CN119382497A - Flyback Converter - Google Patents
Flyback Converter Download PDFInfo
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- CN119382497A CN119382497A CN202411795224.6A CN202411795224A CN119382497A CN 119382497 A CN119382497 A CN 119382497A CN 202411795224 A CN202411795224 A CN 202411795224A CN 119382497 A CN119382497 A CN 119382497A
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- primary side
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- flyback converter
- power conversion
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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
- H02M1/44—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
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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
- H02M7/00—Conversion of AC power input into DC power output; Conversion of DC power input into AC power output
- H02M7/02—Conversion of AC power input into DC power output without possibility of reversal
- H02M7/04—Conversion of AC power input into DC power output without possibility of reversal by static converters
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Dc-Dc Converters (AREA)
Abstract
一种反激变换器。所述反激变换器包括：输入电路、原边控制及功率变换电路以及输出电路，其中：所述输入电路，用于将交流电压转换为直流电压；所述原边控制及功率变换电路，用于对所述直流电压进行功率变换；所述输出电路，用于感应得到功率变换后的电压并输出；其中，所述原边控制及功率变换电路包括：第一原边主绕组、功率开关以及第二原边主绕组；当所述功率开关闭合时，所述第一原边主绕组及所述第二原边主绕组通过所述功率开关串联连接。采用上述方案，可以降低反激式转换器的电磁干扰。
A flyback converter. The flyback converter includes: an input circuit, a primary control and power conversion circuit, and an output circuit, wherein: the input circuit is used to convert AC voltage into DC voltage; the primary control and power conversion circuit is used to perform power conversion on the DC voltage; the output circuit is used to sense and output the voltage after power conversion; wherein the primary control and power conversion circuit includes: a first primary main winding, a power switch, and a second primary main winding; when the power switch is closed, the first primary main winding and the second primary main winding are connected in series through the power switch. The above scheme can reduce the electromagnetic interference of the flyback converter.
Description
Technical Field
The invention relates to the technical field of switching power supplies, in particular to a flyback converter.
Background
Flyback converter (Flyback Converter) is widely applied to alternating current-direct current (AC/DC) and direct current-direct current (DC/DC) conversion, provides insulation and isolation between an input stage and an output stage, is one of switching power supplies, and is widely applied to various consumer electronic products. The scheme with high efficiency and low noise is extremely important for reducing the system cost and improving the user experience.
However, in the topology of the existing flyback converter, there is a certain electromagnetic interference (ElectroMagneticInterference, EMI) problem.
Disclosure of Invention
The invention aims to solve the problem of reducing the electromagnetic interference of a flyback converter.
In order to solve the above problems, an embodiment of the present invention provides a flyback converter, which includes an input circuit, a primary side control and power conversion circuit, and an output circuit, wherein:
The input circuit is used for converting alternating voltage into direct voltage;
the primary side control and power conversion circuit is used for carrying out power conversion on the direct-current voltage;
The output circuit is used for sensing the voltage after power conversion and outputting the voltage;
The primary side control and power conversion circuit comprises a first primary side main winding, a power switch and a second primary side main winding, wherein when the power switch is closed, the first primary side main winding and the second primary side main winding are connected in series through the power switch.
In a possible embodiment, the homonymous end of the first primary winding is connected to one end of the power switch, and the heteronymous end of the second primary winding is directly or indirectly connected to the other end of the power switch.
In one possible embodiment, the output circuit comprises an output winding, wherein the first primary side main winding, the second primary side main winding and the output winding are wound on the same magnetic core layer by layer in a laminating way to form a transformer.
In one possible embodiment, the ratio of the number of turns of the first primary winding to the second primary winding balances the common mode current of the transformer.
In one possible embodiment, the primary side control and power conversion circuit further comprises a primary side controller, and the second primary side main winding is connected with a power supply end of the primary side controller and is used for supplying power to the primary side controller.
In one possible embodiment, the primary side control and power conversion circuit further comprises a rectifier circuit and an energy storage sub-circuit, wherein the rectifier circuit is used for rectifying the voltage provided by the second primary side main winding, and the energy storage sub-circuit is used for storing the voltage rectified by the rectifier circuit and providing the voltage to a power supply end of the primary side controller.
In one possible embodiment, the rectifier sub-circuit comprises a rectifier diode, or a rectifier diode and a fifth resistor connected in series.
In one possible embodiment, the tank sub-circuit includes a first capacitor, or a first capacitor and a second capacitor connected in parallel.
In one possible embodiment, the primary side control and power conversion circuit further comprises a starting resistor, wherein one end of the starting resistor is connected with the input circuit, and the other end of the starting resistor is connected with the first capacitor and the second capacitor.
In one possible embodiment, the primary side control and power conversion circuit further comprises a primary side controller, and the second primary side main winding is further connected with a control signal end of the primary side controller and is used for providing a control signal for the primary side controller so that the primary side controller can execute control operation.
In one possible embodiment, the primary side control and power conversion circuit further comprises a third resistor and a fourth resistor, wherein the control signal end of the primary side controller is connected with the homonymous end of the second primary side main winding through the third resistor, and the control signal end of the primary side controller is connected with the heteronymous end of the second primary side main winding through the fourth resistor.
In one possible embodiment, the primary side control and power conversion circuit further comprises a current acquisition sub-circuit, wherein one end of the current acquisition sub-circuit is connected with the power switch tube, and the other end of the current acquisition sub-circuit is connected with the second primary side main winding.
In one possible embodiment, the primary side control and power conversion circuit further comprises a feedback sub-circuit, wherein one end of the feedback sub-circuit is connected with the second primary side main winding, and the other end of the feedback sub-circuit is connected with the primary side controller and is used for monitoring the output voltage of the flyback converter.
Compared with the prior art, the technical scheme of the embodiment of the invention has the following advantages:
When the scheme of the invention is applied, when the power switch is closed, the first primary side main winding and the second primary side main winding are connected in series through the power switch, so that the second primary side main winding can share the primary side voltage of the transformer, and compared with the mode that only one primary side winding is arranged, the noise source of the primary side winding of the transformer can be decomposed into two parts, including the noise generated by the first primary side main winding and the noise generated by the second primary side main winding, the voltage variation of each noise source is reduced after decomposition, and the electromagnetic interference generated by overlarge voltage variation can be reduced.
Further, the same-name end of the first primary main winding is connected with one end of the power switch, and the different-name end of the second primary main winding is connected with the other end of the power switch, so that when the power switch is closed, the voltage of the same-name end of the first primary main winding is reduced, but the voltage of the different-name end of the second primary main winding is increased, and the common-mode current direction generated by the second primary main winding is opposite to the common-mode current direction generated by the first primary main winding, thereby being beneficial to balancing common-mode currents in the transformer, and solving the EMI problem generated by unbalanced common-mode currents.
Drawings
FIG. 1 is a topology diagram of a flyback converter of the prior art;
FIG. 2 is a schematic diagram of the internal structure of a transformer according to the prior art;
FIG. 3 is a schematic diagram showing the change of the common mode current direction inside a transformer according to the prior art;
FIG. 4 is a topology diagram of a flyback converter according to an embodiment of the present invention;
FIG. 5 is a schematic diagram showing voltage variation curves of the first primary winding and the second primary winding in FIG. 4;
FIG. 6 is a schematic diagram of an internal structure of a transformer according to an embodiment of the present invention;
FIG. 7 is a schematic diagram showing a change of the direction of a common mode current in a transformer according to an embodiment of the present invention;
FIG. 8 is a schematic diagram of the winding of windings inside a transformer;
FIG. 9 is a schematic diagram of winding windings inside a transformer according to an embodiment of the present invention;
FIG. 10 is a topology diagram of another flyback converter according to an embodiment of the present invention;
FIG. 11 is a topology diagram of yet another flyback converter according to an embodiment of the present invention;
FIG. 12 is a topology diagram of yet another flyback converter according to an embodiment of the present invention;
fig. 13 is a topology diagram of another flyback converter according to an embodiment of the present invention.
Detailed Description
Fig. 1 is a topology of a prior art flyback converter. Referring to fig. 1, the flyback converter may include an input circuit 11, a primary side control and power conversion circuit 12, and an output circuit 13. Wherein:
The input circuit 11 comprises a primary rectifier 111 and a filter sub-circuit 112. The AC voltage is rectified by the primary rectifier 111, and then filtered by the filter sub-circuit 112 composed of the first electrolytic capacitor and the inductor, to obtain a dc voltage, and the obtained dc voltage is provided to the primary control and power conversion circuit 12.
The primary control and power conversion circuit 12 includes a primary main winding Np of a transformer, an auxiliary winding Na of a transformer, a primary controller, a power switch, and the like, which are connected in series. The primary side controller and the power switch may be integrated in the power conversion chip U1, and the power switch is located between the switch pin (SW) and the ground pin (GND). The auxiliary winding Na of the transformer is also provided with an auxiliary rectifier D1 and a second electrolytic capacitor C1, and the auxiliary rectifier D1 is positioned at the positive end of the second electrolytic capacitor C1. The direct-current voltage provided by the input circuit 11 is input to the power conversion chip U1 through the primary winding Np of the transformer, and the primary controller can control the on-off of the power switch, so that the power conversion is realized.
In the output circuit 13, the secondary side rectifier 131 is located at the negative end of the output capacitance. The energy of the transformer is transferred to the output winding Ns in a magnetic field induction manner, and stable DC output is realized through the secondary rectifier and the output capacitor.
In the flyback converter with the above topology, referring to fig. 3, when the primary side controller controls the power switch to be turned on, the switch pin (i.e. the connection end of the power switch and the primary side main winding Np of the transformer) of the power conversion chip U1 is shorted to the ground, and at this time, taking the common mode current flowing into the direction of the output winding Ns as an example, the voltage v_np of the same-name end of the primary side main winding Np of the transformer and the voltage v_na of the same-name end of the auxiliary winding Na of the transformer will become low, so as to generate negative common mode current. The voltage v_ns at the opposite end of the output winding Ns becomes high, and a negative common mode current is generated.
In order to balance the negative common mode current, the transformer must generate a positive common mode current to offset the negative common mode current, so that a shielding winding needs to be added to generate a positive common mode current, so that electromagnetic interference caused by unbalanced common mode current is avoided.
Specifically, referring to fig. 2, a shield winding is added between the primary main winding Np and the output winding Ns inside the transformer to achieve common mode current balance. When the primary side is turned on, the voltage v_nss at the same terminal of the shield winding decreases, and a forward common mode current is generated (as shown in fig. 3). At this time, the positive common mode current generated by the shield winding will be balanced with the negative common mode current generated by the primary main winding Np, the auxiliary winding Na, and the output winding Ns.
However, since the shielding winding is added inside the transformer, the primary side main winding Np and the output winding Ns cannot be tightly attached to each other, so that the coupling performance between the primary side main winding Np and the output winding Ns is affected, the leakage inductance of the transformer is large, the voltage conversion efficiency and the temperature of the transformer can be even affected, and the transformer has a certain influence no matter in a sandwich or sequential winding mode. Moreover, as the shielding winding is added in the transformer, the number of layers in the transformer is increased, the process is complex, and the cost of the transformer is increased.
In addition, with the flyback converter with the topological structure, even if a shielding winding is added in the transformer, when a power switch is turned off, the voltage at the switch pin (UI-SW) of the power converter U1 can be changed from zero to (Vin_dc+ nVo). Wherein vin_dc is a direct current voltage provided by an input circuit, n is a turns ratio of a transformer, vo is an output voltage of the transformer, nVo is a voltage drop across the transformer. (vin_dc+ nVo) acts as a main noise source, so that the rate of change (dv/dt) of the voltage at the switch pin (UI-SW) of the power converter U1 with time is large, and thus EMI problems still occur.
In view of the above, the present invention provides a flyback converter, in which, when a power switch is turned on, a first primary winding and a second primary winding are connected in series through the power switch, so that a noise source of the primary winding of the transformer can be decomposed into two parts, namely, the first primary winding and the second primary winding, and the voltage variation of each noise after decomposition is reduced, thereby reducing electromagnetic interference generated by overlarge voltage variation.
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings.
The embodiment of the invention provides a flyback converter which can comprise an input circuit, a primary side control and power conversion circuit and an output circuit. Wherein:
The input circuit is used for converting alternating voltage into direct voltage;
the primary side control and power conversion circuit is used for carrying out power conversion on the direct-current voltage;
The output circuit is used for sensing the voltage after power conversion and outputting the voltage;
The primary side control and power conversion circuit comprises a first primary side main winding, a power switch and a second primary side main winding, wherein when the power switch is closed, the first primary side main winding and the second primary side main winding are connected in series through the power switch.
By adopting the flyback converter, when the power switch is turned on, the first primary side main winding and the second primary side main winding are connected in series through the power switch, so that the noise source of the transformer main winding is decomposed into two parts, namely noise generated by the first primary side main winding and noise generated by the second primary side main winding, and the voltage variation of each noise source is reduced, and the EMI problem caused by overlarge voltage variation can be reduced.
In implementations, the primary side control and power conversion circuit may include a primary side controller and a power switch. The primary side controller and the power switch can be respectively and independently arranged (as shown in fig. 4) or integrated in the same power conversion chip (as shown in fig. 10-13).
The flyback converter in the embodiment of the invention is described in detail below with reference to a specific circuit structure.
Fig. 4 is a schematic diagram of a flyback converter 40 according to an embodiment of the present invention, and referring to fig. 4, the flyback converter 40 may include an input circuit 41, a primary side control and power conversion circuit 42, and an output circuit 43.
The input circuit 41 may include a primary rectifier 411 and a filter sub-circuit 412. The primary side rectifier 411 may be implemented as a rectifier bridge. The filter subcircuit 412 may include electrolytic capacitors, inductors, and the like. The AC voltage is rectified by the primary rectifier 411 and then filtered by the filter sub-circuit 412 to obtain a dc voltage vin_dc.
The output circuit 43 may include an output winding Ns, a secondary rectifier, and an output capacitor. The voltage induced by the output winding Ns is rectified by the secondary side rectifier and then output by the output capacitor.
In implementations, the primary control and power conversion circuit 42 may include a first primary winding Np1, a power switch Q1, and a second primary winding Np2. When the power switch Q1 is turned on, the first primary winding Np1 is connected in series with the second primary winding Np2 through the power switch Q1. The second primary winding Np2 and the first primary winding Np1 constitute a primary winding of the transformer T1. The second primary winding Np2 and the first primary winding Np1 share the energy storage function of the transformer, so that the current density in the transformer is more balanced, and the utilization rate of the transformer is higher.
The primary side control and power conversion circuit 42 may also include a primary side controller U11. The primary side controller U11 further has a Gate terminal Gate and a ground terminal GND. The Gate terminal Gate is connected with the Gate of the power switch Q1, so as to control the on-off of the power switch Q1. The ground GND is connected to one end B of the second primary winding Np 2. When the power switch Q1 is turned on, the voltage at the B end of the second primary winding Np2 changes, so that the B end of the second primary winding Np2 is a dynamic node, so that the main winding noise source of the flyback converter can be divided into two parts, namely, noise generated by the first primary winding Np1 and noise generated by the second primary winding Np 2.
Referring to fig. 5, when the power switch Q1 is turned off, the voltage at the same-name terminal a of the first primary winding Np1 changes from zero to (n1vo+vin_dc), and the voltage at the connection terminal B of the second primary winding Np2 and the power switch Q1 changes from zero to V1. Where n1 is the turns ratio of the first primary main winding Np1 to the output winding Ns. Since the number of turns of the first primary winding Np1 is smaller than that of the primary winding Np in fig. 1, so n1< n, the voltage variation of the same-name terminal a of the first primary winding Np1 is smaller than that of the same-name terminal voltage of the primary winding Np in fig. 1, so that the voltage variation of the first primary winding Np1 is reduced when the power switch Q1 is turned off, and thus electromagnetic interference generated by the first primary winding Np1 can be greatly reduced.
Therefore, by connecting the first primary main winding Np1 and the second primary main winding Np2 in series, electromagnetic interference generated due to excessive voltage variation at the connection terminal of the primary main winding and the primary controller U11 can be greatly reduced.
In an embodiment of the present invention, in order to avoid electromagnetic interference generated by unbalanced common mode current in the transformer T1, referring to fig. 4, the homonymous terminal a of the first primary winding Np1 may be connected to one end of the power switch Q1, and the heteronymous terminal B of the second primary winding Np2 may be directly connected to the other end of the power switch Q1.
At this time, the homonymous end a of the first primary winding Np1 and the heteronymous end B of the second primary winding Np2 are heterogeneous sites, so that the direction of the common mode current generated by the first primary winding Np1 is opposite to the direction of the common mode current generated by the second primary winding Np2, and the direction of the first primary winding Np1 is opposite to the direction of the noise generated by the second primary winding Np2, which is beneficial to the internal common mode current balance of the transformer T1 and reduces the electromagnetic interference problem.
Since the common mode current generated by the second primary winding Np2 is opposite to the common mode current generated by the first primary winding Np1, in one embodiment, the first primary winding Np1, the second primary winding Np2 and the output winding Ns are wound on the same magnetic core layer by layer in a laminating manner, so as to form the transformer T1.
Specifically, referring to fig. 6, a layer of copper wire may be wound on the magnetic core first as the first primary main winding Np1. And winding copper wires above the copper wire layer of the first primary main winding Np1 to form a second primary main winding Np2. Finally, copper wires are wound above the copper wire layer of the second primary main winding Np2 to form an output winding Ns. The first primary winding Np1 is attached to the second primary winding Np2, the second primary winding Np2 is attached to the output winding Ns, no shielding layer is disposed in the transformer T1, and the second primary winding Np2 provides a reverse common mode current.
With reference to fig. 7, when the power switch Q1 is turned on, the voltage v_np1 at the same-name terminal a of the primary winding Np1 decreases, so that a negative common-mode current is generated. The voltage v_np2 across the second primary winding Np2 becomes high, thereby generating a forward common mode current. The voltage v_ns at the opposite end of the output winding Ns becomes high, and a negative common mode current is generated. In this way, the common mode current inside the transformer T1 can be more advantageously balanced.
In an embodiment of the present invention, the winding turn ratio of the first primary winding Np1 and the second primary winding Np2 may be adjusted to balance the common mode current of the transformer T1. At this time, the size of the positive common mode current generated in the transformer T1 can be changed by adjusting the number of windings of the second primary winding Np2, and the size of the negative common mode current generated in the transformer T1 can be changed by adjusting the number of windings of the first primary winding Np1, so that the positive common mode current value generated in the transformer T1 is equal to the negative common mode current value generated in the transformer T1, and the mutual cancellation of the common mode currents is realized.
In an embodiment of the present invention, the sum of the number of windings of the first primary winding and the number of windings of the second primary winding may be equal to the number of windings of the primary winding before improvement, so that the number of copper wires in the transformer may be reduced, that is, the shielding layer may be reduced, so that the coupling between windings in the transformer may be better, and further the conversion efficiency of the transformer may be improved, thereby improving the output efficiency of the transformer.
For example, fig. 8 is a schematic diagram of the internal structure of the transformer before modification. Referring to fig. 8, in the transformer before modification, a polyurethane enamel wire (2 UEW) of 0.23mm may be used to wind 2 layers clockwise from 7 feet (7 (s)) of the magnetic core and wind out from 4 feet (4 (s)) of the magnetic core, each layer is wound 23 turns (Ts), forming a primary main winding Np, and the total number of turns of the primary main winding Np is 46. After the primary main winding Np is formed, a polyurethane enameled wire is adopted to wind 1 layer clockwise from 6 pins of the magnetic core, and wind out from 5 pins to form an auxiliary winding Na, wherein the number of turns of the auxiliary winding Na is 10. After the auxiliary winding Na is formed, a shielding layer and an output winding Ns are formed on the auxiliary winding Na. The number of turns of the shielding layer is 10 turns, and the number of turns of the output winding Ns is 5 turns.
Fig. 9 is a schematic diagram of an internal structure of a transformer according to an embodiment of the present invention. Referring to fig. 9, a polyurethane enamel wire (2 UEW) of 0.29mm is used to wind 2 layers clockwise from 7 feet (7 (s)) of the magnetic core and wind out from 4 feet (4 (s)) of the magnetic core, each layer is wound 18 times, so as to form a first primary main winding Np1, and the total number of turns of the first primary main winding Np1 is 36 times. After the first primary main winding Np1 is formed, a polyurethane enameled wire is adopted to wind 1 layer clockwise from 5 pins of the magnetic core, a second primary main winding Np2 is formed, and the number of turns of the second primary main winding Np2 is 10. After the second primary main winding Np2 is formed, the output winding Ns is formed on the second primary main winding Np 2. Wherein the number of turns of the output winding Ns is 5. At this time, the common mode current balance is achieved inside the transformer.
Comparing fig. 8 and fig. 9, it can be seen that the sum of the number of turns of the first primary winding Np1 and the number of turns of the second primary winding Np2 is equal to the total number of turns of the primary winding Np before improvement, but the common mode current balance is achieved without providing the shielding layer in fig. 9, so that the cost of the transformer can be reduced. Also, the copper wire diameter of the first primary main winding Np1 in fig. 9 is larger than that of the primary main winding Np in fig. 8, i.e., the copper wire is thickened, whereby the transformer impedance can be reduced.
In an implementation, with continued reference to fig. 4, the primary side controller U11 may further be provided with a power terminal VDD, and the second primary side main winding Np2 is connected to the power terminal VDD of the primary side controller U11, for supplying power to the primary side controller U11. At this time, the second primary winding Np2 may supply power to the primary controller U11.
In one embodiment, the primary side control and power conversion circuit 42 may further include a rectifier circuit for rectifying the voltage provided by the second primary side main winding Np2, and a tank circuit for storing the rectified voltage of the rectifier circuit and providing the rectified voltage to the power supply terminal VDD of the primary side controller U11.
In an embodiment, referring to fig. 4, the tank sub-circuit may include a first capacitor C1 and a second capacitor C2, where the first capacitor C1 and the second capacitor C2 are connected in parallel. One end of the first capacitor C1 and one end of the second capacitor C2 are connected to the power supply terminal VDD of the primary side controller U11, and the other end is connected to the synonym terminal B of the second primary side main winding Np 2.
The rectifier sub-circuit may include a rectifier diode D1 and a fifth resistor R5 connected in series. The anode of the rectifying diode D1 is grounded, and the other end of the fifth resistor R5 is connected to the power supply terminal VDD of the primary side controller U11. The voltage of the second primary winding Np2 is rectified by the rectifying diode D1 and the fifth resistor R5 and then provided to the primary controller U11.
In the embodiment shown in fig. 10 to 13, the primary side controller and the power switch are integrated in the same power conversion chip U1. At this time, in the power conversion chip U1, one end of the power switch is used as the switch end SW of the power conversion chip U1, and the other end of the power switch is connected to the ground end GND of the primary side controller. Here, the output circuit is not shown in fig. 11 to 13.
In another embodiment, referring to fig. 10, the tank sub-circuit may include only the first capacitor C1. One end of the first capacitor C1 is connected with a power supply end VDD of a power supply end of the power conversion chip U1, and the other end of the first capacitor C is connected with a synonym end B of the second primary winding Np 2. In this case, in FIG. 10, the charging path is Np 2A C A D1A R5A C1A Np 2A B. Wherein C represents the homonymous end of the second primary winding Np 2.
In another embodiment, referring to fig. 11, the rectifier sub-circuit may include only a rectifier diode D1. The anode of the rectifying diode D1 is grounded, and the cathode is connected with the power end of the power conversion chip U1.
In one embodiment of the present invention, the primary side control and power conversion circuit 42 may further include a start-up resistor, wherein one end of the start-up resistor is connected to the input circuit, and the other end of the start-up resistor is connected to the tank sub-circuit, so as to charge the tank sub-circuit to start the primary side controller.
Specifically, referring to fig. 4, the starting resistor includes a first resistor R1 and a second resistor R2 connected in series, wherein one end of the first resistor R1 is connected to the output end of the input circuit 41, and the other end is connected to the first capacitor C1 and the second capacitor C2, so as to charge the first capacitor C1 and the second capacitor C2. After the charging voltages of the first capacitor C1 and the second capacitor C2 reach the start-up voltage of the primary side controller U11, the primary side controller U11 starts to operate.
In other embodiments, the starting resistor may also include only one resistor or a plurality of resistors connected in series, which will not be described herein.
In a specific implementation, the primary side controller further has a control signal end, and the second primary side main winding is further connected to the control signal end of the primary side controller, and is configured to provide a control signal for the primary side controller, so that the primary side controller performs a control operation.
Referring to fig. 4, when the primary side controller U11 and the power switch Q1 are respectively and independently disposed, the second primary side main winding Np2 may be connected to the control signal terminal DMG of the primary side controller U11, thereby providing a control signal to the control signal terminal DMG of the primary side controller U11.
Specifically, the control signal terminal DMG of the primary side controller U11 may be connected to the second primary side main winding Np2 through a voltage sampling sub-circuit. The voltage sampling sub-circuit may include a third resistor R3 and a fourth resistor R4. One end of the third resistor R3 is connected with the control signal end DMG, and the other end of the third resistor R3 is connected with the homonymous end of the second primary winding Np 2. One end of the fourth resistor R4 is connected with the control signal end DMG, and the other end of the fourth resistor R4 is connected with the synonym end of the second primary winding Np 2.
The third resistor R3 and the fourth resistor R4 form a resistor network, by means of which the primary side controller U11 can collect the voltage signal from the second primary side main winding Np 2. The voltage of the second primary winding Np2 is related to the voltage on the output winding Ns, by collecting the voltage signal of the second primary winding Np2, the on-off of the power switch tube can be controlled based on the voltage signal, and finally the magnitude of the output voltage is affected by the on-off of the power switch tube, so as to realize primary feedback control (PRIMARY SIDE Regulator, PSR).
Referring to fig. 10 to 13, when the primary side controller U11 and the power switch Q1 are integrated in the power conversion chip U1, at this time, the control signal terminal DMG of the primary side controller U11 is used as the control signal terminal DMG of the power conversion chip U1, and a voltage sampling sub-circuit may still be disposed between the power conversion chip U1 and the second primary side main winding Np2 to collect the voltage signal of the second primary side main winding Np2, so as to implement primary side feedback control.
In a specific implementation, based on the input of the control signal terminal DMG, the primary side controller U11 or the power conversion chip U1 may also perform detection of signals such as output voltage, input voltage, valley bottom, and the like.
In some embodiments, the primary side control and power conversion circuit may further include a current acquisition subcircuit. One end of the current collection subcircuit is connected with the power switch tube, the other end of the current collection subcircuit is connected with the second primary winding Np2, and current flowing through the power switch tube can be collected through the current collection subcircuit, so that the current of the power switch tube is monitored.
Specifically, referring to FIG. 4, the current sampling sub-circuit may include a sampling resistor Rcs. The sampling resistor Rcs may be disposed outside the primary side controller U11. At this time, one end of the sampling resistor Rcs is connected to the current sampling end CS of the primary side controller U11, and the other end is connected to the synonym end of the second primary side main winding Np2, so that the synonym end of the second primary side main winding Np2 is indirectly connected to the power switch Q1.
Referring to fig. 12, when the primary side controller U11 and the power switch are integrated in the power conversion chip U1, the current sampling terminal CS of the primary side controller U11 may be used as the current sampling terminal CS of the power conversion chip U1, so as to implement connection with the sampling resistor Rcs.
In some embodiments, referring to fig. 10, 11 and 13, the sampling resistor Rcs may also be integrated inside the power conversion chip U1. Inside the power conversion chip U1, the sampling resistor Rcs is still connected with the power switch tube.
In some embodiments, referring to FIGS. 4, 11 and 13, the primary side control and power conversion circuit may further include a feedback sub-circuit. The feedback sub-circuit may include an optocoupler Q2. Correspondingly, the primary side controller U11 and the power conversion chip U1 may be provided with a feedback end FB, and the feedback end FB is connected to the synonym end B of the second primary side main winding Np2 through the optocoupler Q2. Correspondingly, an optocoupler is also arranged in the output circuit 43, and a monitoring result of the output voltage can be obtained through coupling between the optocouplers, so that the output voltage is fed back to the primary side controller U11 or the power conversion chip U1, and secondary side feedback control (Secondary Side Regulator, SSR) is realized.
In some embodiments, as shown in fig. 10 and 12, optocoupler Q2 may be integrated within power conversion chip U1.
The flyback converter and the flyback converter before improvement in the embodiment of the invention are tested under different input voltages, wherein the flyback converter and the flyback converter before improvement in the embodiment of the invention have the same circuit structure, the capacitance, the inductance value and the like in the circuit are the same, the number of turns of the primary side main winding of the transformer, the number of turns of the output winding and the inductance are the same, and the difference is that the first primary side main winding of the flyback converter in the embodiment of the invention is connected with the second primary side main winding in series through a power switch string.
TABLE 1
Wherein, table 1 is test data of the flyback converter before improvement under the condition that the input voltage is 90V and 115V, and table 2 is test data of the flyback converter under the condition that the input voltage is 90V and 115V in the embodiment of the invention. The test data includes input power, output voltage, output current, output power, board end efficiency, and average value of board end efficiency. The output efficiency refers to the ratio of the output power to the input power of the flyback converter.
TABLE 2
Comparing the test data in table 1 with the test data in table 2, it is known that the transformer structure in the embodiment of the invention obviously increases the output efficiency under the condition that the input voltage and the output current are the same. For example, when the input voltage is 90V and the output current is 3.2A, the output efficiency of the flyback converter before improvement is 86.36%, while in the embodiment of the invention, the output efficiency of the flyback converter is 86.91%, and the output efficiency is improved by 0.55%. When the input voltage is 115V, the average value of the output efficiency of the flyback converter before improvement is 88.29%, while in the embodiment of the invention, the average value of the output efficiency of the flyback converter is 89.34%, and the average value of the output efficiency is improved by 1.05%.
That is, with the flyback converter in the embodiment of the invention, under the same circuit structure, leakage inductance can be effectively optimized due to the change of the transformer structure, voltage conversion efficiency is improved, and output efficiency is further improved.
As can be seen from the above description, in the flyback converter according to the embodiment of the present invention, the first primary winding and the second primary winding are connected in series through the power switch, and the electromagnetic interference caused by the excessive voltage variation can be reduced by changing the connection mode. In addition, the structure of the transformer can be simplified, leakage inductance is optimized, output efficiency is improved, working temperature is reduced, cost of the transformer can be reduced, and stability of the transformer is improved.
Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention, and the scope of the invention should be assessed accordingly to that of the appended claims.
Claims (13)
1. The flyback converter is characterized by comprising an input circuit, a primary side control and power conversion circuit and an output circuit, wherein:
The input circuit is used for converting alternating voltage into direct voltage;
the primary side control and power conversion circuit is used for carrying out power conversion on the direct-current voltage;
The output circuit is used for sensing the voltage after power conversion and outputting the voltage;
The primary side control and power conversion circuit comprises a first primary side main winding, a power switch and a second primary side main winding, wherein when the power switch is closed, the first primary side main winding and the second primary side main winding are connected in series through the power switch.
2. The flyback converter of claim 1 wherein the homonymous end of the first primary winding is connected to one end of the power switch and the heteronymous end of the second primary winding is directly or indirectly connected to the other end of the power switch.
3. The flyback converter of claim 2 wherein the output circuit comprises an output winding, and wherein the first primary winding, the second primary winding and the output winding are wound layer by layer around the same core to form a transformer.
4. A flyback converter as in claim 3, wherein the ratio of the number of turns of the first primary winding to the second primary winding is such as to balance the common mode current of the transformer.
5. The flyback converter of any of claims 1-4 wherein the primary side control and power conversion circuit further comprises a primary side controller and the second primary side primary winding is connected to a power supply terminal of the primary side controller for powering the primary side controller.
6. The flyback converter of claim 5 wherein the primary side control and power conversion circuit further comprises a rectifier circuit for rectifying the voltage supplied by the secondary primary side primary winding and a tank circuit for storing the rectified voltage from the rectifier circuit and providing it to the power supply of the primary side controller.
7. The flyback converter of claim 6 wherein the rectifier sub-circuit comprises a rectifier diode or a rectifier diode and a fifth resistor connected in series.
8. The flyback converter of claim 6 wherein the tank sub-circuit comprises a first capacitor or a first capacitor and a second capacitor connected in parallel.
9. The flyback converter of claim 8 wherein the primary side control and power conversion circuit further comprises a start-up resistor having one end connected to the input circuit and the other end connected to the first capacitor and the second capacitor.
10. The flyback converter of any of claims 1-4 wherein the primary side control and power conversion circuit further comprises a primary side controller and the second primary side primary winding is further coupled to a control signal terminal of the primary side controller for providing control signals to the primary side controller for the primary side controller to perform control operations.
11. The flyback converter of claim 10 wherein the primary side control and power conversion circuit further comprises a third resistor and a fourth resistor, wherein the control signal terminal of the primary side controller is connected to the homonymous terminal of the second primary side main winding through the third resistor, and the control signal terminal of the primary side controller is connected to the heteronymous terminal of the second primary side main winding through the fourth resistor.
12. The flyback converter of claim 10 wherein the primary side control and power conversion circuit further comprises a current harvesting subcircuit having one end connected to the power switching tube and the other end connected to the second primary side main winding.
13. The flyback converter of claim 10 wherein the primary side control and power conversion circuit further comprises a feedback sub-circuit having one end connected to the second primary side main winding and another end connected to the primary side controller for monitoring the output voltage of the flyback converter.
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|---|---|---|---|
| CN202411795224.6A CN119382497A (en) | 2024-12-09 | 2024-12-09 | Flyback Converter |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202411795224.6A CN119382497A (en) | 2024-12-09 | 2024-12-09 | Flyback Converter |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105099205A (en) * | 2015-08-12 | 2015-11-25 | 矽力杰半导体技术(杭州)有限公司 | Switching power supply, flyback converter and transformer |
| CN109245568A (en) * | 2018-09-12 | 2019-01-18 | 杭州海兴电力科技股份有限公司 | A kind of exchange turns direct-current isolating switch power circuit |
| CN111200365A (en) * | 2020-03-02 | 2020-05-26 | 上海南芯半导体科技有限公司 | Control method and control circuit of flyback converter |
| CN116884747A (en) * | 2023-07-11 | 2023-10-13 | 启东力生美集成电路有限公司 | Switching power supply and transformer thereof |
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2024
- 2024-12-09 CN CN202411795224.6A patent/CN119382497A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105099205A (en) * | 2015-08-12 | 2015-11-25 | 矽力杰半导体技术(杭州)有限公司 | Switching power supply, flyback converter and transformer |
| CN109245568A (en) * | 2018-09-12 | 2019-01-18 | 杭州海兴电力科技股份有限公司 | A kind of exchange turns direct-current isolating switch power circuit |
| CN111200365A (en) * | 2020-03-02 | 2020-05-26 | 上海南芯半导体科技有限公司 | Control method and control circuit of flyback converter |
| CN116884747A (en) * | 2023-07-11 | 2023-10-13 | 启东力生美集成电路有限公司 | Switching power supply and transformer thereof |
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