Electromagnetic quadrupole circuit which independently corrects ac and dc components of correction current

An electromagnetic quadrupole driving circuit comprising:

• first switching means giving a driving signal in synchronization with a horizontal synchronization signal, said first switching means being in an OFF state during a synchronization period and being in an ON state during a scanning period;
• a series circuit, provided in parallel to said first switching means, which resonates with a first resonance frequency by an electromagnetic quadrupole coil and a first resonance capacitor connected in series, while said first switching means is in the ON state;
• a second resonance capacitor, provided in parallel to the series circuit, which resonates with a second resonance frequency together with said first resonance capacitor and said electromagnetic quadupole coil when said switching means becomes to be in the OFF state;
• current detecting means for detecting the peak value and the bottom value of current flowing along said electromagnetic quadrupole coil;
• first power supply means for controlling an amplitude of current to be supplied to said electromagnetic quadrupole coil based on said peak value detected by said current detecting means;
• and
• second power supply means for controlling the superposed amount of current to be supplied to said electromagnetic quadrupole coil based on said bottom value detected by said current detecting means.