CN212367124U - Totem-pole bridgeless PFC circuit system and current sampling circuit - Google Patents
Totem-pole bridgeless PFC circuit system and current sampling circuit Download PDFInfo
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- CN212367124U CN212367124U CN202021043515.7U CN202021043515U CN212367124U CN 212367124 U CN212367124 U CN 212367124U CN 202021043515 U CN202021043515 U CN 202021043515U CN 212367124 U CN212367124 U CN 212367124U
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Abstract
The embodiment of the utility model discloses totem pole does not have bridge PFC circuit system and current sampling circuit, this system includes: the PFC inductive current detection circuit comprises a first bridge arm, a second bridge arm, a current sampling circuit and a control circuit, wherein the second bridge arm comprises two switching tubes which are connected in series in the same phase and is connected with the current sampling circuit, the current sampling circuit comprises a current transformer, a sampling switch and the like, the sampling switch in the current sampling circuit is controlled, the current of the two switching tubes of the second bridge arm is collected through the current transformer, and the PFC inductive current can be obtained after the circuits are synthesized. Compared with the existing sampling circuit, the technical scheme of the utility model can realize the full-period current sampling of the totem-pole bridgeless PFC circuit by using less electronic devices; because the two sampling switches are controlled by power frequency, the control is simple and easy to realize, the current sampling difficulty of the totem-pole bridgeless PFC circuit can be reduced, and finally, power factor correction and the like can be realized.
Description
Technical Field
The utility model relates to a power technical field especially relates to a totem pole does not have bridge PFC circuit system and current sampling circuit.
Background
With the rapid development of semiconductor technology, power electronic technology has been widely used in the fields of power supply systems, power systems, post and telecommunications, aerospace, and the like. Today, bulky, low efficiency power supply devices have been replaced by small, high efficiency power supplies, most of which are dc power supplies by rectifying ac power, however, the performance of the rectifying converter will directly affect the quality of the utility grid. At present, in order to reduce pollution of a direct-current power supply system to a power grid, most medium and high power direct-current power supply devices have Power Factor Correction (PFC) circuits, such as a bidirectional power conversion circuit, a totem-pole bridgeless PFC circuit, and the like. For the circuit, the purpose of power factor correction is achieved mainly by controlling the on and off of two main switching tubes on a bridge arm. The key point is to sample the current of the PFC inductor, however, how to quickly and accurately acquire the current of the PFC inductor is the key and difficult point of such circuits.
SUMMERY OF THE UTILITY MODEL
In view of this, the present invention is directed to solve the above technical problems, and provides a totem-pole bridgeless PFC circuit system and a current sampling circuit.
An embodiment of the utility model provides a totem pole does not have bridge PFC circuit system, include: the current sampling circuit comprises a first bridge arm, a second bridge arm, a current sampling circuit and a control circuit, wherein the first bridge arm and the second bridge arm are connected in parallel to a first parallel connection point and a second parallel connection point; the first parallel connection point and the second parallel connection point are used for connecting two ends of a load;
the current sampling circuit comprises a first current transformer, a second current transformer, a demagnetization unit, a full-wave rectification unit, a first sampling switch, a second sampling switch and a sampling resistor, wherein the first current transformer and the second current transformer are respectively provided with two secondary windings;
a primary winding of the first current transformer is positioned between the first parallel connection point and the second connection point and is connected with the first switching tube in series, and a primary winding of the second current transformer is positioned between the second parallel connection point and the second connection point and is connected with the second switching tube in series;
two ends of each secondary winding of each current transformer are connected with one demagnetization unit in parallel; the first output end and the second output end of the two secondary windings of each current transformer are respectively connected with different input ends of the full-wave rectification unit, and the third common output end is connected with a control ground;
different output ends of the full-wave rectification unit are respectively connected with first ends of the first sampling switch and the second sampling switch, and second ends of the first sampling switch and the second sampling switch are connected with the sampling resistor after being connected in parallel;
the control circuit is respectively connected with the control ends of the first switch tube, the second switch tube, the first sampling switch and the second sampling switch.
Further, in the totem-pole bridgeless PFC circuit system, a dotted end and a dotted end of a primary winding of the first current transformer are respectively connected to one end of the first switching tube and the second connection point;
and the homonymous end and the synonym end of the primary winding of the second current transformer are respectively connected with the second connection point and one end of the second switching tube.
Further, in the totem-pole bridgeless PFC circuit system, the second current transformer and the first current transformer have the same structure, and two secondary windings of each current transformer are a first secondary winding and a second secondary winding, respectively;
the homonymous end of the first secondary winding and the heteronymous end of the second secondary winding of each current transformer are respectively used as the first output end and the second output end, and the heteronymous end of the first secondary winding and the homonymous end of the second secondary winding are connected and then used as the third public output end.
Further, in the totem-pole bridgeless PFC circuit system, the full-wave rectification unit includes a first rectification diode, a second rectification diode, a third rectification diode, and a fourth rectification diode;
the first output end of the first current transformer is connected with the anode of the first rectifying diode, and the second output end of the first current transformer is connected with the anode of the second rectifying diode;
the first output end of the second current transformer is connected with the anode of the third rectifying diode, and the second output end of the second current transformer is connected with the anode of the fourth rectifying diode;
the cathodes of the first rectifying diode and the fourth rectifying diode are connected with the first end of the first sampling switch;
and the cathodes of the second rectifying diode and the third rectifying diode are connected with the first end of the second sampling switch.
Further, in the totem-pole bridgeless PFC circuit system, the demagnetization unit is a demagnetization resistor or a voltage regulator tube.
Further, in the totem-pole bridgeless PFC circuit system, the first switch tube and the second switch tube have the same structure, and the first switch tube is an insulated gate field effect transistor, an insulated gate bipolar transistor, or a silicon carbide field effect transistor.
Further, in the totem-pole bridgeless PFC circuit system, the current sampling circuit is configured to sample a current of the first switching tube through the first current transformer when the first switching tube is turned on, and demagnetize the first current transformer by the demagnetization unit corresponding to the first current transformer when the first switching tube is turned off;
the current sampling circuit is also used for sampling current of the second switch tube through the second current transformer when the second switch tube is conducted, and demagnetizing the second current transformer by the demagnetizing unit corresponding to the second current transformer when the second switch tube is disconnected.
Further, in the totem-pole bridgeless PFC circuit system, the control circuit is configured to control the second sampling switch to be turned on and the first sampling switch to be turned off when the ac power source is in a positive half-cycle, so that the current sampling circuit collects a forward current of the PFC inductor;
the control circuit is further configured to control the first sampling switch to be turned on and the second sampling switch to be turned off when the ac power supply is in a negative half-cycle, so that the current sampling circuit collects a negative current of the PFC inductor.
Optionally, the two diodes in the first leg are replaced by two switching tubes.
The embodiment of the utility model provides a still provide a current sampling circuit, include: the current sampling circuit in the totem-pole bridgeless PFC circuit system is adopted, wherein primary windings of the first current transformer and the second current transformer are respectively used for being connected with a main switching tube in a sampled circuit, and the current sampling circuit is used for collecting current of the main switching tube.
The embodiment of the utility model has the following advantage:
the utility model discloses totem pole bridgeless PFC circuit system is through being equipped with current sampling circuit on the second bridge arm that contains two switch tubes, utilize two current transformer that include two secondary winding, demagnetization unit and full-bridge rectification unit, the current sampling circuit of component devices such as two sampling units and sampling resistor, can gather the operating current under the arbitrary moment of switch tube effectively, can obtain PFC inductive current through the synthesis, realized the full period current sampling to totem pole bridgeless PFC circuit. And two sampling switches in the current sampling circuit are controlled by power frequency, the control is simple and easy to realize, the current sampling difficulty of the totem-pole bridgeless PFC circuit is reduced, the application of the totem-pole bridgeless PFC circuit is improved, and the like.
Drawings
In order to illustrate the technical solution of the present invention more clearly, the drawings that are needed in the embodiments will be briefly described below, and it should be understood that the following drawings only illustrate some embodiments of the present invention, and therefore should not be considered as limiting the scope of the present invention. Like components are numbered similarly in the various figures.
Fig. 1 shows a schematic structural diagram of a totem-pole bridgeless PFC circuit system according to an embodiment of the present invention;
fig. 2 is a schematic diagram illustrating a current sampling circuit of a totem-pole bridgeless PFC circuit system according to an embodiment of the present invention collecting a main switching tube current when an ac power supply is in a positive half cycle;
fig. 3 is a schematic diagram illustrating a current sampling circuit of a totem-pole bridgeless PFC circuit system according to an embodiment of the present invention collecting a current of a freewheeling switch tube when an ac power source is in a positive half-cycle;
fig. 4 is a schematic diagram illustrating a current sampling circuit of a totem-pole bridgeless PFC circuit system according to an embodiment of the present invention collecting a main switching tube current when an ac power source is in a negative half cycle;
fig. 5 is a schematic diagram illustrating a current sampling circuit of a totem-pole bridgeless PFC circuit system according to an embodiment of the present invention collecting a current of a freewheeling switch tube when an ac power source is in a negative half-cycle;
fig. 6 shows a schematic structural diagram of a current sampling circuit according to an embodiment of the present invention.
Description of the main element symbols:
100-totem pole bridgeless PFC circuitry; 10-a first leg; 20-a second leg; 30-a current sampling circuit; 40-a control circuit; 1-a first connection point; 2-a second connection point; n1 — first parallel connection point; n2 — second parallel connection point; d1 — first diode; d2 — second diode; CT1 — first current transformer; CT2 — second current transformer; q1-first switch tube; q2-second switch tube; s1 — a first sampling switch; s2 — a second sampling switch; r1 — first demagnetization resistance; r2 — second demagnetization resistance; r3 — third demagnetization resistor; r4-fourth demagnetization resistor; d11 — first rectifying diode; d12 — second rectifying diode; d13 — third rectifying diode; d14-fourth rectifying diode; Vac-AC power supply; rs-sampling resistance; L1-PFC inductance; c1-capacitance; rf-load resistance.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments.
The components of embodiments of the present invention, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, presented in the accompanying drawings, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. Based on the embodiment of the present invention, all other embodiments obtained by the person skilled in the art without creative work belong to the protection scope of the present invention.
Hereinafter, the terms "including", "having", and their derivatives, which may be used in various embodiments of the present invention, are only intended to indicate specific features, numbers, steps, operations, elements, components, or combinations of the foregoing, and should not be construed as first excluding the existence of, or adding to, one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing.
Furthermore, the terms "first," "second," "third," and the like are used solely to distinguish one from another and are not to be construed as indicating or implying relative importance.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the various embodiments of the present invention belong. The terms (such as those defined in commonly used dictionaries) should be interpreted as having a meaning that is consistent with their contextual meaning in the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein in various embodiments of the present invention.
Referring to fig. 1, the present embodiment provides a totem-pole bridgeless PFC circuit system 100, where the totem-pole bridgeless PFC circuit system 100 includes a first bridge arm 10 and a second bridge arm 20, and a current sampling circuit 30 is added to the second bridge arm 20 to perform full-cycle current sampling on two switching tubes on the second bridge arm 20, so as to control on/off of the first switching tube and the second switching tube, thereby implementing power factor correction. The totem-pole bridgeless PFC circuit system 100 is described in detail below.
Exemplarily, the totem-pole bridgeless PFC circuit system 100 includes a first leg 10, a second leg 20, a current sampling circuit 30, and a control circuit 40, where the first leg 10 and the second leg 20 are connected in parallel between a first parallel connection point N1 and a second parallel connection point N2; the first parallel connection point N1 and the second parallel connection point N2 are used to connect two terminals of a load, such as a load resistor Rf. Normally, this second parallel connection point N2 is also used for grounding. Further, as shown in fig. 1, for the first parallel connection point N1 and the second parallel connection point N2, a capacitor C1 may be connected in parallel between the first parallel connection point N1 and the second parallel connection point N2 before the load is connected.
In this embodiment, the first leg 10 includes a first diode D1 and a second diode D2 connected in series in the same direction (or the two diodes may be replaced by two switching tubes); the second bridge arm 20 comprises two switching tubes connected in series in the same phase, which are respectively marked as a first switching tube Q1 and a second switching tube Q2; a PFC inductor L1 and an ac power source Vac are connected between a first connection point 1 between two diodes in the first leg 10 and a second connection point 2 between two switching tubes in the second leg 20, wherein the ac power source Vac and the PFC inductor L1 are connected in series. The current sampling circuit 30 is connected to the second leg 20, and is configured to collect currents of the first switching tube Q1 and the second switching tube Q2 of the second leg 20 when the totem-pole bridgeless PFC circuit operates. Preferably, the first switch tube Q1 and the second switch tube Q2 are the same type of switch tube. Exemplarily, the switching tube may include, but is not limited to, an insulated gate field effect transistor (MOS tube), an insulated gate bipolar transistor (IGBT tube), a silicon carbide field effect transistor, or the like.
Exemplarily, as shown in fig. 1, the current sampling circuit 30 mainly includes a first current transformer CT1 and a second current transformer CT2, a demagnetization unit, a full-wave rectification unit, a first sampling switch S1, a second sampling switch S2, and a sampling resistor Rs. In this embodiment, the first current transformer CT1 and the second current transformer CT2 each include a primary winding and two secondary windings. The primary winding of the first current transformer CT1 is located between the first parallel connection point N1 and the second connection point and is connected in series with the first switch tube Q1 in the second leg 20, and the primary winding of the second current transformer CT2 is located between the second parallel connection point N2 and the second connection point and is connected in series with the second switch tube Q2.
In one embodiment, as shown in fig. 1, the first current transformer CT1 is located between the second connection point and the first switch transistor Q1, and the second current transformer CT2 is also located between the second connection point and the second switch transistor Q2, where the one terminal of the first current transformer CT1, the one terminal of the second current transformer CT2, and the second connection point are all connected to the same potential point. Further, the dotted terminal and the different-dotted terminal of the primary winding of the first current transformer CT1 are respectively connected to one end of the first switching tube Q1 and the second connection point; the dotted terminal and the different-dotted terminal of the primary winding of the second current transformer CT2 are connected to the second connection point and one end of the second switching tube Q2, respectively. Of course, the first current transformer CT1 and the second current transformer CT2 may be located between the parallel connection point and the switch tube, and may be specifically set according to the actual layout requirement, which is not limited herein.
Preferably, the first current transformer CT1 and the second current transformer CT2 may have identical structures. In this embodiment, for the two secondary windings of the first current transformer CT1 and the second current transformer CT2, two ends of each secondary winding are connected in parallel with a demagnetization unit for demagnetization. Exemplarily, the demagnetization unit may include, but is not limited to, a demagnetization resistor or two zener diodes connected in reverse in series, etc., preferably using the same demagnetization resistor.
For convenience of the subsequent description, the two secondary windings of each current transformer will be referred to as a first secondary winding and a second secondary winding, respectively. In this embodiment, the two secondary windings of each current transformer include three output terminals in total, namely a first output terminal, a second output terminal, and a third common output terminal. Exemplarily, the homonymous terminal of the first secondary winding of each current transformer may be used as the first output terminal, and the heteronymous terminal of the second secondary winding may be used as the second output terminal; and connecting the different name end of the first secondary winding and the same name end of the second secondary winding to be used as the third common output end.
In this embodiment, the first output terminal and the second output terminal of each current transformer are respectively connected to different input terminals of the full-wave rectification unit, and the third common output terminals of the two current transformers are connected to the same control ground. It will be appreciated that the above-mentioned control ground refers to the power ground in the board of the control circuit 40.
Exemplarily, the full-wave rectification unit mainly includes four rectifying diodes, namely a first rectifying diode D11, a second rectifying diode D12, a third rectifying diode D13 and a fourth rectifying diode D14. The two current transformers are correspondingly connected with the four rectifying diodes. Taking the first current transformer CT1 as an example, as shown in fig. 1, the same-name end (i.e., the first output end) of the first secondary winding of the first current transformer CT1 is connected to the anode of the first rectifying diode D11, the different-name end (i.e., the second output end) of the second secondary winding is connected to the anode of the second rectifying diode D12, and the third common output ends of the first secondary winding and the second secondary winding are connected to the control ground. Similarly, the first output terminal of the second current transformer CT2 is connected to the anode of the third rectifying diode D13, the second output terminal is connected to the anode of the fourth rectifying diode D14, and the third common output terminal is also connected to the control ground.
In this embodiment, two output terminals of the full-wave rectification unit are respectively connected to the first terminals of the first sampling switch S1 and the second sampling switch S2. Exemplarily, as shown in fig. 1, the cathodes of the first rectifying diode D11 and the fourth rectifying diode D14 are both connected to the first terminal of the first sampling switch S1; the cathodes of the second rectifying diode D12 and the third rectifying diode D13 are connected to the first terminal of the second sampling switch S2.
In this embodiment, the second terminals of the first sampling switch S1 and the second sampling switch S2 are connected in parallel to the sampling resistor Rs. Illustratively, the sampling resistor Rs includes one or more sampling resistors connected in series. For example, as shown in fig. 1, the second terminals of the two sampling switches are connected in parallel and then connected to one terminal of the sampling resistor Rs, and the other terminal of the sampling resistor Rs is connected to the control ground.
In this embodiment, the control circuit 40 is connected to the first switch tube Q1 and the second switch tube Q2 in the second bridge arm 20, and the control circuit 40 is further connected to respective control terminals of the first sampling switch S1 and the second sampling switch S2 for controlling the two sampling switches.
Exemplarily, when the accessed ac power source Vac is in a positive half cycle, the control circuit 40 will control the second sampling switch S2 to be turned on and the first sampling switch S1 to be turned off; when the ac power source Vac is in the negative half cycle, the first sampling switch S1 is controlled to be turned on and the second sampling switch S2 is controlled to be turned off. It is noted that the first sampling switch S1 and the second sampling switch S2 cannot be turned on simultaneously. The control circuit 40 may control the first sampling switch S1 and the second sampling switch S2 to adopt a power frequency of 50Hz or 60 Hz. Through the current sampling circuit 30, the control circuit 40 controls the sampling switch to work frequency, and the current sampling difficulty of the two switching tubes can be reduced.
Since the first switch Q1 is connected in series with the first current transformer and the second switch Q2 is connected in series with the second current transformer, in the embodiment, the current sampling circuit 30 is configured to sample the current of the first switch Q1 through the first current transformer CT1 when the first switch Q1 is turned on, and to demagnetize the first current transformer CT1 through the corresponding demagnetization unit when the first switch Q1 is turned off. In addition, the current sampling circuit 30 is further configured to sample a current of the second switch tube Q2 through the second current transformer CT2 when the second switch tube Q2 is turned on, and demagnetize the second current transformer CT2 through the corresponding demagnetization unit when the second switch tube Q2 is turned off.
The power frequency control is carried out on the two sampling switches in the current sampling circuit 30, so that the currents of the two switching tubes of the second bridge arm 20 in the totem-pole bridgeless PFC circuit can be collected, and the current of the PFC inductor L1 is obtained because the sum of the currents of the two switching tubes is equal to the PFC inductor current, and finally the power factor correction is realized.
The current flow direction during the current sampling process is analyzed in conjunction with the totem-pole bridgeless PFC circuit system 100 shown in fig. 1.
(1) When the ac power source Vac is in the positive half cycle, the second sampling switch S2 is in the closed state, and the first sampling switch S1 is in the open state, so that the current sampling circuit 30 will sample the forward current of the PFC inductor L1. At this time, the second switch Q2 serves as a main switch and the first switch Q1 serves as a follow current tube, so the working process includes two cases of turning on or off the second switch Q2, and the specific working process is analyzed as follows:
a. when the second switch Q2 is turned on and the first switch Q1 is turned off, the current of the current sampling circuit 30 flows as shown in fig. 2:
the current of the PFC inductor L1 increases in the forward direction, and the current flow is from left to right. At this time, current flows into the same-name terminal and the different-name terminal of the primary winding of the second current transformer CT2, and flows through the second switch tube Q2. Meanwhile, the current is coupled to the secondary winding of the second current transformer CT2, because the first sampling switch S1 is in an off state, the second secondary winding cannot form a current loop, and the current of the first secondary winding flows to the homonymous terminal and flows to the heteronymous terminal, that is, the current flows from the homonymous terminal of the first secondary winding of the second current transformer CT2, sequentially passes through the third rectifier diode D13, the second sampling switch S2 and the sampling resistor Rs, and finally flows from the heteronymous terminal of the first secondary winding, thereby forming a first current sampling path.
Further, the current of the secondary winding of the second current transformer CT2 can be obtained by collecting the voltage signal of the sampling resistor Rs, and then the current of the primary winding of the second current transformer CT2 is calculated through the conversion of the winding relation, so that the current when the second switching tube Q2 is switched on is obtained.
At this time, since the first switch Q1 is in the off state, the current flowing through the first switch Q1 is zero; the first current transformer CT1 stores the energy collected when the first switch Q1 was turned on in the previous cycle, so the collected energy needs to be consumed by the first demagnetization resistor R1 and the second demagnetization resistor R2 in the first current transformer CT1 to avoid saturation of the first current transformer CT1, and the work loop of demagnetization is as shown in fig. 2.
b. When the first switch Q1 is turned on and the second switch Q2 is turned off, the current of the current sampling circuit 30 flows as shown in fig. 3:
current flows from the synonym terminal and the synonym terminal of the primary winding of the first current transformer CT1 and flows through the first switch tube Q1. Meanwhile, the current is coupled to the secondary winding of the first current transformer CT1, because the first sampling switch S1 is in an off state, the first secondary winding cannot form a current loop, and the current of the second secondary winding flows to a different name end and flows to a same name end, that is, the current flows from the different name end of the second secondary winding of the first current transformer CT1, sequentially passes through the second rectifier diode D12, the second sampling switch S2 and the sampling resistor Rs, and finally flows from the same name end of the second secondary winding, so that a second current sampling path is formed.
Similarly, the current of the secondary winding of the first current transformer CT1 can be obtained by collecting the voltage signal of the sampling resistor Rs, and the current of the primary winding of the first current transformer CT1 is calculated by conversion, so that the current of the first switching tube Q1 when being switched on is obtained. Similarly, in order to avoid saturation of the second current transformer CT2, the demagnetization operation loop is shown in fig. 3, that is, the demagnetization is performed by the third demagnetization resistor R3 and the fourth demagnetization resistor R4 in the second current transformer CT2, and the demagnetization principle is similar to that of the first current transformer CT1, and therefore, the description is not repeated.
(2) When the accessed ac power source Vac is in a negative half cycle, the first sampling switch S1 is in a closed state, and the second sampling switch S2 is in an open state, so that the current sampling circuit 30 will collect the negative current of the PFC inductor L1. At this time, the first switch transistor Q1 is used as the main switch transistor and the second switch transistor Q2 is used as the follow current transistor. Therefore, the working process also includes two cases of turning on or turning off the first switching tube Q1, and the specific working process is analyzed as follows:
c. when the first switch Q1 is turned on and the second switch Q2 is turned off, the current of the current sampling circuit 30 flows as shown in fig. 4:
the current of the PFC inductor L1 increases in the negative direction, and the current flow is from right to left. At this time, current flows in from the homonymous terminal and the synonym terminal of the primary winding of the first current transformer CT1, and flows through the first switching tube Q1. Meanwhile, the current is coupled to the secondary winding of the first current transformer CT1, since the second sampling switch S2 is in an off state, the second secondary winding cannot form a current loop, and the current of the first secondary winding flows to the homonymous terminal and flows to the heteronymous terminal, that is, the current flows from the homonymous terminal of the first secondary winding of the first current transformer CT1, sequentially passes through the first rectifier diode D11, the first sampling switch S1 and the sampling resistor Rs, and finally flows from the heteronymous terminal of the first secondary winding, thereby forming a third current sampling path.
Similarly, the current of the secondary winding of the first current transformer CT1 can be obtained by collecting the voltage signal of the sampling resistor Rs, and the current of the primary winding of the first current transformer CT1 is calculated by conversion, so that the current of the first switching tube Q1 when being switched on is obtained. Correspondingly, in order to avoid saturation of the second current transformer CT2, the demagnetization operation loop is shown in fig. 4.
d. When the second switch Q2 is turned on and the first switch Q1 is turned off, the current of the current sampling circuit 30 flows as shown in fig. 5:
current flows in from the synonym terminal and the synonym terminal of the primary winding of the second current transformer CT2 and flows through the second switch tube Q2. Meanwhile, the current is coupled to the secondary winding of the second current transformer CT2, since the second sampling switch S2 is in the off state, the first secondary winding cannot form a current loop, and the current of the second secondary winding flows to the different name end and flows to the same name end, that is, the current flows from the different name end of the second secondary winding of the second current transformer CT2, sequentially passes through the fourth rectifier diode D14, the first sampling switch S1 and the sampling resistor Rs, and finally flows from the same name end of the second secondary winding, thereby forming a fourth current sampling path.
Similarly, the current of the secondary winding of the second current transformer CT2 can be obtained by collecting the voltage signal of the sampling resistor Rs, and the current of the primary winding of the second current transformer CT2 is calculated by conversion, so that the current of the second switching tube Q2 when being switched on is obtained. Correspondingly, to avoid saturation of the first current transformer CT1, the demagnetization operation loop is shown in fig. 5.
The totem-pole bridgeless PFC circuit system provided by the embodiment is provided with the current sampling circuit, and the working currents of two switching tubes can be effectively collected by performing power frequency control on two sampling switches in the current sampling circuit, so that the current of the PFC inductor can be obtained through synthesis; because the sampling switch is power frequency control, compared with the existing scheme, the sampling switch is simple to control and easy to realize. The current sampling circuit of the embodiment can sample the working current of the switching tube of the totem-pole bridgeless PFC circuit at any moment, can well solve the problem that the current of the totem-pole bridgeless PFC circuit is difficult to collect, and improves the application of the totem-pole bridgeless PFC circuit and the like.
It will be appreciated that the current of the switching tube can be effectively sampled by the current sampling circuit 30 as shown in fig. 6. It should be noted that, in addition to being applied to the totem-pole bridgeless PFC circuit, the current sampling circuit 30 can also be used as a module, for example, in some power electronic ac rectification circuits, bidirectional power conversion circuits, etc., wherein the primary windings of the first current transformer CT1 and the second current transformer CT2 of the current sampling circuit 30 are respectively used for connecting the main switch tube in the sampled circuit, and further used for collecting the current of the main switch tube. The current sampling circuit 30 is simple to control and easy to implement, and can well solve the problem that the switch tube is difficult to control due to the fact that current sampling is difficult.
In the embodiments provided in the present application, it should be understood that the disclosed apparatus and method may be implemented in other ways. The device embodiments described above are merely illustrative, and for example, the flowcharts and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of devices, methods according to embodiments of the present invention.
The above description is only for the specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto, and any person skilled in the art can easily think of the changes or substitutions within the technical scope of the present invention, and all should be covered within the protection scope of the present invention.
Claims (10)
1. A totem-pole bridgeless PFC circuit system, comprising: the current sampling circuit comprises a first bridge arm, a second bridge arm, a current sampling circuit and a control circuit, wherein the first bridge arm and the second bridge arm are connected in parallel to a first parallel connection point and a second parallel connection point;
the current sampling circuit comprises a first current transformer, a second current transformer, a demagnetization unit, a full-wave rectification unit, a first sampling switch, a second sampling switch and a sampling resistor, wherein the first current transformer and the second current transformer are respectively provided with two secondary windings;
a primary winding of the first current transformer is positioned between the first parallel connection point and the second connection point and is connected with the first switching tube in series, and a primary winding of the second current transformer is positioned between the second parallel connection point and the second connection point and is connected with the second switching tube in series;
two ends of each secondary winding of each current transformer are connected with one demagnetization unit in parallel; the first output end and the second output end of the two secondary windings of each current transformer are respectively connected with different input ends of the full-wave rectification unit, and the third common output end is connected with a control ground;
different output ends of the full-wave rectification unit are respectively connected with first ends of the first sampling switch and the second sampling switch, and second ends of the first sampling switch and the second sampling switch are both connected with the sampling resistor;
the control circuit is respectively connected with the control ends of the first switch tube, the second switch tube, the first sampling switch and the second sampling switch.
2. The totem-pole bridgeless PFC circuit system of claim 1, wherein a homonymous terminal and a synonym terminal of a primary winding of the first current transformer are connected to one end of the first switching tube and the second connection point, respectively;
and the homonymous end and the synonym end of the primary winding of the second current transformer are respectively connected with the second connection point and one end of the second switching tube.
3. The totem-pole bridgeless PFC circuit system of claim 1, wherein the second current transformer has the same structure as the first current transformer, and the two secondary windings of each current transformer are a first secondary winding and a second secondary winding, respectively;
the homonymous end of the first secondary winding and the heteronymous end of the second secondary winding of each current transformer are respectively used as the first output end and the second output end, and the heteronymous end of the first secondary winding and the homonymous end of the second secondary winding are connected and then used as the third public output end.
4. The totem-pole bridgeless PFC circuit system of claim 1, wherein the full-wave rectification unit comprises a first rectification diode, a second rectification diode, a third rectification diode, a fourth rectification diode;
the first output end of the first current transformer is connected with the anode of the first rectifying diode, and the second output end of the first current transformer is connected with the anode of the second rectifying diode;
the first output end of the second current transformer is connected with the anode of the third rectifying diode, and the second output end of the second current transformer is connected with the anode of the fourth rectifying diode;
the cathodes of the first rectifying diode and the fourth rectifying diode are connected with the first end of the first sampling switch;
and the cathodes of the second rectifying diode and the third rectifying diode are connected with the first end of the second sampling switch.
5. The totem-pole bridgeless PFC circuit system of claim 1, wherein the demagnetization unit is a demagnetization resistor or a zener diode.
6. The totem-pole bridgeless PFC circuit system of claim 1, wherein the first switching tube and the second switching tube have the same structure, and the first switching tube is an insulated gate field effect transistor, an insulated gate bipolar transistor, or a silicon carbide field effect transistor.
7. The totem-pole bridgeless PFC circuit system according to any one of claims 1 to 6, wherein the current sampling circuit is configured to sample current of the first switch tube through the first current transformer when the first switch tube is turned on, and demagnetize the first current transformer by the demagnetization unit corresponding to the first current transformer when the first switch tube is turned off;
the current sampling circuit is also used for sampling current of the second switch tube through the second current transformer when the second switch tube is conducted, and demagnetizing the second current transformer by the demagnetizing unit corresponding to the second current transformer when the second switch tube is disconnected.
8. The totem-pole bridgeless PFC circuit system according to any one of claims 1 to 6, wherein the control circuit is configured to control the second sampling switch to be turned on and the first sampling switch to be turned off when the AC power source is in a positive half-cycle, so that the current sampling circuit samples a forward current of the PFC inductor;
the control circuit is further configured to control the first sampling switch to be turned on and the second sampling switch to be turned off when the ac power supply is in a negative half-cycle, so that the current sampling circuit collects a negative current of the PFC inductor.
9. The totem-pole bridgeless PFC circuit system of claim 1, wherein the two diodes in the first leg are replaced with two switching tubes.
10. A current sampling circuit, characterized in that the current sampling circuit according to any one of claims 1 to 9 is adopted, wherein the primary windings of the first current transformer and the second current transformer are respectively used for connecting a main switching tube in a sampled circuit, and the current sampling circuit is used for collecting the current of the main switching tube.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113067458A (en) * | 2021-06-03 | 2021-07-02 | 杭州富特科技股份有限公司 | Current sampling circuit applied to bidirectional AC-DC converter |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113067458A (en) * | 2021-06-03 | 2021-07-02 | 杭州富特科技股份有限公司 | Current sampling circuit applied to bidirectional AC-DC converter |
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