Voltage conversion circuit and energy storage device

Abstract

The application discloses a voltage conversion circuit and an energy storage device. The voltage conversion circuit comprises a direct current conversion circuit, a freewheeling device connected in reverse parallel with the direct current conversion circuit, and an active clamping circuit connected in parallel with the first power switch and coupled with the freewheeling device. The active clamping circuit is used for clamping the voltage across the first power switch to zero and the current flowing through the first power switch to zero at the moment when the first power switch is turned on, and is also used for clamping the voltage across the first power switch to zero at the moment when the first power switch is turned off. The active clamping circuit is used for clamping the voltage across the first power switch to zero and the current flowing through the first power switch to zero at the moment when the first power switch is turned on, and is also used for clamping the voltage across the first power switch to zero at the moment when the first power switch is turned off, thereby reducing power consumption.

Description

Technical Field

[0001] This application belongs to the field of power supply technology, and in particular relates to a voltage conversion circuit and an energy storage device. Background Technology

[0002] In new energy products, charging and discharging batteries is an essential function, which generally uses high-power switching power supplies and inverters. However, traditional voltage-type LLC or CLLC switching power supplies are difficult to achieve with a wide output range, soft switching (high efficiency), and fixed switching frequency in order to achieve high-efficiency power conversion. Summary of the Invention

[0003] The purpose of this application is to provide a voltage conversion circuit and an energy storage device, which aims to solve the problem of high losses caused by traditional voltage-type LLC parallel resonant output switches.

[0004] A first aspect of this application provides a voltage conversion circuit, including a first inductor, an LLC bridge circuit, a second inductor, and a first power switch connected sequentially between the positive and negative terminals of an input bus; a freewheeling device connected in reverse parallel with the first inductor, the LLC bridge circuit, and the second inductor; and an active clamping circuit connected in parallel with the first power switch and coupled to the freewheeling device, wherein:

[0005] The LLC bridge circuit is used to convert the voltage input to the positive terminal of the input bus and the voltage input to the negative terminal of the input bus into power and output it.

[0006] The active clamping circuit is used to clamp the voltage across the first power switch to zero and the current flowing through the first power switch to zero when the first power switch is turned on, and is also used to clamp the voltage across the first power switch to zero when the first power switch is turned off.

[0007] In one embodiment, the active clamping circuit is further configured to clamp the current flowing through the first power switch close to zero when the first power switch is turned off.

[0008] In one embodiment, the active clamping circuit includes:

[0009] The first capacitor is connected in parallel with the first power switch;

[0010] The third inductor and the second power switch, connected in series, are connected in parallel with the first capacitor;

[0011] The first absorption circuit is connected in parallel with the third inductor and coupled to the freewheeling device;

[0012] The first capacitor is used to clamp the voltage across the first power switch to zero when the first power switch is turned off.

[0013] The second power switch is used to turn on before the first power switch turns on, so as to draw current from the first power switch to charge the third inductor. The second power switch is used to turn off before the first power switch turns on completely, so as to release the energy stored in the third inductor using the first absorption circuit and the second power switch.

[0014] In one embodiment, the first absorption circuit includes a first diode, a second diode, and a second capacitor. The first terminal of the second capacitor is connected to the first terminal of the freewheeling device, the first terminal of the third inductor, and the first terminal of the first capacitor. The anode of the second diode is connected to the series node of the third inductor and the second power switch. The second terminal of the second capacitor, the cathode of the first diode, and the anode of the second diode are all connected together. The cathode of the second diode and the second terminal of the freewheeling device are all connected to the positive terminal of the input bus.

[0015] In one embodiment, the LLC bridge circuit is an LLC full-bridge circuit.

[0016] In one embodiment, the LLC full-bridge circuit includes a second absorption circuit, an H-bridge circuit, and an LLC parallel resonant output network. The LLC parallel resonant output network is connected in parallel with the H-bridge circuit, and the second absorption circuit is connected in parallel with the H-bridge circuit to absorb surges generated by the inductance on the LLC parallel resonant output network.

[0017] In one embodiment, a control circuit is further included, which is connected to the H-bridge circuit and the first power switch. The control circuit is used to control the power switch in the H-bridge circuit to turn on and off, so that the current on the freewheeling device is turned off before the first power switch is turned on. The control circuit is also used to control the power switch in the H-bridge circuit to turn on and off, so that the current on the freewheeling device is turned on while the first power switch is turned off.

[0018] In one embodiment, the control circuit controls the power switch in the H-bridge circuit to turn on and off, thereby turning off the current on the freewheeling device while simultaneously turning on the second power switch.

[0019] In one embodiment, the second absorption circuit includes a varistor, the LLC parallel resonant output network includes a fourth capacitor, a fourth inductor and a transformer, the fourth capacitor is connected between the two intermediate nodes of the H-bridge circuit, the fourth inductor is connected in series with the primary winding of the transformer and then in parallel with the fourth capacitor, and the secondary winding of the transformer is used to output the voltage after power conversion.

[0020] A second aspect of this application provides an energy storage device, including the voltage conversion circuit described above.

[0021] The voltage conversion circuit described above sets inductors for storing and releasing energy at both ends of the LLC bridge circuit, and also includes a freewheeling device. The LLC bridge circuit can operate in a fully resonant state, forming a low-loss current source. The switching frequency of the same switch can be significantly increased, thereby reducing the size and cost of the overall capacitor-inductor-transformer. In addition, the output power and output voltage can be adjusted by regulating the current. Furthermore, the active clamping soft switch enables the power switch connected to the bus of the current source to achieve zero-voltage switching, further reducing power consumption. Attached Figure Description

[0022] Figure 1 A block diagram of a voltage conversion circuit provided in one embodiment of this application;

[0023] Figure 2 A schematic diagram of a voltage conversion circuit provided in one embodiment of this application;

[0024] Figure 3 This is a signal waveform diagram provided in one embodiment of this application;

[0025] Figure 4 This is a signal waveform diagram provided in one embodiment of this application. Detailed Implementation

[0026] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0027] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0028] It should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0029] Please see Figure 1 This application provides a voltage conversion circuit, including a first inductor L1, an LLC bridge circuit 100, a second inductor L2, and a first power switch M1 connected sequentially between the positive terminal A and the negative terminal B of the input bus; a freewheeling device D0 connected in reverse parallel with the first inductor L1, the LLC bridge circuit 100, and the second inductor L2; and an active clamping circuit 200 connected in parallel with the first power switch M1 and coupled to the freewheeling device D0, wherein:

[0030] LLC bridge circuit 100 is used to convert the voltage input to the positive terminal A of the input bus and the negative terminal B of the input bus into power and output it.

[0031] The active clamping circuit 200 is used to clamp the voltage across the first power switch M1 to zero and the current flowing through the first power switch M1 to zero when the first power switch M1 is turned on, and also to clamp the voltage across the first power switch M1 to zero when the first power switch M1 is turned off.

[0032] The active clamping circuit 200 is used to clamp the voltage across the first power switch M1 to zero and the current flowing through the first power switch M1 to zero when the first power switch M1 is turned on, so that the first power switch M1 can achieve zero current and zero voltage conduction. The active clamping circuit 200 is also used to clamp the voltage across the first power switch M1 to zero when the first power switch M1 is turned off, so that the first power switch M1 can achieve zero voltage turn-off, thereby reducing the losses caused by the first power switch M1.

[0033] Understandably, the LLC bridge circuit 100 includes an LLC parallel resonant output network and a bridge circuit. The first inductor L1 and the second inductor L2 are used to store and release energy, thus forming a current source-DC converter (DC-DC) circuit with the bridge circuit in the LLC bridge circuit 100 to provide current to the LLC parallel resonant output network, allowing the LLC parallel resonant output network to operate in a fully resonant state. In this way, the EMC (Electromagnetic Magnetic Compatibility) and switching losses of its bridge circuit will be reduced to near zero. Because this loss is close to zero, the switching frequency of the switching devices can be greatly increased, and the size and cost of the LLC parallel resonant output network devices can be reduced, which is beneficial to product miniaturization and cost reduction.

[0034] refer to Figure 3It can be seen that the turn-on and turn-off times of the first power switch M1 are close, which makes the charging and discharging times of the first inductor L1 and the second inductor L2 close, and makes the charging current and discharging current of the first inductor L1 and the second inductor L2 close to the average current. That is, the fluctuation of the ripple current formed by the combination of the two is relatively weak, and the current output ripple of the current source is good.

[0035] In one embodiment, the active clamping circuit 200 is further configured to clamp the current flowing through the first power switch M1 to near zero when the first power switch M1 is turned off. This allows the first power switch M1 to be turned off with near-zero current, further reducing switching losses.

[0036] Please see Figure 2 and Figure 3 In one embodiment, the active clamping circuit 200 includes a first capacitor C1, a third inductor L3 connected in series with a second power switch M2, and a first absorption circuit 220.

[0037] The first capacitor C1 is connected in parallel with the first power switch M1; the third inductor L3 and the second power switch M2, which are connected in series, are connected in parallel with the first capacitor C1; the first absorption circuit 220 is connected in parallel with the third inductor L3 and is coupled to the freewheeling device D0.

[0038] The first capacitor C1 is used to clamp the voltage across the first power switch M1 to zero when the first power switch M1 is turned off. When the first power switch M1 is turned on, the bus current charges the first inductor L1 and the second inductor L2 to store energy, so no current flows through the first capacitor C1, meaning the first capacitor C1 is not charged. Therefore, when the first power switch M1 is turned off, the voltage across the first capacitor C1 is zero, meaning the voltage across the first power switch M1 is also zero. In this way, the first power switch M1 can achieve zero-voltage turn-off. See [link to relevant documentation]. Figure 3 The flag bit 11 in the middle.

[0039] Additionally, when the first power switch M1 is turned off, the current released from the first inductor L1 and the second inductor L2 to the freewheeling device D0 will pass through one end of the first capacitor C1. Therefore, there will be a momentary current charging the first capacitor C1. This momentary current will form a release circuit with the first power switch M1 and then be output to the freewheeling device D0, thus allowing a near-zero current to flow through the first power switch M1 when it is turned off, forming a near-zero current turn-off. See [link to relevant documentation]. Figure 3 The flag bit 11 in the middle.

[0040] The second power switch M2 is used to turn on before the first power switch M1 turns on, so as to draw current from the first power switch M1 and the first capacitor C1 to charge the third inductor L3. This allows the first power switch M1 to achieve zero-voltage, zero-current conduction. The second power switch M2 is used to turn off before the first power switch M1 is fully turned on, so as to release the energy stored in the third inductor L3 using the first absorption circuit 220 and the second power switch M2. This ensures that the energy in the third inductor L3 is completely released before the first power switch M1 turns on again, and then the current is drawn from the first power switch M1 again, allowing the first power switch M1 to achieve zero-voltage, zero-current conduction, reducing losses during switching on and off. See [link to relevant documentation]. Figure 3 The marker bit 12 in the code. Among them, the energy stored in the third inductor L3 by the second power switch M2 is released to the bus; the energy stored in the third inductor L3 by the first absorption circuit 220 is released to the current source circuit.

[0041] In one embodiment, the first absorption circuit 220 includes a first diode D1, a second diode D2, and a second capacitor C2. The first terminal of the second capacitor C2 is connected to the first terminal of the freewheeling device D0, the first terminal of the third inductor L3, and the first terminal of the first capacitor C1. The positive terminal of the second diode D2 is connected to the series node of the third inductor L3 and the second power switch M2. The second terminal of the second capacitor C2, the negative terminal of the first diode D1, and the positive terminal of the second diode D2 are all connected together. The negative terminal of the second diode D2 and the second terminal of the freewheeling device D0 are all connected to the positive terminal A of the input bus.

[0042] When the second power switch M2 is turned off, the third inductor L3, the first diode D1, and the second capacitor C2 form a first discharge circuit when the third inductor L3 releases energy, discharging to the second capacitor C2. Conversely, the third inductor L3, the first diode D1, the second diode D2, and the second capacitor C2 form a second discharge circuit when the third inductor releases energy, discharging to the second capacitor C2. This process extracts energy from the third inductor L3, which is then used to draw current from the first power switch M1 when the second power switch M2 is turned on again. This ensures that the second power switch M2 can be turned on and off with zero voltage and zero current to reduce switching losses. Please refer to [link to relevant documentation]. Figure 3 The marker bits are 21 and 22.

[0043] In one embodiment, the LLC bridge circuit 100 is an LLC full-bridge circuit.

[0044] In one embodiment, the LLC full-bridge circuit includes a second absorption circuit 110, an H-bridge circuit, and an LLC parallel resonant output network 120. The LLC parallel resonant output network 120 is connected in parallel with the H-bridge circuit, and the second absorption circuit 110 is connected in parallel with the H-bridge circuit to absorb surges generated by the inductance on the LLC parallel resonant output network 120. The LLC full-bridge circuit can operate in a fully resonant state, thus reducing the EMC and switching losses of its H-bridge circuit to near zero. Because this loss is close to zero, the switching frequency of the switching devices in the same H-bridge circuit can be significantly increased, thereby reducing the size and cost of the LLC parallel resonant output network 120. The second absorption circuit 110 is used to absorb the impact generated by the first inductor L1 and the second inductor L2 when the switching devices of the H-bridge circuit are unexpectedly turned off or shut down.

[0045] In one embodiment, the H-bridge circuit includes diodes D3, D4, D5, and D6, and power switches M3, M4, M5, and M6. Diodes D3, M3, M4, and D4 are connected in series between the first inductor L1 and the second inductor L2. Diodes D5, M5, M6, and D6 are connected in series between the first inductor L1 and the second inductor L2. Power switches M3 and M4 form a first series intermediate node, and power switches M5 and M6 form a second series intermediate node.

[0046] Please see Figures 2 to 4 The voltage conversion circuit also includes a control circuit, which is connected to the gates (bases) of power switches M3, M4, M5, and M6 in the H-bridge circuit. The control circuit outputs high and low level signals to drive the power switches M3, M4, M5, and M6 to turn on and off. Please refer to the specific control timing diagram. Figure 4 As shown, a high level indicates that the corresponding power switch is turned on, and a low level indicates that the corresponding power switch is turned off.

[0047] The control circuit is connected to the first power switch M1. The control circuit controls the on / off state of the power switches in the H-bridge circuit, causing the current in the freewheeling device D0 to turn off. Specifically, it controls power switches M3 and M6 to turn on, and power switches M4 and M5 to turn off, before turning on the first power switch M1. The control circuit also controls the on / off state of the power switches in the H-bridge circuit, causing the current in the freewheeling device D0 to conduct. Specifically, it controls power switches M4 and M5 to turn on, and simultaneously controls the first power switch M1 to turn off while power switches M3 and M6 are off. This allows the first power switch M1 to achieve zero-voltage switching.

[0048] In one embodiment, the control circuit controls the power switches in the H-bridge circuit to turn on and off, thereby turning off the current on the freewheeling device D0. That is, it controls the power switches M3 and M6 to be turned on and the power switches M4 and M5 to be turned off, while simultaneously controlling the second power switch M2 to be turned on, so that the third inductor L3 can timely draw energy from the first power switch M1 and the first capacitor C1, thereby achieving zero-voltage switching.

[0049] In one embodiment, the second absorption circuit 110 includes a varistor R1, which can be a varistor with a breakdown voltage of, for example, 1200V-1700V. When the power is unexpectedly shut down or all power switches M3, M4, M5, and M6 of the H-bridge circuit are unexpectedly turned off, the varistor R1 and the first power switch M1 or the freewheeling device D0 will form a loop to release / absorb the energy stored in the first inductor L1 and the second inductor L2. In addition to protecting the H-bridge circuit and the first power switch M1, it can also provide zero-voltage and zero-current conduction conditions for the first power switch M1, power switches M3, M4, M5, and M6 when they are turned on again.

[0050] The LLC parallel resonant output network 120 includes C4, a fourth inductor L4, and a transformer. C4 is connected between the two intermediate nodes of the H-bridge circuit. The fourth inductor L4 is connected in series with the primary winding T1a of the transformer and then in parallel with C4. The secondary winding T1b of the transformer is used to output the voltage after power conversion.

[0051] A second aspect of this application provides an energy storage device, including the voltage conversion circuit described above. The energy storage device can be a mobile energy storage device, a portable energy storage device, or other energy storage devices, such as charging piles, etc.

[0052] The aforementioned voltage conversion circuit incorporates inductors for storing and releasing energy at both ends of the LLC bridge circuit 100, along with a freewheeling device D0. The LLC bridge circuit 100 can operate in a fully resonant state, forming a low-loss current source. This allows for a significant increase in the switching frequency of the same switch, thereby reducing the overall size and cost of the capacitor-inductor-transformer. Furthermore, the output power and output voltage can be adjusted by regulating the current magnitude. Additionally, the active clamping soft switching enables zero-voltage switching of the power switch connected to the bus of the current source, further reducing power consumption.

[0053] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A voltage conversion circuit, characterized in that, The system includes a first inductor, an LLC bridge circuit, a second inductor, and a first power switch connected sequentially between the positive and negative terminals of the input bus; a freewheeling device connected in reverse parallel with the first inductor, the LLC bridge circuit, and the second inductor; and an active clamping circuit connected in parallel with the first power switch and coupled to the freewheeling device, wherein: The LLC bridge circuit is used to convert the voltage input to the positive terminal of the input bus and the voltage input to the negative terminal of the input bus into power and output it. The active clamping circuit is used to clamp the voltage across the first power switch to zero and the current flowing through the first power switch to zero when the first power switch is turned on, and is also used to clamp the voltage across the first power switch to zero when the first power switch is turned off. The active clamping circuit includes: The first capacitor is connected in parallel with the first power switch; The third inductor and the second power switch, connected in series, are connected in parallel with the first capacitor; The first absorption circuit is connected in parallel with the third inductor and coupled to the freewheeling device; The first capacitor is used to clamp the voltage across the first power switch to zero when the first power switch is turned off. The second power switch is used to turn on before the first power switch turns on, so as to draw current from the first power switch to charge the third inductor. The second power switch is used to turn off before the first power switch turns on completely, so as to release the energy stored in the third inductor using the first absorption circuit and the second power switch.

2. The voltage conversion circuit according to claim 1, characterized in that, The active clamping circuit is also used to clamp the current flowing through the first power switch close to zero when the first power switch is turned off.

3. The voltage conversion circuit according to claim 1 or 2, characterized in that, The first absorption circuit includes a first diode, a second diode, and a second capacitor. The first terminal of the second capacitor is connected to the first terminal of the freewheeling device, the first terminal of the third inductor, and the first terminal of the first capacitor. The anode of the second diode is connected to the series node of the third inductor and the second power switch. The second terminal of the second capacitor, the cathode of the first diode, and the anode of the second diode are all connected together. The cathode of the second diode and the second terminal of the freewheeling device are all connected to the positive terminal of the input bus.

4. The voltage conversion circuit according to claim 1 or 2, characterized in that, The LLC bridge circuit is an LLC full-bridge circuit.

5. The voltage conversion circuit according to claim 4, characterized in that, The LLC full-bridge circuit includes a second absorption circuit, an H-bridge circuit, and an LLC parallel resonant output network. The LLC parallel resonant output network is connected in parallel with the H-bridge circuit, and the second absorption circuit is connected in parallel with the H-bridge circuit to absorb surges generated by the inductance on the LLC parallel resonant output network.

6. The voltage conversion circuit according to claim 5, characterized in that, It also includes a control circuit, which is connected to the H-bridge circuit and the first power switch. The control circuit is used to control the power switch in the H-bridge circuit to turn on and off, so that the current on the freewheeling device is turned off and then the first power switch is turned on. It is also used to control the power switch in the H-bridge circuit to turn on and off, so that the current on the freewheeling device is turned on and the first power switch is turned off at the same time.

7. The voltage conversion circuit according to claim 6, characterized in that, The control circuit controls the power switch in the H-bridge circuit to turn on and off, so that the current on the freewheeling device is turned off while the second power switch is turned on.

8. The voltage conversion circuit according to claim 5, characterized in that, The second absorption circuit includes a varistor, and the LLC parallel resonant output network includes a fourth capacitor, a fourth inductor, and a transformer. The fourth capacitor is connected between the two intermediate nodes of the H-bridge circuit. The fourth inductor is connected in series with the primary winding of the transformer and then in parallel with the fourth capacitor. The secondary winding of the transformer is used to output the voltage after power conversion.

9. An energy storage device, characterized in that, Includes the voltage conversion circuit according to any one of claims 1 to 8.

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