A current type LLC start-up control circuit and control method, and electronic equipment

Abstract

The present application discloses a current-type LLC start-up control circuit and control method, and electronic equipment, the current-type LLC start-up control circuit includes: an inverter circuit, a resonant circuit power conversion circuit, and a main control circuit; the main control circuit is configured to: in the first start-up stage, generate a first control signal with a first signal frequency; in the second start-up stage, obtain the resonant current signal in the resonant circuit, use the first slope compensation slope to perform slope compensation on the set voltage signal to obtain a first feedback adjustment signal, so as to generate a second control signal using the first feedback adjustment signal and the resonant current signal; wherein the first slope compensation slope is a negative number, and increases successively in each second signal cycle of the second control signal; the inverter circuit is used to receive, and sequentially use the first control signal and the second control signal to adjust the first AC signal of its converted output. In the above manner, the current-type LLC start-up control circuit of the present application can effectively achieve smoother start-up control.

Description

Technical Field

[0001] The present application relates to the field of power supply technology, and in particular to a current-type LLC start-up control circuit and control method, and electronic equipment. Background Art

[0002] With the vigorous development of various electronic products, especially the advent of the cloud computing and big data era, the use of servers has increased dramatically, which has put forward higher requirements for efficient and reliable power supply systems. Among them, LLC resonant converters are usually configured in efficient and reliable power supply systems, and how to adopt better control strategies for LLC resonant converters has become one of the key factors affecting the performance of power supply systems.

[0003] However, existing LLC resonant converters usually have certain limitations in startup control, such as large starting current and poor monotonicity. These problems limit the performance of LLC resonant converters in certain specific application scenarios. Summary of the invention

[0004] The main technical problem solved by the present application is to provide a current-type LLC starting control circuit and control method, and electronic equipment, which can solve the problems of large starting current and poor monotonicity in starting control of the current-type LLC starting control circuit in the prior art, thereby limiting its application scenarios.

[0005] In order to solve the above technical problems, a technical solution adopted by the present application is: to provide a current-type LLC start-up control circuit, wherein the current-type LLC start-up control circuit includes: an inverter circuit, which is used to receive a first DC signal input to convert the first DC signal into a first AC signal; a resonant circuit, which is coupled to the inverter circuit, to receive a first AC signal sent by the inverter circuit, and adjust the first AC signal to a resonant current signal; an electric energy conversion circuit, which is coupled to the resonant circuit and is used to couple with a load circuit to receive a resonant current signal sent by the resonant circuit, and convert the resonant current signal into a second DC signal to output to the load circuit; a main control circuit, The inverter circuit and the resonant circuit are coupled, and the main control circuit is configured to: in the first startup stage, generate a first control signal with a first signal frequency; in the second startup stage, obtain the resonant current signal in the resonant circuit, use the first slope compensation slope to perform slope compensation on the set voltage signal to obtain a first feedback adjustment signal, and use the first feedback adjustment signal and the resonant current signal to generate a second control signal; wherein the first slope compensation slope is a negative number and increases sequentially in each second signal cycle of the second control signal; the inverter circuit is used to receive the first control signal and the second control signal, and sequentially use the first control signal and the second control signal to adjust the first AC signal.

[0006] The inverter circuit includes a first switch subcircuit and a second switch subcircuit, the first switch subcircuit is coupled to the second switch subcircuit, the resonant circuit and the main control circuit, the second switch subcircuit is coupled to the main control circuit, and the second control signal includes a first drive signal and a second drive signal; in the second startup stage, the main control circuit is configured to, in the first half of each second signal cycle, in response to the start time of the second startup stage or the second drive signal is adjusted from the first level to the second level, delay the first drive signal from the second level to the first level for a set time, delay the set time or simultaneously use the first slope compensation slope to perform slope compensation on the set voltage signal to obtain a first feedback adjustment signal signal, so that when the amplitude of the first feedback adjustment signal is less than or equal to the amplitude of the resonant capacitor voltage or the resonant current of the resonant current signal, the first drive signal is adjusted from the first level to the second level; in the second half of each second signal cycle, the first drive signal of each first half cycle is copied to obtain the second drive signal; wherein the main control circuit is also used to sequentially adjust the first slope compensation slope using a preset linear function or a preset arithmetic function in each second signal cycle; the first switch sub-circuit and the second switch sub-circuit are respectively used to receive the first drive signal and the second drive signal, and change the switch state under the action of the first drive signal and the second drive signal respectively, so as to adjust the first AC signal.

[0007] Wherein, the main control circuit is coupled to the power conversion circuit to obtain the second DC signal in the power conversion circuit, so as to switch to the third startup stage when it is determined that the voltage of the second DC signal is at a set voltage threshold; in the third startup stage, the main control circuit is configured to use a second slope compensation slope to perform slope compensation on the set voltage signal to obtain a second feedback adjustment signal, so as to generate a third control signal using the second feedback adjustment signal and the resonant current signal; wherein, the second slope compensation slope is the first slope compensation slope corresponding to the termination moment of the second startup stage; the first switch sub-circuit and the second switch sub-circuit are also used to receive the third control signal, and use the third control signal to adjust the first AC signal.

[0008] Among them, the first signal frequency is 90%-100% of the maximum resonant frequency of the resonant circuit; the duration of the first startup phase is a set multiple of the first signal period of the first control signal.

[0009] The resonant circuit includes a first resonant capacitor, a second resonant capacitor and a resonant inductor, wherein the first end of the first resonant capacitor is coupled to the first end of the first switch sub-circuit and the first end of the main control circuit, the second end of the first resonant capacitor is coupled to the first end of the second resonant capacitor, the second end of the main control circuit and the second end of the power conversion circuit, the second end of the second resonant capacitor is coupled to the second end of the second switch sub-circuit and the third end of the main control circuit, the first end of the resonant inductor is coupled to the second end of the first switch sub-circuit and the first end of the second switch sub-circuit, and the second end of the resonant inductor is coupled to the first end of the power conversion circuit; wherein the main control circuit is used to sample and obtain a first capacitor voltage signal between the first end and the second end of the first resonant capacitor and a second capacitor voltage signal between the first end and the second end of the second resonant capacitor, so as to calculate the resonant capacitor voltage using the first capacitor voltage signal and the second capacitor voltage signal.

[0010] Among them, the current-type LLC start-up control circuit also includes a switch freewheeling circuit, the switch freewheeling circuit includes a first freewheeling resistor, a second freewheeling resistor, a first freewheeling capacitor, a second freewheeling capacitor, a first diode, and a second diode. The first switch sub-circuit includes a first switch tube, and the second switch sub-circuit includes a second switch tube; wherein, the first end of the first freewheeling resistor is coupled to the first end of the first switch tube and the second end of the first diode, the second end of the first freewheeling resistor is coupled to the first end of the first freewheeling capacitor, the second end of the first freewheeling capacitor is coupled to the first end of the first diode, the second end of the first switch tube, the first end of the second switch tube, the first end of the second freewheeling resistor, and the second end of the second diode, the second end of the second freewheeling resistor is coupled to the first end of the second freewheeling capacitor, the second end of the second freewheeling capacitor is coupled to the second end of the second switch tube and the first end of the second diode, and the third end of the first switch tube and the third end of the second switch tube are coupled to the main control circuit.

[0011] The main control circuit includes a first proportional filter correction subcircuit, a second proportional filter correction subcircuit, a third proportional filter correction subcircuit, an isolation op amp subcircuit and a control subcircuit. The first proportional filter correction subcircuit is coupled to the first resonant capacitor and the isolation op amp subcircuit, the second proportional filter correction subcircuit is coupled to the second resonant capacitor and the isolation op amp subcircuit, the isolation op amp subcircuit is coupled to the control subcircuit, and the third proportional filter correction subcircuit is coupled to the power conversion circuit and the control subcircuit. The first proportional filter correction subcircuit is used to obtain a first capacitor voltage signal, and filter and correct the first capacitor voltage signal in sequence to obtain a first filtered signal. The second proportional filter correction subcircuit is used to obtain a first capacitor voltage signal, and filter and correct the first capacitor voltage signal in sequence to obtain a first filtered signal. The subcircuit is used to obtain the second capacitor voltage signal, and filter and correct the second capacitor voltage signal in sequence to obtain the second filtered signal; the third proportional filtering and correction subcircuit is used to obtain the second DC signal, and filter and correct the second DC signal in sequence to obtain the third filtered signal; the isolation amplifier subcircuit is used to receive the first filtered signal and the second filtered signal, so as to isolate, amplify and perform function calculation on the first filtered signal and the second filtered signal in sequence to obtain the resonant capacitor voltage; the control subcircuit is used to receive the resonant capacitor voltage and the third filtered signal, so as to use the resonant capacitor voltage and the third filtered signal to obtain the first drive signal, the second drive signal and the third control signal.

[0012] In order to solve the above technical problems, another technical solution adopted in the present application is: to provide a current-type LLC start-up control method, which includes: receiving a first DC signal input; converting the first DC signal into a first AC signal; adjusting the first AC signal into a resonant current signal; converting the resonant current signal into a second DC signal to output to an external load circuit; in a first start-up stage, generating a first control signal with a first signal frequency; using the first control signal to adjust the first AC signal; in a second start-up stage, using a first slope compensation slope to perform slope compensation on a set voltage signal to obtain a first feedback adjustment signal; using the first feedback adjustment signal and the resonant current signal to generate a second control signal; wherein the first slope compensation slope is a negative number, and increases successively in each second signal cycle of the second control signal; and using the second control signal to adjust the first AC signal.

[0013] Wherein, the second control signal includes a first drive signal and a second drive signal, and in the second startup stage, the step of using the first slope compensation slope to perform slope compensation on the set voltage signal to obtain the first feedback adjustment signal includes: in the second startup stage, in the first half cycle of each second signal cycle, in response to the start time of the second startup stage or the time when the second drive signal is adjusted from the first level to the second level, delaying the first drive signal from the second level to the first level for a set time; delaying the set time or simultaneously using the first slope compensation slope to perform slope compensation on the set voltage signal to obtain the first feedback adjustment signal; the step of using the first feedback adjustment signal and the resonant current signal to generate the second control signal includes: when the amplitude of the first feedback adjustment signal is less than or equal to the amplitude of the resonant capacitor voltage or the resonant current of the resonant current signal, adjusting the first drive signal from the first level to the second level; in the second half cycle of each second signal cycle, copying the first drive signal of each first half cycle to obtain the second drive signal; wherein, each first slope compensation slope of each second signal cycle has a functional relationship of a preset linear function or a preset arithmetic function; the step of using the second control signal to adjust the first AC signal includes: using the first drive signal and the second drive signal to adjust the first AC signal.

[0014] Among them, after the step of using the second control signal to adjust the first AC signal, it also includes: in the third startup stage, using the second slope compensation slope to perform slope compensation on the set voltage signal to obtain a second feedback adjustment signal; wherein the second slope compensation slope is the first slope compensation slope corresponding to the end time of the second startup stage; using the second feedback adjustment signal and the resonant current signal to generate a third control signal; using the third control signal to adjust the first AC signal.

[0015] To solve the above technical problems, another technical solution adopted in the present application is: to provide an electronic device, wherein the electronic device includes a shell and a current-type LLC start-up control circuit connected to the shell; wherein the current-type LLC start-up control circuit is a current-type LLC start-up control circuit as described in any of the above items.

[0016] The beneficial effects of the present application are as follows: different from the prior art, the inverter circuit in the current-type LLC starting control circuit provided by the present application is used to receive a first DC signal input to convert the first DC signal into a first AC signal; the resonant circuit adjusts the first AC signal into a resonant current signal; the power conversion circuit receives the resonant current signal sent by the resonant circuit, and converts the resonant current signal into a second DC signal to output to the load circuit; the main control circuit is configured to: in the first starting stage, generate a first control signal with a first signal frequency; in the second starting stage, obtain the resonant current signal in the resonant circuit, use the first slope compensation slope to perform slope compensation on the set voltage signal to obtain a first feedback adjustment signal, so as to generate a second control signal using the first feedback adjustment signal and the resonant current signal; wherein the first slope compensation slope is a negative number, and in the second control Each second signal cycle of the signal increases successively; the inverter circuit is used to receive the first control signal and the second control signal, and use the first control signal and the second control signal to adjust the first AC signal in turn, so that in the initial stage of the startup operation of the current-type LLC starting control circuit, that is, the initial stage of receiving the first DC signal input, when the instantaneous impact current is large, different control strategies are adopted in different starting stages to timely suppress the instantaneous impact current to avoid losses to the circuit; and different slope compensations are adopted to control the inverter circuit in different second signal cycles of the second control signal, effectively solving the problems of large starting current and poor monotonicity, so as to achieve smoother starting control, and while suppressing the instantaneous impact current, it also effectively guarantees a better gain effect of the resonant circuit, thereby ensuring better performance in a wider range of application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0018] Figure 1 It is a structural schematic diagram of the first embodiment of the current-type LLC start-up control circuit of the present application;

[0019] Figure 2 yes Figure 1 A schematic diagram of a voltage waveform of a second DC signal in the power conversion circuit;

[0020] Figure 3 yes Figure 1 A schematic diagram of a waveform of a first control signal sent by the main control circuit in the first startup phase;

[0021] Figure 4 yes Figure 1 A schematic diagram of a waveform of a second control signal sent by the central control circuit in the second startup phase;

[0022] Figure 5 yes Figure 1 A schematic diagram of a waveform of a third control signal sent by the central control circuit in the third startup phase;

[0023] Figure 6 It is a structural schematic diagram of a second embodiment of the current-type LLC start-up control circuit of the present application;

[0024] Figure 7 It is a flow chart of the first implementation mode of the current type LLC startup control method of the present application;

[0025] Figure 8 It is a flow chart of the second implementation mode of the current type LLC startup control method of the present application;

[0026] Fig. 9 It is a flow chart of the third implementation mode of the current type LLC startup control method of the present application;

[0027] Fig.10 It is a schematic diagram of the framework of an implementation scheme of the electronic device of the present application. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0029] The terms "first", "second" and "third" in this application are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Thus, the features defined as "first", "second" and "third" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. All directional indications (such as up, down, left, right, front, back...) in the implementation mode of this application are only used to explain the relative position relationship, movement, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication also changes accordingly. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally also includes steps or units that are not listed, or optionally also includes other steps or units inherent to these processes, methods, products or devices.

[0030] Reference to "embodiment" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiment may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0031] The present application is described in detail below with reference to the accompanying drawings and implementation methods.

[0032] See also Figure 1 , Figure 1 1 is a schematic diagram of the structure of the first embodiment of the current-source LLC start-up control circuit of the present application. In this embodiment, the current-source LLC start-up control circuit 10 includes: an inverter circuit 11, a resonant circuit 12, an electric energy conversion circuit 13 and a main control circuit 14.

[0033] Among them, a current-type LLC start-up control circuit 10 provided in the present application is specifically used in the power supply of power loads that require DC output, so as to utilize external input DC power, and after corresponding regulation and control of the DC power, it is provided to the power loads in any reasonable electronic equipment such as servers, computers, intelligent communication equipment, etc. for operation, and this embodiment does not impose any restrictions on this.

[0034] Specifically, the inverter circuit 11 is used to receive a first DC signal input, and utilize its internal switching action mechanism, such as the opening and closing action mechanism of switching devices such as IGBT (Insulated Gate Bipolar Transistor), high-frequency transistor, MOSFET (Metal Oxide Semiconductor Field Effect Transistor), etc., to quickly switch the DC power under signal control to generate an alternating voltage waveform and obtain a first AC signal.

[0035] It is worth noting that the first DC signal can be specifically understood as a DC power input provided by an external DC power supply, or it can be a DC power supply output after power conversion and adjustment of a municipal power supply, a photovoltaic power supply, an independent generator or any other reasonable superior AC or DC power supply.

[0036] In addition, the term "coupled" herein refers to any direct and indirect connection means. Therefore, if the first circuit is described as being coupled to the second circuit, it means that the first circuit can be directly connected to the second circuit through electrical connection or signal connection methods such as wireless transmission, optical transmission, etc., or can be indirectly connected to the second circuit through other circuits or connection means.

[0037] The resonant circuit 12 is directly connected to the inverter circuit 11 to receive the first AC signal sent by the inverter circuit 11, and performs one or more of any reasonable signal adjustments such as filtering, shaping, phase shifting, etc. on the first AC signal to obtain a resonant current signal, so as to achieve better output characteristics and ensure that subsequent links, such as power conversion circuits or loads, obtain more stable and efficient power.

[0038] The power conversion circuit 13 is coupled to the resonant circuit 12 to receive the resonant current signal sent by the resonant circuit 12, and performs power conversion and regulation control on the resonant current signal to obtain a stable DC output, that is, a second DC signal Vo, which is then output to the load circuit 101 to meet the power usage of the load circuit 101.

[0039] The load circuit 101 can be understood as a signal function circuit that utilizes the DC output of the current-type LLC start-up control circuit 10 to operate.

[0040] Furthermore, the main control circuit 14 is coupled to the inverter circuit 11 and the resonant circuit 12 . The main control circuit 14 is specifically configured to generate a first control signal having a first signal frequency based on a preset program in a first startup phase.

[0041] It is worth noting that the first startup stage can be specifically understood as the initial stage in which the current-type LLC startup control circuit 10 receives the first DC signal input to start the operation. For the convenience of quantification, the output voltage of the second DC signal Vo provided by the power conversion circuit 13 to the load circuit 101 can be slowly and monotonically increased from 0V (volts) to the target output voltage Vobj, and the entire process of stabilizing at the target output voltage Vobj can be divided into time intervals to obtain the first startup stage and the second startup stage.

[0042] For details, please continue to see Figure 2 and Figure 3 ,in, Figure 2 yes Figure 1 Schematic diagram of the voltage waveform of the second DC signal Vo in the power conversion circuit, Figure 3 yes Figure 1 A schematic diagram of the waveform of the first control signal sent by the main control circuit 14 in the first startup phase.

[0043] It is understandable that the first startup stage can specifically correspond to the output voltage of the second DC signal Vo rising monotonically from 0V to the target output voltage Vobj and stabilizing at the target output voltage Vobj during the entire process of operation, according to the T0-T1 time period determined by a preset duration, or according to the T0-T1 time period corresponding to the output voltage of the second DC signal Vo rising from 0V to a preset voltage value, and the present application does not impose any limitation on this.

[0044] Among them, in the initial stage when the current-type LLC start-up control circuit 10 receives the first DC signal input, there is usually an instantaneous impact current. The first signal frequency can be specifically understood as the control of the inverter circuit 11 achieved by the first control signal, which can effectively suppress the instantaneous impact current currently received by the inverter circuit 11 in time and the corresponding predetermined signal frequency of the first control signal. This application does not limit this.

[0045] Please continue reading Figure 4 , Figure 4 yes Figure 1 Schematic diagram of the waveform of the second control signal sent by the main control circuit 14 in the second startup stage.

[0046] It can be understood that in the second startup stage, that is, in the entire process in which the output voltage based on the second DC signal Vo rises monotonically from 0V to the target output voltage Vobj and stabilizes at the target output voltage Vobj, the T1-T2 time period is divided, and the main control circuit 14 is configured to obtain the resonant current signal from the resonant circuit 12, so as to perform slope compensation on the set voltage signal using the first slope compensation slope to obtain the first feedback adjustment signal.

[0047] It is worth noting that slope compensation is a control technology used to improve the stability of the system and reduce steady-state errors. By superimposing a slope-controllable ramp signal on the set voltage signal, the dynamic response characteristics of the system can be changed. Among them, the first slope compensation slope refers to the slope parameter used for slope compensation. This slope can be adjusted according to the needs of the system to achieve the optimal compensation effect.

[0048] In addition, the set voltage signal can be understood as a constant value pre-set by the main control circuit 14, or it can be a specific output signal in the voltage loop output signal obtained by a PI (proportional integral) controller using feedback adjustment of the second DC signal Vo output to the load circuit 101. It is determined by the actual application scenario and is not limited in this application.

[0049] The main control circuit 14 can generate a first feedback regulation signal by performing slope compensation on the set voltage signal using the first slope compensation slope. The first feedback regulation signal includes the set voltage and signal information after slope compensation.

[0050] Furthermore, the main control circuit 14 compares the first feedback adjustment signal with the resonant current signal to generate a second control signal based on the difference between the two. This is usually achieved through a comparator, which calculates the difference between the two, which is the control error. The second control signal is generated based on the control error to be used for the switching state of the inverter circuit 11, and then adjust the operation of the resonant circuit 12 so that the actual resonant current is as close as possible to the desired set value.

[0051] The first slope compensation slope is specifically a negative number, and increases sequentially in each second signal cycle of the second control signal.

[0052] It is understandable that when the first slope compensation slope is a negative number, the slope compensation performed on the set voltage signal using the first slope compensation slope is specifically negative compensation, that is, the value of the set voltage signal is linearly reduced to obtain the first feedback regulation signal.

[0053] Optionally, the first control signal and the second control signal may specifically be one or more of any reasonable control signals such as a PWM (Pulse Width Modulation) signal or a PFM (Pulse Frequency Modulation) signal, and the present application does not limit this.

[0054] For ease of understanding, taking the second startup stage, the second control signal has multiple second signal periods, which are respectively second signal period 1, second signal period 2, ..., second signal period n (n is an integer greater than 2) as an example, the first slope compensation slope k1, the first slope compensation slope k2, ..., the first slope compensation slope kn of the slope compensation performed in the second signal period 1, the second signal period 2, ..., and the second signal period n of the second control signal can specifically correspond to any reasonable and successively increasing slope compensation parameters such as -1.2, -1, ..., -0.6, or -1.3, -1.1, -0.7, etc., and the present application does not limit this.

[0055] The inverter circuit 11 is used to receive a first control signal and a second control signal, and change the switch state in turn under the action of the first control signal and the second control signal to adjust its output signal, that is, the first AC signal, and further adjust the operation of the resonant circuit 12.

[0056] The first control signal and the second control signal specifically further include a drive signal PWMA and a drive signal PWMB for driving different switch sub-circuits in the inverter circuit 11 .

[0057] It is understandable that if Figure 4 As shown, by using different first slope compensation slopes to perform slope compensation on the set voltage signal, the signal frequencies of the second control signal finally corresponding to the result are different, and the waveform frequencies of the first AC signal obtained by controlling the inverter circuit 11 using the second control signal with different signal frequencies are also different, and different waveform frequencies of the first AC signal will correspond to different resonance states and gain effects of the resonant circuit 12, so that by reasonably setting the first slope compensation slope, a better gain effect of the resonant circuit 12 can be effectively obtained, and by reasonably adjusting the size of the first slope compensation slope, smoother startup control and frequency modulation and voltage stabilization can be achieved.

[0058] Optionally, the main control circuit 14 may specifically include a control chip, an MCU (Micro Controller Unit) circuit, a CPU (Central Processing Unit), a single-chip microcomputer, a field programmable gate array, a programmable logic device, a discrete gate or transistor logic device, discrete hardware, and any other reasonable circuit unit with a signal processing function, and the present application does not limit this.

[0059] The above scheme, when the instantaneous impact current is large, adopts different control strategies in different startup stages during the initial stage of the startup of the current-type LLC starting control circuit 10, that is, at the initial stage of receiving the first DC signal input, to timely suppress the instantaneous impact current so as to avoid loss to the circuit; and controls the inverter circuit 11 by adopting different slope compensations in the second signal period with different second control signals, thereby effectively solving the problems of large starting current and poor monotonicity, so as to achieve smoother starting control, and while suppressing the instantaneous impact current, it also effectively ensures a better gain effect of the resonant circuit 12, thereby ensuring better performance in a wider range of application scenarios.

[0060] Optionally, the first signal frequency of the first control signal generated by the main control circuit 14 in the first startup phase may be 90%-100% of the maximum resonance frequency of the resonance circuit 12, which is not limited in the present application.

[0061] It is worth noting that the resonant circuit 12 is a circuit that can selectively amplify and transmit signals. It can maximize the amplitude of signals at a specific frequency while suppressing interference signals at other frequencies. This circuit is widely used in wireless communication systems, sound amplification, video processing and other fields, and its main functions are: 1. Signal amplification: The resonant circuit 12 can maximize the amplitude of signals at a specific frequency, thereby amplifying them. For example, the amplifier used in the radio works based on the resonance principle. 2. Signal enhancement: The resonant circuit 12 can enhance the signal within a specified frequency range through selective amplification, thereby improving signal quality and transmission efficiency. 3. Signal selection: The resonant circuit 12 can selectively transmit signals of a specific frequency, suppress interference signals of other frequencies, and ensure signal clarity.

[0062] The physical characteristics of the resonant circuit 12 itself will determine a maximum resonant frequency and a minimum resonant frequency; the first control signal can specifically be a PFM signal with a fixed duty cycle of 50%, so that in the first startup stage, that is, the starting stage when the instantaneous impact current input to the current-type LLC startup control circuit 10 is relatively large, by setting the first control signal to the maximum resonant frequency or close to the maximum resonant frequency, the instantaneous impact current can be suppressed in time to avoid losses to the circuit.

[0063] The duration of the first startup phase may specifically be a set multiple m of the first signal period of the first control signal, that is, the duration of T0-T1 is m*1 / f, where m is a positive integer and f is the signal frequency of the first control signal.

[0064] Optionally, the set multiple m can specifically be 1-100, which is not limited in this application.

[0065] In one embodiment, the inverter circuit 11 further includes a first switch sub-circuit (not shown in the figure) and a second switch sub-circuit (not shown in the figure), the first switch sub-circuit is coupled to the second switch sub-circuit, the resonant circuit 12 and the main control circuit 14, the second switch sub-circuit is coupled to the main control circuit 14, and the second control signal includes a first drive signal PWMA and a second drive signal PWMB.

[0066] Among them, Figure 4 As shown, in the second startup stage, the main control circuit 14 is specifically configured to respond to the start time of the second startup stage, that is, time T1, or the time when each second drive signal PWMB is adjusted from the first level to the second level in the first half cycle of each second signal cycle, and at the same time use the first slope compensation slope to perform slope compensation on the set voltage signal to obtain the first feedback adjustment signal, and delay the set time to adjust the first drive signal PWMA from the second level to the first level, so as to adjust the first drive signal PWMA from the first level to the second level when the amplitude of the first feedback adjustment signal is less than or equal to the amplitude of the resonant capacitor voltage or the resonant current of the resonant current signal.

[0067] In other embodiments, the main control circuit 14 can also use the first slope compensation slope to perform slope compensation on the set voltage signal to obtain a first feedback adjustment signal after a delay of a set time at each moment when the second drive signal PWMB is adjusted from the first level to the second level. The present application does not limit this.

[0068] It is worth noting that, when each second driving signal PWMB is adjusted from the first level to the second level, the main control circuit 14 uses the first slope compensation slope to perform slope compensation on the set voltage signal, which is different from the first slope compensation slope corresponding to the first slope compensation slope used to perform slope compensation on the set voltage signal with the delay setting time when each second driving signal PWMB is adjusted from the first level to the second level. Moreover, the first slope compensation slope used for delay is smaller than the first slope compensation slope used for no delay, which is specifically determined by the actual application scenario and is not limited in this application.

[0069] Among them, the resonant capacitor voltage of the resonant current signal is also not equal to the amplitude of the resonant current, but the two satisfy a specific functional relationship. For example, when the resonant capacitor voltage is twice the amplitude of the resonant current and the level state of the first drive signal PWMA is adjusted by using the amplitude of the resonant capacitor voltage or the resonant current, the first slope compensation slope correspondingly adopted by the main control circuit 14 is also different, but satisfies a specific functional relationship, which is specifically determined by the actual application scenario and is not limited in this application.

[0070] Optionally, the set duration may specifically be the on-off dead time of each switch tube in the inverter circuit 11, or may be a specific duration determined according to a specific application scenario, which is not limited in the present application.

[0071] Optionally, the first level can be a high level, and the second level corresponds to a low level or a 0 level; or, the first level can be a low level or a 0 level, and the second level corresponds to a high level, which can be specifically determined by the physical characteristics of each switch tube in the inverter circuit 11, and the present application does not limit this.

[0072] Furthermore, in the second half of each second signal cycle, the main control circuit 14 can directly copy the first drive signal PWMA of each first half of the cycle to obtain the second drive signal PWMB.

[0073] It is understandable that if Figure 4 As shown, in the first half of each second signal cycle, specifically, the first drive signal PWMA has a first level state, and in the second half of each second signal cycle, the first drive signal PWMA continues to be a second level state; and the second drive signal PWMB continues to be the second level state in the first half of each second signal cycle, and in the second half of each second signal cycle, the level change state of the first drive signal PWMA in the first half of each second signal cycle is adjusted and copied to obtain the level change state of the second drive signal PWMB.

[0074] The main control circuit 14 is further configured to sequentially adjust the first slope compensation slope by using a preset linear function or a preset arithmetic function in each second signal period.

[0075] For ease of understanding, taking the second startup stage as an example, the second control signal includes a second signal period 1, a second signal period 2, ..., a second signal period n, and the slope compensation parameters of the corresponding slope compensation correspond to the first slope compensation slope k1, the first slope compensation slope k2, ..., and the first slope compensation slope kn, respectively. The first slope compensation slope k1, the first slope compensation slope k2, ..., and the first slope compensation slope kn can specifically satisfy a specific preset linear function or a preset arithmetic function.

[0076] For example, when a preset arithmetic function with a tolerance of any reasonable value such as 0.1, 0.2 or 0.3 is satisfied, the first slope compensation slope k1 can be specifically a preset initial value of -1.2, the first slope compensation slope k2 corresponds to -1, the first slope compensation slope 3 corresponds to -0.8, and so on, other slope compensation parameters, or slope compensation parameters of a preset arithmetic function with other preset initial values ​​or other tolerances can be obtained, which will not be repeated here; and when a preset linear function with a linear slope of any reasonable value such as 0.9, 0.8 or 0.7 is satisfied, the first slope compensation slope k1 can be specifically a preset initial value of -1, the first slope compensation slope k2 corresponds to -0.9, the first slope compensation slope 3 corresponds to -0.81, and so on, other slope compensation parameters, or slope compensation parameters of a preset linear function with other preset initial values ​​or other linear slopes can be obtained, which will not be repeated here.

[0077] Furthermore, the first switch sub-circuit and the second switch sub-circuit are used to receive the first drive signal PWMA and the second drive signal PWMB, so as to change the switch state under the action of the first drive signal PWMA and the second drive signal PWMB respectively, thereby regulating the first AC signal to adjust the resonant state of the resonant circuit 12.

[0078] It is worth noting that the second signal frequency of the second control signal must also satisfy the requirement of being no greater than the maximum resonant frequency of the resonant circuit 12 and no less than the minimum resonant frequency of the resonant circuit 12, so that in a second signal cycle of the second startup stage, when the second signal frequencies of the first drive signal PWMA and the second drive signal PWMB generated by the main control circuit 14 through slope compensation are equal to the minimum resonant frequency, the first slope compensation slope corresponding to each subsequent second signal cycle of the second startup stage will be constant as the first slope compensation slope when the second signal frequencies of the first drive signal PWMA and the second drive signal PWMB are determined to be the minimum resonant frequency.

[0079] Please continue reading Figure 5 , Figure 5 yes Figure 1 A schematic diagram of the waveform of the third control signal sent by the middle main control circuit 14 in the third startup stage.

[0080] In one embodiment, the main control circuit 14 is further coupled to the power conversion circuit 13 to obtain the second DC signal Vo in the power conversion circuit 13, so as to switch to the third startup stage when it is detected that the voltage of the second DC signal Vo is at a set voltage threshold.

[0081] Optionally, the set voltage threshold may specifically be 80%-100% of the target output voltage Vobj, which is not limited in the present application.

[0082] Among them, in the third startup stage, that is, after time T2, the main control circuit 14 is specifically configured to use a second slope compensation slope to perform slope compensation on the set voltage signal to obtain a second feedback adjustment signal, so as to generate a third control signal using the second feedback adjustment signal and the resonant current signal.

[0083] The second slope compensation slope is specifically the end time of the second startup phase, that is, time T2, or can be understood as the first slope compensation slope kn corresponding to a second signal cycle of the second control signal closest to time T2.

[0084] It can be seen that in the third startup stage, the main control circuit 14 specifically continues to use the second slope compensation slope, that is, the above-mentioned first slope compensation slope kn to perform slope compensation on the set voltage signal to obtain the second feedback adjustment signal, and the third control signal generated by using the second feedback adjustment signal and the resonant current signal can be specifically understood as the periodic replication of the first drive signal PWMA and the second drive signal PWMB of the last second signal cycle in the second startup stage.

[0085] The first switch sub-circuit and the second switch sub-circuit are further configured to receive a third control signal and use the third control signal to adjust the first AC signal to adjust the resonance state of the resonance circuit 12 .

[0086] The above scheme creatively solves the problems of large starting current and poor monotonicity through three-stage starting control, so as to achieve smoother starting control. While suppressing instantaneous impact current, it also effectively ensures a better gain effect of the resonant circuit 12, thereby ensuring better performance in a wider range of application scenarios.

[0087] See also Figure 6 , Figure 6 1 is a schematic diagram of the structure of the second embodiment of the current-type LLC start-up control circuit of the present application. The difference between the current-type LLC start-up control circuit in this embodiment and the first embodiment of the current-type LLC start-up control circuit provided in the present application is that the resonant circuit 22 in the current-type LLC start-up control circuit 20 further includes a first resonant capacitor Cr1, a second resonant capacitor Cr2 and a resonant inductor Lr.

[0088] Among them, the first end of the first resonant capacitor Cr1 is coupled to the first end of the first switch sub-circuit 211 in the inverter circuit 21 and the first end of the main control circuit 24, the second end of the first resonant capacitor Cr1 is coupled to the first end of the second resonant capacitor Cr2, the second end of the main control circuit 24 and the second end of the power conversion circuit 23, the second end of the second resonant capacitor Cr2 is coupled to the second end of the second switch sub-circuit 212 and the third end of the main control circuit 24, the first end of the resonant inductor Lr is coupled to the second end of the first switch sub-circuit 211 and the first end of the second switch sub-circuit 212, and the second end of the resonant inductor Lr is coupled to the first end of the power conversion circuit 23.

[0089] The main control circuit 24 is specifically used to sample and obtain a first capacitor voltage signal V between the first end and the second end of the first resonant capacitor Cr1. Cr1 and a second capacitor voltage signal V between the first and second ends of the second resonant capacitor Cr2 Cr2 , to utilize the first capacitor voltage signal V Cr1 and the second capacitor voltage signal V Cr2 The resonant capacitor voltage is calculated, for example, the resonant capacitor voltage = the first capacitor voltage signal V Cr1 +Second capacitor voltage signal V Cr2 .

[0090] In one embodiment, the current-type LLC start-up control circuit 20 specifically also includes a switch freewheeling circuit 25, which includes a first freewheeling resistor Rc1, a second freewheeling resistor Rc2, a first freewheeling capacitor C1, a second freewheeling capacitor C2, a first diode D1, and a second diode D2. The first switch sub-circuit 211 includes a first switch tube Q1, and the second switch sub-circuit 212 includes a second switch tube Q2.

[0091] Among them, the first end of the first freewheeling resistor Rc1 is coupled to the first end of the first switch tube Q1 and the second end of the first diode D1, the second end of the first freewheeling resistor Rc1 is coupled to the first end of the first freewheeling capacitor C1, the second end of the first freewheeling capacitor C1 is coupled to the first end of the first diode D1, the second end of the first switch tube Q1, the first end of the second switch tube Q2, the first end of the second freewheeling resistor Rc2, and the second end of the second diode D2, the second end of the second freewheeling resistor Rc2 is coupled to the first end of the second freewheeling capacitor C2, the second end of the second freewheeling capacitor C2 is coupled to the second end of the second switch tube Q2 and the first end of the second diode D2, and the third end of the first switch tube Q1 and the third end of the second switch tube Q2 are coupled to the main control circuit 24.

[0092] Optionally, the first switch tube Q1 and the second switch tube Q2 may be specifically a MOS tube, a triode, a thin film transistor, a field effect transistor or any other reasonable switch tube, which is not limited in the present application.

[0093] It is worth noting that, in order to distinguish the two ends of each switch tube except the control end, one of the ends is called the first end and the other end is called the second end. When each switch tube is a triode, the control end, that is, the third end, can be specifically the base, the first end is the collector, and the second end is the emitter; or, the third end can also be specifically the base, the first end is the emitter, and the second end is the collector.

[0094] When the above switch tubes are MOS tubes, thin film transistors or field effect transistors, the third end can be a gate, the first end is a drain, and the second end is a source; or, the third end can be a gate, the first end is a source, and the second end is a drain.

[0095] When each switch tube is a MOS tube, a thin film transistor or a field effect transistor, it can also be a composite transistor or a single transistor, which is not limited in the present application.

[0096] In other embodiments, the inverter circuit 21 may be a full-bridge circuit, a symmetrical half-bridge circuit, an asymmetrical half-bridge circuit, or any other reasonable circuit form for converting DC to AC, and the present application does not limit this.

[0097] It can be understood that by setting the switch freewheeling circuit 25, when the first switch tube Q1 or the second switch tube Q2 is triggered to turn off, the first diode D1 or the second diode D2 can be used to provide a freewheeling channel for the current flowing through the first switch tube Q1 or the second switch tube Q2, and with the help of the first freewheeling resistor Rc1, the second freewheeling resistor Rc2, the first freewheeling capacitor C1, and the second freewheeling capacitor C2, the ZVS (Zero Voltage Switch) is effectively realized to turn on and off, thereby effectively ensuring the efficient and stable power supply performance of the entire current-type LLC starting control circuit 20.

[0098] It is worth mentioning that ZVS turn-on is a soft switching technology commonly used in switching power supplies. It achieves zero voltage turn-on by reducing the voltage to zero before the switch tube is turned on, so as to reduce switching losses and electromagnetic interference.

[0099] In one embodiment, the main control circuit 24 specifically also includes a first proportional filter correction subcircuit 241, a second proportional filter correction subcircuit 242, a third proportional filter correction subcircuit 243, an isolation operational amplifier subcircuit 244 and a control subcircuit 245. The first proportional filter correction subcircuit 241 is coupled to the first resonant capacitor Cr1 and the isolation operational amplifier subcircuit 244, the second proportional filter correction subcircuit 242 is coupled to the second resonant capacitor Cr2 and the isolation operational amplifier subcircuit 244, the isolation operational amplifier subcircuit 244 is coupled to the control subcircuit 245, and the third proportional filter correction subcircuit 243 is coupled to the power conversion circuit 23 and the control subcircuit 245.

[0100] The first proportional filter correction subcircuit 241 is used to obtain the first capacitor voltage signal V Cr1 , and the first capacitor voltage signal V Cr1 The first filter signal is obtained by comparing with the reference value, filtering and correcting in sequence; the second proportional filter correction subcircuit 242 is used to obtain the second capacitor voltage signal V Cr2 , and the second capacitor voltage signal V Cr2 The second filtered signal is obtained by comparing with the reference value, filtering and correcting in sequence; the third proportional filtering correction subcircuit 243 is used to obtain the second DC signal Vo, and compares the second DC signal Vo with the reference value, filtering and correcting in sequence to obtain the third filtered signal, so as to provide a more suitable high-quality input for the isolation amplifier subcircuit 244 and the control subcircuit 245, thereby effectively optimizing the overall performance and reliability of the main control circuit 24 to achieve efficient control.

[0101] The isolation operational amplifier subcircuit 244 is used to receive the first filtered signal and the second filtered signal, and to sequentially isolate, operationally amplify, and perform function calculations on the first filtered signal and the second filtered signal to obtain a resonant capacitor voltage, so as to provide a more suitable high-quality input for the control subcircuit 245, thereby achieving more precise control.

[0102] The control subcircuit 245 is further used to receive the resonant capacitor voltage and the third filtered signal, so as to use the resonant capacitor voltage and the third filtered signal to obtain the first drive signal PWMA, the second drive signal PWMB and the third control signal, thereby using the first drive signal PWMA, the second drive signal PWMB and the third control signal to control the inverter circuit 21.

[0103] In one embodiment, the current-type LLC start-up control circuit 20 specifically also includes a power factor correction circuit 26, which is coupled to the inverter circuit 21 and is used to couple with the AC power supply 102 to receive an AC input signal from the AC power supply 102, and convert the input AC input signal into a smooth, highly stable first DC signal through electronic control technology to output to the inverter circuit 21.

[0104] It is worth noting that the AC power supply 102 can be specifically understood as a municipal power supply, a photovoltaic AC power supply or an independent generator, or an AC power output after power conversion and adjustment of the municipal power supply, the photovoltaic AC power supply, an independent generator or any other reasonable superior power supply.

[0105] In one embodiment, the power conversion circuit 23 further includes an isolation transformer 231 and a rectifier circuit 232. The isolation transformer 231 is coupled to the resonant circuit 22 to receive the resonant current signal sent by the resonant circuit 22 and convert the resonant current signal into a second AC signal, so as to use electromagnetic connection instead of electrical connection to achieve primary and secondary side safety electrical isolation and voltage matching, and meet the primary and secondary side electrical safety insulation requirements.

[0106] The rectifier circuit 232 is coupled to the isolation transformer 231 and is used to couple with the external load circuit 101, and specifically involves transformer isolation and rectification. Specifically, the rectifier circuit 232 receives the second AC signal sent by the isolation transformer 231, and uses a high-frequency rectification technology, such as PWM, synchronous rectification, reverse damping rectification, and any other reasonable rectification method, to obtain a stable DC output, that is, a second DC signal Vo, using the second AC signal to output to the load circuit 101 to meet the power usage of the load circuit 101.

[0107] In one embodiment, the isolation transformer 231 further includes a primary winding 2311 and a secondary winding 2312 , the resonant circuit 22 is coupled to the primary winding 2311 , the primary winding 2311 is coupled to the secondary winding 2312 , and the rectifier circuit 232 is coupled to the secondary winding 2312 .

[0108] In one embodiment, the current-type LLC start-up control circuit 20 specifically also includes a voltage-stabilizing output circuit 27, the voltage-stabilizing output circuit 27 further includes a voltage-stabilizing resistor Ro and a voltage-stabilizing capacitor Co, the rectifier circuit 232 specifically further includes a third diode D3 and a fourth diode D4, and the secondary winding 2312 specifically further includes a first sub-secondary winding 23121 and a second sub-secondary winding 23122.

[0109] Among them, the first end of the third diode D3 is coupled to the first end of the third switch tube T3 and the first end of the first sub-secondary winding 23121, the second end of the third diode D3 is coupled to the second end of the fourth diode D4, the first end of the voltage-stabilizing resistor Ro and the first end of the load circuit 101, the first end of the fourth diode D4 is coupled to the second end of the fourth switch tube T4 and the second end of the second sub-secondary winding 23122, the second end of the voltage-stabilizing resistor Ro is coupled to the first end of the voltage-stabilizing capacitor Co, and the second end of the voltage-stabilizing capacitor Co is coupled to the second end of the third switch tube T3, the first end of the fourth switch tube T4, the second end of the first sub-secondary winding 23121, the first end of the second sub-secondary winding 23122 and the second end of the load circuit 101.

[0110] In other embodiments, the rectifier circuit 232 can specifically be any reasonable circuit form for realizing AC to DC conversion, such as a full-bridge rectifier circuit or a half-bridge rectifier circuit composed of various switching tubes. The first sub-secondary winding 23121 and the second sub-secondary winding 23122 can also be replaced with the same winding, which is determined by the actual application scenario and is not limited in this application.

[0111] It can be understood that the rectifier circuit 232 is used to receive the second AC signal sent by the isolation transformer 231, and convert the second AC signal into a second DC signal Vo, which can specifically be a steamed bun wave, and then use the stabilizing resistor Ro and the stabilizing capacitor Co to rectify the second DC signal Vo into a set DC voltage signal to output to the load circuit 101 to drive the load circuit 101 to work.

[0112] This application also specifically adopts a current-type LLC startup control method, see Figure 7 , Figure 7 This is a flow chart of the first implementation of the current-type LLC startup control method of the present application. Specifically, it may include the following steps:

[0113] S31: receiving a first DC signal input.

[0114] It is understandable that the current-type LLC start-up control method in this embodiment is specifically a control method in which the current-type LLC start-up control circuit uses external input direct current, and after correspondingly regulating and controlling the direct current, provides it to the load circuit. Among them, the current-type LLC start-up control circuit specifically includes an inverter circuit, a resonant circuit, an electric energy conversion circuit and a main control circuit, the resonant circuit is coupled to the inverter circuit, the electric energy conversion circuit is coupled to the resonant circuit, and is used to couple with the load circuit, and the main control circuit is coupled to the inverter circuit and the resonant circuit.

[0115] Specifically, the inverter circuit is used to receive a first DC signal input.

[0116] S32: Convert the first DC signal into a first AC signal.

[0117] Furthermore, the inverter circuit utilizes its internal switching action mechanism, such as the opening and closing action mechanism of switching devices such as IGBT, high-frequency transistor, MOS, etc., to quickly switch the DC power under signal control to generate an alternating voltage waveform and obtain a first AC signal.

[0118] S33: Adjust the first AC signal to a resonant current signal.

[0119] The resonant circuit receives a first AC signal sent by an inverter circuit, and performs one or more of any reasonable signal adjustments such as filtering, shaping, phase shifting, etc. on the first AC signal to obtain a resonant current signal, in order to achieve better output characteristics and ensure that subsequent links, such as a rectifier circuit or a load, obtain more stable and efficient electrical energy.

[0120] S34: Convert the resonant current signal into a second DC signal to output to an external load circuit.

[0121] The power conversion circuit is coupled to the resonant circuit to receive the resonant current signal sent by the resonant circuit, and performs power conversion and regulation control on the resonant current signal to obtain a stable DC output, that is, a second DC signal, which is then output to the load circuit to meet the power usage of the load circuit.

[0122] S35: In the first startup phase, generating a first control signal having a first signal frequency.

[0123] The main control circuit is specifically configured to generate a first control signal having a first signal frequency based on a preset program in a first startup phase.

[0124] It is worth noting that the first startup stage can be specifically understood as the initial stage in which the current-type LLC startup control circuit receives the first DC signal input to start the operation. For the convenience of quantification, the entire process in which the output voltage of the second DC signal provided by the power conversion circuit to the load circuit slowly and monotonically rises from 0V (volts) to the target output voltage Vobj and stabilizes at the target output voltage Vobj can be divided into time intervals to obtain the first startup stage and the second startup stage.

[0125] Specifically, Figure 2 and Figure 3As shown, the first startup stage can specifically correspond to the output voltage of the second DC signal rising monotonically from 0V to the target output voltage Vobj and stabilizing at the target output voltage Vobj during the entire process of operation, according to the T0-T1 time period determined by a preset duration, or according to the T0-T1 time period corresponding to the output voltage of the second DC signal rising from 0V to a preset voltage value, and the present application does not impose any limitation on this.

[0126] Among them, in the initial stage when the current-type LLC start-up control circuit receives the first DC signal input, there is usually an instantaneous impact current. The first signal frequency can be specifically understood as the control of the inverter circuit through the first control signal, which can effectively suppress the instantaneous impact current currently received by the inverter circuit in time and the corresponding pre-set signal frequency of the first control signal. This application does not limit this.

[0127] Optionally, the first signal frequency of the first control signal generated by the main control circuit in the first startup phase may specifically be 90%-100% of the maximum resonant frequency of the resonant circuit, which is not limited in the present application.

[0128] The physical characteristics of the resonant circuit itself will determine a maximum resonant frequency and a minimum resonant frequency; the first control signal can specifically be a PFM signal with a fixed duty cycle of 50%, so that in the first startup stage, that is, the starting stage when the instantaneous impact current input to the current-type LLC startup control circuit is relatively large, by setting the first control signal to the maximum resonant frequency or close to the maximum resonant frequency, the instantaneous impact current can be suppressed in time to avoid losses to the circuit.

[0129] The duration of the first startup phase may specifically be a set multiple m of the first signal period of the first control signal, that is, the duration of T0-T1 is m*1 / f, where m is a positive integer and f is the signal frequency of the first control signal.

[0130] S36: Regulate the first AC signal using the first control signal.

[0131] The inverter circuit is used to receive a first control signal and change a switch state under the action of the first control signal to adjust its output signal, ie, the first AC signal, and further adjust the operation of the resonant circuit.

[0132] S37: In the second startup stage, a first slope compensation slope is used to perform slope compensation on the set voltage signal to obtain a first feedback adjustment signal.

[0133] Specifically, Figure 2 and Figure 4As shown, in the second startup stage, that is, the entire process in which the output voltage based on the second DC signal rises monotonically from 0V to the target output voltage Vobj and stabilizes at the target output voltage Vobj, the T1-T2 time period is divided, and the main control circuit is configured to obtain the resonant current signal from the resonant circuit, so as to perform slope compensation on the set voltage signal using the first slope compensation slope to obtain the first feedback adjustment signal.

[0134] The main control circuit can generate a first feedback regulation signal by performing slope compensation on the set voltage signal using the first slope compensation slope. The first feedback regulation signal includes the set voltage and signal information after slope compensation.

[0135] S38: Generate a second control signal using the first feedback adjustment signal and the resonant current signal.

[0136] Furthermore, the main control circuit compares the first feedback adjustment signal with the resonant current signal to generate a second control signal based on the difference between the two. This is usually achieved through a comparator, which calculates the difference between the two, which is the control error. The second control signal is generated based on the control error to be used for the switching state of the inverter circuit, thereby adjusting the operation of the resonant circuit so that the actual resonant current is as close as possible to the desired set value.

[0137] The first slope compensation slope is specifically a negative number, and increases sequentially in each second signal cycle of the second control signal.

[0138] It is understandable that when the first slope compensation slope is a negative number, the slope compensation performed on the set voltage signal using the first slope compensation slope is specifically negative compensation, that is, the value of the set voltage signal is linearly reduced to obtain the first feedback regulation signal.

[0139] For ease of understanding, taking the second startup stage, the second control signal has multiple second signal periods, which are respectively second signal period 1, second signal period 2, ..., second signal period n (n is an integer greater than 2) as an example, the first slope compensation slope k1, the first slope compensation slope k2, ..., the first slope compensation slope kn of the slope compensation performed in the second signal period 1, the second signal period 2, ..., and the second signal period n of the second control signal can specifically correspond to any reasonable and successively increasing slope compensation parameters such as -1.2, -1, ..., -0.6, or -1.3, -1.1, -0.7, etc., and the present application does not limit this.

[0140] It is understandable that if Figure 4As shown, by using different first slope compensation slopes to perform slope compensation on the set voltage signal, the signal frequencies of the second control signal finally obtained are different, and the waveform frequencies of the first AC signal obtained by controlling the inverter circuit using the second control signal with different signal frequencies are also different, and different waveform frequencies of the first AC signal will correspond to different resonant states and gain effects of the resonant circuit, so that a better gain effect of the resonant circuit can be effectively obtained by reasonably setting the first slope compensation slope, and smoother startup control and frequency modulation and voltage stabilization can be achieved by reasonably adjusting the size of the first slope compensation slope.

[0141] S39: Regulate the first AC signal using the second control signal.

[0142] The inverter circuit is also used to receive a second control signal and change the switch state under the action of the second control signal to adjust its output signal, that is, the first AC signal, and further adjust the operation of the resonant circuit.

[0143] See also Figure 8 , Figure 8 This is a flow chart of the second embodiment of the current-type LLC startup control method of the present application. The current-type LLC startup control method of this embodiment is Figure 7 A flowchart of a detailed implementation of the current-type LLC startup control method in the embodiment of the present invention specifically includes the following steps:

[0144] S41: receiving a first DC signal input.

[0145] S42: Convert the first DC signal into a first AC signal.

[0146] S43: Adjust the first AC signal to a resonant current signal.

[0147] S44: Convert the resonant current signal into a second DC signal to output to an external load circuit.

[0148] S45: In the first startup phase, generating a first control signal having a first signal frequency.

[0149] S46: Regulate the first AC signal using the first control signal.

[0150] Among them, S41, S42, S43, S44, S45 and S46 are Figure 7 S31, S32, S33, S34, S35 and S36 are the same. Please refer to S31, S32, S33, S34, S35 and S36 and their related text descriptions for details, which will not be repeated here.

[0151] S47: In the second startup stage, in the first half of each second signal cycle, in response to the start time of the second startup stage or the time when the second drive signal is adjusted from the first level to the second level, the first drive signal is adjusted from the second level to the first level by delaying the set time.

[0152] Specifically, the inverter circuit further includes a first switch subcircuit and a second switch subcircuit, the first switch subcircuit is coupled to the second switch subcircuit, the resonant circuit and the main control circuit, and the second switch subcircuit is coupled to the main control circuit; and Figure 4 As shown, the second control signal specifically further includes a first drive signal and a second drive signal.

[0153] The main control circuit is specifically configured to, in the first half of each second signal cycle, in response to the start time of the second startup phase, i.e., time T1, or the time when each second drive signal is adjusted from the first level to the second level, delay the first drive signal from the second level to the first level by a set time delay.

[0154] Optionally, the set duration may specifically be the on-off dead time of each switch tube in the inverter circuit, or may be a specific duration determined according to a specific application scenario, which is not limited in the present application.

[0155] S48: Delay the set time or use the first slope compensation slope to perform slope compensation on the set voltage signal to obtain a first feedback adjustment signal.

[0156] Furthermore, the second control signal can be specifically delayed for a set period of time or simultaneously use the first slope compensation slope to perform slope compensation on the set voltage signal at the starting moment of the second startup stage, that is, moment T1, or at the moment when each second drive signal is adjusted from the first level to the second level to obtain the first feedback adjustment signal.

[0157] S49: When the amplitude of the first feedback adjustment signal is less than or equal to the amplitude of the resonant capacitor voltage or the resonant current of the resonant current signal, adjust the first drive signal from the first level to the second level.

[0158] Furthermore, the main control circuit specifically adjusts the first drive signal from the first level to the second level when the amplitude of the first feedback adjustment signal is less than or equal to the amplitude of the resonant capacitor voltage or the resonant current of the resonant current signal.

[0159] S410: In the second half of each second signal cycle, the first driving signal of each first half cycle is copied to obtain a second driving signal.

[0160] In the second half of each second signal cycle, the main control circuit can specifically directly copy the first drive signal of each first half of the cycle to obtain the second drive signal.

[0161] It is understandable that if Figure 4 As shown, in the first half of each second signal cycle, the first drive signal has a first level state, and in the second half of each second signal cycle, the first drive signal continues to be in the second level state; and the second drive signal continues to be in the second level state in the first half of each second signal cycle, and in the second half of each second signal cycle, the level change state of the first drive signal in the first half of each second signal cycle is adjusted and copied to obtain the level change state of the second drive signal.

[0162] The main control circuit is further configured to sequentially adjust the first slope compensation slope using a preset linear function or a preset arithmetic function in each second signal period.

[0163] For ease of understanding, taking the second startup stage as an example, the second control signal includes a second signal period 1, a second signal period 2, ..., a second signal period n, and the slope compensation parameters of the corresponding slope compensation correspond to the first slope compensation slope k1, the first slope compensation slope k2, ..., and the first slope compensation slope kn, respectively. The first slope compensation slope k1, the first slope compensation slope k2, ..., and the first slope compensation slope kn can specifically satisfy a specific preset linear function or a preset arithmetic function.

[0164] For example, when a preset arithmetic function with a tolerance of any reasonable value such as 0.1, 0.2 or 0.3 is satisfied, the first slope compensation slope k1 can be specifically a preset initial value of -1.2, the first slope compensation slope k2 corresponds to -1, the first slope compensation slope 3 corresponds to -0.8, and so on, other slope compensation parameters, or slope compensation parameters of a preset arithmetic function with other preset initial values ​​or other tolerances can be obtained, which will not be repeated here; and when a preset linear function with a linear slope of any reasonable value such as 0.9, 0.8 or 0.7 is satisfied, the first slope compensation slope k1 can be specifically a preset initial value of -1, the first slope compensation slope k2 corresponds to -0.9, the first slope compensation slope 3 corresponds to -0.81, and so on, other slope compensation parameters, or slope compensation parameters of a preset linear function with other preset initial values ​​or other linear slopes can be obtained, which will not be repeated here.

[0165] S411: Regulate the first AC signal using the first drive signal and the second drive signal.

[0166] The first switch subcircuit and the second switch subcircuit are used to receive the first drive signal and the second drive signal to change the switch state under the action of the first drive signal and the second drive signal respectively, thereby regulating the first AC signal to adjust the resonant state of the resonant circuit.

[0167] It is worth noting that the second signal frequency of the second control signal must also satisfy the requirement of being no greater than the maximum resonant frequency of the resonant circuit and no less than the minimum resonant frequency of the resonant circuit, so that in a second signal cycle of the second startup stage, when the second signal frequencies of the first drive signal and the second drive signal generated by the main control circuit through slope compensation are equal to the minimum resonant frequency, the first slope compensation slope corresponding to each subsequent second signal cycle of the second startup stage will be constant as the first slope compensation slope when the second signal frequencies of the first drive signal and the second drive signal are determined to be the minimum resonant frequency.

[0168] See also Fig. 9 , Fig. 9 : is a flow chart of the third embodiment of the current type LLC startup control method of the present application. The current type LLC startup control method of this embodiment is Figure 8 A flowchart of a detailed implementation of the current-type LLC startup control method in the embodiment of the present invention specifically includes the following steps:

[0169] S51: Receive a first DC signal input.

[0170] S52: Convert the first DC signal into a first AC signal.

[0171] S53: Adjust the first AC signal to a resonant current signal.

[0172] S54: Convert the resonant current signal into a second DC signal to output to an external load circuit.

[0173] S55: In the first startup phase, generating a first control signal having a first signal frequency.

[0174] S56: Regulate the first AC signal using the first control signal.

[0175] S57: In the second startup stage, in the first half of each second signal cycle, in response to the start time of the second startup stage or the time when the second drive signal is adjusted from the first level to the second level, the first drive signal is adjusted from the second level to the first level by delaying the set time.

[0176] S58: Delay the set time or use the first slope compensation slope to perform slope compensation on the set voltage signal to obtain a first feedback adjustment signal.

[0177] S59: When the amplitude of the first feedback adjustment signal is less than or equal to the amplitude of the resonant capacitor voltage or the resonant current of the resonant current signal, adjust the first drive signal from the first level to the second level.

[0178] S510: In the second half period of each second signal period, copy the first driving signal of each first half period to obtain a second driving signal.

[0179] S511: Regulate the first AC signal using the first drive signal and the second drive signal.

[0180] Among them, S51, S52, S53, S54, S55, S56, S57, S58, S59, S510 and S511 are Figure 8 S41, S42, S43, S44, S45, S46, S47, S48, S49, S410 and S411 are the same. Please refer to S41, S42, S43, S44, S45, S46, S47, S48, S49, S410 and S411 and their related text descriptions for details. I will not repeat them here.

[0181] S512: In the third startup stage, a second slope compensation slope is used to perform slope compensation on the set voltage signal to obtain a second feedback adjustment signal.

[0182] Specifically, the main control circuit is further coupled to the power conversion circuit to obtain a second DC signal in the power conversion circuit, so as to switch to the third startup stage when it is detected that the voltage of the second DC signal is at a set voltage threshold.

[0183] Optionally, the set voltage threshold may specifically be 80%-100% of the target output voltage Vobj, which is not limited in the present application.

[0184] In the third startup stage, that is, after time T2, the main control circuit is specifically configured to perform slope compensation on the set voltage signal using a second slope compensation slope to obtain a second feedback adjustment signal.

[0185] The second slope compensation slope is specifically the end time of the second startup phase, that is, time T2, or can be understood as the first slope compensation slope kn corresponding to a second signal cycle of the second control signal closest to time T2.

[0186] S513: Generate a third control signal using the second feedback adjustment signal and the resonant current signal.

[0187] The main control circuit generates a third control signal using the second feedback regulation signal and the resonant current signal.

[0188] It can be seen from this that in the third startup stage, the main control circuit specifically continues to use the second slope compensation slope, that is, the above-mentioned first slope compensation slope kn to perform slope compensation on the set voltage signal to obtain the second feedback adjustment signal, and the third control signal generated by using the second feedback adjustment signal and the resonant current signal can be specifically understood as the periodic replication of the first drive signal and the second drive signal of the last second signal cycle in the second startup stage.

[0189] S514: Regulate the first AC signal using the third control signal.

[0190] Furthermore, the first switch sub-circuit and the second switch sub-circuit are also used to receive a third control signal, and use the third control signal to adjust the first AC signal to adjust the resonant state of the resonant circuit.

[0191] The above scheme creatively solves the problems of large starting current and poor monotonicity through three-stage starting control, so as to achieve smoother starting control. While suppressing instantaneous impact current, it also effectively ensures a better gain effect of the resonant circuit, thereby ensuring better performance in a wider range of application scenarios.

[0192] It is understandable that in some other embodiments, the current-type LLC startup control method specifically includes some other more specific circuit units to enable corresponding implementation of other more specific control methods. For details, please refer to Figure 1-Figure 6 And related text descriptions will not be repeated here.

[0193] This application also specifically uses an electronic device, see Fig.10 , Fig.10 Schematic diagram of the framework of an electronic device of the present application. In this embodiment, the electronic device 60 includes a housing 61 and a current-type LLC start-up control circuit 62 connected to the housing 61 .

[0194] Optionally, the electronic device 60 may be any reasonable electronic mechanical device such as a server, a computer, an intelligent communication device, etc., and this application does not limit this.

[0195] It should be noted that the current-type LLC startup control circuit 62 described in this embodiment is the current-type LLC startup control circuit 10 or the current-type LLC startup control circuit 20 described in any one of the above embodiments. Figure 1-Figure 6 And the related text content will not be repeated here.

[0196] The beneficial effects of the present application are as follows: different from the prior art, the inverter circuit in the current-type LLC starting control circuit provided by the present application is used to receive a first DC signal input to convert the first DC signal into a first AC signal; the resonant circuit adjusts the first AC signal into a resonant current signal; the power conversion circuit receives the resonant current signal sent by the resonant circuit, and converts the resonant current signal into a second DC signal to output to the load circuit; the main control circuit is configured to: in the first starting stage, generate a first control signal with a first signal frequency; in the second starting stage, obtain the resonant current signal in the resonant circuit, use the first slope compensation slope to perform slope compensation on the set voltage signal to obtain a first feedback adjustment signal, so as to generate a second control signal using the first feedback adjustment signal and the resonant current signal; wherein the first slope compensation slope is a negative number, and in the second control Each second signal cycle of the signal increases successively; the inverter circuit is used to receive the first control signal and the second control signal, and use the first control signal and the second control signal to adjust the first AC signal in turn, so that in the initial stage of the startup operation of the current-type LLC starting control circuit, that is, the initial stage of receiving the first DC signal input, when the instantaneous impact current is large, different control strategies are adopted in different starting stages to timely suppress the instantaneous impact current to avoid losses to the circuit; and different slope compensations are adopted to control the inverter circuit in different second signal cycles of the second control signal, effectively solving the problems of large starting current and poor monotonicity, so as to achieve smoother starting control, and while suppressing the instantaneous impact current, it also effectively guarantees a better gain effect of the resonant circuit, thereby ensuring better performance in a wider range of application scenarios.

[0197] The above description is only an implementation method of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A current-type LLC start-up control circuit, characterized in that: The current-type LLC start-up control circuit comprises: An inverter circuit, configured to receive a first DC signal input to convert the first DC signal into a first AC signal; a resonant circuit, coupled to the inverter circuit to receive the first AC signal sent by the inverter circuit and adjust the first AC signal to a resonant current signal; an electric energy conversion circuit, coupled to the resonant circuit and used to couple to a load circuit to receive the resonant current signal sent by the resonant circuit and convert the resonant current signal into a second DC signal to output to the load circuit; A main control circuit is coupled to the inverter circuit and the resonant circuit, and the main control circuit is configured to: generate a first control signal with a first signal frequency in a first startup phase; In the second startup stage, the resonant current signal in the resonant circuit is obtained, and a first slope compensation slope is used to perform slope compensation on the set voltage signal to obtain a first feedback adjustment signal, so as to generate a second control signal using the first feedback adjustment signal and the resonant current signal; wherein the first slope compensation slope is a negative number and increases sequentially in each second signal cycle of the second control signal; The inverter circuit is used to receive the first control signal and the second control signal, and adjust the first AC signal using the first control signal and the second control signal in sequence; The inverter circuit includes a first switch subcircuit and a second switch subcircuit, the first switch subcircuit is coupled to the second switch subcircuit, the resonant circuit and the main control circuit, the second switch subcircuit is coupled to the main control circuit, and the second control signal includes a first drive signal and a second drive signal; The main control circuit is coupled to the power conversion circuit to obtain the second DC signal in the power conversion circuit, so as to switch to the third startup stage when it is determined that the voltage of the second DC signal is at a set voltage threshold; In the third startup stage, the main control circuit is configured to use a second slope compensation slope to perform slope compensation on the set voltage signal to obtain a second feedback adjustment signal, so as to generate a third control signal using the second feedback adjustment signal and the resonant current signal; wherein the second slope compensation slope is the first slope compensation slope corresponding to the termination moment of the second startup stage; The first switch sub-circuit and the second switch sub-circuit are further configured to receive the third control signal and use the third control signal to adjust the first AC signal.

2. The current-type LLC startup control circuit according to claim 1, characterized in that: In the second startup stage, the main control circuit is configured to, in the first half cycle of each second signal cycle, in response to the start time of the second startup stage or the second drive signal being adjusted from the first level to the second level, delay the set time length to adjust the first drive signal from the second level to the first level, and delay the set time length or simultaneously use the first slope compensation slope to perform slope compensation on the set voltage signal to obtain the first feedback adjustment signal, so that when the amplitude of the first feedback adjustment signal is less than or equal to the amplitude of the resonant capacitor voltage or the resonant current of the resonant current signal, the first drive signal is adjusted from the first level to the second level; in the second half cycle of each second signal cycle, the first drive signal of each first half cycle is copied to obtain the second drive signal; Wherein, the main control circuit is further used to sequentially adjust the first slope compensation slope by using a preset linear function or a preset arithmetic function in each second signal period; The first switch subcircuit and the second switch subcircuit are used to receive the first drive signal and the second drive signal respectively, and change the switch state under the action of the first drive signal and the second drive signal respectively to adjust the first AC signal.

3. The current-type LLC start-up control circuit according to any one of claims 1-2, characterized in that: The first signal frequency is 90%-100% of the maximum resonant frequency of the resonant circuit; The duration of the first startup phase is a set multiple of the first signal period of the first control signal.

4. The current-type LLC startup control circuit according to claim 2, characterized in that: The resonant circuit comprises a first resonant capacitor, a second resonant capacitor and a resonant inductor, wherein a first end of the first resonant capacitor is coupled to a first end of the first switch subcircuit and a first end of the main control circuit, a second end of the first resonant capacitor is coupled to a first end of the second resonant capacitor, a second end of the main control circuit and a second end of the power conversion circuit, a second end of the second resonant capacitor is coupled to a second end of the second switch subcircuit and a third end of the main control circuit, a first end of the resonant inductor is coupled to a second end of the first switch subcircuit and a first end of the second switch subcircuit, and a second end of the resonant inductor is coupled to a first end of the power conversion circuit; The main control circuit is used to sample and obtain a first capacitor voltage signal between the first end and the second end of the first resonant capacitor and a second capacitor voltage signal between the first end and the second end of the second resonant capacitor, so as to calculate the resonant capacitor voltage using the first capacitor voltage signal and the second capacitor voltage signal.

5. The current-type LLC startup control circuit according to claim 4, characterized in that: The current-type LLC start-up control circuit further includes a switch freewheeling circuit, the switch freewheeling circuit includes a first freewheeling resistor, a second freewheeling resistor, a first freewheeling capacitor, a second freewheeling capacitor, a first diode, and a second diode, the first switch subcircuit includes a first switch tube, and the second switch subcircuit includes a second switch tube; Among them, the first end of the first freewheeling resistor is coupled to the first end of the first switch tube and the second end of the first diode, the second end of the first freewheeling resistor is coupled to the first end of the first freewheeling capacitor, the second end of the first freewheeling capacitor is coupled to the first end of the first diode, the second end of the first switch tube, the first end of the second switch tube, the first end of the second freewheeling resistor, and the second end of the second diode, the second end of the second freewheeling resistor is coupled to the first end of the second freewheeling capacitor, the second end of the second freewheeling capacitor is coupled to the second end of the second switch tube and the first end of the second diode, and the third end of the first switch tube and the third end of the second switch tube are coupled to the main control circuit.

6. The current-type LLC startup control circuit according to claim 4, characterized in that: The main control circuit includes a first proportional filter correction subcircuit, a second proportional filter correction subcircuit, a third proportional filter correction subcircuit, an isolation op amp subcircuit and a control subcircuit, wherein the first proportional filter correction subcircuit is coupled to the first resonant capacitor and the isolation op amp subcircuit, the second proportional filter correction subcircuit is coupled to the second resonant capacitor and the isolation op amp subcircuit, the isolation op amp subcircuit is coupled to the control subcircuit, and the third proportional filter correction subcircuit is coupled to the power conversion circuit and the control subcircuit; The first proportional filtering correction subcircuit is used to obtain the first capacitor voltage signal, and sequentially filter and correct the first capacitor voltage signal to obtain a first filtered signal; The second proportional filtering correction subcircuit is used to obtain the second capacitor voltage signal, and sequentially filter and correct the second capacitor voltage signal to obtain a second filtered signal; The third proportional filtering correction subcircuit is used to obtain the second DC signal, and sequentially filter and correct the second DC signal to obtain a third filtered signal; The isolation amplifier subcircuit is used to receive the first filter signal and the second filter signal, and to sequentially isolate, amplifier, and perform function calculation on the first filter signal and the second filter signal to obtain the resonant capacitor voltage; The control subcircuit is used to receive the resonant capacitor voltage and the third filtered signal, so as to obtain the first drive signal, the second drive signal and the third control signal by using the resonant capacitor voltage and the third filtered signal.

7. A current-type LLC startup control method, characterized in that: The current-type LLC startup control method comprises: receiving a first DC signal input; converting the first DC signal into a first AC signal; adjusting the first AC signal to a resonant current signal; Converting the resonant current signal into a second DC signal to output to an external load circuit; In a first startup phase, generating a first control signal having a first signal frequency; regulating the first AC signal using the first control signal; In the second startup phase, a first slope compensation slope is used to perform slope compensation on the set voltage signal to obtain a first feedback adjustment signal; Generate a second control signal using the first feedback adjustment signal and the resonant current signal; wherein the first slope compensation slope is a negative number and increases sequentially in each second signal cycle of the second control signal; regulating the first AC signal using the second control signal; In the third startup stage, the set voltage signal is slope compensated by using a second slope compensation slope to obtain a second feedback adjustment signal; wherein the second slope compensation slope is the first slope compensation slope corresponding to the end time of the second startup stage; generating a third control signal using the second feedback adjustment signal and the resonant current signal; The first AC signal is regulated using the third control signal.

8. The current-type LLC startup control method according to claim 7, characterized in that: The second control signal includes a first drive signal and a second drive signal. In the second startup phase, the step of using a first slope compensation slope to perform slope compensation on the set voltage signal to obtain a first feedback adjustment signal includes: In the second startup stage, in the first half of each second signal cycle, in response to the start time of the second startup stage or the time when the second drive signal is adjusted from the first level to the second level, the first drive signal is adjusted from the second level to the first level by a delay setting time length; Delaying the set time length or simultaneously using the first slope compensation slope to perform slope compensation on the set voltage signal to obtain the first feedback adjustment signal; The step of generating a second control signal by using the first feedback adjustment signal and the resonant current signal comprises: When the amplitude of the first feedback adjustment signal is less than or equal to the amplitude of the resonant capacitor voltage or the resonant current of the resonant current signal, adjusting the first drive signal from the first level to the second level; In the second half of each second signal cycle, the first drive signal of each first half cycle is copied to obtain the second drive signal; wherein each first slope compensation slope of each second signal cycle has a functional relationship of a preset linear function or a preset arithmetic function; The step of regulating the first AC signal by using the second control signal comprises: The first AC signal is regulated using the first drive signal and the second drive signal.

9. An electronic device, characterized in that: The electronic device comprises a housing and a current-type LLC start-up control circuit connected to the housing; Wherein, the current-type LLC start-up control circuit is the current-type LLC start-up control circuit as described in any one of claims 1-6.

Images