A step-up / step-down control circuit, method and air conditioning equipment

Abstract

The present invention discloses a buck-boost control circuit, method and air conditioning equipment. The circuit includes: a boost module, including a first switch tube and a boost unit, one end of the first switch tube is connected to the boost unit, and the other end is connected to the negative terminal of the output end of the rectifier and the second end of the bus capacitor, and the boost unit is connected to the positive terminal of the output end of the rectifier; a buck module, including a second switch tube and a buck unit, one end of the second switch tube is connected to the output end of the boost unit, and the other end is connected to the input end of the buck unit, the output end of the buck unit is connected to the first end of the bus capacitor, and the buck unit is also connected to the second end of the bus capacitor; the first switch tube and the second switch tube are used to change their duty cycle according to the buck-boost demand, and perform a boost or buck operation; wherein the first switch tube is turned on when the second switch tube is turned off. Through the present invention, the problem of current discontinuity when the switch tube is disconnected can be solved, and the power factor of the circuit can be improved.

Description

Technical Field

[0001] The present invention relates to the field of electronic power technology, and in particular to a step-up and step-down control circuit, method and air conditioning equipment. Background Art

[0002] At present, as the requirements of various countries for energy efficiency are becoming more and more stringent, my country's energy efficiency level has changed from level 3 to level 5. After actual testing, the air-conditioning compressor has low energy efficiency at low frequencies. To address the problem of low energy efficiency at low frequencies, we can significantly improve efficiency by lowering the input voltage. The traditional BOOST boost circuit cannot reduce the input voltage; while the traditional BUCK buck circuit can achieve a step-down operation in the low-frequency band, but cannot support the air conditioner to operate in the high-frequency band. In response to the above problems, a BUCK-BOOST circuit is proposed in the prior art to achieve step-up and step-down control. Figure 1 This is the structural diagram of the existing BUCK-BOOST circuit. By adjusting the duty cycle of the voltage, the voltage can be increased or decreased within any range. However, in this circuit, since there is only one switch tube, when the switch tube is disconnected, the input current in the circuit will be intermittent, resulting in a low power factor and cannot be applied to high-power devices.

[0003] With regard to the problem that the power factor of the buck-boost control circuit in the prior art is low and cannot be applied to high-power equipment, no effective solution has been proposed so far. Summary of the invention

[0004] The embodiments of the present invention provide a buck-boost control circuit, method and air conditioning equipment to solve the problem that the buck-boost control circuit in the prior art has a low power factor and cannot be applied to high-power equipment.

[0005] In order to solve the above technical problems, the present invention provides a buck-boost control circuit, which comprises:

[0006] A boost module, comprising a first switch tube and a boost unit, wherein one end of the first switch tube is connected to the boost unit, and the other end is connected between the negative terminal of the output end of the rectifier and the second end of the bus capacitor, and the boost unit is connected to the positive terminal of the output end of the rectifier;

[0007] A step-down module, comprising a second switch tube and a step-down unit, wherein one end of the second switch tube is connected to the output end of the boost unit, and the other end is connected to the input end of the step-down unit, the output end of the step-down unit is connected to the first end of the bus capacitor, and the step-down unit is also connected to the second end of the bus capacitor;

[0008] The first switch tube and the second switch tube are used to change their duty cycles according to the voltage step-up or step-down requirements to perform a voltage step-up or step-down operation; wherein the first switch tube is turned on when the second switch tube is turned off.

[0009] Furthermore, the buck-boost control circuit further includes:

[0010] The relay is arranged in parallel at both ends of the second switch tube, and is used to control its own on and off according to the power of the load connected in parallel at both ends of the bus capacitor.

[0011] Furthermore, the boost unit comprises:

[0012] A first inductor, a first end of which is connected to the positive terminal of the output end of the rectifier, and a second end of which is respectively connected to the anode of the first unidirectional element and one end of the first switch tube;

[0013] The cathode of the first unidirectional element is connected to one end of the second switch tube.

[0014] Furthermore, the voltage reduction unit comprises:

[0015] A second inductor, a first end of which is connected to the other end of the second switch tube, and a second end of which is connected to the first end of the bus capacitor;

[0016] A second unidirectional element, whose anode is connected to the connection point between the other end of the first switch tube and the negative terminal of the output end of the rectifier and the second end of the bus capacitor, and whose cathode is connected to between the other end of the second switch tube and the second inductor.

[0017] The present invention also provides an air conditioning device, comprising a load and the above-mentioned step-up and step-down control circuit.

[0018] The present invention also provides a buck-boost control method, which is applied to the buck-boost control circuit, and is characterized in that the method comprises:

[0019] Determine the buck-boost requirements;

[0020] The duty ratios of the first switch tube and the second switch tube are controlled according to the step-up and step-down requirements, thereby performing a step-up or step-down operation on the input voltage; wherein, when the second switch tube is turned off, the first switch tube is controlled to be turned on.

[0021] Furthermore, determining the buck-boost requirement includes:

[0022] Determine the power range of the load;

[0023] If the power of the load is greater than the first preset value, it is determined that a voltage boost is required;

[0024] If the load power is less than or equal to the first preset value and greater than or equal to the second preset value, it is determined that neither voltage boost nor voltage reduction is required;

[0025] If the load power is less than a second preset value, it is determined that a voltage reduction is required, wherein the first preset value is greater than the second preset value.

[0026] Furthermore, determining the boost and buck requirements also includes:

[0027] Determine the voltage increase or decrease multiple based on the power value of the load.

[0028] Furthermore, the duty ratios of the first switch tube and the second switch tube are controlled according to the step-up and step-down requirements, thereby performing a step-up or step-down operation on the input voltage, and the formula used is:

[0029] V O =A2 / (1-A1)*V IN ;

[0030] Among them, V IN is the input voltage, V O is the final output voltage of the buck-boost control circuit, A1 is the duty cycle of the first switch tube Q1, A2 is the duty cycle of the second switch tube Q2, and A2 / (1-A1) is the multiple of boost or buck.

[0031] Furthermore, the method further comprises:

[0032] Detecting the power of the load connected in parallel at both ends of the bus capacitor;

[0033] The on-off of the relay is controlled according to the power of the load; wherein the relay is arranged in parallel at both ends of the second switch tube.

[0034] Further, controlling the on and off of the relay according to the power of the load includes:

[0035] Determining the power range of the load;

[0036] If the power of the load is greater than a first threshold, controlling the relay to be turned on;

[0037] If the power of the load is less than or equal to the first threshold value and greater than or equal to the second threshold value, controlling the relay to maintain the current state;

[0038] If the power of the load is less than the second threshold, the relay is controlled to be turned off.

[0039] The present invention also provides a computer-readable storage medium on which a computer program is stored, and when the program is executed by a processor, the above-mentioned step-up and step-down control method is implemented.

[0040] By applying the technical solution of the present invention, the first switch tube and the second switch tube change their own duty cycles according to the buck-boost requirements to perform a boost or buck operation; by controlling the first switch tube to be turned on when the second switch tube is turned off, the problem of current discontinuity when the switch tube is turned off is solved, the power factor is improved, and the above-mentioned buck-boost control circuit can be applied to high-power equipment, thereby broadening the application scope of the above-mentioned buck-boost control circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is the structural diagram of the existing BUCK-BOOST circuit;

[0042] Figure 2 is a structural diagram of a buck-boost control circuit according to an embodiment of the present invention;

[0043] Figure 3 It is a structural diagram of an existing isolated buck-boost control circuit;

[0044] Figure 4 is a structural diagram of a buck-boost control circuit according to another embodiment of the present invention;

[0045] Figure 5 Flow chart of a buck-boost control method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0046] 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.

[0047] 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.

[0048] 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.

[0049] It should be understood that although the terms first, second, etc. may be used to describe the switch tubes in the embodiments of the present invention, the switch tubes should not be limited to these terms. These terms are only used to distinguish different switch tubes. For example, without departing from the scope of the embodiments of the present invention, the first switch tube may also be referred to as the second switch tube, and similarly, the second switch tube may also be referred to as the first switch tube.

[0050] 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.

[0051] 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.

[0052] The optional embodiments of the present invention are described in detail below with reference to the accompanying drawings. Example 1

[0053] The existing BUCK step-down circuit can achieve the bus voltage step-down effect and realize high efficiency in the low-frequency band. According to the volt-second balance principle: (V IN -V O )*A=V O *(1-A), the output voltage and input voltage of the BUCK step-down circuit satisfy the following relationship: Vo=A*V IN , where Vo is the output voltage, V IN is the input voltage, A is the duty cycle of the switch tube. Since the duty cycle A of the switch tube is always less than or equal to 1, in this circuit, Vo≤V IN , the unit cannot run at a higher frequency, affecting user use.

[0054] In the existing BOOST circuit, the output voltage and input voltage satisfy the following relationship: V O =1 / (1-A)*V IN , where Vo is the output voltage, V INis the input voltage, A is the duty cycle of the switch tube. Since the duty cycle A of the switch tube is always greater than or equal to 0, it can be seen from the above formula that the BOOST circuit cannot achieve a voltage reduction effect, that is, it cannot achieve an improvement in efficiency in the low frequency band.

[0055] The structure of the existing BUCK-BOOST circuit is as mentioned above. Figure 1 As shown in the figure, the switch tube Q and the unidirectional conduction diode D are connected to the positive terminal P of the output end of the rectifier in sequence, and an inductor L is set. One end of the inductor L is connected between the switch tube Q and the unidirectional conduction diode D, and the other end is connected to the negative terminal N of the output end of the rectifier. The AC power supply AC is output after passing through the filter circuit and the rectifier in sequence. According to the volt-second balance principle: V IN *A=V O *(1-A), the output voltage and input voltage of the BUCK-BOOST circuit satisfy the following relationship: V O =A / (1-A)*V IN , where Vo is the output voltage, V IN is the input voltage, A is the duty cycle of the switch tube Q. The above BUCK-BOOST circuit can achieve any voltage range, but in actual applications, when the switch tube is disconnected, the input current is intermittent, affecting the improvement of the power factor. In product applications, it can only be used for small-power equipment. High-power equipment cannot be sold because the power factor cannot pass the national standard.

[0056] In order to solve the problem that when the switch tube of the BUCK-BOOST circuit is disconnected, the input current is intermittent, resulting in a low power factor and being unable to be applied to high-power equipment, this embodiment provides a buck-boost control circuit. Figure 2 is a structural diagram of a buck-boost control circuit according to an embodiment of the present invention. Figure 2 As shown, the buck-boost control circuit includes:

[0057] A boost module 1, comprising a first switch tube Q1 and a boost unit 10, wherein one end of the first switch tube Q1 is connected to the boost unit 10, and the other end is connected between the negative terminal N of the output end of the rectifier and the second end of the bus capacitor C, and the boost unit 10 is connected to the positive terminal P of the output end of the rectifier; a buck module 2, comprising a second switch tube Q2 and a buck unit 20, wherein one end of the second switch tube Q2 is connected to the output end of the boost unit 10, and the other end is connected to the input end of the buck unit 20, and the output end of the buck unit 20 is connected to the first end of the bus capacitor C, and the buck unit 20 is also connected to the bus The second end of the line capacitor C; the first switch tube Q1 and the second switch tube Q2 are used to change their own duty cycle according to the buck-boost demand to perform a boost or buck operation; in order to completely solve the problem of current discontinuity when the switch tube is disconnected, resulting in a low power factor of the buck-boost control circuit, the first switch tube Q1 is turned on when the second switch tube Q2 is turned off, so that when the second switch tube Q2 is turned off, the current returns from the positive terminal P at the output end of the rectifier to the negative terminal N at the output end of the rectifier through the boost unit 10 and the first switch tube Q2 in sequence, avoiding reactive power and thereby improving the power factor.

[0058] It should be noted that in this embodiment, it is sufficient to control the first switch tube Q1 to be turned on when the second switch tube Q2 is turned off. As for how long the first switch tube Q1 is turned on and how long the second switch tube Q2 is turned on in the same switching cycle, it is determined by whether the above-mentioned buck-boost control circuit needs to perform a boost operation or a buck operation, as well as the buck-boost multiple.

[0059] According to the volt-second balance principle: V O1 =V IN *(1-A1), V O =A2*V O1 , where V IN is the input voltage, V O1 is the output voltage of the boost unit 10, V O is the output voltage of the buck unit 20 (i.e., the final output voltage of the buck-boost control circuit), A1 is the duty cycle of the first switch tube Q1, and A2 is the duty cycle of the second switch tube Q2. It can be obtained that the final output voltage and input voltage of the buck-boost control circuit of this embodiment satisfy the following relationship: V O =A2 / (1-A1)*V IN , where A2 / (1-A1) is the multiple of boost or buck. The boost-boost control circuit first achieves boost through the boost unit 10 and the first switch, and then achieves buck through the buck unit 20 and the second switch. There is no input current discontinuity, and the power factor can be improved.

[0060] Table 1 below shows the efficiency improvement results of different frequencies using the buck-boost control circuit of this embodiment:

[0061] Table 1 Efficiency improvement results at different frequencies

[0062]

[0063] As shown in the table above, when the frequency of the load is 13Hz, the efficiency of the bus voltage 82V is 12.5% ​​higher than that of the bus voltage 310V (input voltage 220V). When the frequency of the load is 15Hz, the efficiency of the bus voltage 82V is 9.4% higher than that of the bus voltage 310V (input voltage 220V). When the frequency of the load is 20Hz, the efficiency of the bus voltage 82V is 6.4% higher than that of the bus voltage 310V (input voltage 220V). It can be seen that the buck-boost control circuit of this embodiment has a certain efficiency optimization effect for different frequencies. The above-mentioned load refers to the electrical components in the equipment, such as motors, etc. In air-conditioning equipment, the load can be a compressor.

[0064] In the buck-boost control circuit of this embodiment, the first switch tube Q1 and the second switch tube Q2 change their duty ratios according to the buck-boost requirements to perform a boost or buck operation; by controlling the first switch tube Q1 to be turned on when the second switch tube Q2 is turned off, the problem of current discontinuity when the switch tube is turned off is solved, and the power factor is improved, so that the above-mentioned buck-boost control circuit can be applied to high-power equipment, thereby widening the application range of the above-mentioned buck-boost control circuit. Example 2

[0065] The present embodiment provides another buck-boost control circuit. In the buck-boost control circuit of the above embodiment, there is still a problem that the voltage stress of the second switch tube Q2 is relatively high (equal to the sum of the input and output voltages). This places high requirements on the switch tube, resulting in poor overall reliability of the circuit and high cost.

[0066] In the prior art, in order to solve the above problems, an isolated buck-boost control circuit is proposed. Figure 3 : is a structural diagram of an existing isolated buck-boost control circuit. The output voltage and input voltage of the isolated buck-boost control circuit satisfy the following relationship: V O =A / (1-A)*V IN , where Vo is the output voltage, V IN is the input voltage, A is the duty cycle of the switch tube Q, the output voltage is positive, and the voltage stress of the switch tube is equal to the output voltage. However, an isolation transformer is required. The transformer is too large and the cost is very high, so it is difficult to promote the product well.

[0067] Since the above-mentioned isolated buck-boost control circuit requires an isolation transformer, which is too large and very expensive, the above-mentioned solution is not an effective solution to the high voltage stress of the switch tube.

[0068] In view of this situation, in order to solve the problem of high voltage stress of the switch tube, this embodiment provides another buck-boost control circuit. Figure 4 FIG. 4 is a structural diagram of a buck-boost control circuit according to another embodiment of the present invention. Figure 4 As shown, the buck-boost control circuit also includes: a relay K, which is arranged in parallel at both ends of the second switch tube Q2 and is used to control its own on and off according to the power of the load M connected in parallel at both ends of the bus capacitor C.

[0069] When the power of the load M connected in parallel at both ends of the bus capacitor C is high, in order to ensure that the current passing through the load M is not too high, it is necessary to boost the voltage. According to the above relationship: V O =A2 / (1-A1)*V IN When boosting, the duty cycle A2 of the second switch tube Q2 needs to be larger, and its maximum value is 1. At this time, the voltage stress borne by the second switch tube Q2 is larger. In order to prevent the second switch tube Q2 from being subjected to a larger voltage stress when the power of the load M is larger, a relay K is arranged in parallel at both ends of the second switch tube Q2. In specific implementation, the power range of the load M is judged; if the power of the load M is greater than the first threshold value, it indicates that the second switch tube Q2 may be subjected to excessive voltage stress, and the relay K is controlled to be turned on, that is, the relay K is used to work instead of the second switch tube Q2 to avoid the second switch tube Q2 from being subjected to a larger voltage stress. force; if the power of the load M is less than or equal to the first threshold value, and greater than or equal to the second threshold value, it indicates that the risk of the second switch tube Q2 being subjected to a large voltage stress is relatively low, therefore, the relay K can be controlled to maintain the current state, that is, if the relay K is on at this time, the relay K is controlled to continue to be on, and if the relay K is off at this time, the relay K is controlled to continue to be off; if the power of the load M is less than the second threshold value, there is no risk of the second switch tube Q2 being subjected to a large voltage stress, therefore, the control relay is turned off, and the second switch tube Q2 is controlled to be on and off again according to the preset duty cycle according to the buck-boost requirement. Such a setting can prevent the second switch tube Q2 from being subjected to a large voltage stress, thereby reducing the requirements for the second switch tube Q2, thereby reducing the circuit cost, and at the same time ensuring the reliability of the circuit.

[0070] It should be noted that, for the above-mentioned first threshold and second threshold, those skilled in the art can obtain them through experiments according to actual needs and in combination with the parameters of the second switch tube Q2 actually used.

[0071] In a specific implementation, in order to realize the boost function, the boost unit 10 includes: a first inductor L1, a first end of the first inductor L1 is connected to the positive terminal P of the output end of the rectifier, and a second end of the first inductor L1 is respectively connected to the anode of the first unidirectional element D1 and one end of the first switch tube Q1; and a cathode of the first unidirectional element D1 is connected to one end of the second switch tube Q2.

[0072] In order to realize the step-down function, the step-down unit 20 includes: a second inductor L2, a first end of the second inductor L2 is connected to the other end of the second switch tube Q2, and a second end of the second inductor L2 is connected to the first end of the bus capacitor C; and a second unidirectional element D2, an anode of the second unidirectional element D2 is connected to the connection point between the other end of the first switch tube Q1 and the negative terminal P of the output end of the rectifier and the second end of the bus capacitor C, and a cathode of the second unidirectional element D2 is connected to the other end of the second switch tube Q2 and between the second inductor L2. The first unidirectional element D1 and the second unidirectional element D2 can be unidirectional conducting diodes.

[0073] A BUCK step-down circuit is formed by the second switch tube Q2, the second inductor L2, and the second unidirectional element D2. Since the power of the load M is small during step-down, a switch tube with a lower power current level can be used to work. The second switch tube Q2 provides a small duty cycle voltage to charge the bus capacitor C to achieve a low-cost charging effect.

[0074] When the power of the load M is high, by closing the relay K and disconnecting the second switch tube Q2, the first inductor L1, the first switch tube Q1, and the first unidirectional element D1 form a BOOST boost circuit to meet the power requirement of the load M. In addition, the relay K, the second inductor L2, and the second unidirectional element D2 form a low-cost charging circuit. Example 3

[0075] This embodiment provides a step-up / step-down control method. Figure 5 : is a flow chart of a buck-boost control method according to an embodiment of the present invention. Figure 5 As shown, the method includes:

[0076] S101, determining the voltage increase or decrease requirement.

[0077] Whether the output voltage of the rectifier needs to be boosted or bucked can be determined based on the power of the load. In a specific implementation, a first preset value and a second preset value can be set in advance to determine the range of the load power. If the load power is greater than the first preset value, it is determined that a boost is required. If the load power is less than or equal to the first preset value and greater than or equal to the second preset value, it is determined that neither a boost nor a buck is required. If the load power is less than the second preset value, it is determined that a buck is required, wherein the first preset value is greater than the second preset value.

[0078] After determining whether to boost or reduce the voltage, it is also necessary to determine the multiple of the boost or reduce voltage. Therefore, determining the boost or reduce voltage requirements also includes: determining the multiple of the boost or reduce voltage according to the power value of the load. In specific implementation, the corresponding relationship between the load power value and the boost multiple needs to be determined through experiments, and the criterion should be that the current of the load does not exceed its maximum current upper limit after boosting or reducing the voltage.

[0079] S102, controlling the duty ratio of the first switch tube and the second switch tube according to the step-up and step-down requirements, thereby performing a step-up or step-down operation on the input voltage; wherein, when the second switch tube is turned off, the first switch tube is controlled to be turned on.

[0080] In this embodiment, one end of the first switch tube is connected to the boost unit, and the other end is connected between the negative terminal of the output end of the rectifier and the second end of the bus capacitor; one end of the second switch tube is connected to the boost unit, and the other end is connected to the buck unit.

[0081] The buck-boost control method of this embodiment first determines whether the output voltage of the rectifier needs to be boosted or bucked, and controls the duty ratio of the first switch tube and the second switch tube according to the determination result, thereby performing a boost or buck operation on the input voltage; in addition, when the second switch tube is turned off, the first switch tube Q1 is controlled to be turned on, so as to solve the problem of current discontinuity when the switch tube is turned off, improve the power factor, and enable the above-mentioned buck-boost control circuit to be applied to high-power equipment, thereby broadening the application range of the above-mentioned buck-boost control circuit. Example 4

[0082] This embodiment provides another buck-boost control method based on the volt-second balance principle: V O1 =V IN *(1-A1), V O =A2*V O1 , where V IN is the input voltage, V O1 is the output voltage of the boost unit, V O is the output voltage of the buck unit (i.e., the final output voltage of the buck-boost control circuit), A1 is the duty cycle of the first switch tube Q1, and A2 is the duty cycle of the second switch tube Q2. It can be obtained that the final output voltage and input voltage of the buck-boost control circuit of this embodiment satisfy the following relationship: V O =A2 / (1-A1)*V IN , the duty ratio of the first switch tube and the second switch tube is controlled according to the determination result, thereby performing a step-up or step-down operation on the input voltage, and the formula based on which is: V O =A2 / (1-A1)*V IN .

[0083] When the power of the load connected in parallel at both ends of the bus capacitor is high, in order to ensure that the current passing through the load is not too high, it is necessary to boost the voltage. According to the above relationship: V O =A2 / (1-A1)*V IN When boosting, the duty cycle of the second switch tube needs to be larger, and its maximum value is 1. At this time, the voltage stress borne by the second switch tube is larger. In order to avoid the second switch tube from being subjected to a larger voltage stress when the power of the load is large, a relay is arranged in parallel at both ends of the second switch tube. Therefore, the above method also includes: detecting the power of the load connected in parallel at both ends of the bus capacitor; and controlling the on and off of the relay according to the power of the above load.

[0084] Determine the range of the power of the above load; if the power of the above load is greater than the first threshold, it indicates that the second switch tube may be subjected to excessive voltage stress, and the relay is controlled to be turned on, that is, the relay is used to replace the second switch tube to avoid the second switch tube from being subjected to large voltage stress; if the power of the above load is less than or equal to the first threshold, and greater than or equal to the second threshold, it indicates that the risk of the second switch tube being subjected to large voltage stress is relatively low, therefore, the relay can be controlled to maintain the current state, that is, if the relay is turned on at this time, the relay is controlled to continue to be turned on, if the relay is turned off at this time, the relay is controlled to continue to be turned off; if the power of the above load is less than the second threshold, there is no risk of the second switch tube being subjected to large voltage stress, therefore, the relay is controlled to be turned off, and the second switch tube is controlled to be turned on and off again according to the preset duty cycle according to the buck-boost requirement. Such a setting can avoid the second switch tube from being subjected to large voltage stress, thereby reducing the requirements for the second switch tube, thereby reducing the circuit cost, and ensuring the reliability of the circuit at the same time.

[0085] It should be noted that, for the above-mentioned first threshold and second threshold, those skilled in the art can obtain them through experiments according to actual needs and in combination with the parameters of the second switch tube actually used. Example 5

[0086] This embodiment provides an air conditioning device, including a load and also including the buck-boost control circuit in the above embodiment, which is used to improve the power factor and thus broaden the power range of application. Example 6

[0087] This embodiment provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the buck-boost control method in the above embodiment is implemented.

[0088] The circuit embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place, or may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0089] 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, 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.

[0090] 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 control circuit, characterized in that: The buck-boost control circuit comprises: A boost module, comprising a first switch tube and a boost unit, wherein one end of the first switch tube is connected to the boost unit, and the other end is connected between the negative terminal of the output end of the rectifier and the second end of the bus capacitor, and the boost unit is connected to the positive terminal of the output end of the rectifier; A step-down module, comprising a second switch tube and a step-down unit, wherein one end of the second switch tube is connected to the output end of the boost unit, and the other end is connected to the input end of the step-down unit, the output end of the step-down unit is connected to the first end of the bus capacitor, and the step-down unit is also connected to the second end of the bus capacitor; The first switch tube and the second switch tube are used to change their duty cycles according to the voltage step-up or step-down requirements to perform a voltage step-up or step-down operation; wherein the first switch tube is turned on when the second switch tube is turned off.

2. The buck-boost control circuit according to claim 1, characterized in that: The buck-boost control circuit further includes: The relay is arranged in parallel at both ends of the second switch tube, and is used to control its own on and off according to the power of the load connected in parallel at both ends of the bus capacitor.

3. The buck-boost control circuit according to claim 1, characterized in that: The boost unit comprises: A first inductor, a first end of which is connected to the positive terminal of the output end of the rectifier, and a second end of which is respectively connected to the anode of the first unidirectional element and one end of the first switch tube; The cathode of the first unidirectional element is connected to one end of the second switch tube.

4. The buck-boost control circuit according to claim 1, characterized in that: The step-down unit comprises: A second inductor, a first end of which is connected to the other end of the second switch tube, and a second end of which is connected to the first end of the bus capacitor; A second unidirectional element, whose anode is connected to the connection point between the other end of the first switch tube and the negative terminal of the output end of the rectifier and the second end of the bus capacitor, and whose cathode is connected to between the other end of the second switch tube and the second inductor.

5. An air conditioning device, comprising a load, characterized in that: It also includes the buck-boost control circuit according to any one of claims 1 to 4.

6. A buck-boost control method, applied to the buck-boost control circuit according to any one of claims 1 to 4, characterized in that: The method comprises: Determine the buck-boost requirements; The duty ratios of the first switch tube and the second switch tube are controlled according to the step-up and step-down requirements, thereby performing a step-up or step-down operation on the input voltage; wherein, when the second switch tube is turned off, the first switch tube is controlled to be turned on.

7. The step-up / down control method according to claim 6, characterized in that: Determining buck-boost requirements includes: Determine the power range of the load; If the power of the load is greater than the first preset value, it is determined that a voltage boost is required; If the load power is less than or equal to the first preset value and greater than or equal to the second preset value, it is determined that neither voltage boost nor voltage reduction is required; If the load power is less than a second preset value, it is determined that a voltage reduction is required, wherein the first preset value is greater than the second preset value.

8. The step-up / step-down control method according to claim 6, characterized in that: Determine the buck-boost requirements, including: Determine the voltage increase or decrease multiple based on the power value of the load.

9. The buck-boost control method according to claim 6, characterized in that: The duty ratio of the first switch tube and the second switch tube is controlled according to the step-up and step-down requirements, thereby performing a step-up or step-down operation on the input voltage, and the formula used is: <h2 style=";text-align:left;direction:ltr">V<h2 style=";text-align:left;direction:ltr"> O <h2 style=";text-align:left;direction:ltr"> =A2 / (1-A1)*V<h2 style=";text-align:left;direction:ltr"> IN <h2 style=";text-align:left;direction:ltr"> ; Among them, V IN is the input voltage, V O is the final output voltage of the buck-boost control circuit, A1 is the duty cycle of the first switch tube Q1, A2 is the duty cycle of the second switch tube Q2, and A2 / (1-A1) is the multiple of boost or buck.

10. The buck-boost control method according to claim 6, characterized in that: The method further comprises: Detecting the power of the load connected in parallel at both ends of the bus capacitor; The on-off of the relay is controlled according to the power of the load; wherein the relay is arranged in parallel at both ends of the second switch tube.

11. The step-up / down control method according to claim 10, characterized in that: Controlling the on and off of a relay according to the power of the load includes: Determining the power range of the load; If the power of the load is greater than a first threshold, controlling the relay to be turned on; If the power of the load is less than or equal to the first threshold value and greater than or equal to the second threshold value, controlling the relay to maintain the current state; If the power of the load is less than the second threshold, the relay is controlled to be turned off.

12. 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 6 to 11 is implemented.

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