_12_V_TO__20_V

Published:2009/6/30 2:37:00 Author:May | From:SeekIC

Developed for use with mobile equipment when DC voltage higher than that of auto battery is needed. One application is trickle-charging 12-V nickel-cadmium batteries. Un is 555 timer operated as free-running square-wave oscillator. Frequency is determined by R1, R2, and 02; with values shown, it is about 6 kHz.C1 reduces 6-kHz signal radiated back through input lines. If converter is used with high-frequency receiver, insert 100-μH RF chokes in power leads to suppress harmonics of 6 kHz. For 12-V input, typical outputs are 20.4 V at 10 mA, 19.9 V at 20 mA, and 17.7 V at 50 mA. All diodes are 1N914, 1N4148 or equivalent.—G. A. Graham, Low-Power DC.DC Converter; Ham Radio, March 1975, p 54-56.



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