Patent ID: 7276817

Claim:
An output voltage control apparatus for a vehicular AC generator having a rectifier unit that rectifies an AC output voltage and outputs a generator output voltage including a ripple component, the output voltage control apparatus comprising: a control unit that repeats a control period of a specified time width, and performs a control to supply a field current to the vehicular AC generator on an ON period of a controlled time width in each of the control periods, wherein the control unit includes: a voltage detection circuit to detect the generator output voltage and to output a detection voltage including a ripple component; a comparison circuit to compare the detection voltage including the ripple component with a reference voltage and to output an effective comparison output in each of low output sections in which the detection voltage is lower than the reference voltage depends on the ripple component; an ON period counter to count up, in a count enable period set in each of the control periods, a count value while adding the count value in each of the low output sections based on the effective comparison output; and a memory circuit to store a final count value in the count enable period in each of the control periods, and the control unit determines, based on the final count value in each of the control periods, the ON period of the controlled time width in the next control period.