Three-level power factor correction circuit

Abstract

The invention provides a three-level power factor correction circuit, a control earth is separated from a center point, and the control earth is suspending; preferably, the three level power factor correction circuit also includes an electric capacity, the electric capacity is series connection between the control earth and the earth; the three level power factor correction circuit provided by the invention solves the problems existing in the prior art, prevents a sampling circuit from disturbing, removes the hidden danger of module bombing caused by the out of control of the output bus bar DC voltage, and guarantees that the waveform of a three-phase input current does not have serious distortions; the invention has the advantages of easy to realize, inexpensive cost, stable property, favoring to promotion.

Description

technical field [0001] The invention relates to the field of basic electronic circuits, in particular to a three-level power factor correction circuit. Background technique [0002] The existing three-level power factor correction (PFC) circuit is also called Vienna converter, a topology such as figure 1 As shown, A, B, and C are three-phase AC voltage input, VDC+, VDC- are high-voltage DC output, the ground of the sampling circuit and the control circuit in this circuit is called the control ground (GND), and the two output capacitors C1 and capacitor The midpoint of the C2 connection is called the Midpoint. Generally, the ground of the control circuit (including the sampling circuit, the circuit for controlling PWM wave transmission, etc.) is taken at the midpoint, so that the DC output voltage Vp and Vn can be sampled conveniently, where Vp is the voltage between VDC+ and the midpoint , and Vn is the voltage between VDC- and the midpoint. Some three-level power factor ...

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Problems solved by technology

[0003] However, we found that the midpoint is connected to the switching tubes Q3 and Q4. With the switching action of the switching tubes Q3 and Q4, the midpoint is a point with high-frequency disturbance noise

If the control ground is connected to the midpoint, then high-frequency noise is likely to flow from the midpoint to the control ground, which will interfere with the control circuit, mainly the sampling amplifier circuit.

In the past, the size of the power module was relatively large. When laying out the board, the main power circuit was separated from the sampling circuit. The above-mentioned interference effect was relatively small. This problem was not discovered or ignored.

However, as the size of the power module is getting smaller and smaller, the main power circuit and the sampling circuit are generally very close to each other when laying out the board, and the sampling circuit will be connected with a large interference signal. Due to the interference of the sampling, it will have a negative impact on the control. It has a great influence, so that the power module does not work normally, the input current may generate a large harmonic, and the DC voltage of the output bus is easy to get out of control and cause the bombing

In addition, it may also cause serious distortion of the three-phase input current waveform, and the problem of very large harmonics

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