DC fan EMI test improvement circuit

Abstract

The utility model relates to the technical field of EMI (Electro-Magnetic Interference) suppression, in particular to a DC (Direct Current) fan EMI test improvement circuit, which adopts a three-phase inverter bridge and consists of a high-end switch and a low-end switch, the high-end switch and the low-end switch are alternately conducted through PWM (Pulse-Width Modulation) control, an AC voltage is formed at a motor end, however, the action of the high-speed switch can cause high-frequency common-mode noise and influence the electromagnetic compatibility, and the electromagnetic compatibility is influenced. In order to suppress EMI (Electro-Magnetic Interference), a single common-mode inductor is connected to the middle point of each inverter bridge arm of the circuit, the common-mode inductor is provided with a plurality of taps and is used for converging common-mode noise of each bridge arm, the noise is grounded through high-frequency filter capacitors connected in parallel to form a common-mode low-pass filter, and high-frequency interference is effectively reduced; according to the circuit, direct insertion type connection is achieved through one male interface and one female interface, assembling convenience is improved, on the premise that no extra winding technology is added, an EMI suppression scheme is optimized, and stability and production efficiency of a system are improved.

Description

Technical Field

[0001] This utility model relates to the field of electromagnetic interference (EMI) suppression technology, and in particular to an EMI testing improvement circuit for DC fans. Background Technology

[0002] In brushless DC motor applications, the inverter circuit converts direct current (DC) to alternating current (AC) via high-speed switching to drive the motor. However, the presence of high-frequency PWM control generates significant high-frequency common-mode noise during the inverter process, leading to severe electromagnetic interference (EMI) problems. During EMI testing, this high-frequency interference may exceed standard limits, affecting the system's electromagnetic compatibility performance.

[0003] In existing technologies, to address high-frequency EMI interference from inverters, a common approach is to wind several turns of the motor's three-phase wires and then fit a large-sized magnetic ring around them to suppress common-mode noise. However, this method has the following problems: First, adding an extra magnetic ring and winding process to the motor side complicates manufacturing and assembly, increasing both production time and costs. Second, the large size of the magnetic ring can restrict installation within limited equipment space, hindering structural optimization. Furthermore, the filtering effect of this method is significantly affected by the winding method and the performance of the magnetic ring, making it impossible to achieve precise and stable common-mode noise suppression, resulting in low reliability of EMI mitigation.

[0004] Therefore, there is an urgent need for a technical solution that can effectively suppress high-frequency common-mode noise at the inverter circuit end, simplify the manufacturing process, reduce costs, and improve the EMI test pass rate, so as to optimize the electromagnetic compatibility performance of DC fans. Utility Model Content

[0005] The purpose of this invention is to provide an EMI testing improvement circuit for DC fans to solve the problems mentioned in the background art.

[0006] To solve the above-mentioned technical problems, this utility model provides the following technical solution: a DC fan EMI test improvement circuit, including a DC voltage VM, high-side switches K1, K3, K5, low-side switches K2, K4, K6, high-frequency filter capacitors C1-C3, and motor terminal M, characterized in that: the DC voltage VM is directly connected to the high-side switches K1, K3, and K5 respectively, and the low-side switches K2, K4, and K6 are respectively connected to the DC negative terminal.

[0007] According to the above technical solution, the high-end switches K1, K3, K5 and the low-end switches K2, K4, K6 form a three-phase inverter bridge. The midpoint of each bridge arm, between K1 and K2, between K3 and K4, and between K5 and K6, is connected to the tap of the common-mode inductor LC.

[0008] According to the above technical solution, the common mode inductor LC is a single inductor device with taps 1, 3, and 5, which are used to collect the common mode noise of each bridge arm.

[0009] According to the above technical solution, the output terminal of the common-mode inductor LC is connected to the parallel high-frequency filter capacitors C1, C2, and C3, and grounded through the high-frequency filter capacitors C1, C2, and C3 to form a common-mode low-pass filter to reduce high-frequency EMI interference.

[0010] According to the above technical solution, the high-frequency filter capacitors C1, C2, and C3 are connected in parallel and are respectively connected to the output terminal of the common-mode inductor LC.

[0011] According to the above technical solution, the circuit also includes multiple connection terminals and connectors. The terminals marked as 2, 4, and 6 correspond to the motor terminal M and are directly connected by plugging and unplugging through a male and female interface.

[0012] According to the above technical solution, the connection terminals 2, 4, and 6 are used to transmit the AC voltage output by the three-phase inverter bridge to the motor terminal M to realize the driving of the DC fan.

[0013] According to the above technical solution, the circuit uses a PWM control signal to enable the high-end switch and the low-end switch to conduct at high speed alternately, so as to realize the conversion of DC voltage to AC voltage, while effectively suppressing high-frequency electromagnetic interference caused by switching action.

[0014] Compared with the prior art, the beneficial effects achieved by this utility model are:

[0015] 1. Effectively suppress EMI interference: By introducing a single common-mode inductor LC at the midpoint of each arm of the three-phase inverter bridge and setting multiple taps (1, 3, 5) on it, the common-mode noise of each arm is collected and grounded through high-frequency filter capacitors (C1-C3), forming a common-mode low-pass filter, which effectively reduces high-frequency electromagnetic interference and enables the DC fan to pass the EMI test smoothly.

[0016] 2. Simplified manufacturing and assembly process: Compared with traditional methods (such as winding magnetic rings on the three-phase lines of the motor to reduce EMI), this application directly optimizes the common mode noise suppression structure in the inverter bridge, avoiding additional coil winding and magnetic ring installation, reducing production complexity, improving assembly efficiency, and reducing manufacturing costs.

[0017] 3. Improve the stability of the motor system: The use of a common-mode filter network eliminates high-frequency noise, making the motor run more stably, reducing control abnormalities or signal interference caused by EMI problems, and improving system reliability;

[0018] 4. Optimized electrical connection method: Terminal connectors (2, 4, 6) are used, which allow the motor side to be directly plugged in through a male and female interface, avoiding the contact problems that may exist in traditional wiring methods, improving the stability of electrical connection, and simplifying the maintenance and replacement process. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the present invention and form part of the specification. They are used together with the embodiments of the present invention to explain the present invention, but do not constitute a limitation thereof. In the drawings:

[0020] Figure 1 This is a schematic diagram of the DC fan EMI test improvement circuit proposed in this utility model;

[0021] Figure 2 This is a diagram of the common-mode inductor LC structure in the DC fan EMI test improvement circuit proposed in this utility model. Detailed Implementation

[0022] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0023] Example:

[0024] Reference Figure 1-2The DC fan EMI test improvement circuit includes a DC voltage VM, high-side switches K1, K3, and K5, low-side switches K2, K4, and K6, high-frequency filter capacitors C1-C3, and the motor terminal M. The DC voltage VM is directly connected to the high-side switches K1, K3, and K5, while the low-side switches K2, K4, and K6 are located below them and connected to the DC negative terminal. The high-side and low-side switches alternately conduct, thus forming an AC voltage across the motor. At this time, the DC voltage VM, the high-side switches K1, K3, and K5, and the low-side switches K2, K4, and K6 form a three-phase inverter bridge. Furthermore, in this three-phase inverter bridge, each... A common-mode inductor LC is connected to the midpoint of each bridge arm (i.e., between K1 and K2, K3 and K4, K5 and K6). The common-mode inductor LC has multiple taps (1, 3, 5), which are connected to the midpoints of each bridge arm of the three-phase inverter bridge (i.e., between K1 and K2, between K3 and K4, between K5 and K6). The taps converge the common-mode noise generated by each bridge arm to the common-mode inductor LC, and then grounded through parallel filter capacitors (C1-C3) to form a common-mode low-pass filter, which effectively suppresses EMI interference. The parts marked 2, 4, and 6 include connectors and their internal terminals. The terminals correspond to the motor terminals M and are directly plugged in through a male and female interface.

[0025] In this circuit, a stable DC power supply, VM, is first provided by a DC voltage, directly connected to the high-side switches K1, K3, and K5, while the low-side switches K2, K4, and K6 are connected to the DC negative terminal. Under the preset PWM control logic of the controller, the high-side and low-side switches alternately conduct at high speed, thereby supplying the motor terminal M with the modulated AC voltage output from each bridge arm. High-frequency common-mode noise is generated during the high-speed switching process. This noise signal is mainly concentrated at the midpoint of each half-bridge, i.e., between K1 and K2, K3 and K4, and K5 and K6. To effectively suppress this noise, the common-mode inductor LC is designed with multiple taps. Taps marked 1, 3, and 5 are connected to the midpoint of each half-bridge, converging the common-mode noise from each bridge arm. Subsequently, this noise is grounded through parallel high-frequency filter capacitors C1, C2, and C3, forming a common-mode low-pass filter, thereby effectively reducing high-frequency EMI interference. Meanwhile, the parts marked 2, 4, and 6 include connectors and their internal terminals, which are directly plugged into the motor side through a male and female interface to achieve a stable connection. This circuit uses a three-phase inverter bridge to achieve efficient DC to AC conversion and uses a common-mode filter network to effectively suppress the noise generated by high-speed switching, ensuring that the DC fan can still operate stably under strict EMI test conditions.

[0026] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0027] Finally, it should be noted that the above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A DC fan EMI test improvement circuit, including DC voltage VM, high-side switches K1, K3, K5, low-side switches K2, K4, K6, high-frequency filter capacitors C1-C3, and motor terminal M, characterized in that: The direct current voltage VM is directly connected with high-end switches K1, K3, K5 respectively, and the low-end switches K2, K4, K6 are connected to the negative pole of the direct current respectively.

2. The direct current fan EMI test improvement circuit of claim 1, wherein: The high-end switches K1, K3, K5 and the low-end switches K2, K4, K6 form three-phase inverter bridges, and the midpoints of each bridge arm, K1 and K2, K3 and K4, K5 and K6 are connected to the taps of the common-mode inductor LC.

3. The direct current fan EMI test improvement circuit of claim 2, wherein: The common-mode inductor LC is a single inductor device, and has taps 1, 3, 5 for converging common-mode noise of each bridge arm.

4. The direct current fan EMI test improvement circuit of claim 3, wherein: The output of the common-mode inductor LC is connected to the high-frequency filter capacitors C1, C2, C3 in parallel, and grounded through the high-frequency filter capacitors C1, C2, C3, forming a common-mode low-pass filter to reduce high-frequency EMI interference.

5. The direct current fan EMI test improvement circuit of claim 4, wherein: The high-frequency filter capacitors C1, C2, C3 are in parallel structure, and are connected with the output of the common-mode inductor LC respectively.

6. The direct current fan EMI test improvement circuit of any one of claims 1-5, wherein: The circuit further comprises a plurality of connection terminals and connectors, and the terminals marked as 2, 4, 6 correspond to the motor end M and are directly connected through a male-female interface.

7. The direct current fan EMI test improvement circuit of claim 6, wherein: The connection terminals 2, 4, 6 are used to transmit the alternating voltage output by the three-phase inverter bridge to the motor end M to realize the driving of the direct current fan.

8. The D.C. fan EMI test improvement circuit according to any one of claims 1-7, wherein: The circuit uses PWM control signals to make the high-end switches and low-end switches conduct alternately and at high speed to realize the conversion of direct current voltage to alternating voltage, while effectively suppressing the high-frequency electromagnetic interference caused by switching action.

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