a high voltage charging circuit is provided with the ability of rapid charging . the circuit is composed of a turn - on control circuit , a turn - off control circuit and a transistor . the turn - on control circuit is adopted to set a turn - on time of a transistor such that the transformer may store magnetic energy , while the turn - off control circuit is used to set a turn - off time of the transistor such that the transformer may release the magnetic energy to charge a high voltage capacitor . smaller inductance reduces the turn - on time of the power transistor owing to the maximum current of the primary side of the transformer . therefore , a small - sized transformer may be employed to reduce the volume of the charging circuit with nonoccurrence of saturation .