Zero crossover detector circuit

Claim 2

A zero crossover detector circuit for producing an output signal each time an alternating current input signal crosses zero from one poLarity to the other polarity comprising: input circuit means across which said input signal may be applied; first and second amplifier circuits for amplifying said alternating current input signal and producing respective output signals; an inverter circuit for inverting the said output signal of a selected one of said amplifier circuits and producing an output signal; first circuit means responsive to the said output signal of the other one of said amplifier circuits for producing a corresponding direct current reference signal; second circuit means responsive to the said output signal of said inverter circuit for producing a corresponding direct current reference signal; a first comparator circuit for comparing the said output signal of said other one of said amplifier circuits and the said corresponding direct current reference signal for producing an output signal of a selected polarity while the magnitude of said output signal of said other one of said amplifier circuits is greater than that of said corresponding direct current reference signal; a second comparator circuit for comparing the said output signal of said inverter circuit and the said corresponding direct current reference signal for producing an output signal of a polarity the same as said first comparator circuit while the magnitude of said output signal of said inverter circuit is greater than that of said corresponding direct current reference signal; a flip-flop circuit responsive to the said output signal of said first comparator circuit for producing an output signal of a selected one polarity and to the said output signal of said second comparator circuit for producing an output signal of an other polarity; and third comparator circuit means responsive to the said output signal of said inverter circuit and the said output signal of said flip-flop circuit for producing an output signal when the said output signal of said inverter circuit crosses zero from one polarity to the other polarity.

Claim 3

A zero crossover detector circuit for producing an output signal each time an alternating current input signal crosses zero from one polarity to the other polarity comprising: input circuit means across which said input signal may be applied; first and second amplifier circuits for amplifying and inverting said alternating current input signal and producing respective output signals 180* out of phase with said input signal; an inverter circuit for inverting the said output signal of a selected one of said amplifier circuits and producing an output signal in phase with said input signal; first circuit means responsive to the said output signal of the other one of said amplifier circuits for producing a corresponding direct current reference signal; second circuit means responsive to the said output signal of said inverter circuit for producing a corresponding direct current reference signal; a first comparator circuit for comparing the said output signal of said other one of said amplifier circuits and the said corresponding direct current reference signal for producing an output signal of a selected polarity while the magnitude of said output signal of said other one of said amplifier circuits is greater than that of said corresponding direct current reference signal; a second comparator circuit for comparing the said output signal of said inverter circuit and the said corresponding direct current reference signal for producing an output signal of a polarity the same as said first comparator circuit while the magnitude of said output signal of said inverter circuit is greater than that of said corresponding direct current reference signal; an RS type flip-flop circuit having S and R input terminals and a Q output terminal responsive to the application of said output signal of said first comparator circuit to said S input terminal for producing an output signal upon said Q output terminal of a selected one polarity and to the application of said output signal of said second comparator circuit tO said R input terminal for producing an output signal upon said Q output terminal of an other polarity; and third comparator circuit means responsive to the said output signal of said inverter circuit and the said output signal of said flip-flop circuit for producing an output signal when the said output signal of said inverter circuit crosses zero from a negative polarity to a positive polarity.

Claim 4

A zero crossover detector circuit for producing an output signal each time an alternating current input signal crosses zero from one polarity to the other polarity comprising: input circuit means across which said input signal may be applied; first and second amplifier circuits for amplifying and inverting said alternating current input signal and producing respective output signals 180* out of phase with said input signal; an inverter circuit for inverting the said output signal of a selected one of said amplifier circuits and producing an output signal in phase with said input signal; first circuit means responsive to the said output signal of the other one of said amplifier circuits for producing a corresponding direct current reference signal; second circuit means responsive to the said output signal of said inverter circuit for producing a corresponding direct current reference signal; a first comparator circuit for comparing the said output signal of said other one of said amplifier circuits and the said corresponding direct current reference signal for producing an output signal of a selected polarity while the magnitude of said output signal of said other one of said amplifier circuits is greater than that of said corresponding direct current reference signal; a second comparator circuit for comparing the said output signal of said inverter circuit and the said corresponding direct current reference signal for producing an output signal of a polarity the same as said first comparator circuit while the magnitude of said output signal of said inverter circuit is greater than that of said corresponding direct current reference signal; an RS type flip-flop circuit having S and R input terminals and a Q output terminal responsive to the application of said output signal of said first comparator circuit to said S input terminal for producing an output signal upon said Q output terminal of a selected one polarity and to the application of said output signal of said second comparator circuit tO said R input terminal for producing an output signal upon said Q output terminal of an other polarity; and third comparator circuit means responsive to the said output signal of said inverter circuit and the said output signal of said flip-flop circuit for producing an output signal when the said output signal of said inverter circuit crosses zero from a negative polarity to a positive polarity.

Claim 5

A zero crossover detector circuit for producing an output signal each time an alternating current input signal crosses zero from one polarity to the other polarity comprising: input circuit means including an input circuit point and a common circuit point across which said input signal may be applied; first, second and third operational amplifiers each having an inverting input terminal and a non-inverting input terminal and an output terminal; means for connecting said input circuit point to said inverting input terminal of both said first and second operational amplifiers and for connecting said common circuit point to said non-inverting input terminal of both said first and second operational amplifiers; means for connecting said output terminal of said second operational amplifier to said inverting input terminal of said third operational amplifier; means for connecting said common circuit point to said non-inverting input terminal of said third operational amplifier; first, second and third comparator circuits each having a positive input terminal and a negative input terminal and an output terminal; a first diode having anode and cathode electrodes; a first capacitor; a first resistor; means for connecting said output terminal of said first operational amplifier to said negative input terminal of said first comparator circuit and to said anode electrode of said first diode; means for connecting said cathode electrode of said first diode to said positive input terminal of said first comparator circuit; means for connecting said first capacitor and said first resistor in parallel across the junction between said cathode electrode of said first diode and said positive input terminal of said first comparator circuit and said common circuit point; a second diode having an anode and cathode electrodes; a second capacitor; a second resistor; means for connecting said output terminal of said third operational amplifier to said negative input terminal of said second comparator circuit and to said anode electrode of said second diode; means for connecting said cathode electrode of said second diode to said positive input terminal of said second comparator circuit; means for connecting said second capacitor and said second resistor in parallel across the junction between said cathode electrode of said second diode and said positive input terminal of said second comparator circuit and said common circuit point; an RS flip-flop circuit having S and R input terminals and a Q output terminal; means for connecting said output terminal of said first comparator circuit to said S input terminal of said RS flip-flop circuit; means for connecting said output terminal os said second comparator circuit to said R input terminal of said RS flip-flop circuit; means for connecting said output terminal of said third operational amplifier to said positive input terminal of said third comparator circuit; and means for connecting said Q output terminal of said RS flip-flop circuit to said negative input terminal of said third comparator circuit.

Claim 6

A zero crossover detector circuit for producing an output signal each time an alternating current input signal crosses zero from one polarity to the other polarity comprising: input circuit means including an input circuit point and a common circuit point across which said input signal may be applied; first, second and third operational amplifiers each having an inverting input terminal and a non-inverting input terminal and an output terminal; means for connecting said input circuit point to said inverting input terminal of both said first and second operational amplifiers and for connecting said common circuit point to said non-inverting input terminal of both said first and second operational amplifiers; means for connecting said output terminal of said second operational amplifier to said inverting input terminal of said third operational amplifier; means for connecting said common circuit point to said non-inverting input terminal of said third operational amplifier; first, second and third comparator circuits each having a positive input terminal and a negative input terminal and an output terminal; a first diode having anode and cathode electrodes; a first capacitor; a first resistor; means for connecting said output terminal of said first operational amplifier to said negative input terminal of said first comparator circuit and to said anode electrode of said first diode; means for connecting said cathode electrode of said first diode to said positive input terminal of said first comparator circuit; means for connecting said first capacitor and said first resistor in parallel across the junction between said cathode electrode of said first diode and said positive input terminal of said first comparator circuit and said common circuit point; a second diode having an anode and cathode electrodes; a second capacitor; a second resistor; means for connecting said output terminal of said third operational amplifier to said negative input terminal of said second comparator circuit and to said anode electrode of said second diode; means for connecting said cathode electrode of said second diode to said positive input terminal of said second comparator circuit; means for connecting said second capacitor and said second resistor in parallel across the junction between said cathode electrode of said second diode and said positive input terminal of said second comparator circuit and said common circuit point; an RS flip-flop circuit having S and R input terminals and a Q output terminal; means for connecting said output terminal of said first comparator circuit to said S input terminal of said RS flip-flop circuit; means for connecting said output terminal os said second comparator circuit to said R input terminal of said RS flip-flop circuit; means for connecting said output terminal of said third operational amplifier to said positive input terminal of said third comparator circuit; and means for connecting said Q output terminal of said RS flip-flop circuit to said negative input terminal of said third comparator circuit.