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Hello! I am wondering about voltage-current plot in the datasheet of LNK562-564, Figure 1. See attached picture. The datasheet is here:


I don't fully understand the text,

"When the FB pin voltage falls below 1.69 V, the oscillator frequency linearly reduces to typically 48% at the auto-restart threshold voltage of 0.8 V. This function limits
the power supply output current at output voltages below the rated voltage regulation threshold VR (see Figure 1)." What do the three lines in the figure mean? What is the "Rated Power" and I_R & V_R?

Could you explain more in detail? Thank you very much!

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plot.PNG19.44 KB

Hi Dev,
Thanks for your interest on Power Integrations LinkSwitch-LP

The PSU output voltage information is mirrored on the FB pin through the bias winding. This means that when the output voltage goes lower, the FB pin voltage will also becomes low. Increasing the output load by reducing the resistor load value reduces the output voltage until it reach the device constant current mode threshold which is 1.69V measured at the FB pin. When the device enters CC mode operation, it will regulate the output current by reducing the switching frequency linearly from 100%(Full Frequency ) to 48% as the output voltage goes lower until it reach the AR threshold which is 0.8V

CVCC Plot.
The dotted curve is the power supply output voltage(Vo) vs output current(Io) plot. We call it CVCC curve. VR is the nominal output voltage , IR is the nominal output current of the PSU. The 2 solid lines are the upper and lower tolerance of the CVCC curve.

LNK562-564.pdf84.03 KB