Resonant boost circuit and control method and device thereof

Abstract

The application provides a resonant boost circuit and a control method and device thereof. The resonant boost circuit comprises an LC resonant circuit, a boost transformer and a frequency detection circuit. The LC resonant circuit is connected to a primary side coil of the boost transformer and converts direct current into alternating current with a preset frequency according to a control signal input by a master control chip. The boost transformer is used for boosting the alternating current output by the LC resonant circuit to provide a driving voltage for a load connected to a secondary side coil thereof. The frequency detection circuit is used for detecting the current direction and change cycle information of the alternating current of the primary side coil or the secondary side coil of the boost transformer and converting the same into a weak electric signal output to the master control chip, so that the master control chip adjusts the control signal of the LC resonant circuit to make the frequency of the alternating current output by the LC resonant circuit meet the resonant frequency. The application solves the problem of large frequency detection error in the resonant state and has the advantages of simple method, no loss, small error and high safety.

Description

Technical Field

[0001] This invention belongs to the field of electronic circuit technology, and particularly relates to a resonant boost circuit and its control method and device. Background Technology

[0002] In current electronic circuit technology, the use of the LC resonance principle to invert low-voltage DC to high-voltage AC has been applied in various fields. In this resonant circuit, DC is inverted into AC by controlling the on / off time of switching elements. Specifically, the main control chip provides PWM waves with preset duty cycles and frequencies to the switching elements to control their on / off states. After converting DC to AC at a preset frequency, a primary voltage boost is achieved by the resonance between the capacitor and the inductor coil on the primary side of the step-up transformer. However, because the load connected to the secondary side of the step-up transformer generates a high-voltage discharge at startup, with a high frequency and instability, it cannot perfectly initiate oscillation after power-on.

[0003] In existing technologies, to detect the resonant state and frequency, an attenuation bar is typically connected to the secondary side of a step-up transformer and observed using an oscilloscope. However, this detection method has the following drawbacks: the operation of observing the oscillation frequency using an attenuation bar and an oscilloscope is relatively complex; the attenuation bar itself has inductive and capacitive characteristics, which, at high frequencies, are equivalent to being connected as a load, affecting the test results and causing significant errors; and the high-voltage attenuation bar is connected in parallel to the transformer and then to the oscilloscope during the measurement process, which poses a significant safety hazard since the voltage of a step-up transformer can reach several kilovolts. Summary of the Invention

[0004] The present invention provides a resonant boost circuit and its control method and device to solve the problems mentioned in the background art, such as complex operation, large error and safety hazards in the means of observing and adjusting the resonant state.

[0005] To achieve the above objectives, the specific technical solution of the resonant boost circuit of the present invention is as follows:

[0006] One aspect of the present invention provides a resonant boost circuit.

[0007] Includes an LC resonant circuit, a step-up transformer, and a frequency detection circuit.

[0008] The LC resonant circuit is connected to the primary winding of the step-up transformer and converts the DC power output from the DC power supply into AC power of a preset frequency according to the control signal input by the main control chip.

[0009] The step-up transformer is used to step up the AC output of the LC resonant circuit to provide a driving voltage for the load connected to its secondary coil.

[0010] The frequency detection circuit is located on the primary or secondary side of the step-up transformer. It is used to detect the current direction and cycle information of the AC current in the primary or secondary coil of the step-up transformer, and convert the current direction and cycle information into a weak signal and output it to the main control chip. The main control chip adjusts the control signal of the LC resonant circuit according to the current direction and cycle information so that the frequency of the AC current output by the LC resonant circuit meets the resonant frequency.

[0011] Furthermore, the frequency detection circuit includes a detection coil and a current detection branch connected in parallel with the detection coil. The detection coil is located on the primary or secondary side of the step-up transformer and is used to sense the current direction and change period information of the AC current in the primary or secondary coil of the step-up transformer. The current detection branch is used to convert the current direction and change period information of the AC current into a weak current signal and output it to the main control chip.

[0012] Furthermore, the current detection branch includes a forward current detection branch, which includes a first optocoupler. The input anode of the first optocoupler is connected to the first port of the detection coil, the input cathode is connected to the second port of the detection coil, the output collector is connected to a low-voltage power supply, and the output emitter is grounded. A first output port is led out between the output collector of the first optocoupler and the connection terminal of the low-voltage power supply. When the voltage at the first port of the detection coil is higher than that at the second port, the output terminal of the first optocoupler is internally conductive, and the first output port outputs a low-level signal.

[0013] Further, the current detection branch includes a negative current detection branch, which includes a second optocoupler. The input anode of the second optocoupler is connected to the second port of the detection coil, the input cathode is connected to the first port of the detection coil, the output collector is connected to a low-voltage power supply, and the output emitter is grounded. A second output port is led out between the output collector of the second optocoupler and the connection terminal of the low-voltage power supply. When the voltage at the second port of the detection coil is higher than that at the first port, the output terminal of the second optocoupler is internally conductive, and the second output port outputs a low-level signal.

[0014] Furthermore, the forward current detection branch also includes a first resistor, which is connected between the input cathode of the first optocoupler and the second port of the detection coil.

[0015] Furthermore, the forward current detection branch also includes a second resistor, which is connected between the output emitter terminal of the first optocoupler and ground.

[0016] Furthermore, the negative current detection branch also includes a third resistor, which is connected between the input cathode of the second optocoupler and the first port of the detection coil.

[0017] Furthermore, the negative current detection branch also includes a fourth resistor, which is connected between the output emitter terminal of the second optocoupler and ground.

[0018] Furthermore, the LC resonant circuit includes a first switching element, a second switching element, a first inductor, a second inductor, and a first capacitor. The positive terminal of the DC power supply is connected in series with the first inductor and then connected to the current input terminal of the electrical terminal of the first switching element and the first port of the primary winding of the step-up transformer. The negative terminal of the DC power supply is connected in series with the second inductor and then connected to the current output terminal of the electrical terminal of the second switching element and the second port of the primary winding of the step-up transformer. The current output terminal of the electrical terminal of the first switching element and the current input terminal of the electrical terminal of the second switching element are respectively grounded. The first capacitor is connected in parallel with the primary winding of the step-up transformer. The main control chip controls the on-off time of the first and second switching elements by inputting PWM control signals to the enable terminals of the first and second switching elements respectively, so as to control the LC resonant circuit to convert the DC power output by the DC power supply into AC power of a preset frequency.

[0019] Furthermore, the current detection branch includes a second forward current detection branch, which includes a first diode, a third switching element, and a fifth resistor. The anode of the first diode is connected to the first port of the detection coil, and the cathode of the first diode is connected to the enable terminal of the third switching element and one end of the fifth resistor. The other end of the fifth resistor is connected to the second port of the detection coil, which is grounded. The current input terminal of the electrical terminal of the third switching element is connected to a low-voltage power supply, and the current output terminal of the electrical terminal of the third switching element is grounded. A third output port is led out between the current input terminal of the electrical terminal of the third switching element and the connection terminal of the low-voltage power supply. When the voltage at the first port of the detection coil is higher than that at the second port, the first diode conducts, the enable terminal of the third switching element receives a high level input, the electrical terminal of the third switching element conducts, and the third output port outputs a low-level signal.

[0020] Furthermore, the frequency detection circuit includes a sixth resistor, which is connected in series between the detection coil and the current detection branch.

[0021] In another aspect, the present invention provides a control method for the above-described resonant boost circuit, the method comprising:

[0022] Obtain information on the direction and cycle of alternating current in the primary or secondary coil of the step-up transformer;

[0023] Based on the information about the direction and period of the alternating current, determine whether the frequency of the alternating current direction output by the LC resonant circuit is consistent with the resonant frequency.

[0024] If they are inconsistent, the control signal of the LC resonant circuit is adjusted so that the frequency of the AC output by the LC resonant circuit meets the resonant frequency.

[0025] Furthermore, the information on the direction and cycle of the alternating current includes: the duration of the first cycle when the alternating current is in the positive direction and the duration of the second cycle when the alternating current is in the negative direction.

[0026] The step of determining whether the frequency of the alternating current direction change of the LC resonant circuit output from the AC circuit is consistent with the resonant frequency based on the current direction and change period information of the AC circuit includes:

[0027] Determine whether the duration of the first cycle is equal to the duration of the second cycle;

[0028] If they are equal, then determine whether the sum of the first cycle duration and the second cycle duration is equal to the resonant period of the LC resonant circuit;

[0029] If equal, then the frequency of the change in the direction of the AC current output by the LC resonant circuit is consistent with the resonant frequency.

[0030] In another aspect, the present invention provides a control device for the above-described resonant boost circuit, the device comprising:

[0031] The acquisition module is used to acquire information on the direction and cycle of the alternating current in the primary or secondary coil of the step-up transformer.

[0032] The judgment module is used to determine whether the frequency of the change in the direction of the AC current output by the LC resonant circuit is consistent with the resonant frequency, based on the current direction and change period information of the AC current.

[0033] The control module is used to adjust the control signal of the LC resonant circuit so that the frequency of the AC output by the LC resonant circuit satisfies the resonant frequency if there is a discrepancy.

[0034] This invention provides a resonant boost circuit and its control method and apparatus. It utilizes a frequency detection circuit to detect the current direction and cycle information of the AC current in the primary or secondary coil of a boost transformer, and converts this information into a weak electrical signal, which is output to the main control chip. The main control chip then adjusts the control signal of the LC resonant circuit based on the AC current direction and cycle information to ensure that the frequency of the AC current output by the LC resonant circuit meets the resonant frequency. This invention solves the problem of large detection errors in resonance state and frequency. The detection method is simple, lossless, has small errors, and high safety. Furthermore, the resonance state adjustment operation is simple.

[0035] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0036] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0037] Figure 1 A structural block diagram of a resonant boost circuit provided in one embodiment of the present invention;

[0038] Figure 2 A circuit diagram of a resonant boost circuit provided in one embodiment of the present invention;

[0039] Figure 3 The waveform of the AC current output by the LC resonant circuit corresponding to the PWM2 signal output by the main control chip;

[0040] Figure 4 A circuit diagram of a resonant boost circuit provided in another embodiment of the present invention;

[0041] Figure 5 A circuit diagram of a frequency detection circuit provided in another embodiment of the present invention;

[0042] Figure 6 A flowchart illustrating a control method for a resonant boost circuit provided in an embodiment of the present invention;

[0043] Figure 7 This is a schematic diagram of the control device for a resonant boost circuit according to an embodiment of the present invention.

[0044] Explanation of markings in the diagram:

[0045] 101. LC resonant circuit; 102. Load; 103. Frequency detection circuit;

[0046] 701. Acquisition module; 702. Judgment module; 703. Control module. Detailed Implementation

[0047] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0049] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Furthermore, the technical features involved in the different embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0050] Figure 1 A schematic diagram of a resonant boost circuit according to an embodiment is shown, such as Figure 1As shown, the resonant boost circuit of this embodiment includes an LC resonant circuit 101, a boost transformer T1, and a frequency detection circuit 103. The LC resonant circuit 101 is connected to the primary coil of the boost transformer T1 and converts the DC power output from the DC power supply into AC power of a preset frequency according to the control signal input by the main control chip. The boost transformer T1 is used to boost the AC power output by the LC resonant circuit 101 to provide a driving voltage for the load 102 connected to its secondary coil. The frequency detection circuit 103 is located on the primary or secondary side of the boost transformer T1 and is used to detect the current direction and change period information of the AC power in the primary or secondary coil of the boost transformer T1. It converts the current direction and change period information of the AC power into a weak signal and outputs it to the main control chip so that the main control chip can adjust the control signal of the LC resonant circuit 101 according to the current direction and change period information of the AC power so that the frequency of the AC power output by the LC resonant circuit meets the resonant frequency.

[0051] It should be noted that the main control chip in this embodiment of the invention is a control chip that controls the normal operation of the resonant boost circuit. It controls the switching elements of the LC resonant circuit 101 to turn on and off by outputting a PWM square wave signal. It also determines whether the frequency of the AC output from the LC resonant circuit 101 meets the resonant frequency by receiving a weak electrical signal from the frequency detection circuit 103. Therefore, it adjusts the frequency and duty cycle of the output PWM square wave signal to adjust the frequency of the AC output from the LC resonant circuit 101 to meet the resonant frequency. In this embodiment, the weak electrical signal output by the frequency detection circuit 103 can be directly transmitted to the main control chip, or it can be transmitted first to a dedicated receiving chip, which processes the data before transmitting it to the main control chip. This invention does not limit the specific transmission method.

[0052] Furthermore, the frequency detection circuit 103 includes a detection coil and a current detection branch connected in parallel with the detection coil. The detection coil is located on the primary or secondary side of the step-up transformer T1, forming another transformer T2 with the core of the step-up transformer. It is used to sense the direction and period of change of the AC current in the primary or secondary coil of the step-up transformer T1. The current detection branch is used to convert the direction and period of change of the AC current into a weak signal and output it to the main control chip. It should be noted that, in order to improve the safety of the measurement, the number of turns of the detection coil can be set to be less than the number of turns of the primary or secondary coil of the step-up transformer to achieve a voltage reduction effect. Alternatively, the number of turns can be set according to the needs of the thread engineering, which is not limited in this invention.

[0053] To more clearly describe the circuit structure of the resonant boost circuit in the embodiments of the present invention, see attached... Figure 2A schematic diagram of a resonant boost circuit according to another embodiment of the present invention is shown. Figure 2 As can be seen, in the LC resonant circuit of this embodiment, the first switching element Q1, the second switching element Q2, the first inductor L1, the second inductor L2, and the first capacitor C are shown. In the accompanying drawings of this embodiment, the switching element is a MOSFET. However, switching elements with corresponding switching performance can also be selected according to requirements. This invention is not limited in its comparison with the present invention. The following description uses the accompanying drawings as an example. Figure 2 Taking the LC resonant circuit given in the example as an example: The positive terminal of the DC power supply is connected in series with the first inductor L1 and then connected to the current input terminal of the electrical terminal of the first switching element Q1 (i.e., the drain of the first MOSFET) and the first port of the primary winding of the boost transformer. The negative terminal of the DC power supply is connected in series with the second inductor L2 and then connected to the current output terminal of the electrical terminal of the second switching element Q2 (i.e., the gate of the second MOSFET) and the second port of the primary winding of the boost transformer. The current output terminal of the electrical terminal of the first switching element Q1 (i.e., the gate of the first MOSFET) and the current input terminal of the electrical terminal of the second switching element (i.e., the drain of the second MOSFET) are respectively grounded. The first capacitor C is connected in parallel with the primary winding of the boost transformer. The main control chip controls the on and off times of the first switching element Q1 and the second switching element Q2 by inputting PWM control signals to the enable terminal of the first switching element Q1 (i.e., the source of the first MOSFET) and the enable terminal of the second switching element Q2 (i.e., the source of the second MOSFET), so as to control the LC resonant circuit 101 to convert the DC power output by the DC power supply into AC power of a preset frequency.

[0054] Specifically, the main control chip inputs a first control signal PWM1 to the enable terminal of the first switching element Q1 and a second control signal PWM2 to the enable terminal of the second switching element Q2 to control the conduction and cutoff of the first and second switching elements Q1 and Q2. PWM1 and PWM2 are square wave signals. When PWM1 is high, turning on the first switching element Q1, and when PWM2 is low, turning off the second switching element Q2, the DC power supply charges the first capacitor C through the second inductor L2. When PWM1 is low, turning off the first switching element Q1, and when PWM2 is high, turning on the second switching element Q2, the DC power supply charges the first capacitor C through the first inductor L2. Since the first capacitor C is connected in parallel with the primary winding of the step-up transformer T1, they cycle through charging and discharging, generating parallel resonance, resulting in a sinusoidal voltage across the first capacitor C. This converts the DC power output from the DC power supply into AC power of a preset frequency, such as... Figure 3 The waveform of the AC power output by the LC resonant circuit corresponding to the PWM2 signal output by the main control chip is shown.

[0055] In actual circuit operation, various interference factors cause the frequency of the AC output from the LC resonant circuit 101 to fail to meet the resonant frequency, resulting in the resonant boost circuit malfunctioning. Therefore, this embodiment of the invention uses a frequency detection circuit 103 to monitor the frequency of the AC output from the LC resonant circuit 101 in real time. This allows the main control chip to adjust the duty cycle and / or frequency of the control signals of the LC resonant circuit 101 (i.e., the duty cycle and frequency of PWM1 and PWM2) based on the current direction and cycle information of the AC output from the LC resonant circuit 101, so that the frequency of the AC output from the LC resonant circuit 101 meets the resonant frequency.

[0056] Specifically, the frequency detection circuit 103 includes a detection coil and a current detection branch connected in parallel with the detection coil. The detection coil is located on the primary or secondary side of the step-up transformer and is used to sense the current direction and change period information of the AC current in the primary or secondary coil of the step-up transformer. The current detection branch is used to convert the current direction and change period information of the AC current into a weak current signal and output it to the main control chip.

[0057] Furthermore, the current detection branch includes a forward current detection branch, which includes a first optocoupler U1. The input anode of the first optocoupler U1 is connected to the first port A of the detection coil, the input cathode is connected to the second port B of the detection coil, the output collector is connected to a low-voltage power supply, and the output emitter is grounded. A first output port I / O1 is led out between the output collector of the first optocoupler U1 and the connection terminal of the low-voltage power supply. When the voltage at the first port A of the detection coil is higher than that at the second port, the output terminal of the first optocoupler U1 is internally turned on, and the first output port I / O1 outputs a low-level signal. When the voltage at the first port A of the detection coil is lower than that at the second port, the output terminal of the first optocoupler U1 is internally turned off, and the first output port I / O1 outputs a high-level signal.

[0058] Furthermore, the current detection branch includes a negative current detection branch, which includes a second optocoupler U2. The input anode of the second optocoupler U2 is connected to the second port B of the detection coil, the input cathode is connected to the first port A of the detection coil, the output collector is connected to a low-voltage power supply, and the output emitter is grounded. A second output port I / O1 is led out between the output collector of the second optocoupler and the connection terminal of the low-voltage power supply. When the voltage at the second port B of the detection coil is higher than that at the first port, the output terminal of the second optocoupler is internally turned on, and the second output port I / O1 outputs a low-level signal. When the voltage at the first port A of the detection coil is higher than that at the second port, the output terminal of the second optocoupler U2 is internally turned off, and the second output port I / O1 outputs a high-level signal.

[0059] It should be noted that the high-level signal and low-level signal mentioned above are both weak signals. The high-level signal is a signal close to the amplitude of the low-voltage power supply. The amplitude of the low-voltage power supply can be 5V as shown in the attached figure, or it can be other low-level signals according to the input signal requirements of the main control chip. The low-level signal is a signal close to zero level.

[0060] Furthermore, the current detection branch in this embodiment of the invention may include one or both of a positive current detection branch and a negative current detection branch, which can be specifically set according to the control progress. In the above embodiment, when the first output port I / O1 outputs a low-level signal, the direction of the AC current output by the LC resonant circuit 101 can be considered positive; when the second output port I / O1 outputs a low-level signal, the direction of the AC current output by the LC resonant circuit 101 is considered negative. At this time, the first cycle duration of positive conduction is recorded as t1, and the second cycle duration of negative conduction is recorded as t2. Only when t1 = t2 and t1 + t2 = T, where T is the reciprocal of the resonant frequency f, i.e., the resonant period, can the current detection branch in this embodiment of the invention include only a positive current detection branch or only a negative current detection branch. Taking only the positive current detection branch as an example, the first cycle duration of positive conduction when the first output port I / O1 outputs a low-level signal can be taken as t1, and the second cycle duration of negative conduction when the first output port I / O1 outputs a high-level signal can be taken as t2.

[0061] Furthermore, disregarding the error caused by the optocoupler's need to operate only after the voltage crosses zero and exceeds a certain amplitude for switching on and off, only one current detection branch can be selected. Taking the positive current detection branch as an example, when the first output port I / O1 outputs a low-level signal, the direction of the AC current output by the LC resonant circuit 101 is considered positive; when the first output port I / O1 outputs a high-level signal, the direction of the AC current output by the LC resonant circuit 101 is considered negative. By recording the signal output by the first output port I / O1, the direction and period of the AC current output by the LC resonant circuit 101 can be determined.

[0062] Furthermore, to improve circuit safety, resistors can be inserted in series in each branch to limit the current and prevent excessive current from damaging the power devices. For details, please refer to the appendix. Figure 4 The positive current detection branch also includes a first resistor R1, which is connected between the input cathode of the first optocoupler U1 and the second port B of the detection coil. The positive current detection branch also includes a second resistor R2, which is connected between the output emitter of the first optocoupler U1 and ground. The negative current detection branch also includes a third resistor R3, which is connected between the input cathode of the second optocoupler U2 and the first port A of the detection coil. The negative current detection branch also includes a fourth resistor R4, which is connected between the output emitter of the second optocoupler and ground.

[0063] In addition, the current in both the positive current measurement branch and the negative current detection branch can be limited by connecting a sixth resistor R6 (not shown in the figure) in series between the detection coil and the current detection branch. In this case, the first resistor R1 and the third resistor R6 can be omitted.

[0064] Furthermore, when the number of turns of the detection coil is sufficiently small and the voltage across the current detection branch is sufficiently small, and the signal interference to the central control chip is negligible, the current detection branch in this embodiment of the invention may further include the following: Figure 5The second forward current measurement branch shown includes a first diode D1, a third switching element Q3, and a fifth resistor R5. The anode of the first diode D1 is connected to the first port A of the detection coil, and the cathode of the first diode D1 is connected to the enable terminal of the third switching element Q3 and one end of the fifth resistor R5. The other end of the fifth resistor R5 is connected to the second port B of the detection coil, which is grounded. The current input terminal of the electrical terminal of the third switching element Q3 is connected to a low-voltage power supply, and the current output terminal of the electrical terminal of the third switching element Q3 is grounded. A third output port I / O3 is led out between the current input terminal of the electrical terminal of component Q3 and the connection terminal of the low-voltage power supply. When the voltage at the first port A of the detection coil is higher than that at the second port, the first diode D1 is turned on, the enable terminal of the third switching element Q3 receives a high level input, the electrical terminal of the third switching element Q3 is turned on, and the third output port I / O3 outputs a low level signal. When the voltage at the second port B of the detection coil is higher than that at the first port, the first diode D1 is turned off, the enable terminal of the third switching element Q3 receives a low level input, the electrical terminal of the third switching element Q3 is turned off, and the third output port I / O3 outputs a high level signal. It should be noted that since the current detection branch in this embodiment only includes the second positive current detection branch, the first cycle duration of the positive conduction when the first output port I / O1 outputs a low level signal is t1, and the second cycle duration of the negative conduction when the first output port I / O1 outputs a high level signal is t2.

[0065] It should be noted that the third switching element Q3 in this embodiment of the invention is an NPN transistor, but other switching elements or PNP transistors can also be selected as needed. Figure 5 As can be seen from the NPN transistor, the enable terminal of the third switching element Q3 is the base of the NPN transistor, the current input terminal of the electrical terminal of the third switching element Q3 is the collector of the NPN transistor, and the current output terminal of the electrical terminal of the third switching element Q3 is the emitter of the NPN transistor.

[0066] The resonant boost circuit of this invention can not only detect the current direction and period of change of the output current of the LC resonant circuit 101 when the circuit starts oscillating, so that the main control chip can adjust according to the frequency of the output current of the LC resonant circuit 101 to achieve perfect oscillation, but also adjust the control signal in real time during circuit operation to keep the resonant boost circuit in the optimal resonant state in real time.

[0067] Another aspect of the present invention provides a control method for the above-described resonant boost circuit, such as... Figure 6As shown, the control method for a resonant boost circuit provided in this embodiment of the invention includes the following steps:

[0068] S1. Obtain information on the direction and cycle of AC current in the primary or secondary coil of the step-up transformer.

[0069] In this embodiment of the invention, the current direction and change period information of the alternating current includes: the first period duration t1 when the alternating current is positive and the second period duration t2 when the alternating current is negative.

[0070] S2. Based on the current direction and change period information of the AC power, determine whether the frequency of the change of the AC power output by the LC resonant circuit 101 is consistent with the resonant frequency.

[0071] In this embodiment of the invention, determining whether the frequency of the change in the direction of the AC current output by the LC resonant circuit 101 is consistent with the resonant frequency based on the current direction and change period information of the AC current includes: determining whether the first period duration t1 is equal to the second period duration t2; if they are equal, determining whether the sum of the first period duration t1 and the second period duration t2 is equal to the resonant period of the LC resonant circuit 101; if they are equal, then the frequency of the change in the direction of the AC current output by the LC resonant circuit 101 is consistent with the resonant frequency.

[0072] S3. If they are inconsistent, adjust the control signal of the LC resonant circuit 101 so that the frequency of the AC power output by the LC resonant circuit 101 meets the resonant frequency.

[0073] In this embodiment of the invention, the duty cycle and / or frequency of the PWM1 square wave signal and the PWM2 square wave signal are adjusted so that the frequency of the AC power output by the LC resonant circuit 101 satisfies the resonant frequency.

[0074] For the sake of simplicity, the method embodiments are described as a series of actions. However, those skilled in the art should understand that the embodiments of the present invention are not limited to the described order of actions, because according to the embodiments of the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions involved are not necessarily essential to the embodiments of the present invention.

[0075] Figure 7 A schematic diagram of the control device for the resonant boost circuit provided in an embodiment of the present invention is shown, such as... Figure 7 As shown, a control device for a resonant boost circuit according to an embodiment of the present invention includes an acquisition module 701, a judgment module 702, and a control module 703, wherein:

[0076] The acquisition module 701 is used to acquire the current direction and change period information of the AC current in the primary winding or secondary winding of the step-up transformer;

[0077] The judgment module 702 is used to determine whether the frequency of the change of the current direction of the AC power output by the LC resonant circuit is consistent with the resonant frequency based on the current direction and change period information of the AC power.

[0078] The control module 703 is used to adjust the control signal of the LC resonant circuit if there is a discrepancy so that the frequency of the AC output by the LC resonant circuit meets the resonant frequency.

[0079] As the device embodiment is basically similar to the method embodiment, the description is relatively simple, and relevant parts can be found in the description of the method embodiment.

[0080] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0081] This invention provides a resonant boost circuit and its control method and apparatus. It utilizes a frequency detection circuit to detect the current direction and cycle information of the AC current in the primary or secondary coil of a boost transformer, and converts this information into a weak electrical signal, which is output to the main control chip. The main control chip then adjusts the control signal of the LC resonant circuit based on the AC current direction and cycle information to ensure that the frequency of the AC current output by the LC resonant circuit meets the resonant frequency. This invention solves the problem of large detection errors in resonance state and frequency. The detection method is simple, lossless, has small errors, and high safety. Furthermore, the resonance state adjustment operation is simple.

[0082] Those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of the invention and form different embodiments. For example, in the claims, any of the claimed embodiments can be used in any combination.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A resonant boost circuit, characterized by, The LC resonant circuit, the step-up transformer and the frequency detection circuit, The LC resonant circuit is connected to the primary side coil of the step-up transformer, and converts direct current output by a direct current power supply into alternating current of a preset frequency according to a control signal input by a master control chip; The step-up transformer is used for boosting the alternating current output by the LC resonant circuit, so as to provide a driving voltage for a load connected to the secondary side coil of the step-up transformer; The frequency detection circuit is arranged on the primary side or the secondary side of the step-up transformer, and is used for detecting the current direction and the change period information of the alternating current of the primary side coil or the secondary side coil of the step-up transformer, and converting the current direction and the change period information of the alternating current into a weak electric signal output to the master control chip, so that the master control chip adjusts the control signal of the LC resonant circuit according to the current direction and the change period information of the alternating current, so that the frequency of the alternating current output by the LC resonant circuit meets the resonant frequency. The frequency detection circuit comprises a detection coil and a current detection branch arranged in parallel with the detection coil, the detection coil is arranged on the primary side or the secondary side of the step-up transformer, and is used for sensing the current direction and the change period information of the alternating current of the primary side coil or the secondary side coil of the step-up transformer, and the current detection branch is used for converting the current direction and the change period information of the alternating current into a weak electric signal output to the master control chip.

2. The resonant boost circuit of claim 1, wherein, The current detection branch comprises a forward current detection branch, the forward current detection branch comprises a first optocoupler, an input anode end of the first optocoupler is connected to a first port of the detection coil, an input cathode end is connected to a second port of the detection coil, an output collector end is connected to a low-voltage power supply, and an output emitter end is grounded, a first output port is led out between the output collector end of the first optocoupler and a connection terminal of the low-voltage power supply, when the voltage of the first port of the detection coil is higher than that of the second port, the output end of the first optocoupler is internally conductive, and the first output port outputs a low-level signal.

3. The resonant boost circuit according to claim 1 or 2, characterized in that, The current detection branch comprises a negative current detection branch, the negative current detection branch comprises a second optocoupler, an input anode end of the second optocoupler is connected to the second port of the detection coil, an input cathode end is connected to the first port of the detection coil, an output collector end is connected to the low-voltage power supply, and an output emitter end is grounded, a second output port is led out between the output collector end of the second optocoupler and the connection terminal of the low-voltage power supply, when the voltage of the second port of the detection coil is higher than that of the first port, the output end of the second optocoupler is internally conductive, and the second output port outputs a low-level signal.

4. The resonant boost circuit of claim 2, wherein, The forward current detection branch further comprises a first resistor, and the first resistor is connected between the input cathode end of the first optocoupler and the second port of the detection coil.

5. The resonant boost circuit of claim 2, wherein, The forward current detection branch further comprises a second resistor, and the second resistor is connected between the output emitter end of the first optocoupler and the ground.

6. The resonant boost circuit of claim 3, wherein, The negative current detection branch further comprises a third resistor connected between the input cathode end of the second optocoupler and the first port of the detection coil.

7. The resonant boost circuit of claim 3, wherein, The negative current detection branch further comprises a fourth resistor connected between the output emitter end of the second optocoupler and the ground.

8. The resonant boost circuit of claim 1, wherein, The LC resonant circuit comprises a first switch element, a second switch element, a first inductor, a second inductor and a first capacitor. The positive pole of the direct current power supply is connected to the current input end of the electrically conductive terminal of the first switch element and the first port of the primary side coil of the step-up transformer after being connected in series with the first inductor. The negative pole of the direct current power supply is connected to the current output end of the electrically conductive terminal of the second switch element and the second port of the primary side coil of the step-up transformer after being connected in series with the second inductor. The current output end of the electrically conductive terminal of the first switch element and the current input end of the electrically conductive terminal of the second switch element are respectively grounded. The first capacitor is connected in parallel with the primary side coil of the step-up transformer. The main control chip inputs PWM control signals to the enable ends of the first switch element and the second switch element respectively to control the on-off time of the first switch element and the second switch element, so as to control the LC resonant circuit to convert the direct current output by the direct current power supply into alternating current of a preset frequency.

9. The resonant boost circuit of claim 1, wherein, The current detection branch comprises a second positive current detection branch. The second positive current detection branch comprises a first diode, a third switch element and a fifth resistor. The anode of the first diode is connected to the first port of the detection coil. The cathode of the first diode is connected to the enable end of the third switch element and one end of the fifth resistor. The other end of the fifth resistor is connected to the second port of the detection coil. The second port of the detection coil is grounded. The current input end of the electrically conductive terminal of the third switch element is connected to the low-voltage power supply. The current output end of the electrically conductive terminal of the third switch element is grounded. A third output port is led out between the current input end of the electrically conductive terminal of the third switch element and the connection terminal of the low-voltage power supply. When the voltage of the first port of the detection coil is higher than that of the second port, the first diode is turned on, the enable end of the third switch element inputs a high level, the electrically conductive terminal of the third switch element is turned on, and the third output port outputs a low level signal.

10. The resonant boost circuit of claim 3, wherein, The frequency detection circuit comprises a sixth resistor connected in series between the detection coil and the current detection branch.

11. A method of controlling a resonant boost circuit as claimed in any one of claims 1 to 10, characterized by, The method comprises: obtaining the current direction and variation cycle information of the alternating current of the primary side coil or the secondary side coil of the step-up transformer; determining whether the current direction variation frequency of the alternating current output by the LC resonant circuit is consistent with the resonant frequency according to the current direction and variation cycle information of the alternating current; if not, adjusting the control signal of the LC resonant circuit to make the frequency of the alternating current output by the LC resonant circuit meet the resonant frequency.

12. The control method of the resonant step-up circuit according to claim 11, characterized in that, The current direction and change period information of the alternating current includes: a first period length when the current of the alternating current is positive and a second period length when the current of the alternating current is negative; The judging whether the current direction change frequency of the alternating current output by the LC resonant circuit is consistent with the resonant frequency according to the current direction and change period information of the alternating current includes: judging whether the first period length is equal to the second period length; if equal, judging whether the sum of the first period length and the second period length is equal to the resonant period of the LC resonant circuit; if equal, the current direction change frequency of the alternating current output by the LC resonant circuit is consistent with the resonant frequency.

13. A control device for a resonant voltage boosting circuit as claimed in any one of claims 1 to 10, characterized in that, The device includes: an acquisition module, configured to acquire current direction and change period information of alternating current of the primary side coil or the secondary side coil of the step-up transformer; a judging module, configured to judge whether the current direction change frequency of the alternating current output by the LC resonant circuit is consistent with the resonant frequency according to the current direction and change period information of the alternating current; a control module, configured to adjust the control signal of the LC resonant circuit to make the frequency of the alternating current output by the LC resonant circuit satisfy the resonant frequency if not consistent.

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