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Digital Peak Current Mode Controller or LT3750 Capacitor Charger

Klaas Pommes
Prodigy 110 points
Other Parts Discussed in Thread: UCC28C43

Hi,

I need to pre-charge any unknown capacitor when it's connected to the DC-bus to prevend inrush currents.

[DC-BUS 700VDC] -> [My Device] -> [Unknown device with unknown input capacitor @700VDC]

The Input voltage will be 700VDC and the capacitor should be charged to same voltage level als the input.

When the unknown device is connected to the DC-bus it should be charged without inrush current but more controlled.

I thought about using a PCM current mode controller with a maximum Irms(Inductor) of 6A.

After I have read a lot of articles I wondered if it's even possible when I don't know the capacitor value and ESR to prevend the sub-harmonics?

Another Option is the LT3750, is this a better solution to charge the capacitor to 700V?

Kind regards,

  • 0
    TI__Expert 8210 points
    Jack

    If you would like to use a switched mode power supply like a flyback than one of our current mode controllers like UCC28C43 will work here. These devices are current mode controlled, so they can limit the peak current every switching cycle. If you regulate off the aux winding for the regulation, which is called primary side regulation, you can eliminate some of your output unknown concerns.

    Best Regards
  • 0 in reply to Eric Faraci
    Prodigy 110 points

    Eric,

    I decided to use the C2000 with trip zone.

    When the ePWM2 time is equal to 1e-6 (1MHz)

    How could I know what the maximum frequency of ePWM2A is while doing peak current mode, I need to know this for determine cooling for the MOSFET..

    Also if I want an maximum ripple of 2A which means the inductor current should stay between 4A and 6A.

    Should I only make a tripzone for the 6A or also for the 4A?

    Afbeeldingsresultaat voor trip zone C2000 current

    Right now I tried to make the tripzone only for the 6A in simulink but during the charge proces

  • 0 in reply to Klaas Pommes
    TI__Genius 15935 points
    Hi Klaas,

    I am sorry for the late reply. This thread was missed for some reasons.
    1. You can find the HRPWM frequency information in the datasheet and TRM of your device.
    2. It depends on your requirements. If you need another 4A threashold, then you probably can use the other channel of the CMPSS module and get the signal back to the tripzone of PWM module.

    Regards,
    Chen