High-efficiency control method for uninterruptible power supply

Abstract

A high-efficiency control method for an uninterruptible power supply (UPS). The UPS includes a charger configured to convert input AC power into DC power having a first voltage level; a DC-DC converter configured to convert the DC power having the first voltage level into DC power having a DC bus voltage level; a DC bus coupled to the DC-DC converter; an inverter coupled to an output terminal via an output switch and configured to convert DC power having the DC bus voltage level into output AC power; a bypass line including a bypass switch coupled between the input terminal and the output switch; a rectifier coupled between the bypass line and the DC bus; and a controller configured to operate the UPS such that the DC-DC converter provides DC power to the DC bus in a first operating mode and the rectifier provides DC power to the DC bus in a second operating mode. The present invention overcomes at least one disadvantage of the prior art.

Description

Technical Field

[0001] The present invention generally relates to uninterruptible power supplies (UPS). Background Art

[0002] The use of power devices, such as uninterruptible power supplies (UPS), to provide stable and uninterrupted power to sensitive and / or critical loads, such as computer systems and other data processing systems, is a known technology. Known UPSs include online UPS, offline UPS, line interactive UPS, and other devices. Online UPS provides conditioned AC power and backup AC power in the event of a main AC power outage. Offline UPS typically does not provide conditioning of the input AC power, but does provide backup AC power in the event of a main AC power outage. Line interactive UPS, like offline UPS, switches to battery power in the event of a power outage, but typically also includes a multi-tap transformer to regulate the output voltage provided by the UPS. Summary of the Invention

[0003] At least one aspect of the present invention is directed to an uninterruptible power supply (UPS). The UPS includes: an input terminal configured to receive input AC power; an output terminal configured to provide output AC power to a load; a charger coupled to the input terminal, the charger configured to convert the input AC power into DC power having a first voltage level; a DC-DC converter coupled to the charger, the DC-DC converter configured to convert the DC power having the first voltage level into DC power having a DC bus voltage level; a DC bus coupled to the DC-DC converter, the DC bus configured to receive DC power having the DC bus voltage level; an inverter coupled to the output terminal via an output switch, the inverter configured to convert the DC power having the DC bus voltage level into the output AC power, and provide the output AC power to the load via the output switch. an output terminal; a bypass line comprising a bypass switch, the bypass line being coupled between the input terminal and the output switch, and the bypass line being configured to provide the input AC power to the output terminal through the output switch; a rectifier being coupled between the bypass line and the DC bus, and the rectifier being configured to convert the input AC power on the bypass line into DC power having the DC bus voltage level, and to provide the DC power having the DC bus voltage level to the DC bus; and a controller being coupled to the charger, the DC-DC converter, the inverter, and the bypass switch, the controller being configured to operate the uninterruptible power supply: in a first operating mode, to provide DC power to the DC bus through the DC-DC converter; and in a second operating mode, to provide DC power to the DC bus through the rectifier.

[0004] In one embodiment, the controller is further configured to operate the uninterruptible power supply (UPS) to provide DC power derived from the input AC power to the DC bus by operating the charger and the DC-DC converter in the first operating mode. In some embodiments, the UPS further includes a backup power input coupled to the DC-DC converter and configured to receive the backup DC power having the first voltage level from a backup power source. In certain embodiments, the controller is further configured to operate the UPS to provide DC power derived from the backup DC power to the DC bus by operating the DC-DC converter in the first operating mode. In various embodiments, the controller is further configured to operate the charger to provide DC power derived from the input AC power having the first voltage level to the backup power input to charge the backup power source during the second operating mode.

[0005] In some embodiments, the controller is further configured to operate the DC-DC converter to provide DC power having the first voltage level from the DC bus to the backup power supply input to charge the backup power supply during the second operating mode. In various embodiments, the controller is further configured to operate the DC-DC converter and inverter to provide output AC power derived from the backup DC power in a third operating mode. In certain embodiments, the controller is further configured to operate the uninterruptible power supply to decouple the bypass line from the output terminal by controlling the output switch in the first operating mode. In one embodiment, the controller is further configured to operate the uninterruptible power supply to couple the bypass line to the output terminal by controlling the output switch in the second operating mode, such that the input AC power is provided to the output terminal as the output AC power.

[0006] In various embodiments, the DC bus includes a first voltage rail, a second voltage rail, and at least one DC bus capacitor coupled between the first voltage rail and the second voltage rail. In some embodiments, the controller is configured to operate the uninterruptible power supply to charge the at least one DC bus capacitor to the DC bus voltage level in the first operating mode. In one embodiment, the controller is configured to operate the uninterruptible power supply to maintain the DC bus voltage level in the second operating mode.

[0007] Another aspect of the present invention is directed to a non-transitory computer-readable medium having stored thereon a computer-executable instruction sequence for controlling an uninterruptible power supply, wherein the uninterruptible power supply includes an output switch, wherein the output switch is configured to selectively couple a bypass line to an output terminal of the uninterruptible power supply, and the computer-executable instruction sequence includes a plurality of instructions, wherein the plurality of instructions instruct at least one processor to operate the uninterruptible power supply to perform the following steps: receiving input AC power at an input terminal of the uninterruptible power supply; decoupling the bypass line from the output terminal through the output switch; and in response to the decoupling of the bypass line from the output terminal, operating a DC-DC converter to have a first voltage. the DC-DC converter converts the DC power from the bypass line into DC power having a DC bus voltage level; provides the DC power having the DC bus voltage level from the DC-DC converter to a DC bus to charge the DC bus to the DC bus voltage level; in response to the charging of the DC bus, turns off the DC-DC converter through the output switch and couples the bypass line to the output terminal; provides the input AC power to the output terminal through the bypass line; converts the input AC power on the bypass line into DC power having the DC bus voltage level using a rectifier; and provides the DC power having the DC bus voltage level to the DC bus through the rectifier to maintain the DC bus voltage level.

[0008] In one embodiment, the computer-executable instruction sequence includes instructions for causing the at least one processor to execute the uninterruptible power supply (UPS) to: operate a charger coupled to the input terminal to convert the input AC power to DC power having the first voltage level. In some embodiments, the computer-executable instruction sequence includes instructions for causing the at least one processor to execute the uninterruptible power supply (UPS) to: operate the DC-DC converter to convert DC power provided from the charger, thereby operating the DC-DC converter to convert the DC power having the first voltage level to DC power having the DC bus voltage level. In certain embodiments, the computer-executable instruction sequence includes instructions for causing the at least one processor to execute the uninterruptible power supply (UPS) to: receive backup DC power having the first voltage level from a backup power source at a backup power input coupled to the DC-DC converter. In various embodiments, the computer-executable instruction sequence includes instructions that cause the at least one processor to operate the uninterruptible power supply to perform the following steps: converting the backup DC power provided from the backup power supply by operating the DC-DC converter, and operating the DC-DC converter to convert DC power having the first voltage level into DC power having the DC bus voltage level.

[0009] In some embodiments, the sequence of computer-executable instructions includes instructions for causing the at least one processor to operate the uninterruptible power supply to: operate the charger to provide DC power having the first voltage level to the backup power input to charge the backup power supply. In various embodiments, the sequence of computer-executable instructions includes instructions for causing the at least one processor to operate the uninterruptible power supply to: in response to a condition in which the input AC power is unacceptable, operate the DC-DC converter and an inverter coupled to the DC bus to provide output AC power derived from the backup DC power. In one embodiment, the sequence of computer-executable instructions includes instructions for causing the at least one processor to operate the uninterruptible power supply to: provide DC power having a DC bus voltage level from the DC-DC converter to the DC bus, and charge the DC bus to the DC bus voltage level by charging at least one DC bus capacitor to the DC bus voltage level. In some embodiments, the sequence of computer-executable instructions includes instructions for causing the at least one processor to execute the uninterruptible power supply to perform the following steps: operating a bypass switch to couple the input terminal to the output terminal through the bypass line.

[0010] Another aspect of the present invention is directed to a method for operating an uninterruptible power supply (UPS). The UPS includes an output switch configured to selectively couple a bypass line to an output terminal of the UPS. The method includes: receiving input AC power at an input end of the uninterruptible power supply; decoupling the bypass line from the output end through the output switch; in response to the bypass line being decoupled from the output end, operating a DC-DC converter to convert DC power having a first voltage level into DC power having a DC bus voltage level; providing DC power having the DC bus voltage level from the DC-DC converter to a DC bus to charge the DC bus to the DC bus voltage level; in response to the DC bus being charged, turning off the DC-DC converter through the output switch and coupling the bypass line to the output end; providing the input AC power to the output end through the bypass line; using a rectifier to convert the input AC power on the bypass line into DC power having the DC bus voltage level; and providing DC power having the DC bus voltage level to the DC bus through the rectifier to maintain the DC bus voltage level.

[0011] Another aspect of the present invention relates to an assembling method of an uninterruptible power supply, the assembling method comprising: providing a charger, the charger being configured to be coupled to an input terminal, the charger being configured to receive input AC power through the input terminal and converting the input AC power into DC power having a first voltage level; coupling a DC-DC converter to the charger, the DC-DC converter being configured to convert the DC power having the first voltage level into DC power having a DC bus voltage level; coupling a DC bus to the DC-DC converter, the DC bus being configured to receive DC power having the DC bus voltage level; coupling an inverter to the DC bus, the inverter being configured to convert the DC power having the DC bus voltage level into the output AC power, and providing the output AC power to the UPS via an output switch. supplying an output terminal; coupling a bypass line including a bypass switch between the input terminal and the output switch, the bypass line being configured to provide the input AC power to the output terminal through the output switch; coupling a rectifier between the bypass line and the DC bus, the rectifier being configured to convert the input AC power on the bypass line into DC power having the DC bus voltage level and provide the DC power having the DC bus voltage level to the DC bus; and coupling a controller to the charger, the DC-DC converter, the inverter and the bypass switch, the controller being configured to operate the uninterruptible power supply: in a first operating mode, providing DC power to the DC bus through the DC-DC converter; and in a second operating mode, providing DC power to the DC bus through the rectifier. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Various aspects of at least one embodiment are discussed below with reference to the accompanying drawings, which are not intended to be drawn to scale. The included drawings provide illustration and further understanding of the various aspects and embodiments, and are incorporated into and constitute a part of this specification but are not intended to define limitations of the invention. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For clarity, not every component may be labeled in every figure.

[0013] In the picture:

[0014] Figure 1 is a functional block diagram of an uninterruptible power supply (UPS) according to aspects described herein.

[0015] Figure 2 is a functional block diagram of a UPS according to aspects described herein.

[0016] Figure 3is a flow chart of a method for controlling a UPS according to aspects described herein.

[0017] Figure 4A is a diagram illustrating operation of a UPS according to aspects described herein.

[0018] Figure 4B is a diagram illustrating operation of a UPS according to aspects described herein.

[0019] Figure 4C is a diagram illustrating operation of a UPS according to aspects described herein.

[0020] Figure 5 is a graph of various waveforms associated with operation of a UPS according to aspects described herein.

[0021] Figure 6 is a schematic diagram of a UPS according to aspects described herein. DETAILED DESCRIPTION

[0022] The examples of the methods and systems discussed herein are not limited in their application to the following description or the configuration details and arrangement of components shown in the accompanying drawings. The methods and systems can be implemented in other embodiments and can be practiced or executed in various ways. The examples of specific embodiments provided herein are for illustrative purposes only and are not intended to be limiting. In particular, the actions, components, elements, and features discussed in conjunction with any one or more examples are not intended to be excluded from similar effects in any other examples.

[0023] In addition, the wording and terms used herein are for descriptive purposes and should not be construed as limiting. Any reference to an example, embodiment, component, element, or action of a system or method mentioned herein in the singular may also include multiple embodiments, and any reference herein to any embodiment, component, element, or action in the plural may also include only the singular embodiment. References in the singular or plural are not intended to limit the presently disclosed systems or methods, their components, actions, or elements. The use of "including," "comprising," "having," "containing," "involving," and variations thereof herein is intended to encompass the items listed thereafter and their equivalents and other items. References to "or" may be interpreted as inclusive, such that any term described using "or" may indicate any one of the described terms, more than one, and all of the described terms. In addition, in the event of inconsistencies in the usage of terms between this document and the documents incorporated herein by reference, the usage of the terms in the incorporated references supplements this document. For inconsistencies, the usage of the terms in this document shall prevail.

[0024] As mentioned above, power devices, such as uninterruptible power supplies (UPS), are typically used to provide stable and uninterrupted power to sensitive and / or critical loads. When the mains power is available and sufficient to power the load, an offline UPS connects the load directly to the utility power. The offline UPS also includes a charger that uses the utility power to charge a backup power source (e.g., a battery). When the utility power is unavailable or insufficient to power the load, the offline UPS operates a DC-AC inverter to convert the DC power from the backup power source into the required AC power and provide it to the load.

[0025] For example, Figure 1 FIG1 is a block diagram of an embodiment of an offline UPS 100. The UPS 100 includes an input terminal 102, a bypass line 104, a bypass switch 106, a charger 108, a DC-DC converter 110, DC buses 112a and 112b (collectively referred to herein as DC bus 112), an inverter 116, an output switch 118, and an output terminal 120. In one embodiment, the DC bus 112 includes a positive rail 112a and a negative rail 112b. In some embodiments, the UPS 100 may include a battery 112. However, in other embodiments, the battery 112 may be external to the UPS 100.

[0026] Additionally, the USP 100 may include a controller 124. In one embodiment, the controller 124 may be coupled and configured to operate the bypass switch 106, the charger 108, the DC-DC converter 110, the inverter 116, and the output switch 118. In some embodiments, the controller 124 may be external to the USP 100. In some embodiments, the controller 124 includes one or more controllers (or processors).

[0027] The input 102 is coupled to the bypass line 104 and the charger 108. The output 120 is coupled to the bypass line 104 and the inverter 116 via the output switch 118. The charger 108 is coupled to the input 102, the DC-DC converter 110, and the battery 122. The DC-DC converter 110 is coupled to the DC bus 112 and the battery 122. In some embodiments, the battery 122 is coupled to the DC-DC converter 110 via a backup power input 126. In some embodiments, the DC bus 112 includes at least one DC bus capacitor 114, which is coupled between the positive rail 112a and the negative rail 112b. The inverter 116 is coupled to the DC bus 112 and the output switch 118.

[0028] The UPS 100 is typically configured to operate in one of at least two operating modes, including a line mode and a battery mode. The operating mode of the UPS 100 depends on the quality level of the AC power received at the input terminal 102 (e.g., powered from a mains AC source). For example, when the AC power received at the input terminal 102 is acceptable (i.e., within a specified range of acceptable electrical parameters), the UPS 100 can be configured to operate in the line mode. Otherwise, when the AC power received at the input terminal 102 is unacceptable (i.e., not within a specified range of acceptable electrical parameters), the UPS 100 can be configured to operate in the battery mode. In some embodiments, the controller 124 can be coupled to the input terminal 102 and configured to monitor the input terminal 102 to determine whether to operate the UPS in the line mode or the battery mode.

[0029] In the line mode, the bypass switch 106 is closed to connect the input terminal 102 to the output terminal 120 via the output switch 118. The input terminal 102 receives AC power from an external power source (e.g., a mains AC power supply) and provides the received power to the output terminal 120 and the charger 108. The output terminal 120 receives power from the input terminal 102 and provides the power to an external load (not shown). The charger 108 receives AC power from the input terminal 102, converts the AC power to DC power, and charges the battery 122 with the DC power obtained from the input terminal 102.

[0030] When AC power received at the input terminal 102 is unavailable, the UPS 100 operates in battery mode. In battery mode, the bypass switch 106 is open, no AC power is supplied from the input terminal 102 to the output terminal 120, the charger 108 stops charging the battery 122, and the battery 122 discharges stored DC power to the DC-DC converter 110. The DC-DC converter 110 regulates the DC power received from the battery 122 and supplies the regulated DC power to the DC bus 112. The inverter 116 converts the received DC power into AC power and supplies the AC power to the output terminal 120 via the output switch 118 to provide power to an external load.

[0031] To provide uninterrupted power to the load, the offline UPS 100 can be configured to maintain a DC bus voltage on the DC bus 112 coupled between the DC-DC converter 110 and the DC-AC inverter. For example, when operating in line mode, the charger 108 can be configured to provide DC power derived from input AC power to the DC-DC converter 110, and the DC-DC converter 110 can provide DC power to the DC bus 112 to maintain the DC bus voltage (i.e., to charge at least one DC bus capacitor 114). Thus, the efficiency of the UPS 100 may be limited by power conversion losses in the charger 108 and / or the DC-DC converter 110.

[0032] A more efficient offline UPS topology and control method are provided herein. In at least one embodiment, the topology can include a rectifier coupled between the bypass line and a DC bus of the offline UPS. In one embodiment, the control method includes operating the DC-DC converter of the offline UPS to charge the DC bus to a DC bus voltage and maintaining the DC bus voltage using the rectifier. In some embodiments, maintaining the DC bus voltage using the rectifier can improve the efficiency of the offline UPS.

[0033] Figure 2 is a block diagram of an offline UPS 200 according to various aspects described herein. In one embodiment, the UPS 200 may be similar to Figure 1 UPS 100, except that UPS 200 includes a rectifier 202 coupled between bypass line 104 and DC bus 112. As shown, the rectifier 202 can be coupled to the bypass line 104 after the bypass switch 106, so that when the bypass switch 106 is open, the rectifier 202 is disconnected from the input terminal 102.

[0034] Figure 3is a flow chart illustrating a control method 300 according to various aspects described herein. In one embodiment, the control method 300 corresponds to Figure 2 The UPS 200 is configured to operate in various modes. In block 302, the UPS 200 is powered to a startup mode of operation. In the startup mode of operation, the controller 124 monitors the input terminal 102 to detect input AC power. In some embodiments, the controller 124 monitors the input terminal 102 to detect whether the input AC power is acceptable (i.e., a level sufficient to power the load). In block 304, in response to detecting acceptable input AC power, the controller 124 operates the bypass switch 106 and the output switch 118 to a first state. In one embodiment, in the first state, the bypass switch 106 is closed and controls the output switch 118 so that the output terminal 120 is coupled to the inverter 116 (i.e., disconnected from the bypass line 104).

[0035] In box 306, also in the startup mode of operation, the controller 124 enables the DC-DC converter 110. In one embodiment, the controller 124 enables the DC-DC converter 110 by providing a DC enable signal to the DC-DC converter 110. In some embodiments, the DC enable signal controls one or more switches to enable the DC-DC converter 110 to operate. In box 308, after being enabled, the DC-DC converter 110 charges the DC bus 112 to a DC bus voltage level (e.g., 180V). In one embodiment, the DC-DC converter 110 draws DC power from the battery 122 to charge the DC bus 112. In some embodiments, the DC power drawn from the battery 122 has a first voltage level, and the DC-DC converter 110 converts the DC power having the first voltage level to DC power having the DC bus voltage level. For example, Figure 4A As shown, the switches 106 and 118 are set to a first state, and the DC-DC converter 110 provides DC power from the battery 122 to the DC bus 112. In other embodiments, the DC-DC converter 110 operates in conjunction with the charger 108 to convert the input AC power into DC power to charge the DC bus 112. For example, Figure 4BAs shown, the switches 106 and 118 are set in the first state, and the charger 108 and the DC-DC converter 110 operate to provide DC power derived from the input AC power to the DC bus 112. In some embodiments, the charger 108 converts the input AC power to DC power having the first voltage level, and the DC-DC converter 110 converts the DC power having the first voltage level to DC power having the DC bus voltage level. In one embodiment, the DC power provided by the DC-DC converter 110 and derived from at least one of the battery 122 and the input AC power charges at least one DC bus capacitor 114 to the DC bus voltage level (e.g., 180V). In some embodiments, the controller 124 disables the inverter 116 while the DC-DC converter 110 is charging the DC bus 112.

[0036] In one embodiment, once the DC bus 112 has been charged to the DC bus voltage level, the UPS 200 can be converted to the line mode for operation. In box 310, the controller 124 converts the UPS 200 to the line mode for operation by setting the bypass switch 106 and the output switch 118 to a second state. In one embodiment, in the second state, the bypass switch 106 remains closed and the output switch 118 is controlled so that the output terminal 120 is coupled to the bypass line 104. After setting the switches 106 and 118 to the second state, the input AC power is provided to the output terminal 120 as the output AC power. In box 312, the controller 124 turns off the DC-DC converter 110 (e.g., via a DC enable signal). Figure 4C As shown, under the line mode operation, the input AC power is provided to the output terminal 120 as the output AC power. In addition, the rectifier 202 draws AC power from the bypass line 104, converts the AC power to DC power, and provides the DC power to the DC bus 112 to maintain the DC bus voltage level. In some embodiments, the rectifier 202 converts the AC power from the bypass line 104 into DC power having the DC bus voltage level (e.g., 180V). Since the DC-DC converter 110 is turned off during the line mode operation, the power loss associated with the DC-DC converter 110 can be eliminated. In some embodiments, by utilizing the rectifier 202 to maintain the DC bus voltage level, the power loss under line mode operation can be reduced by up to about 20%. In this way, when compared with Figure 1The efficiency of the UPS 200 under the line mode operation may be improved when compared with the UPS 100.

[0037] Although not shown, the controller 124 can also operate the charger 108 to draw AC power from the input 102, convert the AC power to DC power, and provide the DC power to the battery 122 for charging during the line mode operation. In one embodiment, the charger 108 converts the AC power to DC power having a charging voltage level (e.g., a first voltage level). In other embodiments, the DC-DC converter 110 is configured as a bidirectional converter 124 and draws DC power from the DC bus 112 to charge the battery 122. In some embodiments, when the battery 122 is fully charged, the controller 124 turns off the charger 108 in addition to the DC-DC converter 110 to further improve the efficiency of the UPS 200 during the line mode operation.

[0038] Figure 55 is a graph 500 illustrating various waveforms corresponding to the control method 300 according to various aspects described herein. As described above, in the startup mode of operation, the controller 124 monitors the input 102 to detect the input AC power. In some embodiments, the controller 124 monitors the voltage level at the input 102 to detect whether the input AC power is acceptable (i.e., at a level sufficient to power the load) (block 302). Thus, the input voltage 502 may correspond to the voltage level of the input AC power received at the input 102. In response to detecting that the input voltage 502 indicates acceptable input AC power, the controller 124 sets the switches 106, 118 to the first state (block 304) and may drive the DC enable signal 504 low (e.g., to 0V) to enable the DC-DC converter 110 (block 306). Once enabled, the DC-DC converter 110 charges the DC bus 112 to the DC bus voltage level using DC power from the battery 122 or the input AC power (block 308). As shown, in response to enabling the DC-DC converter 110, the DC bus voltage 506 can be charged to the DC bus voltage level (e.g., 180V). After the DC bus voltage 506 has reached the DC bus voltage level, the switches 106, 118 are set to the second state (indicated at 510), and the input voltage 502 is provided to the output terminal 120 as the output voltage 508 (block 310). Once the DC bus voltage 506 stabilizes at the DC voltage level (e.g., 180V), the DC enable signal 504 can be driven high (e.g., 1V) to shut down the DC-DC converter 110 (block 312). Thus, in line mode operation, the input voltage 502 is provided to the output terminal 120 as the output voltage 508, and the rectifier 202 provides DC power to the DC bus 112 to maintain the DC bus voltage 506.

[0039] Figure 61 is a schematic diagram illustrating an offline UPS 600 according to various aspects described herein. The UPS 600 includes an input 602, a rectifier 604, a bypass switch 606, a charger 608, a DC-DC converter 610, a DC bus 612, a DC bus capacitor 614, an inverter 616, output switches 618a and 618b (collectively referred to herein as output switches 618), and an output 620. In some embodiments, the UPS 600 may include a battery 622; however, in other embodiments, the battery 622 may be external to the UPS 100. Additionally, the UPS 600 may include a controller 624 coupled to and configured to operate the components of the UPS 600. In some embodiments, the controller 624 may be external to the UPS 600.

[0040] In one embodiment, the UPS 600 is configured to operate similarly to the UPS 200 described above. For example, in the startup mode of operation, the controller 624 monitors the input terminal 602 to detect input AC power, sets the switches 604 and 618 to the first state, and enables the DC-DC converter 610 to provide DC power from the battery 622 or the input AC power to charge the DC bus 612 (i.e., the DC bus capacitor 614). Once the DC bus 612 has been charged to the DC bus voltage level (e.g., 180V), the controller 624 sets the switches 604 and 618 to the second state. Thus, in line mode operation, the input AC power is provided to the output terminal 620 as the output AC power. Furthermore, once the DC bus 112 stabilizes at the DC bus voltage level, the DC-DC converter 610 is shut down, and the rectifier 604 draws AC power from the bypass line 604 to maintain the DC bus voltage (e.g., 180V). Since the DC-DC converter 610 is turned off, the efficiency of the UPS 600 may be improved during the line mode operation.

[0041] In some embodiments, during line mode operation, the charger 608 draws AC power from the input 602, converts the AC power to DC power, and provides the DC power to charge the battery 622. In other embodiments, the DC-DC converter 610 is configured as a bidirectional converter and draws DC power from the DC bus 612 to charge the battery 622. In some embodiments, when the battery 622 is fully charged, the controller 624 shuts down the charger 608 in addition to the DC-DC converter 610 to further improve the efficiency of the UPS 600 during line mode operation.

[0042] In certain embodiments, the charger 608 is operated only during the startup mode of operation to charge the DC bus 112 and / or to charge the battery 622 during the line mode of operation, which can reduce performance requirements associated with components of the charger 608. For example, the power rating of the switch components included in the bridge between the charger 608 and the battery 622 can be reduced. This can reduce the size and cost of the UPS 600.

[0043] As described above, a more efficient offline UPS topology and control method are provided herein. In at least one embodiment, the topology includes a rectifier coupled between a bypass line and a DC bus of the offline UPS. In one embodiment, the control method includes operating the charger and the DC-DC converter of the offline UPS to charge the DC bus to a DC bus voltage, and maintaining the DC bus voltage using the rectifier. In certain embodiments, maintaining the DC bus voltage using the rectifier can improve the efficiency of the offline UPS.

[0044] Having thus described various aspects of at least one embodiment of the present invention, various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be a part of the present invention and are intended to fall within the spirit and scope of the present invention. Therefore, the foregoing description and accompanying drawings are intended only as examples.

Claims

1. An uninterruptible power supply, characterized in that: The uninterruptible power supply comprises: an input terminal configured to receive input alternating current; an output terminal configured to provide output AC power to a load; a charger coupled to the input terminal, and configured to convert the input AC power into DC power having a first voltage level; a DC-DC converter coupled to the charger, wherein the DC-DC converter is configured to convert the DC power having the first voltage level into a DC power having a DC bus voltage level; a DC bus coupled to the DC-DC converter, wherein the DC bus is configured to receive DC power having the DC bus voltage level; an inverter coupled to the output terminal via an output switch, the inverter being configured to convert DC power having the DC bus voltage level into the output AC power and provide the output AC power to the output terminal via the output switch; a bypass line including a bypass switch, the bypass line being coupled between the input terminal and the output switch, and the bypass line being configured to provide the input AC power to the output terminal through the output switch; a rectifier coupled between the bypass line and the DC bus, the rectifier being configured to convert the input AC power on the bypass line into DC power having the DC bus voltage level and to provide the DC power having the DC bus voltage level to the DC bus; and a controller coupled to the charger, the DC-DC converter, the inverter, and the bypass switch, the controller configured to operate the uninterruptible power supply: providing DC power to the DC bus via the DC-DC converter in a first operating mode; and In a second operating mode, direct current is provided to the direct current bus via the rectifier.

2. The uninterruptible power supply according to claim 1, wherein: The controller is further configured to operate the uninterruptible power supply: In the first operation mode, the charger and the DC-DC converter are operated to provide DC power derived from the input AC power to the DC bus.

3. The uninterruptible power supply according to claim 1, wherein: The uninterruptible power supply further includes a backup power input coupled to the DC-DC converter, and the backup power input is configured to receive the backup DC power having the first voltage level from a backup power source.

4. The uninterruptible power supply according to claim 3, wherein: The controller is further configured to operate the uninterruptible power supply: In the first operation mode, the DC-DC converter is operated to provide DC power derived from the backup DC power to the DC bus.

5. The uninterruptible power supply according to claim 3, wherein: The controller is further configured to operate the charger: Direct current having the first voltage level derived from the input alternating current is provided to the backup power supply input to charge the backup power supply during the second operating mode.

6. The uninterruptible power supply according to claim 3, wherein: The controller is further configured to operate the DC-DC converter: Direct current having the first voltage level from the direct current bus is provided to the backup power supply input to charge the backup power supply during the second operating mode.

7. The uninterruptible power supply according to claim 3, wherein: The controller is further configured to operate the DC-DC converter and the inverter: In a third operating mode, output AC power derived from the backup DC power is provided.

8. The uninterruptible power supply according to claim 1, wherein: The controller is further configured to operate the uninterruptible power supply: The bypass line is decoupled from the output terminal by controlling the output switch in the first operation mode.

9. The uninterruptible power supply according to claim 1, wherein: The controller is further configured to operate the uninterruptible power supply: In the second operation mode, the bypass line is coupled to the output terminal by controlling the output switch, so that the input AC power is provided to the output terminal as the output AC power.

10. The uninterruptible power supply according to claim 1, wherein: The DC bus includes a first voltage rail, a second voltage rail, and at least one DC bus capacitor. The DC bus capacitor is coupled between the first voltage rail and the second voltage rail.

11. The uninterruptible power supply according to claim 10, wherein: The controller is configured to operate the uninterruptible power supply: The at least one DC bus capacitor is charged to the DC bus voltage level in the first operating mode.

12. The uninterruptible power supply according to claim 11, wherein: The controller is configured to operate the uninterruptible power supply: The DC bus voltage level is maintained in the second operating mode.

13. A non-transitory computer-readable medium having stored thereon a sequence of computer-executable instructions for controlling an uninterruptible power supply, characterized in that: The uninterruptible power supply includes an output switch configured to selectively couple a bypass line to an output terminal of the uninterruptible power supply. The computer-executable instruction sequence includes a plurality of instructions instructing at least one processor to operate the uninterruptible power supply to perform the following steps: receiving an input AC power at an input terminal of the uninterruptible power supply; decoupling the bypass line from the output terminal via the output switch; In response to the bypass line being decoupled from the output terminal, operating a DC-DC converter to convert DC power having a first voltage level into DC power having a DC bus voltage level; providing DC power having the DC bus voltage level from the DC-DC converter to a DC bus to charge the DC bus to the DC bus voltage level; In response to a condition in which the DC bus is charged, turning off the DC-DC converter via the output switch and coupling the bypass line to the output terminal; providing the input AC power to the output terminal through the bypass line; converting the input AC power on the bypass line into DC power having the DC bus voltage level using a rectifier; as well as The DC power having the DC bus voltage level is supplied to the DC bus through the rectifier to maintain the DC bus voltage level.

14. The non-transitory computer-readable medium of claim 13, wherein: The computer executable instruction sequence includes instructions for causing the at least one processor to execute the uninterruptible power supply to perform the following steps: A charger coupled to the input terminal is operated to convert the input AC power into DC power having the first voltage level.

15. The non-transitory computer-readable medium of claim 14, wherein: The computer executable instruction sequence includes instructions for causing the at least one processor to execute the uninterruptible power supply to perform the following steps: The DC-DC converter is operated to convert the DC power provided from the charger, and the DC-DC converter is operated to convert the DC power having the first voltage level into the DC power having the DC bus voltage level.

16. The non-transitory computer-readable medium of claim 14, wherein: The computer executable instruction sequence includes instructions for causing the at least one processor to execute the uninterruptible power supply to perform the following steps: A backup DC power with the first voltage level from a backup power source is received at a backup power input coupled to the DC-DC converter.

17. The non-transitory computer-readable medium of claim 16, wherein: The computer executable instruction sequence includes instructions for causing the at least one processor to execute the uninterruptible power supply to perform the following steps: The backup DC power provided from the backup power source is converted by operating the DC-DC converter, which is operated to convert the DC power having the first voltage level into DC power having the DC bus voltage level.

18. The non-transitory computer-readable medium of claim 16, wherein: The computer executable instruction sequence includes instructions for causing the at least one processor to execute the uninterruptible power supply to perform the following steps: The charger is operated to provide direct current having the first voltage level to the backup power input to charge the backup power supply.

19. The non-transitory computer-readable medium of claim 16, wherein: The computer executable instruction sequence includes instructions for causing the at least one processor to execute the uninterruptible power supply to perform the following steps: In response to a condition in which the input AC power is unacceptable, the DC-DC converter and an inverter coupled to the DC bus are operated to provide output AC power derived from the backup DC power.

20. The non-transitory computer-readable medium of claim 13, wherein: The computer executable instruction sequence includes instructions for causing the at least one processor to execute the uninterruptible power supply to perform the following steps: Direct current having a DC bus voltage level is provided to the DC bus from the DC-DC converter, and the DC bus is charged to the DC bus voltage level by charging at least one DC bus capacitor to the DC bus voltage level.

21. The non-transitory computer-readable medium of claim 13, wherein: The computer executable instruction sequence includes instructions for causing the at least one processor to execute the uninterruptible power supply to perform the following steps: A bypass switch is operated to couple the input terminal to the output terminal through the bypass line.

22. A method for assembling an uninterruptible power supply, characterized in that: The assembly method includes the steps of: providing a charger, the charger being configured to be coupled to an input terminal, the charger being configured to receive input AC power through the input terminal and convert the input AC power into DC power having a first voltage level; coupling a DC-DC converter to the charger, the DC-DC converter configured to convert the DC power having the first voltage level into DC power having a DC bus voltage level; coupling a DC bus to the DC-DC converter, the DC bus configured to receive DC power having the DC bus voltage level; coupling an inverter to the DC bus, the inverter configured to convert DC power having the DC bus voltage level into output AC power, and providing the output AC power to an output terminal through an output switch; coupling a bypass line including a bypass switch between the input terminal and the output switch, the bypass line being configured to provide the input AC power to the output terminal through the output switch; a rectifier coupled between the bypass line and the DC bus, the rectifier configured to convert input AC power on the bypass line into DC power having the DC bus voltage level, and provide the DC power having the DC bus voltage level to the DC bus; as well as A controller is coupled to the charger, the DC-DC converter, the inverter, and the bypass switch, the controller being configured to operate the uninterruptible power supply: providing DC power to the DC bus via the DC-DC converter in a first operating mode; and In a second operating mode, direct current is provided to the direct current bus via the rectifier.

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