CN113470948A - High-frequency transformer, flyback switching power supply and power adapter - Google Patents
High-frequency transformer, flyback switching power supply and power adapter Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/28—Coils; Windings; Conductive connections
- H01F27/30—Fastening or clamping coils, windings, or parts thereof together; Fastening or mounting coils or windings on core, casing, or other support
- H01F27/306—Fastening or mounting coils or windings on core, casing or other support
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/34—Special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load losses, reactive currents, harmonics, oscillations, leakage fields
- H01F27/346—Preventing or reducing leakage fields
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/34—Special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load losses, reactive currents, harmonics, oscillations, leakage fields
- H01F27/36—Electric or magnetic shields or screens
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/34—Special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load losses, reactive currents, harmonics, oscillations, leakage fields
- H01F27/38—Auxiliary core members; Auxiliary coils or windings
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/14—Arrangements for reducing ripples from dc input or output
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/36—Means for starting or stopping converters
-
- 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
- H02M1/44—Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
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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
- H02M3/33507—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 with automatic control of the output voltage or current, e.g. flyback converters
- H02M3/33523—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 with automatic control of the output voltage or current, e.g. flyback converters with galvanic isolation between input and output of both the power stage and the feedback loop
Abstract
The application relates to a high-frequency transformer, a flyback switching power supply and a power adapter. The flyback switching power supply includes: high frequency transformer, switch circuit, first rectification filter circuit, control circuit, in the process of high frequency transformer execution primary side transmission to secondary side's electric energy conversion operation, compare in the transformer of sandwich winding method, the winding among the high frequency transformer of this application embodiment can reduce the turn-to-turn electric capacity between primary side and the secondary side, thereby prevent that the high frequency interference of secondary side from spreading to primary side, reach good isolation effect, have good filtering action to high frequency electromagnetic interference, eliminate the low frequency electromagnetic interference that high frequency transformer secondary side fed back to primary side through rectifier bridge and differential mode inductance among the first rectification filter circuit, thereby realize full frequency channel interference filtering's effect, and reduced the cost of using common mode inductance.
Description
Technical Field
The application relates to the technical field of power electronics, in particular to a high-frequency transformer, a flyback switching power supply and a power adapter.
Background
Most power adapters adopt flyback switching power supply circuits, high-frequency transformers in the flyback switching power supply circuits are used as key devices for power conversion and voltage isolation, and the parameter and structural design of the high-frequency transformers seriously affect the key performances of the whole circuit, such as energy conversion efficiency, temperature rise, electromagnetic compatibility (EMC) and the like. For the EMI conduction characteristic of the adapter circuit, the interference sources are mainly a primary switch tube, a secondary diode and a matched load circuit, and the primary and secondary turn-to-turn capacitance of the high-frequency transformer is the main path for the secondary interference to propagate to the primary.
At present, a high-frequency transformer of a switching power supply basically adopts a sandwich winding mode, but the turn-to-turn capacitance between primary stages is increased, so that secondary interference is easier to propagate to a primary stage, and electromagnetic interference carried by an adapter load cannot be effectively filtered.
At present, in order to solve the EMC problem, a mode of adding a shielding layer is usually adopted as an EMI shielding layer between primary and secondary stages, adding the shielding layer or copper foil increases the device cost and the production difficulty and reduces the production efficiency, and the filtering effect is not ideal for the interference from secondary propagation, and also brings higher leakage inductance of the high-frequency transformer.
Disclosure of Invention
In order to solve the technical problem that an electromagnetic interference cannot be effectively filtered by a high-frequency transformer in the conventional flyback switching power supply, the application provides the high-frequency transformer, the flyback switching power supply and a power adapter.
In a first aspect, the present application provides a high frequency transformer comprising a bobbin, a primary winding, an auxiliary winding, and a secondary winding, wherein:
the primary winding is wound on the surface of the framework, the auxiliary winding is wound on the outer surface of the primary winding, and the secondary winding is wound on the outer surface of the auxiliary winding, wherein the auxiliary winding is used for reducing turn-to-turn capacitance between the primary winding and the secondary winding.
Optionally, the primary winding is wound in a manner of being tightly wound around the surface of the framework, and the auxiliary winding is wound in a manner of being fully wound around the primary winding by adopting a plurality of strands of winding wires.
Optionally, an insulating layer is further disposed between the primary winding and the framework, between the primary winding and the auxiliary winding, between the auxiliary winding and the secondary winding, and on an outer surface of the secondary winding.
Optionally, L insulating layers are arranged between the primary winding and the framework, N insulating layers are arranged between the primary winding and the auxiliary winding, M insulating layers are arranged between the auxiliary winding and the secondary winding, wherein L, M, N is any positive integer, L is smaller than M, and M is smaller than N.
In a second aspect, the present application provides a flyback switching power supply, including:
a high-frequency transformer for performing a conversion operation on electric energy transmitted from a primary side of the high-frequency transformer to a secondary side of the high-frequency transformer, wherein the high-frequency transformer is the high-frequency transformer of any one of the first aspect;
the switching circuit is connected with the primary side of the high-frequency transformer and used for controlling the starting and stopping of the conversion operation;
the first rectifying and filtering circuit is connected with the primary side of the high-frequency transformer and used for filtering electromagnetic interference generated in the process of transmitting electric energy from the primary side to the secondary side, wherein the first rectifying and filtering circuit comprises a rectifying bridge and a differential mode circuit, the direct current side of the rectifying bridge is connected with the differential mode circuit, the alternating current side of the rectifying bridge is connected with the alternating current power supply, and the differential mode circuit is connected with a first end of the primary side of the high-frequency transformer;
the suppression circuit is connected with the primary side of the high-frequency transformer in parallel and used for absorbing leakage inductance energy between the primary side and the secondary side;
and the control circuit is connected with the switch circuit and is used for controlling the conduction state of the switch circuit.
Optionally, the differential mode circuit includes a first differential mode inductor, a second differential mode inductor, a first capacitor and a second capacitor, the first end of the first differential mode inductor is connected to the first end of the first capacitor, the first end of the first differential mode inductor is further connected to the rectifier bridge, the second end of the first differential mode inductor is connected to the first end of the second capacitor, the second end of the second capacitor is connected to the first end of the second differential mode inductor, the second end of the second differential mode inductor is connected to the second end of the first capacitor, and the second end of the second differential mode inductor is further connected to the rectifier bridge.
Optionally, the rectifying and filtering circuit further includes:
and the second rectifying and filtering circuit is connected with the secondary side of the high-frequency transformer and is used for stabilizing the direct-current voltage output by the secondary side of the high-frequency transformer.
Optionally, the switching circuit includes a triode, a gate of the triode is connected to the control circuit, a drain of the triode is connected to the suppression circuit, the drain of the triode is further connected to the second end of the primary side of the high-frequency transformer, and a source of the triode is grounded.
Optionally, a winding start point pin of a primary winding of the high-frequency transformer is connected to a drain of the triode, and an end point pin of the primary winding is connected to a positive electrode of the bus.
In a third aspect, the present application provides a power adapter comprising the flyback switching power supply of any of the second aspects.
Based on above-mentioned flyback switching power supply, need not to adopt expensive common mode inductance filtering electromagnetic interference, adopt the differential mode circuit of low cost to replace expensive common mode inductance, in the electric energy conversion operation's of high frequency transformer execution primary side transmission to secondary side in-process, auxiliary winding among the high frequency transformer can reduce the turn-to-turn capacitance between primary side and the secondary side, thereby prevent that the high frequency interference of secondary side from spreading to primary side, reach good isolation, have good filtering action to high frequency electromagnetic interference, eliminate the low frequency electromagnetic interference among the flyback switching power supply through the differential mode inductance among the first rectification filter circuit, thereby realize full frequency channel interference filtering's effect, and reduced the cost of using common mode inductance.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention.
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive exercise.
Fig. 1 is a block diagram of a flyback switching power supply in an embodiment;
FIG. 2 is a schematic diagram of a first rectifying and filtering circuit according to an embodiment;
fig. 3 is a block diagram of a flyback switching power supply in an embodiment;
FIG. 4 is a schematic diagram of the windings of an embodiment of a high frequency transformer;
fig. 5 is a schematic diagram illustrating a measured result of conducted EMI corresponding to the flyback switching power supply in an embodiment;
fig. 6 is a schematic diagram illustrating a measured result of conducted EMI corresponding to the flyback switching power supply in an embodiment;
fig. 7 is a schematic diagram illustrating measured conducted EMI results corresponding to a conventional switching power supply in an embodiment;
fig. 8 is a schematic diagram illustrating measured conducted EMI results corresponding to a conventional switching power supply in an embodiment.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
In an embodiment, fig. 1 is a schematic structural diagram of a flyback switching power supply in an embodiment, and referring to fig. 1, there is provided a flyback switching power supply, where the flyback switching power supply is applied to a power adapter, and the flyback switching power supply specifically includes:
a high frequency transformer 110 for performing a conversion operation on electrical energy transmitted from a primary side of the high frequency transformer 110 to a secondary side of the high frequency transformer 110, wherein the high frequency transformer 110 includes a wound winding for reducing inter-turn capacitance between the primary side and the secondary side.
Specifically, high frequency transformer 110 is the effect in flyback switching power supply and is through electromagnetic induction principle with high-voltage direct current conversion low-voltage direct current, high frequency transformer 110 specifically includes the skeleton, magnetic core and winding, the skeleton is used for fixing the magnetic core, and provide the winding space for winding, namely the magnetic core is located inside the skeleton, winding is at the skeleton surface, compare in high frequency transformer 110 who adopts sandwich wire winding mode, winding through non-sandwich wire winding mode has reduced the interturn electric capacity between high frequency transformer 110 primary side and the secondary side, the interturn electric capacity is the less, impedance is the bigger, make the electromagnetic interference of secondary side be difficult to propagate to primary side, effectively isolated the electromagnetic interference that secondary side propagated to primary side.
And a switching circuit 120 connected to the primary side of the high-frequency transformer 110, for controlling the start and stop of the conversion operation.
Specifically, the switch circuit 120 is further connected to the control circuit 150, and controls the high-frequency transformer 110 to start and stop the electric energy conversion operation according to the control signal of the control circuit 150, and when the control signal is the start signal, the switch circuit 120 is turned on, and controls the high-frequency transformer 110 to prohibit the electric energy conversion operation, and at this time, no energy transmission is performed between the primary side and the secondary side, because the winding of the primary side is essentially an inductor, and when the inductor is turned on, the electric energy is converted into the magnetic energy for storage, that is, the high-frequency transformer converts the electric energy into the magnetic energy for storage at the primary side; in the case that the control signal is an off signal, the switching circuit 120 is turned off, and the primary side of the high-frequency transformer 110 is controlled to transmit electric energy to the secondary side for voltage conversion, that is, the primary side of the high-frequency transformer 110 transmits stored magnetic energy to the secondary side through magnetic coupling, and a winding of the secondary side generates current through magnetic induction, so that the conversion process of transmitting electric energy from the primary side to the secondary side is completed, and the secondary side of the high-frequency transformer 110 supplies power to a load.
Under the condition that the circuit runs abnormally, the switching circuit 120 controls the high-frequency transformer 110 to prohibit the electric energy conversion operation according to the control signal of the control circuit 150, so that the safety isolation effect is achieved, the secondary side of the high-frequency transformer 110 cannot output voltage, the load is protected from being influenced by the abnormal voltage, and the damage of the load to users is also avoided.
The switching circuit 120 includes a transistor, a gate of the transistor is connected to the control circuit 150, a drain of the transistor is connected to the suppression circuit 140, the drain of the transistor is further connected to the second end of the primary side of the high-frequency transformer 110, and a source of the transistor is grounded.
And a first rectifying and filtering circuit 130 connected to the primary side of the high frequency transformer 110 for filtering electromagnetic interference generated during the transmission of the electric energy from the primary side to the secondary side, wherein the first rectifying and filtering circuit 130 includes a rectifying bridge and a differential mode circuit, a direct current side of the rectifying bridge is connected to the differential mode circuit, an alternating current side of the rectifying bridge is connected to the alternating current power source 160, and the differential mode circuit is connected to a first end of the primary side of the high frequency transformer 110.
Specifically, the rectifier bridge in the first rectifying and filtering circuit 130 is configured to convert ac power of the ac power source 160 into dc power and transmit the dc power to the high-frequency transformer 110 for voltage reduction, the differential mode circuit in the first rectifying and filtering circuit 130 is configured to filter electromagnetic interference fed back from the secondary side to the primary side in the voltage conversion process of the high-frequency transformer 110, filter high-frequency interference fed back from the secondary side to the primary side by the structure of the high-frequency transformer 110, filter low-frequency interference fed back from the secondary side to the primary side by the differential mode circuit, and the high-frequency transformer 110 combines with the first rectifying and filtering circuit 130 to filter full-band interference.
And a suppression circuit 140 connected in parallel with the primary side of the high-frequency transformer 110 for absorbing leakage inductance energy between the primary side and the secondary side.
Specifically, the suppression circuit 140 is an RC absorption circuit, and when the switch circuit 120 is turned on, the ac power supply 160, the first rectifying and filtering circuit 130, the suppression circuit 140 and the switch circuit 120 form a closed loop, and at this time, the energy is stored in the suppression circuit 140; in the case that the switch circuit 120 is turned off, the primary side energy is transferred to the secondary side, but there may be leakage inductance energy on the primary side, and in the case that there is no release of the RC absorption circuit, this leakage inductance energy will be directly applied to the switch circuit 120, possibly breaking down the switch circuit 120, and adding the RC absorption circuit will provide a loop for leakage inductance energy release to reduce the impact of the leakage inductance energy on the switch circuit 120 at the moment of switching by the switch circuit 120.
And a control circuit 150 connected to the switch circuit 120 for controlling the on state of the switch circuit 120.
Specifically, the control circuit 150 is configured to monitor an operation condition of the flyback switching power supply, generate a corresponding control signal according to the operation condition of the flyback switching power supply, where the control signal is used to determine an on state of the switching circuit 120, where the on state is on or off, and the on state of the switching circuit 120 is used to determine start and stop of the power conversion operation performed between the primary side and the secondary side of the high-frequency transformer 110, so as to effectively control a separation state between the primary side and the secondary side of the high-frequency transformer 110, and avoid that the high-frequency transformer 110 transmits an excessively high voltage to a load, which may cause damage to the load or harm to life safety of a user.
In one embodiment, the differential mode circuit includes a first differential mode inductor, a second differential mode inductor, a first capacitor, and a second capacitor, a first end of the first differential mode inductor is connected to a first end of the first capacitor, and a first end of the first differential mode inductor is further connected to the rectifier bridge, a second end of the first differential mode inductor is connected to a first end of the second capacitor, a second end of the second capacitor is connected to a first end of the second differential mode inductor, a second end of the second differential mode inductor is connected to a second end of the first capacitor, and a second end of the second differential mode inductor is further connected to the rectifier bridge.
Specifically, referring to fig. 2, the differential-mode inductor has a good filtering effect on electromagnetic interference with an impedance resonance point located in a low frequency band, which is an operating frequency less than 2MHz, and the low-frequency interference fed back from the secondary side to the primary side is effectively filtered through the first differential-mode inductor L1 and the second differential-mode inductor L2 in the differential-mode circuit.
The first rectifying and filtering circuit 130 adopts a CLC filtering structure, wherein C is an electrolytic capacitor, L is a differential mode inductor, the capacitance values of the two electrolytic capacitors may be the same or different, and may be determined according to the actual circuit power and the power supply state, and the inductance values of the two differential mode inductors may be the same or the same, and may be determined according to the actual EMC test effect.
In one embodiment, the rectifying and filtering circuit further comprises:
and a second rectifying and filtering circuit 170, connected to the secondary side of the high frequency transformer 110, for stabilizing the dc voltage output from the secondary side of the high frequency transformer 110.
Specifically, referring to fig. 3, the second rectifying and filtering circuit 170 is configured to filter the high-frequency low-voltage dc power output by the secondary side into low-frequency low-voltage dc power, and the flyback switching power supply automatically adjusts the frequency and duty ratio of the PWM according to the low-frequency low-voltage dc power, so as to maintain the stability of the output voltage.
The second rectifying and smoothing circuit 170 is generally any circuit or module capable of achieving high-frequency smoothing, and in this embodiment, the second rectifying and smoothing circuit 170 is composed of a diode and an electrolytic capacitor, when the switching circuit 120 is turned on, the diode is turned off in the reverse direction, and no energy is transmitted between the primary side and the secondary side of the high-frequency transformer 110; with the switching circuit 120 turned off, the energy stored in the primary side winding of the high-frequency transformer 110 is transferred to the secondary side winding by magnetic coupling, and the diode is turned on, so that the secondary side of the high-frequency transformer 110 supplies power to the load.
In one embodiment, the high frequency transformer 110 further comprises a bobbin, and the wound windings comprise a primary winding, an auxiliary winding, and a secondary winding, wherein:
the primary winding is wound on the surface of the framework, the auxiliary winding is wound on the outer surface of the primary winding, and the secondary winding is wound on the outer surface of the auxiliary winding, wherein the auxiliary winding is used for reducing turn-to-turn capacitance between the primary winding and the secondary winding. A winding start point pin of a primary winding of the high-frequency transformer 110 is connected with a drain electrode of the triode, and an end point pin of the primary winding is connected with a positive electrode of the bus.
Specifically, a primary winding, an auxiliary winding and a secondary winding are sequentially wound on the outer surface of the framework, and winding modes of the windings are determined according to the window area and the turn number requirements of the actually selected magnetic core, wherein the specific winding modes comprise a dense winding full framework, a dense winding non-full framework, a sparse winding non-full framework and the like. The primary winding is wound not more than three layers at most according to the saturation characteristic of the high frequency transformer 110.
And the secondary winding adopts a mode that one or two strands of copper wires are fully wound on the outer surface of the auxiliary winding according to the total number of turns of the winding, the magnitude of secondary current, the edge effect and the skin effect, if a plurality of layers are required to be wound, the secondary winding is wound in a close-wound full-wound mode on one side close to the auxiliary winding, and the secondary winding is wound in a close-wound or loose-wound full-wound mode on the outermost layer far away from the auxiliary winding. Usually, due to the influence of skin effect, the engineering will use the bifilar copper wire winding method for the wire diameter exceeding 0.6mm, for example, the wire diameter obtained by the design in the early stage is 0.65mm, and then two 0.35mm copper wires are selected and wound.
In one embodiment, the primary winding is wound in a close-wound manner around the surface of the bobbin.
Specifically, the primary winding is wound in a close winding and full bobbin winding manner, that is, the primary winding is wound in the full bobbin with no interval, if the primary winding is not wound in the full bobbin, the coupling between the primary winding and the auxiliary winding is poor, and for the high-frequency transformer 110 with strict requirement on output voltage, under the condition that the primary winding is wound in the full bobbin, the output voltage of the high-frequency transformer 110 is easy to control and stable, and the intermodulation range is smaller.
In one embodiment, the auxiliary winding is formed by winding a plurality of strands around the primary winding.
Specifically, the auxiliary winding selects a small-wire-diameter multi-strand winding wire according to the requirements of the window area and the number of turns of the magnetic core and fully winds the outer surface of the primary winding, usually, the current flowing through the auxiliary winding is small, the number of turns is required to be small, and only one layer of winding is fully wound on the outer surface of the primary winding. The auxiliary winding can be used as a chip power supply or a feedback circuit power supply according to different control signals output by the control circuit 150, and turn-to-turn capacitance between the primary winding and the secondary winding can be further increased, so that a shielding enhancement effect is achieved. The auxiliary winding is usually used for supplying power to the chip, but some chips also need to acquire the voltage on the auxiliary winding for feedback.
In one embodiment, an insulating layer is further arranged between the primary winding and the framework, between the primary winding and the auxiliary winding, between the auxiliary winding and the secondary winding, and on the outer surface of the secondary winding.
Specifically, referring to fig. 4, insulating layers are added between the windings and on the outer surface of the secondary winding to achieve a better isolation effect, and the insulating layers may be made of inorganic insulating materials and/or organic insulating materials, wherein the inorganic insulating materials include mica, asbestos, marble, porcelain, glass, colored glaze and the like, and the organic insulating materials include shellac, resin, rubber, cotton yarn and the like. The thickness of the insulating layer can be determined according to the sparsity of winding of the winding, for example, if the winding is sparser, a thicker insulating layer is adopted on the outer surface of the winding; if the winding is tight, a thinner insulating layer is used on the outer surface of the winding.
In one embodiment, L insulating layers are disposed between the primary winding and the bobbin, N insulating layers are disposed between the primary winding and the auxiliary winding, and M insulating layers are disposed between the auxiliary winding and the secondary winding, where L, M, N is any positive integer, L is less than M, and M is less than N.
Specifically, the thickness of the insulating layer can be determined according to the current span between the windings, and in the process of voltage reduction and conversion of the high-frequency transformer 110, the current flowing through the secondary winding is larger than the current flowing through the primary winding, and the current flowing through the primary winding is larger than the current flowing through the auxiliary winding, so that more insulating layers need to be added between the windings with larger current span, the charged parts with different potentials are isolated, and the phenomena of electric leakage, creepage or breakdown are avoided.
In a specific embodiment, the high-frequency transformer 110 adopts an EE22 type thickened magnetic core, the primary winding has 56 turns in total, an enameled wire with the wire diameter of 0.28mm is adopted, the enameled wire is wound in a manner of densely winding and fully winding two layers of frameworks, and a layer of insulating tape is added between the primary winding and the framework of the high-frequency transformer 110; the auxiliary winding adopts an enameled wire with the wire diameter of 0.18mm, 4 strands of enameled wires are wound in parallel for 9 turns in a sparse winding manner, two layers of insulating tapes are added between the auxiliary winding and the primary winding, a secondary winding adopts a triple insulating wire with the wire diameter of 0.35mm, two layers of enameled wires with 14 turns are wound in a full winding manner by adopting a 2-strand parallel winding method, and three layers of insulating tapes are respectively added on the secondary winding, the auxiliary winding and the outermost layer of the winding of the high-frequency transformer 110.
With the high-frequency transformer 110 with the structure, the first differential mode inductor and the second differential mode inductor in the differential mode circuit both adopt I-shaped inductors of 330 mu H/0.5A, and the first capacitor and the second capacitor are aluminum electrolytic capacitors of 10 mu F/400V +33 mu F/400V.
Compared with the high-frequency transformer 110 with a sandwich winding method, the high-frequency transformer 110 with the above-mentioned embodiment has a higher leakage inductance between the primary side and the secondary side and a lower turn-to-turn capacitance, and thus has the following effects on the EMC performance of the flyback switching power supply: the larger leakage inductance can cause the electromagnetic interference with the frequency about 1MHz to increase, but the lower turn-to-turn capacitance can have a better filtering effect on the electromagnetic interference with the high frequency band coupled and propagated to the primary side from the secondary side, the high frequency band refers to the working frequency above 2MHz, and for the electromagnetic interference about 1MHz, the better filtering effect can be realized through the first differential mode inductor and the second differential mode inductor in the first rectifying and filtering circuit 130, and the full-band EMI filtering can be realized through the combination of the high-frequency transformer 110 and the first rectifying and filtering circuit 130 in the above embodiment.
Referring to fig. 5, the measured conducted EMI result corresponding to the flyback switching power supply, referring to fig. 7, the measured conducted EMI result of the switching power supply circuit adopting the scheme of combining the sandwich winding high-frequency transformer and the common mode inductor is shown, the line marked 101 in fig. 5 represents the peak standard, the line marked 102 represents the average standard, the line marked 103 represents the peak test result, the line marked 104 represents the average test result, and similarly, the line marked 201 in fig. 7 represents the peak standard, the line marked 202 represents the average standard, the line marked 203 represents the peak test result, and the line marked 204 represents the average test result. Fig. 6 is a measured result of conducted EMI corresponding to the flyback switching power supply, where fig. 6 shows a quasi-peak value collected at each time point, fig. 7 is a measured result of conducted EMI of the switching power supply circuit using the scheme of combining the sandwich winding high-frequency transformer and the common-mode inductor, and fig. 7 shows a quasi-peak value collected at each time point.
It can be seen that the margin between the peak test result and the peak criteria in fig. 5 is greater than the margin between the peak test result and the peak criteria in fig. 7; the margin between the mean test result and the mean criterion in fig. 5 is greater than the margin between the mean test result and the mean criterion in fig. 7; the largest quasi-peak in fig. 6 is-9.38 and the largest quasi-peak in fig. 8 is-4.34, i.e. the largest quasi-peak in fig. 6 is also smaller than the largest quasi-peak in fig. 8. That is to say, flyback switching power supply in this scheme compares in the switching power supply of sandwich winding's high-frequency transformer 110 combination common mode inductance scheme, can effectively reduce the electromagnetic interference who propagates to the primary side by the secondary side, and have unshielded winding, characteristics that winding structure is simple, better secondary EMI shielding characteristic has, and adopt two differential mode inductances to replace common mode inductance, further reduce overall cost, when actually carrying out PCB system board, the installation common mode inductance needs manual dress, and differential mode inductance can realize the machine and insert the operation, the automated production of being more convenient for, improve production efficiency.
It is noted that, in this document, relational terms such as "first" and "second," and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, article, or apparatus that comprises the element.
The foregoing are merely exemplary embodiments of the present invention, which enable those skilled in the art to understand or practice the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A high frequency transformer, comprising a bobbin, a primary winding, an auxiliary winding, and a secondary winding, wherein:
the primary winding is wound on the surface of the framework, the auxiliary winding is wound on the outer surface of the primary winding, and the secondary winding is wound on the outer surface of the auxiliary winding, wherein the auxiliary winding is used for reducing turn-to-turn capacitance between the primary winding and the secondary winding.
2. The high-frequency transformer according to claim 1, wherein the primary winding is wound by being densely wound around the bobbin surface, and the auxiliary winding is wound by being multi-stranded around the primary winding.
3. The high-frequency transformer according to claim 1, wherein an insulating layer is further provided between the primary winding and the bobbin, between the primary winding and the auxiliary winding, between the auxiliary winding and the secondary winding, and on an outer surface of the secondary winding.
4. The high-frequency transformer according to claim 3, wherein L insulating layers are provided between the primary winding and the bobbin, N insulating layers are provided between the primary winding and the auxiliary winding, and M insulating layers are provided between the auxiliary winding and the secondary winding, wherein L, M, N is any positive integer, and L is less than M, and M is less than N.
5. A flyback switching power supply, comprising:
a high frequency transformer for performing a conversion operation on electric energy transmitted from a primary side of the high frequency transformer to a secondary side of the high frequency transformer, wherein the high frequency transformer is the high frequency transformer according to any one of claims 1 to 4;
the switching circuit is connected with the primary side of the high-frequency transformer and used for controlling the starting and stopping of the conversion operation;
the first rectifying and filtering circuit is connected with the primary side of the high-frequency transformer and used for filtering electromagnetic interference generated in the process of transmitting electric energy from the primary side to the secondary side, wherein the first rectifying and filtering circuit comprises a rectifying bridge and a differential mode circuit, the direct current side of the rectifying bridge is connected with the differential mode circuit, the alternating current side of the rectifying bridge is connected with the alternating current power supply, and the differential mode circuit is connected with a first end of the primary side of the high-frequency transformer;
the suppression circuit is connected with the primary side of the high-frequency transformer in parallel and used for absorbing leakage inductance energy between the primary side and the secondary side;
and the control circuit is connected with the switch circuit and is used for controlling the conduction state of the switch circuit.
6. The flyback switching power supply of claim 5, wherein the differential mode circuit comprises a first differential mode inductor, a second differential mode inductor, a first capacitor and a second capacitor, wherein a first end of the first differential mode inductor is connected to a first end of the first capacitor, the first end of the first differential mode inductor is further connected to the rectifier bridge, a second end of the first differential mode inductor is connected to a first end of the second capacitor, a second end of the second capacitor is connected to a first end of the second differential mode inductor, the second end of the second differential mode inductor is connected to a second end of the first capacitor, and the second end of the second differential mode inductor is further connected to the rectifier bridge.
7. The flyback switching power supply of claim 5, wherein the rectifier filter circuit further comprises:
and the second rectifying and filtering circuit is connected with the secondary side of the high-frequency transformer and is used for stabilizing the direct-current voltage output by the secondary side of the high-frequency transformer.
8. The flyback switching power supply of claim 5, wherein the switching circuit comprises a transistor, a gate of the transistor is coupled to the control circuit, a drain of the transistor is coupled to the suppression circuit, the drain of the transistor is further coupled to the second terminal of the primary side of the high frequency transformer, and a source of the transistor is coupled to ground.
9. The flyback switching power supply of claim 8, wherein a starting point pin of the primary winding of the high frequency transformer is connected to the drain of the transistor, and an ending point pin of the primary winding is connected to the positive pole of the bus.
10. A power adapter, characterized in that it comprises a flyback switching power supply as claimed in any of claims 6-9.
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| CN112201457A (en) * | 2020-08-26 | 2021-01-08 | 珠海格力电器股份有限公司 | High-frequency transformer winding structure, switching power supply circuit and power adapter |
| CN112233888A (en) * | 2020-09-23 | 2021-01-15 | 珠海格力电器股份有限公司 | Transformer device, switching power supply and power adapter |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112201457A (en) * | 2020-08-26 | 2021-01-08 | 珠海格力电器股份有限公司 | High-frequency transformer winding structure, switching power supply circuit and power adapter |
| CN112233888A (en) * | 2020-09-23 | 2021-01-15 | 珠海格力电器股份有限公司 | Transformer device, switching power supply and power adapter |
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