Power supply device and its control method

Abstract

The present invention provides a power supply device and a control method thereof. The power supply device includes an uninterruptible power supply and a frequency control circuit; the uninterruptible power supply is used to generate an alternating voltage; the frequency control circuit is electrically connected to the uninterruptible power supply and is used to control the frequency of the alternating voltage generated by the uninterruptible power supply. The problem that the method adopted in the prior art to ensure the normal operation of the uninterruptible power supply when connected to a transformer load causes a significant increase in hardware cost is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of power supply, and particularly to a power supply device and a control method thereof. Background Art

[0002] Based on the fact that the application of UPS (Uninterrupted Power Supply) is becoming more and more extensive, some end users need to use UPS to connect to industrial transformer loads. In the existing UPS, when the output is connected to an industrial transformer load, the excitation current of the transformer will cause UPS failures, such as overvoltage of the DC (direct current) bus or bus voltage imbalance.

[0003] In the prior art, in order to ensure that the UPS can work properly when connected to a transformer load, usually the capacitance value and rated voltage of the bus capacitor are increased, and at the same time the rated current of the switching device is increased. However, the existing methods significantly increase the hardware cost. Summary of the Invention

[0004] The main object of the present invention is to provide a power supply device and a control method thereof, so as to solve the problem that the hardware cost is significantly increased by the method adopted in the prior art when ensuring that the UPS can work properly when connected to a transformer load.

[0005] To achieve the above object, the present invention provides a power supply device, including an uninterruptible power supply and a frequency control circuit;

[0006] The uninterruptible power supply is used to generate an alternating voltage;

[0007] The frequency control circuit is electrically connected to the uninterruptible power supply and is used to control the frequency of the alternating voltage generated by the uninterruptible power supply.

[0008] During implementation, the uninterruptible power supply includes a positive bus capacitor, a negative bus capacitor, a first switching circuit, a second switching circuit, an inductor, and a storage capacitor;

[0009] A first plate of the positive bus capacitor is electrically connected to a first end of the first switching circuit, and a second plate of the positive bus capacitor is electrically connected to a first plate of the negative bus capacitor;

[0010] A control end of the first switching circuit is electrically connected to a first switching control end, a second end of the first switching circuit is electrically connected to a first end of the inductor, and the first switching circuit is used to control the connection between the first plate of the positive bus capacitor and the first end of the inductor to be conducted or disconnected under the control of a first switching control signal provided by the first switching control end;

[0011] The control terminal of the second switching circuit is electrically connected to the second switching control terminal. The first terminal of the second switching circuit is electrically connected to the first terminal of the inductor. The second terminal of the second switching circuit is electrically connected to the second electrode plate of the negative bus capacitor. The second switching circuit is configured to control the connection between the first terminal of the inductor and the second electrode plate of the negative bus capacitor to be turned on or off under the control of a second switching control signal provided by the second switching control terminal.

[0012] The second terminal of the inductor is electrically connected to the first electrode plate of the storage capacitor. The second electrode plate of the storage capacitor is electrically connected to the first electrode plate of the negative bus capacitor.

[0013] The voltage across the storage capacitor is the AC voltage.

[0014] During implementation, the frequency control circuit is electrically connected to the first switching control terminal and the second switching control terminal respectively, and is configured to control the frequency of the AC voltage by controlling the first switching control signal and the second switching control signal.

[0015] During implementation, the first switching circuit includes a first switching transistor, and the second switching circuit includes a second switching transistor.

[0016] The control electrode of the first switching transistor is electrically connected to the first switching control terminal. The first pole of the first switching transistor is electrically connected to the first electrode plate of the positive bus capacitor. The second pole of the first switching transistor is electrically connected to the first terminal of the inductor.

[0017] The control electrode of the second switching transistor is electrically connected to the second switching control terminal. The first pole of the second switching transistor is electrically connected to the first terminal of the inductor. The second pole of the second switching transistor is electrically connected to the second electrode plate of the negative bus capacitor.

[0018] During implementation, the uninterruptible power supply includes a positive bus capacitor, a negative bus capacitor, a first switching circuit, a second switching circuit, a third switching circuit, a fourth switching circuit, a first conduction control circuit, a second conduction control circuit, an inductor, and a storage capacitor.

[0019] The first electrode plate of the positive bus capacitor is electrically connected to the first terminal of the first switching circuit. The second electrode plate of the positive bus capacitor is electrically connected to the first electrode plate of the negative bus capacitor.

[0020] The control terminal of the first switching circuit is electrically connected to the first switching control terminal. The second terminal of the first switching circuit is electrically connected to the first terminal of the second switching circuit. The first switching circuit is configured to control the connection between the first electrode plate of the positive bus capacitor and the first terminal of the second switching circuit to be turned on or off under the control of a first switching control signal provided by the first switching control terminal.

[0021] The control terminal of the second switching circuit is electrically connected to the second switching control terminal, and the second terminal of the second switching circuit is electrically connected to the first terminal of the inductor; the second switching circuit is configured to control the connection between the second terminal of the first switching circuit and the first terminal of the inductor to be conducted or disconnected under the control of a second switching control signal provided by the second switching control terminal.

[0022] The control terminal of the third switching circuit is electrically connected to the third switching control terminal, the first terminal of the third switching circuit is electrically connected to the first terminal of the inductor, and the second terminal of the third switching circuit is electrically connected to the first terminal of the fourth switching circuit; the third switching circuit is configured to control the connection between the first terminal of the inductor and the first terminal of the fourth switching circuit to be conducted or disconnected under the control of a third switching control signal provided by the third switching control terminal.

[0023] The control terminal of the fourth switching circuit is electrically connected to the fourth switching control terminal, and the second terminal of the fourth switching circuit is electrically connected to the second plate of the negative bus capacitor; the fourth switching circuit is configured to control the connection between the second terminal of the third switching circuit and the second plate of the negative bus capacitor to be conducted or disconnected under the control of a fourth switching control signal provided by the fourth switching control terminal.

[0024] The first conduction control circuit is disposed between the second plate of the positive bus capacitor and the first terminal of the first switching circuit, and the first conduction control circuit is configured to only allow current flowing from the second plate of the positive bus capacitor to the first terminal of the first switching circuit to pass through.

[0025] The second conduction control circuit is disposed between the second terminal of the third switching circuit and the second plate of the positive bus capacitor, and the second conduction control circuit is configured to only allow current between the second terminal of the third switching circuit and the second plate of the positive bus capacitor to pass through.

[0026] The second terminal of the inductor is electrically connected to the first plate of the storage capacitor, the second plate of the storage capacitor is electrically connected to the ground terminal, and the second plate of the positive bus capacitor is electrically connected to the ground terminal.

[0027] The voltage across the storage capacitor is the AC voltage.

[0028] During implementation, the frequency control circuit is electrically connected to the first switching control terminal, the second switching control terminal, the third switching control terminal, and the fourth switching control terminal respectively, and is configured to control the frequency of the AC voltage by controlling the first switching control signal, the second switching control signal, the third switching control signal, and the fourth switching control signal.

[0029] During implementation, the first conduction control circuit includes a first conduction control diode, and the second conduction control circuit includes a second conduction control diode;

[0030] The anode of the first conduction control diode is electrically connected to the second plate of the positive bus capacitor, and the cathode of the first conduction control diode is electrically connected to the second end of the first switch circuit;

[0031] The anode of the second conduction control diode is electrically connected to the second end of the third switch circuit, and the cathode of the second conduction control diode is electrically connected to the second plate of the positive bus capacitor.

[0032] During implementation, the first switch circuit includes a first switch transistor, the second switch circuit includes a second switch transistor, the third switch circuit includes a third switch transistor, and the fourth switch circuit includes a fourth switch transistor;

[0033] The control electrode of the first switch transistor is electrically connected to the first switch control terminal, the first electrode of the first switch transistor is electrically connected to the first plate of the positive bus capacitor, and the second electrode of the first switch transistor is electrically connected to the first electrode of the second switch transistor;

[0034] The control electrode of the second switch transistor is electrically connected to the second switch control terminal, and the second electrode of the second switch transistor is electrically connected to the first end of the inductor;

[0035] The control electrode of the third switch transistor is electrically connected to the third switch control terminal, the first electrode of the third switch transistor is electrically connected to the first end of the inductor, and the second electrode of the third switch transistor is electrically connected to the first electrode of the fourth switch transistor;

[0036] The control electrode of the fourth switch transistor is electrically connected to the fourth switch control terminal, and the second electrode of the fourth switch transistor is electrically connected to the second plate of the negative bus capacitor.

[0037] The present invention also provides a control method for a power supply device, which is applied to the above-mentioned power supply device. The control method for the power supply device includes:

[0038] The uninterruptible power supply generates an alternating voltage;

[0039] The frequency control circuit controls the frequency of the alternating voltage generated by the uninterruptible power supply.

[0040] Specifically, the control method for the power supply device according to the embodiments of the present invention further includes:

[0041] The uninterruptible power supply supplies the alternating voltage to the primary coil of the transformer;

[0042] Within a predetermined time starting from when the uninterruptible power supply provides the AC voltage to the primary coil of the transformer, the frequency control circuit controls to gradually reduce the frequency of the AC voltage.

[0043] Specifically, the control method of the power supply device according to the embodiment of the present invention further includes:

[0044] After a predetermined time starting from when the uninterruptible power supply provides the AC voltage to the primary coil of the transformer, the frequency control circuit controls to maintain the frequency of the AC voltage.

[0045] Specifically, the predetermined time is six inverter cycles;

[0046] The step that within a predetermined time starting from when the uninterruptible power supply provides the AC voltage to the primary coil of the transformer, the frequency control circuit controls to gradually reduce the frequency of the AC voltage includes:

[0047] In the first inverter cycle, the frequency control circuit controls the frequency of the AC voltage to be greater than or equal to 100 Hz and less than or equal to 150 Hz;

[0048] In the second inverter cycle, the frequency control circuit controls the frequency of the AC voltage to be greater than or equal to 78 Hz and less than or equal to 90 Hz;

[0049] In the third inverter cycle, the frequency control circuit controls the frequency of the AC voltage to be greater than or equal to 70 Hz and less than or equal to 73 Hz;

[0050] In the fourth inverter cycle, the frequency control circuit controls the frequency of the AC voltage to be greater than or equal to 60 Hz and less than or equal to 65 Hz;

[0051] In the fifth inverter cycle, the frequency control circuit controls the frequency of the AC voltage to be greater than or equal to 54 Hz and less than or equal to 58 Hz;

[0052] In the sixth inverter cycle, the frequency control circuit controls the frequency of the AC voltage to be greater than or equal to 48 Hz and less than or equal to 52 Hz.

[0053] Compared with the prior art, the power supply device and its control method according to the present invention adopt a frequency control circuit for controlling the frequency of the AC voltage generated by the uninterruptible power supply. By controlling the frequency, it can avoid failures of capacitor components and switching devices in the UPS, improve the reliability and stability of the UPS, and can achieve this without increasing the hardware cost. Description of the Drawings

[0054] Figure 1a is a schematic diagram of an existing transformer;

[0055] Figure 1b In the prior art, it is a schematic diagram showing the relationship between the AC voltage Vp generated by an uninterruptible power supply and time t;

[0056] Figure 1c In the prior art, it is a schematic diagram showing the relationship between the exciting current Im of the primary coil of a transformer and time t;

[0057] Figure 2 It is a structural diagram of the power supply device according to an embodiment of the present invention;

[0058] Figure 3 It is a structural diagram of the power supply device according to another embodiment of the present invention;

[0059] Figure 4 It is a circuit diagram of a specific embodiment of the power supply device according to the present invention;

[0060] Figure 5 As described in the present invention Figure 4 It is a working timing diagram of a specific embodiment of the power supply device shown;

[0061] Figure 6A and Figure 6B show Figure 4 the current path of the embodiment of the power supply device shown in the positive half cycle;

[0062] Figure 7A and Figure 7B show Figure 4 the current path of the embodiment of the power supply device shown in the negative half cycle;

[0063] Figure 8 It is a structural diagram of the power supply device according to another embodiment of the present invention;

[0064] Figure 9 It is a circuit diagram of another specific embodiment of the power supply device according to the present invention;

[0065] Figure 10 As described in the present invention Figure 9 It is a working timing diagram of a specific embodiment of the power supply device shown;

[0066] Figure 11A and Figure 11B show Figure 9 the current path of the embodiment of the power supply device shown in the positive half cycle;

[0067] Figure 12A and Figure 12B show Figure 9 the current path of the embodiment of the power supply device shown in the negative half cycle;

[0068] Figure 13It is a schematic diagram of the frequency conversion process after the uninterruptible power supply provides an AC voltage to the primary coil of the transformer. Specific embodiments

[0069] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0070] All the transistors adopted in all the embodiments of the present invention can be triodes, thin-film transistors or field-effect transistors or other devices with the same characteristics. In the embodiments of the present invention, to distinguish the two poles of the transistor other than the control pole, one pole is called the first pole and the other pole is called the second pole.

[0071] During actual operation, when the transistor is a triode, the control pole can be the base, the first pole can be the collector, and the second pole can be the emitter; or, the control pole can be the base, the first pole can be the emitter, and the second pole can be the collector.

[0072] During actual operation, when the transistor is a thin-film transistor or a field-effect transistor, the control pole can be the base, the first pole can be the drain, and the second pole can be the source; or, the control pole can be the base, the first pole can be the source, and the second pole can be the drain.

[0073] In the related art, the transformer transfers energy by establishing a magnetic field. When the AC voltage provided by the UPS is initially provided to the primary coil of the transformer, a large excitation current will appear on the primary side of the transformer. This excitation current is very unbalanced between the positive half-cycle and the negative half-cycle, and this excitation current will gradually decrease.

[0074] As Figure 1a shown, when the AC voltage Vp is just applied to the primary coil of the transformer T, the excitation current Im of the primary coil of the transformer T will start to be particularly large, making the excitation current Im very unbalanced between the positive half-cycle and the negative half-cycle, and the excitation current Im will gradually decrease.

[0075] Figure 1b is a schematic diagram of the relationship between Vp and time t in the prior art, Figure 1c is a schematic diagram of the relationship between Im and time t in the prior art. The large unbalanced excitation current will cause the UPS to work abnormally. In severe cases, the UPS will be damaged. Time t is the duration of the UPS providing the AC voltage Vp to the primary coil of the transformer.

[0076] Based on this, the power supply device described in the embodiments of the present invention adopts a frequency control circuit to control the frequency of the AC voltage generated by the uninterruptible power supply, and avoids failures of capacitor components and switch components in the UPS, avoids DC bus failures in the UPS, and improves the reliability and stability of the UPS by controlling the frequency.

[0077] In the embodiments of the present invention, the positive half cycle may refer to the cycle when Vp is greater than 0, and the negative half cycle may refer to the cycle when Vp is less than 0, but it is not limited thereto.

[0078] As Figure 2 shown, the power supply device described in the embodiments of the present invention includes an uninterruptible power supply U1 and a frequency control circuit 20;

[0079] The uninterruptible power supply U1 is used to generate an AC voltage Vp;

[0080] The frequency control circuit 20 is electrically connected to the uninterruptible power supply U1 and is used to control the frequency of the AC voltage Vp generated by the uninterruptible power supply U1.

[0081] When the power supply device described in the embodiments of the present invention is working, the uninterruptible power supply U1 provides the AC voltage Vp to the primary coil of the transformer; within a predetermined time after the uninterruptible power supply U1 starts to provide the AC voltage Vp to the primary coil of the transformer, the frequency control circuit 20 controls to gradually reduce the frequency of the AC voltage until the frequency of the AC voltage drops to a predetermined frequency. In this way, when U1 just starts to provide the AC voltage Vp to the primary coil of the transformer, the magnetic flux of the primary coil of the transformer can be reduced, and further the exciting current of the primary coil of the transformer can be reduced. Therefore, failures of capacitor components and switch components in the uninterruptible power supply U1 can be avoided, DC bus failures in the uninterruptible power supply U1 can be avoided, and the reliability and stability of the uninterruptible power supply U1 can be improved.

[0082] According to a specific embodiment, the uninterruptible power supply may include a positive bus capacitor, a negative bus capacitor, a first switch circuit, a second switch circuit, an inductor, and a storage capacitor;

[0083] The first electrode plate of the positive bus capacitor is electrically connected to the first end of the first switch circuit, and the second electrode plate of the positive bus capacitor is electrically connected to the first electrode plate of the negative bus capacitor;

[0084] The control end of the first switch circuit is electrically connected to the first switch control end, the second end of the first switch circuit is electrically connected to the first end of the inductor, and the first switch circuit is used to control the connection between the first electrode plate of the positive bus capacitor and the first end of the inductor to be conducted or disconnected under the control of the first switch control signal provided by the first switch control end;

[0085] The control terminal of the second switching circuit is electrically connected to the second switching control terminal. The first terminal of the second switching circuit is electrically connected to the first terminal of the inductor. The second terminal of the second switching circuit is electrically connected to the second plate of the negative bus capacitor. The second switching circuit is configured to control the connection between the first terminal of the inductor and the second plate of the negative bus capacitor to be turned on or off under the control of a second switching control signal provided by the second switching control terminal.

[0086] The second terminal of the inductor is electrically connected to the first plate of the storage capacitor. The second plate of the storage capacitor is electrically connected to the first plate of the negative bus capacitor.

[0087] The voltage across the storage capacitor is the AC voltage.

[0088] Specifically, the frequency control circuit can be used to control the frequency of the AC voltage by controlling the first switching control signal and the second switching control signal.

[0089] As Figure 3 shown, an embodiment of the uninterruptible power supply may include a positive bus capacitor C1, a negative bus capacitor C1, a first switching circuit 31, a second switching circuit 32, an inductor L, and a storage capacitor C.

[0090] The first plate of the positive bus capacitor C1 is electrically connected to the first terminal of the first switching circuit 31. The second plate of the positive bus capacitor C1 is electrically connected to the first plate of the negative bus capacitor C2.

[0091] The second plate of C1 is electrically connected to the ground terminal GND.

[0092] The control terminal of the first switching circuit 31 is electrically connected to the first switching control terminal S1. The second terminal of the first switching circuit 31 is electrically connected to the first terminal of the inductor L. The first switching circuit 31 is configured to control the connection between the first plate of the positive bus capacitor C1 and the first terminal of the inductor L to be turned on or off under the control of a first switching control signal provided by the first switching control terminal S1.

[0093] The control terminal of the second switching circuit 32 is electrically connected to the second switching control terminal S2. The first terminal of the second switching circuit 32 is electrically connected to the first terminal of the inductor L. The second terminal of the second switching circuit 32 is electrically connected to the second plate of the negative bus capacitor C2. The second switching circuit 32 is configured to control the connection between the first terminal of the inductor L and the second plate of the negative bus capacitor C2 to be turned on or off under the control of a second switching control signal provided by the second switching control terminal S2.

[0094] The second end of the inductor L is electrically connected to the first end of the storage capacitor C, and the second end of the storage capacitor C is electrically connected to the first plate of the negative bus capacitor C2;

[0095] The voltage across the storage capacitor C is the AC voltage;

[0096] The frequency control circuit 20 is electrically connected to the first switch control terminal S1 and the second switch control terminal S2 respectively, and is used to control the frequency of the AC voltage by controlling the first switch control signal and the second switch control signal.

[0097] In Figure 3 In the illustrated embodiment of the power supply device, the inductor L and the storage capacitor C form a two-level low-pass filter.

[0098] In Figure 3 In, the one labeled L1 is the load, and the load L1 can be a transformer load.

[0099] Specifically, the first switch circuit may include a first switch transistor, and the second switch circuit may include a second switch transistor;

[0100] The control electrode of the first switch transistor is electrically connected to the first switch control terminal, the first pole of the first switch transistor is electrically connected to the first plate of the positive bus capacitor, and the second pole of the first switch transistor is electrically connected to the first end of the inductor;

[0101] The control electrode of the second switch transistor is electrically connected to the second switch control terminal, the first pole of the second switch transistor is electrically connected to the first end of the inductor, and the second pole of the second switch transistor is electrically connected to the second plate of the negative bus capacitor.

[0102] More specifically, the first switch circuit may further include a first diode, and the second switch circuit may further include a second diode;

[0103] The anode of the first diode is electrically connected to the second pole of the first switch transistor, and the cathode of the first diode is electrically connected to the first pole of the first switch transistor;

[0104] The anode of the second diode is electrically connected to the second pole of the second switch transistor, and the cathode of the second diode is electrically connected to the first pole of the second switch transistor.

[0105] As Figure 4 shown, on the basis of the illustrated embodiment of the power supply device in Figure 3 shown,

[0106] The first switching circuit includes a first switching transistor Q1 and a first diode D41, and the second switching circuit includes a second switching transistor Q2 and a second diode D42;

[0107] The base of the first switching transistor Q1 is electrically connected to the first switching control terminal S1, the collector of the first switching transistor Q1 is electrically connected to the first plate of the positive bus capacitor C1, and the emitter of the first switching transistor Q1 is electrically connected to the first end of the inductor L;

[0108] The base of the second switching transistor Q2 is electrically connected to the second switching control terminal S2, the collector of the second switching transistor Q2 is electrically connected to the first end of the inductor L, and the emitter of the second switching transistor Q2 is electrically connected to the second plate of the negative bus capacitor C2;

[0109] The anode of the first diode D41 is electrically connected to the emitter of the first switching transistor Q1, and the cathode of the first diode D41 is electrically connected to the collector of the first switching transistor Q1;

[0110] The anode of the second diode D42 is electrically connected to the emitter of the second switching transistor Q2, and the cathode of the second diode D42 is electrically connected to the collector of the second switching transistor Q2;

[0111] The load L1 is connected in parallel with the storage capacitor C.

[0112] In Figure 4 the illustrated embodiment, both Q1 and Q2 are npn-type triodes, but this is not limiting.

[0113] In specific implementation, both Q1 and Q2 can also be pnp-type triodes.

[0114] In Figure 4 the illustrated embodiment, the load L1 is the primary coil of a transformer, but this is not limiting. In Figure 4 the illustrated embodiment, the current flowing through L1 is the exciting current Im of the primary coil of the transformer.

[0115] In actual operation, Q1 and Q2 can also be other types of transistors. For example, they can be thin-film transistors or field-effect transistors. At this time, the control electrode can be the gate, the first electrode can be the source or the drain, and the second electrode can be the drain or the source, but this is not limiting.

[0116] In Figure 4 the illustrated embodiment of the power supply device, C1, C2, Q1, Q2, L, and C form a two-level half-bridge inverter in a UPS.

[0117] As Figure 5As shown, the one labeled TP is the positive half-cycle, and the one labeled TN is the negative half-cycle;

[0118] In the positive half-cycle TP, S1 provides a PWM (pulse width modulation) signal, and S2 provides a low-level signal; in the negative half-cycle TN, S1 provides a low-level signal, and S2 provides a PWM signal.

[0119] In specific implementation, when the uninterruptible power supply just starts to provide the AC voltage Vp for the transformer load, the frequency control circuit 20 can control to gradually increase the duration of TP and the duration of TN to control the gradual reduction of the frequency of the AC voltage Vp.

[0120] In actual operation, in Figure 5 In it, in the positive half-cycle TP, the second switch control signal can also be inverted with respect to the first switch control signal, and in the negative half-cycle TN, the first switch control signal can also be inverted with respect to the second switch control signal, but this is not limited thereto.

[0121] Figure 4 When the embodiment of the power supply device shown is working, the frequency control circuit 20 can control the frequency of the AC voltage Vp generated by the uninterruptible power supply by controlling the first switch control signal and the second switch control signal.

[0122] Figure 6A and Figure 6B show Figure 4 the current path of the embodiment of the power supply device shown in the positive half-cycle.

[0123] As Figure 6A shown, in the positive half-cycle, when Q1 is conducting and Q2 is cut off, the current path is successively through C1, Q1, L, and then through C and L1.

[0124] As Figure 6B shown, in the positive half-cycle, when Q1 is cut off and Q2 is conducting, the current path is successively through L, C and L1, C2, Q2.

[0125] As Figure 6A and Figure 6B shown, the load L1 is a transformer load (that is, C is in parallel with the primary coil of the transformer). When Q1 is conducting, C1 will supply energy to the load L1, and the voltage across C1 will decrease; when Q2 is cut off, due to the nature of the transformer load, the direction of the current flowing through L remains unchanged, and the energy of the transformer load will be released, so the voltage across C2 will increase accordingly.

[0126] Figure 7A and Figure 7B show Figure 4 the current path of the embodiment of the power supply device shown in the negative half-cycle.

[0127] As Figure 7A shown, in the negative half - cycle, when Q2 is conducting and Q1 is cutoff, the current path is successively through C2, C, L1, L, and Q2.

[0128] As Figure 7B shown, in the negative half - cycle, when Q2 is cutoff and Q1 is conducting, the current path is successively through L, Q1, C1, C, and L1.

[0129] As Figure 7A and Figure 7B shown, in the negative half - cycle, when Q2 is conducting and Q1 is cutoff, the voltage across C2 will decrease; when Q2 is cutoff and Q1 is conducting, the voltage across C1 will increase.

[0130] Figure 4 When the power supply device embodiment shown in Figure 4 works, if the load current (when the load L1 is a transformer load, the load current is the exciting current of the primary coil of the transformer) is balanced between the positive and negative half - cycles, the positive DC bus voltage (the positive DC bus voltage is the voltage across C1) and the negative DC bus voltage (the negative DC bus voltage is the voltage across C2) will also remain in a balanced state; while if the load current is unbalanced between the positive and negative half - cycles (such as Figure 1b the waveform of the exciting current of the primary coil of the transformer in Figure 1b , the exciting current in the positive half - cycle is greater than that in the negative half - cycle), the negative DC bus voltage will rise rapidly. Eventually, the negative DC bus voltage will exceed the rated voltage of C2, which will also bring risks to the UPS; in addition, the large unbalanced current in a short time will also cause current stress on Q1 and Q2; based on this, the power supply device described in the embodiment of the present invention adopts the frequency control circuit 20. By controlling the frequency of the AC voltage to gradually decrease when the uninterruptible power supply just provides AC voltage for the transformer load, the exciting current of the primary coil of the transformer can be made to have little difference between the positive and negative half - cycles, thereby reducing the negative DC bus voltage and not causing large current stress on Q1 and Q2, improving the reliability and stability of the uninterruptible power supply.

[0131] According to another specific embodiment, the uninterruptible power supply includes a positive bus capacitor, a negative bus capacitor, a first switch circuit, a second switch circuit, a third switch circuit, a fourth switch circuit, a first conduction control circuit, a second conduction control circuit, an inductor, and a storage capacitor;

[0132] The first plate of the positive bus capacitor is electrically connected to the first end of the first switch circuit, and the second plate of the positive bus capacitor is electrically connected to the first plate of the negative bus capacitor;

[0133] The control terminal of the first switching circuit is electrically connected to the first switch control terminal, and the second terminal of the first switching circuit is electrically connected to the first terminal of the second switching circuit; the first switching circuit is configured to control the connection between the first electrode plate of the positive bus capacitor and the first terminal of the second switching circuit to be conducted or disconnected under the control of a first switching control signal provided by the first switch control terminal;

[0134] The control terminal of the second switching circuit is electrically connected to the second switch control terminal, and the second terminal of the second switching circuit is electrically connected to the first terminal of the inductor; the second switching circuit is configured to control the connection between the second terminal of the first switching circuit and the first terminal of the inductor to be conducted or disconnected under the control of a second switching control signal provided by the second switch control terminal;

[0135] The control terminal of the third switching circuit is electrically connected to the third switch control terminal, the first terminal of the third switching circuit is electrically connected to the first terminal of the inductor, and the second terminal of the third switching circuit is electrically connected to the first terminal of the fourth switching circuit; the third switching circuit is configured to control the connection between the first terminal of the inductor and the first terminal of the fourth switching circuit to be conducted or disconnected under the control of a third switching control signal provided by the third switch control terminal;

[0136] The control terminal of the fourth switching circuit is electrically connected to the fourth switch control terminal, and the second terminal of the fourth switching circuit is electrically connected to the second electrode plate of the negative bus capacitor; the fourth switching circuit is configured to control the connection between the second terminal of the third switching circuit and the second electrode plate of the negative bus capacitor to be conducted or disconnected under the control of a fourth switching control signal provided by the fourth switch control terminal;

[0137] The first conduction control circuit is disposed between the second electrode plate of the positive bus capacitor and the first terminal of the first switching circuit, and the first conduction control circuit is configured to only allow current flowing from the second electrode plate of the positive bus capacitor to the first terminal of the first switching circuit to pass through;

[0138] The second conduction control circuit is disposed between the second terminal of the third switching circuit and the second electrode plate of the positive bus capacitor, and the second conduction control circuit is configured to only allow current flowing from the second terminal of the third switching circuit to the second electrode plate of the positive bus capacitor to pass through;

[0139] The second terminal of the inductor is electrically connected to the first electrode plate of the storage capacitor, the second electrode plate of the storage capacitor is electrically connected to the ground terminal, and the second electrode plate of the positive bus capacitor is electrically connected to the ground terminal;

[0140] The voltage across the storage capacitor is the AC voltage.

[0141] Specifically, the frequency control circuit can be used to control the frequency of the AC voltage by controlling the first switch control signal, the second switch control signal, the third switch control signal, and the fourth switch control signal.

[0142] As Figure 8 shown, the uninterruptible power supply includes a positive bus capacitor C1, a negative bus capacitor C2, a first switch circuit 31, a second switch circuit 32, a third switch circuit 33, a fourth switch circuit 34, a first conduction control circuit 81, a second conduction control circuit 82, an inductor L, and a storage capacitor C;

[0143] The first plate of the positive bus capacitor C1 is electrically connected to the first end of the first switch circuit 31, and the second plate of the positive bus capacitor C1 is electrically connected to the first plate of the negative bus capacitor C1;

[0144] The control end of the first switch circuit 31 is electrically connected to the first switch control end S1, and the second end of the first switch circuit 31 is electrically connected to the first end of the second switch circuit 32; the first switch circuit 31 is used to control the connection between the first plate of the positive bus capacitor C1 and the first end of the second switch circuit 32 to be conducted or disconnected under the control of the first switch control signal provided by the first switch control end S1;

[0145] The control end of the second switch circuit 32 is electrically connected to the second switch control end S2, and the second end of the second switch circuit 32 is electrically connected to the first end of the inductor L; the second switch circuit 32 is used to control the connection between the second end of the first switch circuit 31 and the first end of the inductor L to be conducted or disconnected under the control of the second switch control signal provided by the second switch control end S2;

[0146] The control end of the third switch circuit 33 is electrically connected to the third switch control end S3, the first end of the third switch circuit 33 is electrically connected to the first end of the inductor L, and the second end of the third switch circuit 33 is electrically connected to the first end of the fourth switch circuit 34; the third switch circuit 33 is used to control the connection between the first end of the inductor L and the first end of the fourth switch circuit 34 to be conducted or disconnected under the control of the third switch control signal provided by the third switch control end S3;

[0147] The control end of the fourth switch circuit 34 is electrically connected to the fourth switch control end S4, and the second end of the fourth switch circuit 34 is electrically connected to the second plate of the negative bus capacitor C2; the fourth switch circuit 34 is used to control the connection between the second end of the third switch circuit 33 and the second plate of the negative bus capacitor C2 to be conducted or disconnected under the control of the fourth switch control signal provided by the fourth switch control end S4;

[0148] The first conduction control circuit 81 is disposed between the second electrode plate of the positive bus capacitor C1 and the first end of the first switching circuit 31, and the first conduction control circuit 81 is configured to allow only the current flowing from the second electrode plate of the positive bus capacitor C1 to the first end of the first switching circuit 31 to pass through;

[0149] The second conduction control circuit 82 is disposed between the second end of the third switching circuit 33 and the second electrode plate of the positive bus capacitor C1, and the second conduction control circuit 82 is configured to allow only the current between the second end of the third switching circuit 33 and the second electrode plate of the positive bus capacitor C1 to pass through;

[0150] The second end of the inductor L is electrically connected to the first electrode plate of the storage capacitor C, the second electrode plate of the storage capacitor C is electrically connected to the ground terminal GND, and the second electrode plate of the positive bus capacitor C1 is electrically connected to the ground terminal GND;

[0151] The voltage across the storage capacitor C is the AC voltage Vp;

[0152] The frequency control circuit 20 is electrically connected to the first switch control terminal S1, the second switch control terminal S2, the third switch control terminal S3, and the fourth switch control terminal S4 respectively, and is configured to control the frequency of the AC voltage by controlling the first switch control signal, the second switch control signal, the third switch control signal, and the fourth switch control signal.

[0153] Specifically, the first conduction control circuit may include a first conduction control diode, and the second conduction control circuit may include a second conduction control diode;

[0154] The anode of the first conduction control diode is electrically connected to the second electrode plate of the positive bus capacitor, and the cathode of the first conduction control diode is electrically connected to the second end of the first switching circuit;

[0155] The anode of the second conduction control diode is electrically connected to the second end of the third switching circuit, and the cathode of the second conduction control diode is electrically connected to the second electrode plate of the positive bus capacitor.

[0156] Specifically, the first switching circuit may include a first switching transistor, the second switching circuit may include a second switching transistor, the third switching circuit may include a third switching transistor, and the fourth switching circuit may include a fourth switching transistor;

[0157] The control electrode of the first switching transistor is electrically connected to the first switching control terminal, the first pole of the first switching transistor is electrically connected to the first electrode plate of the positive bus capacitor, and the second pole of the first switching transistor is electrically connected to the first pole of the second switching transistor;

[0158] The control electrode of the second switching transistor is electrically connected to the second switching control terminal, and the second pole of the second switching transistor is electrically connected to the first end of the inductor;

[0159] The control electrode of the third switching transistor is electrically connected to the third switching control terminal, the first pole of the third switching transistor is electrically connected to the first end of the inductor, and the second pole of the third switching transistor is electrically connected to the first pole of the fourth switching transistor;

[0160] The control electrode of the fourth switching transistor is electrically connected to the fourth switching control terminal, and the second pole of the fourth switching transistor is electrically connected to the second electrode plate of the negative bus capacitor.

[0161] More specifically, the first switching circuit may further include a first diode, the second switching circuit may further include a second diode, the third switching circuit may further include a third diode, and the fourth switching circuit may further include a fourth diode;

[0162] The anode of the first diode is electrically connected to the second pole of the first switching transistor, and the cathode of the first diode is electrically connected to the first pole of the first switching transistor;

[0163] The anode of the second diode is electrically connected to the second pole of the second switching transistor, and the cathode of the second diode is electrically connected to the first pole of the second switching transistor;

[0164] The anode of the third diode is electrically connected to the second pole of the third switching transistor, and the cathode of the third diode is electrically connected to the first pole of the third switching transistor;

[0165] The anode of the fourth diode is electrically connected to the second pole of the fourth switching transistor, and the cathode of the fourth diode is electrically connected to the first pole of the fourth switching transistor.

[0166] As Figure 9 shown, based on the embodiment of the power supply device shown in Figure 8 shown,

[0167] The first switching circuit includes a first switching transistor Q1 and a first diode D41, the second switching circuit includes a second switching transistor Q2 and a second diode D42, the third switching circuit includes a third switching transistor Q3 and a third diode D43, and the fourth switching circuit includes a fourth switching transistor Q4 and a fourth diode D44;

[0168] The base of the first switching transistor Q1 is electrically connected to the first switching control terminal S1, the collector of the first switching transistor Q1 is electrically connected to the first plate of the positive bus capacitor C1, and the emitter of the first switching transistor Q2 is electrically connected to the collector of the second switching transistor Q2;

[0169] The anode of D41 is electrically connected to the emitter of Q1, and the cathode of D41 is electrically connected to the collector of Q1;

[0170] The base of the second switching transistor Q2 is electrically connected to the second switching control terminal S2, and the emitter of the second switching transistor Q2 is electrically connected to the first end of the inductor L;

[0171] The anode of D42 is electrically connected to the emitter of Q2, and the cathode of D42 is electrically connected to the collector of Q2;

[0172] The base of the third switching transistor Q3 is electrically connected to the third switching control terminal S3, the collector of the third switching transistor Q3 is electrically connected to the first end of the inductor L, and the emitter of the third switching transistor Q3 is electrically connected to the collector of the fourth switching transistor Q4;

[0173] The anode of D43 is electrically connected to the emitter of Q3, and the cathode of D43 is electrically connected to the collector of Q3;

[0174] The base of the fourth switching transistor Q4 is electrically connected to the fourth switching control terminal S4, and the emitter of the fourth switching transistor Q4 is electrically connected to the second plate of the negative bus capacitor C2;

[0175] The anode of D44 is electrically connected to the emitter of Q4, and the cathode of D44 is electrically connected to the collector of Q4;

[0176] The first conduction control circuit includes a first conduction control diode D1, and the second conduction control circuit may include a second conduction control diode D2;

[0177] The anode of the first conduction control diode D1 is electrically connected to the second end of the positive bus capacitor C1, and the cathode of the first conduction control diode D1 is electrically connected to the emitter of the first switching transistor Q1;

[0178] The anode of the second conduction control diode D2 is electrically connected to the emitter of the third switching transistor Q3, and the cathode of the second conduction control diode D2 is electrically connected to the second plate of the positive bus capacitor C1.

[0179] In Figure 9 the one labeled L1 is a load, and L1 is connected in parallel with C.

[0180] InFigure 9 In the illustrated embodiment of the power supply device, Q1, Q2, Q3, and Q4 are all npn bipolar transistors, but this is not limiting.

[0181] In a specific implementation, Q1, Q2, Qs, and Q4 can also be pnp bipolar transistors.

[0182] In a specific implementation, the above transistors can also be thin film transistors or field effect transistors. In this case, the control electrode is the gate, the first electrode is the source or drain, and the second electrode is the drain or source.

[0183] Figure 10 is Figure 9 Waveform diagrams of the first switch control signal provided by S1, the second switch control signal provided by S2, the third switch control signal provided by S3, and the fourth switch control signal provided by S4 when the illustrated embodiment of the power supply device is operating.

[0184] In Figure 10 , TP is the positive half cycle and TN is the negative half cycle. When the illustrated embodiment of the power supply device of the present invention is operating and L1 is the load of the transformer, that is, when C is connected in parallel with the primary coil of the transformer, the frequency control circuit 20 can control the frequency of the AC voltage Vp by controlling the duration of TP and the duration of TN; Figure 9

[0185] In a specific implementation, when the uninterruptible power supply starts to provide the AC voltage Vp to the transformer load, the frequency control circuit 20 can gradually increase the duration of TP and the duration of TN to gradually decrease the frequency of the AC voltage Vp.

[0186] Figure 10 As shown, in the positive half cycle TP, the first switch control signal provided by Q1 and the third switch control signal provided by Q3 are PWM (pulse width modulation) signals, the second switch control signal provided by Q2 is a high level signal, the fourth switch control signal provided by Q4 is a low level signal, and the first switch control signal and the third switch control signal are out of phase;

[0187] In the negative half cycle TN, the second switch control signal provided by Q2 and the fourth switch control signal provided by Q4 are PWM (pulse width modulation) signals, the second switch control signal provided by Q1 is a low level signal, the third switch control signal provided by Q3 is a high level signal, and the second switch control signal and the fourth switch control signal are out of phase.

[0188] Figure 9 In the illustrated embodiment of the power supply device, the uninterruptible power supply includes a three-level half-bridge inverter.

[0189] In Figure 9 the embodiment of the power supply device shown, L1 is the transformer load, C is connected in parallel with the primary coil of the transformer, and the current flowing through L1 is the exciting current Im of the primary coil of the transformer.

[0190] As Figure 11A shown, in the positive half-cycle, when Q1 is turned on, Q2 is turned on, and Q3 and Q4 are turned off, the current path is successively through C1, Q1, Q2, L, C, and L1;

[0191] As Figure 11B shown, in the positive half-cycle, when Q1 is turned off and Q2 is turned on, the current path is successively through D1, Q2, L, C, and L1.

[0192] [[ID=z16]]As Figure 12A shown, in the negative half-cycle, when Q1 is turned off, Q2 is turned off, Q3 is turned on, and Q4 is turned on, at this time, the current path is successively through Q^3, Q4, C2, C, and L1, L;

[0193] As Figure 12B shown, in the negative half-cycle, when Q2 is turned on, Q1 is turned off, Q4 is turned off, and Q3 is turned on, the current path is successively through Q3, D2, C, and L1, L;

[0194] Figure 9 In the embodiment of the power supply device shown, when working, if the load current (when the load L1 is the transformer load, the load current is the exciting current of the primary coil of the transformer) is balanced between the positive half-cycle and the negative half-cycle, the positive DC bus voltage (the positive DC bus voltage is the voltage across C1) and the negative DC bus voltage (the negative DC bus voltage is the voltage across C2) will also remain in a balanced state; and if the load current is unbalanced between the positive half-cycle and the negative half-cycle (such as Figure 1b the waveform of the exciting current of the primary coil of the transformer in, the exciting current in the positive half-cycle is greater than the exciting current in the negative half-cycle), the negative DC bus voltage will rise rapidly. Eventually, the negative DC bus voltage drop exceeds the rated voltage of C2, which will also bring risks to the UPS; in addition, the large unbalanced current in a short time will also cause current stress on Q1, Q2, Q3, and Q4; based on this, the power supply device described in the embodiment of the present invention adopts the frequency control circuit 20. By controlling the frequency of the AC voltage to gradually decrease when the uninterruptible power supply just provides the AC voltage for the transformer load, the exciting current of the primary coil of the transformer can be made to have little difference between the positive half-cycle and the negative half-cycle, thereby reducing the negative DC bus voltage and not causing large current stress on Q1, Q2, Q3, and Q4, improving the reliability and stability of the uninterruptible power supply.

[0195] An embodiment of the present invention provides a new control method for a power supply device, which can gradually change the frequency of the AC voltage output by the UPS when connecting the transformer, so as to reduce the exciting current of the primary coil of the transformer. This method can effectively solve the problem that the DC bus voltage is too large and exceeds the rated voltage of the corresponding capacitor, and can reduce the current stress of the switching device, and does not increase the hardware cost and does not affect the output voltage performance.

[0196] During actual operation, when the UPS provides an AC voltage to the primary coil of the transformer, the magnetic flux Φ of the primary coil is as follows:

[0197] Φ = Φ m sinωt; where Φ m is the maximum magnetic flux, and ω is the phase angle of the AC voltage;

[0198] The formula for the induced electromotive force e1 is as follows:

[0199]

[0200] where e1 is the induced electromotive force of the primary coil of the transformer,

[0201] where N1 is the number of turns of the primary coil of the transformer, and E 1m is equal to ωN1Φ m ; E 1m is the maximum induced electromotive force;

[0202] The RMS value (root mean square value) E1 of e1 is as follows:

[0203]

[0204] where f is the frequency of the AC voltage output by the UPS;

[0205] If the impedance loss of the transformer is ignored:

[0206] U1 ≈ E1 = 4.44fN1Φ m .

[0207] where U1 is the voltage output by the primary coil of the transformer.

[0208] According to the relationship between the magnetic field and the exciting current in Ohm's law of magnetic circuits, it can be determined that by reducing the magnetic flux, the exciting current will be reduced. The magnetic flux is related to the operating frequency of the transformer when the transformer is running, and the operating frequency of the transformer is also the frequency of the AC voltage provided by the UPS to the primary coil of the transformer. Increasing the frequency can reduce the magnetic flux. Therefore, the exciting current of the primary coil of the transformer decreases as the frequency of the AC voltage increases. Based on the relationship between the exciting current and the power of the AC voltage, in the embodiments of the present invention, after the UPS starts and begins to provide AC voltage to the transformer load, the frequency control circuit gradually reduces the frequency of the AC voltage until the frequency is reduced to the nominal frequency; the RMS value of the AC voltage remains constant during the frequency change.

[0209] The entire frequency conversion process can be as Figure 13 shown in Figure 13 , where the vertical axis is the AC voltage Vp and the horizontal axis is the time t when the UPS provides the AC voltage Vp to the transformer load.

[0210] As Figure 13 shown, the frequency of the AC voltage Vp decreases sequentially within six inverter cycles. In the first inverter cycle, the frequency control circuit controls the frequency of the AC voltage to be 100 Hz; in the second inverter cycle, the frequency control circuit controls the frequency of the AC voltage to be 83.3 Hz; in the third inverter cycle, the frequency control circuit controls the frequency of the AC voltage to be 71.4 Hz; in the fourth inverter cycle, the frequency control circuit controls the frequency of the AC voltage to be 62.5 Hz; in the fifth inverter cycle, the frequency control circuit controls the frequency of the AC voltage to be 55.5 Hz; in the sixth inverter cycle, the frequency control circuit controls the frequency of the AC voltage to be 50 Hz.

[0211] In Figure 13 , the duration of the first inverter cycle is 10 ms, the duration of the second inverter cycle is 12 ms, the duration of the third inverter cycle is 14 ms, the duration of the fourth inverter cycle is 16 ms, the duration of the fifth inverter cycle is 18 ms, and the duration of the sixth inverter cycle is 20 ms, but not limited thereto.

[0212] In specific implementation, after the sixth inverter cycle, the frequency control circuit can control and maintain the frequency of the AC voltage at 50 Hz.

[0213] By adjusting the frequency of the AC voltage as described above, when the UPS just provides AC voltage to the transformer load, the imbalance of the exciting current of the primary winding of the transformer in the positive and negative half-cycles can be improved, thereby reducing the negative DC bus voltage and not causing a large current stress on the switching devices, enhancing the reliability and stability of the uninterruptible power supply.

[0214] The control method of the power supply device according to the embodiment of the present invention is applied to the above-mentioned power supply device, and the control method of the power supply device includes:

[0215] The uninterruptible power supply generates an alternating voltage;

[0216] The frequency control circuit controls the frequency of the alternating voltage generated by the uninterruptible power supply.

[0217] Specifically, the control method of the power supply device according to the embodiment of the present invention may further include:

[0218] The uninterruptible power supply supplies the alternating voltage to the primary coil of the transformer;

[0219] Within a predetermined time after the uninterruptible power supply starts to supply the alternating voltage to the primary coil of the transformer, the frequency control circuit controls to gradually reduce the frequency of the alternating voltage.

[0220] Specifically, the control method of the power supply device according to the embodiment of the present invention may further include:

[0221] After a predetermined time from when the uninterruptible power supply starts to supply the alternating voltage to the primary coil of the transformer, the frequency control circuit controls to maintain the frequency of the alternating voltage.

[0222] In specific implementation, the predetermined time can be selected according to the actual situation.

[0223] According to a specific implementation manner, the predetermined time can be six inverter cycles;

[0224] The step of, within a predetermined time after the uninterruptible power supply starts to supply the alternating voltage to the primary coil of the transformer, the frequency control circuit controls to gradually reduce the frequency of the alternating voltage may include:

[0225] In the first inverter cycle, the frequency control circuit controls the frequency of the alternating voltage to be greater than or equal to 100 Hz and less than or equal to 150 Hz;

[0226] In the second inverter cycle, the frequency control circuit controls the frequency of the alternating voltage to be greater than or equal to 78 Hz and less than or equal to 90 Hz;

[0227] In the third inverter cycle, the frequency control circuit controls the frequency of the alternating voltage to be greater than or equal to 70 Hz and less than or equal to 73 Hz;

[0228] In the fourth inverter cycle, the frequency control circuit controls the frequency of the alternating voltage to be greater than or equal to 60 Hz and less than or equal to 65 Hz;

[0229] In the fifth inversion period, the frequency control circuit controls the frequency of the AC voltage to be greater than or equal to 54 Hz and less than or equal to 58 Hz;

[0230] In the sixth inversion period, the frequency control circuit controls the frequency of the AC voltage to be greater than or equal to 48 Hz and less than or equal to 52 Hz.

[0231] More specifically, in the first inversion period, the frequency control circuit can control the frequency of the AC voltage to be 100 Hz;

[0232] In the second inversion period, the frequency control circuit can control the frequency of the AC voltage to be 83.3 Hz;

[0233] In the third inversion period, the frequency control circuit can control the frequency of the AC voltage to be 71.4 Hz;

[0234] In the fourth inversion period, the frequency control circuit can control the frequency of the AC voltage to be 62.5 Hz;

[0235] In the fifth inversion period, the frequency control circuit can control the frequency of the AC voltage to be 55.5 Hz;

[0236] In the sixth inversion period, the frequency control circuit can control the frequency of the AC voltage to be 50 Hz.

[0237] The specific embodiments of the frequency control circuit for reducing the frequency of the AC voltage listed above, and the values of the predetermined time are only for illustration and do not limit the scope of the present invention.

[0238] The display device provided by the embodiments of the present invention can be any product or component with a display function, such as a mobile phone, a tablet computer, a television, a monitor, a laptop computer, a digital photo frame, a navigator, etc.

[0239] The above is the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A power supply device, characterized in that, It includes an uninterruptible power supply and a frequency control circuit; The uninterruptible power supply is used to generate an alternating voltage to the primary coil of a transformer; The frequency control circuit is electrically connected to the uninterruptible power supply, and is used to control the frequency of the alternating voltage generated by the uninterruptible power supply, and is used to control the gradual reduction of the frequency of the alternating voltage within a predetermined time from when the uninterruptible power supply supplies the alternating voltage to the primary coil of the transformer; The predetermined time is six inverter cycles; The frequency control circuit is used to control the frequency of the alternating voltage to be greater than or equal to 100 Hz and less than or equal to 150 Hz in the first inverter cycle, to be greater than or equal to 78 Hz and less than or equal to 90 Hz in the second inverter cycle, to be greater than or equal to 70 Hz and less than or equal to 73 Hz in the third inverter cycle, to be greater than or equal to 60 Hz and less than or equal to 65 Hz in the fourth inverter cycle, to be greater than or equal to 54 Hz and less than or equal to 58 Hz in the fifth inverter cycle, and to be greater than or equal to 48 Hz and less than or equal to 52 Hz in the sixth inverter cycle.

2. The power supply device according to claim 1, wherein, The uninterruptible power supply includes a positive bus capacitor, a negative bus capacitor, a first switch circuit, a second switch circuit, an inductor, and a storage capacitor; The first plate of the positive bus capacitor is electrically connected to the first end of the first switch circuit, and the second plate of the positive bus capacitor is electrically connected to the first plate of the negative bus capacitor; The control end of the first switch circuit is electrically connected to a first switch control end, the second end of the first switch circuit is electrically connected to the first end of the inductor, and the first switch circuit is used to control the connection between the first plate of the positive bus capacitor and the first end of the inductor to be turned on or off under the control of a first switch control signal provided by the first switch control end; The control end of the second switch circuit is electrically connected to a second switch control end, the first end of the second switch circuit is electrically connected to the first end of the inductor, and the second end of the second switch circuit is electrically connected to the second plate of the negative bus capacitor; The second switch circuit is used to control the connection between the first end of the inductor and the second plate of the negative bus capacitor to be turned on or off under the control of a second switch control signal provided by the second switch control end; The second end of the inductor is electrically connected to the first plate of the storage capacitor, and the second plate of the storage capacitor is electrically connected to the first plate of the negative bus capacitor; The voltage across the storage capacitor is the alternating voltage.

3. The power supply device according to claim 2, wherein, The frequency control circuit is electrically connected to the first switch control end and the second switch control end respectively, and is used to control the frequency of the alternating voltage by controlling the first switch control signal and the second switch control signal.

4. The power supply device according to claim 2, wherein, The first switch circuit includes a first switch transistor, and the second switch circuit includes a second switch transistor; The control electrode of the first switching transistor is electrically connected to the first switching control terminal, the first pole of the first switching transistor is electrically connected to the first electrode plate of the positive bus capacitor, and the second pole of the first switching transistor is electrically connected to the first end of the inductor; The control electrode of the second switching transistor is electrically connected to the second switching control terminal, the first pole of the second switching transistor is electrically connected to the first end of the inductor, and the second pole of the second switching transistor is electrically connected to the second electrode plate of the negative bus capacitor.

5. The power supply device according to claim 1, characterized in that, The uninterruptible power supply includes a positive bus capacitor, a negative bus capacitor, a first switching circuit, a second switching circuit, a third switching circuit, a fourth switching circuit, a first conduction control circuit, a second conduction control circuit, an inductor, and a storage capacitor; The first electrode plate of the positive bus capacitor is electrically connected to the first end of the first switching circuit, and the second electrode plate of the positive bus capacitor is electrically connected to the first electrode plate of the negative bus capacitor; The control terminal of the first switching circuit is electrically connected to the first switching control terminal, and the second end of the first switching circuit is electrically connected to the first end of the second switching circuit; the first switching circuit is used to control the connection between the first electrode plate of the positive bus capacitor and the first end of the second switching circuit to be conducted or disconnected under the control of the first switching control signal provided by the first switching control terminal; The control terminal of the second switching circuit is electrically connected to the second switching control terminal, and the second end of the second switching circuit is electrically connected to the first end of the inductor; the second switching circuit is used to control the connection between the second end of the first switching circuit and the first end of the inductor to be conducted or disconnected under the control of the second switching control signal provided by the second switching control terminal; The control terminal of the third switching circuit is electrically connected to the third switching control terminal, the first end of the third switching circuit is electrically connected to the first end of the inductor, and the second end of the third switching circuit is electrically connected to the first end of the fourth switching circuit; the third switching circuit is used to control the connection between the first end of the inductor and the first end of the fourth switching circuit to be conducted or disconnected under the control of the third switching control signal provided by the third switching control terminal; The control terminal of the fourth switching circuit is electrically connected to the fourth switching control terminal, and the second end of the fourth switching circuit is electrically connected to the second electrode plate of the negative bus capacitor; the fourth switching circuit is used to control the connection between the second end of the third switching circuit and the second electrode plate of the negative bus capacitor to be conducted or disconnected under the control of the fourth switching control signal provided by the fourth switching control terminal; The first conduction control circuit is disposed between the second electrode plate of the positive bus capacitor and the first end of the first switching circuit, and the first conduction control circuit is used to only allow the current flowing from the second electrode plate of the positive bus capacitor to the first end of the first switching circuit to pass through; The second conduction control circuit is disposed between the second end of the third switching circuit and the second electrode plate of the positive bus capacitor, and the second conduction control circuit is used to only allow the current between the second end of the third switching circuit and the second electrode plate of the positive bus capacitor to pass through; The second end of the inductor is electrically connected to the first plate of the storage capacitor, the second plate of the storage capacitor is electrically connected to the ground terminal, and the second plate of the positive bus capacitor is electrically connected to the ground terminal; The voltage across the storage capacitor is the AC voltage.

6. The power supply device according to claim 5, characterized in that The frequency control circuit is electrically connected to the first switch control terminal, the second switch control terminal, the third switch control terminal, and the fourth switch control terminal respectively, and is used to control the frequency of the AC voltage by controlling the first switch control signal, the second switch control signal, the third switch control signal, and the fourth switch control signal.

7. The power supply device as claimed in claim 5, wherein The first conduction control circuit includes a first conduction control diode, and the second conduction control circuit includes a second conduction control diode; The anode of the first conduction control diode is electrically connected to the second plate of the positive bus capacitor, and the cathode of the first conduction control diode is electrically connected to the second end of the first switch circuit; The anode of the second conduction control diode is electrically connected to the second end of the third switch circuit, and the cathode of the second conduction control diode is electrically connected to the second plate of the positive bus capacitor.

8. The power supply device according to claim 5, characterized in that, The first switch circuit includes a first switch transistor, the second switch circuit includes a second switch transistor, the third switch circuit includes a third switch transistor, and the fourth switch circuit includes a fourth switch transistor; The control electrode of the first switch transistor is electrically connected to the first switch control terminal, the first pole of the first switch transistor is electrically connected to the first plate of the positive bus capacitor, and the second pole of the first switch transistor is electrically connected to the first pole of the second switch transistor; The control electrode of the second switch transistor is electrically connected to the second switch control terminal, and the second pole of the second switch transistor is electrically connected to the first end of the inductor; The control electrode of the third switch transistor is electrically connected to the third switch control terminal, the first pole of the third switch transistor is electrically connected to the first end of the inductor, and the second pole of the third switch transistor is electrically connected to the first pole of the fourth switch transistor; The control electrode of the fourth switch transistor is electrically connected to the fourth switch control terminal, and the second pole of the fourth switch transistor is electrically connected to the second plate of the negative bus capacitor.

9. A control method for a power supply device, applied to the power supply device according to any one of claims 1 to 8, characterized in that, The control method of the power supply device includes: The uninterruptible power supply generates an AC voltage; The frequency control circuit controls the frequency of the AC voltage generated by the uninterruptible power supply; The control method of the power supply device further includes: The uninterruptible power supply supplies the AC voltage to the primary coil of the transformer; Within a predetermined time after the uninterruptible power supply supplies the AC voltage to the primary coil of the transformer, the frequency control circuit controls to gradually reduce the frequency of the AC voltage; The predetermined time is six inverter cycles; The step of the frequency control circuit controlling to gradually reduce the frequency of the AC voltage within a predetermined time after the uninterruptible power supply supplies the AC voltage to the primary coil of the transformer includes: In the first inverter cycle, the frequency control circuit controls the frequency of the AC voltage to be greater than or equal to 100 Hz and less than or equal to 150 Hz; In the second inversion period, the frequency control circuit controls the frequency of the AC voltage to be greater than or equal to 78 Hz and less than or equal to 90 Hz; In the third inversion period, the frequency control circuit controls the frequency of the AC voltage to be greater than or equal to 70 Hz and less than or equal to 73 Hz; In the fourth inversion period, the frequency control circuit controls the frequency of the AC voltage to be greater than or equal to 60 Hz and less than or equal to 65 Hz; In the fifth inversion period, the frequency control circuit controls the frequency of the AC voltage to be greater than or equal to 54 Hz and less than or equal to 58 Hz; In the sixth inversion period, the frequency control circuit controls the frequency of the AC voltage to be greater than or equal to 48 Hz and less than or equal to 52 Hz.

10. The control method of the power supply device according to claim 9, characterized in that, It further includes: After a predetermined time from when the uninterruptible power supply provides the AC voltage to the primary coil of the transformer, the frequency control circuit controls to maintain the frequency of the AC voltage.

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