BUCK-LLC two-stage DC/DC converter-based three-loop fixed-frequency control method

Abstract

The present invention discloses a BUCK-LLC two-stage DC / DC converter-based three-loop fixed-frequency control method. According to the method of the invention, the switching frequency of an LLC resonant converter is defined as the resonant frequency of two components; a differential circuit is utilized to acquire the output voltage of the LLC converter and a BUCK converter; a current sensor is utilized to acquire the inductor current of the BUCK converter and perform three-loop control; the output voltage loop of the LLC converter is an outermost loop; the output voltage of the BUCK converter is a middle loop; and the inductor current of the BUCK converter is an inner loop. According to the BUCK-LLC two-stage DC / DC converter-based three-loop fixed-frequency control method of the invention, the gain of the LLC resonant converter remains unchanged; the duty cycle of the switch tube of BUCK converter is adjusted through the three-loop control, so that the output voltage of a BUCK-LLC two-stage DC / DC converter can be adjusted; and compared with a converter adopting a single-loop or dual-control strategy, the converter is faster in dynamic response, better in steady-state performance, higher in power density, stronger in anti-load disturbance ability and has a certain engineering application value.

Description

technical field [0001] The invention relates to a novel BUCK-LLC two-stage DC / DC converter control method, in particular to a three-loop fixed-frequency control method based on the BUCK-LLC two-stage DC / DC converter. Background technique [0002] DC / DC converters have a wide range of applications in the industrial field, such as electric vehicle on-board chargers, LED drives, and DC convergence systems for new energy power generation. Soft switching technology is widely used in DC / DC converters, and it can reduce switching loss and EMI interference in ZVS and ZCS modes. [0003] The soft switching technology of LLC resonant converter can realize the ZVS of the primary switching tube and the ZCS of the secondary diode. Its switching frequency is higher than that of traditional soft switching technology, which can significantly increase the power density of the converter while ensuring efficiency. However, when the input voltage range of the LLC converter is large, the switc...

AI Technical Summary

Problems solved by technology

[0009] 1. The stability of the two-stage DC / DC converter system is poor, and the ability to resist external interference is weak

[0010] 2. The design of the control system is complicated, which is not conducive to the actual engineering application

[0011] 3. The input voltage adjustment range of the two-stage DC / DC converter is narrow, which is not conducive to the application in a wide voltage input range

[0012] 4. The response speed of the control system is slow, which is not conducive to the rapid response of the output voltage

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