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5 to -15 volts DC DC converter circuit diagram electronic project

Using several discrete electronic components can be designed a very simple DC DC converter which converts a positive voltage of 5 volts to a negative voltage of 15 volts. The negative voltage converter is different than most other similar circuits.
Works as a multivibrator IC1 provide an output signal with a relatively high duty cycle. LM311 is designed to work with a single supply of 5 V and allows a high current output for command switching of transistor T1. Duty cycle of the output signal is determined by voltage divider R2-R3, and the oscillation frequency of the C2-R4. Transistor T2 is part of a control loop to change the duty cycle of the oscillator and maintain a value of -15 V to converter output. Maximum output current isabout 200mA (transistor T1 to be installed on a radiator).

Circuit Diagram: 
5 to -15 volts DC DC converter circuit diagram electronic project


Dear electronic,I weantd to build your own Variable Regulator 0-30V 5A by LM723, CA3140, 2N3055 but there are inconsistencies between the PCB and the schema, namely:1) R11 = 150 ohms connected to pin 4 or pin 6 of CA3140?2) P1 (current) = 50k (scheme) or 5k (PCB)?3) R7 = 100k (scheme) or 10k (PCB)?4) pin 5 of the mass of uA723 18V with pin 7 (schema) or only R14 and R17 (PCB)?5) R13 = 1.5 ohms (schema) or 1.5 k (PCB)?Many thanks to those who answer me solve my doubts.Thank you sincerely.

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