CN219372287U - Flyback converter circuit and electronic equipment - Google Patents
Flyback converter circuit and electronic equipment Download PDFInfo
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- CN219372287U CN219372287U CN202320745234.3U CN202320745234U CN219372287U CN 219372287 U CN219372287 U CN 219372287U CN 202320745234 U CN202320745234 U CN 202320745234U CN 219372287 U CN219372287 U CN 219372287U
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
Abstract
The utility model provides a flyback conversion circuit, which comprises: the primary side input circuit, the transformer, the secondary side output rectifying circuit and the auxiliary winding power supply circuit; the primary side input circuit comprises a switching tube control unit, a first switching tube and a fourth resistor, and the auxiliary winding power supply circuit comprises a second switching tube, a first capacitor and a first resistor; the first switching tube is used for: the switching tube is controlled by the switching tube control unit to be turned on or turned off so as to output a first output voltage to the secondary side output rectifying circuit through the transformer and output a second output voltage to the auxiliary winding power supply circuit; the auxiliary winding power supply circuit is used for: the second switch tube is controlled to be conducted in a first preset time, so that the second output voltage and the first output voltage are controlled to be in fixed proportion.
Description
Technical Field
The present utility model relates to the field of flyback circuits, and in particular, to a flyback converter circuit and an electronic device.
Background
In the flyback circuit, when the total output load is heavier due to the existence of leakage inductance of the transformer, the peak voltage of the leakage inductance is higher; in addition, the load of each winding is unbalanced, the discharge time constant of the output filter capacitor is different, so that the conduction time of each winding rectifying tube is different, the conduction time of the winding rectifying tube with lighter load is shorter, and most of the conduction time is coupled to leakage inductance peak voltage, so that the output voltage is higher. The Vcc auxiliary winding is the IC power winding, which is typically the least loaded, and therefore generally appears as the Vcc voltage rises as the output load is weighted, resulting in an excessive Vcc voltage stress.
In the prior art, a 100V Vcc voltage-withstanding process is adopted or a primary linear voltage-stabilizing circuit is added, so that the manufacturing cost of a chip is increased, and the chip integration is not facilitated. In addition, in QR flyback, the valley bottom voltage is typically Vin-N1 Vo, and when the input voltage is high or the output voltage is low, the valley bottom voltage is typically high, resulting in poor turn-on loss and EMI.
Disclosure of Invention
The utility model provides a method for solving the problems of increased cost of chip manufacture caused by reducing Vcc voltage and adverse chip integration.
According to a first aspect of the present utility model, there is provided a flyback converter circuit comprising: the primary side input circuit, the transformer, the secondary side output rectifying circuit and the auxiliary winding power supply circuit; the primary side input circuit comprises a switching tube control unit and a first switching tube, and the auxiliary winding power supply circuit comprises a second switching tube, a first capacitor and a first resistor;
the output end of the switching tube control unit is connected with the control end of the first switching tube, the first end of the first switching tube is connected with the first end of the transformer, the second end of the first switching tube is grounded, the second end of the transformer is connected with the first end of the secondary side output rectifying circuit, the second end of the secondary side output rectifying circuit is connected with an output voltage end, the third end of the transformer is connected with the first end of the first capacitor, the fourth end of the transformer is connected with the first end of the second switching tube, the second end of the second switching tube is connected with the second end of the first capacitor, the control end of the second switching tube is connected with a driving voltage end, and the first resistor is connected with the first capacitor in parallel and grounded;
the first switching tube is used for: the switching tube is controlled by the switching tube control unit to be turned on or turned off so as to output a first output voltage to the secondary side output rectifying circuit through the transformer and output a second output voltage to the auxiliary winding power supply circuit;
the auxiliary winding power supply circuit is used for: the second switch tube is controlled to be conducted in a first preset time, so that the second output voltage and the first output voltage are controlled to be in fixed proportion.
Optionally, the transformer comprises a primary winding, a secondary winding and an auxiliary winding; the first end of the primary winding is connected with the first end of the first switching tube, the second end of the primary winding is coupled to the first end of the secondary winding and the first end of the auxiliary winding, the second end of the secondary winding is connected with the secondary side output rectifying circuit, and the second end of the auxiliary winding is connected with the auxiliary winding power supply circuit.
Optionally, the auxiliary winding power supply circuit is further configured to: and controlling the second switching tube to be conducted within a second preset time, and carrying out reverse excitation on the auxiliary winding through the second output voltage so as to generate exciting current, and further reducing the first valley conducting voltage signal of the first switching tube to a second valley conducting voltage signal and outputting the second valley conducting voltage signal.
Optionally, the second end of the auxiliary winding is further connected to an input end of the switching tube control unit, and the switching tube control unit is further grounded;
the switching tube control unit is configured to: and receiving the second valley turn-on voltage signal and turning on the first switching tube.
Optionally, the auxiliary winding power supply circuit includes a synchronous rectification controller, a first end of the synchronous rectification controller is connected with a first end of the second switching tube, and a second end of the synchronous rectification controller is connected with a second end of the second switching tube;
wherein the synchronous rectification controller is configured to:
when the second output voltage is greater than the first output voltage by N2 times, the second switching tube flows a negative current such that the second output voltage is equal to the first output voltage by N2 times;
wherein N2 is a positive number, and N2 is a turns ratio of the auxiliary winding to the secondary winding.
Optionally, the secondary side output rectifying circuit includes a first diode, a second capacitor and a second resistor; the positive electrode of the first diode is connected with the first output end of the secondary winding, the negative electrode of the first diode is connected with the first end of the second capacitor, the second end of the second capacitor is connected with the second output end of the secondary winding, and the second resistor is connected with the second capacitor in parallel.
Optionally, the flyback converter circuit further includes an RCD snubber circuit, where the RCD snubber circuit includes a third resistor, a third capacitor, and a third diode; the first end and the second end of the third resistor are connected with the first end and the second end of the third capacitor, the second end of the third capacitor is also connected with the negative electrode of the third diode, and the positive electrode of the third diode is connected with the first end of the first switch tube.
Optionally, the RCD snubber circuit further includes a third switching tube, the auxiliary winding power supply circuit further includes a second diode, a first end of the third switching tube is connected to a second end of the third capacitor, a second end of the third switching tube is connected to the switching tube control unit, and a control end of the third switching tube is connected to the first end of the first switching tube; the anode of the second diode is connected with the auxiliary winding, and the cathode of the second diode is connected with the first end of the first capacitor;
wherein the third switching tube is configured to: and absorbing leakage inductance of the transformer and feeding the leakage inductance back to the output ends of the secondary side output rectifying circuit and the auxiliary winding power supply circuit, so that the leakage source peak voltage of the first switching tube is reduced, and the second output voltage and the first output voltage are in fixed proportion.
Optionally, the flyback conversion circuit further includes a fourth capacitor, a first end of the fourth capacitor is connected to the first end of the third resistor, and a second end of the fourth capacitor is grounded.
According to a second aspect of the present utility model there is provided an electronic device comprising a flyback converter circuit as described above.
According to the flyback conversion circuit and the electronic equipment, the second switching tube is arranged in the auxiliary winding power supply circuit and is controlled to be turned on in the first preset time, so that the problem that the power supply voltage (namely the second output voltage) is high when the flyback topology outputs heavy load can be solved.
In the preferred embodiment, the second switching tube is controlled to be turned on at the second preset time, so that the lower valley voltage conduction of the first switching tube is realized, and the turn-on loss and the EMI noise are further reduced.
In other preferred embodiments, the third switching tube is utilized to clamp and flyback the first switching tube, so that peak voltage of the first switching tube is reduced, and then output of subsequent power supply voltage (namely second output voltage) follows the first output voltage, and the problem of high power supply voltage is avoided; in addition, the clamping flyback of the third switching tube also realizes the conduction of lower valley voltage of the first switching tube, thereby further reducing the turn-on loss and the EMI noise.
Drawings
In order to more clearly illustrate the embodiments of the utility model or the technical solutions of the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the description below are only some embodiments of the utility model, and that other drawings can be obtained according to these drawings without inventive faculty for a person skilled in the art.
FIG. 1 is a schematic diagram of a flyback converter circuit according to the prior art;
FIG. 2 is a schematic diagram of a voltage waveform of a flyback converter according to the prior art;
FIG. 3 is a second voltage waveform diagram of the flyback converter according to the prior art;
FIG. 4 is a schematic diagram of a flyback converter according to an embodiment of the present utility model;
FIG. 5 is a schematic diagram of a flyback converter according to an embodiment of the present utility model;
FIG. 6 is a schematic diagram of a voltage waveform of a flyback converter according to an embodiment of the present utility model;
FIG. 7 is a second voltage waveform diagram of the flyback converter according to an embodiment of the present utility model;
FIG. 8 is a schematic diagram of a flyback converter according to an embodiment of the present utility model;
FIG. 9 is a schematic diagram of a flyback converter according to an embodiment of the present utility model;
fig. 10 is a voltage waveform diagram of a flyback converter according to an embodiment of the utility model.
Reference numerals illustrate:
1-primary side input circuit;
101-a switching tube control unit;
q1-a first switching tube;
r4-fourth resistor;
a 2-transformer;
np-primary winding;
ns-secondary winding;
naux-auxiliary winding;
3-secondary side output rectifying circuit;
d1-a first diode;
c2-a second capacitance;
r2-a second resistor;
4-an auxiliary winding power supply circuit;
q2-a second switching tube;
c1-a first capacitance;
r1-a first resistor;
d2—a second diode;
401-synchronous rectification controller;
a 5-RCD absorption circuit;
d3-a third diode;
a C3-third capacitor;
r3-a third resistor;
q3-a third switching tube;
6-fourth capacitance.
Detailed Description
The following description of the embodiments of the present utility model will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present utility model, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.
The terms "first," "second," "third," "fourth" and the like in the description and in the claims and in the above drawings, if any, are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the utility model described herein may be implemented in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
The technical scheme of the utility model is described in detail below by specific examples. The following embodiments may be combined with each other, and some embodiments may not be repeated for the same or similar concepts or processes.
Before the application, the applicant fully researches a flyback converter circuit, and based on the research, proposes the flyback converter circuit shown in fig. 1, and for the flyback converter circuit shown in fig. 1, the heavier the output load is caused by the existence of leakage inductance of a flyback transformer, the higher the peak voltage of the leakage inductance is, the more the output voltage of a path with lighter load is fluctuated; in addition, under QR mode flyback, when the input voltage is greater than N1 x Vo (i.e., the first output voltage, n1=np/Ns) more, the valley voltage is higher, and there is a larger turn-on loss of the main switching tube.
Specifically, please continue to refer to fig. 1, which includes: the primary side input circuit, the transformer, the secondary side output rectifying circuit, the auxiliary winding power supply circuit, the RCD absorption circuit and the fourth capacitor; the primary side input circuit comprises a switching tube control unit, a first switching tube and a fourth resistor, the transformer comprises a primary winding, a secondary winding and an auxiliary winding, the secondary side output rectifying circuit comprises a first diode, a second capacitor and a second resistor, the auxiliary winding power supply circuit comprises a second diode, a first capacitor and a first resistor, and the RCD absorption circuit comprises a third resistor, a third capacitor and a third diode;
the output end of the switching tube control unit is connected with the control end of the first switching tube, the first end of the first switching tube is connected with the first end of the transformer, the second end of the first switching tube is connected with the first end of the fourth resistor, the second end of the fourth resistor is grounded, the second end of the transformer is connected with the first end of the secondary side output rectifying circuit, the second end of the secondary side output rectifying circuit is connected with an output voltage end, the third end of the transformer is connected with the positive electrode of the second diode, the negative electrode of the second diode is connected with the first end of the first capacitor, the fourth end of the transformer is connected with the first end of the second switching tube, the second end of the second switching tube is connected with the second end of the first capacitor, the control end of the second switching tube is connected with a driving voltage end, and the first resistor is connected with the first capacitor in parallel and grounded.
In the above scheme, because the load of each winding is unbalanced, the discharge time constant of the output filter capacitor is different, so that the conduction time of each winding rectifier tube (namely the first diode and the second diode) is different, and the lighter the load, the shorter the conduction time of the winding rectifier tube is, and most of the conduction time is coupled to leakage inductance peak voltage, so that the output voltage is higher. In particular, the auxiliary winding is an IC power winding, which is typically the lightest loaded, and therefore typically appears as a Vcc voltage (i.e., the second output voltage) rising as the output load is weighted, resulting in an overstress Vcc voltage (i.e., the second output voltage).
In QR flyback mode, the valley turn-on voltage is typically Vin-N1 Vo, but when the input voltage is higher or the output voltage is lower, the valley turn-on voltage is typically higher, resulting in poor turn-on loss and EMI.
Specifically, referring to fig. 2 and 3, fig. 2 and 3 are a QR flyback key waveform diagram and a CCM flyback key waveform diagram according to the prior art, respectively, it can be seen that the second output voltage Vcc is always greater than the first output voltage vo×n2, n2=naux/Ns in two modes, and the valley turn-on voltage is higher in the QR flyback mode.
In order to solve the above problems, the prior art adopts the following scheme, specifically, under the wide application scenario of the PD charger, the variation range of the first output voltage is generally 3.3V-21V, and reaches 6.36 times, for example, when 3.3V is output, the second output voltage VCC is just at the under-voltage protection point (for example, 8V); for example, a 21V output, varies at the desired turn ratio, the second output voltage VCC will reach 51V. In an ideal state, the voltage withstanding process of the second output voltage VCC of 60V is only needed, but the actual highest second output voltage VCC can reach more than 90V due to the existence of leakage inductance of the transformer, so that the voltage withstanding process of the second output voltage VCC of 100V is needed or a primary linear voltage stabilizing circuit is added. However, the voltage withstanding technology of the second output voltage VCC of 100V greatly increases the cost of the IC, and the scheme of adding the linear voltage stabilizing circuit increases the area of the IC, thereby being unfavorable for IC integrated design.
In view of this, the present utility model proposes a new flyback converter circuit, in which the second diode D2 is replaced by a switching tube, and the switching tube is controlled to be turned on within a preset time period to solve the above-mentioned problems.
The scheme of the utility model is specifically described as follows:
referring to fig. 4 and 5, the present utility model provides a flyback converter circuit, which includes: a primary side input circuit 1, a transformer 2, a secondary side output rectifying circuit 3 and an auxiliary winding power supply circuit 4; the primary side input circuit 1 comprises a switching tube control unit 101, a first switching tube Q1 and a fourth resistor R4, and the auxiliary winding power supply circuit 4 comprises a second switching tube Q2, a first capacitor C1 and a first resistor R1;
the output end of the switch tube control unit 101 is connected to the control end of the first switch tube Q1, the first end of the first switch tube Q1 is connected to the first end of the transformer 2, the second end of the first switch tube Q1 is connected to the first end of the fourth resistor R4, the second end of the fourth resistor R4 is grounded, the second end of the transformer 2 is connected to the first end of the secondary side output rectifying circuit 3, the second end of the secondary side output rectifying circuit 3 is connected to an output voltage end, the third end of the transformer 2 is connected to the first end of the first capacitor C1, the fourth end of the transformer 2 is connected to the first end of the second switch tube Q2, the second end of the second switch tube Q2 is connected to the second end of the first capacitor C1, the control end of the second switch tube Q2 is connected to a driving voltage end, and the first resistor R1 is connected in parallel with the first capacitor C1 and grounded;
the first switching tube Q1 is configured to: is controlled by the switching tube control unit 101 to be turned on or off so as to output a first output voltage to the secondary side output rectifying circuit 3 and a second output voltage to the auxiliary winding power supply circuit 4 through the transformer 2;
the auxiliary winding power supply circuit 4 is configured to: the second switch tube Q2 is controlled to be conducted within a first preset time, so that the second output voltage and the first output voltage are controlled to be in a fixed proportion.
With respect to the transformer 2, in a preferred embodiment, please continue to refer to fig. 4 and 5, the transformer 2 includes a primary winding Np, a secondary winding Ns, and an auxiliary winding Naux; wherein, the first end of the primary winding Np is connected to the first end of the first switching tube Q1, the second end of the primary winding Np is coupled to the first end of the secondary winding Ns and the first end of the auxiliary winding Naux, the second end of the secondary winding Ns is connected to the secondary side output rectifying circuit 3, and the second end of the auxiliary winding Naux is connected to the auxiliary winding power supply circuit 4.
With respect to the auxiliary winding power supply circuit 4, in a preferred embodiment, please continue to refer to fig. 4 and 5, the auxiliary winding power supply circuit 4 is further configured to: and controlling the second switching tube Q2 to be conducted within a second preset time, and carrying out reverse excitation on the auxiliary winding Naux by the second output voltage to generate exciting current, so as to reduce the first valley conducting voltage signal of the first switching tube Q1 to a second valley conducting voltage signal and output the second valley conducting voltage signal.
Regarding the control procedure of the flyback converter circuit, in a preferred embodiment, please refer to fig. 6 and 7, wherein fig. 6 and 7 are respectively QR mode operation waveforms and CCM operation waveforms.
For the QR mode operation waveform of fig. 6, the following is specific:
at time t1, vgs is at a high level, that is, the first switching tube Q1 is turned on, and at this time, the Vds voltage of the first switching tube Q1 has dropped to a lower valley before t1, so that the first switching tube Q1 is turned on at the valley at time t 1. After Q1 is turned on, the input voltage Vbulk is applied to two ends of the primary winding Np of the transformer 2, the body diodes of the first diode D1 and the second switching tube Q2 are turned off under the back voltage, and the current of the primary winding Np increases linearly.
At time t2, vgs is at low level, that is, the first switching tube Q1 is turned off, and the inductor current of the primary winding Np cannot be suddenly changed, so that the drain electrode of the first switching tube Q1 is continuously charged in the original direction, and the Vds voltage of the first switching tube Q1 is increased.
At time t3, vds voltage rises to vin+n1×vo, and the body diodes of the first diode D1 and the second switching transistor Q2 start to be forward biased and turned on.
At time t4, vg-SR is high, that is, the second switching tube Q2 is driven to be turned on, and the on-time is Ton1, because the body diode of the second switching tube Q2 is turned on first before the second switching tube Q2 is driven to be turned on, the voltage at two ends of the body diode is approximately zero volts, and ZVS is achieved (zero voltage is turned on, that is, when the second switching tube Q2 is turned on, the source-drain voltage is approximately zero).
At time t5, vg-SR is low, i.e. the second switching tube Q2 is driven to turn off, and at the previous time, vds spike oscillation has passed, the second output voltage is less affected by Vds spike voltage, and the first diode D1 is always in the on state during the on period of the second switching tube Q2, so that the second output voltage Vcc is forced to follow the first output voltage Vo, so as to conform to the relationship vcc=vo.
At time t6, vds oscillates to a secondary peak point, vaux oscillates to a valley, and the second switching tube Q2 is turned on again, at this time, the second switching tube Q2 is turned on for a valley, the on duration is Ton2, the second output voltage Vcc is applied to two ends of the auxiliary winding Naux, and the auxiliary winding Naux is excited reversely to generate a negative exciting current (different from a positive exciting current generated when the first switching tube Q1 is turned on), so as to create a condition of turning on a lower valley for the first switching tube Q1.
At time t7, the second switching tube Q2 is turned off, and the reverse exciting current discharges the output capacitor of the first switching tube Q1, so as to assist the first switching tube Q1 to realize the turn-on of the lower valley voltage.
At time t8, when the output capacitor of the first switching tube Q1d discharges to a Valley conduction voltage (i.e., a second Valley conduction voltage Lower Valley) Lower than Vin-N1 x Vo (i.e., a first Valley conduction voltage), the first switching tube Q1 is turned on, so as to realize the turn-on of the Lower Valley voltage.
The above is the operation of one switching cycle (t 1-t 8), and the subsequent waveform repeats the operation at the time t1-t8 to perform the operation of the next cycle.
For the CCM mode operating waveform of fig. 7, the specific is:
in the CCM mode, the exciting current of the transformer 2 is not reset to zero, and free oscillation after the resetting of the exciting current is avoided, so that no operation is performed between the time t6 and the time t8 in actual operation, that is, ton2 cannot be emitted, but the second output voltage Vcc can follow the first output voltage Vo in the Ton1 time, and the influence of the peak voltage of Vds on the Vcc voltage is reduced.
The QR flyback is of a quasi-resonant circuit topological structure, mainly refers to a quasi-resonant flyback topology, and the first switching tube is conducted at the valley bottom; CCM flyback is a continuous conduction mode, and when the first switch is turned on, the excitation current of the transformer is not reset to zero.
In the scheme, the flyback converter circuit working in the QR mode conducts the second switching tube Q2 in the first preset time and the second preset time, so that the influence of the Vds peak voltage on the VCC voltage is reduced, and the lower turn-on of the valley turn-on voltage is realized; however, in the flyback converter circuit operating in the CCM mode, since there is no increase in the valley turn-on voltage, the second switching tube Q2 needs to be turned on only in the first preset time, so that the influence of the Vds spike voltage on the VCC voltage can be reduced.
In other embodiments, the second end of the auxiliary winding Naux is further connected to the input end of the switching tube control unit 101, and the switching tube control unit 101 is further grounded;
the switching tube control unit 101 is configured to: and receiving the second valley turn-on voltage signal and turning on the first switching tube Q1.
In other embodiments, referring to fig. 9, the auxiliary winding power supply circuit 4 includes a synchronous rectification controller 401, a first end of the synchronous rectification controller 401 is connected to a first end of the second switching tube Q2, and a second end of the synchronous rectification controller 401 is connected to a second end of the second switching tube Q2;
wherein the synchronous rectification controller 401 is configured to:
when the second output voltage is greater than the first output voltage by N2 times, the second switching tube Q2 flows a negative current such that the second output voltage is equal to the first output voltage by N2 times;
where N2 is a positive number, n2=naux/Ns, i.e. N2 is the turns ratio of the auxiliary winding to the secondary winding.
Specifically, referring to fig. 10, fig. 10 shows an operation waveform of a flyback converter circuit employing a synchronous rectification controller 401, at time t4, the second switching tube Q2 is driven to be turned on, the on time is Minton, and since the body diode of the second switching tube Q2 is first turned on before the second switching tube Q2 is driven to be turned on, the voltage at two ends is approximately zero volts, and ZVS (zero voltage switch, i.e., when the second switching tube Q2 is turned on, the source-drain voltage is zero).
With respect to the secondary side output rectifying circuit 3, in a preferred embodiment, please continue to refer to fig. 4 and 5, the secondary side output rectifying circuit 3 includes a first diode D1, a second capacitor C2, and a second resistor R2; the positive electrode of the first diode D1 is connected to the first output end of the secondary winding Ns, the negative electrode of the first diode D1 is connected to the first end of the second capacitor C2, the second end of the second capacitor C2 is connected to the second output end of the secondary winding Ns, and the second resistor R2 is connected in parallel with the second capacitor C2.
In one example, the secondary side output rectifying circuit further comprises a synchronous rectifying controller and a switching tube; namely, rectification of the first diode is realized through the synchronous rectification controller and the switching tube.
Of course, the utility model is not limited thereto, and other elements or combinations of elements capable of achieving secondary side rectification are within the scope of the utility model.
With respect to the RCD snubber circuit 5, in a preferred embodiment, please continue to refer to fig. 4 and 5, the flyback converter circuit further includes the RCD snubber circuit 5, and the RCD snubber circuit 5 includes a third resistor R3, a third capacitor C3, and a third diode D3; the first end and the second end of the third resistor R3 are connected with the first end and the second end of the third capacitor C3, the second end of the third capacitor C3 is further connected with the negative electrode of the third diode D3, and the positive electrode of the third diode D3 is connected with the first end of the first switching tube Q1.
In a preferred embodiment, the RCD snubber circuit 5 further includes a third switching tube Q3, the auxiliary winding power supply circuit 4 further includes a second diode D2, a first end of the third switching tube Q3 is connected to a second end of the third capacitor C3, a second end of the third switching tube Q3 is connected to the switching tube control unit 101, and a control end of the third switching tube Q3 is connected to a first end of the first switching tube Q1; the positive electrode of the second diode D2 is connected with the auxiliary winding Naux, and the negative electrode of the second diode D2 is connected with the first end of the first capacitor C1;
wherein the third switching tube Q3 is configured to: and absorbing leakage inductance of the transformer 2 and feeding the leakage inductance back to the output ends of the secondary side output rectifying circuit 3 and the auxiliary winding power supply circuit 4, so as to reduce the drain-source peak voltage of the first switching tube Q1, and enable the second output voltage to be in fixed proportion to the first output voltage.
In the scheme, leakage inductance energy of the transformer 2 is absorbed through active clamp flyback and fed back to the output end, vds peak voltage during heavy load is greatly reduced, deviation between the Vcc voltage of the first output voltage of the auxiliary winding Naux and the Vo voltage of the second output voltage of the auxiliary winding Naux is not too large, and ZVS of the main switching tube Q1 is also realized through the active clamp flyback by using the clamp tube.
In other embodiments, the flyback converter further includes a fourth capacitor 6, where a first end of the fourth capacitor 6 is connected to the first end of the third resistor R3, and a second end of the fourth capacitor 6 is grounded.
The utility model also provides electronic equipment comprising the flyback conversion circuit.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present utility model, and not for limiting the same; although the utility model has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the utility model.
Claims (10)
1. A flyback converter circuit, comprising: the primary side input circuit, the transformer, the secondary side output rectifying circuit and the auxiliary winding power supply circuit; the primary side input circuit comprises a switching tube control unit, a first switching tube and a fourth resistor, and the auxiliary winding power supply circuit comprises a second switching tube, a first capacitor and a first resistor;
the output end of the switching tube control unit is connected with the control end of the first switching tube, the first end of the first switching tube is connected with the first end of the transformer, the second end of the first switching tube is connected with the first end of the fourth resistor, the second end of the fourth resistor is grounded, the second end of the transformer is connected with the first end of the secondary side output rectifying circuit, the second end of the secondary side output rectifying circuit is connected with an output voltage end, the third end of the transformer is connected with the first end of the first capacitor, the fourth end of the transformer is connected with the first end of the second switching tube, the second end of the second switching tube is connected with the second end of the first capacitor, the control end of the second switching tube is connected with a driving voltage end, and the first resistor is connected with the first capacitor in parallel and grounded;
the first switching tube is used for: the switching tube is controlled by the switching tube control unit to be turned on or turned off so as to output a first output voltage to the secondary side output rectifying circuit through the transformer and output a second output voltage to the auxiliary winding power supply circuit;
the auxiliary winding power supply circuit is used for: the second switch tube is controlled to be conducted in a first preset time, so that the second output voltage and the first output voltage are controlled to be in fixed proportion.
2. The flyback converter circuit of claim 1 wherein the transformer comprises a primary winding, a secondary winding, and an auxiliary winding; the first end of the primary winding is connected with the first end of the first switching tube, the second end of the primary winding is coupled to the first end of the secondary winding and the first end of the auxiliary winding, the second end of the secondary winding is connected with the secondary side output rectifying circuit, and the second end of the auxiliary winding is connected with the auxiliary winding power supply circuit.
3. The flyback converter circuit of claim 2 wherein the auxiliary winding supply circuit is further configured to: and controlling the second switching tube to be conducted within a second preset time, and carrying out reverse excitation on the auxiliary winding through the second output voltage so as to generate exciting current, and further reducing the first valley conducting voltage signal of the first switching tube to a second valley conducting voltage signal and outputting the second valley conducting voltage signal.
4. The flyback converter circuit of claim 3 wherein the second end of the auxiliary winding is further connected to the input of the switching tube control unit, the switching tube control unit being further grounded;
the switching tube control unit is configured to: and receiving the second valley turn-on voltage signal and turning on the first switching tube.
5. The flyback converter circuit of claim 4 wherein the auxiliary winding power supply circuit comprises a synchronous rectification controller having a first terminal connected to the first terminal of the second switching tube and a second terminal connected to the second terminal of the second switching tube;
wherein the synchronous rectification controller is configured to:
when the second output voltage is greater than the first output voltage by N2 times, the second switching tube flows a negative current such that the second output voltage is equal to the first output voltage by N2 times;
where N2 is a positive number, n2=naux/Ns, i.e. N2 is the turns ratio of the auxiliary winding to the secondary winding.
6. The flyback converter of claim 5 wherein the secondary side output rectifier circuit comprises a first diode, a second capacitor, and a second resistor; the positive electrode of the first diode is connected with the first output end of the secondary winding, the negative electrode of the first diode is connected with the first end of the second capacitor, the second end of the second capacitor is connected with the second output end of the secondary winding, and the second resistor is connected with the second capacitor in parallel.
7. The flyback converter circuit of claim 6 further comprising an RCD snubber circuit comprising a third resistor, a third capacitor, and a third diode; the first end and the second end of the third resistor are connected with the first end and the second end of the third capacitor, the second end of the third capacitor is also connected with the negative electrode of the third diode, and the positive electrode of the third diode is connected with the first end of the first switch tube.
8. The flyback converter circuit of claim 7 wherein the RCD snubber circuit further comprises a third switching tube, the auxiliary winding supply circuit further comprising a second diode, the first terminal of the third switching tube connected to the second terminal of the third capacitor, the second terminal of the third switching tube connected to the switching tube control unit, the control terminal of the third switching tube connected to the first terminal of the first switching tube; the anode of the second diode is connected with the auxiliary winding, and the cathode of the second diode is connected with the first end of the first capacitor;
wherein the third switching tube is configured to: and absorbing leakage inductance of the transformer and feeding the leakage inductance back to the output ends of the secondary side output rectifying circuit and the auxiliary winding power supply circuit, so that the leakage source peak voltage of the first switching tube is reduced, and the second output voltage and the first output voltage are in fixed proportion.
9. The flyback converter circuit of claim 8 further comprising a fourth capacitor, a first terminal of the fourth capacitor connected to the first terminal of the third resistor, a second terminal of the fourth capacitor connected to ground.
10. An electronic device comprising a flyback converter circuit according to any one of claims 1-9.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202320745234.3U CN219372287U (en) | 2023-03-29 | 2023-03-29 | Flyback converter circuit and electronic equipment |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202320745234.3U CN219372287U (en) | 2023-03-29 | 2023-03-29 | Flyback converter circuit and electronic equipment |
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| Publication Number | Publication Date |
|---|---|
| CN219372287U true CN219372287U (en) | 2023-07-18 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202320745234.3U Active CN219372287U (en) | 2023-03-29 | 2023-03-29 | Flyback converter circuit and electronic equipment |
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| CN (1) | CN219372287U (en) |
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- 2023-03-29 CN CN202320745234.3U patent/CN219372287U/en active Active
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