CN219145253U - Filter circuit and switching power supply - Google Patents
Filter circuit and switching power supply Download PDFInfo
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- CN219145253U CN219145253U CN202222964108.5U CN202222964108U CN219145253U CN 219145253 U CN219145253 U CN 219145253U CN 202222964108 U CN202222964108 U CN 202222964108U CN 219145253 U CN219145253 U CN 219145253U
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
Abstract
The utility model discloses a filter circuit, which is applied to a switching power supply and comprises: the device comprises a rectifying module, a series resonance module and a filtering module; the rectification module, the series resonance module and the filtering module are all connected in parallel and are used for reducing the differential mode interference of the switching frequency below 1 MHz. The series resonance module comprises N-order resonance components which are connected in parallel, N is a natural number which is more than or equal to 1, and each order resonance component is formed by connecting a resonance capacitor and a resonance inductor in series; the series resonance module is connected with the power supply, then connected with the rectifying module in parallel and then connected with the filtering module in parallel, and the filtering module is used as the output end of the filtering circuit to be connected with the input end of a power supply product. According to the method, the impedance of the series resonance module at the resonance frequency point is 0, so that a filtering loop for conducting interference signals is provided, the conduction margin near the corresponding frequency point is increased, and the differential mode interference of the switching frequency within 1MHz is reduced; the circuit has the advantages of simple structure, low cost, small volume and easy design.
Description
Technical Field
The utility model relates to the field of switching power supplies, in particular to a high-power switching power supply with a conductive interference filter circuit.
Background
Electromagnetic compatibility (EMC, full Electromagnetic Compatibility) refers to the ability of a device or system to operate satisfactorily in its electromagnetic environment without causing unacceptable electromagnetic interference to other devices in its environment. EMC therefore includes 2 aspects, firstly, electromagnetic interference (Electromagnetic Interference, i.e., EMI) generated by the device to the environment during normal operation cannot exceed a certain limit; another aspect is that the device has a degree of immunity, i.e. electromagnetic sensitivity (Electromagnetic Susceptibility, EMS), to electromagnetic disturbances present in the environment. The EMI interference is divided into two types, namely a conduction direction and a radiation direction, and the filter circuit provided by the utility model mainly solves the interference of the conduction direction.
The conduction interference limiting standard of the switching power supply in the international certification standard mostly refers to the conduction interference limiting standard in the CISPR32/EN55032CLASS B standard, and is shown in detail in figure 1. It was analyzed that conduction interference below 1MHz is dominated by differential mode components. In order to filter out the differential mode interference within 1MHz, the input live wire (L line) and zero line (N line) are commonly connected with X capacitors in parallel and differential mode inductors in series to form a differential mode filter circuit. However, in the design of high-power and high-power density switching power supply products, large X capacitance and differential mode inductance cannot be adopted due to the limited volume. And the differential mode inductance in the current switching power supply adopts a coil and a ferrite magnetic ring or a magnetic rod as an iron core in the middle of the winding, when the current passing through the coil is large, the iron core is saturated, and the differential mode inductance is similar to an air core coil without the iron core in the state, so that the inductance of the differential mode inductance is reduced sharply, and the function of filtering differential mode interference is lost.
When the test product is a 1500W switching power supply and the filter circuit is not added, a conduction test curve is shown in figure 2, and in a low frequency band, namely a frequency band with the switching frequency smaller than or equal to 1MHz, a quasi-peak curve presents an obvious peak shape, particularly a frequency doubling point of the switching frequency, and the conduction allowance is smaller due to the fact that the peak of the curve is very high; the test data corresponding to FIG. 2 are shown in Table 1, where the conduction average margin measured at a switching frequency of 183kHz is only 2.3dB, and does not meet the high EMI performance requirement (margin requirement. Gtoreq.3 dB).
TABLE 1
| ID | Frequency | Probe | Cable | Atten. | Detector | Meter Read | Meas Level | Limit | Limit Dist. |
| 1 | 183.000kHz | 0.2 | 0.2 | 10.0 | C_AVG | 41.6 | 52.0 | 54.3 | -2.3 |
| 2 | 186.000kHz | 0.2 | 0.2 | 10.0 | QPeak | 48.0 | 58.4 | 64.2 | -5.8 |
Disclosure of Invention
In view of the above, the present utility model provides a filter circuit for solving the problem of conduction interference of high-power and high-power density switching power supply products, especially the problem of insufficient conduction margin of the switching frequency doubling point below 1 MHz.
The utility model aims at realizing the following technical scheme:
in a first aspect, a filter circuit is provided, applied to a switching power supply, and includes: the device comprises a rectifying module, a series resonance module and a filtering module; the rectification module, the series resonance module and the filtering module are all connected in parallel and are used for reducing the differential mode interference of the switching frequency below 1 MHz.
Further, the series resonance module comprises N-order resonance components connected in parallel, N is a natural number greater than or equal to 1, and each order resonance component is formed by connecting a resonance capacitor and a resonance inductor in series; the first end of the resonance capacitor is used as the first end of the resonance component, the second end of the resonance capacitor is connected with the first end of the resonance inductor, and the second end of the resonance inductor is used as the second end of the resonance component; the first-order resonance component is connected with a power supply, the last-order resonance component is connected with the input end of the rectifying module, the output end of the rectifying module is connected with the input end of the filtering module, and the output end of the filtering module is used as the output end of the filtering circuit.
Further, the rectification module is connected with a power supply; the series resonance module comprises N-order resonance components which are connected in parallel, N is a natural number which is more than or equal to 1, and each order resonance component is formed by connecting a resonance capacitor and a resonance inductor in series; the first end of the resonance capacitor is used as the first end of the resonance component, the second end of the resonance capacitor is connected with the first end of the resonance inductor, and the second end of the resonance inductor is used as the second end of the resonance component; the first-order resonance component is connected with the output end of the rectifying module, the last-order resonance component is connected with the input end of the filtering module, and the output end of the filtering module is used as the output end of the filtering circuit.
Further, the rectification module is a full-wave rectification circuit or a half-wave rectification circuit.
Further, the filtering module is a filtering capacitor C.
In a second aspect, a filter circuit is provided, applied to a switching power supply, and includes: the device comprises a rectifying module, a series resonance module and a filtering module; the rectifying module is a rectifying bridge U; the series resonance module comprises N-order resonance components which are connected in parallel, N is a natural number which is more than or equal to 1, and each order resonance component is formed by connecting a resonance capacitor and a resonance inductor in series; the first end of the resonance capacitor is used as the first end of the resonance component, the second end of the resonance capacitor is connected with the first end of the resonance inductor, and the second end of the resonance inductor is used as the second end of the resonance component; the filter module is a filter capacitor C;
the first end of the first-order resonance component is connected with an L line of a power supply, and the second end of the first-order resonance component is connected with an N line of the power supply; the first end of the last-order resonance component is connected with the first input end of the rectifier bridge U, and the second end of the last-order resonance component is connected with the second input end of the rectifier bridge U; the first output end of the rectifier bridge U is connected with the first end of the filter capacitor C; the second output end of the rectifier bridge U is respectively connected with the second end of the filter capacitor C and the ground end GND; the first end of the filter capacitor C is used as a first output end of the filter circuit to be connected with a positive input end of a power supply product, and the second end of the filter capacitor C is used as a second output end of the filter circuit to be connected with a negative input end of the power supply product.
In a third aspect, a filter circuit is provided, applied to a switching power supply, and includes: the device comprises a rectifying module, a series resonance module and a filtering module; the rectification module is a rectification bridge U, the series resonance module comprises N-order resonance components which are connected in parallel, N is a natural number which is more than or equal to 1, and each order resonance component is formed by connecting a resonance capacitor and a resonance inductor in series; the first end of the resonance capacitor is used as the first end of the resonance component, the second end of the resonance capacitor is connected with the first end of the resonance inductor, and the second end of the resonance inductor is used as the second end of the resonance component; the filter module is a filter capacitor C;
the first input end of the rectifier bridge U is connected with an L line of a power supply, the second input end of the rectifier bridge U is connected with an N line of the power supply, the first output end of the rectifier bridge U is connected with the first end of the first-order resonance component, and the second output end of the rectifier bridge U is connected with the second end of the first-order resonance component; the second end of the last-order resonance component is respectively connected with the second end of the filter capacitor C and the ground end GND; the first end of the filter capacitor C is used as a first output end of the filter circuit to be connected with a positive input end of a power supply product, and the second end of the filter capacitor C is used as a second output end of the filter circuit to be connected with a negative input end of the power supply product.
Further, the rectifier bridge U is a full-wave rectifier bridge or a half-wave rectifier bridge.
In a fourth aspect, a switching power supply is provided, comprising a filter circuit as described in any one of the preceding claims.
The working principle of the utility model will be described in detail below with reference to specific embodiments, and is not repeated here.
According to the filter circuit, particularly the series resonance module in the filter circuit, the conduction interference of a high-power switching power supply product, particularly the conduction interference of a switching frequency doubling point below 1MHz can be effectively filtered; the X capacitor and the series differential mode inductor which are larger in volume are not required to be connected in parallel on the live wire and the zero wire of the input source, the volume of the product is obviously reduced, the circuit structure is simple, the cost is low, and the design is easy.
Drawings
The utility model will now be described in further detail with reference to the drawings and to specific examples.
FIG. 1 is a graph showing the CLASS B conduction interference limit in the CISPR32/EN55032 standard;
FIG. 2 is a graph of a conduction test waveform of a switching power supply product of 1500W without the addition of the filter circuit of the present application;
FIG. 3 is a schematic circuit diagram of a first embodiment of the present utility model;
FIG. 4 is a schematic circuit diagram of a second embodiment of the present utility model;
FIG. 5 is a plot of LC series resonant frequency versus impedance;
fig. 6 is a conduction test waveform diagram of a switching power supply product of 1500W with the filter circuit of the present application added.
Detailed Description
In order that the utility model may be more readily understood, a more particular description thereof will be rendered by reference to specific embodiments that are illustrated in the appended drawings. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the utility model.
First embodiment
Referring to fig. 3, a filter circuit provided in the first embodiment is applied to a switching power supply, and includes: the rectification module, the series resonance module and the filtering module; the rectification module, the series resonance module and the filtering module are all connected in parallel and are used for reducing the differential mode interference of the switching frequency below 1 MHz.
The rectification module is a rectification bridge U and is used for transmitting the rectified power supply voltage to the series resonance module; the series resonance module comprises N-order resonance components which are connected in parallel, N is a natural number which is more than or equal to 1, and each order resonance component is formed by connecting a resonance capacitor and a resonance inductor in series; the first end of the resonance capacitor is used as the first end of the resonance component, the second end of the resonance capacitor is connected with the first end of the resonance inductor, and the second end of the resonance inductor is used as the second end of the resonance component; the filter module is a filter capacitor C;
the first end of the first-order resonance component is connected with an L line (positive electrode of a power supply system) of the power supply, and the second end of the first-order resonance component is connected with an N line (negative electrode of the power supply system) of the power supply; the first end of the last-order resonance component is connected with the first input end of the rectifier bridge U, and the second end of the last-order resonance component is connected with the second input end of the rectifier bridge U; the first output end of the rectifier bridge U is connected with the first end of the filter capacitor C; the second output end of the rectifier bridge U is respectively connected with the second end of the filter capacitor C and the ground end GND; the first end of the filter capacitor C is used as a first output end of the filter circuit to be connected with a positive input end of a power supply product, and the second end of the filter capacitor C is used as a second output end of the filter circuit to be connected with a negative input end of the power supply product.
The working principle of this embodiment is analyzed as follows: the frequency-impedance curve of the LC series resonant assembly consisting of the resonant inductance and the resonant capacitance is shown in fig. 5, and the LC impedance at the resonant frequency point f1 is 0; when the frequency of the interference signal generated by the switching power supply is equal to the frequency of the resonant frequency point f1, the interference signal is fed back into the power supply product through the filter circuit and is not transmitted to the conduction tester, so that the input source is interfered. According to the scheme, the impedance of the LC series resonant circuit at a resonant frequency point is 0, so that a filtering loop for conducting interference signals is provided, the conducting margin near the corresponding frequency point is further increased, and the differential mode interference of the switching frequency within 1MHz is reduced.
Referring to Table 1, table 1 shows conduction test data of a switching power supply product of 1500W without the filter circuit, it can be seen that the margin of the average value of the conduction interference at the switching frequency of 183kHz is only 2.3dB, which does not meet the application of high EMI performance requirements (the margin requirement is not less than 3 dB).
TABLE 1
| ID | Frequency | Probe | Cable | Atten. | Detector | Meter Read | Meas Level | Limit | Limit Dist. |
| 1 | 183.000kHz | 0.2 | 0.2 | 10.0 | C_AVG | 41.6 | 52.0 | 54.3 | -2.3 |
| 2 | 186.000kHz | 0.2 | 0.2 | 10.0 | QPeak | 48.0 | 58.4 | 64.2 | -5.8 |
As a specific implementation manner of this embodiment, a filter circuit meeting the requirement of high EMI performance is specifically designed for this point, and only one LC series resonant assembly is required to be designed for the series resonant module, and the design steps are as follows: first selecting a 2uH inductance with proper volume and current, i.e. L 1 =2uh; according to
The corresponding capacitance value is calculated by the formula of (C) 1 =378 nF; and the actual capacitance value is not 378nF, the capacitance C with the capacitance value of 330nF is taken 1 The test curves are shown in FIG. 6, and the test data are shown in Table 2. As can be seen from Table 2, after the switching power supply product of the present scheme is added, the margin of the conduction average value at the switching frequency of 183kHz is 3.8dB, which is 1.5dB more than that of the switching power supply product without the present scheme, thereby meeting the application (margin) of high EMI performance requirementsThe quantity requirement is more than or equal to 3 dB). Therefore, the filter circuit provided by the embodiment can effectively reduce the conduction interference of the switching frequency below 1 MHz.
TABLE 2
| ID | Frequency | Probe | CabIe | Atten. | Detector | Meter Read | Meas Level | Limit | LimitDist. |
| 2 | 183.000kHz | 0.2 | 0.2 | 10.0 | C_AVG | 40.2 | 50.5 | 54.3 | -3.8 |
| 1 | 183.000kHz | 0.2 | 0.2 | 10.0 | QPeak | 46.7 | 57.1 | 64.3 | -7.2 |
Second embodiment
Fig. 4 is a schematic circuit diagram of a filter circuit provided in the second embodiment, which is another optimization mode of the first embodiment, and is different from the first embodiment mainly in the connection mode of the rectifying module and the series resonant module in the filter circuit; the rectification module in this embodiment is connected to the power supply first, and then connected in parallel with the series resonant module, and the circuit structure and the working principle are the same as those of the first embodiment, and are not described here again.
In light of the foregoing, and by using common technical knowledge and conventional means in the art, the implementation circuit of the present utility model may be modified, replaced or altered in various other ways without departing from the basic technical concept of the present utility model, and all the modifications and alterations fall within the scope of the claims of the present utility model.
Claims (9)
1. A filter circuit for use in a switching power supply, comprising: the device comprises a rectifying module, a series resonance module and a filtering module; the rectification module, the series resonance module and the filtering module are all connected in parallel and are used for reducing the differential mode interference of the switching frequency below 1 MHz.
2. The filter circuit of claim 1, wherein: the series resonance module comprises N-order resonance components which are connected in parallel, N is a natural number which is more than or equal to 1, and each order resonance component is formed by connecting a resonance capacitor and a resonance inductor in series; the first end of the resonance capacitor is used as the first end of the resonance component, the second end of the resonance capacitor is connected with the first end of the resonance inductor, and the second end of the resonance inductor is used as the second end of the resonance component; the first-order resonance component is connected with a power supply, the last-order resonance component is connected with the input end of the rectifying module, the output end of the rectifying module is connected with the input end of the filtering module, and the output end of the filtering module is used as the output end of the filtering circuit.
3. The filter circuit of claim 1, wherein: the rectification module is connected with a power supply; the series resonance module comprises N-order resonance components which are connected in parallel, N is a natural number which is more than or equal to 1, and each order resonance component is formed by connecting a resonance capacitor and a resonance inductor in series; the first end of the resonance capacitor is used as the first end of the resonance component, the second end of the resonance capacitor is connected with the first end of the resonance inductor, and the second end of the resonance inductor is used as the second end of the resonance component; the first-order resonance component is connected with the output end of the rectifying module, the last-order resonance component is connected with the input end of the filtering module, and the output end of the filtering module is used as the output end of the filtering circuit.
4. A filter circuit according to any one of claims 1-3, characterized in that: the rectification module is a full-wave rectification circuit or a half-wave rectification circuit.
5. A filter circuit according to any one of claims 1-3, characterized in that: the filter module is a filter capacitor C.
6. A filter circuit for use in a switching power supply, comprising: the device comprises a rectifying module, a series resonance module and a filtering module; the rectifying module is a rectifying bridge U; the series resonance module comprises N-order resonance components which are connected in parallel, N is a natural number which is more than or equal to 1, and each order resonance component is formed by connecting a resonance capacitor and a resonance inductor in series; the first end of the resonance capacitor is used as the first end of the resonance component, the second end of the resonance capacitor is connected with the first end of the resonance inductor, and the second end of the resonance inductor is used as the second end of the resonance component; the filter module is a filter capacitor C;
the first end of the first-order resonance component is connected with an L line of a power supply, and the second end of the first-order resonance component is connected with an N line of the power supply; the first end of the last-order resonance component is connected with the first input end of the rectifier bridge U, and the second end of the last-order resonance component is connected with the second input end of the rectifier bridge U; the first output end of the rectifier bridge U is connected with the first end of the filter capacitor C; the second output end of the rectifier bridge U is respectively connected with the second end of the filter capacitor C and the ground end GND; the first end of the filter capacitor C is used as a first output end of the filter circuit to be connected with a positive input end of a power supply product, and the second end of the filter capacitor C is used as a second output end of the filter circuit to be connected with a negative input end of the power supply product.
7. A filter circuit for use in a switching power supply, comprising: the device comprises a rectifying module, a series resonance module and a filtering module; the rectification module is a rectification bridge U, the series resonance module comprises N-order resonance components which are connected in parallel, N is a natural number which is more than or equal to 1, and each order resonance component is formed by connecting a resonance capacitor and a resonance inductor in series; the first end of the resonance capacitor is used as the first end of the resonance component, the second end of the resonance capacitor is connected with the first end of the resonance inductor, and the second end of the resonance inductor is used as the second end of the resonance component; the filter module is a filter capacitor C;
the first input end of the rectifier bridge U is connected with an L line of a power supply, the second input end of the rectifier bridge U is connected with an N line of the power supply, the first output end of the rectifier bridge U is connected with the first end of the first-order resonance component, and the second output end of the rectifier bridge U is connected with the second end of the first-order resonance component; the second end of the last-order resonance component is respectively connected with the second end of the filter capacitor C and the ground end GND; the first end of the filter capacitor C is used as a first output end of the filter circuit to be connected with a positive input end of a power supply product, and the second end of the filter capacitor C is used as a second output end of the filter circuit to be connected with a negative input end of the power supply product.
8. The filter circuit according to any one of claims 6-7, wherein: the rectifier bridge U is a full-wave rectifier bridge or a half-wave rectifier bridge.
9. A switching power supply comprising a filter circuit as claimed in any one of claims 1 to 8.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202222842813 | 2022-10-27 | ||
| CN2022228428138 | 2022-10-27 |
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| Publication Number | Publication Date |
|---|---|
| CN219145253U true CN219145253U (en) | 2023-06-06 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202222964108.5U Active CN219145253U (en) | 2022-10-27 | 2022-11-08 | Filter circuit and switching power supply |
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| CN (1) | CN219145253U (en) |
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