A totem pole bridgeless circuit

Abstract

The embodiment of the present invention relates to the field of power electronics technology, and provides a totem pole bridgeless circuit. It includes: a current sampling unit, including a first primary winding, a second primary winding, a secondary winding and a sampling circuit, the first primary winding and the second primary winding work alternately in a high-frequency switching cycle to achieve forward and reverse excitation and flux reset in the first three quadrants, the secondary winding is coupled with the first primary winding and the second primary winding respectively, and is used to sense the first current flowing through the first primary winding and the second primary winding; the sampling circuit is connected to the secondary winding, and is used to sample the second current flowing through the secondary winding to obtain a sampling voltage; the control circuit is connected to the first bridge arm unit, the second bridge arm unit and the sampling circuit respectively, and is used to control the switching state of the third switch tube and the fourth switch tube according to the sampling voltage. In the above manner, the embodiment of the present invention can simplify the circuit structure and improve the circuit reliability.

Description

[Technical field]

[0001] The embodiments of the present invention relate to the field of power electronics technology, and in particular to a totem pole bridgeless circuit. [Background technology]

[0002] At present, a totem pole bridgeless circuit with a zero-crossing detection function includes an AC power supply, an inductor, a first bridge arm unit, a second bridge arm unit, a load unit, a first current transformer, and a second current transformer. Among them, the first bridge arm unit, the second bridge arm unit, and the load unit are connected in parallel, the first bridge arm unit includes a first switch tube and a second switch tube connected in series in the same direction, the second bridge arm unit includes a third switch tube and a fourth switch tube connected in series in the same direction, the point between the first switch tube and the second switch tube is the first series point, the point between the third switch tube and the fourth switch tube is the second series point, and the first series point and the second series point are also used to connect the AC power supply and the inductor, and the AC power supply and the inductor are connected in series. The first current transformer is connected in series with the third switch tube, and the second current transformer is connected in series with the fourth switch tube.

[0003] In the positive half cycle of the AC input, the fourth switch tube is the main tube, and the third switch tube is the freewheeling tube. When the fourth switch tube is turned on and the third switch tube is turned off, the AC power supply stores energy in the inductor. When the third switch tube is turned on and the fourth switch tube is turned off, the inductor continues to flow and provides energy to the load unit together with the AC power supply. In the negative half cycle of the AC input, the third switch tube is the main tube, and the fourth switch tube is the freewheeling tube. When the third switch tube is turned on and the fourth switch tube is turned off, the AC power supply stores energy in the inductor. When the fourth switch tube is turned on and the third switch tube is turned off, the inductor continues to flow and provides energy to the load unit together with the AC power supply. The first current transformer and the second current transformer are respectively used to perform zero-crossing detection on the freewheeling tube current. The third switch tube is performed with zero-crossing detection in the positive half cycle of the AC input, and the fourth switch tube is performed with zero-crossing detection in the negative half cycle of the AC input.

[0004] However, no matter in any working stage of the totem pole bridgeless circuit, each current transformer can only perform single-quadrant, unidirectional excitation operation, so an additional control circuit is required to reset the magnetic flux, which makes the circuit structure of the totem pole bridgeless circuit more complicated and reduces reliability. [Summary of the invention]

[0005] The embodiment of the present invention aims to provide a totem pole bridgeless circuit, which can simplify the circuit structure and improve the circuit reliability.

[0006] In order to solve the above technical problems, an embodiment of the present invention provides a totem pole bridgeless circuit, comprising a first bridge arm unit and a second bridge arm unit connected in parallel between a first parallel point and a second parallel point, the first bridge arm unit comprising a first switch tube and a second switch tube connected in series in the same direction, the point between the first switch tube and the second switch tube is a first series point, the second bridge arm unit comprises a third switch tube and a fourth switch tube connected in series in the same direction, the point between the third switch tube and the fourth switch tube is a second series point, the first parallel point and the second parallel point are also used for connecting a load unit in parallel, the first series point and the second series point are also used for connecting a power supply and an inductor, the power supply and the inductor are connected in series, and the totem pole bridgeless circuit further comprises:

[0007] A current sampling unit, comprising a first primary winding, a second primary winding, a secondary winding and a sampling circuit, wherein the first primary winding is arranged between the second series point and the first parallel point, and the second primary winding is arranged between the second series point and the second parallel point, the first primary winding and the second primary winding work alternately in a high-frequency switching cycle to realize forward and reverse excitation and magnetic flux reset in the first three quadrants, the secondary winding is coupled with the first primary winding and the second primary winding respectively, and is used to sense a first current flowing through the first primary winding and the second primary winding; the sampling circuit is connected to the secondary winding, and is used to sample a second current flowing through the secondary winding to obtain a sampling voltage;

[0008] The control circuit is respectively connected to the first bridge arm unit, the second bridge arm unit and the sampling circuit, and is used to determine the zero-crossing point of the inductor current according to the sampling voltage, and control the switching state of the third switch tube and the fourth switch tube according to the zero-crossing point.

[0009] In some embodiments, the control circuit comprises:

[0010] A signal processing unit connected to the sampling circuit, and configured to shape the sampled voltage into a square wave signal, wherein the square wave signal includes a first zero-crossing detection signal and a second zero-crossing detection signal;

[0011] The controller is respectively connected to the first bridge arm unit, the second bridge arm unit and the signal processing unit, and is used to determine the zero-crossing point of the inductor current according to the square wave signal, and control the switching state of the third switch tube and the fourth switch tube according to the zero-crossing point.

[0012] In some embodiments, the signal processing unit includes:

[0013] a first comparing unit, wherein an inverting terminal of the first comparing unit is used to be applied with the sampling voltage, a non-inverting terminal of the first comparing unit is used to be applied with a first threshold voltage, and the first comparing unit is used to shape the sampling voltage into a square wave signal;

[0014] A switch unit is connected to the first comparison output terminal of the first comparison unit and the controller respectively, and is used to select the first zero-crossing detection signal or the second zero-crossing detection signal to be output to the controller.

[0015] In some embodiments, the switch unit comprises:

[0016] A first switch circuit, wherein a first switch input terminal is used to be applied with a second control signal that is the same as that of the second switch tube, a second switch input terminal is connected to the first comparison output terminal and is used to receive the square wave signal, and a first switch output terminal is connected to the controller and is used to output the first zero-crossing detection signal;

[0017] A second switch circuit, a third switch input terminal is used to be applied with a first control signal that is the same as that of the first switch tube, a fourth switch input terminal is connected to the first comparison output terminal and is used to receive the square wave signal, and a second switch output terminal is connected to the controller and is used to output the second zero-crossing detection signal, wherein the controller determines the zero-crossing point of the inductor current according to the first zero-crossing detection signal or the second zero-crossing detection signal.

[0018] In some embodiments, the first switch circuit includes a first AND gate, a first input terminal of the first AND gate is used to be applied with the second control signal, a second input terminal is connected to the first comparison output terminal and is used to receive the square wave signal, and a first output terminal is connected to the controller and is used to output the first zero-crossing detection signal;

[0019] The second switch circuit includes a second AND gate, a third input terminal of the second AND gate is used to be applied with the first control signal, a fourth input terminal is connected to the first comparison output terminal and is used to receive the square wave signal, and a second output terminal is connected to the controller for outputting the second zero-crossing detection signal.

[0020] In some embodiments, the control circuit also includes a protection circuit, which is connected to the sampling circuit and the controller respectively, and is used to convert the sampling voltage into a protection signal, so that the controller controls each switch tube to perform a protection operation according to the protection signal.

[0021] In some embodiments, the protection circuit includes a second comparison unit, an inverting terminal of the second comparison unit is used to be applied with a second threshold voltage, a non-inverting terminal is used to be applied with the sampling voltage, a second comparison output terminal is connected to the controller, and the second comparison unit is used to convert the sampling voltage into a protection signal.

[0022] In some embodiments, the sampling circuit comprises:

[0023] a rectifier circuit, connected to the secondary winding, and configured to rectify the second current;

[0024] A sampling resistor is connected to the rectifier circuit and is used to sample the second current flowing through the rectifier circuit to obtain a sampling voltage.

[0025] In some embodiments, the first primary winding is connected in series with the second primary winding;

[0026] or,

[0027] The first primary winding is arranged between the second series connection point and the third switch tube, and the second primary winding is arranged between the second parallel connection point and the fourth switch tube;

[0028] or,

[0029] The first primary winding is arranged between the first parallel point and the third switch tube, and the second primary winding is arranged between the second parallel point and the fourth switch tube;

[0030] or,

[0031] The first primary winding is arranged between the first parallel point and the third switch tube, and the second primary winding is arranged between the second series point and the fourth switch tube.

[0032] In some embodiments, the control circuit controls the switching states of the third switch tube and the fourth switch tube according to the zero-crossing point, including:

[0033] When the AC voltage of the power supply is in the negative half cycle, the first switch tube is controlled to be continuously turned on, and when the zero crossing point is detected, the fourth switch tube is turned off and the third switch tube is turned on;

[0034] When the AC voltage of the power supply is in the positive half cycle, the second switch tube is controlled to be continuously turned on, and when the zero crossing point is detected, the third switch tube is turned off and the fourth switch tube is turned on.

[0035] The beneficial effect of the present invention is as follows: compared with the prior art, the embodiment of the present invention provides a totem pole bridgeless circuit. By setting a current sampling unit including a first primary winding, a second primary winding, a secondary winding and a sampling circuit, the first primary winding is connected in series with the third switch tube of the second bridge arm unit of the totem pole bridgeless circuit, the second primary winding is connected in series with the fourth switch tube of the second bridge arm unit of the totem pole bridgeless circuit, the first primary winding and the second primary winding work alternately in the high-frequency switching cycle to realize the first three-quadrant forward and reverse excitation and flux reset, the secondary winding is coupled with the first primary winding and the second primary winding respectively, and is used to sense the first current flowing through the first primary winding and the second primary winding, and the sampling circuit is connected to the secondary winding, and is used to sample the second current flowing through the secondary winding to obtain a sampling voltage. Therefore, the embodiment of the present invention can avoid the problem that the current sampling unit can only perform single-quadrant, unidirectional excitation work, resulting in the need to add an additional control circuit for flux reset, thereby simplifying the circuit structure and improving the circuit reliability.

Brief Description of the Drawings

[0036] One or more embodiments are exemplarily described by pictures in the corresponding drawings, and these exemplified descriptions do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0037] Figure 1 A schematic structural diagram of a totem pole bridgeless circuit provided by an embodiment of the present invention;

[0038] Figure 2 for Figure 1 The structural schematic diagram of the sampling circuit shown;

[0039] Figure 3 for Figure 1 The structural schematic diagram of the control circuit shown;

[0040] Figure 4 A circuit diagram of a totem pole bridgeless circuit provided by an embodiment of the present invention;

[0041] Figure 5a for Figure 1 A schematic diagram of one connection between the first primary winding and the second primary winding shown;

[0042] Figure 5b for Figure 1 A schematic diagram of one connection between the first primary winding and the second primary winding shown;

[0043] Figure 5c for Figure 1 A schematic diagram of one connection between the first primary winding and the second primary winding shown;

[0044] Figure 6 for Figure 1 Another circuit diagram of the secondary winding and sampling circuit shown;

[0045] Figure 7a When the AC voltage of the power supply is in the positive half cycle, the fourth switch tube is turned on, and the third switch tube is turned off, the inductor current i L and the secondary winding current i S Schematic diagram of current flow;

[0046] Figure 7b When the AC voltage of the power supply is in the positive half cycle, the third switch tube is turned on, and the fourth switch tube is turned off, the inductor current i L and the secondary winding current i S Schematic diagram of current flow;

[0047] Figure 8a When the AC voltage of the power supply is in the negative half cycle, the third switch tube is turned on, and the fourth switch tube is turned off, the inductor current i L and the secondary winding current i S Schematic diagram of current flow;

[0048] Figure 8b When the AC voltage of the power supply is in the negative half cycle, the fourth switch tube is turned on, and the third switch tube is turned off, the inductor current i L and the secondary winding current i S Schematic diagram of current flow;

[0049] Figure 9a It is a signal waveform diagram of the current flowing through the inductor, the fourth switch tube, the third switch tube, the secondary winding, and the sampling voltage output by the sampling resistor when the AC voltage of the power supply is in the positive half cycle;

[0050] Figure 9b It is a signal waveform diagram of the current flowing through the inductor, the fourth switch tube, the third switch tube, the secondary winding, and the sampling voltage output by the sampling resistor when the AC voltage of the power supply is in the negative half cycle;

[0051] Fig.10a is a signal waveform diagram of the current flowing through the inductor, the sampling voltage and the first threshold voltage input to the first comparison unit, and the first zero-crossing detection signal output by the first switch circuit when the AC voltage of the power supply is in the positive half cycle;

[0052] Fig.10b is a signal waveform diagram of the current flowing through the inductor, the sampling voltage and the second threshold voltage input to the first comparison unit, and the second zero-crossing detection signal output by the second switch circuit when the AC voltage of the power supply is in the negative half cycle;

[0053] Fig.11A signal waveform diagram of the AC voltage of the power supply, the first zero-crossing detection signal output by the first switch circuit, the second zero-crossing detection signal output by the second switch circuit, the first control signal applied to the first switch tube and the second switch circuit, and the second control signal applied to the second switch tube and the first switch circuit;

[0054] Fig.12 It is a signal waveform diagram of the current flowing through the inductor, the sampling voltage output by the sampling resistor, and the protection signal output by the second comparison unit. [Specific implementation method]

[0055] In order to facilitate the understanding of the present application, the present application is described in more detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that when an element is described as "connected" to another element, it can be directly connected to the other element, or there can be one or more intermediate elements therebetween. In addition, the terms "first", "second", etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0056] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used in this specification includes any and all combinations of one or more of the related listed items.

[0057] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0058] See also Figure 1 , is a schematic diagram of a totem pole bridgeless circuit provided by an embodiment of the present invention. Figure 1 As shown, the totem pole bridgeless circuit 100 includes a first bridge arm unit 11 , a second bridge arm unit 12 , a load unit 13 , a power supply 14 , an inductor 15 , a current sampling unit 10 and a control circuit 20 .

[0059] The first bridge arm unit 11 and the second bridge arm unit 12 are connected in parallel, and the connection points of the first bridge arm unit 11 and the second bridge arm unit 12 are respectively the first parallel point 12a and the second parallel point 12b. The first bridge arm unit 11 includes a first switch tube 111 and a second switch tube 112 connected in series in the same direction, and the point between the first switch tube 111 and the second switch tube 112 is the first series point 11a. The second bridge arm unit 12 includes a third switch tube 121 and a fourth switch tube 122 connected in series in the same direction, and the point between the third switch tube 121 and the fourth switch tube 122 is the second series point 11b.

[0060] It can be understood that the first switch tube 111 , the second switch tube 112 , the third switch tube 121 and the fourth switch tube 122 can be semiconductor devices such as bipolar transistors and metal-oxide semiconductor field effect transistors.

[0061] In the present application, the first switch tube 111, the second switch tube 112, the third switch tube 121 and the fourth switch tube 122 are all metal-oxide semiconductor field effect transistors as an example. Figure 4-Figure 8b As shown in any of the figures, the first switch tube 111 includes a first MOS tube Q1 , the second switch tube 112 includes a second MOS tube Q2 , the third switch tube 121 includes a third MOS tube Q3 , and the fourth switch tube 122 includes a fourth MOS tube Q4 .

[0062] Specifically, the gate of the first MOS transistor Q1 is connected to the control circuit 20, and is used to receive the first control signal PWM1 sent by the control circuit 20, the source of the first MOS transistor Q1 is connected to the first series point 11a, and the drain of the first MOS transistor Q1 is connected to the first parallel point 12a. The gate of the second MOS transistor Q2 is connected to the control circuit 20, and is used to receive the second control signal PWM2 sent by the control circuit 20, the drain of the second MOS transistor Q2 is connected to the first series point 11a, and the source of the second MOS transistor Q2 is connected to the second parallel point 12b. The gate of the third MOS transistor Q3 is connected to the control circuit 20, and is used to receive the third control signal PWM3 sent by the control circuit 20, the source of the third MOS transistor Q3 is connected to the second series point 11b, and the drain of the third MOS transistor Q3 is connected to the first parallel point 12a. The gate of the fourth MOS transistor Q4 is connected to the control circuit 20 for receiving the fourth control signal PWM4 sent by the control circuit 20 , the source of the fourth MOS transistor Q4 is connected to the second parallel point 12 b , and the drain of the fourth MOS transistor Q4 is connected to the second series point 11 b .

[0063] The load unit 13 is connected in parallel between the first parallel point 12a and the second parallel point 12b.

[0064] like Figure 4-Figure 8b As shown in any of the figures, the load unit 13 includes a capacitor C1 and a resistor R1, which are connected in parallel and connected in parallel to a first parallel point 12a and a second parallel point 12b. In the freewheeling stage of the inductor L1, the energy stored in the inductor L1 and the AC voltage of the AC power source Vin provide energy for the capacitor C1 and the resistor R1.

[0065] The power source 14 and the inductor 15 are connected in series between the first series connection point 11 a and the second series connection point 11 b .

[0066] like Figure 4-Figure 8bAs shown in any of the figures, the power supply 14 includes an AC power supply Vin, and the inductor 15 includes an inductor L1. The AC power supply Vin and the inductor L1 are connected in series and are connected between a first series connection point 11a and a second series connection point 11b. One end (negative or positive) of the AC power supply Vin is connected to the first series connection point 11a, and the other end (positive or negative) of the AC power supply Vin is connected to one end of the inductor L1, and the other end of the inductor L1 is connected to the second series connection point 11b. At any stage of the operation of the totem pole bridgeless circuit 100, when the main switch tube (including the third switch tube 121 or the fourth switch tube 122) is turned on, the AC power supply Vin, the inductor L1 and the main switch tube form a closed loop, and the AC voltage of the AC power supply Vin charges the inductor L1 to store energy in the inductor L1.

[0067] The current sampling unit 10 includes a first primary winding 101, a second primary winding 102, a secondary winding 103 and a sampling circuit 104. The first primary winding 101 is arranged between the second series point 11b and the first parallel point 12a, and the second primary winding 102 is arranged between the second series point 11b and the second parallel point 12b. The first primary winding 101 and the second primary winding 102 work alternately in a high-frequency switching cycle to achieve forward and reverse excitation and flux reset in the first three quadrants. The secondary winding 103 is coupled to the first primary winding 101 and the second primary winding 102 respectively, and is used to sense the first current flowing through the first primary winding 101 and the second primary winding 102; the sampling circuit 104 is connected to the secondary winding 103, and is used to sample the second current flowing through the secondary winding 103 to obtain a sampling voltage.

[0068] like Figure 4-5c As shown, the first primary winding 101 includes a primary winding NP1, the second primary winding 102 includes a primary winding NP2, the secondary winding 103 includes a secondary winding NS, and the primary winding NP1, the primary winding NP2 and the secondary winding NS form a current transformer CT1 (the magnetic core between the primary winding NP1, the primary winding NP2 and the secondary winding NS is not marked). The first primary winding 101 is arranged between the second series point 11b and the first parallel point 12a, and the second primary winding 102 is arranged between the second series point 11b and the second parallel point 12b, including the following four situations:

[0069] (1) The first primary winding 101 and the second primary winding 102 are connected in series.

[0070] Preferably, see Figure 4The primary of the current transformer CT1 includes two symmetrical windings with middle taps, namely the primary winding NP1 and the primary winding NP2. The same-name end of the primary winding NP1 is connected to the source of the third MOS tube Q3, the opposite-name end of the primary winding NP1 and the middle tap of the same-name end of the primary winding NP2 are connected, and the opposite-name end of the primary winding NP2 is connected to the drain of the fourth MOS tube Q4.

[0071] In some embodiments, the primary winding NP1 and the primary winding NP2 of the current transformer CT1 can be completely independent, the primary winding NP1 and the primary winding NP2 are not directly connected, and the primary winding NP1 and the primary winding NP2 are respectively connected in series with the third MOS transistor Q3 and the fourth MOS transistor Q4, such as the following situations (2)-(4):

[0072] (2) The first primary winding 101 is disposed between the second series point 11 b and the third switch tube 121 , and the second primary winding 102 is disposed between the second parallel point 12 b and the fourth switch tube 122 .

[0073] See also Figure 5a The primary winding NP1 is arranged between the second series connection point 11b and the third switch tube 121, that is, the same-name end of the primary winding NP1 is connected to the source of the third MOS tube Q3, and the opposite-name end of the primary winding NP1 is connected to the second series connection point 11b. The primary winding NP2 is arranged between the second parallel connection point 12b and the fourth switch tube 122, that is, the same-name end of the primary winding NP2 is connected to the source of the fourth MOS tube Q4, and the opposite-name end of the primary winding NP2 is connected to the second parallel connection point 12b.

[0074] (3) The first primary winding 101 is disposed between the first parallel point 12 a and the third switch tube 121 , and the second primary winding 102 is disposed between the second parallel point 12 b and the fourth switch tube 122 .

[0075] See also Figure 5b The primary winding NP1 is arranged between the first parallel point 12a and the third switch tube 121, that is, the same-name end of the primary winding NP1 is connected to the first parallel point 12a, and the opposite-name end of the primary winding NP1 is connected to the drain of the third MOS tube Q3. The primary winding NP2 is arranged between the second parallel point 12b and the fourth switch tube, that is, the same-name end of the primary winding NP2 is connected to the source of the fourth MOS tube Q4, and the opposite-name end of the primary winding NP2 is connected to the second parallel point 12b.

[0076] (4) The first primary winding 101 is disposed between the first parallel point 12 a and the third switch tube 121 , and the second primary winding 102 is disposed between the second series point 11 b and the fourth switch tube 122 .

[0077] See also Figure 5c The primary winding NP1 is arranged between the first parallel point 12a and the third switch tube 121, that is, the same-name end of the primary winding NP1 is connected to the first parallel point 12a, and the opposite-name end of the primary winding NP1 is connected to the drain of the third MOS tube Q3. The primary winding NP2 is arranged between the second series point 11b and the fourth switch tube 122, that is, the same-name end of the primary winding NP2 is connected to the second series point 11b, and the opposite-name end of the primary winding NP2 is connected to the drain of the fourth MOS tube Q4.

[0078] Please also read Figure 2 The sampling circuit 104 includes a rectifier circuit 1041 and a sampling resistor 1042 .

[0079] The rectifying circuit 1041 is connected to the secondary winding 103 and is used for rectifying the second current.

[0080] The sampling resistor 1042 is connected to the rectifier circuit 1041 and is used to sample the second current flowing through the rectifier circuit 1041 to obtain a sampled voltage.

[0081] like Figure 4-5c As shown, the rectifier circuit 1041 includes a full-bridge rectifier circuit, which includes a diode D1, a diode D2, a diode D3 and a diode D4, and the sampling resistor 1042 includes a resistor R2. The anode of the diode D1 is connected to the same-name end of the secondary winding NS and the cathode of the diode D3, the cathode of the diode D1 is connected to the cathode of the diode D2 and one end of the resistor R2, the anode of the diode D2 is connected to the opposite-name end of the secondary winding NS and the cathode of the diode D4, and the anode of the diode D3, the anode of the diode D4 and the other end of the resistor R2 are all grounded.

[0082] When the AC voltage of the power source 14 is in the positive half cycle, the signal waveform of the sampling voltage output by the resistor R2 is as follows: Figure 9a When the AC voltage of the power supply 14 is in the negative half cycle, the signal waveform of the sampling voltage output by the resistor R2 is as follows: Figure 9b shown.

[0083] In some embodiments, see Figure 6The secondary of the current transformer CT1 includes two symmetrical windings with middle taps, namely the secondary winding NS1 and the secondary winding NS2. At this time, the rectifier circuit 1041 includes a full-wave rectifier circuit, and the full-wave rectifier circuit includes a diode D5 and a diode D6. Among them, the same-name end of the secondary winding NS1 is connected to the anode of the diode D5, and the opposite-name end of the secondary winding NS1 is middle-tapped and grounded to one end of the secondary winding NS2. The other end of the secondary winding NS2 is connected to the anode of the diode D6, and the cathode of the diode D5 is connected to the cathode of the diode D6 and one end of the resistor R2, and the other end of the resistor R2 is grounded.

[0084] In summary, the current signal flow of the totem pole bridgeless circuit is roughly as follows:

[0085] When the AC voltage of the AC power source Vin is in the positive half cycle, such as Figure 7a As shown, the control circuit 20 controls the first MOS tube Q1 to turn off and the second MOS tube Q2 to turn on. At this time, the fourth MOS tube Q4 is the main switch tube, and the third MOS tube Q3 is the freewheeling switch tube. The third MOS tube Q3 is turned off and the fourth MOS tube Q4 is turned on. The inductor current i L The current flows to the positive electrode of the AC power supply Vin, one end of the inductor L1, the other end of the inductor L1, the same-name end of the primary winding NP2, the opposite-name end of the primary winding NP2, the drain of the fourth MOS tube Q4, the source of the fourth MOS tube Q4, the source of the second MOS tube Q2, the drain of the second MOS tube Q2, and finally returns to the negative electrode of the AC power supply Vin. In this stage, the AC power supply Vin stores energy in the inductor L1. Correspondingly, the same-name end of the secondary winding NS is positive, and the secondary winding NS current i S The current flows to the same-name end of the secondary winding NS, the anode of the diode D1, the cathode of the diode D1, one end of the resistor R2, the other end of the resistor R2, the anode of the diode D4, the cathode of the diode D4, and finally returns to the opposite-name end of the secondary winding NS. When the AC power supply Vin is in the positive half cycle and the inductor L1 is storing energy, the current transformer CT1 realizes flux reset through the primary winding NP2 and performs forward excitation in the first quadrant.

[0086] When the AC voltage of the AC power source Vin is in the positive half cycle, such as Figure 7b As shown, when the inductor L1 is freewheeling, the fourth MOS tube Q4 is turned off, the third MOS tube Q3 is turned on, and the inductor current i LThe current flows to the positive electrode of the AC power supply Vin, one end of the inductor L1, the other end of the inductor L1, the opposite end of the primary winding NP1, the same end of the primary winding NP1, the source of the third MOS tube Q3, the drain of the third MOS tube Q3, the load unit 13 (capacitor C1 and resistor R1), the source of the second MOS tube Q2, the drain of the second MOS tube Q2, and finally returns to the negative electrode of the AC power supply Vin. In this stage, the inductor L1 is freewheeling through the third MOS tube Q3. Correspondingly, the same end of the secondary winding NS is negative, and the secondary winding NS current i S The current flows to the opposite-name end of the secondary winding NS, the anode of the diode D2, the cathode of the diode D2, one end of the resistor R2, the other end of the resistor R2, the anode of the diode D3, the cathode of the diode D3, and finally returns to the same-name end of the secondary winding NS. When the AC power supply Vin is in the positive half cycle and the inductor L1 is freewheeling through the third MOS tube Q3, the current transformer CT1 realizes flux reset through the primary winding NP1 and performs negative excitation in the third quadrant.

[0087] When the AC voltage of the AC power source Vin is in the negative half cycle, such as Figure 8a As shown, the control circuit 20 controls the first MOS tube Q1 to be turned on and the second MOS tube Q2 to be turned off. At this time, the third MOS tube Q3 is the main switch tube, and the fourth MOS tube Q4 is the freewheeling switch tube. The fourth MOS tube Q4 is turned off, and the third MOS tube Q3 is turned on. The inductor current i L The current flows to the positive electrode of the AC power supply Vin, the source of the first MOS tube Q1, the drain of the first MOS tube Q1, the drain of the third MOS tube Q3, the source of the third MOS tube Q3, the same-name end of the primary winding NP1, the opposite-name end of the primary winding NP1, the other end of the inductor L1, one end of the inductor L1, and finally returns to the negative electrode of the AC power supply Vin. In this stage, the AC power supply Vin stores energy in the inductor L1. Correspondingly, the same-name end of the secondary winding NS is positive, and the secondary winding NS current i S The current flows to the same-name end of the secondary winding NS, the anode of the diode D1, the cathode of the diode D1, one end of the resistor R2, the other end of the resistor R2, the anode of the diode D4, the cathode of the diode D4, and finally returns to the opposite-name end of the secondary winding NS. When the AC power supply Vin is in the negative half cycle and the inductor L1 is storing energy, the current transformer CT1 realizes flux reset through the primary winding NP1 and performs positive excitation in the first quadrant.

[0088] When the AC voltage of the AC power source Vin is in the negative half cycle, such as Figure 8b As shown, when the inductor L1 is freewheeling, the third MOS tube Q3 is turned off, the fourth MOS tube Q4 is turned on, and the inductor current i LThe current flows to the positive electrode of the AC power supply Vin, the source of the first MOS tube Q1, the drain of the first MOS tube Q1, the load unit 13 (capacitor C1 and resistor R1), the source of the fourth MOS tube Q4, the drain of the fourth MOS tube Q4, the opposite end of the primary winding NP2, the same end of the primary winding NP2, the other end of the inductor L1, one end of the inductor L1, and finally returns to the negative electrode of the AC power supply Vin. In this stage, the inductor L1 is freewheeling through the fourth MOS tube Q4. Correspondingly, the same end of the secondary winding NS is negative, and the secondary winding NS current i S The current flows to the opposite-name end of the secondary winding NS, the anode of the diode D2, the cathode of the diode D2, one end of the resistor R2, the other end of the resistor R2, the anode of the diode D3, the cathode of the diode D3, and finally returns to the same-name end of the secondary winding NS. When the AC power supply Vin is in the negative half cycle and the inductor L1 is freewheeling through the fourth MOS tube Q4, the current transformer CT1 realizes flux reset through the primary winding NP2 and performs negative excitation in the third quadrant. It can be seen that the current transformer CT1 of the present application can be reset through the primary winding NP1 or the primary winding NP2, and can be positively excited in the first quadrant and negatively excited in the third quadrant. There is no need to add an additional control circuit to reset the current transformer CT1, and in any stage of the operation of the totem pole bridgeless circuit 100, zero-crossing detection of the third switch tube 121 and the fourth switch tube 122 can be achieved simultaneously, avoiding the problem of only being able to perform zero-crossing detection on the third switch tube 121 or the fourth switch tube 122 due to the current transformer CT1 working in a single quadrant.

[0089] The control circuit 20 is respectively connected to the first bridge arm unit 11, the second bridge arm unit 12 and the sampling circuit 104, and is used to determine the zero-crossing point of the inductor current according to the sampling voltage, and control the switching state of the third switch tube 121 and the fourth switch tube 122 according to the zero-crossing point.

[0090] See also Figure 3 The control circuit 20 includes a signal processing unit 21 and a controller 22 .

[0091] The signal processing unit 21 is connected to the sampling circuit 104 and is used to shape the sampled voltage into a square wave signal, wherein the square wave signal includes a first zero-crossing detection signal and a second zero-crossing detection signal.

[0092] The signal processing unit 21 includes a first comparing unit 211 and a switching unit 212 .

[0093] The inverting terminal of the first comparison unit 211 is used to be applied with the sampling voltage, and the non-inverting terminal is used to be applied with the first threshold voltage. The first comparison unit is used to shape the sampling voltage into a square wave signal.

[0094] The switch unit 212 is connected to the first comparison output terminal of the first comparison unit 211 and the controller 22 respectively, and is used for selecting the first zero-crossing detection signal or the second zero-crossing detection signal to be output to the controller 22 .

[0095] See also Figure 4 , Fig.10a as well as Fig.10b , the first comparison unit 211 includes a comparator U1, the inverting terminal of the comparator U1 is used to be applied with a sampling voltage VR2, and the non-inverting terminal of the comparator U1 is used to be applied with a first threshold voltage VTH1. When the first threshold voltage VTH1 is greater than the sampling voltage VR2, the first comparison output terminal of the comparator U1 outputs a high-level signal, and when the first threshold voltage VTH1 is not greater than the sampling voltage VR2, the first comparison output terminal of the comparator U1 outputs a low-level signal to obtain a square wave signal, and the square wave signal includes a first zero-crossing detection signal and a second zero-crossing detection signal. When the AC voltage of the power supply 14 is in the positive half cycle, the first zero-crossing detection signal ZCD1 is obtained, and when the AC voltage of the power supply 14 is in the negative half cycle, the first zero-crossing detection signal ZCD2 is obtained.

[0096] The switch unit 212 includes a first switch circuit 2121 and a second switch circuit 2122 .

[0097] The first switch input terminal of the first switch circuit 2121 is used to be applied with the second control signal that is the same as that of the second switch tube 112, the second switch input terminal of the first switch circuit 2121 is connected to the first comparison output terminal and is used to receive the square wave signal, and the first switch output terminal of the first switch circuit 2121 is connected to the controller 22 for outputting the first zero-crossing detection signal.

[0098] like Figure 4 As shown, the first switch circuit 2121 includes a first AND gate U3, the first input end of the first AND gate U3 is used to be applied with the second control signal, the second input end of the first AND gate U3 is connected to the first comparison output end and is used to receive the square wave signal, and the first output end of the first AND gate U3 is connected to the controller 22 for outputting the first zero-crossing detection signal.

[0099] See also Fig.11When the AC voltage of the power supply 14 is in the positive half cycle, the first control signal PWM1 is at a low level and the second control signal PWM2 is at a high level. At this time, the first AND gate U3 is selected, and the second control signal PWM2 performs a logic AND operation with the square wave signal to output a first zero-crossing detection signal ZCD1, so that the controller 22 obtains the current information flowing through the third MOS tube Q3 and the fourth MOS tube Q4 according to the first zero-crossing detection signal ZCD1, determines the rising edge of the driving of the third MOS tube Q3 and the fourth MOS tube Q4, that is, determines the zero-crossing point of the inductor current, so as to control the switching state of the third MOS tube Q3 and the fourth MOS tube Q4.

[0100] The third switch input terminal of the second switch circuit 2122 is used to be applied with the same first control signal as the first switch tube 111, the fourth switch input terminal of the second switch circuit 2122 is connected to the first comparison output terminal and is used to receive the square wave signal, and the second switch output terminal of the second switch circuit 2122 is connected to the controller 22 for outputting the second zero-crossing detection signal, wherein the controller 22 determines the zero-crossing point of the inductor current according to the first zero-crossing detection signal or the second zero-crossing detection signal.

[0101] like Figure 4 As shown, the second switch circuit 2122 includes a second AND gate U4, the third input terminal of the second AND gate U4 is used to be applied with the first control signal, the fourth input terminal of the second AND gate U4 is connected to the first comparison output terminal and is used to receive the square wave signal, and the second output terminal of the second AND gate U4 is connected to the controller 22 for outputting the second zero-crossing detection signal.

[0102] Please refer again Fig.11 When the AC voltage of the power supply 14 is in the negative half cycle, the first control signal PWM1 is at a high level and the second control signal PWM2 is at a low level. At this time, the second AND gate U4 is selected, and the first control signal PWM1 performs a logic AND operation with the square wave signal to output a second zero-crossing detection signal ZCD2, so that the controller 22 obtains the current information flowing through the third MOS tube Q3 and the fourth MOS tube Q4 according to the second zero-crossing detection signal ZCD2, determines the rising edge of the driving of the third MOS tube Q3 and the fourth MOS tube Q4, that is, determines the zero-crossing point of the inductor current, so as to control the switching state of the third MOS tube Q3 and the fourth MOS tube Q4.

[0103] In some embodiments, the comparator U1 sets a hysteresis window through a peripheral circuit so that the high level of the square wave signal maintains a certain width, so that the single-chip microcomputer U5 can reliably obtain the square wave signal.

[0104] The controller 22 is respectively connected to the first bridge arm unit 11, the second bridge arm unit 12 and the signal processing unit 21, and is used to determine the zero-crossing point of the inductor current according to the square wave signal, and control the switching state of the third switch tube 121 and the fourth switch tube 122 according to the zero-crossing point.

[0105] In this embodiment, the controller 22 includes a single-chip microcomputer U5 and its peripheral circuits (not shown). The single-chip microcomputer U5 can adopt 51 series, Arduino series, STM32 series, etc.

[0106] In some embodiments, the controller 22 can also be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), an ARM (Acorn RISC Machine) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination of these components; it can also be any traditional processor, controller, microcontroller or state machine; it can also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors combined with a DSP core, or any other such configuration.

[0107] The control circuit 20 controls the switching states of the third switch tube 121 and the fourth switch tube 122 according to the zero crossing point, including: when the AC voltage of the power supply 14 is in the negative half cycle, the first switch tube 111 is controlled to be continuously turned on, and when the zero crossing point is detected, the fourth switch tube 122 is turned off and the third switch tube 121 is turned on; when the AC voltage of the power supply 14 is in the positive half cycle, the second switch tube 112 is controlled to be continuously turned on, and when the zero crossing point is detected, the third switch tube 121 is turned off and the fourth switch tube 122 is turned on.

[0108] In some embodiments, the control circuit 20 also includes a protection circuit 23, which is respectively connected to the sampling circuit 104 and the controller 22, and is used to convert the sampling voltage into a protection signal, so that the controller 22 controls each switch tube to perform a protection operation according to the protection signal.

[0109] The protection circuit 23 includes a second comparison unit 231, an inverting terminal of the second comparison unit 231 is used to be applied with a second threshold voltage, a non-inverting terminal is used to be applied with the sampling voltage, a second comparison output terminal is connected to the controller 22, and the second comparison unit 231 is used to convert the sampling voltage into a protection signal.

[0110] like Figure 4As shown, the second comparison unit 211 includes a comparator U2, an inverting terminal of the comparator U2 is used to be applied with a second threshold voltage VTH2, a non-inverting terminal of the comparator U2 is used to be applied with a sampling voltage VR2, and a second comparison output terminal of the comparator U2 is used to output a protection signal OCP.

[0111] See also Fig.12 When the sampling voltage VR2 is greater than the second threshold voltage VTH2, the second comparison output terminal of the comparator U2 outputs a high-level signal, and when the sampling voltage VR2 is not greater than the second threshold voltage VTH2, the second comparison output terminal of the comparator U2 outputs a low-level signal, thereby obtaining a protection signal OCP, so that the controller 22 controls each switch tube to perform a protection operation according to the protection signal OCP. The control of each switch tube to perform a protection operation according to the protection signal OCP includes: determining whether the protection signal OCP jumps from low to high; if so, performing wave sealing processing or wave-by-wave current limiting processing on the third switch tube 121 and the fourth switch tube 122; if not, not performing a protection operation. Thereby, it is ensured that the third switch tube 121 and the fourth switch tube 122 operate within an acceptable current range.

[0112] In some embodiments, the comparator U2 sets a hysteresis window through a peripheral circuit so that the high level of the protection signal OCP maintains a certain width, so that the single-chip microcomputer U5 can reliably obtain the protection signal OCP.

[0113] The embodiment of the present invention provides a totem pole bridgeless circuit. By setting a current sampling unit including a first primary winding, a second primary winding, a secondary winding and a sampling circuit, the first primary winding is connected in series with the third switch tube of the second bridge arm unit of the totem pole bridgeless circuit, the second primary winding is connected in series with the fourth switch tube of the second bridge arm unit of the totem pole bridgeless circuit, the first primary winding and the second primary winding work alternately in the high-frequency switching cycle to realize the first three-quadrant forward and reverse excitation and flux reset, the secondary winding is coupled with the first primary winding and the second primary winding respectively, and is used to sense the first current flowing through the first primary winding and the second primary winding, and the sampling circuit is connected to the secondary winding, and is used to sample the second current flowing through the secondary winding to obtain a sampling voltage. Therefore, the embodiment of the present invention can avoid the problem that the current sampling unit can only perform single-quadrant, unidirectional excitation work, resulting in the need to add an additional control circuit for flux reset, thereby simplifying the circuit structure and improving the circuit reliability.

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may also be combined, the steps may be implemented in any order, and there are many other changes in different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they may still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A totem pole bridgeless circuit, comprising a first bridge arm unit and a second bridge arm unit connected in parallel between a first parallel point and a second parallel point, wherein the first bridge arm unit comprises a first switch tube and a second switch tube connected in series in the same direction, wherein the point between the first switch tube and the second switch tube is a first series point, and the second bridge arm unit comprises a third switch tube and a fourth switch tube connected in series in the same direction, wherein the point between the third switch tube and the fourth switch tube is a second series point, wherein the first parallel point and the second parallel point are also used to connect a load unit in parallel, and the first series point and the second series point are also used to connect a power supply and an inductor, wherein the power supply and the inductor are connected in series, characterized in that: The totem pole bridgeless circuit further comprises: A current sampling unit, comprising a first primary winding, a second primary winding, a secondary winding and a sampling circuit, wherein the first primary winding is arranged between the second series point and the first parallel point, and the second primary winding is arranged between the second series point and the second parallel point, the first primary winding and the second primary winding work alternately in a high-frequency switching cycle to realize forward and reverse excitation and magnetic flux reset in the first three quadrants, the secondary winding is coupled with the first primary winding and the second primary winding respectively, and is used to sense a first current flowing through the first primary winding and the second primary winding; the sampling circuit is connected to the secondary winding, and is used to sample a second current flowing through the secondary winding to obtain a sampling voltage; The control circuit is respectively connected to the first bridge arm unit, the second bridge arm unit and the sampling circuit, and is used to determine the zero-crossing point of the inductor current according to the sampling voltage, and control the switching state of the third switch tube and the fourth switch tube according to the zero-crossing point.

2. The totem pole bridgeless circuit according to claim 1, characterized in that: The control circuit comprises: A signal processing unit connected to the sampling circuit, and configured to shape the sampled voltage into a square wave signal, wherein the square wave signal includes a first zero-crossing detection signal and a second zero-crossing detection signal; The controller is respectively connected to the first bridge arm unit, the second bridge arm unit and the signal processing unit, and is used to determine the zero-crossing point of the inductor current according to the square wave signal, and control the switching state of the third switch tube and the fourth switch tube according to the zero-crossing point.

3. The totem pole bridgeless circuit according to claim 2, characterized in that: The signal processing unit comprises: a first comparing unit, wherein an inverting terminal of the first comparing unit is used to be applied with the sampling voltage, a non-inverting terminal of the first comparing unit is used to be applied with a first threshold voltage, and the first comparing unit is used to shape the sampling voltage into a square wave signal; A switch unit is connected to the first comparison output terminal of the first comparison unit and the controller respectively, and is used to select the first zero-crossing detection signal or the second zero-crossing detection signal to be output to the controller.

4. The totem pole bridgeless circuit according to claim 3, characterized in that: The switch unit comprises: A first switch circuit, wherein a first switch input terminal is used to be applied with a second control signal that is the same as that of the second switch tube, a second switch input terminal is connected to the first comparison output terminal and is used to receive the square wave signal, and a first switch output terminal is connected to the controller and is used to output the first zero-crossing detection signal; A second switch circuit, a third switch input terminal is used to be applied with a first control signal that is the same as that of the first switch tube, a fourth switch input terminal is connected to the first comparison output terminal and is used to receive the square wave signal, and a second switch output terminal is connected to the controller and is used to output the second zero-crossing detection signal, wherein the controller determines the zero-crossing point of the inductor current according to the first zero-crossing detection signal or the second zero-crossing detection signal.

5. The totem pole bridgeless circuit according to claim 4, characterized in that: The first switch circuit comprises a first AND gate, wherein a first input terminal of the first AND gate is used to be applied with the second control signal, a second input terminal is connected to the first comparison output terminal and is used to receive the square wave signal, and a first output terminal is connected to the controller and is used to output the first zero-crossing detection signal; The second switch circuit includes a second AND gate, a third input terminal of the second AND gate is used to be applied with the first control signal, a fourth input terminal is connected to the first comparison output terminal and is used to receive the square wave signal, and a second output terminal is connected to the controller for outputting the second zero-crossing detection signal.

6. The totem pole bridgeless circuit according to any one of claims 2 to 5, characterized in that: The control circuit also includes a protection circuit, which is connected to the sampling circuit and the controller respectively, and is used to convert the sampling voltage into a protection signal, so that the controller controls each switch tube to perform a protection operation according to the protection signal.

7. The totem pole bridgeless circuit according to claim 6, characterized in that: The protection circuit includes a second comparison unit, an inverting terminal of the second comparison unit is used to be applied with a second threshold voltage, a non-inverting terminal is used to be applied with the sampling voltage, a second comparison output terminal is connected to the controller, and the second comparison unit is used to convert the sampling voltage into a protection signal.

8. The totem pole bridgeless circuit according to any one of claims 1 to 5, characterized in that: The sampling circuit comprises: a rectifier circuit, connected to the secondary winding, and configured to rectify the second current; A sampling resistor is connected to the rectifier circuit and is used to sample the second current flowing through the rectifier circuit to obtain a sampling voltage.

9. The totem pole bridgeless circuit according to any one of claims 1 to 5, characterized in that: The first primary winding is connected in series with the second primary winding; or, The first primary winding is arranged between the second series connection point and the third switch tube, and the second primary winding is arranged between the second parallel connection point and the fourth switch tube; or, The first primary winding is arranged between the first parallel point and the third switch tube, and the second primary winding is arranged between the second parallel point and the fourth switch tube; or, The first primary winding is arranged between the first parallel point and the third switch tube, and the second primary winding is arranged between the second series point and the fourth switch tube.

10. The totem pole bridgeless circuit according to any one of claims 1 to 5, characterized in that: The control circuit controls the switching states of the third switch tube and the fourth switch tube according to the zero-crossing point, including: When the AC voltage of the power supply is in the negative half cycle, the first switch tube is controlled to be continuously turned on, and when the zero crossing point is detected, the fourth switch tube is turned off and the third switch tube is turned on; When the AC voltage of the power supply is in the positive half cycle, the second switch tube is controlled to be continuously turned on, and when the zero crossing point is detected, the third switch tube is turned off and the fourth switch tube is turned on.

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