Uninterruptible power supply and charging circuit thereof

Abstract

The utility model provides a charging circuit of an uninterruptible power supply, and the uninterruptible power supply is provided with a PFC circuit which is used for converting commercial power into bus voltage. The charging circuit comprises a first charging branch and a second charging branch. The first charging branch comprises a first input end, a first switching tube, a first inductor, a first diode and a first output end which are connected in sequence. The second charging branch comprises a second input end, a second switching tube, a second inductor, a second diode and a second output end which are connected in sequence; wherein bus voltage is connected to the first input end and the second input end, the first output end and the second output end are connected with a battery to be charged, one of the first switching tube and the second switching tube is controllably switched on, and the other one is controllably switched off. Therefore, one of the first charging branch and the second charging branch converts the bus voltage into corresponding charging voltage and outputs the charging voltage to the battery to be charged. In addition, the utility model also provides an uninterruptible power supply.

Description

Technical Field

[0001] This utility model relates to the field of UPS technology, and in particular to an uninterruptible power supply and its charging circuit. Background Technology

[0002] In uninterruptible power supplies (UPS), traditional charging circuits typically charge batteries by directly rectifying the mains power. However, in this type of charging circuit, the mains power is not processed by a power factor correction (PFC) circuit, and the direct rectification causes high-order harmonic pollution to the grid current, increasing total harmonic current distortion (THDI) and affecting grid quality. Furthermore, this type of charging circuit is difficult to meet the application requirements for rapid battery charging and precise control of charging voltage and current. Utility Model Content

[0003] In view of this, it is necessary to propose an uninterruptible power supply and its charging circuit.

[0004] In a first aspect, this utility model provides a charging circuit for an uninterruptible power supply (UPS). The UPS includes a PFC circuit for converting mains power into a bus voltage. The charging circuit includes a first charging branch and a second charging branch. The first charging branch includes a first input terminal, a first switching transistor, a first inductor, a first diode, and a first output terminal connected in sequence. The second charging branch includes a second input terminal, a second switching transistor, a second inductor, a second diode, and a second output terminal connected in sequence. The bus voltage is connected to the first input terminal and the second input terminal, respectively. The first output terminal and the second output terminal are connected to a battery to be charged. One of the first switching transistor and the second switching transistor is controllably turned on, and the other is controllably turned off, so that one of the first charging branch and the second charging branch converts the bus voltage into a corresponding charging voltage and outputs it to the battery to be charged.

[0005] Furthermore, the bus voltage includes a first bus voltage and a second bus voltage with opposite polarities, and the battery to be charged includes a first electrode and a second electrode with opposite polarities; the bus voltage and electrodes connected to the same charging branch have the same polarity.

[0006] Furthermore, the charging circuit also includes a reference branch, which has a first reference terminal and a second reference terminal. The reference branch is connected to the first charging branch through a first freewheeling diode and to the second charging branch through a second freewheeling diode.

[0007] Furthermore, after one of the first and second switching transistors is turned off, the current in the corresponding branch flows through the corresponding diode, the second reference terminal, and the corresponding freewheeling diode and is guided to the corresponding inductor.

[0008] Furthermore, the cathode of the first freewheeling diode is connected between the first switching transistor and the first inductor, and the anode of the second freewheeling diode is connected between the second switching transistor and the second inductor.

[0009] Furthermore, the reference branch is provided with a first grounding terminal and a second grounding terminal between the first reference terminal and the second reference terminal, so as to ground the first charging branch and the second charging branch.

[0010] Furthermore, the reference branch is also connected to the first charging branch through a first capacitor and to the second charging branch through a second capacitor, so that when the battery to be charged is connected to the first output terminal and the second output terminal, the first charging branch and the second charging branch respectively form a first BUCK circuit and a second BUCK circuit with the battery.

[0011] Furthermore, the first capacitor is connected between the first inductor and the first diode, and the second capacitor is connected between the second inductor and the second diode.

[0012] Furthermore, the first and second switching transistors are turned on or off sequentially according to a preset control frequency.

[0013] Secondly, this utility model embodiment provides an uninterruptible power supply (UPS), which includes a PFC circuit and a charging circuit for the UPS. The PFC circuit is used to convert mains power into bus voltage. The charging circuit is electrically connected to the PFC circuit so that the bus voltage can be connected to the first input terminal and the second input terminal, and the battery to be charged can be connected to the first output terminal and the second output terminal.

[0014] The aforementioned uninterruptible power supply (UPS) and its charging circuit convert mains power into bus voltage through a PFC circuit within the UPS, and employ two independent charging branches to charge the battery separately, thus avoiding the grid harmonic pollution and high THDI problems caused by the lack of PFC circuitry in existing technologies. Simultaneously, the design of the reference branch, freewheeling diode, and capacitor allows the two independent charging branches to form independent BUCK circuits with the battery, thereby achieving precise control of the charging voltage and current. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0016] Figure 1 A schematic diagram of the charging circuit of an uninterruptible power supply provided for an embodiment of the utility model.

[0017] Figure 2 A first schematic diagram of a BUCK circuit provided for an embodiment of the utility model.

[0018] Figure 3 A second schematic diagram of a BUCK circuit provided for an embodiment of the utility model.

[0019] Figure 4 A structural block diagram of an uninterruptible power supply provided for an embodiment of the utility model.

[0020] Component designations

[0021] Uninterruptible Power Supply-1000 Second Inductor - L6 Charging circuit -100 Second diode - Q6 PFC Circuit-101 Second output terminal - BAT - Rechargeable battery - 102 Reference branch -3 First charging branch - 1 First Reference Terminal - N First input terminal -+BUS Second Reference End - BAT-N First switching transistor - Q3 First grounding terminal - GND1 First Inductor - L5 Second grounding terminal - GND2 First diode - Q5 First freewheeling diode - D17 First output terminal - BAT+ Second freewheeling diode - D18 Second charging branch - 2 First capacitor - C1 Second input terminal -- BUS Second capacitor - C2 Second switching transistor - Q4

[0022] The realization of the purpose, functional features and advantages of this utility model will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0023] In the description of this utility model, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0024] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0025] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0026] To provide a clearer and more accurate understanding of the present invention, a detailed description will now be provided in conjunction with the accompanying drawings. The accompanying drawings illustrate examples of embodiments of the present invention, wherein the same reference numerals denote the same elements. It is to be understood that the scale shown in the accompanying drawings is not the actual scale of the present invention, and is for illustrative purposes only, and is not a drawing based on the original dimensions.

[0027] Please refer to Figure 1 This utility model provides a charging circuit 100 for an uninterruptible power supply (UPS). The UPS 100 is equipped with a PFC circuit 101. The PFC circuit 101 is used to convert mains power into bus voltage. In other words, by inputting the bus voltage obtained after processing by the PFC circuit 101 into the charging circuit 100, this application avoids the grid harmonic pollution and high THDI problems caused by the lack of PFC circuit 101 in existing charging circuits 100.

[0028] like Figure 1 As shown, the charging circuit 100 includes a first charging branch 1 and a second charging branch 2. The first charging branch 1 includes a first input terminal +BUS, a first switching transistor Q3, a first inductor L5, a first diode Q5, and a first output terminal BAT+ connected in sequence. The second charging branch 2 includes a second input terminal -BUS, a second switching transistor Q4, a second inductor L6, a second diode Q6, and a second output terminal BAT- connected in sequence. Specifically, the first switching transistor Q3 includes a drain (D), a source (S), and a gate (G). The first input terminal +BUS is connected to the drain of the first switching transistor Q3. The first inductor L5 is connected to the source of the first switching transistor Q3. The first diode Q5 is configured to conduct in the direction of current from the first inductor L5 to the first output terminal BAT+. Correspondingly, the second switching transistor Q4 also includes a drain, a source, and a gate. The second input terminal -BUS is connected to the source of the second switching transistor Q4. The second inductor L6 is connected to the drain of the second switching transistor Q4. The second diode Q6 is configured to conduct in the direction of current from the second output terminal BAT- to the second inductor L6.

[0029] In this embodiment, the bus voltage is connected to the first input terminal +BUS and the second input terminal -BUS, respectively. The first output terminal BAT+ and the second output terminal BAT- are connected to the battery 102 to be charged. One of the first switch Q3 and the second switch Q4 is controllably turned on, and the other is controllably turned off, so that one of the first charging branch 1 and the second charging branch 2 converts the bus voltage into a corresponding charging voltage and outputs it to the battery 102 to be charged. Specifically, the first switch Q3 and the second switch Q4 are turned on or off sequentially according to a preset control frequency. The preset control frequency is a frequency sequence formed by different control frequencies cycling according to a predetermined time period. The different control frequencies include at least the control frequency for controlling the first switch Q3 and the second switch Q4 to turn on and off. More specifically, the first switch Q3 and the second switch Q4 are output to the gates of the first switch Q3 and the second switch Q4 respectively by a controller (not shown), such as a proportional controller, so that the first switch Q3 and the second switch Q4 are turned on or off sequentially according to the preset control frequency.

[0030] When the first switch Q3 is turned on, the current input to the first input terminal +BUS flows sequentially through the first switch Q3, the first inductor L5, and the first diode Q5 to reach the first output terminal BAT+. Correspondingly, when the second switch Q4 is turned on, the current input to the second input terminal -BUS flows sequentially through the second switch Q4, the second inductor L6, and the second diode Q6 to reach the second output terminal BAT-.

[0031] Furthermore, the bus voltage includes a first bus voltage and a second bus voltage with opposite polarities. The battery to be recharged 102 includes a first electrode and a second electrode with opposite polarities. In this application, the first electrode and the second electrode can be positive and negative, respectively. Bus voltages and electrodes connected to the same charging branch have the same polarity, and the positive and negative electrodes can be connected to the corresponding output terminals according to the current conduction direction of the inductor and output terminal in different charging branches.

[0032] In this embodiment, the charging circuit 100 further includes a reference branch 3. The reference branch 3 has a first reference terminal N and a second reference terminal BAT-N. The reference branch 3 is connected to the first charging branch 1 via a first freewheeling diode D17 and to the second charging branch 2 via a second freewheeling diode D18. More specifically, the cathode of the first freewheeling diode D17 is connected between the first switching transistor Q3 and the first inductor L5, and the anode of the second freewheeling diode D18 is connected between the second switching transistor Q4 and the second inductor L6.

[0033] After one of the first switching transistors Q3 and Q4 is turned off, the current in the corresponding branch flows through the corresponding diode, the second reference terminal BAT-N, and the corresponding freewheeling diode to the corresponding inductor. Specifically, along the current direction of the corresponding charging branch, the cathodes of the first diode Q5 and the second diode Q6 are respectively connected to the second reference terminal BAT-N. When the first switching transistor Q3 is turned off after being turned on for a period of time, due to the freewheeling characteristic of the first inductor L5, a freewheeling path for the first inductor L5 is formed in the first charging branch 1 through the first diode Q5, the second reference terminal BAT-N, and the first freewheeling diode D17. This ensures that the current in the first charging branch 1 can continue to flow to the first output terminal BAT+, avoiding current interruption and overvoltage, damage to the charging branch, etc.

[0034] Correspondingly, when the second switch Q4 is turned off after being turned on for a period of time, since the second inductor L6 also has the characteristic of freewheeling, the second charging branch 2 forms a freewheeling path for the second inductor L6 through the second diode Q6, the second reference terminal BAT-N, and the second freewheeling diode D18, ensuring that the current in the second charging branch 2 can continue to flow to the second output terminal BAT-.

[0035] Furthermore, reference branch 3 is provided with a first ground terminal GND1 and a second ground terminal GND2 between the first reference terminal N and the second reference terminal BAT-N. The first ground terminal GND1 is located on the side closer to the first reference terminal N, and the second ground terminal GND2 is located on the side closer to the second reference terminal BAT-N, so as to provide grounding for the first charging branch 1 and the second charging branch 2.

[0036] Furthermore, reference branch 3 is also connected to the first charging branch 1 via the first capacitor C1 and to the second charging branch 2 via the second capacitor C2. Specifically, the first capacitor C1 is connected between the first inductor L5 and the first diode Q5, and the second capacitor C2 is connected between the second inductor L6 and the second diode Q6. This ensures that when the battery to be charged 102 is connected to the first output terminal BAT+ and the second output terminal BAT-, the first charging branch 1 and the second charging branch 2 respectively form a first BUCK circuit and a second BUCK circuit with the battery. That is, the first BUCK circuit includes the first input terminal +BUS, the first switch Q3, the first inductor L5, the first diode Q5, the first output terminal BAT+, the first capacitor C1, and the battery to be charged 102. The second BUCK circuit includes the second input terminal -BUS, the second switch Q4, the second inductor L6, the second diode Q6, the second output terminal BAT-, the second capacitor C2, and the battery to be charged 102. The following analysis will use the first BUCK circuit as an example, combined with the diagram, to analyze the transfer functions of the first BUCK circuit.

[0037] like Figure 2As shown, the first BUCK circuit is modeled using a small-signal model, and feedforward control of the input voltage is added to establish the following equations:

[0038] 1. Transfer function from inductor current to output voltage:

[0039] G iv (s)=V(s) / I(s)=R / (CRs+1)

[0040] 2. Transfer function from duty cycle to inductor current:

[0041] G di (s)=d(s) / I(s)=[V g [(CRs+1)] / (LCRs) 2 +Ls+R)

[0042] 3. Transfer function from input voltage to output voltage:

[0043]

[0044] 4. Transfer function from duty cycle to output voltage:

[0045] G dv (s)=V(s) / V g (s)=(V g R) / (LCRs 2 +Ls+R)

[0046] 5. Parameters of feedforward control:

[0047] D n (s)=-D / V g

[0048] Where L, C, and R represent the impedances of the inductor, capacitor, and battery 102 to be recharged, respectively, s represents the preset control frequency, and D represents the duty cycle.

[0049] In this application, the transfer function G from inductor current to output voltage... iv (s), combined Figure 3 The controller provides a current loop that describes the effect of inductor current changes on the output voltage, thus reflecting the response characteristics of the output voltage when the load inside the battery 102 changes; the transfer function G from duty cycle to inductor current... di (s) can represent the effect of the switching transistor's duty cycle change on the inductor current; the transfer function from input voltage to output voltage. It can reflect the impact of input voltage fluctuations on output voltage, and thus, combined with input voltage feedforward control, compensate for input voltage fluctuations in advance; the transfer function G from duty cycle to output voltage dv(s) can represent the control effect of duty cycle change on output voltage, and then the adjustment of output voltage can be reflected by adjusting the preset control frequency; the feedforward control parameter can be used to compensate for input voltage fluctuations in advance, enhance the BUCK circuit's ability to suppress input disturbances, and further avoid grid harmonic pollution and high THDI problems.

[0050] Please refer to Figure 4 This utility model embodiment also provides an uninterruptible power supply (UPS) 1000. The UPS 1000 includes a PFC circuit 101 and a charging circuit 100. The PFC circuit 101 converts mains power into a bus voltage. The charging circuit 100 is electrically connected to the PFC circuit 101, allowing the bus voltage to be connected to the first input terminal +BUS and the second input terminal -BUS, and allowing the battery to be charged 102 to be connected to the first output terminal BAT+ and the second output terminal BAT-. The specific features of the charging circuit 100 have been described in detail above and will not be repeated here. In this application, the battery to be charged 102 can be a battery internal to the UPS 1000 or an external battery assembly connected to the charging circuit 100 of the UPS 1000.

[0051] In the above embodiments, the mains power is converted into bus voltage by the PFC circuit of the uninterruptible power supply, and the battery is charged by two independent charging branches, thus avoiding the grid harmonic pollution and high THDI problems caused by the lack of PFC circuit processing in the prior art. At the same time, the design of the reference branch, freewheeling diode and capacitor allows the two independent charging branches to form independent BUCK circuits with the battery, thereby achieving precise control of charging voltage and current.

[0052] Obviously, those skilled in the art can make various modifications and variations to this utility model without departing from the spirit and scope of this application. Therefore, if these modifications and variations of this utility model fall within the scope of the claims of this utility model and their equivalents, this utility model is also intended to include these modifications and variations.

[0053] The above-listed embodiments are merely preferred embodiments of the present utility model and should not be construed as limiting the scope of the present utility model. Therefore, any equivalent variations made in accordance with the claims of the present utility model shall still fall within the scope of the present utility model.

Claims

1. A charging circuit for an uninterruptible power supply, characterized by The uninterruptible power supply is equipped with a PFC circuit for converting mains power into bus voltage; the charging circuit includes: The first charging branch includes a first input terminal, a first switching transistor, a first inductor, a first diode, and a first output terminal connected in sequence. The second charging branch includes a second input terminal, a second switching transistor, a second inductor, a second diode, and a second output terminal connected in sequence. The bus voltage is connected to the first input terminal and the second input terminal respectively, and the first output terminal and the second output terminal are connected to the battery to be charged. One of the first switch and the second switch is controllably turned on and the other is controllably turned off, so that one of the first charging branch and the second charging branch converts the bus voltage into a corresponding charging voltage and outputs it to the battery to be charged.

2. The charging circuit of claim 1, wherein, The bus voltage includes a first bus voltage and a second bus voltage with opposite polarities, and the battery to be charged includes a first electrode and a second electrode with opposite polarities; the bus voltage and electrodes connected to the same charging branch have the same polarity.

3. The charging circuit of claim 1, wherein, The charging circuit further includes a reference branch, which has a first reference terminal and a second reference terminal. The reference branch is connected to the first charging branch through a first freewheeling diode and to the second charging branch through a second freewheeling diode.

4. The charging circuit of claim 3, wherein, After one of the first and second switching transistors is turned off, the current in the corresponding branch flows through the corresponding diode, the second reference terminal, and the corresponding freewheeling diode and is guided to the corresponding inductor.

5. The charging circuit of claim 3, wherein, The cathode of the first freewheeling diode is connected between the first switching transistor and the first inductor, and the anode of the second freewheeling diode is connected between the second switching transistor and the second inductor.

6. The charging circuit of claim 3, wherein, The reference branch has a first grounding terminal and a second grounding terminal between the first reference terminal and the second reference terminal, so that the first charging branch and the second charging branch can be grounded.

7. The charging circuit of claim 3, wherein, The reference branch is also connected to the first charging branch through a first capacitor and to the second charging branch through a second capacitor, so that when the battery to be charged is connected to the first output terminal and the second output terminal, the first charging branch and the second charging branch respectively form a first BUCK circuit and a second BUCK circuit with the battery.

8. The charging circuit of claim 7, wherein, The first capacitor is connected between the first inductor and the first diode, and the second capacitor is connected between the second inductor and the second diode.

9. The charging circuit of claim 1, wherein, The first and second switching transistors are turned on or off sequentially according to a preset control frequency.

10. An uninterruptible power supply, characterized by The uninterruptible power supply includes: PFC circuit, used to convert AC mains power to bus voltage; The charging circuit of the uninterruptible power supply as described in any one of claims 1-9 is electrically connected to the PFC circuit so that the bus voltage can be connected to the first input terminal and the second input terminal, and the battery to be charged can be connected to the first output terminal and the second output terminal.

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