Isolated DC/DC converter from 12V/24V
Dear Sir.
I am planning one isolated DC/DC converter from 10V up 28V input voltage(12V/24V nominal). I intend to use primary regulation in order to reduce parts counts and use the DPA425PN to keep my board cool. So, I would ask you:
(1) Do you have any DI of this one?
(2) Could you show me any way to boost the initial charge from Drain pin to C pin? Or how can I procedure at so low input voltage: 10Volts?
(3) Could you show me a primary regulator circuit, cheap, simple, not so precise; and that do not go into instability?
(4) Could I use the SMT/SMD UF4007 at 24V/50mA output port(at one AN PI one can find an advice us to "do not use ultra fast diodes"); but that output current is so low....
My circuit output parameters: 12V at 300mA and 24V at 50mA both load unregulated; only poorly input voltage regulated.
B.R.
Jorge(jorge.conceicao@toledobrasil.com.br)
Comments
Hi,
DPA-Switch is intended for moderate to high voltage DC-DC designs. Designing for input voltage as low as 10 V is possible but complicates things. This is because, as noted in the DPA-Datasheet, the control pin charging current is reduced at reduced input voltages which affects start-up time, auto-restart frequency and duty cycle.
To answer your specific questions:
1) No we do not have a DI of such a design.
2) I would suggest using PI Xls to do your design but be aware that the above mentioned functionality of the device will change.
3) Yes you can adapt the primary side resistor or zener feedback circuit used for the TOPSwitch family. See AN-32 http://www.powerint.com/sites/default/files/product-docs/an32.pdf page 5 and 6, figures 3 and 4.
4) You should be able to use those diodes but they will not be as efficient in your design see page 12 of AN-19 for a discussion on selecting output rectifiers.
Hope this information helps you move forward.
-Wesley
Thank you Mr.Wesley. You got the point. I suppose that I can accomplish the converter design with your sound indications.
That's the PI's support that we hope here at our country.
B.R.
Jorge
Unfortunately Power Integrations does not make any DCDC IC's that operate down to 10V input. We do have the DPA series, which are designed for 48V nominal input:
http://www.powerint.com/en/products/dpa-switch-family/dpa-switch
Feel free to browse our various appnotes and PSU design reports.