Patent ID: 6194885
Filing Date: 2001-02-27
Classification: H02M,Y02B

Abstract:
A boosting active filter system comprising:a power supply;an input signal line for input of a power-supply voltage of said power supply;a load, anda main circuit having its input end connected to said input signal line and its output end connected to said load, converting said power-supply voltage to a DC voltage and outputting said DC voltage as an output voltage,wherein said main circuit comprises:a full-wave rectifying circuit connected to said input signal line;a reactor having its first end connected to a first output end of said full-wave rectifying circuit;a rectifier diode having its anode electrode connected to a second end of said reactor and its cathode electrode connected to said output end of said main circuit;a load capacitor having its first end connected to said output end of said main circuit and its second end grounded;a switching element having its first main electrode connected to said second end of said reactor and its second main electrode connected to said second end of said load capacitor, performing ON operation when a control voltage applied to its control electrode is at an ON level and performing OFF operation when said control voltage is at an OFF level, anda current detecting resistor having its first end connected to said second main electrode of said switching element and its second end connected to a second output end of said full-wave rectifying circuit,said boosting active filter system further comprising:an overvoltage detecting circuit receiving a signal giving said output voltage and making a comparison between said output voltage and an overvoltage level which is higher than a set value of said output voltage by a given level to output an overvoltage detect signal from its output end when said output voltage rises to said overvoltage level, anda negative feedback control circuit comprising a first input end connected to said output end of said main circuit and a second input end connected to said output end of said overvoltage detecting circuit, controlling a duty factor of said control voltage to said switching element on the basis of negative feedback of said output voltage when said overvoltage detect signal is not provided as its input, and controlling said duty factor of said control voltage to 0% to force said switching element into the OFF state when said overvoltage detect signal is provided as its input.