Start-up control method, device and storage medium for LLC resonant circuit
By adjusting the switching sequence of the bridge switching circuit and regulating the charging of the resonant capacitor in stages, the voltage imbalance and current asymmetry problems during the startup process of the LLC resonant converter were solved, achieving fast startup and stable output.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- MORNSUN GUANGZHOU SCI & TECH
- Filing Date
- 2023-02-27
- Publication Date
- 2026-06-30
AI Technical Summary
LLC resonant converters suffer from system instability, resonant current asymmetry, and excessive current stress due to resonant capacitor voltage imbalance during startup, increasing system cost and prolonging the steady-state arrival time.
By adjusting the timing of the switching transistors in the bridge switching circuit, the charging of the resonant capacitor is adjusted in stages to achieve rapid voltage balance of the resonant capacitor and zero-voltage switching (ZVS) is achieved during the switching process of the transistors, thereby reducing hard switching interference and inrush current.
It effectively shortens the start-up time of the LLC resonant converter, reduces hardware drive costs, and improves the stability of the output voltage and the system.
Smart Images
Figure CN116317518B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of power electronics technology, and in particular to a startup control method, device, and storage medium for an LLC resonant circuit. Background Technology
[0002] LLC resonant converters typically employ Pulse Frequency Modulation (PFM) technology for control. LLC resonant converters control the output voltage by changing the operating frequency, thereby altering the input impedance. Common startup methods include PFM+PWM modulation or a hybrid of both, using a combination of high frequency and varying duty cycle. High-frequency startup places high demands on hardware drivers, increasing system cost. If the initial capacitor voltage is unbalanced, these startup processes can lead to the following problems: 1. Unbalanced resonant capacitor voltage causes asymmetrical resonant current, posing a risk of system instability. 2. The initial unidirectional excitation of the resonant current, without reversal, causes significant current stress. This stress flows directly through the body diode of the lower rectifier diode, potentially causing overheating and damage. If the resonant current does not reach zero during the demagnetizing phase of the resonant inductor, turning on the bridge arm transistors may damage them. 3. Unbalanced resonant capacitor energy increases the time required for the system to reach steady state. Summary of the Invention
[0003] To address the aforementioned problems, the main objective of this invention is to provide a startup control method, apparatus, and storage medium for an LLC resonant circuit, enabling rapid voltage balancing of the resonant capacitor to resolve the energy imbalance issue.
[0004] The technical solution provided by this invention to solve the above-mentioned technical problems is as follows:
[0005] In a first aspect, embodiments of the present invention provide a startup control method for an LLC resonant circuit, wherein the LLC resonant circuit includes a bridge switching circuit, a resonant circuit, a transformer, and a rectifier filter circuit connected in series, wherein the bridge switching circuit includes an upper bridge arm switch and a lower bridge arm switch, and the resonant circuit includes a resonant inductor and a resonant capacitor.
[0006] The startup control method for the LLC resonant circuit includes the following steps:
[0007] The current working status is confirmed as "started," and the system enters the first mode.
[0008] In the first mode, the resonant capacitor voltage is set to zero;
[0009] In the second mode, the upper bridge arm switch is turned on to charge the resonant capacitor, so that the resonant inductor current reaches the maximum resonant inductor current value and the resonant capacitor voltage reaches the first set voltage.
[0010] In the third mode, the lower bridge arm switch is turned on to charge the resonant capacitor, so that the voltage of the resonant capacitor reaches the second set voltage.
[0011] Wherein, the second set voltage is greater than the first set voltage.
[0012] Furthermore, in the first mode, setting the resonant capacitor voltage to zero includes:
[0013] Turn on the lower bridge arm switch to release the resonant capacitor voltage to the load output terminal, thus setting the resonant capacitor voltage to zero.
[0014] The lower bridge arm switch is turned off, and the second mode is entered after the first termination condition is met.
[0015] Further, in the second mode, charging the resonant capacitor to bring the resonant inductor current to the maximum resonant inductor current value and bringing the resonant capacitor voltage to the first set voltage includes:
[0016] Turn on the upper bridge arm switch, charge the resonant capacitor through the resonant inductor, so that the resonant inductor current reaches the maximum resonant inductor current value, and the resonant capacitor voltage reaches the first set voltage;
[0017] The upper bridge arm switch is turned off, the junction capacitance of the upper bridge arm switch is charged, the junction capacitance of the lower bridge arm switch is discharged, and the third mode is entered after the second termination condition is met.
[0018] Furthermore, in the third mode, charging the resonant capacitor to bring its voltage to a second set voltage includes:
[0019] The lower bridge arm switch is turned on, thereby charging the resonant capacitor so that the voltage of the resonant capacitor reaches the second set voltage.
[0020] Turn off the lower bridge arm switch, charge the junction capacitance of the lower bridge arm switch, and discharge the junction capacitance of the upper bridge arm switch.
[0021] Furthermore, it also includes:
[0022] The current working status is determined to be "continue startup," and the system will enter the fourth mode.
[0023] In the fourth mode, the upper bridge arm switch is turned on with zero voltage.
[0024] Furthermore, in the first mode, setting the resonant capacitor voltage to zero includes:
[0025] During the first time period, the lower bridge arm switch is turned on to release the resonant capacitor voltage to the load output terminal, thereby setting the resonant capacitor voltage to zero.
[0026] During the second time period, the lower bridge arm switch is turned off, and the second mode is entered after the second time period ends.
[0027] Further, in the second mode, charging the resonant capacitor to bring the resonant inductor current to the maximum resonant inductor current value and bringing the resonant capacitor voltage to the first set voltage includes:
[0028] During the third time period, the upper bridge arm switch is turned on, and the resonant capacitor is charged through the resonant inductor, so that the resonant inductor current reaches the maximum resonant inductor current value and the resonant capacitor voltage reaches the first set voltage.
[0029] During the fourth time period, the upper bridge arm switch is turned off, the junction capacitance of the upper bridge arm switch is charged, the junction capacitance of the lower bridge arm switch is discharged, and the third mode is entered after the fourth time period ends.
[0030] Furthermore, in the third mode, charging the resonant capacitor to bring its voltage to a second set voltage includes:
[0031] During the fifth time period, the lower bridge arm switch is turned on, thereby charging the resonant capacitor so that the voltage of the resonant capacitor reaches the second set voltage.
[0032] During the sixth time period, the lower bridge arm switch is turned off, the junction capacitance of the lower bridge arm switch is charged, and the junction capacitance of the upper bridge arm switch is discharged.
[0033] Secondly, embodiments of the present invention provide a start-up control device for an LLC resonant circuit, wherein the LLC resonant circuit includes a bridge switching circuit, a resonant circuit, a transformer, and a rectifier filter circuit connected in series, wherein the bridge switching circuit includes an upper bridge arm switch and a lower bridge arm switch, and the resonant circuit includes a resonant inductor and a resonant capacitor.
[0034] The start-up control device for the LLC resonant circuit includes:
[0035] The start determination unit is used to determine that the current working state is the start state and enter the first mode;
[0036] The first mode unit is used to set the resonant capacitor voltage to zero in the first mode.
[0037] The second mode unit is used to charge the resonant capacitor in the second mode, so that the resonant inductor current reaches the maximum current value of the resonant inductor, and so that the resonant capacitor voltage reaches the first set voltage.
[0038] The third mode unit is used to charge the resonant capacitor in the third mode so that the voltage of the resonant capacitor reaches the second set voltage.
[0039] Wherein, the second set voltage is greater than the first set voltage.
[0040] Thirdly, embodiments of the present invention provide a computer storage medium storing a computer program, wherein the computer program, when executed by a processor, implements the steps of the start-up control method for the LLC resonant circuit as described in the first aspect.
[0041] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:
[0042] This invention achieves voltage balance in the resonant capacitor by adjusting the timing of the switching transistors in the bridge switching circuit during startup, thereby regulating the charging of the resonant capacitor in stages and effectively shortening the startup time. Furthermore, this invention achieves zero-voltage switching (ZVS) during the switching process between the upper and lower bridge arm transistors, reducing hard-switching interference and effectively minimizing the startup inrush current of the LLC resonant converter. This not only reduces the cost of the drive hardware but also improves the stability of the output voltage during startup. Attached Figure Description
[0043] The present invention will be further described with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the present invention. For those skilled in the art, other drawings can be obtained based on the following drawings without creative effort.
[0044] Figure 1 This is a schematic diagram of a bridge LLC converter using the control method of the present invention.
[0045] Figure 2 This is a flowchart illustrating the steps of the start-up control method for the LLC resonant circuit of the present invention.
[0046] Figure 3 This is a timing diagram illustrating the control method of the present invention.
[0047] Figure 4 This is a block diagram of the starting control device for the LLC resonant circuit of the present invention. Detailed Implementation
[0048] It should be understood that the specific embodiments described herein are merely illustrative of the invention, and the specific implementation of the invention is not limited thereto. The described embodiments are only a part of the embodiments of the invention, and not all of them. It should be noted that the embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Based on the described embodiments of the invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the invention.
[0049] This invention provides a startup control method for an LLC resonant circuit, applicable to rapid startup during LLC startup / fault recovery. For example... Figure 1 As shown, the LLC resonant circuit includes a bridge switch circuit 101, a resonant circuit 102, a transformer T, and a rectifier filter circuit 103 connected in series. The bridge switch circuit 101 includes an upper bridge arm switch transistor Q1 and a lower bridge arm switch transistor Q2, and the resonant circuit 102 includes a resonant inductor L and a resonant capacitor C.
[0050] refer to Figure 2 The startup control method for an LLC resonant circuit includes the following steps:
[0051] S100: Determine the current working state as the startup state and enter the first mode.
[0052] The startup state can be either the newly started state or the restart state.
[0053] S200, in the first mode, the voltage of the resonant capacitor is set to zero.
[0054] S300 In the second mode, the upper bridge arm switch Q1 is turned on to charge the resonant capacitor C, so that the resonant inductor current reaches the maximum current value of the resonant inductor and the resonant capacitor voltage reaches the first set voltage.
[0055] S400. In the third mode, the lower bridge arm switch Q2 is turned on to charge the resonant capacitor C, causing the resonant capacitor voltage to reach the second set voltage. The second set voltage is greater than the first set voltage.
[0056] This invention, through adjusting the timing of the switching transistors in the bridge switching circuit 101 during startup, regulates the charging of the resonant capacitor C in stages, achieving voltage balance of the resonant capacitor and effectively shortening the startup time. Furthermore, this invention achieves zero-voltage switching (ZVS) during the switching process of the upper bridge arm switch Q1 and the lower bridge arm switch Q2, thereby reducing hard-switching interference and effectively reducing the startup inrush current of the LLC resonant converter. This not only reduces the cost of the drive hardware but also improves the stability of the output voltage during startup.
[0057] In one embodiment, step S200 includes:
[0058] S201. Turn on the lower bridge arm switch Q2 to release the resonant capacitor voltage to the load output terminal, so that the resonant capacitor voltage is set to zero.
[0059] S202, turn off the lower bridge arm switch Q2, and enter the second mode after the first termination condition is met.
[0060] In this embodiment, without adding any additional hardware circuitry, turning on the lower bridge arm switch Q2 can release the energy of any voltage that may exist on the resonant capacitor C to the load output terminal through the resonant circuit 102 and the transformer T, thereby ensuring that the voltage of the resonant capacitor is set to zero.
[0061] In this embodiment, the first termination condition is that the turn-off time of the lower arm switch Q2 reaches a preset first dead time. This first dead time provides a reliable dead time before entering the second mode, thereby avoiding common short circuits of the arm switches.
[0062] In one embodiment, step S300 includes:
[0063] S301. Turn on the upper bridge arm switch Q1, and charge the resonant capacitor C through the resonant inductor L, so that the resonant inductor current reaches the maximum value of the resonant inductor and the resonant capacitor voltage reaches the first set voltage.
[0064] S302, turn off the upper bridge arm switch Q1, charge the junction capacitance of the upper bridge arm switch Q1, discharge the junction capacitance of the lower bridge arm switch Q2, and enter the third mode after the second termination condition is met.
[0065] In this embodiment, the first set voltage is determined based on the input voltage of the actual bridge switch circuit 101. After the upper bridge arm switch Q1 is turned on, it charges the resonant capacitor C through the resonant inductor L, and the resonant inductor current increases linearly, so that the resonant inductor current reaches the maximum current value of the resonant inductor, and the resonant capacitor voltage reaches the first set voltage before proceeding to the next step S302. The second termination condition is that the turn-off time of the upper bridge arm switch Q1 reaches the preset second dead time. After the upper bridge arm switch Q1 is turned off, the resonant inductor current decreases and becomes a forward current. After the upper bridge arm switch Q1 is turned off, the circuit in this embodiment will charge the junction capacitance of the upper bridge arm switch Q1 and discharge the junction capacitance of the lower bridge arm switch Q2. The body diode of the lower bridge arm switch Q2 will be turned on, which facilitates the lower bridge arm switch Q2 to achieve ZVS turn-on or reduce the loss when turning on again after being turned off in the third mode.
[0066] In one embodiment, step S400 includes:
[0067] S401, turn on the lower bridge arm switch Q2, thereby charging the resonant capacitor C, so that the voltage of the resonant capacitor reaches the second set voltage.
[0068] S402: Turn off the lower bridge arm switch Q2, charge the junction capacitance of the lower bridge arm switch Q2, and discharge the junction capacitance of the upper bridge arm switch Q1.
[0069] In this embodiment, the second set voltage is determined based on the input voltage of the actual bridge switch circuit 101, and the second set voltage is greater than the first set voltage. Upon entering the third mode, the resonant current is positive, and the lower bridge arm switch Q2 achieves ZVS turn-on. The resonant current flows through the lower bridge arm switch Q2 to charge the resonant capacitor C. The resonant current gradually decreases to zero and then increases in the opposite direction. When the voltage of the resonant capacitor increases to reach the second set voltage, the resonant current becomes a negative current.
[0070] After entering step S402 in this embodiment, the resonant capacitor voltage reaches a balanced state. After the lower bridge arm switch Q2 is turned off, the circuit will charge the junction capacitance of the lower bridge arm switch Q2 and discharge the junction capacitance of the upper bridge arm switch Q1.
[0071] Preferably, the second set voltage is greater than twice the first set voltage.
[0072] In one embodiment, it further includes:
[0073] The current working status is determined to be "continue startup," and the system will enter the fourth mode.
[0074] In the fourth mode, the upper bridge arm switch Q1 is turned on with zero voltage.
[0075] In this embodiment, the resonant capacitor voltage has reached a balanced state. According to the operation signal, if the next operation is required, the working state is to continue to start, and then it will enter the fourth mode. Since the junction capacitance of the upper bridge arm switch Q1 is discharged in this embodiment, the upper bridge arm switch Q1 can be turned on with zero voltage.
[0076] In another embodiment, step S200 includes:
[0077] S211. During the first time period, turn on the lower bridge arm switch Q2 to release the resonant capacitor voltage to the load output terminal, so that the resonant capacitor voltage is set to zero.
[0078] S212. During the second time period, turn off the lower bridge arm switch Q2, and enter the second mode after the second time period ends.
[0079] In this embodiment, as Figure 3As shown, the first time period is 0 < t ≤ t1. The control signal of the lower-arm switch Q2 controls the lower-arm switch Q2 to turn on. Without adding additional hardware circuits, the energy stored in the resonant capacitor C is released to the load output terminal through the resonant circuit 102 and the transformer T, ensuring that the voltage of the resonant capacitor is set to zero. The second time period is t1 < t ≤ t2. The control signals of the upper-arm switch Q1 and the lower-arm switch Q2 are always off, and the upper-arm switch Q1 and the lower-arm switch Q2 remain in the off state, providing a reliable dead zone before entering the second mode, thus avoiding the common short circuit of the arm switches.
[0080] In another embodiment, step S300 includes:
[0081] S311. During the third time period, turn on the upper-arm switch Q1 to charge the resonant capacitor C through the resonant inductor L, so that the resonant inductor current reaches the maximum current value of the resonant inductor and the resonant capacitor voltage reaches the first set voltage.
[0082] S312. During the fourth time period, turn off the upper-arm switch Q1, charge the junction capacitance of the upper-arm switch Q1, discharge the junction capacitance of the lower-arm switch Q2, and enter the third mode after the fourth time period ends.
[0083] In this embodiment, as Figure 3 shown, during the third time period t2 < t ≤ t3, the control signal of the upper-arm switch Q1 is always on. After turning on the upper-arm switch Q1, charge the resonant capacitor C through the resonant inductor L. The resonant inductor current increases linearly and reaches the maximum current value of the resonant inductor at time t3, and the resonant capacitor voltage reaches the first set voltage. The first set voltage is set according to the input voltage value of the bridge switch circuit 101.
[0084] During the fourth time period t3 < t ≤ t4, the control signals of the upper-arm switch Q1 and the lower-arm switch Q2 are always off. During the time from t3 to t4, the resonant inductor current decreases. The resonant inductor current is a positive current, charging the junction capacitance of the upper-arm switch Q1 and discharging the junction capacitance of the lower-arm switch Q2. The voltage of the upper-arm switch Q1 reaches the input voltage value of the bridge switch circuit, the junction capacitance of the lower-arm switch Q2 discharges, and the body diode of the lower-arm switch Q2 conducts.
[0085] In another embodiment, step S400 includes:
[0086] S411. During the fifth time period, turn on the lower-arm switch Q2 to charge the resonant capacitor C, so that the resonant capacitor voltage reaches the second set voltage.
[0087] S412. During the sixth time period, turn off the lower-arm switch Q2, charge the junction capacitance of the lower-arm switch Q2, and discharge the junction capacitance of the upper-arm switch Q1.
[0088] In this embodiment, as Figure 3 shown, during the fifth time period of t4 < t ≤ t5, the control signal of the lower-arm switch Q2 is normally open. At the moment of t4, the resonant current is still positive, and the lower-arm switch Q2 achieves ZVS turn-on. The resonant current flows through the lower-arm switch Q2 and gradually decreases to zero and then increases in the reverse direction. At the moment of t5, the resonant current is a negative current.
[0089] During the sixth time period of t5 < t ≤ t6, the resonant capacitor C enters the balanced state. Since the resonant current is a negative current, the control signals of the upper-arm switch Q1 and the lower-arm switch Q2 are normally off. At the moment of t5, the resonant current charges the junction capacitance of the lower-arm switch Q2 and discharges the junction capacitance of the upper-arm switch Q1.
[0090] Referring to Figure 4 , an embodiment of the present invention provides a starting control device for an LLC resonant circuit. The LLC resonant circuit includes a bridge switch circuit 101, a resonant circuit 102, a transformer T, and a rectifier filter circuit 103 connected in series in sequence. Among them, the bridge switch circuit 101 includes an upper-arm switch Q1 and a lower-arm switch Q2, and the resonant circuit 102 includes a resonant inductor L and a resonant capacitor C;
[0091] The starting control device for the LLC resonant circuit includes:
[0092] A starting determination unit for determining that the current working state is the starting state and entering the first mode; <00002This invention, through adjusting the timing of the switching transistors in the bridge switching circuit 101 during startup, regulates the charging of the resonant capacitor C in stages, achieving voltage balance of the resonant capacitor and effectively shortening the startup time. Furthermore, this invention achieves zero-voltage switching (ZVS) during the switching process of the upper bridge arm switch Q1 and the lower bridge arm switch Q2, thereby reducing hard-switching interference and effectively reducing the startup inrush current of the LLC resonant converter. This not only reduces the cost of the drive hardware but also improves the stability of the output voltage during startup.
[0098] In one embodiment, the first mode unit includes:
[0099] The zeroing unit is used to turn on the lower bridge arm switch Q2, release the resonant capacitor voltage to the load output terminal, and set the resonant capacitor voltage to zero.
[0100] The first dead zone unit is used to turn off the lower bridge arm switch Q2 and enter the second mode after the first termination condition is met.
[0101] In this embodiment, without adding any additional hardware circuitry, turning on the lower bridge arm switch Q2 can release the energy of any voltage that may exist on the resonant capacitor C to the load output terminal through the resonant circuit 102 and the transformer T, thereby ensuring that the voltage of the resonant capacitor is set to zero.
[0102] In this embodiment, the first termination condition is that the turn-off time of the lower arm switch Q2 reaches a preset first dead time. This first dead time provides a reliable dead time before entering the second mode, thereby avoiding common short circuits of the arm switches.
[0103] In one embodiment, the second mode unit includes:
[0104] The first charging unit is used to turn on the upper bridge arm switch Q1, charge the resonant capacitor C through the resonant inductor L, so that the resonant inductor current reaches the maximum resonant inductor current value, and so that the resonant capacitor voltage reaches the first set voltage.
[0105] The second dead zone unit is used to turn off the upper bridge arm switch Q1, charge the junction capacitance of the upper bridge arm switch Q1, discharge the junction capacitance of the lower bridge arm switch Q2, and enter the third mode after the second termination condition is met.
[0106] In this embodiment, the first set voltage is determined based on the input voltage of the actual bridge switching circuit 101. After the upper bridge arm switch Q1 is turned on, it charges the resonant capacitor C through the resonant inductor L, and the resonant inductor current increases linearly, so that the resonant inductor current reaches the maximum current value of the resonant inductor, and the resonant capacitor voltage reaches the first set voltage before entering the second switching unit. The second termination condition is that the turn-off time of the upper bridge arm switch Q1 reaches the preset second dead time. After the upper bridge arm switch Q1 is turned off, the resonant inductor current decreases and becomes a forward current. After the upper bridge arm switch Q1 is turned off, the circuit in this embodiment will charge the junction capacitance of the upper bridge arm switch Q1 and discharge the junction capacitance of the lower bridge arm switch Q2. The body diode of the lower bridge arm switch Q2 will be turned on, which facilitates the lower bridge arm switch Q2 to achieve ZVS turn-on in the third mode or reduces the loss when turning on after being turned off.
[0107] In one embodiment, the third mode unit includes:
[0108] The second charging unit is used to turn on the lower bridge arm switch Q2, thereby charging the resonant capacitor C so that the voltage of the resonant capacitor reaches the second set voltage.
[0109] The third dead zone unit is used to turn off the lower bridge arm switch Q2, charge the junction capacitance of the lower bridge arm switch Q2, and discharge the junction capacitance of the upper bridge arm switch Q1.
[0110] In this embodiment, the second set voltage is determined based on the input voltage of the actual bridge switch circuit 101, and the second set voltage is greater than the first set voltage. Upon entering the third mode, the resonant current is positive, and the lower bridge arm switch Q2 achieves ZVS turn-on. The resonant current flows through the lower bridge arm switch Q2 to charge the resonant capacitor C. The resonant current gradually decreases to zero and then increases in the opposite direction. When the voltage of the resonant capacitor increases to reach the second set voltage, the resonant current becomes a negative current.
[0111] In this embodiment, after entering the third dead zone unit, the resonant capacitor voltage reaches a balanced state. After the lower bridge arm switch Q2 is turned off, the circuit will charge the junction capacitance of the lower bridge arm switch Q2 and discharge the junction capacitance of the upper bridge arm switch Q1.
[0112] Preferably, the second set voltage is greater than twice the first set voltage.
[0113] In one embodiment, it further includes:
[0114] The continued startup unit is used to determine that the current working state is the continued startup state and enter the fourth mode;
[0115] The fourth mode unit is used to turn on the upper bridge arm switch Q1 with zero voltage in the fourth mode.
[0116] In this embodiment, the resonant capacitor voltage has reached a balanced state. According to the operation signal, if the next operation is required, the working state is the continued start state, and then it will enter the fourth mode unit. Since the junction capacitance of the upper bridge arm switch Q1 is discharged in this embodiment, the upper bridge arm switch Q1 can be turned on with zero voltage.
[0117] It should be noted that for details not disclosed in the start-up control device of the LLC resonant circuit in the embodiments of the present invention, please refer to the details disclosed in the start-up control method of the LLC resonant circuit in the embodiments of the present invention, which will not be repeated here.
[0118] Thirdly, embodiments of the present invention provide a computer storage medium storing a computer program, which, when executed by a processor, implements the steps of the startup control method for the LLC resonant circuit described above.
[0119] It should be noted that for details not disclosed in the computer storage medium in the embodiments of the present invention, please refer to the details disclosed in the startup control method of the LLC resonant circuit in the embodiments of the present invention, which will not be repeated here.
[0120] The above description of the embodiments is only for the purpose of helping to understand the inventive concept of the present invention and is not intended to limit the present invention. For those skilled in the art, any modifications, equivalent substitutions, improvements, etc., made without departing from the principle of the present invention should be included within the protection scope of the present invention.
Claims
1. A startup control method for an LLC resonant circuit, wherein the LLC resonant circuit comprises a bridge switching circuit, a resonant circuit, a transformer, and a rectifier filter circuit connected in series, wherein, The bridge switching circuit includes an upper bridge arm switching transistor and a lower bridge arm switching transistor, and the resonant circuit includes a resonant inductor and a resonant capacitor. The startup control method for the LLC resonant circuit includes the following steps: The current working status is confirmed as "started," and the system enters the first mode. In the first mode, the resonant capacitor voltage is set to zero; In the second mode, the upper bridge arm switch is turned on to charge the resonant capacitor, so that the resonant inductor current reaches the maximum resonant inductor current value and the resonant capacitor voltage reaches the first set voltage. In the third mode, the lower bridge arm switch is turned on to charge the resonant capacitor, so that the voltage of the resonant capacitor reaches the second set voltage. Wherein, the second set voltage is greater than the first set voltage; In the first mode, setting the resonant capacitor voltage to zero includes: Turn on the lower bridge arm switch to release the resonant capacitor voltage to the load output terminal, thus setting the resonant capacitor voltage to zero. The lower bridge arm switch is turned off, and the second mode is entered after the first termination condition is met.
2. The start-up control method for the LLC resonant circuit according to claim 1, characterized in that, In the second mode, charging the resonant capacitor to bring the resonant inductor current to its maximum value and bringing the resonant capacitor voltage to a first set voltage includes: Turn on the upper bridge arm switch, charge the resonant capacitor through the resonant inductor, so that the resonant inductor current reaches the maximum resonant inductor current value, and the resonant capacitor voltage reaches the first set voltage; The upper bridge arm switch is turned off, the junction capacitance of the upper bridge arm switch is charged, the junction capacitance of the lower bridge arm switch is discharged, and the third mode is entered after the second termination condition is met.
3. The start-up control method for the LLC resonant circuit according to claim 1, characterized in that, In the third mode, charging the resonant capacitor to bring its voltage to a second preset voltage includes: The lower bridge arm switch is turned on, thereby charging the resonant capacitor so that the voltage of the resonant capacitor reaches the second set voltage. Turn off the lower bridge arm switch, charge the junction capacitance of the lower bridge arm switch, and discharge the junction capacitance of the upper bridge arm switch.
4. The start-up control method for the LLC resonant circuit according to claim 1, characterized in that, Also includes: The current working status is determined to be "continue startup," and the system will enter the fourth mode. In the fourth mode, the upper bridge arm switch is turned on with zero voltage.
5. The start-up control method for the LLC resonant circuit according to claim 1, characterized in that, In the first mode, setting the resonant capacitor voltage to zero includes: During the first time period, the lower bridge arm switch is turned on to release the resonant capacitor voltage to the load output terminal, thereby setting the resonant capacitor voltage to zero. During the second time period, the lower bridge arm switch is turned off, and the second mode is entered after the second time period ends.
6. The start-up control method for the LLC resonant circuit according to claim 1, characterized in that, In the second mode, charging the resonant capacitor to bring the resonant inductor current to its maximum value and bringing the resonant capacitor voltage to a first set voltage includes: During the third time period, the upper bridge arm switch is turned on, and the resonant capacitor is charged through the resonant inductor, so that the resonant inductor current reaches the maximum resonant inductor current value and the resonant capacitor voltage reaches the first set voltage. During the fourth time period, the upper bridge arm switch is turned off, the junction capacitance of the upper bridge arm switch is charged, the junction capacitance of the lower bridge arm switch is discharged, and the third mode is entered after the fourth time period ends.
7. The start-up control method for the LLC resonant circuit according to claim 1, characterized in that, In the third mode, charging the resonant capacitor to bring its voltage to a second preset voltage includes: During the fifth time period, the lower bridge arm switch is turned on, thereby charging the resonant capacitor so that the voltage of the resonant capacitor reaches the second set voltage. During the sixth time period, the lower bridge arm switch is turned off, the junction capacitance of the lower bridge arm switch is charged, and the junction capacitance of the upper bridge arm switch is discharged.
8. A start-up control device for an LLC resonant circuit, wherein the LLC resonant circuit comprises a bridge switching circuit, a resonant circuit, a transformer, and a rectifier filter circuit connected in series, wherein, The bridge switching circuit includes an upper bridge arm switching transistor and a lower bridge arm switching transistor, and the resonant circuit includes a resonant inductor and a resonant capacitor. The start-up control device for the LLC resonant circuit includes: The start determination unit is used to determine that the current working state is the start state and enter the first mode; The first mode unit is used to set the resonant capacitor voltage to zero in the first mode. The second mode unit is used to charge the resonant capacitor in the second mode, so that the resonant inductor current reaches the maximum current value of the resonant inductor, and so that the resonant capacitor voltage reaches the first set voltage. The third mode unit is used to charge the resonant capacitor in the third mode so that the voltage of the resonant capacitor reaches the second set voltage. Wherein, the second set voltage is greater than the first set voltage; In the first mode, the resonant capacitor voltage is set to zero, including: Turn on the lower bridge arm switch to release the resonant capacitor voltage to the load output terminal, thus setting the resonant capacitor voltage to zero. The lower bridge arm switch is turned off, and the second mode is entered after the first termination condition is met.
9. A computer storage medium, characterized in that, The computer storage medium stores a computer program, which, when executed by a processor, implements the steps of the start-up control method for the LLC resonant circuit as described in any one of claims 1 to 7.