CN108696116B - Totem pole PFC circuit, pulse width control method, air conditioner and storage medium - Google Patents

Totem pole PFC circuit, pulse width control method, air conditioner and storage medium Download PDF

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Publication number
CN108696116B
CN108696116B CN201810560783.7A CN201810560783A CN108696116B CN 108696116 B CN108696116 B CN 108696116B CN 201810560783 A CN201810560783 A CN 201810560783A CN 108696116 B CN108696116 B CN 108696116B
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switch unit
pulse width
unit
current
input
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CN108696116A (en
Inventor
曾贤杰
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Midea Group Co Ltd
GD Midea Air Conditioning Equipment Co Ltd
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Midea Group Co Ltd
GD Midea Air Conditioning Equipment Co Ltd
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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
    • 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
    • H02M1/4233—Arrangements for improving power factor of AC input using a bridge converter comprising active switches
    • 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
    • H02M1/0048—Circuits or arrangements for reducing losses
    • H02M1/0054—Transistor switching losses
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/51—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used
    • H03K17/56—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices
    • H03K17/687—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices the devices being field-effect transistors
    • H03K17/6871—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices the devices being field-effect transistors the output circuit comprising more than one controlled field-effect transistor
    • 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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  • Power Engineering (AREA)
  • Rectifiers (AREA)

Abstract

The invention discloses a totem pole PFC circuit, comprising: the control module is used for controlling the switching state of each switch unit and the pulse width of each switch unit when each switch unit is conducted according to the input voltage and the input current of the input end of the bridge circuit when the input current of the input end of the bridge circuit is smaller than or equal to a preset current threshold value. The invention also discloses a pulse width control method, an air conditioner and a storage medium. The invention realizes that the switching times of each switch unit are reduced, and the proper pulse width is selected for each switch unit according to the input voltage and the input current, so that the switching times can be reduced on the premise of meeting the current harmonic wave requirement of the totem-pole PFC circuit and improving the power factor of the totem-pole PFC circuit, the times of short-circuit current flowing is reduced, the useless power in the circuit is reduced, the switching loss is reduced, and the efficiency of the totem-pole PFC circuit is improved.

Description

Totem pole PFC circuit, pulse width control method, air conditioner and storage medium
Technical Field
The invention relates to the technical field of air conditioners, in particular to a totem-pole PFC circuit, a pulse width control method, an air conditioner and a storage medium.
Background
With the development of Power electronic technology, active PFC (Power Factor Correction) technology is widely used due to its advantages of high Power Factor, small harmonic current, stable output voltage, etc.
At present, a BOOST type PFC is generally used, and the PFC has a simple structure and is convenient to control, but the efficiency is low. Therefore, on some occasions with higher requirements on efficiency, the bridgeless totem-pole PFC circuit is adopted, the number of devices on a loop is reduced, and the efficiency is improved.
In the conventional totem pole PFC circuit, the number of times a predetermined switching unit is turned on/off every half cycle of control of the power supply voltage is controlled, the number of times of short-circuit current in the totem pole PFC circuit is controlled, and the power factor is improved by the short-circuit current. However, when the load is large, the improvement of the power factor is insufficient due to the small number of times of short-circuit current flowing, so that the power of the useless power in the totem-pole PFC circuit is large; if the number of times of short-circuit current flowing is large, the switching loss becomes large; all result in a lower efficiency of the totem pole PFC circuit.
The above is only for the purpose of assisting understanding of the technical aspects of the present invention, and does not represent an admission that the above is prior art.
Disclosure of Invention
The invention mainly aims to provide a totem pole PFC circuit, a pulse width control method, an air conditioner and a storage medium, and aims to solve the technical problem that the existing totem pole PFC circuit is low in efficiency.
In order to achieve the above object, the present invention provides a totem-pole PFC circuit, including:
the bridge circuit is provided with a plurality of switch units connected in a bridge shape, the input end of the bridge circuit is connected with an alternating current power supply, and the output end of the bridge circuit is connected with a load;
a reactor provided between the bridge circuit and the alternating-current power supply;
the bus capacitor is connected with the load in parallel and then is electrically connected with the output end of the bridge circuit;
the control module is used for controlling each switch unit in the bridge circuit to be switched off when the input current of the input end of the bridge circuit is greater than a preset current threshold; and when the input current of the input end of the bridge circuit is less than or equal to a preset current threshold, controlling the switching state of each switching unit and the pulse width of each switching unit when the switching unit is conducted according to the input voltage and the input current of the input end of the bridge circuit.
In one embodiment, the bridge circuit includes a first switch unit, a second switch unit, a third switch unit and a fourth switch unit;
the first switching unit and the second switching unit are connected in series to form a first branch circuit, the third switching unit and the fourth switching unit are connected in series to form a second branch circuit, and the first branch circuit and the second branch circuit are connected in parallel to form the bridge circuit;
a connection point of the first switching unit and the second switching unit is electrically connected to the ac power supply via the reactor; the connection point of the third switch unit and the fourth switch unit is electrically connected with the alternating current power supply;
the connection point of the first switch unit and the third switch unit is electrically connected with the positive electrode of the bus capacitor; and the connecting point of the second switch unit and the fourth switch unit is electrically connected with the negative electrode of the bus capacitor.
In one embodiment, the control module comprises:
the current detection unit is electrically connected with the input end of the bridge circuit and is used for detecting the input current of the input end of the bridge circuit;
the alternating voltage detection unit is electrically connected with the input end of the bridge circuit and is used for detecting the input voltage of the input end of the bridge circuit;
the control unit is electrically connected with the current detection unit and the alternating voltage detection unit respectively, and is used for controlling the switching state of each switching unit and the pulse width of each switching unit when the switching unit is switched on according to the input current detected by the current detection unit and the input voltage detected by the alternating voltage detection unit when the input current detected by the current detection unit is less than or equal to a preset current threshold value.
In one embodiment, the control module further comprises: a drive protection unit and a drive unit;
the driving protection unit is respectively electrically connected with the current detection unit and the driving unit and is used for sending a turn-off control signal to the driving unit when the input current detected by the current detection unit is greater than a preset current threshold;
the driving unit is used for controlling each switch unit in the bridge circuit to be switched off according to the received switching-off control signal;
the control unit is further used for generating a state control signal according to the input current detected by the current detection unit and the input voltage detected by the alternating voltage detection unit when the input current detected by the current detection unit is smaller than or equal to a preset current threshold value, and sending the state control signal to the driving unit;
the driving unit is further used for controlling the switching state of each switching unit in the bridge circuit and the pulse width of each switching unit when the switching unit is conducted according to the received state control signal.
In addition, in order to achieve the above object, the present invention further provides a pulse width control method applied to the above totem pole PFC circuit, where the pulse width control method includes the following steps:
when the input current of the input end of the bridge circuit is smaller than or equal to a preset current threshold, determining whether positive and negative switching exists in the input voltage of the input end of the bridge circuit at present;
when the input voltage has positive and negative switching currently, determining whether the input voltage of the input end is in a positive half period after the positive and negative switching;
when the input voltage of the input end is in a positive half period after positive and negative switching, the first switch unit, the second switch unit and the third switch unit are controlled to be turned off, the fourth switch unit is controlled to be turned on, and the second switch unit, the first switch unit and the pulse width of the second switch unit are controlled to be alternately turned on/off and turned on based on the pulse change times, the pulse time interval and the input current of the input end;
and when the input voltage of the input end is in a negative half period after the positive and negative switching, the first switch unit, the second switch unit and the fourth switch unit are controlled to be turned off, the third switch unit is controlled to be turned on, and the first switch unit, the second switch unit and the pulse width of the first switch unit are controlled to be alternately turned on/off and turned on based on the pulse change times, the pulse time interval and the input current of the input end.
In one embodiment, the number of pulse changes is 3, and the pulse time interval includes a first preset time duration, a second preset time duration and a third preset time duration; the step of controlling the second switching unit, the first switching unit to be alternately turned on/off based on the number of pulse changes, the pulse time interval, and the input current of the input terminal, and the pulse width at which the second switching unit is turned on includes:
calculating a first pulse width based on a first input current of the input end within a first preset time length;
when the conducting time of the fourth switching unit reaches the first preset time, controlling the second switching unit to be conducted in the first pulse width;
when the on-time of the second switch unit reaches the first pulse width, controlling the first switch unit to be on and the second switch unit to be off within a second preset time, and calculating a second pulse width based on a second input current of the input end within the second preset time;
when the on-time of the first switch unit reaches the second preset time, controlling the second switch unit to be on and the first switch unit to be off in the second pulse width;
when the on-time of the second switch unit reaches the second pulse width, controlling the first switch unit to be on and the second switch unit to be off within a third preset time, and calculating a third pulse width based on a third input current of the input end within the third preset time;
when the conducting time of the first switch unit reaches the third preset time, controlling the second switch unit to be conducted and the first switch unit to be switched off in the third pulse width;
and when the on-time of the second switch unit reaches the third pulse width, controlling the first switch unit to be on and the second switch unit to be off.
In one embodiment, the step of calculating the first pulse width based on the first input current at the input terminal for the first preset time period includes:
and obtaining a preset maximum pulse width corresponding to the first pulse width, a corresponding first preset current, a preset minimum pulse width and a corresponding second preset current, and calculating the first pulse width according to a linear interpolation algorithm based on the preset maximum pulse width, the first preset current, the preset minimum pulse width, the second preset current and the first input current.
In an embodiment, after the step of controlling the first switching unit to be turned on and the second switching unit to be turned off when the on-time of the second switching unit reaches the third pulse width, the method further includes:
and when detecting that the current input current of the input end reaches 0, controlling the first switch unit to be switched off.
In one embodiment, the step of controlling the first switching unit and the second switching unit to be alternately turned on/off based on the number of pulse changes, the pulse time interval, and the input current of the input terminal, and the pulse width when the first switching unit is turned on includes:
calculating a fourth pulse width based on a fourth input current of the input terminal within a first preset time period;
when the conducting time of the fourth switching unit reaches the first preset time, controlling the first switching unit to be conducted in the fourth pulse width;
when the on-time of the first switch unit reaches the fourth pulse width, controlling the second switch unit to be on and the first switch unit to be off within a second preset time, and calculating a fifth pulse width based on a fifth input current of the input end within the second preset time;
when the on-time of the second switch unit reaches the fifth preset time, controlling the first switch unit to be on and the second switch unit to be off in the fifth pulse width;
when the on-time of the first switch unit reaches the fifth pulse width, controlling the second switch unit to be on and the first switch unit to be off within a third preset time, and calculating a sixth pulse width based on a sixth input current of the input end within the third preset time;
when the on-time of the second switch unit reaches the third preset time, controlling the first switch unit to be on and the second switch unit to be off in the sixth pulse width;
and when the on-time of the first switch unit reaches the sixth pulse width, controlling the second switch unit to be switched on and the first switch unit to be switched off.
In an embodiment, after the step of controlling the second switching unit to be turned on and the first switching unit to be turned off when the on-duration of the first switching unit reaches the sixth pulse width, the method further includes:
and when the current input current of the input end is detected to reach 0, controlling the second switch unit to be switched off.
In one embodiment, the pulse width control method further includes:
and when the input current of the input end of the bridge circuit is greater than a preset current threshold value, the first switch unit, the second switch unit, the third switch unit and the fourth switch unit are respectively controlled to be turned off.
In addition, to achieve the above object, the present invention also provides an air conditioner, comprising: the totem pole PFC circuit, the memory, the processor, and the pulse width control program stored in the memory and operable on the processor, when executed by the processor, implement the steps of the pulse width control method of any of the above.
In order to achieve the above object, the present invention further provides a storage medium, wherein the storage medium stores a pulse width control program, and the pulse width control program implements the steps of the pulse width control method according to any one of the above aspects when executed by a processor.
According to the invention, when the input current at the input end of the bridge circuit is less than or equal to the preset current threshold, the control module controls the switching state of each switch unit and the pulse width of each switch unit when being conducted according to the input voltage and the input current at the input end of the bridge circuit, so that the switching times of each switch unit are reduced, and meanwhile, the proper pulse width is selected for each switch unit according to the input voltage and the input current, and the switching times are reduced on the premise of meeting the current harmonic wave requirement of the totem-pole PFC circuit and improving the power factor of the totem-pole PFC circuit, so that the times of flowing short-circuit current are reduced, the switch loss is reduced while the useless power in the circuit is reduced, and the efficiency of the totem-pole PFC circuit is improved.
Drawings
FIG. 1 is a schematic diagram of an air conditioner in a hardware operating environment according to an embodiment of the present invention;
fig. 2 is a schematic circuit diagram of a totem-pole PFC circuit according to an embodiment of the present invention;
FIG. 3 is a schematic flow chart of a first embodiment of a pulse width control method according to the present invention;
fig. 4 is a detailed flowchart of the steps of controlling the second switch unit, the first switch unit to be alternately turned on/off, and the pulse width of the second switch unit to be turned on according to the pulse change times, the pulse time interval, and the input current of the input terminal in the second embodiment of the pulse width control method of the present invention;
FIG. 5 Is a schematic diagram showing the time variation of the AC power source voltage Vs, the circuit current Is, and the driving pulses of the switching units Q1-Q4 according to the present invention;
fig. 6 is a detailed flowchart of the steps of controlling the first switch unit and the second switch unit to be alternately turned on/off and controlling the pulse width of the first switch unit when the first switch unit is turned on according to the pulse change times, the pulse time interval and the input current of the input terminal in the third embodiment of the pulse width control method of the present invention.
The reference numbers illustrate:
Figure BDA0001682663840000061
Figure BDA0001682663840000071
the implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
As shown in fig. 1, fig. 1 is a schematic structural diagram of an air conditioner in a hardware operating environment according to an embodiment of the present invention.
As shown in fig. 1, the air conditioner may include: a processor 1001, such as a CPU, a network interface 1004, a user interface 1003, a memory 1005, a communication bus 1002. Wherein a communication bus 1002 is used to enable connective communication between these components. The user interface 1003 may include a Display screen (Display), an input unit such as a Keyboard (Keyboard), and the optional user interface 1003 may also include a standard wired interface, a wireless interface. The network interface 1004 may optionally include a standard wired interface, a wireless interface (e.g., WI-FI interface). The memory 1005 may be a high-speed RAM memory or a non-volatile memory (e.g., a magnetic disk memory). The memory 1005 may alternatively be a storage device separate from the processor 1001.
Optionally, the air conditioner may further include a camera, a Radio Frequency (RF) circuit, a sensor, an audio circuit, a WiFi module, and the like. Such as light sensors, motion sensors, and other sensors. Of course, the air conditioner may also be configured with other sensors such as a gyroscope, a barometer, a hygrometer, a thermometer, an infrared sensor, etc., which are not described herein again.
Those skilled in the art will appreciate that the air conditioner configuration shown in fig. 1 is not intended to be limiting of the air conditioner and may include more or fewer components than shown, or some components may be combined, or a different arrangement of components.
As shown in fig. 1, a memory 1005, which is a kind of computer storage medium, may include therein an operating system, a network communication module, a user interface module, and a switching program of the PFC circuit.
In the air conditioner shown in fig. 1, the network interface 1004 is mainly used for connecting to a backend server and performing data communication with the backend server; the user interface 1003 is mainly used for connecting a client (user side) and performing data communication with the client; and the processor 1001 may be used to invoke a switching procedure of the PFC circuit stored in the memory 1005.
In the present embodiment, an air conditioner includes: the totem pole PFC circuit, the memory 1005, the processor 1001 and the pulse width control program stored in the memory 1005 and operable on the processor 1001 in the embodiment of the present invention, wherein the pulse width control method provided in the embodiment of the present application is executed when the processor 1001 calls the pulse width control program stored in the memory 1005.
The invention also provides a totem-pole PFC circuit, and referring to fig. 2, fig. 2 is a schematic circuit structure diagram of an embodiment of the totem-pole PFC circuit of the invention.
In this embodiment, the totem-pole PFC circuit includes: bridge circuit 20, reactor L, bus capacitor C and control module 10.
The bridge circuit 20 is provided with a plurality of switching units connected in a bridge shape, and the input end of the bridge circuit 20 is connected to an alternating current power source and the output end is connected to a load.
A reactor L is provided between the bridge circuit 20 and the ac power supply. The reactor L stores electric power supplied from an ac power supply as energy, and performs voltage boosting and power factor improvement of the totem-pole PFC circuit by discharging the energy.
The bus capacitor C is electrically connected to the output terminal of the bridge circuit 20 after being connected in parallel with the load.
The control module 10 is configured to control each switch unit in the bridge circuit 20 to turn off when the input current at the input end of the bridge circuit 20 is greater than a preset current threshold; when the input current at the input end of the bridge circuit 20 is less than or equal to the preset current threshold, the control module 10 controls the switching state of each switching unit and the pulse width of each switching unit when the switching unit is turned on according to the input voltage and the input current at the input end of the bridge circuit 20.
In this embodiment, in the operating process of the totem pole PFC circuit, the control module 10 may obtain an input current at an input end of the bridge circuit 20 in real time, and determine whether the obtained input current is greater than a preset current threshold, where when the input current is greater than the preset current threshold, the control module 10 controls each switch unit in the bridge circuit 20 to be turned off, so as to implement overcurrent protection of the totem pole PFC circuit; when the input current is less than or equal to the preset current threshold, the control module 10 obtains the input voltage Vs and the input current at the input end of the bridge circuit 20, and controls the switching state of each switching unit and the pulse width of each switching unit when the switching unit is turned on according to the input voltage and the input current at the input end of the bridge circuit 20, so that the switching frequency of each switching unit is reduced, and simultaneously, a proper pulse width is selected for each switching unit according to the input voltage and the input current, so that the switching frequency is reduced on the premise that the current harmonic requirement of the totem-pole PFC circuit is met, the power factor of the totem-pole PFC circuit is improved, and the switching loss is reduced, and the efficiency is improved.
The preset current threshold value can be reasonably set according to the requirements of the totem-pole PFC circuit.
Further, in an embodiment, the bridge circuit 20 includes a first switching unit Q1, a second switching unit Q2, a third switching unit Q3 and a fourth switching unit Q4.
The first switching unit Q1 is connected in series with the second switching unit Q2 to form a first branch, the third switching unit Q3 is connected in series with the fourth switching unit Q4 to form a second branch, and the first branch and the second branch are connected in parallel to form the bridge circuit 20.
A connection point of the first switching unit Q1 and the second switching unit Q2 is electrically connected to an ac power supply via a reactor L; the connection point of the third switching unit Q3 and the fourth switching unit Q4 is electrically connected to an ac power supply. The connection point of the first switching unit Q1 and the third switching unit Q3 is electrically connected with the anode of the bus capacitor C; the connection point of the second switching unit Q2 and the fourth switching unit Q4 is electrically connected with the negative electrode of the bus capacitor C.
Specifically, the first switch unit Q1, the second switch unit Q2, the third switch unit Q3 and the fourth switch unit Q4 may be MOSFETs (Metal-Oxide-Semiconductor Field-Effect transistors), such as super-junction MOSFETs or SiC-MOSFETs. Preferably, the source of the first switching unit Q1 is electrically connected to the drain of the second switching unit Q2, and the connection point thereof is electrically connected to the ac power supply via the reactor L; the source of the third switching unit Q3 is electrically connected with the drain of the fourth switching unit Q4, and the connection point is electrically connected with an alternating current power supply; the drain electrode of the first switch unit Q1 is electrically connected with the drain electrode of the third switch unit Q3, and the connection point of the first switch unit Q1 is electrically connected with the anode of the bus capacitor C; the source of the second switching unit Q2 is electrically connected to the source of the fourth switching unit Q4, and the connection point thereof is electrically connected to the negative electrode of the bus capacitor C.
There is a parasitic diode inside the first switching unit Q1. The parasitic diode is a part of a pn junction existing between the source and the drain of the first switching unit Q1. The saturation voltage (drain-source voltage in the on state) of the first switching unit Q1 is lower than the forward voltage drop of the parasitic diode. Thus, the current flowing through the source/drain of the first switching unit Q1 has a smaller voltage drop than the current flowing through the parasitic diode, and the conduction loss can be reduced. It is easy to understand that the flow of current through the first switching unit Q1 in the on state reduces conduction loss as compared with the flow of current through the parasitic diode in the first switching unit Q1 in the off state. The same applies to the other switching elements Q2 to Q4.
Further, the control module 10 includes: current detection means 12, alternating voltage detection means 13, and control means 11.
The current detection unit 12 is electrically connected to an input terminal of the bridge circuit 20, and is configured to detect an input current at the input terminal of the bridge circuit 20; the ac voltage detection unit 13 is electrically connected to an input terminal of the bridge circuit 20, and detects an input voltage at the input terminal of the bridge circuit 20.
The control unit 11 is electrically connected to the current detection unit 12 and the ac voltage detection unit 13, respectively. The control unit 11 is configured to control the switching state of each switching unit and the pulse width of each switching unit when each switching unit is turned on in the bridge circuit 20 according to the input current detected by the current detection unit 12 and the input voltage detected by the ac voltage detection unit 13 when the input current detected by the current detection unit 12 is less than or equal to a preset current threshold.
Preferably, in a further embodiment, the control module 10 further comprises: a drive protection unit 14 and a drive unit 15.
The driving protection unit 14 is electrically connected to the current detection unit 12 and the driving unit 15, and configured to send a turn-off control signal to the driving unit 15 when the input current detected by the current detection unit 12 is greater than a preset current threshold. The driving unit 15 is configured to control each switching unit in the bridge circuit 20 to turn off according to the received turn-off control signal, so as to implement overcurrent protection of the totem-pole PFC circuit.
The control unit 11 is further configured to generate a state control signal according to the input current detected by the current detection unit 12 and the input voltage detected by the ac voltage detection unit 13 when the input current detected by the current detection unit 12 is less than or equal to a preset current threshold, and send the state control signal to the driving unit 15; the driving unit 15 is further configured to control the switching state of each switching unit in the bridge circuit 20 and the pulse width of each switching unit when the switching unit is turned on according to the received state control signal.
In other embodiments, the control module 10 further comprises a bus voltage detection unit 16, wherein the bus voltage detection unit 16 is electrically connected to the input terminal of the load for detecting the bus voltage of the load. The bus voltage detection unit 16 is electrically connected to the control unit 11, the control unit 11 is further configured to send a turn-off control signal to the driving unit 15 when the detected bus voltage of the load is outside a preset range, and the driving unit 15 is configured to control each switch unit in the bridge circuit 20 to turn off according to the received turn-off control signal, so as to implement overvoltage/undervoltage protection of the medium load of the totem-pole PFC circuit.
In the totem pole PFC circuit provided in this embodiment, when the input current at the input end of the bridge circuit 20 is less than or equal to the preset current threshold, the control module 10 controls the switching state of each switch unit and the pulse width of each switch unit when the switch unit is turned on according to the input voltage and the input current at the input end of the bridge circuit 20, so that the switching frequency of each switch unit is reduced, and simultaneously, a proper pulse width is selected for each switch unit according to the input voltage and the input current, so that the switching frequency is reduced on the premise that the current harmonic requirement of the totem pole PFC circuit is met and the power factor of the totem pole PFC circuit is improved, thereby reducing the frequency of the short-circuit current flowing through the totem pole PFC circuit, reducing the switching loss while reducing the useless power in the circuit, and improving the efficiency of the totem pole PFC circuit.
The invention further provides a pulse width control method, and referring to fig. 3, fig. 3 is a schematic flow chart of a first embodiment of the pulse width control method of the invention.
In the present embodiment, the pulse width control method is applied to the totem-pole PFC circuit of the above-described embodiment.
The pulse width control method comprises the following steps:
step S100, when the input current of the input end of the bridge circuit is smaller than or equal to a preset current threshold, determining whether positive and negative switching exists in the input voltage of the input end of the bridge circuit at present;
in this embodiment, the control module of the totem pole PFC circuit may acquire the input current at the input end of the bridge circuit in real time, and when the input current at the input end of the bridge circuit is acquired, the control module determines whether the input current at the input end of the bridge circuit is greater than a preset current threshold, and if the input current at the input end of the bridge circuit is less than or equal to the preset current threshold, determines whether positive and negative switching currently exists in the input voltage at the input end of the bridge circuit.
Specifically, if the control module includes a driving protection unit and a driving unit, the input current at the input end of the bridge circuit can be collected in real time through the driving protection unit. When the input current at the input end of the bridge circuit is smaller than or equal to the preset current threshold, the input voltage (namely, the alternating current power supply voltage Vs) detected by the alternating current voltage detection unit is acquired in real time, and whether the alternating current power supply voltage Vs is switched between positive and negative (namely, whether the zero crossing is achieved) is judged.
Step S200, when the input voltage has positive and negative switching currently, determining whether the input voltage of the input end is in a positive half period after the positive and negative switching;
in this embodiment, when there is positive and negative switching of the input voltage, it is determined whether the input voltage at the input terminal after the positive and negative switching is in a positive half period, that is, it is determined whether the currently detected input voltage at the input terminal is greater than 0V, when the input voltage is greater than 0V, the input voltage at the input terminal after the positive and negative switching is in the positive half period, otherwise, the input voltage at the input terminal after the positive and negative switching is in the negative half period.
Step S300, when the input voltage of the input terminal is in a positive half cycle after the positive and negative switching, controlling the first switching unit Q1, the second switching unit Q2 and the third switching unit Q3 to turn off, controlling the fourth switching unit Q4 to turn on, and controlling the second switching unit Q2, the first switching unit Q1 to turn on/off alternately and the pulse width of the second switching unit Q2 when the second switching unit Q2 is turned on based on the number of pulse changes, the pulse time interval and the input current of the input terminal;
in step S400, when the input voltage at the input terminal is in a negative half cycle after the positive and negative switching, the first switch unit Q1, the second switch unit Q2 and the fourth switch unit Q4 are controlled to be turned off, the third switch unit Q3 is controlled to be turned on, and the first switch unit Q1, the second switch unit Q2 are controlled to be alternately turned on/off and the pulse width of the first switch unit Q1 when the input voltage is on is controlled based on the number of pulse changes, the pulse time interval and the input current at the input terminal.
Here, the number of pulse changes, which may be the number of changes from off to on of the first and second switching units Q1 and Q2 or the number of changes from on to off, and the pulse time interval may be stored in advance. When the input voltage of the input end is in a positive half period after the positive and negative switching, the pulse time interval refers to the time interval from the turn-off moment to the turn-on moment of the second switching unit Q2; when the input voltage of the input end is in a negative half cycle after the positive and negative switching, the pulse time interval refers to the time interval from the turn-off moment to the turn-on moment of the first switching unit Q1; the number of the pulse time intervals is consistent with the pulse change times.
For example, when the number of pulse changes is 2, the pulse time interval includes a first time interval and a second time interval. If the input voltage of the input terminal is in a positive half cycle after the positive and negative switching, the control module controls the first switch unit Q1 to be turned off, the second switch unit Q2 to be turned off, the third switch unit Q3 to be turned off, and the fourth switch unit Q4 to be turned on, calculates a pulse width (high level duration) according to the input current of the input terminal in a first time interval, controls the second switch unit Q2 to be turned on in the pulse width when the on duration of the fourth switch unit Q4 reaches the first time interval, controls the first switch unit Q1 to be turned on and the second switch unit Q2 to be turned off in a second time interval when the on duration of the second switch unit Q2 reaches the pulse width, and controls the second switch unit Q2 to be turned on, the second switch unit Q2 to be turned on and the second switch unit Q6754 to be turned on when the on duration of the first switch unit Q1 reaches the second time interval, The first switch unit Q1 is turned off, then when the on duration of the second switch unit Q2 reaches another pulse width, the first switch unit Q1 is controlled to be turned on, the second switch unit Q2 is controlled to be turned off, then the current input current of the input end is monitored in real time, and when the current input current of the input end is detected to reach 0 and is reduced to 0, the first switch unit Q1 is controlled to be turned off.
If the input voltage of the input end is in a negative half-cycle after the positive and negative switching, the control module controls the first switch unit Q1 to be turned off, the second switch unit Q2 to be turned off, the fourth switch unit Q4 to be turned off, and the third switch unit Q3 to be turned on, calculates a pulse width (high level duration) according to the input current of the input end in a first time interval, controls the first switch unit Q1 to be turned on in the pulse width when the on duration of the third switch unit Q3 reaches the first time interval, controls the second switch unit Q2 to be turned on and the first switch unit Q1 to be turned off in a second time interval when the on duration of the first switch unit Q1 reaches the pulse width, controls the first switch unit Q1 to be turned on and the second switch unit Q1 to be turned on when the on duration of the second switch unit Q2 reaches the second time interval, The second switching unit Q2 is turned off, then when the on duration of the first switching unit Q1 reaches another pulse width, the second switching unit Q2 is controlled to be turned on, the first switching unit Q1 is controlled to be turned off, then the current input current of the input end is monitored in real time, and when the current input current of the input end is detected to reach 0, namely, the current input current is reduced to 0, the second switching unit Q2 is controlled to be turned off.
When the input voltage at the input end is in a positive half cycle after positive and negative switching, the third switching unit Q3 is turned off, the fourth switching unit Q4 is turned off, if the second switching unit Q2 is turned on and the first switching unit Q1 is turned off, the totem-pole PFC circuit performs the operation of improving the power factor, the circuit current is (the input current at the input end of the bridge circuit) flowing through the totem-pole PFC circuit is a short-circuit current, and the short-circuit current sequentially flows through the alternating current power supply-reactor L-the second switching unit Q2-the fourth switching unit Q4-the alternating current power supply, and the reactor L accumulates energy through the short-circuit current. Accordingly, when the input voltage at the input terminal is in a negative half cycle after the positive and negative switching, the third switching unit Q3 is turned on, the fourth switching unit Q4 is turned off, and if the second switching unit Q2 is turned off and the first switching unit Q1 is turned on, the totem-pole PFC circuit performs the operation of improving the power factor, the circuit current is (the input current at the input terminal of the bridge circuit) flowing through the totem-pole PFC circuit is a short-circuit current, and the short-circuit current sequentially flows through the ac power supply-the third switching unit Q3-the first switching unit Q1-the reactor L-the ac power supply, and the reactor L accumulates energy through the short-circuit current.
When the input voltage at the input end is in a positive half cycle after the positive and negative switching, the third switching unit Q3 is turned off and the fourth switching unit Q4 is turned on, and when the second switching unit Q2 is turned off and the first switching unit Q1 is turned on, the totem-pole PFC circuit performs a synchronous rectification operation, and a circuit current is (input current at the input end of the bridge circuit) flows through a current path in the totem-pole PFC circuit in the order of the ac power source-reactor L-first switching unit Q1-bus capacitor C-fourth switching unit Q4-the ac power source, releases the energy stored in the reactor L to the bus capacitor C, and boosts the dc voltage of the bus capacitor C. Accordingly, when the input voltage at the input terminal is in the negative half cycle after the positive and negative switching, the third switching unit Q3 is turned on and the fourth switching unit Q4 is turned off, and when the second switching unit Q2 is turned on and the first switching unit Q1 is turned off, the totem-pole PFC circuit performs a synchronous rectification operation, and a circuit current is (input current at the input terminal of the bridge circuit) flows through a current path in the totem-pole PFC circuit in the order of the ac power source-the third switching unit Q3-the bus capacitor C-the second switching unit Q2-the ac power source, and releases the energy accumulated in the reactor L to the bus capacitor C, thereby boosting the dc voltage of the bus capacitor C.
The short-circuit current can reduce distortion of the current waveform, make the current waveform approach a sine wave, improve the power factor of the totem-pole PFC circuit, and suppress harmonics accompanying the harmonic current. In addition, the pulse width of the second switch unit Q2 or the first switch unit Q1 is calculated according to the bus voltage of the load, so that the duration of the short-circuit current in the totem-pole PFC circuit can be reasonably adjusted, the on/off times of each switch can be reasonably controlled according to the pulse change times, the on loss of the switch units can be reduced, the switch loss is reduced, and the efficiency is improved.
For example, in the case where the load is a compressor of an air conditioner, the compressor is hard to drive as the induced voltage of the compressor increases with an increase in the rotation speed, but the allowable limit of the rotation speed of the motor can be increased by alternately performing the above-described "power factor improvement operation" and "synchronous rectification operation" to perform the boosting.
It should be noted that, when the pulse variation times is other preset values, the control processes of step S300 and step S400 are similar to the control process when the pulse variation times is 2, and are not described herein again.
Further, in another embodiment, the pulse width control method further includes: when the input current of the input end of the bridge circuit is larger than a preset current threshold, the first switching unit Q1, the second switching unit Q2, the third switching unit Q3 and the fourth switching unit Q4 are respectively controlled to be turned off.
In this embodiment, in the operating process of the totem pole PFC circuit, the control module may obtain an input current at the input end of the sampling bridge circuit in real time, and determine whether the obtained current of the input current at the input end of the bridge circuit is greater than a preset current threshold, where when the input current at the input end of the bridge circuit is greater than the preset current threshold, the control module controls each switch unit in the bridge circuit to be turned off, so as to implement the overcurrent protection of the totem pole PFC circuit.
Further, in another embodiment, the pulse width control method further includes: the method comprises the steps of detecting the bus voltage of a load in real time, and controlling each switch unit in a bridge circuit to be turned off when the detected bus voltage of the load is out of a preset range, namely controlling the first switch unit Q1, the second switch unit Q2, the third switch unit Q3 and the fourth switch unit Q4 to be turned off respectively, so that overvoltage/undervoltage protection of a middle load of a totem-pole PFC circuit is realized.
The pulse width control method proposed in this embodiment determines whether there is positive-negative switching currently in the input voltage at the input terminal of the bridge circuit when the input current at the input terminal of the bridge circuit is less than or equal to a preset current threshold, then determines whether the input voltage at the input terminal after the positive-negative switching currently exists in a positive half period, then controls the first switching unit Q1, the second switching unit Q2 and the third switching unit Q3 to turn off and controls the fourth switching unit Q4 to turn on when the input voltage at the input terminal after the positive-negative switching currently exists in a positive half period, and controls the second switching unit Q2, the first switching unit Q1 to turn on/off alternately and the pulse width when the second switching unit Q2 is on based on the number of pulse changes, the pulse time interval and the input current at the input terminal, or when the input voltage at the input terminal after the positive-negative switching is in a negative half period, controlling the first, second and fourth switching units Q1, Q2 and Q4 to be turned off, and controlling the third switching unit Q3 to be turned on, and controlling the first and second switching units Q1 and Q2 to be alternately turned on/off and a pulse width at which the first switching unit Q1 is turned on, based on the number of pulse changes, a pulse time interval and an input current of the input terminal; by calculating the pulse width of the second switch unit Q2 or the first switch unit Q1 according to the input current of the input terminal, the duration of the short-circuit current in the totem-pole PFC circuit can be reasonably adjusted, the power factor of the totem-pole PFC circuit can be improved, higher harmonics accompanying the higher harmonic current can be suppressed, the number of times of on/off of each switch can be reasonably controlled according to the pulse change number, the number of times of flowing the short-circuit current can be reduced, the improvement of the power factor and the switching loss in the totem-pole PFC circuit can be reasonably considered, the switching loss can be reduced while the useless power in the circuit is reduced, and the efficiency of the totem-pole PFC circuit can be improved.
Based on the first embodiment, a second embodiment of the pulse width control method of the present invention is proposed, and referring to fig. 4, in this embodiment, the number of pulse changes is 3, and the pulse time interval includes a first preset time length, a second preset time length, and a third preset time length. The first preset time, the second preset time and the third preset time can be reasonably set according to the requirements of the totem-pole PFC circuit.
Step S300 comprises;
step S310, calculating a first pulse width based on a first input current of the input end within a first preset time length;
in this embodiment, when the first switch unit Q1, the second switch unit Q2, and the third switch unit Q3 are controlled to be turned off, and the fourth switch unit Q4 is controlled to be turned on, a first input current at the input end within a first preset time period is obtained, and then a first pulse width is calculated according to the first input current, where the first input current is obtained by randomly sampling the input current at the input end within the first preset time period, or a plurality of sampling times are set within the first preset time period, so as to obtain input currents corresponding to the plurality of sampling times, and then an average value of the input currents corresponding to the plurality of sampling times is calculated, and the average value is used as the first input current.
Specifically, the step S310 includes: and obtaining a preset maximum pulse width corresponding to the first pulse width, a corresponding first preset current, a preset minimum pulse width and a corresponding second preset current, and calculating the first pulse width according to a linear interpolation algorithm based on the preset maximum pulse width, the first preset current, the preset minimum pulse width, the second preset current and the first input current.
The preset maximum pulse width corresponding to the first pulse width, the corresponding first preset current, the preset minimum pulse width, the corresponding second preset current and other parameters can be reasonably set according to the requirements of the PFC circuit in advance, when the first input current is obtained, the first pulse width is calculated according to a linear interpolation algorithm based on the first input current, and then the first pulse width of the second switch unit Q2 is reasonably set, so that the duration time of the short-circuit current in the totem-pole PFC circuit can be reasonably adjusted.
Step S320, when the on-time of the fourth switching unit Q4 reaches the first preset time, controlling the second switching unit Q2 to be turned on within the first pulse width;
in the present embodiment, by controlling the conduction of the second switching element Q2 in the first pulse width, the short-circuit current flows through the totem-pole PFC circuit, so that the distortion of the current waveform is reduced, the current waveform is brought close to a sine wave, the power factor of the totem-pole PFC circuit can be improved, and the harmonics accompanying the harmonic current can be suppressed.
Step S330, when the on-time of the second switch unit Q2 reaches the first pulse width, controlling the first switch unit Q1 to be turned on and the second switch unit Q2 to be turned off within the second preset time, and calculating a second pulse width based on a second input current at the input terminal within the second preset time;
in this embodiment, the second input current is collected in a manner similar to the first input current, and is not described herein again. A similar calculation as for the first pulse width may also be provided for the second pulse width. It should be noted that the parameters such as the preset maximum pulse width corresponding to the second pulse width, the preset current corresponding to the preset maximum pulse width, the preset minimum pulse width corresponding to the second pulse width, and the preset current corresponding to the preset minimum pulse width may be the same as the parameters of the first pulse width, or different parameters may be set according to the requirements of the totem-pole PFC circuit.
Step S340, when the on-time of the first switch unit Q1 reaches the second preset time, controlling the second switch unit Q2 to be turned on and the first switch unit Q1 to be turned off in the second pulse width;
in the present embodiment, the second switching unit Q2 is controlled to be turned on and the first switching unit Q1 is controlled to be turned off in the first pulse width, so that the short-circuit current flows through the totem-pole PFC circuit, thereby reducing distortion of the current waveform, making the current waveform approach a sine wave, improving the power factor of the totem-pole PFC circuit, and suppressing harmonics associated with harmonic currents.
Step S350, when the on-time of the second switch unit Q2 reaches the second pulse width, controlling the first switch unit Q1 to be turned on and the second switch unit Q2 to be turned off within the third preset time, and calculating a third pulse width based on a third input current at the input terminal within the third preset time;
in this embodiment, the third input current is collected in a manner similar to the first input current/the second input current, and is not described herein again. A similar calculation as the first/second pulse widths may also be provided for the third pulse width. It should be noted that the parameters such as the preset maximum pulse width corresponding to the third width, the preset current corresponding to the preset maximum pulse width, the preset minimum pulse width corresponding to the third pulse width, and the preset current corresponding to the preset minimum pulse width may be the same as the parameters of the first pulse width/the second pulse width, or different parameters may be set according to the requirements of the totem-pole PFC circuit.
Step S360, when the on-time of the first switch unit Q1 reaches the third preset time, controlling the second switch unit Q2 to be turned on and the first switch unit Q1 to be turned off in the third pulse width;
in the present embodiment, the second switching unit Q2 is turned on and the first switching unit Q1 is turned off in the third pulse width, so that the short-circuit current flows through the totem-pole PFC circuit, thereby reducing distortion of the current waveform, making the current waveform approach a sine wave, improving the power factor of the totem-pole PFC circuit, and suppressing harmonics associated with harmonic currents.
In step S370, when the on-time of the second switch unit Q2 reaches the third pulse width, the first switch unit Q1 is controlled to be turned on, and the second switch unit Q2 is controlled to be turned off.
Referring to fig. 5, fig. 5 Is a schematic diagram illustrating an ac power voltage Vs, a circuit current Is, and time variations of driving pulses of the switching units Q1 to Q4, in fig. 5, T1, T2, and T3 are respectively a first preset duration, a second preset duration, and a third preset duration, and D1, D2, and D3 are respectively a first pulse width, a second pulse width, and a third pulse width, and in a positive half-cycle of the ac voltage, the fourth switching unit Q4 Is turned on and the third switching unit Q3 Is turned off; after the voltage zero-crossing delay time T1, the second switching unit Q2 is turned on; after the second switching unit Q2 is turned on for a time D1, the second switching unit Q2 is turned off, and the first switching unit Q1 is turned on; after the first switching unit Q1 is turned on for a time T2, the first switching unit Q1 is turned off, and the second switching unit Q2 is turned on; after the second switching unit Q2 is turned on for a time D2, the second switching unit Q2 is turned off, and the first switching unit Q1 is turned on; after the first switching unit Q1 is turned on for a time T3, the first switching unit Q1 is turned off, the second switching unit Q2 is turned on, and after a time D3, the second switching unit Q2 is turned off, and the first switching unit Q1 is turned on. In this way, Q1 and Q2 are alternately turned on/off 3 times, wherein the input current Is (circuit current) of the totem-pole PFC circuit rises when the second switching unit Q2 Is turned on, and falls when the first switching unit Q1 Is turned on.
Further, in an embodiment, after step S370, the method further includes: when the current input current of the input end is detected to reach 0, the first switch unit Q1 is controlled to be turned off.
Referring to fig. 5, turning off the first switching unit Q1 before the end of the positive half cycle of the ac voltage can prevent a reverse current from flowing through the bus capacitor C.
According to the pulse width control method provided by the embodiment, the first pulse width, the second pulse width and the third pulse width are calculated based on the first input current, the second input current and the third input current, the second switch unit Q2 is controlled to be switched on and the first switch unit Q1 is controlled to be switched off respectively in the first pulse width, the second pulse width and the third pulse width, so that short-circuit currents with different duration time lengths flow through the totem-pole PFC circuit respectively in the first pulse width, the second pulse width and the third pulse width, the duration time of the short-circuit current in the totem-pole PFC circuit can be reasonably adjusted, the distortion of a current waveform can be reduced, the power factor of the totem-pole PFC circuit can be improved, higher harmonics of currents accompanied with the higher harmonics can be suppressed, the switching loss is reduced according to the number of pulse changes, the efficiency is improved, and meanwhile, the power factor of the totem-pole PFC circuit.
Based on the second embodiment, a third embodiment of the pulse width control method of the present invention is proposed, and referring to fig. 6, in this embodiment, step S400 includes;
step S410, calculating a fourth pulse width based on a fourth input current of the input end within a first preset time length;
step S420, when the on-time of the fourth switching unit Q4 reaches the first preset time, controlling the first switching unit Q1 to be turned on within the fourth pulse width;
step S430, when the on-time of the first switch unit Q1 reaches the fourth pulse width, controlling the second switch unit Q2 to be turned on and the first switch unit Q1 to be turned off within the second preset time, and calculating a fifth pulse width based on a fifth input current at the input terminal within the second preset time;
step S440, when the on-time of the second switch unit Q2 reaches the fifth preset time, controlling the first switch unit Q1 to be turned on and the second switch unit Q2 to be turned off in the fifth pulse width;
step S450, when the on-time of the first switch unit Q1 reaches the fifth pulse width, controlling the second switch unit Q2 to be turned on and the first switch unit Q1 to be turned off within the third preset time, and calculating a sixth pulse width based on a sixth input current at the input terminal within the third preset time;
step S460, when the on-time of the second switch unit Q2 reaches the third preset time, controlling the first switch unit Q1 to be turned on and the second switch unit Q2 to be turned off in the sixth pulse width;
in step S470, when the on-time of the first switch unit Q1 reaches the sixth pulse width, the second switch unit Q2 is controlled to be turned on, and the first switch unit Q1 is controlled to be turned off.
In this embodiment, the fourth/fifth/sixth input current is collected in a manner similar to the first/second/third input current, and is not described herein again. A similar calculation as the first/second/third pulse width may be set for the fourth/fifth/sixth pulse width. It should be noted that the parameters such as the preset maximum pulse width corresponding to the fourth/fifth/sixth pulse width, the preset current corresponding to the preset maximum pulse width, the preset minimum pulse width corresponding to the fourth/fifth/sixth pulse width, and the preset current corresponding to the preset minimum pulse width may be the same as the parameters of the first/second/third pulse width, or different parameters may be set according to the requirements of the totem pole PFC circuit.
In this embodiment, the first switch unit Q1 is controlled to be turned on and the second switch unit Q2 is controlled to be turned off in the fourth pulse width/the fifth pulse width/the sixth pulse width, so that the short-circuit current flows through the totem-pole PFC circuit, the duration of the short-circuit current in the totem-pole PFC circuit can be reasonably adjusted, and the power factor of the totem-pole PFC circuit can be improved.
Referring to fig. 5, in a negative half cycle of the ac voltage, the fourth switching unit Q4 is turned off and the third switching unit Q3 is turned on; after the voltage zero-crossing delay time T1, the first switching unit Q1 is turned on; after the first switch unit Q1 is turned on for a time D1, the second switch unit Q2 is turned on, and the first switch unit Q1 is turned off; after the second switching unit Q2 is turned on for a time T2, the second switching unit Q2 is turned off, and the first switching unit Q1 is turned on; after the first switching unit Q1 is turned on for a time D2, the first switching unit Q1 is turned off, and the second switching unit Q2 is turned on; after the second switching unit Q2 is turned on for a time T3, the second switching unit Q2 is turned off, the first switching unit Q1 is turned on, and after a time D3, the first switching unit Q1 and the second switching unit Q2 are turned on. In this way, Q1 and Q2 are alternately turned on/off 3 times, wherein the input current Is (circuit current) of the totem-pole PFC circuit rises when the second switching unit Q2 Is turned on, and falls when the first switching unit Q1 Is turned on.
Further, in an embodiment, after step S470, the method further includes: and when the current input current of the input end is detected to reach 0, the second switch unit Q2 is controlled to be turned off.
Referring to fig. 5, turning off the second switching unit Q2 before the end of the negative half cycle of the alternating voltage can prevent a reverse current from flowing through the bus capacitor C.
According to the pulse width control method provided by the embodiment, the first switch unit Q1 is controlled to be switched on and the second switch unit Q2 is controlled to be switched off respectively in the first pulse width, the fifth pulse width and the sixth pulse width by the fourth pulse width, the fifth pulse width and the sixth pulse width which are calculated based on the fourth input current, the fifth input current and the third input current, so that short-circuit currents with different durations flow through the totem-pole PFC circuit in the fourth pulse width, the fifth pulse width and the sixth pulse width respectively, the duration of the short-circuit current in the totem-pole PFC circuit can be reasonably adjusted, the distortion of the current waveform can be reduced, the power factor of the totem-pole PFC circuit can be improved, higher harmonics accompanying with the higher harmonic current can be suppressed, the switching loss is reduced according to the number of pulse changes, the efficiency is improved, and meanwhile, the power factor of the totem-pole PFC circuit is reasonably considered.
In addition, an embodiment of the present invention further provides a storage medium, namely a computer-readable storage medium, where a pulse width control program is stored, and the pulse width control program, when executed by a processor, implements the steps of the pulse width control method.
It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or system. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or system that comprises the element.
The above-mentioned serial numbers of the embodiments of the present invention are merely for description and do not represent the merits of the embodiments.
Through the above description of the embodiments, those skilled in the art will clearly understand that the method of the above embodiments can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware, but in many cases, the former is a better implementation manner. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which is stored in a storage medium (e.g., ROM/RAM, magnetic disk, optical disk) as described above and includes instructions for enabling a terminal device (e.g., a mobile phone, a computer, a server, an air conditioner, or a network device) to execute the method according to the embodiments of the present invention.
The above description is only a preferred embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by using the contents of the present specification and the accompanying drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.

Claims (13)

1. A totem-pole PFC circuit, comprising:
the bridge circuit is provided with a plurality of switch units connected in a bridge shape, the input end of the bridge circuit is connected with an alternating current power supply, and the output end of the bridge circuit is connected with a load;
a reactor provided between the bridge circuit and the alternating-current power supply;
the bus capacitor is connected with the load in parallel and then is electrically connected with the output end of the bridge circuit;
the control module is used for controlling each switch unit in the bridge circuit to be switched off when the input current of the input end of the bridge circuit is greater than a preset current threshold; when the input current of the input end of the bridge circuit is less than or equal to a preset current threshold, controlling the switching state of each switching unit and the pulse width of each switching unit when the switching unit is conducted according to the input voltage and the input current of the input end of the bridge circuit;
the bridge circuit comprises a first switch unit, a second switch unit, a third switch unit and a fourth switch unit;
the control module is further configured to control the first switch unit, the second switch unit, and the third switch unit to turn off and control the fourth switch unit to turn on when the input voltage at the input terminal is in a positive half-cycle after the positive and negative switching, and control the second switch unit, the first switch unit to turn on/off alternately and control the pulse width of the second switch unit when the second switch unit is turned on based on the number of pulse changes, the pulse time interval, and the input current at the input terminal.
2. The totem pole PFC circuit of claim 1,
the first switching unit and the second switching unit are connected in series to form a first branch circuit, the third switching unit and the fourth switching unit are connected in series to form a second branch circuit, and the first branch circuit and the second branch circuit are connected in parallel to form the bridge circuit;
a connection point of the first switching unit and the second switching unit is electrically connected to the ac power supply via the reactor; the connection point of the third switch unit and the fourth switch unit is electrically connected with the alternating current power supply;
the connection point of the first switch unit and the third switch unit is electrically connected with the positive electrode of the bus capacitor; and the connecting point of the second switch unit and the fourth switch unit is electrically connected with the negative electrode of the bus capacitor.
3. The totem-pole PFC circuit of claim 1, wherein the control module comprises:
the current detection unit is electrically connected with the input end of the bridge circuit and is used for detecting the input current of the input end of the bridge circuit;
the alternating voltage detection unit is electrically connected with the input end of the bridge circuit and is used for detecting the input voltage of the input end of the bridge circuit;
the control unit is respectively electrically connected with the current detection unit and the alternating voltage detection unit and is used for controlling the switching state of each switching unit and the pulse width of each switching unit when the switching unit is switched on according to the input current detected by the current detection unit and the input voltage detected by the alternating voltage detection unit when the input current detected by the current detection unit is less than or equal to a preset current threshold value.
4. The totem-pole PFC circuit of claim 3, wherein the control module further comprises: a drive protection unit and a drive unit;
the driving protection unit is respectively electrically connected with the current detection unit and the driving unit and is used for sending a turn-off control signal to the driving unit when the input current detected by the current detection unit is greater than a preset current threshold;
the driving unit is used for controlling each switch unit in the bridge circuit to be switched off according to the received switching-off control signal;
the control unit is further used for generating a state control signal according to the input current detected by the current detection unit and the input voltage detected by the alternating voltage detection unit when the input current detected by the current detection unit is smaller than or equal to a preset current threshold value, and sending the state control signal to the driving unit;
the driving unit is further used for controlling the switching state of each switching unit in the bridge circuit and the pulse width of each switching unit when the switching unit is conducted according to the received state control signal.
5. A pulse width control method applied to the totem-pole PFC circuit of claim 2, the pulse width control method comprising the steps of:
when the input current of the input end of the bridge circuit is smaller than or equal to a preset current threshold, determining whether positive and negative switching exists in the input voltage of the input end of the bridge circuit at present;
when the input voltage has positive and negative switching currently, determining whether the input voltage of the input end is in a positive half period after the positive and negative switching;
when the input voltage of the input end is in a positive half period after positive and negative switching, the first switch unit, the second switch unit and the third switch unit are controlled to be turned off, the fourth switch unit is controlled to be turned on, and the second switch unit, the first switch unit and the pulse width of the second switch unit are controlled to be alternately turned on/off and turned on based on the pulse change times, the pulse time interval and the input current of the input end;
and when the input voltage of the input end is in a negative half period after the positive and negative switching, the first switch unit, the second switch unit and the fourth switch unit are controlled to be turned off, the third switch unit is controlled to be turned on, and the first switch unit, the second switch unit and the pulse width of the first switch unit are controlled to be alternately turned on/off and turned on based on the pulse change times, the pulse time interval and the input current of the input end.
6. The pulse width control method of claim 5, wherein the number of pulse variations is 3, and the pulse time interval includes a first preset time period, a second preset time period, and a third preset time period; the step of controlling the second switching unit, the first switching unit to be alternately turned on/off based on the number of pulse changes, the pulse time interval, and the input current of the input terminal, and the pulse width at which the second switching unit is turned on includes:
calculating a first pulse width based on a first input current of the input end within a first preset time length;
when the conduction time of the fourth switch unit reaches the first preset time, controlling the second switch unit to be conducted in the first pulse width;
when the on-time of the second switch unit reaches the first pulse width, controlling the first switch unit to be on and the second switch unit to be off within a second preset time, and calculating a second pulse width based on a second input current of the input end within the second preset time;
when the on-time of the first switch unit reaches the second preset time, controlling the second switch unit to be on and the first switch unit to be off in the second pulse width;
when the on-time of the second switch unit reaches the second pulse width, controlling the first switch unit to be on and the second switch unit to be off within a third preset time, and calculating a third pulse width based on a third input current of the input end within the third preset time;
when the conducting time of the first switch unit reaches the third preset time, controlling the second switch unit to be conducted and the first switch unit to be switched off in the third pulse width;
and when the on-time of the second switch unit reaches the third pulse width, controlling the first switch unit to be on and the second switch unit to be off.
7. The pulse width control method of claim 6, wherein the step of calculating the first pulse width based on the first input current at the input terminal for the first predetermined duration comprises:
and obtaining a preset maximum pulse width corresponding to the first pulse width, a corresponding first preset current, a preset minimum pulse width and a corresponding second preset current, and calculating the first pulse width according to a linear interpolation algorithm based on the preset maximum pulse width, the first preset current, the preset minimum pulse width, the second preset current and the first input current.
8. The pulse width control method according to claim 6, wherein after the step of controlling the first switching unit to be turned on and the second switching unit to be turned off when the on-period of the second switching unit reaches the third pulse width, the method further comprises:
and when detecting that the current input current of the input end reaches 0, controlling the first switch unit to be switched off.
9. The pulse width control method according to claim 6, wherein the step of controlling the first switching unit, the second switching unit to be alternately turned on/off based on the number of pulse changes, the pulse time interval, and the input current of the input terminal, and the pulse width at which the first switching unit is turned on includes:
calculating a fourth pulse width based on a fourth input current of the input terminal within a first preset time period;
when the conducting time of the fourth switching unit reaches the first preset time, controlling the first switching unit to be conducted in the fourth pulse width;
when the on-time of the first switch unit reaches the fourth pulse width, controlling the second switch unit to be on and the first switch unit to be off within a second preset time, and calculating a fifth pulse width based on a fifth input current of the input end within the second preset time;
when the on-time of the second switch unit reaches a fifth preset time, controlling the first switch unit to be on and the second switch unit to be off in the fifth pulse width;
when the on-time of the first switch unit reaches the fifth pulse width, controlling the second switch unit to be on and the first switch unit to be off within a third preset time, and calculating a sixth pulse width based on a sixth input current of the input end within the third preset time;
when the on-time of the second switch unit reaches the third preset time, controlling the first switch unit to be on and the second switch unit to be off in the sixth pulse width;
and when the on-time of the first switch unit reaches the sixth pulse width, controlling the second switch unit to be switched on and the first switch unit to be switched off.
10. The pulse width control method according to claim 9, wherein after the step of controlling the second switching unit to be turned on and the first switching unit to be turned off when the on-period of the first switching unit reaches the sixth pulse width, the method further comprises:
and when the current input current of the input end is detected to reach 0, controlling the second switch unit to be switched off.
11. The pulse width control method according to any one of claims 5 to 10, further comprising:
and when the input current of the input end of the bridge circuit is greater than a preset current threshold value, the first switch unit, the second switch unit, the third switch unit and the fourth switch unit are respectively controlled to be turned off.
12. An air conditioner, characterized in that the air conditioner comprises: the totem pole PFC circuit of claim 2, a memory, a processor, and a pulse width control program stored on the memory and executable on the processor, the pulse width control program when executed by the processor implementing the steps of the pulse width control method of any one of claims 5 to 11.
13. A storage medium, characterized in that the storage medium has stored thereon a pulse width control program which, when executed by a processor, implements the steps of the pulse width control method according to any one of claims 5 to 11.
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