An ac-dc conversion system

Abstract

The invention discloses an AC-DC conversion system, comprising the following elements connected in sequence: an input circuit, a rectifier bridge, a buck-boost PFC main circuit and a resonant DC-DC conversion. The buck-boost PFC main circuit is connected with a PFC controller. The PFC controller is connected with a bus voltage control circuit and a bus voltage sampling circuit. The bus voltage control circuit is connected with an input voltage isolation sampling circuit and an output current sampling circuit. The bus voltage control circuit outputs a bus voltage reference signal according to the input voltage and the load information. The invention has the advantages that the setting of the bus voltage is not limited by the input voltage and can be higher or lower than the AC input voltage, which is favorable for the optimized design of the system; and that the working state of the circuits can be adjusted according to the input voltage condition and the load condition so that the circuits operate in their best states over the full input voltage range and full load range, achieving high efficiency and high power density.

Description

technical field [0001] The present invention relates to an AC-DC electric energy conversion system, specifically a high-efficiency, high-power-density AC-DC electric energy converter and its Control Method. Background technique [0002] An AC-DC converter usually includes a power factor correction (PFC) front stage and a direct current conversion (DC-DC) post stage. Among them, the PFC stage usually adopts BOOST boost topology. Its characteristic is that the BOOST rectified output voltage, that is, the bus voltage must be higher than the AC input voltage. It is greater than 373.3Vdc, and the problems caused by it include: 1. The loss of the front stage increases significantly when the low voltage is input, which limits the increase of the power density of the whole machine; The adjustable range is small, usually only 373.3 ~ 400Vdc, which limits the optimization space of the latter stage. In low-power occasions, BUCK-type step-down PFC is also often used, and its output v...

AI Technical Summary

Problems solved by technology

Among them, the PFC stage usually adopts BOOST boost topology. Its characteristic is that the BOOST rectified output voltage, that is, the bus voltage must be higher than the AC input voltage. It is greater than 373.3Vdc, and the problems caused by it include: 1. The loss of the front stage increases significantly when the low voltage is input, which limits the increase of the power density of the whole machine; The adjustable range is small, usually only 373.3 ~ 400Vdc, which limits the optimization space of the subsequent stage

In low-power occasions, BUCK-type step-down PFC is also often used, and its output voltage must be lower than the input voltage, which makes: 1. When high-voltage input, the loss of the front stage is large, which is not conducive to the improvement of power density; 2. When AC When the input voltage is lower than the bus voltage, due to the limitation of step-down characteristics, the input current is theoretically zero, which increases the harmonics of the input current

[0003] Therefore, in the prior art such as figure 1 and figure 2 The BOOST PFC and BUCK PFC shown cannot take into account the system efficiency at different input voltages. At the same time, the adjustment of the bus voltage is limited by their respective operating characteristics, which reduces the optimization space of the subsequent stage when the output voltage or load changes.

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