DC-DC converter and bidirectional DC-DC converter and uninterruptible power supply including the same

Abstract

The present invention provides a DC-DC converter and a bidirectional DC-DC converter and an uninterruptible power supply including the same, wherein the DC-DC converter includes: a first inductor, a first switch tube and a second inductor connected in sequence; a third inductor, a first diode and a fourth inductor connected in sequence; a first capacitor and a second capacitor, wherein one end of the first capacitor is connected to a node formed by the first inductor and the first switch tube, and the other end is connected to a node formed by the first diode and the third inductor; one end of the second capacitor is connected to a node formed by the first switch tube and the second inductor, and the other end is connected to a node formed by the first diode and the fourth inductor. The DC-DC converter of the present invention can step down or step up charging of a rechargeable battery, or step down or step up discharging of a rechargeable battery, and can be applied to uninterruptible power supplies in parallel.

Description

Technical Field

[0001] The present invention relates to the field of electronic circuits, and in particular to a DC-DC converter and a bidirectional DC-DC converter and an uninterruptible power supply comprising the same. Background Art

[0002] The DC-DC converter is an electrical device widely used in uninterruptible power supplies. The input of the DC-DC converter is connected to a rechargeable battery, and its output is connected to the positive and negative DC bus bars in the uninterruptible power supply. When the mains fails, the DC-DC converter boosts the DC power in the rechargeable battery and outputs it to the positive and negative DC bus bars.

[0003] Figure 1 The first circuit diagram of a DC-DC converter in the prior art is connected between the DC bus of an uninterruptible power supply and a rechargeable battery and is in a charging mode. Figure 1 As shown, the DC-DC converter 1 includes an inductor L11, a capacitor C11 and an inductor L13 connected in sequence between the positive DC bus 11 and the negative electrode of the rechargeable battery B, as well as an insulated gate bipolar transistor T11 and a diode D12. The node formed by the inductor L11 and the capacitor C11 is connected to the collector of the insulated gate bipolar transistor T11, the node formed by the capacitor C11 and the inductor L13 is connected to the anode of the diode D12, and the emitter of the insulated gate bipolar transistor T11 and the cathode of the diode D12 are both connected to the negative DC bus 12 and the positive electrode of the rechargeable battery B.

[0004] Figure 1 The DC-DC converter 1 shown can only be controlled to transfer the electric energy on the capacitor between the positive and negative DC bus bars to the rechargeable battery B, but cannot transfer the electric energy in the rechargeable battery B to the capacitor between the positive and negative DC bus bars, so that bidirectional energy transmission cannot be achieved. In order to achieve bidirectional energy transmission, the cost of the circuit module of the uninterruptible power supply will increase.

[0005] In practical applications of uninterruptible power supplies, in order to improve power density, it is often necessary to connect multiple uninterruptible power supply power modules in parallel.

[0006] Figure 2 Is to include two Figure 1 The circuit diagram of the uninterruptible power supply of the DC-DC converter is shown in parallel, as Figure 2 As shown, the positive electrode of the rechargeable battery B is simultaneously connected to the negative DC busbars 121 and 122 of the two uninterruptible power supplies, so each control device ( Figure 2 (not shown) cannot independently control the voltage on the negative DC bus of the corresponding uninterruptible power supply. It can be seen that Figure 1The DC-DC converter 1 shown cannot be applied to multiple uninterruptible power supplies connected in parallel.

[0007] Figure 3 The second circuit diagram of the prior art DC-DC converter is connected between the DC bus of the uninterruptible power supply and the rechargeable battery and is in the discharge mode, such as Figure 3 As shown, the DC-DC converter 2 includes an inductor L21, a capacitor C21 and an inductor L23 connected in sequence between the positive DC bus 21 and the negative electrode of the rechargeable battery B, as well as an insulated gate bipolar transistor T22 and a diode D21. The node formed by the inductor L21 and the capacitor C21 is connected to the cathode of the diode D21, the node formed by the capacitor C21 and the inductor L23 is connected to the emitter of the insulated gate bipolar transistor T22, and the anode of the diode D21 and the collector of the insulated gate bipolar transistor T22 are both connected to the negative DC bus 22 and the positive electrode of the rechargeable battery B.

[0008] Figure 3 The DC-DC converter 2 shown can only be controlled to transfer the electric energy in the rechargeable battery B to the capacitor between the positive and negative DC bus bars, but cannot transfer the electric energy on the capacitor between the positive and negative DC bus bars to the rechargeable battery B, and cannot realize bidirectional energy transmission. In order to realize bidirectional energy transmission, the cost of the circuit module of the uninterruptible power supply will increase.

[0009] Figure 4 Is to include two Figure 3 The circuit diagram of the uninterruptible power supply of the DC-DC converter is shown in parallel, as Figure 4 As shown, the positive electrode of the rechargeable battery B is simultaneously connected to the negative DC busbars 221 and 222 of the two uninterruptible power supplies, and each control device ( Figure 4 (not shown) is also unable to independently control the voltage on the negative DC bus of the corresponding uninterruptible power supply. It can be seen that Figure 3 The DC-DC converter 2 shown cannot be applied to multiple uninterruptible power supplies connected in parallel. Summary of the invention

[0010] In view of the above technical problems existing in the prior art, the present invention provides a DC-DC converter, comprising:

[0011] A first inductor, a first switch tube and a second inductor connected in sequence;

[0012] A third inductor, a first diode and a fourth inductor connected in sequence;

[0013] a first capacitor, one end of which is connected to a node formed by connecting the first inductor and the first switch tube, and the other end of which is connected to a node formed by connecting the first diode and the third inductor; and

[0014] A second capacitor has one end connected to a node formed by connecting the first switch tube and the second inductor, and the other end connected to a node formed by connecting the first diode and the fourth inductor.

[0015] Preferably, when the first switch tube is turned on, the first inductor, the first switch tube and the second inductor form a first current path, and the third inductor, the first capacitor, the first switch tube, the second capacitor and the fourth inductor form a second current path; when the first switch tube is turned off, the first inductor, the first capacitor, the first diode, the second capacitor and the second inductor form a third current path, and the third inductor, the first diode and the fourth inductor form a fourth current path.

[0016] Preferably, the first switching tube is a first insulated gate bipolar transistor, whose collector is connected to a node formed by connecting one end of the first inductor and the first capacitor, and whose emitter is connected to a node formed by connecting one end of the second inductor and the second capacitor, wherein the other end of the first inductor and the other end of the second inductor are respectively used to connect to the positive and negative electrodes of the first DC power supply device, and the third inductor and the fourth inductor are respectively used to connect to the negative and positive electrodes of the second DC power supply device.

[0017] Preferably, the DC-DC converter further includes a second diode connected in reverse parallel to the first switch tube, and a second switch tube connected in reverse parallel to the first diode.

[0018] Preferably, it also includes a control device, which is used to provide a pulse width modulation signal to the first switch tube to make it alternately turned on and off.

[0019] Preferably, it also includes a control device for

[0020] Control the second switch tube to be turned off, and provide a pulse width modulation signal to the first switch tube to make it alternately turned on and off; or

[0021] The first switch tube is controlled to be turned off, and a pulse width modulation signal is provided to the second switch tube to make it alternately turned on and off.

[0022] The present invention also provides a bidirectional DC-DC converter, comprising:

[0023] A first inductor, a first capacitor, and a second inductor connected in sequence;

[0024] A first switch tube having a first diode connected in reverse parallel, wherein a cathode of the first diode is connected to a node formed by connecting the first inductor and the first capacitor;

[0025] A second switch tube having a second diode connected in reverse parallel, wherein an anode of the second diode is connected to a node formed by connecting the first capacitor and the second inductor;

[0026] The anode of the first diode is connected to the cathode of the second diode.

[0027] Preferably, the first switching tube is a first insulated gate bipolar transistor, whose collector is connected to a node formed by connecting one end of the first inductor and the first capacitor, and whose emitter and the other end of the first inductor are respectively used to connect to the negative electrode and the positive electrode of the first DC power supply device; the second switching tube is a second insulated gate bipolar transistor, whose emitter is connected to a node formed by connecting the first capacitor and one end of the second inductor, and whose collector and the other end of the second inductor are respectively used to connect to the positive electrode and the negative electrode of the second DC power supply device.

[0028] Preferably, the bidirectional DC-DC converter further includes:

[0029] a second capacitor connected between the anode of the first diode and the cathode of the second diode;

[0030] a third inductor connected to the anode of the first diode;

[0031] A fourth inductor is connected to the cathode of the second diode.

[0032] Preferably, the bidirectional DC-DC converter further includes a control device for

[0033] Control the second switch tube to be turned off, and provide a pulse width modulation signal to the first switch tube to make it turn on and off alternately; or

[0034] The first switch tube is controlled to be turned off, and a pulse width modulation signal is provided to the second switch tube to make it turn on and off alternately.

[0035] The present invention also provides an uninterruptible power supply, comprising:

[0036] The DC-DC converter as described above or the bidirectional DC-DC converter as described above, wherein the DC-DC converter or the bidirectional DC-DC converter is connected between the positive and negative DC bus bars and the rechargeable battery;

[0037] a power factor correction circuit, whose input end is used to be connected to an AC power supply, and whose output end is connected to the positive and negative DC bus bars; and

[0038] The inverter has an input end connected to the positive and negative DC bus bars, and an output end for providing AC power.

[0039] The DC-DC converter of the present invention can charge or discharge a rechargeable battery by stepping down or stepping up the voltage, and can be applied to uninterruptible power supply in parallel. The bidirectional DC-DC converter of the present invention can also realize bidirectional transmission of energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The embodiments of the present invention are further described below with reference to the accompanying drawings, in which:

[0041] Figure 1 The invention is a circuit diagram of the first DC-DC converter in the prior art, which is connected between the DC bus of an uninterruptible power supply and a rechargeable battery and is in a charging mode.

[0042] Figure 2 is to include two Figure 1 The circuit diagram of the uninterruptible power supply with DC-DC converters connected in parallel.

[0043] Figure 3 The second DC-DC converter in the prior art is connected between the DC bus of the uninterruptible power supply and the rechargeable battery and is in a discharge mode.

[0044] Figure 4 is to include two Figure 3 The circuit diagram of the uninterruptible power supply with DC-DC converters connected in parallel.

[0045] Figure 5 is a circuit diagram of a DC-DC converter according to a first embodiment of the present invention.

[0046] Figure 6 and Figure 7 yes Figure 5 The circuit diagram of the DC-DC converter shown is connected between the DC bus of the uninterruptible power supply and the rechargeable battery and is in charging mode.

[0047] Figure 8 and Fig. 9 yes Figure 5 The circuit diagram of the DC-DC converter shown is connected between the DC bus of the uninterruptible power supply and the rechargeable battery and is in the discharge mode.

[0048] Fig.10 Is to include two Figure 6 The circuit diagram of the uninterruptible power supply with DC-DC converters connected in parallel is shown.

[0049] Fig.11 Is to include two Figure 8 The circuit diagram of the uninterruptible power supply with DC-DC converters connected in parallel is shown.

[0050] Fig.12is a circuit diagram of a DC-DC converter according to a second embodiment of the present invention.

[0051] Fig.13 yes Fig.12 The circuit diagram shown is a DC-DC converter connected between the DC bus of an uninterruptible power supply and a rechargeable battery.

[0052] Fig.14 yes Fig.13 The equivalent circuit diagram of the DC-DC converter in charging mode is shown.

[0053] Fig.15 yes Fig.13 The equivalent circuit diagram of the DC-DC converter in discharge mode is shown in

[0054] Fig.16 Is to include two Fig.12 The circuit diagram of the uninterruptible power supply with DC-DC converters connected in parallel is shown.

[0055] Fig.17 is a circuit diagram of a bidirectional DC-DC converter according to a third embodiment of the present invention.

[0056] Fig.18 yes Fig.17 A circuit diagram showing a bidirectional DC-DC converter connected between a DC bus of an uninterruptible power supply and a rechargeable battery.

[0057] Fig.19 and Fig. 20 yes Fig.18 The equivalent circuit diagram of the DC-DC converter in charging mode is shown.

[0058] Fig.21 and Fig. 22 yes Fig.18 The equivalent circuit diagram of the DC-DC converter in discharge mode is shown.

[0059] Fig.23 is a circuit diagram of a bidirectional DC-DC converter according to a fourth embodiment of the present invention. DETAILED DESCRIPTION

[0060] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings.

[0061] Figure 51 is a circuit diagram of a DC-DC converter according to a first embodiment of the present invention. The DC-DC converter 3 includes an inductor L31, an insulated gate bipolar transistor T31 and an inductor L32 connected in sequence, an inductor L33, a diode D32 and an inductor L34 connected in sequence, and a capacitor C31 and a capacitor C32, wherein one end of the capacitor C31 is connected to a node formed by connecting the inductor L31 and the collector of the insulated gate bipolar transistor T31, and the other end is connected to the anode of the diode D32; one end of the capacitor C32 is connected to a node formed by connecting the inductor L32 and the emitter of the insulated gate bipolar transistor T31, and the other end is connected to the cathode of the diode D32.

[0062] Among them, one end of the inductor L31 and one end of the inductor L32 are respectively used to connect to the positive and negative electrodes of a DC power supply device (such as a capacitor or a rechargeable battery), and one end of the inductor L34 and one end of the inductor L33 are respectively used as the positive output terminal and negative output terminal of the DC-DC converter 3, which are used to connect to the positive and negative electrodes of another DC power supply device (such as a capacitor or a rechargeable battery).

[0063] Combination Figure 1 and Figure 5 It can be seen that the DC-DC converter 3 and Figure 1 The difference of the DC-DC converter 1 shown is that it also includes an inductor L32 connected to the emitter of the insulated gate bipolar transistor T31, a capacitor C32 connected between the emitter of the insulated gate bipolar transistor T31 and the cathode of the diode D32, and an inductor L34 connected to the cathode of the diode D32.

[0064] In addition, combined Figure 3 and Figure 5 It can be seen that the DC-DC converter 3 and Figure 3 The difference of the DC-DC converter 2 shown is that it also includes an inductor L31 connected to the collector of the insulated gate bipolar transistor T31, a capacitor C31 connected between the collector of the insulated gate bipolar transistor T31 and the anode of the diode D32, and an inductor L33 connected to the anode of the diode D32.

[0065] The working principle of the DC-DC converter 3 will be described below in conjunction with the circuit diagrams of the DC-DC converter 3 in the charging mode and the discharging mode.

[0066] Figure 6 and Figure 7 yes Figure 5 The circuit diagram of the DC-DC converter shown in FIG. 1 is connected between the DC bus of the uninterruptible power supply and the rechargeable battery and is in charging mode. Figure 6 and Figure 7As shown, the other end of the inductor L31 and the other end of the inductor L32 are connected to the positive DC bus 31 and the negative DC bus 32 respectively, and the other end of the inductor L33 and the other end of the inductor L34 are connected to the negative electrode and the positive electrode of the rechargeable battery B respectively.

[0067] In the charging mode, a pulse width modulation signal is provided to the gate of the insulated gate bipolar transistor T31 (ie, its control terminal) to make it alternately turned on and off.

[0068] When the insulated gate bipolar transistor T31 is turned on, Figure 6 As shown, the positive DC bus 31, the inductor L31, the insulated gate bipolar transistor T31, the inductor L32 and the negative DC bus 32 form a current path, wherein the current direction is as shown in FIG. Figure 6 As shown by the dashed single arrow in the figure, at this time, the inductor L31 and the inductor L32 store energy. At the same time, the inductor L33, the capacitor C31, the insulated gate bipolar transistor T31, the capacitor C32, the inductor L34 and the rechargeable battery B form another current path, in which the current direction is as follows: Figure 6 As shown by the dotted double arrows in FIG. 1 , at this time, the capacitors C31 and C32 release energy and store it in the inductor L34 , the rechargeable battery B and the inductor L33 .

[0069] When the insulated gate bipolar transistor T31 is turned off, the positive DC bus 31, the inductor L31, the capacitor C31, the diode D32, the capacitor C32, the inductor L32 and the negative DC bus 32 form a current path, and the current direction is as follows: Figure 7 As shown by the dashed single arrow in , the inductor L31 and the inductor L32 release energy and store it in the capacitor C31 and the capacitor C32. At the same time, the inductor L33, the diode D32, the inductor L34 and the rechargeable battery B form another current path, and its current direction is as follows Figure 7 As shown by the dotted double arrows in FIG. 1 , at this time, the inductor L33 and the inductor L34 release energy and store it in the rechargeable battery B.

[0070] Combination Figure 6 and Figure 7 It can be known that the electric energy on the capacitor between the positive DC bus 31 and the negative DC bus 32 is finally stored in the rechargeable battery B, so that the rechargeable battery B is charged.

[0071] Assume that the voltage between the positive and negative DC bus is Udc, the voltage of the rechargeable battery is Uo, and the voltage at the node formed by the connection of inductor L31 and capacitor C31 is U B1 , the voltage at the node formed by the connection of inductor L32 and capacitor C32 is U B2 , the voltage at the node formed by the connection of inductor L33 and capacitor C31 is U A1 , the voltage at the node formed by the connection of inductor L34 and capacitor C32 is UA2 The voltage across capacitor C31 is U C1 , the voltage across capacitor C32 is U C2 The period of the pulse width modulation signal is T, the duty cycle of the pulse width modulation signal is d, and the on time and off time of the insulated gate bipolar transistor T31 in one pulse width modulation signal period are Ton and Toff respectively. Take one period of the pulse width modulation signal as an example for explanation.

[0072] When the insulated gate bipolar transistor T31 is turned on, the following equation is satisfied:

[0073] U B1 =U B2 AndU A1 =U A2 -U C1 -U C2

[0074] Then U B1 -U B2 =0 and U A1 -U A2 =-U C1 -U C2

[0075] When the insulated gate bipolar transistor T31 is turned off, the following equation is satisfied:

[0076] U B1 =U B2 +U C1 +U C2 AndU A1 =U A2

[0077] Then U B1 -U B2 =U C1 +U C2 AndU A1 -U A2 =0

[0078] In one switching cycle T, the following equation is satisfied:

[0079]

[0080]

[0081] The average voltage of inductors L31, L32, L33, and L34 in one switching cycle is 0, so

[0082] (U B1 -U B2 ) = Udc

[0083] (UA1 -U A2 ) = -Uo

[0084] but

[0085]

[0086] but

[0087] It can be seen that Uo / Udc=d / (1-d). When the duty cycle d<0.5, the rechargeable battery B is charged at a reduced voltage. When the duty cycle d>0.5, the rechargeable battery B is charged at a increased voltage.

[0088] Figure 8 and Fig. 9 yes Figure 5 The circuit diagram of the DC-DC converter shown in FIG. 1 is connected between the DC bus of the uninterruptible power supply and the rechargeable battery and is in the discharge mode. Figure 6 and Figure 7 The inductor L31 and the inductor L32 shown are connected to the positive and negative electrodes of the rechargeable battery B respectively, and Figure 6 and Figure 7 The inductor L33 and the inductor L34 shown are connected to the negative DC bus 32 and the positive DC bus 31 respectively to obtain Figure 8 and Fig. 9 The circuit shown.

[0089] In the discharge mode, a pulse width modulation signal is provided to the gate of the insulated gate bipolar transistor T32' to turn it on and off alternately.

[0090] When the insulated gate bipolar transistor T32' is turned on, Figure 8 As shown, the rechargeable battery B, the inductor L34', the insulated gate bipolar transistor T32' and the inductor L33' form a current path, and the current direction is as follows Figure 8 As shown by the dashed single arrow in the figure, the electric energy in the rechargeable battery B is stored in the inductor L33' and the inductor L34'. At the same time, the negative DC bus 32, the inductor L32', the capacitor C32', the insulated gate bipolar transistor T32', the capacitor C31', the inductor L31' and the positive DC bus 31 form a current path, and the current direction is as shown in FIG. Figure 8 As shown by the dotted double arrows in FIG. 1 , at this time, the capacitors C31 ′ and C32 ′ release energy and store it in the inductors L31 ′ and L32 ′, as well as the capacitors between the positive DC bus 31 and the negative DC bus 32 .

[0091] When the insulated gate bipolar transistor T32' is turned off, Fig. 9As shown, the rechargeable battery B, the inductor L34', the capacitor C32', the diode D32', the capacitor C31', and the inductor L33' form a current path, and the current direction is as follows Fig. 9 As shown by the dashed single arrow in the figure, at this time, the inductor L34' and the inductor L33' release energy and store it in the capacitor C32' and the capacitor C31'. At the same time, the negative DC bus 32, the inductor L32', the diode D32', the inductor L31' and the positive DC bus 31 form another current path, and its current direction is as follows: Fig. 9 As shown by the dotted double arrows in FIG. 1 , the inductor L32 ′ and the inductor L31 ′ release energy and store it in the capacitor between the positive DC bus 31 and the negative DC bus 32 .

[0092] Combination Figure 8 and Fig. 9 It can be seen that the electric energy in the rechargeable battery B is finally stored in the capacitor between the positive and negative DC buses.

[0093] Assume that the voltage between the positive and negative DC bus is Udc, the voltage of the rechargeable battery is Uo, and the voltage at the node formed by the inductor L31' and the capacitor C31' is U B1 , the voltage at the node formed by the connection of inductor L32' and capacitor C32' is U B2 , the voltage at the node formed by the connection of inductor L33' and capacitor C31' is U A1 , the voltage at the node formed by the connection of inductor L34' and capacitor C32' is U A2 The voltage across capacitor C31' is U C1 , the voltage across capacitor C32' is U C2 The period of the pulse width modulation signal is T, the duty cycle of the pulse width modulation signal is d, and the on time and off time of the insulated gate bipolar transistor T32' in one pulse width modulation signal period are Ton and Toff respectively. Take one period of the pulse width modulation signal as an example for explanation.

[0094] When the insulated gate bipolar transistor T32' is turned on, the following equation is satisfied

[0095] U A1 =U A2 AndU B1 =U B2 +U C1 +U C2

[0096] Then U A1 -U A2 =0 and U B1 -U B2 =U C1 +U C2

[0097] When the insulated gate bipolar transistor T32' is turned off, the following equation is satisfied:

[0098] U A1 =U A2 -U C1 -U C2 AndU B1 =U B2

[0099] Then U A1 -U A2 =-U C1 -U C2 AndU B1 -U B2 =0

[0100] In one switching cycle T, the following equation is satisfied:

[0101]

[0102]

[0103] The average voltage of inductors L31', L32', L33', and L34' in one switching cycle is 0, so

[0104] (U B1 -U B2 ) = Udc

[0105] (U A1 -U A2 ) = -Uo

[0106] but

[0107]

[0108]

[0109] It can be seen that Udc / Uo=d / (1-d). When the duty cycle d<0.5, the rechargeable battery B is discharged at a reduced voltage. When the duty cycle d>0.5, the rechargeable battery B is discharged at a increased voltage.

[0110] Fig.10 Is to include two Figure 6 The circuit diagram of the uninterruptible power supply of the DC-DC converter is shown in parallel, as Fig.10 As shown, the negative DC bus of each uninterruptible power supply is connected to the positive electrode of the rechargeable battery B through an inductor, a capacitor and an inductor in turn, and the negative DC bus of multiple uninterruptible power supplies are isolated from each other. Each control device ( Fig.10The two uninterruptible power supplies (not shown) can independently control the voltage on the negative DC bus of the corresponding uninterruptible power supply, thereby charging the rechargeable battery B using the electrical energy on the capacitor between the positive and negative DC buses of the uninterruptible power supply.

[0111] Fig.11 Is to include two Figure 8 The circuit diagram of the uninterruptible power supply of the DC-DC converter is shown in parallel, as Fig.11 As shown, the negative DC bus of each uninterruptible power supply is connected to the positive electrode of the rechargeable battery B through an inductor, a capacitor and an inductor in turn, and the negative DC bus of multiple uninterruptible power supplies are isolated from each other. Each control device ( Fig.11 The two devices (not shown) can independently control the voltage on the negative DC bus of the corresponding uninterruptible power supply, thereby enabling the rechargeable battery B to discharge and store the rechargeable battery B in the capacitor between the positive and negative DC buses of the corresponding uninterruptible power supply.

[0112] Fig.12 1 is a circuit diagram of a DC-DC converter according to a second embodiment of the present invention. Fig.12 As shown, the DC-DC converter 4 and Figure 5 The difference of the DC-DC converter 3 shown is that it further includes a diode D41 connected in reverse parallel to the insulated gate bipolar transistor T41 and an insulated gate bipolar transistor T42 connected in reverse parallel to the diode D42.

[0113] Among them, one end of the inductor L41 and one end of the inductor L42 are respectively used to connect to the positive and negative electrodes of a DC power supply device (such as a capacitor or a rechargeable battery), and one end of the inductor L44 and one end of the inductor L43 are respectively used as the positive output terminal and negative output terminal of the DC-DC converter 4, which are used to connect to the positive and negative electrodes of another DC power supply device (such as a capacitor or a rechargeable battery). Or one end of the inductor L44 and one end of the inductor L43 are respectively used to connect to the positive and negative electrodes of a DC power supply device (such as a capacitor or a rechargeable battery), and one end of the inductor L41 and one end of the inductor L42 are respectively used as the positive output terminal and negative output terminal of the DC-DC converter 4, which are used to connect to the positive and negative electrodes of another DC power supply device (such as a capacitor or a rechargeable battery).

[0114] Fig.13 yes Fig.12 The DC-DC converter shown in the figure is connected between the DC bus of the uninterruptible power supply and the rechargeable battery. Fig.13 As shown, the inductors L41 and L42 are connected to the positive DC bus 41 and the negative DC bus 42 respectively, and the inductors L43 and L44 are connected to the negative electrode and the positive electrode of the rechargeable battery B respectively.

[0115] The working principle of the DC-DC converter 4 is explained below with reference to the equivalent circuit diagrams of the DC-DC converter 4 in the charging mode and the discharging mode.

[0116] In charging mode, the control device ( Fig.13 The insulated gate bipolar transistor T42 is controlled to be turned off and a pulse width modulation signal is provided to the gate of the insulated gate bipolar transistor T41 to make it alternately turned on and off. Fig.14 yes Fig.13 The equivalent circuit diagram of the DC-DC converter in charging mode is shown in FIG. Figure 6 and Figure 7 The circuit shown is the same, and its specific control process is not repeated here. It can also realize step-down charging or step-up charging of the rechargeable battery B.

[0117] In discharge mode, the control device ( Fig.13 The insulated gate bipolar transistor T41 is controlled to be turned off (not shown), and a pulse width modulation signal is provided to the gate of the insulated gate bipolar transistor T42 to make it alternately turned on and off. Fig.15 yes Fig.13 The equivalent circuit diagram of the DC-DC converter in discharge mode is shown in FIG. Figure 8 and Fig. 9 The circuit shown is the same, and its specific control process is not repeated here. It can also enable the rechargeable battery B to achieve boost discharge or buck discharge.

[0118] Combination Fig.14 and Fig.15 It can be seen that the DC-DC converter 4 is a bidirectional DC-DC converter, which does not need to be connected to an additional charger or DC converter, saving costs. It can enable the rechargeable battery B to achieve boost discharge or buck discharge, and can also achieve buck charging or boost charging of the rechargeable battery B. In the process of charging the rechargeable battery, by changing the duty cycle d of the pulse width modulation signal, the capacitor between the positive and negative DC bus bars can be deeply discharged, and the rechargeable battery B can be charged from a voltage close to 0 volts without generating an impact current.

[0119] Fig.16 Is to include two Fig.12 The circuit diagram of the uninterruptible power supply of the DC-DC converter shown in parallel, each control device ( Fig.16 Each of the two uninterruptible power supplies (not shown) can individually control the DC-DC converters in the corresponding uninterruptible power supplies, thereby independently controlling the voltage on the negative DC bus of each uninterruptible power supply.

[0120] Fig.17 is a circuit diagram of a bidirectional DC-DC converter according to a third embodiment of the present invention. Fig.17As shown, the bidirectional DC-DC converter 5 includes an inductor L51, a capacitor C51 and an inductor L53 connected in sequence, an insulated gate bipolar transistor T51 with an anti-parallel diode D51, and an insulated gate bipolar transistor T52 with an anti-parallel diode D52, wherein the cathode of the diode D51 is connected to the node formed by the inductor L51 and the capacitor C51, the anode of the diode D52 is connected to the node formed by the capacitor C51 and the inductor L53, and the anode of the diode D51 is connected to the cathode of the diode D52.

[0121] Among them, one end of the inductor L51 and the emitter of the insulated gate bipolar transistor T51 (i.e., the anode of the diode D51) are respectively used to connect to the positive and negative electrodes of a DC power supply device (e.g., a capacitor or a rechargeable battery), and the collector of the insulated gate bipolar transistor T51 (i.e., the cathode of the diode D52) and one end of the inductor L53 are respectively used as the positive output terminal and the negative output terminal of the bidirectional DC-DC converter 5, which are used to connect to the positive and negative electrodes of another DC power supply device (e.g., a capacitor or a rechargeable battery). Or the cathode of the diode D52 and one end of the inductor L53 are respectively used to connect to the positive and negative electrodes of a DC power supply device (e.g., a capacitor or a rechargeable battery), and one end of the inductor L51 and the anode of the diode D51 are respectively used as the positive output terminal and the negative output terminal of the bidirectional DC-DC converter 5, which are used to connect to the positive and negative electrodes of another DC power supply device (e.g., a capacitor or a rechargeable battery).

[0122] Combination Figure 1 and Fig.17 It can be seen that the bidirectional DC-DC converter 5 and Figure 1 The difference of the DC-DC converter 1 shown is that it further includes a diode connected in reverse parallel to the insulated gate bipolar transistor T11 and an insulated gate bipolar transistor connected in reverse parallel to the diode D12.

[0123] In addition, combined Figure 3 and Fig.17 It can be seen that the bidirectional DC-DC converter 5 and Figure 3 The difference of the DC-DC converter 2 shown is that it further includes an insulated gate bipolar transistor connected in anti-parallel with the diode D21 and a diode connected in anti-parallel with the insulated gate bipolar transistor T22.

[0124] Fig.18 yes Fig.17The bidirectional DC-DC converter shown is connected to the circuit diagram between the DC bus of the uninterruptible power supply and the rechargeable battery, wherein the inductor L51 is connected to the positive DC bus 51, the inductor L53 is connected to the negative electrode of the rechargeable battery B, and the positive electrode of the rechargeable battery B, the emitter of the insulated gate bipolar transistor T51, the anode of the diode D51, the cathode of the diode D52, and the collector of the insulated gate bipolar transistor T52 are all connected to the negative DC bus 52.

[0125] The working principle of the bidirectional DC-DC converter 5 will be described below in conjunction with the equivalent circuit diagrams of the bidirectional DC-DC converter 5 in the charging mode and the discharging mode.

[0126] In charging mode, the control device ( Fig.18 The insulated gate bipolar transistor T52 is controlled to be turned off and a pulse width modulation signal is provided to the gate of the insulated gate bipolar transistor T51 to make it alternately turned on and off. Fig.19 and Fig. 20 yes Fig.18 The equivalent circuit diagram of the DC-DC converter in charging mode is shown.

[0127] like Fig.19 As shown, when the insulated gate bipolar transistor T51 is turned on, the positive DC bus 51, the inductor L51, the insulated gate bipolar transistor T51 and the negative DC bus 52 form a current path, in which the current direction is as shown in FIG. Fig.19 As shown by the dashed single arrow in the figure, the inductor L51 stores energy. At the same time, the inductor L53, the capacitor C51, the insulated gate bipolar transistor T51 and the rechargeable battery B form another current path, in which the current direction is as follows: Fig.19 As shown by the dotted double arrows in , at this time, the capacitor C51 releases energy and stores it in the rechargeable battery B and the inductor L53.

[0128] like Fig. 20 As shown, when the insulated gate bipolar transistor T51 is turned off, the positive DC bus 51, the inductor L51, the capacitor C51, the diode D52 and the negative DC bus 52 form a current path, and the current direction is as shown in FIG. Fig. 20 As shown by the dashed single arrow in the figure, the inductor L51 releases energy and stores it in the capacitor C51. At the same time, the inductor L53, the diode D52 and the rechargeable battery B form another current path, and the current direction is as follows: Fig. 20 As shown by the dotted double arrows in FIG. 1 , at this time, the inductor L53 releases energy and stores it in the rechargeable battery B.

[0129] Combination Fig.19 and Fig. 20 It can be known that the electric energy on the capacitor between the positive DC bus 51 and the negative DC bus 52 is finally stored in the rechargeable battery B, so that the rechargeable battery B is charged.

[0130] Assume that the voltage value between the positive DC bus 51 and the negative DC bus 52 is Udc, the voltage value of the rechargeable battery B is Uo, and the voltage at the node formed by the connection of the inductor L51 and the capacitor C51 is U B1 , the voltage at the node formed by the connection of inductor L53 and capacitor C51 is U A1 , the voltage across the emitter of the insulated gate bipolar transistor T51 and the cathode of the diode D52 is U2. The voltage across the capacitor C51 is U C1 , the period of the pulse width modulation signal is T, the duty cycle of the pulse width modulation signal is d, and the on time and off time of the insulated gate bipolar transistor T51 in one pulse width modulation signal period are Ton and Toff respectively. Take one period of the pulse width modulation signal as an example for explanation.

[0131] When the insulated gate bipolar transistor T51 is turned on, the following equation is satisfied:

[0132] U B1 =U2andU A1 =U2-U C1

[0133] Then U B1 -U2=0 and U A1 -U2=-U C1

[0134] When the insulated gate bipolar transistor T51 is turned off, the following equation is satisfied:

[0135] U B1 =U2+U C1 AndU A1 =U2

[0136] Then U B1 -U2=U C1 AndU A1 -U2=0

[0137] In one switching cycle T, the following equation is satisfied:

[0138]

[0139]

[0140] The average voltage of inductor L51 and inductor L53 in one switching cycle is 0, so,

[0141] (U B1 -U2) average value = Udc

[0142] (U A1 -U2) average value = Uo

[0143]

[0144]

[0145]

[0146] It can be seen that Uo / Udc=-d / (1-d). When the duty cycle d<0.5, the rechargeable battery B is charged at a reduced voltage. When the duty cycle d>0.5, the rechargeable battery B is charged at a increased voltage.

[0147] In discharge mode, the control device ( Fig.18 The insulated gate bipolar transistor T51 is controlled to be turned off (not shown), and a pulse width modulation signal is provided to the gate of the insulated gate bipolar transistor T52 to make it alternately turned on and off. Fig.21 and Fig. 22 yes Fig.18 The equivalent circuit diagram of the DC-DC converter in discharge mode is shown.

[0148] like Fig.21 As shown, when the insulated gate bipolar transistor T52 is turned on, the rechargeable battery B, the insulated gate bipolar transistor T52 and the inductor L53 form a current path, in which the current direction is as shown in FIG. Fig.21 As shown by the dashed single arrow in the figure, the inductor L53 stores energy. At the same time, the negative DC bus 52, the insulated gate bipolar transistor T52, the capacitor C51, the inductor L51 and the positive DC bus 51 form another current path, in which the current direction is as follows: Fig.21 As shown by the dotted double arrows in , at this time, the capacitor C51 releases energy and stores it in the inductor L51 and the capacitor between the positive DC bus 51 and the negative DC bus 52 .

[0149] like Fig. 22 As shown, when the insulated gate bipolar transistor T52 is turned off, the rechargeable battery B, the diode D51, the capacitor C51 and the inductor L53 form a current path, in which the current direction is as follows Fig. 22 As shown by the dashed single arrow in , the rechargeable battery B and the inductor L53 release energy and store it in the capacitor C51. At the same time, the negative DC bus 52, the diode D51, the inductor L51 and the positive DC bus 51 form another current path, in which the current direction is as follows Fig. 22 As shown by the dotted double arrows in FIG. 5 , at this time, the inductor L51 releases energy and stores it in the capacitor between the positive DC bus 51 and the negative DC bus 52 .

[0150] Combination Fig.21 and Fig. 22 It can be seen that the discharge of the rechargeable battery B is achieved, and its electric energy is finally stored in the capacitor between the positive DC bus 51 and the negative DC bus 52 .

[0151] Assume that the voltage value between the positive DC bus 51 and the negative DC bus 52 is Udc, the voltage value of the rechargeable battery is Uo, and the voltage at the node formed by the connection of the inductor L51 and the capacitor C51 is U B1 , the voltage at the node formed by the connection of inductor L53 and capacitor C51 is U A1 , the voltage across the diode D51 and the collector of the insulated gate bipolar transistor T52 is U2. The voltage across the capacitor C51 is U C1 , the period of the pulse width modulation signal is T, the duty cycle of the pulse width modulation signal is d, and the on time and off time of the insulated gate bipolar transistor T52 in one pulse width modulation signal period are Ton and Toff respectively. Take one period of the pulse width modulation signal as an example for explanation.

[0152] When the insulated gate bipolar transistor T52 is turned on, the following equation is satisfied:

[0153] U A1 =U2andU B1 =U2+U C1

[0154] Then U A1 -U2=0 and U B1 -U2=U C1

[0155] When the insulated gate bipolar transistor T52 is turned off, the following equation is satisfied:

[0156] U A1 =U2-U C1 AndU B1 =U2

[0157] Then U A1 -U2=-U C1 AndU B1 -U2=0

[0158] In one switching cycle, the following equation is satisfied:

[0159]

[0160]

[0161] The average voltage of inductor L51 and inductor L53 in one switching cycle is 0, so,

[0162] (U B1 -U2) average value = Udc

[0163] (U A1 -U2) average value = -Uo

[0164] but

[0165]

[0166] but

[0167] It can be seen that Udc / Uo=d / (1-d). When the duty cycle d<0.5, the rechargeable battery B realizes step-down discharge. When the duty cycle d>0.5, the rechargeable battery B realizes step-up discharge.

[0168] The bidirectional DC-DC converter 5 of the present invention can controllably transfer the electric energy in the capacitor between the DC buses to the rechargeable battery B, and transfer the electric energy in the rechargeable battery B to the capacitor between the DC buses, thereby realizing bidirectional energy transmission.

[0169] Fig.23 is a circuit diagram of a bidirectional DC-DC converter according to a fourth embodiment of the present invention. Fig.17 As shown, the bidirectional DC-DC converter 6 and Fig.17 The difference between the bidirectional DC-DC converter 5 is that it also includes an inductor L62 connected to the anode of the diode D61, a capacitor C62 connected between the anode of the diode D61 and the cathode of the diode D62, and an inductor L64 connected to the cathode of the diode D62.

[0170] Combination Fig.12 As shown in the DC-DC converter 4, the bidirectional DC-DC converter 6 of this embodiment is Fig.12 The DC-DC converter 4 shown has the same topological structure, and its working principle is not repeated here. It can be seen that the bidirectional DC-DC converter 6 can also be applied to multiple uninterruptible power supplies in parallel.

[0171] In other embodiments of the present invention, switching transistors such as metal oxide semiconductor field effect transistors (MOSFET) are used to replace the insulated gate bipolar transistors in the above embodiments.

[0172] The present invention also provides an uninterruptible power supply, which includes the DC-DC converter or bidirectional DC-DC converter of the above-mentioned embodiment of the present invention, as well as a power factor correction circuit (PFC) and an inverter; wherein the DC-DC converter or bidirectional DC-DC converter is connected between the positive and negative DC bus bars and the rechargeable battery, the input end of the PFC is connected to an AC power source (such as a mains power supply), and the output end thereof is connected to the positive and negative DC bus bars, the input end of the inverter is connected to the positive and negative DC bus bars, and the output end thereof is used to provide AC power to the load.

[0173] Although the present invention has been described through preferred embodiments, the present invention is not limited to the embodiments described herein but includes various changes and modifications that may be made without departing from the scope of the present invention.

Claims

1. An uninterruptible power supply system, comprising at least two uninterruptible power supplies, wherein the at least two uninterruptible power supplies share a rechargeable battery, and the uninterruptible power supply comprises: A DC-DC converter, wherein the DC-DC converter is connected between the positive and negative DC bus bars and the rechargeable battery; The DC-DC converter comprises: A first inductor, a first switch tube and a second inductor connected in sequence; A third inductor, a first diode and a fourth inductor connected in sequence; a first capacitor, one end of which is connected to a node formed by connecting the first inductor and the first switch tube, and the other end of which is connected to a node formed by connecting the first diode and the third inductor; and A second capacitor, one end of which is connected to a node formed by connecting the first switch tube and the second inductor, and the other end of which is connected to a node formed by connecting the first diode and the fourth inductor; a power factor correction circuit, whose input end is used to be connected to an AC power supply, and whose output end is connected to the positive and negative DC bus bars; and The inverter has an input end connected to the positive and negative DC bus bars, and an output end for providing AC power.

2. The uninterruptible power supply system according to claim 1, characterized in that: When the first switch tube is turned on, the first inductor, the first switch tube and the second inductor form a first current path, and the third inductor, the first capacitor, the first switch tube, the second capacitor and the fourth inductor form a second current path; When the first switch tube is turned off, the first inductor, the first capacitor, the first diode, the second capacitor and the second inductor form a third current path, and the third inductor, the first diode and the fourth inductor form a fourth current path.

3. The uninterruptible power supply system according to claim 2, characterized in that: The first switching tube is a first insulated gate bipolar transistor, whose collector is connected to a node formed by connecting one end of the first inductor and a first capacitor, and whose emitter is connected to a node formed by connecting one end of the second inductor and the second capacitor, wherein the other end of the first inductor and the other end of the second inductor are respectively used to connect to the positive and negative electrodes of the first DC power supply device, and the third inductor and the fourth inductor are respectively used to connect to the negative and positive electrodes of the second DC power supply device.

4. The uninterruptible power supply system according to any one of claims 1 to 3, characterized in that: The DC-DC converter further includes a second diode connected in reverse parallel to the first switch tube, and a second switch tube connected in reverse parallel to the first diode.

5. The uninterruptible power supply system according to any one of claims 1 to 3, characterized in that: It also includes a control device, which is used to provide a pulse width modulation signal to the first switch tube to make it alternately turned on and off.

6. The uninterruptible power supply system according to claim 4, characterized in that: Also included is a control device for Control the second switch tube to be turned off, and provide a pulse width modulation signal to the first switch tube to make it alternately turned on and off; or The first switch tube is controlled to be turned off, and a pulse width modulation signal is provided to the second switch tube to make it alternately turned on and off.

7. An uninterruptible power supply system, comprising at least two uninterruptible power supplies, wherein the at least two uninterruptible power supplies share a rechargeable battery, and the uninterruptible power supply comprises: A bidirectional DC-DC converter, wherein the bidirectional DC-DC converter is connected between the positive and negative DC bus bars and the rechargeable battery; The bidirectional DC-DC converter comprises: A first inductor, a first capacitor, and a second inductor connected in sequence; A first switch tube having a first diode connected in reverse parallel, wherein a cathode of the first diode is connected to a node formed by connecting the first inductor and the first capacitor; A second switch tube having a second diode connected in reverse parallel, wherein an anode of the second diode is connected to a node formed by connecting the first capacitor and the second inductor; wherein the anode of the first diode is connected to the cathode of the second diode; a second capacitor connected between the anode of the first diode and the cathode of the second diode; a third inductor connected to the anode of the first diode; a fourth inductor connected to the cathode of the second diode; a power factor correction circuit, whose input end is used to be connected to an AC power supply, and whose output end is connected to the positive and negative DC bus bars; and The inverter has an input end connected to the positive and negative DC bus bars, and an output end for providing AC power.

8. The uninterruptible power supply system according to claim 7, characterized in that: The first switch tube is a first insulated gate bipolar transistor, whose collector is connected to a node formed by connecting one end of the first inductor and the first capacitor, and whose emitter and the other end of the first inductor are respectively used to connect to the negative electrode and the positive electrode of the first DC power supply device; The second switch tube is a second insulated gate bipolar transistor, whose emitter is connected to a node formed by connecting the first capacitor and one end of the second inductor, and whose collector and the other end of the second inductor are respectively used to connect to the positive and negative electrodes of the second DC power supply device.

9. The uninterruptible power supply system according to any one of claims 7-8, characterized in that: Also included is a control device for Control the second switch tube to be turned off, and provide a pulse width modulation signal to the first switch tube to make it turn on and off alternately; or The first switch tube is controlled to be turned off, and a pulse width modulation signal is provided to the second switch tube to make it turn on and off alternately.

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