This DC to DC Converter use Max 541 from Maxim, IC1 is a switching regulator that generates a 45-kHz signal that drives the gate of MOSFET Q1 BUZ71A from Motorolla. The source of this power supply comes from a 12V car battery voltage. This DC to DC converter have an output +-15V and 5V.
D1, D2, and D3 are Schottky diodes. The 5 V output is sensed as a reference; feedback to the chip turns off the gate signal to Q1 if the voltage rises above 5 V.
T1 has Trifilar windings that assume about 2% regulation for a 10-to 100-mA load change on the ± 15-V supplies. R1/D4 provide overvoltage protection. T1 has a primary inductance of about 21 H. Core size should allow 4 A peak currents. The turn ratios are 111/2 turns each for the 15-V supplies, 111/2 turns for the primary, and four turns for the 5 V secondary. The efficiency is about 75%.
100uF 25V (2)
100 ohm 1/2W