An electromagnetic interference filter circuit and PD charger

Abstract

The application relates to the technical field of electromagnetic interference filtering, in particular to an electromagnetic interference filtering circuit and a PD charger. The circuit comprises an input processing module, an input end of the input processing module receiving an original input signal, and an output end of the input processing module being connected with a first input end of a primary winding unit; an input end of a first secondary winding unit being electrically connected with an output end of the primary winding unit, the first secondary winding unit being provided with a shielding layer for inhibiting a first interference frequency band, and the first secondary winding unit being provided with a first patch capacitor for inhibiting a second interference frequency band; an output end of the first secondary winding unit being connected with an input end of an output adjusting module, an output end of the output adjusting module being connected with a second input end of the primary winding unit to adjust an output signal of the primary winding unit, and a connection position of the output adjusting module and the primary winding unit being provided with a second patch capacitor for inhibiting a third interference frequency band. The application can realize the beneficial effects of miniaturization and low cost.

Description

Technical Field

[0001] This application relates to the technical field of electromagnetic interference filtering, and in particular to an electromagnetic interference filtering circuit and a PD charger. Background Technology

[0002] In the field of power supply design for electronic devices, especially in switching power supplies with power ratings such as PD30W and PD35W, EMI (Electromagnetic Interference) is one of the key indicators for ensuring product compliance with industry standards and market access requirements. To suppress electromagnetic interference generated during power supply operation, ensure stable circuit operation in complex electromagnetic environments, and avoid interference with other devices, a dedicated EMI filtering stage is typically required in the circuit. In existing technologies, conventional solutions for achieving EMI filtering generally rely on adding a common-mode inductor to the circuit. The common-mode inductor, through its inductive characteristics, impedes common-mode interference signals, thereby suppressing interference; this is a widely adopted and mature technology in the industry.

[0003] However, the use of common-mode inductors has significant technical drawbacks. First, common-mode inductors themselves have a certain size and weight, which increases the overall size of the power supply product, hindering the development of miniaturized and thinner devices, and also restricting the space for internal circuit layout. Second, as an independent component, the procurement and assembly costs of common-mode inductors directly increase the overall production cost of the power supply product. Furthermore, the presence of common-mode inductors makes it difficult to further improve the power density of the circuit. These problems are particularly prominent in applications with high requirements for space, cost, and performance. Utility Model Content

[0004] To overcome the shortcomings of the prior art, this application provides an electromagnetic interference filtering circuit and a PD charger. By optimizing the circuit design, it overcomes the dependence on common-mode inductors in traditional solutions, thereby achieving the beneficial effects of miniaturization and low cost.

[0005] The technical solution adopted by this application to solve its technical problem is: In a first aspect, this application provides an electromagnetic interference filtering circuit, the circuit comprising: an input processing module, a transformer module, an output adjustment module, and an output processing module; the transformer module comprising a primary winding unit, a first-stage winding unit, and a second-stage winding unit; The input terminal of the input processing module is connected to an external DC signal source to receive the original input signal, and the output terminal is connected to the first input terminal of the primary winding unit. The input terminal of the first primary winding unit is electrically connected to the output terminal of the primary winding unit. The first primary winding unit is provided with a shielding layer for suppressing the first interference frequency band, and the first primary winding unit is provided with a first patch capacitor for suppressing the second interference frequency band. The output terminal of the primary winding unit is connected to the input terminal of the output adjustment module, and the output terminal of the output adjustment module is connected to the second input terminal of the primary winding unit to adjust the output signal of the primary winding unit. A second patch capacitor for suppressing the third interference frequency band is provided at the connection between the output adjustment module and the primary winding unit. The input terminal of the second-stage winding unit is electrically connected to the output terminal of the primary winding unit, the output terminal of the second-stage winding unit is connected to the input terminal of the output processing module, and the output terminal of the output processing module is connected to an external load.

[0006] Optionally, the shielding layer has 12 layers to suppress radiated interference signals from 0 to 50 MHz.

[0007] Optionally, the input processing module includes: The input protection unit is equipped with a thermistor and a fuse. The input terminal of the input protection unit is connected to the DC signal source. The thermistor and the fuse prevent overcurrent and overheating caused by the original input signal. A rectifier and filter unit, wherein the input terminal of the rectifier and filter unit is connected to the output terminal of the input protection unit, and the output terminal of the rectifier and filter unit is connected to the first input terminal of the primary winding unit.

[0008] Optionally, the rectifier and filter unit includes a bridge rectifier of model Z4RGP30MPH.

[0009] Optionally, the primary winding unit includes a spike absorption component and a primary winding; the transformer module includes a transformer, wherein the primary coil of the transformer is the primary winding; The input terminal of the spike absorption component is connected to the output terminal of the rectifier filter unit, and the output terminal of the spike absorption component is connected to the first terminal of the primary winding.

[0010] Optionally, the primary winding unit includes a primary winding and a voltage protection component; The first patch capacitor is connected in parallel to both ends of the first primary winding to suppress radiated interference signals of 100 to 200 MHz. The output terminal of the primary winding is connected to the input terminal of the voltage protection component, and the output terminal of the voltage protection component is connected to the input terminal of the output adjustment module.

[0011] Optionally, the output adjustment module includes a control chip of model SCV3052C; The power supply terminal of the control chip is connected to the output terminal of the rectifier and filter unit; The feedback terminal of the control chip is connected to the output terminal of an external voltage feedback circuit, and the input terminal of the voltage feedback circuit is connected to the output terminal of the output processing module. The zero-detection terminal of the control chip is connected to the output terminal of the voltage protection component; The output terminal of the control chip is connected to the second terminal of the primary winding.

[0012] Optionally, the connection point between the control chip and the primary winding is connected to one end of the second surface-mount capacitor; The other end of the second patch capacitor is grounded to suppress radiated interference signals from 50 to 100 MHz.

[0013] Secondly, this application provides a PD charger equipped with the aforementioned electromagnetic interference filtering circuit.

[0014] The working principle of this application is as follows: The input processing module receives the raw input signal from an external DC signal source, performs preliminary filtering and noise suppression, and then transmits the signal to the primary winding unit of the transformer module. The primary winding unit performs preliminary voltage transformation and electrical isolation on the signal, and its output terminal is connected to the first primary winding unit. The first primary winding unit further processes the signal, and the signal processed by the first primary winding unit is sent to the output adjustment module. The output adjustment module processes the signal to obtain an adjustment signal to adjust the output of the primary winding unit. In this case, the adjusted primary winding unit transmits the signal to the second primary winding unit through isolation, and the output processing module transmits the output signal to the external load device.

[0015] The beneficial effects of this application are: the primary winding unit suppresses conducted and radiated interference in the 0-50MHz frequency band by setting a specific shielding layer, and absorbs auxiliary power supply interference by the first patch capacitor, suppressing radiated signals in the 100-200MHz frequency band; in addition, after receiving the output signal of the primary winding unit, the output adjustment module eliminates the 50-100MHz interference signal generated by the MOSFET switch by the second patch capacitor at the connection point with the primary winding unit.

[0016] In summary, this application achieves full-band interference suppression from 0-200MHz through optimized design of surface-mount capacitors and shielding layers, replacing the function of traditional common-mode inductors, significantly reducing circuit space and cost, while avoiding the circuit layout limitations caused by common-mode inductors, thereby improving power density. Attached Figure Description

[0017] Figure 1This is a schematic diagram of the module connection of the electromagnetic interference filtering circuit provided in the embodiments of this application; Figure 2 This is a schematic diagram of the unit connections of the electromagnetic interference filtering circuit provided in the embodiments of this application; Figure 3 This is a schematic diagram of the electromagnetic interference filtering circuit provided in the embodiments of this application.

[0018] Figure label: T1A, primary winding; T1B, first primary winding; C7, first surface mount capacitor; C8, second surface mount capacitor; U2, control chip. Detailed Implementation

[0019] The present application will be further described below with reference to the accompanying drawings and embodiments.

[0020] The following will clearly and completely describe the concept, specific structure, and resulting technical effects of this application in conjunction with embodiments and accompanying drawings, so as to fully understand the purpose, features, and effects of this application. Obviously, the described embodiments are only a part of the embodiments of this application, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are all within the scope of protection of this application. Furthermore, all connections / linkages involved in the patent do not simply refer to direct contact between components, but rather to the ability to form a better connection structure by adding or reducing connecting accessories according to specific implementation conditions. The various technical features in this application can be combined interactively without contradicting each other.

[0021] Reference Figure 1 , Figure 1 This is a schematic diagram of the electromagnetic interference filtering circuit provided in an embodiment of this application. Several key modules involved in the circuit design include: an input processing module, a transformer module, an output adjustment module, and an output processing module. The transformer module includes a primary winding unit, a first-stage winding unit, and a second-stage winding unit, which are described in detail below: Regarding the input processing module, the input terminal of the input processing module is connected to an external DC signal source to receive the original input signal, and the output terminal is connected to the first input terminal of the primary winding unit.

[0022] Specifically, the input processing module is a functional module in the circuit used to receive and preliminarily process external input signals. Its input terminal is connected to an external DC signal source that provides DC power to obtain the unprocessed raw input signal. The output terminal of this module is connected to the first input terminal of the primary winding unit in the transformer module, transmitting the processed signal to the primary winding unit. This design ensures that the raw input signal undergoes necessary preprocessing before entering the transformer module.

[0023] More specifically, refer to Figure 2 , Figure 3 , Figure 2 This is a schematic diagram of the unit connections of the electromagnetic interference filtering circuit provided in this embodiment, showing several key units involved in the circuit module provided in this embodiment. It can be seen that the input processing module includes: The input protection unit is equipped with a thermistor and a fuse. The input terminal of the input protection unit is connected to the DC signal source. The thermistor and the fuse prevent overcurrent and overheating caused by the original input signal. A rectifier and filter unit, wherein the input terminal of the rectifier and filter unit is connected to the output terminal of the input protection unit, and the output terminal of the rectifier and filter unit is connected to the first input terminal of the primary winding unit.

[0024] Among them, the input protection unit is used to prevent abnormal input signals from damaging the circuit; the thermistor is a component whose resistance value changes with temperature; the fuse is a safety component that melts to cut off the circuit when the current is abnormally high; the DC signal source is a power supply device that provides DC power; and the rectification and filtering unit is a functional unit that rectifies and filters the input signal.

[0025] Specifically, the input processing module includes an input protection unit and a rectification and filtering unit. The input protection unit is equipped with a thermistor and a fuse, and its input terminal is connected to a DC signal source. The thermistor and fuse prevent overcurrent and overheating caused by the original input signal, so as to quickly cut off or limit the current when the input signal is overcurrent or overheating, and prevent abnormal signals from damaging subsequent circuit components.

[0026] Specifically, the input terminal of the rectifier and filter unit is connected to the output terminal of the input protection unit, and its output terminal is connected to the first input terminal of the primary winding unit. After receiving the protected signal, the rectifier and filter unit performs rectification and filtering to remove AC components and interference from the signal, and outputs a stable DC signal to the primary winding unit, ensuring that the signal input to the primary winding unit meets the operating requirements and improving the overall safety and stability of the circuit.

[0027] More specifically, the rectifier and filter unit includes a bridge rectifier of model Z4RGP30MPH.

[0028] Regarding the transformer module, the winding in the transformer module refers to the coil structure inside the transformer used for electromagnetic induction. Voltage transformation and energy transfer are achieved through the turns ratio of the winding. It includes a primary winding unit, a first-stage winding unit, and a second-stage winding unit, with each unit corresponding to an independent winding.

[0029] Regarding the primary winding unit, the winding of the primary winding unit receives preprocessed signals from the input processing module to achieve voltage transformation and electrical isolation; Specifically, the primary winding unit includes a spike absorption component and a primary winding T1A; the transformer module includes a transformer, and the primary coil of the transformer is the primary winding T1A; The input terminal of the spike absorption component is connected to the output terminal of the rectifier filter unit, and the output terminal of the spike absorption component is connected to the first terminal of the primary winding T1A.

[0030] Specifically, the primary winding unit consists of a spike absorption component and a primary winding T1A. The spike absorption component includes a capacitor and a resistor that are grounded and connected in parallel to ground. The transformer module contains a transformer, and the primary coil of this transformer is the primary winding T1A. The input terminal of the spike absorption component is connected to the output terminal of the rectifier and filter unit, and its output terminal is connected to the first terminal of the primary winding T1A. Through the connection between the spike absorption component and the primary winding T1A, the signal output from the rectifier and filter unit is first processed by the spike absorption component before being transmitted to the primary winding T1A, which serves as the primary coil of the transformer. This effectively absorbs spike signals in the circuit, preventing spike signals from affecting the primary coil of the transformer, ensuring the stability of the transformer's operation, and reducing interference from spike signals to subsequent circuits, thereby improving the overall signal transmission quality of the circuit.

[0031] Regarding the first-stage winding unit, the winding of the first-stage winding unit is connected to the output terminal of the primary winding unit, and together with the shielding layer and surface-mount capacitor, it suppresses electromagnetic interference in a specific frequency band. Specifically, the input terminal of the first-stage winding unit is electrically connected to the output terminal of the primary winding unit. The first-stage winding unit is provided with a shielding layer for suppressing a first interference frequency band, and the first-stage winding unit is provided with a first surface-mount capacitor C7 for suppressing a second interference frequency band.

[0032] Specifically, the input terminal of the primary winding unit and the output terminal of the primary winding unit are connected by a circuit to transmit electrical signals. This unit is equipped with a shielding layer and a first surface-mount capacitor C7. The shielding layer is used to suppress interference in a specific range of first interference frequency bands, while the first surface-mount capacitor C7 targets interference in a second interference frequency band of another range.

[0033] The first interference band consists of radiated interference signals from 0 to 50 MHz, and the second interference band consists of radiated interference signals from 100 to 200 MHz.

[0034] More specifically, embodiments of this application propose that the shielding layer has 12 layers to suppress radiated interference signals from 0 to 50 MHz.

[0035] The number of turns refers to the number of turns of the shielding layer wound on the transformer, which is a parameter for measuring the physical structure of the shielding layer.

[0036] Specifically, the shielding layer has 12 turns, and its main function is to suppress radiated interference signals in the frequency range of 0 to 50 MHz. By increasing the number of turns from 6 to 12, the inductance of the shielding layer changes. This is because, according to Faraday's law of electromagnetic induction, the inductance of a coil is directly proportional to the number of turns; as the number of turns increases, the inductance increases accordingly. The main function of the transformer shielding layer is to generate a magnetic field through induced current to counteract the interference magnetic field generated when the transformer is operating. When the number of turns in the shielding layer increases, leading to an increase in inductance, the shielding layer can generate a greater inductive reactance at the same frequency. This allows the shielding layer to more effectively induce current, thereby generating a stronger magnetic field to counteract the interference magnetic field, thus enhancing the shielding effect.

[0037] By increasing the number of turns in the shielding layer and adjusting its inductance, the shielding layer can more effectively induce a current in the opposite direction to the interfering magnetic field within this frequency band, thereby generating a canceling magnetic field. This canceling effect can significantly reduce conducted and radiated interference generated during transformer operation, enabling the optimized EMI filter circuit to meet the EMI performance requirements for certification without using a common-mode inductor.

[0038] More specifically, refer to Figure 2 , Figure 3 The primary winding unit includes a primary winding T1B and a voltage protection component; The first patch capacitor C7 is connected in parallel across the two ends of the first primary winding T1B to suppress radiated interference signals of 100 to 200 MHz. The output terminal of the primary winding T1B is connected to the input terminal of the voltage protection component, and the output terminal of the voltage protection component is connected to the input terminal of the output adjustment module.

[0039] Specifically, by connecting a first surface-mount capacitor C7 in parallel across the primary winding T1B, when radiated interference exists in the circuit at this frequency, the first surface-mount capacitor C7 will present a low impedance, guiding the interference signal to the ground terminal. This prevents the interference signal from radiating outward through the primary winding T1B or entering subsequent circuits, thereby specifically suppressing radiated interference signals in the 100 to 200 MHz frequency band and reducing the impact of this frequency band interference on the circuit. After receiving the signal output from the primary winding T1B, the voltage protection component performs voltage protection processing on the signal before transmitting the processed signal to the output adjustment module. This ensures that the signal voltage input to the output adjustment module is within a safe range, improving the accuracy of signal detection and the overall stability of the circuit.

[0040] Regarding the output adjustment module, the output terminal of the primary winding unit is connected to the input terminal of the output adjustment module, and the output terminal of the output adjustment module is connected to the second input terminal of the primary winding unit to adjust the output signal of the primary winding unit. A second surface-mount capacitor C8 for suppressing the third interference frequency band is provided at the connection between the output adjustment module and the primary winding unit.

[0041] Specifically, the output terminal of the primary winding unit is connected to the input terminal of the output adjustment module, transmitting the processed signal to the output adjustment module; the output terminal of the output adjustment module is connected to the second input terminal of the primary winding unit, forming a feedback loop to dynamically adjust the output signal of the primary winding unit. Along the connection path between the output adjustment module and the primary winding unit, the second surface-mount capacitor C8 is used to suppress electromagnetic interference in the third interference frequency band.

[0042] The third interference band consists of radiated interference signals in the 50 to 100 MHz frequency range.

[0043] The output adjustment module contains a control chip U2, which integrates PWM, comparator, sampler, oscillator, reference voltage generator and power switch. These components work together to complete functions such as signal sampling, comparison, reference voltage provision, timing control and power regulation.

[0044] More specifically, refer to Figure 2 , Figure 3 The output adjustment module includes a control chip U2 with model number SCV3052C; The power supply terminal of the control chip U2 is connected to the output terminal of the rectifier and filter unit; The feedback terminal of the control chip U2 is connected to the output terminal of an external voltage feedback circuit, and the input terminal of the voltage feedback circuit is connected to the output terminal of the output processing module. The zero-detection terminal of the control chip U2 is connected to the output terminal of the voltage protection component; The output terminal of the control chip U2 is connected to the second terminal of the primary winding T1A.

[0045] Specifically, the control chip U2, model SCV3052C, obtains operating power from the rectifier and filter unit through the power supply terminal, receives voltage feedback signals from the output processing module through the voltage feedback circuit, and receives signals from the voltage protection component through the zero detection terminal. After combining this information, it controls the primary winding T1A through the output terminal to realize real-time monitoring and adjustment of the circuit status.

[0046] More specifically, at the connection point between the control chip U2 and the primary winding T1A, one end of the second surface-mount capacitor C8 is connected; The other end of the second patch capacitor C8 is grounded to suppress radiated interference signals from 50 to 100 MHz.

[0047] Specifically, by connecting one end of the second surface-mount capacitor C8 to the connection point between the control chip U2 and the primary winding T1A, and grounding the other end, the capacitor's suppression characteristics for specific frequency band signals are utilized to attenuate radiated interference signals in the 50 to 100 MHz frequency band. The grounded capacitor can guide the interference signals in this frequency band to ground, reducing the impact of interference signals on the transmission path between the control chip U2 and the primary winding T1A. This prevents interference signals from interfering with the normal operation of the control chip U2 and the signal transmission of the primary winding T1A, further improving the circuit's anti-interference capability and signal transmission stability.

[0048] Regarding the output processing module, the input terminal of the secondary winding unit is electrically connected to the output terminal of the primary winding unit, the output terminal of the secondary winding unit is connected to the input terminal of the output processing module, and the output terminal of the output processing module is connected to an external load.

[0049] Specifically, the output processing module contains rectifier and filter devices, which are functional modules that perform final processing on the circuit output signal to adapt to the requirements of external devices. External load refers to the terminal equipment or system powered by the circuit.

[0050] Secondly, this application provides a PD charger equipped with the aforementioned electromagnetic interference filtering circuit.

[0051] The above is a detailed description of the preferred embodiments of this application. However, the invention of this application is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of this application. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. An electromagnetic interference filtering circuit, characterized in that, The circuit includes: an input processing module, a transformer module, an output adjustment module, and an output processing module; the transformer module includes a primary winding unit, a first-stage winding unit, and a second-stage winding unit; The input terminal of the input processing module is connected to an external DC signal source to receive the original input signal, and the output terminal is connected to the first input terminal of the primary winding unit. The input terminal of the first primary winding unit is electrically connected to the output terminal of the primary winding unit. The first primary winding unit is provided with a shielding layer for suppressing the first interference frequency band, and the first primary winding unit is provided with a first patch capacitor for suppressing the second interference frequency band. The output terminal of the primary winding unit is connected to the input terminal of the output adjustment module, and the output terminal of the output adjustment module is connected to the second input terminal of the primary winding unit to adjust the output signal of the primary winding unit. A second patch capacitor for suppressing the third interference frequency band is provided at the connection between the output adjustment module and the primary winding unit. The input terminal of the second-stage winding unit is electrically connected to the output terminal of the primary winding unit, the output terminal of the second-stage winding unit is connected to the input terminal of the output processing module, and the output terminal of the output processing module is connected to an external load.

2. The electromagnetic interference filtering circuit according to claim 1, characterized in that, The shielding layer has 12 layers and is used to suppress radiated interference signals from 0 to 50 MHz.

3. The electromagnetic interference filtering circuit according to claim 1, characterized in that, The input processing module includes: The input protection unit is equipped with a thermistor and a fuse. The input terminal of the input protection unit is connected to the DC signal source. The thermistor and the fuse prevent overcurrent and overheating caused by the original input signal. A rectifier and filter unit, wherein the input terminal of the rectifier and filter unit is connected to the output terminal of the input protection unit, and the output terminal of the rectifier and filter unit is connected to the first input terminal of the primary winding unit.

4. The electromagnetic interference filtering circuit according to claim 3, characterized in that, The rectifier and filter unit includes a bridge rectifier of model Z4RGP30MPH.

5. The electromagnetic interference filtering circuit according to claim 3, characterized in that, The primary winding unit includes a spike absorption component and a primary winding; the transformer module includes a transformer, and the primary coil of the transformer is the primary winding. The input terminal of the spike absorption component is connected to the output terminal of the rectifier filter unit, and the output terminal of the spike absorption component is connected to the first terminal of the primary winding.

6. The electromagnetic interference filtering circuit according to claim 5, characterized in that, The primary winding unit includes a primary winding and a voltage protection component; The first patch capacitor is connected in parallel to both ends of the first primary winding to suppress radiated interference signals of 100 to 200 MHz. The output terminal of the primary winding is connected to the input terminal of the voltage protection component, and the output terminal of the voltage protection component is connected to the input terminal of the output adjustment module.

7. The electromagnetic interference filtering circuit according to claim 6, characterized in that, The output adjustment module includes a control chip of model SCV3052C; The power supply terminal of the control chip is connected to the output terminal of the rectifier and filter unit; The feedback terminal of the control chip is connected to the output terminal of an external voltage feedback circuit, and the input terminal of the voltage feedback circuit is connected to the output terminal of the output processing module. The zero-detection terminal of the control chip is connected to the output terminal of the voltage protection component; The output of the control chip is connected to the second end of the primary winding.

8. The electromagnetic interference filtering circuit according to claim 7, characterized in that, The connection point between the control chip and the primary winding is connected to one end of the second surface-mount capacitor. The other end of the second patch capacitor is grounded to suppress radiated interference signals from 50 to 100 MHz.

9. A PD charger, characterized in that, It is equipped with an electromagnetic interference filtering circuit as described in any one of claims 1-8.

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