DPA425R starting Problem

If the DPA's L pin is enabled for UV (has a resistor connected to the L pin to the Buss Voltage), the current going into the L pin needs to be 52 uA for the device to start operating. The L pin voltage is 2.6 Volts. If R40 in your schematic is open, then the start up voltage will be 19.8 Volts (with a 330k Ohm resistor to the buss voltage as shown in your schematic). I would try a 270k or 300k Ohm resistor for 18 Volt operation.
Note: I used the maximum values for L pin current and voltage to make sure the power supply will start under worst case conditions.

Z. Cochrane

sorry. I forgot to mention that i have disabled L pin in my PCB. what will be the approximate startup current for this wattage?

IF i want my power supply to start up exactly at 18V and switch off at 60V, what value of resistor has to be connected at L pin to achieve this?

This is not possible without external circuit. The ratio between UV and OV is internally set at 1:2.7 (see IUV and IOV parameters in datasheet). Therefore setting UV at 18 V will give OV at ~50 V.

Cheers

PI-Chekov

Ok but after disabling L pin also why power supply is starting at 25V?

By disabling did you connect the L pin to the SOURCE pin? If you did - what do you mean by starting? For example does the supply try to start but only reaches regulation at above 25 V?

Cheers

PI-Chekov

I have connected L pin to source. Am using 265V,2A DC source. Is this source is sufficient to provide start up current?. when i switch on the power supply board at 20V unit will try to switch on, but it will not. At that time source's voltage is dipping. what is the meaning for this? is the source is unable to provide start up current? then what is the approximate start up current for this?

The device current limit is up to 5A therefore the source should be able to provide this as during startup the device with operate all the way to its internal current limit.

Cheers

PI-Chekov

Now am facing one more problem. I replaced mur120 with mur160 in the output rectifier for +12V & -12V outputs. when the temperture reaches about 55degC the diode starts burning in both the outputs. But with mur120 there is no burning problem. what is the actual problem?

Now am facing one more problem. I replaced mur120 with mur160 in the output rectifier for +12V & -12V outputs. when the temperture reaches about 55degC the diode starts burning in both the outputs. But with mur120 there is no burning problem. what is the actual problem?

Is MUR160 is direct replacement for MUR120?

Is it possible to design power supply of input range 290 VAC to 1040 VAC input in power integrations for 3W output?