Flyback design 12V to 5V

[Hacked_27]

Hello all!
I am designing flyback converter with input 12v (car battery) to two outputs of 5V and 1A per output, basicly car cell phone charger.
I chose LTC3803 controller and first make simulations in LT spice, and all goes well with perfect coupling but when i include leakage inductance voltage drops are big, on full load voltage drops to 4V. i regulate feedback from third winding so that my two outputs are completely isolated, third winding also supply current to chip. i am posting dropbox link to my schematic.
i will be using off shelf transformer VP5-0083-R. on datasheet it states it has 0.105uH leakage inductance, my primary inductance is 21.2uH so 0.995 is coupling factor if i am correct?

Any tips for better cross regulation are welcome.

 

[BradtheRad]

Do you really need to isolate the power source from the output supplies?
Maybe instead you could get by with two buck converters. Each will reduce the 12V to 5V, each using a single winding.

Each buck converter can be individually adjusted. The output voltages will be easy to regulate independently.

Your link is to a netlist at an external website. Forum guidelines recommend that you put your netlist in your post, and add syntax tags to create a scrollable window within your post.

 

[Hacked_27]

Well i am working on my final year thesis on flyback, so i want to design simple practical solution
I adjusted the regulation, i put additional 500 ohm resistor on bias winding, it lower the efficiency but regulate a bit better, on full load voltage is 4.7V, efficiency is 84%, when no load is applied 5.3V and power consumption is 480mW.
Is that ok voltage for charging cell phones?

 

[BradtheRad]

Yes, it should work if your cell phone is designed to charge from a 5V supply, or USB connection.