Control circuit, control method and harmonic converter

Abstract

A control circuit, a control method and a harmonic converter are disclosed. A start control signal correspondingly changing with the duration of the soft start process is generated as a loop variable,the loop variable shows different change trends when the resonant current intensity is in different intervals, and thus, a resonant circuit can be started by controlling the converter. The change speed of the soft start loop variable is dynamically adjusted according to the actual current of the resonant circuit, so that the resonant circuit can be started quickly without causing over-current. Atthe same time, there is no need to make corresponding adjustment according to the application example, and the design process of the resonant circuit is simplified.

Description

technical field [0001] The invention relates to the technical field of power electronics, in particular to a control circuit, a control method and a resonant converter. Background technique [0002] Currently, the 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 will easily cause the resonant circuit to over-current. [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 of the resonant circuit is detected to be overcurrent, the corresponding...

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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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