Degauss circuit for use in an electronically actuated door lock
Abstract:
A novel and useful degauss circuit for use with electromagnetic door locks. The door lock circuit is configured to provide a constant current to the electromagnetic coil load. A pulse width modulation (PWM) controller varies the frequency and/or duty cycle to a switch in series with the coil. Coil current feedback is used to adjust the PWM frequency and/or duty cycle so as to maintain the current through the coil at a certain level to maintain a desired holding force on the door lock. A degauss circuit inline with the current flowing through the coil is provided. When triggered either in an uncontrolled or controlled manner, a series RLC circuit that includes the coil inductance and resistance causes ringing to occur whereby the coil current reverses direction with sufficient amplitude and duration to degauss the coil.
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