Integration type A/D conversion method, integration type A/D converter, and battery charger utilizing such converter

摘要

In the invention, an integrator integrates a current indicative of an input signal to generate at its output end a voltage (referred to as integral output voltage) by means of a condenser. At a point in time when the integral output voltage has reached a predetermined level, or at a point in time determined by timing of a predetermined period, the integral output voltage is reduced in absolute value by flowing into or out of the condenser a constant current supplied by a constant current source. The direction of the constant current depends on the polarity of the output of the integrator. A counter counting up or down clocks stops counting while the constant current is flowing. This permits use of a low-frequency A/D converter to convert the input signal at a reduced power and extend the dynamic range of the A/D converter.