non-inverting inputs. Their inverting inputs receive a feedback voltage as is typical for op amp topologies. However, the positive and negative rails for each op amp may be selectively coupled into the non-inverting input depending on a desired performance mode (as seen and described in
With one of the two switches closed creating a short to the diode or lower rail of the op amps 2014 and 2016, the non-inverting inputs and thus the rails of the amplifier 2006 track the amplified linear signal, but due to the diodes 2018 are clamped at 0V during negative half cycles. The result is a strong blending of D and H modes such that the preamplifier output is a variable PWM (See
On the other extreme, Class D dominates or is even the only signal provided by the Class D-H preamplifier (see
As seen, the performance mode selectors are configured to select a blended state of D and H modes for the preamplifier that can range from fully switching or Class D to nearly fully linear or Class H and including blended state therebetween. Blending can be controlled by selection of resistor and capacitor values during manufacturing. However, it can also be selected by adjusting the switches in the performance mode selectors 2010 and 2012 during operation. For instance, adjusting a duty cycle of these switches, or the linear output if linear switches are used, will adjust a blending between D and H modes. Additionally, while the performance mode selectors 2010 and 2012 can control blending from D to H modes and anywhere in between, closing the lower of the two switches in the performance mode selectors 2010 and 2012 enables clamping the lower end of each PWM pulse to 0V as shown in
It should be appreciated that
It should be noted that while traditional Class H amplifiers use stepped changes between rail values, in this disclosure, the Class H amplifier uses infinitely variable rails. This can be accomplished, for instance, by using op amps to drive the rails of the Class D amplifier, as seen in
Similar to
The low-voltage amplifiers 2202, 2204, 2206, other than the first and last or Nth, are floating. Each low-voltage amplifier 2202, 2204, 2206 is also powered or biased by an earth-referenced power supply. For instance, in
In some embodiments, each low-voltage amplifier 2202, 2204, 2206 can have at least one input that is biased or controlled by an impedance network (having at least two impedance components in
Like the low-voltage amplifiers other than the first and Nth or last, the low-voltage amplifier cells, except the first and Nth or last, are floating. This, along with being isolated from the power supply 2240, and the feedforward connections 2210, 2214, 2216, means that the cascoded high-voltage amplifier 2200 can respond to changes in input signal using low voltage cells. In other words, the impedance networks and feedforward connections can also use components tailored for low voltage operation or rated up to 50V, which are often off-the-shelf and low-cost components.
Additionally, it should be noted that since the voltage drop across any one low-voltage amplifier 2202, 2204, 2206 or low-voltage amplifier cell 2230, 2232, 2234 is low voltage (i.e., less than or equal to 50V), power dissipation is relatively low and evenly distributed across the cascoded high-voltage amplifier 2200. In the case where the chain of cells gets too long in a certain direction, for instance, from a packaging standpoint, the chain can follow a u-shaped or s-shaped path to maintain a compact package. Further, circuit boards can be stacked in order to add even more cells while still maintaining a relatively compact overall high-voltage amplifier package.
While the low-voltage linear amplifiers so far discussed achieve high output with relatively inexpensive and less complex devices than prior art high-voltage amplifiers, they still operate hotter than Class D or switching amplifiers. Accordingly, embodiments of the aforementioned VCVS power amplifier cells (or low-voltage amplifiers) are now described that have class D or switching topologies, at least for pulsed signals. This allows smaller, cooler, and/or faster switching and in a smaller package. For pulsed signals, low-voltage linear amplifiers will be described. The cascoded high-voltage amplifier 2200 can include a voltage input 2220 that may be a part of the first cell 2230 or arranged between the preamplifier 2238 and the cascoded high-voltage amplifier 2200. The voltage input 2220 is coupled to an output of the preamplifier 2238 and is configured to receive an amplified version of a low-voltage signal from the signal source 2201. The low-voltage input signal can be linear at the preamplifier 2238 input and PWM at the preamplifier 2238 output. DC, AC, and arbitrary waveforms can be implemented. Pulsed waveforms are best addressed by the topology of
A voltage output 2222 may or may not be a part of the last or Nth amplifier cell 2234, and the voltage output 2222 can be configured for coupling to a load 2203 via a filter 2236, though the filter 2236 may also be distributed through the cascoded high-voltage amplifier 2200 after each cell 2230, 2232, 2234. The load 2203 can take a variety of forms such as, but not limited to, a speaker's voice coil, a digital circuit on a circuit board, a plasma in a plasma processing chamber, or the rotor or stator of an electrical motor. In other words, the cascoded high-voltage amplifier 2200 with Class D-H preamplifier 2238 can be coupled between a signal source 2201, and a load 2203. Electrical connections well known to those of skill in the art can be made between (1) the signal source 2201 and the preamplifier 2238, and (2) between the cascoded high-voltage amplifier 2200 and the load 2203.
The low-voltage amplifiers 2202, 2204, 2206, can be, but are not limited to, a variable DC source, class D amplifier, variable power source or supply, voltage-controlled voltage source, DC-DC converter, signal booster, op amp, differential pair, symmetrical circuit, etc. In some cases, the low-voltage amplifiers 2202, 2204, 2206 can be voltage sources, though current and power sources can also be implemented. It should also be understood that the low-voltage amplifiers 2202, 2204, 2206 are not limited in response time, and can therefore provide low-latency signal tracking of any linear signal including, but not limited to, AC and arbitrary waveforms. In some cases, digital amplifiers can be used for the low-voltage amplifiers 2202, 2204, 2206 where higher frequency input signals are used (e.g., greater than 5 MHz). In some cases, the low-voltage amplifiers 2202, 2204, 2206 can be replaced with high-voltage amplifiers, such as those using components rated to greater than 50V. These situations may be seen where an especially large output voltage is desired.
In some cases, the first low-voltage amplifier 2202 is different than the remaining low-voltage amplifiers 2204, 2206 or may not even be an amplifier. For instance, a buffer or other device having a gain of 1 could be used in place of the low-voltage amplifier 2202. Said another way, the first amplifying cell 2230 can have a gain of 1 and subsequent amplifying cells have a gain greater than 1. Similarly, the low-voltage amplifiers 2202, 2204, 2206 may have the same gain, while in other situations different gains may be used. In one embodiment, the second through last or Nth low-voltage amplifier 2204, 2206 have a gain of 2, while in another embodiment, all of the low-voltage amplifiers 2202, 2204, 2206 have a gain of 2.
Each low-voltage amplifier cell 2230, 2232, 2234 can have an input and an output. The first low-voltage amplifier cell 2230 can be configured to amplify the preamplifier 2238 output with a first gain to provide an amplified version of the input voltage at the first output of the first low-voltage amplifier 2202, which can be provided to an input of the second low-voltage amplifier cell 2232. The second low-voltage amplifier cell 2232 can include a second low-voltage amplifier 2204 configured to amplify the first output by a second gain. The first low-voltage amplifier cell 2230 can include a first feedforward connection 2210 between the first input of the first low-voltage amplifier 2202 and a first input of the second low-voltage amplifier 2204. The first input of the second low-voltage amplifier 2204 can be formed by a sum of the output of the first low-voltage amplifier 2202 and the first feedforward connection 2210. For instance, this summing can be performed by a voltage divider comprising impedance components 2208 and 2226 (e.g., resistors). In an embodiment, the output of the first low-voltage amplifier 2202 can be coupled to the first input of the second low-voltage amplifier 2204, and the input of the first low-voltage amplifier 2202 can be coupled to the first input of the second low-voltage amplifier 2204. This coupling can be made via a voltage divider such that the second low-voltage amplifier 2204 is at a voltage less than the output of the first low-voltage amplifier 2202 but greater than the input of the first low-voltage amplifier 2202. Said another way, the output of the first low-voltage amplifier 2202 is coupled to the input of the second low-voltage amplifier 2204 via an impedance component 2208, such that voltage actually drops between an output of one low-voltage amplifier and an input of a next low-voltage amplifier. Thus, while the overall cascoded high-voltage amplifier 2200 amplifies the input signal at input voltage 2220, voltage actually drops between low-voltage amplifiers.
As noted, the first low-voltage amplifier 2202 or low-voltage amplifier cell 2230 can be referenced to ground.
Each feedforward connection 2210, 2214, 2216 may pass through an impedance component (e.g., 2226, 2228) in route to an input of a next low-voltage amplifier. Similarly, each output of a low-voltage amplifier 2202, 2204, 2206 or low-voltage amplifier cell 2230, 2232, 2234 may pass through an impedance component (e.g., 2208, 2212) in route to the input of the next low-voltage amplifier. Said another way, each low-voltage amplifier except the Nth or last one, can be coupled to a next or next adjacent low-voltage amplifier via an impedance component. The impedance components can include resistors or other resistive devices, though reactive components and components having both resistive and inductive components could also be implemented. In other terms, devices seeing a voltage drop can be implemented as the impedance components so long as they are selected to achieve a desired voltage drop from low-voltage amplifier output to low-voltage amplifier input that achieves a desired gain across a respective low-voltage amplifier cell (i.e., from one low-voltage amplifier output to an output of a next low-voltage amplifier). The impedance components 2207, 2224, 2208, 2226, 2212, 2228 can be part of impedance component networks, one impedance component network for each low-voltage amplifier cell 2230, 2232, 2234 or each low-voltage amplifier 2202, 2204, 2206. In
As noted earlier, the low-voltage amplifier cells 2232, 2234, except the first low-voltage amplifier cell 2230 are each provided with power isolated from a grounded source of the power (e.g., power supply 2240). In other words, all but a first low-voltage amplifier cell 2230 and a final or Nth amplifier cell 2234, in the chain is floating and receives power from DC-DC converters that are isolated, or include isolation from, the power supply 2240 (or their power supply where each cell has a separate power supply). Packaging for the cascoded high-voltage amplifier 2200 may also support the isolation boundary, for instance a PCB without any conductive traces that cross the isolation boundary, or a PCB with elongated slits formed therein in a zigzagging pattern may reduce a cross section of the PCT spanning the isolation boundary thereby increasing dielectric resistance at the isolation boundary. In
Further, feedforward connections 2210, 2214, 2216 between adjacent low-voltage amplifier cells 2230, 2232, 2234 level shift the entire chain of low-voltage amplifier cells 2230, 2232, 2234 without high-voltage isolation (such as optoisolators) along the feedforward connections 2210, 2214, 2216. At the same time, isolation, floating cells, and the feedforward connections enable the cascoded high-voltage amplifier 2200 with Class D-H preamplifier 2238 to avoid or minimize use of high-voltage components and high-voltage isolation for a cooler-running and more compact form factor than is known in the art. Furthermore, for linear signals the low-voltage amplifiers 2202, 2204, and 2206 can use Class D topologies for even further performance, size, and cooling advantages. What is more, by distributing amplification duties across N low-voltage amplifier cells, this disclosure more evenly achieves spatial distribution of thermal effects thereby avoiding hot spots in the cascoded high-voltage amplifier 2200. Yet, further, by removing optoisolators often associated with feedback circuits in high voltage applications, the disclosure removes delays associated with signals that have to pass through optoisolators, thus making the cascoded high-voltage amplifier 2200 with a Class D-H preamplifier 2238 more responsive to input signals and transients.
Each low-voltage amplifier cell 2230, 2232, 2234 can be configured to amplify an input voltage to that cell (in the case of all but the first low-voltage amplifier cell, this would be the output of the previous low-voltage amplifier cell). In some cases, all low-voltage amplifier cells 2230, 2232, 2234 can have the same gain, referred to as A. In other cases, different low-voltage amplifier cells 2230, 2232, 2234 may have different gains, for instance the first low-voltage amplifier cell 2230 can have a gain B and the remaining low-voltage amplifier cells 2232, 2234 can have the gain A. The gain A, whether equal to B or not, can equal 2. However, the gain A (and optionally B as well) can be greater than 2 and in some cases can be an exponential of 2 (i.e., 2C, where C is a positive integer), such that A (and optionally B) can equal 2, 4, 8, 16, etc. In some embodiments, the gain A (and optionally B) can equal 2C and can be less than a ratio of the output voltage over the input voltage. For instance, where the input voltage is 1V and the output voltage is 500V, C can be any positive integer such that 2C<500/1 (i.e., C is a positive integer less than 9) and hence there could be up to 256 amplifying cells (29). In other words, the first and second gain are equal to 2C and less than the output voltage/the input voltage, where C is a positive integer. Regardless of the gain of each low-voltage amplifier cell 2230, 2232, 2234 or the number N of low-voltage amplifier cells, the serial topology of the low-voltage amplifier cells 2230, 2232, 2234 means that a common current is seen at the output of each low-voltage amplifier 2202, 2204, 2206.
The number N of low-voltage amplifier cells 2230, 2232, 2234 is not limited, but preferably will be equal to a total gain of the cascoded high-voltage amplifier 2200 divided by at least a maximum voltage to be seen across any given low-voltage amplifier cell 2230, 2232, 2234. However, in some embodiments, this same topology can apply to situations where some or all of the low-voltage amplifier cells may not be considered low voltage, for instance, where a voltage across each cell is 75V, or 250V, or some other higher valuer above 50V. Such a compromise of the low voltage nature may be worthwhile for higher output voltage embodiments of the cascoded high-voltage amplifier 2200 with Class D-H preamplifier 2238.
A DC-DC converter can bias each of the low-voltage amplifiers 2202, 2204, and 2206. These converters can be isolated from an earth-referenced power bus. For instance, each DC-DC converter can use a transformer to both down convert voltage from the earth-referenced power bus 2250 as well as provide isolation from the ‘high-voltage’ side of the isolation boundary (it should be noted that the earth-referenced power bus 2250 may also be low voltage).
For the purposes of clarity, one will note that the gain of a low-voltage amplifier cell and the gain of a low-voltage amplifier are different. For instance, the gain of each low-voltage amplifier cell can be 2, and the gain of each low-voltage amplifier depends on the low-voltage amplifier in question.
Turning to
The low-voltage amplifier cell also includes two feedforward connections. The first of these couples an input of a previous low-voltage amplifier cell to a first input of the low-voltage amplifier. The second and optional feedforward connection couples the input of the low-voltage amplifier cell to a next low-voltage amplifier cell (unless this is the last or Nth low-voltage amplifier cell). Furthermore,
This disclosure describes high speed linear amplifiers of which there are many topologies to achieve this goal.
Throughout this disclosure, the power stage, or VCVS amplifier, has been shown and described serially. This is optimal for high voltage output, but where a high current output is desired, the power stage can use a parallel configuration of cells.
The terms and expressions employed herein are used as terms and expressions of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described or portions thereof. Each of the various elements disclosed herein may be achieved in a variety of manners. This disclosure should be understood to encompass each such variation, be it a variation of an embodiment of any apparatus embodiment, a method or process embodiment, or even merely a variation of any element of these. Particularly, it should be understood that the words for each element may be expressed by equivalent apparatus terms or method terms-even if only the function or result is the same. Such equivalent, broader, or even more generic terms should be considered to be encompassed in the description of each element or action. Such terms can be substituted where desired to make explicit the implicitly broad coverage to which this invention is entitled.
As but one example, it should be understood that all action may be expressed as a means for taking that action or as an element which causes that action. Similarly, each physical element disclosed should be understood to encompass a disclosure of the action which that physical element facilitates. Such changes and alternative terms are to be understood to be explicitly included in the description.
As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as a system, method or computer program product. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon.
As used herein, the recitation of “at least one of A, B and C” is intended to mean “either A, B, C or any combination of A, B and C.” The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the disclosure. Thus, the present disclosure is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
One aspect of the disclosure is a cascoded high-voltage amplifier including a voltage input, a first variable DC source, a second variable DC source, and some number of additional variable DC sources up to an Nth variable DC source. Details of this embodiment can be described with reference to
In some instances, the gain of each of the variable DC sources is equal, and in some cases can be substantially 2. The output voltage, or high-voltage version of the input voltage, is N*A times the input voltage, wherein N is the number of variable DC sources in the cascoded high-voltage amplifier, and wherein A is the gain of each variable DC source. To maintain isolation of the various cells 130, 132, 134, they are also isolated from a power supply 140 and more specifically, powered by voltage sources that are isolated from ground, for instance, via the isolation devices shown in
One aspect of the disclosure is a cascoded high-voltage amplifier comprising N amplifier cells, a voltage input, and a high voltage output. The N amplifier cells can each have a gain of A. The voltage input can be configured to receive an input voltage. The high voltage output can be configured to provide an N*A times amplified version of the input voltage. A first of the N amplifier cells can take a voltage divided version of the input voltage as one of two inputs. The second amplifier cell can comprise a first input having a first input voltage formed by a first voltage divider that couples to an output of the first amplifier cell and ground, a second input having a second input voltage formed by a second voltage divider that couples to an output of the second amplifier cell and ground. A third amplifier cell can comprise a third input having a third input voltage formed by a third voltage divider that couples to an output of the first amplifier cell and an output of the second amplifier cell, and a fourth input having a fourth input voltage formed by a fourth voltage divider that couples an output of the third amplifier cell and an output of the first amplifier cell. A Nth amplifier cell provides the high voltage output.
Another aspect of the disclosure is a cascoded high-voltage amplifier comprising a chain of voltage-controlled voltage sources, the amplifier comprising a voltage input, a first voltage-controlled voltage source, and an N-1 voltage-controlled voltage sources. The voltage input is configured to receive a ground-referenced input signal. The first voltage-controlled voltage source is coupled to the ground-referenced input signal and configured to generate an amplified version of the ground-referenced input signal. The N-1 voltage-controlled voltage sources form a voltage-stepped-chain with the first voltage-controlled voltage source, each producing a level-shifted version of an output of a previous one of the voltage-controlled voltage sources. Level shifting results from a low-voltage feedforward between inputs of adjacent ones of the voltage-controlled voltage sources, The voltage-controlled voltage sources have substantially equal gain A. the high-voltage at the output of the amplifier can be equally split between the N cells or N voltage-controlled voltage sources. Each of the voltage-controlled voltage sources, except the first, are powered by an earth-referenced power supply or a regulated power supply that is isolated from its power source. The first voltage-controlled voltage source can have a grounded power supply. The first voltage-controlled voltage source has an input coupled to ground whereas the N-1 voltage-controlled voltage sources are floating.
In some aspects, the first and second amplifying cells each may comprise at least one switch having a switching speed substantially the same as a switching speed of the at least a pair of switches in the switched preamplifier. In this way, the power amplifier can operate as a linear amplifier yet amplify the signal of a switching preamplifier. Although switching power amplifiers have been known to receive linearly amplified preamplifier signals, the reverse is not known in the art.
In some cases, the first feedforward connection may include an impedance component configured to control a gain of the second amplifying cell. This impedance component may be a resistor, a capacitor, an inductor, or any other suitable component that can provide an impedance to the signal passing through the feedforward connection. The impedance provided by this component may be used to control the gain of the second amplifying cell, potentially providing precise control over the amplification process. For instance, by adjusting the impedance of the component, the gain of the second amplifying cell may be increased or decreased as desired, allowing for flexible control over the output of the amplifier.
In some embodiments, the power amplifier may further comprise a third through Nth amplifying cells. These additional one or more amplifying cells may be coupled to the second amplifying cell and may be configured to amplify an output of the second amplifying cell. The inclusion of a third or more amplifying cells may provide additional stages of amplification, potentially enhancing the overall gain and output power of the amplifier, or reducing an amplification load on each cell.
In some cases, the third amplifying cell may have a second feedforward connection between the second amplifying cell and the third amplifying cell. In some aspects, the second feedforward connection may include an impedance component configured to control a gain of the third amplifying cell. This impedance component may be a resistor, a capacitor, an inductor, or any other suitable component that can provide an impedance to the signal passing through the feedforward connection. The impedance provided by this component may be used to control the gain of the third amplifying cell, potentially providing precise control over the amplification process. For instance, by adjusting the impedance of the component, the gain of the third amplifying cell may be increased or decreased as desired, allowing for flexible control over the output of the amplifier.
In some aspects, the first amplifying cell and the second amplifying cell of the power amplifier may each be configured to amplify the output of the preamplifier by a gain of at least 2. This high gain may allow for efficient amplification of low voltage signals to high voltage outputs. For instance, a low voltage input signal to the preamplifier may be amplified by the first amplifying cell by a first gain, and then further amplified by the second amplifying cell by a second gain, resulting in a high voltage output signal from the power amplifier. The specific gains of the first and second amplifying cells may be adjusted based on the requirements of the specific application, such as the desired output voltage or power level. In some cases, the first and second gain are the same.
In some aspects, the switched preamplifier may comprise at least a pair of switches in parallel. This configuration may allow for efficient switching of the input signal, potentially improving the performance of the amplifier. The switches may be configured to turn on and off in sync with each other, ensuring that the input signal is accurately represented in the output of the preamplifier. The specific configuration and operation of the switches may be determined based on the requirements of the specific application, such as the desired switching speed or the characteristics of the input signal.
In some cases, the switched preamplifier in the amplifier may comprise variable rails. These variable rails may allow for flexible control over the voltage levels within the preamplifier, potentially enhancing the efficiency and performance of the amplifier. The variable rails may be adjusted based on the input signal, allowing for dynamic control over the amplification process. For instance, when the input signal is at a high level, the voltage of the variable rails may be increased to provide a higher gain. On the other hand, when the input signal is at a low level, the voltage of the variable rails may be decreased to provide a lower gain. This dynamic adjustment of the voltage of the variable rails may allow for real-time control over the gain of the preamplifier, potentially improving the performance of the amplifier in response to changes in the input signal or operating conditions.
In some embodiments, the switched preamplifier may include a control circuit configured to adjust the voltage of the variable rails based on the input signal. This control circuit may be further configured to adjust the voltage of the variable rails in response to a change in the input signal, providing dynamic control over the amplification process. This dynamic adjustment of the voltage of the variable rails may allow for real-time control over the gain of the preamplifier, potentially improving the performance of the amplifier in response to changes in the input signal or operating conditions.
In some embodiments, the switches in the preamplifier and/or the first and second amplifying cells may be of any suitable type, such as mechanical switches, solid-state switches, or any other type of switch that can control the flow of current. The specific type and configuration of the switches may be determined based on the requirements of the specific application, such as the desired switching speed, the characteristics of the input signal, or the operating conditions of the amplifier. However, in an embodiment, the switches in the first and second amplifying cells can be MOSFETs or switches having similar or faster switching speeds.
In some embodiments, a common current passes through the first and second amplifying cells.
In some embodiments, a voltage across either of the first and second amplifying cells may be less than or equal to 50 volts. This voltage limit may help to protect the amplifying cells from damage due to overvoltage conditions, potentially enhancing the reliability and lifespan of the amplifier. The voltage limit may also help to reduce power dissipation and heat generation in the amplifying cells, potentially enhancing the efficiency of the amplifier. Lastly, this voltage limit may avoid the need for safety mechanisms and systems associated with high-voltage operation through all but the output of the amplifier.
In some embodiments, a Class D-H amplifier or preamplifier is provided. The Class D-H amplifier or preamplifier receives a low voltage input signal that is fed to a Class D or switching amplifier as well as two variable sources that track the input signal and provide variable rail voltages to power the Class D or switching amplifier. Thus, the Class D or switching amplifier provides a pulsed output with a variable amplitude, the variable amplitude governed by variation in the rail voltages. The variable sources can be controlled by performance mode selectors that dictate whether the variable sources provide a fixed or variable rail. If a variable rail is provided, the performance mode selectors dictate how much the rail varies. Additionally, the performance mode selectors can cause a corresponding one of the two variable sources to clamp to 0V when that variable source otherwise would go negative while tracking the input signal. The Class D-H amplifier or preamplifier is configured to handle linear or pulsed input signals, with an optional PWM converter being arranged upstream of the Class D amplifier when the input signal is linear.
The present Application for Patent is a Continuation-in-Part of patent application Ser. No. 18/309,421 entitled “Cascoded High-Voltage Amplifier” filed Apr. 28, 2023, pending, and assigned to the assignee hereof and hereby expressly incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 18309421 | Apr 2023 | US |
| Child | 18633590 | US |
