CN100395951C - A method for suppressing common-mode interference of power converters - Google Patents

Abstract

A power converter common-mode interference suppression method is composed of a rectification filter circuit and a boost (Boost) circuit. In the boost circuit, the inductance is changed from the positive bus of the DC input to the negative bus of the DC input. , the diode is changed to a common anode diode, and it is connected from the positive bus of the DC output to the negative bus of the DC output. The invention directly connects the nodes on the direct current input positive bus, so its potential is stable, and the distributed capacitance of the MOSFET drain to the ground and the distributed capacitance of the nodes on the positive bus have little influence on the common mode interference. And because the circuit can output a stable DC voltage when it is in normal working state, the influence of the common-anode diode distributed capacitance on the common-mode interference can be ignored. The distributed capacitance of wires that has a greater impact on common-mode interference can be reduced through reasonable wiring of the printed circuit board, thereby achieving the purpose of suppressing common-mode interference. The invention is simple and practical, and can be applied to some existing topologies of power converters.

Description

A method for suppressing common-mode interference of power converters

technical field

The present invention relates to a common-mode electromagnetic interference (EMI) suppression method for a power converter.

Background technique

The source of the power converter's conducted common-mode electromagnetic interference is mainly caused by the displacement current generated in the distributed capacitance of the electric node in the circuit whose potential changes drastically with time and flows through the ground loop.

Usually, the drain of a metal oxide field effect transistor (MOSFET) is fixed on an external heat sink through its heat dissipation metal shell through an insulating gasket, and the heat sink is grounded. Therefore, there is a large distributed capacitance between the drain of the MOSFET and the ground. In the same way, for common diodes, the heat-dissipating metal shell of the package is connected to the cathode of the diode, and is also fixed on the external heat sink through an insulating gasket, that is, the distributed capacitance of the cathode of the diode to ground is formed. In addition, the wires in the circuit also have distributed capacitance to the ground.

In this circuit, the potential of the node connected to the drain of the MOSFET changes drastically with the on-off state of the MOSFET, that is, the du/dt is very large. The ground-distributed capacitance of the MOSFET and the ground-distributed capacitance of the wire connected to it will generate a large displacement current, which will flow into the ground loop through the radiator to form a common-mode interference current.

Generally, the distributed capacitance generated by wires can be reduced through reasonable wiring of the printed circuit board, but the distributed capacitance existing to the drain of the MOSFET to the ground cannot be reduced.

In order to suppress the common-mode interference in this circuit, many scholars have proposed some methods, such as: the common-mode current anti-phase offset method, which requires an additional winding and a MOSFET, which increases the cost; common-mode current passive elimination method, which still requires an additional winding and an additional capacitor; the method of dynamic node balancing, which is difficult to apply to a boost power factor correction (Boost PFC) circuit, and increases the circuit

The dynamic node in, increases the difficulty of printed circuit board layout.

Contents of the invention

The purpose of the present invention is to reduce the influence of the MOSFET drain on the sub-capacitance that exists on the ground by constructing a steady-state node in the circuit, that is, to provide a power converter with a stable node potential and a small influence of the distributed capacitance on the common-mode interference. Mode interference suppression method.

The purpose of the present invention is achieved by the following scheme: it is composed of a rectification filter circuit and a boost boost circuit, in which the inductance is made from the positive output node of the rectifier filter circuit and the drain node of the power field effect tube Connect between the negative output node of the rectification filter circuit directly connected in the original circuit and the drain node of the power field effect tube, directly connect the positive output node of the rectification filter circuit and the drain node of the power field effect tube, and connect them The commonly used diode is changed to a common anode diode whose heat dissipation metal shell is connected to the anode, and it is connected between the drain node of the power field effect transistor and the positive node of the energy storage capacitor to the power field effect directly connected in the original circuit. Between the source node of the transistor and the negative node of the energy storage capacitor, the drain node of the power field effect transistor is directly connected with the positive node of the energy storage capacitor.

Because the present invention connects the inductance on the positive output end of the rectification filter circuit to the negative output end of the rectification filter circuit and removes the diode between the drain electrode of the power field effect transistor and the positive electrode of the energy storage capacitor, a common anode diode is used to connect the power field effect transistor Between the source and the negative pole of the energy storage capacitor, there are no components on the positive bus of the DC input and DC output, so the potential of the wire node is stable, and the distributed capacitance existing between the drain of the MOSFET and the positive output terminal of the rectification filter circuit The distributed capacitance of the node has little effect on the common mode interference. And because the output DC voltage is stable in the normal working state, the influence of the distributed capacitance of the anode of the common anode diode to the ground and the partial capacitance of the negative output terminal line of the rectifier filter circuit to the ground of the DC output terminal to the ground can be ignored. At this time, when the MOSFET switches, only the node connecting the inductor and the cathode of the common anode diode in the circuit has a high potential change rate, and the distributed capacitance of this node to the ground will become the main factor affecting the common mode interference, but through the printed circuit Reasonable layout of the board can easily reduce the distributed capacitance of the node to the ground. And it is simple and practical, and can be applied to some existing power converter topologies, such as boost power factor correction (Boost PFC) circuit, step-down (Buck) circuit, step-down (Buck-Boost) circuit, etc.

Description of drawings

Fig. 1 is a schematic circuit diagram of the present invention;

Figure 2 is a prior art reference diagram.

Detailed ways

Referring to Fig. 1, the present invention is composed of a rectification filter circuit and a boost Boost circuit. The rectification filter circuit is composed of 4 diode bridge rectifiers connected in parallel with a capacitor _C1 . In the circuit, there are node n5 connected to the positive output terminal of the rectifier filter circuit and node n6 to the negative output terminal of the rectifier filter circuit. The boost boost circuit is composed of a metal oxide field effect transistor (MOSFET) Q, a radiator T, an inductor L, a common anode diode D and an energy storage capacitor _C2 . The MOSFET is connected to the drain node n1 and the source node n2 in the circuit, and its drain d is connected to the drain node n1, and there is a large distributed capacitance C _m between the drain d and the ground; the inductance L is connected to the rectifier filter circuit negative between the output node n6 and the source node n2. The energy storage capacitor _C2 is connected to the positive node n3 and the negative node n4 in the circuit. The common anode diode D is connected between the source node n2 of the MOSFET and the negative node n4 of the energy storage capacitor C2. The heat dissipation metal shells of the MOSFET and the common anode diode D are respectively fixed on the heat dissipation pipe T through insulating gaskets. At this time, the distributed capacitance C _d of the positive anode diode D to the heat pipe T is actually the distributed capacitance of the diode anode to the ground. C _p1 , C _p2 , C _p3 and C _p4 in the circuit are the distributed capacitances of the wires connected to the drain node n1, the source node n2 of the power field effect transistor Q, the positive node n3 and the negative node n4 of the energy storage capacitor C2 to the ground respectively . It can be seen that the drain node n1 of the power field effect transistor Q and the positive node n3 of the energy storage capacitor C2 are directly connected, so their potentials are stable, and the distributed capacitances C _m , C _p1 and C _p3 have little influence on the common mode interference. At the same time, the output DC voltage is stable when the circuit is working normally, so the potential of the negative node n4 of the energy storage capacitor C2 is also stable, and the influence of the distributed capacitors C _d and C _p4 on common-mode interference can be ignored. At this time, when the metal oxide field effect transistor Q is switched, only the source node n2 of the power field effect transistor Q in the circuit has a high du/dt potential, and the capacitance C _p2 becomes the main factor affecting the common mode interference, which is passed through Reasonable wiring of the printed circuit board can easily reduce this capacitance, thereby achieving the purpose of suppressing the common mode interference of the circuit.

Claims (1)

1. power inverter common mode disturbances inhibition method, comprise current rectifying and wave filtering circuit and the Boost circuit that boosts, it is characterized in that: in the described Boost of boosting circuit be with inductance (L) by reconfiguration between the drain node (n1) of current rectifying and wave filtering circuit positive output node (n5) and power field effect pipe (Q) to the source node (n2) of direct-connected current rectifying and wave filtering circuit negative output node (n6) in primary circuit and power field effect pipe (Q), the drain node (n1) of current rectifying and wave filtering circuit positive output node (n5) and power field effect pipe (Q) directly is connected, change its diode into co-anode diode (D), reconfiguration directly is connected power field effect pipe (Q) drain node (n1) with storage capacitor (C2) cathode node (n3) to direct-connected power field effect pipe (Q) source node (n2) in primary circuit and storage capacitor (C2) the negative pole node (n4) between power field effect pipe (Q) drain node (n1) and storage capacitor (C2) cathode node (n3) by being connected on.

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