Patent Description:
The use of power devices, such as uninterruptible power supplies (UPS), to provide regulated, uninterrupted power for sensitive and/or critical loads, such as computer systems and other data processing systems, is known. Known uninterruptible power supplies include on-line UPS's, off-line UPS's, line interactive UPS's, as well as others. On-line UPS's provide conditioned AC power as well as back-up AC power upon interruption of a primary source of AC power. Off-line UPS's typically do not provide conditioning of input AC power but do provide back-up AC power upon interruption of the primary AC power source. Line interactive UPS's are similar to off-line UPS's in that they switch to battery power when a blackout occurs but also typically include a multi-tap transformer for regulating the output voltage provided by the UPS. Documents <CIT>, <CIT> and <CIT> disclose examples of UPS methods and systems according to available prior art.

At least one aspect of the present disclosure is directed to an Uninterruptible Power Supply (UPS). The UPS includes an input configured to receive input AC power, a DC output configured to provide output DC power to a load, an AC output configured to provide output AC power to the load, a charger coupled to the input and configured to convert the input AC power into DC power, a DC bus coupled to the charger and configured to receive the DC power, a DC-DC converter coupled to the DC bus and configured to convert the DC power from the DC bus into the output DC power, a bypass line coupled between the input and the AC output and configured to provide the input AC power to the AC output as the AC output power, and a controller coupled to the charger and configured to monitor a current demand at the DC output relative to a demand threshold operate, in response to a determination that the current demand at the DC output is below the demand threshold, the UPS in a first mode of operation by enabling the charger to provide DC power to the DC bus and operate, in response to a determination that the current demand at the DC output is above the demand threshold, the UPS in a second mode of operation by disabling the charger.

In one embodiment, the UPS includes an auxiliary power interface coupled to the DC bus, the auxiliary power interface configured to provide DC power from the DC bus to an auxiliary power source and to receive DC power from the auxiliary power source. In some embodiments, during the first mode of operation, the auxiliary power source is configured to receive the DC power provided by the charger for charging the auxiliary power source. In certain embodiments, the UPS includes a DC-DC converter coupled to the DC bus and configured to convert the DC power from the DC bus into the output DC power. In various embodiments, during the second mode of operation, the controller is further configured to operate the DC-DC converter to convert the DC power provided by the auxiliary power source into the output DC power.

In some embodiments, the demand threshold is a predetermined threshold. In one embodiment, the UPS is configured to operate in the first mode of operation to support the load while the load is drawing AC power from the AC output. In various embodiments, the UPS is configured to operate in the second mode of operation to support the load while the load is drawing DC power from the DC output.

Another aspect of the present disclosure is directed to an Uninterruptible Power Supply (UPS). The UPS includes an input configured to receive input AC power, a DC output configured to provide output DC power to a load, an AC output configured to provide output AC power to the load, a charger coupled to the input and configured to convert the input AC power into DC power, a DC bus coupled to the charger and configured to receive the DC power, a DC-DC converter coupled to the DC bus and configured to convert the DC power from the DC bus into the output DC power, a bypass line coupled between the input and the AC output and configured to provide the input AC power to the AC output as the AC output power, and a controller coupled to the charger and configured to monitor a current demand at the AC output relative to a demand threshold, operate, in response to a determination that the current demand at the AC output is above the demand threshold, the UPS in a first mode of operation by enabling the charger to provide DC power to the DC bus, and operate, in response to a determination that the current demand at the AC output is below the demand threshold, the UPS in a second mode of operation by disabling the charger.

In one embodiment, the UPS includes an auxiliary power interface coupled to the DC bus, the auxiliary power interface configured to provide DC power from the DC bus to an auxiliary power source and to receive DC power from the auxiliary power source. In some embodiments, during the first mode of operation, the auxiliary power source is configured to receive the DC power provided by the charger for charging the auxiliary power source. In various embodiments, a DC-DC converter coupled to the DC bus and configured to convert the DC power from the DC bus into the output DC power. In certain embodiments, during the second mode of operation, the controller is further configured to operate the DC-DC converter to convert the DC power provided by the auxiliary power source into the output DC power.

Another aspect of the present disclosure is directed to a non-transitory computer-readable medium storing thereon sequences of computer-executable instructions for operating an Uninterruptible Power Supply (UPS). The sequences of computer-executable instructions include instructions that instruct at least one processor to control the UPS to receive input AC power at an input from an input power source, provide, via a DC output, output DC power to a load, provide, via an AC output, output AC power to the load, monitor a current demand at the DC output relative to a demand threshold, operate, in response to a determination that the current demand at the DC output is below the demand threshold, the UPS in a first mode of operation by enabling a charger coupled to the input to convert the input AC power into DC power, and operate, in response to a determination that the current demand at the DC output is above the demand threshold, the UPS in a second mode of operation by disabling the charger.

In one embodiment, the sequences of instructions include instructions that instruct the at least one processor to control the UPS to provide, in the first mode of operation, the DC power from the charger to a DC bus to charge an auxiliary power source coupled to the DC bus, and provide, in the second mode of operation, DC power from the auxiliary power source to a DC-DC converter coupled to the DC bus, the DC-DC converter being configured to convert the DC power from the auxiliary power source into the output DC power. In some embodiments, the UPS is operated in the first mode of operation to support the load while the load is drawing AC power from the AC output. In various embodiments, the UPS is operated in the second mode of operation to support the load while the load is drawing DC power from the DC output.

The figures are included to provide illustration and a further understanding of the various aspects and embodiments, and are incorporated in and constitute a part of this specification, but are not intended as a definition of the limits of the invention. In the figures:.

Any references to examples, embodiments, components, elements or acts of the systems and methods herein referred to in the singular may also embrace embodiments including a plurality, and any references in plural to any embodiment, component, element or act herein may also embrace embodiments including only a singularity. References in the singular or plural form are not intended to limit the presently disclosed systems or methods, their components, acts, or elements. The use herein of "including," "comprising," "having," "containing," "involving," and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. References to "or" may be construed as inclusive so that any terms described using "or" may indicate any of a single, more than one, and all of the described terms. In addition, in the event of inconsistent usages of terms between this document and documents incorporated herein by reference, the term usage in the incorporated references is supplementary to that of this document; for irreconcilable inconsistencies, the term usage in this document controls.

As discussed above, power supplies, such as uninterruptible power supplies (UPS), are often times used to provide regulated, uninterrupted power to sensitive and/or critical loads. An offline UPS connects a load directly to utility power when utility power is available and sufficient to power a load. The offline UPS also includes a charger which utilizes the utility power to charge a backup power source (e.g., a battery). When utility power is unavailable or insufficient to power the load, the offline UPS operates a DC/AC inverter to convert DC power from the backup power source into desired AC power, which is provided to the load.

An online UPS rectifies input AC power provided by an electric utility using a Power Factor Correction converter circuit (PFC) to provide DC power to at least one DC bus. The rectified DC power on the DC bus(es) may be used to charge a battery while mains power is available. In the absence of mains power, the battery discharges and provides DC power to the DC bus(es). From the DC power on the DC bus(es), an inverter generates an AC output voltage that is provided to a load. Since power is provided to the DC bus(es) from either mains or the battery, the output power of the UPS is uninterrupted if the mains fails and the battery is sufficiently charged. Online UPS's may also operate in a bypass mode where unconditioned power with basic protection is provided directly from an AC power source to a load via a bypass line.

Similarly, a UPS can be configured as a Direct Current (DC)-UPS. A DC-UPS utilizes an AC/DC converter to convert input AC power provided by an electric utility into DC power and provide the converted DC power to at least one DC bus. The DC power on the DC bus(es) may be used to charge a battery while mains power is available. In the absence of mains power, the battery discharges and provides DC power to the DC bus(es). From the DC power on the DC bus(es), a DC/DC converter generates a DC output voltage that is provided to a load. DC-UPS's may also include an AC output coupled to the input to provide AC output power to the load.

<FIG> is a block diagram of one embodiment of a UPS <NUM>. In one example, the UPS <NUM> is configured as a DC-UPS. The UPS <NUM> includes an input <NUM>, a charger <NUM>, a DC bus <NUM>, a DC/DC converter <NUM>, a DC output <NUM>, an AC output <NUM>, and a backup power interface <NUM>. In some examples, the backup power interface <NUM> is configured to receive backup DC power from a battery <NUM>. In certain examples, the UPS <NUM> may include the battery <NUM>; however, in other examples the battery <NUM> may be external to the UPS <NUM>.

In addition, a controller <NUM> may be included in the UPS <NUM>. In one example, the controller <NUM> is coupled to and configured to operate the charger <NUM> and the DC/DC converter <NUM>. In certain examples, the controller <NUM> is external to the UPS <NUM>. In some examples, the controller <NUM> includes one or more general computing processors, specialized processors, or microcontrollers. The controller <NUM> may include specially-programmed, special-purpose hardware, for example, an application-specific integrated circuit (ASIC), or more generally designed hardware, such as a field programmable gate array (FPGA), or a general purpose processor. In some examples, the controller <NUM> is connected to one or more memory devices, such as a disk drive, memory, flash memory, embedded or on-chip memory, or other device for storing data. In certain examples, the controller <NUM> may be one or more controllers including one or more components such as one or more processors.

As shown, the input <NUM> is coupled to the charger <NUM> and the AC output <NUM>. The DC bus <NUM> is coupled between the charger <NUM> and the DC/DC converter <NUM>. The DC output <NUM> is coupled to the DC/DC converter <NUM>. The backup power interface <NUM> is coupled to the DC bus <NUM>.

The UPS <NUM> is generally configured to operate in one of at least two modes of operation, including an AC mode and DC mode. In one example, the mode of operation of the UPS <NUM> is dependent upon a quality level of AC power received at the input <NUM>. For example, when the AC power received at the input <NUM> is acceptable (i.e., within a specified range of acceptable electrical parameters), the UPS <NUM> may be configured to operate in the AC mode. Otherwise, when the AC power received at the input <NUM> is not acceptable (i.e., not within a specified range of acceptable electrical parameters), the UPS <NUM> may be configured to operate in the DC mode. In some examples, the controller <NUM> is coupled to the input <NUM> and configured to monitor the input <NUM> to determine whether to operate the UPS <NUM> in the AC mode or the DC mode.

In the AC mode, the input <NUM> receives AC power from an external source (for example, from a utility mains AC power supply) and provides the received power to the AC output <NUM> and to the charger <NUM>. The AC output <NUM> receives the AC power from the input <NUM> and provides the AC power to an external load (not shown). While not shown, a filter circuit may be employed between the input <NUM> and the AC output <NUM>. The charger <NUM> receives the AC power from the input <NUM>, converts the AC power into DC power, and charges the battery <NUM> (via the backup power interface <NUM>) with the DC power derived from the input <NUM>.

In the DC mode, the charger <NUM> is turned off (i.e., disabled) and discontinues charging the battery <NUM>. The battery <NUM> discharges stored DC power to the DC/DC converter <NUM>, via the backup power interface <NUM> and the DC bus <NUM>. The DC/DC converter <NUM> regulates DC power received from the battery <NUM> and provides regulated DC power to the DC output <NUM>. The DC output <NUM> receives the power from the DC/DC converter <NUM> and provides the DC power to the external load.

In some cases, DC-UPS's (e.g., UPS <NUM>) can be used to provide power to Information Technology (IT) equipment. The IT load may have multiple operating states with its own intelligent decision-making unit (e.g., controller). For example, the IT load may have an AC input and a DC input and be configured to operate in an AC mode and a DC mode. As such, the DC-UPS and the IT load may together form a power supply system having a plurality of operational configurations.

It is typically desired for the DC-UPS and the load to both be operating in a similar configuration (e.g., both in an AC mode or both in a DC mode). However, often times the UPS (e.g., <NUM>) is developed by one entity (e.g., a vendor) while the load (e.g., <NUM>) is developed by another entity (e.g., a customer). As such, the vendor may have limited or no access to detailed-design descriptions and/or behavior of the load. This may pose a challenge to the vendor to ensure that the UPS works in the same mode as the load (e.g., AC or DC mode). For example, the UPS may utilize different criteria (e.g., thresholds) than the load for determining which mode to operate in. In many cases, there may be no communication between the UPS and load, and the UPS may be unable to determine which mode the load is operating in, or vice versa.

As such, an improved system and method for controlling a UPS is provided herein. In at least one embodiment, the current demand at the DC output and/or the AC output of the UPS is monitored relative to a demand threshold. In one example, based on a comparison of the current demand and the demand threshold, the UPS is operated in either the AC mode or the DC mode to match the operating mode of the load. In some examples, transitioning the UPS between the AC and DC modes of operation includes enabling/disabling the charger of the UPS.

<FIG> a block diagram of one embodiment of a power supply system <NUM> in accordance with aspects described herein. As shown, the power supply system <NUM> includes the UPS <NUM> and a load <NUM>. In one example, the load <NUM> is an IT load having a DC input <NUM> and an AC input <NUM>. The DC output <NUM> of the UPS <NUM> is coupled to the DC input <NUM> of the load <NUM>. Likewise, the AC output <NUM> of the UPS <NUM> is coupled to the AC input <NUM> of the load <NUM>.

As described above, the load <NUM> may be configured to operate in an AC mode and a DC mode. In one example, the load <NUM> includes a load controller <NUM> configured to operate the load <NUM> in the AC and DC modes. In some examples, the load controller <NUM> monitors the AC input <NUM> and/or the DC input <NUM> to determine whether to operate the load <NUM> in the AC mode or the DC mode. For example, when the AC power provided by the UPS <NUM> to the AC input <NUM> is acceptable (i.e., above a power quality threshold), the load controller <NUM> may operate the load <NUM> in the AC mode. Similarly, when the AC power provided by the UPS <NUM> to the AC input <NUM> is unacceptable (i.e. below a power quality threshold), the load controller <NUM> may operate the load <NUM> in the DC mode.

In some examples, there is no communication between the UPS <NUM> and the load <NUM>, and the UPS <NUM> may be unable to determine which mode the load <NUM> is operating in, or vice versa. For example, the UPS <NUM> may utilize different criteria (e.g., thresholds) than the load <NUM> for determining which mode to operate in (e.g., AC or DC). As such, the power supply system <NUM> may operate in various desirable and undesirable configurations depending on the quality level of the input AC power.

For example, <FIG> is a table <NUM> illustrating various operational configurations of the power supply system <NUM> in accordance with aspects described herein. In a first scenario <NUM>, the AC power received at both the input <NUM> of the UPS <NUM> and the AC input <NUM> of the load <NUM> is recognized as being "acceptable" by both the UPS <NUM> and the load <NUM>. As a result, both the UPS <NUM> and the load <NUM> operate in their respective AC modes of operation. In the AC mode of the UPS <NUM>, the received AC power is provided to the AC output <NUM> and to the charger <NUM>. The AC output <NUM> receives the power from the input <NUM> and provides the AC power to the AC input <NUM> of the load <NUM>. The charger <NUM> converts the AC power into DC power and charges the battery <NUM>. While operating in the AC mode, the load <NUM> draws AC power via the AC input <NUM>. As such, the DC/DC converter <NUM> of the UPS <NUM> operates in a no-load state, since the load <NUM> is not drawing power via the DC input <NUM>.

In a second scenario <NUM>, the AC power received at both the input <NUM> of the UPS <NUM> and the AC input <NUM> of the load <NUM> is recognized as being "acceptable" by the UPS <NUM> and "unacceptable" by the load <NUM>. As a result, the UPS <NUM> operates in the AC mode and the load <NUM> operates in the DC mode. In the AC mode of the UPS <NUM>, the received AC power is provided to the AC output <NUM> and to the charger <NUM> for charging of the battery <NUM>. However, since the load <NUM> is operating in the DC mode, the load <NUM> draws power via the DC input <NUM>. In order to support the load <NUM>, the DC/DC converter <NUM> is operated at a full-load state to support the power draw of the load <NUM> at the DC output <NUM> of the UPS <NUM>.

In a third scenario <NUM>, the AC power received at both the input <NUM> of the UPS <NUM> and the AC input <NUM> of the load <NUM> is recognized as being "unacceptable" by the UPS <NUM> and "acceptable" by the load <NUM>. As a result, the UPS <NUM> operates in the DC mode and the load <NUM> operates in the AC mode. In the DC mode of the UPS <NUM>, the charger <NUM> is turned off (i.e., disabled) and the battery <NUM> discharges stored DC power to the DC/DC converter <NUM>, via the backup power interface <NUM> and the DC bus <NUM>. The DC/DC converter <NUM> regulates the DC power received from the battery <NUM> and provides regulated DC power to the DC output <NUM>. However, since the load <NUM> is operating in the AC mode, the load <NUM> draws power via the AC input <NUM>.

In a fourth scenario <NUM>, the AC power received at both the input <NUM> of the UPS <NUM> and the AC input <NUM> of the load <NUM> is recognized as being "unacceptable" by both the UPS <NUM> and the load <NUM>. As a result, both the UPS <NUM> and the load <NUM> operate in their respective DC modes of operation. In the DC mode of the UPS <NUM>, the charger <NUM> is turned off (i.e., disabled) and the battery <NUM> discharges stored DC power to the DC/DC converter <NUM>, via the backup power interface <NUM> and the DC bus <NUM>. The DC/DC converter <NUM> regulates the DC power received from the battery <NUM> and provides regulated DC power to the DC output <NUM>. While operating in the DC mode, the load <NUM> draws DC power via the DC input <NUM>.

In some examples, by operating the UPS <NUM> and the load <NUM> in different modes, performance of the UPS <NUM> can be degraded. For example, in the second scenario <NUM>, an excessive amount of heat is generated from the charger <NUM> and the DC/DC converter <NUM> operating simultaneously. Likewise, in the third scenario <NUM>, the battery <NUM> is continuously loaded by the DC/DC converter <NUM> and is drained off (or partially discharged) while the DC/DC converter <NUM> operates in a no-load state. As such, it may be desired to prevent the power supply system <NUM> from operating in these undesirable scenarios.

<FIG> a block diagram of one embodiment of a power supply system <NUM> in accordance with aspects described herein. As shown, the power supply system <NUM> includes a UPS <NUM> and the load <NUM>. In one example, the UPS <NUM> is similar to the UPS <NUM> of <FIG>, except the UPS <NUM> includes a current sensor <NUM> configured to monitor (or sense) current at the DC output <NUM> of the UPS <NUM>.

In some examples, the current sensor <NUM> is included in the controller <NUM> of the UPS <NUM>; however, in other examples, the current sensor <NUM> is external to the controller <NUM>. It should be appreciated that this disclosure is not limited to a particular type of current sensor. For example, the current sensor <NUM> may be any type of current sensor used to detect, monitor, or measure current (e.g., Hall-effect sensor). In certain examples, the current sensor <NUM> provides values indicating the current demand at the DC output <NUM> to the controller <NUM>. In other examples, the controller <NUM> includes additional circuitry (e.g., Analog-to-Digital Converter) configured to process one or more signals provided by the current sensor <NUM> to determine the current demand at the DC output <NUM>. In some examples, the controller <NUM> is configured to use the values or signals provided from the current sensor <NUM> to determine the power demand at the DC output <NUM>.

<FIG> is a state diagram <NUM> illustrating operation of the power supply system <NUM> in accordance with aspects described herein. In some examples, the state diagram <NUM> corresponds to a control method carried out by the controller <NUM> of the UPS <NUM>.

In one example, the load <NUM> is configured to operate in either the AC mode or the DC mode based the quality of the AC power provided to the load <NUM> by the UPS <NUM>. As shown, when the AC power provided by the UPS <NUM> is recognized as being "unacceptable" by the load <NUM> (i.e., "Condition A"), the load <NUM> operates in the DC mode. As such, the load <NUM> begins to draw power from the DC output <NUM> of the UPS <NUM> (via the DC input <NUM> of the load <NUM>).

As described above, the controller <NUM> is configured to monitor the current demand at the DC output <NUM> (via the current sensor <NUM>). In some examples, the controller <NUM> is configured to monitor the current demand at the DC output <NUM> relative to a demand threshold. In one example, the demand threshold is a predetermined threshold; however, in other examples, the demand threshold may be a dynamic threshold configured to update based on one or more operating conditions/parameters of the UPS <NUM> or the load <NUM>. In response to a determination that the current demand at the DC output <NUM> is above the demand threshold, the UPS <NUM> is configured to operate in the DC mode. As such, the UPS <NUM> can detect that the load <NUM> is operating in the DC mode and transition to its corresponding DC mode without communicating with the load <NUM>. In certain examples, the UPS <NUM> transitions to the DC mode by disabling the charger <NUM> to reduce the amount of heat generated by the UPS <NUM> while the DC/DC converter <NUM> is operated to support the load <NUM>.

Similarly, when the AC power provided by the UPS <NUM> is recognized as being "acceptable" by the load <NUM> (i.e., "Condition B"), the load <NUM> operates in the AC mode and begins to draw power from the AC output <NUM> of the UPS <NUM> (via the AC input <NUM> of the load <NUM>). As such, the current demand at the DC output <NUM> of the UPS <NUM> begins to decrease. In response to a determination that the current demand at the DC output <NUM> is below the demand threshold, the UPS <NUM> transitions to the AC mode. As such, the UPS <NUM> can detect that the load <NUM> is operating in the AC mode and transition to its corresponding AC mode without communicating with the load <NUM>. In certain examples, the UPS <NUM> transitions to the AC mode by enabling the charger <NUM> to charge the battery <NUM>, preventing the battery <NUM> from being drained off by the DC/DC converter <NUM> while providing AC power to the AC output <NUM> to support the load <NUM>.

In some examples, the current sensor <NUM> can be configured to monitor the current demand at the input of the DC/DC converter <NUM> to provide an indication of the current demand at the DC output <NUM>. In other examples, the controller <NUM> is configured to monitor one or more internal parameters of the DC/DC converter <NUM> to infer the current demand at the DC output <NUM>.

<FIG> a block diagram of another embodiment of a power supply system <NUM> in accordance with aspects described herein. As shown, the power supply system <NUM> includes a UPS <NUM> and the load <NUM>. In one example, the UPS <NUM> is similar to the UPS <NUM> of <FIG>, except the UPS <NUM> includes a current sensor <NUM> configured to monitor (or sense) current at the AC output <NUM> of the UPS <NUM>. In some examples, the current sensor <NUM> is substantially the same as the current sensor <NUM> of the UPS <NUM>.

In one example, the load <NUM> is configured to operate in either the AC mode or the DC mode based on the quality of the AC power provided to the load <NUM> by the UPS <NUM>. As shown, when the AC power provided by the UPS <NUM> is recognized as being "unacceptable" by the load <NUM> (i.e., "Condition A"), the load <NUM> operates in the DC mode. As such, the load <NUM> begins to draw power from the DC output <NUM> of the UPS <NUM> (via the DC input <NUM> of the load <NUM>).

As described above, the controller <NUM> is configured to monitor the current demand at the AC output <NUM> (via the current sensor <NUM>). In some examples, the controller <NUM> is configured to monitor the current demand at the AC output <NUM> relative to a demand threshold. In one example, the demand threshold is a predetermined threshold; however, in other examples, the demand threshold is a dynamic threshold configured to update based on one or more operating conditions/parameters of the UPS <NUM> or the load <NUM>. In response to a determination that the current demand at the AC output <NUM> is below the demand threshold, the UPS <NUM> is configured to operate in the DC mode. As such, the UPS <NUM> can detect that the load <NUM> is operating in the DC mode and transition to its corresponding DC mode without communicating with the load <NUM>. In certain examples, the UPS <NUM> transitions to the DC mode by disabling the charger <NUM> to reduce the amount of heat generated by the UPS <NUM> while the DC/DC converter <NUM> is operated to support the load <NUM>.

Similarly, when the AC power provided by the UPS <NUM> is recognized as being "acceptable" by the load <NUM> (i.e., "Condition B"), the load <NUM> operates in the AC mode and begins to draw power from the AC output <NUM> of the UPS <NUM> (via the AC input <NUM> of the load <NUM>). As such, the current demand at the AC output <NUM> of the UPS <NUM> begins to increase. In response to a determination that the current demand at the AC output <NUM> is above the demand threshold, the UPS <NUM> transitions to the AC mode. As such, the UPS <NUM> can detect that the load <NUM> is operating in the AC mode and transition to its corresponding AC mode without communicating with the load <NUM>. In certain examples, the UPS <NUM> transitions to the AC mode by enabling the charger <NUM> to charge the battery <NUM>, preventing the battery <NUM> from being drained off by the DC/DC converter <NUM> while providing AC power to the AC output <NUM> to support the load <NUM>.

In some examples, the UPS (e.g., <NUM> or <NUM>) can be configured to monitor the current demand at both the DC output <NUM> and the AC output <NUM>. By monitoring both the DC output <NUM> and the AC output <NUM>, the UPS may be capable of anticipating a mode transition of the load <NUM>. As such, the UPS may transition between the AC mode and the DC mode with a faster response time, which can be beneficial in specific high performance applications.

Claim 1:
An Uninterruptible Power Supply, UPS, (<NUM>), the UPS comprising:
an input (<NUM>) configured to receive input AC power;
a DC output (<NUM>) configured to provide output DC power to a load;
an AC output (<NUM>) configured to provide output AC power to the load;
a charger (<NUM>) coupled to the input (<NUM>) and configured to convert the input AC power into DC power;
a DC bus coupled to the charger (<NUM>) and configured to receive the DC power;
a DC-DC converter (<NUM>) coupled to the DC bus and configured to convert the DC power from the DC bus into the output DC power;
a bypass line coupled between the input and the AC output and configured to provide the input AC power to the AC output as the AC output power; and
a controller (<NUM>) coupled to the charger (<NUM>) and configured to:
monitor a current demand at the DC output (<NUM>) relative to a demand threshold;
operate, in response to a determination that the current demand at the DC output (<NUM>) is below the demand threshold, the UPS (<NUM>) in a first mode of operation by enabling the charger to provide DC power to the DC bus; and
operate, in response to a determination that the current demand at the DC output (<NUM>) is above the demand threshold, the UPS (<NUM>) in a second mode of operation by disabling the charger (<NUM>).