Mains Voltage Zero-Crossing Detector
AssigneeMicrochip Technology Incorporated
InventorsRichard Hull, John Charais, Gabriel Rosca
Life of this patent
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Abstract
A mains voltage zero-crossing detector has a constant voltage forced on an external node by driving transistor devices with appropriate control signals provided by a feedback loop around a highly power efficient class B configuration comprising an operational amplifier having single ended dual outputs and a class B control circuit. Mains power zero crossings may then be detected by monitoring the drive current of devices driven by this amplifier. Wherein Class B control and current mode detection provide accurate detection of the driven signal without depending on any voltage threshold that may depend on temperature, process fabrication and/or supply voltage.
Claims29
A mains voltage zero-crossing detector, comprising:
- a first output driver coupled between an first rail voltage and an external node;
- a second output driver coupled between a second rail voltage and the external node;
- an amplifier having first and second differential inputs, and first and second single ended outputs, wherein a first output thereof is coupled to a control input of the first output driver and a second output thereof is coupled to a control input of the second output driver;
- a feedback network coupled between the output node and the second input of the amplifier;
- a voltage reference coupled to the first input of the amplifier;
- a class B control circuit coupled to the control inputs of the first and second output drivers, wherein the class B control circuit forces one of the first or second output drivers off when the other output driver is conducting, and releases control back to the amplifier as it stops conducting;
- a current mode detector circuit coupled to the control inputs of the first and second output drivers, wherein the current mode detector circuit provides mains voltage zero-crossing detection based upon currents to control inputs of the first and second output drivers.
A circuit arrangement for detecting mains voltage zero-crossings, comprising:
- an external node of an integrated circuit device that is configured for coupling to a mains power alternating current (AC) voltage through a high value impedance;
- first and second output drivers operable to couple the external node to either a first supply rail voltage or second supply rail voltage;
- and
- a zero-crossing detector providing control of the first and second output drivers such that a substantially constant voltage is forced at the external node whether current is being sinked from or sourced to the mains AC voltage, and a current thereof is monitored in determining voltage zero-crossings of the mains AC voltage.
A method for detecting mains voltage zero-crossings, said method comprising the steps of:
- configuring an external node of an integrated circuit device for coupling to a mains power alternating current (AC) voltage through a high value impedance;
- providing first and second output drivers operable to couple the external node to either a first supply rail voltage or second supply rail voltage;
- and
- providing a zero-crossing detector to control of the first and second output drivers such that a substantially constant voltage is forced at the external node whether current is being sinked from or sourced to the mains AC voltage;
- and
- monitoring current of signals controlling the first and second output drivers for determining voltage zero-crossings of the mains AC voltage.
Dependencies are inferred from the claim text.