Lamp monitor with latch circuit

Claim 2

A vehicle lamp monitor for providing a warning signal when lamp failure occurs and for continuing the warning signal whenever the vehicle is operated until a correction is made, wherein the vehicle has a vehicle power supply, an ignition switch means, and a lamp circuit including lamp switch means for operatively connecting the lamp to the power supply, the monitor comprising a lamp failure detector coupled to the lamp circuit for detecting a lamp failure during operation of the lamp circuit, a latch circuit connected to the power supply independently of said switch means and coupled to the lamp failure detector for assuming a failure state when a lamp failure is detected and thereafter maintaining such failure state while the failure condition persists independently of the state of the switch means, a warning circuit coupled to the latch circuit and connected through the ignition switch means to the power supply for providing a warning signal when the ignition switch is closed and the latch circuit is in the failure state.

Claim 3

A vehicle lamp monitor for providing a warning signal when lamp failure occurs and for continuing the warning signal whenever the vehicle is operated until a correction is made, wherein the vehicle has a vehicle power supply, an ignition switch means, and a lamp circuit including lamp switch means for operatively connecting the lamp to the power supply, the monitor comprising a comparator coupled to the lamp circuit for detecting a lamp failure during operation of the lamp circuit, an inverting circuit coupled to the output of the comparator for inverting the output, a latch circuit comprising a non-inverting amplifier connected to the power supply independently of said switch means and having its input connected to the inverting circuit output and through a resistor to the amplifier output so that the latch circuit is driven to a given state by positive action of the comparator and maintains that state when the comparator is disabled, and a warning circuit coupled to the latch circuit and connected through the ignition switch means to the power supply for providing a warning signal when the ignition switch is closed and the latch circuit is in the failure state.

Claim 4

A vehicle lamp monitor for providing a warning signal when lamp failure occurs and for continuing the warning signal whenever the vehicle is operated until a correction is made, wherein the vehicle has a vehicle power supply, an ignition switch means, and a lamp circuit including lamp switch means for operatively connecting the lamp to the power supply, the monitor comprising a comparator coupled to the lamp circuit for detecting a lamp failure during operation of the lamp circuit, an inverting circuit coupled to the output of the comparator for inverting the output, a latch circuit comprising a non-inverting amplifier connected to the power supply independently of said switch means and having its input connected to the inverting circuit output and through a resistor to the amplifier output so that the latch circuit is driven to a given state by positive action of the comparator and maintains that state when the comparator is disabled, and a warning circuit coupled to the latch circuit and connected through the ignition switch means to the power supply for providing a warning signal when the ignition switch is closed and the latch circuit is in the failure state.