CN109951062B - Resonant converter and control method for resonant converter - Google Patents
Resonant converter and control method for resonant converter Download PDFInfo
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- CN109951062B CN109951062B CN201711395285.3A CN201711395285A CN109951062B CN 109951062 B CN109951062 B CN 109951062B CN 201711395285 A CN201711395285 A CN 201711395285A CN 109951062 B CN109951062 B CN 109951062B
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Abstract
The present disclosure relates to a resonant converter and a control method for a resonant converter. The resonant converter includes: a resonance conversion unit, a synchronous rectifier connected with the resonance conversion unit, a feedback controller and a feedforward controller, wherein the feedback controller is used for executing feedback control based on an output signal of the resonance converter; and the feedforward controller is used for executing feedforward control based on a synchronous control signal of the synchronous rectifier so as to reduce or eliminate overshoot of the output voltage of the resonant converter by adjusting the working frequency of the resonant conversion unit in advance to adjust the gain of the resonant converter. Furthermore, the control method for the resonant converter according to the present disclosure can be implemented by being pre-programmed in the processor to adapt to the load change without detecting the voltage drop of the synchronous rectification MOSFET tube and without adding an additional control circuit. Thus, hardware costs are saved.
Description
Technical Field
The present disclosure relates to the field of converters, and in particular to a resonant converter and a control method for a resonant converter.
Background
This section provides background information related to the present disclosure, which is not necessarily prior art.
Typically, the converter may use a synchronous rectification circuit to improve efficiency. However, the output voltage overshoots at the start-up of the synchronous rectification circuit. Therefore, the present disclosure provides a resonant converter and an effective control method of the resonant converter to improve the problem of output voltage overshoot in the prior art.
Disclosure of Invention
This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.
An object of the present disclosure is to provide a resonant converter and a control method for the resonant converter, according to which the overshoot of the output voltage due to the change of the tube drop of the synchronous rectification MOSFET can be reduced or eliminated by adjusting the operating frequency of the resonant converter in advance by a feedforward controller.
According to an aspect of the present disclosure, there is provided a resonant converter including: a resonance conversion unit, a synchronous rectifier connected with the resonance conversion unit, a feedback controller and a feedforward controller, wherein the feedback controller is used for executing feedback control based on an output signal of the resonance converter; and the feedforward controller is used for executing feedforward control based on a synchronous control signal of the synchronous rectifier so as to reduce or eliminate overshoot of the output voltage of the resonant converter by adjusting the working frequency of the resonant conversion unit in advance to adjust the gain of the resonant converter.
Preferably, the resonant conversion unit is an LLC resonant conversion circuit composed of a primary side L of a transformer, an inductor L and a capacitor C connected in series.
Preferably, the feed forward controller controls the operating frequency of the resonant conversion unit at the same time or before the synchronous rectifier is turned on.
Preferably, the synchronous rectifier is a full bridge rectifier.
Preferably, the resonant converter according to the present disclosure further comprises a switching unit for adjusting an operating frequency of the resonant converting unit.
Preferably, the resonant converter according to the present disclosure further comprises a digital signal processor for controlling the switching unit.
Preferably, the digital signal processor is pre-programmed with the output load to cause the digital signal processor to control the operating frequency of the resonant converter based on the output of the feedback controller and the feedforward controller.
Preferably, the digital signal processor is pre-programmed to cause the digital signal processor to perform the steps of: obtaining a first transfer function from a control signal to an output signal under each of a plurality of output loads, wherein the control signal is a difference between the output signal and a reference signal; obtaining a second transfer function from a synchronous control signal of a synchronous rectifier under each of a plurality of output loads to the output signal; acquiring corresponding control parameters of the feedforward controller based on the first transfer function and the second transfer function to generate a control parameter list of the feedforward controller; setting an actual control parameter of the feedforward controller based on an actual output load and the list of control parameters; and setting the working frequency of the resonance conversion unit according to the sum of the output of the feedforward controller and the output of the feedback controller.
Preferably, the actual control parameter of the feedforward controller is obtained by interpolation of a known control parameter from the plurality of loads.
According to another aspect of the present disclosure, there is provided a resonant converter comprising: a resonance conversion unit; a synchronous rectifier; and a processor pre-programmed to perform the steps of: the overshoot of the output voltage of the resonant converter is reduced or eliminated by adjusting the working frequency of the resonant conversion unit in advance to adjust the gain of the resonant converter.
Preferably, the resonant conversion unit is an LLC resonant conversion circuit consisting of a primary side L of a transformer, an inductor L and a capacitor C connected in series.
Preferably, the processor adjusts the operating frequency of the resonant conversion unit at the same time or before the synchronous rectifier is turned on.
Preferably, the synchronous rectifier is a full bridge rectifier.
Preferably, the resonant converter according to the present disclosure further comprises a switching unit for adjusting an operating frequency of the resonant converting unit.
Preferably, the processor is a digital signal processor for controlling the switching unit.
Preferably, the digital signal processor is pre-programmed to control the switching unit based on different loads and/or synchronous control signals of the synchronous rectifier.
According to yet another aspect of the present disclosure, there is provided a control method for a resonant converter including a resonant conversion unit and a synchronous rectifier connected to the resonant conversion unit, the control method including: performing feedback control based on an output signal of the resonant converter; and performing a feed-forward control based on a synchronous control signal of the synchronous rectifier to reduce or eliminate an overshoot of an output voltage of the resonant converter by adjusting an operating frequency of the resonant conversion unit in advance to adjust a gain of the resonant converter.
Using the control method for a resonant converter according to the present disclosure, the operating frequency of the resonant converter, in particular the LLC resonant converter, can be changed each time the synchronous rectifier is turned on to compensate for the voltage drop in the diodes of the synchronous rectifier, thereby preventing output voltage overshoot.
The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
Drawings
The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. In the drawings:
fig. 1 shows a topology of a resonant converter according to an embodiment of the present disclosure;
fig. 2 shows a topology of a resonant converter according to another embodiment of the present disclosure;
FIG. 3 illustrates a topology of a resonant converter prior to providing a synchronous rectifier pulse width modulation signal according to one embodiment of the present disclosure;
FIG. 4 illustrates a topology of a resonant converter in providing a synchronous rectifier pulse width modulated signal according to one embodiment of the present disclosure;
FIG. 5 shows a block diagram of a transfer function according to one embodiment of the present disclosure;
FIG. 6 shows a block diagram of a transfer function according to another embodiment of the present disclosure;
fig. 7 shows gain curves of a resonant converter for different loads according to an embodiment of the present disclosure; and
fig. 8 shows a gain curve of a resonant converter for a fixed load according to one embodiment of the present disclosure.
While the disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure. It is noted that throughout the several views, corresponding reference numerals indicate corresponding parts.
Detailed Description
Examples of the present disclosure will now be described more fully with reference to the accompanying drawings. The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.
The following example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those skilled in the art. Numerous specific details are set forth such as examples of specific units, devices, and methods to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms, and that neither should be construed to limit the scope of the disclosure. In certain example embodiments, well-known processes, well-known structures, and well-known technologies are not described in detail.
The increase in the voltage step (overshoot) is due to the sudden drop in the voltage across the diode in the switching element in the synchronous rectifier when the synchronous rectifier is turned on, causing an overshoot in the output voltage.
As shown in fig. 1-3, the internal diodes D1, D2, D3 and D4 of Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) Q1, Q2, Q3 and Q4 may act as rectifiers before the driver 1 and the driver 2 of the synchronous rectifier 130 have a control signal, such as a Pulse Width Modulation (PWM) signal, as shown in fig. 3. Output voltage V of resonant converter O ＝V W -2*V diode Wherein V is W Represents the secondary side voltage of the transformer T1, and V diode Representing the forward voltage of diode D1, D2, D3, or D4.
When the driver 1 or 2, e.g. the PWM signal, drives the MOSFET Q1/Q4 or Q2/Q3, a voltage overshoot at Vo occurs because 2V x V diode Slow control loop response.
Then, when the PWM of driver 1 and driver 2 is turned off, the internal diodes D1/D4 and D2/D3 of MOSFETs Q1/Q4 and Q2/Q3 may act as rectifiers.
Next, when the PWM of the driver 1 and the driver 2 is turned on, the MOSFETs Q1/Q4 and Q2/Q3 may be used as small impedance switches in consideration of the drain-source on-resistance Rdson of the MOSFETs Q1, Q2, Q3, and Q4 as shown in fig. 4.
As shown in fig. 4, I1 ═ I2, Rdson1 ═ Rdson2 ═ Rdson3 ═ Rdson4, then the output voltage Vo _1 of the resonant converter is Vw-I1 ═ Rdson1+ Rdson2, where Vw denotes the secondary side voltage of the transformer T1, I1 and I2 denote the currents flowing through the MOSFETs Q1/Q4 and Q2/Q3, respectively, and Rdson1, Rdson2, Rdson3, Rdson4 denote the drain-source on resistances of the MOSFETs Q1, Q2, Q3, and Q4, respectively.
At the instant the synchronous PWM is turned on, if Vf > > I1 × Rdson1, then Vo _1> > Vo (where Vf is the forward voltage of the internal diode of the MOSFET), an overshoot of the output voltage will occur.
For such voltage overshoot, the control method in the prior art is to perform control after the rectifier is turned on or after the voltage overshoot of the output terminal is detected, that is, the conventional feedback control method, as shown in fig. 5, the controller detects whether the output voltage overshoots by comparing the output voltage Vo with the reference voltage Vref. Where Io represents the load current and SYNC-ON represents the ON state of the control signal of the synchronous rectifier. G1, G2, G3, and G6 are merely exemplary of the processing of the control signal and the synchronous rectified signal.
However, the conventional feedback control method often fails to achieve the desired effect because of a very slow voltage feedback loop characteristic, which causes a large overshoot of the output voltage. The present invention aims to introduce a feedforward control method based ON the conventional feedback control method, as shown in fig. 6, to predict the output voltage overshoot in advance according to the states of the load (by detecting the load current Io) and the synchronous rectification control signal (SYNC-ON), that is, to reduce or even eliminate the output voltage overshoot by adjusting the operating frequency of the resonant converter in advance. Likewise, G1 to G6 are merely exemplary of the processing of the control signal and the synchronous rectification signal.
The control method according to the present disclosure may be a composite control method with both output voltage negative feedback and disturbance signal feed forward, unlike the conventional feedback control method in which control is performed after the synchronous rectifier is turned on or after a voltage step at the output terminal is detected.
According to an embodiment of the present disclosure, there is provided a resonant converter including: a resonance conversion unit, a synchronous rectifier connected with the resonance conversion unit, a feedback controller and a feedforward controller, wherein the feedback controller is used for executing feedback control based on an output signal of the resonance converter; and the feedforward controller is used for executing feedforward control based on a synchronous control signal of the synchronous rectifier so as to reduce or eliminate overshoot of the output voltage of the resonant converter by adjusting the working frequency of the resonant conversion unit in advance to adjust the gain of the resonant converter. According to a preferred embodiment of the present disclosure, the feed forward controller may control the operating frequency of the resonant conversion unit at the same time or before the synchronous rectifier is turned on.
Using a resonant converter according to the present disclosure may prevent voltage steps at the output voltage when the synchronous rectifier is conducting.
According to one embodiment of the present disclosure, the resonant conversion unit may be an LLC resonant conversion circuit consisting of a primary side L of a transformer, an inductor L and a capacitor C connected in series. As shown in fig. 1, the resonant conversion unit 120 may include a primary side P1 of a transformer T1, an inductor L1, and a capacitor C2 connected in series to form an LLC series resonant conversion circuit.
According to one embodiment of the present disclosure, the synchronous rectifier 130 may be, for example, a full bridge rectifier composed of Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) Q1, Q2, Q3, and Q4 on the secondary S1 side of the transformer T1 as shown in fig. 1. According to one embodiment of the present disclosure, Q1 and Q4 may be driven with the same synchronous driver 1, while Q2 and Q3 may be driven with the same synchronous driver 2. Here, it should be apparent to those skilled in the art that the full-bridge rectifier shown in fig. 1 is merely exemplary, and the present disclosure is not limited thereto.
According to an embodiment of the present disclosure, the resonant converter may further include a switching unit constituting a chopper, the switching unit being configured to adjust an operating frequency of the resonant conversion unit. As shown in fig. 2, the resonant converter according to the present disclosure may include a switching unit 110, the switching unit 110 being located upstream of the resonant converting unit 120. The switching unit 110 may adjust the operating frequency of the resonant converting unit 120 while turning on the synchronous rectifier 130. Here, it should be apparent to those skilled in the art that the switching unit 110 is merely exemplary, and those skilled in the art can set the switching unit according to actual needs. Alternatively, the function of the switching unit can be realized by hardware or software according to actual needs by those skilled in the art.
According to one embodiment of the present disclosure, the resonant converter may further include a capacitor C1, such as shown in fig. 1, and the capacitor C1 may be connected across the output of the synchronous rectifier 130 for filtering and smoothing the output of the synchronous rectifier 130. Here, it should be clear to those skilled in the art that the capacitor C1 is only exemplary, and those skilled in the art can arrange components to achieve similar functions according to actual needs.
According to one embodiment of the present disclosure, a resonant converter may power a load. Resonant converters may provide different output powers (e.g., 0, 10%, 20%,. 100%) to the load.
According to an embodiment of the present disclosure, the resonant converter may further include a Digital Signal Processor (DSP) (not shown) for controlling the switching unit 110. According to an embodiment of the present disclosure, the DSP may be pre-programmed to control the switching unit 110 based on the gain of the resonant converter, thereby adjusting the operating frequency of the resonant converting unit 120.
According to one embodiment of the present disclosure, the DSP may be pre-programmed to perform the following steps: obtaining a first transfer function from a control signal to an output signal under each of a plurality of output loads, wherein the control signal is a difference between the output signal and a reference signal; obtaining a second transfer function from a synchronous control signal of a synchronous rectifier under each of a plurality of output loads to the output signal; acquiring corresponding control parameters of a feedforward controller based on the first transfer function and the second transfer function to generate a control parameter list of the feedforward controller; setting an actual control parameter of the feedforward controller based on an actual output load and the list of control parameters; and setting the working frequency of the resonance conversion unit according to the sum of the output of the feedforward controller and the output of the feedback controller. According to a preferred embodiment of the present disclosure, the actual control parameters of the feedforward controller may be obtained by interpolation of known control parameters from the plurality of loads.
For example, after setting main data of the resonant converter such as an Lm value of the main transformer, an inductance value Lr of the resonant inductor, a capacitance value Cr of the resonant capacitor, a resonant frequency fr, and a K value, a gain curve of the LLC converter as shown in fig. 7 can be obtained, where Y (x, Q, K, f) represents an LLC gain, and can be expressed as equation (1) below.
Wherein x represents the LLC operating frequency, Q is
k is Lm/Lr, and f is the LLC resonant frequency. As shown in fig. 7, where different loads (e.g., 0, 10%, 20%. 100%) are represented using different Q values. According to the example of fig. 7 of the present disclosure, Q1: -0.4, Q2: -0.478, Q3: -0376, Q4: ═ 0.6, Q5: ═ 0.28, Q6: ═ 0.3, Q7: ═ 0.193, Q8: ═ 0.367 and Q9: ═ 0.1; k1: -6; and f1: -120 kHZ, while the operating frequency x of the LLC may for example range from 40kHZ to 270kHZ (in practice possibly to 280 kHZ).
As can be seen from fig. 7, the target gain (i.e., the target output voltage) can be obtained by changing the operating frequency of the LLC even under different loads.
According to one embodiment of the present disclosure, for example, one may choose Q3 (100% load) as an example, and fig. 8 shows details of the LLC gain when a fixed Q3 (100% load) changes the operating frequency from 40kHz to 270 kHz. Here, it should be clear to a person skilled in the art that the range of the LLC operating frequency is merely exemplary and can be set by a person skilled in the art according to actual needs. In the design model according to the invention, the actual operating frequency is from 70kHz to 260 kHz.
As shown in fig. 8, the gain Y can be expressed as:
where Q3 represents 100% output load, Q3: ═ 0.39, k1: ═ 6, and f1: ═ 120 kHz.
As can be seen from fig. 8, when the output voltage is lower than the normal voltage, if a gain larger than 1 is to be obtained, the LLC operating frequency x can be adjusted to be smaller than 120 kHz. And when the output voltage is higher than the normal voltage, if the LLC gain is to be made smaller than 1, the LLC operating frequency x can be adjusted to be larger than 120 kHz.
In other words, the gains in the gain curves are in one-to-one correspondence with the LLC operating frequency.
Accordingly, a control method for a resonant converter according to the present disclosure may include generating a list of gains and frequencies including a correspondence of gain to LLC operating frequency. According to one embodiment of the present disclosure, the gain and frequency list may be stored in, for example, a DSP chip to set the correct LLC operating frequency in advance by looking up the gain and frequency list in advance before the synchronous rectifier is turned on, so that the required output voltage can be obtained quickly.
According to an embodiment of the present disclosure, setting the operating frequency of the resonance converting unit 120 may further include: based on the gain and frequency list, the operating frequency of the resonance converting unit 120 is increased to a corresponding level and then smoothly decreased by monitoring the output voltage. Here, it should be clear to those skilled in the art that the operating frequency of the resonant converting unit 120 may be increased to a level higher than the corresponding level in the gain and frequency list according to actual needs.
It should be clear to those skilled in the art that the enumeration of 100% load in this disclosure is merely exemplary, and for other output power loads, it can be implemented in a similar manner as 100% load. The present disclosure is not described in detail herein.
Furthermore, the present disclosure also provides a resonant converter comprising: a resonance conversion unit; a synchronous rectifier; and a processor pre-programmed to perform the steps of: the overshoot of the output voltage of the resonant converter is reduced or eliminated by adjusting the working frequency of the resonant conversion unit in advance to adjust the gain of the resonant converter.
According to one embodiment of the present disclosure, the resonant conversion unit is an LLC resonant conversion circuit composed of a primary side L of a transformer, an inductor L and a capacitor C connected in series.
According to one embodiment of the present disclosure, the processor adjusts an operating frequency of the resonant conversion unit at the same time or before turning on the synchronous rectifier.
According to one embodiment of the present disclosure, the synchronous rectifier is a full bridge rectifier.
According to an embodiment of the present disclosure, the resonant converter further comprises a switching unit for adjusting an operating frequency of the resonant converting unit.
According to one embodiment of the present disclosure, the processor is a digital signal processor for controlling the switching unit.
According to one embodiment of the disclosure, the digital signal processor is pre-programmed to control the switching unit based on different loads and/or synchronous control signals of the synchronous rectifier.
According to yet another aspect of the present disclosure, there is also provided a control method for a resonant converter including a resonant conversion unit and a synchronous rectifier connected to the resonant conversion unit, the control method including: performing feedback control based on an output signal of the resonant converter; and performing a feed-forward control based on the synchronous control signal of the synchronous rectifier to reduce or eliminate an overshoot of the output voltage of the resonant converter by adjusting an operating frequency of the resonant converting unit in advance to adjust a gain of the resonant converter.
According to one embodiment of the present disclosure, the resonant conversion unit is an LLC resonant conversion circuit composed of a primary side L of a transformer, an inductor L and a capacitor C connected in series.
According to an embodiment of the present disclosure, the operating frequency of the resonant conversion unit is controlled at the same time or before the synchronous rectifier is turned on.
According to one embodiment of the present disclosure, the synchronous rectifier is a full bridge rectifier.
According to an embodiment of the present disclosure, the resonant converter further comprises a switching unit for adjusting an operating frequency of the resonant converting unit.
According to an embodiment of the present disclosure, the resonant converter further comprises a digital signal processor for controlling the switching unit.
According to one embodiment of the present disclosure, the digital signal processor is pre-programmed with the condition of the output load to cause the digital signal processor to control the operating frequency of the resonant converter based on the output of the feedback control and the feedforward control.
According to one embodiment of the disclosure, the digital signal processor is pre-programmed to cause the digital signal processor to perform the steps of: obtaining a first transfer function from a control signal to an output signal under each of a plurality of output loads, wherein the control signal is a difference between the output signal and a reference signal; obtaining a second transfer function from a synchronous control signal of a synchronous rectifier to an output signal at each of a plurality of output loads; acquiring corresponding control parameters of the feedforward controller based on the first transfer function and the second transfer function to generate a control parameter list of the feedforward controller; setting an actual control parameter of the feedforward controller based on an actual output load and the list of control parameters; and setting the working frequency of the resonance conversion unit according to the sum of the output of the feedforward controller and the output of the feedback controller.
According to one embodiment of the present disclosure, the actual control parameter of the feedforward controller is obtained by interpolation of a known control parameter from the plurality of loads.
Various embodiments of components of a resonant converter and a control method thereof according to an embodiment of the present disclosure have been described in detail above, and a description thereof will not be repeated.
In the apparatus and method of the present disclosure, it is apparent that each component or each step may be decomposed and/or recombined. Such decomposition and/or recombination should be considered as equivalents of the present disclosure. Also, the steps of executing the series of processes described above may naturally be executed chronologically in the order described, but need not necessarily be executed chronologically. Some steps may be performed in parallel or independently of each other.
Although the embodiments of the present disclosure have been described in detail with reference to the accompanying drawings, it should be understood that the above-described embodiments are merely illustrative of the present disclosure and do not constitute a limitation of the present disclosure. Various modifications and alterations to the above-described embodiments may be apparent to those skilled in the art without departing from the spirit and scope of the disclosure. Accordingly, the scope of the disclosure is to be defined only by the claims appended hereto, and by their equivalents.
Claims (15)
1. A resonant converter, comprising: a resonance conversion unit, a synchronous rectifier connected with the resonance conversion unit, a feedback controller and a feedforward controller,
the feedback controller is used for executing feedback control based on the output signal of the resonant converter; and
the feedforward controller is configured to perform feedforward control based on a synchronous control signal of the synchronous rectifier to reduce or eliminate overshoot of an output voltage of the resonant converter by adjusting an operating frequency of the resonant converter unit in advance to adjust a gain of the resonant converter, wherein the feedforward controller controls the operating frequency of the resonant converter unit simultaneously with or before the synchronous rectifier is turned on.
2. The resonant converter according to claim 1, wherein the resonant conversion unit is an LLC resonant conversion circuit consisting of a primary side L of a transformer, an inductor L and a capacitor C connected in series.
3. A resonant converter according to claim 1 or 2, wherein the synchronous rectifier is a full bridge rectifier.
4. A resonant converter according to claim 1 or 2, further comprising a switching unit for adjusting an operating frequency of the resonant converting unit.
5. The resonant converter of claim 4, further comprising a digital signal processor for controlling the switching unit.
6. The resonant converter of claim 5, wherein the digital signal processor is pre-programmed with output load conditions to cause the digital signal processor to control the operating frequency of the resonant converter based on the outputs of the feedback controller and the feedforward controller.
7. The resonant converter of claim 6, wherein the digital signal processor is pre-programmed to cause the digital signal processor to perform the steps of:
obtaining a first transfer function from a control signal to an output signal under each of a plurality of output loads, wherein the control signal is a difference between the output signal and a reference signal;
obtaining a second transfer function from a synchronous control signal of a synchronous rectifier under each of a plurality of output loads to the output signal;
acquiring corresponding control parameters of the feedforward controller based on the first transfer function and the second transfer function to generate a control parameter list of the feedforward controller;
setting an actual control parameter of the feedforward controller based on an actual output load and the list of control parameters; and
and setting the working frequency of the resonance conversion unit according to the sum of the output of the feedforward controller and the output of the feedback controller.
8. The resonant converter of claim 7, wherein the actual control parameters of the feedforward controller are obtained by interpolation of known control parameters from the plurality of output loads.
9. A resonant converter, comprising:
a resonance converting unit;
a synchronous rectifier; and
a processor, said processor being pre-programmed to perform the steps of:
overshoot of the output voltage of the resonant converter is reduced or eliminated by adjusting the operating frequency of the resonant converter unit in advance to adjust the gain of the resonant converter, wherein the operating frequency of the resonant converter unit is adjusted simultaneously with or before the synchronous rectifier is turned on.
10. The resonant converter according to claim 9, wherein the resonant conversion unit is an LLC resonant conversion circuit consisting of a primary side L of a transformer, an inductor L and a capacitor C connected in series.
11. A resonant converter according to claim 9 or 10, wherein the synchronous rectifier is a full bridge rectifier.
12. The resonant converter according to claim 9 or 10, further comprising a switching unit for adjusting an operating frequency of the resonant converting unit.
13. The resonant converter of claim 12, wherein the processor is a digital signal processor for controlling the switching unit.
14. The resonant converter according to claim 13, wherein the digital signal processor is pre-programmed to control the switching unit based on different loads and/or synchronous control signals of the synchronous rectifier.
15. A control method for a resonant converter comprising a resonant converting unit and a synchronous rectifier connected to the resonant converting unit, the control method comprising:
performing feedback control based on an output signal of the resonant converter; and
performing a feed-forward control based on a synchronous control signal of the synchronous rectifier to reduce or eliminate overshoot of an output voltage of the resonant converter by adjusting an operating frequency of the resonant converter unit in advance to adjust a gain of the resonant converter, wherein the operating frequency of the resonant converter unit is adjusted simultaneously with or before the synchronous rectifier is turned on.
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| CN102201739A (en) * | 2011-05-27 | 2011-09-28 | 华北电力大学（保定） | Symmetrical half-bridge LLC resonant bidirectional DC-DC converter |
| CN104756389A (en) * | 2012-11-19 | 2015-07-01 | 苹果公司 | AC-DC resonant converter that provides high efficiency and high power density |
| CN103840646A (en) * | 2012-11-23 | 2014-06-04 | 南京博兰得电子科技有限公司 | Resonant converting device |
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