UPS and method of operating UPS

Abstract

An uninterruptible power supply (UPS) includes an input, a backup power input, positive and negative DC buses, a converter, and at least one controller. The converter includes a first inductor, a second inductor, a first converter switch coupling the first inductor to a neutral connection, a second converter switch coupling the second inductor to a positive DC bus, a third converter switch coupling the second inductor to the negative DC bus; and a fourth converter switch coupling the second inductor to the backup power input. The at least one controller is configured to: in response to determining that the acceptable AC power is unavailable at the input, operate the converter in a standby mode of operation; operating the first converter switch in a backup mode of operation to provide DC power derived from the backup DC power to the positive DC bus via the first inductor; the fourth converter switch is operated in a backup mode of operation to provide DC power derived from the backup DC power to the negative DC bus via the second inductor.

Description

[0001] This application is a divisional application of the invention patent application with the application date of June 14, 2022, the application number of 202210669425.6, and the invention title of "AC Switch PFC with Integrated Charger and DC-DC for Online UPS System". Technical Field

[0002] Embodiments of the present disclosure generally relate to power conversion, and more particularly, to AC-DC power conversion in an uninterruptible power supply. Background Art

[0003] An uninterruptible power supply (UPS) is used to provide backup power to electrical equipment or loads when the main power supply or mains fails. Typical loads include computer systems, but other loads such as heating / ventilation / air conditioning systems, lighting systems, network switches and routers, and secure data center management systems can also receive backup power between 1 and 20 kVA for several hours. Summary of the Invention

[0004] At least one aspect of the present disclosure relates to an uninterruptible power supply (UPS). The UPS includes an input terminal, a backup power input terminal, a positive DC bus and a negative DC bus, and a converter. The input terminal is configured to receive input AC power having an input AC voltage, the backup power input terminal is configured to be coupled to a backup power supply and provide DC power to the backup power supply for charging, the positive DC bus and the negative DC bus are galvanically coupled to the backup power input terminal, the converter is coupled to the input terminal, the backup power input terminal, and the positive DC bus and the negative DC bus, the converter includes a first inductor, a second inductor, a first converter switch configured to couple the first inductor to a neutral connection, a second converter switch configured to couple the second inductor to the positive DC bus, and a third converter switch configured to couple the second inductor to the negative DC bus, wherein the UPS is voltage-frequency independent.

[0005] In one embodiment, the UPS includes a controller that is coupled to a converter and configured to: during the positive half-cycle of the input AC voltage in a first operating mode, operate a first converter switch to supply DC power derived from the input AC power to the positive DC bus via a first inductor, and operate at least one of a second converter switch or a third converter switch to supply DC power derived from at least one of the positive DC bus or the negative DC bus to a backup power input via a second inductor; during the negative half-cycle of the input AC voltage in the first operating mode, operate the first converter switch to supply DC power derived from the input AC power to the negative DC bus via the first inductor, and operate at least one of the second converter switch or the third converter switch to supply DC power derived from at least one of the positive DC bus or the negative DC bus to the backup power input via the second inductor. In some embodiments, the UPS includes an input selection circuit that is configured to couple the converter to the input during the first operating mode and couple the converter to the backup power input during a second operating mode. In various embodiments, the controller is configured to monitor the input AC power, operate the UPS in the first operating mode in response to determining that the input AC power is acceptable, and operate the UPS in the second operating mode in response to determining that the input AC power is unacceptable. In certain embodiments, the backup power input is configured to receive backup DC power from a backup power source, and the converter further includes a fourth converter switch configured to couple the second inductor to the backup power input.

[0006] In some embodiments, the controller is configured to: operate the first converter switch in a second operating mode to supply DC power derived from standby DC power to the positive DC bus via the first inductor, and operate the fourth converter switch in the second operating mode to supply DC power derived from standby DC power to the negative DC bus via the second inductor. In one embodiment, the converter further includes a fifth converter switch configured to couple the second inductor to a neutral connection, and the controller is configured to: operate the fifth converter switch in the second operating mode to supply DC power derived from standby DC power to the positive DC bus via the second inductor, and operate the fourth converter switch in the second operating mode to supply DC power derived from standby DC power to the negative DC bus via the second inductor. In one embodiment, the first converter switch is a bidirectional switch circuit including a first switch and a second switch coupled in series. In certain embodiments, the converter includes a first diode coupled between the first converter switch and the positive DC bus, a second diode coupled between the first converter switch and the negative DC bus, a fourth converter switch configured to couple the second inductor to a standby power input, and a fifth converter switch configured to couple the second inductor to a neutral connection. In various embodiments, the first inductor, the first switch of the first converter switch, the body diode of the second switch of the first converter switch, and the first diode are configured to operate as a boost converter in a first operating mode during the positive half-cycle of the input AC voltage to supply DC power derived from the input AC power to the positive DC bus.

[0007] In some embodiments, the second inductor, the body diodes of the third converter switch and the fourth converter switch are configured to operate as a buck-boost converter in the first operating mode to supply DC power derived from the negative DC bus to the standby power input. In one embodiment, the first inductor, the second switch of the first converter switch, the body diode of the first switch of the first converter switch, and the second diode are configured to operate as a boost converter in the first operating mode during the negative half-cycle of the input AC voltage to supply DC power derived from the input AC power to the negative DC bus. In various embodiments, the second inductor, the second converter switch, and the body diode of the fifth converter switch are configured to operate as a buck converter in the first operating mode to supply DC power derived from the positive DC bus to the standby power input. In certain embodiments, the first inductor, the first switch of the first converter switch, the body diode of the second switch of the first converter switch, and the first diode are configured to operate as a boost converter in the second operating mode to supply DC power derived from standby DC power to the positive DC bus.

[0008] In one embodiment, the second inductor, the fourth converter switch, the body diode of the second converter switch, and the fifth converter switch are configured to operate as a boost converter in a second operating mode to provide DC power derived from standby DC power to the positive DC bus. In some embodiments, the second inductor, the fourth converter switch, the body diode of the third converter switch, and the fifth converter switch are configured to operate as a buck-boost converter during the second operating mode to provide DC power derived from standby DC power to the negative DC bus. In various embodiments, the UPS includes an output and an inverter, the output being configured to provide output AC power to a load, the inverter being coupled to the output and being configured to convert DC power from the positive DC bus and the negative DC bus into output AC power and provide the output AC power to the output.

[0009] Another aspect of the present disclosure relates to a non-transitory computer-readable medium having stored thereon a sequence of computer-executable instructions for controlling an uninterruptible power supply (UPS) that includes an input, a standby power input, a positive DC bus, a negative DC bus, and a converter. The input is configured to receive input AC power having an input AC voltage, the standby power input is configured to be coupled to a standby power source and provide DC power to the standby power source for charging, the converter is coupled to the input, the standby power input, and the positive and negative DC buses, and the converter includes a first inductor, a second inductor, a first converter switch configured to couple the first inductor to a neutral connection, a second converter switch configured to couple the second inductor to the positive DC bus, and a third converter switch configured to couple the second inductor to the negative DC bus. The sequence of computer-executable instructions includes instructions that direct at least one processor to perform the following: during a first operating mode and during a positive half-cycle of the input AC voltage, operate the first converter switch to provide DC power derived from the input AC power to the positive DC bus via the first inductor, and operate at least one of the second converter switch or the third converter switch to provide DC power derived from at least one of the positive DC bus or the negative DC bus to the standby power input via the second inductor; during the first operating mode and during a negative half-cycle of the input AC voltage, operate the first converter switch to provide DC power derived from the input AC power to the negative DC bus via the first inductor, and operate at least one of the second converter switch or the third converter switch to provide DC power derived from at least one of the positive DC bus or the negative DC bus to the standby power input via the second inductor.

[0010] In one embodiment, the instruction sequence includes instructions that cause the at least one processor to: monitor input AC power received at an input terminal, operate the UPS in a first operating mode in response to determining that the input AC power is acceptable, and operate the UPS in a second operating mode in response to determining that the input AC power is unacceptable. In some embodiments, the UPS includes an input terminal selection circuit, and the instruction sequence includes instructions that cause the at least one processor to: control the input terminal selection circuit to couple a converter to the input terminal during the first operating mode, and control the input terminal selection circuit to couple the converter to a backup power input terminal during the second operating mode. In various embodiments, the backup power input terminal is further configured to receive backup DC power from a backup power source, and the converter includes a fourth converter switch configured to couple a second inductor to the backup power input terminal. In certain embodiments, the instruction sequence includes instructions that cause the at least one processor to: operate a first converter switch in the second operating mode to provide DC power derived from the backup DC power to a positive DC bus via a first inductor, and operate the fourth converter switch in the second operating mode to provide DC power derived from the backup DC power to a negative DC bus via the second inductor.

[0011] In some embodiments, the converter includes a fifth converter switch configured to couple the second inductor to a neutral connection, and the instruction sequence includes instructions that cause the at least one processor to: operate the fifth converter switch in the second operating mode to provide DC power derived from the backup DC power to the positive DC bus via the second inductor, and operate the fourth converter switch in the second operating mode to provide DC power derived from the backup DC power to the negative DC bus via the second inductor.

[0012] Another aspect of the present disclosure relates to a method of assembling an uninterruptible power supply (UPS), the method including: providing an input terminal configured to receive input AC power having an input AC voltage, providing a backup power input terminal configured to be coupled to a backup power source and supply DC power to the backup power source for charging, electrically coupling a positive DC bus and a negative DC bus to the backup power input terminal, and coupling a converter to the input terminal, the backup power input terminal, and the positive and negative DC buses, the converter including a first inductor, a second inductor, a first converter switch configured to couple the first inductor to a neutral connection, a second converter switch configured to couple the second inductor to the positive DC bus, and a third converter switch configured to couple the second inductor to the negative DC bus, wherein the UPS is voltage-frequency independent.

[0013] At least one aspect of the present disclosure also relates to an uninterruptible power supply (UPS) that includes an input terminal, a standby power input terminal, a positive DC bus and a negative DC bus, a converter, and at least one controller. The input terminal is configured to receive input AC power having an input AC voltage. The standby power input terminal is configured to be coupled to a standby power supply and receive standby DC power from the standby power supply and provide DC power to the standby power supply for charging. The positive DC bus and the negative DC bus are electrically coupled to the standby power input terminal. The converter is coupled to the input terminal, the standby power input terminal, and the positive DC bus and the negative DC bus. The converter includes a first inductor, a second inductor, a first converter switch configured to couple the first inductor to a neutral connection, a second converter switch configured to couple the second inductor to the positive DC bus, a third converter switch configured to couple the second inductor to the negative DC bus, and a fourth converter switch configured to couple the second inductor to the standby power input terminal. The at least one controller is configured to: in response to determining that acceptable AC power is not available at the input terminal, operate the converter in a standby operation mode, operate the first converter switch in the standby operation mode to provide DC power derived from the standby DC power to the positive DC bus via the first inductor, and operate the fourth converter switch in the standby operation mode to provide DC power derived from the standby DC power to the negative DC bus via the second inductor.

[0014] At least one aspect of the present disclosure also relates to a method of operating an uninterruptible power supply (UPS). The UPS has an input terminal, a standby power input terminal, a positive DC bus and a negative DC bus, and a converter. The input terminal is configured to receive input AC power having an input AC voltage. The standby power input terminal is configured to be coupled to a standby power supply and receive standby DC power from the standby power supply and provide DC power to the standby power supply for charging. The positive DC bus and the negative DC bus are electrically coupled to the standby power input terminal. The converter is coupled to the input terminal, the standby power input terminal, and the positive DC bus and the negative DC bus. The converter includes a first inductor, a second inductor, a first converter switch, a second converter switch, a third converter switch, and a fourth converter switch. The first converter switch is configured to couple the first inductor to a neutral connection. The second converter switch is configured to couple the second inductor to the positive DC bus. The third converter switch is configured to couple the second inductor to the negative DC bus. The fourth converter switch is configured to couple the second inductor to the standby power input terminal. The method includes: in response to determining that acceptable AC power is not available at the input terminal, controlling the UPS to operate in a standby operation mode; operating the first converter switch in the standby operation mode to provide DC power derived from the standby DC power to the positive DC bus via the first inductor; and operating the fourth converter switch in the standby operation mode to provide DC power derived from the standby DC power to the negative DC bus via the second inductor.

[0015] At least one aspect of the present disclosure also relates to at least one non - transitory computer - readable medium having stored thereon a sequence of computer - executable instructions for operating an uninterruptible power supply (UPS). The UPS has an input terminal, a backup power input terminal, a positive DC bus, a negative DC bus, and a converter. The input terminal is configured to receive input AC power having an input AC voltage. The backup power input terminal is configured to be coupled to a backup power source and to receive backup DC power from the backup power source and to supply DC power to the backup power source for charging. The positive DC bus and the negative DC bus are electrically coupled to the backup power input terminal. The converter is coupled to the input terminal, the backup power input terminal, the positive DC bus, and the negative DC bus. The converter includes a first inductor, a second inductor, a first converter switch, a second converter switch, a third converter switch, and a fourth converter switch. The first converter switch is configured to couple the first inductor to a neutral connection. The second converter switch is configured to couple the second inductor to the positive DC bus. The third converter switch is configured to couple the second inductor to the negative DC bus. The fourth converter switch is configured to couple the second inductor to the backup power input terminal. The sequence of computer - executable instructions includes instructions that direct at least one processor to: in response to determining that acceptable AC power is not available at the input terminal, control the UPS to operate in a backup operation mode; operate the first converter switch in the backup operation mode to supply DC power derived from the backup DC power to the positive DC bus via the first inductor; and operate the fourth converter switch in the backup operation mode to supply DC power derived from the backup DC power to the negative DC bus via the second inductor.

[0016] At least one aspect of the present disclosure also relates to an uninterruptible power supply (UPS). The UPS includes an input terminal, a backup power input terminal, a positive DC bus and a negative DC bus, a converter, and at least one controller. The input terminal is configured to receive input AC power having an input AC voltage. The backup power input terminal is configured to be coupled to a backup power source and receive backup DC power from the backup power source and supply DC power to the backup power source for charging. The positive DC bus and the negative DC bus are electrically coupled to the backup power input terminal. The converter is coupled to the input terminal, the backup power input terminal, and the positive DC bus and the negative DC bus. The converter includes a first inductor, a second inductor, a first converter switch, a second converter switch, a third converter switch, a fourth converter switch, and a fifth converter switch. The first converter switch is configured to couple the first inductor to a neutral connection. The second converter switch is configured to couple the second inductor to the positive DC bus. The third converter switch is configured to couple the second inductor to the negative DC bus. The fourth converter switch is configured to couple the second inductor to the backup power input terminal. The fifth converter switch is configured to couple the second inductor to the neutral connection. The at least one controller is configured to: operate the converter in a backup operation mode in response to determining that acceptable AC power is not available at the input terminal; operate the fifth converter switch in the backup operation mode to supply DC power derived from the backup DC power to the positive DC bus via the second inductor; and operate the fourth converter switch in the backup operation mode to supply DC power derived from the backup DC power to the negative DC bus via the second inductor. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Aspects of at least one embodiment are discussed below with reference to the drawings, which are not intended to be drawn to scale. The drawings are included to provide an illustration and a further understanding of the various aspects and embodiments, and are incorporated into and form a part of this specification, but are not intended as a definition of the limits of the invention. In the drawings, each identical or nearly identical component that is illustrated in various drawings is represented by the same reference numeral. For clarity, not every component may be labeled in every drawing. In the drawings:

[0018] Figure 1 is a functional block diagram of a UPS according to aspects described herein;

[0019] Figure 2 is a schematic diagram of a UPS front-end topology according to aspects described herein;

[0020] Figure 3A and Figure 3B is Figure 2 a schematic diagram of the UPS front-end topology of, showing the PFC function during an online operation mode according to aspects described herein;

[0021] Figure 4A and Figure 4B is Figure 2 a schematic diagram of a UPS front-end topology, showing the charger function during the online operation mode according to various aspects described herein;

[0022] Figure 5A and Figure 5B is Figure 2 a schematic diagram of a UPS front-end topology, showing the standby operation mode according to various aspects described herein; and

[0023] Figure 6 is Figure 2 a schematic diagram of a UPS front-end topology, showing the standby operation mode during the positive DC bus cycle according to various aspects described herein. Detailed Description

[0024] Examples of the methods and systems discussed herein are not limited in application to the details of the construction and arrangement of the components set forth in the following description or shown in the drawings. The methods and systems are capable of being implemented in other embodiments and of being practiced or carried out in various ways. The examples of the detailed description provided herein are for illustrative purposes only and not limiting. In particular, the actions, components, elements, and features discussed in connection with any one or more examples are not intended to be excluded from a similar role in any other examples.

[0025] Furthermore, the language and terminology used herein are for the purpose of the description and should not be regarded as limiting. Any reference to examples, embodiments, components, elements, or actions of the systems and methods herein in the singular may also cover embodiments comprising a plurality, and any reference to any embodiments, components, elements, or actions herein in the plural may also cover embodiments comprising only the singular. References in the singular or plural forms are not intended to limit the presently disclosed systems or methods, their components, actions, or elements. The terms "including," "comprising," "having," "containing," "involving," and variations thereof used herein are intended to cover the items listed thereafter and their equivalents as well as additional items. References to "or" may be construed as inclusive such that any terms described using "or" may indicate any one of the described terms, any combination of the described terms, or all of the described terms. Additionally, in the case of inconsistent term usage between this document and the documents incorporated herein by reference, the term usage in the incorporated references is supplementary to the term usage in this document; for irreconcilable inconsistencies, the term usage in this document prevails.

[0026] As described above, power devices such as uninterruptible power supplies (UPSs) can be used to provide regulated and uninterrupted power to sensitive and / or critical loads. An online UPS uses a power factor correction converter (PFC) circuit to rectify the input AC power provided by an electric utility to provide DC power to at least one DC bus. The rectified DC power on the DC bus can be used to charge a battery when line power is available. In the absence of line power, the battery discharges and provides DC power to the DC bus. Based on the DC power on the DC bus, an inverter generates an AC output terminal voltage provided to the load. Since power is provided to the DC bus from the line or the battery, the output power of the UPS is not interrupted if the line fails and the battery is fully charged. The online UPS can also operate in a bypass mode, where unregulated power with basic protection is provided directly from the AC power source to the load via a bypass line.

[0027] In many cases, the front-end topology of an online UPS includes a PFC converter to provide DC power to the DC bus when the AC line is available, and includes a separate DC / DC converter to provide DC power from the battery to the DC bus when the AC line is not available. In some cases, the front-end topology can include a separate charger (i.e., DC / DC converter) configured to charge the battery. Thus, these front-end UPS topologies typically have a high component count, which can lead to increased cost, increased system complexity, and reduced power density. Additionally, such front-end UPS topologies typically include components that are unused or idle during at least one operating mode of the UPS.

[0028] This document provides a more cost-effective and compact front-end topology for an online UPS. In at least one embodiment, the front-end topology includes an integrated converter configured to operate as a PFC converter, a DC / DC converter, and a battery charger. In one example, the integrated converter is configured to provide power to a positive DC bus and a negative DC bus while charging the battery using power from the positive and negative DC buses. In some examples, the improved front-end topology can have a reduced component count, thereby increasing the power density of the UPS and reducing cost.

[0029] Figure 1FIG. 0 is a block diagram of an embodiment of an online UPS 100 that can provide regulated power from input AC power received at input terminal 102 and backup DC power from a backup power source 112 (e.g., a battery) to output terminal 110. The UPS 100 can be configured to provide output AC power with voltage and frequency independent of the input AC power. In some examples, the backup power source 112 can be included within the UPS 100; however, in other examples, the backup power source 112 can be external to the UPS 100. The UPS 100 includes a converter 104, a DC bus 106, an inverter 108, and a controller 114 for controlling the converter 104 and the inverter 108. The DC bus 106 is coupled between the converter 104 and the inverter 108.

[0030] The input terminal 102 is configured to receive input AC power having an input voltage level from an AC power source. The controller 114 monitors the input AC power received by the input terminal 102 and is configured to operate the UPS 100 in different operating modes based on the status of the input AC power received by the input terminal 102. When the AC power supplied to the input terminal 102 is acceptable (i.e., above an input power quality threshold), the controller 114 operates the UPS 100 in an online operating mode.

[0031] In the online operating mode, the AC power from the input terminal 102 is supplied to the converter 104. The controller 114 operates the converter 104 to convert the AC power to DC power and supply the DC power to the DC bus 106. The DC power from the DC bus 106 is supplied to the inverter 108. Additionally, the DC power from the DC bus 106 can be supplied directly from the converter 104 or via a separate DC / DC converter (e.g., a charger) to the battery 112 for charging. The controller 114 operates the inverter 108 to convert the DC power into regulated AC power and supply the regulated AC power to a load coupled to the output terminal 110.

[0032] When the AC power supplied to the input terminal 102 is unacceptable (i.e., below the input power quality threshold), the controller 114 operates the UPS 100 in a backup operating mode. In the backup operating mode, the DC power from the backup power source 112 is supplied to the DC bus 106. The inverter 108 receives the DC power from the DC bus 106, and the controller 114 operates the inverter 108 to convert the DC power from the DC bus 106 into regulated AC power and supply the regulated AC power to the output terminal 110.

[0033] As described above, many online UPS topologies employ separate DC / DC converters to convert input AC power and standby DC power. For example, in such a topology, converter 104 may include a PFC converter and a separate DC / DC converter. The PFC converter is configured to supply DC power derived from the input AC power to the DC bus 106 during the online operation mode, and the separate DC / DC converter is configured to supply DC power derived from the standby DC power to the DC bus 106 during the standby operation mode. In some examples, the DC / DC converter may be configured to charge the battery 112 from the DC bus; however, in other examples, converter 104 (or UPS 100) may include a separate charger (i.e., DC / DC converter) to charge the battery 112.

[0034] While such topologies can be utilized to provide uninterrupted power, using multiple converters requires the use of additional components. For example, a charger may include additional components such as switches, diodes, inductors, transformers (e.g., step-down transformers), etc., to supply DC power derived from the input AC power or the DC bus to the battery for charging. Thus, these multiple converter topologies may increase cost and complexity while reducing the power density of the UPS.

[0035] Additionally, in certain environments (e.g., developing economies), frequent and prolonged power outages may drive the need for large (or high-power) battery packs. In such cases, the charger included in converter 104 (or UPS 100) may be configured as a high-power charger. In other examples, the charger may be configured as a high-power charger to support a particular type of battery (e.g., lithium) and / or provide particular features (e.g., fast charging). In some examples, configuring the charger as a high-power converter may further increase the size and cost of UPS 100.

[0036] Accordingly, it may be advantageous to configure the front-end topology (e.g., converter 104) of UPS 100 to be an integrated converter capable of supplying DC power derived from the input AC power or the standby DC power to the DC bus 106 and using the DC power derived from the DC bus 106 to charge the battery 112.

[0037] Figure 2 is a schematic diagram of a front-end topology 200 in accordance with aspects described herein. In one example, the front-end topology 200 is configured to be included in an online UPS (i.e., a voltage-frequency independent UPS). For example, the front-end topology 200 includes components respectively corresponding to Figure 1The converters 104 of the UPS 100 and the converters 204 and DC bus 206 of the DC bus 106. In some examples, the DC bus 206 includes a positive DC bus 206a and a negative DC bus 206b.

[0038] As shown, the front-end topology 200 includes an input terminal 202 coupled to the input AC source 203 and a backup power input terminal 214 coupled to a backup power source 212 (e.g., a battery). In certain examples, the backup power source 212 may be included within the UPS; however, in other examples, the backup power source 212 may be separate from the UPS. In some examples, the front-end topology 200 is configured with a direct-through neutral connection to the input terminal 202 and the backup power source 212 to minimize EMI / EMC issues.

[0039] In one example, the converter 204 includes a first converter switch 216, a second converter switch 218, a third converter switch 220, a fourth converter switch 222, and a fifth converter switch 224, an input terminal selection circuit 226, a first inductor 228, a second inductor 230, a first diode 232, and a second diode 234. In one embodiment, the converter switches 216-224 are metal oxide semiconductor field effect transistors (MOSFETs); however, in other embodiments, different types of switches or transistors (e.g., insulated gate bipolar transistors (IGBTs)) may be utilized. In some examples, each switch has a gate, a drain, and a source. In this context, the "drain" may refer to any device terminal through which current enters the switch. Similarly, the "source" may refer to any device terminal through which current leaves the switch.

[0040] In some instances, the first converter switch 216 is a bidirectional switch circuit that includes a first switch 216a serially coupled with a second switch 216b. Thus, the first converter switch 216 can operate in a first state by turning on (i.e., closing) the first switch 216a and turning off (i.e., opening) the second switch 216b to provide a conduction path through the body diodes of the first switch 216a and the second switch 216b. Similarly, the first converter switch 216 can operate in a second state by turning on (i.e., closing) the second switch 216b and turning off (i.e., opening) the first switch 216a to provide a conduction path through the body diodes of the second switch 216b and the first switch 216a.

[0041] As shown, the input terminal selection circuit 226 is configured to couple the first inductor 228 to one of the input terminal 202 or the standby power input terminal 214. In one example, the first end of the first inductor 228 is coupled to the first converter switch 216, the anode of the first diode 232, and the cathode of the second diode 234, and the second end of the first inductor 228 is coupled to the input terminal selection circuit 226. The cathode of the first diode 232 is coupled to the positive DC bus 206a, and the anode of the second diode 234 is coupled to the negative DC bus 206b. In some examples, the first end of the second inductor 230 is coupled to the first converter switch 218 and the fifth converter switch 224, and the second end of the second inductor 230 is coupled to the third converter switch 220 and the fourth converter switch 222. The second converter switch 218 is coupled between the first end of the second inductor 230 and the positive DC bus 206a, and the fifth converter switch 224 is coupled between the first end of the second inductor 230 and the neutral line. The third converter switch 220 is coupled between the second end of the second inductor 230 and the negative DC bus 206b, and the fourth converter switch 222 is coupled between the second end of the second inductor 230 and the standby power input terminal 214.

[0042] In one example, the positive DC bus capacitor 236a is coupled between the positive DC bus 206a and the neutral line, and the negative DC bus capacitor 236b is coupled between the negative DC bus 206b and the neutral line. In some examples, the DC bus capacitors 236a, 236b are polarized capacitors. For example, the positive DC bus capacitor 236a may have a positive side coupled to the positive DC bus 206a and a negative side coupled to the neutral line. Similarly, the negative DC bus capacitor 236b may have a positive side coupled to the neutral line and a negative side coupled to the negative DC bus 206b. As Figure 2 shown, the DC buses 206a, 206b are current-coupled to the standby power input terminal 214.

[0043] In at least one example, the converter 204 of the front-end topology 200 can operate in various operating modes. For example, in the online operating mode of the UPS, the control input terminal selection circuit 226 couples the second end of the first inductor 228 to the input terminal 202, so that the AC power from the input terminal 202 is provided to the converter 204. The converter 204 converts the AC power into DC power and provides the DC power to the DC buses 206a, 206b. Additionally, during the online operating mode, the converter 204 can be operated to provide the DC power derived from the DC buses 206a, 206b to the standby power input terminal 214 to charge the standby power supply 212.

[0044] In some examples, the converter 204 is configured to operate as a bi-directional converter. Thus, the converter 204 can be considered "bi-directional" because the converter 204 can supply power to the backup power input 214 (i.e., the backup power supply 212), and can also draw power from the backup power input 214. In contrast, certain unidirectional chargers can be configured to supply power to an energy storage device or input, but cannot draw power from the energy storage device or input.

[0045] Figure 3A And Figure 3B are schematic diagrams showing the PFC function of the converter 204 during the positive and negative half-cycles of the input AC voltage corresponding to the online operating mode of the UPS.

[0046] As Figure 3A shown, during the online operating mode and the positive half-cycle of the input AC voltage, the first converter switch 216 is operated to supply DC power derived from the input AC power (supplied by the input AC source 203) to the positive DC bus 206a. In some examples, the first converter switch 216, the first inductor 228, and the first diode 232 operate as a PFC boost converter to supply DC power to the positive DC bus 206a.

[0047] In one example of the online operating mode during the positive half-cycle of the input AC voltage, the first switch 216a of the first converter switch 216 is turned on and off to provide PFC boost converter operation. For example, when the first switch 216a is turned on (i.e., closed), the first end of the first inductor 228 is coupled to the neutral line. Thus, a conduction path 302 for the input AC power is provided through the first converter switch 216, thereby exciting the inductor 228. In one example, the conduction path 302 includes the body diode of the second switch 216b of the first converter switch 216. Similarly, when the first switch 216a is turned off (i.e., opened), the first inductor 228 is decoupled from the neutral line. In this way, a conduction path 304 for the input AC power is provided through the first inductor 228 and the first diode 232 to supply DC power to the positive DC bus 206a and charge the positive DC bus capacitor 236a.

[0048] As Figure 3B shown, during the online operating mode and the negative half-cycle of the input AC voltage, the first converter switch 216 is operated to supply DC power derived from the input AC power (supplied by the input AC source 203) to the negative DC bus 206b. In some examples, the first converter switch 216, the first inductor 228, and the second diode 234 operate as a PFC boost converter to supply DC power to the negative DC bus 206b.

[0049] In an example of the online operating mode during the negative half-cycle of the input AC voltage, the second switch 216b of the first converter switch 216 is turned on and off to provide PFC boost converter operation. For example, when the second switch 216b is turned on (i.e., closed), the first end of the first inductor 228 is coupled to the neutral line. Thus, a conductive path 402 for the input AC power is provided through the first converter switch 216, thereby exciting the first inductor 228. In one example, the conductive path 402 includes the body diode of the first switch 216a of the first converter switch 216. Similarly, when the second switch 216b is turned off (i.e., open), the first inductor 228 is decoupled from the neutral line. Thus, a conductive path 404 for the input AC power is provided through the first inductor 228 and the second diode 234 to provide DC power to the negative DC bus 206b and charge the negative DC bus capacitor 236b.

[0050] As described above, during the online operating mode of the UPS, the converter 204 can be operated to provide the DC power derived from the DC buses 206a, 206b to the backup power input 214 to charge the backup power supply 212. In one example, in the online operating mode, the converter 204 can charge the backup power supply 212 using the DC power derived from the positive DC bus 206A and / or the negative DC bus 206B during the positive and negative half-cycles of the input AC voltage.

[0051] Figure 4A and Figure 4B are schematic diagrams showing the charger function of the converter 204 during the online operating mode of the UPS.

[0052] As Figure 4A shown, during the online operating mode, the third converter switch 220 can be operated to provide the DC power derived from the negative DC bus 206B (i.e., the negative DC bus capacitor 236B) to the backup power input 214 to charge the backup power supply 212. In some examples, the body diodes of the third converter switch 220, the second inductor 230, and the fourth converter switch 222 operate as a buck-boost converter to provide the DC power derived from the negative DC bus 206B to the backup power input 214.

[0053] In one example, the third converter switch 220 is turned on and off to provide buck-boost converter operation. For example, when the third converter switch 220 is turned on (i.e., closed), the second end of the second inductor 230 is coupled to the negative DC bus 206b. Thus, a conduction path 306 for the DC power stored by the negative DC bus capacitor 236b is provided through the third converter switch 220, thereby exciting the second inductor 230. In one example, the conduction path 306 includes the body diode of the fifth converter switch 224; however, in some examples, the fifth converter switch 224 may be turned on (i.e., closed) to minimize losses. Similarly, when the third converter switch 220 is turned off (i.e., open), the second inductor 230 is decoupled from the negative DC bus 236b. Thus, a conduction path 308 is provided through the body diode of the fourth converter switch 222 and the body diode of the fifth converter switch 224 (or the fifth converter switch 224), thereby allowing the second inductor 230 to stop being excited and provide DC power to the standby power input 214 to charge the standby power supply 212. In some examples, the DC power provided to the standby power input 214 may have a voltage level different from (e.g., lower than) the voltage level of the negative DC bus 206B.

[0054] In one example, in the online operating mode of the UPS, the converter 204 can be operated to provide the DC power derived from the negative DC bus 206b to the standby power input 214 during both the positive and negative half-cycles of the input AC voltage. For example, when the converter 204 supplies power to the positive DC bus 206A (e.g., Figure 3A ), and the negative DC bus 206B (e.g., Figure 3B ), the third converter switch 220 can be operated as described above.

[0055] Similarly, as Figure 4B shown, during the online operating mode, the second converter switch 218 can be operated to provide the DC power derived from the positive DC bus 206A (i.e., the positive DC bus capacitor 236A) to the standby power input 214 to charge the standby power supply 212. In some examples, the body diodes of the second converter switch 218, the second inductor 230, and the fifth converter switch 224 operate as a buck converter to provide the DC power derived from the positive DC bus 206A to the standby power input 214.

[0056] In one example, the second converter switch 218 is turned on and off to provide buck converter operation. For example, when the second converter switch 218 is turned on (i.e., closed), the first end of the second inductor 230 is coupled to the positive DC bus 206a. In this way, a conduction path 406 for the DC power stored by the positive DC bus capacitor 236a is provided through the second converter switch 218, thereby exciting the second inductor 230. In one example, the conduction path 406 includes the body diode of the fourth converter switch 222; however, in some examples, the fourth converter switch 222 can be turned on (i.e., closed) to minimize losses. Similarly, when the second converter switch 218 is turned off (i.e., opened), the second inductor 230 is decoupled from the positive DC bus 236a. In this way, a conduction path 408 is provided through the body diode of the fourth converter switch 222 (or the fourth converter switch 222) and the body diode of the fifth converter switch 224, thereby allowing the second inductor 230 to stop being excited and provide DC power to the standby power input 214 to charge the standby power supply 212. In some examples, the DC power provided to the standby power input 214 can have a voltage level different from (e.g., lower than) the voltage level of the positive DC bus 206a.

[0057] In one example, in the online operation mode of the UPS, the converter 204 can be operated to provide DC power derived from the positive DC bus 206a to the standby power input 214 during the positive and negative half-cycles of the input AC voltage. For example, when the converter 204 provides power to the positive DC bus 206a (e.g., Figure 3A ), and the negative DC bus 206b (e.g., Figure 3B ), the second converter switch 218 can be operated as described above.

[0058] In one example, the charging capacity of the converter 204 corresponds to the power demand at the output 110 of the UPS 100 (i.e., the output of the inverter 108). For example, when the UPS is not experiencing full load at the output 110, the converter 204 can be operated with a charging capacity up to 50% of the capacity of the inverter 110. In this way, the charging capacity of the converter 204 can be scaled or adjusted based on the power demand at the output 110 of the UPS 100 (i.e., the load on the inverter 108). In some examples, the second inductor 230 can be sized (e.g., increased) to provide a different charging capacity (up to the full capacity of the inverter 110).

[0059] In the standby operation mode, the control input selection circuit 226 couples the second end of the inductor 228 to the standby power input 214, such that standby DC power from the standby power supply 212 is provided to the converter 204. The converter 204 converts the standby DC power to DC power and supplies the DC power to the DC buses 206a, 206b.

[0060] Figure 5A and Figure 5B is a schematic diagram showing the operation of the converter 204 during the standby operation mode of the UPS.

[0061] As Figure 5A shown, during the standby operation mode and the positive DC bus cycle, the first converter switch 216 is operated to supply DC power derived from the standby DC power (provided by the standby power supply 212) to the positive DC bus 206a. In some examples, the first converter switch 216, the first inductor 228, and the first diode 232 operate as a boost converter to supply DC power to the positive DC bus 206a.

[0062] In an example of the standby operation mode during the positive DC bus cycle, the first switch 216a of the first converter switch 216 is turned on and off to provide boost converter operation. For example, when the first switch 216a is turned on (i.e., closed), the first end of the first inductor 228 is coupled to the neutral line. Thus, a conduction path 502 for the standby DC power is provided through the first converter switch 216, thereby exciting the first inductor 228. In one example, the conduction path 502 includes the body diode of the second switch 216b of the first converter switch 216. Similarly, when the first switch 216a is turned off (i.e., open), the first inductor 228 is decoupled from the neutral line. In this way, a conduction path 504 for the standby DC power is provided through the first inductor 228 and the first diode 232 to supply DC power to the positive DC bus 206a and charge the positive DC bus capacitor 236a.

[0063] As Figure 5B shown, during the standby operation mode and the negative DC bus cycle, the fourth converter switch 222 is operated to supply DC power derived from the standby DC power to the negative DC bus 206b. In some examples, the fourth converter switch 222, the second inductor 230, and the body diode of the third converter switch 220 operate as a buck-boost converter to supply DC power to the negative DC bus 206b.

[0064] In one example of the standby operation mode during the negative DC bus cycle, the fourth converter switch 222 is turned on and off to provide buck-boost converter operation. For example, when the fourth converter switch 222 is on (i.e., closed), the second end of the second inductor 230 is coupled to the standby power input 214. Thus, a conduction path 506 for standby DC power is provided through the fourth converter switch 222, thereby exciting the second inductor 230. In one example, the conduction path 506 includes a fifth converter switch 224, which is on (i.e., closed) during the negative DC bus cycle. Similarly, when the fourth converter switch 222 is off (i.e., open), the second inductor 230 is decoupled from the standby power input 214. In this way, a conduction path 508 is provided through the body diode of the third converter switch 220, allowing the second inductor 230 to stop being excited and supply DC power to the negative DC bus 206b and charge the negative DC bus capacitor 236b.

[0065] In one example, the positive DC bus cycle during the standby operation mode corresponds to the positive half-cycle of the output AC voltage. Similarly, the negative DC bus cycle during the standby operation mode corresponds to the negative half-cycle of the output AC voltage. In some examples, the output AC voltage is provided by an inverter (e.g., Figure 1 inverter 108) coupled to the DC buses 206a, 206b.

[0066] In certain examples, an alternative control scheme can be used to supply DC power to the DC buses 206a, 206b during the standby operation mode. For example, Figure 6 is a schematic diagram showing an alternative operation of the converter 204 for the positive DC bus cycle during the standby operation mode of the UPS.

[0067] As Figure 6 shown, during the standby operation mode and the positive DC bus cycle, the fifth converter switch 224 can be operated to supply DC power derived from standby DC power (provided by the standby power supply 212) to the positive DC bus 206a. In some examples, the body diodes of the fifth converter switch 224, the second inductor 230, and the second converter switch 218 operate as a boost converter to supply DC power to the positive DC bus 206a.

[0068] In one example of the standby operation mode during the positive DC bus cycle, the fifth converter switch 224 is turned on and off to provide boost converter operation. For example, when the fifth converter switch 224 is turned on (i.e., closed), the first end of the second inductor 230 is coupled to the neutral line. In this way, a conduction path 602 for standby DC power is provided through the fifth converter switch 224, thereby exciting the second inductor 230. In one example, the conduction path 602 includes the fourth converter switch 222, which is turned on (i.e., closed) during the positive DC bus cycle. Similarly, when the fifth converter switch 224 is turned off (i.e., open), the second inductor 230 is decoupled from the neutral line. In this way, a conduction path 604 is provided through the body diode of the second converter switch 218, thereby allowing the second inductor 230 to stop being excited and provide DC power to the positive DC bus 206a and charge the positive DC bus capacitor 236a.

[0069] In one example, the converter 204 can be configured to utilize Figure 6 a control scheme during the positive DC bus cycle of the standby operation mode, and utilize Figure 5B a control scheme during the negative DC bus cycle of the standby operation mode. In some examples, to support Figure 6 the control scheme, the second inductor 230 is sized (e.g., increased) to match the full capacity of the inverter 108. Due to the sizing of the second inductor 230, the converter 204 can operate at a charging capacity up to the full capacity of the inverter 108 during the online operation mode.

[0070] As described above, a more cost-effective and compact front-end topology for an online UPS is provided herein. In at least one embodiment, the front-end topology includes an integrated converter configured to operate as a PFC converter, a DC / DC converter, and a battery charger. In one example, the integrated converter is configured to provide power to the positive DC bus and the negative DC bus while charging the battery using the power from the positive DC bus and the negative DC bus. In some examples, by charging the battery from the DC bus using different components of the integrated converter while providing power to the DC bus, a separate charger and associated components can be eliminated from the front-end topology (and the UPS). In this way, the improved front-end topology can have a reduced number of components, thereby increasing the power density of the UPS and reducing costs.

[0071] In at least one embodiment, an uninterruptible power supply is described herein that includes an input terminal, an energy storage device interface, an output terminal, a power factor correction circuit (PFC), a capacitor, a bi-directional converter, and a switch. The input terminal is configured to receive input power from an input power source and has a line neutral connection coupled to a reference node. The energy storage device interface is configured to be coupled to an energy storage device to provide backup power and has an energy storage device neutral connection coupled to the reference node. The output terminal is configured to provide output power derived from at least one of the input power and the backup power. The power factor correction circuit (PFC) includes a PFC input terminal. The capacitor is coupled to the PFC and is current-coupled to the energy storage device interface. The bi-directional converter is coupled to the input terminal and is coupled to the energy storage device interface. The switch is coupled to the energy storage device interface and the PFC input terminal.

[0072] Having thus described several aspects of at least one embodiment of the present invention, it should be understood that various changes, modifications, and improvements will readily occur to those skilled in the art. These changes, modifications, and improvements are intended to be part of the present disclosure and are intended to be within the spirit and scope of the present invention. Accordingly, the foregoing description and drawings are merely illustrative.

Claims

1. An uninterruptible power supply (UPS), the UPS comprising: An input terminal configured to receive input AC power having an input AC voltage; A standby power input terminal configured to be coupled to a standby power supply and receive standby DC power from the standby power supply and supply DC power to the standby power supply for charging; A positive DC bus and a negative DC bus, the positive DC bus and the negative DC bus being electrically coupled to the standby power input terminal; A converter coupled to the input terminal, the standby power input terminal, and the positive DC bus and the negative DC bus, the converter comprising: A first inductor, A second inductor, A first converter switch configured to couple the first inductor to a neutral connection, A second converter switch configured to couple the second inductor to the positive DC bus, A third converter switch configured to couple the second inductor to the negative DC bus, and A fourth converter switch configured to couple the second inductor to the standby power input terminal; and At least one controller configured to: Operate the converter in a standby operation mode in response to determining that acceptable AC power is not available at the input terminal, Operate the first converter switch in the standby operation mode to supply DC power derived from the standby DC power to the positive DC bus via the first inductor, and Operate the fourth converter switch in the standby operation mode to supply DC power derived from the standby DC power to the negative DC bus via the second inductor.

2. The UPS according to claim 1, wherein, The at least one controller is further configured to: Operate the converter in a normal operation mode in response to determining that acceptable AC power is available at the input terminal.

3. The UPS according to claim 1, wherein, The at least one controller is further configured to operate the fourth converter switch in the standby operation mode to supply DC power derived from the standby DC power to the negative DC bus via the second inductor.

4. The UPS according to claim 3, wherein, Operating the fourth converter switch to supply DC power derived from the standby DC power to the negative DC bus via the second inductor includes operating the fourth converter switch to operate as a component of a buck-boost converter.

5. The UPS according to claim 3, wherein, Operating the fourth converter switch to supply DC power derived from the standby DC power to the negative DC bus via the second inductor includes controlling the fourth converter switch to couple the second inductor to the standby power input terminal and conduct power from the standby power input terminal to the second inductor via the fourth converter switch.

6. The UPS according to claim 5, wherein, Conducting power to the second inductor will energize the second inductor, and wherein operating the fourth converter switch to supply DC power derived from the standby DC power to the negative DC bus further includes controlling the fourth converter switch to decouple the second inductor from the standby power input terminal.

7. The UPS according to claim 6, wherein, Controlling the fourth converter switch to decouple the second inductor from the standby power input will de-energize the second inductor, and de-energizing the second inductor includes the second inductor releasing stored energy to the negative DC bus.

8. The UPS according to claim 2 further includes at least one controller, wherein, The converter further includes a fifth converter switch configured to couple the second inductor to the neutral connection, and the at least one controller is configured to: Operate the fifth converter switch in a standby operating mode to supply DC power derived from the standby DC power to the positive DC bus via the second inductor; And Operate the fourth converter switch in the standby operating mode to supply DC power derived from the standby DC power to the negative DC bus via the second inductor.

9. The UPS according to claim 1, further comprising at least one controller configured to operate the fourth converter switch to operate as a component of a buck-boost converter.

10. The UPS according to claim 1, further comprising at least one controller configured to control the fourth converter switch to couple the second inductor to the standby power input, thereby conducting power from the standby power input to the second inductor via the fourth converter switch.

11. The UPS according to claim 10, wherein, Conducting power to the second inductor will energize the second inductor, and wherein the at least one controller is further configured to control the fourth converter switch to decouple the second inductor from the standby power input.

12. The UPS according to claim 11, wherein, Controlling the fourth converter switch to decouple the second inductor from the standby power input will de-energize the second inductor, and de-energizing the second inductor includes the second inductor releasing stored energy to the negative DC bus.

13. A method of operating an uninterruptible power supply (UPS) having an input, a standby power input, a positive DC bus, a negative DC bus, and a converter, the input being configured to receive input AC power having an input AC voltage, the standby power input being configured to be coupled to a standby power source and receive standby DC power from the standby power source and supply DC power to the standby power source for charging, the positive DC bus and the negative DC bus being electrically coupled to the standby power input; the converter being coupled to the input, the standby power input, and the positive DC bus and the negative DC bus, the converter including a first inductor, a second inductor, a first converter switch, a second converter switch, a third converter switch, and a fourth converter switch, the first converter switch being configured to couple the first inductor to the neutral connection, the second converter switch being configured to couple the second inductor to the positive DC bus, the third converter switch being configured to couple the second inductor to the negative DC bus, the fourth converter switch being configured to couple the second inductor to the standby power input, the method comprising: In response to determining that acceptable AC power is not available at the input terminal, control the UPS to operate in a standby operation mode; Operate the first converter switch in the standby operation mode to supply DC power derived from the standby DC power to the positive DC bus via the first inductor; And Operate the fourth converter switch in the standby operation mode to supply DC power derived from the standby DC power to the negative DC bus via the second inductor.

14. At least one non-transitory computer-readable medium storing a sequence of computer-executable instructions for operating an uninterruptible power supply (UPS), the UPS having an input terminal, a standby power input terminal, a positive DC bus and a negative DC bus, and a converter, the input terminal being configured to receive input AC power having an input AC voltage, the standby power input terminal being configured to be coupled to a standby power source and receive standby DC power from the standby power source and supply DC power to the standby power source for charging, the positive DC bus and the negative DC bus being electrically coupled to the standby power input terminal; the converter being coupled to the input terminal, the standby power input terminal, and the positive DC bus and the negative DC bus, the converter including a first inductor, a second inductor, a first converter switch, a second converter switch, a third converter switch, and a fourth converter switch, the first converter switch being configured to couple the first inductor to a neutral connection, the second converter switch being configured to couple the second inductor to the positive DC bus, the third converter switch being configured to couple the second inductor to the negative DC bus, the fourth converter switch being configured to couple the second inductor to the standby power input terminal, the sequence of computer-executable instructions including instructions that direct at least one processor to perform the following operations: In response to determining that acceptable AC power is not available at the input terminal, control the UPS to operate in a standby operation mode; Operate the first converter switch in the standby operation mode to supply DC power derived from the standby DC power to the positive DC bus via the first inductor; and Operate the fourth converter switch in the standby operation mode to supply DC power derived from the standby DC power to the negative DC bus via the second inductor.

15. An uninterruptible power supply (UPS), the UPS comprising: An input terminal configured to receive input AC power having an input AC voltage; A standby power input terminal configured to be coupled to a standby power source and receive standby DC power from the standby power source and supply DC power to the standby power source for charging; A positive DC bus and a negative DC bus, the positive DC bus and the negative DC bus being electrically coupled to the standby power input terminal; A converter coupled to the input terminal, the standby power input terminal, and the positive DC bus and the negative DC bus, the converter including: A first inductor, A second inductor, A first converter switch configured to couple the first inductor to a neutral connection, A second converter switch configured to couple the second inductor to the positive DC bus, A third converter switch configured to couple the second inductor to the negative DC bus, and A fourth converter switch configured to couple the second inductor to the standby power input; and A fifth converter switch configured to couple the second inductor to the neutral connection; and At least one controller configured to: Operate the converter in a standby operation mode in response to determining that acceptable AC power is not available at the input, Operate the fifth converter switch in the standby operation mode to provide DC power derived from the standby DC power to the positive DC bus via the second inductor, and Operate the fourth converter switch in the standby operation mode to provide DC power derived from the standby DC power to the negative DC bus via the second inductor.

16. The UPS according to claim 15, wherein, Operating the fourth converter switch to provide DC power derived from the standby DC power to the negative DC bus via the second inductor includes operating the fourth converter switch to operate as a component of a buck-boost converter.

17. The UPS according to claim 15, wherein, Operating the fourth converter switch to provide DC power derived from the standby DC power to the negative DC bus via the second inductor includes controlling the fourth converter switch to couple the second inductor to the standby power input and conduct power from the standby power input to the second inductor via the fourth converter switch.

18. The UPS according to claim 17, wherein, Conducting power to the second inductor will energize the second inductor, and wherein operating the fourth converter switch to provide DC power derived from the standby DC power to the negative DC bus further includes controlling the fourth converter switch to decouple the second inductor from the standby power input.

19. The UPS according to claim 18, wherein, Controlling the fourth converter switch to decouple the second inductor from the standby power input will de-energize the second inductor, and wherein de-energizing the second inductor includes the second inductor releasing stored energy to the negative DC bus.

20. The UPS according to claim 15, further comprising at least one controller configured to operate the fourth converter switch to operate as a component of a buck-boost converter.

21. The UPS according to claim 15, wherein, Conducting power to the second inductor will energize the second inductor, and wherein the at least one controller is further configured to control the fourth converter switch to decouple the second inductor from the standby power input.

22. The UPS according to claim 21, wherein, Controlling the fourth converter switch to decouple the second inductor from the standby power input will de-energize the second inductor, and wherein de-energizing the second inductor includes the second inductor releasing stored energy to the negative DC bus.

Images