Power Electronics With Integrated Ultracapacitor Energy Storage

A system includes a set of ultracapacitors, an input characterized by a first nominal voltage, an output characterized by a second nominal voltage, a direct current to direct current (DC-DC) converter, and switching power electronics electrically connected to the set of ultracapacitors. The DC-DC converter is configured to convert power from the input at the first nominal voltage to power at the output at the second nominal voltage. The DC-DC converter includes a magnetic coupling system that electromagnetically couples a first side of the DC-DC converter to a second side of the DC-DC converter. The magnetic coupling system electromagnetically couples the switching power electronics to the second side of the DC-DC converter.

FIELD

The present disclosure relates to power electronics and more particularly to DC-DC power electronics.

BACKGROUND

An ultracapacitor is an electrochemical energy storage device that acts similarly to a battery. Ultracapacitors differ from batteries in that ultracapacitors typically contain less energy storage by both weight and volume, ultracapacitors have greater power density, ultracapacitors exhibit significantly longer life (both calendar life and cycle life), and ultracapacitors follow the voltage characteristics according to the capacitor equation (specifically, J=½ CV2, where J is the energy stored, C is the capacitance, and V is the potential difference across the capacitor). An ultracapacitor (also called a supercapacitor) generally has a higher capacitance than a standard capacitor (such as an electrolytic capacitor). For example, the capacitance of an ultracapacitor may be 1, 2, or more orders of magnitude greater (for a given weight or volume) than a standard capacitor. In various implementations, an ultracapacitor may be based on an electrostatic double-layer capacitor or an electrochemical pseudocapacitor.

Because of their properties compared with batteries, ultracapacitors are generally used for short-duration high-power long-life applications, while batteries are used for longer run-time energy-dense applications that are accepted to have shorter life. Ultracapacitors are therefore suitable for certain long-life applications where short-duration pulse power is required, such as airbags. In the case of a collision, the vehicle powernet may become inoperative due to damage to the engine (alternator), battery compartment, and/or fuse box. The ultracapacitor inside of the airbag unit stores enough electrical energy to deploy the airbag without relying on other energy sources, ensuring continued function even when the overall vehicle electrical system is damaged. The long-life characteristics of the ultracapacitor ensures the airbag is functional for the design life.

SUMMARY

A system includes a set of ultracapacitors, an input characterized by a first nominal voltage, an output characterized by a second nominal voltage, and a direct current to direct current (DC-DC) converter configured to convert power from the input at the first nominal voltage to power at the output at the second nominal voltage. The system includes switching power electronics electrically connected to the set of ultracapacitors. The DC-DC converter includes a magnetic coupling system that electromagnetically couples a first side of the DC-DC converter to a second side of the DC-DC converter. The magnetic coupling system electromagnetically couples the switching power electronics to the second side of the DC-DC converter.

In other features, the magnetic coupling system includes a first winding electrically connected to the first side of the DC-DC converter and a second winding electrically connected to the second side of the DC-DC converter. The first winding and the second winding are wrapped around a core. In other features, the second winding includes a tap electrically connected to the switching power electronics. In other features, the magnetic coupling system includes a third winding electrically connected to the switching power electronics. The third winding is wrapped around the core.

In other features, the DC-DC converter includes a switching device configured to convert the first nominal voltage into pulsating DC. In other features, the switching device includes an H-bridge. In other features, the DC-DC converter includes a rectification device configured to convert pulsating DC into the second nominal voltage. In other features, the first nominal voltage is greater than 100 Volts. The second nominal voltage is one of approximately 12 Volts and approximately 48 Volts. In other features, the switching power electronics include an H-bridge.

In other features, the set of ultracapacitors includes a plurality of ultracapacitors connected in series and/or parallel. In other features, the system includes a second DC-DC converter configured to, in a first operating mode, provide power from the second side of the DC-DC converter to the set of ultracapacitors, and in a second operating mode, provide power from the set of ultracapacitors to the second side of the DC-DC converter. In other features, the second side of the DC-DC converter includes a rectifier connected to the output.

In other features, the magnetic coupling system includes a first transformer having a first core. The magnetic coupling system includes a second transformer having a second core. The first core and the second core are separate. The second transformer is connected between the second side of the DC-DC converter and the set of ultracapacitors. In other features, the system includes a switching device that is connected between the second transformer and the set of ultracapacitors.

A system includes a set of ultracapacitors, a first switching device including (i) a first terminal connected to an internal node and (ii) a second terminal, a second switching device connected between the internal node and the set of ultracapacitors, and a third switching device connected between the internal node and a reference terminal. The system includes a magnetic coupling system configured to electromagnetically couple an input to the second terminal of the first switching device and the reference terminal. The system includes an inductive device connected between the internal node and an output. The input is characterized by a first nominal voltage. The output characterized by a second nominal voltage.

In other features, the magnetic coupling system includes a transformer. A first winding of the transformer is connected to the input. A second winding of the transformer is connected between the second terminal of the first switching device and the reference terminal. In other features, the system includes a fourth switching device connected across the output. In other features, the first switching device includes a transistor. The second switching device includes a transistor. The third switching device includes a transistor. The fourth switching device includes a transistor. In other features, the first nominal voltage is greater than 100 Volts. The second nominal voltage is one of approximately 12 Volts and approximately 48 Volts. In other features, the set of ultracapacitors includes a plurality of ultracapacitors connected in parallel and/or series.

DETAILED DESCRIPTION

Introduction

A typical low-voltage vehicle powernet is 12 volts (12V). Some vehicles also incorporate a higher-voltage (such as 48V) powernet. Traditional vehicles derive the 12V energy from an alternator on the engine, buffered by a 12V battery that is typically located in the engine compartment (which itself is often under the hood of the vehicle). Electrification of vehicles increases the need for highly reliable electrical power. Some examples include electrically activated anti-lock brakes, drive-by-wire braking, electrically activated emergency parking brakes, electrically activated door locks, and drive-by-wire steering. Other applications include soft-shutdown of CPUs in case of power loss and “phone-home” emergency GPS transponders.

Battery electric vehicles (BEV) and hybrid electric vehicles (HEV) have a large battery pack that is used in conjunction with an electric motor to provide traction power (propulsion) to the vehicle. To provide sufficient power for propulsion, the battery pack may output a high voltage (for example, greater than 48V and, in various implementations, greater than 100V, 200V, 600V, 750V, or 1000V). This voltage is protected using specialized wire, connectors, and interfaces. The high voltage is constrained to the fewest possible uses, such as the propulsion motor, air conditioning compressor, and power steering assist. The rest of the vehicle uses the low-voltage 12V and/or 48V powernets. The 12V powernet in these cases is powered by a DC-DC converter that inputs power from the high-voltage battery pack and outputs 12V for the low-voltage vehicle powernet.

The present disclosure describes a system for achieving energy storage via a set of ultracapacitors. The set of ultracapacitors includes one or more ultracapacitors. When the set includes multiple ultracapacitors, the ultracapacitors may be electrically arranged in series, parallel, or a combination of series and parallel. A set (or network) of ultracapacitors with a total capacitance (C) can be abstracted and simplified to a single ultracapacitor (C).

A simplified DC-DC converter can be envisioned as a high-voltage direct current (HVDC) input feeding a switching device that breaks the DC voltage into a series of pulses. The switching device may be referred to as a chopper and may be implemented using an “H-bridge” formed from transistors, such as metal-oxide semiconductor field effect transistors (MOSFETs) and/or insulated gate bipolar transistors (IGBTs). In an H-bridge, a first pair of switches respectively connects two input terminals to one output terminal, and another pair of switches respectively connects the two input terminals to another output terminal. Within each pair of switches, the switches are controlled oppositely (one is open when the other is closed) so that the two input terminals are not shorted together.

The pulses are fed into a transformer primary with a specified winding ratio that results in a desired voltage on the secondary. The output waveform (from the secondary) is rectified to create the desired low-voltage output, such as 12V or 48V. In some implementations, the low-voltage output is approximately 12V or 48V (in various implementations, approximately means within 20% above or below these values). The rectification may be performed using, for example, diodes and/or synchronously switching transistors. The output can be modulated based on output voltage, current, and/or power demands by adjusting the pulse modulation in the input chopper.

The loss of the high-voltage supply would cause a near-immediate loss of the low-voltage powernet. Loss of the high-voltage supply can occur as a result of cell failure in the battery pack, wire harness failure, connector failure, physical damage, etc. As another example, a failure of the DC-DC converter would also result in loss of the low-voltage powernet. According to the present disclosure, a set of ultracapacitors can be used to store energy while the high-voltage powernet and DC-DC converter is functioning and, in the case of their failure, supply—at least temporarily—energy to the low-voltage powernet.

In an example implementation shown inFIG.1A, an HVDC input is chopped (for example, by an H-bridge116) into an alternating waveform, the output of which is connected to a transformer primary winding. The transformer secondary winding is connected to a rectifier, which is represented inFIG.1Aby a single diode112. The output of the rectifier is low-voltage (for example, 12V) power.

Another secondary winding is located on the shared transformer core and is connected through switching power electronics108(for example, an H-bridge) to a set of ultracapacitors104. This arrangement gives the set of ultracapacitors104bi-directional capability to monitor and control the bus voltage. In case of high-voltage failure, the set of ultracapacitors104can power the rectifier, and therefore the low-voltage powernet, until the set of ultracapacitors104is depleted. In various implementations, the additional winding on the shared transformer may impact efficiency.

In various implementations, one or more windings of a transformer (for example, the transformer primary and/or transformer secondary) may be implemented by an autoformer or other type of magnetic electrical component. For example, as shown inFIG.1B, an autoformer relies on two windings, one with multiple taps, to magnetically couple the H-bridge116, the diode112, and the switching power electronics108.

Bidirectional Converter

In another example implementation shown inFIG.2, a high-voltage network200provides power to a low-voltage network204through a DC-DC converter208. For example, the DC-DC converter208may include a switching device212, such as an H-bridge, that chops the DC of the high-voltage network200into pulsating DC. The pulsating DC is provided to a transformer216that steps down the voltage and provides the stepped-down pulsating DC to a rectifier220. For example only, the rectifier220may include diodes and/or switching transistors. In various implementations, the transformer216may be coupled to the transformer248. For example, one or more windings of the transformer216and the transformer248may be wrapped around a common core.

The output of the DC-DC converter208is fed to an ultracapacitor bank240—that is, a set ultracapacitors connected in parallel and/or series—through a bidirectional DC-DC converter244. The bidirectional DC-DC converter244can provide power to the ultracapacitor bank240when the high-voltage network200and the DC-DC converter208are functioning; when either stops functioning, the bidirectional DC-DC converter244can provide energy from the ultracapacitor bank240to the low-voltage network204. In various implementations, the bidirectional DC-DC converter244includes a transformer248and a switching device252. The transformer248may be dedicated—that is, not sharing a core in common with the transformer216—or may include a winding electromagnetically coupled to the transformer216(such as wrapping around some or all of the core of the transformer216).

Synchronous Rectification

In another example implementation shown inFIG.3A, a set of ultracapacitors304is integrated directly into the synchronous rectification of the 12V output (the low voltage output-LV Out312). In this manner, the set of ultracapacitors304can either charge or discharge, depending on the synchronous switching of transistors G1, G2, and G3. In case of high-voltage failure, the set of ultracapacitors304can discharge into the 12V output via switching of G2and G3.

InFIG.3A, HV In316is connected to a first winding of a transformer328. A second winding of the transformer328is connected to G1and reference terminal320. G1, G2, and G3are connected to internal node324. G2is connected to the set of ultracapacitors304.

When charging the set of ultracapacitors304, the high voltage (HV In316) is rectified by G1and routed into the set of ultracapacitors304using G2synchronously with G1. When discharging the set of ultracapacitors, the set of ultracapacitors is switched into the inductor308a(connected to internal node304and LV out312) using G2asynchronously with G1. In case of high-voltage failure, G1is disabled and the set of ultracapacitors is switched into the inductor using G2.

The output of transistors G1and G2may be smoothed to generate low-ripple DC by a low-pass filter308formed by an inductor308aand a capacitor308barranged in series. In various implementations, the capacitor308bis not an ultracapacitor.

FIG.3Ais only one example of a simplified rectifier topology. Rectification can be achieved by a variety topologies. For example, inFIG.3B, another simplified schematic shows a synchronous rectifier in which the capacitor308bofFIG.3Ais replaced by transistor G4. When transistor G2and transistor G4are activated, a loop forms that builds magnetic field in the inductor. When G4is deactivated, the magnetic field of the inductor308adissipates into LV Out312. This unique arrangement allows for synchronous rectification as well as boost conversion from the set of ultracapacitors304. This allows the set of ultracapacitors304to power LV Out312even when the voltage across the set of ultracapacitors304is less than the nominal voltage of LV Out312.

CONCLUSION

The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. In the written description and claims, one or more steps within a method may be executed in a different order (or concurrently) without altering the principles of the present disclosure. Similarly, one or more instructions stored in a non-transitory computer-readable medium may be executed in a different order (or concurrently) without altering the principles of the present disclosure. Unless indicated otherwise, numbering or other labeling of instructions or method steps is done for convenient reference, not to indicate a fixed order.

Further, although each of the embodiments is described above as having certain features, any one or more of those features described with respect to any embodiment of the disclosure can be implemented in and/or combined with features of any of the other embodiments, even if that combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and permutations of one or more embodiments with one another remain within the scope of this disclosure.

Spatial and functional relationships between elements (for example, between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including “connected,” “engaged,” “coupled,” “adjacent,” “next to,” “on top of,” “above,” “below,” and “disposed.” Unless explicitly described as being “direct,” when a relationship between first and second elements is described in the above disclosure, that relationship encompasses a direct relationship where no other intervening elements are present between the first and second elements as well as an indirect relationship where one or more intervening elements are present between the first and second elements.

As noted below, the term “set” generally means a grouping of one or more elements. However, in various implementations a “set” may, in certain circumstances, be the empty set (in other words, the set has zero elements in those circumstances). As an example, a set of search results resulting from a query may, depending on the query, be the empty set. In contexts where it is not otherwise clear, the term “non-empty set” can be used to explicitly denote exclusion of the empty set—that is, a non-empty set will always have one or more elements.

A “subset” of a first set generally includes some of the elements of the first set. In various implementations, a subset of the first set is not necessarily a proper subset: in certain circumstances, the subset may be coextensive with (equal to) the first set (in other words, the subset may include the same elements as the first set). In contexts where it is not otherwise clear, the term “proper subset” can be used to explicitly denote that a subset of the first set must exclude at least one of the elements of the first set. Further, in various implementations, the term “subset” does not necessarily exclude the empty set. As an example, consider a set of candidates that was selected based on first criteria and a subset of the set of candidates that was selected based on second criteria; if no elements of the set of candidates met the second criteria, the subset may be the empty set. In contexts where it is not otherwise clear, the term “non-empty subset” can be used to explicitly denote exclusion of the empty set.

In this application, including the definitions below, the term “module” can be replaced with the term “controller” or the term “circuit.” In this application, the term “controller” can be replaced with the term “module.” The term “module” may refer to, be part of, or include: an Application Specific Integrated Circuit (ASIC); a digital, analog, or mixed analog/digital discrete circuit; a digital, analog, or mixed analog/digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); processor hardware (shared, dedicated, or group) that executes code; memory hardware (shared, dedicated, or group) that is coupled with the processor hardware and stores code executed by the processor hardware; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip.

The module may include one or more interface circuits. In some examples, the interface circuit(s) may implement wired or wireless interfaces that connect to a local area network (LAN) or a wireless personal area network (WPAN). Examples of a LAN are Institute of Electrical and Electronics Engineers (IEEE) Standard 802.11-2020 (also known as the WIFI wireless networking standard) and IEEE Standard 802.3-2018 (also known as the ETHERNET wired networking standard). Examples of a WPAN are IEEE Standard 802.15.4 (including the ZIGBEE standard from the ZigBee Alliance) and, from the Bluetooth Special Interest Group (SIG), the BLUETOOTH wireless networking standard (including Core Specification versions 3.0, 4.0, 4.1, 4.2, 5.0, and 5.1 from the Bluetooth SIG).

Some or all hardware features of a module may be defined using a language for hardware description, such as IEEE Standard 1364-2005 (commonly called “Verilog”) and IEEE Standard 1076-2008 (commonly called “VHDL”). The hardware description language may be used to manufacture and/or program a hardware circuit. In some implementations, some or all features of a module may be defined by a language, such as IEEE 1666-2005 (commonly called “SystemC”), that encompasses both code, as described below, and hardware description.

The memory hardware may also store data together with or separate from the code. Shared memory hardware encompasses a single memory device that stores some or all code from multiple modules. One example of shared memory hardware may be level 1 cache on or near a microprocessor die, which may store code from multiple modules. Another example of shared memory hardware may be persistent storage, such as a solid state drive (SSD) or magnetic hard disk drive (HDD), which may store code from multiple modules. Group memory hardware encompasses a memory device that, in combination with other memory devices, stores some or all code from one or more modules. One example of group memory hardware is a storage area network (SAN), which may store code of a particular module across multiple physical devices. Another example of group memory hardware is random access memory of each of a set of servers that, in combination, store code of a particular module. The term memory hardware is a subset of the term computer-readable medium.

The apparatuses and methods described in this application may be partially or fully implemented by a special-purpose computer created by configuring a general-purpose computer to execute one or more particular functions embodied in computer programs. Such apparatuses and methods may be described as computerized or computer-implemented apparatuses and methods. The functional blocks and flowchart elements described above serve as software specifications, which can be translated into the computer programs by the routine work of a skilled technician or programmer.

The term non-transitory computer-readable medium does not encompass transitory electrical or electromagnetic signals propagating through a medium (such as on a carrier wave). Non-limiting examples of a non-transitory computer-readable medium are nonvolatile memory circuits (such as a flash memory circuit, an erasable programmable read-only memory circuit, or a mask read-only memory circuit), volatile memory circuits (such as a static random access memory circuit or a dynamic random access memory circuit), magnetic storage media (such as an analog or digital magnetic tape or a hard disk drive), and optical storage media (such as a CD, a DVD, or a Blu-ray Disc).

The term “set” generally means a grouping of one or more elements. The elements of a set do not necessarily need to have any characteristics in common or otherwise belong together. The phrase “at least one of A, B, and C” should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.” The phrase “at least one of A, B, or C” should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR.