UCD3138: UCD3138 LLC Burst Mode

Jie Wang

Part Number: UCD3138

I want to use UCD3138 to control the LLC converter. Currently, frequency adjustment can be achieved based on sampling values, but during light load, burst mode debugging was not successful. Therefore, there are some questions that need help to be answered:

1. For resonance mode, the output of the filter has two values, one is the duty cycle and the other is the period. So, what value corresponds to the threshold of burst mode?

2. The following is the code for my burst mode. Please help me check if there are any issues.(The current code corresponds the threshold of burst mode to the duty cycle)

LoopMuxRegs.LLCTRL.bit.LL_FILTER_SEL = 0;
LoopMuxRegs.LLENTHRESH.bit.TURN_ON_THRESH = 10000;
LoopMuxRegs.LLDISTHRESH.all = 8000;

LoopMuxRegs.LLCTRL.bit.LL_EN = 1;

Although the filter output duty cycle is below the threshold, PWM still outputs normally.

over 1 year ago

0 Peter Ban over 1 year ago

TI__Prodigy 480 points

Hi Jie,

1. It should be "Filter Duty".

2. Have you checked whether the values of the relevant registers are as expected through the memory debugger?

3. Or maybe you forget to set below register.

LoopMuxRegs.LLDISTHRESH.bit.TURN_OFF_THRESH = HWBMTHRESH_SU;// Turn off threshold

Regards,

Peter

0 Jie Wang over 1 year ago in reply to Peter Ban

Prodigy 55 points

Hi Peter

Thank you very much for your reply.

As you said, I set the register like this:

LoopMuxRegs.LLCTRL.bit.LL_FILTER_SEL = 0;
LoopMuxRegs.LLENTHRESH.bit.TURN_ON_THRESH = 12000;
LoopMuxRegs.LLDISTHRESH.bit.TURN_OFF_THRESH = 8000;
LoopMuxRegs.LLCTRL.bit.LL_EN = 1;

However, the phenomenon remains the same as before.

As shown in the figure below, the filter duty has already fallen below the off threshold, but PWM still operates normally.