LLC converter, control circuit, soft start method, apparatus, and chip

A control circuit, comprising an inductor-inductor-capacitor (LLC) converter, wherein the LLC converter comprises a switch circuit and a resonant tank, the control circuit comprising,

• a current collector configured to detect a current of the resonant tank;
• a first drive signal generator configured to generate a first drive signal, wherein the first drive signal is a pulse signal having a fixed frequency and a fixed duty cycle;
• a logical signal generator configured to generate a logical signal, wherein the logical signal is a pulse signal, the current is less than a current threshold in a time period corresponding to a width of a pulse in the logical signal, and the current is greater than or equal to the current threshold within a time interval between two adjacent pulses in the logical signal;
• and
• a second drive signal generator configured to generate a second drive signal based on the logical signal and the first drive signal, wherein the second drive signal is a second pulse signal, the second drive signal is at a preset level in a time period in which the current is greater than or equal to the current threshold, the second drive signal at the preset level is configured to turn off a power switch in the switch circuit, and the second drive signal is the same frequency and duty cycle as the first drive signal in a time period in which the current is less than the current threshold.

An inductor-inductor-capacitor (LLC) converter soft start method for a LLC converter comprising a resonant tank and a switch circuit, the soft start method comprising:

• detecting a current of the resonant tank;
• generating a logical signal based on a current and a current threshold, wherein the logical signal is a pulse signal, the current is less than the current threshold in a time period corresponding to a width of a pulse in the logical signal, and the current is greater than or equal to the current threshold within a time interval between two adjacent pulses in the logical signal;
• then generating a second drive signal based on the current and a first drive signal, wherein the first drive signal is a pulse signal having a fixed frequency and a fixed duty cycle, the second drive signal is a pulse signal, the second drive signal is at a preset level in a time period in which the current is greater than or equal to a current threshold, the second drive signal at the preset level is used to turn off a power switch in the switch circuit, and the second drive signal has the same frequency and duty cycle as the first drive signal in a time period in which the current is less than the current threshold, including performing AND logical operation processing on the logical signal and the first drive signal to obtain the second drive signal, wherein a level of the logical signal is a high level in the time period in which the current is less than the current threshold, and the level of the logical signal is a low level in the time period in which the current is greater than or equal to the current threshold;
• and
• outputting the second drive signal to the switch circuit, wherein the second drive signal is used to drive the power switch in the switch circuit.