Trigger activated adjustable pulse width generator circuit for automotive exhaust after-treatment and injection
AssigneeContinental Automotive Systems, Inc.
InventorsDouglas Edward Cosby, Perry Robert Czimmek
Life of this patent
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Abstract
A method adjusts a pulse width of a signal. The method provides a fixed voltage input trigger pulse (34), of a certain pulse width, to a pulse width generator circuit (10) and provides an output pulse (52) from the pulse width generator circuit such that a pulse width of the output pulse is longer than the certain pulse width, without changing a voltage or frequency of the input trigger pulse. The method is used to drive an injector of a diesel reductant delivery system to inject fluid into an exhaust flow path.
Claims17
A method of adjusting a pulse width of a signal, the method comprising:
- providing a fixed voltage input trigger pulse, of a certain pulse width, to a pulse width generator circuit, the pulse width generator circuit including first and second comparator circuits, first and second D flip-flops, and a current mirror, and
- providing an output pulse from the pulse width generator circuit such that a pulse width of the output pulse is longer than the certain pulse width, without changing a voltage or frequency of the input trigger pulse,
- wherein the step of providing the output pulse includes:
- receiving the input trigger pulse at the first comparator circuit, with output of the first comparator circuit being provided to an input of the first flip-flop, and output of the first flip-flop being connected to a clock of the second flip-flop such that when the second flip-flop receives a rising edge from the first flip-flop, an output of the second flip-flop is pushed high and remains high until being reset by a signal from the second comparator circuit, wherein the output of the second flip-flop defines the output pulse.
A pulse width generator circuit for adjusting duration of an output pulse, the pulse width generator circuit comprising:
- first and second comparator circuits,
- first and second D flip-flops, and
- a current mirror,
- wherein the first comparator circuit is constructed and arranged to receive a fixed voltage input trigger pulse, of a certain pulse width, with output of the first comparator circuit being connected to an input of the first flip-flop, and output of the first flip-flop being connected to a clock of the second flip-flop such that when the second flip-flop receives a rising edge from the first flip-flop, an output of the second flip-flop is pushed high and remains high until being reset by a signal from the second comparator circuit,
- wherein the second comparator circuit receives a variable inverting input and an output of the second comparator circuit is connected with a capacitor and with the second flip-flop so that as soon as the capacitor charges to a reset voltage, a reset of the second flip-flop is activated and the output of the second flip-flop goes to zero,
- wherein the current mirror is connected to the output of the second flip-flop to provide a constant charging current for the capacitor, with the output of the second flip-flop being the source of the output pulse and a voltage input of the current mirror, as well as a reset input to the second comparator circuit for resetting the second flip-flop to zero, and
- wherein the output of the second flip-flop defines the output pulse having a pulse width longer than the certain pulse width, without changing a voltage or frequency of the input trigger pulse.
Dependencies are inferred from the claim text.