CN113708644B - Simplified synchronous rectification method and device for CLLC resonant converter - Google Patents
Simplified synchronous rectification method and device for CLLC resonant converter Download PDFInfo
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- 230000002441 reversible effect Effects 0.000 description 6
- 239000003990 capacitor Substances 0.000 description 4
- 238000010586 diagram Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
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- 238000013461 design Methods 0.000 description 1
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- 230000005284 excitation Effects 0.000 description 1
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
- H02M3/33576—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
- H02M3/33592—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
- H02M3/33576—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
- H02M3/33584—Bidirectional converters
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
Abstract
The application discloses a simplified synchronous rectification method and device of a CLLC resonant converter, wherein the synchronous rectification method comprises the following steps: and if the current load current is greater than the lowest load current, starting synchronous rectification. If the current switching frequency is lower than or equal to the resonant frequency, the secondary side switching tube and the primary side switching tube are simultaneously turned on; and after the first time period is started, the secondary side switching tube and the primary side switching tube are simultaneously turned off. If the current switching frequency is higher than the resonant frequency, the secondary side switching tube is turned on for a second time period after the primary side switching tube is lagged; and after the secondary side switching tube is turned on for a third time period, the secondary side switching tube and the primary side switching tube are turned off at the same time. The application determines whether to start synchronous rectification by judging the magnitude relation between the current load current and the lowest load current, greatly simplifies the implementation process of synchronous rectification of the secondary side, and can accurately control the synchronous switching tube only through the known current switching frequency during synchronous rectification.
Description
Technical Field
The application belongs to the technical field of power electronics, and particularly relates to a simplified synchronous rectification method and device of a CLLC resonant converter.
Background
With the continuous development of technical industries such as electric automobiles, distributed power supplies, aviation power supply systems, uninterruptible Power Supplies (UPS), and the like, a bidirectional DC/DC converter (BDC) has become a research hotspot in the current power electronics academia and industry. These applications require BDC to achieve a wide range of voltage regulation over a wide load range while possessing as much higher power density and lower electromagnetic interference as possible on the basis of high efficiency operation.
Generally, BDC can be divided into an isolated type and a non-isolated type. On one hand, the isolated BDC can reduce the volume and the weight of the BDC through a high-frequency transformer, so that the flexibility of application and control is improved; on the other hand, since BDC is generally used to connect two dc buses, electrical isolation can improve stability and safety thereof. Thus, compared to non-isolated BDC, isolated BDC is easier to meet the technical requirements of industrial applications.
In the isolated BDC, the LLC resonant DC/DC converter has been widely studied for the advantage of soft switching characteristics thereof, but in the reverse operation thereof, since the exciting inductance is clamped by the input voltage, the resonant cavity becomes a series resonant circuit composed of the resonant inductance and the capacitance, so that the LLC resonant converter has substantially no boost characteristics in the reverse operation, and the soft switching advantage thereof may be lost in the reverse operation. To overcome this disadvantage, a CLLC type resonant converter has been proposed by the scholars, as shown in fig. 1. The CLLC structure is developed on the basis of the LLC structure, and a resonant capacitor is added to the secondary side of the transformer, so that bidirectional blocking can be realized on one hand, and the problem of magnetic bias saturation of the transformer due to asymmetric voltage square waves is avoided; on the other hand, compared with an LLC circuit, the secondary side capacitor is taken as a non-negligible factor in the resonance process, so that the circuit has reverse step-up and step-down capability, and the design in a wide-range output application is simplified.
The primary side and the secondary side of the bidirectional CLLC resonant converter are all fully controlled power devices, such as MOSFETs, and in the forward and reverse operation process, current flows through parasitic diodes of MOS tubes during secondary side rectification, so that non-negligible loss is generated. Therefore, a synchronous rectification technology is generally adopted, namely, the MOS tube is turned on when the anti-parallel diode of the MOS tube is conducted, so that the conduction loss of the MOS tube at the secondary side of the CLLC can be greatly reduced.
The existing synchronous rectification scheme can be roughly divided into two schemes of hardware and software. The hardware scheme mainly adopts a synchronous rectification chip, and a voltage or current detection circuit and the like are required to be added, so that the system cost is increased, and on the other hand, the DCDC bidirectional switching application is difficult to realize due to the adoption of fixed hardware assistance; the software scheme is mainly based on traditional FHA model control or a table look-up method, and the like, the FHA model has larger error at the position deviated from the resonance point, so that the FHA model cannot guide accurate rectifying tube switching action, the table look-up method is to obtain approximate rectifying tube switching time by fitting a large amount of data measured through experiments, but the table look-up method is difficult to induce the running condition of a full load range because multiple modes often exist in CLLC running.
Disclosure of Invention
The application provides a simplified synchronous rectification method and device for a CLLC resonant converter, which can solve or at least partially solve the technical problems.
To achieve the aim, the application adopts the following technical scheme:
in a first aspect, a simplified CLLC resonant converter synchronous rectification method is provided, comprising:
acquiring the current load current;
if the current load current is greater than the lowest load current, starting synchronous rectification, and determining the action of a secondary side switching tube according to the current switching frequency; if the present load current is less than the lowest load current, the synchronous rectification is turned off.
Optionally, the act of determining the secondary side switching tube according to the current switching frequency includes:
if the current switching frequency is lower than or equal to the resonant frequency, the secondary side switching tube and the primary side switching tube are simultaneously turned on; after the secondary side switching tube and the primary side switching tube are simultaneously turned on for a first time, the secondary side switching tube and the primary side switching tube are simultaneously turned off; the first duration is determined by the switching cycle time corresponding to the resonant frequency;
if the current switching frequency is higher than the resonant frequency, the secondary side switching tube is turned on for a second time period after the primary side switching tube is lagged; and after the secondary side switching tube is turned on for a third time period, the secondary side switching tube and the primary side switching tube are turned off at the same time.
Optionally, the value range of the second duration is 100-999 nanoseconds, and the third duration is determined by the switching period time corresponding to the resonant frequency and the second duration.
Optionally, before the step of obtaining the magnitude of the present load current, the method further includes:
the magnitude of the lowest load current is determined.
Optionally, a hysteresis loop is arranged near the lowest load current, and if the current load current is in the hysteresis loop, the on or off state of synchronous rectification is kept unchanged.
In a second aspect, a simplified CLLC resonant converter synchronous rectification apparatus is provided, comprising:
the acquisition module is used for acquiring the current load current;
the rectification module is used for starting synchronous rectification if the current load current is larger than the lowest load current, and determining the action of the secondary side switching tube according to the current switching frequency; and for switching off the synchronous rectification if the present load current is less than the minimum load current.
Optionally, the rectifying module includes:
the first rectifying unit is used for switching on the secondary side switching tube and the primary side switching tube simultaneously if the current switching frequency is lower than or equal to the resonant frequency; after the secondary side switching tube and the primary side switching tube are simultaneously turned on for a first time, the secondary side switching tube and the primary side switching tube are simultaneously turned off; the first duration is determined by the switching cycle time corresponding to the resonant frequency;
the second rectifying unit is used for switching on the secondary side switching tube for a second time period after the primary side switching tube if the current switching frequency is higher than the resonant frequency; and after the secondary side switching tube is turned on for a third time period, the secondary side switching tube and the primary side switching tube are turned off at the same time.
Optionally, the value range of the second duration is 100-999 nanoseconds, and the third duration is determined by the switching period time corresponding to the resonant frequency and the second duration.
Optionally, the method further comprises:
and the determining module is used for determining the magnitude of the lowest load current.
Optionally, a hysteresis loop is arranged near the lowest load current, and if the current load current is in the hysteresis loop, the rectifying module keeps the on or off state of synchronous rectification unchanged.
Compared with the prior art, the embodiment of the application has the following beneficial effects:
the simplified synchronous rectification method and device of the CLLC resonant converter provided by the embodiment of the application have the advantages that the rectification method is a pure software scheme, an additional synchronous rectification chip or a voltage and current detection circuit is not needed, whether synchronous rectification is started or not is determined by judging the magnitude relation between the current load current and the lowest load current, the implementation process of synchronous rectification of a secondary side is greatly simplified, and the synchronous switching tube can be accurately controlled only through the known current switching frequency during synchronous rectification.
Drawings
In order to more clearly illustrate the embodiments of the application or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
The structures, proportions, sizes, etc. shown in the present specification are shown only for the purposes of illustration and description, and are not intended to limit the scope of the application, which is defined by the claims, so that any structural modifications, changes in proportions, or adjustments of sizes, which do not affect the efficacy or the achievement of the present application, should fall within the scope of the application.
FIG. 1 is a topology diagram of a bi-directional CLLC resonant converter provided by an embodiment of the application;
fig. 2 is a simplified equivalent circuit diagram of three working states P, N, O provided by the embodiment of the application from left to right;
FIG. 3 is a graph showing different load frequency (Iout-fn) mode boundaries according to an embodiment of the present application;
fig. 4 is a flow chart of a simplified synchronous rectification method of a CLLC resonant converter according to an embodiment of the present application.
Detailed Description
In order to make the objects, features and advantages of the present application more obvious and understandable, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is apparent that the embodiments described below are only some embodiments of the present application, not all embodiments of the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
Example 1
Please refer to fig. 1 to 3.
As shown in fig. 1, a typical topology of a CLLC bidirectional resonant converter is shown in fig. 1. The input side and the output side of the circuit select a full-bridge structure and totally comprise 8 switching tubes; the primary side comprises a resonant inductor Lr and a resonant capacitor Cr1; the excitation inductance Lm of the transformer has a turn ratio of n to 1; and adding a resonant capacitor Cr2 to the secondary side of the transformer. When the circuit works in a forward working state, primary sides Sp 1-Sp 4 are used as main switching tubes, sp1 and Sp4 signals are synchronous, sp2 and Sp3 signals are synchronous, the same bridge arm switching tube complementarily and symmetrically works by driving signals with a 50% duty ratio, under the condition that synchronous rectification is not implemented on a secondary side, driving signals Ss 1-Ss 4 are closed, the switching tube is turned off, and the anti-parallel diode does not control rectification. When the circuit works in the reverse state, the secondary sides Ss 1-Ss 4 are used as main switching tubes, and the primary sides Sp 1-Sp 4 are used in anti-parallel connection with diodes, so that the control method can be similar to the forward direction. The CLLC bidirectional resonant converter is similar to the LLC resonant converter in output principle and method, and the magnitude of the output voltage Vo is regulated by changing the gain of the switching frequency control circuit.
In a steady state operation state, the voltage and current waveforms in the resonant network of the CLLC bidirectional resonant converter are symmetrical to each other in the front half switching period and the rear half switching period, so the working process of the CLLC bidirectional resonant converter in the front half switching period is analyzed to be unfolded, and at the moment, the switching tubes Sp1 and Sp4 are turned on, and the switching tubes Sp2 and Sp3 are turned off.
When the switching frequency or the load current is different, the CLLC resonant converter works in different operation modes, and according to different current conduction states of the parasitic diode for secondary side rectification, the CLLC operation mode can be divided into three states in the positive half cycle of the input voltage: p, N, O, the equivalent circuit in three states is shown in fig. 2; p, N, O state equivalent circuits are respectively arranged from left to right.
From the rectifying side, the different working modes of the CLLC are different permutations and combinations of the three states P, O, N. All possible operating modes can be determined according to the principle of volt-second balance when the circuit is in steady state operation. Possible modes of operation for CLLC resonant converters are: p, O, NP, OP, PO, PN, NOP, OPO and 9 kinds of PON.
Fig. 3 shows frequency-load curves of the present embodiment in different modes, wherein the maximum output frequency fmax, the minimum output frequency fmin and the maximum load current Imax determine the operating range of the converter. fmax and fmin are the maximum output and minimum output, respectively, of the switching frequency. It can be seen that within the designed operating range, there are only OPO, PO, P, O, NOP and NP modes of operation.
Further, when the load current is greater than Imin (minimum load current), the CLLC has only three modes of PO and NP as well as P mode at the resonance frequency point. Therefore, synchronous rectification can be started when the load current is larger than Imin, and corresponding switching action is carried out on the secondary side switching tube; and when the load current is smaller than Imin, the secondary side switching tube is closed, and partial efficiency parameters of the converter under the light load condition are sacrificed, so that the implementation process of secondary side synchronous rectification can be greatly simplified. On the basis, the time for opening the switching tube in the PO mode is analyzed and calculated, and the time for opening the switching tube under different frequency and load conditions is almost consistent with the time for opening the resonant frequency point. For example, the resonance frequency of the embodiment is 200kHz, at this frequency, the time that the primary side switching tube is turned on in one switching period is 2.5us, and under the conditions of different frequencies and loads of the PO mode, the time that the secondary side switching tube needs to be turned on is only slightly greater than or equal to 2.5us, and the deviation is within hundreds of nanoseconds, and the deviation has no influence basically in consideration of the dead zone of driving in actual implementation; in the NP mode, the N state also lasts only a few hundred nanoseconds at most.
Therefore, the implementation procedure of the simplified CLLC resonant converter synchronous rectification method provided in this embodiment is as follows:
1. firstly, determining the lowest load current Imin for starting synchronous rectification, then detecting the magnitude of the load current, and starting synchronous rectification by the converter when the load current is higher than the Imin; when the load current is less than Imin, the converter turns off synchronous rectification. In the implementation, a hysteresis loop near the Imin can be set, so that frequent switching of the secondary side switching tube when the load current is near the Imin is avoided.
2. After the synchronous rectification is determined to be started, the secondary side switching tube opening action is determined according to the switching frequency of the current output. If the current switching frequency is lower than or equal to the resonant frequency, the resonant converter works in PO and P modes, at the moment, the secondary side switching tube and the primary side switching tube are simultaneously turned on, and are turned off in advance after a period of time ts is continued, wherein ts is determined by the switching period time corresponding to the resonant frequency; if the current switching frequency is higher than the resonant frequency, the resonant converter works in the NP mode, and at the moment, the secondary side switching tube is delayed by a period of time to be turned on, and in the embodiment, different frequencies and loads can be compatible after a period of time of 100 nanoseconds, and the secondary side switching tube and the primary side switching tube are turned off simultaneously after the secondary side switching tube is continuously turned on for a period of time.
The simplified synchronous rectification method of the CLLC resonant converter provided by the embodiment is a pure software scheme, an additional synchronous rectification chip or a voltage and current detection circuit is not needed, whether synchronous rectification is started or not is determined by judging the magnitude relation between the current load current and the lowest load current, the implementation process of synchronous rectification of a secondary side is greatly simplified, and the synchronous switching tube can be accurately controlled only through the known current switching frequency during synchronous rectification.
It should be noted that this embodiment emphasizes a purely software solution, and no additional synchronous rectification chip or voltage and current detection circuit is needed. Since the load is generally provided with a current detection function, the present embodiment can directly obtain the load current without requiring an additional voltage current detection circuit as in the prior art.
It should be understood that the foregoing embodiment is only one specific implementation of the technical solution of the present application. The synchronous rectification of the CLLC resonant converter can be realized by using the simplified CLLC resonant converter synchronous rectification method provided by the application.
Example two
As shown in fig. 4, a summary is performed on the basis of the first embodiment, and the simplified synchronous rectification method of the CLLC resonant converter provided in this embodiment includes the following steps:
s1, acquiring the current load current;
s2, if the current load current is larger than the lowest load current, starting synchronous rectification, and determining the action of a secondary side switching tube according to the current switching frequency; if the present load current is less than the lowest load current, the synchronous rectification is turned off.
The action of determining the secondary side switching tube according to the current switching frequency comprises the following steps:
s21, if the current switching frequency is lower than or equal to the resonant frequency, the secondary side switching tube and the primary side switching tube are simultaneously turned on; after the secondary side switching tube and the primary side switching tube are simultaneously turned on for a first time, the secondary side switching tube and the primary side switching tube are simultaneously turned off; the first duration is determined by the switching cycle time corresponding to the resonant frequency;
s22, if the current switching frequency is higher than the resonant frequency, the secondary side switching tube is turned on for a second time period after the primary side switching tube is lagged; and after the secondary side switching tube is turned on for a third time period, the secondary side switching tube and the primary side switching tube are turned off at the same time.
Specifically, the step S1 is preceded by the further step of:
s0, determining the magnitude of the lowest load current.
Further, the value range of the second duration is 100-999 nanoseconds, and the third duration is determined by the switching period time corresponding to the resonant frequency and the second duration.
As an alternative to this embodiment, a hysteresis loop is provided near the lowest load current, and if the present load current is within the hysteresis loop, the on or off state of synchronous rectification is kept unchanged.
The embodiment also provides a simplified synchronous rectifying device of the CLLC resonant converter, which is used for implementing the synchronous rectifying method, and specifically comprises the following steps:
a determining module for determining the magnitude of the lowest load current;
the acquisition module is used for acquiring the current load current;
the rectification module is used for starting synchronous rectification if the current load current is larger than the lowest load current, and determining the action of the secondary side switching tube according to the current switching frequency; and the synchronous rectification device is also used for switching off the synchronous rectification if the current load is smaller than the lowest load current.
Specifically, the rectification module includes:
the first rectifying unit is used for switching on the secondary side switching tube and the primary side switching tube simultaneously if the current switching frequency is lower than or equal to the resonant frequency; after the secondary side switching tube and the primary side switching tube are simultaneously turned on for a first time, the secondary side switching tube and the primary side switching tube are simultaneously turned off; the first duration is determined by the switching cycle time corresponding to the resonant frequency;
the second rectifying unit is used for switching on the secondary side switching tube for a second time period after the primary side switching tube if the current switching frequency is higher than the resonant frequency; and after the secondary side switching tube is turned on for a third time period, the secondary side switching tube and the primary side switching tube are turned off at the same time.
Specifically, the value range of the second duration is 100-999 nanoseconds, and the third duration is determined by the switching period time corresponding to the resonant frequency and the second duration.
Specifically, a hysteresis loop is arranged near the lowest load current, and if the current load current is in the hysteresis loop, the rectification module keeps the synchronous rectification on or off state unchanged.
The simplified synchronous rectification method and device of the CLLC resonant converter provided by the embodiment have the advantages that the rectification method is a pure software scheme, an additional synchronous rectification chip or a voltage and current detection circuit is not needed, whether synchronous rectification is started or not is determined by judging the size between the current load current and the lowest load current, the implementation process of synchronous rectification of a secondary side is greatly simplified, and the synchronous switching tube can be accurately controlled only through the known current switching frequency during synchronous rectification.
The above embodiments are only for illustrating the technical solution of the present application, and not for limiting the same; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present application.
Claims (8)
1. A simplified CLLC resonant converter synchronous rectification method, comprising:
acquiring the current load current;
if the current load current is greater than the lowest load current, starting synchronous rectification, and determining the action of a secondary side switching tube according to the current switching frequency; if the current load current is smaller than the lowest load current, the synchronous rectification is turned off;
the determining the action of the secondary side switching tube according to the current switching frequency comprises the following steps:
if the current switching frequency is lower than or equal to the resonant frequency, the secondary side switching tube and the primary side switching tube are simultaneously turned on; after the secondary side switching tube and the primary side switching tube are simultaneously turned on for a first time, the secondary side switching tube and the primary side switching tube are simultaneously turned off; the first duration is determined by the switching cycle time corresponding to the resonant frequency;
if the current switching frequency is higher than the resonant frequency, the secondary side switching tube is turned on for a second time period after the primary side switching tube is lagged; and after the secondary side switching tube is turned on for a third time period, the secondary side switching tube and the primary side switching tube are turned off at the same time.
2. The simplified CLLC resonant converter synchronous rectification method of claim 1, wherein said second duration has a value ranging from 100 to 999 nanoseconds, and said third duration is determined by a switching cycle time corresponding to a resonant frequency and said second duration.
3. The simplified CLLC resonant converter synchronous rectification method of claim 1, further comprising, prior to said obtaining a magnitude of said present load current:
the magnitude of the lowest load current is determined.
4. The simplified CLLC resonant converter synchronous rectification method of claim 1, wherein a hysteresis loop is provided near a lowest load current, and if a present load current is within the hysteresis loop, an on or off state of synchronous rectification is maintained unchanged.
5. A simplified CLLC resonant converter synchronous rectification apparatus, comprising:
the acquisition module is used for acquiring the current load current;
the rectification module is used for starting synchronous rectification if the current load current is larger than the lowest load current, and determining the action of the secondary side switching tube according to the current switching frequency; and for turning off the synchronous rectification if the present load current is less than the minimum load current;
the rectifying module includes:
the first rectifying unit is used for switching on the secondary side switching tube and the primary side switching tube simultaneously if the current switching frequency is lower than or equal to the resonant frequency; after the secondary side switching tube and the primary side switching tube are simultaneously turned on for a first time, the secondary side switching tube and the primary side switching tube are simultaneously turned off; the first duration is determined by the switching cycle time corresponding to the resonant frequency;
the second rectifying unit is used for switching on the secondary side switching tube for a second time period after the primary side switching tube if the current switching frequency is higher than the resonant frequency; and after the secondary side switching tube is turned on for a third time period, the secondary side switching tube and the primary side switching tube are turned off at the same time.
6. The simplified CLLC resonant converter synchronous rectification apparatus of claim 5, wherein said second duration has a value ranging from 100 ns to 999 ns, and said third duration is determined by a switching cycle time corresponding to a resonant frequency and said second duration.
7. The simplified CLLC resonant converter synchronous rectification apparatus of claim 5, further comprising:
and the determining module is used for determining the magnitude of the lowest load current.
8. The simplified CLLC resonant converter synchronous rectification apparatus of claim 5, wherein a hysteresis loop is provided near a lowest load current, said rectification module maintaining said synchronous rectification on or off state unchanged if said present load current is within said hysteresis loop.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111007464.1A CN113708644B (en) | 2021-08-30 | 2021-08-30 | Simplified synchronous rectification method and device for CLLC resonant converter |
Applications Claiming Priority (1)
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