Tuesday, November 6, 2012

Game Gear Boy, part 2 - Power board

The pin out for the power board is shown in the pic below. 


The heart of this power board is the MB3775.  This is a dual PWM switching regulator.  It has a supply range of 3.6V to 18V.  It can have up to two output voltages.  I believe that they are using this regulator to generate the 5V.  According to the datasheet it has a maximum output of +20V.  I think that they using a voltage doubler in order to create the 34V.  Setting the second output voltage to 17V and running it through the doubler would yield 34V.  The 1.28V is a reference voltage created by the MB3775.  The 9V output is the source voltage passed through. 

I was hoping to use the 34V output of this power supply to create the 12V supply for the LCD monitor.  The datasheet says that the maximum output current is 75mA.   This will not do.

Using the 9V supply as a baseline I found an adjustable boost regulator that will give me 12V at around 1.2A.  The regulator is a MC34063A

Here is the schematic that I made to boost the voltage from 9V to 12V with the maximum current set at 1.4A.  


Here's the PCB layout of the schematic.  It's a simple circuit so I was able to get it all on one layer.


Here's the 3D image of the board with the components populated.


I plan to etch this design in a copper clad board.  I will be posting an article on that after I gather up the materials.

~Todd

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