CN113381605A - Boost-buck control circuit and method and air conditioning equipment - Google Patents

Boost-buck control circuit and method and air conditioning equipment Download PDF

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Publication number
CN113381605A
CN113381605A CN202110580768.0A CN202110580768A CN113381605A CN 113381605 A CN113381605 A CN 113381605A CN 202110580768 A CN202110580768 A CN 202110580768A CN 113381605 A CN113381605 A CN 113381605A
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China
Prior art keywords
buck
voltage
boost
switching tube
load
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CN202110580768.0A
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Chinese (zh)
Inventor
杨帆
郑嘉良
许烁
李修贤
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Gree Electric Appliances Inc of Zhuhai
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Gree Electric Appliances Inc of Zhuhai
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Priority to CN202110580768.0A priority Critical patent/CN113381605A/en
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/12—Arrangements for reducing harmonics from ac input or output
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/42—Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
    • H02M1/4208—Arrangements for improving power factor of AC input
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
    • H02M3/33523—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters with galvanic isolation between input and output of both the power stage and the feedback loop
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention discloses a buck-boost control circuit and method and air conditioning equipment. Wherein, this circuit includes: the boost module comprises a first switch tube and a boost unit, one end of the first switch tube is connected with the boost unit, the other end of the first switch tube is connected between the negative terminal of the output end of the rectifying circuit and the second end of the bus capacitor, and the boost unit is connected with the positive terminal of the output end of the rectifying circuit; the voltage reduction module comprises a second switch tube and a voltage reduction unit, one end of the second switch tube is connected with the output end of the voltage boosting unit, the other end of the second switch tube is connected with the input end of the voltage reduction unit, the output end of the voltage reduction unit is connected with the first end of the bus capacitor, and the voltage reduction unit is also connected with the second end of the bus capacitor; the first switching tube and the second switching tube are used for changing the duty ratio of the first switching tube and the second switching tube according to the voltage boosting and reducing requirement and executing voltage boosting or voltage reducing operation; the first switch tube is conducted when the second switch tube is turned off. The invention can solve the problem of current interruption when the switching tube is disconnected and improve the power factor of the circuit.

Description

Boost-buck control circuit and method and air conditioning equipment
Technical Field
The invention relates to the technical field of electronic power, in particular to a buck-boost control circuit and method and air conditioning equipment.
Background
Through practical tests, the energy efficiency of the air conditioner compressor is low at low frequency. Aiming at the problem of low-frequency energy efficiency, the efficiency can be remarkably improved by reducing the input voltage. The traditional BOOST circuit cannot reduce input voltage; the conventional BUCK circuit can realize the BUCK operation of the low frequency band, but cannot support the operation of the air conditioner in the high frequency band. In view of the above problems, a BUCK-BOOST circuit is proposed in the prior art to implement BUCK-BOOST control, and fig. 1 is a structural diagram of the conventional BUCK-BOOST circuit, which can implement BUCK-BOOST control in any voltage range by adjusting a duty ratio of a voltage.
Aiming at the problems that a buck-boost control circuit in the prior art has a low power factor and cannot be applied to high-power equipment, an effective solution is not provided at present.
Disclosure of Invention
The embodiment of the invention provides a buck-boost control circuit, a buck-boost control method and air conditioning equipment, and aims to solve the problem that the buck-boost control circuit in the prior art is low in power factor and cannot be applied to high-power equipment.
In order to solve the above technical problem, the present invention provides a buck-boost control circuit, including:
the boost module comprises a first switching tube and a boost unit, one end of the first switching tube is connected with the boost unit, the other end of the first switching tube is connected between a negative terminal of the output end of the rectifying circuit and the second end of the bus capacitor, and the boost unit is connected with a positive terminal of the output end of the rectifying circuit;
the voltage reduction module comprises a second switch tube and a voltage reduction unit, one end of the second switch tube is connected with the output end of the voltage boosting unit, the other end of the second switch tube is connected with the input end of the voltage reduction unit, the output end of the voltage reduction unit is connected with the first end of the bus capacitor, and the voltage reduction unit is also connected with the second end of the bus capacitor;
the first switch tube and the second switch tube are used for changing the duty ratio of the first switch tube and the second switch tube according to the voltage boosting and reducing requirement and executing voltage boosting or voltage reducing operation; the first switching tube is conducted when the second switching tube is turned off.
Further, the buck-boost control circuit further comprises:
and the relays are arranged at two ends of the second switch tube in parallel and are used for controlling the on-off of the relays according to the power of the loads connected in parallel at two ends of the bus capacitor.
Further, the boosting unit includes:
a first inductor, a first end of which is connected with a positive terminal of the output end of the rectifier, and a second end of which is respectively connected with an anode of the first unidirectional element and one end of the first switch tube;
and the cathode of the first unidirectional element is connected with one end of the second switching tube.
Further, the voltage dropping unit includes:
a first end of the second inductor is connected with the other end of the second switching tube, and a second end of the second inductor is connected with a first end of the bus capacitor;
and the anode of the second unidirectional element is connected between the connection point of the other end of the first switching tube and the negative terminal of the output end of the rectifier and the second end of the bus capacitor, and the cathode of the second unidirectional element is connected between the other end of the second switching tube and the second inductor.
The invention also provides air conditioning equipment which comprises a load and the buck-boost control circuit.
The invention also provides a buck-boost control method which is applied to the buck-boost control circuit and is characterized by comprising the following steps:
determining the voltage increasing and decreasing requirements;
controlling duty ratios of a first switching tube and a second switching tube according to the voltage boosting and reducing requirement, and further performing voltage boosting or voltage reducing operation on input voltage; and under the condition that the second switching tube is switched off, the first switching tube is controlled to be switched on.
Further, determining the buck-boost requirement includes:
judging the range of the power of the load;
if the power of the load is greater than a first preset value, determining that boosting is needed;
if the load power is less than or equal to a first preset value and greater than or equal to a second preset value, determining that neither voltage boosting nor voltage reduction is needed;
and if the load power is smaller than a second preset value, determining that voltage reduction is needed, wherein the first preset value is larger than the second preset value.
Further, determining the buck-boost requirement further comprises:
and determining the times of boosting or reducing according to the power value of the load.
Further, according to the voltage boosting and reducing requirement, duty ratios of the first switch tube and the second switch tube are controlled, and then voltage boosting or voltage reducing operation is performed on input voltage, and the formula according to the voltage boosting and reducing requirement is as follows:
VO＝A2/(1-A1)*VIN；
wherein, VINFor input voltage, VOThe final output voltage of the buck-boost control circuit), a1 is the duty cycle of the first switching tube Q1, a2 is the duty cycle of the second switching tube Q2, and a2/(1-a1) is a multiple of boost or buck.
Further, the method further comprises:
detecting the power of a load connected in parallel at two ends of the bus capacitor;
controlling the on-off of the relay according to the power of the load; the relay is connected in parallel to two ends of the second switch tube.
Further, the controlling the on-off of the relay according to the power of the load comprises:
judging the range of the power of the load;
if the power of the load is larger than a first threshold value, controlling the relay to be conducted;
if the power of the load is smaller than or equal to a first threshold value and larger than or equal to a second threshold value, controlling the relay to keep the current state;
and if the power of the load is less than a second threshold value, controlling the relay to be switched off.
The invention also provides a computer readable storage medium, on which a computer program is stored, which when executed by a processor implements the above buck-boost control method.
By applying the technical scheme of the invention, the duty ratio of the first switching tube and the second switching tube is changed according to the voltage boosting and reducing requirement, and the voltage boosting or reducing operation is executed; when the second switch tube is turned off, the first switch tube is controlled to be conducted, the problem of current interruption when the switch tube is turned off is solved, the power factor is improved, the buck-boost control circuit can be applied to high-power equipment, and the application range of the buck-boost control circuit is widened.
Drawings
FIG. 1 is a block diagram of a conventional BUCK-BOOST circuit;
fig. 2 is a block diagram of a buck-boost control circuit according to an embodiment of the invention;
fig. 3 is a structural diagram of a conventional isolated buck-boost control circuit;
fig. 4 is a block diagram of a buck-boost control circuit according to another embodiment of the present invention;
fig. 5 is a flowchart of a buck-boost control method according to an embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail with reference to the accompanying drawings, and it is apparent that the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the examples of the present invention and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise, and "a plurality" typically includes at least two.
It should be understood that the term "and/or" as used herein is merely one type of association that describes an associated object, meaning that three relationships may exist, e.g., a and/or B may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.
It should be understood that although the terms first, second, etc. may be used to describe the switching tubes in embodiments of the present invention, these switching tubes should not be limited by these terms. These terms are only used to separate different switch tubes. For example, 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 without departing from the scope of the embodiments of the present invention.
The words "if", as used herein, may be interpreted as "at … …" or "at … …" or "in response to a determination" or "in response to a detection", depending on the context. Similarly, the phrases "if determined" or "if detected (a stated condition or event)" may be interpreted as "when determined" or "in response to a determination" or "when detected (a stated condition or event)" or "in response to a detection (a stated condition or event)", depending on the context.
It is also noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that an article or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such article or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in the article or device in which the element is included.
Alternative embodiments of the present invention are described in detail below with reference to the accompanying drawings.
Example 1
The conventional BUCK voltage reduction circuit can realize the voltage reduction effect of a bus, realize the high efficiency of a low frequency band, and is based on a volt-second balance principle: (V)IN-VO)*A＝VO(1-a), the output voltage and the input voltage of the BUCK step-down circuit satisfy the following relation: vo is A VINWhere Vo is the output voltage, VINFor the input voltage, A is the duty ratio of the switching tube, because the duty ratio A of the switching tube is always less than or equal to 1, in the circuit, Vo is less than or equal to VINAnd the unit cannot run at a higher frequency, so that the use of a user is influenced.
In the conventional BOOST circuit, the output voltage and the input voltage satisfy the following relationship: vO＝1/ (1-A)*VINWhere Vo is the output voltage, VINFor input voltage, A is the duty cycle of switch tube, because the duty cycle A of switch tube is more than or equal to 0 all the time, can know through above-mentioned formula that BOOST circuit can't realize the step-down effect, can't realize improving the efficiency promotion of low-frequency channel promptly.
The conventional BUCK-BOOST circuit is configured as shown in fig. 1 mentioned above, in which a switching tube Q and a unidirectional conducting diode D are sequentially connected to a positive terminal P of an output terminal of a rectifier, and an inductor L is provided, one end of the inductor L is connected between the switching tube Q and the unidirectional conducting diode D, the other end of the inductor L is connected to a negative terminal N of the output terminal of the rectifier, and an AC power supply AC sequentially passes through a filter circuit and the rectifier and is then output, according to a volt-second balance principle: vIN*A＝VO(1-A), the output voltage and the input voltage of the BUCK-BOOST circuit satisfy the following relations: vO＝A/(1-A)*VINWhere Vo is the output voltage, VINThe BUCK-BOOST circuit can realize any voltage range for input voltage and A is the duty ratio of the switching tube Q, but in practical application, when the switching tube is disconnected, input current is interrupted, and power factor is influencedThe improvement of (2) can only be used for small-power equipment in product application, and large-power equipment cannot be sold due to the fact that the power factor cannot pass the national standard.
In order to solve the problem that when the switching tube of the BUCK-BOOST circuit is turned off, the input current is interrupted, which results in a low power factor and cannot be applied to a high-power device, this embodiment provides a BUCK-BOOST control circuit, fig. 2 is a structural diagram of the BUCK-BOOST control circuit according to an embodiment of the present invention, and as shown in fig. 2, the BUCK-BOOST control circuit includes:
the boost module 1 comprises a first switch tube Q1 and a boost unit 10, wherein one end of the first switch tube Q1 is connected with the boost unit 10, the other end of the first switch tube Q1 is connected between a 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 with a positive terminal P of the output end of the rectifier; the voltage reduction module 2 comprises a second switch tube Q2 and a voltage reduction unit 20, one end of the second switch tube Q2 is connected with the output end of the voltage boost unit 10, the other end of the second switch tube Q2 is connected with the input end of the voltage reduction unit 20, the output end of the voltage reduction unit 20 is connected with the first end of the bus capacitor C, and the voltage reduction unit 20 is also connected with the second end of the bus capacitor C; the first switch tube Q1 and the second switch tube Q2 are used for changing the duty ratio of the first switch tube Q1 and the second switch tube Q2 according to the voltage increasing and decreasing requirements and executing voltage increasing or decreasing operations; in order to thoroughly solve the problem that the power factor of the buck-boost control circuit is low due to the fact that current is discontinuous when the switching tube is disconnected, the first switching tube Q1 is turned on when the second switching tube Q2 is turned off, so that when the second switching tube Q2 is turned off, current returns to the negative terminal N of the output end of the rectifier through the positive terminal P of the output end of the rectifier and the boosting unit 10 and the first switching tube Q2 in sequence, reactive power is avoided, and the power factor is further improved.
It should be noted that, in this embodiment, it is only necessary to ensure that the first switch Q1 is controlled to be turned on when the second switch Q2 is turned off, and as to how long the first switch Q1 is turned on and how long the second switch Q2 is turned on in the same switching period, it is determined by whether the step-up/step-down control circuit needs to perform the step-up operation or the step-down operation, and the multiple of the step-up/step-down operation.
According to the volt-second equilibrium principle:VO1＝VIN*(1-A1)，VO＝A2*VO1wherein V isINFor input voltage, VO1Is the output voltage, V, of the booster cell 10OFor the output voltage of the voltage step-down 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, so that the final output voltage and the input voltage of the buck-boost control circuit of the present embodiment satisfy the following relationship: vO＝A2/(1-A1)*VINWherein A2/(1-A1) is the multiple of the pressure increase or the pressure decrease. This step-up and step-down control circuit realizes stepping up through the unit 10 that steps up and first switch earlier, and rethread step-down unit 20 and second switch realize stepping down, do not have the discontinuous condition of input current, can realize improving power factor.
The following table 1 shows the efficiency improvement results of different frequencies using the buck-boost control circuit of this embodiment:
TABLE 1 efficiency improvement results for different frequencies
Figure BDA0003085944780000071
As shown in the above table, when the frequency of the load is 13Hz, the efficiency of the bus voltage 82V is improved by 12.5% compared with the efficiency of the bus voltage 310V (input voltage 220V), when the frequency of the load is 15Hz, the efficiency of the bus voltage 82V is improved by 9.4% compared with the efficiency of the bus voltage 310V (input voltage 220V), and when the frequency of the load is 20Hz, the efficiency of the bus voltage 82V is improved by 6.4% compared with the efficiency of the bus voltage 310V (input voltage 220V). Therefore, the buck-boost control circuit has certain efficiency optimization effect on different frequencies. The load refers to electrical equipment in equipment, such as a motor and the like, and in air conditioning equipment, the load can be a compressor.
In the buck-boost control circuit of the embodiment, the first switch tube Q1 and the second switch tube Q2 change their duty ratios according to the buck-boost requirement, and perform the boost or buck operation; when the second switch tube Q2 is turned off, the first switch tube Q1 is controlled to be turned on, so that the problem of current interruption when the switch tube is turned off is solved, the power factor is improved, the buck-boost control circuit can be applied to high-power equipment, and the application range of the buck-boost control circuit is widened.
Example 2
In the buck-boost control circuit of the present embodiment, there is a problem that the voltage stress of the second switch Q2 is relatively high (equal to the sum of the input voltage and the output voltage), which results in relatively high requirements on the switch, and thus, the reliability of the whole circuit is relatively poor, and the cost is relatively high.
In the prior art, in order to solve the above problem, an isolated buck-boost control circuit is proposed, and fig. 3 is a structural diagram of the isolated buck-boost control circuit in the prior art, where an output voltage and an input voltage of the isolated buck-boost control circuit satisfy the following relationship: vO＝A/(1-A)*VINWhere Vo is the output voltage, VINFor input voltage, A is the duty cycle of switch tube Q, and output voltage is positive polarity, and switch tube voltage stress equals output voltage, but needs isolation transformer, and the transformer is too big, and the cost is very high, can't be fine carry out the product promotion.
Because the isolated buck-boost control circuit needs an isolation transformer, the transformer is too large in size and very high in cost, and therefore the scheme is not an effective scheme for solving the problem of high voltage stress of the switching tube.
In view of the above, in order to solve the problem of high voltage stress of the switching tube, the present embodiment provides another buck-boost control circuit, fig. 4 is a structural diagram of a buck-boost control circuit according to another embodiment of the present invention, and as shown in fig. 4, the buck-boost control circuit further includes: and the relay K is arranged at two ends of the second switching tube Q2 in parallel and is used for controlling the on-off of the relay K according to the power of the load M connected with two ends of the bus capacitor C in parallel.
When the power of the load M connected in parallel at the two ends of the bus capacitor C is high, in order to ensure that the current passing through the load M is not too high, boosting needs to be performed according to the above relation: vO＝A2/(1-A1) *VINDuring boosting, the duty cycle a2 of the second switch Q2 needs to be large, and the maximum value is 1, and at this time, the second switch Q2 receivesThe applied voltage stress is large, in order to avoid that the second switch tube Q2 bears large voltage stress when the power of the load M is large, relays K are arranged in parallel at two ends of the second switch tube Q2, and in specific implementation, the range of the power of the load M is judged; if the power of the load M is greater than the first threshold, it indicates that the second switching tube Q2 may bear an excessive voltage stress, and the relay K is controlled to be turned on, that is, the relay K replaces the second switching tube Q2 to work, so as to prevent the second switching tube Q2 from bearing a large voltage stress; if the power of the load M is less than or equal to the first threshold and greater than or equal to the second threshold, it indicates that the risk that the second switching tube Q2 bears a large voltage stress is relatively low, and therefore, the relay K may be controlled to maintain the current state, that is, if the relay K is turned on at this time, the relay K is controlled to continue to be turned on, and if the relay K is turned off at this time, the relay K continues to be turned off; if the power of the load M is smaller than the second threshold, the risk that the second switching tube Q2 bears large voltage stress does not exist, so the relay is controlled to be turned off, and the second switching tube Q2 is controlled to be turned on and off again according to the buck-boost requirement and the preset duty ratio. So set up, can avoid second switch tube Q2 to bear great voltage stress to reduce the requirement to second switch tube Q2, and then reduce circuit cost, guarantee the reliability of circuit simultaneously.
It should be noted that, for the first threshold and the second threshold, those skilled in the art can obtain the first threshold and the second threshold through experiments according to actual needs and in combination with parameters of the second switching tube Q2 actually used.
In specific implementation, in order to implement the boosting function, the boosting unit 10 includes: a first end of the 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 connected to the anode of the first unidirectional element D1 and one end of the first switching tube Q1, respectively; the cathode of the first unidirectional element D1 is connected to one end of the second switch tube Q2.
In order to implement the voltage reduction function, the voltage reduction unit 20 includes: a first end of a second inductor L2 is connected with the other end of the second switch tube Q2, and a second end of the second inductor L2 is connected with a first end of the bus capacitor C; and the second unidirectional element D2 is also included, the anode of the second unidirectional element D2 is connected between the connection point of the other end of the first switching tube Q1 and the negative terminal P of the output end of the rectifier and the second end of the bus capacitor C, and the cathode of the second unidirectional element D2 is connected between the other end of the second switching tube Q2 and the second inductor L2. The first unidirectional element D1 and the second unidirectional element D2 may be unidirectional turn-on diodes.
A BUCK voltage reduction circuit is formed by the second switch tube Q2, the second inductor L2 and the second unidirectional element D2, the switch tube with a lower power current grade can be used for working due to the fact that the power of a load M is small during voltage reduction, and small duty ratio voltage is provided through the second switch tube Q2 to charge the bus capacitor C to achieve the low-cost charging effect.
When the power of the applied load M is high, the relay K is closed, the second switching tube Q2 is switched off, the first inductor L1, the first switching tube Q1 and the first unidirectional element D1 form a BOOST circuit, the power requirement of the load M is met, and in addition, the relay K, the second inductor L2 and the second unidirectional element D2 form a low-cost charging circuit.
Example 3
The present embodiment provides a buck-boost control method, and fig. 5 is a flowchart of the buck-boost control method according to the embodiment of the present invention, as shown in fig. 5, the method includes:
and S101, determining the voltage boosting and reducing requirement.
Determining whether the output voltage of the rectifier needs to be boosted or reduced, wherein the determination can be made according to the power of the load, and when the implementation is specific, a first preset value and a second preset value can be preset, and the range of the power of the load is judged; if the power of the load is greater than a first preset value, it is determined that voltage boosting is needed, if the power of the load is less than or equal to the first preset value and greater than or equal to a second preset value, it is determined that voltage boosting and voltage reduction are not needed, and if the power of the load is less than the second preset value, it is determined that voltage reduction is needed, wherein the first preset value is greater than the second preset value.
After determining to boost or buck, it is further necessary to determine the multiple of boost or buck, and therefore, determining the boost or buck requirement further includes: and determining the times of boosting or reducing according to the power value of the load. In specific implementation, the correspondence between the load power value and the boost multiple needs to be determined through experiments, and the criterion that the current of the load does not exceed the maximum current upper limit after the voltage is boosted or reduced is taken as the criterion.
S102, controlling duty ratios of a first switching tube and a second switching tube according to the voltage boosting and reducing requirement, and further performing voltage boosting or voltage reducing operation on input voltage; and under the condition that the second switching tube is switched off, the first switching tube is controlled to be switched on.
In this embodiment, one end of the first switch tube is connected to the voltage boosting unit, the other end of the first switch tube 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 voltage boosting unit, and the other end of the second switch tube is connected to the voltage reducing unit.
According to the voltage boosting and reducing control method, firstly, whether the output voltage of the rectifier needs to be boosted or reduced is determined, duty ratios of a first switching tube and a second switching tube are controlled according to a determination result, and then boosting or reducing operation is carried out on the input voltage; in addition, under the condition that the second switch tube is turned off, the first switch tube Q1 is controlled to be turned on, the problem of current interruption when the switch tube is turned off is solved, the power factor is improved, the voltage boosting and reducing control circuit can be applied to high-power equipment, and the application range of the voltage boosting and reducing control circuit is widened.
Example 4
The embodiment provides another buck-boost control method, which is based on the volt-second balance principle: vO1＝VIN*(1-A1)，VO＝A2*VO1Wherein V isINFor input voltage, VO1Is the output voltage of the booster cell, VOFor 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 Q1, and a2 is the duty cycle of the second switch Q2, it can be seen that the final output voltage and the input voltage of the buck-boost control circuit of the present embodiment satisfy the following relationship: vO＝A2/(1-A1)*VINControlling the duty ratio of the first switching tube and the second switching tube according to the determined resultAnd further performing a step-up or step-down operation on the input voltage according to the formula: vO＝A2/(1-A1)*VIN。
When the power of the load connected in parallel at two ends of the bus capacitor is high, in order to ensure that the current passing through the load is not too high, the voltage needs to be boosted according to the relation: vO＝A2/(1-A1)*VINWhen boosting, the duty cycle of the second switch tube needs to be large, the maximum value is 1, at this time, the voltage stress borne by the second switch tube is large, in order to avoid that the second switch tube bears large voltage stress when the power of the load is large, relays are arranged at two ends of the second switch tube in parallel, therefore, the method further comprises the following steps: detecting the power of a load connected in parallel at two ends of a bus capacitor; and controlling the on-off of the relay according to the power of the load.
Judging the range of the power of the load; if the power of the load is greater than the first threshold value, the second switch tube is indicated to possibly bear overlarge voltage stress, the relay is controlled to be conducted, the relay is used for replacing the second switch tube to work, and the second switch tube is prevented from bearing large voltage stress; if the power of the load is smaller than or equal to the first threshold and larger than or equal to the second threshold, it indicates that the risk that the second switching tube bears larger voltage stress is lower, and therefore, the relay can be controlled to keep the current state, namely if the relay is switched on at the moment, the relay is controlled to be switched on continuously, and if the relay is switched off at the moment, the relay is controlled to be switched off continuously; if the power of the load is smaller than a second threshold value, the risk that the second switching tube bears larger voltage stress does not exist, so that the relay is controlled to be switched off, and the second switching tube is controlled to be switched on and off again according to the voltage increasing and reducing requirement and the preset duty ratio. So set up, can avoid the second switch tube to bear great voltage stress to reduce the requirement to the second switch tube, and then reduce circuit cost, guarantee the reliability of circuit simultaneously.
It should be noted that, for the first threshold and the second threshold, a person skilled in the art may obtain the first threshold and the second threshold through experiments according to actual needs and in combination with parameters of the second switching tube that are actually used.
Example 5
The embodiment provides an air conditioning equipment, which comprises a load and a buck-boost control circuit in the embodiment, and is used for improving the power factor and further widening the applied power range.
Example 6
The present embodiment provides a computer-readable storage medium on which a computer program is stored, which when executed by a processor implements the buck-boost control method in the above-described embodiments.
The above-described circuit embodiments are only illustrative, and the units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment.
Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware. With this understanding in mind, the above-described technical solutions may be embodied in the form of a software product, which can be stored in a computer-readable storage medium such as ROM/RAM, magnetic disk, optical disk, etc., and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the methods described in the embodiments or some parts of the embodiments.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims (12)

1. A buck-boost control circuit, comprising:
the boost module comprises a first switching tube and a boost unit, one end of the first switching tube is connected with the boost unit, the other end of the first switching tube is connected between a negative terminal of the output end of the rectifying circuit and the second end of the bus capacitor, and the boost unit is connected with a positive terminal of the output end of the rectifying circuit;
the voltage reduction module comprises a second switch tube and a voltage reduction unit, one end of the second switch tube is connected with the output end of the voltage boosting unit, the other end of the second switch tube is connected with the input end of the voltage reduction unit, the output end of the voltage reduction unit is connected with the first end of the bus capacitor, and the voltage reduction unit is also connected with the second end of the bus capacitor;
the first switch tube and the second switch tube are used for changing the duty ratio of the first switch tube and the second switch tube according to the voltage boosting and reducing requirement and executing voltage boosting or voltage reducing operation; the first switching tube is conducted when the second switching tube is turned off.
2. The buck-boost control circuit of claim 1, further comprising:
and the relays are arranged at two ends of the second switch tube in parallel and are used for controlling the on-off of the relays according to the power of the loads connected in parallel at two ends of the bus capacitor.
3. The buck-boost control circuit of claim 1, wherein the boost unit comprises:
a first inductor, a first end of which is connected with a positive terminal of the output end of the rectifier, and a second end of which is respectively connected with an anode of the first unidirectional element and one end of the first switch tube;
and the cathode of the first unidirectional element is connected with one end of the second switching tube.
4. The buck-boost control circuit of claim 1, wherein the buck unit comprises:
a first end of the second inductor is connected with the other end of the second switching tube, and a second end of the second inductor is connected with a first end of the bus capacitor;
and the anode of the second unidirectional element is connected between the connection point of the other end of the first switching tube and the negative terminal of the output end of the rectifier and the second end of the bus capacitor, and the cathode of the second unidirectional element is connected between the other end of the second switching tube and the second inductor.
5. An air conditioning apparatus comprising a load, characterized by further comprising the buck-boost control circuit of any one of claims 1 to 4.
6. A buck-boost control method applied to the buck-boost control circuit of any one of claims 1 to 4, wherein the method comprises:
determining the voltage increasing and decreasing requirements;
controlling duty ratios of a first switching tube and a second switching tube according to the voltage boosting and reducing requirement, and further performing voltage boosting or voltage reducing operation on input voltage; and under the condition that the second switching tube is switched off, the first switching tube is controlled to be switched on.
7. The buck-boost control method of claim 6, wherein determining the buck-boost requirement comprises:
judging the range of the power of the load;
if the power of the load is greater than a first preset value, determining that boosting is needed;
if the load power is less than or equal to a first preset value and greater than or equal to a second preset value, determining that neither voltage boosting nor voltage reduction is needed;
and if the load power is smaller than a second preset value, determining that voltage reduction is needed, wherein the first preset value is larger than the second preset value.
8. The buck-boost control method of claim 6, wherein determining a buck-boost requirement further comprises:
and determining the times of boosting or reducing according to the power value of the load.
9. The buck-boost control method according to claim 6, wherein duty cycles of the first switching tube and the second switching tube are controlled according to the buck-boost requirement, so as to perform a boost or buck operation on an input voltage according to the following formula:
VO＝A2/(1-A1)*VIN；
wherein, VINFor input voltage, VOThe final output voltage of the buck-boost control circuit), a1 is the duty cycle of the first switching tube Q1, a2 is the duty cycle of the second switching tube Q2, and a2/(1-a1) is a multiple of boost or buck.
10. The buck-boost control method of claim 6, further comprising:
detecting the power of a load connected in parallel at two ends of the bus capacitor;
controlling the on-off of the relay according to the power of the load; the relay is connected in parallel to two ends of the second switch tube.
11. The buck-boost control method according to claim 10, wherein controlling the on/off of the relay according to the power of the load comprises:
judging the range of the power of the load;
if the power of the load is larger than a first threshold value, controlling the relay to be conducted;
if the power of the load is smaller than or equal to a first threshold value and larger than or equal to a second threshold value, controlling the relay to keep the current state;
and if the power of the load is less than a second threshold value, controlling the relay to be switched off.
12. A computer-readable storage medium, on which a computer program is stored, which program, when being executed by a processor, carries out the method according to any one of claims 6 to 11.
CN202110580768.0A 2021-05-26 2021-05-26 Boost-buck control circuit and method and air conditioning equipment Pending CN113381605A (en)

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Application Number Priority Date Filing Date Title
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114204802A (en) * 2021-11-17 2022-03-18 深圳技术大学 Charging circuit

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114204802A (en) * 2021-11-17 2022-03-18 深圳技术大学 Charging circuit
CN114204802B (en) * 2021-11-17 2023-05-16 深圳技术大学 Charging circuit

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