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Double phase shift modulation for three-level DC/DC converter

IP.com Disclosure Number: IPCOM000247520D
Publication Date: 2016-Sep-14

Publishing Venue

The IP.com Prior Art Database

Related People

DaWei Yao: AUTHOR [+4]

Abstract

This disclosure disclosure offers an alternative modulation solution for three-level phase shift converter to reduce filter inductor size and then improve the power density, as well as maintaining the high efficiency and cost-effectiveness of the converter. For high power AC/DC conversion applications, such as EV charger and telecommunication power supply, the DC/DC stage is usually fed by a three-phase active power factor correction (PFC) rectifier, and thus the input voltage is 600V~800V, for which the three-level DC/DC converters are widely used to make 650V MOSFETs applicable in order to improve the conduction and switching performances of the converter.

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1 DISCLOSURE TITLE:

Double phase shift modulation for three-level DC/DC converter


2 INVENTOR:

Louis-Sheng Zong, Xiaobo Yang, Forrest-Guoxing Fan, and Dawei Yao

3 ABSTRACT OF THE DISCLOSURE


3.1 Background of the disclosure

  This disclosure disclosure offers an alternative modulation solution for three-level phase shift converter to reduce filter inductor size and then improve the power density, as well as maintaining the high efficiency and cost-effectiveness of the converter.

  For high power AC/DC conversion applications, such as EV charger and telecommunication power supply, the DC/DC stage is usually fed by a three-phase active power factor correction (PFC) rectifier, and thus the input voltage is 600V~800V, for which the three-level DC/DC converters are widely used to make 650V MOSFETs applicable in order to improve the conduction and switching performances of the converter.


3.2 Statement of the problem

  The existing widely used modulation method for three-level DC/DC converters is phase shift modulation which is inherited from the conventional phase shift full bridge converter (PSFB). It has two main disadvantages as below:

  1) The filter inductor on the secondary side is usually large, because the output current ripple must be designed to comply with the related standards, for example, CHADEMO and COMBO for EV charger converter. However, reducing the size of the filter inductor can make important contribution to increasing power density.

  2) The voltage balance of the two cascaded input capacitors of the three level DC/DC converter is critical to the safe operation of devices. Most of the existing topologies use complex voltage balance mechanism, which is usually achieved with additional close-loop control. That not only requires two voltage sensors and related auxiliary circuits, but also consumes calculation resources of the controller. Therefore, a simple voltage auto-balance capability is desired to reduce hardware and software expense.

Several prior arts are found to resolve the issues mentioned above.


3.3 Prior solutions of 3 level DC/DC converter

  Nine prior solutions are listed and shown in Fig.1. Solution 1 and 2 are the most fundamental one-leg three-level DC/DC converters which were proposed very early. The size reduction of the inductor was not taken into consideration.

  Solution 3-6 provide three levels on the rectifier side, and the filter inductor can be reduced by properly selecting the duty cycles under the different voltage levels. However, in these solutions, two transformers are used in the converter, which reduces the power density and the cost- effectiveness. Among them, solution 3-5 utilize the midpoint of input capacitors to excite the additional transformer which minimizes the number of used devices. In solution 6, two individual legs operate independently to excite the two transformer, which increases the number of devices.

  Based on two neutral point clamp (NPC) three-level converter, solution 7 and 8 pro...