Control circuit, control method and resonant converter

Abstract

Disclosed are a control circuit, a control method and a resonant converter. By generating a start control signal that changes correspondingly following the duration of the soft start process as a loop variable, the loop variable presents different changing trends when the resonant current intensity is in different intervals, and then controls the converter so that the The resonant circuit starts. Therefore, according to the actual situation of the resonant circuit current, the change speed of the soft-start loop variable is dynamically adjusted, so that the resonant circuit can start quickly without causing the resonant circuit current to over-current. Resonant circuit design process.

Description

Technical field [0001] The present invention relates to the field of power electronics technology, in particular to a control circuit, a control method and a resonant converter. Background technique [0002] At present, LLC (resonant circuit) topology is a relatively common circuit used in switching power supplies. When the LLC topology is started, since the initial voltage on the resonant capacitor is zero, a large instantaneous inrush current will be formed, which can easily cause overcurrent in the resonant circuit. [0003] One solution in the prior art is to use the resonant capacitor voltage as a control variable during the soft-start process to control the resonant capacitor voltage fluctuation of the resonant circuit to gradually increase from low to high to prevent overcurrent. At the same time, a resonant current detection circuit and a protection circuit are configured. Once the resonant current overcurrent of the resonant circuit is detected, the corresponding power tu...

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Problems solved by technology

[0004] However, by controlling the voltage of the resonant capacitor to prevent overcurrent, it is necessary to adjust the fluctuation of the voltage of the resonant capacitor according to the specific application example. If the increase rate is too large, it will cause overcurrent in the resonant cavity; if the increase rate is too slow, the system startup time will be too long , affecting power performance

At the same time, since the transmission power of the resonant circuit is determined by the resonant capacitor voltage and the resonant current, the resonant current detection circuit and the protection circuit are used to prevent overcurrent, which may cause the problem of asymmetrical resonant current waveform and affect the performance of the power supply. It may even cause the resonant circuit to transmit insufficient power during the startup process and fail to start normally.

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