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UCD3138HSFBEVM-029: Constant Current issue

FLORIAN BUISSON
Prodigy 10 points
Part Number: UCD3138HSFBEVM-029
Other Parts Discussed in Thread: UCD3138

Hello,
I'm trying to use the UCD3138HSFB-029 in CC mode but it doesn't work.

Here is the setup:
UCD3138HSFB-029 powered with 45Vdc, 4A limitation. Load: variable resistive load (11 Ohms max)
in GUI Fusion: CP limited to 15W, CC limited to 1.5A and CPCC enable.

When starting up the UCD, I have 12Vdc output, in CV mode.
When the load current reaches such a level to have full power as specified in GUI Fusion (15W), the output voltage to be regulated reduced, the higher the load current, the lower the output voltage regulation point, in this way, the constant power operation is achieved. --> CP OK.

From this point, if I increase the current to go to CC (reduce the resistive load), the power stage stay ON for 2 secondes, then stop for 1 seconde then retry for 2 secondes ... And so on.
Is this comportment the hiccup mode ?

If yes, it seems to be in contradiction with the EVM user guide wich says "In hiccup state, the power stage stays on for 1s, and then goes to idle state and try to turn
on again."

I looked for the primary current if the cycle-by-cycle current limit was triggered but the inrush curent is always lower than the limit (16A)

I understand thanks to several answers in TI.E2E forum that CPCC module is not a good choice to work in CP or CC mode, and the firmware function developped in EVM firmware standard_interrupt.c is better. Do you have any application note with this function ?


Can you please help me to maintain a constant current ?

  • 0
    TI__Expert 3470 points

    "From this point, if I increase the current to go to CC (reduce the resistive load), the power stage stay ON for 2 secondes, then stop for 1 seconde then retry for 2 secondes ... And so on."

    Can you share waveform captured here?

    thanks 

  • 0
    Prodigy 10 points

    Hi,

    Here are the waveforms.

    CH1: output voltage

    CH2: Primary current measured throught TP16 voltage

    CH3: output current. Please note that there is a non negligeable error in UCD current measurement with copper sence. Two external currentmeters indicate 3.9 Adc when GUI Fusion indicates 1.5 Adc (Current limlit). Can we fix this issue by updating the copper resistance in the firmware ?

    CH4: DPWM_0A

    The resistive load is decreased by hand (smooth).

    SC1

    Primary inrush current don't exceed 8A at each restart

    Hereafter is a quick load variation by hand

    I saw in other discussions that an application note exist for CPCC function. can you send it please ?

    Thank's

  • +1 in reply to FLORIAN BUISSON
    TI__Expert 3470 points

    1, Can you check if the "cc_flag" has been set in memory debugger? according to the following red coding, if the cc_flag has been set, the output voltage will be shut down after 2S, and then run to hiccup state.

    if(cpcc_on)
    {
    vref = (unsigned int) (pout/iout);
    vdac = vref * 6.26; //vref *2.5 *1000/256/1.56 scaler fron adc to dac
    if(vdac > timer_interrupt_temporary_1)
    {
    vdac = timer_interrupt_temporary_1;
    }
    }
    else
    vdac = timer_interrupt_temporary_1;

    FeCtrl0Regs.EADCDAC.bit.DAC_VALUE = vdac;
    timer_interrupt_temporary_1 = vdac;

    handle_current_sharing();

    if(cc_flag ==1)
    {
    cc_counter++;
    if(cc_counter > 20000) // constant current for 2s
    {
    if(cc_shutdown_disable == 0) //cc_shutdown_disable = 1, power supply remain at CC and does not enter hiccup mode for auto-validation test measurement purpose
    {
    MiscAnalogRegs.GLBIOEN.all |= 0xFF;
    supply_state = STATE_HICCUP;
    }
    cc_counter = 0;
    //cc_flag =0;
    }
    }
    else
    {
    cc_counter = 0;
    }
    }

    2，The primary purpose of this EVM is to demonstrate how the UCD3138 controls the HSFB. Measuring output copper is to simplify the SCH. If you need high precision current sensing, you can select a resistance sensor.

    3, the CPCC function is implemented by the firmware. The source code is included in the demo code. There are no additional application notes. 

    thanks 

  • 0 in reply to Bliss Zhou
    Prodigy 10 points

    Thank you for the support.

    With "if ( cc_flag == 1)" in comment, CC mode works well.