A switch power input filter protection circuit compatible with G3 carrier and anti-harmonic

Abstract

The application discloses a switch power input filter protection circuit compatible with G3 carrier and anti-harmonic, and belongs to the technical field of power electronic filtering.The switch power input filter protection circuit comprises an AC input terminal, a surge suppression module, a power-on buffer current limiting module, a hierarchical EMI filter module and a rectification and voltage stabilization module; the hierarchical EMI filter module comprises a front X2 safety capacitor, a common mode inductor, an anti-saturation differential mode inductor and a rear X2 safety capacitor; and the AC input terminal, the surge suppression module, the power-on buffer current limiting module, the hierarchical EMI filter module and the rectification and voltage stabilization module are sequentially connected.The switch power input filter protection circuit can realize power grid harmonic impact protection, bidirectional electromagnetic interference suppression and lossless transmission of a carrier signal without increasing complex active devices and without changing a main topology of a power supply, and simultaneously considers low cost and high reliability.

Description

Technical Field

[0001] This invention relates to the field of power electronic filtering technology, and in particular to a switching power supply input filtering protection circuit that is compatible with G3 carrier wave and anti-harmonic. Background Technology

[0002] Currently, a large number of nonlinear, low-quality loads without EMI filtering are connected to civilian low-voltage power distribution networks. Inferior electric vehicle chargers are a typical example. These loads continuously inject low-frequency, high-amplitude harmonics and periodic voltage spikes into the power grid, causing severe distortion of the grid voltage waveform. In switching power supply equipment equipped with G3-PLC power line carrier communication, to suppress high-frequency switching noise from feeding back into the power line and avoid degrading the signal-to-noise ratio of the carrier communication, conventional circuits use a filtering topology with a single-stage X2 safety capacitor connected in series with a differential-mode inductor at the AC input. This topology is simple, can suppress high-frequency switching noise in the MHz band, and is widely used in low-cost civilian carrier power supplies.

[0003] However, the above filtering topology has the following drawbacks:

[0004] 1. Conventional differential mode inductors have low saturation current margin in their magnetic cores. Under continuous excitation by low-frequency harmonics in the power grid, the magnetic core repeatedly experiences local saturation, resulting in severe inductor heating. Long-term operation leads to aging of the enameled wire insulation and burnout due to inter-turn short circuits.

[0005] 2. The instantaneous peak surge of the power grid is directly applied to the two ends of the single-stage X capacitor. The capacitor dielectric is subjected to alternating impact stress for a long time, which makes it very easy for the capacitance to decay, bulge and break down, resulting in a high failure rate of the equipment.

[0006] 3. Conventional filter circuits do not have graded impedance design. To ensure the filtering effect, large-capacity capacitors and large-capacity inductors are usually selected, which causes serious attenuation in the G3 carrier communication frequency band of 20kHz~500kHz, resulting in decreased communication sensitivity and increased packet loss and bit error rate.

[0007] 4. Existing protection solutions mostly involve simply increasing device parameters or adding active filter circuits. The former degrades carrier communication performance, while the latter is costly, bulky, and complex in structure, making it unsuitable for mass production of miniaturized switching power supplies for civilian use.

[0008] In summary, existing conventional filtering topologies struggle to simultaneously address the challenges of protecting harsh power grid components, achieving low-attenuation carrier signal transmission, and facilitating low-cost passive integration. Summary of the Invention

[0009] The purpose of this invention is to solve the problems existing in the prior art and provide a switching power supply input filtering protection circuit that is compatible with G3 carrier and anti-harmonics. It can achieve grid harmonic impulse protection, bidirectional electromagnetic interference suppression and lossless carrier signal transmission without adding complex active devices or changing the main power supply topology, while taking into account low cost and high reliability.

[0010] The objective of this invention is achieved through the following technical solution:

[0011] A switching power supply input filtering protection circuit compatible with G3 carrier and harmonic suppression includes an AC input terminal, a surge suppression module, a power-on buffer current limiting module, a graded EMI filtering module, and a rectification and voltage regulation module. The graded EMI filtering module includes a pre-amplified X2 safety capacitor, a common-mode inductor, an anti-saturation differential-mode inductor, and a post-amplified X2 safety capacitor. The output terminal of the AC input terminal is connected to a live wire and a neutral wire. A varistor is connected in parallel between the live wire and the neutral wire to form a surge suppression module. An NTC thermistor is connected in series on the live wire downstream of the surge suppression module to form a power-on buffer current limiting module. A pre-amplified X2 safety capacitor is connected in parallel between the live wire and the neutral wire downstream of the power-on buffer current limiting module. The live wire and the neutral wire downstream of the pre-amplified X2 safety capacitor are connected in series with the two coils of the common-mode inductor, respectively. An anti-saturation differential-mode inductor is connected in series on the live wire downstream of the common-mode inductor. A post-amplified X2 safety capacitor is connected in parallel between the live wire and the neutral wire downstream of the anti-saturation differential-mode inductor. The live wire and the neutral wire downstream of the post-amplified X2 safety capacitor are connected to the rectification and voltage regulation module.

[0012] Preferably, the varistor is model 14D471K.

[0013] Preferably, the NTC thermistor is model 5D-11, with a nominal resistance of 5Ω at room temperature.

[0014] Preferably, the total capacitance of the front X2 safety capacitor and the rear X2 safety capacitor is ≤0.33μF.

[0015] Preferably, the capacitance of the front X2 safety capacitor is 0.22μF, and the capacitance of the rear X2 safety capacitor is 0.1μF.

[0016] Preferably, the common-mode inductor is manufactured using a dual-wire symmetrical winding process, and the inductance is 10mH~20mH.

[0017] Preferably, the anti-saturation differential mode inductor uses a manganese-zinc high Bs magnetic core with an inductance of 1mH.

[0018] Preferably, when used in a switching power supply with a rated power of 40W, the saturation current of the anti-saturation differential mode inductor is ≥3A.

[0019] The advantages of this invention are:

[0020] 1. Excellent component protection performance: The front protection structure of varistor + NTC thermistor is adopted to weaken the harmonic impact energy of the power grid, eliminate the magnetic saturation phenomenon of differential mode inductor, and reduce the dielectric fatigue loss of X capacitor; after 1000 hours of continuous operation under harsh power grid conditions, the inductor temperature rise does not exceed 12K and the capacitor capacity decay is less than 2%, which greatly extends the service life of the equipment.

[0021] 2. Strong carrier communication compatibility: Adopting a proprietary parameter combination of graded small-capacity capacitors and low-inductance differential-mode inductors, the signal attenuation of the G3 carrier band by filtering components is avoided, improving the communication signal-to-noise ratio by 8dB and reducing the packet loss rate from 4.2% of conventional circuits to 0.3%;

[0022] 3. Bidirectional interference isolation: It can block external harmonic interference from the power grid side and suppress high-frequency noise backflow inside the switching power supply, thus optimizing electromagnetic compatibility performance in both directions and meeting the GB / T17626 national standard for electromagnetic compatibility.

[0023] 4. Low cost and easy mass production: All components are passive and universal, eliminating the need for active control chips. The circuit structure is simple, the PCB area is small, and it is directly compatible with existing carrier switching power supply circuit boards, resulting in a very low increase in mass production costs.

[0024] 5. Wide adaptability to harsh power grids: Specifically adapted to distorted power grids equipped with a large number of inferior electric vehicle chargers, suitable for complex application scenarios such as old residential areas and rural low-voltage power distribution networks. Attached Figure Description

[0025] Figure 1 A schematic diagram of a switching power supply input filter protection circuit compatible with G3 carrier and anti-harmonics provided for embodiments of this specification;

[0026] In the diagram: 1-AC input terminal; 2-surge suppression module; 21-varistor; 3-power-on buffer current limiting module; 31-NTC thermistor; 4-tiered EMI filter module; 41-front-mounted X2 safety capacitor; 42-common-mode inductor; 43-anti-saturation differential-mode inductor; 44-rear-mounted X2 safety capacitor; 5-rectifier and voltage regulator module. Detailed Implementation

[0027] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0028] like Figure 1As shown, this embodiment provides a switching power supply input filtering protection circuit compatible with G3 carrier and harmonic suppression, including an AC input terminal 1, a surge suppression module 2, a power-on buffer current limiting module 3, a graded EMI filter module 4, and a rectification and voltage regulation module 5; the graded EMI filter module 4 includes a pre-amplified X2 safety capacitor 41, a common-mode inductor 42, an anti-saturation differential-mode inductor 43, and a post-amplified X2 safety capacitor 44; the output terminal of the AC input terminal 1 is connected to a live wire 11 and a neutral wire 12, and a varistor 21 is connected in parallel between the live wire 11 and the neutral wire 12 to form the surge suppression module 2, and an NTC thermocouple is connected in series on the live wire 11 downstream of the surge suppression module 2. A sensitive resistor 31 forms a power-on buffer current limiting module 3. A pre-amplified X2 safety capacitor 41 is connected in parallel between the live wire 11 and the neutral wire 12 downstream of the power-on buffer current limiting module 3. The live wire 11 and the neutral wire 12 downstream of the pre-amplified X2 safety capacitor 41 are connected in series with the two coils of the common mode inductor 42, respectively. An anti-saturation differential mode inductor 43 is connected in series on the live wire 11 downstream of the common mode inductor 42. A post-amplified X2 safety capacitor 44 is connected in parallel between the live wire 11 and the neutral wire 12 downstream of the anti-saturation differential mode inductor 43. The live wire 11 and the neutral wire 12 downstream of the post-amplified X2 safety capacitor 44 are connected to the rectifier and voltage regulator module 5. The output terminal of the rectifier and voltage regulator module 5 is used to connect to the main conversion circuit of the switching power supply.

[0029] Specifically, this embodiment applies to a G3 power line carrier switching power supply with a rated AC220V input and a rated power of 40W. The specific component selection is as follows: Varistor 21 is model 14D471K, with AC operating voltage matching the 220V residential power grid, used to quickly absorb instantaneous high-voltage spikes. NTC thermistor 31 is model 5D-11, with a nominal resistance of 5Ω at room temperature, used to suppress power-on inrush current and harmonic peak current. The front-mounted X2 safety capacitor 41 has a capacitance of 0.22μF / 275VAC, and the rear-mounted X2 safety capacitor 44 has a capacitance of 0.1μF / 275VAC, arranged in a two-stage configuration with a total capacitance ≤0.33μF. The common-mode inductor 42 uses a double-wire symmetrical parallel winding process, with a copper wire diameter of 0.35mm and an inductance of 10mH~20mH, specifically 15mH in this embodiment, used to suppress common-mode harmonic interference from the power grid. The anti-saturation differential mode inductor 43 uses a manganese-zinc high-Bs magnetic core with an inductance of 1mH. When used in a 40W rated power switching power supply, the saturation current of the anti-saturation differential mode inductor 43 is ≥3A. The rectifier and voltage regulator module 5 uses KBPC1010.

[0030] In this embodiment, the circuit is connected sequentially along the AC power transmission direction and integrated into the EMI filtering area of ​​the switching power supply input, eliminating the need for additional auxiliary circuits.

[0031] As described above, the main working principle of this embodiment is as follows:

[0032] High-voltage surge discharge: The instantaneous high-voltage spikes generated by poor nonlinear loads in the power grid are quickly clamped by the front-end varistor, limiting the abnormal high voltage within the safe threshold and preventing the high-voltage pulse from directly impacting the downstream capacitive and inductive components;

[0033] Peak current suppression: NTC thermistors dampen and suppress grid harmonic peak currents and instantaneous surge currents upon power-on, reducing instantaneous electrical stress on inductors and capacitors and preventing instantaneous saturation of differential mode inductor cores;

[0034] Hierarchical electromagnetic filtering: The front-side X capacitor filters out high-frequency differential-mode interference from the mains side, the common-mode inductor blocks low-frequency common-mode harmonics, the anti-saturation differential-mode inductor specifically absorbs high-frequency switching noise generated by the switching power supply itself to prevent noise backflow into the mains and interfere with the carrier wave, and the rear-side X capacitor smooths the voltage ripple at the rectified input terminal.

[0035] Carrier compatibility adaptation: By limiting the total capacitance of the two-stage X capacitors and fixing the low inductance parameter of the differential mode inductor, the impedance of the G3 carrier communication frequency band from 20kHz to 500kHz is strictly controllable, the carrier signal transmission attenuation is less than 0.5dB, and the communication sensitivity is lossless.

[0036] A harsh simulated power grid was constructed, and six unfiltered, substandard electric bicycle chargers were connected in parallel for a long-term aging test.

[0037] 1. Temperature performance: The maximum temperature rise of the differential mode inductor in a conventional single-stage filter circuit is 48K, while the maximum temperature rise of the inductor in this embodiment is 11K, with no heat saturation phenomenon.

[0038] 2. Component reliability: In conventional circuits, the X capacitor experiences an average capacitance decrease of 16.5% after 1000 hours of aging, and bulging occurs. In this embodiment, the capacitor's maximum capacitance decrease is 1.8%, and there are no abnormalities in appearance.

[0039] 3. Communication performance: The G3 carrier signal receiving sensitivity has no attenuation, and the demodulation bit error rate is ≤0.3%, which is far superior to conventional circuits;

[0040] 4. Electromagnetic compatibility: Conducted interference and radiated interference both meet the testing standards for civil power line carrier equipment.

[0041] The above are merely preferred embodiments of the present invention, and are implementations based on the overall concept of the present invention. Furthermore, the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A switching power supply input filter protection circuit compatible with G3 carrier wave and harmonic suppression, characterized in that, The system includes an AC input terminal, a surge suppression module, a power-on buffer current limiting module, a tiered EMI filter module, and a rectification and voltage regulation module. The tiered EMI filter module includes a pre-amplified X2 safety capacitor, a common-mode inductor, an anti-saturation differential-mode inductor, and a post-amplified X2 safety capacitor. The output terminal of the AC input terminal is connected to a live wire and a neutral wire. A varistor is connected in parallel between the live wire and the neutral wire to form a surge suppression module. An NTC thermistor is connected in series on the live wire downstream of the surge suppression module to form a power-on buffer current limiting module. A pre-amplified X2 safety capacitor is connected in parallel between the live wire and the neutral wire downstream of the power-on buffer current limiting module. The live wire and the neutral wire downstream of the pre-amplified X2 safety capacitor are connected in series with the two coils of the common-mode inductor, respectively. An anti-saturation differential-mode inductor is connected in series on the live wire downstream of the common-mode inductor. A post-amplified X2 safety capacitor is connected in parallel between the live wire and the neutral wire downstream of the anti-saturation differential-mode inductor. The live wire and the neutral wire downstream of the post-amplified X2 safety capacitor are connected to the rectification and voltage regulation module.

2. The switching power supply input filtering protection circuit compatible with G3 carrier and harmonic suppression according to claim 1, characterized in that, The varistor is model 14D471K.

3. The switching power supply input filtering protection circuit compatible with G3 carrier and harmonic suppression according to claim 1, characterized in that, The NTC thermistor is model 5D-11, with a nominal resistance of 5Ω at room temperature.

4. The switching power supply input filter protection circuit compatible with G3 carrier and harmonic suppression according to claim 1, characterized in that, The total capacitance of the front X2 safety capacitor and the rear X2 safety capacitor is ≤0.33μF.

5. The switching power supply input filtering protection circuit compatible with G3 carrier and harmonic suppression according to claim 1, characterized in that, The capacitance of the front X2 safety capacitor is 0.22μF, and the capacitance of the rear X2 safety capacitor is 0.1μF.

6. The switching power supply input filtering protection circuit compatible with G3 carrier and harmonic suppression according to claim 1, characterized in that, The common-mode inductor is manufactured using a dual-wire symmetrical winding process, with an inductance of 10mH to 20mH.

7. The switching power supply input filtering protection circuit compatible with G3 carrier and harmonic suppression according to claim 1, characterized in that, The anti-saturation differential mode inductor uses a manganese-zinc high Bs magnetic core and has an inductance of 1mH.

8. The switching power supply input filtering protection circuit compatible with G3 carrier and harmonic suppression according to claim 1, characterized in that, When used in a switching power supply with a rated power of 40W, the saturation current of the anti-saturation differential mode inductor is ≥3A.

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