A control method, control device and switching power supply

Abstract

The application discloses a control method, a control device and a switching power supply. The switching power supply comprises an AC-DC converter, the AC-DC converter comprises a bridgeless PFC circuit in the front stage and a DC-DC circuit in the rear stage, all the switching tubes of the bridge arms of the bridgeless PFC circuit are high-frequency controllable switching tubes, the driving pulses of the two switching tubes of the same bridge arm are complementary, the duty cycles of the upper switching tubes of the bridge arms of the first switching circuit and the second switching circuit are respectively the first duty cycle and the third duty cycle, the control method comprises the following steps: obtaining the PF value of the AC-DC converter in real time, comparing the PF value with a preset value, and obtaining a control signal; adjusting one of the first duty cycle and the third duty cycle according to the control signal, and the other duty cycle is given in advance or changes along with the adjusted duty cycle, so that the PF value of the AC-DC converter reaches the expected value. The control method can improve the PF value of the AC-DC converter.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of power electronics, and particularly relates to a control method, a control device and a switching power supply. BACKGROUND

[0002] AC-DC converters with unit power factor correction (PFC) are widely used in the industrial fields such as plug-in hybrid and electric vehicle charging, uninterruptible power supply, server power supply, residential direct current distribution system, etc.

[0003] Most of the current AC-DC converters adopt a two-stage structure; the front stage is a PFC stage, which reduces input current harmonics to improve power factor and provides a stable DC bus voltage; the rear stage is a DC-DC stage, which is usually composed of an isolated DC-DC converter to achieve current isolation and voltage conversion gain adjustment, and to provide a stable DC output voltage for the load. However, the two-stage structure contains many switching devices, which brings about the disadvantages of complex circuit structure, complex control, high cost, low power density, low reliability, etc.

[0004] In order to reduce the complexity and cost of the circuit structure, the front stage PFC circuit and the rear stage DC-DC converter are combined, and part of the devices are reused, so that the single-stage AC-DC structure has great prospects. In 2015, Mahdi Ghasemi of Tabiat Modares University published a paper entitled "Analyzing a Bridgeless Single Stage LLC Resonant PFC Converter Controlled by Frequency and Pulse Width Modulations Techniques", which proposed a single-stage AC-DC converter based on totem pole bridgeless PFC+LLC. The pulse frequency modulation (PFC) and pulse width modulation (PWM) techniques are used to realize the PFC function and soft switching function, and the switching loss and electro-magnetic interference (EMI) are low; however, the inventors of the present application found that a non-controllable diode bridge arm is used in this scheme, and the PFC unit works in the discontinuous current mode (DCM), so that the DC bus voltage is too high, and the current ripple of the PFC inductor is large. In 2018, Wuxi Youdian Technology Co., Ltd. applied for a patent with the publication number CN209593841U, "Single-stage isolated LED drive power supply based on GaN device", which replaces the diode in the front stage totem pole bridgeless PFC with a switch tube. The switch tube is turned on alternately and complementarily according to the power frequency cycle, which reduces the conduction loss of the original diode bridge arm; however, the inventors of the present application found that the PFC unit in this control mode also works in the DCM mode, and the problems of high bus voltage and large PFC inductor current ripple are still not solved. In 2022, Huawei Digital Energy Technology Co., Ltd. applied for a PCT with the publication number WO2023217372A1, "Ac / dc power converter", based on the totem pole bridgeless PFC+LLC architecture, using the power frequency bridge arm+high frequency bridge arm structure, and proposing the PFM+PWM control method, which effectively reduces the DC bus voltage and the PFC inductor current ripple; however, the inventors of the present application found that the power frequency tube is turned off near the zero crossing point, and the PFC unit works in the DCM mode, which causes the PFC inductor current ripple to be still large.

[0005] In summary, by using the new control method, through reasonable control of the single-stage AC-DC converter switching device, the PF value is improved, the PFC inductor current ripple and the DC bus voltage are reduced under the premise of ensuring the stability of the DC output voltage, which has important significance.

[0006] It should be noted that the information disclosed in the background section is only intended to deepen the understanding of the overall background of the present application, and should not be regarded as acknowledging or implying in any form that the information constitutes prior art known to those skilled in the art. SUMMARY

[0007] Therefore, the technical problem to be solved by the present application is to provide a control method, a control device and a switching power supply, which overcome at least one of the above-mentioned deficiencies in the prior art.

[0008] As a first aspect of the present application, the technical solutions of the embodiments of the provided control method are as follows:

[0009] A control method applied to an AC-DC converter, the AC-DC converter comprising a bridgeless PFC circuit in the front stage and a DC-DC circuit in the rear stage, the bridgeless PFC circuit comprising at least one PFC inductor, and a first switching circuit, a second switching circuit and a DC bus capacitor connected in parallel between a first node and a second node, each of the first switching circuit and the second switching circuit comprising at least one bridge arm, all the switching tubes of the bridge arms being high-frequency controllable switching tubes and the driving pulses of the two switching tubes of the same bridge arm being complementary, the duty cycle of the upper switching tube of each bridge arm of the first switching circuit being a first duty cycle D1, and the duty cycle of the upper switching tube of each bridge arm of the second switching circuit being a third duty cycle D3; wherein the control method comprises:

[0010] obtaining a control signal by comparing the PF value of the AC-DC converter with a preset value in real time;

[0011] adjusting one of the first duty cycle and the third duty cycle according to the control signal, and the other duty cycle being given in advance or changing following the adjusted duty cycle, so that the PF value of the AC-DC converter reaches the desired value, wherein D1∈[0, 1] and D3∈[0, 1].

[0012] Further, the value of the first duty cycle is given and the value of the third duty cycle is adjusted so that the PF value of the AC-DC converter reaches the desired value within all times of one power frequency cycle;

[0013] or the value of the third duty cycle is given and the value of the first duty cycle is adjusted so that the PF value of the AC-DC converter reaches the desired value within all times of one power frequency cycle.

[0014] or in the first half of a power frequency cycle, given the value of the first duty cycle, adjust the value of the third duty cycle so that the PF value of the AC-DC converter reaches the desired value; in the second half of the power frequency cycle, given the value of the third duty cycle, adjust the value of the first duty cycle so that the PF value of the AC-DC converter reaches the desired value;

[0015] or in the first half of a power frequency cycle, given the value of the third duty cycle, adjust the value of the first duty cycle so that the PF value of the AC-DC converter reaches the desired value; in the second half of the power frequency cycle, given the value of the first duty cycle, adjust the value of the third duty cycle so that the PF value of the AC-DC converter reaches the desired value.

[0016] Further, in the time corresponding to the δ phase angle range in which the input voltage of the AC-DC converter changes from negative to positive in a power frequency cycle, and the time corresponding to the θ phase angle range in which the input voltage of the AC-DC converter changes from positive to negative, the value of D3 is given in advance to be kept at 0.5±a set value; in the rest of the power frequency cycle, if the input voltage of the AC-DC converter is negative, the value of D1 is given in advance to be 0, and if the input voltage of the AC-DC converter is positive, the value of D1 is given in advance to be 1;

[0017] or in the time corresponding to the δ phase angle range in which the input voltage of the AC-DC converter changes from negative to positive in a power frequency cycle, and the time corresponding to the θ phase angle range in which the input voltage of the AC-DC converter changes from positive to negative, the value of D1 is given in advance to be kept at 0.5±a set value; in the rest of the power frequency cycle, if the input voltage of the AC-DC converter is negative, the value of D3 is given in advance to be 0, and if the input voltage of the AC-DC converter is positive, the value of D3 is given in advance to be 1;

[0018] wherein δ∈(0, 180°], θ∈(180, 360°].

[0019] Further, the set value is 0.1.

[0020] Further, in the time corresponding to the α phase angle range in which the input voltage of the AC-DC converter changes from negative to positive in a power frequency cycle, the value of D1 is given in advance to monotonically increase; in the time corresponding to the β phase angle range in which the input voltage of the AC-DC converter changes from positive to negative in the power frequency cycle, the value of D1 is given in advance to monotonically decrease; in the rest of the power frequency cycle, if the input voltage of the AC-DC converter is negative, the value of D1 is given in advance to be 0, and if the input voltage of the AC-DC converter is positive, the value of D1 is given in advance to be 1.

[0021] or the value of D3 is monotonously increasing in the time corresponding to the alpha phase angle range in which the input voltage of the AC-DC converter changes from negative to positive in one power frequency cycle; the value of D3 is monotonously decreasing in the time corresponding to the beta phase angle range in which the input voltage of the AC-DC converter changes from positive to negative in the power frequency cycle; and the value of D3 is 0 if the input voltage of the AC-DC converter is negative and the value of D3 is 1 if the input voltage of the AC-DC converter is positive in the rest of the power frequency cycle;

[0022] wherein, alpha is in (0, 180°] and beta is in (180, 360°].

[0023] Further, in one power frequency cycle, D1 is a sine curve with a 0.5 DC bias; or in one power frequency cycle, D3 is a sine curve with a 0.5 DC bias.

[0024] Further, by predefining the sum of the first duty ratio and the third duty ratio, when one of the first duty ratio and the third duty ratio is adjusted according to the control signal, the other duty ratio will change along with the change of the adjusted duty ratio.

[0025] Further, the sum of the first duty ratio and the third duty ratio is pre-defined as 1.

[0026] Further, the switching frequency of each switch tube in the first switching circuit and the switching frequency of each switch tube in the second switching circuit are independent of each other.

[0027] Further, the switching frequency of each switch tube in the first switching circuit is f1, and the switching frequency of each switch tube in the second switching circuit is f2, and f2 = 2 x f1.

[0028] Further, the internal phase shift control is adopted among each bridge arm in the first switching circuit with a first phase shift angle, the internal phase shift control is adopted among each bridge arm in the second switching circuit with a second phase shift angle, the external phase shift control is adopted between the first switching circuit and the second switching circuit with a third phase shift angle, the switching frequency of each switch tube in the first switching circuit is f1, and the switching frequency of each switch tube in the second switching circuit is f2, and the control quantity for stabilizing the output voltage of the AC-DC converter includes one or any number of combinations of the first phase shift angle, the second phase shift angle, the third phase shift angle, f1 and f2.

[0029] Further, in the entire power frequency cycle range, the PFC inductors are all in continuous conduction mode.

[0030] As a second aspect of the present application, the embodiment of the control device provided in the technical solutions as follows:

[0031] A control device applied to an AC-DC converter, the AC-DC converter comprising a bridgeless PFC circuit in the front stage and a DC-DC circuit in the rear stage, the bridgeless PFC circuit comprising at least one PFC inductor, and a first switching circuit, a second switching circuit and a DC bus capacitor connected in parallel between a first node and a second node, each of the first switching circuit and the second switching circuit comprising at least one bridge arm, the switching tubes of all the bridge arms being high-frequency controllable switching tubes and the driving pulses of the two switching tubes of the same bridge arm being complementary, the duty cycles of the upper switching tubes of each bridge arm of the first switching circuit being D1, and the duty cycles of the upper switching tubes of each bridge arm of the second switching circuit being D3; wherein the control device comprises:

[0032] a control signal acquisition module for acquiring the PF value of the AC-DC converter in real time and comparing it with a preset value to obtain a control signal;

[0033] a duty cycle adjustment module for adjusting one of the first duty cycle and the third duty cycle according to the control signal, and the other duty cycle being given in advance or changing with the adjusted duty cycle, so that the PF value of the AC-DC converter reaches the expected value, wherein D1∈[0, 1] and D3∈[0, 1].

[0034] As a third aspect of the present application, the embodiment of the switching power supply provided in the technical solutions as follows:

[0035] A switching power supply comprising an AC-DC converter, the AC-DC converter comprising a bridgeless PFC circuit in the front stage and a DC-DC circuit in the rear stage, the bridgeless PFC circuit comprising at least one PFC inductor, and a first switching circuit, a second switching circuit and a DC bus capacitor connected in parallel between a first node and a second node, each of the first switching circuit and the second switching circuit comprising at least one bridge arm, the switching tubes of all the bridge arms being high-frequency controllable switching tubes and the driving pulses of the two switching tubes of the same bridge arm being complementary, the duty cycles of the upper switching tubes of each bridge arm of the first switching circuit being D1, and the duty cycles of the upper switching tubes of each bridge arm of the second switching circuit being D3; wherein the switching power supply comprises the control device of any one of the second aspect.

[0036] The term meaning is explained as follows:

[0037] High-frequency controllable switch tube: the "high frequency" in the "high-frequency controllable switch tube" of the application refers to the switching frequency of the switch tube, and belongs to the same technical branch as the "high frequency" in the background technology "high-frequency bridge arm", and belongs to a different technical branch as the "power frequency" in the background technology "power-frequency bridge arm", and the frequency range of the "high frequency" is above 10 kHz, and the frequency of the "power frequency" is 50 Hz or 60 Hz.

[0038] The structure of the conventional single-stage AC-DC converter is that the first switch circuit is usually a low-frequency / power-frequency switch bridge arm, the second switch circuit is usually a high-frequency bridge arm, and the PFC inductor current of the AC-DC converter is usually in discontinuous mode, which can cause problems such as large PFC inductor current wave of the AC-DC converter, high DC bus voltage, low PF value, high THD, etc., and the application embodiment sets all the switch tubes of the bridge arms in the first switch circuit and the second switch circuit as high-frequency controllable switch tubes, and the driving pulses of the two switch tubes of the same bridge arm are complementary, the duty cycle of the upper switch tube of each bridge arm in the first switch circuit is a first duty cycle, and the duty cycle of the upper switch tube of each bridge arm in the second switch circuit is a third duty cycle, one of the first duty cycle and the third duty cycle is adjusted, and the other duty cycle is pre-defined or changes following the change of the adjusted duty cycle, so that the PF value of the AC-DC converter reaches the desired value, and the application has the following beneficial effects compared with the prior art through principle analysis and simulation verification of the embodiment:

[0039] (1) The first switch circuit and the second switch circuit are both set as high-frequency circuits, so that the switch tubes of the two switch circuits can be controlled to adjust the PF value of the single-stage AC-DC circuit within the power frequency cycle, so that the PF value can be adjusted to the desired value faster, and the PFC unit can work in the inductor current continuous mode;

[0040] (2) Since the switch tubes of the two switch circuits can be controlled within the power frequency cycle, the output ripple can be further adjusted by combining phase shift and switching frequency, etc., to ensure a high PF value while reducing the input current ripple, and the DC bus voltage is controllable and low.

[0041] Other features and advantages of the application will be set forth in the following description of the application, and in part will become apparent to those skilled in the art from the description, or can be learned by practice of the application. The objects and other advantages of the application can be achieved and obtained by the structure specifically pointed out in the specification, claims and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1A The first principle diagram of the AC-DC converter suitable for the application;

[0043] Figure 1BSecond principle block diagram of AC-DC converter applicable to the present application

[0044] Figure 1C Third principle block diagram of AC-DC converter applicable to the present application

[0045] Figure 2 Flow chart of control method of first embodiment of the present application

[0046] Figure 3A Voltage and duty cycle curve corresponding to first control strategy based on Figure 1B control method of first embodiment of the present application

[0047] Figure 3B Simulation waveform corresponding to Figure 3A control strategy

[0048] Figure 4A Voltage and duty cycle curve corresponding to second control strategy based on Figure 1B control method of first embodiment of the present application

[0049] Figure 4B Simulation waveform corresponding to Figure 4A control strategy

[0050] Figure 5 Voltage and duty cycle curve corresponding to third control strategy based on Figure 1C control method of first embodiment of the present application, and partial enlarged driving timing diagram

[0051] Figure 6A Voltage and duty cycle curve corresponding to fourth control strategy based on Figure 1B control method of first embodiment of the present application

[0052] Figure 6B Simulation waveform corresponding to Figure 6A control strategy

[0053] Figure 7A Voltage and duty cycle curve corresponding to fifth control strategy based on Figure 1B control method of first embodiment of the present application

[0054] Figure 7B Simulation waveform corresponding to Figure 7A control strategy

[0055] Figure 8A Voltage and duty cycle curve corresponding to sixth control strategy based on Figure 1B control method of first embodiment of the present application

[0056] Figure 8B Simulation waveform corresponding to Figure 8AA simulation waveform diagram corresponding to the control strategy;

[0057] Figure 9 A principle block diagram of the control device of the second embodiment of the present application. DETAILED DESCRIPTION

[0058] It should be noted that the embodiments and features of the embodiments in the present application can be combined with each other without conflict.

[0059] In order for those skilled in the technical field to better understand the scheme of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the scope of protection of the present application.

[0060] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily have to describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so as to describe the embodiments of the present application. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0061] It should be understood that, in the specification, claims and drawings of the present application, when describing a step succeeding to another step, the step can directly succeed to the other step, or succeed to the other step through a third step; when describing an element / unit "succeeding" to another element / unit, the element / unit can be "directly connected" to the other element / unit, or "connected" to the other element / unit through a third element / unit. In addition, the drawings of the present application are only schematic drawings of the present application, and are not necessarily drawn to scale. The same reference signs in the drawings represent the same or similar parts, and thus repeated description thereof will be omitted. Some block diagrams shown in the drawings are functional entities, which do not necessarily have to correspond to physically or logically independent entities. These functional entities can be implemented by software, or in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0062] The AC-DC converter to which this invention applies includes a bridgeless PFC circuit in the front stage and a DC-DC circuit in the back stage. The bridgeless PFC circuit includes at least one PFC inductor, and a first switching circuit, a second switching circuit, and a DC bus capacitor connected in parallel between the first node and the second node. The first switching circuit and the second switching circuit each include at least one bridge arm. The switching transistors of the bridge arms are all high-frequency controllable switching transistors, and the drive pulses of the two switching transistors in the same bridge arm are complementary. The duty cycle of the upper-side switching transistors of each bridge arm of the first switching circuit is a first duty cycle D1, and the duty cycle of the upper-side switching transistors of each bridge arm of the second switching circuit is a third duty cycle D3.

[0063] Figure 1A This is a first principle block diagram of an AC-DC converter to which this invention applies, where 101 is an AC voltage source; 102 is the PFC inductor L in a bridgeless PFC circuit. b ; 103 is the first switching circuit in the bridgeless PFC circuit, containing one bridge arm, which is composed of two high-frequency controllable switches S1 and S2, with the two switches controlling each other complementaryly; 104 is the second switching circuit in the bridgeless PFC circuit, containing one bridge arm, which is composed of two high-frequency controllable switches S3 and S4, with the two switches controlling each other complementaryly; 105 is the DC bus capacitor C in the bridgeless PFC circuit. bus The corresponding DC bus voltage can usually fluctuate within a certain range; 106 is the subsequent DC-DC circuit, which is a functional block diagram.

[0064] Figure 1B This is a second principle block diagram of the AC-DC converter to which this invention applies, and... Figure 1A The difference lies in the fact that the subsequent DC-DC circuit provides a specific circuit, which is a half-bridge LLC topology, and the primary half-bridge switch of the subsequent DC-DC circuit reuses the switches S1 and S2 in the first switching circuit of the preceding PFC circuit.

[0065] Figure 1C This is a third principle block diagram of the AC-DC converter to which this invention applies, and... Figure 1A The difference lies in that the second switching circuit includes two bridge arms: a second bridge arm composed of controllable switches S3 and S4, and a third bridge arm composed of controllable switches S5 and S6. Furthermore, it includes two PFC inductors: a first PFC inductor L... b1 Second PFC inductor L b2 One end of each of the two PFC inductors is connected to the midpoint of the two bridge arms of the second switching circuit, and the other end is connected to one end of the AC voltage source.

[0066] It should be noted that, Figure 1A , Figure 1B and Figure 1CThe application is applicable to some examples of AC-DC converters, and thus cannot limit the protection scope of the application. For example, for Figure 1A The PFC inductor L b The PFC inductor can be arranged between the midpoint of the first bridge arm and one end of the AC voltage source, between the midpoint of the second bridge arm and the other end of the AC voltage source, or between the midpoint of the first bridge arm and one end of the AC voltage source and between the midpoint of the second bridge arm and the other end of the AC voltage source. For Figure 1B The DC-DC circuit in the latter stage can be replaced by various bridge circuits or rectifier circuits using transformer isolation, such as full-bridge rectification, full-wave rectification, and current-doubler rectification. For Figure 1C The DC-DC circuit in the latter stage can use various isolated full-bridge circuits, such as full-bridge converter circuits, full-bridge LLC circuits, DAB circuits, and CLLC circuits. The specific design of the AC-DC converter circuit can be selected by those skilled in the art as needed, and the application is not limited.

[0067] First embodiment

[0068] The control method provided in this embodiment is applied to an AC-DC converter, which includes a bridgeless PFC circuit in the former stage and a DC-DC circuit in the latter stage. The bridgeless PFC circuit includes at least one PFC inductor and a first switching circuit, a second switching circuit, and a DC bus capacitor connected in parallel between a first node and a second node. The first switching circuit and the second switching circuit each include at least one bridge arm, and the switching tubes of all the bridge arms are high-frequency controllable switching tubes, and the driving pulses of the two switching tubes in the same bridge arm are complementary. The duty cycle of the upper switching tube in each bridge arm of the first switching circuit is a first duty cycle D1, and the duty cycle of the upper switching tube in each bridge arm of the second switching circuit is a third duty cycle D3. Figure 2 The flowchart of the control method of the first embodiment of the application is shown in Figure 2 which includes

[0069] In the control signal acquisition step S100, the PF value of the AC-DC converter is acquired in real time, and compared with a preset value to obtain a control signal.

[0070] In the duty cycle adjustment step S200, one of the first duty cycle and the third duty cycle is adjusted according to the control signal, and the other duty cycle is given in advance or changes with the adjusted duty cycle, so that the PF value of the AC-DC converter reaches the expected value, where D1∈[0, 1] and D3∈[0, 1].

[0071] As a specific implementation of the control method in this embodiment, for all time periods of a power frequency cycle, given a value of the first duty cycle, the value of the third duty cycle is adjusted to make the PF value of the AC-DC converter reach the desired value; or for all time periods of a power frequency cycle, given a value of the third duty cycle, the value of the first duty cycle is adjusted to make the PF value of the AC-DC converter reach the desired value; or for the first half of a power frequency cycle, given a value of the first duty cycle, the value of the third duty cycle is adjusted to make the PF value of the AC-DC converter reach the desired value; and for the second half of the power frequency cycle, given a value of the third duty cycle, the value of the first duty cycle is adjusted to make the PF value of the AC-DC converter reach the desired value; or for the first half of a power frequency cycle, given a value of the third duty cycle, the value of the first duty cycle is adjusted to make the PF value of the AC-DC converter reach the desired value; and for the second half of the power frequency cycle, given a value of the first duty cycle, the value of the third duty cycle is adjusted to make the PF value of the AC-DC converter reach the desired value.

[0072] Figure 3A The control method of the first embodiment is based on Figure 1B The voltage and duty cycle curves corresponding to the first control strategy, where the output voltage v of the AC power supply is... ac Set to 110V power frequency, its amplitude V ac Approximately 155.5V, DC bus voltage V bus Set it to 400V. For example... Figure 3A As shown, in one power frequency cycle, δ = θ = 180°; the duty cycle D3 is pre-set to remain at 0.5 throughout the entire power frequency cycle, and the PF value of the AC-DC converter is adjusted by controlling the duty cycle D1. Simultaneously, within the δ phase angle range, v corresponds to... ac >0, corresponding to v within the phase angle θ range ac <0.

[0073] like Figure 3B The figure shown is a simulation waveform diagram corresponding to the first control strategy in the first embodiment of the present invention. Figure 3B It can be seen that throughout the entire power frequency cycle, the duty cycle D3 of switch S3 remains stable at around 0.5, which is consistent with the theoretical analysis. From Figure 3B It can be seen that the bus voltage V bus It fluctuates between 390V and 410V, with a DC component of 400V; the current i of the PFC inductor L It exhibits a sinusoidal distribution and low current ripple; V o This refers to the DC output voltage of a single-stage AC-DC converter, V. o When stabilized at 12V, its DC output voltage ripple is 30mV. Simulation results show that the power factor (PF) is as high as 99.96%.

[0074] As a specific implementation of the control method in this embodiment, the value of D3 is pre-set to be maintained at 0.5 ± a set value for the time corresponding to the δ phase angle range of the AC-DC converter's input voltage changing from negative to positive and the time corresponding to the θ phase angle range of the AC-DC converter's input voltage changing from positive to negative within one power frequency cycle; for the remaining time of this power frequency cycle, if the input voltage of the AC-DC converter is negative, the value of D1 is pre-set to be 0, and if the input voltage of the AC-DC converter is positive, the value of D1 is pre-set to be 1; or within one power frequency cycle... The time corresponding to the δ phase angle range of the AC-DC converter's input voltage changing from negative to positive, and the time corresponding to the θ phase angle range of the AC-DC converter's input voltage changing from positive to negative, are pre-set with the value of D1 maintained at 0.5 ± a set value. For the remaining time of this power frequency cycle, if the AC-DC converter's input voltage is negative, the pre-set value of D3 is 0; if the AC-DC converter's input voltage is positive, the pre-set value of D3 is 1; where δ ∈ (0, 180°) and θ ∈ (180, 360°). Further, the set value is 0.1.

[0075] Figure 4A The control method of the first embodiment is based on Figure 1B The second control strategy corresponds to the voltage and duty cycle curves, where the output voltage v of the AC power supply is... ac Set to 265V power frequency, its amplitude V ac Approximately 375V, DC bus voltage V bus Set it to 400V. For example... Figure 4A As shown, in one power frequency cycle, at v ac The range of δ phase angle changing from negative to positive (δ = 65°) and v ac Within the phase angle range θ (θ = 65°) from positive to negative, the duty cycle D3 is pre-set to be maintained at 0.5, and the PF value of the AC-DC converter is adjusted by controlling the duty cycle D1; within the remaining phase angle range of the power frequency cycle, when v ac When <0, the pre-defined duty cycle D1 remains at 0, and when v ac When the value is greater than 0, the duty cycle D1 is pre-set to remain at 1, and then the PF value of the AC-DC converter is adjusted by controlling the duty cycle D3.

[0076] Figure 4B for Figure 4A The simulation waveforms corresponding to the control strategy, from Figure 4B It can be seen that, Figure 4A Within the corresponding δ phase angle range and θ phase angle range, the duty cycle D3 of switch S3 remains stable at around 0.5; within the remaining phase angle range, when v acWhen the value is less than 0, the pre-defined duty cycle D1 remains stable at around 0. ac When the duty cycle is greater than 0, the pre-defined duty cycle D1 remains stable at around 1, which is consistent with the theoretical analysis. From Figure 4B It can also be seen that the bus voltage V bus It fluctuates between 390V and 410V, with a DC component of 400V; the current i of the PFC inductor L It exhibits a sinusoidal distribution and low current ripple; V o This refers to the DC output voltage of a single-stage AC-DC converter, V. o Stable at 12V, its DC output voltage ripple is 50mV. Furthermore, simulation results show a power factor (PF) as high as 99.95%.

[0077] Figure 5 The control method of the first embodiment is based on Figure 1C The third control strategy corresponds to the voltage and duty cycle curves, and the enlarged drive timing diagram. In this control strategy, the duty cycle of switch S1 is defined as DS1, the duty cycle of switch S2 as DS2, the duty cycle of switch S3 as DS3, the duty cycle of switch S4 as DS4, the duty cycle of switch S5 as DS5, and the duty cycle of switch S6 as DS6, and DS1 = D1, DS3 = DS5 = D3. Figure 5 As can be seen from the voltage and duty cycle curves, the control strategy employed is similar to... Figure 4A Within the δ and θ phase angle ranges of one power frequency cycle, the duty cycle D3 is pre-set to be maintained at 0.5, and the PF value of the AC-DC converter is adjusted by controlling the duty cycle D1; within the remaining phase angle range of the power frequency cycle, when v ac When <0, the pre-defined duty cycle D1 remains at 0, and when v ac When the value is greater than 0, the pre-defined duty cycle D1 is kept at 1, and the PF value of the AC-DC converter is adjusted by controlling the duty cycle D3. Figure 5 The driving timing diagram after partial magnification shows that the duty cycles of the two bridge arms in the second switching circuit are equal, and the phase shift φ between the two bridge arms is 180°. In addition, σ is the external phase shift between the first and second switching circuits, so that the duty cycles DS1 and DS3 are symmetrical about the middle.

[0078] As a specific implementation of the control method in this embodiment, during the time corresponding to the α phase angle range where the input voltage of the AC-DC converter changes from negative to positive in one power frequency cycle, the value of D1 is pre-given and monotonically increases; during the time corresponding to the β phase angle range where the input voltage of the AC-DC converter changes from positive to negative in the same power frequency cycle, the value of D1 is pre-given and monotonically decreases; for the remaining time in the power frequency cycle, if the input voltage of the AC-DC converter is negative, the value of D1 is pre-given and 0; if the input voltage of the AC-DC converter is positive, the value of D1 is pre-given and 1; or during... During one power frequency cycle, the value of D3 is given to monotonically increase during the time corresponding to the α phase angle range where the input voltage of the AC-DC converter changes from negative to positive; during the time corresponding to the β phase angle range where the input voltage of the AC-DC converter changes from positive to negative during the same power frequency cycle, the value of D3 is given to monotonically decrease; during the remaining time of the same power frequency cycle, if the input voltage of the AC-DC converter is negative, the value of D3 is given to be 0, and if the input voltage of the AC-DC converter is positive, the value of D3 is given to be 1; where α∈(0, 180°], β∈(180, 360°).

[0079] Figure 6A The control method of the first embodiment is based on Figure 1B The voltage and duty cycle curves corresponding to the fourth control strategy, where the output voltage v of the AC power supply is... ac Set to 265V power frequency, its amplitude V ac Approximately 375V, DC bus voltage V bus Set it to 400V. For example... Figure 6A As shown, in one power frequency cycle, at v ac Within the phase angle range of α (α = 20°) from negative to positive, the duty cycle D1 of the pre-defined switch S1 linearly changes from 0 to 1; in v ac Within the β phase angle range (β = 20°) from positive to negative, the duty cycle D1 of the pre-defined switch S1 linearly changes from 1 to 0. Within the remaining phase angle range of the power frequency cycle, when v ac When <0, the pre-defined duty cycle D1 remains at 0, and when v ac When the value is greater than 0, the duty cycle D1 is pre-set to remain at 1. Throughout the entire power frequency cycle, the PF value of the AC-DC converter is adjusted by controlling the duty cycle D3.

[0080] like Figure 6B for Figure 6A The simulation waveforms corresponding to the control strategy, from Figure 6B It can be seen that in v ac During the phase angle α (α = 20°) range from negative to positive, the duty cycle D1 of switch S1 linearly changes from 0 to 1 and remains constant; in v acFrom a phase angle β changing from positive to negative (β = 20°), the duty cycle D1 of switch S1 linearly changes from 1 to 0 and remains there until the next power frequency cycle, which is consistent with theoretical analysis. Figure 6B It can be seen that the bus voltage V bus It fluctuates between 390V and 410V, with a DC component of 400V; the current i of the PFC inductor L It exhibits a sinusoidal distribution and low current ripple; V o This refers to the DC output voltage of a single-stage AC-DC converter, V. o When stabilized at 12V, its DC output voltage ripple is 60mV. Simulation results show that the power factor (PF) is as high as 99.93%.

[0081] As a specific implementation of the control method in this embodiment, D1 is pre-given as a sine curve with a DC bias of 0.5 within one power frequency cycle; or D3 is pre-given as a sine curve with a DC bias of 0.5 within one power frequency cycle.

[0082] Figure 7A The control method of the first embodiment is based on Figure 1B The fifth control strategy corresponds to the voltage and duty cycle curves, where the output voltage v of the AC power supply is... ac Set to 265V power frequency, its amplitude V ac Approximately 375V, DC bus voltage V bus Set it to 400V. For example... Figure 7A As shown, during the entire power frequency cycle, the duty cycle D1 is pre-given as a sine wave with a DC bias of 0.5 (i.e., a sine wave symmetrical about 0.5), and then the PF value of the AC-DC converter is adjusted by controlling the duty cycle D3.

[0083] like Figure 7B for Figure 7A The simulation waveforms corresponding to the control strategy, from Figure 7B It can be seen that the duty cycle of switch S1 is a symmetrical sine wave about 0.5 throughout the entire power frequency cycle, which is consistent with the theoretical analysis. From Figure 7B It can be seen that the bus voltage V bus It fluctuates between 390V and 410V, with a DC component of 400V; the current i of the PFC inductor L It exhibits a sinusoidal distribution and low current ripple; V o This refers to the DC output voltage of a single-stage AC-DC converter, V. o When stabilized at 12V, its DC output voltage ripple is 75mV. Simulation results show that the power factor (PF) is as high as 99.95%.

[0084] As a specific implementation of the control method in this embodiment, by pre-setting the sum of a first duty cycle and a third duty cycle, when one of the first and third duty cycles is adjusted according to the control signal, the other duty cycle will change accordingly. Further, the sum of the first and third duty cycles is pre-set to be 1.

[0085] Figure 8A The control method of the first embodiment is based on Figure 1B The voltage and duty cycle curves corresponding to the sixth control strategy, where the output voltage v of the AC power supply is shown. ac Set to 265V power frequency, its amplitude V ac Approximately 375V, DC bus voltage V bus Set it to 400V. For example... Figure 8A As shown, the duty cycle D1 of switch S1 and the duty cycle D3 of switch S3 are pre-defined to be symmetrical about 0.5 throughout the entire power frequency cycle, that is, D1 = 0.5 + Δ, D3 = 0.5 - Δ, which satisfies the condition D1 + D3 = 1; and then the PF value of the AC-DC converter is adjusted by controlling one of the duty cycles D3.

[0086] like Figure 8B for Figure 8A The simulation waveforms corresponding to the control strategy, from Figure 8B It can be seen that throughout the entire power frequency cycle, the duty cycle D1 of switch S1 and the duty cycle D3 of switch S3 are symmetrical about 0.5, satisfying D1 + D3 = 1, which is consistent with the theoretical analysis. From Figure 8B It can be seen that the bus voltage V bus It fluctuates between 390V and 410V, with a DC component of 400V; the current i of the PFC inductor L It exhibits a sinusoidal distribution and low current ripple; V o This refers to the DC output voltage of a single-stage AC-DC converter, V. o When stabilized at 12V, its DC output voltage ripple is 80mV. Simulation results show that the power factor (PF) is as high as 99.94%.

[0087] As a specific implementation of the control method in this embodiment, the switching frequencies of each switch in the first switching circuit and the switching frequencies of each switch in the second switching circuit are independent of each other, thereby increasing the optimization freedom of the converter, improving the overall efficiency of the converter and reducing the cost of the switch.

[0088] As a specific implementation of the control method in this embodiment, the switching frequency of each switch in the first switching circuit is f1, and the switching frequency of each switch in the second switching circuit is f2, where f2 = 2 × f1, thereby reducing the switching loss of the first switch and the cost of the device.

[0089] As a specific embodiment of the control method of the embodiment, the inner phase shift control is adopted between each bridge arm in the first switch circuit and the phase shift angle is the first phase shift angle, the inner phase shift control is adopted between each bridge arm in the second switch circuit and the phase shift angle is the second phase shift angle, the outer phase shift control is adopted between the first switch circuit and the second switch circuit and the phase shift angle is the third phase shift angle, the switching frequency of each switch tube in the first switch circuit is f1, the switching frequency of each switch tube in the second switch circuit is f2, and the control quantity for stabilizing the output voltage of the AC-DC converter includes one or any number of combinations of the first phase shift angle, the second phase shift angle, the third phase shift angle, f1 and f2, thereby increasing the optimization degree of freedom of the converter and improving the efficiency and overall performance of the converter.

[0090] As a specific embodiment of the control method of the embodiment, the PFC inductors are all in continuous conduction mode in the whole power frequency cycle range, thereby reducing the total harmonic distortion and the input current ripple, and further reducing the design complexity of the PFC inductors.

[0091] Second embodiment

[0092] The embodiment provides a control device applied to an AC-DC converter, the AC-DC converter including a bridgeless PFC circuit located in a front stage and a DC-DC circuit located in a rear stage, the bridgeless PFC circuit including at least one PFC inductor and a first switch circuit, a second switch circuit and a DC bus capacitor connected in parallel between a first node and a second node, the first switch circuit and the second switch circuit each including at least one bridge arm, the switch tubes of all the bridge arms being high-frequency controllable switch tubes and the driving pulses of the two switch tubes of the same bridge arm being complementary, the duty cycles of the upper switch tubes of each bridge arm of the first switch circuit all being D1, and the duty cycles of the upper switch tubes of each bridge arm of the second switch circuit all being D3. Figure 9 The principle block diagram of the control device of the second embodiment of the application is shown in Figure 9 The control device includes:

[0093] The control signal acquisition module 100 is configured to acquire the PF value of the AC-DC converter in real time, compare the PF value with a preset value, and obtain a control signal.

[0094] The duty cycle adjustment module 200 is configured to adjust one of the first duty cycle and the third duty cycle according to the control signal, and the other duty cycle is given in advance or changes with the adjusted duty cycle, so that the PF value of the AC-DC converter reaches the expected value, wherein D1∈[0, 1] and D3∈[0, 1].

[0095] The technical means adopted by the control device of the embodiment corresponds to the control method of the first embodiment, and has the same beneficial effects, and thus will not be described again.

[0096] In addition, the preferred technical means or further improved means of each step in the control method of the first embodiment can be extended to the corresponding units of the embodiment, and the embodiment will not be described one by one.

[0097] Third embodiment

[0098] The embodiment provides a switching power supply, which comprises an AC-DC converter, the AC-DC converter comprises a front-stage bridgeless PFC circuit and a rear-stage DC-DC circuit, the bridgeless PFC circuit comprises at least one PFC inductor, and a first switching circuit, a second switching circuit and a DC bus capacitor connected in parallel between a first node and a second node, the first switching circuit and the second switching circuit each comprise at least one bridge arm, the switching tubes of all the bridge arms are high-frequency controllable switching tubes, and the driving pulses of the two switching tubes of the same bridge arm are complementary, the duty ratios of the upper switching tubes of each bridge arm of the first switching circuit are all D1, and the duty ratios of the upper switching tubes of each bridge arm of the second switching circuit are all D3; wherein the switching power supply comprises any one control device in the second embodiment.

[0099] The switching power supply of the embodiment is beneficial to improving the PF value of the AC-DC converter, reducing the current ripple of the PFC inductor, reducing the DC bus voltage and improving the overall efficiency of the AC-DC converter due to comprising the control device of any one of the second embodiment.

[0100] It can be known from common technical knowledge that the application can be realized through other embodiments without departing from the spirit or essential characteristics thereof. Therefore, the above disclosed embodiments are only examples in all aspects, and are not the only ones. All changes within the scope of the application or within the scope equivalent to the application are included in the application.

Claims

1. A control method applied to an AC-DC converter, the AC-DC converter comprising a bridgeless PFC circuit in the front stage and a DC-DC circuit in the rear stage, the bridgeless PFC circuit comprising at least one PFC inductor, and a first switching circuit, a second switching circuit, and a DC bus capacitor connected in parallel between a first node and a second node, the first switching circuit and the second switching circuit each comprising at least one bridge arm, all bridge arms having high-frequency controllable switching transistors and the drive pulses of the two switching transistors in the same bridge arm being complementary, the duty cycle of the upper-side switching transistors of each bridge arm of the first switching circuit being a first duty cycle D1, and the duty cycle of the upper-side switching transistors of each bridge arm of the second switching circuit being a third duty cycle D3; characterized in that, The control method includes: The PF value of the AC-DC converter is acquired in real time and compared with a preset value to obtain a control signal; The duty cycle of the AC-DC converter is adjusted according to the control signal, wherein one of the first duty cycle and the third duty cycle is predetermined or changes with the adjusted duty cycle, so that the PF value of the AC-DC converter reaches the desired value, where D1∈[0,1] and D3∈[0,1]. Specifically, when the sum of the first duty cycle and the third duty cycle is given in advance, and one of the first duty cycle and the third duty cycle is adjusted according to the control signal, the other duty cycle will change in accordance with the adjustment of the duty cycle.

2. The control method according to claim 1, characterized in that: For all time during a power frequency cycle, given the value of the first duty cycle, the value of the third duty cycle is adjusted so that the PF value of the AC-DC converter reaches the desired value; Alternatively, given a third duty cycle value for all time within a power frequency cycle, the value of the first duty cycle is adjusted so that the PF value of the AC-DC converter reaches the desired value. Alternatively, within the first half of a power frequency cycle, given the value of the first duty cycle, the value of the third duty cycle is adjusted so that the PF value of the AC-DC converter reaches the desired value. In the latter half of the power frequency cycle, given the value of the third duty cycle, the value of the first duty cycle is adjusted so that the PF value of the AC-DC converter reaches the desired value. Alternatively, within the first half of a power frequency cycle, given a third duty cycle value, the first duty cycle value is adjusted so that the PF value of the AC-DC converter reaches the desired value. During the latter half of the power frequency cycle, given the value of the first duty cycle, the value of the third duty cycle is adjusted so that the PF value of the AC-DC converter reaches the desired value.

3. The control method according to claim 1, characterized in that: During one power frequency cycle, the input voltage of the AC-DC converter changes from negative to positive. δ The time corresponding to the phase angle range, and the change in the input voltage of the AC-DC converter from positive to negative. θ For the time corresponding to the phase angle range, the value of D3 is pre-set to be maintained at 0.5 ± the set value; for the rest of the power frequency cycle, if the input voltage of the AC-DC converter is negative, the value of D1 is pre-set to be 0, and if the input voltage of the AC-DC converter is positive, the value of D1 is pre-set to be 1. Alternatively, the input voltage of the AC-DC converter may change from negative to positive within one power frequency cycle. δ The time corresponding to the phase angle range, and the change in the input voltage of the AC-DC converter from positive to negative. θ For the time corresponding to the phase angle range, the value of D1 is pre-set to be maintained at 0.5 ± the set value; for the rest of the power frequency cycle, if the input voltage of the AC-DC converter is negative, the value of D3 is pre-set to be 0, and if the input voltage of the AC-DC converter is positive, the value of D3 is pre-set to be 1. in, δ ∈(0, 180°]、 θ ∈(180, 360°).

4. The control method according to claim 3, characterized in that: The set value is 0.

1.

5. The control method according to claim 1, characterized in that: During one power frequency cycle, the input voltage of the AC-DC converter changes from negative to positive. α The time corresponding to the phase angle range is pre-defined, with the value of D1 increasing monotonically; during this power frequency cycle, the input voltage of the AC-DC converter changes from positive to negative. β For the time corresponding to the phase angle range, the value of D1 is given to decrease monotonically; for the rest of the power frequency cycle, if the input voltage of the AC-DC converter is negative, the value of D1 is given to be 0, and if the input voltage of the AC-DC converter is positive, the value of D1 is given to be 1. Alternatively, the input voltage of the AC-DC converter may change from negative to positive within one power frequency cycle. α The time corresponding to the phase angle range is pre-defined, with the value of D3 increasing monotonically; during this power frequency cycle, the input voltage of the AC-DC converter changes from positive to negative. β For the time corresponding to the phase angle range, the value of D3 is given to decrease monotonically; for the rest of the power frequency cycle, if the input voltage of the AC-DC converter is negative, the value of D3 is given to be 0, and if the input voltage of the AC-DC converter is positive, the value of D3 is given to be 1. in, α ∈(0, 180°]、 β ∈(180, 360°).

6. The control method according to claim 1, characterized in that: Within one power frequency cycle, D1 is pre-defined as a sine curve with a DC bias of 0.

5. Alternatively, within one power frequency cycle, D3 can be pre-defined as a sine curve with a DC bias of 0.

5.

7. The control method according to claim 1, characterized in that: The sum of the first duty cycle and the third duty cycle is pre-defined as 1.

8. The control method according to claim 1, characterized in that: The switching frequencies of each transistor in the first switching circuit and the switching frequencies of each transistor in the second switching circuit are independent of each other.

9. The control method according to claim 8, characterized in that: the switching frequency of each switching transistor in the first switching circuit is... f 1. The switching frequency of each switching transistor in the second switching circuit is: f 2, f 2 = 2 × f 1.

10. The control method according to claim 1, characterized in that: The first switching circuit uses internal phase-shift control between its bridge arms, with a phase shift angle of the first phase shift angle. The second switching circuit uses internal phase-shift control between its bridge arms, with a phase shift angle of the second phase shift angle. The first and second switching circuits use external phase-shift control between them, with a phase shift angle of the third phase shift angle. The switching frequency of each switching transistor in the first switching circuit is... f 1. The switching frequency of each switching transistor in the second switching circuit is: f 2. The control quantities for stabilizing the output voltage of the AC-DC converter include the first phase shift angle, the second phase shift angle, and the third phase shift angle. f 1 and f A combination of one or any number of 2.

11. The control method according to claim 1, characterized in that: Throughout the entire power frequency cycle, the PFC inductor remains in continuous conduction mode.

12. A control device applied to an AC-DC converter, the AC-DC converter comprising a bridgeless PFC circuit in the front stage and a DC-DC circuit in the rear stage, the bridgeless PFC circuit comprising at least one PFC inductor, and a first switching circuit, a second switching circuit, and a DC bus capacitor connected in parallel between a first node and a second node, the first switching circuit and the second switching circuit each comprising at least one bridge arm, all bridge arms having high-frequency controllable switching transistors and the drive pulses of the two switching transistors in the same bridge arm being complementary, the duty cycle of the upper-side switching transistors of each bridge arm of the first switching circuit being a first duty cycle D1, and the duty cycle of the upper-side switching transistors of each bridge arm of the second switching circuit being a third duty cycle D3; characterized in that, The control device includes: The control signal acquisition module is used to acquire the PF value of the AC-DC converter in real time and compare it with a preset value to obtain the control signal. The duty cycle adjustment module is used to adjust one of the first duty cycle and the third duty cycle according to the control signal. The other duty cycle is given in advance or changes with the adjusted duty cycle, so that the PF value of the AC-DC converter reaches the desired value, where D1∈[0,1] and D3∈[0,1]. Specifically, when the sum of the first duty cycle and the third duty cycle is given in advance, and one of the first duty cycle and the third duty cycle is adjusted according to the control signal, the other duty cycle will change in accordance with the adjustment of the duty cycle.

13. A switching power supply, the switching power supply comprising an AC-DC converter, the AC-DC converter comprising a bridgeless PFC circuit in the front stage and a DC-DC circuit in the rear stage, the bridgeless PFC circuit comprising at least one PFC inductor, and a first switching circuit, a second switching circuit, and a DC bus capacitor connected in parallel between a first node and a second node, the first switching circuit and the second switching circuit each comprising at least one bridge arm, all bridge arm switching transistors being high-frequency controllable switching transistors and the drive pulses of the two switching transistors in the same bridge arm being complementary, the duty cycle of the upper switching transistor of each bridge arm of the first switching circuit being D1, and the duty cycle of the upper switching transistor of each bridge arm of the second switching circuit being D3; characterized in that, The switching power supply includes the control device as described in claim 12.

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