SECONDARY POWER SUPPLY Russian patent published in 1998 - IPC

FIELD: conversion of ac voltage, for example that of commercial frequency, into electrically isolated DC voltage for feeding various pieces of electronic equipment. SUBSTANCE: secondary power supply has diode bridge 1 whose input leads are connected through input capacitor 2 to ac supply mains 3. Voltage picked off output leads of bridge 1 arrives at filter capacitor 4. Supply voltage is passed to DC pulse converter 8 through transistor 6 which is driven in conduction only after voltage across capacitor 4 reaches desired level depending on control voltage of voltage regulator diode 5. Thyristor 5 is turned on and base of transistor 6 starts passing current limited by resistor 11. In this way, supply voltage is applied to converter 8 only after certain energy is stored in capacitor 4 and not immediately after supply mains 3 is energized. This makes it possible for converter 8 to function in starting mode characterized by higher input current compared with its rated value. Voltage across capacitor 4, that is, across input of converter 8, decreases within rather low limits in starting mode so that value of capacitor 4 is high and is used to smooth down low-frequency output-voltage ripples of supply mains 3. EFFECT: reduced value of input capacitor due to forcing starting current by energy stored in filter, this capacitance being dependent on converter functioning under rated conditions. 1 dwg