Switching Power Supply isolated!!

[gauchosuizo]

hi

I need a PSS Isolated with an input range from 12V - 42V and an output from 12 V 300mA. I think, a flyback circuit will be very well. Has anybody some circuit or know some IC to do this??

Thanks and greetings from Switzerland

Pablo

 

[rauol]

8) U can use any standard Current mode controller (UC 3845)
www.ti.com

 

[gauchosuizo]

hi

I've looked at the datashet from the UC3845 and the max input voltage is 30V. I need a input range from 12V to 42V and I don't know, if the UC3845 with an external circuit comes to an input voltage from 42V? If yes, do you have maybe an exemple(circuit)?

Thanks

Pablo

 

[Ante]

Take a look at the LT1339, maybe that’s what you need.

Ante :roll:

 

[flatulent]

On the isolation issue. If you have a resistance value you can use feedback resistors of greater value. Another approach is to have an active circuit on the load side that measures the output and uses opto isolation methods to send the error signal back to the primary side.

 

[Buddy]

I think you can just connect 2 power supplies together!

 

[gauchosuizo]

hi

thanks for your answer. I will check the LT1339.

Aloha Pablo

 

[rauol]

gauchosuizo
I've looked at the datashet from the UC3845 and the max input voltage is 30V. I need a input range from 12V to 42V and I don't know, if the UC3845 with an external circuit comes to an input voltage from 42V?

8) What u should look is the minimum starting voltage and the undervoltage cutoff point for the controller ic. The UC 3845 is suitable for 12 V startup and any way the VCC is given through a startup resistor and an auxillary supply so the maximim voltage can be designed for even higher input voltages.

As u see that the UC 3842 is used in mains system and the startup resistor is given from the HIGH Voltage bus, after startup the auxillary takes over and supplies the running current. please note that the startup current required is only around 0.5 to 1 ma compared to 10 to 20 ma working Current.

UC 3845 device will be a very low cost device compared to LT device.

 

[gauchosuizo]

hi

raoul thanks for your tips. I have to study better the datasheet :sm30:
Do you have, maybe, an example with the UC3845 for a flyback PS?

Thanks Pablo

PD: I want to do a DC/DC Converter IN: 12V-42V, OUT: 12V 300mA

 

[rauol]

raoul thanks for your tips. I have to study better the datasheet
Do you have, maybe, an example with the UC3845 for a flyback PS?

Many application notes available on
www.ti.com search for 2842 or 3845