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Original question:

LM5170-Q1: How to get higher voltages without changing the topology of 2 switch solution

LM5170-Q1: How to get higher voltages without changing the topology of 2 switch solution

Prodigy 60 points
atish tailor

Part Number: LM5170-Q1

Unfortunately, the other thread got locked however just to continue where we last left it,

First of all thank you Youhao and Garrett.

For the first stage, Is there any reason why I cannot use a clamp to drop 46V and run at cira 126V? That way, the ramp measurement and controller believes its actually at 80V?

Alternatively, the Ramp R and C can also be adjusted to ensure it remains within the recommended 5V (although the datasheet implies up to 14V is ok)

For the second stage current sense, I can use a differential amplifier with unity gain?

I accept its a convoluted solution but principally, can you think of any more issues?

Best regards

Atish

Prodigy 60 points
atish tailor

1 Reply

  • Mastermind 22060 points
    Youhao Xi
    Hi Atish,

    Thank you for your interests in the Lm5170. Regarding the RAMP, we really require the RAMP peak voltage to be 5V when the input line is 48V. We want the RAMP and the HV voltage to stay in that ratio for proper operation.

    RAMP 14V is just the absolute max rating. For normal operation, RAMP voltage should be stay at about 10V max, or it will be tip clipping by VCC voltage.

    Regarding the current sense, can you show your idea in a schematic?

    Thanks,
    Youhao

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