dc/dc converter and its control method

Abstract

The present invention relates to a DC / DC converter and its control method. The DC / DC converter includes a BUCK input stage step-down circuit, an FB_ZVZCS phase-shifting full-bridge DC / DC isolation conversion circuit and a rectifier bridge circuit composed of rectifier diodes , the input end of the BUCK input stage step-down circuit is connected to the input voltage, the output end of the BUCK input stage step-down circuit is connected to the input end of the FB_ZVZCS phase-shifted full-bridge DC / DC isolation conversion circuit, and the FB_ZVZCS shift The output end of the full-phase full-bridge DC / DC isolation conversion circuit is connected to the primary side of the transformer, the secondary side of the transformer is connected to the input end of the rectifier bridge circuit, and the output of the rectifier bridge circuit is connected to a load. The invention has a wide input voltage range, high system efficiency, better adaptability to changing working conditions, and low power consumption. It adopts the control mode of overall control and synchronous segmental soft start, and controls the two-stage topological circuit as a whole, which is stable high performance and reliability.

Description

technical field [0001] The invention belongs to the technical field of power electronics and relates to a switching power supply, in particular to a DC / DC converter and a control method thereof. Background technique [0002] New high-efficiency soft-switching technology and adaptive control algorithm are important ways to solve isolated DC / DC high frequency, high power, wide voltage input and output, and high adaptability to complex environments. [0003] see figure 1 , the traditional hard-switching isolated DC / DC converter includes H-bridge, isolation transformer and secondary rectifier. The topology of the DC / DC converter is simple, and the control method adopts various control methods such as phase-shift control. However, the existing hard-switching isolated DC / DC converters have the following disadvantages: [0004] (1) When the switching device is turned on and off, the overlapping area of ​​voltage and current is large, and the switching loss is relatively large, wh...

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Problems solved by technology

[0004] (1) When the switching device is turned on and off, the overlapping area of ​​voltage and current is large, and the switching loss is large, especially in high-frequency and high-power workplaces, which makes it difficult to design the heat dissipation system

[0005] (2) The grid voltage on the primary side fluctuates greatly. In the case of a fixed transformer ratio, the output voltage range of the converter is narrow

[0006] (3) Due to large network voltage and load fluctuations, the positive and negative half-cycle waveforms of the transformer are instantaneously asymmetrical, and the transformer is prone to one-way saturation

[0007] (4) In the case of high voltage input, the secondary side rectifier diode bears a large voltage, and the voltage utilization rate of power electronic devices is limited

[0009] (1) The auxiliary circuit is designed with a load, which increases the risk of system failure

[0010] (2) The soft switch with secondary side composed of switching devices to form resonance increases the voltage stress of the secondary side rectifier device, the peak value can be doubled at most, and the control is complicated

[0011] (3) Due to the limitation of the input stage topology, this topology still has various problems caused by large voltage range and large load fluctuations

[0013] (1) The passive control algorithm with a single parameter has poor versatility and cannot adapt to complex and changeable working conditions

[0014] (2) The control of DC / DC cascade topology has shortcomings such as slow response and poor stability

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