Filter circuit and power module
By combining a dual-filter structure with a damping resistor, the problem of insufficient interference suppression in the high-frequency band of traditional filters is solved, achieving EMI suppression in a compact structure in high power density applications, and improving the stability and anti-interference capability of the circuit.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- SALCOMP SHENZHEN CO LTD
- Filing Date
- 2025-04-14
- Publication Date
- 2026-06-12
AI Technical Summary
Existing EMI filtering solutions are insufficient in suppressing interference in the high-frequency band, and traditional filters tend to become bulky and lose more power when improving filtering performance, making it difficult to balance equipment size, energy loss and stability in high-density applications.
A dual-filter structure is adopted, including a common-mode inductor and a first π-type filter module and a second π-type filter module connected in series. Through a hierarchical filtering design, the common-mode inductor suppresses common-mode interference, the π-type filter module filters differential-mode interference in stages, and the damping resistor suppresses the resonant peak, thus realizing multi-stage filtering to improve the EMI suppression effect.
It significantly improves EMI suppression within a limited space, enhances circuit anti-interference capability, reduces resonance risk, and improves circuit stability, making it suitable for high power density applications.
Smart Images
Figure CN224356026U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of electronic technology, and in particular to a filter circuit and a power supply module. Background Technology
[0002] In modern electronic circuits, electromagnetic interference (EMI) and electromagnetic compatibility (EMC) issues are becoming increasingly prominent, especially in high-frequency operating applications such as switching power supplies, frequency converters, and inverters. The numerous rapid switching actions in these circuits generate significant electromagnetic noise. If this noise cannot be effectively suppressed, it may interfere with the stable operation of surrounding sensitive equipment and the system itself, and even lead to functional failure.
[0003] Existing EMI filtering solutions typically employ conventional LC filters or single-stage π-type filter structures. However, with the continuous increase in switching frequencies and power density of devices, the interference suppression effect of single-stage filters may be insufficient in the mid-to-high frequency range. On the one hand, the filtering attenuation capability of single-stage filters is limited at high frequencies; on the other hand, increasing the value of single-stage components to improve filtering performance can easily lead to a bulky filter structure, increased losses, and even the induction of high-Q resonance peaks at specific frequencies, causing instability or affecting the power conversion efficiency of the circuit. Furthermore, some traditional filtering designs fail to consider multiple aspects such as device size, energy loss, and stability, making it difficult to meet the practical needs of high-density applications. Utility Model Content
[0004] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes a filter circuit and power supply module that can achieve high-efficiency filtering while also taking into account the overall size and cost control of the circuit.
[0005] In one aspect, this application provides a filter circuit.
[0006] A filtering circuit according to an embodiment of this application includes: a first input port and a second input port for receiving an input signal with interference; a first output port and a second output port for outputting a filtered signal; a common-mode inductor, the second input terminal of the first input terminal of the common-mode inductor being connected to the first input port and the second input port respectively; a first π-type filtering module, the first input terminal of the first π-type filtering module being connected to the first output terminal of the common-mode inductor, and the second input terminal of the first π-type filtering module being connected to the second output terminal of the common-mode inductor; a second π-type filtering module, the first input terminal of the second π-type filtering module being connected to the first output terminal of the first π-type filtering module, the second input terminal of the second π-type filtering module being connected to the second output terminal of the first π-type filtering module, the first output terminal of the second π-type filtering module being connected to the first output port, and the second output terminal of the second π-type filtering module being connected to the second output port.
[0007] The filtering circuit according to the embodiments of this application has at least the following beneficial effects: A common-mode inductor is reasonably arranged between the first input port and the second input port, and a dual filtering structure is formed by sequentially combining a first π-type filtering module and a second π-type filtering module. The common-mode inductor can effectively suppress common-mode interference signals, while the first π-type filtering module and the second π-type filtering module can filter differential-mode interference in stages, significantly improving the attenuation capability for mid-to-high frequency spike interference, making the EMI suppression of the circuit more complete. Through a segmented differential-mode filtering design, a wide range of interference frequency bands are filtered in multiple stages, avoiding the high-Q resonance problem that may occur at specific high-frequency points in a single-stage filter, thereby improving the stability and reliability of the filter over a wider frequency range. By arranging different filtering modules in series, comprehensive suppression of common-mode and differential-mode interference is achieved within a limited space, while ensuring that the operating ranges of each filtering device do not interfere with each other, facilitating effective deployment in high-power-density applications. In summary, the filtering circuit, while maintaining a compact structure, can significantly improve the EMI suppression effect, enhance the circuit's anti-interference capability, reduce resonance risk, and improve circuit stability.
[0008] According to some embodiments of this application, the first π-type filter module includes a first differential-mode capacitor, a first differential-mode inductor, and a second differential-mode capacitor. One end of the first differential-mode capacitor is connected to the first input terminal of the first π-type filter module, and the other end is connected to the second input terminal of the first π-type filter module. One end of the first differential-mode inductor is connected to the second input terminal of the first π-type filter module, and the other end is connected to the second output terminal of the first π-type filter module. One end of the second differential-mode capacitor is connected to the second output terminal of the first π-type filter module, and the other end is connected to the first output terminal of the first π-type filter module. The first input terminal of the first π-type filter module is connected to the first output terminal of the first π-type filter module.
[0009] According to some embodiments of this application, the second π-type filter module includes a second differential-mode capacitor, a second differential-mode inductor, and a third differential-mode inductor. One end of the second differential-mode capacitor is connected to the first input terminal of the second π-type filter module, and the other end is connected to the second input terminal of the second π-type filter module. One end of the second differential-mode inductor is connected to the first input terminal of the second π-type filter module, and the other end is connected to the first output terminal of the second π-type filter module. One end of the third differential-mode inductor is connected to the second input terminal of the second π-type filter module, and the other end is connected to the second output terminal of the second π-type filter module.
[0010] According to some embodiments of this application, the second π-type filter module further includes a first common-mode capacitor and a second common-mode capacitor. One end of the first common-mode capacitor is connected to the first output terminal of the second π-type filter module, and the other end is grounded. One end of the second common-mode capacitor is connected to the second output terminal of the second π-type filter module, and the other end is grounded.
[0011] According to some embodiments of this application, a first resistor is connected in parallel across the first differential capacitor. The first resistor is used to discharge the residual high voltage of the first differential capacitor while suppressing the high Q-value oscillation of the first π-type filter module.
[0012] According to some embodiments of this application, a second resistor is connected in parallel across the two ends of the first differential mode inductor, and the second resistor is used to suppress the resonant peak value of the first π-type filter module.
[0013] According to some embodiments of this application, a third resistor is connected in parallel across the two ends of the second differential mode inductor, the third resistor being used to suppress the resonant peak value of the second π-type filter module.
[0014] According to some embodiments of this application, a fuse is connected in series between the first input port and the first input terminal of the common mode inductor.
[0015] According to some embodiments of this application, a thermistor is connected in series between the second input port and the second input terminal of the common-mode inductor.
[0016] Secondly, this application also provides a power supply module, including a filter circuit according to any embodiment of the first aspect. Attached Figure Description
[0017] The present application will be further described below with reference to the accompanying drawings and embodiments, wherein:
[0018] Figure 1 This is a circuit topology diagram of the filter circuit in an embodiment of this application.
[0019] Figure label:
[0020] Common mode inductor 100; first π-type filter module 200; second π-type filter module 300. Detailed Implementation
[0021] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.
[0022] In the description of this application, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.
[0023] In the description of this application, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.
[0024] In the description of this application, unless otherwise expressly defined, terms such as "setup," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this application in conjunction with the specific content of the technical solution.
[0025] In the description of this application, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0026] In a first aspect, embodiments of this application provide a one-wave circuit, the basic architecture of which includes the following components:
[0027] Input / output ports: First input port and second input port are used to receive input signals with interference, such as L-line and N-line input signals from AC power supply respectively; First output port and second output port transmit the filtered signal to the back-end circuit.
[0028] Common-mode rejection stage: Common-mode inductor L1 is connected across the input ports, with its first input terminal connected in series with the first input port and its second input terminal connected in series with the second input port, used to suppress common-mode interference.
[0029] Cascaded filter structure: The first π-type filter module 200 is connected to the output side of the common-mode inductor L1, and its input terminal is connected to the two output terminals of L1 respectively, forming the first-stage differential-mode filter network; the second π-type filter module 300 is connected in series to the output side of the first π-type filter module 200, and its output terminal is directly connected to the first output port and the second output port, forming the second-stage differential-mode filter network.
[0030] The first π-type filter module 200 and the second π-type filter module 300 each perform different levels of filtering duties: the first π-type filter module 200 is used to initially attenuate larger-amplitude differential-mode interference in the input signal; while the second π-type filter module 300 further eliminates or weakens residual differential-mode noise, thereby achieving deeper interference suppression over a wider frequency band. In this way, the EMI suppression performance of the overall circuit is greatly improved through the multi-stage cascaded filter structure.
[0031] Understandable, such as Figure 1 As shown, the first π-type filter module 200 consists of a first differential-mode capacitor CX1, a first differential-mode inductor L2, and a second differential-mode capacitor CX2. Specifically, the first differential-mode capacitor CX1 is connected across the two input terminals of the first π-type filter module 200, mainly used to initially reduce high-frequency differential-mode interference in the input signal; the first differential-mode inductor L2 is connected in series between the input and output terminals, causing a voltage drop across the interference current and further attenuating it; the second differential-mode capacitor CX2 is again connected across the corresponding output terminals to further reduce the remaining differential-mode interference components. In this structure, the first differential-mode capacitor CX1 and the second differential-mode capacitor CX2 complement each other, forming a symmetrical distribution, and together with the first differential-mode inductor L2 in the middle, constitute a typical π-type filter structure. This structure has good filtering characteristics in suppressing high-frequency differential-mode noise and can significantly reduce the risk of subsequent circuits suffering from differential-mode interference. According to actual needs, a small-value resistor can be connected in parallel across the above inductors or capacitors to achieve better suppression of resonant peaks or residual voltages, thereby improving the overall stability and safety of the filter.
[0032] Understandably, the second π-type filter module 300 includes a second differential-mode capacitor CX2, a second differential-mode inductor L3, and a third differential-mode inductor L4, for example. Figure 1In this configuration, the second differential-mode capacitor CX2 also serves as a component of the first π-type filter module 200. Specifically, one end of the second differential-mode capacitor CX2 is connected to the first input terminal (i.e., the first output terminal) of the second π-type filter module 300, and the other end is connected to the second input terminal (i.e., the second output terminal) of the second π-type filter module 300, providing a bypass for high-frequency noise between the two signal lines. One end of the second differential-mode inductor L3 is connected to the first input terminal of the second π-type filter module 300, and the other end is connected to the first output terminal, further attenuating residual high-frequency components in the first signal path. One end of the third differential-mode inductor L4 is connected to the second input terminal of the second π-type filter module 300, and the other end is connected to the second output terminal, responsible for suppressing high-frequency interference in the second signal path. In practical applications, the second differential mode inductor L3 and the third differential mode inductor L4 can be selected with the same inductance value to ensure the balance of the output signal. Typical values can be selected in the range of 5μH to 50μH, and it is especially important to consider that the rated current value must be higher than the normal operating current of the circuit. Compared with the first differential mode inductor L2 in the first π-type filter module 200, the second and third differential mode inductors can have the same or smaller inductance values, depending on the system's further requirements for high-frequency interference suppression.
[0033] By combining the first π-type filter module 200 and the second π-type filter module 300, the entire filter circuit exhibits a "double π cascade" topology, which can effectively suppress interference over a wider frequency band, avoid resonance problems that may occur with single-stage filtering, and has a smoother attenuation characteristic, reducing the filtering dead zone that may occur at specific frequency points.
[0034] In some embodiments, such as Figure 1As shown, the second π-type filter module 300, in addition to including the second differential-mode capacitor CX2, the second differential-mode inductor L3, and the third differential-mode inductor L4, also includes a first common-mode capacitor CB2 and a second common-mode capacitor CB1 to enhance the suppression effect of common-mode interference. Specifically, one end of the first common-mode capacitor CB2 is connected to the first output terminal X1 of the second π-type filter module 300, and the other end is grounded to PGND; while one end of the second common-mode capacitor CB1 is connected to the second output terminal X2 of the second π-type filter module 300, and the other end is also grounded to PGND. These common-mode capacitors play a crucial role in the EMC suppression circuit. First, the common-mode capacitors provide a low-impedance discharge path for the common-mode interference signal, enabling high-frequency common-mode interference to be effectively discharged to ground, thereby suppressing the further propagation of common-mode interference along the transmission line. Second, since the common-mode capacitors CB1 and CB2 are located at the two output terminals of the second π-type filter module 300 respectively, this symmetrical configuration ensures that the filtering characteristics of the filter circuit for the two input lines remain consistent, which helps to maintain the balance of circuit operation. It is worth noting that common-mode capacitors and differential-mode filter components can also have a synergistic effect. When common-mode interference is converted into differential-mode interference by differential-mode components, it can be partially absorbed by differential-mode capacitors such as CX2. Similarly, differential-mode interference may also be converted into common-mode interference through parasitic effects, in which case common-mode capacitors such as CB1 and CB2 can play an important role. This complementary cooperation between common-mode and differential-mode filter components can also significantly improve the overall suppression capability of the filter circuit against complex electromagnetic interference.
[0035] Understandably, in order to further improve the filtering stability of the first π-type filter module 200 and the second π-type filter module 300, corresponding impedance components can be connected in parallel across the differential-mode inductor and differential-mode capacitor respectively, thereby effectively suppressing the resonance peak and discharging the residual voltage. For example... Figure 1 As shown, in the first π-type filter module 200, in addition to performing high-frequency differential mode filtering, the first differential mode capacitor CX1 is also connected in parallel with a first resistor RX1 (RX2). The resistor can be selected with an appropriate resistance value, which can both discharge high voltage to avoid the capacitor leaving excessively high voltage during shutdown or switching, and suppress the oscillation phenomenon caused by high Q value, thereby reducing the resonance peak of the circuit at high frequency.
[0036] Similarly, in the first π-type filter module 200, a second resistor R25 is connected in parallel across the first differential-mode inductor L2. Since the combination of inductance and capacitance forms a resonant circuit, without proper damping, resonant peaks can easily occur in certain frequency bands, causing the filter gain to actually increase at specific frequencies. By connecting a damping resistor in parallel across the inductor, the loop Q value can be effectively reduced, making the high-frequency response flatter and thus reducing electromagnetic interference to downstream circuits. The selection of this damping resistor needs to strike a balance between filtering performance and power loss, ensuring peak suppression without excessively weakening the filtering effect.
[0037] A third resistor R24 can also be connected in parallel across the two ends of the second differential-mode inductor. This damping resistor can further suppress the resonant peak generated by the differential-mode filter circuit in the second π-type filter module 300. In particular, for the arc-shaped rise or spike region in the relatively high-frequency range, the damping resistor can effectively absorb some high-frequency energy, so that the circuit as a whole maintains stable and smooth filtering characteristics.
[0038] Understandably, in some embodiments, to ensure that the filter circuit can be effectively and promptly protected in the event of a sudden overload or surge current, such as... Figure 1 As shown, a fuse and a thermistor can be connected in series across the two ends of the filter circuit in the embodiment. For example, a fuse F1 is connected in series between the L line (typically corresponding to the AC power supply) and the first input terminal of the common-mode inductor L1 at the first input port, and a thermistor NTC1 is connected in series between the N line (typically corresponding to the AC power supply) and the second input terminal of the common-mode inductor L1 at the second input port. The fuse F1, located between the first input port and the first input terminal of the common-mode inductor L1, constitutes the pre-stage protection for the input line. If an overload or short circuit occurs in the circuit, such as an unexpected rise in the input port current to a level far exceeding the rated value, the fuse will quickly melt, thereby protecting downstream devices from high current surges and reducing the risk of damage to the circuit and load components. The breaking capacity, rated current, and fusing characteristics of the fuse should be comprehensively considered in light of the actual application power rating and transient surge current. Fast-blow fuses are generally preferred for faster response when peak currents occur; time-delay fuses can also be selected depending on the specific project requirements. The thermistor NTC1 is positioned between the second input port and the second input terminal of the common-mode inductor L1. When the circuit is initially powered on or a surge current occurs, NTC1 exhibits a high resistance value, effectively suppressing the instantaneous large current inrush. Subsequently, as its own temperature rises, the resistance value decreases significantly, thereby reducing power consumption during normal operation. The cold-state resistance, rated current, and thermal recovery characteristics of NTC1 need to be matched with the maximum starting current, normal operating power, and ambient temperature range of the power supply system. Appropriate NTC parameters can ensure surge current suppression while keeping steady-state heat loss within an acceptable range.
[0039] Secondly, embodiments of this application also provide a power module, wherein the power module includes the filtering circuit of any one of the first aspects, and thus has all the beneficial effects of the first aspect of this application.
[0040] The embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this application. Furthermore, unless otherwise specified, the embodiments and features described in the embodiments of this application can be combined with each other.
Claims
1. A filter circuit, characterized in that, include: The first input port and the second input port are used to receive input signals with interference. The first and second output ports are used to output the filtered signal. A common-mode inductor, wherein the second input terminal of the first input terminal of the common-mode inductor is connected to the first input port and the second input port, respectively; A first π-type filter module, wherein the first input terminal of the first π-type filter module is connected to the first output terminal of the common-mode inductor, and the second input terminal of the first π-type filter module is connected to the second output terminal of the common-mode inductor; The second π-type filter module has its first input terminal connected to the first output terminal of the first π-type filter module, its second input terminal connected to the second output terminal of the first π-type filter module, its first output terminal connected to the first output port, and its second output terminal connected to the second output port.
2. The filter circuit according to claim 1, characterized in that, The first π-type filter module includes a first differential-mode capacitor, a first differential-mode inductor, and a second differential-mode capacitor. One end of the first differential-mode capacitor is connected to the first input terminal of the first π-type filter module, and the other end is connected to the second input terminal of the first π-type filter module. One end of the first differential-mode inductor is connected to the second input terminal of the first π-type filter module, and the other end is connected to the second output terminal of the first π-type filter module. One end of the second differential-mode capacitor is connected to the second output terminal of the first π-type filter module, and the other end is connected to the first output terminal of the first π-type filter module. The first input terminal of the first π-type filter module is connected to the first output terminal of the first π-type filter module.
3. The filter circuit according to claim 1, characterized in that, The second π-type filter module includes a second differential-mode capacitor, a second differential-mode inductor, and a third differential-mode inductor. One end of the second differential-mode capacitor is connected to the first input terminal of the second π-type filter module, and the other end is connected to the second input terminal of the second π-type filter module. One end of the second differential-mode inductor is connected to the first input terminal of the second π-type filter module, and the other end is connected to the first output terminal of the second π-type filter module. One end of the third differential-mode inductor is connected to the second input terminal of the second π-type filter module, and the other end is connected to the second output terminal of the second π-type filter module.
4. The filter circuit according to claim 3, characterized in that, The second π-type filter module further includes a first common-mode capacitor and a second common-mode capacitor. One end of the first common-mode capacitor is connected to the first output terminal of the second π-type filter module, and the other end is grounded. One end of the second common-mode capacitor is connected to the second output terminal of the second π-type filter module, and the other end is grounded.
5. The filter circuit according to claim 2, characterized in that, A first resistor is connected in parallel across the first differential capacitor. The first resistor is used to discharge the residual high voltage of the first differential capacitor and suppress the high Q value oscillation of the first π-type filter module.
6. The filtering circuit according to claim 2, characterized in that, A second resistor is connected in parallel across the two ends of the first differential mode inductor. The second resistor is used to suppress the resonant peak value of the first π-type filter module.
7. The filter circuit according to claim 3, characterized in that, A third resistor is connected in parallel across the two ends of the second differential mode inductor. The third resistor is used to suppress the resonant peak value of the second π-type filter module.
8. The filter circuit according to any one of claims 1 to 7, characterized in that, A fuse is connected in series between the first input port and the first input terminal of the common mode inductor.
9. The filter circuit according to any one of claims 1 to 7, characterized in that, A thermistor is connected in series between the second input port and the second input terminal of the common-mode inductor.
10. A power supply module, characterized in that, Includes the filter circuit described in any one of claims 1 to 9.