WO2018157796A1

WO2018157796A1 - Resonant converter

Info

Publication number: WO2018157796A1
Application number: PCT/CN2018/077436
Authority: WO
Inventors: 王跃斌; 崔荣明; 宋栋梁
Original assignee: 深圳市皓文电子有限公司
Priority date: 2017-02-28
Filing date: 2018-02-27
Publication date: 2018-09-07
Also published as: CN106787771A

Abstract

A resonant converter comprises a driving signal adjustment module and a driving signal generation module. The driving signal adjustment module collect a voltage value of a current direct-current output of the resonant converter, generates a first control signal and a second control signal according to the collected direct-current voltage value and transmits the first control signal and the second control signal to the driving signal generation module. The driving signal generation module adjusts parameters of driving signals sent to a switch device of a switch unit according to the first control signal and the second control signal, so as to control a duty cycle or a conduction angle and a switch frequency of the switch device in the switch unit, so that the voltage value of the direct-current output is stabilized in a set range, the first control signal controls the duty cycle or the conduction angle, and the second control signal controls the switch frequency. The resonant converter is easy to implement protection control, has a zero-crossing switch that does not easily fail, and has a small device stress.

Description

Resonant converter

Technical field

This invention relates to the field of power supplies and, more particularly, to a resonant converter.

Background technique

Resonant switching converter The main power circuit of the converter is mainly composed of a switching device, a rectifying device and a resonance network. Since the resonant switching converter operates in a zero voltage (ZVS) switch or / and a zero current (ZCS) switching state, it has the advantages of high switching frequency, small circuit size, and high power density. In the prior art, both a variable frequency control strategy and a fixed frequency control strategy can be applied to a resonant switching converter. In these control strategies, the variable frequency control strategy changes the frequency of the excitation source (usually the voltage source) through the switching device, thereby changing the impedance value of each component of the resonant network, thereby achieving the purpose of controlling the transmission power; the fixed frequency control strategy is changed by the switching device The magnitude of the excitation source (usually the voltage source), which in turn achieves the purpose of controlling the transmission power. However, on the one hand, the variable frequency control strategy often leads to problems such as large circulating current energy of the resonant switching converter, wide range of switching frequency variation, low utilization rate of magnetic components and difficulty in starting/protection control in wide load and wide input applications; The frequency control strategy also causes problems such as zero voltage switching/zero current switching failure of the resonant switching converter and large voltage and current stress of the device in such occasions. Therefore, the prior art resonant switching converter has the defects of difficulty in protection control, easy occurrence of zero-crossing switch failure, and large device stress.

technical problem

Type the technical problem description paragraph here.

Technical solution

The technical problem to be solved by the present invention is that the above-mentioned protection control of the prior art is difficult to implement, the defect of the zero-crossing switch is easy to occur, and the device stress is large, and the protection control is easy to be realized, the zero-crossing switch is not easy to be failed, and the device stress is small. A resonant converter.

The technical solution adopted by the present invention to solve the technical problem is to construct a resonant converter including a switching unit for converting an input DC voltage into a square wave pulse, the square wave pulse passing through a resonance network, a high frequency transformer and a rectifying unit And a DC output that is a set voltage value, further comprising a driving signal adjustment module and a driving signal generating module; the driving signal adjusting module collecting a current DC output voltage value of the resonant converter, according to the collected DC voltage value Generating a first control signal and a second control signal to the driving signal generating module; the driving signal generating module adjusts a signal sent to the switching device of the switching unit according to the first control signal and the second control signal Driving a parameter of the signal, thereby controlling a duty ratio or a conduction angle and a switching frequency of the switching device in the switching unit, such that a voltage value of the DC output is stable within a set range; wherein the first control signal The duty cycle or conduction angle is controlled and the second control signal controls the switching frequency.

Further, the difference between the adjusted duty ratio or the conduction angle of the first control signal and the DC output voltage and the reference voltage collected by the driving signal adjustment module is proportional to the result of the error amplification; There is a linear relationship between the second control signal and the first drive signal.

Further, the first control signal and the second control signal satisfy the following linear relationship:

v _δ + V _k v _fs = V _f

The first control signal is v _δ , the second control signal is v _fs , and V _k , V _f are constants greater than zero determined by design parameters of the resonant converter.

Further, under the adjustment of the first control signal and the second control signal, the frequency of the driving signal output by the driving signal adjustment module and the duty ratio or the conduction angle correspond to each other when the driving signal is occupied When the ratio or conduction angle is a set value, the frequency is another set value.

Further, the driving signal adjustment module includes a voltage sampling module, an error amplification module, and a linear coupling module; wherein the voltage sampling module is sampled by a DC output terminal to obtain a sampling voltage and output to the error amplification module; The error amplifying module takes the difference between the sampling voltage and the reference voltage and proportionally integrates the obtained difference to obtain an error voltage; the linear coupling module obtains an error voltage, and after performing operation with the set voltage, respectively generates the a first control signal and the second control signal; the first control signal and the second control signal are sent to the drive signal generating module.

Further, the driving signal generating module includes a waveform generating module, a comparing module and a driving module; wherein the waveform generating module adjusts an internal controlled current source according to the second control signal to generate a peak constant, a frequency and the The second control signal is proportional to the triangular wave; meanwhile, a narrow pulse sequence having the same frequency as the triangular wave peak is generated at the peak time of the triangular wave, and the narrow pulse sequence is transmitted to the driving module; The first control signal and the triangular wave are sent to the driving module; the two rising edge trigger circuits of the driving module respectively detect a rising edge of the narrow pulse sequence and a rising edge of the comparison result And respectively flipping the output level of the rising edge trigger circuit at the rising edge time, and the output level of the rising edge trigger circuit or the output level of the rising edge trigger circuit is outputted to the logic gate On the control terminals of the different switching devices, a drive signal of the resonant converter switching unit is formed.

Further, the linear coupling module includes a first subtractor, a second subtractor, a multiplier, and a limiter circuit; an error voltage is connected to one input end of the first subtractor, and the first subtractor is further Inputting a set first voltage, an output of the first subtractor is respectively output to an input end of the comparator and an input end of the multiplier through a limiter circuit; another of the multiplier An input is coupled to the set second voltage, the multiplier output is coupled to an input of the second subtractor; and the other input of the second subtractor is coupled to the set third voltage, An output of the second subtractor is coupled to an input of the waveform generating module; the error voltage and an output of the multiplier are coupled to a negative input of the first subtractor and the second subtractor, respectively .

Further, the first voltage, the second voltage, and the third voltage are both positive voltages; wherein, the first voltage magnitude determines a minimum duty ratio or a conduction angle of the resonant converter, the third voltage The size determines the maximum switching frequency of the resonant converter.

Still further, the switching unit comprises a full bridge or half bridge structure, the resonant network comprising a series resonant network, a parallel resonant network, an LCC or an LLC resonant network adapted to the switching unit.

Further, the rectifying unit includes a diode rectification, a double current rectification, a full wave rectification or a synchronous rectification circuit.

Beneficial effect

A resonant converter embodying the present invention has the following advantageous effects: the error voltage obtained by sampling the output is used to generate a first linear relationship between the duty cycle or the conduction angle and the frequency of the drive signal. The control signal and the second control signal, by setting a parameter of a unit or a module that generates the first control signal and the second control signal, disperse the required adjustment amount to a duty ratio or a conduction angle and a frequency of the driving signal, This results in a superimposed effect, thereby achieving the effect of achieving a larger modulation range with a smaller adjustment amount. Therefore, it is easy to implement protection control, the zero-crossing switch is not easy to fail, and the device stress is small.

DRAWINGS

1 is a schematic structural view of an embodiment of a resonant converter of the present invention;

2 is a schematic structural diagram of a driving signal adjustment module in the embodiment;

3 is a schematic structural diagram of a driving signal generating module in the embodiment;

4 is a schematic structural view of a linear coupling module in the embodiment;

Figure 5 is a circuit diagram of a resonant converter in one of the embodiments;

FIG. 6 is a waveform diagram of each key node in FIG. 5.

BEST MODE FOR CARRYING OUT THE INVENTION

The description of the preferred embodiment of the invention is entered here.

Embodiments of the invention

The embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

As shown in FIG. 1, in a resonant converter embodiment of the present invention, the resonant converter includes a switching unit that converts an input DC voltage into a square wave pulse, and the square wave pulse passes through a resonant network, a high frequency transformer. And the rectifying unit is a DC output of a set voltage value, further comprising a driving signal adjusting module and a driving signal generating module; the driving signal adjusting module collecting the current DC output voltage value of the resonant converter, according to the collected The DC voltage value generates a first control signal and a second control signal and is transmitted to the driving signal generating module; the driving signal generating module adjusts a switch sent to the switching unit according to the first control signal and the second control signal a parameter of a driving signal on the device, thereby controlling a duty ratio or a conduction angle and a switching frequency of the switching device in the switching unit, such that a voltage value of the DC output is stabilized within a set range; wherein A control signal controls a duty cycle or a conduction angle, and the second control signal controls a switching frequency. In other words, in the embodiment, the driving signal adjustment module in the resonant converter obtains the current DC output voltage from the DC output end of the resonant converter, and performs operation or transformation according to the obtained current voltage to obtain the first control. a signal and a second control signal, the first control signal and the second control signal are sent to a driving signal generating module, and the driving signal generating module generates a switch driving signal according to the input first control signal and the second control signal, and Output to the switch unit to control the switch of the switching device in the switch unit; when the current voltage is large, the switch drive signal output to the switch device reduces the duty ratio or conduction angle of the switch device, and causes the switching frequency of the switch device Decreasing, thereby causing the DC output voltage to decrease; when the current voltage is small, the switching drive signal output to the switching device increases the duty ratio or the conduction angle of the switching device, and increases the switching frequency of the switching device, thereby The DC output voltage rises. Thus, the output DC voltage of the above resonant converter is maintained at a set output voltage accessory. In this embodiment, the driving signal outputted to the switching device is changed according to the change of the DC output voltage. Specifically, the change of the output DC voltage causes the first control signal and the second control signal to change. The first control signal causes a change in a parameter of a duty ratio or a conduction angle of the switching device in the driving signal, for example, a pulse width of the driving signal; and a second control signal causes a parameter change in a driving signal to control a switching frequency of the switching device, For example, the frequency of the drive signal. In the present embodiment, the duty ratio or the conduction angle is changed simultaneously with the frequency, that is, in the present embodiment, the output DC voltage is stabilized by simultaneously changing the duty ratio or the conduction angle and the switching frequency.

It is worth mentioning that in the present embodiment, the definition of the duty ratio or the conduction angle is the same as the definition of the duty ratio or the conduction angle in the prior art. The two actually have the same parameter, which refers to the length of the on-time of the switching device in a switching cycle. It is customary to refer to the conduction angle when the switching unit is a full-bridge circuit, and in the case where the switching unit is a half-bridge circuit. , usually called the duty cycle. For the switch drive signal, both correspond to the pulse width of the drive signal.

In this embodiment, if the first control signal is v _δ and the second control signal is v _fs , the first control signal and the second control signal satisfy the following linear relationship: v _δ + V _k v _fs = V _f ; where V _k , V _f are constants greater than zero, the value of which is determined by the parameter design process of the resonant converter. In fact, the above linear relationship is determined by the specific circuit structure in this embodiment, and the above constants are also embodied in specific circuit parameters. In other words, in the present embodiment, due to the limitation of the specific circuit and the electric quantity parameter, the linear relationship between the first control signal and the second control signal is presented. At the same time, due to the above linear relationship, the frequency and duty ratio or the duty ratio of the driving signal output by the driving signal adjusting module are adjusted by the selection and setting of the circuit parameters under the adjustment of the first control signal and the second control signal. The corner angles correspond to each other, and a one-to-one correspondence can be realized. When the duty ratio or the conduction angle of the driving signal is a set value, the frequency is another set value; when the driving signal has a set value At the duty cycle or conduction angle, the drive signal has a set frequency at the same time. In this way, for the entire resonant converter, the benefits of duty cycle or conduction angle adjustment, switching frequency adjustment, and the adverse effects of the two adjustment modes can be avoided, that is, obtained by a small adjustment amount. Larger adjustment range.

Fig. 2 shows a more specific structure of the drive signal adjusting module in this embodiment. In FIG. 2, the driving signal adjustment module includes a voltage sampling module, an error amplification module, and a linear coupling module; wherein the voltage sampling module is sampled by a DC output terminal to obtain a sampling voltage and output to the error amplification module; The error amplifying module takes the difference between the sampling voltage and the reference voltage and proportionally integrates the obtained difference to obtain an error voltage; the linear coupling module obtains an error voltage, and after calculating the voltage with the set voltage, respectively generates a Decoding the first control signal and the second control signal; the first control signal and the second control signal are sent to the driving signal generating module.

Fig. 3 shows the specific structure of the drive signal generating module in this embodiment. In FIG. 3, the driving signal generating module includes a waveform generating module, a comparing module, and a driving module; wherein the waveform generating module adjusts an internal controlled current source according to the second control signal to generate a peak constant, a frequency and a Generating a triangular wave proportional to the second control signal; at the same time, generating a narrow pulse sequence in phase with the peak of the triangular wave and delivering the narrow pulse sequence to the driving module; that is, for the triangular wave That is, each time its peak appears, a narrow pulse is generated; thus, the frequency of the triangular wave peak appears to be the same as the frequency of the narrow pulse; meanwhile, the rising edge of the triangular wave peak is aligned with the rising edge of the pulse. The comparison module compares the first control signal with the triangular wave, and sends the comparison result to the driving module; the driving module includes two parallel rising edge trigger circuits and logic non-gates, the two rising edges An input end of the trigger circuit is respectively connected to the first control signal and the second control signal, and an output end thereof is directly or through The logic NOT gate is outputted to the control terminals of the different switching devices in the switching unit, and the switching device is controlled to be turned on and off to form the above-mentioned driving signal or switching driving signal; in the above structure, two rising edge trigger circuits Detecting a rising edge of the narrow pulse sequence and a rising edge timing of the comparison result, respectively, and inverting an output level of the rising edge trigger circuit at the rising edge time, respectively, the two output levels are directly or through logic The non-gate is transmitted as a drive signal to the control terminals of the different switching devices in the switching unit. Among them, a rising edge trigger circuit transmits a direct output driving level and a non-gate driving level to two adjacent bridge arms, respectively.

4 shows a specific structure of the linear coupling module in the embodiment, the linear coupling module includes a first subtractor, a second subtractor, a multiplier, and a limiter circuit; the error voltages are respectively connected to the first subtraction method And an input end of the multiplier, the other input end of the first subtractor inputs a set first voltage, and the output end of the first subtractor is output to the comparator end through a limiter circuit; The other input of the multiplier is coupled to the set second voltage, the multiplier output is coupled to an input of the second subtractor; the other input of the second subtractor is set A third voltage connection, an output of the second subtractor being coupled to an input of the waveform generation module. Wherein the error voltage and the output of the multiplier are respectively connected to the negative input terminals of the first subtractor and the second subtractor. In this embodiment, the first voltage, the second voltage, and the third voltage are set in advance, and the setting is based on circuit parameters of the resonant converter, for example, output voltage, output current, and high frequency transformer. The number of turns in the primary and secondary, and so on. Meanwhile, the first voltage, the second voltage, and the third voltage determine a linear relationship between the first control signal and the second control signal.

Through the selection of the above structure and parameters, in the embodiment, under the adjustment of the first control signal and the second control signal, the frequency and duty ratio or conduction angle of the driving signal output by the driving signal adjustment module Corresponding to each other, when the duty ratio or the conduction angle of the driving signal is a set value, the frequency is another set value. For example, in one case in this embodiment, each duty ratio of the adjusted driving waveform can be made to uniquely correspond to a switching frequency, for example, 90% of the duty ratio corresponds to a switching frequency of 100 kHz, 50 The duty ratio of % corresponds to a switching frequency of 110 kHz and so on.

In general, in the present embodiment, compared with the existing self-sustained oscillation phase shift control, the duty ratio or the conduction angle of the driving waveform and the switching frequency are linear, simplifying the design of the control circuit; The control dimensions are related to each other, which enhances the stability of the system. At the same time, the technical solution in this embodiment is compared with the existing variable frequency control technology, and the resonant switching converter has a switching frequency when the input voltage or the output power changes. The narrower range of variation is beneficial to improve the utilization of magnetic components in the resonant switching converter, and simplifies the design process of the filter in the resonant switching converter. The resonant switching converter startup/protection function is easier to implement.

In addition, the technical solution in this embodiment is compared with the existing fixed frequency control technology, and the resonant switching converter can always maintain zero voltage or zero current soft switching state operation in a wide input voltage or wide load application. Compared with the existing variable frequency control technology and the fixed frequency control technology, the resonant switching converter adopting the technical scheme of the embodiment has a smaller circulating current energy during operation in a wide input voltage or a wide load application, and improves Device efficiency.

Fig. 5 and Fig. 6 are circuit diagrams showing the resonant converter in one case in the present embodiment and waveform diagrams of respective points in the circuit. In Figs. 5 and 6, the application circuit diagram of the technical solution in the present embodiment in the LCC resonant converter is shown. For LCC resonant converters, when the output power ( P _o ) decreases or the input voltage ( V _in ) increases, the conduction angle ( δ ) or the switching frequency ( f _s ) needs to be reduced to maintain the output voltage constant; When P _o ) rises or the input voltage ( V _in ) decreases, increase the conduction angle ( δ ) or decrease the switching frequency ( f _s ) to maintain the output voltage constant.

For specific implementation, please refer to FIG. 5. FIG. 5 shows a quasi-fixed-frequency controlled LCC resonant converter in the embodiment, including a power supply 1, a switching network 2, a resonant network and a transformer 3, a rectifying portion 4, and a filtering network. 5. Load 6 and control circuit (the control circuit includes the aforementioned drive signal generation module and drive signal adjustment module). The power source 1, the switch network 2, the resonance network and the transformer 3, the rectifying portion 4, the filter network 5, and the load 6 are sequentially connected. The power supply 1 is a DC power supply V _in ; the switching network 2 is a full bridge switching circuit, wherein S1 and S2 form a leading bridge arm, S3 and S4 form a lag bridge arm; the resonant network and the transformer 3 comprise a series resonant inductor L _r , a series resonant capacitor C _s , parallel resonant capacitor C _p , transformer T _r匝 ratio is n: 1; rectification part 4 is a double current rectification circuit; filter network 4 is an LC filter circuit; load 6 is a resistive load R _L .

The control circuit includes a voltage sampling module 8, an error amplifier 7, a reference voltage 11, a linear coupling module 12, a waveform generating module 21, a comparison module 20, and a driving module 30. The waveform generating module 21, the comparing module 20, and the driving module 30 constitute the above. The drive signal generation module and the remaining part constitute a drive signal adjustment module. The linear coupling module 12 is composed of a first voltage source 13 that generates a first voltage V _d , a first subtractor 14 , a second subtractor 16 , a multiplier 15 , a second voltage source that generates a second voltage V _k , and generates a third A third voltage source 18 of voltage V _F and a limiting circuit 19 are formed.

In this embodiment, the specific working process and principle of the above circuit is: the voltage sampling module 8 detects the output voltage and generates an error signal v _e through the error amplifier 7; the linear coupling module 12 receives v _e and generates a switching frequency control signal v _fs ( a second control signal) and a conduction angle control signal v _δ (first control signal); the waveform generation module 21 receives v _fs to generate a triangular wave v _saw and a pulse signal v _p , respectively; and the comparison module 20 receives v _saw and v _δ to generate Comparing the results v _cmp ; the drive module 30 receives v _cmp and v _p and generates a switch drive signal to control the operation of the main power circuit switching device.

Fig. 5 is a waveform diagram of each key point of the above circuit of the embodiment. The horizontal axis is time (ms). In Figure 4, in the order from top to bottom, the vertical axis of the first waveform is the full bridge circuit output voltage v _AB (V) and the resonant current i _r (A); The vertical axis of the second waveform is the triangular carrier v _saw and the conduction angle control signal v _δ ; the third waveform and the fourth waveform are the gate drive signals of the switch 1 (S1) and the switch 4 (S4), respectively. The waveform in Figure 4 is obtained under the following conditions: input voltage V _in = 300V, output voltage V _o = 48V, output power P _o = 1500W, resonant inductance L _r = 105.66μH, series resonant capacitor and parallel resonant capacitor C _s = C _p = 59.19nF, transformer turns ratio n = 2.7.

Further, in the present embodiment, the above-described switching unit may include a full-bridge or half-bridge structure, and the resonant network includes a series resonant network, a parallel resonant network, an LCC or an LLC resonant network adapted to the switching unit. The rectifying unit includes diode rectification, current doubler rectification, full wave rectification or synchronous rectification circuit. That is to say, in any case, the rectifying and filtering unit can adopt multiple structure rectification of various structures or types; or a synchronous rectification circuit can be used, for example, a full-bridge rectification circuit using diode rectification, and full synchronous rectification Bridge rectifier circuit, full-wave rectification circuit using diode rectification or full-wave rectification circuit using synchronous rectification.

In the present embodiment, the above technical solution can be applied to a two-element resonant converter such as series resonance or parallel resonance, or a multi-element resonant converter such as LLC or LCC, in addition to the LCC resonant converter in the present embodiment.

The above-mentioned embodiments are merely illustrative of several embodiments of the present invention, and the description thereof is more specific and detailed, but is not to be construed as limiting the scope of the invention. It should be noted that a number of variations and modifications may be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, the scope of the invention should be determined by the appended claims.

Industrial applicability

Type the industrial usability description paragraph here.

Sequence table free content

Type the sequence table free content description paragraph here.

Claims

A resonant converter includes a switching unit that converts an input DC voltage into a square wave pulse, and the square wave pulse passes through a resonant network, a high frequency transformer, and a rectifying unit to become a DC output of a set voltage value, and is characterized The driving signal adjustment module further includes a driving signal adjustment module and a driving signal generating module; the driving signal adjusting module collects a current DC output voltage value of the resonant converter, and generates a first control signal and a second control signal according to the collected DC voltage value. And transmitting to the driving signal generating module; the driving signal generating module adjusting parameters of a driving signal sent to the switching device of the switching unit according to the first control signal and the second control signal, thereby controlling the switch a duty ratio or a conduction angle and a switching frequency of the switching device in the unit, such that a voltage value of the DC output is stabilized within a set range; wherein the first control signal controls a duty ratio or a conduction angle, The second control signal controls the switching frequency.
The resonant converter according to claim 1, wherein a difference between a duty ratio or a conduction angle of the first control signal and a DC output voltage and a reference voltage collected by the driving signal adjustment module The result of the error amplification is proportional; there is a linear relationship between the second control signal and the first driving signal.
The resonant converter according to claim 2, wherein said first control signal and said second control signal satisfy a linear relationship as follows:

v δ + V k v fs = V f

The first control signal is v δ , the second control signal is v fs , and V k , V f are constants greater than zero determined by design parameters of the resonant converter.
The resonant converter according to claim 3, wherein the frequency and duty ratio or conduction of the driving signal output by the driving signal adjusting module is adjusted under the adjustment of the first control signal and the second control signal The angles correspond to each other. When the duty ratio or the conduction angle of the driving signal is a set value, the frequency is another set value.
The resonant converter according to claim 4, wherein the driving signal adjustment module comprises a voltage sampling module, an error amplification module and a linear coupling module; wherein the voltage sampling module is sampled by a DC output terminal to obtain a sampling voltage And outputting to the error amplifying module; the error amplifying module takes the difference between the sampling voltage and the reference voltage and proportionally integrates the obtained difference to obtain an error voltage; the linear coupling module obtains an error voltage, and And generating the first control signal and the second control signal respectively after calculating the set voltage; the first control signal and the second control signal are sent to the driving signal generating module.
The resonant converter according to claim 5, wherein said driving signal generating module comprises a waveform generating module, a comparing module and a driving module; wherein said waveform generating module adjusts internal control according to said second control signal a current source, generating a triangular wave whose peak value is constant and whose frequency is proportional to the second control signal; meanwhile, a narrow pulse sequence having the same frequency as the peak value of the triangular wave is generated at the peak time of the triangular wave, and the narrow pulse sequence is transmitted Go to the driving module; the comparison module compares the first control signal with the triangular wave, and sends the comparison result to the driving module; the two rising edge trigger circuits of the driving module respectively detect the narrow pulse a rising edge of the sequence and a rising edge timing of the comparison result, and respectively flipping an output level of the rising edge trigger circuit at the rising edge time, an output level of the rising edge trigger circuit or the rising edge trigger circuit The output level is outputted to the control terminals of different switching devices through the logic gates to form the resonant converter. Turn off the drive signal of the unit.
The resonant converter according to claim 6, wherein said linear coupling module comprises a first subtractor, a second subtractor, a multiplier and a limiter circuit; and an error voltage is coupled to one of said first subtractors Input, the other input end of the first subtractor inputs a set first voltage, and the output end of the first subtractor is respectively output to an input end of the comparator and the multiplier through a limiter circuit One input of the multiplier; the other input of the multiplier is coupled to a set second voltage, the multiplier output is coupled to an input of the second subtractor; and the other of the second subtractor The input end is coupled to the set third voltage, the output of the second subtractor is coupled to the input of the waveform generating module; the error voltage and the output of the multiplier are respectively coupled to the first The negative input of the subtractor and the second subtractor.
The resonant converter according to claim 7, wherein said first voltage, said second voltage, and said third voltage are both positive voltages; wherein said first voltage magnitude determines a minimum duty of said resonant converter The ratio of the third voltage determines the maximum switching frequency of the resonant converter.
The resonant converter according to any one of claims 1-8, wherein the switching unit comprises a full bridge or a half bridge structure, and the resonant network comprises a series resonant network adapted to the switching unit, Parallel resonant network, LCC or LLC resonant network.
The resonant converter according to claim 9, wherein said rectifying unit comprises diode rectification, current doubler rectification, full wave rectification or a synchronous rectification circuit in the form of the above circuit.