CN220732579U

CN220732579U - Power factor correction circuit and switching converter

Info

Publication number: CN220732579U
Application number: CN202322074891.2U
Authority: CN
Inventors: 汪本强
Original assignee: Shenzhen Huntkey Electric Co Ltd
Current assignee: Shenzhen Huntkey Electric Co Ltd
Priority date: 2023-08-02
Filing date: 2023-08-02
Publication date: 2024-04-05
Anticipated expiration: 2033-08-02

Abstract

The utility model is applicable to the power electronics technical field, provides a power factor correction circuit and switching converter, and the circuit includes energy storage module, switch module, isolation module, first current sampling module, second current sampling module and control module. The first current sampling module is used for converting the first current flowing through the switch module based on the electromagnetic induction principle to obtain a converted current, obtaining a first voltage based on the converted current, and outputting the first voltage to the control module; the second current sampling module is used for obtaining a second voltage based on a second current directly flowing through the second current sampling module and outputting the second voltage to the control module, wherein the second current comprises a current flowing through a load; the control module is used for outputting corresponding on signals and off signals according to the first voltage, the second voltage, the input power supply voltage and the load voltage, so that the input current and the output voltage of the power factor correction circuit meet preset conditions. The power consumption can be reduced, and the circuit structure is simplified.

Description

Power factor correction circuit and switching converter

Technical Field

The application belongs to the technical field of power electronics, and particularly relates to a power factor correction circuit and a switching inverter.

Background

Active power factor correction (Active Power Factor Correction, APFC) technology is widely used in many industries because of its advantages of improving the power factor of the power electronics on the network access side, reducing line loss, saving energy, reducing harmonic pollution of the power grid, improving the power supply quality of the power grid, and the like.

The APFC technology is implemented as follows: the input voltage of the APFC circuit is used as a reference signal, and the input current is adjusted, so that the input current tracks the input voltage, the low-frequency component of the input current and the low-frequency component of the input voltage are approximately the same frequency and the same phase, and the power factor is improved and the harmonic wave is suppressed. Therefore, accurate detection of the input current to the APFC circuit is particularly important.

In the prior art, two main ways of detecting the input current of the APFC circuit are adopted, wherein one way is to directly connect a current sampling device (such as a sampling resistor) in series in a loop to sample the current, but the way can cause larger power consumption; the other way is to convert the primary side large current of the loop into the secondary side small current (such as a current transformer) to sample the current of the loop according to the electromagnetic induction principle, but the circuit structure of the current sampling circuit designed by the way is relatively complex, so that the circuit reliability is lower, the physical space occupied by the circuit structure is larger, and the design cost is higher.

Disclosure of Invention

In view of this, the embodiment of the application provides a power factor correction circuit and a switching converter, so as to solve the technical problem that the input current sampling circuit of the existing APFC circuit can not reduce power consumption and meet the design requirement of simplifying the circuit structure.

In a first aspect, there is provided a power factor correction circuit comprising:

the energy storage module is connected with the switch module through the first current sampling module and is used for being connected with an input power supply, storing electric energy when the switch module is turned on, and releasing the electric energy when the switch module is turned off;

the switch module is connected with the control module and is respectively connected with the isolation module and the energy storage module through the first current sampling module, and is used for being conducted according to a conduction signal output by the control module or being turned off according to a turn-off signal output by the control module;

the isolation module is connected with the energy storage module, is connected with the switch module through the first current sampling module and is used for connecting a load, and is used for being turned off when the switch module is turned on and is used for being turned on when the switch module is turned off;

The first current sampling module is respectively connected with the switch module and the control module and is used for converting a first current based on an electromagnetic induction principle to obtain a conversion current, obtaining a first voltage based on the conversion current and outputting the first voltage to the control module, wherein the first current comprises a current flowing through the switch module;

the second current sampling module is connected in series between the second end of the load and the electrical loop of the second end of the switch module, and is connected with the control module, and is used for obtaining a second voltage based on a second current directly flowing through the second current sampling module and outputting the second voltage to the control module, wherein the second current comprises a current flowing through the load;

the control module is respectively connected with the switch module, the input power supply, the load, the first current sampling module and the second current sampling module and is used for outputting corresponding on signals and off signals according to the first voltage, the second voltage, the output voltage of the input power supply and the input voltage of the load so that the input current of the energy storage module and the output voltage of the energy storage module meet preset conditions.

In a possible implementation manner of the first aspect, the first current sampling module includes:

the current transformer unit is respectively connected with the voltage acquisition unit and the switch module and is used for converting the first current into the converted current;

and the voltage acquisition unit is connected with the control module and is used for acquiring the first voltage based on the conversion current and outputting the first voltage to the control module.

In a possible implementation manner of the first aspect, the second current sampling module includes a first resistor;

the first end of the first resistor is connected with the second end of the switch module and the second end of the input power supply, and the second end of the first resistor is used for being connected with the second end of the load.

In a possible implementation manner of the first aspect, the energy storage module includes a first inductor, the switching module includes a first switching tube, and the isolation module includes a first diode;

the first end of first inductance is used for connecting the first end of input power, the second end of first inductance is connected respectively the first end of first current sampling module with the positive pole of first diode, the negative pole of first diode is used for connecting the first end of load, the second end of first current sampling module is connected the first end of first switch tube, the second end of first switch tube is connected the first end of second current sampling module and is used for connecting the second end of input power, the control module is connected to the control end of first switch tube, the second end of second current sampling module is used for connecting the second end of load.

In a possible implementation manner of the first aspect, the current transformer unit includes a current transformer and a second diode, the current transformer includes a primary coil and a secondary coil;

the first end of the primary coil is respectively connected with the second end of the first inductor and the anode of the first diode, the second end of the primary coil is connected with the first end of the first switch tube, the first end of the secondary coil is connected with the cathode of the second diode, the second end of the secondary coil is respectively connected with the first end of the voltage acquisition unit, the second end of the first switch tube and the first end of the second current sampling module, the anode of the second diode is respectively connected with the second end of the voltage acquisition unit and the first end of the control module, and the second end of the control module is used for grounding.

In a possible implementation manner of the first aspect, the voltage acquisition unit includes a second resistor;

the first end of the second resistor is respectively connected with the second end of the secondary coil, the second end of the first switching tube and the first end of the second current sampling module, and the second end of the second resistor is respectively connected with the anode of the second diode and the first end of the control module.

In a possible implementation manner of the first aspect, the switch module further includes a third resistor and a fourth resistor;

the first end of the third resistor is connected with the control end of the first switching tube and the first end of the fourth resistor respectively, the second end of the third resistor is connected with the control end of the control module, and the second end of the fourth resistor is connected with the second end of the first switching tube and the first end of the second current sampling module respectively.

In a possible implementation manner of the first aspect, the current transformer unit further includes a fifth resistor;

the first end of the fifth resistor is connected with the first end of the secondary coil and the cathode of the second diode respectively, and the second end of the fifth resistor is connected with the second end of the secondary coil and the first end of the first resistor respectively.

In a possible implementation manner of the first aspect, the power factor correction circuit further includes a first capacitor and a second capacitor;

the first end of the first capacitor is connected with the first end of the energy storage module and the first end used for being connected with the input power supply, and the second end of the first capacitor is respectively connected with the second end of the switch module and the first end of the second current sampling module and the second end used for being connected with the input power supply;

The first end of the second capacitor is connected with the second end of the isolation module and the first end used for being connected with the load, and the second end of the second capacitor is connected with the second end of the second current sampling module and the second end used for being connected with the load.

In a second aspect, an embodiment of the present application further provides a switching converter, where the switching inverter includes the power factor correction circuit provided in any one of the foregoing embodiments.

The power factor correction circuit and the switching converter provided by the embodiment of the application have the following beneficial effects:

the power factor correction circuit comprises an energy storage module, a switch module, an isolation module, a first current sampling module, a second current sampling module and a control module, wherein the first current sampling module is used for converting first current flowing through the switch module based on an electromagnetic induction principle to obtain conversion current and obtaining first voltage based on the conversion current, and the second current sampling module is connected between a second end of a load and an electrical loop of the second end of the switch module in series and used for obtaining second voltage based on second current flowing through the isolation module loop.

According to the power factor correction circuit, when the switch module is turned on, the first current sampling module is used for detecting the first current flowing through the switch module to obtain the first voltage and transmitting the first voltage to the control module, when the switch module is turned off, the second current sampling module is used for obtaining the second voltage based on the second current flowing through the isolation module loop and transmitting the second voltage to the control module, and the control module outputs corresponding on signals and off signals to control the working state of the switch module according to the first detection voltage and the second detection voltage, so that the input current (namely the input current of the power factor correction circuit) of the energy storage module meets preset conditions, and therefore the power factor is improved.

When the switch module is conducted, the second current sampling module is not put into operation, and current sampling is carried out only through the first current sampling module, so that the loss of output electric energy caused by the second current sampling module directly connected in series in the circuit loop is not additionally caused; when the switch module is turned off, the second current sampling module replaces the first current sampling module to sample the current, and compared with the mode of converting the primary side large current of the loop into the secondary side small current by utilizing the electromagnetic induction principle, the current sampling mode of the switch module under all working modes (namely the on state and the off state) is completed, and the complexity of the whole circuit structure is reduced. By the mode, on the basis of reducing the power consumption, the whole circuit structure of the power factor correction circuit is simplified, so that the power factor correction circuit has higher reliability, smaller volume and lower design cost.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required for the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic structural diagram of a power factor correction circuit according to an embodiment of the present application;

fig. 2 is a schematic structural diagram of a power factor correction circuit according to another embodiment of the present disclosure;

fig. 3 is a schematic circuit diagram of a power factor correction circuit according to an embodiment of the present disclosure;

fig. 4 is a schematic circuit diagram of a power factor correction circuit according to another embodiment of the present disclosure;

fig. 5 is a schematic circuit diagram of a power factor correction circuit according to another embodiment of the present disclosure;

fig. 6 is a schematic circuit diagram of a power factor correction circuit according to another embodiment of the present disclosure;

fig. 7 is a schematic waveform diagram of each voltage in a pfc circuit according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application will be further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the present application.

It should be noted that the terms used in the implementation section of the embodiments of the present application are only used to explain the specific embodiments of the present application, and are not intended to limit the present application. In the description of the embodiments of the present application, unless otherwise indicated, "/" means or, for example, a/B may represent a or B; "and/or" herein is merely an association relationship describing a relationship, meaning that there may be three relationships, e.g., a and/or B, may mean: a exists alone, A and B exist together, and B exists alone.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. The terms "comprising," including, "" having, "and variations thereof mean" including but not limited to.

The active power factor correction (Active Power Factor Correction, APFC) technology is widely applied in a plurality of industries because of the advantages of improving the power factor of a power electronic device on the network access side, reducing line loss, saving energy, reducing harmonic pollution of a power grid, improving the power supply quality of the power grid and the like.

The APFC technology is implemented as follows: the input voltage of the APFC circuit is used as a reference signal, and the input current is adjusted, so that the input current tracks the input voltage, and the low-frequency component of the input current and the low-frequency component of the input voltage are in the same frequency and phase as much as possible, thereby improving the power factor and inhibiting the harmonic wave. From this, it can be seen that accurate detection of the input current of the APFC circuit is a precondition for accurate adjustment of the input current.

In the prior art, two main ways of detecting the input current of the APFC circuit are adopted, wherein one way is to sample the current by directly connecting a current sampling device (such as a sampling resistor) in series in a loop, but the way can cause larger power consumption, and by way of example, the input current of the APFC circuit is sampled by directly connecting a sampling resistor in series in a main loop of the APFC circuit, because the sampling resistor is a pure power dissipation element, that is, when a current flows through the sampling resistor, the sampling resistor inevitably consumes electric power, and the consumed power is proportional to the power to be 2 of the current flowing through the sampling resistor, that is, the larger the current flowing through the sampling resistor (the larger the output power of the APFC circuit), the larger the consumed power of the sampling resistor, therefore, the mode of sampling the input current of the APFC circuit by using the sampling resistor only can cause larger power dissipation, so that the efficiency of the APFC circuit is reduced; the other way is to convert the primary side large current of the loop into the secondary side small current to sample the current of the loop according to the electromagnetic induction principle, but the way needs to add a current conversion function module (such as a current transformer) in the circuit, so that the circuit implementation scheme and wiring mode arrangement of the function module are also considered, and the circuit structure of the current sampling circuit designed in the way is relatively complex, so that the circuit reliability is lower, the physical space occupied by the circuit structure is larger, and the design cost is higher.

In order to solve the above-mentioned problems, the embodiments of the present application provide a power factor correction circuit and a switching converter, so that when detecting an input current of the power factor correction circuit, on the basis of reducing power consumption, the circuit structure of the whole current sampling circuit can be simplified, thereby enabling the power factor correction circuit to have lower power consumption, higher reliability, smaller volume and lower design cost.

Referring to fig. 1, fig. 1 is a schematic structural diagram of a power factor correction circuit according to an embodiment of the present application. As shown in fig. 1, the power factor correction circuit 10 includes an energy storage module 101, a switching module 102, an isolation module 103, a first current sampling module 104, a second current sampling module 105, and a control module 106.

The energy storage module 101 is connected to the isolation module 103 and to the switch module 102 via the first current sampling module 104, and is used for connecting the input power source 20, for storing electrical energy when the switch module 102 is on, and for discharging electrical energy when the switch module 102 is off.

The energy storage module 101 includes, but is not limited to, an inductor, a boost circuit structure formed by the inductor, and the like, when the switch module 102 is turned on, a first electric loop formed by the energy storage module 101, the switch module 102, the first current sampling module 104 and the input power source 20 is turned on, the energy storage module 101 stores energy, when the switch module 102 is turned off, the first electric loop is turned off, and a second electric loop formed by the energy storage module 101, the isolation module 103, the load 30 and the input power source 20 is turned on, the electric energy stored in the energy storage module 101 is released, and if other energy storage units (such as capacitors) exist at the rear end output, and when the sum of the electric quantity provided by the input power source 20 in a single switching period and the electric quantity of the energy storage module 101 is greater than the electric quantity consumed by the load in a single switching period, the released electric energy and the electric energy of the energy storage units (such as capacitors) are overlapped, so that the boost function can be realized.

The switch module 102 is connected with the control module 106, and is respectively connected with the energy storage module 101 and the isolation module 103 through the first current sampling module 104, and is used for conducting according to a conducting signal output by the control module 106 or is used for switching off according to a switching-off signal output by the control module 106.

The switch module 102 adjusts the working state by the control signal (i.e. the on signal or the off signal) output by the control module 106, so that the input current of the energy storage module 101 (i.e. the input current of the power factor correction circuit 10) and the input voltage of the load 30 (i.e. the output voltage of the power factor correction circuit 10) meet the preset conditions, and the power factor is improved. It should be noted that the above-mentioned preset condition refers to that the input current of the rate factor correction circuit 10 follows the input voltage (i.e. the output voltage of the input power source 20) as far as possible, that is, the low-frequency component of the input current is as same as the low-frequency component of the input voltage as possible (for example, the frequency and the phase of the input current and the input voltage reach a similarity of 90%), so as to improve the input power factor of the circuit, where the specific implementation requirement of the similarity of the frequency and the phase of the input current and the input voltage can be set by specific working conditions, and is not limited herein. In addition, it should be noted that, the more the frequency of the input current and the input voltage and the phase of the input current and the input voltage are approximated, the higher the input power factor, and when the frequency and the phase of the input current and the input voltage are all identical, the input power factor is 1, that is, the input power factor reaches the highest level.

The isolation module 103 is connected to the energy storage module 101 and to the switching module 102 via the first current sampling module 104 and is used for connecting the load 30, for switching off when the switching module 102 is switched on and for switching on when the switching module 102 is switched off. The isolation module 103 may include, but is not limited to, a diode, an electrical isolation structure made up of diodes, and the like. The isolation module 103 is turned off when the switch module 102 is turned on, so that when other energy storage units (such as capacitors) are arranged at the rear end of the isolation module, the energy storage units are prevented from discharging energy to the ground, and electric energy is wasted, and when the switch module 102 is turned off, the isolation module is turned on to form a complete power supply loop, so that the power supply requirement of the rear-end load equipment is met, or the charging requirement of the rear-end energy storage equipment is met.

The first current sampling module 104 is respectively connected to the switch module 102 and the control module 106, and is configured to convert a first current based on an electromagnetic induction principle to obtain a converted current, obtain a first voltage based on the converted current, and output the first voltage to the control module 106, where the first current includes a current flowing through the switch module 102.

The first current sampling module 104 is configured to sample a current of a first electrical loop (i.e., a current flowing through the switching module 102) formed by the energy storage module 101, the switching module 102, the first current sampling module 104, and the input power 20 when the switching module 102 is turned on. The primary side large current (i.e. the current of the loop where the switch module 102 is located) can be converted into the secondary side small current for sampling by using the electromagnetic induction principle, so as to achieve the purpose of indirect measurement. Compared with the mode of directly connecting the sampling resistor in series with the primary side for current sampling, the method not only avoids larger conduction loss of the sampling resistor and improves conversion efficiency, but also can avoid the risks of overheat failure of the sampling resistor or abnormal operation of the switch module 102 (such as failure caused by short-circuit fault), damage to the control module 106 caused by overhigh voltage at two ends of the sampling resistor (for example, the voltage at two ends of the sampling resistor is higher than the maximum specification voltage which can be born by the control module 106), and the like.

The second current sampling module 105 is configured to be connected in series between the second end of the load 30 and the electrical circuit of the second end of the switch module 102, and is connected to the control module 106, and configured to obtain a second voltage based on a second current directly flowing through the second current sampling module 105, and output the second voltage to the control module 106, where the second current includes a current flowing through the isolation module 103 and the load 30.

The second current sampling module 105 is configured to sample a current of a second electrical loop (i.e., a current flowing through the isolation module 103 and the load 30) formed by the energy storage module 101, the isolation module 103, the load 30, and the input power source 20 when the switch module 102 is turned off. Compared with an indirect sampling mode based on an electromagnetic induction principle, the circuit current is sampled by using the current sampling element or the circuit structure directly connected in series in the electric circuit, so that the circuit is more convenient and quicker, and the design of the circuit structure is relatively simple, thereby improving the reliability of the whole circuit, reducing the volume of the circuit and reducing the design cost.

The control module 106 is connected to the switch module 102, the first current sampling module 104, the second current sampling module 105, the input power supply 20, and the load 30, and is configured to output corresponding on signals and off signals according to the first voltage and the second voltage, and the output voltage of the input power supply 20 and the input voltage of the load 30, so as to control the working state of the switch module 102, so that the input current of the energy storage module 101 and the input voltage of the load 30 meet preset conditions.

The control module 106 may include, but is not limited to, an MCU (Microcontroller Unit, microcontroller), a DSP (Digital Signal Processing ), a dedicated control chip, and the like. The control module 106 obtains the input current of the power factor correction circuit 10 based on the first voltage obtained by the first current sampling module 104 and the second voltage obtained by the second current sampling module 105; and according to the input current of the energy storage module 101, the output voltage of the input power supply 20 and the input voltage of the load 30, and based on the control modes such as the peak current method, the average current method, the hysteresis current method, etc., a corresponding on signal or off signal is output to the switch module 102, so as to adjust the working state of the switch module 102, so that the input current of the energy storage module 101 and the input voltage of the load 30 meet the preset conditions, thereby improving the input power factor. It should be noted that, the control modes of the peak current method, the average current method, the hysteresis current method and the like are input current control modes of a conventional power factor correction circuit, and specific working principles thereof can be described with reference to related technologies, and are not described herein.

The power factor correction circuit 10 shown in fig. 1 operates as follows:

The pfc circuit 10 may be divided into two modes, namely a first mode when the switching module 102 is on and a second mode when the switching module 102 is off. In the first working mode, the input power supply 20, the energy storage module 101, the switch module 102 and the first current sampling module 104 form a first loop, and the first current sampling module 104 samples the current of the first loop based on the electromagnetic induction principle to obtain a first voltage and transmits the first voltage to the control module 106; in the second working mode, a second loop is formed by the input power supply 20, the energy storage module 101, the isolation module 103, the load 30 and the second current sampling module 105, and at this time, the second current sampling module 105 directly samples the current flowing through the loop to obtain a second voltage and outputs the second voltage to the control module 106; the control module 106 obtains the input current of the pfc circuit 10, that is, the superposition of the first current and the second current, according to the first voltage for representing the first loop current (i.e., the first current described above) and the second voltage for representing the second loop current (i.e., the second current described above), and the control module 106 adjusts the operating state of the switching module 102 based on the input current of the pfc circuit 10 (i.e., the input current of the energy storage module 101), the input voltage of the pfc circuit 10 (i.e., the output voltage of the input power supply 20), the output voltage of the pfc circuit 10 (i.e., the input voltage of the load 30), and the preset control mode, so that the input current and the output voltage of the pfc circuit 10 satisfy the preset conditions, and finally, the output power factor is improved.

It should be noted that, the input voltage of the pfc circuit 10 (i.e., the output voltage of the input power supply 20) and the output voltage of the pfc circuit 10 (i.e., the input voltage of the load 30) may be obtained by detecting and acquiring the input voltage by an external input voltage detection device and transmitting the detected input voltage to the control module 106, or by detecting and acquiring the input voltage by a voltage detection module built in the control module 106, which is not limited herein. In addition, the above-mentioned preset control method may include, but is not limited to, a conventional peak current method, an average current method, a hysteresis current method, and the like.

As can be seen from the foregoing, when the switch module 102 is turned on, the power factor correction circuit 10 provided in this embodiment of the present application is capable of detecting the first current flowing through the switch module 102 through the first current sampling module 104 based on the electromagnetic induction principle and transmitting the first voltage to the control module 106, when the switch module 102 is turned off, obtaining the second voltage through the second current sampling module 105 based on the second current flowing through the isolation module 103 and the load 30 and transmitting the second voltage to the control module 106, and outputting corresponding on signals and off signals to control the working state of the switch module 102 through the control module 106 according to the first voltage, the second voltage, the output voltage of the input power supply 20 and the input voltage of the load 30, so that the input current of the power factor correction circuit 10 (i.e. the input current of the energy storage module 101) and the output voltage of the power factor correction circuit 10 (i.e. the input voltage of the load 30) meet the preset conditions, thereby improving the output power factor.

Because the second current sampling module 105 is not put into operation and only performs current sampling through the first current sampling module 104 when the switch module 102 is turned on, the loss of the output electric energy caused by the second current sampling module 105 directly connected in series in the circuit loop is not additionally caused; when the switch module 102 is turned off, the second current sampling module 105 replaces the first current sampling module 104 to sample the current, so that the complexity of the whole circuit structure is reduced compared with the mode of converting the primary side large current of the loop into the secondary side small current by using the electromagnetic induction principle, and completing the current sampling of all the working modes (namely the on state and the off state) of the switch module 102. By the mode, on the basis of reducing the power consumption, the whole circuit structure of the power factor correction circuit is simplified, so that the power factor correction circuit has higher reliability, smaller volume and lower design cost.

In some embodiments, referring to fig. 2, the first current sampling module 104 includes a current transformer 1041 and a voltage acquisition unit 1042.

The current transformer 1041 is connected to the voltage acquisition unit 1042 and the switch module 102, respectively, and is used for converting the first current flowing through the switch module 102 into a converted current based on the electromagnetic induction principle; the voltage obtaining unit 1042 is connected to the control module 106, and configured to obtain a first voltage based on the converted current and output the first voltage to the control module 106. The current transformer unit 1041 may include, but is not limited to, a current transformer, other circuit structures based on a primary coil, a secondary coil, and a magnetic core, and the voltage acquisition unit 1042 may include, but is not limited to, a single resistor, a resistor network, a voltage acquisition circuit structure composed of a resistor and other circuit elements, and the like.

In some embodiments, referring to fig. 3, fig. 3 illustrates a circuit structure of a power factor correction circuit, and in the embodiment illustrated in fig. 3, the second current sampling module 105 includes a first resistor R1.

The first end of the first resistor R1 is connected to the second end of the switch module 102 and is used to connect to the second end of the input power 20, and the second end of the first resistor R1 is used to connect to the second end of the load 30. The first resistor R1 directly samples the current of the loop in which it is located to obtain the voltage difference between the two ends thereof, thereby obtaining the first voltage and transmitting the first voltage to the control module 106.

In some embodiments, referring to fig. 3 again, in the embodiment shown in fig. 3, the energy storage module 101 includes a first inductor L1, the switch module 102 includes a first switch tube Q1, and the isolation module 103 includes a first diode D1.

The first end of the first inductor L1 is used for connecting the first end of the input power supply 20, the second end of the first inductor L1 is respectively connected with the first end of the first current sampling module 104 and the anode of the first diode D1, the cathode of the first diode D1 is used for connecting the first end of the load 30, the second end of the first current sampling module 104 is connected with the first end of the first switching tube Q1, the second end of the first switching tube Q1 is connected with the first end of the second current sampling module 105 and the second end used for connecting the input power supply 20, the control end of the first switching tube Q1 is connected with the control module 106, and the second end of the second current sampling module 105 is used for connecting the second end of the load 30.

The first switching tube Q1 in the embodiment shown in fig. 3 is an NMOS tube, where the drain electrode of the NMOS tube corresponds to the first end of the switching tube, the source electrode of the NMOS tube corresponds to the second end of the switching tube, and the gate electrode of the NMOS tube corresponds to the control end of the switching tube, that is, when the control end of the first switching tube Q1 is at a high level, the first switching tube Q1 is turned on, and when the control end of the first switching tube Q1 is at a low level, the first switching tube Q1 is turned off. When the first switching tube Q1 is turned on, the first inductor L1 stores electric energy, the first diode D1 is turned off reversely, and when the first switching tube Q1 is turned off, the first inductor L1 releases electric energy, and the first diode D1 is turned on in the forward direction. In some embodiments, the rear end of the first diode D1 is provided with an energy storage unit (such as a capacitor), so that the electric energy stored in the first inductor L1 and the electric energy stored in the energy storage unit can be overlapped, thereby realizing the boosting effect.

In some embodiments, referring to fig. 4, fig. 4 shows a circuit structure of another power factor correction circuit, and in the embodiment shown in fig. 4, a current transformer unit 1041 includes a current transformer TR1 and a second diode D2, where the current transformer TR1 includes a primary coil and a secondary coil.

The first end of the primary coil of the current transformer TR1 is respectively connected to the second end of the first inductor L1 and the anode of the first diode D1, the second end of the primary coil of the current transformer TR1 is connected to the first end of the first switching tube Q1, the first end of the secondary coil of the current transformer TR1 is connected to the cathode of the second diode D2, the second end of the secondary coil of the current transformer TR1 is respectively connected to the first end of the voltage acquisition unit 1042, the second end of the first switching tube Q1 and the first end of the second current sampling module 105, the anode of the second diode D2 is respectively connected to the second end of the voltage acquisition unit 1042 and the first end of the control module 106, and the second end of the control module 106 is used for grounding.

When current (i.e., the first current) flows through the primary coil of the current transformer TR1, the secondary coil of the current transformer TR1 induces a corresponding conversion current, and through setting the turns ratio of the primary coil and the secondary coil of the current transformer TR1, the conversion between the first current and the conversion current with a preset ratio can be realized, for example, when the turns ratio of the primary coil and the secondary coil is 1:100, the first current with 1A can be converted into the conversion current with 0.01A; the voltage obtaining unit 1042 obtains a first voltage based on the converted current and transmits the first voltage to the control module 106, where the first voltage can be used to characterize the first current, i.e. sampling of the first current is achieved.

In some embodiments, referring to fig. 4 again, the voltage obtaining unit 1042 includes a second resistor R2.

The first end of the second resistor R2 is connected to the second end of the secondary coil of the current transformer TR1, the second end of the first switching tube Q1 and the first end of the second current sampling module 105, respectively, and the second end of the second resistor R2 is connected to the anode of the second diode D2 and the first end of the control module 106, respectively. That is, the above-mentioned converted current is converted into a form of a first voltage through the second resistor R2, and the first voltage is transmitted to the control module 106, thereby realizing the sampling of the above-mentioned first current.

In some embodiments, referring to fig. 5, fig. 5 shows a circuit structure of another power factor correction circuit, and in the embodiment shown in fig. 5, the switch module 102 further includes a third resistor R3 and a fourth resistor R4.

The first end of the third resistor R3 is connected to the control end of the first switching tube Q1 and the first end of the fourth resistor R4, the second end of the third resistor R3 is connected to the control end of the control module 106, and the second end of the fourth resistor R4 is connected to the second end of the first switching tube Q1 and the first end of the second current sampling module 105. The third resistor R3 is a current limiting resistor, and is used for preventing the gate of the first switching tube Q1 from being damaged due to overcurrent, and the fourth resistor R4 is a bias resistor, and is used for ensuring that the gate charge of the first switching tube Q1 is discharged and reliably turned off.

In some embodiments, referring to fig. 5 again, the current transformer 1041 further includes a fifth resistor R5.

The first end of the fifth resistor R5 is connected to the first end of the secondary winding of the current transformer TR1 and the cathode of the second diode D2, respectively, and the second end of the fifth resistor R5 is connected to the second end of the secondary winding of the current transformer TR1 and the first end of the first resistor R1, respectively. The fifth resistor R5 may be used in a core reset current path of the current transformer TR1 to make the secondary winding reset voltage of the current transformer TR1 lower than a set value.

In some embodiments, referring to fig. 6, fig. 6 shows a circuit structure of another power factor correction circuit, and in the embodiment shown in fig. 6, the power factor correction circuit 10 further includes a first capacitor C1 and a second capacitor C2.

The first end of the first capacitor C1 is connected to the first end of the energy storage module 101 and the first end for connecting to the input power source 20, and the second end of the first capacitor C1 is connected to the second end of the switch module 102 and the first end of the second current sampling module 105, and the second end for connecting to the input power source 20, respectively; the first end of the second capacitor C2 is connected 103 to the second end of the isolation module and to the first end of the load 30, and the second end of the second capacitor C2 is connected to the second end of the second current sampling module 105 and to the second end of the load 30. The first capacitor C1 and the second capacitor C2 are filter capacitors, the first capacitor C1 is used for reducing ripple of the input voltage of the pfc circuit 10, and the second capacitor C2 is used for reducing ripple of the output voltage of the pfc circuit 10.

In the following, taking the circuit configuration of the pfc circuit shown in fig. 4 as an example, the sampling principle of the input current of the pfc circuit 10 is described as follows:

wherein the current sampling signal can be characterized by the following formula, namely:

U(IS，GND)＝U(IS，VI-)+U(VI-，GND) (1)

wherein U (IS, GND) IS the voltage difference between the current sampling signal input node IS and the ground GND, U (IS, VI-) IS the voltage difference between the current sampling signal input node IS and the second terminal VI-of the input power source 20, and U (VI-, GND) IS the voltage difference between the second terminal VI-of the input power source 20 and the ground GND.

As can be seen from the circuit structure analysis of the pfc circuit shown in fig. 3, the voltage difference between the current sampling signal input node IS and the second terminal VI-of the input power source 20 in the formula (1) IS equal to the voltage across the second resistor R2, namely:

U(IS，VI-)＝U(R2)＝I(Q1)*R2/N (2)

wherein U (IS, VI-) IS the voltage difference between the current sampling signal input node IS and the second end VI-of the input power supply 20, U (R2) IS the voltage at the two ends of the second resistor R2, I (Q1) IS the current flowing through the first switching tube Q1, namely the first current, and N IS the ratio of the number of secondary coil turns to the number of primary coil turns of the current transformer TR 1.

In addition, the voltage difference between the second terminal VI-of the input power supply 20 and the ground GND in the above formula (1) is equal to the voltage across the first resistor R1, that is:

U(VI-，GND)＝U(R1)＝I(D1)*R1(3)

Wherein U (VI-, GND) is the voltage difference between the second terminal VI-of the input power supply 20 and the ground GND, U (R1) is the voltage across the first resistor R1, and I (D1) is the current flowing through the first diode D1, i.e. the second current.

When the power factor correction circuit 10 is in the first operation mode (i.e., the first switching tube Q1 is turned on), the potential difference between the first end of the first switching tube Q1 and the potential of the second end thereof is close to 0V, and at this time, the current flows from the first end vi+ of the input power 20, flows back to the second end VI-of the input power 20 through the first inductor L1, the primary winding of the current transformer TR1, the first end of the first switching tube Q1 and the second end of the first switching tube Q1. The current I (Q1) (i.e., the first current) in the loop formed by the input power supply 20, the first inductance L1, the primary winding of the current transformer TR1, the first terminal of the first switching tube Q1, and the second terminal of the first switching tube Q1 increases with a certain slope.

At this time, as shown in fig. 3, since the primary winding of the current transformer TR1 is in the same loop as the first end of the first switching tube Q1 and the second end of the first switching tube Q1, and the voltage drop across the primary winding of the current transformer TR1 is negligible, that is, corresponds to a short circuit, the potential difference between the anode of the first diode D1 and the second end of the first switching tube Q1 is close to 0V, at this time, the voltage across the first diode D1 is reverse biased, no current flows through the first diode D1, and the first resistor R1 is also in the same loop as the first diode D1, so the current flowing through the first resistor R1 is also 0A, that is, at this time, the voltage across the first resistor R1 is 0V.

Therefore, in the first operation mode of the pfc circuit 10, the above formula (1) may be simplified as the following formula:

U(IS，GND)_1＝I(Q1)*R2/N (5)

when the power factor correction circuit 10 is in the second working mode (i.e. the first switching tube Q1 is turned off), the first current I (Q1) reaches the peak value I (q1_m) before the first switching tube Q1 is turned off, and the first diode D1 is turned on under the electromotive force of the first inductor L1 at this time, the current peak value I (d1_m) at the turn-on time of the first diode D1 is equal to the peak value I (q1_m) of the first current I (Q1); at this time, current flows from the first terminal vi+ of the input power supply, through the first inductor L1, the first diode D1, the load 30, the first resistor R1, and back to the second terminal VI-of the input power supply 20. Since the primary winding of the current transformer TR1 is in the same loop as the first switching tube Q1, the current of the primary winding of the current transformer TR1, i.e., the first current I (Q1), is 0A, i.e., the voltage across the second resistor R2 is 0V.

Therefore, in the second operation mode of the pfc circuit 10, the above formula (1) may be expressed simply as:

U(IS，GND)_2＝U(VI-，GND)＝I(D1)*R1 (6)

for example, in the power factor correction circuit 10 shown in fig. 3, the ratio of the number of secondary turns to the number of primary turns of the current transformer TR1 is 100, the resistance of the first resistor R1 is 0.01Ω, the resistance of the second resistor R2 is 1Ω, and the peak current I (d1_m) flowing through the first switching tube Q1 and the peak current I (q1_m) flowing through the first diode D1 are both 10A.

At this time, the peak value of the sampling signal output voltage U (IS, GND) _1 of the power factor correction circuit 10 in the first operation mode IS equal to the peak value of the sampling signal output voltage U (IS, GND) _2 of the power factor correction circuit 10 in the second operation mode, both of which are 0.1V.

As can be seen from the above, the ratio of the sampled signal output voltage value U (IS, GND) _1 to the first current I (Q1) in the first operation mode of the power factor correction circuit 10 and the ratio of the sampled signal output voltage value U (IS, GND) _2 to the second current I (D1) in the second operation mode can be made the same by reasonable parameter configuration. That IS, the current-sampled output voltage signal U (IS, GND) has exactly the same conversion ratio of the current signal to the voltage signal in the first and second operation modes, i.e., the value of the current-sampled output voltage signal U (IS, GND) IS proportional to the value of the current it samples.

It should be noted that, in the embodiment shown in fig. 4, by connecting the sampling resistor (i.e., the first resistor R1) in series between the cathode of the first diode D1, the load 30, and the electrical circuit of the first switching tube Q1, the above-mentioned second current is sampled, and compared with the manner in which the sampling resistor is disposed between the second end of the first switching tube Q1 and the electrical circuit of the second end of the input power source 20, the above-mentioned manner in which the input current is sampled can reduce the overall power consumption, and in addition, when the first switching tube Q1 fails and fails in a short-circuit fault, the current flowing through both ends of the sampling resistor is instantaneously increased, so that the voltage drop generated at both ends of the sampling resistor exceeds the maximum pressure-bearing threshold of the control module 106, resulting in the probability that the control module 106 is damaged, thereby improving the reliability of the circuit; in addition, by sampling the current of the first loop (i.e., the loop formed by the input power source 20, the first inductor L1, and the first switching tube Q1) by the first current sampling module 104 formed by the current sensor TR1, the second diode D2, and the second resistor R2 when the first switching tube Q1 is turned on, and sampling the current of the second loop (i.e., the loop formed by the input power source 20, the first inductor L1, the first diode D1, the load 30, and the first resistor R1) by the second current sampling module 105 formed by the first resistor R1 when the first switching tube Q1 is turned off, the complexity of the overall circuit structure can be reduced, and the overall circuit structure can be made more reliable, smaller in size, and lower in design cost, than the way of sampling the loop current by providing the circuit structure based on the electromagnetic induction principle in both the first loop and the second loop.

In some embodiments, referring to fig. 3 and 7 together, fig. 7 shows waveforms of voltages of the power factor correction circuit 10 shown in fig. 3, wherein U (G, GND) IS a voltage at a control terminal of the first switching tube Q1, U (IS, VI-) IS a voltage between the current sampling signal input node IS and the second terminal VI-of the input power supply 20, U (VI-, GND) IS a voltage between the second terminal VI-of the input power supply 20 and the ground GND, U (IS, GND) IS a voltage between the current sampling signal input node IS and the ground GND, V IS a voltage, t IS a time, ton IS an on time of the first switching tube Q1, and Toff IS an off time of the first switching tube Q1.

As can be seen from fig. 7, the current sampling output voltage signal, i.e., U (IS, GND), IS formed by sectionally combining the rectified output voltage of the secondary winding of the current transformer TR1, i.e., U (IS, VI), in the first operation mode of the pfc circuit 10, and the voltage across the first resistor R1, i.e., U (VI-, GND), in the second operation mode of the pfc circuit 10.

The embodiment of the present application further provides a switching converter, which includes the power factor correction circuit 10 provided in any of the embodiments, and is configured to convert a voltage input by the input power source 20 to obtain a converted voltage and output the converted voltage, so as to improve a power factor of the input power source 20.

The above embodiments are only for illustrating the technical solution of the present application, and are not limiting; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present application, and are intended to be included in the scope of the present application.

Claims

1. A power factor correction circuit, comprising:

The isolation module is connected with the energy storage module, is connected with the switch module through the first current sampling module, and is used for connecting a load, and is used for being turned off when the switch module is turned on and is used for being turned on when the switch module is turned off;

the control module is connected with the switch module, the first current sampling module, the second current sampling module, the input power supply and the load respectively and is used for outputting corresponding on signals and off signals according to the first voltage, the second voltage, the output voltage of the input power supply and the input voltage of the load so as to enable the input current of the energy storage module and the input voltage of the load to meet preset conditions.

2. The power factor correction circuit of claim 1, wherein the first current sampling module comprises:

3. The power factor correction circuit of claim 2, wherein the second current sampling module comprises a first resistor;

4. The power factor correction circuit of claim 3, wherein the energy storage module comprises a first inductor, the switching module comprises a first switching tube, and the isolation module comprises a first diode;

5. The power factor correction circuit of claim 4, wherein the current transformer unit comprises a current transformer and a second diode, the current transformer comprising a primary coil and a secondary coil;

6. The power factor correction circuit according to claim 5, wherein the voltage acquisition unit includes a second resistor;

7. The power factor correction circuit of claim 4, wherein the switching module further comprises a third resistor and a fourth resistor;

8. The power factor correction circuit of claim 5, wherein the current transformer unit further comprises a fifth resistor;

9. The power factor correction circuit according to any one of claims 1 to 8, further comprising a first capacitor and a second capacitor;

10. A switching converter comprising a power factor correction circuit as claimed in any of claims 1 to 9.