CN111555630B - DC/DC converter and synchronous rectification control method and device thereof - Google Patents
DC/DC converter and synchronous rectification control method and device thereof Download PDFInfo
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- CN111555630B CN111555630B CN202010440699.9A CN202010440699A CN111555630B CN 111555630 B CN111555630 B CN 111555630B CN 202010440699 A CN202010440699 A CN 202010440699A CN 111555630 B CN111555630 B CN 111555630B
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/0003—Details of control, feedback or regulation circuits
- H02M1/0032—Control circuits allowing low power mode operation, e.g. in standby mode
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/0048—Circuits or arrangements for reducing losses
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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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Abstract
The application discloses a DC/DC converter and a synchronous rectification control method and device thereof, and the method and device are applied to the DC/DC converter. Specifically, when the DC/DC converter works, a first control signal is output to the main power circuit; the synchronous rectification circuit can work in deep light load, light load and heavy load states according to the negative current state of the output inductor, the three states respectively correspond to the states of a rectification switching tube of the synchronous rectification circuit, namely a complete diode, a partial diode and a switching tube, so that the output inductor current has no negative backflow current in the whole switching period, the internal consumption of a circuit is avoided, the power loss caused by the conduction voltage drop of the rectification diode when a large current is output can be avoided, and the problem of low output efficiency of a DC/DC converter during light load is solved.
Description
Technical Field
The present invention relates to the field of power supply technologies, and in particular, to a DC/DC converter and a synchronous rectification control method and apparatus thereof.
Background
In a low-voltage large-current DC/DC converter, a traditional diode or Schottky diode rectification mode is adopted, and the rectification loss is large due to large forward conduction voltage drop, so that the conversion efficiency is low. The power MOSFET device is a preferred rectifying device of the low-voltage large-current DC/DC converter at present due to the characteristics of low on-resistance, short switching time, high input impedance and the like.
The inventor of the application finds in practice that due to the bidirectional conduction characteristic of the power MOSFET device, the inductor current of the DC/DC converter at light load is no longer in the discontinuous mode, but can continue to flow in the reverse direction. This reverse free-wheeling current is also called circulating current, and the energy of the circulating current is totally consumed in the internal circuit, so that the circulating current is purely consumed in the internal circuit, and the output efficiency of the DC/DC converter is low when the load is light.
Disclosure of Invention
In view of this, the present application provides a DC/DC converter and a synchronous rectification control method and apparatus thereof, which consider both the increase of output loss due to the reverse freewheeling of the inductor current and the forward conduction voltage drop of the diode rectification, and solve the problem of low synchronous rectification output efficiency of the DC/DC converter under light load.
In order to achieve the above object, the following solutions are proposed:
a synchronous rectification control method applied to a DC/DC converter including at least a main power circuit and a synchronous rectification circuit connected through a transformer, the synchronous rectification control method comprising the steps of:
when the DC/DC converter works, outputting a first control signal to the main power circuit;
judging whether the load state of the DC/DC converter is in a deep light load state or not;
if the load state is a deep light load state, namely when only a small part of output inductance current is supplied to a load and is far smaller than the output inductance reverse follow current, a low-level control signal is output to the synchronous rectification circuit, so that all rectification switching tubes of the synchronous rectification circuit work in a full diode state;
and if the load state is not the deep light load state, outputting the first control signal or the second control signal to the synchronous rectification circuit, wherein the second control signal and the first control signal are in a complementary relationship.
Optionally, the outputting the first control signal or the second control signal to the synchronous rectification circuit includes:
if the load state is a light load state, namely the output inductance current still has reverse freewheeling current, but the output loss caused by the forward conduction voltage drop of the rectifier diode is more, the first control signal is output to the synchronous rectifier circuit;
and if the load state is a heavy load state, namely in a switching period, when the inductive current is always output in the forward direction, outputting the second control signal to the synchronous rectification circuit.
A synchronous rectification control device applied to a DC/DC converter including at least a main power circuit and a synchronous rectification circuit connected by a transformer, the synchronous rectification control device comprising a digital controller and a synchronous rectification control circuit, wherein:
the digital controller is used for outputting a first control signal to the main power circuit, outputting the first control signal and a second control signal to the synchronous rectification control circuit, and outputting a switching signal to the synchronous rectification control circuit according to the load state of the DC/DC converter, wherein the load state is a deep light load state, a light load state or a heavy load state;
the synchronous rectification control circuit is used for outputting a low-level control signal to the synchronous rectification circuit based on the switching signal when the load state is the deep light load state, and the low-level control signal is used for controlling all rectification switching tubes of the synchronous rectification circuit to work in a diode state;
the synchronous rectification control circuit is further configured to output the first control signal or the second control signal to the synchronous rectification circuit based on the switching signal when the load state is the light load state or the heavy load state.
Optionally, the digital controller is provided with a first control output end, a second control output end, a third control output end, a fourth control output end, a first switching signal output end and a second switching signal output end, wherein:
the first control output end and the second control output end are used for outputting the first control signal;
the third control output and the fourth control output are used for outputting the second control signal;
the first switching signal output end is used for outputting a first switching signal, and the first switching signal is used for controlling the synchronous rectification control circuit to output the low-level control signal to the synchronous rectification circuit when the load state is the deep light load state;
the second switching signal output end is configured to output a second switching signal, and the second switching signal is configured to control the synchronous rectification control circuit to output the first control signal or the second control signal to the synchronous rectification circuit when the load state is the light load state or the heavy load state.
Optionally, the synchronous rectification control circuit includes a first switching circuit and a second switching circuit, where:
the second switching circuit is provided with a first control input end, a second control input end, a third control input end, a fourth control input end, a first switching signal input end, a second switching signal input end, a fifth control output end and a sixth control output end;
the first control input end and the second control input end are used for receiving the first control signal output by the digital controller;
the third control input and the fourth control input are used for receiving the second control signal output by the digital controller;
the second switching signal input end is used for receiving the second switching signal;
the fifth control output end and the sixth control output end are used for outputting the first control signal or the second control signal based on the second switching signal when the load state is the light load state or the heavy load state;
the first switching circuit is provided with a first switching signal input end, a first control end and a second control end;
the first switching signal input end is used for receiving a first switching signal output by the digital controller;
the first control end is connected with the fifth control output end and used for pulling down the fifth control output end to be low level based on the first switching signal when the load state is the deep light load state;
the second control end is connected with the sixth control output end and used for pulling down the sixth control output end to be low level based on the first switching signal when the load state is the deep light load state.
Optionally, the first switching circuit includes an input resistor, a first switching tube, a first diode and a second diode, where:
one end of the input resistor is used as the input end of the first switching signal, and the other end of the input resistor is connected with the grid electrode of the first switching tube;
the source electrode of the first switching tube is grounded, and the drain electrode of the third switching tube is respectively connected with the cathode of the first diode and the cathode of the second diode;
the anode of the first diode is used as the first control end, and the anode of the second diode is used as the second control end.
Optionally, the second switching circuit includes a third diode, a fourth diode, a fifth diode, a sixth diode, a first output resistor, a second output resistor, and a switching control circuit, wherein:
the anode of the third diode is used as the first control input end, the cathode of the third diode is connected with one end of the first output resistor, and the other end of the first output resistor is used as the fifth control output end;
the anode of the fourth diode is connected with the cathode of the third control input end and the cathode of the third diode;
the anode of the fifth diode is the second control input end, the cathode of the fifth diode is connected with one end of the second output resistor, and the other end of the second output resistor is used as the sixth control output end;
the anode of the sixth diode is used as the fourth control input end, and the cathode of the sixth diode is connected with the cathode of the fifth diode;
the input end of the switching control circuit is the second switching signal input end, and the switching control signal is used for controlling the fifth control output end and the sixth control output end to output the first control signal or the second control signal based on the level of the second switching signal.
Optionally, the switching control circuit includes a first input resistor, a second input resistor, an inverter, a second switch tube, and a third switch tube, where:
one end of the first input resistor is used as the second switching signal input end and is connected with one end of the second input resistor, and the other end of the second input resistor is connected with the gate electrode of the third switching tube;
the other end of the first input resistor is connected with the input end of the phase inverter, and the output end of the phase inverter is connected with the grid electrode of the second switching tube;
one end of the second switch tube is grounded, and the other end of the second switch tube is respectively connected with the first control input end and the second control input end;
one end of the third switching tube is grounded, and the other end of the third switching tube is connected with the third control input end and the fourth control input end respectively.
A DC/DC converter comprises a main power circuit and a synchronous rectification circuit which are connected through a transformer, and further comprises the synchronous rectification control device.
The technical scheme can be seen that the application discloses a DC/DC converter and a synchronous rectification control method and device thereof, and the method and device are applied to the DC/DC converter, and particularly output a first control signal to a main power circuit when the DC/DC converter works; when the load state of the DC/DC converter is a deep light load state, outputting a low-level control signal to the synchronous rectification circuit so as to enable all rectification switching tubes of the synchronous rectification circuit to work in a diode state; when the load state is not a deep light load state, and the reverse freewheeling current of the output inductor is reduced along with the increase of the load current, the output loss caused by the forward conduction voltage drop of the rectifier switch tube in the diode state is more, and at the moment, in order to ensure the optimal output efficiency, a first control signal which is the same as the driving signal of the main power control circuit is output to the synchronous rectification circuit, so that the synchronous rectification circuit works in a partial diode conduction state, namely a light load state; when the output inductive current is increased to only the forward current along with the load, the load state is a heavy load state, and a second control signal which is complementary to the first control signal is output to the synchronous rectification circuit. Therefore, the problem that the output efficiency of the DC/DC converter is low in a deep light load state is solved.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the embodiments or the prior art descriptions will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a circuit diagram of a main power circuit and a synchronous rectification circuit of a DC/DC converter;
fig. 2 is a flowchart of a synchronous rectification control method according to an embodiment of the present application;
fig. 3 is a block diagram of a synchronous rectification control device according to an embodiment of the present application;
FIG. 4 is a block diagram of another synchronous rectification control device according to an embodiment of the present application;
fig. 5 is a block diagram of a synchronous rectification control circuit according to an embodiment of the present application;
FIG. 6 is a block diagram of another synchronous rectification control circuit in accordance with an embodiment of the present application;
FIG. 7a is a schematic diagram of a timing waveform of the DC/DC converter according to the embodiment of the present application during deep light load;
FIG. 7b is a schematic diagram of a timing waveform of the DC/DC converter according to the embodiment of the present application during a light load;
fig. 7c is a schematic diagram of a timing waveform of the DC/DC converter according to the embodiment of the present application during a heavy load.
Detailed Description
The technical solutions in 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 obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The DC/DC converter in this application is a power MOSFET device based converter whose main circuit includes a main power circuit 100 and a synchronous rectification circuit 200 connected by a transformer T, as shown in fig. 1. The main power circuit is used for receiving input direct current, inverting the input direct current and inputting the inverted direct current into the transformer T, and rectifying transformed alternating current by the synchronous rectification circuit to obtain required direct current voltage.
The main power circuit in this embodiment includes a first main power switch Q1 and a second main power switch Q2 connected together as shown. The synchronous rectification circuit comprises four synchronous rectification switching tubes connected together as shown in the figure, namely a first synchronous rectification switching tube SR1, a second synchronous rectification switching tube SR2, a third synchronous rectification switching tube SR3 and a fourth synchronous rectification switching tube SR 4.
When the DC/DC converter works, a first control signal input into the main power circuit and a second control signal input into the synchronous rectification circuit are depended on, the first control signal and the second control signal are both square wave signals with adjustable pulse width, the first control signal comprises two control signals with 180-degree phase difference, and the two control signals are respectively output to the gates of the first main power switch tube Q1 and the second main power switch tube Q2; the second control signal also includes two control signals with a phase difference of 180 degrees, one control signal is used for controlling the gates of the first synchronous rectification switch SR1 and the first synchronous rectification switch SR4, and the other control signal is used for controlling the gates of the second synchronous rectification switch SR2 and the third synchronous rectification switch SR 3.
Based on the above description, the present application provides the following embodiments to solve the problem of low output efficiency of the DC/DC converter at light load.
Example one
Fig. 2 is a flowchart of a synchronous rectification control method according to an embodiment of the present application.
As shown in fig. 2, the synchronous rectification control method provided in this embodiment is applied to the DC/DC converter described above, and specifically includes the following steps:
s1, outputting the first control signal to the main power circuit.
As mentioned above, the first control signal includes two control signals with a phase difference of 180 degrees, and the two control signals are respectively output to the first main power switch tube and the second main power switch tube of the main power circuit, so as to output a sine wave meeting a preset requirement to the transformer for boosting or reducing voltage, generally boosting voltage.
And S2, judging whether the DC/DC converter is in a deep light load state or not.
That is, it is determined whether the current load state of the DC/DC converter is in a deep light load state, where the deep light load state is a state where most of the inductive current in the synchronous rectification circuit is reverse freewheeling current, that is, when only a small part of the output inductive current is supplied to the load, or the current supplied to the load is much smaller than the reverse freewheeling current of the output inductor, the reactive power at this time is greater than the output power thereof, thereby causing unnecessary electric energy waste.
If the current load state is not in the deep light load state, executing step S4; otherwise, if the load state is in the deep light load state, step S3 is executed.
And S3, outputting a low-level control signal to the synchronous rectification circuit.
That is, when the load state of the DC/DC converter is a deep light load state, the low-level control signals are output to the gates of the four synchronous rectification switching tubes SR1, SR2, SR3, and SR4 in the synchronous rectification circuit, so that the four synchronous rectification switching tubes operate in the diode mode, and the circulation current is cut off because the diode mode is completely cut off.
And S4, outputting the first control signal or the second control signal to the synchronous rectification circuit.
Namely, when the load state of the DC/DC converter is not in a deep light load state, a first control output first control signal or a second control signal is output to the synchronous rectification circuit, namely, a corresponding square wave signal is output to a synchronous switching tube of the synchronous rectification circuit, so that the synchronous rectification circuit works in a synchronous rectification mode. Generally speaking, the output inductance increases with the load, the reverse freewheeling current decreases, and the resulting circulating current also decreases, but at this time, because the forward conduction voltage drop of the diode leads to more output loss, it is necessary to jump out of the deep light-load state and enter the light-load state, and the output inductance continues to increase with the load, and when there is no reverse freewheeling current, it enters the heavy-load mode.
When the output inductive current still has reverse follow current, but the output loss caused by the forward conduction voltage drop of the rectifier diode is more, in order to ensure the optimal output efficiency, the synchronous rectification circuit works in a partial diode conduction state, namely a light load state, the control signal of the synchronous rectification circuit is the same as the control signal of the main power circuit, and the optimal output efficiency is ensured at the moment.
Specifically, when the load state is a light load state, a first control signal is output to the synchronous rectification circuit, and when the load state is a heavy load state, a second control signal is output to the synchronous rectification circuit, wherein the second control signal and the pulse width of the first control signal are in a complementary relation.
As can be seen from the foregoing technical solutions, the present embodiment provides a synchronous rectification control method, which is applied to a DC/DC converter, and specifically, when the DC/DC converter operates, outputs a first control signal to a main power circuit; when the load state of the DC/DC converter is a deep light load state, outputting a low-level control signal to the synchronous rectification circuit so as to enable all rectification switching tubes of the synchronous rectification circuit to work in a diode state; when the load state is not the deep light load state, the first control signal or the second control signal in a complementary relationship is output to the synchronous rectification circuit. Therefore, when the DC/DC converter is in a deep light load state, the synchronous rectification switching tube under the control of the low-level control signal works in a diode mode, and at the moment, the circulating current is cut off, so that pure internal consumption is avoided, and the problem that the output efficiency of the DC/DC converter is low in the deep light load state is solved.
When the DC/DC converter outputs light load, the output inductance increases along with the load, the reverse freewheeling current is reduced, and the caused circulating current is also reduced, at the moment, more output loss is caused because of the forward conduction voltage drop of the diode, so the synchronous rectification control signal adopts the first control signal which is the same as that of the main power circuit, the influence of the reverse freewheeling current of the inductance and the forward conduction voltage drop of the diode on the output efficiency can be considered, and the problem of lower output efficiency of the DC/DC converter during light load is optimized.
In addition, the second control signal which is complementary to the first control signal of the main power circuit is output to the synchronous rectification circuit when the synchronous rectification circuit is in a heavy load state, so that the heavy load is ensured to be output with optimal efficiency. By the control process, all output efficiencies in the whole output range can be guaranteed to be the highest.
Example two
Fig. 3 is a block diagram of a synchronous rectification control device according to an embodiment of the present application.
As shown in fig. 3, the synchronous rectification control device provided in this embodiment is applied to a DC/DC converter, and is used for outputting a corresponding control signal to the DC/DC converter according to a load state of the DC/DC converter, so as to maximize an output efficiency of the DC/DC converter, and specifically includes a digital controller 10 and a synchronous rectification control circuit 20.
The digital controller is used for outputting a first control signal to the main power circuit, outputting a first control signal and a second control signal to the synchronous rectification control circuit, and outputting a switching signal to the synchronous rectification control circuit according to the load state of the DC/DC converter, wherein the load state is a deep light load state, a light load state or a heavy load state;
the synchronous rectification control circuit is used for outputting a low-level control signal to the synchronous rectification circuit based on the switching signal when the load state is a deep light load state, and the low-level control signal is used for controlling all rectification switching tubes of the synchronous rectification circuit to work in a diode state; the synchronous rectification control circuit is also used for outputting a first control signal or a second control signal to the synchronous rectification circuit based on the switching signal when the load state is a light load state or a heavy load state.
The digital controller may be implemented by using an MCU, and specifically includes a first control output terminal 11, a second control output terminal 12, a third control output terminal 13, a fourth control output terminal 14, a first switching signal output terminal 15, and a second switching signal output terminal 16, as shown in fig. 4.
The first control output end and the second control output end are used for outputting first control signals D11 and D12, and the phase difference between the first control signal D11 and the second control signal D12 is 180 degrees; the third control output terminal and the fourth control output terminal are used for outputting second control signals D21 and D22, and the phase difference between the first control signal D21 and the second control signal D22 is 180 degrees; in addition, the respective signals of the first control signal and the respective signals of the second control signal, such as D11 and D21, are complementary to each other.
The first switching signal output end is used for outputting a first switching signal SD _ DR, and the first switching signal is used for controlling the synchronous rectification control circuit to output a low-level control signal to the synchronous rectification circuit when the load state is a deep light load state;
the second switching signal output end is used for outputting a second switching signal, and the second switching signal is used for controlling the synchronous rectification control circuit to output a first control signal or a second control signal to the synchronous rectification circuit when the DC/DC converter is in a light load state or a heavy load state. Specifically, the synchronous rectification control circuit is controlled to output a first control signal when the DC/DC converter is in a light load state, and the synchronous rectification control circuit is controlled to output a second control signal when the DC/DC converter is in a heavy load state.
The synchronous rectification control circuit comprises a first switching circuit 21 and a second switching circuit 22, the second switching circuit 22 is provided with a first control input 221, a second control input 222, a third control input 223, a fourth control input 224, a second switching signal input 225, a fifth control output 226 and a sixth control output 227;
the first control input and the second control input are used for receiving first control signals D11 and D12 output by the digital controller; the third control input and the fourth control input are used for receiving second control signals D21 and D22 output by the digital controller; the second switching signal input end is used for receiving a second switching signal SR _ Select; the fifth control output end and the sixth control output end are used for outputting a first control signal or a second control signal based on the second switching signal when the load state is a light load state or a heavy load state;
the first switching circuit 21 is provided with a first switching signal input terminal 211, a first control terminal 212, and a second control terminal 213;
the first switching signal input end is used for receiving a first switching signal output by the digital controller; the first control end is connected with the fifth control output end and used for pulling down the fifth control output end to be a low level based on the first switching signal when the load state is a deep light load state; the second control end is connected with the sixth control output end and used for pulling down the sixth control output end to be low level based on the first switching signal when the load state is a deep light load state.
The first switching circuit comprises an input resistor R0, a first switching tube K1, a first diode D1 and a second diode D2, as shown in fig. 5, one end of the input resistor is used as a first switching signal input end, and the other end is connected to the gate of the first switching tube;
the source electrode of the first switching tube is grounded, and the drain electrode of the third switching tube is respectively connected with the cathode of the first diode and the cathode of the second diode; the positive pole of the first diode is used as a first control end, and the positive pole of the second diode is used as a second control end.
The second switching circuit includes a third diode D3, a fourth diode D4, a fifth diode D5, a sixth diode D6, a first output resistor R1, a second output resistor R2, and a switching control circuit 201.
The anode of the third diode is used as a first control input end, the cathode of the third diode is connected with one end of a first output resistor, and the other end of the first output resistor is used as a fifth control output end; the anode of the fourth diode is a third control input end, and the cathode of the fourth diode is connected with the cathode of the third diode;
the anode of the fifth diode is a second control input end, the cathode of the fifth diode is connected with one end of a second output resistor, and the other end of the second output resistor is used as a sixth control output end; the anode of the sixth diode is used as a fourth control input end, and the cathode of the sixth diode is connected with the cathode of the fifth diode;
the input end of the switching control circuit is a second switching signal input end, and the switching control signal is used for controlling the fifth control output end and the sixth control output end to output the first control signal or the second control signal based on the level of the second switching signal.
The switching control circuit 201 includes a first input resistor R3, a second input resistor R4, an inverter U, a second switch tube K2 and a third switch tube K3, as shown in fig. 6.
One end of the first input resistor is used as a second switching signal input end and is connected with one end of the second input resistor, and the other end of the second input resistor is connected with a gate pole of the third switching tube; the other end of the first input resistor is connected with the input end of the phase inverter, and the output end of the phase inverter is connected with the grid electrode of the second switching tube; one end of the second switch tube is grounded, and the other end of the second switch tube is connected with the first control input end and the second control input end respectively; one end of the third switching tube is grounded, and the other end of the third switching tube is respectively connected with the third control input end and the fourth control input end.
When the load state of the DC/DC converter is in a deep light load state, the first switching control signal is at a high level, and at this time, the first switching tube is turned on, so that the gate levels of the four synchronous rectification switching tubes SR1, SR2, SR3, and SR4 in the synchronous rectification circuit are pulled down, so that the four synchronous rectification switching tubes operate in a diode mode, and since the diode mode may be completely turned off, the loop current is cut off, and the timing waveform at this time is as shown in fig. 7 a.
When the load state of the DC/DC converter is a light load state, outputting a first control signal to the synchronous rectification circuit, wherein the time sequence waveform at the moment is shown in FIG. 7 b; when the load state is a heavy load state, a second control signal is output to the synchronous rectification circuit, the second control signal and the pulse width of the first control signal are in a complementary relationship, and the time sequence waveform is shown in fig. 7 c.
As can be seen from the foregoing technical solutions, the present embodiment provides a synchronous rectification control device, which is applied to a DC/DC converter, and is specifically configured to output a first control signal to a main power circuit when the DC/DC converter operates; when the load state of the DC/DC converter is a deep light load state, outputting a low-level control signal to the synchronous rectification circuit so as to enable all rectification switching tubes of the synchronous rectification circuit to work in a diode state; when the load state is not the deep light load state, the first control signal or the second control signal in a complementary relationship is output to the synchronous rectification circuit. Therefore, when the DC/DC converter is in a deep light load state, the synchronous rectification switching tube under the control of the low-level control signal works in a diode mode, and at the moment, the circulating current is cut off, so that pure internal consumption is avoided, and the problem that the output efficiency of the DC/DC converter is low in the deep light load state is solved.
EXAMPLE III
The present embodiment further provides a DC/DC converter, which includes a main power circuit and a synchronous rectification circuit connected by a transformer, and further includes the synchronous rectification control device provided in the previous embodiment.
The synchronous rectification control device is specifically used for outputting a first control signal to the main power circuit when the DC/DC converter works; when the load state of the DC/DC converter is a deep light load state, outputting a low-level control signal to the synchronous rectification circuit so as to enable all rectification switching tubes of the synchronous rectification circuit to work in a diode state; when the load state is not the deep light load state, the first control signal or the second control signal in a complementary relationship is output to the synchronous rectification circuit. Therefore, when the DC/DC converter is in a deep light load state, the synchronous rectification switching tube under the control of the low-level control signal works in a diode mode, and at the moment, the circulating current is cut off, so that pure internal consumption is avoided, and the problem that the output efficiency of the DC/DC converter is low in the deep light load state is solved.
The embodiments in the present specification are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, apparatus, or computer program product. Accordingly, embodiments of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, embodiments of the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
Embodiments of the present invention are described with reference to flowchart illustrations and/or block diagrams of methods, terminal devices (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing terminal to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing terminal, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing terminal to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing terminal to cause a series of operational steps to be performed on the computer or other programmable terminal to produce a computer implemented process such that the instructions which execute on the computer or other programmable terminal provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
While preferred embodiments of the present invention have been described, additional variations and modifications of these embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the embodiments of the invention.
Finally, it should also be noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or terminal that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or terminal. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or terminal that comprises the element.
The technical solutions provided by the present invention are described in detail above, and the principle and the implementation of the present invention are explained in this document by applying specific examples, and the descriptions of the above examples are only used to help understanding the method and the core idea of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.
Claims (6)
1. A synchronous rectification control device applied to a DC/DC converter including at least a main power circuit and a synchronous rectification circuit connected by a transformer, characterized in that the synchronous rectification control device includes a digital controller and a synchronous rectification control circuit, wherein:
the digital controller is used for outputting a first control signal to the main power circuit, outputting the first control signal and a second control signal to the synchronous rectification control circuit, and outputting a switching signal to the synchronous rectification control circuit according to the load state of the DC/DC converter, wherein the load state is a deep light load state, a light load state or a heavy load state;
the synchronous rectification control circuit is used for outputting a low-level control signal to the synchronous rectification circuit based on the switching signal when the load state is the deep light load state, and the low-level control signal is used for controlling all rectification switching tubes of the synchronous rectification circuit to work in a diode state;
the synchronous rectification control circuit is further used for outputting the first control signal or the second control signal to the synchronous rectification circuit based on the switching signal when the load state is the light load state or the heavy load state;
the synchronous rectification control circuit comprises a first switching circuit and a second switching circuit, wherein:
the second switching circuit is provided with a first control input end, a second control input end, a third control input end, a fourth control input end, a second switching signal input end, a fifth control output end and a sixth control output end;
the first control input end and the second control input end are used for receiving the first control signal output by the digital controller;
the third control input and the fourth control input are used for receiving the second control signal output by the digital controller;
the second switching signal input end is used for receiving the second switching signal;
the fifth control output end and the sixth control output end are used for outputting the first control signal or the second control signal based on the second switching signal when the load state is the light load state or the heavy load state;
the first switching circuit is provided with a first switching signal input end, a first control end and a second control end;
the first switching signal input end is used for receiving a first switching signal output by the digital controller;
the first control end is connected with the fifth control output end and used for pulling down the fifth control output end to be low level based on the first switching signal when the load state is the deep light load state;
the second control end is connected with the sixth control output end and used for pulling down the sixth control output end to be low level based on the first switching signal when the load state is the deep light load state.
2. The synchronous rectification control device of claim 1, wherein the digital controller is provided with a first control output, a second control output, a third control output, a fourth control output, a first switching signal output and a second switching signal output, wherein:
the first control output end and the second control output end are used for outputting the first control signal;
the third control output and the fourth control output are used for outputting the second control signal;
the first switching signal output end is used for outputting a first switching signal, and the first switching signal is used for controlling the synchronous rectification control circuit to output the low-level control signal to the synchronous rectification circuit when the load state is the deep light-load state;
the second switching signal output end is configured to output a second switching signal, and the second switching signal is configured to control the synchronous rectification control circuit to output the first control signal or the second control signal to the synchronous rectification circuit when the load state is the light load state or the heavy load state.
3. The synchronous rectification control device of claim 1, wherein the first switching circuit comprises an input resistor, a first switching tube, a first diode and a second diode, wherein:
one end of the input resistor is used as the first switching signal input end, and the other end of the input resistor is connected with the grid electrode of the first switching tube;
the source electrode of the first switch tube is grounded, and the drain electrode of the first switch tube is respectively connected with the cathode of the first diode and the cathode of the second diode;
the anode of the first diode is used as the first control end, and the anode of the second diode is used as the second control end.
4. The synchronous rectification control device of claim 1, wherein the second switching circuit comprises a third diode, a fourth diode, a fifth diode, a sixth diode, a first output resistor, a second output resistor, and a switching control circuit, wherein:
the anode of the third diode is used as the first control input end, the cathode of the third diode is connected with one end of the first output resistor, and the other end of the first output resistor is used as the fifth control output end;
the anode of the fourth diode is connected with the cathode of the third control input end and the cathode of the third diode;
the anode of the fifth diode is the second control input end, the cathode of the fifth diode is connected with one end of the second output resistor, and the other end of the second output resistor is used as the sixth control output end;
the anode of the sixth diode is used as the fourth control input end, and the cathode of the sixth diode is connected with the cathode of the fifth diode;
the input end of the switching control circuit is the second switching signal input end, and the switching control circuit is configured to control the fifth control output end and the sixth control output end to output the first control signal or the second control signal based on the level of the second switching signal.
5. The synchronous rectification control device of claim 4, wherein the switching control circuit comprises a first input resistor, a second input resistor, an inverter, a second switching tube and a third switching tube, wherein:
one end of the first input resistor is used as the second switching signal input end and is connected with one end of the second input resistor, and the other end of the second input resistor is connected with the gate pole of the third switching tube;
the other end of the first input resistor is connected with the input end of the phase inverter, and the output end of the phase inverter is connected with the grid electrode of the second switching tube;
one end of the second switch tube is grounded, and the other end of the second switch tube is respectively connected with the first control input end and the second control input end;
one end of the third switching tube is grounded, and the other end of the third switching tube is connected with the third control input end and the fourth control input end respectively.
6. A DC/DC converter comprising a main power circuit and a synchronous rectification circuit connected by a transformer, and further comprising a synchronous rectification control device as claimed in any one of claims 1 to 5.
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| US6426884B1 (en) * | 2000-11-06 | 2002-07-30 | Ericsson, Inc. | Reducing reverse currents in a synchronous rectifier circuit |
| US20110211370A1 (en) * | 2010-03-01 | 2011-09-01 | Texas Instruments Incorporated | Systems and Methods of Resonant DC/DC Conversion |
| CN103036405B (en) * | 2011-09-30 | 2015-06-17 | 雅达电源制品（深圳）有限公司 | Synchronous rectification switching tube driving method and device of phase-shifted full-bridge circuit |
| US20150194900A1 (en) * | 2014-01-06 | 2015-07-09 | Bel Fuse (Macao Commercial Offshore) Limited | Power converter with modulated secondary-side synchronous rectification |
| CN110838793B (en) * | 2019-10-21 | 2021-07-20 | 浙江大学 | Synchronous rectification circuit and control strategy applied to bidirectional CLLC resonant converter |
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