Automobile headlamp and running light control system

  • US 5,666,028 A
  • Filed: 04/06/1994
  • Issued: 09/09/1997
  • Est. Priority Date: 04/06/1994
  • Status: Expired due to Term
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First Claim
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1. A controller for a vehicle headlamp system comprising an ambient light sensor providing an ambient light level signal indicative of the ambient light level, a dual slew rate capacitor timer for increasing or decreasing a delay time period for switching the headlamp operating state in accordance with the ambient light level signal and a headlamp operating state signal, the capacitor timer including a circuit for increasing the delay time period at a first rate of change and decreasing the delay time period at a second rate of change wherein the first rate of change is greater than the second rate of change, an analog signal comparator responsive to the capacitor timer for switching the headlamp operating state after the delay time period has elapsed, the dual slew rate capacitor timer including an integrating operational amplifier having a variable input resistance network connected to at least one input terminal of the integrating operational amplifier, a capacitor connected between an inverting input terminal and an output terminal of the integrating operational amplifier, a shared timing capacitor for energizing the headlamp approximately one second after a vehicle ignition switch is turned to a "run" position when the ambient light level is below a predetermined low ambient light threshold, said shared capacitor timer including a variable delay exit circuit for controlling an exit delay time period during which the headlamp operating in an energized state remains energized after the vehicle ignition has been turned off.

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