Current sampling circuit, current sampling method and switching power supply

Abstract

The invention provides a current sampling circuit, a current sampling method and a switching power supply, and relates to the technical field of power electronics. The current sampling circuit comprises a turn-on current sampling circuit and a turn-off current sampling circuit. The conduction current sampling circuit is connected to any end of the power switch unit, and the driving end of the conduction current sampling circuit and the driving end of the power switch unit receive the same driving signal so as to sample the first inductive current of the power inductor under the condition that the power switch unit is conducted; and the turn-off current sampling circuit is connected with any end of the filtering device so as to sample the second inductive current of the power inductor under the condition that the power switch unit is turned off. According to the invention, the inductive current of the whole switching period can be sampled.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to a current sampling circuit, a current sampling method and a switching power supply. Background Art

[0002] In order to improve power efficiency, a power factor correction (PFC) circuit is usually added to the AC input source of a high-power power supply to increase the power factor of the input AC signal as much as possible.

[0003] The traditional bridge rectifier PFC circuit has low efficiency and serious heat generation due to the existence of the rectifier bridge. The emergence of the new bridgeless PFC circuit not only improves the efficiency but also reduces the difficulty of heat dissipation.

[0004] For bridgeless PFC circuits, current sampling is an important factor affecting their normal operation. Existing solutions usually can only sample the inductor current when it is turned on, and then obtain the inductor current when it is turned off through digital calculation, which makes the method of determining the inductor current more complicated. In addition, when sampling the inductor current when it is turned on, it is also necessary to judge the positive and negative half-cycles of the AC input source, which is more cumbersome. Summary of the invention

[0005] The purpose of the present application is to provide a current sampling circuit, a current sampling method and a switching power supply to address the deficiencies in the above-mentioned prior art, so as to sample the inductor current in the entire switching cycle.

[0006] To achieve the above purpose, the technical solution adopted in the embodiment of the present application is as follows: In a first aspect, an embodiment of the present application provides a current sampling circuit, which is applied to a bridgeless PFC circuit, wherein a first end of an AC input source, a power inductor, a power switch unit, and a second end of the AC input source in the bridgeless PFC circuit are connected in sequence; a first end of the AC input source, the power inductor, a first unidirectional device, a filter device, a fourth unidirectional device, and a second end of the AC input source in the bridgeless PFC circuit are connected in sequence; a second end of the AC input source, a third unidirectional device, the filter device, a second unidirectional device, the power inductor, and a first end of the AC input source in the bridgeless PFC circuit are connected in sequence; The current sampling circuit comprises: an on-current sampling circuit and an off-current sampling circuit; The conduction current sampling circuit is connected to either end of the power switch unit, and the driving end of the conduction current sampling circuit and the driving end of the power switch unit receive the same driving signal to sample the first inductor current of the power inductor when the power switch unit is turned on; The shutdown current sampling circuit is connected to either end of the filter device to sample the second inductor current of the power inductor when the power switch unit is turned off.

[0007] Optionally, the power switch unit includes: a first power tube and a second power tube connected in back-to-back direction; the on-current sampling circuit is connected at a first position between the power inductor and the first power tube, or the on-current sampling circuit is connected at a second position between the second power tube and the second end of the AC input source.

[0008] Optionally, the shutdown current sampling circuit is connected at a third position between the third unidirectional device and the filter device, or the shutdown current sampling circuit is connected at a fourth position between the filter device and the fourth unidirectional device.

[0009] Optionally, the conduction current sampling circuit includes: a first current transformer, a fifth unidirectional device, a sixth unidirectional device, a seventh unidirectional device, an eighth unidirectional device, a degaussing device, a first sampling resistor and a third power tube; The primary side of the first current transformer is connected at the first position, or at the second position; The input end of the fifth unidirectional device is connected to the output end of the sixth unidirectional device, the output end of the fifth unidirectional device is connected to the output end of the seventh unidirectional device, the input end of the seventh unidirectional device is connected to the output end of the eighth unidirectional device, the input end of the sixth unidirectional device is connected to the input end of the eighth unidirectional device, one end of the secondary side of the first current transformer is connected between the fifth unidirectional device and the sixth unidirectional device, and the other end of the secondary side of the first current transformer is connected between the seventh unidirectional device and the eighth unidirectional device; The demagnetization device is connected in parallel between the output end of the fifth unidirectional device and the input end of the sixth unidirectional device, the first sampling resistor is connected in parallel between the output end of the seventh unidirectional device and the input end of the eighth unidirectional device, and the third power tube is arranged between the output end of the seventh unidirectional device and the first sampling resistor.

[0010] Optionally, the conduction current sampling circuit includes: a first current transformer, a fifth unidirectional device, a sixth unidirectional device, a demagnetization device, a first sampling resistor and a third power tube; The primary side of the first current transformer is connected at the first position, or at the second position; One end and the other end of the secondary side of the first current transformer are respectively connected to the input end of the fifth unidirectional device and the input end of the sixth unidirectional device, the output end of the fifth unidirectional device is connected to the output end of the sixth unidirectional device, and is also connected to the output end of the degaussing device, the center tap of the secondary side of the first current transformer is connected to the input end of the degaussing device, the first sampling resistor is connected in parallel to both ends of the degaussing device, and the third power tube is arranged between the output end of the degaussing device and the first sampling resistor.

[0011] Optionally, the output end of the shutdown current sampling circuit is connected to the first sampling resistor, so as to sample the first inductor current of the power inductor through the first sampling resistor when the power switch unit is turned on, and to sample the inductor discharge current of the power inductor through the first sampling resistor when the power switch unit is turned off.

[0012] Optionally, the shutdown current sampling circuit includes: a second sampling resistor, the output end of the second sampling resistor is connected to one end of the first sampling resistor and the connection point of the third power tube, and the other end of the first sampling resistor serves as the sampling output end of the on-current sampling circuit.

[0013] Optionally, the shutdown current sampling circuit includes: a second current transformer, a ninth unidirectional device, a tenth unidirectional device and a first voltage regulator tube; The primary side of the second current transformer is connected between the third unidirectional device and the filter device, or connected between the filter device and the fourth unidirectional device; The same-name end of the secondary side of the second current transformer is connected to the input end of the ninth unidirectional device and the output end of the tenth unidirectional device, the output end of the ninth unidirectional device is connected to one end of the first sampling resistor as the sampling output end of the conduction current sampling circuit, the non-same-name end of the secondary side of the second current transformer is connected to the output end of the first voltage regulator tube and the other end of the first sampling resistor, and the input end of the first voltage regulator tube is connected to the input end of the tenth unidirectional device.

[0014] Optionally, the demagnetization device is a second voltage regulator diode, and the fifth unidirectional device, the sixth unidirectional device, the seventh unidirectional device, and the eighth unidirectional device are all diodes, the anode of the diode is the input end of the unidirectional device, and the cathode of the diode is the output end of the unidirectional device.

[0015] In a second aspect, an embodiment of the present application further provides a current sampling method, which is applied to the current sampling circuit as described in any one of the first aspects, and the method includes: When the inductor charging loop of the bridgeless PFC circuit is turned on, sampling the first inductor current through the conduction current sampling circuit; When the inductor charging loop of the bridgeless PFC circuit is turned off, sampling the second inductor current by turning off the current sampling circuit; An inductor current of a power inductor in the bridgeless PFC circuit is determined according to the first inductor current and the second inductor current.

[0016] In a third aspect, an embodiment of the present application further provides a switching power supply, comprising a bridgeless PFC circuit and a current sampling circuit as described in any one of the first aspects.

[0017] The beneficial effects of this application are: The current sampling circuit, current sampling method and switching power supply provided by the present application provide a turn-on current sampling circuit and a turn-off current sampling circuit in a bridgeless PFC circuit, so that during the entire switching cycle of the AC input source, the inductor current of the power inductor can be sampled when the power switch unit is turned on, and the inductor current of the power inductor can be sampled when the power switch unit is turned off. The calculation method of the inductor current is simple, and the power switch unit can be controlled by the same drive signal regardless of the positive half-cycle or the negative half-cycle of the AC input source. The current sampling process does not need to determine whether the AC input source is in the positive half-cycle or the negative half-cycle, making the control method simpler. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 The circuit principle frame provided in the embodiment of the present application Figure 1 ; Figure 2 The circuit principle frame provided in the embodiment of the present application Figure 2 ; Figure 3 The circuit operating waveform provided by the embodiment of the present application; Figure 4 The circuit principle frame provided in the embodiment of the present application Figure 3 ; Figure 5 The circuit provided in the embodiment of the present application Figure 1 ; Figure 6 The circuit provided in the embodiment of the present application Figure 2 ; Figure 7 The circuit provided in the embodiment of the present application Figure 3 ; Figure 8 A schematic diagram of a flow chart of a current sampling method provided in an embodiment of the present application; Fig. 9 A schematic diagram of a switching power supply provided in an embodiment of the present application. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0021] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0022] In addition, the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0023] It should be noted that, in the absence of conflict, the features in the embodiments of the present application may be combined with each other.

[0024] In a possible implementation, an embodiment of the present application provides a current sampling circuit applied to a bridgeless PFC circuit. Figure 1 The circuit principle frame provided in the embodiment of the present application Figure 1 ,like Figure 1 As shown, the AC input source U in the bridgeless PFC circuit AC The first end of the power inductor L, the power switch unit 15 and the AC input source U AC The second end of the bridgeless PFC circuit is connected in sequence; the AC input source U AC The first end of the power inductor L, the first unidirectional device 11, the filter device 13, the fourth unidirectional device 14 and the AC input source U ACThe second end of the bridgeless PFC circuit is connected in sequence; the AC input source U AC The second end of the third unidirectional device 13, the filter device 16, the second unidirectional device 12, the power inductor L and the AC input source U AC The first ends of are connected in sequence.

[0025] The current sampling circuit includes: an on-current sampling circuit 21 and an off-current sampling circuit 22; the on-current sampling circuit 21 is connected to either end of the power switch unit 15, and the driving end of the on-current sampling circuit 21 and the driving end of the power switch unit 15 receive the same driving signal DRIVE to sample the first inductor current of the power inductor L when the power switch unit 15 is on; the off-current sampling circuit 22 is connected to either end of the filter device 16 to sample the second inductor current of the power inductor L when the power switch unit 15 is off.

[0026] In this embodiment, if Figure 1 As shown, the on-current sampling circuit 21 is arranged on either side of the power switch unit 15. When the power switch unit 15 is turned on, the AC input source U AC A current loop is formed between the power inductor L and the power switch unit 15. The current of the power inductor L increases with time. The on-current sampling circuit 21 samples the current flowing through to calculate the first inductor current in the on state.

[0027] The shutdown current sampling circuit 22 is arranged on either side of the filter device 16. When the power switch unit 15 is turned off, the AC input source U AC A current loop is formed between the power inductor L, the first unidirectional device 11 and the fourth unidirectional device 14 (or the second unidirectional device 12 and the third unidirectional device 13), and the filter device 16. The current of the power inductor L decreases over time. The shutdown current sampling circuit 22 samples the current flowing through to calculate the second inductor current in the shutdown state.

[0028] In the positive half cycle of the AC input source, when the power switch unit 15 is turned on, the current flows from the AC input source U AC Start, pass through the power inductor L and the power switch unit 15 and then return to the AC input source U AC The on-current sampling circuit 21 samples the current flowing through to calculate the first inductor current in the on-state during the positive half cycle of the AC input source.

[0029] In the positive half cycle of the AC input source, when the power switch unit 15 is turned off, the current flows from the AC input source U AC The AC input source U is returned to the AC input source U after passing through the power inductor L, the first unidirectional device 11, the filter device 16 and the fourth unidirectional device 14. ACThe shutdown current sampling circuit 22 samples the current flowing through to calculate the second inductor current in the shutdown state during the positive half cycle of the AC input source.

[0030] In the negative half cycle of the AC input source, when the power switch unit 15 is turned on, the current flows from the AC input source U AC Start, pass through the power switch unit 15 and the power inductor L and then return to the AC input source U AC The on-current sampling circuit 21 samples the current flowing through to calculate the first inductor current in the on-state during the negative half cycle of the AC input source.

[0031] In the negative half cycle of the AC input source, when the power switch unit 15 is turned off, the current flows from the AC input source U AC The AC input source U is returned to the AC input source U after passing through the third unidirectional device 13, the filter device 16, the second unidirectional device 12 and the power inductor L. AC The shutdown current sampling circuit 22 samples the current flowing through to calculate the second inductor current in the shutdown state during the negative half cycle of the AC input source.

[0032] The current sampling circuit provided in the above embodiment sets a turn-on current sampling circuit and a turn-off current sampling circuit in the bridgeless PFC circuit, so that during the entire switching cycle of the AC input source, the inductor current of the power inductor when the power switch unit is turned on can be sampled, and the inductor current of the power inductor when the power switch unit is turned off can be sampled. The calculation method of the inductor current is simple, and the power switch unit can be controlled by the same drive signal regardless of whether it is in the positive half cycle or the negative half cycle of the AC input source. The current sampling process does not need to determine whether the AC input source is in the positive half cycle or the negative half cycle, so that the control method is simpler.

[0033] In some embodiments, Figure 1 As shown, the power switch unit 15 may include: a first power tube and a second power tube connected in reverse, and the on-current sampling circuit 21 is connected to a first position between the power inductor L and the first power tube, or the on-current sampling circuit 21 is connected to the second power tube and the AC input source U AC a second position between the second ends of the device.

[0034] In this embodiment, the first power tube and the second power tube connected in back-to-back direction are driven by the same driving signal DRIVE. The first power tube and the second power tube are connected in back-to-back direction, which can avoid the current backflow problem when the first power tube and the second power tube are turned off, thereby ensuring circuit safety.

[0035] The on-current sampling circuit 21 can be flexibly selected to be connected to a first position between the power inductor L and the first power tube, or a second position between the second power tube and the second end of the AC input source UAC, both of which can realize sampling of the inductor current when the power switch unit 15 is in the on state.

[0036] In other embodiments, Figure 1 As shown, the shutdown current sampling circuit 22 is connected at a third position between the third unidirectional device 13 and the filter device 16 , or the shutdown current sampling circuit 22 is connected at a fourth position between the filter device 16 and the fourth unidirectional device 14 .

[0037] In this embodiment, the shutdown current sampling circuit 22 can flexibly select to be connected at the third position between the third unidirectional device 13 and the filter device 16, or at the fourth position between the filter device 16 and the fourth unidirectional device 14, both of which can realize the sampling of the inductor current in the shutdown state of the power switch unit 15.

[0038] Based on the above embodiments, the on-current sampling circuit 21 can be connected at the first position or the second position, and the off-current sampling circuit 22 can be connected at the third position or the fourth position. In this way, the current sampling circuit used in the PFC circuit has four implementation methods, namely, the on-current sampling circuit 21 is connected at the first position, and the off-current sampling circuit 22 is connected at the third position, or, the on-current sampling circuit 21 is connected at the first position, and the off-current sampling circuit 22 is connected at the fourth position, or, the on-current sampling circuit 21 is connected at the second position, and the off-current sampling circuit 22 is connected at the third position, or, the on-current sampling circuit 21 is connected at the second position, and the off-current sampling circuit 22 is connected at the fourth position.

[0039] The connection positions of the above four types of on-current sampling circuits 21 and off-current sampling circuits 22 do not affect the working modes of the on-current sampling circuits 21 and the off-current sampling circuits 22, and can all sample the inductor current of the positive half-cycle and negative half-cycle AC input sources in the on-state and the off-state.

[0040] In one possible implementation, Figure 2 The circuit principle frame provided in the embodiment of the present application Figure 2 ,like Figure 2 As shown, the conduction current sampling circuit 21 includes: a first current transformer, a fifth unidirectional device 25, a sixth unidirectional device 26, a seventh unidirectional device 27, an eighth unidirectional device 28, a degaussing device 29, a first sampling resistor R CS1 and the third power tube.

[0041] The primary side CT1_A of the first current transformer is connected at the first position, or at the second position; the input end of the fifth unidirectional device 25 is connected to the output end of the sixth unidirectional device 26, the output end of the fifth unidirectional device 25 is connected to the output end of the seventh unidirectional device 27, the input end of the seventh unidirectional device 27 is connected to the output end of the eighth unidirectional device 28, the input end of the sixth unidirectional device 26 is connected to the input end of the eighth unidirectional device 28, one end of the secondary side CT1_B of the first current transformer is connected between the fifth unidirectional device 25 and the sixth unidirectional device 26, and the other end of the secondary side CT1_B of the first current transformer is connected between the seventh unidirectional device 27 and the eighth unidirectional device 28; the demagnetization device 29 is connected in parallel between the output end of the fifth unidirectional device 25 and the input end of the sixth unidirectional device 26, and the first sampling resistor R CS1 The third power tube is connected in parallel between the output end of the seventh unidirectional device 27 and the input end of the eighth unidirectional device 28. CS1 between.

[0042] In this embodiment, the third power tube and the first power tube and the second power tube in the power switch unit 15 are driven by the same driving signal DRIVE. When the first power tube and the second power tube in the power switch unit 15 are turned on, the third power tube is also turned on. When the first power tube and the second power tube in the power switch unit 15 are turned off, the third power tube is also turned off.

[0043] For example, Figure 3 The circuit working waveform provided in the embodiment of the present application is as follows: Figure 3 As shown, in the positive half cycle of the AC input source, during the time period t1-t2, the first power tube, the second power tube and the third power tube are turned on at the same time. In the bridgeless PFC circuit, the current flows from the AC input source U AC Starting from, it flows through the power inductor L, the first power tube, the second power tube, the primary side CT1_A of the first current transformer in turn, and finally returns to the AC input source U AC , the inductor current increases with time. In the on-current sampling circuit 21, the current flows out from the same-name end of the secondary side CT1_B of the first current transformer, and flows through the fifth unidirectional device 25, the third power tube, and the first sampling resistor R in sequence. CS1 , the eighth unidirectional device 28, and finally returns to the non-same-name end of the secondary side CT1_B of the first current transformer, and the inductor current flows through the first sampling resistor R CS1 The current ratio is equal to the turns ratio of the secondary side CT1_B of the first current transformer and the original CT1_A of the first current transformer. CS1 The voltage across the two ends is V CSThe inductor current in the on state can be obtained. During the time period t2-t3, the first power tube, the second power tube, and the third power tube are cut off at the same time. In the bridgeless PFC circuit, the current flows from the AC input source U AC The current flows through the power inductor L, the first unidirectional device 11, the filter device 16 and the load, the shutdown current sampling circuit 22, the fourth unidirectional device 14, and finally returns to the AC input source U AC , the inductor current decreases with time, and the inductor current in the off state is sampled by the off current sampling circuit 22, while in the on current sampling circuit 21, the current starts from the non-same-name end of the secondary side CT1_B of the first current transformer, flows through the seventh unidirectional device 27, the demagnetization device 29, and the sixth unidirectional device 26 in sequence, and finally returns to the same-name end of the secondary side CT1_B of the first current transformer, thereby demagnetizing the first current transformer. The inductor current signals sampled by the on current sampling circuit 21 and the off current sampling circuit 22 are combined to obtain the complete inductor current.

[0044] In the negative half cycle of the AC input source, the t4-t5 period, the first power tube, the second power tube, and the third power tube are turned on at the same time. In the bridgeless PFC circuit, the current flows from the AC input source U AC Starting from, it flows through the primary side CT1_A of the first current transformer, the second power tube, the first power tube, the power inductor L, and finally returns to the AC input source U AC , the inductor current increases in the reverse direction. In the on-current sampling circuit 21, the current flows out from the non-same-name end of the secondary side CT1_B of the first current transformer, and flows through the seventh unidirectional device 27, the third power tube, and the first sampling resistor R in sequence. CS1 , the sixth unidirectional device 26, and finally returns to the same-name end of the secondary side CT1_B of the first current transformer, and the inductor current flows through the first sampling resistor R CS1 The ratio of the current is equal to the turns ratio of the secondary side CT1_B of the first current transformer to the primary side CT1_A of the first current transformer, and the first sampling resistor R CS1 The voltage at both ends can be used to obtain the inductor current. During the t5-t6 period, the first power tube, the second power tube, and the third power tube are cut off at the same time. In the bridgeless PFC circuit, the current flows from the AC input source U AC The current flows through the third unidirectional device 13, the filter device 16 and the load, the shutdown current sampling circuit 22, the second unidirectional device 12, the power inductor L, and finally returns to the AC input source U AC, the inductor current decreases in the reverse direction, and at this time the current is sampled by the off-current sampling circuit 22, and in the on-current sampling circuit 21, at this time the current starts from the same-name end of the secondary side CT1_B of the first current transformer, flows through the fifth unidirectional device 25, the demagnetization device, the eighth unidirectional device 28 in sequence, and finally returns to the non-same-name end of the secondary side CT1_B of the first current transformer, thereby demagnetizing the first current transformer. The inductor current signals obtained by the on-current sampling circuit 21 and the off-current sampling circuit 22 are combined to obtain the complete inductor current.

[0045] It should be noted that the placement of the same-name ends and non-same-name ends of the primary CT1_A and the secondary CT1_B of the first current transformer is only an example. In fact, the same-name ends and non-same-name ends of the primary CT1_A and the secondary CT1_B of the first current transformer can be placed randomly, and this embodiment does not limit this.

[0046] In the current sampling circuit provided by the above embodiment, the first power tube, the second power tube and the third power tube share the same driving signal, and there is no need to judge the positive and negative half cycles of the AC input source. The control method is simple, and the same-name ends and non-same-name ends of the primary and secondary sides of the first current transformer can be randomly placed, and the circuit implementation is very flexible.

[0047] In one possible implementation, Figure 4 The circuit principle frame provided in the embodiment of the present application Figure 3 ,like Figure 4 As shown, the conduction current sampling circuit 21 may include: a first current transformer, a fifth unidirectional device 25, a sixth unidirectional device 26, a degaussing device 29, a first sampling resistor R CS1 and the third power tube.

[0048] The primary side CT1_A of the first current transformer is connected at the first position, or at the second position; one end and the other end of the secondary side CT1_B of the first current transformer are respectively connected to the input end of the fifth unidirectional device 25 and the input end of the sixth unidirectional device 26, the output end of the fifth unidirectional device 25 is connected to the output end of the sixth unidirectional device 26, and is connected to the output end of the degaussing device 29, the center tap of the secondary side CT1_B of the first current transformer is connected to the input end of the degaussing device 29, and the first sampling resistor R CS1 The third power tube is connected in parallel at both ends of the degaussing device 29, and is arranged at the output end of the degaussing device 29 and the first sampling resistor R CS1 between.

[0049] In this embodiment, the third power tube and the first power tube and the second power tube in the power switch unit 15 are driven by the same driving signal DRIVE. When the first power tube and the second power tube in the power switch unit 15 are turned on, the third power tube is also turned on. When the first power tube and the second power tube in the power switch unit 15 are turned off, the third power tube is also turned off.

[0050] In a possible implementation, the output end of the shutdown current sampling circuit 22 is connected to the first sampling resistor R CS1 , so that when the power switch unit 15 is turned on, the first sampling resistor R CS1 The first inductor current of the sampled power inductor L passes through the first sampling resistor R when the power switch unit 15 is turned off. CS1 The second inductor current of the power inductor L is sampled.

[0051] In this embodiment, if Figure 2 As shown, if the shutdown current sampling circuit 22 is arranged between the third unidirectional device 13 and the filter device 16, then the end of the shutdown current sampling circuit 22 connected to the filter device 16 is the output end of the shutdown current sampling circuit 22; if the shutdown current sampling circuit 22 is arranged between the filter device 16 and the fourth unidirectional device 14, then the end of the shutdown current sampling circuit 22 connected to the fourth unidirectional device 14 is the output end of the shutdown current sampling circuit 22.

[0052] The output end of the shutdown current sampling circuit 22 is connected to the first sampling resistor R CS1 , so that when the power switch unit 15 is turned off, the current flowing through the shutdown current sampling circuit 22 passes through the first sampling resistor R CS1 , with the first sampling resistor R CS1 The inductor current in the off state is obtained by up-sampling.

[0053] In one possible implementation, the demagnetizing device is a second voltage regulator diode, the fifth unidirectional device, the sixth unidirectional device, the seventh unidirectional device, and the eighth unidirectional device are all diodes, the anode of the diode is the input end of the unidirectional device, and the cathode of the diode is the output end of the unidirectional device.

[0054] The shutdown current sampling circuit 22 includes: a second sampling resistor R CS2 , the second sampling resistor R CS2 The output end is connected to the first sampling resistor R CS1 The connection point between one end of the first sampling resistor R CS1 The other end of is used as the sampling output end of the conduction current sampling circuit 21.

[0055] In this embodiment, Figure 5 The circuit provided in the embodiment of the present application Figure 1, Figure 6 The circuit provided in the embodiment of the present application Figure 2 ,like Figure 5 and Figure 6 As shown, the first unidirectional device 11 to the eighth unidirectional device 28 are diodes D1 to D8 respectively, and the filter device 16 is a capacitor C O The first power device, the second power device and the third power device are MOS tubes Q1, Q2 and Q3 respectively, and the degaussing device 29 is a second voltage regulator tube DZ2.

[0056] In some embodiments, Figure 5 As shown, the primary side CT1_A of the first current transformer of the on-current sampling circuit 21 is set at position 2, and the second sampling resistor RCS2 of the off-current sampling circuit 22 is set at position 4. The connection relationship is: the AC input source U AC One end of is connected to one end of the power inductor L, and the other end is connected to the anode of the diode D3, the cathode of the diode D4, and the non-same-name end of the primary side CT1_A of the first current transformer. The other end of the power inductor L is connected to the anode of the diode D1, the cathode of the diode D2, and the drain of the first power tube Q1. The gate of the first power tube Q1 and the gate of the second power tube Q2 are connected together to receive the drive signal DRIVE. The source of the first power tube Q1 and the source of the second power tube Q2 are also connected together. The drain of the second power tube Q2 is connected to the same-name end of the primary side CT1_A of the first current transformer. The cathode of the diode D1, the cathode of the diode D3 and the capacitor C O The positive electrode and the load R L One end is connected to the anode of diode D2, the anode of diode D4 and the first sampling resistor R CS1 And the second sampling resistor R CS2 One end of the capacitor C O The negative electrode and the load R L The other end and the second sampling resistor R CS2 The other end of the diode D5 is connected to the cathode of the diode D7, the cathode of the second voltage regulator tube DZ2 and the drain of the third power tube Q3 are connected, the anode of the diode D6, the anode of the diode D8, the anode of the second voltage regulator tube DZ2 and the first sampling resistor R CS1 The anode of the diode D5 and the cathode of the diode D6 are connected to the same-name end of the secondary side CT1_B of the first current transformer, the anode of the diode D7 and the cathode of the diode D8 are connected to the non-same-name end of the secondary side CT1_B of the first current transformer, and the source of the third power tube Q3 and the capacitor C O CS is the current sampling point.

[0057] like Figure 3 The circuit waveform shown is Figure 5The circuit shown works as follows: When the AC input source is in the positive half cycle, during the time period t1-t2, the first power tube Q1, the second power tube Q2, and the third power tube Q3 are turned on at the same time, the diodes D1, D2, D3, D4, D6, and D7 are turned off, and the diodes D5 and D8 are turned on. In the bridgeless PFC circuit, the current flows from the AC input source U AC Starting from, it flows through the power inductor L, the first power tube Q1, the second power tube Q2, the primary side CT1_A of the first current transformer, and finally returns to the AC input source U AC , the inductor current increases with time. In the on-current sampling circuit 21, the current flows out from the same-name end of the secondary side CT1_B of the first current transformer, and flows through the diode D5, the third power tube Q3, and the second sampling resistor R CS2 , the first sampling resistor R CS1 , diode D8, and finally returns to the non-same-name end of the secondary side CT1_B of the first current transformer. The inductor current and the current flowing through the second sampling resistor R CS2 , the first sampling resistor R CS1 The ratio of the current is equal to the turns ratio of the secondary side CT1_B of the first current transformer to the primary side CT1_A of the first current transformer, and the first sampling resistor R CS1 and the second sampling resistor R CS2 The voltage at both ends, namely the sampling point CS and the capacitor C O The voltage between the cathode and cathode leads to the inductor current in the on state.

[0058] During the time period t2-t3, the first power tube Q1, the second power tube Q2, and the third power tube Q3 are turned off at the same time, the diodes D2, D3, D5, and D8 are turned off, the diodes D1, D4, D6, and D7 are turned on, and the second voltage regulator DZ2 is reversely broken down. In the bridgeless PFC circuit, the current flows from the AC input source U AC Starting from, the current flows through the power inductor L, diode D1, capacitor C in sequence O and load R L , the second sampling resistor R CS2 , diode D4, and finally returns to the AC input source U AC , the inductor current decreases. In the on-current sampling circuit 21, at this time, the current starts from the non-same-name end of the secondary side CT1_B of the first current transformer, flows through the diode D7, the second voltage regulator DZ2, the diode D6 in sequence, and finally returns to the same-name end of the secondary side CT1_B of the first current transformer, thereby demagnetizing the first current transformer CT1. Similarly, by sampling the first sampling resistor R CS1 and the second sampling resistor R CS2 The voltage at both ends, namely the sampling point CS and the capacitor CO The voltage between the negative electrodes can be used to obtain the inductor current in the off state. The inductor current signals sampled when the first power tube Q1, the second power tube Q2, and the third power tube Q3 are turned on and off can be combined to obtain a complete inductor current of a positive half cycle.

[0059] When the AC input source is in the negative half cycle, during the time period t4-t5, the first power tube Q1, the second power tube Q2, and the third power tube Q3 are turned on at the same time, the diodes D1, D2, D3, D4, D5, and D8 are turned off, and the diodes D6 and D7 are turned on. In the bridgeless PFC circuit, the current flows from the AC input source U AC Starting from, it flows through the primary side of the first current transformer CT1_A, the second power tube Q2, the first power tube Q1, the power inductor L, and finally returns to the AC input source U AC , the inductor current increases in the reverse direction. In the on-current sampling circuit 21, the current flows out from the non-same-name end of the secondary side CT1_B of the first current transformer, and flows through the diode D7, the third power tube Q3, the second sampling resistor R CS2 , the first sampling resistor R CS1 , diode D6, and finally returns to the same-name end of the secondary side CT1_B of the first current transformer. The inductor current and the current flowing through the second sampling resistor R CS2 , the first sampling resistor R CS1 The current ratio is equal to the turns ratio of the secondary side CT1_B of the first current transformer to the primary side CT1_A of the first current transformer, and the current ratio of the first sampling resistor R CS1 and the second sampling resistor R CS2 The voltage at both ends, namely the sampling point CS and the capacitor C O The voltage between the negative terminals can be used to obtain the inductor current.

[0060] During the time period t5-t6, the first power tube Q1, the second power tube Q2, and the third power tube Q3 are turned off at the same time, the diodes D1, D4, D6, and D7 are turned off, the diodes D2, D3, D5, and D8 are turned on, and the second voltage regulator DZ2 is reversely broken down. In the bridgeless PFC circuit, the current flows from the AC input source U AC Starting from, it flows through diode D3 and capacitor C O and load R L , the second sampling resistor R CS2 , diode D2, power inductor L, and finally return to the AC input source U AC, the inductor current decreases in the reverse direction. In the on-current sampling circuit 21, at this time, the current starts from the same-name end of the secondary side CT1_B of the first current transformer, flows through the diode D5, the second voltage regulator DZ2, and the diode D8 in sequence, and finally returns to the non-same-name end of the secondary side CT1_B of the first current transformer, thereby demagnetizing the first current transformer CT1. Similarly, by sampling the first sampling resistor R CS1 and the second sampling resistor R CS2 The voltage at both ends, namely the sampling point CS and the capacitor C O The voltage between the negative electrodes can be used to obtain the inductor current. By combining the inductor current signals sampled when the first power tube Q1, the second power tube Q2, and the third power tube Q3 are turned on and off, a complete inductor current of a negative half cycle can be obtained.

[0061] In other embodiments, Figure 6 As shown, Figure 5 The connection relationship shown is different in the structure of the on-current sampling circuit 21. Specifically, the non-same-name end of the upper winding of the secondary side CT1_B of the first current transformer is connected to the anode of the diode D5, the same-name end of the lower winding of the secondary side CT1_B of the first current transformer is connected to the anode of the diode D6, the cathode of the diode D5, the cathode of the diode D6, the cathode of the second voltage regulator tube DZ2 and the drain of the third power tube Q3 are connected, and the same-name end or the non-same-name end of the upper winding of the secondary side CT1_B of the first current transformer is connected to the anode of the second voltage regulator tube DZ2 and the first sampling resistor R CS1 The other end, the source of the third power tube Q3 and the capacitor C O CS is the current sampling point.

[0062] like Figure 3 The circuit waveform shown is Figure 6 The circuit shown works as follows: When the AC input source is in the positive half cycle, during the time period t1-t2, the first power tube Q1, the second power tube Q2, and the third power tube Q3 are turned on at the same time, the diodes D1, D2, D3, D4, and D5 are turned off, and the diode D6 is turned on. In the bridgeless PFC circuit, the current flows from the AC input source U AC Starting from, it flows through the power inductor L, the first power tube Q1, the second power tube Q2, the primary side CT1_A of the first current transformer, and finally returns to the AC input source U AC , the inductor current increases with time. In the on-current sampling circuit, the current flows out from the same-name end of the lower winding of the secondary side CT1_B of the first current transformer, and flows through the diode D6, the third power tube Q3, and the second sampling resistor R CS2 , the first sampling resistor R CS1, and finally returns to the non-same-name end of the lower winding of the secondary side CT1_B of the first current transformer, and the inductor current flows through the second sampling resistor R CS2 , the first sampling resistor R CS1 The ratio of the current is equal to the turns ratio of the lower winding of the secondary CT1_B of the first current transformer to the primary CT1_A of the first current transformer, and the first sampling resistor R CS1 and the second sampling resistor R CS2 The voltage at both ends, namely the sampling point CS and the capacitor C O The voltage between the cathode and cathode leads to the inductor current in the on state.

[0063] During the time period t2-t3, the first power tube Q1, the second power tube Q2, and the third power tube Q3 are turned off at the same time, the diodes D2, D3, and D6 are turned off, the diodes D1, D4, and D5 are turned on, and the second voltage regulator DZ2 is reversely broken down. In the bridgeless PFC circuit, the current flows from the AC input source U AC Starting from, the current flows through the power inductor L, diode D1, capacitor C in sequence O and load R L , the second sampling resistor R CS2 , diode D4, and finally returns to the AC input source UAC, and the inductor current decreases. In the on-current sampling circuit, at this time, the current starts from the non-same-name end of the winding on the secondary side CT1_B of the first current transformer, flows through the diode D5 and the second voltage regulator DZ2 in sequence, and finally returns to the same-name end of the winding on the secondary side CT1_B of the first current transformer, thereby demagnetizing the first current transformer CT1. Similarly, by sampling the first sampling resistor R CS1 and the second sampling resistor R CS2 The voltage at both ends, namely the sampling point CS and the capacitor C O The voltage between the negative electrodes can be used to obtain the inductor current in the off state. The inductor current signals sampled when the first power tube Q1, the second power tube Q2, and the third power tube Q3 are turned on and off can be combined to obtain a complete inductor current of a positive half cycle.

[0064] When the AC input source is in the negative half cycle, during the time period t4-t5, the first power tube Q1, the second power tube Q2, and the third power tube Q3 are turned on at the same time, the diodes D1, D2, D3, D4, and D6 are turned off, and the diode D5 is turned on. In the bridgeless PFC circuit, the current flows from the AC input source U AC Starting from, it flows through the primary side of the first current transformer CT1_A, the second power tube Q2, the first power tube Q1, the power inductor L, and finally returns to the AC input source U AC, the inductor current increases in the reverse direction. In the on-current sampling circuit, the current flows out from the non-same-name end of the winding on the secondary side CT1_B of the first current transformer, and flows through the diode D5, the third power tube Q3, and the second sampling resistor R CS2 , the first sampling resistor R CS1 , and finally returns to the same-name end of the winding on the secondary side CT1_B of the first current transformer. The inductor current and the current flowing through the second sampling resistor R CS2 , the first sampling resistor R CS1 The current ratio is equal to the turns ratio of the winding on the secondary side CT1_B of the first current transformer and the primary side CT1_A of the first current transformer. CS1 and the second sampling resistor R CS2 The voltage at both ends, that is, the voltage between the sampling point CS and the negative electrode of the capacitor CO, can be used to obtain the inductor current.

[0065] During the time period t5-t6, the first power tube Q1, the second power tube Q2, and the third power tube Q3 are turned off at the same time, the diodes D1, D4, and D5 are turned off, the diodes D2, D3, and D6 are turned on, and the second voltage regulator DZ2 reversely breaks down. In the bridgeless PFC circuit, the current flows from the AC input source U AC Starting from, it flows through diode D3 and capacitor C O and load R L , the second sampling resistor R CS2 , diode D2, power inductor L, and finally return to the AC input source U AC , the inductor current decreases in the reverse direction. In the on-current sampling circuit, at this time, the current starts from the same-name end of the lower winding of the secondary side CT1_B of the first current transformer, flows through the diode D5 and the second voltage regulator DZ2 in sequence, and finally returns to the non-same-name end of the lower winding of the secondary side CT1_B of the first current transformer, thereby demagnetizing the first current transformer CT1. Similarly, by sampling the first sampling resistor R CS1 and the second sampling resistor R CS2 The voltage at both ends, namely the sampling point CS and the capacitor C O The voltage between the negative electrodes can be used to obtain the inductor current. By combining the inductor current signals sampled when the first power tube Q1, the second power tube Q2, and the third power tube Q3 are turned on and off, a complete inductor current of a negative half cycle can be obtained.

[0066] In the current sampling circuit provided by the above embodiment, no matter whether the AC input source is in the positive half cycle or the negative half cycle, when the first power tube, the second power tube, and the third power tube are turned on, the sampling current flows from the second sampling resistor through the first sampling resistor. When the first power tube, the second power tube, and the third power tube are turned off, the sampling current only flows through the second sampling resistor, and the current direction remains unchanged. The first power tube, the second power tube, and the third power tube can share a driving signal. Therefore, the current sampling method adopted by the current sampling circuit does not need to judge the positive and negative half cycles of the AC input source, and the control is simpler. In addition, the same-name end and the non-same-name end of the first current transformer can be placed at will without affecting the flow direction of the sampling current on the sampling resistor.

[0067] In another possible implementation, the shutdown current sampling circuit 22 includes: a second current transformer, a ninth unidirectional device, a tenth unidirectional device, and a first voltage regulator tube.

[0068] The primary side of the second current transformer is connected between the third unidirectional device and the filter device, or, connected between the filter device and the fourth unidirectional device; the same-name end of the secondary side of the second current transformer is connected to the input end of the ninth unidirectional device and the output end of the tenth unidirectional device, the output end of the ninth unidirectional device is connected to one end of the first sampling resistor as the sampling output end of the conduction current sampling circuit, the non-same-name end of the secondary side of the second current transformer is connected to the output end of the first voltage regulator tube and the other end of the first sampling resistor, and the input end of the first voltage regulator tube is connected to the input end of the tenth unidirectional device.

[0069] In this embodiment, Figure 7 The circuit provided in the embodiment of the present application Figure 3 ,like Figure 7 As shown, the ninth unidirectional device and the tenth unidirectional device are diode D9 and diode D10 respectively, and the first voltage regulator tube is ZD1.

[0070] The connection method of the bridgeless PFC circuit and the on-current sampling circuit 21 is the same as Figure 5 The same is not repeated here.

[0071] The connection mode of the shutdown current sampling circuit 22 is as follows: the same-name end of the primary side CT2_A of the second current transformer is connected to the negative electrode of the capacitor CO, the non-same-name end of the primary side CT2_A of the second current transformer is connected to the anode of the diode D4, the same-name end of the secondary side CT2_B of the second current transformer is connected to the anode of the diode D9 and the cathode of the diode D10, and the cathode of the diode D9 is connected to the first sampling resistor R CS1 The anode of the diode D10 is connected to the anode of the first voltage regulator tube DZ1, and the non-same-name end of the secondary side CT2_B of the second current transformer and the cathode of the first voltage regulator tube DZ1 are connected to the first sampling resistor R CS1 The other end of CS is the current sampling point.

[0072] like Figure 3 The circuit waveform shown is Figure 7 The circuit shown works as follows: When the AC input source is in the positive half cycle, during the time period t1-t2, the first power tube Q1, the second power tube Q2, and the third power tube Q3 are turned on at the same time, the diodes D1, D2, D3, D4, D6, D7, and D9 are turned off, the diodes D5, D8, and D10 are turned on, and the first voltage regulator DZ1 is reversely broken down. In the bridgeless PFC circuit, the current flows from the AC input source U AC Starting from, it flows through the power inductor L, the first power tube Q1, the second power tube Q2, the primary side CT1_A of the first current transformer, and finally returns to the AC input source U AC , the inductor current increases with time. In the on-current sampling circuit 21, the current flows out from the same-name end of the secondary side CT1_B of the first current transformer, and flows through the diode D5, the third power tube Q3, the first sampling resistor R CS1 , diode D8, and finally returns to the non-same-name end of the secondary side CT1_B of the first current transformer. The inductor current and the current flowing through the first sampling resistor R CS1 The current ratio is equal to the turns ratio of the secondary CT1_B of the first current transformer to the primary CT1_A of the first current transformer. The inductor current can be obtained by sampling the voltage across the first sampling resistor RCS1. In the shutdown current sampling circuit 22, the current flows out from the non-same-name end of the secondary CT2_B of the second current transformer, flows through the first voltage regulator DZ1 and the diode D10 in sequence, and returns to the same-name end of the secondary CT2_B of the second current transformer, thereby demagnetizing the second current transformer CT2.

[0073] During the time period t2-t3, the first power tube Q1, the second power tube Q2, and the third power tube Q3 are turned off at the same time, the diodes D2, D3, D5, D8, and D10 are turned off, the diodes D1, D4, D6, D7, and D9 are turned on, and the second voltage regulator DZ2 is reversely broken down. In the bridgeless PFC circuit, the current flows from the AC input source U AC Starting from, the current flows through the power inductor L, diode D1, capacitor C in sequence O and load R L , the primary side of the second current transformer CT2_A, diode D4, and finally back to the AC input source U AC, the inductor current decreases. In the on-current sampling circuit 21, at this time, the current starts from the non-same-name end of the secondary side CT1_B of the first current transformer, flows through the diode D7, the second voltage regulator DZ2, and the diode D6 in sequence, and finally returns to the same-name end of the secondary side CT1_B of the first current transformer, thereby demagnetizing the first current transformer CT1. In the off-current sampling circuit 22, the current flows out from the same-name end of the secondary side CT2_B of the second current transformer, flows through the diode D9, the first sampling resistor R CS1 , back to the non-same-name end of the secondary side CT2_B of the second current transformer, the inductor current and the current flowing through the first sampling resistor R CS1 The ratio of the current is equal to the turns ratio of the secondary side CT2_B of the second current transformer to the primary side CT2_A of the second current transformer. CS1 The voltage at both ends can be used to obtain the inductor current in the off state. The inductor current signals sampled when the first power tube Q1, the second power tube Q2, and the third power tube Q3 are turned on and off can be combined to obtain the inductor current of the complete positive half cycle.

[0074] When the AC input source is in the negative half cycle, during the time period t4-t5, the first power tube Q1, the second power tube Q2, and the third power tube Q3 are turned on at the same time, the diodes D1, D2, D3, D4, D5, D8, and D9 are turned off, the diodes D6, D7, and D10 are turned on, and the first voltage regulator DZ1 is reversely broken down. In the bridgeless PFC circuit, the current flows from the AC input source U AC Starting from, it flows through the primary side of the first current transformer CT1_A, the second power tube Q2, the first power tube Q1, the power inductor L, and finally returns to the AC input source U AC , the inductor current increases in the reverse direction with time. In the on-current sampling circuit 21, the current flows out from the non-same-name end of the secondary side CT1_B of the first current transformer, and flows through the diode D7, the third power tube Q3, the first sampling resistor R CS1 , diode D6, and finally returns to the same-name terminal of the secondary side CT1_B of the first current transformer. The inductor current and the current flowing through the first sampling resistor R CS1 The ratio of the current is equal to the turns ratio of the secondary side CT1_B of the first current transformer to the primary side CT1_A of the first current transformer, and the first sampling resistor R CS1 In the shutdown current sampling circuit 22, the current flows out from the non-same-name end of the secondary side CT2_B of the second current transformer, flows through the first voltage regulator DZ1 and the diode D10 in sequence, and returns to the same-name end of the secondary side CT2_B of the second current transformer, thereby demagnetizing the second current transformer CT2.

[0075] During the time period t5-t6, the first power tube Q1, the second power tube Q2, and the third power tube Q3 are turned off at the same time, the diodes D1, D4, D6, D7, and D10 are turned off, the diodes D2, D3, D5, D8, and D9 are turned on, and the second voltage regulator DZ2 is reversely broken down. In the bridgeless PFC circuit, the current flows from the AC input source U AC Starting from, it flows through diode D3 and capacitor C O and load R L , the primary side of the second current transformer CT2_A, diode D2, power inductor L, and finally return to the AC input source U AC , the inductor current decreases in the reverse direction. In the on-current sampling circuit 21, at this time, the current starts from the same-name end of the secondary side CT1_B of the first current transformer, flows through the diode D5, the second voltage regulator DZ2, and the diode D8 in sequence, and finally returns to the same-name end of the secondary side CT1_B of the first current transformer, thereby demagnetizing the first current transformer CT1. In the off-current sampling circuit 22, the current flows out from the same-name end of the secondary side CT2_B of the second current transformer, flows through the diode D9, the first sampling resistor R CS1 , back to the non-same-name end of the secondary side CT2_B of the second current transformer, the inductor current and the current flowing through the first sampling resistor R CS1 The current ratio is equal to the turns ratio of the secondary side CT2_B of the second current transformer and the primary side CT2_A of the second current transformer. CS1 The voltage at both ends can be used to obtain the inductor current. The inductor current signals sampled when the first power tube Q1, the second power tube Q2, and the third power tube Q3 are turned on and off can be combined to obtain the complete inductor current of the negative half cycle.

[0076] In some embodiments, Figure 7 The shutdown current sampling circuit shown can also be used with Figure 6 The on-state current sampling circuit combination shown is used as a current sampling circuit, wherein, Figure 7 The cathode of diode D9 is shown connected Figure 6 The first sampling resistor R CS1 One end of Figure 7 The cathode of the first voltage regulator tube DZ1 is connected to Figure 6 The first sampling resistor R CS1 The other end of its working principle combines Figure 6 The working principle of the on-state current sampling circuit shown in Figure 7 The working principle of the shutdown current sampling circuit shown is not repeated here.

[0077] In the current sampling circuit provided by the above embodiment, no matter whether the AC input source is in the positive half cycle or the negative half cycle, no matter whether the first power tube, the second power tube, and the third power tube are turned on or in the medium, the sampling current flows through the first sampling resistor in the same direction and the current direction remains unchanged. The first power tube, the second power tube, and the third power tube can share a driving signal. Therefore, the current sampling method adopted by the current sampling circuit does not need to judge the positive and negative half cycles of the AC input source, and the control is simpler. In addition, the same-name end and the non-same-name end of the first current transformer and the same-name end and the non-same-name end of the second current transformer can be placed at will without affecting the flow direction of the sampling current on the sampling resistor.

[0078] Based on the current sampling circuit provided in the above embodiment, the embodiment of the present application also provides a current sampling method. Figure 8 A flow chart of a current sampling method provided in an embodiment of the present application is shown in FIG. Figure 8 As shown, the method may include: S101 . When the inductor charging loop of the bridgeless PFC circuit is turned on, a first inductor current is sampled by a current sampling circuit.

[0079] S102: When the inductor charging loop of the bridgeless PFC circuit is turned off, sampling the second inductor current by turning off the current sampling circuit.

[0080] S103: Determine the inductor current of the power inductor in the bridgeless PFC circuit according to the first inductor current and the second inductor current.

[0081] In one possible implementation, Fig. 9 A schematic diagram of a switching power supply provided in an embodiment of the present application, such as Fig. 9 As shown, the switching power supply may include: a bridgeless PFC circuit and a current sampling circuit.

[0082] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A current sampling circuit, characterized in that: Applied to a bridgeless PFC circuit, the first end of the AC input source, the power inductor, the power switch unit and the second end of the AC input source in the bridgeless PFC circuit are connected in sequence; the first end of the AC input source, the power inductor, the first unidirectional device, the filter device, the fourth unidirectional device and the second end of the AC input source in the bridgeless PFC circuit are connected in sequence; the second end of the AC input source, the third unidirectional device, the filter device, the second unidirectional device, the power inductor and the first end of the AC input source in the bridgeless PFC circuit are connected in sequence; The current sampling circuit comprises: an on-current sampling circuit and an off-current sampling circuit; The conduction current sampling circuit is connected to either end of the power switch unit, and the driving end of the conduction current sampling circuit and the driving end of the power switch unit receive the same driving signal to sample the first inductor current of the power inductor when the power switch unit is turned on; The shutdown current sampling circuit is connected to either end of the filter device to sample the second inductor current of the power inductor when the power switch unit is turned off.

2. The current sampling circuit according to claim 1, characterized in that: The power switch unit includes: a first power tube and a second power tube connected in back-to-back direction; the on-current sampling circuit is connected at a first position between the power inductor and the first power tube, or the on-current sampling circuit is connected at a second position between the second power tube and the second end of the AC input source.

3. The current sampling circuit according to claim 1, characterized in that: The shutdown current sampling circuit is connected at a third position between the third unidirectional device and the filter device, or the shutdown current sampling circuit is connected at a fourth position between the filter device and the fourth unidirectional device.

4. The current sampling circuit according to claim 2, characterized in that: The conduction current sampling circuit comprises: a first current transformer, a fifth unidirectional device, a sixth unidirectional device, a seventh unidirectional device, an eighth unidirectional device, a degaussing device, a first sampling resistor and a third power tube; The primary side of the first current transformer is connected at the first position, or at the second position; The input end of the fifth unidirectional device is connected to the output end of the sixth unidirectional device, the output end of the fifth unidirectional device is connected to the output end of the seventh unidirectional device, the input end of the seventh unidirectional device is connected to the output end of the eighth unidirectional device, the input end of the sixth unidirectional device is connected to the input end of the eighth unidirectional device, one end of the secondary side of the first current transformer is connected between the fifth unidirectional device and the sixth unidirectional device, and the other end of the secondary side of the first current transformer is connected between the seventh unidirectional device and the eighth unidirectional device; The demagnetization device is connected in parallel between the output end of the fifth unidirectional device and the input end of the sixth unidirectional device, the first sampling resistor is connected in parallel between the output end of the seventh unidirectional device and the input end of the eighth unidirectional device, and the third power tube is arranged between the output end of the seventh unidirectional device and the first sampling resistor.

5. The current sampling circuit according to claim 2, characterized in that: The conduction current sampling circuit comprises: a first current transformer, a fifth unidirectional device, a sixth unidirectional device, a demagnetization device, a first sampling resistor and a third power tube; The primary side of the first current transformer is connected at the first position, or at the second position; One end and the other end of the secondary side of the first current transformer are respectively connected to the input end of the fifth unidirectional device and the input end of the sixth unidirectional device, the output end of the fifth unidirectional device is connected to the output end of the sixth unidirectional device, and is also connected to the output end of the degaussing device, the center tap of the secondary side of the first current transformer is connected to the input end of the degaussing device, the first sampling resistor is connected in parallel to both ends of the degaussing device, and the third power tube is arranged between the output end of the degaussing device and the first sampling resistor.

6. The current sampling circuit according to claim 4 or 5, characterized in that: The output end of the shutdown current sampling circuit is connected to the first sampling resistor, so as to sample the first inductor current of the power inductor through the first sampling resistor when the power switch unit is turned on, and sample the inductor discharge current of the power inductor through the first sampling resistor when the power switch unit is turned off.

7. The current sampling circuit according to claim 6, characterized in that: The off-current sampling circuit includes: a second sampling resistor, an output end of the second sampling resistor is connected to one end of the first sampling resistor, and the other end of the first sampling resistor serves as a sampling output end of the on-current sampling circuit.

8. The current sampling circuit according to claim 6, characterized in that: The shutdown current sampling circuit comprises: a second current transformer, a ninth unidirectional device, a tenth unidirectional device and a first voltage regulator tube; The primary side of the second current transformer is connected between the third unidirectional device and the filter device, or connected between the filter device and the fourth unidirectional device; The same-name end of the secondary side of the second current transformer is connected to the input end of the ninth unidirectional device and the output end of the tenth unidirectional device, the output end of the ninth unidirectional device is connected to one end of the first sampling resistor as the sampling output end of the conduction current sampling circuit, the non-same-name end of the secondary side of the second current transformer is connected to the output end of the first voltage regulator tube and the other end of the first sampling resistor, and the input end of the first voltage regulator tube is connected to the input end of the tenth unidirectional device.

9. The current sampling circuit according to claim 4, characterized in that: The demagnetizing device is a second voltage regulator diode, and the fifth unidirectional device, the sixth unidirectional device, the seventh unidirectional device, and the eighth unidirectional device are all diodes, the anode of the diode is the input end of the unidirectional device, and the cathode of the diode is the output end of the unidirectional device.

10. A current sampling method, characterized in that: Applied to the current sampling circuit according to any one of claims 1 to 9, the method comprises: When the inductor charging loop of the bridgeless PFC circuit is turned on, sampling the first inductor current through the conduction current sampling circuit; When the inductor charging loop of the bridgeless PFC circuit is turned off, sampling the second inductor current by turning off the current sampling circuit; An inductor current of a power inductor in the bridgeless PFC circuit is determined according to the first inductor current and the second inductor current.

11. A switching power supply, characterized in that: It comprises a bridgeless PFC circuit and a current sampling circuit as claimed in any one of claims 1 to 9.

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