Vehicle headlamp control circuits
First Claim
1. A vehicle headlamp control circuit including an incident light detector element and means responsive to only the a.c. component of the detection element output at a frequency related to the street lighting main electricity supply frequency in the locality in which the circuit is intended to be used, characterised by including an averaging circuit for providing a control signal in accordance with the average value of said a.c. component whereby the vehicle lighting is controlled in accordance with the average value of the magnitude of the amplitude of the a.c. component.
0 Assignments
0 Petitions
Accused Products
Abstract
An automatic vehicle headlamp intensity adjustement circuit includes a high sensor. A tuned rectifier circuit for producing a d.c. signal of magnitude dependent on the amplitude of the 50Hz (or other local supply frequency) component of the signal picked up by the sensor. A lamp current modulating circuit is controlled by this d.c. signal through the intermediary of an averaging circuit. The averaging circuit has a relatively long time constant and a timer is connected to reduce this time constant if the d.c. signal continues to fall for more than a predetermined period of time.
16 Citations
10 Claims
- 1. A vehicle headlamp control circuit including an incident light detector element and means responsive to only the a.c. component of the detection element output at a frequency related to the street lighting main electricity supply frequency in the locality in which the circuit is intended to be used, characterised by including an averaging circuit for providing a control signal in accordance with the average value of said a.c. component whereby the vehicle lighting is controlled in accordance with the average value of the magnitude of the amplitude of the a.c. component.
- 4. A vehicle headlamp control circuit comprising an incident light detector element, an a.c. amplifier for amplifying the output of said detector element, a band pass filter circuit connected to said amplifier and tuned to twide the frequency of the street lighting electricity mains supply in the locality in which it is intended to use the control circuit, rectifier means connected to the filter circuit and providing a d.c. output signal fluctuating in accordance with the amplitude of said a.c. component, an averaging circuit connected to the rectifier means and providing a d.c. signal related to the average amplitude of the a.c. signal, and modulating means connected to the averaging circuit and controlling the vehicle headlamp current in accordance with output of said averaging circuit.
Specification