Control method, control device and switching power supply

Abstract

The invention discloses a control method, a control device and a switching power supply, the control method is applied to a three-phase converter, and the control method comprises the following steps in a time interval: a sampling signal acquisition step: acquiring a first sampling signal representing the state of each phase, the state can represent the size relation of the maximum average switching current absolute value of each phase of bridge arm; in the working mode selection step, the working mode of the corresponding phase bridge arm is selected according to the first sampling signal of each phase, and when the maximum average switching current absolute value represented by the first sampling signal is maximum, the corresponding phase bridge arm works in a clamping mode; when the maximum average switching current absolute value represented by the first sampling signal is centered, the corresponding phase bridge arm works in a CRM mode; and when the maximum average switching current absolute value represented by the first sampling signal is minimum, the corresponding phase bridge arm works in a TCM mode. According to the invention, soft switching conditions can be provided for the three bridge arms of the three-phase converter.

Description

Technical Field

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

[0002] With the rapid development of switching power supply technology, three-phase converters are widely used in various industrial equipment and civil devices. Traditional three-phase converters usually adopt hard switching (CCM) modulation schemes, and the switching loss of switching devices is very large. With the development trend of lightweight and high-frequency three-phase converters, it is difficult for hard switching modulation schemes to simultaneously ensure the high operating frequency, high power density and high efficiency of the converter; therefore, many researchers have proposed a series of soft switching modulation schemes, which eliminate the overlap of voltage and current during the switching process of the device, thereby greatly reducing the switching loss.

[0003] However, traditional soft switching modulation schemes are difficult to analyze and design due to the three-phase coupling, and usually require the addition of passive or active devices to provide soft switching conditions, such as Figure 1 As shown in the figure, a three-phase converter circuit diagram of the prior art is provided with a passive device (i.e., the inductor Lo on the DC voltage side) to provide soft switching conditions. The voltage across the switch tube can be periodically resonated to zero, so that all switching actions are completed during the period when the bus voltage Vbus=0 (i.e., the voltage across the capacitor Co). However, the voltage stress of the converter switch tube of this traditional soft switching modulation scheme is high, and the volume of the additional auxiliary resonant circuit is large, so it is difficult to be used as an effective high power density soft switching solution. Summary of the invention

[0004] 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 realize decoupling control of a three-phase converter, which is beneficial to provide soft switching conditions for the converter without adding additional passive or active devices, thereby improving product efficiency and reducing product size.

[0005] As a first aspect of the present invention, the technical solution of the control method embodiment provided is as follows:

[0006] A control method is applied to a three-phase converter, wherein the three-phase converter comprises a three-phase filter, a three-phase bridge circuit and a bus capacitor, wherein each phase filter in the three-phase filter comprises a filter inductor and a filter capacitor, wherein each phase bridge arm in the three-phase bridge circuit comprises an upper switch tube and a lower switch tube, wherein one end of each phase filter capacitor and one end of the filter inductor are connected to the input end of the corresponding phase of the three-phase converter, the other end of each phase filter capacitor is connected together, the other end of each phase filter inductor is connected to the midpoint of the corresponding phase bridge arm, and each bus capacitor is connected in parallel with each bridge arm, wherein the control method comprises the following steps within a time interval:

[0007] A sampling signal acquisition step, acquiring a first sampling signal representing the state of each phase, wherein the state can represent the magnitude relationship of the absolute value of the maximum average switching current of each phase bridge arm;

[0008] The working mode selection step selects the working mode of the corresponding phase bridge arm according to the first sampling signal of each phase, wherein: when the absolute value of the maximum average switching current represented by the first sampling signal is the largest, the corresponding phase bridge arm works in the clamping mode; when the absolute value of the maximum average switching current represented by the first sampling signal is centered, the corresponding phase bridge arm works in the CRM mode; when the absolute value of the maximum average switching current represented by the first sampling signal is the smallest, the corresponding phase bridge arm works in the TCM mode.

[0009] Preferably, the first sampling signal of each phase is obtained by detecting the current of each phase filter inductor, wherein: the phase with the largest absolute value of the average current of the filter inductor corresponds to the largest absolute value of the average switching current of the phase; the phase with a middle absolute value of the average current of the filter inductor corresponds to the middle absolute value of the average switching current of the phase; the phase with the smallest absolute value of the average current of the filter inductor corresponds to the smallest absolute value of the average switching current; or the first sampling signal of each phase is obtained by detecting the input voltage of each phase of the three-phase converter, wherein: the phase with the largest average input voltage corresponds to the largest absolute value of the average switching current; the phase with a middle average input voltage corresponds to the middle absolute value of the average switching current; the phase with the smallest average input voltage corresponds to the smallest absolute value of the average switching current.

[0010] Furthermore, the clamping mode includes: when the maximum average switching current of the phase bridge arm selected to work in the clamping mode is a positive value, the voltage across the bridge arm is clamped to a positive DC bus voltage; when the maximum average switching current of the phase bridge arm selected to work in the clamping mode is a negative value, the voltage across the bridge arm is clamped to a negative DC bus voltage.

[0011] Furthermore, the switching frequency of the bridge arm working in the CRM mode is the same as the switching frequency of the bridge arm working in the TCM mode.

[0012] Further, for the bridge arm selected to work in the CRM mode, the main pulse width modulation signal is generated by an RS trigger, and the auxiliary pulse width modulation signal is complementary to the main pulse width modulation signal ignoring the dead time; the S signal of the RS trigger is the zero-crossing detection signal of the bridge arm selected to work in the CRM mode, which is used to realize that the bridge arm selected to work in the CRM mode works in the CRM mode; the R signal of the RS trigger is the control loop signal of the corresponding phase, which is used to make the electrical parameters output by the three-phase converter reach the expected value;

[0013] Among them, when the three-phase converter works in the rectification state: when the phase input voltage corresponding to the bridge arm selected to work in the TCM mode is greater than zero, the lower switch tube is the main tube and the upper switch tube is the auxiliary tube; when the phase input voltage corresponding to the bridge arm selected to work in the TCM mode is less than zero, the upper switch tube is the main tube and the lower switch tube is the auxiliary tube;

[0014] Among them, when the three-phase converter operates in the inverter state: when the phase input voltage corresponding to the bridge arm selected to work in the TCM mode is greater than zero, the upper switch tube is the main tube and the lower switch tube is the auxiliary tube; when the phase input voltage corresponding to the bridge arm selected to work in the TCM mode is less than zero, the lower switch tube is the main tube and the upper switch tube is the auxiliary tube.

[0015] Furthermore, the control loop adopts a peak current loop or an average current loop.

[0016] Further, for the bridge arm selected to work in the TCM mode, the main PWM signal is generated by an RS trigger, the auxiliary PWM signal ignores the dead time and is complementary to the main PWM signal plus a delay time, and the delay time is set to achieve the bridge arm selected to work in the TCM mode to work in the TCM mode; the S signal of the RS trigger is the zero-crossing detection signal of the bridge arm selected to work in the CRM mode at this time, which is used to achieve the switching frequency synchronization of the bridge arm selected to work in the TCM mode and the bridge arm selected to work in the CRM mode at this time, and its purpose is to limit the peak switching frequency of the bridge arm selected to work in the TCM mode; the R signal of the RS trigger is the control loop signal of the corresponding phase, which is used to make the electrical parameters output by the three-phase converter reach the expected value;

[0017] Among them, when the three-phase converter works in the rectification state: when the phase input voltage corresponding to the bridge arm selected to work in the TCM mode is greater than zero, the lower switch tube is the main tube and the upper switch tube is the auxiliary tube; when the phase input voltage corresponding to the bridge arm selected to work in the TCM mode is less than zero, the upper switch tube is the main tube and the lower switch tube is the auxiliary tube;

[0018] Among them, when the three-phase converter operates in the inverter state: when the phase input voltage corresponding to the bridge arm selected to work in the TCM mode is greater than zero, the upper switch tube is the main tube and the lower switch tube is the auxiliary tube; when the phase input voltage corresponding to the bridge arm selected to work in the TCM mode is less than zero, the lower switch tube is the main tube and the upper switch tube is the auxiliary tube.

[0019] Further, when the a-phase bridge arm of the three-phase converter operates in the clamping mode and the voltage across the a-phase bridge arm is clamped to the positive DC bus voltage, the b-phase bridge arm operates in the TCM mode, and the c-phase bridge arm operates in the CRM mode, the delay time is represented by T delayExpressed as follows, the following equation is used to solve:

[0020]

[0021] Where: Va is the a-phase input voltage of the three-phase converter; Vb is the b-phase input voltage of the three-phase converter; Vc is the c-phase input voltage of the three-phase converter; Va is the a-phase input voltage of the three-phase converter; Vb is the b-phase input voltage of the three-phase converter; ibvag is the average current of the b-phase filter inductor; k is the current coefficient, which is determined by the power or feedback loop;

[0022] Among them, a switching cycle is divided into 5 time periods, including:

[0023] The t1 period is the time when the filter inductor of phase c is excited. During this stage, the filter inductor of phase b is also excited.

[0024] The t2 time period is the time when the b-phase filter inductor continues to be excited;

[0025] The time period t3 is the time it takes for the filter inductance of phase b to be demagnetized to zero;

[0026] The time period t4 is the delay time T delay , in this stage, the b-phase filter inductor is reversely excited;

[0027] During the t5 period, the b-phase filter inductor is demagnetized, and the end time of t5 is the start time of the next switching cycle.

[0028] Furthermore, the phase filter inductor current corresponding to the bridge arm working in the TCM mode is demagnetized to 0 at the beginning of the next switching cycle.

[0029] As a second aspect of the present invention, the technical solution of the control device embodiment provided is as follows:

[0030] A control device is applied to a three-phase converter, the three-phase converter includes a three-phase filter, a three-phase bridge circuit and a bus capacitor, each phase filter in the three-phase filter includes a filter inductor and a filter capacitor, each phase bridge arm in the three-phase bridge circuit includes an upper switch tube and a lower switch tube, one end of each phase filter capacitor and one end of the filter inductor are connected to the input end of the corresponding phase, the other end of each phase filter capacitor is connected together, the other end of each phase filter inductor is connected to the midpoint of the corresponding phase bridge arm, and the bus capacitor is connected in parallel with each bridge arm, wherein: the control device includes a unit that performs the following work content within a time interval:

[0031] A sampling signal acquisition unit, used to acquire a first sampling signal representing the state of each phase, wherein the state can represent the magnitude relationship of the absolute value of the maximum average switching current of each phase bridge arm;

[0032] The working mode selection unit is used to select the working mode of the corresponding phase bridge arm according to the first sampling signal of each phase, wherein: when the absolute value of the maximum average switching current represented by the first sampling signal is the largest, the corresponding phase bridge arm works in the clamping mode; when the absolute value of the maximum average switching current represented by the first sampling signal is centered, the corresponding phase bridge arm works in the CRM mode; when the absolute value of the maximum average switching current represented by the first sampling signal is the smallest, the corresponding phase bridge arm works in the TCM mode.

[0033] As a third aspect of the present invention, the technical solution of the switching power supply embodiment provided is as follows:

[0034] A switching power supply comprises a three-phase converter, wherein the three-phase converter comprises a three-phase filter, a three-phase bridge circuit and a bus capacitor, wherein each phase filter in the three-phase filter comprises a filter inductor and a filter capacitor, wherein each phase bridge arm in the three-phase bridge circuit comprises an upper switch tube and a lower switch tube, wherein one end of each phase filter capacitor and one end of the filter inductor are connected to the input end of the corresponding phase, the other ends of each phase filter capacitor are connected together, and the other ends of each phase filter inductor are connected to the midpoint of the corresponding phase bridge arm, and the bus capacitor is connected in parallel with each bridge arm, wherein the switching power supply further comprises the control device described in any one of the second aspects above.

[0035] Compared with the prior art, the present invention has the following technical effects:

[0036] (1) The three-phase converter used in the embodiment of the present invention does not need to add any additional passive or active devices to provide an auxiliary ZVS network. The corresponding phase bridge arm is selected to operate in the clamping mode, CRM mode or TCM mode according to the first sampling signal of each phase, so that each bridge arm can naturally achieve soft switching, greatly reducing switching losses, which is conducive to the high frequency and planarization of the product, improving the efficiency of the product and reducing the volume of the product.

[0037] (2) The three-phase converter applied in the embodiment of the present invention can greatly limit the variation range of the switching frequency of the three-phase converter when the bridge arm working in the CRM mode and the bridge arm working in the TCM mode are operated at the same switching frequency, so that the magnetic components and EMI circuits can be conveniently designed, thereby reducing the cost of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A schematic diagram of a three-phase converter circuit using a conventional soft-switching modulation scheme;

[0039] Figure 2 A circuit schematic diagram of a three-phase converter using a three-phase decoupled CRM modulation scheme;

[0040] Figure 3 A three-phase converter topology structure applicable to the present invention;

[0041] Figure 4 is a flow chart of a control method according to a first embodiment of the present invention;

[0042] Figure 5 A key waveform diagram of the control method of the first embodiment of the present invention in the range of 90° to 120°;

[0043] Figure 6 This is a principle block diagram of a control device according to a second embodiment of the present invention. DETAILED DESCRIPTION

[0044] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the present invention and its beneficial effects are further described in detail below in combination with specific implementation methods and drawings of the specification, but the specific implementation methods of the present invention are not limited thereto. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this application.

[0045] It should be noted that the terms "including" and "having" and any variations thereof described in the specification and claims of the present application are intended to cover non-exclusive inclusions. For example, the inclusion of a series of components, unit circuits, or control timings is not necessarily limited to those components, unit circuits, or control timings clearly listed, but may include components, unit circuits, or control timings that are not clearly listed or are inherent to these circuits. The embodiments in the present application and the features in the embodiments may be combined with each other without conflict.

[0046] 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 microcontroller devices.

[0047] With the development trend of lightweight and high-frequency three-phase converters, soft switching control methods suitable for three-phase converters have become a hot topic of research. CRM, as an effective way to achieve soft switching, has been widely used by relevant researchers on single-phase converters and has a good power factor. However, for a three-phase converter system, only two of the three phases are independent, because the sum of the currents in the three phases is always zero. This coupling characteristic of the three-phase converter makes it impossible to achieve independent CRM control for the three phases at the same time.

[0048] Different from the traditional soft switching control modulation scheme that provides soft switching conditions by adding passive or active devices, patent CN112821790B and document "Adaptive Hysteresis Current Based ZVS Modulation and Voltage Gain Compensation for High-Frequency Three-Phase Converters" disclose a scheme that electrically couples the midpoint of the filter capacitor in the three filter circuits of the three-phase converter with the midpoint of the DC capacitor of the capacitor module, such as Figure 2 As shown. This circuit connection can achieve decoupling of the three phases, so that the current in each phase is determined only by the switching state of the phase, and the three phases can be independently controlled as CRM operation. However, this scheme shows a very wide switching frequency variation range under typical operating conditions, thereby increasing the related switching losses. Therefore, this CRM method of decoupling the three phases is not suitable for high-frequency design.

[0049] Patent CN113541522B discloses a design using five-stage discontinuous pulse width modulation (DPWM). By using DPWM, one of the three phases is always clamped to the positive DC bus or the negative DC bus at any time in a single line voltage cycle of the AC power supply, while the other two phases maintain PWM operation. This solution clamps the phase with the largest current, reduces switching losses, and improves overall efficiency, but because one phase is clamped, its THD is worse than continuous pulse width modulation.

[0050] In order to facilitate control, the inventor of the present application has proposed a control scheme based on DPWM modulation to achieve three-phase decoupling, so that the three phases work in clamp mode, CRM mode and TCM mode respectively. The three-phase converter topology applicable to the present invention is as follows: Figure 3 As shown. The control scheme of the present invention will divide a single line voltage cycle of the AC power supply into six time intervals for control switching, so as to determine the peak value and polarity of the AC power supply voltage in each time interval, and then determine the DPWM clamping mode. The current in the phase operating in the clamping mode depends on the sum of the currents in the other two independently controlled phases. Therefore, DPWM can be used as a decoupling method, so that independent CRM control can be achieved for three phases at the same time during the entire line voltage cycle of the AC power supply.

[0051] Continuing with the 60°~120° interval as an example, this time interval is further divided into two time periods to determine the peak value of the AC power supply voltage in each time period, and then determine the phase under the CRM mode or TCM mode. For example, in the 60°~90° interval, the absolute value of the average voltage of phase B is greater than that of phase C. Under the condition of unit power factor, phase B has a larger average switching current than phase C at this time. Therefore, in this time period, the second phase bridge arm, that is, phase B, is selected to work in the CRM mode, and the third phase bridge arm, that is, phase C, is selected to work in the TCM mode; in the 90°~120° interval, the absolute value of the average voltage of phase B is less than that of phase C. Therefore, in this time period, the second phase bridge arm, that is, phase C, is selected to work in the CRM mode, and the third phase bridge arm, that is, phase B, is selected to work in the TCM mode.

[0052] First embodiment

[0053] This embodiment provides a control method for Figure 3 The three-phase converter shown in the figure includes a three-phase filter, a three-phase bridge circuit and a bus capacitor. Each phase filter in the three-phase filter includes a filter inductor and a filter capacitor. Each phase bridge arm in the three-phase bridge circuit includes an upper switch tube and a lower switch tube. One end of each phase filter capacitor and one end of the filter inductor are connected to the input end of the corresponding phase of the three-phase converter. The other end of each phase filter capacitor is connected together. The other end of each phase filter inductor is connected to the midpoint of the corresponding phase bridge arm. Each bus capacitor is connected in parallel with each bridge arm.

[0054] See also Figure 3 , wherein: the a-phase filter in the three-phase filter includes a filter inductor La and a filter capacitor Ca, the b-phase filter includes a filter inductor Lb and a filter capacitor Cb, and the c-phase filter includes a filter inductor Lc and a filter capacitor Cc; the a-phase bridge arm in the three-phase bridge circuit includes an upper switch tube S1 and a lower switch tube S2, the b-phase bridge arm includes an upper switch tube S3 and a lower switch tube S4, and the c-phase bridge arm includes an upper switch tube S5 and a lower switch tube S6; the bus capacitor Co is connected in parallel with each bridge arm, and the voltage across the bus capacitor Co is the bus voltage (this voltage is the same voltage as the Vbus of the background technology and the following Vo).

[0055] Figure 4 This is a flow chart of a control method according to a first embodiment of the present invention, wherein the control method comprises the following steps within a time interval:

[0056] A sampling signal acquisition step S100 is to acquire a first sampling signal representing the state of each phase, where the state can represent the magnitude relationship of the absolute value of the maximum average switch current of each phase bridge arm;

[0057] The working mode selection step S200 selects the working mode of the corresponding phase bridge arm according to the first sampling signal of each phase, wherein: when the absolute value of the maximum average switching current represented by the first sampling signal is the largest, the corresponding phase bridge arm works in the clamping mode; when the absolute value of the maximum average switching current represented by the first sampling signal is centered, the corresponding phase bridge arm works in the CRM mode; when the absolute value of the maximum average switching current represented by the first sampling signal is the smallest, the corresponding phase bridge arm works in the TCM mode.

[0058] The control method of this embodiment will switch according to the phase when it is applied specifically, and divide a single line voltage cycle (i.e., a power frequency cycle) of the AC switching power supply into six time intervals on average, so that the bridge arm working in the clamping mode will switch once every 60° in a single line voltage cycle, and the bridge arm working in the CRM mode or TCM mode will switch once every 30° in a single line voltage cycle, thereby determining the distribution of the operation modes of all three phase bridge arms in the full line voltage cycle. For example, in the range of 60° to 90°, the A-phase bridge arm is selected to work in the clamping mode, the B-phase bridge arm is selected to work in the CRM mode, and the C-phase bridge arm is selected to work in the TCM mode; in the range of 90° to 120°, the A-phase bridge arm is selected to work in the clamping mode, the C-phase bridge arm is selected to work in the CRM mode, and the B-phase bridge arm is selected to work in the TCM mode; in the range of 120° to 150°, the C-phase bridge arm is selected to work in the clamping mode, the A-phase bridge arm is selected to work in the CRM mode, and the B-phase bridge arm is selected to work in the TCM mode.

[0059] When the control method provided in this embodiment is applied to a three-phase converter, there is no need to add additional passive or active devices to provide an auxiliary ZVS network. The corresponding phase bridge arm is selected to operate in the clamping mode, CRM mode or TCM mode according to the first sampling signal of each phase, so that each bridge arm can naturally achieve soft switching, greatly reducing switching losses, which is beneficial to the high frequency and planarization of the product, improving the efficiency of the product and reducing the volume of the product.

[0060] Under the condition of unit power factor, the three-phase converter of the present invention has the same variation trend of the filter inductor current of each phase, the input current of each phase and the switch current of each bridge arm of each phase. Therefore, the present embodiment can obtain the first sampling signal of each phase by detecting the current of each filter inductor, wherein: the phase with the largest absolute value of the average current of the filter inductor indicates that the absolute value of the corresponding phase average switch current is the largest; the phase with the middle absolute value of the average current of the filter inductor indicates that the absolute value of the corresponding phase average switch current is in the middle; the phase with the smallest absolute value of the average current of the filter inductor indicates that the absolute value of the corresponding phase average switch current is the smallest; or the first sampling signal of each phase can be obtained by detecting the input voltage of each phase of the three-phase converter, wherein: the phase with the largest average input voltage indicates that the absolute value of the corresponding phase average switch current is the largest; the phase with the middle average input voltage indicates that the absolute value of the corresponding phase average switch current is in the middle; the phase with the smallest average input voltage indicates that the absolute value of the corresponding phase average switch current is the smallest.

[0061] Specifically, when the maximum average switching current of the phase bridge arm selected to work in the clamping mode is positive, the voltage across the bridge arm is clamped to the positive DC bus voltage; when the maximum average switching current of the phase bridge arm selected to work in the clamping mode is negative, the voltage across the bridge arm is clamped to the negative DC bus voltage. For example, in the range of 60° to 120°, phase A has the largest average input voltage and is positive polarity. Under the condition of unity power factor, phase A also has the largest average switching current at this time. Therefore, in this time interval, the phase A bridge arm is selected to be clamped to the positive DC bus, corresponding to Figure 3 The middle switch S1 always remains in the on state, and S2 always remains in the off state.

[0062] Furthermore, the switching frequencies of the bridge arm working in the CRM mode and the bridge arm working in the TCM mode are the same. When the control method provided in this embodiment operates the bridge arm working in the CRM mode and the bridge arm working in the TCM mode with the same switching frequency, the variation range of the switching frequency of the three-phase converter can be greatly limited, so that magnetic devices and EMI circuits can be conveniently designed, thereby reducing product costs.

[0063] For the bridge arm selected to work in the CRM mode, the main pulse width modulation signal is generated by an RS trigger, and the auxiliary tube pulse width modulation signal ignores the dead time and complements the main pulse width modulation signal; the S signal of the RS trigger is the zero-crossing detection signal of the bridge arm selected to work in the CRM mode, which is used to realize that the bridge arm selected to work in the CRM mode works in the CRM mode; the R signal of the RS trigger is the control loop signal of the corresponding phase, which is used to make the electrical parameters output by the three-phase converter reach the expected value. The zero-crossing detection signal represents the zero-crossing moment of the current of the bridge arm selected to work in the CRM mode; the control loop of the corresponding phase adopts a peak current loop or an average current loop, and the peak current loop or the average current loop are both commonly used technologies known to those skilled in the art. The CRM mode controlled by the peak current loop or the average current loop can independently control the bridge arm selected to work in the CRM mode, and can obtain a good power factor and THD value; wherein, when the three-phase converter works in the rectification state: the phase input corresponding to the bridge arm selected to work in the TCM mode When the voltage is greater than zero, the lower switch tube is the main tube and the upper switch tube is the auxiliary tube; when the phase input voltage corresponding to the bridge arm selected to work in the TCM mode is less than zero, the upper switch tube is the main tube and the lower switch tube is the auxiliary tube; wherein, when the three-phase converter works in the inverter state: when the phase input voltage corresponding to the bridge arm selected to work in the TCM mode is greater than zero, the upper switch tube is the main tube and the lower switch tube is the auxiliary tube; when the phase input voltage corresponding to the bridge arm selected to work in the TCM mode is less than zero, the lower switch tube is the main tube and the upper switch tube is the auxiliary tube.

[0064] For the bridge arm selected to work in the TCM mode, the main PWM signal is generated by an RS trigger, the auxiliary PWM signal ignores the dead time and is complementary to the main PWM signal plus a delay time, and the delay time is set to achieve the bridge arm selected to work in the TCM mode to work in the TCM mode; the S signal of the RS trigger is the zero-crossing detection signal of the bridge arm selected to work in the CRM mode at this time, which is used to achieve the switching frequency synchronization of the bridge arm selected to work in the TCM mode and the bridge arm selected to work in the CRM mode at this time , the purpose of which is to limit the peak switching frequency of the bridge arm selected to work in the TCM mode; the R signal of the RS trigger is the control loop signal of the corresponding phase, which is used to make the electrical parameters output by the three-phase converter reach the expected value; wherein, when the three-phase converter works in the rectification state: when the phase input voltage corresponding to the bridge arm selected to work in the TCM mode is greater than zero, the lower switch tube is the main tube and the upper switch tube is the auxiliary tube; when the phase input voltage corresponding to the bridge arm selected to work in the TCM mode is less than zero, the upper switch tube is the main tube and the lower switch tube is the auxiliary tube;

[0065] Among them, when the three-phase converter works in the inverter state: when the phase input voltage corresponding to the bridge arm selected to work in the TCM mode is greater than zero, the upper switch tube is the main tube and the lower switch tube is the auxiliary tube; when the phase input voltage corresponding to the bridge arm selected to work in the TCM mode is less than zero, the lower switch tube is the main tube and the upper switch tube is the auxiliary tube; the control loop can adopt the traditional single-phase PFC control loop.

[0066] When the a-phase bridge arm of the three-phase converter works in the clamping mode and the voltage across the a-phase bridge arm is clamped to the positive DC bus voltage, the b-phase bridge arm works in the TCM mode, and the c-phase bridge arm works in the CRM mode, the above delay time is represented by T dealy The calculation includes the following steps:

[0067] Step 1: Sample the three-phase AC power supply phase voltages va, vb, vc and the output side DC bus voltage Vo;

[0068] Step 2: Calculate the duration of each working mode within a single line voltage cycle according to the time interval of the three-phase converter;

[0069] Figure 5 For the key waveform diagram of the control method of the first embodiment of the present invention in the range of 90° to 120°, please refer to Figure 5, Ia, Ib, Ic are the inductor ripple currents flowing into the a-phase bridge arm, the b-phase bridge arm, and the c-phase bridge arm, respectively. The inductor ripple currents flowing into each phase bridge arm in the time period t1 to t5 have different current slopes, where t1 can be obtained by timing the conduction duration of the switch tube S5 by the timer inside the controller, (t1+t2) can be obtained by timing the conduction time of the switch tube S5 to the conduction time of the switch tube S4 by the timer inside the controller, and t3 can be obtained by timing the conduction duration of the switch tube S4 by the timer inside the controller. Considering that the ideal converter ignores the dead time, according to the volt-second balance principle, t4 and t5 can be derived from the following equations:

[0070]

[0071] Where: Va is the a-phase input voltage of the three-phase converter; Vb is the b-phase input voltage of the three-phase converter; Vc is the c-phase input voltage of the three-phase converter; Va is the a-phase input voltage of the three-phase converter; Vb is the b-phase input voltage of the three-phase converter; ibvag is the average current of the b-phase filter inductor; k is the current coefficient, which is determined by the power or feedback loop;

[0072] Among them, a switching cycle is divided into 5 time periods, including:

[0073] The t1 period is the time when the filter inductor of phase c is excited. During this stage, the filter inductor of phase b is also excited.

[0074] The t2 time period is the time when the b-phase filter inductor continues to be excited;

[0075] The time period t3 is the time it takes for the filter inductance of phase b to be demagnetized to zero;

[0076] Time period t4 is the delay time T delay , in this stage, the b-phase filter inductor is reversely excited;

[0077] During the t5 period, the b-phase filter inductor is demagnetized, and the end time of t5 is the start time of the next switching cycle.

[0078] Step 3: Assign the value of t4 obtained by solving to the b bridge arm auxiliary tube shutdown time delay T delay The control device updates the b bridge arm auxiliary pipe shut-off time delay T in real time according to the derivation result. delay , to realize the b-phase bridge arm working in TCM mode.

[0079] Furthermore, the phase filter inductor current corresponding to the bridge arm working in the TCM mode is demagnetized to 0 at the beginning of the next switching cycle, so as to achieve zero voltage switching of the main bridge arm of phase b.

[0080] Second embodiment

[0081] The present embodiment provides a control device, which is applied to a three-phase converter. The three-phase converter includes a three-phase filter, a three-phase bridge circuit and a bus capacitor. Each phase filter in the three-phase filter includes a filter inductor and a filter capacitor. Each phase bridge arm in the three-phase bridge circuit includes an upper switch tube and a lower switch tube. One end of each phase filter capacitor and one end of the filter inductor are connected to the input end of the corresponding phase. The other end of each phase filter capacitor is connected together. The other end of each phase filter inductor is connected to the midpoint of the corresponding phase bridge arm. The bus capacitor is connected in parallel with each bridge arm. Figure 6 This is a principle block diagram of a control device according to a second embodiment of the present invention, wherein: the control device includes a unit that performs the following work contents within a time interval:

[0082] The sampling signal acquisition unit 100 is used to acquire a first sampling signal representing the state of each phase, and the state can represent the magnitude relationship of the absolute value of the maximum average switching current of each phase bridge arm;

[0083] The working mode selection unit 200 is used to select the working mode of the corresponding phase bridge arm according to the first sampling signal of each phase, wherein: when the absolute value of the maximum average switching current represented by the first sampling signal is the largest, the corresponding phase bridge arm works in the clamping mode; when the absolute value of the maximum average switching current represented by the first sampling signal is centered, the corresponding phase bridge arm works in the CRM mode; when the absolute value of the maximum average switching current represented by the first sampling signal is the smallest, the corresponding phase bridge arm works in the TCM mode.

[0084] The technical means adopted by the control device of this embodiment are consistent with the control method of the first embodiment, and the beneficial effects are the same, so they are not repeated; 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.

[0085] Third embodiment

[0086] The present embodiment provides a switching power supply, including a three-phase converter, the three-phase converter includes a three-phase filter, a three-phase bridge circuit and a bus capacitor, each phase filter in the three-phase filter includes a filter inductor and a filter capacitor, each phase bridge arm in the three-phase bridge circuit includes an upper switch tube and a lower switch tube, one end of each phase filter capacitor and one end of the filter inductor are connected to the input end of the corresponding phase, the other end of each phase filter capacitor is connected together, the other end of each phase filter inductor is connected to the midpoint of the corresponding phase bridge arm, and the bus capacitor is connected in parallel with each bridge arm, wherein: the switching power supply also includes any one of the control devices in the second embodiment.

[0087] Since the switching power supply of this embodiment includes any one of the control devices in the second embodiment, the three-phase bridge arms of the three-phase converter respectively operate in the clamping mode, CRM mode and TCM mode within any single line voltage cycle of the AC power supply, so that each bridge arm can naturally achieve soft switching, greatly reducing switching losses, which is conducive to the high frequency and planarization of the product, improving the efficiency of the product and reducing the size of the product.

[0088] It should be understood that, although specific embodiments of the present invention are described to help better understand and appreciate the present invention, there are other embodiments equivalent to the embodiments. In the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The above embodiments are given as examples in a graphical and non-limiting manner, so any modification or replacement of all or part of the technical features in the technical solution recorded in the embodiment without departing from the spirit or essence of the present invention should be deemed to be included in the scope of the claims.

Claims

1. A control method, applied to a three-phase converter, the three-phase converter comprising a three-phase filter, a three-phase bridge circuit and a bus capacitor, each phase filter in the three-phase filter comprising a filter inductor and a filter capacitor, each phase bridge arm in the three-phase bridge circuit comprising an upper switch tube and a lower switch tube, one end of each phase filter capacitor and one end of the filter inductor are connected to the input end of the corresponding phase of the three-phase converter, the other end of each phase filter capacitor is connected together, the other end of each phase filter inductor is connected to the midpoint of the corresponding phase bridge arm, each bus capacitor is connected in parallel with each bridge arm, characterized in that: The control method comprises the following steps within a time interval: A sampling signal acquisition step, acquiring a first sampling signal representing the state of each phase, wherein the state can represent the magnitude relationship of the absolute value of the maximum average switching current of each phase bridge arm; The working mode selection step selects the working mode of the corresponding phase bridge arm according to the first sampling signal of each phase, wherein: when the absolute value of the maximum average switching current represented by the first sampling signal is the largest, the corresponding phase bridge arm works in the clamping mode; when the absolute value of the maximum average switching current represented by the first sampling signal is centered, the corresponding phase bridge arm works in the CRM mode; when the absolute value of the maximum average switching current represented by the first sampling signal is the smallest, the corresponding phase bridge arm works in the TCM mode.

2. The control method according to claim 1, characterized in that: The first sampling signal of each phase is obtained by detecting the current of the filter inductor of each phase, wherein: the phase with the largest absolute value of the average current of the filter inductor indicates that the corresponding phase has the largest absolute value of the average switch current; the phase with the middle absolute value of the average current of the filter inductor indicates that the corresponding phase has the middle absolute value of the average switch current; the phase with the smallest absolute value of the average current of the filter inductor indicates that the corresponding phase has the smallest absolute value of the average switch current; Alternatively, the first sampling signal of each phase is obtained by detecting the input voltage of each phase of the three-phase converter, wherein: the phase with the largest input voltage average value corresponds to the largest phase average switching current absolute value; the phase with a middle input voltage average value corresponds to the middle phase average switching current absolute value; the phase with the smallest input voltage average value corresponds to the smallest phase average switching current absolute value.

3. The control method according to claim 1, characterized in that: The clamp modes include: When the maximum average switch current of the phase bridge arm selected to work in the clamping mode is positive, the voltage across the bridge arm is clamped to the positive DC bus voltage; When the maximum average switch current of the phase bridge arm selected to work in the clamping mode is negative, the voltage across the bridge arm is clamped to a negative DC bus voltage.

4. The control method according to claim 1, characterized in that: The switching frequency of the bridge arm working in the CRM mode is the same as that of the bridge arm working in the TCM mode.

5. The control method according to claim 1, characterized in that: For the bridge arm selected to work in the CRM mode, the main pulse width modulation signal is generated by an RS trigger, and the auxiliary pulse width modulation signal is complementary to the main pulse width modulation signal ignoring the dead time; the S signal of the RS trigger is the zero-crossing detection signal of the bridge arm selected to work in the CRM mode, which is used to realize that the bridge arm selected to work in the CRM mode works in the CRM mode; the R signal of the RS trigger is the control loop signal of the corresponding phase, which is used to make the electrical parameters output by the three-phase converter reach the expected value; Among them, when the three-phase converter works in the rectification state: when the phase input voltage corresponding to the bridge arm selected to work in the TCM mode is greater than zero, the lower switch tube is the main tube and the upper switch tube is the auxiliary tube; when the phase input voltage corresponding to the bridge arm selected to work in the TCM mode is less than zero, the upper switch tube is the main tube and the lower switch tube is the auxiliary tube; Among them, when the three-phase converter operates in the inverter state: when the phase input voltage corresponding to the bridge arm selected to work in the TCM mode is greater than zero, the upper switch tube is the main tube and the lower switch tube is the auxiliary tube; when the phase input voltage corresponding to the bridge arm selected to work in the TCM mode is less than zero, the lower switch tube is the main tube and the upper switch tube is the auxiliary tube.

6. The control method according to claim 5, characterized in that: The control loop adopts a peak current loop or an average current loop.

7. The control method according to claim 1, characterized in that: For the bridge arm selected to work in the TCM mode, the main PWM signal is generated by an RS trigger, the auxiliary PWM signal ignores the dead time and is complementary to the main PWM signal plus a delay time, and the delay time is set to achieve the bridge arm selected to work in the TCM mode to work in the TCM mode; the S signal of the RS trigger is the zero-crossing detection signal of the bridge arm selected to work in the CRM mode at this time, which is used to achieve the switching frequency synchronization of the bridge arm selected to work in the TCM mode and the bridge arm selected to work in the CRM mode at this time, and its purpose is to limit the peak switching frequency of the bridge arm selected to work in the TCM mode; the R signal of the RS trigger is the control loop signal of the corresponding phase, which is used to make the electrical parameters output by the three-phase converter reach the expected value; Among them, when the three-phase converter works in the rectification state: when the phase input voltage corresponding to the bridge arm selected to work in the TCM mode is greater than zero, the lower switch tube is the main tube and the upper switch tube is the auxiliary tube; when the phase input voltage corresponding to the bridge arm selected to work in the TCM mode is less than zero, the upper switch tube is the main tube and the lower switch tube is the auxiliary tube; Among them, when the three-phase converter operates in the inverter state: when the phase input voltage corresponding to the bridge arm selected to work in the TCM mode is greater than zero, the upper switch tube is the main tube and the lower switch tube is the auxiliary tube; when the phase input voltage corresponding to the bridge arm selected to work in the TCM mode is less than zero, the lower switch tube is the main tube and the upper switch tube is the auxiliary tube.

8. The control method according to claim 7, characterized in that: When the a-phase bridge arm of the three-phase converter works in the clamping mode and the voltage across the a-phase bridge arm is clamped to the positive DC bus voltage, the b-phase bridge arm works in the TCM mode, and the c-phase bridge arm works in the CRM mode, the delay time is represented by T delay Expressed as follows, the following equation is used to solve: Where: Va is the a-phase input voltage of the three-phase converter; Vb is the b-phase input voltage of the three-phase converter; Vc is the c-phase input voltage of the three-phase converter; Va is the a-phase input voltage of the three-phase converter; Vb is the b-phase input voltage of the three-phase converter; ibvag is the average current of the b-phase filter inductor; k is the current coefficient, which is determined by the power or feedback loop; Among them, a switching cycle is divided into 5 time periods, including: The t1 time period is the time when the c-phase filter inductor is excited. During this stage, the b-phase filter inductor is also excited. The t2 time period is the time when the b-phase filter inductor continues to be excited; The time period t3 is the time it takes for the filter inductance of phase b to be demagnetized to zero; The time period t4 is the delay time T delay , in this stage, the b-phase filter inductor is reversely excited; During the t5 period, the b-phase filter inductor is demagnetized, and the end time of t5 is the start time of the next switching cycle.

9. The control method according to claim 1, characterized in that: The phase filter inductor current corresponding to the bridge arm working in the TCM mode is demagnetized to 0 at the beginning of the next switching cycle.

10. A control device, applied to a three-phase converter, the three-phase converter comprising a three-phase filter, a three-phase bridge circuit and a bus capacitor, each phase filter in the three-phase filter comprising a filter inductor and a filter capacitor, each phase bridge arm in the three-phase bridge circuit comprising an upper switch tube and a lower switch tube, one end of each phase filter capacitor and one end of the filter inductor are connected to the input end of the corresponding phase, the other end of each phase filter capacitor is connected together, the other end of each phase filter inductor is connected to the midpoint of the corresponding phase bridge arm, and the bus capacitor is connected in parallel with each bridge arm, characterized in that: The control device includes a unit that performs the following work contents within a time interval: A sampling signal acquisition unit, used to acquire a first sampling signal representing the state of each phase, wherein the state can represent the magnitude relationship of the absolute value of the maximum average switching current of each phase bridge arm; The working mode selection unit is used to select the working mode of the corresponding phase bridge arm according to the first sampling signal of each phase, wherein: when the absolute value of the maximum average switching current represented by the first sampling signal is the largest, the corresponding phase bridge arm works in the clamping mode; when the absolute value of the maximum average switching current represented by the first sampling signal is centered, the corresponding phase bridge arm works in the CRM mode; when the absolute value of the maximum average switching current represented by the first sampling signal is the smallest, the corresponding phase bridge arm works in the TCM mode.

11. A switching power supply, comprising a three-phase converter, the three-phase converter comprising a three-phase filter, a three-phase bridge circuit and a bus capacitor, each phase filter in the three-phase filter comprising a filter inductor and a filter capacitor, each phase bridge arm in the three-phase bridge circuit comprising an upper switch tube and a lower switch tube, one end of each phase filter capacitor and one end of the filter inductor are connected to the input end of the corresponding phase, the other end of each phase filter capacitor is connected together, the other end of each phase filter inductor is connected to the midpoint of the corresponding phase bridge arm, and the bus capacitor is connected in parallel with each bridge arm, characterized in that: The switching power supply further comprises the control device as claimed in claim 10.

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