Patent ID: 6420832
Filing Date: 2002-07-16
Classification: H05B

Abstract:
A flasher circuit for a school bus of the type adapted for flashing right and left side lamps alternately, said flasher circuit comprising;first and second voltage supply terminals adapted for connection with a vehicle battery, a first pair of output terminals adapted for connection of one of said lamps therebetween and a second pair of output terminals adapted for connection of the other lamp therebetween, a first FET and a second FET, each of said FETs having a gate, drain and source lead, the source lead of the first FET being connected to one terminal of said first pair of output terminals and the source lead of said second FET being connected to one terminal of said second pair of output terminals, the other terminal of said first pair of output terminals and the other terminal of said second pair of output terminals being connected with said second voltage supply terminal, a source of switching voltage for switching said FETs, control means for applying said switching voltage during alternate time slots to the gate lead of said first and second FETs for turning said FETs on and energizing said first and second lamps during said alternate time slots thereby flashing said lamps alternately, and a manual switching means coupled with said control means for initiating the flashing of said lamps, a current sensing means connected between said first voltage supply terminal and the drain leads of said first and second FETs for generating a first signal voltage corresponding to the actual load current, a load current limiting circuit including a reference voltage source for generating a second signal voltage corresponding to a preset limit value of load current and means for changing the reference voltage between a higher level and a lower level. and comparator means having inputs coupled with said sensing means and said reference voltage source for comparing said first and second signal voltages, said comparator means having an output coupled to said control means for disconnecting said switching voltage from said gate electrodes in response to the first signal voltage exceeding said second signal voltage.