Rectifier, system and method for power rectification

Abstract

The present disclosure provides a rectifier, system and method for power rectification, wherein the method comprises a plurality of steps: receiving an input AC power source; providing the input AC power source to at least one diode bridge to generate a DC power source; providing the DC power source to at least one group of diodes through the at least one diode bridge; providing the DC power source to at least one output inductor through the at least one group of diodes; and providing the DC power source to an output through the at least one output inductor.

Description

Technical Field

[0001] The present invention relates to a rectifier, a system and a method for rectifying a power supply. Background Art

[0002] The power supply device used provides management, such as: Uninterruptible Power Supplies (UPS). Uninterruptible power supplies for sensitive and / or critical loads, such as computer systems and other data processing systems, are known in the art. Known UPS include online UPS, offline UPS and line-interactive UPS. Online UPS provides conditioned AC power and backup AC power when the main AC power is interrupted. Offline UPS usually does not provide conditioning of the input AC power, but provides backup AC power when the main AC power is interrupted. Online interactive UPS are similar to offline UPS in that they switch to battery power in the event of a power outage, but usually also include a multi-tap transformer for regulating the output voltage provided by the UPS.

[0003] A conventional online UPS uses a power factor correction circuit (PFC) to rectify the input power provided by the power company to provide power to the direct current (DC) bus. The rectified DC voltage is usually used to charge the battery when the mains is available and to provide power to the DC bus. In the absence of mains, the battery provides power to the DC bus. The DC-AC inverter generates an alternating current (AC) output voltage from the DC bus to the load. Since the DC bus is powered by the mains or the battery, if the mains fails and the battery is fully charged, the output power of the UPS will not be interrupted. Conventional offline UPS usually connects the load directly to the mains. When the mains is insufficient to power the load, the offline UPS will run a DC-AC inverter to convert the DC power from the backup power source (such as a battery) into the required AC power and provide it to the load. Each of the aforementioned types of UPS can be implemented in conjunction with a power modulation stage, which can include a power converter module and a power inverter module. Summary of the invention

[0004] At least one aspect of the present invention discloses a method, which includes: receiving an input alternating current (AC) power supply; providing the input AC power supply to at least one diode bridge to generate a direct current (DC) power supply; providing the DC power supply to at least one group of diodes through the at least one diode bridge; providing the DC power supply to at least one output inductor through the at least one group of diodes; and providing the DC power supply to an output through the at least one output inductor.

[0005] In one embodiment, the method includes: providing the input AC power to a primary winding of a transformer; providing the transformed AC power to a first secondary winding and a second secondary winding through the primary winding of the transformer; and providing the transformed AC power to the at least one diode bridge through the first secondary winding and the second secondary winding. In one embodiment, the method includes: providing the input AC power to the at least one diode bridge to generate DC power, including providing the input AC power to a first diode bridge and a second diode bridge; providing the DC power to the at least one group of diodes, including providing the DC power to a first group of diodes and a second group of diodes; and providing the DC power to the at least one output inductor, including providing the DC power to a first output inductor and a second output inductor.

[0006] In at least one embodiment, the first diode bridge, the first group of diodes and the first output reactor are alternately turned on with the second diode bridge, the second group of diodes and the second output reactor. In some embodiments, the first output reactor and the second output reactor are configured to be alternately turned on without reaching saturation. In one embodiment, the at least one output reactor is configured to operate in a continuous conduction mode in response to a rectifier providing at least 0.5% of the rated load.

[0007] In an embodiment, the method further comprises selectively controlling one or more switch elements to: limit a charging current flowing to an output capacitor; and limit a discharging current flowing to the output capacitor. In some embodiments, the method further comprises providing the DC power to the at least one output reactor via the at least one diode bridge.

[0008] According to one aspect of the present invention, a system of an uninterruptible power supply (UPS) is provided, the system comprising: an input configured to receive an input AC power source; an energy storage device configured to store energy and provide a backup power source; an output of the UPS configured to provide an output power source obtained from at least one of the AC power source and the backup power source; and a rectifier coupled to the input and coupled to the output of the UPS. The rectifier comprises: at least one diode bridge coupled to the input; at least one group of diodes coupled to the at least one diode bridge; at least one output reactor coupled to the at least one group of diodes; and a rectifier output coupled to the at least one output reactor.

[0009] In some embodiments, the rectifier further comprises a transformer having: a primary winding coupled to the output; at least one secondary winding configured to be coupled to the primary winding according to an extended delta configuration. In some embodiments, the at least one diode bridge comprises a first diode bridge and a second diode bridge, and the at least one set of diodes comprises: a first set of diodes coupled to the first diode bridge; and a second set of diodes coupled to the second diode bridge.

[0010] In some embodiments, the at least one output reactor comprises: an output reactor having a first input tap, a second input tap, and an output tap; wherein the first input tap is coupled to the first set of diodes, the second input tap is coupled to the second set of diodes, and the output tap is coupled to the rectifier output. In one embodiment, the output reactor is also coupled to the first diode bridge and the second diode bridge. In one embodiment, the at least one output reactor comprises: a first output reactor having an output tap; and a second output reactor having an output tap.

[0011] In at least one embodiment, the first output inductor is configured to couple to the first diode bridge and the second group of diodes; the output tap of the first output inductor is configured to couple to the rectifier output; the second output inductor is configured to couple to the second diode bridge and the first group of diodes; and the output tap of the second output inductor is configured to couple to the rectifier output.

[0012] In an embodiment, the system further comprises: a switch circuit coupled to the at least one output reactor and the rectifier output; and an output capacitor configured to be coupled to the switch circuit. In at least one embodiment, the switch circuit is configured to: selectively limit a discharge current of the output capacitor in response to detecting a short circuit at the rectifier output; and selectively limit a charging current flowing to the output capacitor in response to detecting that a pre-charge condition is not met.

[0013] According to one aspect of the present invention, a rectifier is provided, which includes: an input configured to receive an input AC power source; at least one diode bridge coupled to the input; at least one group of diodes coupled to the at least one diode bridge; at least one output inductor coupled to the at least one group of diodes; and a rectifier output coupled to the at least one output inductor.

[0014] In one embodiment, the at least one diode bridge comprises a first diode bridge and a second diode bridge, and the at least one group of diodes comprises: a first group of diodes coupled to the first diode bridge; and a second group of diodes coupled to the second diode bridge. In some embodiments, the at least one output reactor comprises: an output reactor having a first input tap, a second input tap, and an output tap; wherein the first input tap is coupled to the first group of diodes, the second input tap is coupled to the second group of diodes, and the output tap is coupled to the rectifier output. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings are not drawn to scale. In the drawings, each identical or nearly identical component shown in various figures will be represented by the same number. For clarity, not every component will be labeled in every figure. In the drawings:

[0016] Figure 1A A schematic diagram of a rectifier is shown.

[0017] Figure 1B A schematic diagram showing an output reactor.

[0018] Figure 2A A schematic diagram of a rectifier according to an embodiment is shown.

[0019] Figure 2B A schematic diagram showing a first output reactor and a second output reactor according to an embodiment.

[0020] Figure 3 A schematic diagram of a rectifier according to an embodiment is shown.

[0021] Figure 4A schematic diagram of a rectifier according to an embodiment is shown.

[0022] Figure 5 A block diagram of an uninterruptible power supply is shown. DETAILED DESCRIPTION

[0023] Aspects and examples are generally directed to an improved power rectifier. Some embodiments of the improved rectifier include novel component configurations to maximize power conversion efficiency, improve output voltage stability, and simplify design requirements.

[0024] The examples of the methods and systems discussed herein are not limited to the construction details of the application and the component arrangements set forth in the following description or shown in the accompanying drawings in the application. 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 objects in any other examples.

[0025] In addition, the wording and terms used herein are for descriptive purposes and should not be considered limiting. Any reference to the examples, embodiments, components, elements or actions of the systems and methods mentioned herein in the singular may also include multiple embodiments, and any reference to any embodiment, component, element or action herein in the plural may also include only singular embodiments. References in the singular or plural form are not intended to limit the currently disclosed systems or methods, their components, actions or elements. The use of "including", "comprising", "having", "containing", "involving" and their variations herein is intended to cover the items listed thereafter and their equivalents and other items. References to "or" may be interpreted as inclusive, so that any term described using "or" may indicate any of a single, more than one, and all of the terms described. In addition, in the event of inconsistency in the usage of terms between this document and the documents incorporated herein by reference, the terms in the included references are supplementary to this document; for inconsistencies, the terms in this document shall prevail.

[0026] Rectifiers can be broadly classified as active rectifiers or passive rectifiers. Active rectifiers, such as switching regulators, include one or more switching elements that are selectively controlled to produce rectified DC power. In contrast, passive rectifiers may not utilize switching elements to produce rectified DC power.

[0027] A typical passive rectifier may be able to achieve very high efficiency. For example, where the passive rectifier includes a diode bridge, most of the losses may be due to losses in the diode bridge. The losses through the passive components (e.g., diodes) may be considered relatively small compared to the losses through the active components in an active rectifier (e.g., switches).

[0028] Some conventional passive rectifiers can be configured to rectify a three-phase alternating current (AC) power supply. Embodiments of three-phase rectifier topologies include 6-pulse, 12-pulse, 18-pulse and 24-pulse rectifier topologies. Generally speaking, a higher number of pulses usually requires a more complex transformer winding structure and a larger number of diodes. However, a higher number of pulses usually produces a higher power factor and reduces the total harmonic distortion (THD) of the drawn line current.

[0029] For example, Figure 1A A general rectifier 100 is shown. The rectifier 100 is configured according to a 24-pulse topology. The rectifier 100 includes a transformer 102, a first diode bridge 104, a second diode bridge 106, an output reactor 108, a plurality of output diodes 110, and optionally an output filter capacitor 112. The transformer 102 includes a primary winding 114, a first secondary winding 116, and a second secondary winding 118. The transformer 102 is configured in an extended delta configuration according to topologies known in the art. However, alternative configurations of the transformer 102 are possible.

[0030] In a 12-pulse rectifier topology, the output can be tapped directly from the midpoint of the output reactor 108 without the output diode 110. However, in this configuration, the input THD may be unacceptably high. The output diode 110 connected to the two taps on the output reactor 108 allows current to flow alternately through the output diode 110, thereby achieving 24 pulses of input current with reduced input THD.

[0031] like Figure 1B1 , the output reactor 108 and the output diode 110 are described in more detail. The output reactor 108 includes a first winding 120, a second winding 122 and a third winding 124. The output diode 110 includes a first diode 123 and a second diode 125. The first winding 120 and the second winding 122 are connected via a first node 126. The second winding 122 and the third winding 124 are connected via a second node 128. The first winding 120 and the third winding 124 have the same number of windings. The windings of the second winding 122 are twice as many as those of the first winding 120 and the third winding 124.

[0032] In the embodiment, the instantaneous voltage of the first node 126 is greater than the instantaneous voltage of the second node 128. Therefore, the first diode 123 will conduct current, while the second diode 125 will not conduct current because the voltage on the cathode of the first diode 123 and the second diode 125 (substantially equal to the voltage of the first node 126) is greater than the voltage on the anode of the second diode 125 (equal to the voltage of the second node 128). Therefore, the second diode 125 is in a reverse biased non-conductive state.

[0033] A first current 130 is conducted to the first node 126 via the first winding 120. A second current 132 is conducted to the first node 126 via the second winding 122 and the third winding 124. The sum of the currents is conducted via the first diode 123 to generate an output current 134. Since the winding ratio is 1:2:1, in the embodiment, the first current 130 is approximately 75% of the output current 134, and the second current 132 is approximately 25% of the output current 134.

[0034] At other points in time, the instantaneous voltage at the second node 128 will be greater than the instantaneous voltage across the first node 126, and vice versa. For example, since the first current 130 originates from the first secondary winding 116 and the second current 132 originates from the second secondary winding 118, the relative voltages of the first node 126 and the second node 128 will vary depending on the voltage provided by the secondary winding of the transformer 102.

[0035] In one example, there is a 30° phase shift between the voltages generated by the secondary windings of the transformer 102. Therefore, the ripple voltages generated by each of the 6-pulse diode bridges 104 and 106 are identical in waveform, but offset by 1 / 12 of a line period. An AC voltage at six times the line frequency appears across the reactor windings 120-124, resulting in an AC voltage difference between the first node 126 and the second node 128. Ideally, the amount of time that the instantaneous voltage of the first node 126 is greater than the voltage of the second node 128 is approximately the same as the amount of time that the instantaneous voltage of the first node 126 is less than the voltage of the second node 128.

[0036] The rectifier 100 has several disadvantages. For example, the first problem is that the rectifier 100 has high diode losses, partly due to the addition of the output diode 110. Further, the current flowing through each phase of the power rectified by the rectifier 100 must flow through a diode in each of the first diode bridge 104, the second diode bridge 106, and the output diode 110. Because each diode consumes power and thus reduces the efficiency of the rectifier 100, the efficiency of the power supply generally decreases as the number of diodes in the current path increases. In addition, all current flows through the output diode 110, so the output diode 110 consumes a large amount of power.

[0037] A second problem with the rectifier 100 is that the first secondary winding 116 and the second secondary winding 118 generally must have very balanced impedances, and therefore very balanced leakage inductances, to maintain an ideal current balance between the first secondary winding 116 and the second secondary winding 118. If current balance is not maintained, various detrimental effects may occur, including increased input THD, reduced efficiency, and increased temperature of the transformer 102. As discussed below, saturation of the output reactor 108 exacerbates this imbalance.

[0038] A third problem with the rectifier 100 is that the output reactor 108 must typically include an air-gap core or a low permeability core material due to the unbalance of the first secondary winding 116 and the second secondary winding 118. Otherwise, the winding unbalance may cause the core of the output reactor 108 to saturate. Although the implementation of an air-gap core may avoid saturation of the output reactor 108, the output voltage characteristics may be negatively affected. For example, when the output load is less than about 10% of the rated load, it may be difficult to accurately control the output voltage.

[0039] Embodiments of the present disclosure provide rectifier topologies that address at least some of the aforementioned shortcomings of prior art rectifier topologies. Some embodiments provide a rectifier in which multiple current paths include two diodes instead of three, none of which are directly connected to the rectifier output, thereby reducing diode losses. In addition, some embodiments reduce the current imbalance caused by transformer winding imbalance by several times compared to prior art topologies. Finally, some embodiments eliminate or mitigate the risk of output reactor core saturation, which makes it possible to design a simpler reactor that does not require an air gap core. Therefore, at loads significantly less than the rated load, more precise output voltage control cannot be provided.

[0040] like Figure 2A The rectifier 200 according to one embodiment of the present invention is shown. The rectifier 200 includes a transformer 202, a first diode bridge 204, a second diode bridge 206, a first output inductor 208, a second output inductor 210, a first group of diodes 212, a second group of diodes 214, a capacitor 216, an input 218 and an output 220. The transformer 202 includes a primary winding 222, a first secondary winding 224 and a second secondary winding 226.

[0041] The input 218 is coupled to the primary winding 222 and is configured to be coupled to a power source (e.g., an AC mains power source). The primary winding 222 is coupled to the input 218 and is inductively coupled to the first secondary winding 224 and the second secondary winding 226. The first secondary winding 224 is inductively coupled to the primary winding 222 and is coupled to the first diode bridge 204 and the first set of diodes 212. The second secondary winding 226 is inductively coupled to the primary winding 222 and is coupled to the second diode bridge 206 and the second set of diodes 214.

[0042] The first diode bridge 204 is coupled to the first secondary winding 224, the first output reactor 208, the first set of diodes 212 and the second diode bridge 206. The second diode bridge 206 is coupled to the second secondary winding 226, the second output reactor 210, the second set of diodes 214 and the first diode bridge 204.

[0043] The first output reactor 208 is coupled to the first diode bridge 204, the second set of diodes 214, the output 220, the capacitor 216, and the second output reactor 210. The second output reactor 210 is coupled to the second diode bridge 206, the first set of diodes 212, the output 220, the capacitor 216, and the first output reactor 208.

[0044] The first set of diodes 212 is coupled to the first secondary winding 224, the first diode bridge 204, and the second output reactor 210. The second set of diodes 214 is coupled to the second secondary winding 226, the second diode bridge 206, and the first output reactor 208. The capacitor 216 is coupled to the first output reactor 208, the second output reactor 210, and the output 220. The output 220 is coupled to the first output reactor 208, the second output reactor 210, the capacitor 216, and is configured to be coupled to a load (not shown).

[0045] Now combine Figure 2B The operation of the rectifier 200 is described. Figure 2B The first output inductor 208 and the second output inductor 210 are shown. For the sake of clarity, the voltage characteristics of the first output inductor 208 and the second output inductor 210 are discussed by taking the first output inductor 208 as an example, and the current characteristics of the first output inductor 208 and the second output inductor 210 are discussed by taking the second output inductor 210 as an example.

[0046] The first output inductor 208 includes a first winding 230 and a second winding 232, and the second output inductor 210 includes a third winding 234 and a fourth winding 236. The first winding 230 is coupled to a first node 238 at a first connection and to a second node 240 at a second connection. The second winding 232 is coupled to the second node 240 at a first connection and to the third node 242 at a second connection. The third winding 234 is coupled to the fourth winding 236 via the fourth node 244. The third winding 234 conducts a first current 246 to the second node 240. The fourth winding 236 conducts a second current 248 to the second node 240. An output current 250 is provided from the second node 244.

[0047] The first output reactor 208 and the second output reactor 210 provide a voltage proportional to the turns ratio of the windings of the reactors. For example, with reference to the first output reactor 208, the voltage of the first node 240 can be expressed as:

[0048]

[0049] Wherein, Vout is the voltage of the first node 240, Va is the voltage of the third node 238, Vb is the voltage of the fourth node 242, N1 is the number of windings of the first winding 230, and N2 is the number of windings of the second winding 232. The second output inductor 210 can provide an output voltage according to a similar relationship.

[0050] Similarly, the first output inductor 208 and the second output inductor 210 provide a current proportional to the turns ratio of the windings of the inductors. For example, with reference to the second output inductor 210, the first current 246 and the second current 248 can be expressed as:

[0051]

[0052]

[0053] Wherein Ia corresponds to the first current 246, Ib corresponds to the second current 248, Iout corresponds to the output current 250, N1 is the number of windings of the third winding 234, and N2 is the number of windings of the fourth winding 236. The first output inductor 208 can provide an output current according to a similar relationship.

[0054] In some embodiments, it may be advantageous to provide current only from one of the first output inductor 208 and the second output inductor 210. For example, current may be provided only by the output inductor that provides a greater instantaneous output voltage under given circumstances according to equation (1). When one output inductor provides current according to equations (2) and (3), the other output inductor may provide zero or negligible current.

[0055] In some embodiments, the turns ratio of the first output inductor 208 and the second output inductor 210 can be selected to reduce the total THD. For example, a turns ratio of 1:3 can be considered an ideal turns ratio that minimizes the total THD. In the case of a turns ratio of 1:3 with respect to the second output inductor 210, the magnitude of the first current 246 can be approximately three times the magnitude of the second current 248, and therefore, 25% of the output current 250 comes from the first current 246, and 75% of the output current 250 comes from the second current 248.

[0056] In other embodiments, alternating turns ratios may be implemented. In addition, in some embodiments, the first output inductor 208 and the second output inductor 210 may have the same turns ratio, and in other embodiments, the first output inductor 208 and the second output inductor 210 may have different turns ratios.

[0057] A first advantage of the rectifier 200 over the rectifier 100 includes reduced diode losses. The current provided by the first output inductor 208 and the second output inductor 210 flows through a plurality of diodes, which may correspond to a plurality of phases of the AC power provided by the rectifier 200. Figure 2AIn the illustrated embodiment, the input 218 is configured to receive a three-phase AC power source. Thus, the first diode bridge 204 and the second diode bridge 206 each include six diodes, and the first set of diodes 212 and the second set of diodes 214 each include three diodes.

[0058] Although the total number of diodes in the rectifier 200 is greater than the total number of diodes in the conventional rectifier 100, the average current through the diodes in the rectifier 200 is less than the average current through the diodes in the rectifier 100. In addition, each current path in the rectifier 200 includes at most two diodes, while each current path in the rectifier 100 includes at most three diodes.

[0059] The conduction losses through a diode depend at least in part on the average current and the root-mean-square (RMS) current through the diode. For example, the typical losses through a diode can be expressed as:

[0060]

[0061] Among them, P loss is the power loss through the diode, I avg is the average current through the diode, V (T0) is the threshold voltage of the diode, I RMS is the RMS current through the diode, r T is the slope resistance of the diode.

[0062] According to equation (4), the diode loss is proportional to the voltage threshold of the diode and the slope resistance of the diode. In some embodiments, it may be relatively easy to select a diode with a negligible small slope resistance. Therefore, the power loss due to the slope resistance can be substantially minimized. However, the threshold voltage may be more difficult to minimize. Because the threshold voltage is non-negligible and can be relatively fixed, minimizing the average current I avg To minimize the power loss through the diode P loss Could be advantageous.

[0063] In the prior art rectifier 100, the output diode 110 continuously conducts the average current. When the first diode 123 and the second diode 125 are alternately turned on in equal proportions, the first diode 123 and the second diode 125 each conduct half of the average current. Each diode of the first diode bridge 104 and the second diode bridge 106 is configured to conduct one of the three phases of the input power, and thus will conduct a current of approximately 1 / 6 of the average current.

[0064] In the rectifier 200, the first diode bridge 204 and the second diode bridge 206 are alternately turned on, and the first group of diodes 212 and the second group of diodes 214 are alternately turned on, wherein each diode in the first diode bridge 204, the second diode bridge 206, the first group of diodes 212 and the second group of diodes 214 conducts one of the three phases of the input power supply. Half of the diodes of the rectifier 200 conduct current, which is provided to the positive terminal of the first output reactor 208 or the second output reactor 210, and half of the diodes of the rectifier 200 conduct current, which is provided to the negative terminal of the first output reactor 208 or the second output reactor 210.

[0065] In some embodiments, the positive windings of the first output reactor 208 and the second output reactor 210 have more turns than the corresponding negative windings. In these embodiments, half of the diodes of the rectifier 200 that provide current to the positive terminals of the first output reactor 208 and the second output reactor 210 conduct approximately 1 / 6 of the output current, respectively. Half of the diodes of the rectifier 200 that provide current to the negative terminals of the first output reactor 208 and the second output reactor 210 conduct approximately 1 / 18 of the output current, or the amount of current provided to the positive terminals of the first output reactor 208 and the second output reactor 210 divided by an exemplary turns ratio, for example: three.

[0066] In summary, in the rectifier 100, twelve diodes (i.e., diodes from the first diode bridge 104 and the second diode bridge 106) conduct a current of approximately 1 / 6 of the average current, and two diodes (i.e., the output diodes 110) conduct a current of approximately half of the average current. In the rectifier 200, nine diodes (i.e., diodes conducting current provided to the positive terminals of the first output reactor 208 and the second output reactor 210) each conduct a current of approximately 1 / 6 of the average current, and nine diodes (i.e., diodes conducting current provided to the negative terminals of the first output reactor 208 and the second output reactor 210) each conduct a current of approximately 1 / 18 of the average current. Therefore, in the case where the power loss is related to the average current according to equation (4), the power loss of the rectifier 200 is reduced by approximately 33% relative to the rectifier 100.

[0067] A second advantage of the rectifier 200 over the rectifier 100 includes mitigating saturation of the reactor. For example, the transformer 102 of the rectifier 100 includes two secondary windings, each of which provides current to the rectifier 100. If there is any imbalance between the two secondary windings, such as an imbalance between leakage impedances, a net non-zero DC current is provided to the output rectifier 108, which will cause a magnetic field accumulation.

[0068] Since the output rectifier 108 is continuously turned on, due to the net non-zero DC current, the magnetic field will continue to accumulate in the output inductor 108, and the accumulated magnetic energy cannot be released. In order to avoid the output inductor 108 from reaching saturation, the output inductor 108 is usually implemented with an air gap core or other low permeability material to solve the inevitable magnetic field accumulation. As mentioned above, implementing an air gap core or other low permeability material will bring some disadvantages.

[0069] In contrast, the rectifier 200 resists the substantial imbalance between the first secondary winding 224 and the second secondary winding 226. Unlike the single output inductor 108 that is always on, the first output inductor 208 and the second output inductor 210 are alternately turned on. Therefore, even if there is a large imbalance between the first secondary winding 224 and the second secondary winding 226, the first output inductor 208 and the second output inductor 210 are able to release the accumulated magnetic energy during the time period when they are not conducting current. Each of the first output inductor 208 and the second output inductor 210 starts a new conduction cycle from an approximately zero current state and does not reach saturation.

[0070] The saturation resistance exhibited by the first output inductor 208 and the second output inductor 210 further improves the load balance of the transformer 202. For some embodiments of the transformer 202, there may be at least a small imbalance between the impedances of the first secondary winding 224 and the second secondary winding 226. The imbalance of the impedances of the first secondary winding 224 and the second secondary winding 226 may lead to an imbalance in the load current, and the saturation of the first output inductor 208 and the second output inductor 210 may further aggravate the imbalance in the load current.

[0071] However, as described above, the first output inductor 208 and the second output inductor 210 resist the effects of saturation. Therefore, the imbalance of the load current provided by the first secondary winding 224 and the second secondary winding 226 is correspondingly reduced and significantly easier to manage compared to the transformer 102. For example, for the same winding imbalance, the imbalance of the load current provided by the first secondary winding 224 and the second secondary winding 226 can be less than three times the imbalance of the load current provided by the first secondary winding 116 and the second secondary winding 118.

[0072] The anti-saturation property also improves the output characteristics of the rectifier 200 compared to the rectifier 100. At relatively low loads, the excitation current in the output inductor 108 (relatively large due to the air gap or low permeability magnetic core) may be large relative to the output load current. Below a certain threshold load current, the voltage across the output inductor 108 may approach zero and enter discontinuous conduction mode (DCM). The output voltage of the rectifier 100 may rise unfavorably because the voltage is not the average voltage from the first diode bridge 104 and the second diode bridge 106, but follows the highest voltage from the diode bridges 104, 106.

[0073] On the contrary, since the first output reactor 208 and the second output reactor 210 can be implemented with a higher permeability magnetic core, the self-inductance increases and the excitation current decreases, so that the load power threshold between DCM and continuous conduction mode (Continuous Conduction Mode, CCM) is greatly reduced. For example, in some embodiments, the threshold can be about 0.5% of the rated load (for example, a 2kW threshold for a 400kW rating). Therefore, for example, compared with the rectifier 100, the rectifier 200 can maintain the load demand with a significantly lower voltage demand.

[0074] Figure 3 A rectifier 300 according to an embodiment of the present invention is shown. The rectifier 300 includes a transformer 302, a first diode bridge 304, a second diode bridge 306, an output reactor 308, a plurality of first diodes 310, a plurality of second diodes 312, a capacitor 314, an input 316, and an output 318. The transformer 302 includes a primary winding 320, a first secondary winding 322, and a second secondary winding 324.

[0075] The input 316 is coupled to the primary winding 320 and is configured to be coupled to a power source (e.g., an AC mains power source). The primary winding 320 is coupled to the input 316 and is inductively coupled to a first secondary winding 322 and a second secondary winding 324. The first secondary winding 322 is inductively coupled to the primary winding 320 and is coupled to the first diode bridge 304 and the first diode 310. The second secondary winding 324 is inductively coupled to the primary winding 320 and is coupled to the second diode bridge 306 and the second diode 312.

[0076] The first diode bridge 304 is coupled to the first secondary winding 322, the output reactor 308, the first diode 310, and the second diode bridge 306. The second diode bridge 306 is coupled to the second secondary winding 324, the output reactor 308, the second diode 312, and the first diode bridge 304. The output reactor 308 is coupled to the first diode bridge 304, the second diode 310, the output 318, the capacitor 314, the second diode 312, and the second diode bridge 306.

[0077] The first diode 310 is coupled to the first secondary winding 322, the first diode bridge 304, and the output reactor 308. The second diode 312 is coupled to the second secondary winding 324, the second diode bridge 306, and the output reactor 308. The capacitor 314 is coupled to the output reactor 308 and an output 318. The output 318 is coupled to the output reactor 308, the capacitor 314, and is configured to be coupled to a load (not shown).

[0078] The rectifier 300 may be particularly advantageous because only one output reactor 308 is implemented. In some examples, it may be more cost-effective to reduce the number of output reactors. However, the output reactor 308 may be implemented with a higher volt-ampere (VA) rating to accommodate the reduction in the number of output reactors.

[0079] Figure 4 A rectifier 400 according to another embodiment of the present invention is shown. The rectifier 400 includes a transformer 402, a first diode bridge 404, a second diode bridge 406, a first output inductor 408, a second output inductor 410, a plurality of first diodes 412, a plurality of second diodes 414, a capacitor 416, an input 418, an output 420, a first switch 422, and a second switch 424. The transformer 402 includes a primary winding 426, a first secondary winding 428, and a second secondary winding 430. The rectifier 400 is configured to be communicatively coupled to a controller 432.

[0080] The input 418 is coupled to the primary winding 426 and is configured to be coupled to a power source (e.g., an AC mains power source). The primary winding 426 is coupled to the input 418 and is inductively coupled to the first secondary winding 428 and the second secondary winding 430. The first secondary winding 428 is inductively coupled to the primary winding 426 and is coupled to the first diode bridge 404 and the first diode 412. The second secondary winding 430 is inductively coupled to the primary winding 426 and is coupled to the second diode bridge 406 and the second diode 414.

[0081] The first diode bridge 404 is coupled to the first secondary winding 428, the first output reactor 408, the first diode 412 and the second diode bridge 406. The second diode bridge 406 is coupled to the second secondary winding 430, the second output reactor 410, the second diode 414 and the first diode bridge 404.

[0082] The first output reactor 408 is coupled to the first diode bridge 404, the second diode 414, the output 420, the first switch 422 and the second output reactor 410. The second output reactor 410 is coupled to the second diode bridge 406, the first diode 412, the output 420, the first switch 422 and the first output reactor 408.

[0083] The first diode 412 is coupled to the first secondary winding 428, the first diode bridge 404, and the second output reactor 410. The second diode 414 is coupled to the second secondary winding 430, the second diode bridge 406, and the first output reactor 408. The capacitor 416 is coupled to the second switch 424. The output 420 is coupled to the first output reactor 208, the second output reactor 210, the first switch 422, and is configured to be coupled to a load (not shown).

[0084] The first switch 422 is coupled to the first output reactor 408, the second output reactor 410, the output 420, and the second switch 424, and is configured to be communicatively coupled to the controller 432. The second switch 424 is coupled to the first switch 422 and the capacitor 416, and is configured to be communicatively coupled to the controller 432. The controller 432 is configured to be communicatively coupled to the first switch 422 and the second switch 424.

[0085] The rectifier 400 is similar to the rectifier 200 and additionally includes a first switch 422 and a second switch 424. The first switch 422 and the second switch 424 can be configured to selectively allow current to pass in response to receiving a control signal from a controller 432. For example, when the rectifier 400 is initially powered on, the controller 432 can control the first switch 422 and the second switch 424 to limit the amount of current passing through the switches 422, 424 so that the capacitor 416 is not subjected to excessive in-rush current. After the capacitor 416 is sufficiently charged (e.g., as indicated by a minimum amount of charge on the capacitor 416 after a pre-charge condition is satisfied), the switches 422, 424 can remain in a closed and conductive configuration.

[0086] In addition to modulating the charging current of the capacitor 416, the switches 422, 424 may also be utilized where it is advantageous to limit the discharge current from the capacitor 416. For example, in the event of a short circuit to the output 420, the switches 422, 424 may be actuated to an open and non-conductive position to prevent the potentially adverse effects of a large amount of current being discharged from the capacitor 416. The controller 432 may be connected to a current sensor (not shown) configured to measure the output current of the rectifier 400 to detect such a short circuit event.

[0087] Although the switches 422, 424 are shown as MOSFETs, alternative implementations of the switches 422, 424 are possible. For example, the switches 422, 424 may be implemented as PTC thermistors, NTC thermistors, BJTs, etc. In addition, although two switches are shown, an alternative number of switches may be implemented. The switches 424, 426 may generally be referred to as switch circuits, or may be referred to as being included in switch circuits.

[0088] Furthermore, although the foregoing embodiments illustrate the transformers 202, 302, 402 as extended delta transformers, alternative embodiments providing phase-shifted voltages are possible. For example, the transformers 202, 302, 402 may include wye-connected transformers, non-extended delta transformers, or a combination of both.

[0089] Improved rectifiers have been disclosed. Embodiments of the disclosed rectifiers achieve significant improvements in power conversion efficiency and enhanced output power quality. The rectifiers disclosed herein may be implemented as standalone components, or may be implemented as part of a larger network of multiple devices. For example, the rectifiers disclosed herein may be implemented as part of an uninterruptible power supply (UPS).

[0090] For example, Figure 5 is a block diagram of a UPS 500. The UPS 500 includes an input 502, an AC / DC converter 504, a DC linker 506, a DC / DC converter 508, a battery 510, a controller 512, a DC / AC inverter 514, and an output 516. The input 502 is coupled to the AC / DC converter 504 and an AC power source (not shown), such as an AC mains power source. The AC / DC converter 504 is coupled to the input 502 and the DC linker 506, and is communicatively coupled to the controller 512.

[0091] The DC linker 506 is coupled to the AC / DC converter 504, the DC / DC converter 508, and the DC / AC inverter 514. The DC / DC converter 508 is coupled to the DC linker 506 and the battery 510, and is communicatively coupled to the controller 512. The battery 510 is coupled to the DC / DC converter 508. The DC / AC inverter 514 is coupled to the DC linker 506 and the output 516, and is communicatively coupled to the controller 512. The output 516 is coupled to the DC / AC inverter 514, and is coupled to an external load (not shown).

[0092] The input 502 is configured to couple to a DC main power source and receive an input AC power source having an input voltage level. For example, the input 502 can be configured to receive a single-phase AC main power source, a three-phase AC main power source, or an input power source having a different number of phases. The UPS 500 is configured to operate in different operating modes based on the input voltage level of the AC power provided to the input 502. When the AC power provided to the input 502 is acceptable (i.e., by having parameters that meet specified values), the UPS 500 operates in a normal operating mode.

[0093] In a normal operation mode, the AC power received at the input 502 is provided to the AC / DC converter 504. The AC / DC converter 504 converts the AC power to DC power and provides the DC power to the DC linker 506. In some examples, the AC / DC converter 504 may include the rectifier 200, the rectifier 300, and / or the rectifier 400. The DC linker 506 distributes the DC power to the DC / DC converter 508 and the DC / AC inverter 514. The DC / DC converter 508 converts the received DC power and provides the converted DC power to the battery 510 to charge the battery 510. The DC / AC inverter 514 receives the DC power from the DC linker 506, converts the DC power to regulated AC power, and provides the regulated AC power to the output 516 for delivery to the load.

[0094] When the AC power provided to the input 502 from the AC main power source is unacceptable (i.e., by having parameters that do not meet specified values), the UPS 500 will operate in a backup operating mode. In the backup operating mode, DC power is discharged from the battery 510 to the DC / DC converter 508. The DC / DC converter 508 converts the received DC power and provides the DC power to the DC linker 506. The DC linker 506 provides the received power to the DC / AC inverter 514. The DC / AC inverter 514 receives the DC power from the DC linker 506, converts the DC power to regulated AC power, and provides the regulated AC power to the output 516.

[0095] During the backup mode of operation, power to the DC linker 506 is provided by the battery 510, and in the normal mode of operation, power to the DC linker 506 is provided by a power source connected to the input 502. The power to the DC linker 506 is then extracted by a DC / AC inverter 514 to generate AC power, and the AC power is provided to an external load connected to the output 516. In alternative embodiments, the battery 510 may be replaced by an alternative energy storage device such as a capacitor or a flywheel.

[0096] In the UPS 500, an AC / DC converter may be implemented using one of the rectifiers 200, 300, 400. In alternative embodiments, the rectifiers 200, 300, 400 may be implemented in conjunction with alternative types of UPS. For example, in some embodiments, the rectifiers 200, 300, 400 may be implemented in DC UPSs configured to provide uninterruptible DC power instead of AC power. In some embodiments, the DC UPS may not include an inverter.

[0097] Alternative embodiments may further include components of different numbers or configurations. For example, the first group of diodes 212 described above is shown as including three diodes, which may be equal to the number of phases of the input power supply. In alternative embodiments, the first group of diodes 212 may include a number of diodes that is not equal to the number of phases of the input power supply. For example, each diode in the first group of diodes 212 may be replaced by two or more diodes connected in parallel. Similar principles apply to other diodes shown in conjunction with the rectifiers 200, 300, 400.

[0098] Thus, having described several aspects of at least one embodiment, those skilled in the art will readily appreciate various changes, modifications and improvements. Such changes, modifications and improvements are intended to be part of this disclosure and are intended to be within the scope of this disclosure. Therefore, the foregoing description and drawings are intended only as examples.

Claims

1. A method for power rectification, characterized in that: The method comprises the steps of: receiving input AC power; Providing the input AC power to a first group of diode bridges, a second group of diode bridges, a first group of diodes and a second group of diodes to generate a DC power, wherein a corresponding input of a plurality of diodes of the first group of diodes is coupled to a corresponding midpoint of a corresponding diode bridge of the first group of diode bridges, a corresponding input of a plurality of diodes of the second group of diodes is coupled to a corresponding midpoint of a corresponding diode bridge of the second group of diode bridges, a corresponding output of the first group of diode bridges and the second group of diodes is coupled to a first output reactor, a corresponding output of the second group of diode bridges and the first group of diodes is coupled to a second output reactor, and the first group of diodes includes diodes different from those of the second group of diodes; providing the DC power supply to the first output reactor and the second output reactor through the first diode bridge group, the second diode bridge group, the first diode group, and the second diode group; and The DC power is provided to an output through the first output reactor and the second output reactor.

2. The method for power rectification according to claim 1, characterized in that: Providing the input AC power to a primary winding of a transformer; Providing transformed AC power to a first secondary winding and a second secondary winding through the primary winding of the transformer; and The transformed AC power is provided to the first group of diode bridges and the second group of diode bridges through the first secondary winding and the second secondary winding.

3. The method for power rectification according to claim 1, characterized in that: The first group of diode bridges, the first group of diodes and the first output reactor and the corresponding second group of diode bridges, the second group of diodes and the second output reactor are alternately turned on.

4. The method for power rectification according to claim 3, characterized in that: The first output reactor and the second output reactor are configured to be alternately turned on without reaching a saturation state.

5. The method for power rectification according to claim 1, characterized in that: The first and second output reactors are configured to operate in a continuous conduction mode in response to a rectifier consisting of the first and second sets of diode bridges providing at least 0.5% of a rated load.

6. The method for power rectification according to claim 1, characterized in that: The method further comprises selectively controlling one or more switching elements to: limiting a charging current flowing to an output capacitor; and A discharge current flowing to the output capacitor is limited.

7. A system for uninterruptible power supply, characterized in that: The system comprises: an input configured to receive an input AC power source; an energy storage device configured to store energy and provide backup power; an output of an uninterruptible power supply configured to provide output power derived from at least one of the AC power source and the backup power source; and a rectifier coupled to the input and to the output of the uninterruptible power supply, the rectifier comprising: a first diode bridge and a second diode bridge coupled to the input; a first group of diodes and a second group of diodes coupled to the first group of diode bridges and the second group of diode bridges, wherein a respective input of the plurality of diodes of the first group of diodes is coupled to a respective midpoint of a respective diode bridge of the first group of diode bridges, a respective input of the plurality of diodes of the second group of diodes is coupled to a respective midpoint of a respective diode bridge of the second group of diode bridges, and the first group of diodes includes different diodes than the second group of diodes; a first output reactor coupled to a corresponding output of the first diode bridge and the second diode bridge; a second output reactor coupled to a corresponding output of the second set of diode bridges and the first set of diodes; and A rectifier output is coupled to the first output inductor and the second output inductor.

8. The uninterruptible power supply system as claimed in claim 7, characterized in that: The rectifier further comprises a transformer, wherein the transformer has: a primary winding coupled to the input; At least one secondary winding is configured according to an extended delta configuration and is coupled to the primary winding.

9. The uninterruptible power supply system as claimed in claim 7, characterized in that: The first output inductor includes: a first input tap coupled to the corresponding output of the first group of diode bridges; a second input tap coupled to the corresponding output of the second group of diodes; and an output tap coupled to the rectifier output; the second output inductor includes: a first input tap coupled to the corresponding output of the second group of diode bridges; and a second input tap coupled to the corresponding output of the first group of diodes; and an output tap coupled to the rectifier output.

10. The uninterruptible power supply system as claimed in claim 7, characterized in that: The first output inductor has an output tap, and the second output inductor has an output tap.

11. The uninterruptible power supply system as claimed in claim 10, characterized in that: An output tap of the first output reactor is configured to be coupled to the rectifier output; and An output tap of the second output reactor is configured to be coupled to the rectifier output.

12. The uninterruptible power supply system as claimed in claim 7, characterized in that: The system further comprises: a switch circuit coupled to the first output inductor, the second output inductor and the rectifier output; and An output capacitor is configured to be coupled to the switch circuit.

13. The uninterruptible power supply system as claimed in claim 12, characterized in that: The switch circuit is configured to: In response to detecting a short circuit at the rectifier output, selectively limiting a discharge current of the output capacitor; and In response to detecting that a pre-charge condition is not satisfied, a charging current flowing to the output capacitor is selectively limited.

14. A rectifier, characterized in that: The rectifier comprises: an input configured to receive an input AC power source; a first diode bridge and a second diode bridge coupled to the input; a first group of diodes and a second group of diodes coupled to the first group of diode bridges and the second group of diode bridges, wherein a respective input of the plurality of diodes of the first group of diodes is coupled to a respective midpoint of a respective diode bridge of the first group of diode bridges, a respective input of the plurality of diodes of the second group of diodes is coupled to a respective midpoint of a respective diode bridge of the second group of diode bridges, and the first group of diodes includes different diodes than the second group of diodes; a first output reactor coupled to a corresponding output of the first diode bridge and the second diode bridge; a second output reactor coupled to a corresponding output of the second set of diode bridges and the first set of diodes; and A rectifier output is coupled to the first output inductor and the second output inductor.

15. The rectifier according to claim 14, characterized in that: The first output inductor includes: a first input tap coupled to the corresponding output of the first group of diode bridges; a second input tap coupled to the corresponding output of the second group of diodes; and an output tap coupled to the rectifier output; the second output inductor includes: a first input tap coupled to the corresponding output of the second group of diode bridges; a second input tap coupled to the corresponding output of the first group of diodes; and an output tap coupled to the rectifier output.

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