A current sampling circuit and bridgeless rectification system

Abstract

The present invention belongs to the field of switching power supplies and provides a current sampling circuit and a bridgeless rectifier system. During the period when both the first switch tube and the second switch tube are turned on, the main winding of the current transformer isolates and couples the current in the excitation circuit of the power factor correction circuit to the secondary winding of the current transformer, and the current sampling circuit where the secondary winding of the current transformer is located outputs a sampling signal through the sampling output terminal. During this period, the current transformer is in a magnetic reset process; during the period when both the first switch tube and the second switch tube are turned off, the closed discharge circuit where the secondary winding of the current transformer is located discharges through the reset resistor to complete the magnetic reset process of the current transformer. During this period, the current transformer is in a magnetic reset process. Therefore, the current sampling circuit in the present invention has a strong anti-interference ability. By adopting the current sampling circuit in the present invention, the current sampling accuracy of the bridgeless rectifier system can be improved and the anti-interference ability of the bridgeless rectifier system can be improved.

Description

Technical Field

[0001] The present invention belongs to the field of switching power supplies, and in particular relates to a current sampling circuit and a bridgeless rectification system. Background Art

[0002] With the growing adoption of green, environmentally friendly, and energy-saving concepts, the demand for power conversion efficiency in power supply systems is increasing. Traditional bridge rectification has become a major bottleneck limiting the efficiency of switching power supplies. New bridgeless rectification systems not only effectively address efficiency issues but also alleviate the heat dissipation problem of bridge rectifiers. However, existing bridgeless rectification systems have poor interference immunity. Furthermore, the current sampling circuit in a bridgeless rectification system operates in a high-frequency switching state synchronized with the main switch, placing relatively high demands on PWM timing accuracy, which affects current sampling precision.

[0003] Therefore, the existing bridgeless rectifier system has the problems of poor anti-interference ability and low current sampling accuracy. Summary of the Invention

[0004] The present invention provides a current sampling circuit and a bridgeless rectifier system, aiming to solve the problems of poor anti-interference capability and low current sampling accuracy in existing bridgeless rectifier systems.

[0005] A first aspect of the present invention provides a current sampling circuit, wherein the current sampling circuit is connected to a power factor correction circuit via a current transformer, and the power factor correction circuit comprises:

[0006] An AC signal source, a choke device, a first switching tube, a second switching tube, a main winding of the current transformer, a first unidirectional conductive device, a second unidirectional conductive device, a third unidirectional conductive device, a fourth unidirectional conductive device, an energy storage device, and a load;

[0007] The first end of the AC signal source is connected to the first end of the choke device, the second end of the choke device, the cathode of the second unidirectional conductive device, and the first end of the first switching tube are commonly connected to the anode of the first unidirectional conductive device, the second end of the first switching tube is connected to the first end of the second switching tube, the second end of the second switching tube is connected to the first end of the main winding of the AC transformer, the second end of the main winding of the AC transformer, the anode of the third unidirectional conductive device, and the cathode of the fourth unidirectional conductive device are commonly connected to the second end of the AC signal source, the cathode of the first unidirectional conductive device, the cathode of the third unidirectional conductive device, and the first end of the energy storage device are commonly connected to the first end of the load, the second end of the load, the second end of the energy storage device, and the anode of the fourth unidirectional conductive device are commonly connected to the anode of the second unidirectional conductive device;

[0008] The control terminals of the first switching transistor and the second switching transistor are connected to a driving signal for controlling the synchronous on and off of the first switching transistor and the second switching transistor. During a positive half cycle of the AC signal output by the AC signal source, the driving signal drives the first switching transistor and the second switching transistor to be turned on during a current rise period of the choke device in the power factor correction circuit, and drives the first switching transistor and the second switching transistor to be turned off during a current fall period of the choke device. During a negative half cycle of the AC signal output by the AC signal source, the driving signal drives the first switching transistor and the second switching transistor to be turned off during a current rise period of the choke device in the power factor correction circuit, and drives the first switching transistor and the second switching transistor to be turned on during a current fall period of the choke device.

[0009] It is characterized in that the current sampling circuit includes:

[0010] The secondary winding of the current transformer, the fifth unidirectional conductive device, the sixth unidirectional conductive device, the third switch tube, the seventh unidirectional conductive device, the eighth unidirectional conductive device, the fourth switch tube, the first reset resistor, the second reset resistor and the sampling resistor;

[0011] A low-frequency control signal is connected to the control terminal of the third switch tube, and the low-frequency control signal is inverted by an inverter and then connected to the control terminal of the fourth switch tube. The low-frequency control signal outputs a high level during a positive half-cycle of the AC signal output by the AC signal source to turn on the third switch tube and turn off the fourth switch tube, and outputs a low level during a negative half-cycle of the AC signal to turn off the third switch tube and turn on the fourth switch tube.

[0012] The anode of the fifth unidirectional conductive device and the cathode of the sixth unidirectional conductive device are commonly connected to the first end of the secondary winding of the current transformer. The anode of the seventh unidirectional conductive device and the cathode of the eighth unidirectional conductive device are commonly connected to the second end of the secondary winding of the current transformer. The cathode of the fifth unidirectional conductive device and the first end of the first reset resistor are commonly connected to the first end of the third switching transistor. The cathode of the seventh unidirectional conductive device and the first end of the second reset resistor are commonly connected to the first end of the fourth switching transistor. The first end of the sampling resistor, the anode of the eighth unidirectional conductive device, and the anode of the sixth unidirectional conductive device are commonly connected to ground. The second end of the first reset resistor, the second end of the third switching transistor, the second end of the second reset resistor, the second end of the fourth switching transistor, and the second end of the sampling resistor are commonly connected to form a sampling output end of the current sampling circuit. The resistance values ​​of the first reset resistor and the second reset resistor are both much greater than the resistance value of the sampling resistor.

[0013] Alternatively, the anode of the fifth unidirectional conductive device and the cathode of the sixth unidirectional conductive device are commonly connected to the first end of the secondary winding of the current transformer, the anode of the seventh unidirectional conductive device and the cathode of the eighth unidirectional conductive device are commonly connected to the second end of the secondary winding of the current transformer, the anode of the sixth unidirectional conductive device and the first end of the second reset resistor are commonly connected to the second end of the fourth switching transistor, the anode of the eighth unidirectional conductive device and the first end of the first reset resistor are commonly connected to the second end of the third switching transistor, the second end of the second reset resistor, the second end of the first reset resistor, the first end of the fourth switching transistor, the first end of the third switching transistor, and the first end of the sampling resistor are commonly connected to ground, and the cathodes of the fifth unidirectional conductive device and the seventh unidirectional conductive device are commonly connected to the second end of the sampling resistor to form a sampling output end of the current sampling circuit; the resistance values ​​of the first reset resistor and the second reset resistor are both much greater than the resistance value of the sampling resistor;

[0014] In the positive half cycle of the AC signal output by the AC signal source:

[0015] During a period when the first, second, and third switching tubes are on and the fourth switching tube is off, the AC signal source, the choke device, the first, second switching tubes, and the primary winding of the current transformer form a first excitation closed loop. The primary winding of the current transformer isolates and couples the current in the first excitation closed loop to the secondary winding of the current transformer. The secondary winding of the current transformer generates an induced current and forms a first current sampling loop with the fifth unidirectional conductive device, the third switching tube, the sampling resistor, and the eighth unidirectional conductive device, and outputs a sampling signal through the sampling output terminal. During this period, the current transformer is in an excitation process.

[0016] During a period when the first switching tube, the second switching tube, and the fourth switching tube are turned on and the third switching tube is turned off, the AC signal source, the choke device, the first unidirectional conductive device, the energy storage device, and the fourth unidirectional conductive device form a first demagnetization closed loop, and the current transformer is demagnetized; the sixth unidirectional conductive device, the secondary winding of the current transformer, the seventh unidirectional conductive device, the second reset resistor, and the sampling resistor form a first closed discharge loop. During this period, the current transformer is in a demagnetization process;

[0017] In the negative half cycle of the AC signal output by the AC signal source:

[0018] During a period when the first, second, and fourth switching tubes are on and the third switching tube is off, the AC signal source, the choke device, the first, second switching tubes, and the primary winding of the current transformer form a second excitation closed loop. The primary winding of the current transformer isolates and couples the current in the second excitation closed loop to the secondary winding of the current transformer. The secondary winding of the current transformer generates an induced current and forms a second current sampling loop with the seventh unidirectional conductive device, the fourth switching tube, the sampling resistor, and the sixth unidirectional conductive device, and outputs a sampling signal through the sampling output terminal. During this period, the current transformer is in an excitation process.

[0019] During a period when the first switching tube, the second switching tube, and the third switching tube are turned off and the fourth switching tube is turned on, the AC signal source, the choke device, the third unidirectional conductive device, the energy storage device, and the second unidirectional conductive device form a second demagnetization closed loop, and the current transformer is demagnetized; the fifth unidirectional conductive device, the secondary winding of the current transformer, the eighth unidirectional conductive device, the sampling resistor, and the first reset resistor form a second closed discharge loop. During this period, the current transformer is in a demagnetization process.

[0020] Furthermore, the choke device is an inductor.

[0021] Furthermore, the first switching tube and the second switching tube are respectively a first MOS tube and a second MOS tube; the drain, source and gate of the first MOS tube are respectively the first end, second end and control end of the first switching tube, and the source, drain and gate of the second MOS tube are respectively the first end, second end and gate of the second switching tube.

[0022] Furthermore, the first unidirectional conductive device, the second unidirectional conductive device, the third unidirectional conductive device and the fourth unidirectional conductive device are respectively a first diode, a second diode, a third diode and a fourth diode.

[0023] Furthermore, the energy storage device is a polar capacitor, and the positive electrode and the negative electrode of the polar capacitor are the first end and the second end of the energy storage device respectively.

[0024] Furthermore, the load is a first resistor.

[0025] Furthermore, the fifth unidirectional conductive component and the sixth unidirectional conductive component are a fifth diode and a sixth diode respectively.

[0026] Furthermore, the seventh unidirectional conductive device and the eighth unidirectional conductive device are a seventh diode and an eighth diode respectively.

[0027] Furthermore, the third switching tube and the fourth switching tube are respectively a third MOS tube and a fourth MOS tube, the drain, source and gate of the third MOS tube are respectively the first end, second end and control end of the third switching tube, and the source, drain and gate of the fourth MOS tube are respectively the first end, second end and control end of the fourth switching tube.

[0028] A second aspect of the present invention further provides a bridgeless rectifier system, which includes not only the power factor correction circuit described above, but also the current sampling circuit described above.

[0029] In the present invention, during the period when the first switch tube, the second switch tube, and the third switch tube are turned on and the fourth switch tube is turned off, or during the period when the first switch tube, the second switch tube, and the fourth switch tube are turned on and the third switch tube is turned off, the main winding of the current transformer isolates and couples the current in the excitation circuit of the power factor correction circuit to the secondary winding of the current transformer, and the current sampling circuit where the secondary winding of the current transformer is located outputs a sampling signal through the sampling resistor. During this period, the current transformer is in a magnetic setting process; during the period when the first switch tube, the second switch tube, and the fourth switch tube are turned off and the third switch tube is turned on, or during the period when the first switch tube, the second switch tube, the third switch tube are turned off and the fourth switch tube is turned on, during this period, the current transformer is in a magnetic reset process, and the closed discharge circuit where the secondary winding of the current transformer is located discharges through the reset resistor to complete the magnetic reset process of the current transformer. Therefore, the current sampling circuit in the present invention has a strong anti-interference ability. By adopting the current sampling circuit in the present invention, the current sampling accuracy of the bridgeless rectifier system and the anti-interference ability of the bridgeless rectifier system can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 This is a module structure diagram of a current sampling circuit provided by an embodiment of the present invention;

[0032] Figure 2 is another module structure diagram of a current sampling circuit provided by an embodiment of the present invention;

[0033] Figure 3 1 is a module structure diagram of a power factor correction circuit provided by an embodiment of the present invention;

[0034] Figure 4This is a circuit structure diagram of a power factor correction circuit provided by an embodiment of the present invention;

[0035] Figure 5 is a circuit structure diagram of a current sampling circuit provided by an embodiment of the present invention;

[0036] Figure 6 is another circuit structure diagram of a current sampling circuit provided by an embodiment of the present invention;

[0037] Figure 7 This is a timing diagram of related waveforms within one AC signal cycle output by an AC signal source provided by an embodiment of the present invention;

[0038] Figure 8 1 is a schematic diagram of a first excitation closed loop in a power factor correction circuit during the period t0-t1 provided by an embodiment of the present invention;

[0039] Figure 9 1 is a schematic diagram of a first current sampling loop in a current sampling circuit during the period t0-t1 provided by an embodiment of the present invention;

[0040] Figure 10 2 is a schematic diagram of a first demagnetization closed loop in a power factor correction circuit during the period t1-t2 provided by an embodiment of the present invention;

[0041] Figure 11 is a schematic diagram of a first closed discharge loop in a current sampling circuit during the period t1-t2 provided by an embodiment of the present invention;

[0042] Figure 12 1 is a schematic diagram of a second excitation closed loop in a power factor correction circuit during the period t3-t4 provided by an embodiment of the present invention;

[0043] Figure 13 1 is a schematic diagram of a second current sampling loop in a current sampling circuit during the period t3-t4 provided by an embodiment of the present invention;

[0044] Figure 14 2 is a schematic diagram of a second demagnetization closed loop in a power factor correction circuit during the period t4-t5 provided by an embodiment of the present invention;

[0045] Figure 15 2 is a schematic diagram of a second closed discharge loop in a current sampling circuit during the period t4-t5 provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0047] Figure 1 The module structure of the current sampling circuit provided by the embodiment of the present invention is shown. Figure 3 The module structure of the power factor correction circuit provided by the embodiment of the present invention is shown. For ease of description, only the parts related to the embodiment of the present invention are shown, which are detailed as follows:

[0048] See also Figure 1 and Figure 3 , Figure 1 The current sampling circuit shown in the figure is connected to the current transformer CT (the current transformer CT includes the current transformer main winding CT-A and the current transformer secondary winding CT-B) Figure 3 The power factor correction circuit shown is connected as Figure 3 As shown, the power factor correction circuit includes an AC signal source AC, a choke device 1, a first switch tube 2, a second switch tube 3, a main winding CT-A of a current transformer, a first unidirectional conductive device 4, a second unidirectional conductive device 5, a third unidirectional conductive device 6, a fourth unidirectional conductive device 7, an energy storage device 8 and a load 9.

[0049] A first end of the AC signal source AC is connected to a first end of the choke device 1. A second end of the choke device 1, a cathode of the second unidirectional conductive device 5, and a first end of the first switching device 2 are commonly connected to an anode of the first unidirectional conductive device 4. The second end of the first switching device 2 is connected to a first end of the second switching device 3. The second end of the second switching device 3 is connected to a first end of a main winding CT-A of the AC transformer. The second end of the main winding CT-A of the AC transformer, an anode of the third unidirectional conductive device 6, and a cathode of the fourth unidirectional conductive device 7 are commonly connected to a second end of the AC signal source AC. The cathode of the first unidirectional conductive device 4, the cathode of the third unidirectional conductive device 6, and a first end of the energy storage device 8 are commonly connected to a first end of a load 9. The second end of the load 9, the second end of the energy storage device 8, and an anode of the fourth unidirectional conductive device 7 are commonly connected to an anode of the second unidirectional conductive device 5.

[0050] The control end of the first switching tube 2 and the control end of the second switching tube 3 are connected to a drive signal Drive for controlling the synchronous on and off of the first switching tube 2 and the second switching tube 3. During the positive half cycle of the AC signal output by the AC signal source AC, the drive signal Drive drives the first switching tube 2 and the second switching tube 3 to be turned on during the current rising period of the choke device 1 in the power factor correction circuit, and drives the first switching tube 2 and the second switching tube 3 to be turned off during the current falling period of the choke device 1; during the negative half cycle of the AC signal output by the AC signal source AC, the drive signal drives the first switching tube 2 and the second switching tube 3 to be turned off during the current rising period of the choke device 1 in the power factor correction circuit, and drives the first switching tube 2 and the second switching tube 3 to be turned on during the current falling period of the choke device 1.

[0051] like Figure 1 As shown, the current sampling circuit includes a secondary winding CT-B of a current transformer, a fifth unidirectional conductive device 10, a sixth unidirectional conductive device 11, a third switch 14, a seventh unidirectional conductive device 12, an eighth unidirectional conductive device 13, a fourth switch 15, a first reset resistor R2, a second reset resistor R3, and a sampling resistor R4. A low-frequency control signal SW_line is connected to the control terminal of the third switch 14. The low-frequency control signal SW_line is inverted by an inverter and then connected to the control terminal of the fourth switch 15. The low-frequency control signal SW_line outputs a high level during the positive half-cycle of the AC signal output by the AC signal source AC, turning on the third switch 14 and turning off the fourth switch 15. The low-frequency control signal SW_line outputs a low level during the negative half-cycle of the AC signal, turning off the third switch 14 and turning on the fourth switch 15.

[0052] The anode of the fifth unidirectional conductive device 10 and the cathode of the sixth unidirectional conductive device 11 are commonly connected to the first end of the secondary winding CT-B of the current transformer. The anode of the seventh unidirectional conductive device 12 and the cathode of the eighth unidirectional conductive device 13 are commonly connected to the second end of the secondary winding CT-B of the current transformer. The cathode of the fifth unidirectional conductive device 10 and the first end of the first reset resistor R2 are commonly connected to the first end of the third switch tube 14. The cathode of the seventh unidirectional conductive device 12 and the first end of the second reset resistor R3 are commonly connected to the first end of the fourth switch tube 15. The first end of the sampling resistor R4, the anode of the eighth unidirectional conductive device 13, and the anode of the sixth unidirectional conductive device 11 are commonly connected to ground. The second end of the first reset resistor R2 and the third The second end of the switch tube 14, the second end of the second reset resistor R3, the second end of the fourth switch tube 15, and the second end of the sampling resistor R4 are connected together to form a sampling output end Isense of the current sampling circuit. The resistance of the first reset resistor R2 and the resistance of the second reset resistor R3 are both much greater than the resistance of the sampling resistor R4. Those skilled in the art will appreciate that when the resistance of the first reset resistor R2 is greater than 1000 times the resistance of the sampling resistor R4, it can be considered that the resistance of the first reset resistor R2 is much greater than the resistance of the sampling resistor R4. When the resistance of the second reset resistor R3 is greater than 1000 times the resistance of the sampling resistor R4, it can be considered that the resistance of the second reset resistor R3 is much greater than the resistance of the sampling resistor R4.

[0053] Figure 2 Another module structure of the current sampling circuit provided by an embodiment of the present invention is shown. For ease of description, only the parts related to the embodiment of the present invention are shown, which are described in detail as follows:

[0054] See also Figure 2 and Figure 3 , Figure 2 The current sampling circuit shown in the figure uses the current transformer CT and Figure 3 The power factor correction circuit is connected as shown. Figure 2 As shown, the current sampling circuit includes a secondary winding CT-B of a current transformer, a fifth unidirectional conductive device 10, a sixth unidirectional conductive device 11, a third switch 14, a seventh unidirectional conductive device 12, an eighth unidirectional conductive device 13, a fourth switch 15, a first reset resistor R2, a second reset resistor R3, and a sampling resistor R4. A low-frequency control signal SW_line is connected to the control terminal of the third switch 14. The low-frequency control signal SW_line is inverted by an inverter and then connected to the control terminal of the fourth switch 15. The low-frequency control signal SW_line outputs a high level during the positive half-cycle of the AC signal output by the AC signal source AC, turning on the third switch 14 and turning off the fourth switch 15. The low-frequency control signal SW_line outputs a low level during the negative half-cycle of the AC signal, turning off the third switch 14 and turning on the fourth switch 15.

[0055] The anode of the fifth unidirectional conductive device 10 and the cathode of the sixth unidirectional conductive device 11 are commonly connected to the first end of the secondary winding CT-B of the current transformer. The anode of the seventh unidirectional conductive device 12 and the cathode of the eighth unidirectional conductive device 13 are commonly connected to the second end of the secondary winding CT-B of the current transformer. The anode of the sixth unidirectional conductive device 11 and the first end of the second reset resistor R3 are commonly connected to the second end of the fourth switch tube 15. The anode of the eighth unidirectional conductive device 13 and the first end of the first reset resistor R2 are commonly connected to the second end of the third switch tube 14. The second end of the second reset resistor R3, the second end of the first reset resistor R1, the first end of the fourth switch tube 15, the first end of the third switch tube 14, and the sampling resistor R4 are commonly connected. The first end is commonly connected to ground. The cathode of the fifth unidirectional conductive device 10, the cathode of the seventh unidirectional conductive device 12, and the second end of the sampling resistor R4 are commonly connected to form a sampling output end Isense of the current sampling circuit. The resistance of the first reset resistor R2 and the resistance of the second reset resistor R3 are both much greater than the resistance of the sampling resistor R4. Those skilled in the art will appreciate that when the resistance of the first reset resistor R2 is greater than 1000 times the resistance of the sampling resistor R4, it can be considered that the resistance of the first reset resistor R2 is much greater than the resistance of the sampling resistor R4. When the resistance of the second reset resistor R3 is greater than 1000 times the resistance of the sampling resistor R4, it can be considered that the resistance of the second reset resistor R3 is much greater than the resistance of the sampling resistor R4.

[0056] During the positive half cycle of the AC signal output by the AC signal source AC:

[0057] During the period when the first switching tube 2, the second switching tube 3, and the third switching tube 14 are on and the fourth switching tube 15 is off, the AC signal source AC, the choke device 1, the first switching tube 2, the second switching tube 3, and the main winding CT-A group of the current transformer form a first excitation closed loop. The main winding CT-A of the current transformer isolates and couples the current in the first excitation closed loop to the secondary winding CT-B of the current transformer. The secondary winding CT-B of the current transformer generates an induced current and forms a first current sampling loop with the fifth unidirectional conductive device 10, the third switching tube 14, the sampling resistor R3, and the eighth unidirectional conductive device 13, and outputs a sampling signal through the sampling output terminal Isense. During this period, the current transformer CT is in the excitation process.

[0058] During the period when the first switching tube 2, the second switching tube 3, and the fourth switching tube 15 are on and the third switching tube 14 is off, the AC signal source AC, the choke device 1, the first unidirectional conductive device 4, the energy storage device 8, and the fourth unidirectional conductive device 7 form a first demagnetization closed loop, and the current transformer CT is demagnetized. The sixth unidirectional conductive device 11, the secondary winding CT-B of the current transformer, the seventh unidirectional conductive device 12, the second reset resistor R3, and the sampling resistor R4 form a first closed discharge loop. During this period, the current transformer is in the demagnetization process.

[0059] During the negative half cycle of the AC signal output by the AC signal source AC:

[0060] During the period when the first switching transistor 2, the second switching transistor 3, and the fourth switching transistor 15 are on and the third switching transistor 14 is off, the AC signal source AC, the choke device 1, the first switching transistor 2, the second switching transistor 3, and the main winding CT-A of the current transformer form a second excitation closed loop. The main winding CT-A of the current transformer isolates and couples the current in the second excitation closed loop to the secondary winding CT-B of the current transformer. The secondary winding CT-B of the current transformer generates an induced current and forms a second current sampling loop with the seventh unidirectional conductive device 12, the fourth switching transistor 15, the sampling resistor R4, and the sixth unidirectional conductive device 11, and outputs a sampling signal through the sampling output terminal Isense. During this period, the current transformer CT is in the excitation process.

[0061] During the period when the first switching tube 2, the second switching tube 3, and the third switching tube 14 are turned off and the fourth switching tube 15 is turned on, the AC signal source AC, the choke device 1, the third unidirectional conductive device 6, the energy storage device 8, and the second unidirectional conductive device 5 form a second demagnetization closed loop, and the current transformer CT is demagnetized. The fifth unidirectional conductive device 10, the secondary winding CT-B of the current transformer, the eighth unidirectional conductive device 13, the sampling resistor R4, and the first reset resistor R2 form a second closed discharge loop. During this period, the current transformer CT is in the demagnetization process.

[0062] In an embodiment of the present invention, during a period when the first switch tube 2, the second switch tube 3, and the third switch tube 14 are turned on and the fourth switch tube 15 is turned off, or during a period when the first switch tube 2, the second switch tube 3, and the fourth switch tube 15 are turned on and the third switch tube 14 is turned off, the main winding CT-A of the current transformer isolates and couples the current in the excitation circuit of the power factor correction circuit to the secondary winding CT-B of the current transformer, and the current sampling circuit where the secondary winding CT-B of the current transformer is located outputs a sampling signal through the sampling resistor R4. During this period, the current transformer CT is in a magnetic setting process; during a period when the first switch tube 2, the second switch tube 3, and the fourth switch tube 15 are turned off and the third switch tube 14 is turned on, or during a period when the first switch tube 2, the second switch tube 3, the third switch tube 14 are turned off and the fourth switch tube 15 is turned on, the current transformer CT is in a magnetic reset process, and the closed discharge circuit where the secondary winding CT-B of the current transformer is located discharges through the first reset resistor R2 or the second reset resistor R3, completing the magnetic reset process of the current transformer CT. Therefore, the current sampling circuit in the embodiment of the present invention has strong anti-interference capabilities. By using the current sampling circuit in the embodiment of the present invention, the current sampling accuracy of the bridgeless rectifier system can be improved, and the anti-interference capability of the bridgeless rectifier system can be improved. In addition, the embodiment of the present invention has simple requirements for the transmission timing of the low-frequency control signal. Because the low-frequency control signal is in a low-frequency state, the timing accuracy requirements are not high, and the anti-interference capability is strong. Finally, the embodiment of the present invention only requires a secondary winding of the current transformer, which can greatly reduce the cost of the current transformer, thereby reducing the cost of the current sampling circuit and the bridgeless rectifier system in the embodiment of the present invention.

[0063] Figure 4 (correspond Figure 3 ) shows the circuit structure of the power factor correction circuit provided by the embodiment of the present invention. For the convenience of description, only the part related to the embodiment of the present invention is shown, which is described in detail as follows:

[0064] As an embodiment of the present invention, Figure 4 As shown, in the power factor correction circuit, the choke device 1 is an inductor L; the first switching transistor 2 and the second switching transistor 3 are respectively a first MOS transistor Q1 and a second MOS transistor Q2, the drain, source and gate of the first MOS transistor Q1 are respectively the first end, the second end and the control end of the first switching transistor 2, and the source, drain and gate of the second MOS transistor Q2 are respectively the first end, the second end and the control end of the second switching transistor 3; the first unidirectional conductive device 4, the second unidirectional conductive device 5, the third unidirectional conductive device 6 and the fourth unidirectional conductive device 7 are respectively a first diode D1, a second diode D2, a third diode D3 and a fourth diode D4; the energy storage device 8 is a polar capacitor C, the positive electrode and the negative electrode of the polar capacitor C are respectively the first end and the second end of the energy storage device 8; and the load 9 is a first resistor R1.

[0065] Figure 5 (correspond Figure 1 ) shows the circuit structure of the current sampling circuit provided by an embodiment of the present invention, Figure 6 (correspond Figure 2 ) shows the circuit structure of the current sampling circuit provided by an embodiment of the present invention. For ease of description, only the part related to the embodiment of the present invention is shown, which is described in detail as follows:

[0066] As an embodiment of the present invention, Figure 5 and Figure 6 As shown, in the current sampling circuit, the fifth unidirectional conductive device 10 and the sixth unidirectional conductive device 11 are respectively a fifth diode D5 and a sixth diode D6; the seventh unidirectional conductive device 12 and the eighth unidirectional conductive device 13 are respectively a seventh diode D7 and an eighth diode D8; the third switch transistor 14 and the fourth switch transistor 15 are respectively a third MOS transistor Q3 and a fourth MOS transistor Q4, the drain, source and gate of the third MOS transistor Q3 are respectively a first end, a second end and a control end of the third switch transistor 14, and the drain, source and gate of the fourth MOS transistor Q4 are respectively a first end, a second end and a control end of the fourth switch transistor 15.

[0067] by Figure 5 Taking the current sampling circuit shown in the figure as an example, the current sampling circuit is further explained below in combination with the working principle. Figure 6 The working principle of the current sampling circuit shown in the figure is the same as that of the current sampling circuit described below. Figure 5 The working principle of the current sampling circuit is the same as that of the example. Please refer to the following Figure 5 The relevant description and explanation of the working principle of the current sampling circuit shown, Figure 6 The working principle of the current sampling circuit shown is not described in detail below:

[0068] Figure 7 FIG. 1 is a schematic diagram of the timing of related waveforms within one AC signal cycle output by the AC signal source according to an embodiment of the present invention. Figure 7 As shown, the AC signal output by the AC signal source AC is Vin, I is the inductor current of the inductor, Drive is the driving signal for driving the first MOS transistor Q1, the second MOS transistor Q2 and the third MOS transistor Q3, I Q1 , I Q2 is the current of the first MOS tube Q1 and the second MOS tube Q2, V is the sampling signal, SW_line is the driving signal for driving the third MOS tube Q3 and the fourth MOS tube Q4. For the sake of convenience, the above signals are all represented in Figure 7The positive half cycle of the AC signal is divided into three intervals: t0-t1, t1-t2, and t2-t3. The negative half cycle of the AC signal is divided into three intervals: t3-t4, t4-t5, and t5-t6. The working principles and states of the power factor correction circuit and current sampling circuit in each interval are described below:

[0069] In the positive half cycle of the AC signal, that is, the interval t0-t3:

[0070] (1) In the positive half cycle of the AC signal, t0-t1:

[0071] Figure 8 The first excitation closed loop in the power factor correction circuit during the period t0-t1 provided by the embodiment of the present invention is shown. Figure 9 The first current sampling loop in the current sampling circuit during the period t0-t1 provided by an embodiment of the present invention is shown. For ease of illustration, only the portion related to the embodiment of the present invention is shown, which is described in detail as follows:

[0072] In the interval t0-t1, the first MOS transistor Q1, the second MOS transistor Q2 and the third MOS transistor Q3 are turned on synchronously. Figure 8 As shown, the first MOS transistor Q1 and the second MOS transistor Q2 in the power factor correction circuit are turned on, and the AC signal source AC, the inductor L, the first MOS transistor Q1, the second MOS transistor Q2, and the main winding CT-A of the current transformer form a first excitation closed loop. The main winding CT-A of the current transformer isolates and couples the current in the first excitation closed loop to the secondary winding CT-B of the current transformer.

[0073] like Figure 9 As shown, the third MOS transistor Q3 in the current sampling circuit is turned on, the fourth MOS transistor is turned off, and the secondary winding CT-B of the current transformer generates an induced current, which forms a first current sampling loop with the fifth diode D5, the third MOS transistor Q3, the sampling resistor R4, and the eighth diode D8, and outputs a sampling signal through the sampling output terminal Isense. During this period, the first reset resistor R2 is bypassed by the third MOS transistor Q3, and the sampling current flows entirely into the sampling resistor R4. During this period, the current transformer CT is in the excitation process. The signal voltage of the sampling resistor in this interval (i.e., the sampling signal) can be equivalent to: V = I*R / n,

[0074] Where V is the sampling signal voltage, I is the inductor current of the inductor L in the power factor correction circuit, R is the resistance of the sampling resistor R4, and n is the coil turns ratio of the secondary winding CT-B of the current transformer to the main winding CT-A of the current transformer, that is, the coil turns of the main winding CT-A of the current transformer: the coil turns of the secondary winding CT-B of the current transformer = 1:n.

[0075] (2) In the positive half cycle of the AC signal t1-t2:

[0076] Figure 10 FIG. 1 shows the first demagnetization closed loop in the power factor correction circuit during the period t1-t2 provided by an embodiment of the present invention. Figure 11 The first closed discharge loop in the current sampling circuit during the period t1-t2 provided by an embodiment of the present invention is shown. For ease of illustration, only the portion related to the embodiment of the present invention is shown, which is described in detail as follows:

[0077] In the interval t1-t2, the first MOS transistor Q1, the second MOS transistor Q2, and the fourth MOS transistor Q4 are turned off, and the third MOS transistor Q3 is turned on. Figure 10 As shown, the first MOS transistor Q1 and the second MOS transistor Q2 in the power factor correction circuit are turned off. Due to the continuity of the inductor current I, the current no longer flows through the main winding CT-A of the current transformer. The AC signal source AC, the inductor L, the first diode D1, the polar capacitor C and the fourth diode D4 form a first demagnetization closed loop, and the current transformer CT is demagnetized. Figure 11 As shown, the third MOS transistor Q3 in the current sampling circuit is turned on, the fourth MOS transistor Q4 is turned off, and the sixth diode D6, the secondary winding CT-B of the current transformer, the seventh diode D7, and the second reset resistor R3 form a first closed discharge loop. During this period, the current transformer CT is in the demagnetization process. At this time, although the third MOS transistor Q3 is in the on state, the current transformer CT is in the demagnetization process. Because the resistance of the second reset resistor R3 is much greater than that of the sampling resistor R4, the reset voltage during this period is mainly concentrated on the second reset resistor R3.

[0078] (3) In the positive half cycle of the AC signal, t2-t3:

[0079] See also Figure 7 During the positive half-cycle of the AC signal, t2-t3, the power factor correction circuit and current sampling circuit repeat the processes described above during t0-t1 and t1-t2. During this period, the principles and states of the power factor correction circuit and current sampling circuit are identical to those during t0-t1 and t1-t2. Please refer to the description and explanation of the processes during the positive half-cycle of the AC signal, t0-t1 and t1-t2, and will not be repeated here.

[0080] In the negative half cycle of the AC signal, that is, the interval t3-t6:

[0081] (4) In the negative half cycle of the AC signal, t3-t4:

[0082] Figure 12 The second excitation closed loop in the power factor correction circuit during the period t3-t4 provided by the embodiment of the present invention is shown. Figure 13The second current sampling loop in the current sampling circuit during the period t3-t4 provided by an embodiment of the present invention is shown. For ease of illustration, only the portion related to the embodiment of the present invention is shown, which is described in detail as follows:

[0083] In the interval t3-t4, the first MOS transistor Q1, the second MOS transistor Q2, and the fourth MOS transistor Q4 are turned on, and the third MOS transistor Q3 is turned off. Figure 12 As shown, the first MOS transistor Q1 and the second MOS transistor Q2 in the power factor correction circuit are turned on, and the AC signal source AC, the inductor L, the first MOS transistor Q1, the second MOS transistor Q2 and the main winding CT-A of the current transformer form a second excitation closed loop. The main winding CT-A of the current transformer isolates and couples the current in the second excitation closed loop to the secondary winding CT-B of the current transformer. Figure 13 As shown, the secondary winding CT-B of the current transformer generates an induced current and forms a second current sampling loop with the seventh diode D7, the fourth MOS transistor Q4, the sampling resistor R4, and the sixth diode D6. The sampling signal is output through the sampling output terminal Isense. During this period, the second reset resistor R3 is bypassed by the fourth MOS transistor Q4, and the sampling current flows entirely into the sampling resistor R4. During this period, the current transformer CT is in the excitation process. The signal voltage of the sampling resistor in this interval (i.e., the sampling signal) can be equivalent to: V = I * R / n,

[0084] Where V is the sampling signal voltage, I is the inductor current of the inductor L in the power factor correction circuit, R is the resistance of the sampling resistor R4, and n is the coil turns ratio of the secondary winding CT-B of the current transformer to the main winding CT-A of the current transformer, that is, the coil turns of the main winding CT-A of the current transformer: the coil turns of the secondary winding CT-B of the current transformer = 1:n.

[0085] (5) In the negative half cycle of the AC signal, t4-t5:

[0086] Figure 14 FIG. 2 shows the second demagnetization closed loop in the power factor correction circuit during the period t4-t5 provided by an embodiment of the present invention. Figure 15 The second closed discharge loop in the current sampling circuit during the period t4-t5 provided by an embodiment of the present invention is shown. For ease of illustration, only the portion related to the embodiment of the present invention is shown, which is described in detail as follows:

[0087] In the interval t4-t5, the first MOS transistor Q1, the second MOS transistor Q2, and the third MOS transistor Q3 are turned off, and the fourth MOS transistor Q4 is turned on. Figure 14As shown, the first MOS transistor Q1 and the second MOS transistor Q2 in the power factor correction circuit are turned off. Due to the continuity of the inductor current I, the current no longer flows through the main winding CT-A of the current transformer. The AC signal source AC, the inductor L, the third diode D3, the polar capacitor C and the second diode D2 form a second demagnetization closed loop, and the current transformer CT is demagnetized. Figure 15 As shown, the third MOS transistor Q3 in the current sampling circuit is turned off, the fourth MOS transistor is turned on, and the fifth diode D5, the secondary winding CT-B of the current transformer, the eighth diode D8, the sampling resistor R4, and the first reset resistor R2 form a second closed discharge loop. During this period, the current transformer CT is in the demagnetization process. At this time, although the fourth MOS transistor Q4 is in the on state, the current transformer CT is in the demagnetization process. Because the resistance of the first reset resistor R2 is much greater than that of the sampling resistor R4, the reset voltage during this period is mainly concentrated on the first reset resistor R2.

[0088] (6) In the negative half cycle of the AC signal, t5-t6:

[0089] See also Figure 7 During the positive half-cycle of the AC signal, between t5 and t6, the power factor correction circuit and current sampling circuit repeat the processes between t3 and t4 and between t4 and t5. During this period, the principles and states of the power factor correction circuit and current sampling circuit are identical to those of the processes between t3 and t4 and between t4 and t5. Please refer to the description and explanation of the processes between t3 and t4 and between t4 and t5 for the positive half-cycle of the AC signal, and will not be repeated here.

[0090] In the embodiment of the present invention, during a period when the first MOS transistor Q1, the second MOS transistor Q2, and the third MOS transistor Q3 are turned on and the fourth MOS transistor Q4 is turned off, or during a period when the first MOS transistor Q1, the second MOS transistor Q2, and the fourth MOS transistor Q4 are turned on and the third MOS transistor Q3 is turned off, the main winding CT-A of the current transformer isolates and couples the current in the excitation circuit of the power factor correction circuit to the secondary winding CT-B of the current transformer, and the current sampling circuit where the secondary winding CT-B of the current transformer is located outputs a sampling signal through the sampling resistor R4. During this period, the current transformer CT is in a magnetic setting process. During a period when the first MOS transistor Q1, the second MOS transistor Q2, and the fourth MOS transistor Q4 are turned off and the third MOS transistor Q3 is turned on, or during a period when the first MOS transistor Q1, the second MOS transistor Q2, and the third MOS transistor Q3 are turned off and the fourth MOS transistor Q4 is turned on, the current transformer CT is in a magnetic reset process. The closed discharge circuit where the secondary winding CT-B of the current transformer is located discharges through the first reset resistor R2 or the second reset resistor R3, completing the magnetic reset process of the current transformer CT. Therefore, the current sampling circuit in the embodiment of the present invention has strong anti-interference capabilities. By using the current sampling circuit in the embodiment of the present invention, the current sampling accuracy of the bridgeless rectifier system can be improved, and the anti-interference capability of the bridgeless rectifier system can be improved. In addition, the embodiment of the present invention has simple requirements for the transmission timing of the low-frequency control signal. Because the low-frequency control signal is in a low-frequency state, the timing accuracy requirements are not high, and the anti-interference capability is strong. Finally, the embodiment of the present invention only requires a secondary winding of the current transformer, which can greatly reduce the cost of the current transformer, thereby reducing the cost of the current sampling circuit and the bridgeless rectifier system in the embodiment of the present invention.

[0091] In view of the advantage that the above-mentioned current sampling circuit can improve the current sampling accuracy and anti-interference capability of the bridgeless rectifier system, an embodiment of the present invention also provides a bridgeless rectifier system, which includes not only the power factor correction circuit described in the above-mentioned embodiment, but also the current sampling circuit described in the above-mentioned embodiment.

[0092] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A current sampling circuit, wherein the current sampling circuit is connected to a power factor correction circuit via a current transformer, wherein the power factor correction circuit comprises: An AC signal source, a choke device, a first switching tube, a second switching tube, a main winding of the current transformer, a first unidirectional conductive device, a second unidirectional conductive device, a third unidirectional conductive device, a fourth unidirectional conductive device, an energy storage device, and a load; The first end of the AC signal source is connected to the first end of the choke device, the second end of the choke device, the cathode of the second unidirectional conductive device, and the first end of the first switching tube are commonly connected to the anode of the first unidirectional conductive device, the second end of the first switching tube is connected to the first end of the second switching tube, the second end of the second switching tube is connected to the first end of the main winding of the current transformer, the second end of the main winding of the current transformer, the anode of the third unidirectional conductive device, and the cathode of the fourth unidirectional conductive device are commonly connected to the second end of the AC signal source, the cathode of the first unidirectional conductive device, the cathode of the third unidirectional conductive device, and the first end of the energy storage device are commonly connected to the first end of the load, and the second end of the load, the second end of the energy storage device, and the anode of the fourth unidirectional conductive device are commonly connected to the anode of the second unidirectional conductive device; A drive signal for controlling the synchronous on and off of the first and second switching transistors is commonly connected to the control terminals of the first and second switching transistors. During a positive half cycle of the AC signal output by the AC signal source, the drive signal drives the first and second switching transistors to be turned on during a rising current of the choke device in the power factor correction circuit, and drives the first and second switching transistors to be turned off during a falling current of the choke device. In the negative half cycle of the AC signal output by the AC signal source, the driving signal drives the first switching tube and the second switching tube to be turned off during a current rise period of the choke device in the power factor correction circuit, and drives the first switching tube and the second switching tube to be turned on during a current fall period of the choke device; It is characterized in that the current sampling circuit includes: The secondary winding of the current transformer, the fifth unidirectional conductive device, the sixth unidirectional conductive device, the third switch tube, the seventh unidirectional conductive device, the eighth unidirectional conductive device, the fourth switch tube, the first reset resistor, the second reset resistor and the sampling resistor; A low-frequency control signal is connected to the control terminal of the third switch tube, and the low-frequency control signal is inverted by an inverter and then connected to the control terminal of the fourth switch tube. The low-frequency control signal outputs a high level during a positive half-cycle of the AC signal output by the AC signal source to turn on the third switch tube and turn off the fourth switch tube, and outputs a low level during a negative half-cycle of the AC signal to turn off the third switch tube and turn on the fourth switch tube. The anode of the fifth unidirectional conductive device and the cathode of the sixth unidirectional conductive device are commonly connected to the first end of the secondary winding of the current transformer. The anode of the seventh unidirectional conductive device and the cathode of the eighth unidirectional conductive device are commonly connected to the second end of the secondary winding of the current transformer. The cathode of the fifth unidirectional conductive device and the first end of the first reset resistor are commonly connected to the first end of the third switching transistor. The cathode of the seventh unidirectional conductive device and the first end of the second reset resistor are commonly connected to the first end of the fourth switching transistor. The first end of the sampling resistor, the anode of the eighth unidirectional conductive device, and the anode of the sixth unidirectional conductive device are commonly connected to ground. The second end of the first reset resistor, the second end of the third switching transistor, the second end of the second reset resistor, the second end of the fourth switching transistor, and the second end of the sampling resistor are commonly connected to form a sampling output end of the current sampling circuit. The resistance values ​​of the first reset resistor and the second reset resistor are both much greater than the resistance value of the sampling resistor. Alternatively, the anode of the fifth unidirectional conductive device and the cathode of the sixth unidirectional conductive device are commonly connected to the first end of the secondary winding of the current transformer, the anode of the seventh unidirectional conductive device and the cathode of the eighth unidirectional conductive device are commonly connected to the second end of the secondary winding of the current transformer, the anode of the sixth unidirectional conductive device and the first end of the second reset resistor are commonly connected to the second end of the fourth switching transistor, the anode of the eighth unidirectional conductive device and the first end of the first reset resistor are commonly connected to the second end of the third switching transistor, the second end of the second reset resistor, the second end of the first reset resistor, the first end of the fourth switching transistor, the first end of the third switching transistor, and the first end of the sampling resistor are commonly connected to ground, and the cathodes of the fifth unidirectional conductive device and the seventh unidirectional conductive device are commonly connected to the second end of the sampling resistor to form a sampling output end of the current sampling circuit; the resistance values ​​of the first reset resistor and the second reset resistor are both much greater than the resistance value of the sampling resistor; In the positive half cycle of the AC signal output by the AC signal source: During a period when the first, second, and third switching tubes are on and the fourth switching tube is off, the AC signal source, the choke device, the first, second switching tubes, and the primary winding of the current transformer form a first excitation closed loop. The primary winding of the current transformer isolates and couples the current in the first excitation closed loop to the secondary winding of the current transformer. The secondary winding of the current transformer generates an induced current and forms a first current sampling loop with the fifth unidirectional conductive device, the third switching tube, the sampling resistor, and the eighth unidirectional conductive device, and outputs a sampling signal through the sampling output terminal. During this period, the current transformer is in an excitation process. During a period when the first, second, and fourth switching tubes are turned off and the third switching tube is turned on, the AC signal source, the choke device, the first unidirectional conductive device, the energy storage device, and the fourth unidirectional conductive device form a first demagnetization closed loop, and the current transformer is demagnetized; the sixth unidirectional conductive device, the secondary winding of the current transformer, the seventh unidirectional conductive device, the second reset resistor, and the sampling resistor form a first closed discharge loop. During this period, the current transformer is in a demagnetization process. In the negative half cycle of the AC signal output by the AC signal source: During a period when the first, second, and fourth switching tubes are on and the third switching tube is off, the AC signal source, the choke device, the first, second switching tubes, and the primary winding of the current transformer form a second excitation closed loop. The primary winding of the current transformer isolates and couples the current in the second excitation closed loop to the secondary winding of the current transformer. The secondary winding of the current transformer generates an induced current and forms a second current sampling loop with the seventh unidirectional conductive device, the fourth switching tube, the sampling resistor, and the sixth unidirectional conductive device, and outputs a sampling signal through the sampling output terminal. During this period, the current transformer is in an excitation process. During a period when the first, second, and third switching tubes are turned off and the fourth switching tube is turned on, the AC signal source, the choke device, the third unidirectional conductive device, the energy storage device, and the second unidirectional conductive device form a second demagnetization closed loop, and the current transformer is demagnetized; the fifth unidirectional conductive device, the secondary winding of the current transformer, the eighth unidirectional conductive device, the sampling resistor, and the first reset resistor form a second closed discharge loop. During this period, the current transformer is in a demagnetization process. Wherein, the choke device is an inductor; The load is a first resistor.

2. The current sampling circuit according to claim 1, wherein: The first switching tube and the second switching tube are respectively a first MOS tube and a second MOS tube; the drain, source and gate of the first MOS tube are respectively a first end, a second end and a control end of the first switching tube, and the source, drain and gate of the second MOS tube are respectively a first end, a second end and a control end of the second switching tube.

3. The current sampling circuit according to claim 1, wherein: The first unidirectional conductive device, the second unidirectional conductive device, the third unidirectional conductive device, and the fourth unidirectional conductive device are respectively a first diode, a second diode, a third diode, and a fourth diode.

4. The current sampling circuit according to claim 1, wherein: The energy storage device is a polar capacitor, and the positive electrode and the negative electrode of the polar capacitor are the first end and the second end of the energy storage device respectively.

5. The current sampling circuit according to claim 1, wherein: The fifth unidirectional conductive component and the sixth unidirectional conductive component are a fifth diode and a sixth diode respectively.

6. The current sampling circuit according to claim 1, wherein: The seventh unidirectional conductive component and the eighth unidirectional conductive component are a seventh diode and an eighth diode respectively.

7. The current sampling circuit according to claim 1, wherein: The third switching tube and the fourth switching tube are respectively a third MOS tube and a fourth MOS tube, the drain, source and gate of the third MOS tube are respectively the first end, second end and control end of the third switching tube, and the drain, source and gate of the fourth MOS tube are respectively the first end, second end and control end of the fourth switching tube.

8. A bridgeless rectifier system, characterized in that: The bridgeless rectifier system includes the current sampling circuit according to any one of claims 1 to 7.

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