CN110417251B - PFC circuit and air conditioner - Google Patents
PFC circuit and air conditioner Download PDFInfo
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- CN110417251B CN110417251B CN201910618776.2A CN201910618776A CN110417251B CN 110417251 B CN110417251 B CN 110417251B CN 201910618776 A CN201910618776 A CN 201910618776A CN 110417251 B CN110417251 B CN 110417251B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
- H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
- H02H7/125—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for rectifiers
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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
- H02M1/4258—Arrangements for improving power factor of AC input using a single converter stage both for correction of AC input power factor and generation of a regulated and galvanically isolated DC output voltage
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- 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
Abstract
The invention discloses a PFC circuit and an air conditioner, wherein the PFC circuit comprises: a reactor; a rectifying circuit; the PFC driving circuit outputs a corresponding PFC driving signal according to the received control signal; the PFC switch circuit outputs the power supply accessed by the first input/output end to the second input/output end according to the PFC driving signal, or outputs the power supply accessed by the second input/output end to the first input/output end; the detection end of the overcurrent protection circuit is connected with the second input/output end of the PFC switch circuit, and the output end of the overcurrent protection circuit is connected with the PFC drive circuit; and the overcurrent protection circuit controls the PFC driving circuit to stop outputting the PFC driving signal when detecting that the current flowing through the PFC switching circuit reaches a preset current threshold value. The invention improves the reliability of the PFC circuit and solves the problems of large loss and low energy efficiency of the PFC circuit.
Description
Technical Field
The invention relates to the technical field of PFC circuits, in particular to a PFC circuit and an air conditioner.
Background
A Power Factor Correction (PFC) circuit is generally introduced into existing electronic Power equipment, so that on one hand, the utilization rate of a Power supply to mains supply can be improved when alternating current is converted into direct current through the PFC circuit, and the electric energy loss in the conversion process is reduced, so that energy can be saved; on the other hand, harmonic pollution in the power grid can be reduced through the PFC circuit.
At present, a PFC circuit generally adopts a bridge stack to convert alternating current into direct current, and then adopts a BOOST circuit to BOOST, so as to realize power factor correction, however, the bridge stack has a large volume and large on-state loss, which easily causes large loss and low energy efficiency of the PFC circuit. In addition, the PFC circuit does not provide a protection method for key devices, such as a switching tube, and the like, and thus has a high damage rate, which also has a certain influence on the reliability of the operation of an electronic product using the PFC circuit.
Disclosure of Invention
The invention mainly aims to provide a PFC circuit and an air conditioner, aiming at reducing the power consumption of the PFC circuit and improving the reliability of the PFC circuit.
In order to achieve the above object, the present invention provides a PFC circuit, including:
one end of the reactor is connected with a live wire end of an alternating current power supply;
the input end of the rectifying circuit is connected with the other end of the reactor;
the PFC driving circuit outputs a corresponding PFC driving signal according to the received control signal;
the controlled end of the PFC switch circuit is connected with the output end of the PFC driving circuit, and the first input/output end of the PFC switch circuit is connected with the other end of the reactor; a second input/output end of the PFC switch circuit is connected with a zero line end of the alternating current power supply; the PFC switch circuit outputs the power supply accessed by the first input/output end to the second input/output end according to the PFC driving signal, or outputs the power supply accessed by the second input/output end to the first input/output end;
the detection end of the over-current protection circuit is connected with the second input/output end of the PFC switch circuit, and the output end of the over-current protection circuit is connected with the PFC drive circuit; and the overcurrent protection circuit controls the PFC driving circuit to stop outputting the PFC driving signal when detecting that the current flowing through the PFC switching circuit reaches a preset current threshold value.
Optionally, the PFC driving circuit includes a first driving switch, a first resistor, a second resistor, and a signal isolation device, where a first end of the first resistor is a controlled end of the PFC driving circuit, and a second end of the first resistor is interconnected with the controlled end of the first driving switch and a first end of the second resistor; the input end of the first driving switch and the second end of the second resistor are connected with a first direct current power supply, the output end of the first driving switch is connected with the input end of the signal isolation device, and the output end of the signal isolation device is the output end of the PFC driving circuit.
Optionally, the PFC switch circuit includes a first switch tube and a first diode, a controlled end of the first switch tube is a controlled end of the FC switch circuit, an input end of the first switch tube is a first input/output end of the PFC switch circuit, an output end of the first switch tube is connected to an anode of the first diode, and a cathode of the first diode is a second input/output end of the PFC switch circuit.
Optionally, the PFC switch circuit includes a second switch tube and a second diode, a controlled end of the second switch tube is a controlled end of the FC switch circuit, an anode of the second diode is a first input/output end of the PFC switch circuit, and a cathode of the second diode is connected to an input end of the second switch tube; the output end of the second switch tube is a second input/output end of the PFC switch circuit.
Optionally, the PFC switch circuit includes a third switch tube and a fourth switch tube, a controlled end of the third switch tube and a controlled end of the fourth switch tube are connected to the output end of the PFC driver circuit, a first conductive end of the third switch tube is a first input/output end of the PFC switch circuit, a second conductive end of the third switch tube is connected to a first conductive end of the fourth switch tube, and a second conductive end of the fourth switch tube is a second input/output end of the PFC switch circuit.
Optionally, the PFC switch circuit further includes a third diode and a fourth diode, an anode of the third diode is connected to the first conductive terminal of the fourth switch tube, and a cathode of the third diode is connected to the reactor; and the anode of the fourth diode is connected with the second conductive end of the third switching tube, and the cathode of the fourth diode is connected with the live wire end of the alternating current power supply.
Optionally, the over-current protection circuit includes a current detection unit and a comparison control unit, a detection end of the current detection unit is a detection end of the over-current protection circuit, an output end of the current detection unit is connected with a first input end of the comparison control unit, a second input end of the comparison control unit is connected to a reference current signal, and an output end of the comparison control unit is an output end of the over-current protection circuit; the comparison control unit is used for controlling the PFC driving circuit to stop outputting the PFC driving signal when the direct current signal is larger than the reference current signal.
Optionally, the current detection unit includes a transformer, an ac-dc converter, a third resistor, and a fourth resistor, one end of a primary coil of the transformer is connected to the second input/output end of the PFC switch circuit, and the other end of the primary coil of the transformer is grounded; two ends of the secondary side coil of the transformer are correspondingly connected with two input ends of the alternating current-direct current converter one by one; the first output end of the alternating current-direct current converter is connected with the first input end of the comparison control unit and the first end of the fourth resistor through the fourth resistor, and the second output end of the alternating current-direct current converter and the second end of the fourth resistor are both grounded.
Optionally, the comparison control circuit includes a comparator, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, and a second driving switch, an inverting input terminal of the comparator is the first input terminal of the comparison control unit, a non-inverting input terminal of the comparator is connected to a common terminal of the fifth resistor and the sixth resistor, and an output terminal of the comparator is connected to a first terminal of the seventh resistor; the first end of the fifth resistor is connected with a first direct-current power supply, and the second end of the fifth resistor is grounded through the sixth resistor; a second end of the seventh resistor is interconnected with a controlled end of the second drive switch and a first end of the eighth resistor; the input end of the second driving switch and the second end of the eighth resistor are both grounded, and the output end of the second driving switch is connected with the PFC driving circuit.
The invention also provides an air conditioner which comprises the PFC circuit.
The PFC circuit outputs a corresponding PFC driving signal according to a received PFC control signal to drive the PFC switch circuit to work, and accesses the AC power output by the reactor through the first input/output end and then outputs the AC power to the second input/output end according to the PFC driving signal, or outputs the AC power accessed by the second input/output end to the first input/output end and the reactor, so that the waveform of the input current of the PFC circuit follows the waveform of the input voltage, and the power factor correction of the accessed AC power is realized. The invention also controls the PFC driving circuit to stop outputting the PFC driving signal by setting the overcurrent protection circuit when detecting that the current flowing through the PFC switching circuit reaches the preset current threshold value, thereby controlling the PFC switching circuit to stop working. The overcurrent protection circuit can solve the problem that a switch device in the PFC switch circuit is damaged due to overcurrent, and improves the reliability of the PFC circuit. In addition, the invention does not need to arrange a rectifier bridge and corrects the power factor of the accessed alternating current power supply, thereby solving the problems of large size of a bridge stack, large on-state loss, easy loss of a PFC circuit and low energy efficiency.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
Fig. 1 is a schematic diagram of functional modules of a PFC circuit according to an embodiment of the present invention;
fig. 2 is a schematic circuit diagram of another embodiment of a PFC circuit according to the present invention;
fig. 3 is a schematic circuit diagram of a PFC circuit according to another embodiment of the present invention;
fig. 4 is a schematic circuit diagram of a PFC circuit according to another embodiment of the present invention.
The reference numbers illustrate:
| reference numerals | Name (R) | Reference numerals | Name (R) | |
| 10 | Rectifying circuit | U1 | |
|
| 20 | PFC drive circuit | U2 | |
|
| 30 | PFC switch circuit | U3 | Comparator with a |
|
| 40 | Overcurrent protection circuit | U4 | |
|
| 50 | Energy storage filter circuit | R1～R8 | First to |
|
| 41 | Current detection unit | | Transformer device | |
| 42 | Comparison control unit | Q1～Q4 | First to fourth switching tubes | |
| 411 | AC-DC converter | D1～D4 | First to fourth diodes | |
| L1 | Electric reactor |
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
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that, if directional indications (such as up, down, left, right, front, and back … …) are involved in the embodiment of the present invention, the directional indications are only used to explain the relative positional relationship between the components, the movement situation, and the like in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indications are changed accordingly.
In addition, if there is a description of "first", "second", etc. in an embodiment of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.
The invention provides a PFC circuit.
Referring to fig. 1, in an embodiment of the present invention, the PFC circuit includes:
a reactor L1, one end of the reactor L1 being connected to a live line terminal L of an ac power supply;
a rectifier circuit 10, an input end of which is connected to the other end of the reactor L1;
a PFC driving circuit 20 for outputting a corresponding PFC driving signal according to the received control signal;
a PFC switch circuit 30, a controlled terminal of the PFC switch circuit 30 being connected to the output terminal of the PFC drive circuit 20, and a first input/output terminal of the PFC switch circuit 30 being connected to the other terminal of the reactor L1; a second input/output end of the PFC switch circuit 30 is connected to a zero line end N of the ac power supply; the PFC switch circuit 30 outputs the power supply connected to the first input/output terminal to the second input/output terminal according to the PFC driving signal, or outputs the power supply connected to the second input/output terminal to the first input/output terminal;
the detection end of the over-current protection circuit 40 is connected with the second input/output end of the PFC switch circuit 30, and the output end of the over-current protection circuit 40 is connected with the PFC drive circuit 20; the over-current protection circuit 40 controls the PFC driving circuit 20 to stop outputting the PFC driving signal when detecting that the current flowing through the PFC switching circuit 30 reaches a preset current threshold.
In this embodiment, the reactor L1 and the PFC switch circuit 30 form a PFC main circuit, which may be a boost PFC circuit, a buck PFC circuit, or a boost PFC circuit, and this embodiment may be a low-frequency active boost PFC circuit. One end of the reactor L1 is connected to the live wire end of the ac input terminal, and the other end is connected to the rectifier circuit 10, and the live wire end of the ac input terminal is connected to the second input/output terminal of the PFC switch circuit 30, respectively. The PFC circuit may be applied to a switching power supply, a frequency converter, and other circuit modules, and correspondingly, the PFC circuit may be disposed on an electronic control board of the switching power supply or on an electronic control board provided with the frequency converter. The electric control board is also provided with a main controller MCU, the main controller MCU can be a main controller MCU for controlling the work of devices such as a compressor, a fan and the like in the outdoor unit of the air conditioner, or the main controller MCU is a main controller MCU specially used for the control of the PFC circuit, the main controller MCU drives the PFC circuit with low frequency in the power frequency period of the alternating current power supply, and the work frequency can be 1 time or a few times. The PFC driving circuit 20 in the PFC circuit outputs a corresponding PFC driving signal according to a PFC control signal output by the outdoor unit main controller MCU based on the control of the outdoor unit main controller MCU. The power supply voltage of the control chip on the electronic control board is usually 3.3V or 5V, the voltage of the output PFC control signal is also usually 3.3V or 5V, and the switching tube in the PFC circuit is usually set as a relay or a power tube, and requires a driving voltage of 9V, 12V or higher to drive, for this purpose, the PFC driving circuit 20 is set to amplify the received PFC control signal and output the amplified PFC control signal to the PFC switching circuit 30. Specifically, the main controller MCU may be a high-level pulse PFC control signal and a low-level pulse PFC control signal, and when receiving the high-level pulse PFC control signal, the PFC driving circuit 20 outputs a driving signal to drive the PFC switching circuit 30 to be turned on, and when receiving the low-level pulse PFC control signal, the PFC driving circuit 20 outputs a driving signal to drive the PFC switching circuit 30 to be turned off. Alternatively, when receiving the pulse PFC control signal of the low level, the PFC driving circuit 20 outputs a driving signal to drive the PFC switching circuit 30 to turn on, and when receiving the pulse PFC control signal of the high level, the PFC driving circuit 20 outputs a driving signal to drive the PFC switching circuit 30 to turn off.
Under the condition that the PFC switch circuit 30 is turned on, in the positive half cycle of the ac power supply, the ac power is supplied from the live line of the ac input terminal, is stored in the energy by the reactor L1, and is then output to the first input/output terminal of the PFC switch circuit 30 and then to the second input/output terminal of the PFC switch circuit 30; and during the negative half cycle of the alternating current power supply, the alternating current is accessed to the second input/output end of the PFC switch circuit 30 from the zero line of the alternating current input end, the first input/output end of the PFC switch circuit 30 is output to the reactor L1, and is output to the live wire of the alternating current input end after being stored with energy by the reactor L1. Or, during the positive half cycle of the ac power supply, the ac power is switched in from the live wire of the ac input terminal, stored in energy by the reactor L1, and then output to the first input/output terminal of the PFC switch circuit 30, and then output through the second input/output terminal of the PFC switch circuit 30; on the other hand, in the negative half cycle of the ac power supply, the PFC switching circuit 30 is turned off, so that the ac power supply is output to the rectifier circuit 10 through the reactor L1. Alternatively, the PFC switch circuit 30 is in an off state at the positive half cycle of the ac power supply; during the positive half cycle of the alternating current power supply, the alternating current is connected to the second input/output end of the PFC switch circuit 30 from the zero line of the alternating current input end, the first input/output end of the PFC switch circuit 30 is output to the reactor L1, and is output to the live wire of the alternating current input end after being stored with energy by the reactor L1. By the arrangement, power factor correction of the accessed alternating current power supply can be realized without a rectifier bridge, and the reduction of the power consumption of the PFC circuit is facilitated.
The rectifier circuit 10 may be implemented by two diodes connected in series in sequence, or may be implemented by four diodes, four diodes are taken as an example in the present embodiment, and the four diodes are respectively labeled as D41, D42, D43, and D44; after the two diodes D41, D42 are connected in series, they are connected in parallel with the other two diodes D43, D44 connected in series. The reactor L1 is connected to a common end of two groups of diodes connected in series, cathodes of the two groups of diodes D41 and D43 connected in parallel are connected to a dc bus, and anodes of the diodes D42 and D44 are connected to a zero line end of an ac input end.
In this embodiment, the over-current protection circuit 40 is configured to detect a current flowing through the switching circuit of the PFC switch circuit 30, when the current flowing through the PFC switch circuit 30 is detected to be smaller than a preset current threshold, the over-current protection circuit 40 does not operate, and when the current flowing through the PFC switch circuit 30 is detected to reach the preset current threshold, the PFC drive circuit 20 is controlled to stop outputting the PFC drive signal, so as to control the PFC switch circuit 30 to stop working. With this arrangement, when the current flowing through the PFC switch circuit 30 exceeds the threshold, the switch device in the PFC switch circuit 30 can be prevented from being damaged.
According to the PFC circuit, the PFC driving circuit 20 outputs a corresponding PFC driving signal according to a received PFC control signal so as to drive the PFC switch circuit 30 to work, and accesses the alternating current power output by the reactor L1 through the first input/output end according to the PFC driving signal and then outputs the alternating current power to the second input/output end, or outputs the alternating current power accessed by the second input/output end to the first input/output end and the reactor L1, so that the waveform of the input current of the PFC circuit follows the waveform of the input voltage, and power factor correction is performed on the accessed alternating current power. In the invention, by setting the overcurrent protection circuit 40, when it is detected that the current flowing through the PFC switch circuit 30 reaches the preset current threshold, the PFC drive circuit 20 is controlled to stop outputting the PFC drive signal, so as to control the PFC switch circuit 30 to stop working. The overcurrent protection circuit 40 can solve the problem that a switch device in the PFC switch circuit 30 is damaged due to overcurrent, and the reliability of the PFC circuit is improved. In addition, the invention does not need to arrange a rectifier bridge and corrects the power factor of the accessed alternating current power supply, thereby solving the problems of large size of a bridge stack, large on-state loss, easy loss of a PFC circuit and low energy efficiency.
Referring to fig. 2 to 4, in an embodiment, the PFC driving circuit 20 includes a first driving switch U1, a first resistor R1, a second resistor R2 and a signal isolation device U2, a first end of the first resistor R1 is a controlled end of the PFC driving circuit 20, and a second end of the first resistor R1 is interconnected with the controlled end of the first driving switch U1 and a first end of the second resistor R2; the input end of the first driving switch U1 and the second end of the second resistor R2 are connected with a first direct current power supply VCC1, the output end of the first driving switch U1 is connected with the input end of the signal isolation device U2, and the output end of the signal isolation device U2 is the output end of the PFC driving circuit 20.
In this embodiment, first drive switch U1 can adopt the triode, the switch tube of MOS pipe realizes, and first drive switch U1 of this embodiment adopts the PNP triode to realize, and signal isolation device U2 can adopt opto-coupler, diode, relay, sensor etc. can realize that the component of signal isolation realizes, and this embodiment is optional for the opto-coupler, and wherein, the collecting electrode and the positive pole of the luminous coupling emitting diode of PNP triode are connected. The collector of the opto-coupler phototriode is connected with a second direct current power supply VCC2, the emitter is connected with the controlled end of the PFC switch circuit 30, and the opto-coupler also provides a driving power supply for the PFC switch circuit 30. Of course, in other implementations, the first driving switch U1 may also be implemented by an NPN transistor, and the NPN transistor is connected to the cathode of the led. The components and connection relationship of the PFC driving circuit 20 may be adaptively changed according to a specific scheme, and are not limited herein. The PNP transistor is turned on when receiving the PFC control signal of the low level, thereby driving the optocoupler to be turned on and outputting a corresponding driving signal to the PFC switch circuit 30. The PNP transistor is turned off when receiving the PFC control signal of high level, thereby driving the optocoupler to be turned off, and further stopping outputting the corresponding driving signal to the PFC switch circuit 30.
Referring to fig. 2, in an embodiment, the PFC switch circuit 30 includes a first switch Q1 and a first diode D1, the controlled terminal of the first switch Q1 is the controlled terminal of the PFC switch circuit 30, the input terminal of the first switch Q1 is the first input/output terminal of the PFC switch circuit 30, the output terminal of the first switch Q1 is connected to the anode of the first diode D1, and the cathode of the first diode D1 is the second input/output terminal of the PFC switch circuit 30. In this embodiment, the PFC switch circuit 30 further includes a resistor R21 and a resistor R22, wherein the resistor R21 is serially connected between the output terminal of the PFC driving circuit 20 and the controlled terminal of the first switch transistor Q1; the resistor R22 is serially connected between the controlled terminal and the input terminal of the first switch transistor Q1. The resistor R21 is a current limiting resistor, and the resistor R22 is a bias resistor.
Further, in the above embodiment, the first switching transistor Q1 is a MOS transistor or an IGBT.
In this embodiment, when receiving a PFC control signal output by the main controller MCU, the PFC switch circuit 30 drives and controls the MOS transistor or the IGBT in the main loop to be turned on, the first diode D1 connected in series with the MOS transistor is also turned on, the voltage of the live wire at the ac input end is positive with respect to the voltage of the neutral wire in the positive half cycle, and the current path of the main loop is the live wire at the ac input end-the reactor L1- (FUSE 1) -the IGBT device (or MOS transistor) Q1-the first diode D1-the neutral wire at the ac input end; in a positive half period, the voltage of the zero line of the alternating current input end is positive relative to the voltage of the live line, no matter whether the MOS tube or the IGBT is conducted or not, the first diode D1 is in a cut-off state, and the PFC circuit does not work. By adjusting the pulse width, pulse frequency, etc. of the first switching tube Q1 output by the PFC driving circuit 20, the on-time, on-frequency, etc. of the first switching tube Q1 are further controlled, so as to implement power factor correction on the accessed ac power supply.
Referring to fig. 3, in an embodiment, the PFC switch circuit 30 includes a second switch Q2 and a second diode D2, the controlled terminal of the second switch Q2 is the controlled terminal of the PFC switch circuit 30, the anode of the second diode D2 is the first input/output terminal of the PFC switch circuit 30, and the cathode of the second diode D2 is connected to the input terminal of the second switch Q2; the output terminal of the second switching tube Q2 is a second input/output terminal of the PFC switching circuit 30. In this embodiment, the PFC switch circuit 30 further includes a resistor R23 and a resistor R24, wherein the resistor R23 is serially connected between the output terminal of the PFC driving circuit 20 and the controlled terminal of the second switch Q2; the resistor R24 is serially connected between the controlled terminal and the input terminal of the second switch tube Q2. The resistor R23 is a current limiting resistor, and the resistor R24 is a bias resistor.
Further, the second switching tube Q2 is a MOS tube or an IGBT.
In this embodiment, when receiving a PFC control signal output by the main controller MCU, the PFC switch circuit 30 drives and controls the MOS or IGBT in the main circuit to be turned on, the second diode D2 connected in series therewith is also turned on, the voltage of the zero line at the ac input end is positive with respect to the voltage of the live line in the negative half cycle, and the current path of the main circuit is the zero line-IGBT device (or MOS) Q1-the second diode D2-the reactor L1- (FUSE 1) -the live line at the ac input end; in the positive half period, the voltage of the live wire at the alternating current input end is positive relative to the voltage of the zero wire, and no matter whether the MOS tube or the IGBT is conducted or not, the second diode D2 is in a cut-off state, and the PFC circuit does not work. The power factor correction of the accessed alternating current power supply is realized by adjusting the pulse width, the pulse frequency and the like of the second switching tube Q2 output by the PFC driving circuit 20, and further controlling the conduction time, the conduction frequency and the like of the second switching tube Q2.
Referring to fig. 4, in an embodiment, the PFC switch circuit 30 includes a third switch tube Q3 and a fourth switch tube Q4, the controlled terminal of the third switch tube Q3 and the fourth switch tube Q4 are connected to the output terminal of the PFC driver circuit 20, the first conductive terminal of the third switch tube Q3 is a first input/output terminal of the PFC switch circuit 30, the second conductive terminal of the third switch tube Q3 is connected to the first conductive terminal of the fourth switch tube Q4, and the second conductive terminal of the fourth switch tube Q4 is a second input/output terminal of the PFC switch circuit 30.
In this embodiment, the third switching transistor Q3 and the fourth switching transistor Q4 may be MOS transistors or IGBTs. When the third switching tube Q3 and the fourth switching tube Q4 are implemented by using IGBTs, the third switching tube Q3 and the fourth switching tube Q4 are arranged oppositely, that is, the emitter of the third switching tube Q3 is connected with the emitter of the fourth switching tube Q4. In this embodiment, the PFC switch circuit 30 further includes a resistor R25, a resistor R26, a resistor R27, and a resistor R28, wherein the resistor R25 is serially connected between the output terminal of the PFC driver circuit 20 and the controlled terminal of the third switching tube Q3; the resistor R24 is arranged in series between the controlled end and the input end of the third switching tube Q3; the resistor R27 is serially connected between the output end of the PFC driving circuit 20 and the controlled end of the fourth switching tube Q4; the resistor R28 is serially connected between the controlled end and the input end of the fourth switch tube Q4. The resistors R25 and R27 are current limiting resistors, and the resistors R26 and R28 are bias resistors.
The PFC switch circuit 30 further includes a third diode D3 and a fourth diode D4, an anode of the third diode D3 is connected to the first conductive terminal of the fourth diode D4, and a cathode of the third diode D3 is connected to the reactor L1; an anode of the fourth diode D4 is connected to the second conductive terminal of the third switching tube Q3, and a cathode of the fourth diode D4 is connected to a live line terminal L of an ac power supply. The third diode D3 is connected in anti-parallel with the third switch tube Q3, and the fourth diode D4 is connected in anti-parallel with the fourth switch tube Q4.
When the third switching tube Q3 and the fourth switching tube Q4 are implemented by using IGBTs, when receiving a PFC control signal output by the main controller MCU, the PFC switching circuit 30 drives and controls the conduction of the IGBTs in the PFC switching circuit 30 in the main loop, that is, the third switching tube Q3 and the fourth switching tube Q4 are driven to be conducted. In a positive half cycle, the voltage of the live wire at the alternating current input end is positive relative to the voltage of the zero line, at the moment, the IGBT corresponding to the fourth switching tube Q4 is in a cut-off state, the fourth diode D4 connected in parallel with the IGBT in an opposite direction is conducted, and the path of the main loop current is the live wire at the alternating current input end, namely the reactor L1- (FUSE FUSE1) -the third switching tube Q3-the fourth diode D4-the live wire at the alternating current input end; in a negative half cycle, the voltage of the zero line of the alternating current input end is positive relative to the voltage of the live line, at the moment, the IGBT corresponding to the third switching tube Q3 is in a cut-off state, and the path of conducting the main loop current by the third diode D3 in reverse parallel connection with the third switching tube is the zero line of the alternating current input end, the fourth switching tube Q4, the third diode D3, the reactor L1- (FUSE FUSE1) and the live line of the alternating current input end. By adjusting the pulse width, pulse frequency and the like of the third switching tube Q3 and the fourth switching tube Q4 output by the PFC driving circuit 20, the on-time, on-frequency and the like of the third switching tube Q3 and the fourth switching tube Q4 are further controlled, and power factor correction of the accessed alternating current power supply is realized.
Referring to fig. 2, in an embodiment, the overcurrent protection circuit 40 includes a current detection unit 41 and a comparison control unit 42, a detection end of the current detection unit 41 is a detection end of the overcurrent protection circuit 40, an output end of the current detection unit 41 is connected to a first input end of the comparison control unit 42, a second input end of the comparison control unit 42 is connected to a reference current signal, and an output end of the comparison control unit 42 is an output end of the overcurrent protection circuit 40; the current detecting unit 41 is configured to convert the detected ac current signal into a dc current signal with a corresponding magnitude and output the dc current signal, and the comparison control unit 42 is configured to control the PFC driving circuit 20 to stop outputting the PFC driving signal when the dc current signal is greater than the reference current signal.
In this embodiment, the current detection unit 41 is an isolated current detection circuit, and the current detection through the PFC switch circuit 30 can be realized by the isolated current detection circuit, and the input and output isolation of the current detection signal can also be realized. It can be understood that in this embodiment, the current detection unit 41 detects an ac current signal, the current detection unit 41 may also be configured to convert the detected ac current signal into a dc current signal with a corresponding magnitude and output the dc current signal, the comparison control unit 42 compares the accessed dc current signal with a reference current signal, and when the dc current signal is greater than the reference current signal, it indicates that the current flowing through the PFC switch circuit 30 reaches a preset current threshold, and further controls the PFC driving circuit 20 to stop outputting the PFC driving signal.
Referring to fig. 2, in an embodiment, the current detecting unit 41 includes a transformer T1, an ac-dc converter 411, a third resistor R3, and a fourth resistor R4, one end of a primary winding of the transformer T1 is connected to the second input/output terminal of the PFC switch circuit 30, and the other end of the primary winding of the transformer T1 is grounded; two ends of the secondary coil of the transformer T1 are connected with two input ends of the ac-dc converter 411 in a one-to-one correspondence manner; a first output terminal of the ac-dc converter 411 is connected to the first input terminal of the comparison control unit 42 and the first terminal of the fourth resistor R4 through the fourth resistor R4, and a second output terminal of the ac-dc converter 411 and the second terminal of the fourth resistor R4 are both grounded.
In this embodiment, the transformer T1 is used to collect the ac current signal of the primary winding and is coupled to the ac-dc converter 411 of the secondary winding, the ac-dc converter 411 converts the ac current signals with negative phase and positive phase into dc current signals with positive phase, the third resistor R3 and the fourth resistor R4 are connected in series to divide the voltage, the preset current threshold value can be set by adjusting the voltage division ratio of the third resistor R3 and the fourth resistor R4, specifically, by adjusting the resistances of the third resistor R3 and the fourth resistor R4, when the comparison control circuit detects that the current flowing through the PFC switch circuit 30 reaches the preset current threshold value, and controlling the PFC driving circuit 20 to stop outputting the PFC driving signal, so that the PFC driving circuit 20 controls the PFC switch to stop working.
Referring to fig. 2, in an embodiment, the comparison control circuit includes a comparator U3, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8 and a second driving switch U4, an inverting input terminal of the comparator U3 is a first input terminal of the comparison control unit 42, a non-inverting input terminal of the comparator U3 is connected to a common terminal of the fifth resistor R5 and the sixth resistor R6, and an output terminal of the comparator U3 is connected to a first terminal of the seventh resistor R7; a first end of the fifth resistor R5 is connected to a first direct current power source VCC1, and a second end of the fifth resistor R5 is connected to ground through the sixth resistor R6; a second terminal of the seventh resistor R7 is interconnected with a controlled terminal of the second drive switch U4 and a first terminal of the eighth resistor R8; an input end of the second driving switch U4 and a second end of the eighth resistor R8 are both grounded, and an output end of the second driving switch U4 is connected to the PFC driving circuit 20.
In this embodiment, the second driving switch U4 can be implemented by an electronic switch such as a triode, an MOS transistor, or the like, and the second driving switch U4 is an electronic switch that is triggered to be turned on at a high level and turned off at a low level. The non-inverting input end of the comparator U3 is connected to a reference current signal, the inverting input end receives a detected current signal flowing through the PFC switch circuit 30, that is, a current detection signal, when the current detection signal is smaller than the reference current signal, the comparator U3 outputs a high-level control signal, and further the second drive switch U4 is turned on, so that the optocoupler, the diode, the relay, the sensor and the like can work as signal isolation elements, and when the current detection signal is greater than or equal to the reference current signal, the comparator U3 outputs a low-level control signal to control the second drive switch U4 to be turned off, so that the optocoupler, the diode, the relay, the sensor and the like stop working, and stop outputting the PFC switch drive signal. The fifth resistor R5 and the sixth resistor R6 divide the voltage of the first dc power VCC1 and output the divided voltage to the non-inverting input terminal of the comparator, so as to provide a reference voltage, i.e., a reference current signal, for the comparator, and the reference current signal can be adjusted by adjusting the fifth resistor R5 and the sixth resistor R6.
Referring to fig. 2 or fig. 4, in an embodiment, the PFC circuit further includes a tank filter circuit 50, and an input terminal of the tank filter circuit 50 is connected to an output terminal of the rectifier circuit 10.
In this embodiment, the energy storage filter circuit 50 is used for storing the output electric energy and filtering the output voltage to stabilize the output voltage. The energy storage filter circuit 50 may be implemented by using capacitors (C1, C2), and may specifically be implemented by using two capacitors connected in series, when two capacitors (C1, C2) are used for implementation, the two capacitors (C1, C2) are connected in series between two output ends of the rectifier circuit 10, and a zero line of the ac input end is connected with a common end of the two capacitors (C1, C2), so as to implement voltage-doubling rectification with the rectifier circuit 10. I.e. the voltage value at the output of the rectifier circuit 10 is twice as large as at the input of the rectifier circuit 10.
The invention also provides an air conditioner which comprises the PFC circuit. The detailed structure of the PFC circuit can refer to the above embodiments, and is not described herein again; it can be understood that, because the air conditioner of the present invention uses the PFC circuit, the embodiment of the air conditioner of the present invention includes all technical solutions of all embodiments of the PFC circuit, and the achieved technical effects are also completely the same, and are not described herein again.
The above description is only an alternative embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (9)
1. A PFC circuit, comprising:
one end of the reactor is connected with a live wire end of an alternating current power supply;
the input end of the rectifying circuit is connected with the other end of the reactor;
the PFC driving circuit outputs a corresponding PFC driving signal according to the received control signal;
the controlled end of the PFC switch circuit is connected with the output end of the PFC driving circuit, and the first input/output end of the PFC switch circuit is connected with the other end of the reactor; a second input/output end of the PFC switch circuit is connected with a zero line end of the alternating current power supply; the PFC switch circuit outputs the power supply accessed by the first input/output end to the second input/output end according to the PFC driving signal, or outputs the power supply accessed by the second input/output end to the first input/output end;
the detection end of the over-current protection circuit is connected with the second input/output end of the PFC switch circuit, and the output end of the over-current protection circuit is connected with the PFC drive circuit; the over-current protection circuit controls the PFC driving circuit to stop outputting a PFC driving signal when detecting that the current flowing through the PFC switching circuit reaches a preset current threshold value; the PFC driving circuit comprises a first driving switch, a first resistor, a second resistor and a signal isolation device, wherein a first end of the first resistor is a controlled end of the PFC driving circuit, and a second end of the first resistor is connected with the controlled end of the first driving switch and a first end of the second resistor; the input end of the first driving switch and the second end of the second resistor are connected with a first direct current power supply, the output end of the first driving switch is connected with the input end of the signal isolation device, and the output end of the signal isolation device is the output end of the PFC driving circuit;
the over-current protection circuit comprises a current detection unit and a comparison control unit, wherein the comparison control unit comprises a second driving switch, the second driving switch is started when the current flowing through the PFC switch circuit does not reach a preset current threshold value so as to control the signal isolation device to work, and is closed when the current reaches the preset current threshold value so as to control the signal isolation device to stop working;
the PFC circuit further comprises an energy storage filter circuit, and the input end of the energy storage filter circuit is connected with the output end of the rectification circuit.
2. The PFC circuit of claim 1, wherein the PFC switch circuit comprises a first switch tube and a first diode, the controlled terminal of the first switch tube is the controlled terminal of the PFC switch circuit, the input terminal of the first switch tube is the first input/output terminal of the PFC switch circuit, the output terminal of the first switch tube is connected to the anode of the first diode, and the cathode of the first diode is the second input/output terminal of the PFC switch circuit.
3. The PFC circuit of claim 1, wherein the PFC switching circuit comprises a second switching tube and a second diode, the controlled terminal of the second switching tube is the controlled terminal of the PFC switching circuit, the cathode of the second diode is the first input/output terminal of the PFC switching circuit, and the anode of the second diode is connected with the output terminal of the second switching tube; the input end of the second switch tube is a second input/output end of the PFC switch circuit.
4. The PFC circuit of claim 1, wherein the PFC switch circuit comprises a third switch tube and a fourth switch tube, the controlled end of the third switch tube and the controlled end of the fourth switch tube are connected with the output end of the PFC driving circuit, the first conductive end of the third switch tube is a first input/output end of the PFC switch circuit, the second conductive end of the third switch tube is connected with the first conductive end of the fourth switch tube, and the second conductive end of the fourth switch tube is a second input/output end of the PFC switch circuit.
5. The PFC circuit of claim 4, wherein the PFC switching circuit further comprises a third diode and a fourth diode, an anode of the third diode being connected to the first conductive terminal of the fourth switching tube, a cathode of the third diode being connected to the other end of the reactor; and the anode of the fourth diode is connected with the second conductive end of the third switching tube, and the cathode of the fourth diode is connected with the zero line end of the alternating current power supply.
6. The PFC circuit of any one of claims 1 to 5, wherein a detection end of the current detection unit is a detection end of the over-current protection circuit, an output end of the current detection unit is connected with a first input end of the comparison control unit, a second input end of the comparison control unit is connected with a reference current signal, and an output end of the comparison control unit is an output end of the over-current protection circuit; the comparison control unit is used for controlling the PFC driving circuit to stop outputting the PFC driving signal when the direct current signal is larger than the reference current signal.
7. The PFC circuit of claim 6, wherein the current detection unit comprises a transformer, an AC-DC converter, a third resistor and a fourth resistor, wherein one end of a primary winding of the transformer is connected to the second input/output terminal of the PFC switching circuit, and the other end of the primary winding of the transformer is connected to a zero line terminal of an AC power supply; two ends of the secondary side coil of the transformer are correspondingly connected with two input ends of the alternating current-direct current converter one by one; the first output end of the alternating current-direct current converter is connected with the first input end of the comparison control unit and the first end of the fourth resistor through the third resistor, and the second output end of the alternating current-direct current converter and the second end of the fourth resistor are both grounded.
8. The PFC circuit of claim 6, wherein the comparison control unit further comprises a comparator, a fifth resistor, a sixth resistor, a seventh resistor, and an eighth resistor, wherein an inverting input of the comparator is the first input of the comparison control unit, a non-inverting input of the comparator is connected to a common terminal of the fifth resistor and the sixth resistor, and an output of the comparator is connected to a first terminal of the seventh resistor; the first end of the fifth resistor is connected with a first direct-current power supply, and the second end of the fifth resistor is grounded through the sixth resistor; a second end of the seventh resistor is interconnected with a controlled end of the second drive switch and a first end of the eighth resistor; the input end of the second driving switch and the second end of the eighth resistor are both grounded, and the output end of the second driving switch is connected with the PFC driving circuit.
9. An air conditioner characterized by comprising the PFC circuit according to any one of claims 1 to 8.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910618776.2A CN110417251B (en) | 2019-07-09 | 2019-07-09 | PFC circuit and air conditioner |
| PCT/CN2020/100625 WO2021004451A1 (en) | 2019-07-09 | 2020-07-07 | Pfc circuit and air conditioner |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910618776.2A CN110417251B (en) | 2019-07-09 | 2019-07-09 | PFC circuit and air conditioner |
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| CN110417251B true CN110417251B (en) | 2021-08-13 |
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| CN110417251B (en) * | 2019-07-09 | 2021-08-13 | 广东美的制冷设备有限公司 | PFC circuit and air conditioner |
| CN111641334B (en) * | 2020-06-05 | 2021-11-23 | 广东美的制冷设备有限公司 | Variable frequency control device and air conditioner |
| CN111579631B (en) * | 2020-06-11 | 2021-04-27 | 中国地质大学（武汉） | Interface conversion circuit of plasma mass spectrometer driven by laser ablation system |
| CN112701903B (en) * | 2021-01-22 | 2022-03-18 | Oppo广东移动通信有限公司 | Control circuit, switching power supply and electronic equipment |
| CN114498545A (en) * | 2021-12-27 | 2022-05-13 | 珠海格力电器股份有限公司 | Overcurrent failure protection circuit and electronic equipment |
| CN114566956B (en) * | 2022-03-08 | 2023-03-10 | 珠海格力电器股份有限公司 | Zero-live wire adjusting circuit and method and air conditioner |
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| WO2021004451A1 (en) | 2021-01-14 |
| CN110417251A (en) | 2019-11-05 |
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