Patent ID: 7589504
Filing Date: 2009-09-15
Classification: G03B,H02J,Y02B,Y02E,Y10S

Abstract:
1. A capacitor charging apparatus, including a primary circuit receiving a power supply voltage and including a switch means adapted to turn on in response to a switch drive signal and connected in series with a primary winding of a transformer, said transformer having a secondary winding connectable to a capacitor to be charged, said apparatus comprising: primary current detection means for detecting a primary current detection signal generated in association with the primary current flowing through said primary winding when said switch means is turned on in response to said switch drive signal; a primary current peak detection circuit adapted to generate a primary current peak detection signal for stopping said switch drive signal to turn off said switch means when said primary current detection signal has reached a predetermined peak detection level; a voltage dividing circuit arranged to generate a first voltage obtained by dividing a charging voltage across said capacitor; an off-time detection circuit adapted to start clocking an off-time of said primary circuit in response to the stopping of said switch drive signal corresponding to said primary current peak detection signal, and generate said switch drive signal when finishing clocking said off-time, thereby then turning on said switch means, said off-time detection circuit is arranged to receive said first voltage, and said off-time is shortened as said charging voltage increases; and a full-charge detection circuit arranged to receive said first voltage and output a full-charge detection signal when said first voltage exceeds a predetermined fully charged voltage, to thereby stop said switch drive signal and inform external devices that said capacitor is fully charged.