Electricity: motive power systems – Braking – Automatic and/or with time-delay means
Patent
1973-09-28
1976-02-03
Schaefer, Robert K.
Electricity: motive power systems
Braking
Automatic and/or with time-delay means
318317, 318328, 318331, 318342, H02P 536, H02P 506
Patent
active
039367118
ABSTRACT:
There is disclosed a motor speed control circuit for use in battery-powered tape recorders, tape players and record players in which the motor speed is made independent of power supply voltage swings, temperature and loading. The circuit is comprised of three sections including a discriminator-comparator section, a protection circuit and an output circuit. The discriminator-comparator circuit provides that the control signal to the motor be independent of power supply variations. A tachometer signal of an AC nature is coupled into the discriminator-comparator circuit which generates a pulsed current. The number of current pulses generated over a given time interval corresponds to the frequency of the tachometer signal. These pulses are subtracted from a reference current which difference is integrated, with the integrated current difference indicating the difference in speed of the motor between the desired speed and the actual speed. The tachometer signal is fed directly to the discriminator-comparator without the necessity of providing pulse-shaping circuits. The output circuit converts this difference current to a variable voltage across the motor to control its speed. This conversion from a current drive to a voltage drive is accomplished in a common-emitter configuration such that the drive circuitry does not drop the voltage applied to the motor by any significant extent. The protection circuit utilizes current-limiting circuitry which is independent of supply voltage to provide overload protection and also to prevent overheating of the motor speed control circuit by limiting the current to the circuit either during overload or when a predetermined temperature has been exceeded.
REFERENCES:
patent: 3260949 (1966-07-01), Voorhoeve
patent: 3458792 (1969-07-01), Jabbar
patent: 3609494 (1971-09-01), Takahashi
patent: 3777235 (1973-12-01), Lahti
Bingham Michael D.
Feldhaus John J.
Jones, Jr. Maurice J.
Motorola Inc.
Schaefer Robert K.
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