Patent ID: 7071655
Filing Date: 2006-07-04
Classification: H02J,H02M

Abstract:
1. An AC adapter for use in charging a secondary battery which is contained in or mounted on a main body, said AC adapter comprising: a primary side circuit for turning, by using a switching element, an input DC voltage applied to a primary winding of a transformer on and off; a secondary side circuit for rectifying and smoothing an AC voltage induced in a secondary winding of said transformer to produce an adapter voltage; a voltage control circuit for detecting a variation of said adapter voltage to produce a voltage control signal; a constant current control circuit for detecting a charging current flowing in said secondary side circuit to produce a constant current control signal; a photocoupler for feeding said voltage control signal and said constant current control signal as a feedback signal back to said primary side circuit; a switching control circuit for controlling, in response to said feedback signal, on and off of said switching element; and detection means, disposed in said secondary side circuit, for detecting when said charging current decreases to less than a set current value due to a drastic decrease of said charging current to produce a detected signals; wherein said voltage control circuit repeats operations comprising gradually lowering said adapter voltage and increasing, in response to said detected signal, said adapter voltage by a predetermined voltage, so that said AC adapter carries out a constant voltage charging with a necessary minimum voltage difference which is a potential difference between said adapter voltage and a battery voltage of said secondary battery on a constant current charging.