Patent ID: 7710080

Claim:
A control circuit of a capacitor charging apparatus, the capacitor charging apparatus including a transformer and an output capacitor charged with current flowing through a secondary coil of the transformer, which charges the output capacitor by performing a switching control of a switching transistor provided on a path leading to a primary coil of the transformer, the control circuit comprising: an off-signal generator which monitors current flowing through the primary coil of the transformer and which outputs an off signal of a predetermined level when the current rises up to a predetermined peak current; a first on-signal generator which monitors voltage across the primary coil of the transformer and which outputs a first on signal of a predetermined level when the voltage across the primary coil thereof drops down to a first predetermined threshold voltage; a second on-signal generator which monitors a monitoring voltage corresponding to an output voltage appearing at the output capacitor and sets an off-time based on the monitoring voltage and which outputs a second on signal of a predetermined level after the off signal of the predetermined level has been outputted from said off-signal generator and then the off-time has elapsed; and a switching control unit which receives the off signal from said off-signal generator and receives the first and the second on signal from said first and said second on-signal generator and which turns off the switching transistor according to the off signal and turns on the switching transistor according to the first and the second on signal.