Buck-boost circuit, frequency converter, electric equipment and control method

Abstract

The invention discloses a buck-boost circuit, a frequency converter, electric equipment and a control method. The buck-boost circuit comprises a buck module, the input end of which is connected with a DC power supply and the output end of which is connected with a load; the input end of the boosting module is connected with the direct-current power supply, and the output end is connected with a load; and the change-over switch is arranged between the step-down module and the step-up module and is used for controlling one of the step-down module and the step-up module to be switched on according to the output voltage of the direct-current power supply and the target direct-current bus voltage. According to the invention, the voltage stress of the switching device can be reduced, thereby reducing the switching loss and the reverse recovery time of the diode, achieving the reduction of the heating of the switching tube, breaking through the frequency limitation of the switching tube, widening the switching frequency range of the switching tube, and widening the output voltage range.

Description

Technical Field

[0001] The present invention relates to the field of electronic power technology, and in particular to a step-up / step-down circuit, a frequency converter, an electrical device and a control method. Background Art

[0002] With the reduction of permanent magnet synchronous motor manufacturing cost and the popularization of manufacturing technology, many electrical equipment use full DC variable frequency drive technology. In specific applications, the electronic control system rectifies the input AC power supply into DC input through the rectifier circuit, and then boosts it to the bus voltage set by the system through the boost circuit for use by the subsequent inverter circuit. The PMSM space vector pulse width modulation (SVPWM) control method is the mainstream control scheme for current variable frequency drive. By selecting appropriate vectors in the vector space to generate an AC voltage output with almost no harmonics, higher power quality and efficiency can be obtained. Therefore, the above method is widely used in high-performance AC motor drive, inverter control and other fields.

[0003] At present, the driving scheme of the motor is generally based on the traditional boost circuit, and there is no DC-DC buck circuit. This design method has the following defects: 1. When the motor is running at low frequency and low voltage, since the bus voltage is at least times the input AC voltage effective value Vrms (for example, when the input voltage is 220V, it is about 311V without the DC-DC buck function), the compressor is operated in the low current constant torque area for a long time, the current limit circle is much smaller than the voltage limit circle, the utilization rate of the bus voltage is low, and the energy storage element in the inverter circuit has a high proportion of energy storage loss. 2. When the motor is running at low frequency and low voltage, the duty cycle of the switch tube in the IPM circuit is relatively small, and it may not be in the optimal operating range of the element. The resulting dead zone curve change is likely to lead to an increase in the output high-order harmonic content, causing vibration, heat and iron loss, resulting in energy loss. In response to the above two problems, the prior art introduces a buck-boost circuit in the bus voltage control to achieve the functions of boosting and bucking, so as to widen the voltage range of the bus. However, the existing buck-boost boost-boost circuit uses a common switch tube in the boost-boost circuit, and controls the boost or buck by controlling the duty cycle of the switch tube. The voltage stress of the switch device is large, which will cause higher switching losses and increase the reverse recovery time of the diode, resulting in heat generation, thereby limiting the switching frequency.

[0004] Currently, no effective solution has been proposed to the problem that the switching device voltage stress of the buck-boost circuit in the prior art is large, which will cause higher switching losses and increase the reverse recovery time of the diode, resulting in heat generation and thus limiting the switching frequency. Summary of the invention

[0005] The embodiments of the present invention provide a buck-boost circuit, a frequency converter, an electrical device and a control method to solve the problem in the prior art that the voltage stress of the switching device of the buck-boost circuit is large, which will cause higher switching losses and increase the reverse recovery time of the diode, resulting in heat generation, thereby limiting the switching frequency.

[0006] In order to solve the above technical problems, the present invention provides a buck-boost circuit, which comprises:

[0007] A step-down module, an input end of which is connected to a DC power supply, and an output end of which is connected to a load;

[0008] A boost module, an input end of which is connected to the DC power supply, and an output end of which is connected to a load;

[0009] A switching switch is arranged between the step-down module and the step-up module, and is used to control the step-down module and the step-up module to selectively conduct according to the output voltage of the DC power supply and the target DC bus voltage.

[0010] Furthermore, the switching switch is a single-pole double-throw switch, a fixed end of which is connected to the positive electrode of the load, and a movable end of which can be selectively connected to the positive output end of the buck module or the positive output end of the boost module.

[0011] Furthermore, the voltage reduction module comprises:

[0012] A first inductor, a first end of which is connected to the positive terminal of the DC power supply, and a second end of which is connected to the first switch tube;

[0013] The first switch tube has a second end connected to the first end of the second inductor;

[0014] The second inductor has a second end connected to the first end of the first capacitor;

[0015] The first output capacitor has a second end connected to the negative terminal of the DC power supply;

[0016] A first diode, a second diode and a third inductor are arranged in series, wherein the cathode of the first diode is connected between the first end of the first inductor and the positive terminal of the DC power supply, the anode of the first diode is connected to the cathode of the second diode, the anode of the second diode is connected to the first end of the third inductor, and the second end of the third inductor is connected between the second end of the first capacitor and the negative terminal of the DC power supply;

[0017] A first capacitor, a first end of which is connected between the second end of the first inductor and the first switch tube, and a second end of which is connected between the first diode and the second diode;

[0018] A second capacitor, a first end of which is connected between the second end of the first switch tube and the first end of the second inductor, a second end of which is connected to the anode of a third diode, and a cathode of the third diode is connected between the second end of the second inductor and the first end of the first output capacitor;

[0019] A fourth diode has a cathode connected between the second end of the second capacitor and the anode of the third diode, and an anode connected between the second end of the first output capacitor and the second end of the third inductor.

[0020] Furthermore, the boost module comprises:

[0021] a third capacitor, a first end of which is connected to the positive electrode of the DC power supply, and a second end of which is connected to the anode of the fifth diode;

[0022] a second output capacitor and a third output capacitor connected in series, wherein the second output capacitor is connected to the cathode of the fifth diode, and the third output capacitor is connected to the negative electrode of the DC power supply;

[0023] a sixth diode, a fourth capacitor and a second switch tube, wherein the cathode of the sixth diode is connected between the second end of the third capacitor and the anode of the fifth diode, the anode of the sixth diode is connected to the first end of the fourth capacitor, the second end of the fourth capacitor is connected to the first end of the second switch tube, and the second end of the second switch tube is connected between the third output capacitor and the negative electrode of the DC power supply;

[0024] a fourth inductor, an excitation inductor and a coupling inductor, wherein the first end of the fourth inductor is connected between the first end of the third capacitor and the positive electrode of the DC power supply, the second end of the fourth inductor is connected to the first end of the excitation inductor, the second end of the excitation inductor is connected between the second end of the fourth capacitor and the first end of the second switch tube, the first end of the coupling inductor is connected between the second end of the fourth capacitor and the first end of the second switch tube, and the second end of the coupling inductor is connected between the second output capacitor and the third output capacitor;

[0025] a seventh diode, an eighth diode and a ninth diode, wherein the anode of the seventh diode is connected between the anode of the sixth diode and the first end of the fourth capacitor, and the cathode of the seventh diode is connected to the second end of the coupling inductor; the anode of the eighth diode is connected between the second end of the second switch tube and the third output capacitor, and the cathode of the eighth diode is connected to the second end of the coupling inductor; the anode of the ninth diode is connected to the third output capacitor, and the cathode of the ninth diode is connected to the anode of the eighth diode;

[0026] A fifth capacitor, a first end of which is connected to the anode of the eighth diode, and a second end of which is connected to the second end of the second switch tube.

[0027] The present invention also provides a frequency converter, comprising the above-mentioned step-up and step-down circuit.

[0028] The present invention also provides an electrical device, comprising the above-mentioned frequency converter.

[0029] Furthermore, the electrical equipment includes at least one of the following: a variable frequency compressor, a variable frequency air conditioner, a variable frequency refrigerator, and a variable frequency washing machine.

[0030] The present invention also provides a control method, which is applied to the above-mentioned buck-boost circuit, and the control method includes:

[0031] Determine the magnitude relationship between the target DC bus voltage and the output voltage of the DC power supply;

[0032] If the target DC bus voltage is less than the output voltage of the DC power supply, the voltage reduction module is controlled to be turned on;

[0033] If the target DC bus voltage is greater than the output voltage of the DC power supply, the boost module is controlled to be turned on.

[0034] Furthermore, before controlling the voltage reduction module to start, the method further includes:

[0035] Controlling the first output capacitor in the step-down module to charge according to a first preset charging cycle;

[0036] After the first output capacitor is fully charged, the voltage reduction module is controlled to be turned on.

[0037] Further, controlling the first output capacitor of the step-down module to charge according to a preset charging cycle includes:

[0038] After entering the charging cycle, controlling the first switch tube in the buck module to turn on;

[0039] After a first preset time period, the first switch tube is controlled to be turned off, and after entering the next charging cycle, the first switch tube is controlled to be turned on again.

[0040] Furthermore, before controlling the boost module to start, the method further includes:

[0041] Controlling the second output capacitor and the third output capacitor in the boost module to charge according to a preset charging cycle;

[0042] After the second output capacitor and the third output capacitor are fully charged, the boost module is controlled to start.

[0043] Further, controlling the second output capacitor and the third output capacitor in the boost module to be charged according to a preset charging cycle includes:

[0044] After entering the charging cycle, controlling the second switch tube in the boost module to turn on;

[0045] After a second preset time period, the second switch tube is controlled to be turned off, and after entering the next charging cycle, the second switch tube is controlled to be turned on again.

[0046] The present invention also provides a computer-readable storage medium on which a computer program is stored, and the program implements the above control method when executed by a processor.

[0047] The present invention also provides an electronic device, comprising:

[0048] one or more processors;

[0049] The storage device is used to store one or more programs, and when the one or more programs are executed by the one or more processors, the one or more processors implement the above-mentioned control method.

[0050] By applying the technical solution of the present invention, independent boost modules and buck modules are provided to respectively realize the functions of boosting or bucking. The switching of the boost module and the buck module is realized by switching the switch. The switch tube is not shared, which reduces the voltage stress of the switch device, thereby reducing the switching loss and the reverse recovery time of the diode, and reducing the heating of the switch tube, thereby breaking through the frequency limitation of the switch tube, widening the switching frequency range of the switch tube, and widening the output voltage range. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is the control principle diagram of the SVPWM control method based on the traditional boost circuit;

[0052] Figure 2 is a structural diagram of a buck-boost circuit according to an embodiment of the present invention;

[0053] Figure 3 is a structural diagram of an equivalent circuit in a buck mode according to an embodiment of the present invention;

[0054] Figure 4 is a structural diagram of an equivalent circuit in a boost mode according to an embodiment of the present invention;

[0055] Figure 5 is a flow chart of a control method according to an embodiment of the present invention;

[0056] Figure 6 FIG. 4 is a schematic diagram of the hardware structure of an electronic device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only 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 ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0058] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings, and "multiple" generally includes at least two.

[0059] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0060] It should be understood that although the terms first, second, third, etc. may be used to describe inductors in the embodiments of the present invention, these inductors should not be limited to these terms. These terms are only used to distinguish different inductors. For example, without departing from the scope of the embodiments of the present invention, the first inductor may also be referred to as the second inductor, and similarly, the second inductor may also be referred to as the first inductor.

[0061] As used herein, the words "if" and "if" may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0062] It should also be noted that the term "includes", "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, so that a commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprising a ..." do not exclude the existence of other identical elements in the commodity or device including the elements.

[0063] The optional embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0064] Example 1

[0065] Figure 1 The control principle diagram of the SVPWM control method based on the traditional boost circuit is as follows: Figure 1 As shown, the three switch tubes of the upper bridge arm of the inverter circuit correspond to six effective switch states, and each state corresponds to the output voltage V1, V2, V3, V4, V5, and V6. According to the superposition principle, when the bus voltage Vdc is determined, the maximum voltage output of the inverter circuit is represented by a regular hexagon composed of the above six voltage vertices in the two-phase stationary coordinate system. The output voltage limit circle is the inscribed circle of the regular hexagon, that is, the dotted circle in the figure, and the solid circle in the figure is the current limit circle of the motor. When the motor runs in the constant torque area, the back electromotive force is less than the maximum voltage. At this time, RV=aRi, and the radius Ri of the current limit circle is less than the radius RV of the voltage limit circle. When the bus voltage remains unchanged, as the output power of the compressor increases, its operating state will gradually enter the constant power area and constant voltage area. When the compressor is in the constant voltage area, it works above the rated speed. Restricted by the voltage limit circle, the output torque and power will decrease sharply with the increase of the speed.

[0066] In order to solve the above problems, the buck-boost circuit is introduced in the prior art to realize the functions of boosting and bucking, so as to expand the voltage range of the bus. However, the existing buck-boost boost-boost circuit uses a common switch tube in the boost-boost circuit, and controls the boost or buck by controlling the duty cycle of the switch tube. The voltage stress of the switch device is large, which will cause higher switching loss and increase the reverse recovery time of the diode, resulting in heat generation, thereby limiting the switching frequency. When the input voltage is low, the boost circuit will also have problems of insufficient gain and extreme duty cycle, which will reduce the wide voltage operation capability of the whole machine.

[0067] In view of the above problems in the prior art, this embodiment provides a buck-boost circuit. Figure 2 is a structural diagram of a buck-boost circuit according to an embodiment of the present invention, Figure 2 As shown, the buck-boost circuit includes: a buck module 10, whose input end is connected to a DC power supply, and whose output end is connected to a load; a boost module 20, whose input end is connected to the DC power supply, and whose output end is connected to the load; a switching switch S, which is arranged between the buck module 10 and the boost module 20, and is used to control the buck module 10 and the boost module 20 to selectively conduct according to the output voltage of the DC power supply and the target DC bus voltage.

[0068] In the specific implementation, the magnitude relationship between the target DC bus voltage Vdc and the output voltage Vin of the DC power supply is first determined; when the target DC bus voltage Vdc is less than the output voltage Vin of the DC power supply, the buck module is controlled to be turned on; when the target DC bus voltage Vdc is greater than the output voltage Vin of the DC power supply, the boost module is controlled to be turned on.

[0069] It should be noted that if the target DC bus voltage Vdc is equal to the output voltage Vin of the DC power supply, there is no need to perform step-up or step-down. The step-up or step-down circuit can be directly cut out of the circuit and the DC bus can be powered directly by the DC power supply.

[0070] The buck-boost circuit of this embodiment is provided with an independent boost module and buck module to respectively realize the function of boosting or bucking. The switching of the boost module and the buck module is realized by switching the switch. The switch tube is not shared, which reduces the voltage stress of the switching device, thereby reducing the switching loss and the reverse recovery time of the diode, and reducing the heat generation of the switch tube, thereby breaking through the frequency limit of the switch tube, widening the switching frequency range of the switch tube, and widening the output voltage range.

[0071] In this embodiment, a suitable control parameter a can be set according to the duty cycle characteristics of the switch tube, so that a>100%, and RV=aRi in the full power range of the compressor, and its voltage limit circle is always greater than the current limit circle. In this way, the compressor is not limited by the bus voltage during high-power operation and can output the maximum torque, and the switch tube can always operate in the high-efficiency duty cycle range, thereby improving the bus voltage utilization rate and reducing power loss.

[0072] As described above, the switching of the step-up and step-down modules is achieved by switching the switch S. The switch is a single-pole double-throw switch, whose fixed end is connected to the positive electrode of the load, and whose movable end can be selectively connected to the positive output end of the step-down module 10 or the positive output end of the step-up module 20.

[0073] In order to reduce the switching loss and reverse recovery time of the diode during the step-down process, the switch and diode can be controlled to be turned off at zero current as much as possible. Figure 2As shown, the step-down module 10 includes: a first inductor, a first end of which is connected to the positive terminal of the DC power supply, and a second end of which is connected to the first switch tube; the first switch tube, a second end of which is connected to the first end of the second inductor; the second end of the second inductor, a first end of which is connected to the first end of the first capacitor; the first output capacitor, a second end of which is connected to the negative terminal of the DC power supply; a first diode, a second diode and a third inductor arranged in series, the cathode of the first diode is connected between the first end of the first inductor and the positive terminal of the DC power supply, the anode of the first diode is connected to the cathode of the second diode, the anode of the second diode is connected to the first end of the third inductor, and the second end of the third inductor is connected to to between the second end of the first capacitor and the negative terminal of the DC power supply; a first capacitor, whose first end is connected between the second end of the first inductor and the first switching tube, and whose second end is connected between the first diode and the second diode; a second capacitor, whose first end is connected between the second end of the first switching tube and the first end of the second inductor, and whose second end is connected to the anode of a third diode, and whose cathode is connected between the second end of the second inductor and the first end of the first output capacitor; a fourth diode, whose cathode is connected between the second end of the second capacitor and the anode of the third diode, and whose anode is connected between the second end of the first output capacitor and the second end of the third inductor.

[0074] Before controlling the buck module to start, first control the first output capacitor in the buck module to charge according to the first preset charging cycle; after the first output capacitor is fully charged, control the buck module to start, and during the charging process, the switch S is still placed at point 2. Controlling the first output capacitor of the buck module to charge according to the preset charging cycle includes: after entering the charging cycle, controlling the first switch tube in the buck module to turn on; after a first preset time, controlling the first switch tube to turn off, until entering the next charging cycle, and controlling the first switch tube to turn on again. That is, when t=nT, the first switch tube S1 is controlled to be turned on, at this time, the second diode D2 and the third diode D3 are turned on, the second diode D1 and the fourth diode D4 are turned off by the reverse voltage, the first inductor L1 is charged by the output voltage Vin of the DC power supply, the second inductor L2 and the second capacitor C2 are charged by the output voltage Vin of the power supply and the first capacitor C1, wherein the first capacitor C1 and the third inductor Lr are discharged in series resonance, and after the first switch tube S1 is continuously turned on for a period of time D0, that is, at the moment t=(n+D0)T, the second diode D2 is turned off with zero current, thereby solving its reverse recovery problem and reducing the loss. At this time, the resonant discharge of the first capacitor C1 and the third inductor Lr ends, the first capacitor C1 stops discharging, the first switch tube S1 and the third diode D3 are still turned on, the first diode D1, the second diode D2, and the fourth diode D4 are turned off, and the output voltage Vin of the DC power supply charges the first inductor L1, the second capacitor C2, and the first output capacitor Co1 through the first switch tube S1. After the switch tube S1 is continuously turned on for a time length D (i.e., the above-mentioned first preset time length), at the moment t=(n+D)T, the switch tube S1 is controlled to be turned off. At the moment when the switch tube is turned off, the current flowing through the second diode D2 is 0, and at this time, the current flowing through the first switch tube S1 is=the current flowing through the first inductor L1 iL1. The second stage realizes the zero current shutdown (ZCS) of the first switch tube S1, reducing the switching loss. Subsequently, the second diode D2 and the third diode D3 are turned off by the reverse voltage, the first diode D1 and the fourth diode D4 are turned on, and the first inductor L1 charges the first capacitor C1 through the first diode D1. The second inductor L2 continues to flow through the second capacitor C2, the fourth diode D4, the load resistor Ro, and the first output capacitor Co1, and the second capacitor C2 is discharged. After the next cycle begins, that is, at t = (n + 1) T, the first switch tube S1 is controlled to be turned on again, and the buck circuit enters the next charging cycle. After a time tcbu, Vco1 = VDC, and the first output capacitor Co1 is fully charged, the switch S is controlled to be placed at point 1. Figure 3 : is an equivalent circuit structure diagram in the buck mode according to an embodiment of the present invention, such as Figure 3 As shown, at this time, the buck module 10 is turned on (solid line) and the boost module 20 is turned off (dashed line).

[0075] When the input voltage is low, the boost circuit will also have problems such as insufficient gain and limited duty cycle, which will reduce the wide voltage operation capability of the whole machine. In order to solve the above technical problems and reduce the switching loss and reverse recovery time of the diode in the boost process, Figure 2 As shown, the boost module 20 includes: a third capacitor, a first end of which is connected to the positive electrode of the DC power supply, and a second end of which is connected to the anode of the fifth diode;

[0076] a second output capacitor and a third output capacitor connected in series, wherein the second output capacitor is connected to the cathode of the fifth diode, and the third output capacitor is connected to the negative electrode of the DC power supply;

[0077] a sixth diode, a fourth capacitor and a second switch tube, wherein the cathode of the sixth diode is connected between the second end of the third capacitor and the anode of the fifth diode, the anode of the sixth diode is connected to the first end of the fourth capacitor, the second end of the fourth capacitor is connected to the first end of the second switch tube, and the second end of the second switch tube is connected between the third output capacitor and the negative electrode of the DC power supply;

[0078] a fourth inductor, an excitation inductor and a coupling inductor, wherein the first end of the fourth inductor is connected between the first end of the third capacitor and the positive electrode of the DC power supply, the second end of the fourth inductor is connected to the first end of the excitation inductor, the second end of the excitation inductor is connected between the second end of the fourth capacitor and the first end of the second switch tube, the first end of the coupling inductor is connected between the second end of the fourth capacitor and the first end of the second switch tube, and the second end of the coupling inductor is connected between the second output capacitor and the third output capacitor;

[0079] a seventh diode, an eighth diode and a ninth diode, wherein the anode of the seventh diode is connected between the anode of the sixth diode and the first end of the fourth capacitor, and the cathode of the seventh diode is connected to the second end of the coupling inductor; the anode of the eighth diode is connected between the second end of the second switch tube and the third output capacitor, and the cathode of the eighth diode is connected to the second end of the coupling inductor; the anode of the ninth diode is connected to the third output capacitor, and the cathode of the ninth diode is connected to the anode of the eighth diode;

[0080] A fifth capacitor, a first end of which is connected to the anode of the eighth diode, and a second end of which is connected to the second end of the second switch tube.

[0081] As the unit pressure and compressor frequency increase, the radius of the compressor current limit circle also increases. When the target DC bus voltage Vdc>Vin, the control boost module is turned on. Before the control boost module is turned on,

[0082] The second output capacitor and the third output capacitor in the boost module are controlled to charge according to a preset charging cycle; until the second output capacitor and the third output capacitor are fully charged, the boost module is controlled to be turned on, and during the charging process, the switch S is still placed at point 1. The second output capacitor and the third output capacitor in the boost module are controlled to charge according to a preset charging cycle, including: after entering the charging cycle, the second switch tube in the boost module is controlled to be turned on; after a second preset time, the second switch tube is controlled to be turned off until entering the next charging cycle, and the second switch tube is controlled to be turned on again, that is, after entering the charging cycle, the second switch tube S2 is controlled to be turned on, at this time, the seventh diode D7 and the ninth diode D9 are turned on, and the fifth diode D5, the sixth diode D6 and the eighth diode D8 are turned off. The output voltage Vin of the input DC power supply charges the excitation inductor Np through the second switch tube S2. The secondary side of the coupled inductor Ns charges the fourth capacitor C4 through the seventh diode D7. When t=t1, the secondary side current of the coupled inductor Ns becomes zero. At this time, the second switch tube S2 continues to be turned on, the fifth diode D5 and the eighth diode D8 are turned on, and the sixth diode D6, the seventh diode D7 and the ninth diode D9 are turned off. The output voltage Vin of the DC power supply continues to charge the excitation inductor Np through the second switch tube S2. The second output capacitor Co2 is charged by the output voltage Vin of the DC power supply, the third capacitor C3 (clamping capacitor) and the energy of the secondary side of the coupling inductor Ns. At the same time, the secondary side of the coupling inductor Ns charges C5. After the second switch tube S2 is continuously turned on for the second preset time, that is, at t=t2, the second switch tube S2 is controlled to be turned off, the regional diode D5, the sixth diode D6 and the eighth diode D8 are turned on, and the seventh diode D7 and the ninth diode D9 are turned off. The third capacitor C3 is charged by the energy of the fourth capacitor C4, the fourth inductor Lk and the excitation inductor Np, and the energy of the leakage inductance is recovered. The second output capacitor Co2 is charged by the fourth capacitor C4 and the secondary side of the coupling inductor Ns. At t=t3, the current iLk flowing through the fourth inductor Lk is equal to the current iLm flowing through the excitation inductor Np. The sixth diode D6 and the sixth diode D9 are turned on, and the fifth diode D5, the seventh diode D7 and the eighth diode D8 are turned off. The third capacitor C3 is charged by the energy of the fourth capacitor C4, the fourth inductor Lk and the excitation inductor Np. The output voltage Vin of the DC power supply, the fifth capacitor C5 and the secondary side of the coupling inductor Ns charge the third output capacitor Co3 and provide energy to the load. When t=t4, the sixth diode D6 is turned off, the seventh diode D7 is turned on, and the energy of the secondary side of the coupling inductor Ns charges the fourth capacitor C4 through the seventh diode D7. In addition, the output voltage Vin of the DC power supply, the fifth capacitor C5 and the secondary side of the coupling inductor Ns continue to charge the third output capacitor Co3 and provide energy to the load. At t=t5, the second switch tube S2 is turned on, and the boost circuit enters the next charging cycle.After time tcbo, Vco2+Vco3=Vdc, the second output capacitor Co2 and the third output capacitor Co3 are fully charged, and S is placed at point 2. Figure 4 : is an equivalent circuit structure diagram in boost mode according to an embodiment of the present invention, such as Figure 4 As shown, at this time, the boost module 20 is turned on (solid line) and the buck module 10 is turned off (dashed line).

[0083] Example 2

[0084] The present embodiment provides an inverter, including the buck-boost circuit of the above embodiment, which is used to realize the switching of the boost module and the buck module by switching the switch, without sharing the switch tube, reducing the voltage stress of the switching device, thereby reducing the switching loss and the reverse recovery time of the diode, and reducing the heat generation of the switch tube, thereby breaking through the frequency limitation of the switch tube, widening the switching frequency range of the switch tube, and widening the output voltage range.

[0085] Example 3

[0086] The present embodiment provides an electrical device, including the frequency converter of the above embodiment, which is used to realize the switching of the boost module and the buck module by switching the switch, without sharing the switch tube, reducing the voltage stress of the switch device, thereby reducing the switching loss and the reverse recovery time of the diode, and reducing the heating of the switch tube, thereby breaking through the frequency limit of the switch tube, widening the switching frequency range of the switch tube, and widening the output voltage range.

[0087] In some embodiments of the present invention, the electrical equipment includes at least one of the following: a variable frequency compressor, a variable frequency air conditioner, a variable frequency refrigerator, and a variable frequency washing machine.

[0088] Example 4

[0089] This embodiment provides a control method, which is applied to the buck-boost circuit of the above embodiment. Figure 5 is a flow chart of a control method according to an embodiment of the present invention, as shown in Figure 5 As shown, the control method includes:

[0090] S101, determining the magnitude relationship between the target DC bus voltage Vdc and the output voltage Vin of the DC power supply.

[0091] S102, if Vdc<Vin, the buck module is controlled to turn on.

[0092] S103, if Vdc>Vin, the boost module is controlled to turn on.

[0093] It should be noted that if the target DC bus voltage is equal to the output voltage of the DC power supply, there is no need to perform step-up or step-down. The step-up or step-down circuit can be directly cut out of the circuit and the DC bus can be powered directly by the DC power supply.

[0094] The control method of this embodiment realizes the switching of the boost module and the buck module by switching the switch, does not share the switch tube, reduces the voltage stress of the switch device, thereby reducing the switching loss and the reverse recovery time of the diode, reduces the heating of the switch tube, and further breaks through the frequency limit of the switch tube, broadens the switching frequency range of the switch tube, and broadens the output voltage range.

[0095] During the step-down process, in order to achieve a DC bus voltage that is stable and meets the voltage requirements, the first output capacitor needs to be charged. Therefore, before controlling the step-down module to start, the above method also includes: controlling the first output capacitor in the step-down module to charge according to a first preset charging cycle; until the first output capacitor is fully charged, controlling the step-down module to start. Controlling the first output capacitor of the step-down module to charge according to a preset charging cycle includes: after entering the charging cycle, controlling the first switch tube in the step-down module to turn on; after a first preset time, controlling the first switch tube to turn off until entering the next charging cycle, and then controlling the first switch tube to turn on again. That is, when t=nT, the first switch tube S1 is controlled to be turned on, at this time, the second diode D2 and the third diode D3 are turned on, the second diode D1 and the fourth diode D4 are turned off by the reverse voltage, the first inductor L1 is charged by the output voltage Vin of the DC power supply, the second inductor L2 and the second capacitor C2 are charged by the output voltage Vin of the power supply and the first capacitor C1, wherein the first capacitor C1 and the third inductor Lr are discharged in series resonance, and after the first switch tube S1 is continuously turned on for a period of time D0, that is, at the moment t=(n+D0)T, the second diode D2 is turned off with zero current, thereby solving its reverse recovery problem and reducing the loss. At this time, the resonant discharge of the first capacitor C1 and the third inductor Lr ends, the first capacitor C1 stops discharging, the first switch tube S1 and the third diode D3 are still turned on, the first diode D1, the second diode D2, and the fourth diode D4 are turned off, and the output voltage Vin of the DC power supply charges the first inductor L1, the second capacitor C2, and the first output capacitor Co1 through the first switch tube S1. After the switch tube S1 is continuously turned on for a time length D (i.e., the above-mentioned first preset time length), at the moment t=(n+D)T, the switch tube S1 is controlled to be turned off. At the moment when the switch tube is turned off, the current flowing through the second diode D2 is 0, and at this time, the current flowing through the first switch tube S1 is=the current flowing through the first inductor L1 iL1. The second stage realizes the zero current shutdown (ZCS) of the first switch tube S1, reducing the switching loss. Subsequently, the second diode D2 and the third diode D3 are turned off by the reverse voltage, the first diode D1 and the fourth diode D4 are turned on, and the first inductor L1 charges the first capacitor C1 through the first diode D1. The second inductor L2 continues to flow through the second capacitor C2, the fourth diode D4, the load resistor Ro, and the first output capacitor Co1, and the second capacitor C2 is discharged. After the next cycle begins, that is, at t = (n + 1) T, the first switch tube S1 is controlled to be turned on again, and the buck circuit enters the next charging cycle. After a time tcbu, Vco1 = VDC, and the first output capacitor Co1 is fully charged, the switch S is controlled to be placed at point 1. Figure 3 : is an equivalent circuit structure diagram in the buck mode according to an embodiment of the present invention, such as Figure 3 As shown, at this time, the buck module 10 is turned on (solid line) and the boost module 20 is turned off (dashed line).

[0096] As the unit pressure and compressor frequency increase, the radius of the current limit circle of the compressor also increases. When the target DC bus voltage Vdc>Vin, the boost module is controlled to be turned on. During the boost process, in order to achieve a DC bus voltage that is stable and meets the voltage requirements, the second output capacitor and the third output capacitor need to be charged. Before the boost module is controlled to be turned on, the method also includes: controlling the second output capacitor and the third output capacitor in the boost module to be charged according to a preset charging cycle; until the second output capacitor and the third output capacitor are fully charged, the boost module is controlled to be turned on. Controlling the second output capacitor and the third output capacitor in the boost module to be charged according to a preset charging cycle includes: after entering the charging cycle, controlling the second switch tube in the boost module to be turned on; after a second preset time, controlling the second switch tube to be turned off until entering the next charging cycle, and controlling the second switch tube to be turned on again. That is, after entering the charging cycle, the second switch tube S2 is controlled to be turned on, at which time the seventh diode D7 and the ninth diode D9 are turned on, and the fifth diode D5, the sixth diode D6 and the eighth diode D8 are turned off. The output voltage Vin of the DC power supply charges the excitation inductor Np through the second switch tube S2. The secondary side of the coupled inductor Ns charges the fourth capacitor C4 through the seventh diode D7. When t=t1, the secondary side current of the coupled inductor Ns becomes zero. At this time, the second switch tube S2 continues to be turned on, the fifth diode D5 and the eighth diode D8 are turned on, and the sixth diode D6, the seventh diode D7 and the ninth diode D9 are turned off. The output voltage Vin of the DC power supply continues to charge the excitation inductor Np through the second switch tube S2. The second output capacitor Co2 is charged by the output voltage Vin of the DC power supply, the third capacitor C3 (clamping capacitor) and the energy of the secondary side of the coupled inductor Ns. At the same time, the secondary side of the coupled inductor Ns charges C5. After the second switch tube S2 is continuously turned on for the second preset time, that is, at t=t2, the second switch tube S2 is controlled to be turned off, the regional diode D5, the sixth diode D6 and the eighth diode D8 are turned on, and the seventh diode D7 and the ninth diode D9 are turned off. The third capacitor C3 is charged by the energy of the fourth capacitor C4, the fourth inductor Lk and the excitation inductor Np, and the energy of the leakage inductance is recovered. The second output capacitor Co2 is charged by the secondary side of the fourth capacitor C4 and the coupling inductor Ns. At t=t3, the iLk current flowing through the fourth inductor Lk is equal to the current iLm flowing through the excitation inductor Np. The sixth diode D6 and the sixth diode D9 are turned on, and the fifth diode D5, the seventh diode D7 and the eighth diode D8 are turned off. The third capacitor C3 is charged by the energy of the fourth capacitor C4, the fourth inductor Lk and the excitation inductor Np. The output voltage Vin of the DC power supply, the secondary side of the fifth capacitor C5 and the coupling inductor Ns charge the third output capacitor Co3 and provide energy to the load.When t=t4, the sixth diode D6 is turned off, the seventh diode D7 is turned on, and the energy on the secondary side of the coupled inductor Ns charges the fourth capacitor C4 through the seventh diode D7. In addition, the output voltage Vin of the DC power supply, the fifth capacitor C5 and the secondary side of the coupled inductor Ns continue to charge the third output capacitor Co3 and provide energy to the load. At t=t5, the second switch tube S2 is turned on, and the boost circuit enters the next charging cycle. After time tcbo, Vco2+Vco3=Vdc, the second output capacitor Co2 and the third output capacitor Co3 are fully charged, and S is placed at point 2. Figure 4 : is an equivalent circuit structure diagram in boost mode according to an embodiment of the present invention, such as Figure 4 As shown, at this time, the boost module 20 is turned on (solid line) and the buck module 10 is turned off (dashed line).

[0097] Example 5

[0098] This embodiment provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the above control method is implemented.

[0099] Example 6

[0100] This embodiment provides an electronic device, including:

[0101] one or more processors;

[0102] The storage device is used to store one or more programs, and when the one or more programs are executed by the one or more processors, the one or more processors implement the above-mentioned control method.

[0103] Figure 6 FIG. 1 is a schematic diagram of the hardware structure of an electronic device according to an embodiment of the present invention. Figure 6 As shown, the electronic device includes:

[0104] One or more processors 610 and memory 620, Figure 6 A processor 610 is taken as an example.

[0105] The electronic device may further include: an input device 630 and an output device 640 .

[0106] The processor 610, the memory 620, the input device 630 and the output device 640 may be connected via a bus or other means. Figure 6 The example of connecting through bus is taken in the following.

[0107] The memory 620 is a non-volatile computer-readable storage medium that can be used to store non-volatile software programs, non-volatile computer executable programs and modules, such as program instructions / modules corresponding to the control method in the embodiment of the present invention. The processor 610 executes various functional applications and data processing of the server by running the non-volatile software programs, instructions and modules stored in the memory 620, that is, implementing the above method embodiment.

[0108] The memory 620 may include a program storage area and a data storage area, wherein the program storage area may store an application required for operating the device and at least one function; the data storage area may store data created according to the use of the control method, etc. In addition, the memory 620 may include a high-speed random access memory, and may also include a non-volatile memory, such as at least one disk storage device, a flash memory device, or other non-volatile solid-state storage devices.

[0109] The input device 630 can receive input digital or character information and generate key signal input related to user settings and function control of the electronic device. The output device 640 can include a display device such as a display screen.

[0110] The one or more modules are stored in the memory 620, and when executed by the one or more processors 610, perform the control method in any of the above method embodiments.

[0111] The electronic device can execute the method provided by the embodiment of the present invention, and has the functional modules and beneficial effects corresponding to the execution method. For technical details not described in detail in this embodiment, please refer to the method provided by the embodiment of the present invention.

[0112] The electronic device of the embodiment of the present invention exists in various forms, including but not limited to:

[0113] (1) Mobile communication devices: These devices are characterized by their mobile communication functions and their main purpose is to provide voice and data communications. These terminals include: smart phones (such as iPhone), multimedia phones, functional phones, and low-end phones.

[0114] (2) Ultra-mobile personal computer devices: These devices fall into the category of personal computers, have computing and processing capabilities, and generally also have mobile Internet access features. These terminals include: PDA, MID and UMPC devices, such as iPad.

[0115] (3) Portable entertainment devices: These devices can display and play multimedia content. They include audio and video players (such as iPods), handheld game consoles, e-books, smart toys, and portable car navigation devices.

[0116] (4) Server: A device that provides computing services. The server consists of a processor, hard disk, memory, device bus, etc. The server is similar to a general computer architecture, but because it needs to provide highly reliable services, it has higher requirements in terms of processing power, stability, reliability, security, scalability, and manageability.

[0117] (5) Other electronic devices with data interaction functions, such as televisions, large-screen cars, etc.

[0118] The circuit embodiments described above are merely illustrative, wherein the modules described as separate components may or may not be physically separated, and the components shown as modules may or may not be physical modules, i.e., they may be located in one place or distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the present embodiment.

[0119] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A step-up / step-down circuit, characterized in that: The circuit comprises: A step-down module, an input end of which is connected to a DC power supply, and an output end of which is connected to a load; A boost module, an input end of which is connected to the DC power supply, and an output end of which is connected to a load; A switching switch is arranged between the step-down module and the step-up module, and is used to control the step-down module and the step-up module to selectively conduct according to the output voltage of the DC power supply and the target DC bus voltage.

2. The circuit according to claim 1, characterized in that The switching switch is a single-pole double-throw switch, a fixed end of which is connected to the positive electrode of the load, and a movable end of which can be selectively connected to the positive output end of the buck module or the positive output end of the boost module.

3. The circuit according to claim 1, characterized in that The step-down module comprises: A first inductor, a first end of which is connected to the positive terminal of the DC power supply, and a second end of which is connected to the first switch tube; The first switch tube has a second end connected to the first end of the second inductor; The second inductor has a second end connected to the first end of the first capacitor; The first output capacitor has a second end connected to the negative terminal of the DC power supply; A first diode, a second diode and a third inductor are arranged in series, wherein the cathode of the first diode is connected between the first end of the first inductor and the positive terminal of the DC power supply, the anode of the first diode is connected to the cathode of the second diode, the anode of the second diode is connected to the first end of the third inductor, and the second end of the third inductor is connected between the second end of the first capacitor and the negative terminal of the DC power supply; A first capacitor, a first end of which is connected between the second end of the first inductor and the first switch tube, and a second end of which is connected between the first diode and the second diode; A second capacitor, a first end of which is connected between the second end of the first switch tube and the first end of the second inductor, a second end of which is connected to the anode of a third diode, and a cathode of the third diode is connected between the second end of the second inductor and the first end of the first output capacitor; A fourth diode has a cathode connected between the second end of the second capacitor and the anode of the third diode, and an anode connected between the second end of the first output capacitor and the second end of the third inductor.

4. The circuit according to claim 1, characterized in that The boost module comprises: a third capacitor, a first end of which is connected to the positive electrode of the DC power supply, and a second end of which is connected to the anode of the fifth diode; a second output capacitor and a third output capacitor connected in series, wherein the second output capacitor is connected to the cathode of the fifth diode, and the third output capacitor is connected to the negative electrode of the DC power supply; a sixth diode, a fourth capacitor and a second switch tube, wherein the cathode of the sixth diode is connected between the second end of the third capacitor and the anode of the fifth diode, the anode of the sixth diode is connected to the first end of the fourth capacitor, the second end of the fourth capacitor is connected to the first end of the second switch tube, and the second end of the second switch tube is connected between the third output capacitor and the negative electrode of the DC power supply; a fourth inductor, an excitation inductor and a coupling inductor, wherein the first end of the fourth inductor is connected between the first end of the third capacitor and the positive electrode of the DC power supply, the second end of the fourth inductor is connected to the first end of the excitation inductor, the second end of the excitation inductor is connected between the second end of the fourth capacitor and the first end of the second switch tube, the first end of the coupling inductor is connected between the second end of the fourth capacitor and the first end of the second switch tube, and the second end of the coupling inductor is connected between the second output capacitor and the third output capacitor; a seventh diode, an eighth diode and a ninth diode, wherein the anode of the seventh diode is connected between the anode of the sixth diode and the first end of the fourth capacitor, and the cathode of the seventh diode is connected to the second end of the coupling inductor; the anode of the eighth diode is connected between the second end of the second switch tube and the third output capacitor, and the cathode of the eighth diode is connected to the second end of the coupling inductor; the anode of the ninth diode is connected to the third output capacitor, and the cathode of the ninth diode is connected to the anode of the eighth diode; A fifth capacitor, a first end of which is connected to the anode of the eighth diode, and a second end of which is connected to the second end of the second switch tube.

5. A frequency converter, characterized in that: The invention comprises the buck-boost circuit according to any one of claims 1 to 4.

6. An electrical equipment, characterized in that: Including the frequency converter described in claim 5.

7. The electrical equipment according to claim 6, characterized in that: The electrical equipment includes at least one of the following: a variable frequency compressor, a variable frequency air conditioner, a variable frequency refrigerator, and a variable frequency washing machine.

8. A control method, applied to the buck-boost circuit according to any one of claims 1 to 4, characterized in that: The control method comprises: Determine the magnitude relationship between the target DC bus voltage and the output voltage of the DC power supply; If the target DC bus voltage is less than the output voltage of the DC power supply, the voltage reduction module is controlled to be turned on; If the target DC bus voltage is greater than the output voltage of the DC power supply, the boost module is controlled to be turned on.

9. The control method according to claim 8, characterized in that: Before controlling the voltage reduction module to start, the method further includes: Controlling the first output capacitor in the step-down module to charge according to a first preset charging cycle; After the first output capacitor is fully charged, the voltage reduction module is controlled to be turned on.

10. The control method according to claim 9, characterized in that: Controlling the first output capacitor of the step-down module to charge according to a preset charging cycle includes: After entering the charging cycle, controlling the first switch tube in the buck module to turn on; After a first preset time period, the first switch tube is controlled to be turned off, and after entering the next charging cycle, the first switch tube is controlled to be turned on again.

11. The control method according to claim 8, characterized in that: Before controlling the boost module to start, the method further includes: Controlling the second output capacitor and the third output capacitor in the boost module to charge according to a preset charging cycle; After the second output capacitor and the third output capacitor are fully charged, the boost module is controlled to start.

12. The control method according to claim 11, characterized in that: Controlling the second output capacitor and the third output capacitor in the boost module to charge according to a preset charging cycle, comprising: After entering the charging cycle, controlling the second switch tube in the boost module to turn on; After a second preset time period, the second switch tube is controlled to be turned off, and after entering the next charging cycle, the second switch tube is controlled to be turned on again.

13. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the method according to any one of claims 8 to 12 is implemented.

14. An electronic device, characterized in that: include: one or more processors; A storage device for storing one or more programs, which, when executed by the one or more processors, enables the one or more processors to implement the method according to any one of claims 8 to 12.

Images