The present invention relates to integrated circuit devices and, more particularly, to integrated circuit devices for power switching applications.
Wide bandgap (WBG) power devices such as SiC and GaN power devices can provide superior performance characteristics relative to Si power devices for many high power applications. For example, as disclosed in an article by J. Burm et al., entitled “Wide Band-Gap FETs for High Power Amplifiers,” Journal of Semiconductor Technology and Science, Vol. 6, No. 3, pp. 175-182, September (2006), wide bandgap semiconductor materials having band-gap energy levels in a range from about 2 eV to about 6 eV may be utilized to provide high breakdown voltages for high power generation in power amplifiers and low dielectric constants for better isolation and lower coupling. Similarly, as disclosed in an article by J. Reed et al., entitled “Modeling Power Semiconductor Losses in HEV Powertrains using Si and SiC Devices,” Vehicle Power and Propulsion Conference (VPPC), 2010 IEEE, Sep. 1-3, 2010), silicon carbide (SiC) power devices were shown to have potential benefits over conventional silicon-based devices, particularly in high power electronic converters.
Examples of high power switches that embody wide bandgap semiconductors are disclosed in U.S. Pat. Nos. 7,556,994 and 7,820,511 to Sankin et al., which illustrates normally-off vertical JFET integrated power switches, U.S. Pat. No. 7,230,273 to Kitabatake et al., which describes a plurality of wide bandgap switching elements connected in parallel to increase device yield, and U.S. Pat. No. 8,017,978 to Lidow et al., which illustrates multiple power devices of different type connected in series. Notwithstanding these devices, there continues to be a need for more efficient devices for high power switching applications, including those having lower switching losses and lower cost.
High power switching devices according to embodiments of the present invention are utilized to efficiently provide load currents during both light/partial loading conditions and heavy loading conditions. In some of these embodiments of the invention, a hybrid switching circuit is provided, which includes first and second switching devices containing first and second unequal bandgap semiconductor materials, respectively. These first and second switching devices can be electrically coupled as a hybrid switch, which supports parallel conduction in response to first and second control signals received at first and second control terminals of the first and second switching devices, respectively. These first and second switching devices may be three or more terminal switching devices of different type. For example, the first switching device may be a three or more terminal switching device selected from a group consisting of junction field effect transistors (JFETs), insulated-gate field effect transistors (IGFETs) and high electron mobility transistors (HEMTs), and the second switching device may be an insulated-gate bipolar transistor (IGBT). Moreover, the first switching device may include a wide bandgap semiconductor material and the second switching device may utilize silicon. The wide bandgap semiconductor material may be selected from a group consisting of silicon carbide (SiC), gallium nitride (GaN) and diamond.
The hybrid switching circuit may further include a control circuit, which is configured to drive the first and second switching devices with first and second periodic control signals having first and second unequal duty cycles, respectively. The first duty cycle may be greater than the second duty cycle and the active phases of the second periodic control signal may occur exclusively within the active phases of the first periodic control signal. According to preferred aspects of these embodiments of the invention, the active-to-inactive transitions of the second periodic control signal should precede corresponding active-to-inactive transitions of the first periodic control signal. The inactive-to-active transitions of the first periodic control signal can also precede corresponding inactive-to-active transitions of the second periodic control signal, so that turn-on and turn-off switching losses are mostly determined by the first switching device.
Among other applications, these above-described power switching devices may be utilized within many IGBT-based topologies where switching losses are typically very high. For example, in a neutral-point clamped (NPC) inverter (a/k/a “three-level inverter”), a hybrid switch may be used for the “outer” devices because these typically have higher switching losses (i.e., more switching operations per output period) than the “inner” devices. Thus, an NPC inverter according to an embodiment of the invention may include a bus responsive to a DC voltage and a pair of bus capacitors electrically connected in series across the bus. A plurality of parallel inverter “legs” are provided, which are electrically connected across the bus. This plurality of parallel inverter legs includes a first totem pole arrangement of four silicon IGBTs electrically connected in series. First and second wide bandgap transistors are provided, which are electrically connected in parallel with first and fourth IGBTs in the first totem pole arrangement. First and second free-wheeling diodes are provided, which are electrically coupled across second and third IGBTs in the first totem pole arrangement. A first clamp diode is provided, which is electrically connected between a common node in the pair of bus capacitors and a first node in the first totem pole arrangement that is shared by the first and second IGBTs. A second clamp diode is also provided, which is electrically connected between the common node in the pair of bus capacitors and a second node in the first totem pole arrangement that is shared by the third and fourth IGBTs.
A control circuit is also provided, which is configured to drive the first wide bandgap transistor and the first IGBT with first and second periodic control signals having unequal duty cycles when the first totem pole arrangement is driving a first load connected thereto with a first load current. The control circuit is also configured to drive the second wide bandgap transistor and the fourth IGBT with third and fourth periodic control signals having unequal duty cycles. According to preferred aspects of these embodiments of the invention, the first duty cycle is greater than the second duty cycle and the active phases of the second periodic control signal occur exclusively within the active phases of the first periodic control signal. For example, the active-to-inactive transitions of the second periodic control signal may precede corresponding active-to-inactive transitions of the first periodic control signal and the inactive-to-active transitions of the first periodic control signal may precede corresponding inactive-to-active transitions of the second periodic control signal.
The present invention now will be described more fully with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout.
It will be understood that when an element or layer is referred to as being “on,” “connected to” or “coupled to” another element or layer (and variants thereof), it can be directly on, connected or coupled to the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to” or “directly coupled to” another element or layer (and variants thereof), there are no intervening elements or layers present. Like reference numerals refer to like elements throughout.
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 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 invention.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. 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 “comprising”, “including”, having” and variants thereof, when used in this specification, specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. In contrast, the term “consisting of” when used in this specification, specifies the stated features, steps, operations, elements, and/or components, and precludes additional features, steps, operations, elements and/or components.
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 the present invention 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 will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
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According to some embodiments of the present invention, each of the hybrid switches 12a-12f illustrated by
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In the drawings and specification, there have been disclosed typical preferred embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims.