A control method and controller of an LLC resonant circuit and the LLC resonant circuit

Abstract

The application relates to a control method of an LLC resonant circuit, a controller and the LLC resonant circuit. The method comprises the following steps: determining a reference voltage in response to a result that a bus voltage is greater than or equal to a first voltage threshold or in response to a result that the bus voltage belongs to a first voltage interval and a trend of the bus voltage is downward; determining an initial duty ratio based on the reference voltage and the bus voltage; generating a target PWM signal based on the initial duty ratio; and controlling a working state of a high-voltage side driving circuit by using the target PWM signal, so that electric energy of a bus capacitor is transmitted to an energy storage unit. When the bus voltage is too high, the energy storage unit is used to release the bus voltage, and the target PWM signal is generated based on a suitable reference voltage, so that the bus voltage can be quickly released, the release current is prevented from being too large, and the safety of the LLC resonant circuit during the release process is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of resonant circuit, in particular to a control method of LLC resonant circuit, a controller and LLC resonant circuit. BACKGROUND

[0002] LLC resonant circuit is widely used in inverter, as a front-stage boost circuit of inverter, and a rear-stage circuit is H4 bridge inverter, two-pole circuits are coupled together through bus capacitor. When two machines are connected in parallel, there is parallel circulating current in no-load working condition, and the parallel circulating current can cause slow rise of bus voltage, and further trigger bus overvoltage.

[0003] In order to prevent bus overvoltage and ensure circuit stability, bus voltage needs to be discharged. In related technologies, the control method is to increase discharge resistance, and the bus voltage is discharged by controlling the discharge resistance, but it can cause excessive loss of inverter and increase cost. Or adjust the circulating current direction, when the bus voltage of the local machine is too high, the output current of the local machine is increased to discharge the voltage, but it can easily cause current control divergence and oscillation, and further cause system failure. SUMMARY

[0004] Embodiments of the present application aim to provide a control method of LLC resonant circuit, a controller and LLC resonant circuit, which can realize fast discharge of bus capacitor voltage, improve safety of LLC resonant circuit in the discharge process, and reduce cost.

[0005] To solve the above technical problems, embodiments of the present application provide the following technical solutions:

[0006] In a first aspect, the embodiments of the present application provide a control method of LLC resonant circuit, the LLC resonant circuit comprising energy storage unit, low-voltage side drive circuit, transformer, high-voltage side drive circuit and bus capacitor connected in sequence, and the method comprises:

[0007] In response to a result that the bus voltage is greater than or equal to a first voltage threshold or a result that the bus voltage belongs to a first voltage interval and a trend of the bus voltage is downward, a reference voltage is determined, wherein the bus voltage is a voltage of the bus capacitor, a lower limit value of the first voltage interval is a second voltage threshold, and an upper limit value of the first voltage interval is the first voltage threshold;

[0008] An initial duty cycle is determined based on the reference voltage and the bus voltage;

[0009] A target PWM signal is generated based on the initial duty cycle;

[0010] The working state of the high-voltage side drive circuit is controlled by using the target PWM signal, so that the electric energy of the bus capacitor is transmitted to the energy storage unit.

[0011] In some embodiments, the determining the reference voltage comprises:

[0012] obtaining a first battery voltage, wherein the first battery voltage is a battery voltage of the energy storage unit at a current time;

[0013] determining the reference voltage based on the first battery voltage, wherein a ratio between the reference voltage and the first battery voltage belongs to a preset ratio interval.

[0014] In some embodiments, the determining the initial duty cycle based on the reference voltage and the bus voltage comprises:

[0015] calculating the initial duty cycle by the following formula:

[0016] ;

[0017] wherein, is the initial duty cycle, is the reference voltage, is the bus voltage, and N is a turns ratio of a transformer in the LLC resonant circuit.

[0018] In some embodiments, at an initial time of wave emission, a duty cycle of the target PWM signal is the initial duty cycle.

[0019] In some embodiments, at a time after the initial time of wave emission, the generating the target PWM signal based on the initial duty cycle comprises:

[0020] obtaining an integral loop coefficient;

[0021] inputting the integral loop coefficient into an integrator to obtain a compensation amount;

[0022] adding the compensation amount and the initial duty cycle to obtain a target duty cycle;

[0023] generating the target PWM signal based on the target duty cycle, wherein a duty cycle of the target PWM signal is the target duty cycle.

[0024] In some embodiments, the high-voltage side drive circuit comprises first to fourth switching tubes, wherein the first switching tube and the second switching tube are connected in series between a first end and a second end of a secondary winding of the transformer, the third switching tube and the fourth switching tube are connected in series between the first end and the second end of the secondary winding of the transformer, and the controlling the working state of the high-voltage side drive circuit by using the target PWM signal comprises:

[0025] The target PWM signal is used to control the working state of the high-voltage side drive circuit to switch between a first state and a second state, wherein the first state is that the first switch tube and the fourth switch tube are simultaneously turned on, and the second switch tube and the third switch tube are simultaneously turned off; the second state is that the first switch tube and the fourth switch tube are simultaneously turned off, and the second switch tube and the third switch tube are simultaneously turned on.

[0026] In some embodiments, before the target PWM signal is used to control the working state of the high-voltage side drive circuit, the method further comprises:

[0027] The switch tubes in the low-voltage side drive circuit are controlled to be in an off state.

[0028] In some embodiments, the method further comprises:

[0029] In response to the result that the bus voltage is less than the second voltage threshold or in response to the result that the bus voltage belongs to the first voltage interval and the trend of the bus voltage is rising, a primary side PWM signal is generated and output;

[0030] The working state of the low-voltage side drive circuit is controlled based on the primary side PWM signal, so that the energy of the energy storage unit is transmitted to the bus capacitor.

[0031] In some embodiments, before the working state of the low-voltage side drive circuit is controlled based on the primary side PWM signal, the method further comprises:

[0032] The switch tubes in the high-voltage side drive circuit are controlled to be in an off state.

[0033] In a second aspect, the embodiments of the present application provide a controller, the controller comprising:

[0034] at least one processor; and,

[0035] The non-volatile memory is in communication connection with the at least one processor, and the non-volatile memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to execute the control method of the LLC resonant circuit as described above.

[0036] In a third aspect, the embodiments of the present application provide an LLC resonant circuit, the LLC resonant circuit comprising an energy storage unit, a low-voltage side drive circuit, a transformer, a high-voltage side drive circuit and a bus capacitor connected in sequence, and further comprising a controller as described above, wherein the controller is electrically connected with the control end of the switch tube in the high-voltage side drive circuit and the control end of the switch tube in the low-voltage side drive circuit, respectively.

[0037] In various embodiments of the present application, the control method of the LLC resonant circuit comprises: first, determining a reference voltage in response to a result that the bus voltage is greater than or equal to a first voltage threshold or in response to a result that the bus voltage belongs to a first voltage interval and the trend of the bus voltage is downward, wherein the bus voltage is the voltage of the bus capacitor, the lower limit value of the first voltage interval is a second voltage threshold, and the upper limit value of the first voltage interval is the first voltage threshold; then, determining an initial duty ratio based on the reference voltage and the bus voltage; then, generating a target PWM signal based on the initial duty ratio; and finally, controlling the working state of the high-voltage side driving circuit by using the target PWM signal, so that the electric energy of the bus capacitor is transmitted to the energy storage unit.

[0038] The control method of the LLC resonant circuit generates a target PWM signal when the bus voltage is too high, controls the working state of the high-voltage side driving circuit, so that the electric energy of the bus capacitor is transmitted to the energy storage unit, and the bus capacitor virtual pressure is recovered and stored by using the energy storage unit, thereby realizing the discharge of the bus voltage, and the discharge is realized by using the circuit composition of the LLC resonant circuit itself, thereby reducing the circuit cost. At the same time, the control method generates a target PWM signal based on a suitable reference voltage, which can not only quickly discharge the bus voltage, but also ensure that the discharge current is not too large during the discharge process, thereby avoiding damage to the devices in the resonant circuit and improving the safety of the LLC resonant circuit during the discharge process. BRIEF DESCRIPTION OF DRAWINGS

[0039] One or more embodiments are illustrated by way of example in the drawings that are for illustrative purposes only and are not intended to limit the embodiments, and elements having the same reference numerals in the drawings represent similar elements, unless otherwise specified. The drawings in the drawings do not constitute a proportional limit.

[0040] Figure 1 is one of the circuit structure schematic diagrams of the LLC resonant circuit provided by the embodiments of the present application;

[0041] Figure 2 is a flowchart of the control method of the LLC resonant circuit provided by the embodiments of the present application;

[0042] Figure 3 is a timing diagram of the bus voltage V bus provided by the embodiments of the present application;

[0043] Figure 4 is Figure 2 a flowchart of step S30 in

[0044] Figure 5 is a change diagram of the hysteresis flag provided by the embodiments of the present application;

[0045] Figure 6is a schematic diagram of a control model for generating a target PWM signal;

[0046] Figure 7 is a flowchart of a control method of an LLC resonant circuit provided by an embodiment of the present application;

[0047] Figure 8 is a timing diagram of a bus voltage, a bleeding current, and an amplitude of a target PWM signal provided by an embodiment of the present application;

[0048] Figure 9 is a structural schematic diagram of a control device of an LLC resonant circuit provided by an embodiment of the present application;

[0049] Figure 10 is a hardware structural schematic diagram of a controller provided by an embodiment of the present application. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0051] Please refer to Figure 1 , an embodiment of the present application provides a circuit structural schematic diagram of an LLC resonant circuit, as shown in Figure 1 , the LLC resonant circuit comprises an energy storage unit, a low-voltage side drive circuit 20, a transformer Tr, a high-voltage side drive circuit 10 and a bus capacitor C connected in sequence BUS , wherein, Figure 1 The energy storage unit is taken as a battery BAT as an example.

[0052] The high-voltage side drive circuit 10 is composed of switching tubes, Figure 1 , for example, the high-voltage side drive circuit 10 comprises four MOS tubes, namely MOS tube Q1 to MOS tube Q4, MOS tube Q1 and MOS tube Q2 constitute a first bridge arm 11, the connection point of MOS tube Q1 and MOS tube Q2 is a first midpoint A point of the first bridge arm 11, MOS tube Q3 and MOS tube Q4 constitute a second bridge arm 12, and the connection point of MOS tube Q3 and MOS tube Q4 is a second midpoint B point of the second bridge arm 12.

[0053] The low-voltage side drive circuit 20 is composed of switching tubes, Figure 1The low-voltage side drive circuit 20 includes four MOS tubes, for example, MOS tube Q5 to MOS tube Q8. The MOS tube Q5 and the MOS tube Q6 constitute the third bridge arm 21, and the connection point of the MOS tube Q5 and the MOS tube Q6 is the third midpoint C point of the third bridge arm 21. The MOS tube Q7 and the MOS tube Q8 constitute the fourth bridge arm 22, and the connection point of the MOS tube Q7 and the MOS tube Q8 is the fourth midpoint D point of the fourth bridge arm 22.

[0054] The low-voltage side drive circuit 20 further includes a resonant inductor L1 and a resonant capacitor C1. The transformer Tr includes a primary winding and a secondary winding. The resonant inductor L1 is connected between one end of the primary winding and the third midpoint C point. The resonant capacitor C1 is connected between the other end of the primary winding and the fourth midpoint D point. The positive pole of the battery BAT is connected to one end of the third bridge arm 21 and one end of the fourth bridge arm 22, respectively. The negative pole of the battery BAT is connected to the other end of the third bridge arm 21 and the other end of the fourth bridge arm 22, respectively.

[0055] The other end of the secondary winding is connected to the other end of the first bridge arm 11 and the other end of the second bridge arm 12, respectively. The bus capacitor C BUS is connected between the first midpoint A point and the second midpoint B point.

[0056] The LLC resonant circuit further includes a controller (not shown in the figure). The controller is electrically connected to the control ends of the four switch tubes in the low-voltage side drive circuit 20. The controller outputs a control signal to the low-voltage side drive circuit 20 to control the conduction and turn-off of the four switch tubes. The control signal is a PWM signal. The duty cycle of the PWM signal determines the amount of energy transmitted by the battery BAT to the bus capacitor C BUS .

[0057] The battery BAT is used to provide low-voltage side input energy. The four switch tubes in the low-voltage side drive circuit 20 adopt a diagonal alternating conduction mode. The low-voltage direct current output by the battery BAT forms an alternating voltage through the low-voltage side drive circuit 20.

[0058] The alternating voltage is input to the primary winding of the transformer Tr and is coupled to the secondary winding through electromagnetic induction. The turns ratio relationship between the primary winding and the secondary winding can configure the boost ratio.

[0059] When the four switch tubes in the high-voltage side drive circuit 10 are all in the turn-off state (to reduce switching loss), the alternating voltage is rectified by the body diodes of the four switch tubes in the high-voltage side drive circuit 10 to obtain a rectified voltage. The rectified voltage charges the bus capacitor C BUS .

[0060] LLC resonant circuit is widely used in inverter, as the inverter front-end boost circuit, the latter circuit is H4 bridge inverter, two-pole circuit through the bus capacitor C BUS Coupled together. When two machines are connected in parallel, there is a parallel circulating current in the no-load operating condition, and the parallel circulating current can cause the bus voltage to slowly rise, thereby triggering the bus overvoltage.

[0061] In order to prevent bus overvoltage and ensure circuit stability, the bus voltage needs to be discharged. The control method in the related art is to increase the discharge resistance, and the bus voltage is discharged by controlling the discharge resistance, but it will cause the inverter to have too large loss and increase the cost. Or adjust the circulating current direction, when the bus voltage of the local machine is too high, increase the output current of the local machine to discharge the voltage, but it is easy to cause current control divergence and cause oscillation, and further cause system failure.

[0062] Based on the above problems, the embodiment of the application provides a control method of LLC resonant circuit, which comprises the following steps: first, in response to the result that the bus voltage is greater than or equal to a first voltage threshold or in response to the result that the bus voltage belongs to a first voltage interval and the trend of the bus voltage is downward, determining a reference voltage, wherein the bus voltage is the voltage of the bus capacitor, the lower limit value of the first voltage interval is a second voltage threshold, and the upper limit value of the first voltage interval is the first voltage threshold; then, determining an initial duty ratio based on the reference voltage and the bus voltage; then, generating a target PWM signal based on the initial duty ratio; and finally, controlling the working state of the high-voltage side driving circuit by using the target PWM signal, so that the electric energy of the bus capacitor is transmitted to the energy storage unit.

[0063] The control method of the LLC resonant circuit generates a target PWM signal when the bus voltage is too high, controls the working state of the high-voltage side driving circuit, so that the electric energy of the bus capacitor is transmitted to the energy storage unit, and the bus capacitor virtual pressure is recovered and stored by using the energy storage unit, thereby achieving the discharge of the bus voltage. Moreover, the discharge is realized by using the circuit composition of the LLC resonant circuit itself, thereby reducing the circuit cost. Moreover, the control method generates the target PWM signal based on a suitable reference voltage, so that the bus voltage can be quickly discharged, and the discharge current can be prevented from being too large during the discharging process, thereby avoiding the damage of the devices in the resonant circuit and improving the safety of the LLC resonant circuit during the discharging process.

[0064] Please refer to Figure 2 , Figure 2 is a flowchart of a control method of an LLC resonant circuit provided by the embodiment of the application. The control method of the LLC resonant circuit can be executed by a controller in the LLC resonant circuit, or can be executed by another controller arranged additionally, or can be executed by an electronic device. The following embodiments take the controller as an example to illustrate the control method, and the method S100 comprises but is not limited to the following steps:

[0065] S10: In response to the result that the bus voltage is greater than or equal to the first voltage threshold or in response that the bus voltage belongs to the first voltage range and the trend of the bus voltage is decreasing, a reference voltage is determined, wherein the bus voltage is the voltage of the bus capacitor, the lower limit of the first voltage range is the second voltage threshold, and the upper limit of the first voltage range is the first voltage threshold.

[0066] S20: Determine the initial duty cycle based on the reference voltage and the bus voltage;

[0067] Bus voltage V bus The trend is as follows Figure 3 As shown, the bus voltage V bus The bus voltage V changes over time. bus It can be in four states, the first state being the bus voltage V. bus If the voltage is greater than or equal to the first voltage threshold V1, it indicates that the bus voltage exceeds the overvoltage threshold, and the bus voltage is too high. The second state is the bus voltage V. bus It belongs to the first voltage range [V1, V2], and the bus voltage V bus If the trend is downward, it indicates that the bus voltage gradually decreases from an excessively high voltage over time, but the bus voltage has not yet returned to its normal value. The third state is the bus voltage V. bus If the voltage is less than the second voltage threshold V2, it indicates that the bus voltage has decreased to below the overvoltage recovery threshold over time, and the bus voltage has returned to its normal value. The fourth state is the bus voltage V. bus It belongs to the first voltage range [V1, V2], and the bus voltage V bus If the trend is upward, it indicates that the bus voltage is gradually increasing from the normal value over time, and there is a tendency for it to rise to excessively high voltage.

[0068] When the bus voltage is greater than or equal to the first voltage threshold, or when the bus voltage is in the first voltage range and the trend of the bus voltage is decreasing, it indicates that the bus voltage is too high or that the bus voltage is slowly decreasing from the high voltage but has not yet returned to the normal value. The controller needs to control the high-voltage side drive circuit to perform a switching action, so that the bus voltage discharges to the battery, and the voltage of the bus capacitor is recovered and stored by the battery to realize the discharge of the bus voltage.

[0069] The bus capacitor transfers energy to the battery through the high-voltage side drive circuit, transformer, and primary side drive circuit. The energy output by the bus capacitor induces a high-frequency AC voltage at the primary winding that matches the secondary winding, i.e., the induced voltage. The primary side drive circuit converts this induced voltage into a stable DC voltage. When this DC voltage is higher than the current voltage of the battery, a charging voltage difference is formed, generating a discharge current to charge the battery, thus realizing the discharge of the battery from the bus voltage.

[0070] The controller controls the high-voltage side drive circuit to perform switching action through a PWM signal, and the duty cycle of the PWM signal determines the size of the energy transmitted from the bus capacitor to the battery and the size of the induced voltage or the size of the discharge current.

[0071] At the initial moment of wave generation, that is, the initial moment of outputting the PWM signal to the high-voltage side drive circuit, the controller outputs an initial duty cycle to the high-voltage side drive circuit, and the size of the initial duty cycle determines the size of the induced voltage or the size of the discharge current output from the bus capacitor to the battery at the initial moment.

[0072] If the initial duty cycle is too large, it will cause a large current on the battery side, and even a tube explosion phenomenon, damaging the device. If the initial duty cycle is too small, it will cause a slow hysteresis response, and the subsequent PWM signal needs to be adjusted multiple times on the basis of the initial duty cycle to adjust the duty cycle of the PWM signal to an appropriate value, and the adjustment time is too long.

[0073] Therefore, a suitable reference voltage needs to be set, and a suitable initial duty cycle is set based on the reference voltage, so as to ensure fast response and prevent large current and ensure safety.

[0074] In some embodiments, the bus capacitor transmits energy to the battery, and if the voltage transmitted from the bus capacitor to the battery at the initial moment of wave generation, that is, the induced voltage, is equal to the current battery voltage, the initial discharge current can be zero, and the duty cycle corresponding to the initial discharge current of zero is determined as the initial duty cycle.

[0075] Specifically, first, a first battery voltage is obtained, wherein the first battery voltage is the battery voltage of the energy storage unit at the current moment, and then a reference voltage is determined based on the first battery voltage, wherein the ratio between the reference voltage and the first battery voltage belongs to a preset proportion interval.

[0076] If the energy storage unit is a battery, the first battery voltage is the battery voltage of the battery at the current moment, and the voltage with a ratio to the first battery voltage that meets the preset proportion interval is determined as the reference voltage. The first battery voltage is , the reference voltage is , the preset proportion interval is [a, b], and The value range of , , wherein a and b can be set as needed, for example, a is 95% and b is 110%.

[0077] Preferably, the reference voltage is equal to the first battery voltage , and the reference voltage is determined based on the first battery voltage.Determine the initial duty ratio Dref, then the bus capacitor transmits energy to the battery, the initial duty ratio Dref corresponding PWM signal is used to drive the high voltage side drive circuit, the induced voltage generated is the reference voltage , and the reference voltage is equal to the battery voltage , that is, the induced voltage generated is equal to the battery voltage of the battery at the current moment, the current moment of the discharge current is zero, which will not cause damage to the device.

[0078] If the initial moment of the wave is transmitted to the battery side of the bus capacitor, the reference voltage (i.e. the induced voltage) is calculated by the following formula:

[0079] (1)

[0080] Wherein, is the reference voltage, is the bus voltage, D ref is the initial duty ratio, and N is the number of turns of the transformer.

[0081] Then the initial duty ratio calculation formula can be derived from formula (1):

[0082] (2)

[0083] Therefore, based on the initial duty ratio Dref, the initial PWM signal is regenerated, and at the initial moment of the wave, the initial PWM signal is used to drive the working state of the high voltage side drive circuit, so that the bus capacitor outputs energy to the battery side, and the induced voltage generated by the output energy is the reference voltage , which is proportional to the battery voltage of the battery at the current moment, so that the induced voltage is proportional to the battery voltage of the battery at the current moment, and the proportional relationship is small (such as 95% or 110% in the above embodiment), that is, the induced voltage and the battery voltage of the battery at the current moment are small, the initial discharge current is small, which reduces the damage to the device.

[0084] In some embodiments, the reference voltage is equal to the battery voltage of the battery at the current moment, so that the induced voltage and the battery voltage of the battery at the current moment have no pressure difference, and the initial discharge current is zero, which will not cause damage to the device.

[0085] And in the subsequent control process, the initial duty ratio Dref is used as the reference to adjust the duty ratio of the PWM signal used to drive the high voltage side drive circuit, without multiple adjustments, the appropriate PWM signal can be adjusted to control the bus voltage to discharge quickly, improve the response speed, and thus improve the safety of the circuit.

[0086] S30: generating a target PWM signal based on the initial duty ratio;

[0087] In some embodiments, at the initial wave emitting moment, the initial PWM signal is the target PWM signal, and a duty cycle of the target PWM signal is an initial duty cycle, and the initial PWM signal is used to control the working state of the high-voltage side driving circuit.

[0088] At a moment after the initial wave emitting moment, a duty cycle of the target PWM signal is determined based on the initial duty cycle within a preset range centered on the initial duty cycle, for example, the duty cycle of the target PWM signal is D, and D belongs to any value in the interval [D ref -D, D ref +D], where D can be set as needed or determined according to an empirical value.

[0089] In some embodiments, the initial duty cycle can be subjected to PI control to obtain the duty cycle of the target PWM signal.

[0090] Specifically, at the moment after the initial wave emitting moment, as shown in FIG. 3, step S30 includes: Figure 4

[0091] S31: obtaining an integral loop coefficient;

[0092] S32: inputting the integral loop coefficient into an integrator to obtain a compensation amount;

[0093] S33: adding the compensation amount and the initial duty cycle to obtain a target duty cycle;

[0094] S34: generating the target PWM signal based on the target duty cycle, where a duty cycle of the target PWM signal is the target duty cycle.

[0095] In the embodiments of the present application, the controller is a hysteresis controller, and the hysteresis controller is started by a hysteresis flag Flag. The hysteresis flag depends on a real-time voltage of the bus capacitor, i.e., a real-time bus voltage. Changes of the hysteresis flag Flag are as shown in FIG. 4. Figure 5 When the bus voltage exceeds a first voltage threshold V1, or the bus voltage belongs to a first voltage interval [V 1， V2] and a trend of the bus voltage is downward, it is indicated that the bus voltage is too high or that the bus voltage is decreasing from a too high voltage but has not yet decreased to a normal voltage range. The hysteresis flag is set, and the hysteresis flag Flag is 1. When the bus voltage is less than a second voltage threshold V2, or the bus voltage belongs to the first voltage interval [V 1， V2] and the trend of the bus voltage is upward, it is indicated that the bus voltage falls back to the normal voltage range or that the bus voltage is increasing from the normal voltage range but has not yet increased to the too high voltage. The hysteresis flag is cleared, and the hysteresis flag Flag is 0. ​

[0096] When the hysteresis flag Flag is 1, PI control is performed on the initial duty ratio to obtain a duty ratio of the target PWM signal, and the target PWM signal is used to drive the working state of the high-voltage side driving circuit. When the hysteresis flag Flag is 0, the target PWM signal is set to 0.

[0097] The control model is as shown in Figure 6 The program-controlled switch is used to represent the hysteresis flag, and is arranged at the front end of a PWM output module used to output the target PWM signal.

[0098] If the hysteresis flag Flag is 0, the program-controlled switch inputs 0 into the PWM output module, so that the target PWM signal is 0. If the hysteresis flag Flag is 1, the program-controlled switch inputs the target duty ratio into the PWM output module, so that the PWM output module generates and outputs the target PWM signal based on the target duty ratio.

[0099] The target duty ratio is determined by an integral ring and the initial duty ratio. First, the integral ring coefficient is input into an integrator to accumulate an output of a slow-changing compensation amount over time, and then the compensation amount is added to the initial duty ratio to obtain the target duty ratio. The compensation amount dynamically corrects the initial duty ratio to eliminate deviation and obtain a more accurate target duty ratio. The target duty ratio is input into the PWM output module, and the PWM output module generates and outputs the target PWM signal.

[0100] The integral ring coefficient determines the bus voltage descending slope. The integral ring is used to slowly reduce the bus voltage. The coefficient of the integral ring is set according to needs. In the embodiment of the present application, the integral ring coefficient is 0.01.

[0101] In some embodiments, the maximum value of the target duty ratio is limited to limit the maximum current transmitted from the bus capacitor to the battery. In the embodiment of the present application, the maximum value of the target duty ratio is 50%.

[0102] S40: The working state of the high-voltage side driving circuit is controlled by using the target PWM signal, so that the electrical energy of the bus capacitor is transmitted to the energy storage unit.

[0103] The target PWM signal is output to the control end of a switch tube in the high-voltage side driving circuit to control the conduction or turn-off of the switch tube, so that the high-voltage side driving circuit switches between different working states to achieve the purpose of transmitting the electrical energy of the bus capacitor to the energy storage unit.

[0104] If the high-voltage side driving circuit includes four switch tubes, the circuit structure is as shown in Figure 1As shown in the middle, the target PWM signal is used to control the working state of the high-voltage side drive circuit to switch between the first state and the second state, where the first state is that the first switch and the fourth switch are simultaneously turned on, and the second switch and the third switch are simultaneously turned off; the second state is that the first switch and the fourth switch are simultaneously turned off, and the second switch and the third switch are simultaneously turned on.

[0105] That is, the target PWM signal controls one pair of diagonal switches to be turned on and the other pair of diagonal switches to be turned off in an alternating diagonal wave manner, so that the bus voltage generates an induced voltage through the high-voltage side drive circuit, and the bus capacitor flows into the battery to make the battery recover and store the bus voltage.

[0106] In some embodiments, before the target PWM signal is used to control the working state of the high-voltage side drive circuit, the controller also controls the switches in the low-voltage side drive circuit to be turned off, so that the body diodes of the switches in the low-voltage side drive circuit form a rectifier bridge. Then the energy output from the bus capacitor to the battery generates an alternating voltage at the primary winding of the transformer, and the alternating voltage is rectified through the body diodes of the switches in the low-voltage side drive circuit to obtain a direct current induced voltage, which charges the battery. Turning off the switches in the low-voltage side drive circuit can further reduce switching loss.

[0107] In some embodiments, as the bus voltage slowly decreases and returns to a normal value, the controller stops outputting the target PWM signal and outputs a primary PWM signal to the low-voltage side drive circuit, so that the battery continues to charge the bus capacitor.

[0108] Specifically, as shown in Figure 7 the method S100 further includes:

[0109] S50: in response to the result that the bus voltage is less than the second voltage threshold or in response to the result that the bus voltage belongs to the first voltage interval and the trend of the bus voltage is rising, generating and outputting a primary PWM signal;

[0110] S60: controlling the working state of the low-voltage side drive circuit based on the primary PWM signal, so that the energy of the energy storage unit is transmitted to the bus capacitor.

[0111] When the bus voltage is less than the second voltage threshold or the bus voltage belongs to the first voltage interval and the trend of the bus voltage is rising, it indicates that the bus voltage returns to normal value or the bus voltage exceeds the normal value but has not risen to an excessively high voltage, and there is no need to perform voltage bleeding again. Therefore, the controller generates and outputs the primary side PWM signal, which acts on the control end of the switch tube in the low-voltage side driving circuit to control the conduction or turn-off of the switch tube in the low-voltage side driving circuit, so that the low-voltage side driving circuit switches between different working states, and then the electrical energy of the energy storage unit is converted into an alternating voltage through the low-voltage side driving circuit, the alternating voltage is boosted through the transformer, rectified through the high-voltage side driving circuit, and converted into a direct current voltage, which charges the bus capacitor to achieve the purpose of transmitting the electrical energy of the energy storage unit to the bus capacitor.

[0112] In some embodiments, the second voltage threshold is equal to the first voltage threshold minus 20V.

[0113] In some embodiments, before controlling the working state of the low-voltage side driving circuit based on the primary side PWM signal, the controller controls the switch tube in the high-voltage side driving circuit to be in the turn-off state, so that the body diode of the switch tube in the high-voltage side driving circuit forms a rectifier bridge. Turning off the switch tube in the high-voltage side driving circuit can further reduce the switching loss.

[0114] Please refer to Figure 8 , Figure 8 is one of the timing diagrams of the bus voltage, the bleeding current and the amplitude of the target PWM signal provided by the embodiments of the present application. In the embodiments of the present application, the reference voltage is equal to the first battery voltage , and the initial duty cycle D is determined based on the reference voltage ref When the bus voltage exceeds the first voltage threshold, the controller outputs the target PWM signal, and the duty cycle of the target PWM signal is the initial duty cycle D ref , the bleeding current slowly increases, and the controller generates the target duty cycle based on the integral ring, the integral coefficient and the initial duty cycle D ref , and generates and outputs the target PWM signal based on the target duty cycle. The amplitude of the target PWM signal (the target duty cycle) gradually increases, the bleeding current slowly rises, the bus voltage bleeds, and the bus voltage slowly decreases.

[0115] When the bus voltage belongs to the first voltage interval and the trend of the bus voltage is falling, the target PWM signal is continuously outputted, the bus voltage continues to bleed, and the bus voltage continues to fall.

[0116] When the bus voltage decreases to the second voltage threshold, the controller stops outputting the target PWM signal, the amplitude of the target PWM signal is 0, the bleeder current is 0, and the bus capacitor no longer charges the energy storage unit.

[0117] When the bus voltage gradually rises again, the bus voltage belongs to the first voltage interval, and the trend of the bus voltage is rising, the output of the target PWM signal is still stopped.

[0118] When the bus voltage rises again and is greater than or equal to the first voltage threshold, the next round of voltage bleeder is started, so that the bus voltage decreases to ensure the safety of the circuit.

[0119] In summary, the control method of the LLC resonant circuit generates a target PWM signal when the bus voltage is too high, controls the working state of the high-voltage side drive circuit, and transmits the energy of the bus capacitor to the energy storage unit. The bus capacitor virtual pressure is recovered and stored by using the energy storage unit, the bus voltage is bleeded, and the bleeder is realized by using the circuit composition of the LLC resonant circuit itself, without the need to additionally set a bleeder resistor, which reduces the circuit cost. At the same time, the control method generates a target PWM signal based on a suitable reference voltage, which can quickly bleed the bus voltage and ensure that the bleeder current is not too large during the bleeder process, avoiding damage to the devices in the resonant circuit and improving the safety of the LLC resonant circuit during the bleeder process.

[0120] It should be noted that in the above various embodiments, the above steps do not necessarily have a certain sequence, and those skilled in the art can understand from the description of the embodiments of the present application that the above steps can have different execution sequences in different embodiments, that is, they can be executed in parallel, or they can be executed in exchange, etc.

[0121] As another aspect of the embodiments of the present application, the embodiments of the present application provide an LLC resonant circuit control device applied to the above-mentioned controller. The LLC resonant circuit control device can be a software module, the software module includes a plurality of instructions stored in a memory, and a processor can access the memory to call the instructions for execution to complete the LLC resonant circuit control method described in the above various embodiments.

[0122] In some embodiments, the control device of the LLC resonant circuit can also be built by hardware devices, for example, the control device of the LLC resonant circuit can be built by one or more chips, and each chip can work in coordination with each other to complete the control method of the LLC resonant circuit described in each of the above embodiments. For another example, the control device of the LLC resonant circuit can also be built by various logic devices, such as general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field programmable gate arrays (FPGA), single-chip microcomputers, ARM (Acorn RISC Machine) or other programmable logic devices, discrete gates or transistor logic, discrete hardware components, or any combination of these components.

[0123] Please refer to Figure 9 , Figure 9 is a structural schematic diagram of a control device of an LLC resonant circuit provided by the embodiments of the present application, as shown in Figure 9 , the control device 700 of the LLC resonant circuit includes a first determination module 701, a second determination module 702, a generation module 703, and a control module 704.

[0124] The first determination module 701 is configured to determine a reference voltage in response to a result that a bus voltage is greater than or equal to a first voltage threshold or in response to a result that the bus voltage belongs to a first voltage interval and a trend of the bus voltage is downward, wherein the bus voltage is a voltage of a bus capacitor, a lower limit value of the first voltage interval is a second voltage threshold, and an upper limit value of the first voltage interval is the first voltage threshold. The second determination module 702 is configured to determine an initial duty ratio based on the reference voltage and the bus voltage. The generation module 703 is configured to generate a target PWM signal based on the initial duty ratio. The control module 704 is configured to control a working state of the high-voltage side driving circuit by using the target PWM signal, so that electric energy of the bus capacitor is transmitted to the energy storage unit.

[0125] It should be noted that, since the control device of the LLC resonant circuit and the control method of the LLC resonant circuit in the above embodiments are based on the same inventive concept, the corresponding contents in the method embodiment are also applicable to the device embodiment, which will not be described in detail here.

[0126] In summary, the control device of the LLC resonant circuit generates a target PWM signal when the bus voltage is too high, controls the working state of the high-voltage side drive circuit, so that the electric energy of the bus capacitor is transmitted to the energy storage unit, and the bus capacitor virtual pressure is recovered and stored by using the energy storage unit, the bus voltage is discharged, and the discharge is realized by using the circuit composition of the LLC resonant circuit itself, without the need to additionally set a discharge resistor, thereby reducing the circuit cost. At the same time, the control method generates a target PWM signal based on a suitable reference voltage, which can not only quickly discharge the bus voltage, but also ensure that the discharge current is not too large during the discharge process, thereby avoiding damage to the devices in the resonant circuit and improving the safety of the LLC resonant circuit during the discharge process.

[0127] Please refer to Figure 10 , Figure 10 is a structural schematic diagram of a controller provided by an embodiment of the present application. As shown in Figure 10 , the controller 800 includes one or more processors 801 and a memory 802. Among them, Figure 10 take one processor 801 as an example.

[0128] The processor 801 and the memory 802 can be connected through a bus or other means, Figure 10 take the connection through the bus as an example.

[0129] The memory 802 is a kind of non-volatile computer readable storage medium, which can be used to store non-volatile software programs, non-volatile computer executable programs and modules, such as program instructions / modules corresponding to the control device of the LLC resonant circuit in the embodiment of the present application. The processor 801 executes the non-volatile software program, instruction and module stored in the memory 802, thereby performing various functional applications and data processing of the LLC resonant circuit control device, i.e. realizing the functions of each module or unit of the LLC resonant circuit control method provided by the above method embodiment and the above device embodiment.

[0130] The memory 802 can include a high-speed random access memory, and can also include a non-volatile memory, such as at least one magnetic disk storage device, a flash memory device, or other non-volatile solid-state storage device. In some embodiments, the memory 802 can optionally include a memory remotely arranged with respect to the processor 801, which can be connected to the processor 801 through a network. Examples of the above network include but are not limited to the Internet, an intranet, a local area network, a mobile communication network and a combination thereof.

[0131] The program instructions / modules are stored in the memory 802, and when executed by the one or more processors 801, the LLC resonant circuit control method in any of the above method embodiments is executed.

[0132] The embodiment of the present application further provides a non-transitory computer readable storage medium, which stores computer executable instructions, and the computer executable instructions are executed by one or more processors, for example, the processor 801 in the computer 800, so that the one or more processors can execute the control method of the LLC resonant circuit in any method embodiment. Figure 10 The embodiment of the present application further provides a non-transitory computer readable storage medium, which stores computer executable instructions, and the computer executable instructions are executed by one or more processors, for example, the processor 801 in the computer 800, so that the one or more processors can execute the control method of the LLC resonant circuit in any method embodiment.

[0133] The embodiment of the present application further provides a non-transitory computer readable storage medium, which stores computer executable instructions, and the computer executable instructions are executed by one or more processors, for example, the processor 801 in the computer 800, so that the one or more processors can execute the control method of the LLC resonant circuit in any method embodiment. Figure 10 The embodiment of the present application further provides a non-transitory computer readable storage medium, which stores computer executable instructions, and the computer executable instructions are executed by one or more processors, for example, the processor 801 in the computer 800, so that the one or more processors can execute the control method of the LLC resonant circuit in any method embodiment.

[0134] The embodiment of the present application further provides a computer program product, which comprises a computer program stored on a non-transitory computer readable storage medium, and the computer program comprises program instructions, and when the program instructions are executed by a controller, the controller executes the control method of the LLC resonant circuit.

[0135] Those skilled in the art can clearly understand that each embodiment can be realized by means of software and a general hardware platform, and of course, can also be realized by hardware. Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiments can be completed by a computer program instructing related hardware, and the computer program can be stored in a non-transitory computer readable storage medium, and the computer program comprises program instructions, and when the program instructions are executed by a controller, the controller executes the processes of each method embodiment. The storage medium can be a disc, an optical disc, a read-only memory (ROM) or a random access memory (RAM).

[0136] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit them; under the idea of the present application, the technical features in the above examples or different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes of different aspects of the present application as described above, which are not provided in details for simplicity; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A control method for an LLC resonant circuit, characterized in that, The LLC resonant circuit includes an energy storage unit, a low-voltage side drive circuit, a transformer, a high-voltage side drive circuit, and a bus capacitor connected in sequence. The method includes: A reference voltage is determined in response to a bus voltage greater than or equal to a first voltage threshold or in response to a bus voltage belonging to a first voltage range and the bus voltage trend being downward. The bus voltage is the voltage of the bus capacitor, the lower limit of the first voltage range is a second voltage threshold, and the upper limit of the first voltage range is the first voltage threshold. The initial duty cycle is determined based on the reference voltage and the bus voltage; Generate the target PWM signal based on the initial duty cycle; The target PWM signal is used to control the operating state of the high-voltage side drive circuit so that the electrical energy of the bus capacitor is transferred to the energy storage unit; The determination of the reference voltage includes: Obtain the first battery voltage, wherein the first battery voltage is the battery voltage of the energy storage unit at the current moment; The reference voltage is determined based on the first battery voltage, wherein the ratio between the reference voltage and the first battery voltage belongs to a preset ratio range, the preset ratio range being [a, b], where a is 95% and b is 110%; When the bus voltage exceeds the first voltage threshold, the target PWM signal is output. When the bus voltage is within the first voltage range and the trend of the bus voltage is decreasing, the target PWM signal continues to be output to continue controlling the bus voltage discharge.

2. The method according to claim 1, characterized in that, The determination of the initial duty cycle based on the reference voltage and the bus voltage includes: The initial duty cycle is calculated using the following formula: ； in, The initial duty cycle, The reference voltage, The bus voltage is N, and the turns ratio of the transformer in the LLC resonant circuit is N.

3. The method according to claim 1, characterized in that, At the initial moment of wave generation, the duty cycle of the target PWM signal is the initial duty cycle.

4. The method according to claim 3, characterized in that, At a time after the initial wave transmission moment, the generation of the target PWM signal based on the initial duty cycle includes: Obtain the integral ring coefficients; The integral loop coefficients are input into the integrator to obtain the compensation amount; The target duty cycle is obtained by adding the compensation amount to the initial duty cycle. The target PWM signal is generated based on the target duty cycle, wherein the duty cycle of the target PWM signal is the target duty cycle.

5. The method according to claim 1, characterized in that, The high-voltage side drive circuit includes a first to a fourth switching transistor, wherein the first and second switching transistors are connected in series between the first and second terminals of the secondary winding of the transformer, and the third and fourth switching transistors are connected in series between the first and second terminals of the secondary winding of the transformer. Controlling the operating state of the high-voltage side drive circuit using the target PWM signal includes: The target PWM signal is used to control the operation state of the high-voltage side drive circuit to switch between a first state and a second state. In the first state, the first switch and the fourth switch are turned on simultaneously, and the second switch and the third switch are turned off simultaneously. In the second state, the first switch and the fourth switch are turned off simultaneously, and the second switch and the third switch are turned on simultaneously.

6. The method according to any one of claims 1-5, characterized in that, Before using the target PWM signal to control the operating state of the high-voltage side drive circuit, the method further includes: All switching transistors in the low-voltage side drive circuit are kept in the off state.

7. The method according to any one of claims 1-5, characterized in that, The method further includes: In response to the bus voltage being less than the second voltage threshold or in response to the bus voltage belonging to the first voltage range and the bus voltage trending upward, a primary-side PWM signal is generated and output. The operating state of the low-voltage side drive circuit is controlled based on the primary-side PWM signal, so that the electrical energy of the energy storage unit is transferred to the bus capacitor.

8. The method according to claim 7, characterized in that, Before controlling the operating state of the low-voltage side drive circuit based on the primary-side PWM signal, the method further includes: All switching transistors in the high-voltage side drive circuit are kept in the off state.

9. A controller, characterized in that, The controller includes: At least one processor; and, A non-volatile memory communicatively connected to the at least one processor, the non-volatile memory storing instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the control method for the LLC resonant circuit as described in any one of claims 1-8.

10. An LLC resonant circuit, characterized in that, The LLC resonant circuit includes an energy storage unit, a low-voltage side drive circuit, a transformer, a high-voltage side drive circuit, and a bus capacitor connected in sequence, and also includes a controller as described in claim 9, wherein the controller is electrically connected to the control terminal of the switch in the high-voltage side drive circuit and the control terminal of the switch in the low-voltage side drive circuit, respectively.

Images