Patent ID: 7071668

Claim:
A power circuit for feeding a load current to a load in which said load current repeats periodically and alternates a burst flow in a burst period and a non-burst flow in a non-burst period comprising: a power source section made up of a direct current power source having one terminal connected to a negative polarity; a source power controlling section to control a current fed from a second terminal of said power source section connected to an input terminal to limit voltage drop in said power source section and to feed said current to a load connected to an output terminal; and an energy storing section having a storage capacitor connected between said output terminal and a negative polarity; wherein said source power controlling section is provided with a current controlling circuit to control a resistance value of a detecting resistor section, said detecting resistor section having one terminal connected to said negative polarity, according to a result of detection of a voltage input from said power source section, and a switching circuit which has a circuit part comprising a switching device connected between an input terminal and an output terminal of said source power controlling section and a capacitor connected between said output terminal of said source power controlling section and a negative polarity, and which controls a flowing period of an output current by exerting control on said switching device according to a control signal produced by detecting a change in an input power voltage using a voltage value occurring at another terminal of said detecting resistor; and wherein a circuit constant of said source power controlling section, electrostatic capacity and internal resistance of said storage capacitor are determined by following equations: T 1+ T 2 ≦T load where “T 1 +T 2 ” denotes a flowing period (Sec) of a power current and “Tload” denotes a load period (Sec): Vo /2 ≧IC×{Rc +( T load× D on)/( C× 100)}= Vo 3 where “Vo” denotes a voltage (V) of said storage capacitor when there is no load current, “IC” denotes a current (A) of said storage capacitor, “Rc” denotes an internal resistance (Ω) of said storage capacitor, “Don” denotes a duty ratio (%) of a load, “C” denotes a capacity (F) of a storage capacitor, and “Vo 3 ” denotes an amount of a voltage drop (V) of a storage capacitor voltage occurring during a burst period.