I am wondering if your power supply must shut down if input below 18V and higher than 75V.  If the power supply  requires input under voltage protection only or input over voltage protection only .  Datasheet fig 13 and fig 14 will solve your problem. But you have to modify the top resistor value. If you really need both protection, PLS let me know, and I may have some idea to solve your problem.

Regards

Can you help me ? I am facing the same issue.

Hi Biprarshi_1

May you please give me more info on the Design specs you are seeking to achieve? Is you input voltage range 18- 75V? What output power does your design need to deliver? Do you need both UVP and OVP? if not, the comment above (posted by PI-Cochrane on the 11th of April 2013) may point you toward the resolution of your problem.

Let me know

Regards

PI-Star Lord

Here are my design Specs:

1. Voltage Range : 18V-60V

2. Power Supply : 30W , 12V output voltage/2.5A load current

I am using DPA426R in my application. I need my DPA Switch to turn ON at 18V and Turn off switching at 60V. From the datasheet, I came to know that the OV/UV threshold is preset at 2.7. ( Here comes the catch, According to the datasheet, UV can be independently disabled irrespective of OV and vice-versa. BUT, the ratio of OV/UV remains SAME! i.e even if I am disabling the UV and only enabling OV protection by connecting a diode between Control Pin and Line Pin (between two resistors on L pin & DC Bias Bus), the UV threshold is also set at OV/2.7 which is not 18V. Due to this, DPA switch starts at 24V, not 18V. The only solution is by disabling both UV and OV by connecting L to Source. But in this case I have no way of ensuring overvoltage protection of the DPA Switch. What is the possible solution for this if I need to ensure OV protection in my application?

Hi Biprarshi_1.

You can modify the ratio between OV and UV by using a similar circuit to the one in figure 14 in the datasheet. Please see attached file for more details.

When your input voltage reaches 16V the DPA Switch is technically ready to start switching (Drain Supply voltage pp26 of the datasheet).

Using the OV only circuit (see attached) you can supply extra current to the L pin to reach the required Iuv at low input voltage (given that V Drain is aboveor equal to 16V) .The amount of current supplied from the control pin will depends on the value of RLS2.

You can determine the ideal Value of RLS1 and RLS2 to meet VOVP and VUVP by solving a system of linear equation which is just the KCL to the node just above the L Pin ( node that connects RLS1 and RLS2). You can see the system of linear equation in the file attached

Please bear in mind to take into account tolerances for the values of the parameters involved (IOV, IUV, VC, VL). These can be found in the datasheet.

Hope this helps.

Regards

PI-Star Lord