CN109660120A - Switching circuit, control method of switching circuit, power supply device and air conditioner - Google Patents

Abstract

The invention discloses a switching circuit, a control method of the switching circuit, a power supply device and an air conditioner, wherein the switching circuit comprises a BUCK circuit, a BOOST circuit and a controller; the input end of the switching circuit is connected with the output end of the rectifying circuit, and the output end of the switching circuit is connected with the inverter; the controller is configured to obtain an input voltage output by the rectifier circuit, determine whether the input voltage is between a first preset voltage threshold and a second preset voltage threshold to adjust an output voltage, and maintain an input current and the input voltage at the same phase to perform power factor correction. Therefore, the technical problem of low voltage regulation efficiency is solved.

Description

Switching circuit, control method of switching circuit, power supply device, and air conditioner

technical field

The present invention relates to the technical field of power supplies, and in particular, to a switching circuit, a control method of the switching circuit, a power supply device and an air conditioner.

Background technique

Generally, during the peak period of electricity consumption in summer, the actual voltage is often low and the voltage is unstable; in remote areas, field construction sites, the environment of the power supply transformer is harsh, and the voltage rise may occur due to the short circuit between the primary sides of the transformer.

Existing frequency conversion air conditioners generally use DC frequency conversion technology, which needs to rectify the power frequency alternating current into direct current, and then drive the DC frequency conversion compressor through the inverter. The DC voltage obtained by only using diode rectification is determined by the external power frequency AC. Therefore, the external voltage fluctuation will cause the DC voltage fluctuation, and the rectification will cause serious pollution to the power grid, mainly including large current harmonics, input The power factor is low. In order to suppress this phenomenon, the national power department has put forward corresponding harmonic standards. When the power is above 75W, the electrical equipment must meet the harmonic standards.

Existing air conditioners using DC frequency conversion technology generally use a single BOOST power factor correction circuit, which can increase the DC voltage to a normal value when the power frequency voltage is lower than the standard voltage range (+7%, -10%), and suppress current harmonics , improve the input power factor. However, the single BOOST power factor correction circuit can only cope with the working condition when the power frequency voltage is not higher than the standard voltage, and cannot cope with the working condition of excessive voltage, and the switching loss of the single BOOST power factor correction circuit is too large, and the voltage boosting ability is limited. Poor grid adaptability.

SUMMARY OF THE INVENTION

The main purpose of the present invention is to provide a switching circuit, a control method of the switching circuit, a power supply device and an air conditioner, aiming at solving the technical problem of low voltage adjustment efficiency by adding a switching circuit in the prior art.

In order to achieve the above object, the present invention proposes a switching circuit, the switching circuit includes a BUCK circuit, a BOOST circuit and a controller; wherein, the input end of the switching circuit is connected to the output end of the rectifier circuit, and the output end of the switching circuit is connected. The terminal is connected to the inverter;

The controller is configured to obtain the input voltage output by the rectifier circuit, and determine whether the input voltage is between a first preset voltage threshold and a second preset voltage threshold, wherein the first preset voltage threshold is less than the second preset voltage threshold;

When the input voltage is lower than the first preset voltage threshold, generate a first control signal according to the input voltage, switch to the BOOST circuit according to the first control signal, and turn off the BUCK circuit;

When the input voltage is higher than the second preset voltage threshold, generate a second control signal according to the input voltage, switch to the BUCK circuit according to the second control signal, and turn off the BOOST circuit;

the BOOST circuit, for adjusting the output voltage according to the first control signal;

The BUCK circuit is configured to adjust the output voltage according to the second control signal.

Preferably, the controller is further configured to generate a preset control signal according to the input voltage when the input voltage is between the first preset voltage threshold and the second preset voltage threshold, and according to the The preset control signal controls the input voltage to pass through the BUCK circuit and the BOOST circuit, and the BUCK circuit and the BOOST circuit adjust the output voltage according to the preset control signal.

Preferably, the BUCK circuit is also used to keep the input current and the input voltage in the same phase to perform power factor correction; the BOOST circuit is also used to keep the input current and the input voltage in the same phase to perform power factor correction factor correction.

Preferably, the buck circuit includes a first switch tube, a first capacitor, a second switch tube, a first diode, a first inductor, a second inductor, a second diode, a third diode and a second capacitance; where,

The input end of the first switch tube is respectively connected to the first output end of the rectifier circuit and the input end of the second switch tube, and the output end of the first switch tube is connected to the first output end of the first capacitor. The second end of the first capacitor is connected to the second output end of the rectifier circuit, and the output end of the second switch tube is connected to the negative electrode of the first diode and the second output end of the first inductor. The first ends are respectively connected, the anode of the first diode is connected to the second end of the first capacitor, the second end of the first inductor is connected to the anode of the second diode, the The first end of the second inductor is connected to the first end of the first inductor, the second end of the second inductor is connected to the anode of the third diode, and the cathode of the third diode is connected to The cathode of the second diode is connected to the cathode of the second diode, the cathode of the second diode is also connected to the first end of the second capacitor, and the second end of the second capacitor is connected to the first diode The positive electrode of the first capacitor and the second end of the first capacitor are respectively connected.

Preferably, the BOOST circuit includes a second switch, a first inductor, a third switch, a second inductor, a fourth switch, a second diode, a third diode and a second capacitor; wherein,

The input end of the second switch tube is connected to the first output end of the rectifier circuit, and the output end of the second switch tube is connected to the first end of the first inductor and the first end of the second inductor connected respectively, the second end of the first inductor is connected to the input end of the third switch tube and the anode of the second diode respectively, the second end of the second inductor is connected to the fourth switch The input end of the tube and the anode of the third diode are respectively connected, the cathode of the second diode is connected to the cathode of the third diode, and the cathode of the second diode is also connected to the cathode of the third diode. The first end of the second capacitor is connected, the output end of the third switch tube, the output end of the fourth switch tube and the second end of the second capacitor are respectively connected with the second output of the rectifier circuit. end connection.

The present invention also provides a control method for the switching circuit as described above, the control method comprising:

The controller obtains the input voltage output by the rectifier circuit, and determines whether the input voltage is between a first preset voltage threshold and a second preset voltage threshold, wherein the first preset voltage threshold is smaller than the first preset voltage threshold. Two preset voltage thresholds;

When the input voltage is lower than the first preset voltage threshold, a first control signal is generated according to the input voltage, switched to the BOOST circuit according to the first control signal, and the BUCK circuit is turned off. The BOOST circuit adjusts the output voltage according to the first control signal;

When the input voltage is higher than the second preset voltage threshold, a second control signal is generated according to the input voltage, switched to the BUCK circuit according to the second control signal, and the BOOST circuit is turned off. The buck circuit adjusts the output voltage according to the second control signal.

Preferably, the control method further includes:

When the input voltage is between the first preset voltage threshold and the second preset voltage threshold, a preset control signal is generated according to the input voltage, and the input voltage is controlled according to the preset control signal Through the BUCK circuit and the BOOST circuit, the BUCK circuit and the BOOST circuit adjust the output voltage according to the preset control signal.

Preferably, the control method further includes:

the BUCK circuit is further configured to maintain the input current in the same phase as the input voltage to perform power factor correction;

The BOOST circuit is also used to maintain the input current in the same phase as the input voltage to perform power factor correction.

The present invention also provides a power supply device, the power supply device includes the above-mentioned switching circuit, or a control method applied to the above-mentioned switching circuit; wherein, the power supply device further includes a rectifier circuit and an inverter; The input end of the rectifier circuit is connected to the output end of the AC power supply, and the output end of the inverter is connected to the load;

The rectifier circuit is used for rectifying the AC power output by the AC power source and then inputting it to the switching circuit.

The present invention also provides an air conditioner, which includes the above-mentioned power supply device.

The technical scheme of the present invention forms a switching circuit by adopting a BUCK circuit, a BOOST circuit and a controller. Wherein, the controller obtains the input voltage output by the rectifier circuit, determines whether the input voltage is between a first preset voltage threshold and a second preset voltage threshold to adjust the output voltage, the buck circuit and the The BOOST circuit is also used to maintain the input current in the same phase as the input voltage to perform power factor correction. Thus, the technical problem of low voltage adjustment efficiency is solved.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can also be obtained according to the structures shown in these drawings without creative efforts.

FIG. 1 is a functional block diagram of an embodiment of a switching circuit or a power supply device according to the present invention;

2 is a circuit structure diagram of an embodiment of the BUCK circuit and the BOOST circuit of the present invention;

Fig. 3 is the circuit structure diagram of the first embodiment of the buck circuit work of the present invention;

Fig. 4 is the circuit structure diagram of the second embodiment of the buck circuit work of the present invention;

Fig. 5 is the control principle block diagram of the third embodiment of the buck circuit work of the present invention;

Fig. 6 is the circuit structure diagram of the first embodiment of the operation of the BOOST circuit of the present invention;

Fig. 7 is the circuit structure diagram of the second embodiment of the BOOST circuit operation of the present invention;

8 is a block diagram of the control principle of the third embodiment of the operation of the BOOST circuit of the present invention;

FIG. 9 is a schematic flowchart of a first embodiment of a control method for a switching circuit of the present invention.

Description of reference numbers:

label name label name 100 Rectifier circuit L1～L2 The first inductor to the second inductor 200 switching circuit D1～D3 first diode to third diode 210 Buck circuit S1～S4 The first switch tube to the fourth switch tube 220 BOOST circuit C1～C2 The first capacitor to the second capacitor 230 controller 300 Inverter

The realization, functional characteristics and advantages of the present invention will be further described with reference to the accompanying drawings in conjunction with the embodiments.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relationship between various components under a certain posture (as shown in the accompanying drawings). The relative positional relationship, the movement situation, etc., if the specific posture changes, the directional indication also changes accordingly.

In addition, the descriptions involving "first", "second", etc. in the present invention are only for descriptive purposes, and should not be understood as indicating or implying their relative importance or implying the number of indicated technical features. Thus, a feature delimited with "first", "second" may expressly or implicitly include at least one of that feature. In addition, the technical solutions between the various embodiments can be combined with each other, but must be based on the realization by those of ordinary skill in the art. When the combination of technical solutions is contradictory or cannot be realized, it should be considered that the combination of such technical solutions does not exists, and it is not within the protection scope of the present invention.

The present invention provides a switching circuit.

1 , in the embodiment of the present invention, the switching circuit 200 includes a BUCK circuit 210 , a BOOST circuit 220 and a controller 230 ; wherein the input end of the switching circuit 200 is connected to the output end of the rectifier circuit 100 , and the switching circuit 200 is The output end of the circuit 200 is connected to the inverter 300;

The controller 230 is configured to obtain the input voltage output by the rectifier circuit 100, and determine whether the input voltage is between a first preset voltage threshold and a second preset voltage threshold, wherein the first preset voltage The threshold is less than the second preset voltage threshold;

When the input voltage is lower than the first preset voltage threshold, generate a first control signal according to the input voltage, switch to the BOOST circuit 220 according to the first control signal, and turn off the BUCK circuit 210 ;

When the input voltage is higher than the second preset voltage threshold, generate a second control signal according to the input voltage, switch to the BUCK circuit 210 according to the second control signal, and turn off the BOOST circuit 220 ;

the BOOST circuit 220, configured to adjust the output voltage according to the first control signal;

The buck circuit 210 is configured to adjust the output voltage according to the second control signal.

The BUCK circuit 210 is also used to keep the input current and the input voltage in the same phase to perform power factor correction; the BOOST circuit 220 is also used to keep the input current and the input voltage in the same phase to perform power factor correction Correction.

It should be noted that this embodiment can be applied to an inverter air conditioner, and the switching circuit 200 is added between the rectifier circuit 100 and the inverter 300 to form a power supply device, which can be used according to actual conditions. the grid voltage, the controller 230 obtains the input voltage output by the rectifier circuit 100, determines whether the input voltage is between the first preset voltage threshold and the second preset voltage threshold, and selects to switch to The BOOST circuit 220 or the BUCK circuit 210; the BOOST circuit 220 or the BUCK circuit 210 can implement the power factor correction function, suppress current harmonics, improve the input power factor, and reduce the switching loss, so as to improve the adaptability of the power grid .

It is worth noting that, in this embodiment, the BOOST circuit 220 adopts a parallel interleaved BOOST circuit; it is easy to understand that the controller 230 may be composed of a control chip with strong processing capability and a peripheral circuit, for example, refer to Texas The control chips of the instrument UCC28060, UCC29910a, etc. will not be repeated here.

It is easy to understand that the first preset voltage threshold is the lowest critical value of the input voltage standard range when the entire circuit is working normally, and the second preset voltage threshold is the input voltage when the entire circuit is working normally. The highest critical value of the standard range, that is, the first preset voltage threshold should be smaller than the second preset voltage threshold.

Referring to Fig. 2, it is a circuit structure diagram of the BUCK circuit and the BOOST circuit of the present invention;

Specifically, the controller 230 is further configured to generate a preset control signal according to the input voltage when the input voltage is between the first preset voltage threshold and the second preset voltage threshold, and according to The preset control signal controls the input voltage to pass through the BUCK circuit 210 and the BOOST circuit 220 , and the BUCK circuit 210 and the BOOST circuit 220 adjust the output voltage according to the preset control signal.

It should be noted that, if the input voltage is within the standard range, that is, between the first preset voltage threshold and the second preset voltage threshold, the selection switching is not performed, and the preset control is performed according to the The signal controls the input voltage via the circuit shown in Figure 2; it is easy to understand that the inductance of the two circuits is a common inductance.

The technical solution of the present invention forms a switching circuit 200 by setting the BUCK circuit 210 , the BOOST circuit 220 and the controller 230 . The controller 230 obtains the input voltage output by the rectifier circuit 100, and determines whether the input voltage is between a first preset voltage threshold and a second preset voltage threshold, wherein the first preset voltage threshold is less than the second preset voltage threshold; when the input voltage is lower than the first preset voltage threshold, generate a first control signal according to the input voltage, and switch to the BOOST according to the first control signal The circuit 220 turns off the BUCK circuit 210, and the BOOST circuit 220 adjusts the output voltage according to the first control signal; when the input voltage is higher than the second preset voltage threshold, generates a voltage according to the input voltage The second control signal is switched to the BUCK circuit 210 according to the second control signal, and the BOOST circuit 220 is turned off. The BUCK circuit 210 adjusts the output voltage according to the second control signal; when the input voltage is at When between the first preset voltage threshold and the second preset voltage threshold, a preset control signal is generated according to the input voltage, and the input voltage is controlled to pass through the buck circuit 210 according to the preset control signal and the BOOST circuit 220, the BUCK circuit 210 and the BOOST circuit 220 adjust the output voltage according to the preset control signal; the BUCK circuit 210 is also used to keep the input current and the input voltage in the same phase to Power factor correction is performed; the BOOST circuit 220 is also used to maintain the input current in the same phase as the input voltage to perform power factor correction. In this way, the grid voltage is unstable, the output voltage is reduced when the grid voltage is too high, the output voltage is increased when the grid voltage is too low, and power factor correction is performed to suppress current harmonics to improve the input power factor.

Referring to Fig. 3, it is the circuit structure diagram of the first embodiment of the buck circuit work of the present invention;

Specifically, the buck circuit 210 includes a first switch S1, a first capacitor C1, a second switch S2, a first diode D1, a first inductor L1, a second inductor L2, a second diode D2, The third diode D3 and the second capacitor C2; wherein,

The input end of the first switch S1 is connected to the first output end of the rectifier circuit 100 and the input end of the second switch S2 respectively, and the output end of the first switch S1 is connected to the first The first end of the capacitor C1 is connected, the second end of the first capacitor C1 is connected to the second output end of the rectifier circuit 100, and the output end of the second switch tube S2 is connected to the first diode D1 The cathode of the first inductor L1 is connected to the first end of the first inductor L1 respectively, the anode of the first diode D1 is connected to the second end of the first capacitor C1, and the second end of the first inductor L1 is connected to the second end of the first capacitor C1. The anode of the second diode D2 is connected, the first end of the second inductor L2 is connected to the first end of the first inductor L1, and the second end of the second inductor L2 is connected to the third The anode of the diode D3 is connected to the anode of the third diode D3, the cathode of the third diode D3 is connected to the cathode of the second diode D2, and the cathode of the second diode D2 is also connected to the cathode of the second capacitor C2. The first end is connected, and the second end of the second capacitor C2 is connected to the anode of the first diode D1 and the second end of the first capacitor C1 respectively.

It should be noted that, in the first embodiment of the operation of the buck circuit, as shown in FIG. 3 , when the input voltage is higher than the second preset voltage threshold, a second control signal is generated according to the input voltage, Switch to the buck circuit 210 according to the second control signal, and turn off the BOOST circuit 220; when the buck circuit 210 is working, the first switch S1 is always closed, the third switch and all The fourth switch tube S4 is always in an off state, and during the whole working process, the second control signal received by the control end of the BUCK circuit 210 will also control the second switch tube S2 to switch on and off continuously. disconnected state.

Referring to Fig. 4, it is the circuit structure diagram of the second embodiment of the buck circuit work of the present invention;

Further, in the second embodiment of the BUCK circuit, the closed state of the second switch tube S2 is shown in FIG. 4(a) (the AC power supply, the rectifier circuit 100, the inverter 300 and the load are omitted). When the first diode D1 is actually turned off, the second diode D2 and the third transistor D3 are turned on, and the input voltage Ui is supplied to the first inductor L1 and the second The inductor L2 is charged, the first inductor L1 and the second inductor L2 can be regarded as a whole in the BUCK circuit 210, and the sum of the current through the first inductor L1 and the second inductor L2 is equal to the input current Ii. When the second switch S2 is closed, the input current Ii gradually increases.

Further, in the second embodiment of the buck circuit, the disconnected state of the second switch tube S2 is shown in FIG. 4(b) (the AC power supply, the rectifier circuit 100, the inverter 300 and the load are omitted), At this time, the first diode D1, the second diode D2 and the third diode D3 are all turned on, and the electrical energy stored in the first inductor L1 and the second inductor L2 Continue to output to the second capacitor C2, while the input voltage Ui charges the first capacitor C1, so that the input current Ii gradually decreases. The function of the first capacitor C1 is to prevent the input current Ii from being interrupted. If the capacitance value of the first capacitor C1 is too large, large current harmonics will be generated. The capacitance value should not be too large in selection.

Further, in the second embodiment of the operation of the BUCK circuit, in one voltage cycle, the total ratio of the second switch S2 being closed is D, that is, the duty cycle, and the final output voltage is Uo:Uo=D Ui, therefore, as long as the overall overall ratio D is well controlled, when the input voltage Ui is too large, the output voltage Uo can be maintained in a normal range to achieve the purpose of reducing voltage.

It should be noted that, in the second embodiment of the operation of the buck circuit, the power factor correction function of the buck circuit 210 is to control the waveform of the input current Ii and the waveform of the input voltage Ui in the same phase, as shown in FIG. 4( c ). As shown, the total ratio of the second switch S2 being closed in one voltage cycle is D, but the duty cycle at each moment is a time-varying value that changes with the change of the input voltage waveform.

Referring to Fig. 5, it is the control principle block diagram of the third embodiment of the buck circuit work of the present invention;

It should be noted that, in this embodiment, it is a block diagram of the control principle of the BUCK part, and four variables are required, three of which are real-time detection quantities: input voltage Ui, input current Ii, output voltage Uo, a given quantity, and the reference output voltage Uo_ref, this quantity is determined according to the input voltage required by the load, such as the DC inverter compressor motor. The controller 230 obtains the input voltage output by the rectifier circuit 100, and determines whether the input voltage is between a first preset voltage threshold and a second preset voltage threshold, and when the input voltage is higher than the second preset voltage threshold When the voltage threshold is preset, a second control signal is generated according to the input voltage, and is switched to the buck circuit 210 according to the second control signal, and the control terminal of the second switch S2 of the buck circuit 210 receives the The second control signal regulates the output voltage.

It is worth noting that there are many control methods for the BUCK part, and this picture is one of them, which will not be repeated here. The function of the PI regulator is to avoid the sudden change of the control signal caused by the instantaneous change of the input voltage, because there are inductors and capacitors in the circuit, which can suppress the sudden change of voltage and current.

Referring to FIG. 6, it is a circuit structure diagram of the first embodiment of the operation of the BOOST circuit of the present invention;

Specifically, the BOOST circuit 220 includes a second switch S2, a first inductor L1, a third switch S3, a second inductor L2, a fourth switch S4, a second diode D2, and a third diode D3 and the second capacitor C2; wherein,

The input end of the second switch S2 is connected to the first output end of the rectifier circuit 100 , and the output end of the second switch S2 is connected to the first end of the first inductor L1 and the second inductor The first ends of L2 are respectively connected, the second end of the first inductor L1 is connected to the input end of the third switch tube S3 and the anode of the second diode D2 respectively, and the second end of the second inductor L2 The second terminal is connected to the input terminal of the fourth switch tube S4 and the anode of the third diode D3 respectively, and the cathode of the second diode D2 is connected to the cathode of the third diode D3 , the cathode of the second diode D2 is also connected to the first end of the second capacitor C2, the output end of the third switch tube S3, the output end of the fourth switch tube S4 and the The second ends of the two capacitors C2 are respectively connected to the second output ends of the rectifier circuit 100 .

It should be noted that, in the first embodiment of the operation of the BOOST circuit, as shown in FIG. 6 , when the input voltage is lower than the first preset voltage threshold, a first control signal is generated according to the input voltage, Switch to the BOOST circuit 220 according to the first control signal, and turn off the BUCK circuit 210; when the BOOST circuit 220 is working, the first switch tube S1 is always in an off state, and the first capacitor C1 does not participate in circuit work, the second switch tube S2 is always in a closed state, and the first diode D1 is actually disconnected. During the entire working process, the control end of the BOOST circuit 220 receives the The first control signal also controls the third switch S3 and the fourth switch S4 to switch on and off continuously.

Referring to FIG. 7, it is a circuit structure diagram of the second embodiment of the BOOST circuit operation of the present invention;

Further, in the second embodiment of the operation of the BOOST circuit, the third switch S3 and the fourth switch S4 are both closed as shown in Figure 7(a) (the AC power supply, the rectifier circuit 100, Inverter 300 and load), the second diode D2 and the third diode D3 are turned off at this time, and the input voltage Ui is supplied to the first inductor L1 and the second inductor L2 is charged, the inductor current increases, and the electrical energy stored in the second capacitor C2 is output to the subsequent inverter 300 .

Further, in the second embodiment of the operation of the BOOST circuit, the third switch S3 and the fourth switch S4 are both disconnected as shown in Figure 7(b) (the AC power supply and the rectifier circuit 100 are omitted). , the inverter 300 and the load), at this time the second diode D2 and the third diode D3 are turned on, the input voltage Ui and the first inductor L1 and the second The inductor L2 simultaneously outputs electrical energy to the second capacitor C2, and then outputs the electrical energy to the subsequent inverter 300, so that the inductor current decreases. Wherein, when both the third switch S3 and the fourth switch S4 are turned off, the input voltage Ui is equal to the voltage UL on the inductor plus the output voltage Uo: Ui _{= UL} +Uo, Uo ₌ Ui-UL , wherein, the input voltage Ui is the waveform of the absolute value of the sine wave determined by the grid voltage and rectified by the rectifier circuit 100; The voltage regulation effect of capacitor C2, the instantaneous change is very small.

The U _L is a time-varying value with current: When the inductor current rises, that is, when the third switch S3 and the fourth switch S4 are both closed, the voltage UL on the _inductor is a positive value; and when the inductor current drops, that is, the third switch When both S3 and the fourth switch S4 are turned off, the voltage UL on the inductor will instantaneously become negative, so the output voltage _Uo will increase; therefore, the output voltage Uo: Uo is the third switch The instantaneous value before the tube S3 and the fourth switch tube S4 are closed (when the third switch tube S3 and the fourth switch tube S4 are closed); Uo ₌ Ui-UL (the third switch tube S3 and the fourth switch tube S4 are closed); When both S3 and the fourth switch tube S4 are disconnected, U _L is a negative value at this time); the effective value of the final output voltage Uo: Wherein, the D is the total closing ratio of the switching device in one voltage cycle, that is, the duty cycle.

Further, in the second embodiment of the BOOST circuit, one of the third switch S3 and the fourth switch S4 is closed, and the other is disconnected as shown in Figures 7(c) and 7(d). ) (the AC power supply, the rectifier circuit 100, the inverter 300 and the load are omitted): if the third switch S3 and the fourth switch S4 can only have two states of being both disconnected or both closed, Then the parallel interleaved BOOST circuit is actually the same as the single BOOST circuit. Theoretically, if the D (duty ratio) of a single BOOST circuit is close to 1, then the final output voltage Uo can be arbitrarily amplified, but in fact, the ability of the output second capacitor C2 to maintain the voltage is limited, so the boost capability of a single BOOST circuit is limited, and the current output by the power supply to the second capacitor C2 is discontinuous, so the output voltage Uo is not very stable. Therefore, one of the third switch S3 and the fourth switch S4 is closed, and the other is open to avoid the shortcomings of the single BOOST circuit, that is, one inductance is in the energy storage state of current up, and the other inductance is in the current state. Decreasing the output power to the state of the second capacitor C2 maximizes the continuity of the current output to the second capacitor C2. The stability of the output voltage Uo is increased, the boosting capability of the circuit is strengthened, and the grid voltage is too low.

It should be noted that, in the second embodiment of the BOOST circuit operation, the power factor correction function of the BOOST circuit 220 is to control the waveform of the input current Ii and the waveform of the input voltage Ui in the same phase, as shown in FIG. 7(e) As shown, the duty cycle of the third switch S3 and the fourth switch S4 in one voltage cycle varies with the waveform of the input voltage at each moment.

Referring to FIG. 8 , it is a block diagram of the control principle of the third embodiment of the operation of the BOOST circuit of the present invention;

It should be noted that, in this embodiment, it is a block diagram of the control principle of the BOOST part, and four variables are required, three of which are real-time detection quantities: input voltage Ui, input current Ii, output voltage Uo, a given quantity, and the reference output voltage Uo_ref, this quantity is determined according to the input voltage required by the load, such as the DC inverter compressor motor. The controller 230 obtains the input voltage output by the rectifier circuit 100, and determines whether the input voltage is between a first preset voltage threshold and a second preset voltage threshold, and when the input voltage is lower than the first preset voltage threshold When the voltage threshold is preset, a first control signal is generated according to the input voltage, and switched to the BOOST circuit 220 according to the first control signal, the third switch S3 and the fourth switch of the BOOST circuit 220 The control terminals of the switch tube S4 respectively receive the second control signal to adjust the output voltage.

It is worth noting that there are many control methods for the BOOST part, and this picture is one of them, which will not be repeated here. Compared with the control of the BUCK part, there is an additional load distribution part, which balances and distributes the closing and breaking of the third switch S3 and the fourth switch S4.

Referring to FIG. 9 , it is a schematic flowchart of a first embodiment of a control method for a switching circuit of the present invention;

The present invention also provides a control method for the switching circuit as described above, the control method comprising:

Step S10: the controller 230 obtains the input voltage output by the rectifier circuit 100, and determines whether the input voltage is between a first preset voltage threshold and a second preset voltage threshold, wherein the first preset voltage The threshold value is smaller than the second preset voltage threshold value.

Step S21: when the input voltage is lower than the first preset voltage threshold, generate a first control signal according to the input voltage, switch to the BOOST circuit 220 according to the first control signal, and turn off the The BUCK circuit 210, the BOOST circuit 220 adjusts the output voltage according to the first control signal.

Step S22: when the input voltage is higher than the second preset voltage threshold, generate a second control signal according to the input voltage, switch to the BUCK circuit 210 according to the second control signal, and turn off the BOOST circuit 220, the buck circuit 210 adjusts the output voltage according to the second control signal.

Step S23: When the input voltage is between the first preset voltage threshold and the second preset voltage threshold, generate a preset control signal according to the input voltage, and control the control signal according to the preset control signal. The input voltage is passed through the BUCK circuit 210 and the BOOST circuit 220 , and the BUCK circuit 210 and the BOOST circuit 220 adjust the output voltage according to the preset control signal.

While the above process is being performed, the BUCK circuit 210 is also used to keep the input current and the input voltage in the same phase to perform power factor correction; the BOOST circuit 220 is also used to keep the input current and the input voltage in the same phase for the same phase to perform power factor correction.

It should be noted that, in this embodiment, the input voltage output by the rectifier circuit 100 is obtained by the controller 230, and it is determined whether the input voltage is between the first preset voltage threshold and the second preset voltage threshold within a certain range. The output voltage is adjusted, and the BUCK circuit 210 and the BOOST circuit 220 are also used to keep the input current and the input voltage in the same phase to perform power factor correction. In this way, the grid voltage is unstable, the output voltage is reduced when the grid voltage is too high, the output voltage is increased when the grid voltage is too low, and power factor correction is performed to suppress current harmonics to improve the input power factor.

In addition, the present invention also provides a power supply device, the power supply device includes the switching circuit described in any one of the above or a control method applied to the switching circuit as described above; wherein, the power supply device further includes a rectifier circuit 100 and Inverter 300; the input end of the rectifier circuit 100 is connected to the output end of the AC power supply, and the output end of the inverter 300 is connected to the load;

The rectifier circuit 100 is configured to rectify the AC power output by the AC power source and then input it to the switching circuit.

It is easy to understand that the power supply device has at least the beneficial effects brought about by the above-mentioned embodiments.

It should be noted that, in this embodiment, the power supply device includes the switching circuit described in any one of the above or the control method applied to the switching circuit as described above.

In addition, the present invention also provides an air conditioner, which includes the above-mentioned power supply device.

It is easy to understand that the air conditioner has at least the beneficial effects brought about by the above-mentioned embodiments. It is worth noting that, in this embodiment, the air conditioner includes the above-mentioned power supply device; wherein, the air conditioner may be a (DC) inverter air conditioner, and the power supply device may be used as the (DC) inverter air conditioner front-end power supply unit for the compressor motor of the compressor.

The above descriptions are only the preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. Under the inventive concept of the present invention, the equivalent structural transformations made by the contents of the description and drawings of the present invention, or the direct/indirect application Other related technical fields are included in the scope of patent protection of the present invention.

Claims (10)

1. A switching circuit is characterized by comprising a BUCK circuit, a BOOST circuit and a controller; the input end of the switching circuit is connected with the output end of the rectifying circuit, and the output end of the switching circuit is connected with the inverter;

the controller is used for acquiring the input voltage output by the rectifying circuit and judging whether the input voltage is between a first preset voltage threshold and a second preset voltage threshold, wherein the first preset voltage threshold is smaller than the second preset voltage threshold;

when the input voltage is lower than the first preset voltage threshold, generating a first control signal according to the input voltage, switching to the BOOST circuit according to the first control signal, and turning off the BUCK circuit;

when the input voltage is higher than the second preset voltage threshold, generating a second control signal according to the input voltage, switching to the BUCK circuit according to the second control signal, and turning off the BOOST circuit;

the BOOST circuit is used for adjusting output voltage according to the first control signal;

the BUCK circuit is used for adjusting output voltage according to the second control signal.

2. The switching circuit of claim 1, wherein the controller is further configured to generate a preset control signal according to the input voltage when the input voltage is between the first preset voltage threshold and the second preset voltage threshold, and control the input voltage to pass through the BUCK circuit and the BOOST circuit according to the preset control signal, and the BUCK circuit and the BOOST circuit adjust an output voltage according to the preset control signal.

3. The switching circuit of claim 2, wherein the BUCK circuit is further to maintain an input current in a same phase as the input voltage to perform power factor correction; the BOOST circuit is also used to maintain the input current in phase with the input voltage to perform power factor correction.

4. The switching circuit according to claim 3, wherein the BUCK circuit comprises a first switch tube, a first capacitor, a second switch tube, a first diode, a first inductor, a second diode, a third diode and a second capacitor; wherein,

the input end of the first switch tube is connected with the first output end of the rectifying circuit and the input end of the second switch tube respectively, the output end of the first switch tube is connected with the first end of the first capacitor, the second end of the first capacitor is connected with the second output end of the rectifying circuit, the output end of the second switch tube is connected with the cathode of the first diode and the first end of the first inductor respectively, the anode of the first diode is connected with the second end of the first capacitor, the second end of the first inductor is connected with the anode of the second diode, the first end of the second inductor is connected with the first end of the first inductor, the second end of the second inductor is connected with the anode of the third diode, the cathode of the third diode is connected with the cathode of the second diode, and the cathode of the second diode is also connected with the first end of the second capacitor, and the second end of the second capacitor is respectively connected with the anode of the first diode and the second end of the first capacitor.

5. The switching circuit according to claim 3, wherein the BOOST circuit comprises a second switch tube, a first inductor, a third switch tube, a second inductor, a fourth switch tube, a second diode, a third diode, and a second capacitor; wherein,

the input end of the second switch tube is connected with the first output end of the rectification circuit, the output end of the second switch tube is connected with the first end of the first inductor and the first end of the second inductor respectively, the second end of the first inductor is connected with the input end of the third switch tube and the anode of the second diode respectively, the second end of the second inductor is connected with the input end of the fourth switch tube and the anode of the third diode respectively, the cathode of the second diode is connected with the cathode of the third diode, the cathode of the second diode is further connected with the first end of the second capacitor, and the output end of the third switch tube, the output end of the fourth switch tube and the second end of the second capacitor are connected with the second output end of the rectification circuit respectively.

6. A control method of a switching circuit according to any one of claims 1 to 5, characterized in that the control method comprises:

the controller acquires an input voltage output by the rectifying circuit, and judges whether the input voltage is between a first preset voltage threshold and a second preset voltage threshold, wherein the first preset voltage threshold is smaller than the second preset voltage threshold;

when the input voltage is lower than the first preset voltage threshold, generating a first control signal according to the input voltage, switching to the BOOST circuit according to the first control signal, and turning off the BUCK circuit, wherein the BOOST circuit adjusts output voltage according to the first control signal;

when the input voltage is higher than the second preset voltage threshold value, a second control signal is generated according to the input voltage, the BUCK circuit is switched to the BUCK circuit according to the second control signal, the BOOST circuit is turned off, and the BUCK circuit adjusts the output voltage according to the second control signal.

7. The control method of the switching circuit according to claim 6, further comprising:

when the input voltage is between the first preset voltage threshold and the second preset voltage threshold, generating a preset control signal according to the input voltage, controlling the input voltage to pass through the BUCK circuit and the BOOST circuit according to the preset control signal, and adjusting output voltage by the BUCK circuit and the BOOST circuit according to the preset control signal.

8. The control method of the switching circuit according to claim 7, further comprising:

the BUCK circuit is also used for keeping the input current and the input voltage in the same phase to perform power factor correction;

the BOOST circuit is also used to maintain the input current in phase with the input voltage to perform power factor correction.

9. A power supply device characterized by comprising the switching circuit according to any one of claims 1 to 5, or a control method applied to the switching circuit according to any one of claims 6 to 8; the power supply device also comprises a rectifying circuit and an inverter; the input end of the rectification circuit is connected with the output end of the alternating current power supply, and the output end of the inverter is connected with the load;

the rectification circuit is used for rectifying the alternating current output by the alternating current power supply and then inputting the rectified alternating current to the switching circuit.

10. An air conditioner characterized by comprising the power supply device according to claim 9.