Large power high efficiency thermal equilibrium LLC resonant converter and control method thereof

Abstract

The invention relates to a large power high efficiency thermal equilibrium LLC resonant converter and a control method thereof. The large power high efficiency thermal equilibrium LLC resonant converter comprises an inversion circuit, a resonant network, high frequency transformers, and an output rectification circuit. The high frequency transformer is constituted by 2n transformers, and the primary windings of the 2n transformers are serially connected together, and the secondary windings of the 2n transformers are parallely connected together, and then are connected with the output rectification circuit. The primary windings are parallely connected with excitation inductors, and the resonant network is constituted by resonant capacitors, the primary excitation inductor of the2n-1th transformer, and the primary excitation inductor of the 2nth high frequency transformer, which are serially connected together. The resonant converter works in six working modes in a switching period. The high frequency transformers are used to replace the resonant inductors, and then the high frequency transformers are used as the resonant inductors, and are also used as the excitation inductors and the transformers, and therefore material costs are saved, output ripple, output precision, and other performances are greatly improved.

Description

Technical field [0001] This application relates to an LLC resonant converter, in particular to a high-power and high-efficiency thermally balanced LLC resonant converter and a control method thereof. Background technique [0002] LLC resonant converter is a kind of soft switching. It uses fewer components to realize zero voltage turn-on of the primary side switch tube and zero current turn-off of the secondary side diode, thereby achieving lower switching losses. Such as figure 1 As shown, the LLC resonant converter includes an inverter circuit, a resonance circuit, a high-frequency transformer, and a rectifier circuit; the inverter circuit can be a two-level or three-level asymmetric half-bridge circuit and a full-bridge circuit; the resonance circuit is composed of The resonant capacitor, the resonant inductance and the primary inductance of the high frequency transformer are connected in series. When working, the inverter circuit outputs a complementary level with a fixed 50%...

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Problems solved by technology

[0003] Under the rated operating conditions of LLC, the resonant circuit can work near the resonant frequency. At this time, the efficiency of the resonant converter is the highest, but when the input or output voltage changes, it needs to adjust the frequency to adapt to this voltage change. With the frequency shift, the circuit The loss will increase and the system efficiency will decrease. The resonant inductor and transformer will have difficulty in heat dissipation due to the increase of copper loss and magnetic loss, especially when the output of the LLC converter is under high-voltage light load and low-voltage heavy load, the resonant inductor and transformer are prone to thermal imbalance. , and the solution to the heat dissipation problem can only be solved by increasing the window area of ​​the magnetic core and increasing the wire diameter, that is, by sacrificing the power density of the converter; the LLC resonant circuit can realize soft Switch, if the range of output voltage is more than 2 times, in theory, the LLC gain can be adjusted by reducing the inductance of the excitation inductance, thereby increasing its working range, but with the decrease of the excitation inductance, the reactive power of the primary current The weight is also greatly increased, resulting in an increase in loss and core component volume

Especially when high-power converters such as chargers may work in a wide range of output voltages, this incompatibility is more prominent. Therefore, it is necessary to improve the existing resonant circuit topology to solve the above-mentioned existing resonant circuit. Problems in High Power Wide Output Range Applications

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