Three-level Buck circuit and control method thereof

Abstract

The invention provides a three-level Buck circuit and a control method thereof. The three-level Buck circuit comprises an input capacitor, an output capacitor and at least one bridge arm, wherein eachbridge arm comprises a charging unit, a suspension capacitor, two inner tubes, two outer tubes and an inductor; the charging units are connected to the two ends of the outer tubes which are not connected with a low-voltage side in parallel. When the three-level Buck circuit is connected to a power supply, a main part of an input voltage originally applied to the two ends of the outer tubes is greatly reduced through the voltage division of the charging units and the suspension capacitors, so that overvoltage damage to the outer tubes is avoided; meanwhile, the charging units are used for pre-charging the suspension capacitors, so that the problem of overvoltage damage of the other outer tubes due to the fact that the outer tubes are conducted to charge the suspension capacitors can be avoided, and the safety of the three-level Buck circuit is improved.

Description

technical field [0001] The invention belongs to the technical field of power electronics, and more specifically, relates to a three-level Buck circuit and a control method thereof. Background technique [0002] With the rise of power electronic converter system voltage, the withstand voltage requirements of its related switching devices are also gradually increasing. However, due to the influence of semiconductor process performance and other aspects, the development of cost-effective devices has a certain lag, and it cannot be satisfied in the short term. Therefore, how to use lower voltage level devices and lower cost to realize high-voltage power conversion has become a research hotspot, and the proposal of multi-level technology can better solve this problem. [0003] figure 1 In the three-level Buck circuit shown, in normal operation, the first outer tube K1 and the first inner tube K2 are alternately conducted. Under ideal conditions, the conduction of the first outer...

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Problems solved by technology

[0004] In view of this, the object of the present invention is to provide a three-level Buck circuit and its control method to solve the problem that the first outer tube is prone to overvoltage breakdown when it is started, resulting in the failure of the first outer tube and the problem of charging the floating capacitor. Turning on the first outer tube leads to the overvoltage breakdown failure of the second outer tube, which in turn leads to the failure of the flying capacitor type three-level Buck circuit

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