DAP041 datasheet(31/40 Pages) ONSEMI

31 / 40 page

SCY99194

http://onsemi.com

Figure 59. Needs for Line Compensation For True Overpower Protection

To compensate this and have an accurate overpower

protection, an offset proportional to the input voltage is

added on the CS signal by turning on an internal current

source: by adding an external resistor in series between the

sense resistor and the CS pin, a voltage offset is created

across it by the current. The compensation can be adjusted

by changing the value of the resistor.

But this offset is unwanted to appear when the current

sense signal is small, i.e. in light load conditions, where it

would be in the same order of magnitude. Therefore the

compensation current is only added when the FB voltage is

higher than VFB(OPCE). However, because the HV pin can be

connected to an ac voltage, there is needed an additional

circuitry to read or at least closely estimate the actual voltage

on the bulk capacitor.

Figure 60. Overpower Protection Current Relation to Feedback Voltage

DAP041 Datasheet(PDF) 31 Page - ON Semiconductor