SECONDARY POWER SUPPLY Russian patent published in 1999 - IPC

FIELD: step-down AC-to-DC voltage changing. SUBSTANCE: supply voltage picked off input 3 is rectified by diode bridge 1 and passed to load 11, 12 and to ripple capacitor 10 for charging it. Output voltage is reduced by means of capacitor 2 and control circuit set up of integrated circuits 13, 14, 15. Output voltage is maintained constant in case of load power or supply voltage fluctuations by means of transistor 5 which is driven in conduction when output voltage rises above specified value determined by division ratio of voltage divider 9 and high value of voltage U_ref across comparator 15. Conducting transistor 5 ensures uninterrupted current through capacitor 2. Transistor 5 is cut off as soon as output voltage of device has dropped below specified level determined by division ratio of voltage divider 5 and voltage level across comparator 15. Pulse currents through transistor 5 and diode bridge 1 are eliminated. EFFECT: improved reliability. 1 dwg