Digital voltage and phase monitor for AC power line
First Claim
1. A digital control circuit for controlling the connection of power from an AC power supply to a AC load, the circuit comprising:
- switch means for controlling the connection between the AC power supply signal and the AC load,conversion means for generating a DC voltage responsive to the AC power supply signal voltage,first and second scaling means each coupled to the conversion means for scaling the DC voltage to form first and second independently adjustable digital monitoring signals each monitoring signal responsive to the AC power supply signal and capable of generating a different voltage level, the first digital monitoring signal traversing a first predetermined logic level when the Ac power supply line voltage is in an under-voltage condition and the second digital monitoring signal traversing a second predetermined logic level when the AC power supply line voltage is in an over-voltage condition; and
first and second digital comparator means, each comprising a digital logic gate coupled to receive a corresponding one of said digital monitoring signals and including independent feedback means for providing separately adjustable hystersis, each logic gate having an internally generated voltage level that is used as a reference to determine the logic state of the corresponding digital monitoring signal, the first and second comparator means generating a fault condition signal when either of said corresponding digital monitoring signals traverses the internal reference voltage of the corresponding digital logic gate.
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Accused Products
Abstract
A digital voltage protection circuit (138) and a phase monitor circuit (154, 160, 162, 168) disconnect AC-powered user equipment (22,182) from the AC power supply (141) whenever the AC power line voltage is outside a predetermined operating voltage window and when any two phases of the power supply (141) are separated by more than a predetermined phase angle. The user equipment (182) is automatically reconnected to the power supply (141) only after the power line voltage and phase remain continuously within operating range for a predetermined delay period. The voltage monitor (138) contains a digital comparator (18) that uses integrated circuit digital logic thresholds as reference voltages for setting upper and lower voltage window limits. The controller protects the user equipment from both over-voltage and under-voltage (brownout) conditions and from phase errors.
60 Citations
20 Claims
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1. A digital control circuit for controlling the connection of power from an AC power supply to a AC load, the circuit comprising:
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switch means for controlling the connection between the AC power supply signal and the AC load, conversion means for generating a DC voltage responsive to the AC power supply signal voltage, first and second scaling means each coupled to the conversion means for scaling the DC voltage to form first and second independently adjustable digital monitoring signals each monitoring signal responsive to the AC power supply signal and capable of generating a different voltage level, the first digital monitoring signal traversing a first predetermined logic level when the Ac power supply line voltage is in an under-voltage condition and the second digital monitoring signal traversing a second predetermined logic level when the AC power supply line voltage is in an over-voltage condition; and first and second digital comparator means, each comprising a digital logic gate coupled to receive a corresponding one of said digital monitoring signals and including independent feedback means for providing separately adjustable hystersis, each logic gate having an internally generated voltage level that is used as a reference to determine the logic state of the corresponding digital monitoring signal, the first and second comparator means generating a fault condition signal when either of said corresponding digital monitoring signals traverses the internal reference voltage of the corresponding digital logic gate. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A circuit for monitoring a three-phase power supply signal and controlling the connection between the power supply signal and a load, the circuit comprising;
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switch means for controlling the connection between the three phase power supply signal and the load (20), digital voltage level monitoring means coupled to the three-phase power supply signal for disconnecting the power supply from the AC load when any phase of the power supply signal is outside a predetermined voltage window (138A, 138B, 138C), the digital voltage level monitoring means including conversion means for generating a DC voltage responsive to the AC power supply signal voltage. first and second scaling means each coupled to the covnersion means for scaling the DC voltage to form first and second separately controllable digit monitoring signals each responsive to the AC power supply signal, the first digital monitoring signal traversing a first predetermined logic level when the AC power supply line voltage is in an under-voltage condition and the second digital monitoring signal traversing a second predetermined logic level when the AC power supply line voltage in in an over-voltage condition, and first and second digital comparator means, each comprising a digital logic gate coupled to receive a corresponding one of said digital monitoring signals and including means for providing separately adjustable hystersis, each logic gate having an internally generated voltage level that is used as a reference to determine the logic state of the corresponding digital monitoring signal, the first and second comparator means generating a fault condition signal when either of said corresponding digital monitoring signals traverses the internal reference voltage of the corresponding digital logic gate; and digital phase monitoring means coupled to the power supply signal for disconnecting the power supply from the AC load when any two phases of the power supply are within a predetermined phase angle, the phase monitoring means having an internally generated voltage level that is used as a reference to determine a digital logic state for each of said two phases, the logic state of the two phases compared to determine when said phases are within the predetermined phase angle (154, 160, 162,
169). - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method for controlling a power signal connection between an AC power line and AC-powered user equipment, the method comprising the steps of:
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converting the AC power line voltage into a DC monitor voltage; scaling the DC monitor voltage to form first and second independently controllable digital logic signals each responsive to the AC power supply signal and capable of generating a different voltage amplitude; monitoring the first and second digital logic signals with a digital logic circuit, the first digital signal traversing a first predetermined logic level when the AC power supply line voltage is in an under-voltage condition and the second digital signal traversing a second predetermined logic level when the AC power supply line voltage is in an over-voltage condition (138, 154, 160,
162);generating a fault condition signal when one of the first and second digital logic signals indicate either an under-voltage or over-voltage condition, respectively; and independently controlling hystersis in the digital logic circuit for both the first and second digital logic signals so that each digital logic signal has a first independently controllable fault activation voltage level for activating a fault condition in the digital logic circuit and a second separately controllable fault deactivation voltage level for deactivating the fault condition. - View Dependent Claims (19, 20)
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Specification