Control method, control device and switching power supply

Abstract

The invention 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 located at a preceding stage and a DC-DC circuit located at a backward stage, switching tubes of all bridge arms of the bridgeless PFC circuit are high-frequency controllable switching tubes, and driving pulses of two switching tubes of the same bridge arm are complementary. Duty ratios of switch tubes on the upper sides of bridge arms of the first switch circuit and the second switch circuit are respectively a first duty ratio and a third duty ratio, and the control method comprises the following steps: acquiring a PF value of the AC-DC converter in real time, and comparing the PF value with a preset value to obtain a control signal; one of the first duty ratio and the third duty ratio is adjusted according to the control signal, and the other duty ratio is given in advance or changes along with changes of the adjusted duty ratio, so that the PF value of the AC-DC converter reaches an expected value. The control method provided by the invention can improve the PF value of the AC-DC converter.

Description

Technical Field

[0001] The present invention belongs to the field of power electronics, and in particular relates to a control method, a control device and a switching power supply. Background Art

[0002] AC-DC converters with unity power factor correction (PFC) are widely used in industrial fields such as plug-in hybrid and electric vehicle charging, uninterruptible power supplies, server power supplies, residential DC distribution systems, etc.

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

[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 some components are reused. The resulting single-stage AC-DC structure has great prospects. In 2015, Mahdi Ghasemi of Tabiat Modares University proposed a single-stage AC-DC converter based on totem bridgeless PFC+LLC in his paper "Analyzing a Bridgeless Single Stage LLC Resonant PFC Converter Controlled by Frequency and Pulse Width Modulations Techniques", which adopted pulse frequency modulation (Pulse Frequency Modulation, PFC) and pulse width modulation (Pulse Width Modulation, PWM) technology to achieve PFC function and soft switching function, and its switching loss and electromagnetic interference (Electro-Magnetic Interference, EMI) are low; however, the inventor of the present application found through research that an uncontrollable diode bridge arm is used in the scheme, and the PFC unit operates in the discontinuous current mode (DCM) mode of the inductor current, which results in excessive DC bus voltage and large current ripple of the PFC inductor. In the patent "Single-stage isolated LED driver power supply based on GaN devices" with publication number CN209593841U applied by Wuxi Youdian Technology Co., Ltd. in 2018, the diode in the previous totem bridgeless PFC was replaced with a switching tube, which conducts positive and negative complementary alternations according to the power frequency cycle, reducing the conduction loss of the original diode bridge arm; however, the inventor of this application found through research that in this control method, the PFC unit also works in the inductor current DCM mode, and the problems of high bus voltage and large PFC inductor current ripple are still not solved. In the PCT "Ac / dc power converter" with publication number WO2023217372A1 applied by Huawei Digital Energy Technology Co., Ltd. in 2022, based on the totem bridgeless PFC+LLC architecture, the industrial frequency bridge arm + high-frequency bridge arm structure is adopted, and a PFM+PWM control method is proposed. This control method effectively reduces the DC bus voltage and PFC inductor current ripple; however, the inventor of this application found through research that the industrial frequency tube is turned off near the zero point, and the PFC unit operates in the inductor current DCM mode, resulting in the PFC inductor current ripple is still large.

[0005] In summary, it is of great significance to adopt a new control method and reasonably control the switching devices of a single-stage AC-DC converter to improve the PF value and reduce the PFC inductor current ripple and DC bus voltage while ensuring the stability of the DC output voltage.

[0006] It should be noted that the above information disclosed in the background technology section is only intended to deepen the understanding of the overall background technology of this application, and should not be regarded as admitting or suggesting in any form that the information constitutes prior art already known to those skilled in the art. Summary of the invention

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

[0008] As a first aspect of the present invention, the technical solution of the control method provided is as follows:

[0009] A control method is applied to an AC-DC converter, wherein the AC-DC converter includes a bridgeless PFC circuit at a front stage and a DC-DC circuit at a rear stage, wherein the bridgeless PFC circuit includes 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, wherein the first switch circuit and the second switch circuit each include at least one bridge arm, the switch tubes of all bridge arms are high-frequency controllable switch tubes and the driving pulses of the two switch tubes in the same bridge arm are complementary, the duty cycle of the upper switch tubes of each bridge arm of the first switch circuit is a first duty cycle D1, and the duty cycle of the upper switch tubes of each bridge arm of the second switch circuit is a third duty cycle D3; wherein the control method includes:

[0010] Acquire the PF value of the AC-DC converter in real time and compare it with a preset value to obtain a control signal;

[0011] One of the first duty cycle and the third duty cycle is adjusted according to the control signal, and the other duty cycle is predetermined or changes with the adjusted duty cycle, so that the PF value of the AC-DC converter reaches a desired value, where D1∈[0,1], D3∈[0,1].

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

[0013] Or, during the entire time of a power frequency cycle, a third duty cycle is given, and the first duty cycle is adjusted so that the PF value of the AC-DC converter reaches a desired value;

[0014] Alternatively, in the first half of a power frequency cycle, 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 expected value; in the second half of the power frequency cycle, 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 expected value;

[0015] Alternatively, in the first half of an industrial frequency cycle, 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 expected value; in the second half of the industrial frequency cycle, 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 expected value.

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

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

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

[0019] Furthermore, the set value is 0.1.

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

[0021] Alternatively, during a period 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 D3 is pre-set to increase monotonically; during a period 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 D3 is pre-set to decrease monotonically; during 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;

[0022] Among them, α∈(0, 180°], β∈(180, 360°].

[0023] Further, within one power frequency cycle, D1 is preset as a sine curve with a DC offset of 0.5; or within one power frequency cycle, D3 is preset as a sine curve with a DC offset of 0.5.

[0024] Furthermore, by presetting the sum of the first duty cycle and the third duty cycle, when one of the first duty cycle and the third duty cycle is adjusted according to the control signal, the other duty cycle will change following the change of the adjusted duty cycle.

[0025] Further, the sum of the first duty cycle and the third duty cycle is predetermined to be 1.

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

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

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

[0029] Furthermore, within the entire power frequency cycle range, the PFC inductor is in continuous conduction mode.

[0030] As a second aspect of the present invention, the technical solution of the embodiment of the control device provided is as follows:

[0031] A control device is applied to an AC-DC converter, the AC-DC converter comprising a bridgeless PFC circuit at a front stage and a DC-DC circuit at a rear stage, the bridgeless PFC circuit comprising 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 comprising at least one bridge arm, the switch tubes of all bridge arms are high-frequency controllable switch tubes and the driving pulses of the two switch tubes in the same bridge arm are complementary, the duty cycle of the upper switch tubes of each bridge arm of the first switch circuit is D1, and the duty cycle of the upper switch tubes of each bridge arm of the second switch circuit is D3; wherein the control device comprises:

[0032] A control signal acquisition module, used to acquire the PF value of the AC-DC converter in real time and compare it with a preset value to obtain a control signal;

[0033] A duty cycle adjustment module is used to adjust one of the first duty cycle and the third duty cycle according to the control signal, and the other duty cycle is predetermined or changes with the adjusted duty cycle, so that the PF value of the AC-DC converter reaches a desired value, wherein D1∈[0,1], D3∈[0,1].

[0034] As a third aspect of the present invention, the technical solution of the embodiment of the switching power supply provided is as follows:

[0035] A switching power supply, comprising an AC-DC converter, the AC-DC converter comprising a bridgeless PFC circuit at a front stage and a DC-DC circuit at a rear stage, the bridgeless PFC circuit comprising 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 comprising at least one bridge arm, the switch tubes of all bridge arms are high-frequency controllable switch tubes and the driving pulses of the two switch tubes in the same bridge arm are complementary, the duty cycle of the upper switch tubes of each bridge arm of the first switch circuit is D1, and the duty cycle of the upper switch tubes of each bridge arm of the second switch circuit is D3; wherein the switching power supply comprises the control device described in any one of the second aspects above.

[0036] Explanation of terminology:

[0037] High-frequency controllable switching tube: The "high frequency" in the "high-frequency controllable switching tube" of the present invention refers to the switching frequency of the switching tube, which 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 from the "industrial frequency" in the background technology "industrial frequency bridge arm". The frequency range of the "high frequency" of the present invention is above 10kHz, and the frequency of the "industrial frequency" is 50Hz or 60Hz.

[0038] The structure of the traditional single-stage AC-DC converter is that the first switch circuit is usually a low-frequency / industrial 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 a discontinuous mode, which will lead to large PFC inductor current waves, high DC bus voltage, low PF value, high THD and other problems of the AC-DC converter. In the embodiment of the present invention, the switch tubes of all bridge arms in the first switch circuit and the second switch circuit are set as high-frequency controllable switch tubes and the driving pulses of the two switch tubes in the same bridge arm are complementary. The duty cycle of the upper switch tubes of each bridge arm of the first switch circuit is the first duty cycle, and the duty cycle of the upper switch tubes of each bridge arm of the second switch circuit is the third duty cycle. By adjusting one of the first duty cycle and the third duty cycle, the other duty cycle is predetermined or changes with the adjusted duty cycle, so that the PF value of the AC-DC converter reaches the expected value. The present invention is verified by principle analysis combined with simulation of the embodiment, and the beneficial effects compared with the prior art are as follows:

[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 within the power frequency cycle to adjust the PF value of the single-stage AC-DC circuit, so that the PF value can be adjusted to the desired value more quickly, and the PFC unit can be operated in the inductor current continuous mode;

[0040] (2) Since the switch tubes of the two switching circuits can be controlled within the power frequency cycle, the phase shift and switching frequency can be further combined to adjust the subsequent stage gain and stabilize the output ripple, thereby ensuring a higher PF value while reducing the input current ripple, and the DC bus voltage is controllable and low.

[0041] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1A A first principle block diagram of an AC-DC converter applicable to the present invention;

[0043] Figure 1BA second principle block diagram of an AC-DC converter applicable to the present invention;

[0044] Figure 1C A third principle block diagram of an AC-DC converter applicable to the present invention;

[0045] Figure 2 is a flow chart of a control method according to a first embodiment of the present invention;

[0046] Figure 3A The control method of the first embodiment is based on Figure 1B The voltage and duty cycle curve corresponding to the first control strategy;

[0047] Figure 3B for Figure 3A Simulation waveform diagram corresponding to the control strategy;

[0048] Figure 4A The control method of the first embodiment is based on Figure 1B The voltage and duty cycle curve corresponding to the second control strategy;

[0049] Figure 4B for Figure 4A Simulation waveform diagram corresponding to the control strategy;

[0050] Figure 5 The control method of the first embodiment is based on Figure 1C The voltage and duty cycle curve corresponding to the third control strategy, and the drive timing diagram after partial enlargement;

[0051] Fig. 6A The control method of the first embodiment is based on Figure 1B The voltage and duty cycle curve corresponding to the fourth control strategy;

[0052] Figure 6B for Fig. 6A Simulation waveform diagram corresponding to the control strategy;

[0053] Fig. 7A The control method of the first embodiment is based on Figure 1B The voltage and duty cycle curve corresponding to the fifth control strategy;

[0054] Figure 7B for Fig. 7A Simulation waveform diagram corresponding to the control strategy;

[0055] Fig. 8A The control method of the first embodiment is based on Figure 1B The voltage and duty cycle curve corresponding to the sixth control strategy;

[0056] Figure 8B for Fig. 8ASimulation waveform diagram corresponding to the control strategy;

[0057] Fig. 9 It is a principle block diagram of a control device according to a second embodiment of the present invention. DETAILED DESCRIPTION

[0058] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0059] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction 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. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0060] It should be noted that 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 interchanged where appropriate, so that the embodiments of the present application are described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, the process, method, system, product or equipment 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 equipment.

[0061] It should be understood that in the specification, claims and drawings of the specification, when it is described that a step is connected to another step, the step may be directly connected to the other step, or connected to the other step through a third step; when it is described that an element / unit is "connected" to another element / unit, the element / unit may 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 disclosure are only schematic diagrams of the present disclosure and are not necessarily drawn to scale. The same symbols in the drawings represent the same or similar parts, and thus repeated descriptions thereof will be omitted. Some of the block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented using software, or implemented in one or more hardware modules or integrated circuits, or implemented in different networks and / or processor devices and / or microcontrollers.

[0062] The AC-DC converter applicable to the present invention includes a bridgeless PFC circuit located at the front stage and a DC-DC circuit located at the back stage. The bridgeless PFC circuit includes 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 include at least one bridge arm. The switch tubes of the bridge arms are all high-frequency controllable switch tubes and the driving pulses of the two switch tubes in the same bridge arm are complementary. The duty cycle of the upper switch tubes of each bridge arm of the first switch circuit is a first duty cycle D1, and the duty cycle of the upper switch tubes of each bridge arm of the second switch circuit is a third duty cycle D3.

[0063] Figure 1A The first principle block diagram of the AC-DC converter applicable to the present invention, wherein 101 is an AC voltage source; 102 is a PFC inductor L in a bridgeless PFC circuit b 103 is a first switch circuit in the bridgeless PFC circuit, which includes a bridge arm, which is a first bridge arm composed of two high-frequency controllable switch tubes S1 and S2, and the two switch tubes are complementary controlled; 104 is a second switch circuit in the bridgeless PFC circuit, which includes a bridge arm, which is a second bridge arm composed of two high-frequency controllable switch tubes S3 and S4, and the two switch tubes are complementary controlled; 105 is a DC bus capacitor C in the bridgeless PFC circuit bus , the corresponding DC bus voltage can usually fluctuate within a certain range; 106 is a subsequent DC-DC circuit, which is a functional block diagram.

[0064] Figure 1B The second principle block diagram of the AC-DC converter applicable to the present invention is Figure 1A The difference is that the rear-stage DC-DC circuit provides a specific circuit, which is a half-bridge LLC topology, and the primary half-bridge switch tube of the rear-stage DC-DC circuit reuses the switch tubes S1 and S2 in the first switch circuit of the front-stage PFC circuit.

[0065] Figure 1C The third principle block diagram of the AC-DC converter applicable to the present invention is Figure 1A The difference is that the second switch circuit includes two bridge arms, namely, a second bridge arm composed of controllable switch tubes S3 and S4 and a third bridge arm composed of controllable switch tubes S5 and S6, and the PFC inductor includes two, namely, a first PFC inductor L b1 , the second PFC inductor L b2 One end of the two PFC inductors is respectively connected to the midpoint of the two bridge arms of the second switch circuit, and the other end is simultaneously connected to one end of the AC voltage source.

[0066] It should be noted that Figure 1A , Figure 1B and Figure 1CThese are just some examples of AC-DC converters to which the present invention is applicable, and therefore cannot be used to limit the scope of protection of the present invention. Figure 1A , where the PFC inductor L b The PFC inductor can be set 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. Figure 1B , the post-stage DC-DC circuit can be replaced by various bridge circuits or rectifier circuits using transformer isolation, such as full-bridge rectification, full-wave rectification, current doubler rectification, etc.; Figure 1C The post-stage DC-DC circuit can adopt various types of isolated full-bridge circuits, such as full-bridge converter circuit, full-bridge LLC circuit, DAB circuit, CLLC circuit, etc. The specific design of the AC-DC converter circuit can be selected by technicians in this field as needed, and the present invention does not limit it.

[0067] First embodiment

[0068] The present embodiment provides a control method, which is applied to an AC-DC converter. The AC-DC converter includes a bridgeless PFC circuit at a front stage and a DC-DC circuit at a rear stage. The bridgeless PFC circuit includes 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 include at least one bridge arm. The switch tubes of all bridge arms are high-frequency controllable switch tubes and the driving pulses of the two switch tubes in the same bridge arm are complementary. The duty cycle of the upper switch tubes of each bridge arm of the first switch circuit is a first duty cycle D1, and the duty cycle of the upper switch tubes of each bridge arm of the second switch circuit is a third duty cycle D3. Figure 2 This is a flow chart of the control method of the first embodiment of the present invention, see Figure 2 , which includes

[0069] A control signal acquisition step S100 is to acquire the PF value of the AC-DC converter in real time and compare it with a preset value to obtain a control signal;

[0070] The duty cycle adjustment step S200 adjusts one of the first duty cycle and the third duty cycle according to the control signal, and the other duty cycle is predetermined 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], D3∈[0,1].

[0071] As a specific implementation of the control method of this embodiment, during the entire time of an industrial frequency cycle, 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 expected value; or during the entire time of an industrial frequency cycle, 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 expected value; or during the first half of an industrial frequency cycle, 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 expected value; during the second half of the industrial frequency cycle, 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 expected value; or during the first half of an industrial frequency cycle, 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 expected value; and during the second half of the industrial frequency cycle, 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 expected value.

[0072] Figure 3A The control method of the first embodiment is based on Figure 1B The voltage and duty cycle curve corresponding to the first control strategy, where the output voltage v of the AC power supply ac Set to 110V power frequency, with amplitude V ac About 155.5V, DC bus voltage V bus Set to 400V. Figure 3A As shown, in one power frequency cycle, δ = θ = 180°; the duty cycle D3 is predetermined to be maintained at 0.5 during the entire power frequency cycle, and the PF value of the AC-DC converter is adjusted by controlling the duty cycle D1. At the same time, within the δ phase angle range, the corresponding v ac >0, corresponding to v in the phase angle range of θ ac <0.

[0073] like Figure 3B The figure shows the simulation waveform corresponding to the first control strategy in the first embodiment of the present invention. Figure 3B It can be seen that in the entire power frequency cycle, the duty cycle D3 of the switch tube S3 is stable at about 0.5, which is consistent with the theoretical analysis. Figure 3B It can be seen that the bus voltage V bus It fluctuates between 390V and 410V, and its DC component is 400V; the current i L Sinusoidal distribution and low current ripple; V o is the DC output voltage of the single-stage AC-DC converter, the output voltage V o The DC output voltage ripple is 30mV and the PF value is as high as 99.96%.

[0074] As a specific implementation of the control method of this embodiment, during the time corresponding to the δ phase angle range in which the input voltage of the AC-DC converter changes from negative to positive, and during the time corresponding to the θ phase angle range in which the input voltage of the AC-DC converter changes from positive to negative in one power frequency cycle, the value of D3 is predetermined to be maintained at 0.5±the set value; during the rest of the power frequency cycle, if the input voltage of the AC-DC converter is negative, the value of D1 is predetermined to be 0, and if the input voltage of the AC-DC converter is positive, the value of D1 is predetermined to be 1; or during one power frequency cycle The value of D1 is predetermined to be maintained at 0.5±the set value during the time corresponding to the δ phase angle range in which the input voltage of the AC-DC converter changes from negative to positive, 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; during the rest of the power frequency cycle, if the input voltage of the AC-DC converter is negative, the value of D3 is predetermined to be 0, and if the input voltage of the AC-DC converter is positive, the value of D3 is predetermined to be 1; wherein, δ∈(0, 180°], 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 voltage and duty cycle curve corresponding to the second control strategy is shown in the figure, where the output voltage v of the AC power supply is ac Set to 265V power frequency, with amplitude V ac About 375V, DC bus voltage V bus Set to 400V. Figure 4A As shown, in one power frequency cycle, at v ac The δ phase angle range from negative to positive (δ = 65°) and v ac Within the phase angle range of θ (θ=65°) from positive to negative, the duty cycle D3 is preset 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 <0, the preset duty cycle D1 remains at 0. ac >0, the duty cycle D1 is predetermined to be maintained at 1, and the PF value of the AC-DC converter is adjusted by controlling the duty cycle D3.

[0076] Figure 4B for Figure 4A The simulation waveform corresponding to the control strategy is shown in Figure 2. Figure 4B It can be seen that in Figure 4A In the corresponding δ phase angle range and θ phase angle range, the duty cycle D3 of the switch tube S3 is stable at about 0.5; in the remaining phase angle range, when v ac<0, the preset duty cycle D1 is stable at around 0. ac >0, the preset duty cycle D1 is stable at about 1, which is consistent with the theoretical analysis. Figure 4B It can also be seen that the bus voltage V bus It fluctuates between 390V and 410V, and its DC component is 400V; the current i L Sinusoidal distribution and low current ripple; V o is the DC output voltage of the single-stage AC-DC converter, the output voltage V o The DC output voltage ripple is 50mV and the PF value is as high as 99.95%.

[0077] Figure 5 The control method of the first embodiment is based on Figure 1C The voltage and duty cycle curve corresponding to the third control strategy, and the partially enlarged drive timing diagram, in which the duty cycle of switch S1 is defined as DS1, the duty cycle of switch S2 is DS2, the duty cycle of switch S3 is DS3, the duty cycle of switch S4 is DS4, the duty cycle of switch S5 is DS5, the duty cycle of switch S6 is DS6, and DS1=D1, DS3=DS5=D3. Figure 5 The voltage and duty cycle curves show that the control strategy adopted is similar to Figure 4A In the phase angle range of δ and the phase angle range of θ in one power frequency cycle, the duty cycle D3 is preset to be maintained at 0.5, and the PF value of the AC-DC converter is adjusted by controlling the duty cycle D1; in the remaining phase angle range of the power frequency cycle, when v ac <0, the preset duty cycle D1 remains at 0. ac >0, the duty cycle D1 is predetermined to be maintained at 1, and the PF value of the AC-DC converter is adjusted by controlling the duty cycle D3. Figure 5 In the partially enlarged driving timing diagram, the duty cycles of the two bridge arms in the second switch 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 switch circuit and the second switch circuit, so that the duty cycles DS1 and DS3 are symmetrical about the middle.

[0078] As a specific implementation of the control method of this embodiment, during a period 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 pre-set to increase monotonically; during a period 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 pre-set to decrease monotonically; during 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 0, and if the input voltage of the AC-DC converter is positive, the value of D1 is pre-set to 1; or During a period of time corresponding to the α phase angle range in which the input voltage of the AC-DC converter changes from negative to positive in an industrial frequency cycle, the value of D3 is pre-set to increase monotonically; during a period of 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 industrial frequency cycle, the value of D3 is pre-set to decrease monotonically; during the rest of the industrial 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; wherein α∈(0, 180°], β∈(180, 360°].

[0079] Fig. 6A The control method of the first embodiment is based on Figure 1B The voltage and duty cycle curve corresponding to the fourth control strategy, where the output voltage v of the AC power supply ac Set to 265V power frequency, with amplitude V ac About 375V, DC bus voltage V bus Set to 400V. Fig. 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 predetermined switch tube S1 changes linearly from 0 to 1; ac Within the phase angle range of β (β=20°) from positive to negative, the duty cycle D1 of the predetermined switch tube S1 changes linearly from 1 to 0. Within the remaining phase angle range of the power frequency cycle, when v ac <0, the preset duty cycle D1 remains at 0. ac >0, the predetermined duty cycle D1 is maintained at 1. In 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 Fig. 6A The simulation waveform corresponding to the control strategy is shown in Figure 2. Figure 6B It can be seen that in v ac In the range of α phase angle (α = 20°) from negative to positive, the duty cycle D1 of the switch tube S1 changes linearly from 0 to 1 and remains constant; acFrom the positive to negative range of the β phase angle (β = 20°), the duty cycle D1 of the switch tube S1 changes linearly from 1 to 0 and remains until the next power frequency cycle, which is consistent with the theoretical analysis. Figure 6B It can be seen that the bus voltage V bus It fluctuates between 390V and 410V, and its DC component is 400V; the current i L Sinusoidal distribution and low current ripple; V o is the DC output voltage of the single-stage AC-DC converter, the output voltage V o The DC output voltage ripple is 60mV and the PF value is as high as 99.93%.

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

[0082] Fig. 7A The control method of the first embodiment is based on Figure 1B The voltage and duty cycle curve corresponding to the fifth control strategy, where the output voltage v of the AC power supply ac Set to 265V power frequency, with amplitude V ac About 375V, DC bus voltage V bus Set to 400V. Fig. 7A As shown, in the entire power frequency cycle, the duty cycle D1 is preset to be a sine wave with a DC bias of 0.5 (ie, a sine wave symmetrical about 0.5), and the PF value of the AC-DC converter is adjusted by controlling the duty cycle D3.

[0083] like Figure 7B for Fig. 7A The simulation waveform corresponding to the control strategy is shown in Figure 2. Figure 7B It can be seen that the duty cycle of the switch tube S1 is a sine wave symmetrical about 0.5 during the entire power frequency cycle, which is consistent with the theoretical analysis. Figure 7B It can be seen that the bus voltage V bus It fluctuates between 390V and 410V, and its DC component is 400V; the current i L Sinusoidal distribution and low current ripple; V o is the DC output voltage of the single-stage AC-DC converter, the output voltage V o The DC output voltage ripple is 75mV and the PF value is as high as 99.95%.

[0084] As a specific implementation of the control method of this embodiment, by presetting the sum of the first duty cycle and the third duty cycle, when one of the first duty cycle and the third duty cycle is adjusted according to the control signal, the other duty cycle will change with the change of the adjusted duty cycle. Further, the sum of the first duty cycle and the third duty cycle is preset to be 1.

[0085] Fig. 8A The control method of the first embodiment is based on Figure 1B The voltage and duty cycle curve corresponding to the sixth control strategy, where the output voltage v of the AC power supply ac Set to 265V power frequency, with amplitude V ac About 375V, DC bus voltage V bus Set to 400V. Fig. 8A As shown, the duty cycle D1 of the switch tube S1 and the duty cycle D3 of the switch tube S3 are pre-set to be symmetrical about 0.5 in the entire power frequency cycle, that is, D1=0.5+Δ, D3=0.5-Δ, satisfying the condition of 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 Fig. 8A The simulation waveform corresponding to the control strategy is shown in Figure 2. Figure 8B It can be seen that in the entire power frequency cycle, the duty cycle D1 of the switch tube S1 and the duty cycle D3 of the switch tube S3 are symmetrical about 0.5, satisfying D1+D3=1, which is consistent with the theoretical analysis. Figure 8B It can be seen that the bus voltage V bus It fluctuates between 390V and 410V, and its DC component is 400V; the current i L Sinusoidal distribution and low current ripple; V o is the DC output voltage of the single-stage AC-DC converter, the output voltage V o The DC output voltage ripple is 80mV and the PF value is as high as 99.94%.

[0087] As a specific implementation method of the control method of this embodiment, the switching frequency of each switch tube in the first switch circuit and the switching frequency of each switch tube in the second switch 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 tube.

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

[0089] As a specific implementation method of the control method of this embodiment, internal phase shift control is adopted between each bridge arm in the first switching circuit, and the phase shift angle is the first phase shift angle, internal phase shift control is adopted between each bridge arm in the second switching circuit, and the phase shift angle is the second phase shift angle, external phase shift control is adopted between the first switching circuit and the second switching circuit, and the phase shift angle is the third phase shift angle, the switching frequency of each switching tube in the first switching circuit is f1, and the switching frequency of each switching tube in the second switching circuit is f2. The control quantity for controlling the output voltage stability of the AC-DC converter includes one or a combination of any number of the first phase shift angle, the second phase shift angle, the third phase shift angle, f1 and f2, thereby increasing the optimization freedom of the converter and improving the efficiency and overall performance of the converter.

[0090] As a specific implementation of the control method of this embodiment, the PFC inductor is in continuous conduction mode within the entire power frequency cycle, thereby reducing total harmonic distortion and input current ripple, thereby reducing the design complexity of the PFC inductor.

[0091] Second embodiment

[0092] The present embodiment provides a control device, which is applied to an AC-DC converter. The AC-DC converter includes a bridgeless PFC circuit at a front stage and a DC-DC circuit at a rear stage. The bridgeless PFC circuit includes 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 include at least one bridge arm. The switch tubes of all bridge arms are high-frequency controllable switch tubes and the driving pulses of the two switch tubes in the same bridge arm are complementary. The duty cycle of the upper switch tubes of each bridge arm of the first switch circuit is D1, and the duty cycle of the upper switch tubes of each bridge arm of the second switch circuit is D3. Fig. 9 For a functional block diagram of a control device according to a second embodiment of the present invention, see Fig. 9 , wherein the control device comprises:

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

[0094] The duty cycle adjustment module 200 is used to adjust one of the first duty cycle and the third duty cycle according to the control signal, and the other duty cycle is predetermined 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], D3∈[0,1].

[0095] The technical means adopted by the control device of this embodiment correspond to and are consistent with the control method of the first embodiment, and have the same beneficial effects, so they will not be described in detail.

[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 this embodiment, and this embodiment will not describe them one by one.

[0097] Third embodiment

[0098] The present embodiment provides a switching power supply, which includes an AC-DC converter, the AC-DC converter includes a bridgeless PFC circuit at the front stage and a DC-DC circuit at the back stage, the bridgeless PFC circuit includes 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 include at least one bridge arm, the switch tubes of all bridge arms are high-frequency controllable switch tubes and the driving pulses of the two switch tubes in the same bridge arm are complementary, the duty cycle of the upper switch tubes of each bridge arm of the first switch circuit is D1, and the duty cycle of the upper switch tubes of each bridge arm of the second switch circuit is D3; wherein, the switching power supply includes any one of the control devices in the second embodiment.

[0099] Since the switching power supply of this embodiment includes any one of the control devices in the second embodiment, it is beneficial to improve the PF value of the AC-DC converter, reduce the current ripple of the PFC inductor, reduce the DC bus voltage, and improve the overall efficiency of the AC-DC converter.

[0100] It is known from common technical knowledge that the present application can be implemented by other embodiments that do not deviate from its spirit or essential features. Therefore, the above disclosed embodiments are only illustrative in all respects and are not exclusive. All changes within the scope of the present application or within the scope equivalent to the present application are included in the present application.

Claims

1. A control method, applied to an AC-DC converter, the AC-DC converter comprising a bridgeless PFC circuit at a front stage and a DC-DC circuit at a rear stage, the bridgeless PFC circuit comprising 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 comprising at least one bridge arm, the switch tubes of all bridge arms are high-frequency controllable switch tubes and the driving pulses of the two switch tubes in the same bridge arm are complementary, the duty cycle of the upper switch tubes of each bridge arm of the first switch circuit is a first duty cycle D1, and the duty cycle of the upper switch tubes of each bridge arm of the second switch circuit is a third duty cycle D3; characterized in that The control method comprises: Acquire the PF value of the AC-DC converter in real time and compare it with a preset value to obtain a control signal; One of the first duty cycle and the third duty cycle is adjusted according to the control signal, and the other duty cycle is predetermined or changes with the adjusted duty cycle, so that the PF value of the AC-DC converter reaches a desired value, where D1∈[0,1], D3∈[0,1].

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

3. The control method according to claim 1, characterized in that: During a power frequency cycle, the value of D3 is predetermined to be maintained at 0.5±the set value during the time corresponding to the δ phase angle range in which the input voltage of the AC-DC converter changes from negative to positive, and during the time corresponding to the θ phase angle range in which the input voltage of the AC-DC converter changes from positive to negative. During the rest of the power frequency cycle, if the input voltage of the AC-DC converter is negative, the value of D1 is predetermined to be 0, and if the input voltage of the AC-DC converter is positive, the value of D1 is predetermined to be 1. Or, during a power frequency cycle, the value of D1 is predetermined to be maintained at 0.5±the set value during the time corresponding to the δ phase angle range in which the input voltage of the AC-DC converter changes from negative to positive, and during the time corresponding to the θ phase angle range in which the input voltage of the AC-DC converter changes from positive to negative. During the rest of the power frequency cycle, if the input voltage of the AC-DC converter is negative, the value of D3 is predetermined to be 0, and if the input voltage of the AC-DC converter is positive, the value of D3 is predetermined to be 1. Among them, 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 a period 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 pre-set to increase monotonically; during a period 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 pre-set to decrease monotonically; during 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, during a period 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 D3 is pre-set to increase monotonically; during a period 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 D3 is pre-set to decrease monotonically; during 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; Among them, α∈(0, 180°], β∈(180, 360°].

6. The control method according to claim 1, characterized in that: In one power frequency cycle, D1 is pre-set as a sine curve with a 0.5 DC offset; Alternatively, within one power frequency cycle, D3 is pre-set as a sine curve with a 0.5 DC offset.

7. The control method according to claim 1, characterized in that: By presetting the sum of the first duty cycle and the third duty cycle, when one of the first duty cycle and the third duty cycle is adjusted according to the control signal, the other duty cycle will change following the change of the adjusted duty cycle.

8. The control method according to claim 1, characterized in that: It is predetermined that the sum of the first duty cycle and the third duty cycle is 1.

9. The control method according to claim 1, characterized in that: The switching frequency of each switch tube in the first switch circuit and the switching frequency of each switch tube in the second switch circuit are independent of each other.

10. The control method according to claim 9, wherein 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 f2 = 2 x f1.

11. The control method according to claim 1, characterized in that: Internal 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, internal 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, external 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, and the switching frequency of each switch tube in the second switch circuit is f2, and the control quantity for controlling the output voltage stability of the AC-DC converter includes one or a combination of any number of the first phase shift angle, the second phase shift angle, the third phase shift angle, f1 and f2.

12. The control method according to claim 1, characterized in that: In the whole power frequency cycle range, the PFC inductor is in continuous conduction mode.

13. A control device, applied to an AC-DC converter, the AC-DC converter comprising a bridgeless PFC circuit at a front stage and a DC-DC circuit at a rear stage, the bridgeless PFC circuit comprising 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 comprising at least one bridge arm, the switch tubes of all bridge arms are high-frequency controllable switch tubes and the driving pulses of the two switch tubes in the same bridge arm are complementary, the duty cycle of the upper switch tubes of each bridge arm of the first switch circuit is D1, and the duty cycle of the upper switch tubes of each bridge arm of the second switch circuit is D3; characterized in that The control device comprises: A control signal acquisition module, used to acquire the PF value of the AC-DC converter in real time and compare it with a preset value to obtain a control signal; A duty cycle adjustment module is used to adjust one of the first duty cycle and the third duty cycle according to the control signal, and the other duty cycle is predetermined or changes with the adjusted duty cycle, so that the PF value of the AC-DC converter reaches a desired value, wherein D1∈[0,1], D3∈[0,1].

14. A switching power supply, comprising an AC-DC converter, the AC-DC converter comprising a bridgeless PFC circuit at a front stage and a DC-DC circuit at a rear stage, the bridgeless PFC circuit comprising 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 comprising at least one bridge arm, the switch tubes of all bridge arms are high-frequency controllable switch tubes and the driving pulses of the two switch tubes in the same bridge arm are complementary, the duty cycle of the upper switch tubes of each bridge arm of the first switch circuit is D1, and the duty cycle of the upper switch tubes of each bridge arm of the second switch circuit is D3; characterized in that The switching power supply comprises the control device according to claim 13.

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