Automatic head switching control method and apparatus for multi-modal video cassette recorders

An automatic head switching control apparatus in a multi-modal VCR having a drum driven by a drum motor, said drum having a plurality of heads, said automatic head switching control apparatus comprising:

• a drum reference counter for generating a reference signal according to broadcast mode information to control drum phase of the drum;
• a head switching signal generator for generating a head switching signal according to the broadcast mode information using a drum phase generation (DPG) signal and a drum frequency generation (DFG) signal supplied from the drum, delay data, and a shift command signal of a head switching point of time for each head;
• p1 a format detector, coupled to an output end of the head switching signal generator, for comparing the head switching signal with a vertical sync signal of a video signal and detecting whether an interval of time between both the head switching signal and the vertical sync signal is in a predetermined range to judge whether a format corresponding to a first mode is met;
• a controller for applying the broadcast mode information to the drum reference counter and head switching signal generator, and supplying the delay data and the shift command signal of the head switching point of time for each head to the head switching signal generator according to the output of the format detector;
• a storage portion for storing the delay data generated when the format detector judges that the format is met for said first mode and an offset correction value for obtaining delay data adapted for a second mode from the delay data adapted for said first mode;
• and
• a drum phase detector for comparing the head switching signal output from the head switching signal generator with the reference signal output from the drum reference counter to generate a drum phase control signal for altering velocity of the drum motor.