Circuit DC to DC Converter ::
5VDC to +12V and -12V Isolated
dual Switching Regulator with LM2587

This circuit Dc converter step up voltage, For 5VDC to +12V and -12V Isolated dual Switching Regulator by IC LM2587-12V.
Voltage supply input 4V to 6V, Output current 0.3A.
Detail other see in circuit.

Detail IC LM2587

SIMPLE SWITCHER 5A Flyback Regulator

The LM2587 series of regulators are monolithic integrated circuits specifically designed for flyback, step-up (boost), and forward converter applications.

Output Range 1.23V min, 5V, 12V, 3.3V
InputMin Voltage 4 Volt
InputMax Voltage 40 Volt

Applications
1.Flyback regulator
2. Multiple-output regulator
3. Simple boost regulator
4. Forward converter

Source: http://www.national.com/pf/LM/LM2587.html