CN111555631B - DC/DC converter and pre-bias control method and device thereof - Google Patents

DC/DC converter and pre-bias control method and device thereof Download PDF

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CN111555631B
CN111555631B CN202010441545.1A CN202010441545A CN111555631B CN 111555631 B CN111555631 B CN 111555631B CN 202010441545 A CN202010441545 A CN 202010441545A CN 111555631 B CN111555631 B CN 111555631B
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control signal
output
circuit
converter
input
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CN111555631A (en
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熊亮亮
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BEIJING SUPLET POWER CO LTD
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BEIJING SUPLET POWER CO LTD
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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
    • 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
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • 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
    • H02M1/36—Means for starting or stopping converters
    • 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

Abstract

The application discloses a DC/DC converter and a pre-bias control method and a pre-bias control device thereof, wherein the method and the device are particularly used for respectively outputting first control signals to a main power circuit and a synchronous rectification circuit of the DC/DC converter when the DC/DC converter is in the starting process, and the duty ratio of the first control signals changes from small to large in the starting process; and when the DC/DC converter finishes starting and enters a normal working state, outputting a second control signal to the main power circuit, and outputting a third control signal to the synchronous rectification circuit, wherein the third control signal and the second control signal are in a complementary relation. Therefore, in the starting process of the DC/DC converter, the driving control signal of the synchronous rectification switching tube and the driving control signal of the main power switching power tube are in the same phase and gradually change from small to large, and the problem that the synchronous rectification switching tube is damaged due to reverse current flowing caused by overlarge duty ratio of the synchronous rectification tube in starting is effectively solved.

Description

DC/DC converter and pre-bias control method and device thereof
Technical Field
The present disclosure relates to the field of power supply technologies, and more particularly, to a DC/DC converter and a pre-bias control method and apparatus thereof.
Background
In the technical field of DC/DC converters, a synchronous rectification technology is generally adopted to improve conversion efficiency, but a synchronous rectification control mode must face the problem of pre-bias. In the conventional sense, the conversion efficiency can be improved to the maximum extent only by adopting a synchronous rectification technology and requiring the drive signal of a synchronous rectification switching tube to be complementary with the drive signal of a main power switching tube, but in the process of starting and establishing the output voltage, the duty ratio of the main power switching tube is gradually expanded, the duty ratio is gradually increased from small to large, and if the drive signal of the synchronous rectification switching tube and the drive signal of the main power switching tube are in a complementary relationship, the duty ratio of the synchronous rectification switching tube is changed from large to small.
At this time, if a bias voltage exists on the output side, the situation that the current flows in the reverse direction due to the fact that the duty ratio of the synchronous rectification switching tube is far larger than that of the main power switching tube before the actual output voltage of the converter reaches the bias voltage and the actual output voltage is lower than the bias voltage can occur, and due to the fact that the output impedance of the synchronous rectification circuit is small, large reverse current is easy to occur at the moment, and the large reverse current can cause damage to the synchronous rectification switching tube.
Disclosure of Invention
In view of this, the present application provides a DC/DC converter, and a pre-bias control method and device thereof, which are used to solve the problem that a synchronous rectification switch tube is damaged due to a large reverse-flow current when the DC/DC converter is started.
In order to achieve the above object, the following solutions are proposed:
a pre-bias control method applied to a DC/DC converter including a main power circuit and a synchronous rectification circuit connected by a transformer, the pre-bias control method comprising the steps of:
when the DC/DC converter is in a starting process, first control signals are respectively output to the main power circuit and the synchronous rectification circuit, and the duty ratio of the first control signals changes from small to large in the starting process;
and when the DC/DC converter finishes starting and enters a normal working state, outputting the second control signal to the main power circuit, and outputting a third control signal to the synchronous rectification circuit, wherein the duty ratio of the third control signal is in a complementary relation with the duty ratio of the second control signal.
A pre-bias control apparatus applied to a DC/DC converter including a main power circuit and a synchronous rectification circuit connected through a transformer, the pre-bias control apparatus comprising a digital controller and a pre-bias control circuit, wherein:
the digital controller is used for outputting the first control signal to the main power circuit, the duty ratio of the first control signal changes from small to large in the starting process of the DC/DC converter, a second control signal is output to the main power circuit after the DC/DC converter finishes starting, and the duty ratio of the second control signal is the same as the duty ratio of the first control signal when the DC/DC converter finishes starting;
the pre-bias control circuit is used for outputting the first control signal to the synchronous rectification circuit in the starting process of the DC/DC converter and is also used for outputting a third control signal to the synchronous rectification circuit after the DC/DC converter is started, and the duty ratio of the third control signal and the duty ratio of the second control signal form a complementary relationship.
Optionally, the digital controller is provided with a first output end, a second output end, a third output end, a fourth output end and a switching signal output end, wherein:
the first output terminal and the second output terminal are used for outputting the first control signal or the second control signal to the main power circuit and the pre-bias control circuit;
the third output terminal and the fourth output terminal are used for outputting the third control signal to the pre-bias control circuit;
the switching signal is used for outputting a switching control signal, and the switching control signal is used for controlling the pre-bias control circuit to output the first control signal or the third control signal to the synchronous rectification circuit.
Optionally, the pre-bias control circuit is provided with a first input end, a second input end, a third input end, a fourth input end, a switching signal input end, a fifth output end and a sixth output end, wherein:
the first input end is connected with the first output end;
the second input end is connected with the second output end;
the third input end is connected with the third output end;
the fourth input end is connected with the fourth output end;
the switching signal input end is connected with the switching signal output end;
the fifth output end and the sixth output end are used for outputting the first control signal or the third control signal to the synchronous rectification circuit under the control of the switching signal.
Optionally, the pre-bias control circuit includes a first diode, a second diode, a third diode, a fourth diode, a first output resistor, a second output resistor, and a switching control circuit, wherein:
the positive electrode of the first diode is the first input end, the negative electrode of the first diode is connected with one end of the first output resistor, and the other end of the first output resistor is the fifth output end;
the anode of the second diode is the third input end, and the cathode of the second diode is connected with the cathode of the first diode;
the anode of the third diode is the second input end, the cathode of the third diode is connected with one end of the second output resistor, and the other end of the second output resistor is the sixth output end;
the anode of the fourth diode is the fourth input end, and the cathode of the fourth diode is connected with the cathode of the third diode;
the switching control circuit is used for connecting only the first input end with the fifth output end and simultaneously connecting only the second input end with the sixth input end when the DC/DC converter is in a starting process under the control of the switching control signal;
the switching control circuit is configured to connect only the third input terminal to the fifth output terminal and connect only the fourth input terminal to the sixth input terminal after the DC/DC converter completes a start-up process under control of the switching control signal.
Optionally, the switching control circuit includes a first input resistor, a second input resistor, a phase inverter, a first switch tube and a second switch tube, wherein:
the input end of the phase inverter is the switching control signal input end and is connected with one end of the first input resistor, and the output end of the phase inverter is connected with one end of the second input resistor;
the other end of the first input resistor is connected with a gate pole of the first switching tube;
the other end of the second input resistor is connected with a gate pole of the second switching tube;
one end of the first switch tube is grounded, and the other end of the first switch tube is connected with the third input end and the fourth input end respectively;
one end of the second switch tube is grounded, and the other end of the second switch tube is respectively connected with the first input end and the second input end;
the switching control signal is a pulse signal.
Optionally, the first switch tube and the second switch tube are both NMOS tubes or PMOS tubes.
A DC/DC converter comprising a main power circuit and a synchronous rectification circuit connected by a transformer, and further comprising a pre-bias control device as described above.
The technical scheme includes that the method and the device are specifically used for respectively outputting first control signals to a main power circuit and a synchronous rectification circuit of the DC/DC converter when the DC/DC converter is in a starting process, and the duty ratio of the first control signals changes from small to large in the starting process; and when the DC/DC converter finishes starting and enters a normal working state, outputting a second control signal to the main power circuit, and outputting a third control signal to the synchronous rectification circuit, wherein the third control signal and the second control signal are in a complementary relation. Therefore, in the starting process of the DC/DC converter, the driving control signal of the synchronous rectification switching tube and the driving control signal of the main power switching power tube are in the same phase and gradually change from small to large, and the problem that the synchronous rectification switching tube is damaged due to reverse current flowing caused by overlarge duty ratio of the synchronous rectification tube in starting is effectively 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 flow chart of a pre-bias control method according to an embodiment of the present application;
fig. 2 is a circuit diagram of a main circuit of a DC/DC converter according to an embodiment of the present application;
FIG. 3 is a circuit diagram of a pre-bias control device and a main circuit according to an embodiment of the present disclosure;
FIG. 4 is a circuit diagram of another pre-bias control device and a main circuit according to an embodiment of the present disclosure;
FIG. 5 is a circuit diagram of a pre-bias control device and a main circuit according to an embodiment of the present disclosure;
FIG. 6 is a circuit diagram of a pre-bias control circuit according to an embodiment of the present application;
fig. 7 is a circuit diagram of another pre-bias control circuit according to an embodiment of the present application.
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.
Example one
Fig. 1 is a flowchart of a pre-bias control method according to an embodiment of the present disclosure.
The pre-bias control method provided by the present embodiment is applied to a DC/DC converter whose main circuit includes a main power circuit 10 for receiving power input and a synchronous rectification circuit 20 for outputting a preset voltage, which are connected through a transformer T, as shown in fig. 2. The main power circuit converts the input direct current into alternating current, and the alternating current is transformed by a transformer and then output to a synchronous rectification circuit for rectification and output, wherein the transformer can be a boosting transformer or a step-down transformer.
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 in fig. 2. The main power circuit is connected with the synchronous rectification circuit through a transformer T. The synchronous rectification circuit comprises four synchronous rectification switching tubes connected together as shown in fig. 2, 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.
As shown in fig. 1, the pre-bias control method provided in this embodiment includes the following steps:
and S1, judging whether the DC/DC converter is in a starting state or not.
Specifically, after the DC/DC converter is turned on, the real-time output voltage thereof increases from zero until the required target output voltage is reached, that is, the process in which the real-time output voltage reaches the target output voltage from zero is a starting process, and once the real-time output voltage reaches the target output voltage for the first time, the starting is determined to be completed.
Therefore, whether the DC/DC converter is in a starting state or not can be judged by measuring the real-time output voltage. When the DC/DC converter outputs the startup state, step S2 is executed; when the DC/DC converter has completed the startup state and enters the normal operation state, step S3 is executed.
And S2, outputting a first control signal to the main power circuit and the synchronous rectification circuit.
That is, when the DC/DC converter is in the start state, the first control signal is simultaneously outputted to the main power circuit and the synchronous switch circuit, and as mentioned above, the first control signal includes two control signals, i.e., D11 and D12 having the same duty ratio but a phase difference of 180 °.
D11 is used for output to the first main power switch Q1, and D12 is used for output to the second main power switch Q2. Meanwhile, the D11 is also output to the first rectifier switch tube SR1 and the third rectifier switch tube SR3, and the D12 is also output to the second rectifier switch tube SR2 and the fourth rectifier switch tube SR 4.
At this time, the main power switch tube of the main power circuit and the synchronous rectification switch tube in the synchronous rectification circuit operate under the drive of the same control signal. Specifically, the duty ratio of the first control signal changes from a small value to a small value during the starting process of the DC/DC converter, so that the filtering energy storage capacitor of the synchronous rectification circuit is slowly charged.
S3, the second control signal is output to the main power circuit, and the third control signal is output to the synchronous rectification circuit.
After the DC/DC converter finishes starting, a second control signal is output to the main power circuit from the time when the DC/DC converter finishes starting, the second control signal includes two control signals, which are D21 and D22 with the same duty ratio and 180 ° phase difference, respectively, D21 is used for driving the first main power switch Q1, and D22 is used for driving the second main power switch Q2. The second control signal is actually a continuation of the above first control signal, and the phase and duty ratio of the first control signal at the time of starting the output to the main power circuit are both the same as those of the first control signal at the time of completion of the start-up of the DC/DC converter.
Meanwhile, a third control signal is also output to the synchronous rectification circuit, the third control signal comprises two control signals, namely D31 and D32 with the same duty ratio but 180 ° phase difference, the D31 is output to the first rectification switch tube SR1 and the third rectification switch tube SR3, and the D32 is output to the second rectification switch tube SR2 and the fourth rectification switch tube SR 4.
The duty ratio of the third control signal is complementary to that of the second control signal, and the phase difference is the same as that between the two groups of control signals when other DC/DC converters work normally.
It can be seen from the foregoing technical solutions that, the present embodiment provides a pre-bias control method, which is applied to a DC/DC converter, and specifically, when the DC/DC converter is in a starting process, first control signals are respectively output to a main power circuit and a synchronous rectification circuit of the DC/DC converter, and a duty ratio of the first control signal changes from small to large in the starting process; and when the DC/DC converter finishes starting and enters a normal working state, outputting a second control signal to the main power circuit, and outputting a third control signal to the synchronous rectification circuit, wherein the third control signal and the second control signal are in a complementary relation. Therefore, in the starting process of the DC/DC converter, the driving control signal of the synchronous rectification switching tube and the driving control signal of the main power switching power tube are in the same phase and gradually change from small to large, and the problem that the synchronous rectification switching tube is damaged due to reverse current flowing caused by overlarge duty ratio of the synchronous rectification tube in starting is effectively solved.
Example two
Fig. 3 is a flowchart of a pre-bias control method according to an embodiment of the present disclosure.
As shown in fig. 3, the pre-bias control apparatus provided in the present embodiment is applied to a DC/DC converter including a main power circuit 10 for receiving an input of electric energy and a synchronous rectification circuit 20 for outputting a preset voltage, which are connected through a transformer T.
The main power circuit includes a first main power switch Q1 and a second main power switch Q2 connected together as shown in fig. 3. The main power circuit is connected with the synchronous rectification circuit through a transformer T. The synchronous rectification circuit comprises four synchronous rectification switching tubes connected together as shown in fig. 3, 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.
The pre-bias control means comprises a digital controller 30 and a pre-bias control circuit 40.
The digital controller is provided with a first output 31, a second output 32, a third output 33, a fourth output 34 and a switching signal output 35. The first output end is connected with the control signal input end of the first main power switch tube, and the second output end is connected with the control signal input end of the second main power switch tube.
The pre-bias control circuit is provided with a first input 41, a second input 42, a third input 43, a fourth input 44 and a switching signal input 45. The first input end is connected with the first output end, the second input end is connected with the second output end, the third input end is connected with the third output end, the fourth input end is connected with the fourth output end, and the switching signal input end is connected with the switching signal output end.
In addition, the pre-bias control circuit is further provided with a fifth output end 46 and a sixth output end 47, the fifth output end is used for connecting a first synchronous rectification switching tube and a third synchronous rectification switching tube of the synchronous rectification circuit, and the sixth output end is used for connecting a second synchronous rectification switching tube and a fourth synchronous rectification switching tube of the synchronous rectification circuit.
After the DC/DC converter is powered on and started, the digital controller is firstly used for judging whether the DC/DC converter is in a starting state or not.
Specifically, after the DC/DC converter is turned on, the real-time output voltage thereof increases from zero until the required target output voltage is reached, that is, the process in which the real-time output voltage reaches the target output voltage from zero is a starting process, and once the real-time output voltage reaches the target output voltage for the first time, the starting is determined to be completed. Therefore, whether the DC/DC converter is in a starting state or not can be judged by measuring the real-time output voltage.
If the DC/DC converter is in a starting state, first control signals D11 and D12 are output through a first output terminal and a second output terminal of the DC/DC converter, the first control signals are simultaneously output to a first main power switch tube and a second main power switch tube of a main power circuit, and simultaneously the first control signals are also output to a pre-bias control circuit, the duty ratios of D11 and D12 of the first control signals are the same, but the phase difference between the D11 and the D12 is 180 degrees.
The first control signal is also simultaneously output to a first input end and a second input end of the pre-bias control circuit respectively; meanwhile, the digital controller also outputs third control signals D31 and D32 to the third input terminal and the fourth input terminal of the pre-bias control circuit through the third output terminal and the fourth output terminal thereof, respectively.
At this stage, the switching signal output terminal outputs a switching control signal to the switching signal input terminal of the pre-bias control circuit, the switching control signal is at a high level or a low level, at this time, the pre-bias control circuit sends the first control signal to the fifth output terminal and the sixth output terminal under the control of the corresponding level signal, so that the fifth output terminal outputs the D11 of the first control signal to the first synchronous rectification switching tube and the third synchronous rectification switching tube of the synchronous rectification circuit, and outputs the D12 of the first control signal to the second synchronous rectification switching tube and the fourth synchronous rectification switching tube of the synchronous rectification switching tube circuit, as shown in fig. 4.
At this time, the main power switch tube of the main power circuit and the synchronous rectification switch tube in the synchronous rectification circuit operate under the drive of the same control signal. Specifically, the duty ratio of the first control signal changes from a small value to a small value during the starting process of the DC/DC converter, so that the filtering energy storage capacitor of the synchronous rectification circuit is slowly charged.
After the DC/DC converter is started, a second control signal is output to the main power circuit from the time when the DC/DC converter is started, wherein the second control signal comprises two control signals which are respectively D21 and D22 with the same duty ratio but 180-degree phase difference, D21 is used for outputting to a first main power switch tube Q1, and D22 is used for outputting to a second main power switch tube Q2. The second control signal is actually a continuation of the above first control signal, and the phase and duty ratio of the first control signal at the time of starting the output to the main power circuit are both the same as those of the first control signal at the time of completion of the start-up of the DC/DC converter.
Meanwhile, the digital controller also outputs the third control signals to the third input end and the fourth input end of the pre-bias control circuit through the third output end and the fourth output end of the digital controller, and the third control signals comprise two control signals, namely D31 and D32 with the same duty ratio and 180-degree phase difference respectively.
The pre-bias control circuit sends D31 and D32 of the third control signal to the fifth output terminal and the sixth output terminal under the control of the switching control signal of the corresponding level, so that the fifth output terminal outputs D31 of the third control signal to the first synchronous rectification switching tube and the third synchronous rectification switching tube of the synchronous rectification circuit, and outputs D32 of the third control signal to the second synchronous rectification switching tube and the fourth synchronous rectification switching tube of the synchronous rectification switching tube circuit, as shown in fig. 5.
The duty ratio of the third control signal is complementary to that of the second control signal, and the phase difference is the same as that between the two groups of control signals when other DC/DC converters work normally.
It can be seen from the foregoing technical solutions that, the embodiment provides a pre-bias control device, where the pre-bias control device includes a digital controller and a pre-bias control circuit, the digital controller is configured to output a first control signal to a main power circuit, a duty ratio of the first control signal changes from small to large in a starting process of a DC/DC converter, and a second control signal is output to the main power circuit after the DC/DC converter is started, and the duty ratio of the second control signal is the same as the duty ratio of the first control signal when the DC/DC converter is started; the pre-bias control circuit is used for outputting a first control signal to the synchronous rectification circuit in the starting process of the DC/DC converter and is also used for outputting a third control signal to the synchronous rectification circuit after the DC/DC converter is started, and the third control signal and the second control signal are in a complementary relation. The main power circuit synchronous rectification circuit is in the same phase with the driving control signal of the main power switching power tube in the starting process of the DC/DC converter, the driving control signal of the synchronous rectification switching tube and the driving control signal of the main power switching power tube are gradually changed from small to large, and the problem that the synchronous rectification switching tube is damaged due to reverse current flowing caused by overlarge duty ratio of the synchronous rectification tube in the starting process is effectively solved.
In the present embodiment, the pre-bias control circuit includes a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a first output resistor R1, a second output resistor R2, and a switching control circuit 48, as shown in fig. 6.
The anode of the first diode D1 is used as a first input end of the pre-bias control circuit, the cathode of the first diode D1 is connected with one end of a first output resistor, and the other end of the first output resistor R1 is used as a fifth output end of the pre-bias control circuit; the anode of the second diode D2 is used as the third input end of the pre-bias control circuit, and the cathode is connected with the cathode of the first diode;
the anode of the third diode D3 is used as the second input end of the pre-bias control circuit, the cathode of the third diode D3 is connected with one end of the second output resistor R2, and the other end of the second output resistor is used as the sixth output end of the pre-bias control circuit; the anode of the fourth diode D4 is used as the fourth input end of the pre-bias control circuit, and the cathode is connected with the cathode of the third diode D3;
the switching control circuit is used for connecting the first input end with the fifth output end and connecting the second input end with the sixth input end simultaneously when the DC/DC converter is in a starting process under the control of the switching control signal; i.e. the third input is isolated from the fifth input and the fourth input is isolated from the sixth input.
When the DC/DC converter completes the start-up process, the switching control circuit is further configured to connect only the third input terminal to the fifth output terminal and simultaneously connect only the fourth input terminal to the sixth input terminal under the control of the switching control signal. I.e. the first input is isolated from the fifth input and the second input is isolated from the sixth input.
The switching control circuit in this embodiment includes a first input resistor R3, a second input resistor R4, an inverter U, a first switch transistor K1, and a second switch transistor K2, as shown in fig. 7. The first switch tube and the second switch tube can be NMOS tubes or PMOS tubes.
The input end of the inverter U is used as the switching control signal input end of the pre-bias control circuit, the input end of the inverter U is connected with one end of the first input resistor R3, and the output end of the inverter U is connected with one end of the second input resistor R4.
The other end of the first input resistor R3 is connected with the gate of the first switching tube K1; the other end of the second input resistor R4 is connected with the gate of the second switching tube K2; one end of the first switch tube K1 is grounded, and the other end of the first switch tube K1 is respectively connected with the third input end and the fourth input end of the pre-bias control circuit;
one end of the second switch tube K2 is grounded, and the other end of the second switch tube K2 is connected with the first input end and the second input end of the pre-bias control circuit respectively; the switching control signal is a pulse signal.
When the DC/DC converter is in a starting state, the switching control signal R _ Select output by the digital controller is at a high level, a first switching tube in the synchronous rectification control circuit is switched on, the third control signals D31 and D32 are forced to be pulled low, and due to the existence of the inverter, the gate signal of the second switch tube in the synchronous rectification control circuit is low, the second switch tube is not conducted, the driving signal of the synchronous rectification circuit is completely provided by the first control signals D11 and D12, wherein the first control signal is the first control signal for driving the main power circuit, therefore, in the starting process, the driving signals of all the synchronous rectification circuit switching tubes are the same as the driving signals of all the main power switching tubes, the control mode can well solve the starting problem when the biased voltage is output, and can effectively prevent the occurrence of current back-flow;
when the DC/DC converter is started, namely the digital controller judges that the output is established, the output switching control signal SR _ Select is in low level, the first switch tube in the synchronous rectification control circuit is turned off and is changed from low level state to high resistance state, and is completely controlled by the output signal of the digital controller, and due to the existence of the inverter, the second switch tube of the second switch tube in the synchronous rectification control circuit is in high level and is turned on, the second control signal is only output to the main power circuit and is forced to be pulled down in the pre-bias control circuit, the third control signals D31 and D32 are output to the synchronous rectification switch tube of the synchronous rectification circuit and are complementary with the drive control signal of the main power switch tube, so after the output starting process is finished, the drive signal of the synchronous rectification switch tube of the synchronous rectification circuit is complementary with the drive signal of the main power switch tube, to achieve optimization of output efficiency in the conventional sense.
EXAMPLE III
The present embodiment provides a DC/DC converter including a main power circuit and a synchronous rectification circuit connected by a transformer, and the above pre-bias control apparatus.
The pre-bias control device comprises a digital controller and a pre-bias control circuit, wherein the digital controller is used for outputting a first control signal to the main power circuit, the duty ratio of the first control signal changes from small to large in the starting process of the DC/DC converter, a second control signal is output to the main power circuit after the DC/DC converter finishes starting, and the duty ratio of the second control signal is the same as that of the first control signal when the DC/DC converter finishes starting; the pre-bias control circuit is used for outputting a first control signal to the synchronous rectification circuit in the starting process of the DC/DC converter and is also used for outputting a third control signal to the synchronous rectification circuit after the DC/DC converter is started, and the third control signal and the second control signal are in a complementary relation. The main power circuit synchronous rectification circuit is in the same phase with the driving control signal of the main power switching power tube in the starting process of the DC/DC converter, the driving control signal of the synchronous rectification switching tube and the driving control signal of the main power switching power tube are gradually changed from small to large, and the problem that the synchronous rectification switching tube is damaged due to reverse current flowing caused by overlarge duty ratio of the synchronous rectification tube in the starting process is effectively 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 "include", "including" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or terminal device including a series of elements includes not only those elements but also other elements not explicitly listed or inherent to such process, method, article, or terminal device. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in the process, method, article, or terminal equipment comprising 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 (8)

1. A pre-bias control method applied to a DC/DC converter, wherein the DC/DC converter comprises a main power circuit and a synchronous rectification circuit which are connected through a transformer, and the pre-bias control method is characterized by comprising the following steps:
when the DC/DC converter is in a starting process, first control signals are respectively output to the main power circuit and the synchronous rectification circuit, and the duty ratio of the first control signals changes from small to large in the starting process; the first control signal comprises two paths of control signals, namely D11 and D12 which have the same duty ratio and 180-degree phase difference respectively; the D11 is used for outputting to a first main power switch tube, the D12 is used for outputting to a second main power switch tube, meanwhile, the D11 is also output to a first rectifying switch tube and a third rectifying switch tube, and the D12 is also output to a second rectifying switch tube and a fourth rectifying switch tube;
and when the DC/DC converter finishes starting and enters a normal working state, outputting a second control signal to the main power circuit, and outputting a third control signal to the synchronous rectification circuit, wherein the duty ratio of the third control signal is in a complementary relation with the duty ratio of the second control signal.
2. A pre-bias control device for a DC/DC converter comprising a main power circuit and a synchronous rectification circuit connected by a transformer, wherein the pre-bias control device comprises a digital controller and a pre-bias control circuit, wherein:
the digital controller is used for outputting a first control signal to the main power circuit, the duty ratio of the first control signal changes from small to large in the starting process of the DC/DC converter, a second control signal is output to the main power circuit after the DC/DC converter finishes starting, and the duty ratio of the second control signal is the same as the duty ratio of the first control signal when the DC/DC converter finishes starting; the first control signal comprises two paths of control signals, namely D11 and D12 which have the same duty ratio and 180-degree phase difference respectively; the D11 is used for outputting to a first main power switch tube, the D12 is used for outputting to a second main power switch tube, meanwhile, the D11 is also output to a first rectifying switch tube and a third rectifying switch tube, and the D12 is also output to a second rectifying switch tube and a fourth rectifying switch tube;
the pre-bias control circuit is used for outputting the first control signal to the synchronous rectification circuit in the starting process of the DC/DC converter and is also used for outputting a third control signal to the synchronous rectification circuit after the DC/DC converter is started, and the duty ratio of the third control signal and the duty ratio of the second control signal form a complementary relationship.
3. The pre-bias control device of claim 2, wherein the digital controller is provided with a first output, a second output, a third output, a fourth output, and a switching signal output, wherein:
the first output terminal and the second output terminal are used for outputting the first control signal or the second control signal to the main power circuit and the pre-bias control circuit;
the third output terminal and the fourth output terminal are used for outputting the third control signal to the pre-bias control circuit;
the switching signal is used for outputting a switching control signal, and the switching control signal is used for controlling the pre-bias control circuit to output the first control signal or the third control signal to the synchronous rectification circuit.
4. The pre-bias control device of claim 3, wherein the pre-bias control circuit is provided with a first input, a second input, a third input, a fourth input, a switching signal input, a fifth output, and a sixth output, wherein:
the first input end is connected with the first output end;
the second input end is connected with the second output end;
the third input end is connected with the third output end;
the fourth input end is connected with the fourth output end;
the switching signal input end is connected with the switching signal output end;
the fifth output end and the sixth output end are used for outputting the first control signal or the third control signal to the synchronous rectification circuit under the control of the switching signal.
5. The pre-bias control device of claim 4, wherein the pre-bias control circuit comprises a first diode, a second diode, a third diode, a fourth diode, a first output resistance, a second output resistance, and a switching control circuit, wherein:
the positive electrode of the first diode is the first input end, the negative electrode of the first diode is connected with one end of the first output resistor, and the other end of the first output resistor is the fifth output end;
the anode of the second diode is the third input end, and the cathode of the second diode is connected with the cathode of the first diode;
the anode of the third diode is the second input end, the cathode of the third diode is connected with one end of the second output resistor, and the other end of the second output resistor is the sixth output end;
the anode of the fourth diode is the fourth input end, and the cathode of the fourth diode is connected with the cathode of the third diode;
the switching control circuit is used for connecting the first input end with the fifth output end only and connecting the second input end with the sixth input end only when the DC/DC converter is in a starting process under the control of the switching control signal;
the switching control circuit is configured to connect only the third input terminal to the fifth output terminal and connect only the fourth input terminal to the sixth input terminal after the DC/DC converter completes a start-up process under control of the switching control signal.
6. The pre-bias control device of claim 5, wherein the switching control circuit comprises a first input resistor, a second input resistor, an inverter, a first switch and a second switch, wherein:
the input end of the phase inverter is the switching control signal input end and is connected with one end of the first input resistor, and the output end of the phase inverter is connected with one end of the second input resistor;
the other end of the first input resistor is connected with a gate pole of the first switching tube;
the other end of the second input resistor is connected with a gate pole of the second switching tube;
one end of the first switch tube is grounded, and the other end of the first switch tube is connected with the third input end and the fourth input end respectively;
one end of the second switch tube is grounded, and the other end of the second switch tube is respectively connected with the first input end and the second input end;
the switching control signal is a pulse signal.
7. The pre-bias control device of claim 6, wherein the first switch transistor and the second switch transistor are both NMOS transistors or PMOS transistors.
8. A DC/DC converter comprising a main power circuit and a synchronous rectification circuit connected by a transformer, further comprising a pre-bias control device as claimed in any one of claims 2 to 7.
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