EMI suppression circuit in AC high-voltage brushless tool

Abstract

The invention discloses an EMI suppression circuit in an alternating-current high-voltage brushless tool, which comprises a resistor R3, two capacitors Y2 and a rectifier bridge BD, the number of the capacitors Y2 is two, the two capacitors Y2 are connected in series, the resistor R3 and the capacitors Y2 are connected in series, and the output end of the rectifier bridge BD is connected with the two capacitors Y2. According to the invention, the power supply rectification and filter circuit is used for converting alternating current into direct current, filtering the direct current through a capacitor and finally supplying power to the motor; due to the directivity of the rectifier bridge BD, the current can only flow to the motor from DC + and cannot flow reversely; the negative influence of the counter electromotive force generated by the motor on the power supply can be prevented, and the power supply can be protected from the influence of the voltage peak; the resistor R3 may be used to limit the current flowing through the rectifier bridge BD to ensure that it does not exceed a safe operating range.

Description

Technical Field

[0001] The invention relates to the technical field of suppression circuits, in particular to an EMI suppression circuit in an AC high-voltage brushless tool. Background Art

[0002] At present, conventional electromagnetic compatibility suppression methods mainly rely on busbar filtering with power inductors and capacitors as the main body, which can suppress the leakage of electromagnetic interference to a certain extent, but the cost is high and the volume is large, and the filter position is far away from the interference source, so the electromagnetic interference suppression effect is limited. In recent years, with the rapid development of society and the recovery of exports to Europe, there are more and more stringent EMI suppression requirements for electronic and electrical products. The EMI suppression method of brushless DC motors mainly reduces the space radiation emission by limiting the switching speed of power MOS and adding common mode chokes in the energy circuit.

[0003] The existing publication number CN220653136U discloses a three-phase brushless motor electromagnetic interference suppression circuit, which belongs to the field of brushless motor EMI suppression, including a basic drive circuit and a resistor-capacitor filter network. The basic drive circuit includes a three-phase bridge drive circuit, a sampling resistor, and a three-phase brushless motor M1. The resistor-capacitor filter network includes a filter capacitor and a filter resistor. The present invention utilizes a filter network composed of a filter capacitor and a filter resistor, and establishes the filter network between the phase line, GND, and PE to filter the electromagnetic interference of the drive circuit. And compared with the traditional bus filter circuit with power inductors and capacitors as the main body, the present invention directly implements resistor-capacitor filtering on the motor phase line, which is closer to the source of noise and has a better filtering effect; at the same time, the present invention innovatively combines the two discharge paths of GND and PE to establish a resistor-capacitor filter network, which has a better filtering effect on electromagnetic interference and can effectively suppress the electromagnetic interference of the three-phase brushless motor.

[0004] Although the existing suppression circuit can achieve a certain suppression effect, its suppression effect is relatively poor. Therefore, we propose an EMI suppression circuit in an AC high-voltage brushless tool. Summary of the invention

[0005] The object of the present invention is to provide an EMI suppression circuit in an AC high-voltage brushless tool to solve the problems in the prior art.

[0006] To achieve the above-mentioned purpose, the present invention provides the following technical solution: an EMI suppression circuit in an AC high-voltage brushless tool, comprising a resistor R3, a capacitor Y2 and a rectifier bridge BD, wherein two capacitors Y2 are provided, and the two capacitors Y2 are connected in series with each other, the resistor R3 and the capacitor Y2 are connected in series, and the output end of the rectifier bridge BD is connected to the two capacitors Y2.

[0007] Preferably, the four diodes of the rectifier bridge BD are connected to four endpoints respectively, and two diodes of the rectifier bridge BD are connected to the live wire and the ground wire respectively.

[0008] Preferably, it further comprises a motor, wherein the positive pole of the motor is connected to DC+, and the negative pole of the motor is connected to DC-.

[0009] Preferably, it further comprises a casing, wherein the casing is connected to the ground wire via a resistor R3.

[0010] Compared with the prior art, the present invention has the following beneficial effects:

[0011] 1. Power rectification and filtering circuit, used to convert AC power into DC power, filter it through capacitors, and finally power the motor.

[0012] 2. Due to the directionality of the rectifier bridge BD, current can only flow from DC+ to the motor, but not in the opposite direction; it can prevent the back EMF generated by the motor from negatively affecting the power supply and help protect the power supply from voltage spikes; resistor R3 may be used to limit the current flowing through the rectifier bridge BD to ensure that it does not exceed the safe operating range. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0014] Figure 1 It is a circuit diagram of the present invention. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention.

[0016] See also Figure 1In an embodiment of the present invention, an EMI suppression circuit in an AC high-voltage brushless tool includes a resistor R3, a capacitor Y2 and a rectifier bridge BD, wherein two capacitors Y2 are provided, and the two capacitors Y2 are connected in series with each other, the resistor R3 and the capacitor Y2 are connected in series, and the output end of the rectifier bridge BD is connected to the two capacitors Y2. When the power is turned on, the current will flow through the rectifier bridge BD and enter the motor. Due to the directionality of the rectifier bridge BD, the current can only flow from DC+ to the motor, but not in the opposite direction. This can prevent the back electromotive force generated by the motor from negatively affecting the power supply, and helps to protect the power supply from voltage spikes. The resistor R3 may be used to limit the current flowing through the rectifier bridge BD to ensure that it does not exceed the safe operating range.

[0017] Preferably, the four diodes of the rectifier bridge BD are respectively connected to four endpoints, and two of the diodes of the rectifier bridge BD are respectively connected to the live wire and the ground wire; the rectifier bridge BD is composed of four diodes and is used to convert alternating current into direct current; the output ends of the rectifier bridge BD are marked with "DC+" and "DC-", indicating the positive and negative poles of direct current.

[0018] Preferably, it further comprises a motor, wherein the positive pole of the motor is connected to DC+, and the negative pole of the motor is connected to DC-.

[0019] Preferably, it further comprises a casing, wherein the casing is connected to the ground wire via a resistor R3.

[0020] The working principle of the present invention is: the power rectification and filtering circuit is used to convert the alternating current into direct current, and filter it through the capacitor to finally supply power to the motor.

[0021] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An EMI suppression circuit in an AC high-voltage brushless tool, characterized in that: It includes a resistor R3, a capacitor Y2 and a rectifier bridge BD. The capacitor Y2 is provided with two capacitors, and the two capacitors Y2 are connected in series. The resistor R3 and the capacitor Y2 are connected in series. The output end of the rectifier bridge BD is connected to the two capacitors Y2.

2. The EMI suppression circuit in an AC high-voltage brushless tool according to claim 1, characterized in that: The four diodes of the rectifier bridge BD are connected to four endpoints respectively, and two diodes of the rectifier bridge BD are connected to the live wire and the ground wire respectively.

3. The EMI suppression circuit in an AC high-voltage brushless tool according to claim 1, characterized in that: A motor is also included, wherein the positive pole of the motor is connected to DC+, and the negative pole of the motor is connected to DC-.

4. The EMI suppression circuit in an AC high-voltage brushless tool according to claim 3, characterized in that: The device also includes a casing, which is connected to the ground wire via a resistor R3.

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