Varicap power sources. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Power Supplies
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To power varicaps, a stabilized voltage is required, which can be changed from 0 to 40 V. If varicaps are used in equipment with low-voltage power, a special voltage converter is required.
On the D1 chip, a rectangular pulse generator with a repetition rate of 90 kHz is assembled. Transistor V1 operates in key mode for an inductive load. At the moment of switching of the transistor, pulses appear on the coil L1, rectified by the diode V2. The DC voltage is stabilized by the parametric stabilizer R2, V3-V5, from which it is supplied to the varicaps.
Coil L1 is wound on two K10 x 6 x 3 rings folded together from 600 HN ferrite. The winding consists of 200 turns of wire PEV-2 - 0,1. The converter must be shielded as it is a source of radio interference. Chip D1 is powered directly from a 12 V source through a 270 ohm limiting resistor (not shown in the diagram). To protect the transistor from overloads, a current-limiting resistor with a resistance of 1 kOhm and a dissipation power of 0,25 W should be included in the base circuit.
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