PFC circuit
By introducing a PFC circuit with inductors and bidirectional switching transistors into the UPS system, bidirectional energy flow of the bus voltage is achieved, solving the problem of high bus voltage and ensuring the continuous online operation of the UPS and the stable operation of downstream equipment.
Patent Information
- Application Number
- CN202520021114.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-06
- Publication Date
- 2025-12-23
- Estimated Expiration
- 2035-01-06
AI Technical Summary
When a UPS is running in parallel, complex load types may cause high voltage on the bus. Existing unidirectional PFC circuits cannot completely suppress voltage fluctuations, leading to the triggering of high voltage protection on the bus and even power outages of downstream equipment.
A PFC circuit, including an inductor, a bidirectional switching circuit, and a bidirectional conducting switching transistor, is adopted to feed energy back to the grid when the bus voltage fluctuates, suppress high voltage on the bus, and ensure that the UPS remains online.
It effectively suppresses high voltage on the busbar, prevents power outages in downstream equipment, ensures continuous online operation of the UPS, and improves system stability and efficiency.
Smart Images
Figure CN223713852U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to power supply technical field especially relates to a PFC circuit. BACKGROUND
[0002] UPS (Uninterruptible Power System, uninterruptible power supply) is a constant voltage and constant frequency power supply device containing energy storage device and inverter as the main component, mainly used for providing uninterrupted power supply for single computer, computer network system or other power electronic equipment. When the mains input is normal, UPS supplies the load after voltage stabilization of the mains, at this time, UPS is equivalent to an AC mains voltage stabilizer and charges the battery in the machine at the same time; when the mains is interrupted (accident power failure), UPS immediately supplies 220V AC power to the load through the inverter conversion mode of the battery in the machine, so that the load maintains normal work and protects the load software and hardware from damage, which can provide protection for equipment under the condition of excessive voltage and low voltage to ensure stable voltage of the equipment. With the development of informatization, the power of back-end electrical equipment gradually increases, and the load type gradually becomes complex. The industry mainly uses the UPS parallel connection mode to cope with the increasing power demand of the back-end, but when using UPS parallel operation, if a complex load type is encountered, it may cause energy mutual infusion between UPSs, causing bus high voltage. In view of this problem, at present, the industry mainly uses one-way PFC circuit (such as Figure 1 ) to cooperate with software logic and algorithm to ensure that the bus voltage fluctuation is within an acceptable range, but in some working conditions, this scheme cannot completely suppress voltage fluctuation, for example, energy from the inverter side flows back to the bus, causing the bus voltage to rise and triggering the bus high voltage protection. In this case, only closing the output or cutting the bypass can protect the UPS internal device, which is not conducive to the stable operation of the back-end equipment, and even there is a risk of power failure of the back-end equipment. INVENTION CONTENTS
[0003] Therefore, it is necessary to provide a PFC circuit that can suppress bus high voltage and ensure continuous online of UPS in view of the above problems.
[0004] A PFC circuit is used for connecting between a power grid and a bus, the PFC circuit comprising an inductor, a first diode, a first capacitor, a bidirectional switch circuit, a second diode, a second capacitor, and a bidirectionally conductible third switch tube and a fourth switch tube, the inductor comprising a first end and a second end, the first end of the inductor being connected with an L end of the power grid, a positive electrode of the first diode being connected with the second end of the inductor, a negative electrode of the first diode being connected with a positive electrode of the bus, one end of the bidirectional switch circuit being connected with the second end, the other end of the bidirectional switch circuit being connected with an N end of the power grid, a negative electrode of the second diode being connected with the second end, a positive electrode of the second diode being connected with a negative electrode of the bus, the first capacitor being connected between the positive electrode of the bus and the N end of the power grid, the third switch tube being connected in parallel with the first diode, the second capacitor being connected between the negative electrode of the bus and the N end of the power grid, and the fourth switch tube being connected in parallel with the second diode.
[0005] In one of the embodiments, the bidirectional switch circuit comprises a first switch tube and a second switch tube connected in reverse series, and the first switch tube and the second switch tube are both MOSFET switch tubes.
[0006] In one of the embodiments, the first switch tube and the second switch tube are both NMOSFET switch tubes.
[0007] In one of the embodiments, a drain of the first switch tube is connected with the second end of the inductor, a source of the first switch tube is connected with a source of the second switch tube, and a drain of the second switch tube is connected with the N end of the power grid.
[0008] In one of the embodiments, the third switch tube is an IGBT switch tube or a SiC MOSFET switch tube.
[0009] In one of the embodiments, the fourth switch tube is an IGBT switch tube or a SiC MOSFET switch tube.
[0010] In one of the embodiments, the inductor is a core inductor.
[0011] The PFC circuit of the utility model, through parallel connection of the first diode with the bidirectionally conductible third switch tube, parallel connection of the second diode with the bidirectionally conductible fourth switch tube, when the power supply system is in normal operation, the PFC circuit can be used as a rectifier circuit to obtain power from the power grid and supply power to the bus, when the bus voltage fluctuates upward, the PFC circuit works in the inverter state to feed back the energy of the bus to the power grid, thereby suppressing the high voltage of the bus, avoiding power failure of the rear-end equipment, and ensuring stable operation of the rear-end equipment and continuous online of the UPS. BRIEF DESCRIPTION OF DRAWINGS
[0012] Figure 1 It is a circuit schematic diagram of a traditional VIENNA-LIKE circuit.
[0013] Figure 2 The circuit principle diagram of the PFC circuit for an embodiment of the utility model;
[0014] Figure 3 The circuit topology diagram of the PFC circuit in the rectification state for an embodiment of the utility model;
[0015] Figure 4 The circuit topology diagram of the PFC circuit in the inversion state for an embodiment of the utility model. DETAILED DESCRIPTION
[0016] In order to make the above objectives, characteristics and advantages of the utility model more apparent, obvious and easy to understand, the specific embodiments of the utility model are described in detail below in combination with the drawings. In the following description, a lot of specific details are set forth in order to fully understand the utility model. However, the utility model can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the utility model, so the utility model is not limited by the specific embodiments disclosed below.
[0017] In view of the deficiencies of the one-way PFC circuit in controlling bus voltage fluctuation in the industry, the scheme discloses a PFC circuit capable of inhibiting bus high voltage and ensuring the continuous online of UPS, which is used for being connected between a power grid and a bus, and realizes the energy flow between the power grid and the bus. Figures 2-4 The PFC circuit of the embodiment includes an inductor L1, a first diode D1, a first capacitor C P , a bidirectional switch circuit, a second diode D2, a second capacitor C N and bidirectionally conductible third and fourth switch tubes Q3 and Q4, the inductor L1 includes a first end and a second end, the first end of the inductor L1 is connected with the L end of the power grid, the anode of the first diode D1 is connected with the second end of the inductor L1, the cathode of the first diode D1 is connected with the positive pole of the bus (BUS+), one end of the bidirectional switch circuit is connected with the second end, the other end of the bidirectional switch circuit is connected with the N end of the power grid, the cathode of the second diode D2 is connected with the second end, the anode of the second diode D2 is connected with the negative pole of the bus (BUS-), the first capacitor C P is connected between the positive pole of the bus and the N end of the power grid, the third switch tube Q3 is connected in parallel with the first diode D1, the second capacitor C N is connected between the negative pole of the bus and the N end of the power grid, and the fourth switch tube Q4 is connected in parallel with the second diode D2.
[0018] The inductor is used to adjust the phase difference between the current and the voltage in the PFC circuit, so that the power factor of the power grid is close to 1, to improve the use efficiency of the backend equipment connected to the bus. Preferably, the inductor L1 is a core inductor. By using the core inductor, the inductive current of the inductor L1 will be increased due to the increase of the magnetic field density by the core. In addition, the core can effectively guide the magnetic field, reduce the occurrence of leakage inductance phenomenon, delay the trend of performance degradation of the inductor L1, and reduce the power loss of the inductor L1.
[0019] Further, in an embodiment, the bidirectional switch circuit includes a first switch tube Q1 and a second switch tube Q2 connected in reverse series, and the first switch tube Q1 and the second switch tube Q2 are both MOSFET switch tubes. Further preferably, the first switch tube Q1 and the second switch tube Q2 are both NMOSFET switch tubes, the drain of the first switch tube Q1 is connected to the second end of the inductor L1, the source of the first switch tube Q1 is connected to the source of the second switch tube Q2, and the drain of the second switch tube Q2 is connected to the N end of the power grid. In this embodiment, by setting the bidirectional switch circuit composed of two NMOSFET switch tubes connected in reverse series, the PFC circuit can be protected under both forward voltage and reverse voltage, preventing the PFC circuit from being damaged by overvoltage or reverse voltage, and reducing the power loss in the circuit and improving the system efficiency.
[0020] In the scheme, only the third switch Q3 and the fourth switch Q4 are bidirectional switch, so as to realize the bidirectional flow of energy in the PFC circuit. In an embodiment, the third switch Q3 is an IGBT switch or a SiC MOSFET switch; and the fourth switch Q4 is an IGBT switch or a SiC MOSFET switch. The IGBT (Insulated Gate Bipolar Transistor) switch is a composite full-controlled voltage-driven power semiconductor device composed of BJT (Bipolar Junction Transistor) and MOS (Insulated Gate Field Effect Transistor), which has the advantages of low saturation voltage drop, large current density, small driving power, fast switching speed, etc. The IGBT can only be turned on under the forward voltage and cut off under the reverse voltage. When the forward voltage is applied, the current flows in the first direction at the IGBT body; when the reverse voltage is applied, the IGBT body is cut off, and the current flows in the second direction through the body diode and the parallel diode of the IGBT. The SiC MOSFET switch is a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) switch containing silicon carbide, which can be turned on under the forward voltage and can be turned on under the reverse voltage. When the forward voltage is applied to the SiC MOSFET switch, the current flows in the first direction at the SiC MOSFET switch; when the reverse voltage is applied to the SiC MOSFET switch, the current flows in the second direction opposite to the first direction at the SiC MOSFET switch. Preferably, the third switch Q3 is an IGBT switch, and the fourth switch Q4 is an IGBT switch.
[0021] In the working process of the PFC circuit, please combine Figure 3 When the PFC circuit is used for power factor correction, the PFC circuit is in a rectification state. In the positive half cycle, the grid energy flows through the inductor L1, the first diode D1, the body diode of the third switch Q3 (the third switch is in a reverse cut-off state), the first capacitor C P Return to the N end of the grid to realize rectification and power factor correction. Please combine Figure 4When the bus voltage fluctuates upward, the third switch tube Q3 is forwardly conducted, and the bus energy is fed back to the power grid reversely, thereby inhibiting the rise of the bus voltage.
[0022] The PFC circuit of the utility model is implemented by connecting the third switch tube Q3 which can conduct in both directions in parallel with the first diode D1 and connecting the fourth switch tube which can conduct in both directions in parallel with the second diode D2, so that the PFC circuit can work as a rectifier circuit to obtain power from the power grid and supply power to the bus when the power supply system is in normal operation; when the bus voltage fluctuates upward, the PFC circuit works in the inverter state to feed the bus energy back to the power grid, thereby inhibiting the bus high voltage and avoiding the power failure of the rear-end equipment, ensuring the stable operation of the rear-end equipment and the continuous online of the UPS.
[0023] The technical features of the above-described embodiments can be combined arbitrarily, and to make the description concise, all possible combinations of the technical features in the above-described embodiments are not described, however, as long as the combinations of the technical features do not exist contradictory, they should be considered as the scope of the present disclosure.
[0024] The above-described embodiments only express several implementation manners of the utility model, the description is more specific and detailed, however, it should not be understood as the limitation of the scope of the utility model patent. It should be pointed out that for ordinary skilled in the art, on the premise of not departing from the concept of the utility model, a number of modifications and improvements can be made, which all belong to the protection scope of the utility model. Therefore, the protection scope of the utility model patent should be subject to the appended claims.
Claims
1. A PFC circuit for connection between the power grid and the busbar, characterized in that, The device includes an inductor, a first diode, a first capacitor, a bidirectional switching circuit, a second diode, a second capacitor, and a third and fourth bidirectional switching transistor. The inductor has a first terminal and a second terminal. The first terminal of the inductor is connected to the L terminal of the power grid. The anode of the first diode is connected to the second terminal of the inductor, and the cathode of the first diode is connected to the positive terminal of the bus. One end of the bidirectional switching circuit is connected to the second terminal, and the other end of the bidirectional switching circuit is connected to the N terminal of the power grid. The cathode of the second diode is connected to the second terminal, and the anode of the second diode is connected to the negative terminal of the bus. The first capacitor is connected between the positive terminal of the bus and the N terminal of the power grid. The third switching transistor is connected in parallel with the first diode. The second capacitor is connected between the negative terminal of the bus and the N terminal of the power grid. The fourth switching transistor is connected in parallel with the second diode.
2. The PFC circuit according to claim 1, characterized in that, The bidirectional switching circuit includes a first switch and a second switch connected in reverse series, both of which are MOSFET switches.
3. The PFC circuit according to claim 2, characterized in that, Both the first and second switching transistors are NMOSFET switching transistors.
4. The PFC circuit according to claim 3, characterized in that, The drain of the first switching transistor is connected to the second terminal of the inductor, the source of the first switching transistor is connected to the source of the second switching transistor, and the drain of the second switching transistor is connected to the N terminal of the power grid.
5. The PFC circuit according to claim 1, characterized in that, The third switch is an IGBT switch or a SiCMOSFET switch.
6. The PFC circuit according to claim 1, characterized in that, The fourth switch is an IGBT switch or a SiCMOSFET switch.
7. The PFC circuit according to claim 1, characterized in that, The inductor is an iron-core inductor.