Transformation System and its Control Method

Abstract

This application provides a conversion system and its control method. The conversion system includes a PFC circuit, a bus capacitor, and a resonant converter. The input terminal of the PFC circuit is electrically coupled to an AC source, and the output terminal of the PFC circuit is electrically connected to the bus capacitor and the input terminal of the resonant converter. The control method includes the following steps: obtaining the ripple voltage phase of the bus capacitor; generating a time-varying control signal based on the ripple voltage phase; and periodically adjusting the gain of the resonant converter based on the time-varying control signal to expand the frequency range of the drive signal of the switching transistor output to the resonant converter, thereby reducing the noise intensity of a single frequency band and achieving the effect of suppressing EMI noise.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a conversion system and its control method. Background Technology

[0002] In power supply products that include resonant converters, the resonant converter is usually the main source of noise. Electromagnetic interference (EMI) generated by switching devices and magnetic components in the circuit flows into the power grid after passing through parasitic capacitance to ground, making it difficult for the product to meet the relevant electromagnetic compatibility (EMC) test standards.

[0003] In existing technologies, one approach is to add filter circuits to filter out EMI noise, thereby suppressing its transmission to the power grid. However, this requires multi-stage filter circuits to achieve the desired filtering effect, increasing product size and cost. Furthermore, the filter is susceptible to spatial coupling interference, which can partially compromise its filtering performance. Another method for suppressing EMI noise is to add a shielding cover outside the resonant converter or the filter circuit to prevent spatial coupling interference from affecting filter performance. However, this approach requires additional grounded metal components, increasing cost and space requirements. It also necessitates special design to meet safety regulations and is unsuitable for environments with numerous noise sources. Summary of the Invention

[0004] This application provides a conversion system and its control method, which aims to suppress EMI noise by changing the control strategy of the conversion system without changing the hardware structure of the conversion system.

[0005] In a first aspect, this application provides a control method for a converter system. The converter system includes a PFC circuit, a bus capacitor, and a resonant converter. The input terminal of the PFC circuit is electrically coupled to an AC source, and the output terminal of the PFC circuit is electrically connected to the bus capacitor and the input terminal of the resonant converter. The control method includes the following steps:

[0006] Obtain the phase of the ripple voltage of the bus capacitor;

[0007] A time-varying control signal is generated based on the phase of the ripple voltage;

[0008] Based on the time-varying control signal, the gain of the resonant converter is periodically adjusted to expand the frequency range of the drive signal output to the switching transistors in the resonant converter.

[0009] Optionally, the control method further includes:

[0010] Obtain the phase of the AC signal at the input terminal of the PFC circuit, and obtain the phase of the ripple voltage of the bus capacitor based on the phase of the AC signal.

[0011] Optionally, the resonant converter includes a primary-side circuit, a resonant circuit, and a secondary-side circuit connected in sequence. The primary-side circuit includes a first bridge arm and a second bridge arm. The first bridge arm includes a first switch and a second switch. The second bridge arm includes a third switch and a fourth switch.

[0012] The time-varying control signal is either a phase shift angle or a phase shift time. The steps of periodically adjusting the gain of the resonant converter based on the phase shift angle or phase shift time specifically include:

[0013] Based on the phase shift angle or phase shift time, the turn-on time of the fourth switch is controlled to be delayed by the phase shift angle or phase shift time compared to the turn-on time of the first switch; and the turn-on time of the third switch is controlled to be delayed by the phase shift angle or phase shift time compared to the turn-on time of the second switch.

[0014] Optionally, the direction of change of the phase shift angle or phase shift time on the gain of the resonant converter is the same as the direction of change of the gain of the resonant converter by the ripple voltage of the bus capacitor.

[0015] Optionally, the time-varying control signal is an output reference ripple. The step of periodically adjusting the gain of the resonant converter based on the output reference ripple specifically includes:

[0016] The output reference ripple is superimposed on an original output reference signal to obtain an adjusted output reference signal;

[0017] Based on the adjusted output reference signal, the frequency of the drive signal is adjusted through closed-loop control so that the actual output signal of the resonant converter follows the adjusted output reference signal.

[0018] Optionally, the actual output signal and the output reference signal are a voltage signal or a current signal.

[0019] Optionally, the resonant converter includes a primary circuit, a resonant circuit, and a secondary circuit connected in sequence, wherein the primary circuit is a full-bridge circuit or a half-bridge circuit.

[0020] Optionally, the direction of change of the output reference ripple on the gain of the resonant converter is the same as the direction of change of the ripple voltage of the bus capacitor on the gain of the resonant converter.

[0021] Optionally, the variation period of the time-varying control signal is the same as the variation period of the ripple voltage of the bus capacitor.

[0022] Optionally, the AC source can be a single-phase AC source or a three-phase AC source.

[0023] Optionally, the resonant converter is an LLC resonant converter or an LC resonant converter.

[0024] Secondly, this application provides a conversion system, including: a PFC circuit, a bus capacitor, a resonant converter, and a controller;

[0025] The input terminal of the PFC circuit is electrically coupled to an AC source, and the output terminal of the PFC circuit is electrically connected to the bus capacitor and the input terminal of the resonant converter. The controller is coupled to the resonant converter and includes:

[0026] The time-varying signal generation unit is used to generate a time-varying control signal based on the phase of the ripple voltage of the bus capacitor.

[0027] The drive signal adjustment unit is used to periodically adjust the gain of the resonant converter according to the time-varying control signal, so as to increase the frequency range of a drive signal output to the resonant converter.

[0028] Optionally, the controller also includes:

[0029] The phase calculation unit is used to obtain the phase of the AC signal at the input terminal of the PFC circuit and calculate the ripple voltage phase of the bus capacitor based on the phase of the AC signal.

[0030] Optionally, the resonant converter includes a primary-side circuit, a resonant circuit, and a secondary-side circuit connected in sequence; the primary-side circuit includes a first bridge arm and a second bridge arm, the first bridge arm includes a first switch and a second switch, and the second bridge arm includes a third switch and a fourth switch.

[0031] The time-varying control signal is either a phase shift angle or a phase shift time.

[0032] The drive signal conditioning unit is used to control the turn-on time of the fourth switch to be delayed by a phase shift angle or a phase shift time compared to the turn-on time of the first switch, based on the phase shift angle or phase shift time; and to control the turn-on time of the third switch to be delayed by a phase shift angle or a phase shift time compared to the turn-on time of the second switch.

[0033] Optionally, the direction of change of the phase shift angle or phase shift time on the gain of the resonant converter is the same as the direction of change of the gain of the resonant converter by the ripple voltage of the bus capacitor.

[0034] Optionally, the time-varying control signal is an output reference ripple.

[0035] The drive signal conditioning unit is used to superimpose the output reference ripple with an original output reference signal to obtain an adjusted output reference signal, and adjust the frequency of the drive signal through closed-loop control according to the adjusted output reference signal so that the actual output signal of the resonant converter follows the adjusted output reference signal.

[0036] Optionally, the actual output signal and the output reference signal are a voltage signal or a current signal.

[0037] Optionally, the direction of change of the output reference ripple on the gain of the resonant converter is the same as the direction of change of the ripple voltage of the bus capacitor on the gain of the resonant converter.

[0038] Optionally, the variation period of the time-varying control signal is the same as the variation period of the ripple voltage of the bus capacitor.

[0039] Optionally, the AC source can be a single-phase AC source or a three-phase AC source.

[0040] Thirdly, this application provides a control method for a resonant converter. The resonant converter includes a primary circuit, a resonant circuit, and a secondary circuit connected in sequence. The primary circuit includes a first bridge arm and a second bridge arm. The first bridge arm includes a first switch and a second switch. The second bridge arm includes a third switch and a fourth switch. The control method includes the following steps:

[0041] Based on a periodically changing preset phase shift angle or preset phase shift time, drive signals for the first to fourth switching transistors are generated to cause the gain of the resonant converter to change periodically.

[0042] Based on the gain change of the resonant converter, the frequency range of the drive signal output to the first to fourth switching transistors is adjusted through closed-loop control.

[0043] Optionally, the resonant converter is an LLC resonant converter or an LC resonant converter.

[0044] This application provides a conversion system and its control method. A time-varying control signal is generated based on the phase of the ripple voltage of the bus capacitor. The gain of the resonant converter is then periodically adjusted based on the time-varying control signal. The direction of the change in the gain of the resonant converter by the time-varying control signal is superimposed on the direction of the change in the gain of the resonant converter by the ripple voltage of the bus capacitor. This expands the frequency range of the drive signal of the switching transistors output to the resonant converter, thereby reducing the average and quasi-peak values ​​of noise in each frequency band, and achieving the purpose of reducing noise and improving EMC performance. Attached Figure Description

[0045] Figure 1 A schematic diagram of the structure of the transformation system on which the control method provided in an embodiment of this application is based;

[0046] Figure 2 A schematic diagram of the structure of the transformation system on which the control method provided in another embodiment of this application is based;

[0047] Figure 3A schematic diagram of the structure of the transformation system on which the control method provided in another embodiment of this application is based;

[0048] Figure 4 A schematic diagram of the structure of the transformation system on which the control method provided in another embodiment of this application is based;

[0049] Figure 5 A schematic diagram of the structure of the transformation system on which the control method provided in another embodiment of this application is based;

[0050] Figure 6 A schematic flowchart illustrating a control method provided in an embodiment of this application;

[0051] Figure 7 This is a schematic diagram of the characteristics of a resonant converter provided in one embodiment of this application;

[0052] Figure 8 This is a schematic diagram illustrating the relationship between the input signal and the ripple voltage signal provided in an embodiment of this application;

[0053] Figure 9 A schematic diagram showing the relationship between the output reference ripple and the ripple voltage signal is provided for another embodiment of this application;

[0054] Figure 10 A schematic flowchart illustrating a control method for a resonant converter provided in an embodiment of this application;

[0055] Figure 11 This is a schematic diagram of the structure of a transformation system provided in an embodiment of this application;

[0056] Figure 12 This is a schematic diagram of the structure of a transformation system provided in another embodiment of this application;

[0057] Figure 13 This is a schematic diagram of the structure of a transformation system provided in another embodiment of this application;

[0058] Figure 14 This is a schematic diagram of the structure of a transformation system provided in another embodiment of this application. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0060] In existing converter systems, EMI noise suppression is typically achieved by adding filters or protective shields. However, both of these methods require changes to the hardware structure of the converter system, increasing its cost and size. The control method and converter system provided in this application suppress EMI noise through software control, without altering the hardware structure. Under light or heavy loads, the controller of the resonant converter automatically adjusts its operating frequency to maintain a stable output voltage. The fluctuation range of the resonant converter's operating frequency depends on the load level, bus voltage fluctuation range, and resonant cavity parameters. However, the operating frequency range of a resonant converter that relies solely on automatic controller adjustment is typically narrow, often leading to significant EMI noise. This invention adds a time-varying control signal to the control loop to periodically change the gain of the resonant converter, thereby expanding the frequency range of the drive signals for the switching transistors output to the resonant converter and reducing the noise intensity in a single frequency band.

[0061] First, the transformation system on which the control method provided in one embodiment of this application is based is described. For example... Figure 1 As shown, the conversion system is an AC-DC conversion system, which includes a power factor correction (PFC) circuit 101, a bus capacitor 102, and a resonant converter 103.

[0062] In this circuit, the input terminal of the PFC circuit 101 is electrically coupled to an AC source, the output terminal of the PFC circuit 101 is electrically connected to the bus capacitor 102, and the output terminal of the PFC circuit 101 is also electrically connected to the input terminal of the resonant converter 103. The PFC circuit 101 is used to correct the power factor of the conversion system, the bus capacitor 102 is used to stabilize the input voltage of the resonant converter 103, and the resonant converter 103 is used to realize voltage conversion.

[0063] The specific circuit structures of PFC circuit 101 and resonant converter 103 are described below, but are not limited to the specific circuit structures described in the following embodiments; other circuit structures may be used.

[0064] like Figure 2 As shown, as Figure 1In one specific implementation of the conversion system shown, when the AC source is a single-phase AC source, the PFC circuit 101 is used to correct the power factor of the conversion system and convert the single-phase AC source into DC output. The PFC circuit 101 includes first diodes D1 to D6, a ninth switch Q9, and a first inductor L1. Each diode includes an anode and a cathode. The anode of the first diode D1 is connected to the cathode of the second diode D2, the anode of the third diode D3 is connected to the cathode of the fourth diode D4, the cathode of the first diode D1 is connected to the cathode of the third diode D3, and the anode of the second diode D2 is connected to the anode of the fourth diode D4, i.e., the first diodes D1 to D4 form a diode rectifier bridge. The cathode of the first diode D1 is connected to the anode of the sixth diode D6 through the first inductor L1. The anode of the sixth diode D6 is also connected to the first terminal of the ninth switch Q9, and the second terminal of the ninth switch Q9 is connected to the anodes of the second diode D2 and the fourth diode D4. The PFC circuit 101 may also include a fifth diode D5, the anode of which is connected to the cathode of the first diode and the cathode of the third diode, and the cathode of the fifth diode D5 is connected to the cathode of the sixth diode D6.

[0065] The resonant converter 103 includes a primary circuit 1031, a resonant circuit 1032, and a secondary circuit 1033. The input terminal of the primary circuit 1031 is connected to the output terminal of the PFC circuit 101 and both ends of the bus capacitor 102. The output terminal of the primary circuit 1031 is connected to the input terminal of the resonant circuit 1032, and the output terminal of the resonant circuit 1032 is connected to the input terminal of the secondary circuit 1033.

[0066] In this embodiment, the primary-side circuit 1031 is a full-bridge circuit, specifically including a first bridge arm and a second bridge arm. The first bridge arm includes a first switch Q1 and a second switch Q2, and the second bridge arm includes a third switch Q3 and a fourth switch Q4. Each switch has a first terminal, a second terminal, and a control terminal. The second terminal of the first switch Q1 is connected to the first terminal of the second switch Q2, and the second terminal of the third switch Q3 is connected to the first terminal of the fourth switch Q4. The first terminal of the first switch Q1 is connected to the first terminal of the third switch Q3, and the second terminal of the second switch Q2 is connected to the second terminal of the fourth switch Q4.

[0067] The resonant circuit 1032 includes a transformer T, a resonant capacitor Cr, and a resonant inductor Lr. The resonant capacitor Cr and the resonant inductor Lr are connected in series with the primary winding of the transformer T. When considering the magnetizing inductance of the primary winding of the transformer T, the magnetizing inductance of the transformer T, the resonant capacitor Cr, and the resonant inductor Lr constitute an LLC resonant circuit, and the resonant converter 103 is an LLC resonant converter. The input terminals of the resonant circuit 1032 are connected to the midpoints of the first and second bridge arms of the primary circuit 1031, respectively. The secondary winding of the transformer T is connected to the input terminal of the secondary circuit 1033. When the magnetizing inductance of the transformer T is not considered, the resonant capacitor Cr and the resonant inductor Lr constitute an LC series resonant circuit, and the resonant converter 103 is an LC resonant converter.

[0068] In one embodiment, the secondary circuit 1033 is a full-bridge structure, comprising a third bridge arm, a fourth bridge arm, and a first voltage-regulating capacitor Co1. The third bridge arm includes a fifth switch Q5 and a sixth switch Q6, and the fourth bridge arm includes a seventh switch Q7 and an eighth switch Q8. Each switch has a first terminal, a second terminal, and a control terminal. The second terminal of the fifth switch Q5 is connected to the first terminal of the sixth switch Q6, and the second terminal of the seventh switch Q7 is connected to the first terminal of the eighth switch Q8. One end of the first voltage-regulating capacitor Co1 is connected to the first terminal of the seventh switch Q7, and the other end of the first voltage-regulating capacitor Co1 is connected to the second terminal of the eighth switch Q8.

[0069] In some other embodiments, the secondary circuit may also be a full-wave rectifier circuit, which is not limited in this application.

[0070] like Figure 3 As shown, as Figure 1 Another specific implementation of the conversion system shown is as follows: when the AC source is a three-phase AC source, the PFC circuit 101 is used to correct the power factor of the conversion system and convert the three-phase AC source into DC output. The specific circuit structure of the resonant converter 103 in this embodiment is similar to... Figure 2 The specific circuit structure of the resonant converter 103 shown is basically the same. The PFC circuit 101 in this embodiment can be a PFC circuit structure well known to those skilled in the art, and will not be described in detail here.

[0071] like Figure 4 As shown, as Figure 1 Another specific implementation of the transformation system shown, the structure of the transformation system and Figure 2The difference in the structure of the transformation system shown is as follows: In this embodiment, the primary-side circuit 1031 is a half-bridge circuit, specifically including a first bridge arm, a first capacitor C1, and a second capacitor C2. The first bridge arm includes a first switch Q1 and a second switch Q2. The second terminal of the first switch Q1 is connected to the first terminal of the second switch Q2. The second terminal of the first capacitor C1 is connected to the first terminal of the second capacitor C2. The first terminal of the first switch Q1 is connected to the first terminal of the first capacitor C1. The second terminal of the second switch Q2 is connected to the second terminal of the second capacitor C2. One input terminal of the resonant circuit 1032 is connected to the midpoint of the first bridge arm, and the other input terminal is connected to the connection node of the first capacitor C1 and the second capacitor C2.

[0072] like Figure 5 As shown, another embodiment of this application provides a DC-DC conversion system, which includes a resonant converter 104, which includes a primary circuit 1041, a resonant circuit 1042, and a secondary circuit 1043. Figure 5 The structure of the resonant converter 104 shown is the same as... Figure 2 The structure of the resonant converter 103 is the same, so it will not be described again here.

[0073] The following describes a control method provided by an embodiment of this application, such as... Figure 6 As shown, one embodiment of this application provides a control method, which is based on Figures 1 to 4 In any of the embodiments shown in the diagram, the AC source in the conversion system is a single-phase AC source or a three-phase AC source, and the resonant converter is an LLC resonant converter or an LC resonant converter. The control method is executed within the controller and includes the following steps:

[0074] S1001, The controller obtains the ripple voltage phase of the bus capacitor.

[0075] The bus capacitor 102 is electrically connected to the output terminal of the PFC circuit 101, which is also electrically connected to the input terminal of the resonant converter 103. The input terminal of the PFC circuit 101 is electrically connected to an AC source. When acquiring the ripple voltage phase of the bus capacitor 102, the ripple voltage signal of the bus capacitor 102 can be directly acquired by a sensor, and then the ripple voltage phase can be extracted from the ripple voltage signal.

[0076] S1002, The controller generates a time-varying control signal based on the phase of the ripple voltage.

[0077] The time-varying control signal is used to periodically adjust the gain of the resonant converter 103. The calculation formula for the resonant converter 103 is shown below:

[0078]

[0079] Where M represents the gain of the resonant converter 103, V O V represents the output voltage of the resonant converter. in V represents the input voltage of the resonant converter. rec This represents the voltage drop of the rectifier diode in the secondary circuit of a resonant converter or the voltage drop of the synchronous rectifier, where n represents the turns ratio of the transformer.

[0080] According to formula (1), the gain of the resonant converter 103 is related to its input and output voltages. Since the phase of the ripple voltage of the bus capacitor reflects the change in the input voltage of the resonant converter 103, it can be seen from formula (1) that the ripple voltage of the bus capacitor will cause the gain of the resonant converter 103 to change periodically. At this time, the controller in the converter system executes the original closed-loop control, adjusting the switching frequency to adapt to the gain change caused by the ripple voltage. However, since the fluctuation range of the ripple voltage of the bus capacitor is related to various factors, for cases where the fluctuation range of the ripple voltage is small, the corresponding range of the switching frequency of the resonant converter is also small, making it difficult for the converter system to meet EMC requirements near a specific frequency.

[0081] To expand the switching frequency range of the resonant converter, the controller in this application generates a time-varying control signal based on the phase of the ripple voltage of the bus capacitor. This time-varying control signal affects the gain of the resonant converter. EMI noise can only be effectively suppressed when the effect of the time-varying control signal on the gain is the same as the effect of the bus capacitor ripple voltage on the gain—that is, when both the time-varying control signal and the ripple voltage simultaneously increase or decrease the operating frequency of the resonant converter. Therefore, this application generates a time-varying control signal based on the ripple voltage phase.

[0082] It is understood that the time-varying control signal used to adjust the gain of the resonant converter in this application has multiple embodiments. In one embodiment, the time-varying control signal is a phase shift angle or phase shift time, that is, by periodically adjusting the phase shift angle or phase shift time, the equivalent duty cycle of the resonant converter is changed, thereby achieving the purpose of adjusting the gain. In another embodiment, the time-varying control signal is the duty cycle of the switching transistor in the primary circuit, that is, by periodically adjusting the duty cycle of the switching transistor in the primary circuit, the gain of the resonant converter changes periodically. It is worth noting that the maximum duty cycle must be less than 50%. In yet another embodiment, the time-varying control signal is the duration (delay time) during which the switching transistor in the secondary circuit continues to conduct after the resonant current on the resonant inductor crosses zero. During the duration of the continuous conduction of the switching transistor in the secondary circuit, the resonant current in the primary circuit continuously increases. By periodically adjusting the delay time... The time-varying control signal can be used to achieve periodic changes in gain. In another embodiment, the time-varying control signal is the leadtime, which is the time by which the secondary circuit's switching transistor turns on before the resonant current crosses zero. Since the secondary voltage of the transformer changes from positive to zero, or from zero to positive, or from negative to zero, or from zero to negative earlier after the secondary circuit's switching transistor turns on earlier, the gain of the resonant converter can also be periodically adjusted by periodically adjusting the lead time. In yet another embodiment, the time-varying control signal can also be the output reference ripple, i.e., by superimposing a periodically changing output reference ripple on the output reference voltage of the resonant converter. Since the actual output voltage of the resonant converter changes with the output reference voltage, the gain of the resonant converter will also change periodically. Of course, there may be other implementation methods for adjusting the gain of the resonant converter, and this case is not limited to these.

[0083] S1003 The controller periodically adjusts the gain of the resonant converter according to the time-varying control signal to expand the frequency range of the drive signal of the switching transistors output to the resonant converter.

[0084] in, Figure 7 This is a characteristic curve of an LLC resonant converter. The horizontal axis represents the frequency of the resonant converter, and the vertical axis represents its gain. The gain of the resonant converter is related to the operating frequency. The resonant converter typically operates in Region 1, which involves generating a basic control signal, which in turn generates a drive signal. This drive signal is transmitted to the control terminals of the switching transistors in the resonant converter to control its operation within Region 1. Within Region 1, the gain decreases as the operating frequency increases. When the gain changes due to ripple voltage from the bus capacitor, the operating frequency of the resonant converter is increased or decreased to adapt to the gain change, thereby maintaining a stable output voltage and ensuring that the actual output voltage follows the output reference voltage.

[0085] After adding a time-varying control signal to the original closed-loop control loop of the resonant converter, since this time-varying control signal is also used to periodically adjust the gain of the resonant converter, and since the time-varying control signal is generated based on the phase of the ripple voltage, the effects of the time-varying control signal on gain adjustment and the ripple voltage on gain adjustment will be superimposed. When the two are positively superimposed, the range of change of the resonant converter's gain will be expanded. Due to the effect of closed-loop control, the controller can only adapt to the change of the resonant converter's gain by adjusting the range of change of the resonant converter's operating frequency. That is, when the range of change of the resonant converter's gain expands, the range of change of the resonant converter's operating frequency also expands accordingly.

[0086] In the control method provided in this application embodiment, the noise intensity of a single frequency band is reduced by widening the frequency of the drive signal of the switching transistor in the resonant converter, thereby reducing the noise of the resonant converter from the source from a control perspective.

[0087] Another embodiment of this application provides a control method, which is based on Figure 2 or Figure 3 The conversion system shown is characterized by a single-phase or three-phase AC source, and the primary circuit of the resonant converter is a full-bridge inverter circuit. The control method specifically includes the following steps:

[0088] S2001. Obtain the phase of the ripple voltage of the bus capacitor.

[0089] In this circuit, the bus capacitor 102 is electrically connected to the output terminal of the PFC circuit 101, which is also electrically connected to the input terminal of the resonant converter 103. The input terminal of the PFC circuit 101 is electrically coupled to an AC source. When acquiring the ripple voltage phase of the bus capacitor 102, in one embodiment, the ripple voltage signal on the bus capacitor 102 can be directly acquired, and the ripple voltage phase can be obtained. In another embodiment, the phase of the AC signal at the input terminal of the PFC circuit can be acquired first, and then the ripple voltage phase of the bus capacitor can be calculated based on the phase of the AC signal at the input terminal of the PFC circuit. This method of indirectly acquiring the ripple voltage phase of the bus capacitor through the AC signal phase eliminates the need for corresponding sampling circuits and signal processing steps, saving hardware and software resources, and achieving higher accuracy.

[0090] Taking a sinusoidal AC signal at the input of a PFC circuit as an example, based on the knowledge of those skilled in the art regarding the prior art, the relationship between the phase and frequency of the ripple voltage and the phase and frequency of the AC signal at the input of the PFC circuit can be derived, such as... Figure 8As shown, the frequency of the bus ripple voltage is twice the frequency of the AC signal at the input of the PFC circuit. When the voltage phase at the PFC circuit input is 45 degrees, it corresponds to the minimum bus voltage, i.e., the minimum bus ripple voltage. When the voltage phase at the PFC circuit input is 135 degrees, it corresponds to the maximum bus voltage, i.e., the maximum bus ripple voltage. In other words, the phase of the bus capacitor ripple voltage can be calculated by acquiring the phase of the AC voltage signal at the PFC circuit input, or by directly acquiring the phase of the AC signal.

[0091] S2002. Generate a time-varying control signal based on the ripple voltage phase, wherein the time-varying control signal is a phase shift angle or a phase shift time.

[0092] When the phase shift time or phase shift angle is 0, the diagonal switches in the two arms of the primary circuit of the resonant converter conduct simultaneously. That is, the first switch Q1 of the first arm and the fourth switch Q4 of the second arm conduct simultaneously, as do the second switch Q2 of the first arm and the third switch Q3 of the second arm. By adjusting the phase shift angle or phase shift time, there is a phase difference in the conduction times of the diagonal switches in the two arms, causing a change in the effective duty cycle. To ensure that the output voltage remains constant, the controller adjusts the operating frequency of the resonant converter through the original closed-loop control to compensate for the effect of the phase shift angle or phase shift time on the gain.

[0093] Furthermore, since bus voltage ripple also affects gain, to maximize the operating frequency range of the resonant converter, it is necessary to ensure that the ripple voltage signal of the bus capacitor and the time-varying control signal adjust the frequency in the same direction. That is, the ripple voltage signal and the time-varying control signal should simultaneously increase or decrease the frequency. The ripple voltage phase is used as a reference for the phase shift time or phase shift angle, ensuring that the ripple voltage phase and phase shift time, or the ripple voltage phase and phase shift angle, change the resonant converter's gain in the same direction.

[0094] S2003. The gain of the resonant converter is periodically adjusted according to the time-varying control signal to expand the frequency range of the drive signal of the switching transistors output to the resonant converter.

[0095] Specifically, the gain of the resonant converter is periodically adjusted according to the phase shift angle or phase shift time, including: controlling the turn-on time of the fourth switch Q4 to be delayed by a phase shift angle or phase shift time compared to the turn-on time of the first switch Q1; and controlling the turn-on time of the third switch Q3 to be delayed by a phase shift angle or phase shift time compared to the turn-on time of the second switch Q2.

[0096] Preferably, the direction of change of the phase shift angle or phase shift time on the gain of the resonant converter is the same as the direction of change of the ripple voltage of the bus capacitor on the gain of the resonant converter, and the change period of the phase shift angle or phase shift time is the same as the change period of the ripple voltage of the bus capacitor.

[0097] The following is a detailed explanation of the phase relationship between bus voltage ripple and phase shift angle or phase shift time: When the resonant converter operates in region 1, as the voltage of the bus capacitor increases, the gain of the resonant converter needs to decrease to ensure that the output voltage remains constant. Therefore, the frequency of the drive signal of the switching transistor in the resonant converter will increase to reduce the gain. Conversely, when the voltage of the bus capacitor decreases, the gain of the resonant converter needs to increase to ensure that the output voltage remains constant. Therefore, the frequency of the drive signal of the switching transistor in the resonant converter will decrease to increase the gain.

[0098] Furthermore, as the phase shift time or phase shift angle increases, the effective duty cycle of the resonant converter decreases. To maintain a constant output voltage, the gain needs to be increased. This means that under the closed-loop control of the original controller in the converter system, the frequency of the drive signal for the switching transistors in the resonant converter will decrease to compensate for the gain change caused by the decreased duty cycle. Conversely, as the phase shift time or phase shift angle decreases, the effective duty cycle of the resonant converter increases. To maintain a constant output voltage, the gain needs to be reduced. The controller will then increase the frequency of the drive signal for the switching transistors in the resonant converter to compensate for the gain change caused by the increased duty cycle.

[0099] When a time-varying control signal is arbitrarily applied to change the gain of the resonant converter, the closed-loop regulation of the resonant converter will achieve stable output by changing the frequency of the resonant converter's drive signal. When the frequency of the applied time-varying control signal is different from the frequency of the bus ripple voltage, the regulating effects of the bus ripple voltage and the time-varying control signal on the resonant converter's operating frequency will randomly superimpose, sometimes reinforcing each other and sometimes canceling each other out. This can lead to low consistency across large batches and inconsistent EMI effects of the same converter system at different times. When the frequency of the applied time-varying control signal is the same as the frequency of the bus ripple voltage, both the bus ripple voltage and the time-varying control signal will increase or decrease the operating frequency of the resonant converter, further increasing or decreasing the operating frequency, thus reinforcing each other and reducing the noise intensity of a single frequency band.

[0100] Therefore, ideally, the direction of change of the phase shift angle or phase shift time on the gain of the resonant converter should be the same as the direction of change of the ripple voltage of the bus capacitor on the gain of the resonant converter, so as to achieve a mutually reinforcing effect. When the ripple voltage signal of the bus capacitor changes in the opposite direction to the phase shift time, or when the ripple voltage signal of the bus capacitor changes in the opposite direction to the phase shift angle, the frequency range of the drive signal of the switching transistor in the resonant converter can be maximized, that is, the positive accumulation of the regulation frequency can be guaranteed. The variation period of the time-varying control signal is the same as the variation period of the ripple voltage of the bus capacitor, ensuring the consistency of the regulation frequency effect.

[0101] The operating frequency range of the resonant converter is determined by the peak-to-peak value (pp) of the added phase shift time. The larger the pp value of the phase shift time, the wider the frequency range. The pp value of the phase shift time refers to the difference between the maximum and minimum values ​​of the phase shift time of the transistor drive signal.

[0102] The beneficial effects of the control method provided in the embodiments of this application are described below: The PFC circuit, bus capacitor and resonant converter circuit structure and parameters are the same in the two conversion systems. The difference between the two is that the first conversion system does not introduce a phase-shift control strategy, that is, the conversion system only uses basic control signals. The second conversion system introduces a phase-shift control strategy, that is, in addition to using basic control signals, the conversion system also uses a phase-shift control strategy. The phase-shift control strategy refers to the control method described in S2001 to S2003. The frequency of the drive signal of the switching transistor in the resonant converter changes from a variation range of 20kHz to a variation range of 40kHz, and the EMI noise intensity is reduced by 15dB.

[0103] In the control method provided in this application embodiment, by adding a phase shift angle or phase shift time that is opposite to the change direction of the bus voltage ripple, the operating frequency range of the resonant converter is widened, thereby reducing the average and quasi-peak values ​​of noise in each frequency band, so as to improve EMC performance.

[0104] Another embodiment of this application provides a control method, which is also based on Figures 1 to 4 In any of the conversion systems shown, the primary circuit of the resonant converter is a full-bridge circuit or a half-bridge circuit, the AC source is a single-phase AC source or a three-phase AC source, and the resonant converter is an LLC resonant converter or an LC resonant converter. The control method specifically includes the following steps:

[0105] S3001, Obtain the phase of the ripple voltage of the bus capacitor.

[0106] This step has been described in detail in the above embodiments and will not be repeated here.

[0107] S3002. Generate a time-varying control signal based on the ripple voltage phase, wherein the time-varying control signal is an output reference ripple.

[0108] Similar to the principle of changing the phase shift time or phase shift angle, adding a reference ripple signal to the output reference signal of the resonant converter can also change the gain of the resonant converter, thereby changing the frequency of the drive signal of the switching transistor in the resonant converter to compensate for the change in gain and achieve the purpose of widening the frequency variation range.

[0109] S3003. The gain of the resonant converter is periodically adjusted according to the time-varying control signal to expand the frequency range of the drive signal output to the switching transistor in the resonant converter.

[0110] Specifically, the gain of the resonant converter is periodically adjusted based on the output reference ripple. This includes: superimposing the output reference ripple with the original output reference signal to obtain an adjusted output reference signal; and adjusting the frequency of the drive signal through closed-loop control based on the adjusted output reference signal so that the actual output signal of the resonant converter follows the adjusted output reference signal. The actual output signal and the output reference signal are either voltage signals or current signals.

[0111] Preferably, the direction of change of the output reference ripple on the gain of the resonant converter is the same as the direction of change of the ripple voltage of the bus capacitor on the gain of the resonant converter.

[0112] Taking the output reference ripple and output reference signal as voltage signals as an example, with the input voltage constant, the output reference ripple is superimposed on the original output reference voltage to obtain the output reference voltage Vo_ref, which changes periodically. When the output reference voltage Vo_ref increases, the gain of the resonant converter increases. By controlling the frequency of the drive signal of the switching transistor in the resonant converter to decrease, the actual output voltage of the resonant converter follows the increase of the output reference voltage Vo_ref. When the output reference voltage Vo_ref decreases, the gain of the resonant converter decreases. By controlling the frequency of the drive signal of the switching transistor in the resonant converter to increase, the actual output voltage of the resonant converter follows the decrease of the output reference voltage Vo_ref. Therefore, when the output reference voltage ripple reaches its maximum, the operating frequency of the resonant converter is the lowest; when the output reference voltage ripple reaches its minimum, the operating frequency of the resonant converter is the highest.

[0113] Considering that the bus capacitor voltage also has ripple, the impact of the bus capacitor ripple voltage on the gain of the resonant converter has been explained in the above embodiments and will not be repeated here. According to the above adjustment rules, when the output reference ripple and the bus ripple voltage are out of phase, such as... Figure 9As shown, both have the same effect on the gain of the resonant converter, thus maximizing the frequency variation range of the drive signal for the switching transistor in the resonant converter.

[0114] The amplitude fluctuation range (pp value) of the output reference signal refers to the difference between the maximum and minimum values ​​of the output reference ripple. A larger amplitude fluctuation range corresponds to a larger frequency range of the drive signal for the switching transistors in the resonant converter. For example, when the amplitude fluctuation range of the output reference signal is 100mV, the corresponding frequency range is 180k-200k. When the amplitude fluctuation range of the output reference signal is 150mV, the corresponding frequency range is 190k-220k. It is evident that the EMI suppression performance is better when the amplitude fluctuation range of the output reference signal is 150mV compared to when it is 100mV. It is important to note that the relationship between the amplitude fluctuation range and the frequency range of the applied ripple signal is not linear; specific parameters need to be set according to the requirements for EMI suppression performance.

[0115] The beneficial effects of the control method provided in the embodiments of this application are described below: The PFC circuit, bus capacitor and resonant converter circuit structure and parameters are the same in the two conversion systems. The difference between the two is that the first conversion system does not introduce an output reference ripple control strategy, that is, the conversion system only uses basic control signals. The second conversion system introduces an output reference ripple control strategy, that is, in addition to using basic control signals, the conversion system also introduces output reference ripple. The output reference ripple control strategy refers to the control method described in S3001 to S3003. The frequency variation range of the drive signal of the switching transistor in the resonant converter changes from 10kHz to 20kHz, and the EMI noise intensity is reduced by 6dB.

[0116] In the control method provided in this application embodiment, by adding an output reference ripple that is out of phase with the bus ripple voltage, the gain of the resonant converter is periodically adjusted, thereby expanding the frequency variation range of the drive signal of the switching transistor in the resonant converter, so that the average value and quasi-peak value of the noise in each frequency band are reduced, thereby achieving the purpose of improving EMC performance.

[0117] like Figure 10 As shown, another embodiment of this application provides a control method for a resonant converter, which is based on Figure 5 The conversion system shown is a DC-DC conversion system, and the resonant converter is either an LLC resonant converter or an LC resonant converter. The control method specifically includes the following steps:

[0118] S4001. Generate drive signals for the first to fourth switching transistors based on a periodically changing preset phase shift angle or preset phase shift time.

[0119] The drive signal is used to control the turn-on time of the fourth switch Q4 to be delayed by a phase shift angle or phase shift time compared to the turn-on time of the first switch Q1, and to control the turn-on time of the third switch Q3 to be delayed by a phase shift angle or phase shift time compared to the turn-on time of the second switch Q2.

[0120] When the phase shift time or phase shift angle is 0, the diagonal switches in both bridge arms conduct simultaneously. That is, the first switch Q1 and the fourth switch Q4 in the primary circuit conduct simultaneously, and the second switch Q2 and the third switch Q3 in the primary circuit conduct simultaneously. By adding periodically changing phase shift angles or phase shift times, the phase difference or time difference between the conduction times of the diagonal switches in the two bridge arms changes periodically, causing the effective duty cycle to change periodically, and thus causing the gain of the resonant converter to change periodically.

[0121] S4002. Based on the gain change of the resonant converter, the frequency range of the drive signal output to the first to fourth switching transistors is adjusted through closed-loop control.

[0122] Specifically, when the phase shift time or phase shift angle increases, the effective duty cycle of the resonant converter decreases. Since the output voltage of the resonant converter still needs to remain constant, the gain of the resonant converter needs to increase. Under the action of closed-loop control, this leads to a decrease in the frequency of the drive signal output to the switching transistors in the resonant converter. Conversely, when the phase shift time or phase shift angle decreases, the effective duty cycle of the resonant converter increases. Again, since the output voltage of the resonant converter still needs to remain constant, the gain of the resonant converter needs to decrease. Under the action of closed-loop control, this leads to an increase in the frequency of the drive signal output to the switching transistors in the resonant converter.

[0123] In the control method provided in this application embodiment, by adding periodically changing phase shift angles or phase shift times to the control loop, the frequency range of the drive signals of the switching transistors in the resonant converter is widened, so that the average value and quasi-peak value of noise in each frequency band are reduced, thereby improving EMC performance.

[0124] like Figure 11 As shown, another embodiment of this application also provides a conversion system 200, which includes a PFC circuit 201, a bus capacitor 202, a resonant converter 203, and a controller 204.

[0125] In this embodiment, the input terminal of the PFC circuit 201 is electrically coupled to an AC source, the output terminal of the PFC circuit 201 is electrically connected to the bus capacitor 202, and the output terminal of the PFC circuit 201 is also electrically connected to the input terminal of the resonant converter 203. The controller 204 is coupled to the resonant converter 203. In some other embodiments, the controller 204 is further coupled to the PFC circuit 201.

[0126] The PFC circuit 201 is used to convert AC signals into DC signals and correct the power factor of the conversion system. The bus capacitor 202 is used to stabilize the input voltage of the resonant converter 203, which performs voltage conversion. The controller 204 is used to control the operating state of the resonant converter. In some embodiments, the controller 204 can also simultaneously control the operating state of the PFC circuit 201.

[0127] The controller 204 includes a time-varying signal generation unit 2041 and a drive signal conditioning unit 2042. The output terminal of the time-varying signal generation unit 2041 is coupled to the input terminal of the drive signal conditioning unit 2042. The time-varying signal generation unit 2041 generates a time-varying control signal based on the phase of the ripple voltage of the bus capacitor. The drive signal conditioning unit 2042 periodically adjusts the gain of the resonant converter 203 according to the time-varying control signal, so as to increase the frequency range of the drive signal output to the resonant converter 203.

[0128] The working principle of the conversion system is described below: According to formula (1), the gain of the resonant converter 203 is related to the input and output signals of the resonant converter 203. Since the ripple voltage phase of the bus capacitor reflects the change in the input voltage of the resonant converter 203, a time-varying control signal is generated based on the ripple voltage phase. That is, the time-varying signal generation unit 2041 obtains the ripple voltage phase of the bus capacitor and then generates a time-varying control signal based on the ripple voltage phase of the bus capacitor. The drive signal adjustment unit 2042 is used to periodically adjust the gain of the resonant converter according to the time-varying control signal, so as to increase the frequency range of the drive signal output to the resonant converter 203.

[0129] Continue to refer to Figure 7 and Figure 8 The gain of a resonant converter is related to its operating frequency. Typically, the resonant converter operates in region 1, which involves generating a basic control signal, which in turn generates a drive signal. This drive signal is transmitted to the control terminals of the switching transistors within the resonant converter to control its operation within region 1. Within region 1, the voltage gain decreases with increasing frequency. When gain changes due to ripple voltage, the operating frequency of the resonant converter is increased or decreased to adapt to these gain changes, thereby maintaining a stable output voltage.

[0130] The time-varying control signal is also used to periodically adjust the gain of the resonant converter. Since the time-varying control signal is generated based on the phase of the ripple voltage, the effects of the time-varying control signal on the gain adjustment and the ripple voltage on the gain adjustment will be superimposed. When the two are positively superimposed, the range of the resonant converter's gain variation will be expanded. Due to the closed-loop control, the controller can only adapt to the gain variation of the resonant converter by adjusting the range of the resonant converter's operating frequency. That is, when the range of the resonant converter's gain variation expands, the range of the resonant converter's operating frequency variation will also expand accordingly.

[0131] In the conversion system provided in this application embodiment, by widening the frequency of the driving signal of the resonant converter, the noise intensity of a single frequency band is reduced, thereby reducing the noise of the resonant converter from the source from a control perspective.

[0132] like Figure 12 As shown, another embodiment of this application also provides a conversion system 300, which includes a PFC circuit 301, a bus capacitor 302, a resonant converter 303, and a controller 304.

[0133] Due to the PFC circuit 301 and the resonant converter 303 and Figure 2 The circuit structures are all the same, so they will not be described again here.

[0134] The controller 304 includes a time-varying signal generation unit 3041, a drive signal conditioning unit 3042, and a phase calculation unit 3043. The input terminal of the phase calculation unit 3043 is coupled to the input terminal of the PFC circuit 301, the output terminal of the phase calculation unit 3043 is coupled to the input terminal of the time-varying signal generation unit 3041, and the output terminal of the time-varying signal generation unit 3041 is coupled to the input terminal of the drive signal conditioning unit 3042.

[0135] Phase calculation unit 3043 is used to acquire the phase of the AC signal at the input terminal of PFC circuit 301 and calculate the ripple voltage phase of the bus capacitor based on the AC signal phase. Time-varying signal generation unit 3041 is used to generate a time-varying control signal based on the ripple voltage phase of the bus capacitor. The time-varying control signal is a phase shift angle or a phase shift time. Drive signal adjustment unit 3042 is used to generate drive signals for the first to fourth switching transistors based on the phase shift angle or phase shift time. Specifically, it controls the turn-on time of the fourth switching transistor Q4 to be delayed by a phase shift angle or phase shift time compared to the turn-on time of the first switching transistor Q1; and controls the turn-on time of the third switching transistor Q3 to be delayed by a phase shift angle or phase shift time compared to the turn-on time of the second switching transistor Q2.

[0136] Preferably, the direction of change of the phase shift angle or phase shift time on the gain of the resonant converter is the same as the direction of change of the gain of the resonant converter by the ripple voltage of the bus capacitor. The period of change of the phase shift angle or phase shift time is the same as the period of change of the ripple voltage of the bus capacitor.

[0137] Preferably, the AC source is a single-phase AC source or a three-phase AC source.

[0138] Preferably, the resonant converter 103 is an LLC resonant converter or an LC resonant converter.

[0139] The working principle of this transformation system has been explained in detail above, and will not be repeated here.

[0140] In the conversion system provided in this application embodiment, by adding a phase shift angle or phase shift time that is opposite to the bus ripple voltage, the frequency range of the drive signal of the switching transistor in the resonant converter is widened. This reduces the average and quasi-peak noise of each frequency band, thereby achieving the goal of reducing noise and improving EMC performance.

[0141] like Figure 13 As shown, another embodiment of this application also provides a conversion system 400, which includes a PFC circuit 401, a bus capacitor 402, a resonant converter 403, and a controller 404.

[0142] The input terminal of the PFC circuit 401 is electrically coupled to an AC source, the output terminal of the PFC circuit 401 is electrically connected to the bus capacitor 402, the output terminal of the PFC circuit 401 is also electrically connected to the input terminal of the resonant converter 403, and the controller 404 is coupled to the resonant converter 403.

[0143] The controller 404 includes a time-varying signal generation unit 4041, a drive signal conditioning unit 4042, and a phase calculation unit 4043. The input terminal of the phase calculation unit 4043 is coupled to the input terminal of the PFC circuit 401, the output terminal of the phase calculation unit 4043 is coupled to the input terminal of the time-varying signal generation unit 4041, and the output terminal of the time-varying signal generation unit 4041 is coupled to the input terminal of the drive signal conditioning unit 4042.

[0144] Phase calculation unit 4043 is used to acquire the phase of the AC signal at the input terminal of PFC circuit 401 and calculate the ripple voltage phase of the bus capacitor based on the AC signal phase. Time-varying signal generation unit 4041 is used to generate a time-varying control signal based on the ripple voltage phase of the bus capacitor. The time-varying control signal is an output reference ripple. Drive signal adjustment unit 4042 is used to superimpose the output reference ripple with the original output reference signal to obtain an adjusted output reference signal, and adjust the frequency of the drive signal through closed-loop control based on the adjusted output reference signal so that the actual output signal of the resonant converter follows the changes of the adjusted output reference signal. The actual output signal and the output reference signal are either a voltage signal or a current signal.

[0145] Preferably, the direction of change of the output reference ripple on the gain of the resonant converter is the same as the direction of change of the bus capacitor ripple voltage on the gain of the resonant converter. The variation period of the output reference ripple is the same as the variation period of the bus capacitor ripple voltage.

[0146] It is worth noting that this application focuses on specific embodiments where the time-varying control signal is the phase shift angle, phase shift time, and output reference ripple, but it is not limited to these. In another embodiment, the time-varying control signal can also be the duty cycle of the switching transistor in the primary circuit of the resonant converter, or it can be the time (delay time) during which the switching transistor in the secondary circuit continues to conduct after the resonant current crosses zero, or the time (lead time) during which the switching transistor in the secondary circuit turns on in advance before the resonant current crosses zero, etc.

[0147] The working principle of this transformation system has been explained in detail above, and will not be repeated here.

[0148] In the conversion system provided in this application embodiment, the output reference ripple is determined according to the ripple voltage phase of the bus capacitor, so as to periodically adjust the gain of the resonant converter, thereby expanding the frequency variation range of the driving signal of the resonant converter, so that the average value and quasi-peak value of the noise in each frequency band will be reduced, so as to achieve the purpose of reducing noise and improving EMC performance.

[0149] like Figure 14 As shown, another embodiment of this application also provides a conversion system 500, which includes a PFC circuit 501, a bus capacitor 502, a resonant converter 503, a first controller 504, a second controller 505, an EMI filter 506, an AC circuit 507, a communication circuit 509, and an optocoupler isolation circuit 508.

[0150] In this circuit, the output of AC circuit 507 is electrically connected to the input of EMI filter 506, the output of EMI filter 506 is electrically connected to the input of PFC circuit 501, the output of PFC circuit 501 is connected to bus capacitor 502, and the output of PFC circuit 501 is also electrically connected to the input of resonant converter 503. First controller 504 is coupled to PFC circuit 501, and second controller 505 is coupled to resonant converter 503. First controller 504 and second controller 505 are coupled through optocoupler isolation circuit 508, and both first controller 504 and second controller 505 are coupled to communication circuit 509.

[0151] AC circuit 507 can be a single-phase AC source or a three-phase AC source, or a power converter with AC output. The first controller 504 controls the PFC circuit and also collects signals from the AC source, such as current, voltage, and temperature signals, and calculates and outputs the ripple voltage phase of the bus capacitor based on the current or voltage signal. The second controller 505 collects the primary and secondary voltage, current, and temperature signals of the resonant converter. The second controller 505 also obtains the ripple voltage phase of the bus capacitor from the first controller 504 through an optocoupler isolation circuit 508, and controls the resonant converter 503 based on the collected signal. More specifically, a time-varying control signal with opposite phase is generated based on the ripple voltage phase, and after modulation, a pulse width modulation (PWM) signal is generated. The PWM signal controls the switching transistors in the resonant converter 503. The communication circuit 509 collects all voltage, current, and temperature signals, and can also collect enable and fault signals in the conversion system, enabling real-time reporting of fault information to the host computer.

[0152] Preferably, the first controller 504 and the second controller 505 are digital signal processors (DSPs).

[0153] In the conversion system provided in this application embodiment, the noise of the resonant converter is reduced from the source by widening the frequency of the driving signal of the resonant converter and reducing the noise intensity of a single frequency band.

[0154] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A control method of a conversion system, the conversion system comprising a PFC circuit, a bus capacitor and a resonant converter, an input of the PFC circuit being electrically coupled to an AC source, an output of the PFC circuit being electrically connected to the bus capacitor and an input of the resonant converter, characterized in that, The control method comprises the following steps: obtaining the phase of the ripple voltage of the bus capacitor; generating a time-varying control signal according to the phase of the ripple voltage; periodically adjusting the gain of the resonant converter according to the time-varying control signal to expand the frequency range of the drive signal of the switch tube output to the resonant converter; wherein the change direction of the time-varying control signal to the gain of the resonant converter is the same as the change direction of the ripple voltage of the bus capacitor to the gain of the resonant converter.

2. The control method according to claim 1, characterized by, The control method further comprises: obtaining the phase of the AC signal at the input end of the PFC circuit, and obtaining the phase of the ripple voltage of the bus capacitor according to the phase of the AC signal.

3. The control method according to claim 1, characterized by, The resonant converter comprises a primary side circuit, a resonant circuit and a secondary side circuit connected in sequence, the primary side circuit comprises a first bridge arm and a second bridge arm, the first bridge arm comprises a first switch tube and a second switch tube, and the second bridge arm comprises a third switch tube and a fourth switch tube. The time-varying control signal is a phase shift angle or a phase shift time, and the step of periodically adjusting the gain of the resonant converter according to the phase shift angle or the phase shift time comprises: controlling the turn-on time of the fourth switch tube to be delayed by the phase shift angle or the phase shift time compared with the turn-on time of the first switch tube, and controlling the turn-on time of the third switch tube to be delayed by the phase shift angle or the phase shift time compared with the turn-on time of the second switch tube.

4. The control method according to claim 3, characterized by The change direction of the phase shift angle or the phase shift time to the gain of the resonant converter is the same as the change direction of the ripple voltage of the bus capacitor to the gain of the resonant converter.

5. The control method according to claim 1, characterized by, The time-varying control signal is an output reference ripple, and the step of periodically adjusting the gain of the resonant converter according to the output reference ripple comprises: superimposing the output reference ripple on an original output reference signal to obtain an adjusted output reference signal; adjusting the frequency of the drive signal through closed-loop control according to the adjusted output reference signal, so that the actual output signal of the resonant converter follows the adjusted output reference signal.

6. The control method according to claim 5, characterized by The actual output signal and the output reference signal are a voltage signal or a current signal.

7. The control method according to claim 5, characterized by, The resonant converter comprises a primary side circuit, a resonant circuit and a secondary side circuit connected in sequence, and the primary side circuit is a full-bridge circuit or a half-bridge circuit.

8. The control method according to claim 5, characterized by, The change direction of the output reference ripple to the gain of the resonant converter is the same as the change direction of the ripple voltage of the bus capacitor to the gain of the resonant converter.

9. The control method according to claim 1, characterized by, The change period of the time-varying control signal is the same as the change period of the ripple voltage of the bus capacitor.

10. The control method according to claim 1, characterized by, The AC source is a single-phase AC source or a three-phase AC source.

11. The control method according to claim 1, characterized by, The resonant converter is an LLC resonant converter or an LC resonant converter.

12. A conversion system characterized by, It comprises: a PFC circuit, a bus capacitor, a resonant converter and a controller; An input terminal of the PFC circuit is electrically coupled with an AC source, an output terminal of the PFC circuit is electrically connected with the bus capacitor and an input terminal of the resonant converter, the controller is coupled with the resonant converter, and the controller comprises: a time-varying signal generation unit configured to generate a time-varying control signal according to a ripple voltage phase of the bus capacitor; a drive signal adjustment unit configured to periodically adjust a gain of the resonant converter according to the time-varying control signal, so that a frequency range of a drive signal output to the resonant converter is enlarged, and a change direction of the gain of the resonant converter by the time-varying control signal is the same as a change direction of the gain of the resonant converter by the ripple voltage of the bus capacitor.

13. The transform system of claim 12, wherein, The controller further comprises: a phase calculation unit configured to acquire an AC signal phase of the input terminal of the PFC circuit, and calculate the ripple voltage phase of the bus capacitor according to the AC signal phase.

14. The transform system of claim 12, wherein, The resonant converter comprises a primary side circuit, a resonant circuit and a secondary side circuit connected in sequence, the primary side circuit comprises a first bridge arm and a second bridge arm, the first bridge arm comprises a first switch tube and a second switch tube, and the second bridge arm comprises a third switch tube and a fourth switch tube. The time-varying control signal is a phase shift angle or a phase shift time, The drive signal adjustment unit is configured to control a turn-on time of the fourth switch tube to be delayed from a turn-on time of the first switch tube by the phase shift angle or the phase shift time, and control a turn-on time of the third switch tube to be delayed from a turn-on time of the second switch tube by the phase shift angle or the phase shift time.

15. The transform system of claim 14, wherein, The phase shift angle or the phase shift time has the same change direction on the gain of the resonant converter as the ripple voltage of the bus capacitor.

16. The conversion system of claim 12, wherein The time-varying control signal is an output reference ripple, The drive signal adjustment unit is configured to superimpose the output reference ripple and an original output reference signal to obtain an adjusted output reference signal, and adjust a frequency of the drive signal by closed-loop control according to the adjusted output reference signal, so that an actual output signal of the resonant converter follows the adjusted output reference signal.

17. The conversion system of claim 16, wherein The actual output signal and the output reference signal are a voltage signal or a current signal.

18. The transform system of claim 16, wherein, The output reference ripple has the same change direction on the gain of the resonant converter as the ripple voltage of the bus capacitor.

19. The transform system of claim 12, wherein, A change period of the time-varying control signal is the same as a change period of the ripple voltage of the bus capacitor.

20. The transform system of claim 12, wherein, The AC source is a single-phase AC source or a three-phase AC source.

21. A control method of a resonant converter, the resonant converter comprising a primary circuit, a resonant circuit and a secondary circuit connected in sequence, the primary circuit comprising a first bridge arm and a second bridge arm, the first bridge arm comprising a first switch tube and a second switch tube, the second bridge arm comprising a third switch tube and a fourth switch tube, characterized in that, The control method comprises the following steps: generating drive signals of the first to fourth switch tubes according to a periodically changed preset phase shift angle or preset phase shift time, so that the gain of the resonant converter is periodically changed; and According to the gain variation of the resonant converter, the frequency range of the driving signals output to the first to fourth switch tubes is adjusted to be expanded through closed-loop control.

22. The control method of the resonant converter according to claim 21, characterized by, The resonant converter is an LLC resonant converter or an LC resonant converter.

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