RS232 power supply circuit diagram

This RS232 power supply circuit diagram is an simple RS-232 Line Driver Power Supply, that operates from an input voltage as low as 4.2V, and delivers an output of ±12V at ±40 mA with an efficiency of better than 70%.
This RS232 power supply circuit provides a load regulation of ±1.25% (from 10% to 100% of full load) and a line regulation of ±0.08%. Other notable features include a cycle-by-cycle current limit and an output voltage ripple of less than 40 mVp-p.
This power supply circuit is based on the LM1578A switching regulator designed by National Semiconductor and can be used to convert the already existing supply into a separate ±12V supply for powering the interface line drivers.
The transformer used in the power supply was a Pulse Engineering PE-64287 with turns ratio of Np:Ns:Ns = 1:1.6:1.6 and primary inductance of 50 μ . Values for components are : R1 = 10 kΩ ,R2 = 240 kΩ ,R3 = 240 kΩ, R4 = 0.1Ω, C1 = 1000 pF ,C2 = 18 pF ,C3 = 220 μF ,C4 = 220 μF,C5 = 100 μF,C6 = 0.1 μF and all diodes are 1N5819 type .