Patent ID: 6061224
Filing Date: 2000-05-09
Classification: H01F,H01H

Abstract:
A solenoid driver circuit comprising:(a) an input terminal for receiving a solenoid actuation pulse, an output terminal for connection to a terminal of a solenoid coil, a ground terminal, a pull-in current duration adjustment terminal, and a hold-in current duty cycle adjustment terminal;(b) a pull-in current duration circuit having a first input coupled to the input terminal and a second input coupled to the pull-in current adjustment terminal and producing a pull-in current duration control pulse in response to the solenoid actuation pulse, the duration of the pull-in current duration control pulse being determined by a signal level on the pull-in current adjustment terminal;(c) an oscillator producing a triangular waveform signal;(d) a hold-in current duty cycle control circuit having a first input coupled to receive the triangular waveform signal and a second input coupled to the hold-in current duty cycle adjustment terminal to produce a PWM signal, and the hold-in current duty cycle control circuit including a third input coupled to the pull-in current duration adjustment terminal and logically ORing the pull-in current duration control pulse with the PWM signal to produce a switch drive signal on an output conductor;(e) an output transistor having a control electrode coupled to the output conductor of the hold-in current duty cycle control circuit, and a current-carrying terminal coupled to the output terminal of the solenoid driver circuit; and(f) the hold-in current duty cycle control circuit applying the switch drive signal to the control electrode, the switch drive signal including a pull-in current pulse turning on the output transistor for the duration of the pull-in current duration control pulse to cause a pull-in current of like duration to be established in the solenoid coil followed by a sequence of PWM hold-in current pulses repetitively turning the output transistor on and off until the end of the solenoid actuation pulse.