CN114726222A - Asymmetric half-bridge flyback converter, switch control method thereof and power supply device - Google Patents

Asymmetric half-bridge flyback converter, switch control method thereof and power supply device Download PDF

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Publication number
CN114726222A
CN114726222A CN202210324850.1A CN202210324850A CN114726222A CN 114726222 A CN114726222 A CN 114726222A CN 202210324850 A CN202210324850 A CN 202210324850A CN 114726222 A CN114726222 A CN 114726222A
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current
flyback converter
switching tube
bridge
low
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杨帅
东伟
盛琳
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Meraki Integrated Shenzhen Technology Co ltd
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Meraki Integrated Shenzhen Technology 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
    • 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
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The application is suitable for the technical field of electronic converters, and provides an asymmetric half-bridge flyback converter, a switch control method thereof and power supply equipment, wherein a sampling resistor in the asymmetric half-bridge flyback converter is connected between a resonant capacitor and a second input end of a half-bridge structure, and the switch control method comprises the following steps: acquiring the primary side current of the transformer and the change rate of the primary side current when the low-side switching tube is conducted; determining a target current change stage where the half-bridge flyback converter is located according to the change rate; if the target current change stage is an exciting current reduction stage, the primary side current is a negative value, and the primary side current is equal to the preset current threshold, the low-side switching tube is controlled to be disconnected, so that the soft switching function of the high-side switching tube can be realized when the asymmetric half-bridge flyback converter is converted from a high-output voltage scene to a low-output voltage scene, and the electric energy conversion efficiency and the stability of the asymmetric half-bridge flyback converter are improved.

Description

Asymmetric half-bridge flyback converter, switch control method thereof and power supply device
Technical Field
The application belongs to the technical field of electronic converters, and particularly relates to an asymmetric half-bridge flyback converter, a switch control method of the asymmetric half-bridge flyback converter and power supply equipment.
Background
An asymmetric half-bridge (AHB) flyback converter is a novel soft switching converter, which is used as a kind of switching power supply and is generally applied to the field of isolated dc-dc conversion. In practical application, by adjusting the on-time of the high-side switching tube and the on-time of the low-side switching tube in the half-bridge structure of the AHB flyback converter, not only can the output Voltage be adjusted, but also the soft switching (i.e., Zero Voltage Switch, ZVS) function of the low-side switching tube and the high-side switching tube can be realized, thereby improving the electric energy conversion efficiency of the AHB flyback converter.
In the prior art, in order to ensure that a switching tube in an AHB flyback converter can still realize a ZVS function in a wide output voltage range scene, a conventional switching control strategy is as follows: according to the ratio of the maximum output voltage required by an actual scene to the actual output voltage of the AHB flyback converter, the resonance time of leakage inductance and a resonance capacitor in the AHB flyback converter is linearly prolonged, the conduction time of the low-side switching tube is calculated according to the prolonged resonance time, and the low-side switching tube is controlled to be turned off according to the calculated conduction time of the low-side switching tube. However, the conventional switching control strategy is only applicable to a high-output voltage scene with a fixed output voltage, and when the AHB flyback converter is converted from the high-output voltage scene to a low-output voltage scene, the calculated on-time of the low-side switching tube is used to turn off the low-side switching tube, so that the primary side of the transformer cannot have enough negative current, the high-side switching tube cannot realize the ZVS function, and the electric energy conversion efficiency and reliability of the AHB flyback converter are reduced.
Disclosure of Invention
In view of this, embodiments of the present application provide an asymmetric half-bridge flyback converter, a switching control method thereof, and a power supply device, so as to solve the technical problems that when a high-output voltage scene is converted into a low-output voltage scene by an asymmetric half-bridge flyback converter due to a conventional switching control method, a soft switching function of a high-side switching tube cannot be realized, and the power conversion efficiency and stability of the asymmetric half-bridge flyback converter are reduced.
In a first aspect, an embodiment of the present application provides a switching control method for an asymmetric half-bridge flyback converter, where the asymmetric half-bridge flyback converter includes a half-bridge structure composed of a high-side switching tube and a low-side switching tube, a leakage inductance, an excitation inductance, a transformer, a resonant capacitor, and a sampling resistor; the first input end and the second input end of the half-bridge structure are respectively connected with the anode and the cathode of a direct-current power supply, the leakage inductance, the excitation inductance, the resonant capacitor and the sampling resistor are sequentially connected in series between the output end and the second input end of the half-bridge structure, and the primary coil of the transformer is connected in parallel with the excitation inductance; the switch control method comprises the following steps:
acquiring the primary side current of the transformer and the change rate of the primary side current when the low-side switching tube is conducted;
determining a target current change stage where the half-bridge flyback converter is located according to the change rate;
and if the target current change stage is an exciting current reduction stage, the primary side current is a negative value, and the primary side current is equal to a preset current threshold, controlling the low-side switching tube to be switched off.
In an optional implementation manner of the first aspect, if the target current change stage is an excitation current reduction stage, the primary current is a negative value, and the primary current is equal to a preset current threshold, controlling the low-side switching tube to be turned off includes:
if the target current change stage is an exciting current reduction stage, monitoring whether the primary side current is changed from a positive value to a negative value in real time;
if the primary side current is changed from a positive value to a negative value, starting a timer to start timing;
and when the timing duration of the timer is equal to a preset duration threshold, controlling the low-side switching tube to be disconnected.
In an optional implementation manner of the first aspect, the preset duration threshold is determined according to the following formula:
Teng＝(Ineg*lmag*Vomax)/(Vout 2*Np)；
wherein Teng is the preset duration threshold, Ineg is the preset current threshold, and VoutIs the actual output voltage of the asymmetric half-bridge flyback converter, NpIs the turns ratio of the primary winding to the secondary winding of the transformer, lmagIs the inductance, V, of the excitation inductanceomaxThe maximum output voltage of the asymmetric half-bridge flyback converter.
In an optional implementation manner of the first aspect, the determining a target current variation phase in which the half-bridge flyback converter is located according to the variation rate includes:
and if the magnitude corresponding to the change rate is the first magnitude, determining that the target current change stage where the half-bridge flyback converter is located is a resonant discharge stage.
In an optional implementation manner of the first aspect, the determining a target current variation phase in which the half-bridge flyback converter is located according to the variation rate includes:
if the magnitude corresponding to the change rate is a second magnitude, determining that a target current change stage where the half-bridge flyback converter is located is a harmonic excitation current reduction stage; the first order of magnitude is greater than the second order of magnitude.
In an optional implementation manner of the first aspect, the method further includes:
and if the target current change stage is an exciting current reduction stage, the primary side current is a negative value, and the primary side current is smaller than the preset current threshold, maintaining the conduction of the low-side switching tube.
In an optional implementation manner of the first aspect, the method further includes:
and if the target current change stage is a resonance discharge stage, maintaining the conduction of the low-side switch tube.
In a second aspect, an embodiment of the present application provides a switch control apparatus, where the asymmetric half-bridge flyback converter includes a half-bridge structure composed of a high-side switching tube and a low-side switching tube, a leakage inductance, an excitation inductance, a transformer, a resonant capacitor, and a sampling resistor; the first input end and the second input end of the half-bridge structure are respectively connected with the anode and the cathode of a direct-current power supply, the leakage inductance, the excitation inductance, the resonant capacitor and the sampling resistor are sequentially connected in series between the output end and the second input end of the half-bridge structure, and the primary coil of the transformer is connected in parallel with the excitation inductance; the switch control device includes:
the first acquisition unit is used for acquiring the primary side current of the transformer and the change rate of the primary side current when the low-side switching tube is conducted;
the first determining unit is used for determining a target current change stage where the half-bridge flyback converter is located according to the change rate;
and the switch control unit is used for controlling the low-side switching tube to be switched off if the target current change stage is an exciting current reduction stage, the primary side current is a negative value, and the primary side current is equal to a preset current threshold value.
In a third aspect, an embodiment of the present application provides an asymmetric half-bridge flyback converter, including a half-bridge structure composed of a high-side switching tube and a low-side switching tube, a leakage inductance, an excitation inductance, a transformer, a resonant capacitor, and a sampling resistor;
the first input end and the second input end of the half-bridge structure are respectively connected with the anode and the cathode of a direct-current power supply, the leakage inductance, the excitation inductance, the resonant capacitor and the sampling resistor are sequentially connected in series between the output end and the second input end of the half-bridge structure, and the primary coil of the transformer is connected in parallel with the excitation inductance; the first end that switches on of high limit switch tube is regarded as half-bridge structure's first input, the second end that switches on of high limit switch tube with the first end that switches on of low limit switch tube connects altogether and regards as half-bridge structure's output, the second end that switches on of low limit switch tube is regarded as half-bridge structure's second input.
In a fourth aspect, embodiments of the present application provide a power supply apparatus, including a dc power supply, a switch control device as described in the second aspect, and an asymmetric half-bridge flyback converter as described in the third aspect, where the asymmetric half-bridge flyback converter is connected to the dc power supply and the switch control device.
The implementation of the asymmetric half-bridge flyback converter, the switch control method and device thereof, and the power supply device provided by the embodiment of the application has the following beneficial effects:
according to the switching control method of the asymmetric half-bridge flyback converter, the sampling resistor is arranged between the resonant capacitor and the second input end of the half-bridge structure, so that not only can the primary side current of the transformer be detected when the high-side switch tube is conducted, but also the primary side current of the transformer can be detected when the low-side switch tube is conducted. Based on this, in the embodiment of the application, when the low-side switching tube is turned on, the primary current of the transformer and the change rate of the primary current are obtained, and it is determined that the half-bridge flyback converter is in an excitation current reduction stage according to the change rate, and the primary current of the transformer is a negative value, and when the primary current of the transformer is equal to a preset current threshold, the low-side switching tube is controlled to be turned off, so that sufficient negative current can be accumulated for the primary side of the transformer when the low-side switching tube is turned on, thereby providing a basis for the high-side switching tube to realize the ZVS function, so that the asymmetric half-bridge flyback converter can also realize the soft switching function of the high-side switching tube when a high-output voltage scene is converted into a low-output voltage scene, and thus the electric energy conversion efficiency and the stability of the asymmetric half-bridge flyback converter are improved.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.
Fig. 1 is a schematic diagram of a conventional asymmetric half-bridge flyback converter;
fig. 2 is a schematic diagram of a waveform of a primary current of a transformer corresponding to a conventional asymmetric half-bridge flyback converter;
fig. 3 is a schematic structural diagram of an asymmetric half-bridge flyback converter according to an embodiment of the present disclosure;
fig. 4 is a schematic flowchart of a switching control method of an asymmetric half-bridge flyback converter according to an embodiment of the present application;
fig. 5 is a schematic waveform diagram of a primary side current of a transformer according to an embodiment of the present application;
fig. 6 is a flowchart illustrating a specific implementation of S43 in a switching control method of an asymmetric half-bridge flyback converter according to an embodiment of the present disclosure;
fig. 7 is a schematic flow chart of a switching control method of an asymmetric half-bridge flyback converter according to another embodiment of the present application;
fig. 8 is a schematic structural diagram of a switch control device according to another embodiment of the present application;
fig. 9 is a schematic structural diagram of a switch control device according to another embodiment of the present application;
fig. 10 is a schematic structural diagram of a power supply apparatus according to an embodiment of the present application.
Detailed Description
It is noted that the terminology used in the description of the embodiments of the present application is for the purpose of describing particular embodiments of the present application only and is not intended to be limiting of the present application. In the description of the embodiments of the present application, "/" means "or" unless otherwise specified, for example, a/B may mean a or B; "and/or" herein is merely an associative relationship describing an association, meaning that there may be three relationships, e.g., a and/or B, may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of the present application, "a plurality" means two or more, and "at least one", "one or more" means one, two or more, unless otherwise specified.
In the following, the terms "first", "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a definition of "a first" or "a second" feature may explicitly or implicitly include one or more of the features.
Reference throughout this specification to "one embodiment" or "some embodiments," or the like, means that a particular feature, structure, or characteristic described in connection with the embodiment is included in one or more embodiments of the present application. Thus, appearances of the phrases "in one embodiment," "in some embodiments," "in other embodiments," or the like, in various places throughout this specification are not necessarily all referring to the same embodiment, but rather "one or more but not all embodiments" unless specifically stated otherwise. The terms "comprising," "including," "having," and variations thereof mean "including, but not limited to," unless expressly specified otherwise.
The structure of a conventional asymmetric half-bridge (AHB) flyback converter is shown in fig. 1. V _ dc is a direct-current input voltage of the AHB flyback converter, the switching tube Q1 and the switching tube Q2 form a half-bridge structure in the AHB flyback converter (the switching tube Q1 is generally called a high-side switching tube, the switching tube Q2 is generally called a low-side switching tube), Lr is a leakage inductance, Lm is an excitation inductance, Tr2 is a transformer, Cr is a resonant capacitor, Rsen1 is a sampling resistor, D1 is a rectifier diode, C2 is a filter capacitor, R1 is a filter resistor, and R2 is a load of the AHB flyback converter.
In a specific application, the controlled end of the switching tube Q1 and the controlled end of the switching tube Q2 are further connected to a controller (not shown), and the controller outputs a switching control signal to the controlled end of the switching tube Q1 or the controlled end of the switching tube Q2 to realize on-off control of the switching tube Q1 and the switching tube Q2.
The operation process of the AHB flyback converter includes a plurality of switching cycles, and in each switching cycle, the conversion of the dc input voltage V _ dc is realized by alternately turning on the switching tube Q1 and the switching tube Q2. The following describes the operating principle of the conventional AHB flyback converter with reference to a change curve of the primary current of the transformer in one switching period shown in fig. 2, taking one switching period as an example.
After a switching period begins, the controller controls the switching tube Q1 to be turned on, controls the switching tube Q2 to be turned off, and controls the leakage inductance Lr to be connected in series with the excitation inductance Lm, so that under the action of the direct-current input voltage V _ dc, the primary side current of the transformer Tr2 (namely, the current flowing through the leakage inductance Lr) rises linearly, the transformer Tr2 stores magnetic field energy, and the filter capacitor C2 on the secondary side of the transformer Tr2 supplies power to a load. Meanwhile, the controller monitors the voltage Vcs across the sampling resistor Rsen1 to monitor the primary current of the transformer Tr 2.
When the controller monitors that the primary side current of the transformer Tr2 reaches a preset current peak value Iset, the controller controls the switching tube Q1 to be switched off, after the switching tube Q1 is switched off, the primary side current of the transformer Tr2 starts to fall, but because the primary side current of the transformer Tr2 is a positive value at the moment, the Voltage at two ends of the body diode of the switching tube Q1 can rise, the Voltage at two ends of the body diode of the switching tube Q2 falls, and when the Voltage at two ends of the body diode of the switching tube Q2 falls to 0, the controller controls the switching tube Q2 to be switched on, so that the switching tube Q2 can realize a soft switching (namely Zero Voltage switching, ZVS) function.
In addition, when the voltage across the body diode of the switching tube Q2 drops to 0, the voltage across the excitation inductance Lm is reversed, at this time, the leakage inductance Lr resonates with the resonant capacitance Cr, and the rectifier diode D1 on the secondary side of the transformer Tr2 is positively biased to be on, the energy stored in the transformer Tr2 starts to be transferred to the secondary side of the transformer Tr, when the primary side current of the transformer Tr2 is equal to the excitation current, the transformer Tr2 stops transferring energy to the secondary side, at this time, the controller will continue to control the switching tube Q2 to be in the on state, so that the voltage on the resonant capacitance C1 is used as the voltage excitation source of the excitation inductance Lm to generate the negative excitation current, when the negative excitation current reaches the preset current threshold Ineg, the controller controls the switching tube Q2 to be off, after the switching tube Q2 is off, the negative excitation current will cause the voltage across the body diode of the switching tube Q1 to drop, and when the voltage across the body diode of the switching tube Q1 drops to 0, the controller controls the switching tube Q1 to be conducted, and enters the next switching period, so that the switching tube Q1 can realize the ZVS function.
In order to meet the requirement of a wide output voltage range in an actual application scenario, a resonance parameter and an excitation parameter of the AHB flyback converter are usually designed according to a highest output voltage required by the actual application scenario, and a specific design strategy is that a time duration of a half resonance period of the AHB flyback converter is set to a time duration required by the excitation current to drop from a preset current peak Iset to 0, so that a zero-crossing point of the resonance current and a zero-crossing point of the excitation current can be located at the same position (i.e., a position t1 shown in (a) in fig. 2), and the AHB flyback converter has optimal power conversion efficiency. In addition, in order to ensure that the high-side switching tube of the AHB flyback converter can still realize ZVS function in a wide output voltage range, the traditional switching control strategy is as follows: according to the ratio of the maximum output voltage required by an actual scene to the actual output voltage of the AHB flyback converter, the resonant time duration of the leakage inductance Lr and the resonant capacitance Cr is linearly extended, that is, Ttrans in fig. 2 is extended; and calculating the conduction time of the low-side switching tube according to the prolonged resonance time, wherein the specific calculation strategy is that the conduction time Tlg of the low-side switching tube is (V)omax/Vout)*TtransWherein V isomaxMaximum output voltage, V, required for a practical sceneoutIs the actual output voltage, T, of the AHB flyback convertertransIs the extended resonance time; and finally, switching off the low-side switching tube according to the calculated on-time of the low-side switching tube, namely, controlling the low-side switching tube to be switched off after the on-time of the low-side switching tube reaches the calculated on-time Tlg.
However, the above-mentioned conventional switching control strategy is only applicable to high output voltage scenarios where the output voltage is fixed, when the AHB flyback converter is converted from a high output voltage scene to a low output voltage scene, the descending speed of the exciting current of the transformer is slowed, and the primary side current of the transformer is intersected with the exciting current after passing through a zero crossing point, i.e., at t0 shown in fig. 2 (b), if the on-time of the low-side switching tube calculated as above is used to perform the off-control of the low-side switching tube in this case, the time period during which the primary side current of the transformer drops from the intersection point to 0, i.e., Tzero shown in fig. 2 (b), is ignored, so that the primary side of the transformer cannot have a sufficient negative current, therefore, the ZVS function of the high-side switching tube cannot be realized, and the electric energy conversion efficiency and the reliability of the AHB flyback converter are further reduced.
In order to solve the above technical problem, an embodiment of the present invention first provides an AHB flyback converter, which can be applied to the field of an isolated dc-dc converter requiring a wide output voltage range. Fig. 3 is a schematic structural diagram of an AHB flyback converter according to an embodiment of the present disclosure. As shown in fig. 3, the AHB flyback converter includes a half-bridge structure 31 composed of a high-side switching tube Q1 and a low-side switching tube Q2, a leakage inductance Lr, an excitation inductance Lm, a transformer Tr2, a resonant capacitor Cr, a sampling resistor Rsen1, a rectifier diode D1, a filter capacitor C2, and a filter resistor R1.
A first conduction end of the high-side switching tube Q1 is used as a first input end of the half-bridge structure 31 and is connected with the positive electrode of the direct-current power supply; a second conduction end of the low-side switching tube Q2 is used as a second input end of the half-bridge structure 31 and is connected with the negative electrode of the direct-current power supply; the second conducting end of the high-side switching tube Q1 and the first conducting end of the low-side switching tube Q2 are connected together and used as the output end of the half-bridge structure 31; the controlled end of the high-side switch tube Q1 and the controlled end of the low-side switch tube Q2 are both connected with the switch control device 32; the leakage inductance Lr, the excitation inductance Lm, the resonant capacitance Cr and the sampling resistance Rsen1 are sequentially connected in series between the output end of the half-bridge structure 31 and the negative electrode of the dc power supply; the primary coil of the transformer Tr2 is connected in parallel with the magnetizing inductance Lm. The anode of the rectifier diode D1 is connected to the different-name end of the secondary coil of the transformer Tr2, the cathode of the rectifier diode D1 is connected to the first end of the filter capacitor C2, the second end of the filter capacitor C2 is connected to the first end of the filter resistor R1, and the second end of the filter resistor R1 is connected to the same-name end of the secondary coil of the transformer Tr 2.
In a specific application, the switch control device 32 may be a controller, and the switch control device 32 may be disposed inside the AHB flyback converter or outside the AHB flyback converter, and is specifically set according to an actual requirement, and is not particularly limited herein.
In the embodiment of the present application, since the sampling resistor Rsen1 is disposed between the resonant capacitor Cr and the second input terminal of the half-bridge structure 31, not only the detection of the primary current of the transformer Tr2 when the high-side switching tube is turned on, but also the detection of the primary current of the transformer Tr2 when the low-side switching tube is turned on can be realized, so as to provide a hardware basis for the switching control method of the AHB flyback converter in the subsequent embodiment.
Based on the AHB flyback converter provided in the embodiment of the present application, the embodiment of the present application further provides a switch control method based on the AHB flyback converter, and an execution main body of the switch control method may be the switch control device 32 in the embodiment corresponding to fig. 3. Referring to fig. 4, a schematic flowchart of a switching control method based on an AHB flyback converter according to an embodiment of the present application is shown in fig. 4, where the switching control method may include steps S41 to S43, which are detailed as follows:
s41: and acquiring the primary side current of the transformer and the change rate of the primary side current when the low-side switching tube is switched on.
In the embodiment of the application, the switch control device can monitor the on-off state of the low-side switching tube in real time, and when the low-side switching tube is monitored to be in the on state, the primary side current of the transformer and the change rate of the primary side current are obtained.
In an embodiment of the present application, when the switching control device detects that the low-side switching tube is in the on state, the primary current of the transformer at this time can be obtained by detecting the voltage across the sampling resistor Rsen 1. Specifically, the switching control device may determine a ratio of a voltage across the sampling resistor Rsen1 when the low-side switch is turned on to a resistance of the sampling resistor Rsen1 as the primary current of the transformer when the low-side switch is turned on.
By way of example and not limitation, after the switching control device obtains the primary current of the transformer when the low-side switch is turned on, the primary current of the transformer at that time may be subjected to a time differentiation process to obtain a change rate of the primary current of the transformer when the low-side switch is turned on.
S42: and determining a target current change stage of the half-bridge flyback converter according to the change rate.
In the embodiment of the application, when the low-side switching tube is turned on in advance, the current change stage of the AHB flyback converter can be divided into a resonant discharge stage and an excitation current reduction stage according to different current waveform frequencies corresponding to different current change stages. Referring to fig. 5, a waveform diagram of a primary side current of a transformer according to an embodiment of the present disclosure is shown in fig. 5, where Ttrans corresponds to a resonant discharge phase, and Tmag corresponds to an excitation current reduction phase. The current waveform frequency corresponding to the resonant discharge stage is
Figure BDA0003573001170000091
The current waveform frequency corresponding to the excitation current reduction stage is
Figure BDA0003573001170000092
Wherein lrAn inductive reactance being a leakage inductance Lr, crIs the capacitance value of the resonant capacitor Cr,/magIs the inductive reactance of the magnetizing inductance Lm.
Current waveform frequency F corresponding to resonant discharge stage1Usually much larger than the current waveform frequency F corresponding to the excitation current falling stage2And the magnitude of the two is different greatly, so that the magnitude of the change rate of the primary side current corresponding to the resonant discharge stage is different greatly from the magnitude of the change rate of the primary side current corresponding to the excitation current reduction stage. Based on this, the current waveform frequency F corresponding to the resonant discharge stage can be aimed at1Current waveform frequency F corresponding to the stage of exciting current decrease2And respectively setting a first order of magnitude and a second order of magnitude as a judgment basis of the current change stage. Wherein the first order of magnitude is greater than the second order of magnitude, and the first order of magnitude and the second order of magnitude can be obtained through experimental measurement.
Based on this, in an embodiment of the present application, S42 may specifically include the following steps:
if the magnitude corresponding to the change rate is a first magnitude, determining that a target current change stage where the half-bridge flyback converter is located is a resonant discharge stage;
and if the magnitude corresponding to the change rate is a second magnitude, determining that the target current change stage where the half-bridge flyback converter is located is an excitation current reduction stage.
S43: and if the target current change stage is an exciting current reduction stage, the primary side current is a negative value, and the magnitude of the primary side current is equal to a preset current threshold value, controlling the low-side switching tube to be switched off.
In this embodiment of the present application, when the AHB flyback converter is in an excitation current decreasing stage (i.e., a period corresponding to Tmag in fig. 5), the primary current of the transformer sequentially goes through two sub-stages, where the first sub-stage is a stage where the primary current of the transformer continuously decreases from a positive value to 0 (i.e., a period corresponding to Tzero in fig. 5), and the second sub-stage is a stage where the primary current of the transformer continuously decreases from 0 to a negative value and the magnitude of the primary current continuously increases (i.e., a period corresponding to Tneg in fig. 5). In order to enable the high-side switching tube in the half-bridge structure to realize the ZVS function, the primary side of the transformer needs to have enough negative current, that is, the primary side current of the transformer needs to reach a preset current threshold value to disconnect the low-side switching tube.
In this embodiment, the preset current threshold may be according to the formula Ineg ═ (2 × C)oss*Vin)/TdAnd (4) determining to obtain.
Wherein Ineg is a predetermined current threshold, CossIs the capacitance value, V, of the parasitic capacitance of the switching tube in a half-bridge configurationinIs the output voltage of the DC power supply, TdThe dead time is used for describing the time between the disconnection of the low-side switch tube and the conduction of the high-side switch tube.
Based on this, in an embodiment of the present application, when the switching control device determines that the AHB flyback converter is in the excitation current reduction stage and detects that the primary current of the transformer is a negative value, the switching control device may monitor the primary current of the transformer, and control the low-side switching tube to be turned off when the primary current of the transformer is equal to the preset current threshold.
In another embodiment of the present application, since the AHB flyback converter is in the field current reduction stage, the reduction rate of the primary current of the transformer is (V)out*Np)/lmagTherefore, the time period required for the primary side current of the transformer to drop from 0 to-Ineg is (Ineg × l)mag)/(Vout*Np). In order to make the AHB flyback converter suitable for an application scenario with a wide output voltage range, the time length required for the primary current of the transformer to drop from 0 to-Ineg needs to be adjusted according to the maximum output voltage required by the application scenario. Specifically, the adjusted duration may be (Ineg × l)mag*Vomax)/(Vout 2*Np) Wherein Ineg is a predetermined current threshold, VoutIs the actual output voltage, N, of the AHB flyback converterpIs the turns ratio of the primary winding to the secondary winding of the transformer, lmagInductance, V, of magnetizing inductance LmomaxThe maximum output voltage of the AHB flyback converter (i.e. the maximum output voltage required by the actual application scenario).
In this embodiment, the adjusted duration may be defined as a preset duration threshold, that is, the preset duration threshold Teng may be set to (Ineg × l)mag*Vomax)/(Vout 2*Np). Based on this, S43 can be specifically realized by S431 to S4323 as shown in fig. 6, which is detailed as follows:
s431: if the target current change stage is an exciting current reduction stage, monitoring whether the primary side current is changed from a positive value to a negative value in real time;
s432: if the primary side current is changed from a positive value to a negative value, starting a timer to start timing;
s433: and when the timing duration of the timer is equal to a preset duration threshold, controlling the low-side switching tube to be disconnected.
In this embodiment, the switch control device starts the timer to start timing when the switch control device monitors that the primary side current of the transformer changes from a positive value to a negative value, and controls the low-side switching tube to be switched off when the timing duration is equal to the preset duration threshold. The disconnection control of the low-side switching tube is realized by monitoring the duration of the primary side current of the transformer in the negative value phase, so that the method is convenient and simple, and the accuracy of the disconnection control of the low-side switching tube can be improved.
As can be seen from the above, in the switching control method of the asymmetric half-bridge flyback converter provided in this embodiment, the sampling resistor is disposed between the resonant capacitor and the second input end of the half-bridge structure, so that not only can the detection of the primary current of the transformer when the high-side switching tube is turned on be realized, but also the detection of the primary current of the transformer when the low-side switching tube is turned on can be realized. Based on this, in the embodiment of the application, when the low-side switching tube is turned on, the primary current of the transformer and the change rate of the primary current are obtained, and it is determined that the half-bridge flyback converter is in an excitation current reduction stage according to the change rate, and the primary current of the transformer is a negative value, and when the primary current of the transformer is equal to a preset current threshold, the low-side switching tube is controlled to be turned off, so that sufficient negative current can be accumulated for the primary side of the transformer when the low-side switching tube is turned on, thereby providing a basis for the high-side switching tube to realize the ZVS function, so that the asymmetric half-bridge flyback converter can also realize the soft switching function of the high-side switching tube when a high-output voltage scene is converted into a low-output voltage scene, and thus the electric energy conversion efficiency and the stability of the asymmetric half-bridge flyback converter are improved.
Referring to fig. 7, a schematic flowchart of a switching control method of an asymmetric half-bridge flyback converter according to another embodiment of the present application is provided. As shown in fig. 7, the switch control method provided in this embodiment is different from the switch control method corresponding to fig. 4 in that the switch control method in this embodiment further includes S44 and S45, which are detailed as follows:
s44: and if the target current change stage is a resonance discharge stage, maintaining the conduction of the low-side switch tube.
In this embodiment, when the switch control device detects that the AHB flyback converter is in the resonant discharge stage, it indicates that the excitation current reduction stage has not been reached yet, and therefore the switch control device continues to control the low-side switching tube to be in the on state.
S45: and if the target current change stage is an exciting current reduction stage, the primary side current is a negative value, and the primary side current is smaller than the preset current threshold, maintaining the conduction of the low-side switching tube.
In this embodiment, when the switch control device detects that the AHB flyback converter is in the field current decrease stage, and the side current of the transformer is a negative value, but the primary side current of the transformer is smaller than the preset current threshold, it indicates that there is not enough negative current on the primary side of the transformer to enable the high-side switching tube to implement the ZVS function, so that the switch control device continues to control the low-side switching tube to be in the on state at this time.
In the present embodiment, S43, S44, and S45 are exclusive steps, and when S43 is executed, the switch control device does not execute S44 and S45; the switch control means does not execute S43 and S45 in the case of executing S44; when executing S45, the switch control device does not execute S43 and S44.
It can be seen from the above that, in the switching control method of the asymmetric half-bridge flyback converter provided in this embodiment, when the AHB flyback converter is in the resonant discharge stage, or when the AHB flyback converter is in the excitation current reduction stage but the primary side negative current of the transformer does not reach the preset current threshold, the low-side switching tube is controlled to maintain the on-state, so that the primary side of the transformer can be ensured to accumulate sufficient negative current, a basis is provided for the high-side switching tube to realize the ZVS function, and it is ensured that the high-side switching tube can still realize the ZVS function under the condition that the AHB flyback converter meets the requirement of the wide output voltage range, thereby improving the electric energy conversion efficiency of the AHB flyback converter, and increasing the application range of the AHB flyback converter.
Based on the switching control method of the asymmetric half-bridge flyback converter provided in the above embodiments, embodiments of the switching control device implementing the embodiments of the method are further provided in the embodiments of the present invention. Please refer to fig. 8, which is a schematic structural diagram of a switch control device according to an embodiment of the present disclosure. For convenience of explanation, only the portions related to the present embodiment are shown. As shown in fig. 8, the switching control device 80 may include: a first acquisition unit 81, a first determination unit 82, and a switch control unit 83. Wherein:
the first obtaining unit 81 is configured to obtain a primary current of the transformer and a change rate of the primary current when the low-side switching tube is turned on.
The first determining unit 82 is configured to determine a target current variation phase in which the half-bridge flyback converter is located according to the variation rate.
The switch control unit 83 is configured to control the low-side switching tube to be turned off if the target current change stage is an excitation current reduction stage, the primary side current is a negative value, and the magnitude of the primary side current is equal to a preset current threshold.
Optionally, the switch control unit 83 may specifically include: the device comprises a current direction monitoring unit, a timing unit and a turn-off control unit. Wherein:
and the current direction monitoring unit is used for monitoring whether the primary side current changes from a positive value to a negative value in real time if the target current change stage is an exciting current reduction stage.
The timing unit is used for starting a timer to start timing if the primary side current is changed from a positive value to a negative value.
And the turn-off control unit is used for controlling the low-side switching tube to be switched off when the timing duration of the timer is equal to a preset duration threshold value.
Optionally, the preset duration threshold is determined according to the following formula:
Teng＝(Ineg*lmag*Vomax)/(Vout 2*Np)；
wherein Teng is the preset duration threshold, Ineg is the preset current threshold, and VoutIs the actual output voltage of the asymmetric half-bridge flyback converter, NpIs the turns ratio of the primary winding to the secondary winding of the transformer, lmagIs the inductance, V, of the excitation inductanceomaxFor said asymmetric half-bridge flyback conversionThe maximum output voltage of the device.
Optionally, the first determining unit 82 is specifically configured to determine that the target current variation phase where the half-bridge flyback converter is located is a resonant discharge phase if the magnitude corresponding to the variation rate is a first magnitude.
Optionally, the first determining unit 82 is specifically configured to determine that the target current change stage where the half-bridge flyback converter is located is a harmonic excitation current reduction stage if the magnitude corresponding to the change rate is a second magnitude; the first order of magnitude is greater than the second order of magnitude.
Optionally, the switch control unit 83 is further configured to maintain the low-side switching tube to be turned on if the target current change stage is an excitation current reduction stage, the primary side current is a negative value, and the magnitude of the primary side current is smaller than the preset current threshold.
Optionally, the switch control unit 83 is further configured to maintain the low-side switching tube to be turned on if the target current change stage is a resonant discharge stage.
It should be noted that, for the information interaction, the execution process, and other contents between the above units, the specific functions and the technical effects brought by the method embodiments of the present application are based on the same concept, and specific reference may be made to the method embodiment part, which is not described herein again.
It will be clear to those skilled in the art that, for convenience and simplicity of description, the above division of the functional units is merely illustrated, and in practical applications, the above function distribution may be performed by different functional units according to needs, that is, the internal structure of the switch control device is divided into different functional units to perform all or part of the above described functions. Each functional unit in the embodiments may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit, and the integrated unit may be implemented in a form of hardware, or in a form of software functional unit. In addition, specific names of the functional units are only used for distinguishing one functional unit from another, and are not used for limiting the protection scope of the application. The specific working process of the units in the system may refer to the corresponding process in the foregoing method embodiment, and is not described herein again.
Referring to fig. 9, fig. 9 is a schematic structural diagram of a switch control device according to another embodiment of the present application. As shown in fig. 9, the switch control device 9 provided in this embodiment may include: a processor 90, a memory 91, and a computer program 92 stored in the memory 91 and operable on the processor 90, such as a program corresponding to a switching control method of an asymmetric half-bridge flyback converter. The processor 90 implements steps in the switching control method of the asymmetric half-bridge flyback converter described above, such as S41-S43 shown in fig. 4, when executing the computer program 92. Alternatively, the processor 90, when executing the computer program 92, implements the functions of the various modules/units of the switch control device embodiments described above, such as the functions of the units 81-83 shown in FIG. 8.
Illustratively, the computer program 92 may be partitioned into one or more modules/units, which are stored in the memory 91 and executed by the processor 90 to accomplish the present application. One or more of the modules/units may be a series of computer program instruction segments capable of performing specific functions, which are used to describe the execution of the computer program 92 in the switch control device 9. For example, the computer program 92 may be divided into a first obtaining unit, a first determining unit and a switch control unit, and the specific functions of each unit are described with reference to the related description in the embodiment corresponding to fig. 8, which is not repeated herein.
The processor 90 may be a Central Processing Unit (CPU), other general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, etc. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.
It will be appreciated by those skilled in the art that fig. 9 is merely an example of the switch control device 9 and does not constitute a limitation of the switch control device 9 and may include more or less components than those shown, or some components may be combined, or different components.
The embodiment of the application also provides power supply equipment. Referring to fig. 10, a schematic structural diagram of a power supply apparatus according to an embodiment of the present disclosure is shown in fig. 10, where the power supply apparatus may include a dc power supply 101, a switch control device 102, and an asymmetric half-bridge flyback converter 103. The asymmetric half-bridge flyback converter 103 is connected to the dc power supply 101 and the switching control device 102.
Specifically, a first input end and a second input end of the asymmetric half-bridge flyback converter 103 are respectively connected to the positive electrode and the negative electrode of the dc power supply 101, and a first controlled end and a second controlled end of the asymmetric half-bridge flyback converter 103 are both connected to the switch control device 102.
Based on this, the first input terminal and the second input terminal of the half-bridge structure 13 in fig. 3 may be respectively used as the first input terminal and the second input terminal of the asymmetric half-bridge flyback converter 103, and the controlled terminal of the high-side switching tube Q1 and the controlled terminal of the low-side switching tube Q2 may be respectively used as the first controlled terminal and the second controlled terminal of the asymmetric half-bridge flyback converter 103. For other contents of the asymmetric half-bridge flyback converter, reference may be made to the related description in the embodiment corresponding to fig. 3, and details are not repeated here.
The switch control device 102 may be the switch control device in the embodiment corresponding to fig. 8 or fig. 9, and for the specific content of the switch control device, reference may be made to the related description in the embodiment corresponding to fig. 8 or fig. 9, which is not repeated herein.
In the above embodiments, the description of each embodiment has its own emphasis, and parts that are not described or illustrated in a certain embodiment may refer to the description of other embodiments.
Those of ordinary skill in the art will appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the technical solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.
The above-mentioned embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present application and are intended to be included within the scope of the present application.

Claims (10)

1. A switch control method of an asymmetric half-bridge flyback converter is characterized in that the asymmetric half-bridge flyback converter comprises a half-bridge structure consisting of a high-side switch tube and a low-side switch tube, leakage inductance, excitation inductance, a transformer, a resonant capacitor and a sampling resistor; the first input end and the second input end of the half-bridge structure are respectively connected with the anode and the cathode of a direct-current power supply, the leakage inductance, the excitation inductance, the resonant capacitor and the sampling resistor are sequentially connected in series between the output end and the second input end of the half-bridge structure, and the primary coil of the transformer is connected in parallel with the excitation inductance; the switch control method comprises the following steps:
acquiring the primary side current of the transformer and the change rate of the primary side current when the low-side switching tube is conducted;
determining a target current change stage where the half-bridge flyback converter is located according to the change rate;
and if the target current change stage is an exciting current reduction stage, the primary side current is a negative value, and the magnitude of the primary side current is equal to a preset current threshold value, controlling the low-side switching tube to be switched off.
2. The switch control method according to claim 1, wherein if the target current change phase is an excitation current reduction phase, the primary side current is a negative value, and the magnitude of the primary side current is equal to a preset current threshold, the controlling the low-side switching tube to be turned off comprises:
if the target current change stage is an exciting current reduction stage, monitoring whether the primary side current is changed from a positive value to a negative value in real time;
if the primary side current is changed from a positive value to a negative value, starting a timer to start timing;
and when the timing duration of the timer is equal to a preset duration threshold, controlling the low-side switching tube to be disconnected.
3. The switch control method according to claim 1, wherein the preset duration threshold is determined according to the following formula:
Teng＝(Ineg*lmag*Vomax)/(Vout 2*Np)；
wherein Teng is the preset duration threshold, Ineg is the preset current threshold, and VoutIs the actual output voltage of the asymmetric half-bridge flyback converter, NpIs the turns ratio of the primary winding to the secondary winding of the transformer, lmagIs the inductance, V, of the excitation inductanceomaxThe maximum output voltage of the asymmetric half-bridge flyback converter.
4. The switching control method according to claim 1, wherein the determining a target current variation phase in which the half-bridge flyback converter is located according to the variation rate comprises:
and if the magnitude corresponding to the change rate is the first magnitude, determining that the target current change stage where the half-bridge flyback converter is located is a resonant discharge stage.
5. The method according to claim 4, wherein the determining the target current variation phase of the half-bridge flyback converter according to the variation rate comprises:
if the magnitude order corresponding to the change rate is a second magnitude order, determining that a target current change stage where the half-bridge flyback converter is located is a harmonic excitation current reduction stage; the first order of magnitude is greater than the second order of magnitude.
6. The switch control method according to any one of claims 1 to 5, characterized by further comprising:
and if the target current change stage is an exciting current reduction stage, the primary side current is a negative value, and the primary side current is smaller than the preset current threshold, maintaining the conduction of the low-side switching tube.
7. The switch control method according to any one of claims 1 to 5, characterized by further comprising:
and if the target current change stage is a resonance discharge stage, maintaining the conduction of the low-side switch tube.
8. A switch control device of an asymmetric half-bridge flyback converter is characterized in that the asymmetric half-bridge flyback converter comprises a half-bridge structure consisting of a high-side switching tube and a low-side switching tube, leakage inductance, excitation inductance, a transformer, a resonant capacitor and a sampling resistor; the first input end and the second input end of the half-bridge structure are respectively connected with the anode and the cathode of a direct-current power supply, the leakage inductance, the excitation inductance, the resonant capacitor and the sampling resistor are sequentially connected in series between the output end and the second input end of the half-bridge structure, and the primary coil of the transformer is connected in parallel with the excitation inductance; the switch control device includes:
the first acquisition unit is used for acquiring the primary side current of the transformer and the change rate of the primary side current when the low-side switching tube is conducted;
the first determining unit is used for determining a target current change stage where the half-bridge flyback converter is located according to the change rate;
and the switch control unit is used for controlling the low-side switching tube to be switched off if the target current change stage is an exciting current reduction stage, the primary side current is a negative value, and the primary side current is equal to a preset current threshold value.
9. An asymmetric half-bridge flyback converter is characterized by comprising a half-bridge structure consisting of a high-side switching tube and a low-side switching tube, leakage inductance, excitation inductance, a transformer, a resonant capacitor and a sampling resistor;
the first input end and the second input end of the half-bridge structure are respectively connected with the anode and the cathode of a direct-current power supply, the leakage inductance, the excitation inductance, the resonant capacitor and the sampling resistor are sequentially connected in series between the output end and the second input end of the half-bridge structure, and a primary coil of the transformer is connected in parallel with the excitation inductance; the first end that switches on of high limit switch tube is regarded as the first input of half-bridge structure, the second end that switches on of high limit switch tube with the first end that switches on of low limit switch tube connects altogether and regards as the output of half-bridge structure, the second end that switches on of low limit switch tube is regarded as the second input of half-bridge structure.
10. A power supply apparatus comprising a dc power supply, a switching control device according to claim 8, and an asymmetric half-bridge flyback converter according to claim 9, the asymmetric half-bridge flyback converter being connected to the dc power supply and the switching control device.
CN202210324850.1A 2022-03-30 2022-03-30 Asymmetric half-bridge flyback converter, switch control method thereof and power supply device Pending CN114726222A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115549457A (en) * 2022-09-29 2022-12-30 杰华特微电子股份有限公司 Protection circuit and control method of flyback converter

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115549457A (en) * 2022-09-29 2022-12-30 杰华特微电子股份有限公司 Protection circuit and control method of flyback converter

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