Wide Input voltage using DPA switch
I try to use DPA switch to design wide input (18V to 75V) power supply. When using the PI Expert, its result gives the actual input window is 18V to 47.2V and notes the OV threshold below VIN-MAX. That means the power supply will turn off at 47V rather than 75V. This is not acceptiable for me because the wide input window is important for us for the energy storage.
I followed the PI's "FIX" procedure to try to increase R1 and R2 resistor values but after that, I re-run the simulation, the program changes the resistor value back to original value.
I need to know how I can have my power supply can run in the window 18V to 75V.
Thanks
See attached files
Comments
See my attached as above.
Hi,
As what you can find from the DPA data sheet, basically the UV and OV level is determined by the Iuv and Iov from the parameter table in page 22. So if a single resistor is used for UV and OV threshold, the UV and OV level will be fixed by the ratio between the Iuv/Iov. In the PI-Expert, this resistor is calculated based on the UV threshold only, then based on the OV/ UV ratio, the OV level will be automatically set. It turns out on your design, the resistor is two low for OV protection if you set the UV level to be 15V.
In your design, do you request both UV and OV function? If only one is requested, you can calculated the resistor manually based on this request, and disable the other function with external circuits. You can refer to figure 13 an 14 for external circuits. If you have manually modified this resistor value in your PI-expert design, do not run the simulation again, it will basically reset the manual setting and recalculate the design from the beginning.
Please let me know if you have further question.
Hi,
I am sorry, I am not sure that I clearly understood the issue.
Would you please help to attached your PI-expert design that I can have a check?
Thanks