US 5,473,533 A · Method and apparatus for efficient phase and frequency coherence locking optimized for digital systems

Abstract

Phase and frequency locking of a controlled signal to a reference signal is obtained in a digital phase locked loop using efficient computational procedures which are carried out rapidly with minimal computational burden on a digital processor. During each cycle of the controlled signal, the time difference between the periods and the phases of the reference signal and the controlled signal are measured. These measured variables determine the predicted changes of the period of the controlled signal to bring the controlled signal into phase and frequency lock with the reference. The change allowed in the period between each discrete cycle is constrained to be less than or equal to a selected maximum amount of time. The predicted changes of period are determined such that the direction and amount of change in period during at least the first discrete cycle is such that for subsequent changes in period, the change will be at the maximum allowed amount of time change, thereby minimizing the total time required to achieve phase and frequency lock. The next cycle of the controlled signal is then changed in accordance with the change determined in this manner, with recalculation of the predicted changes during each cycle of the controlled signal to allow tracking of changes in the reference signal. The reference signal can be AC line power provided to an uninterruptible power supply, which uses the controlled signal to control an inverter to supply AC power derived from a battery when the main AC power fails.

Claims10

Dependent claims

A method for obtaining phase and frequency locking of a controlled signal to a reference signal comprising the steps of:

(a) measuring the time difference in the periods of the reference signal and the controlled signal at a cycle of the controlled-signal;
(b) measuring the time difference in the phases of the reference signal and the controlled signal at the cycle of the controlled signal;
(c) given a selected maximum amount of time that the period of the controlled signal is allowed to change between each cycle of the controlled signal, determining predicted changes of period to bring the controlled signal into phase and frequency lock with the reference signal such that the direction and amount of change in the period of the controlled signal during at least the next cycle at which the period is changed is selected such that for subsequent changes in period of the controlled signal to bring it into phase and frequency lock, the change in period would be at the maximum amount of time that can be changed per cycle;
and
(d) changing the period of the next cycle of the controlled signal in accordance with the predicted change so determined.

2 more elements

A method for obtaining phase and frequency locking of a controlled signal to a reference signal comprising the steps of:

(a) measuring the time difference in the periods of the reference signal and the controlled signal at each cycle of the controlled signal;
(b) measuring the time difference in the phases of the reference signal and the controlled signal at each cycle of the controlled signal;
(c) given a selected maximum amount of time that the period of the controlled signal is allowed to change between each cycle of the controlled signal, at each cycle of the controlled signal determining predicted changes of period to bring the controlled signal into phase and frequency lock with the reference signal such that the direction and amount of change in the period of the controlled signal during at least the next cycle at which the period is changed is selected such that for subsequent changes in period of the controlled signal to bring it into phase and frequency lock, the change in period would be at the maximum amount of time that can be changed per cycle;
and
(d) changing the period of the next cycle of the controlled signal in accordance with the predicted change so determined;
and then
(e) repeating steps (a) through (d) for each new cycle of the controlled signal.

4 more elements

Apparatus for obtaining phase and frequency locking to a reference signal comprising:

(a) controlled signal generator means for providing a controlled signal that can be adjusted in phase and frequency;
(b) means for measuring the time difference in the periods of the reference signal and the controlled signal at each cycle of the controlled signal, means for measuring a the time difference in the phases of the reference signal and the controlled signal at each cycle of the controlled signal, and given a selected maximum amount of time that the period of the controlled signal is allowed to change between each cycle of the controlled signal, means for determining predicted changes of period to bring the controlled signal into phase and frequency lock with the reference signal such that the direction and amount of change in the period of the controlled signal during at least the next cycle at which the period is changed is selected such that for subsequent changes in period of the controlled signal to bring it into phase and frequency lock, the change in period will be at the maximum amount of time that can be changed per cycle;
and
(c) means for changing the period of the next cycle of the controlled signal provided from the controlled signal generator means in accordance with the predicted change so determined at each new cycle of the controlled signal to bring the controlled signal into phase and frequency coherence with the reference signal.

1 more element

An uninterruptible power supply comprising:

(a) an auxiliary power supply battery;
(b) power transfer means including an inverter, connected to the auxiliary power supply battery and to AC line power, for responding to control signals to provide power to an AC output from either the AC line power or from the battery through the inverter;
(c) a controller which provides control signals to the power transfer means, the controller including controlled signal generator means for providing a controlled signal that can be adjusted in phase and frequency, means for measuring the time difference in the periods of the AC line power as a reference signal and the controlled signal at each cycle of the controlled signal, a selected point in time, means for measuring the time difference in the phases of the reference signal and the controlled signal at the selected point in time, and given a selected maximum amount of time that the period of the controlled signal is allowed to change between each cycle of the controlled signal, means for determining predicted changes of period to bring the controlled signal into phase and frequency lock with the reference signal such that the direction and amount of change in the period of the controlled signal during at least the next cycle at which the period is changed is selected such that for subsequent changes in period of the controlled signal to bring it into phase and frequency lock with the reference signal, the change in period will be at the maximum amount of time that can be changed per cycle, means for changing the period of the next cycle of the controlled signal provided from the controlled signal generator means in accordance with the predicted change so determined during each new cycle of the controlled signal to bring the controlled signal into phase and frequency coherence with the reference signal, and further including means for controlling the power transfer means when a fault has occurred in AC line power to provide AC power derived from the battery through the inverter to the AC output, the AC output power being provided from the inverter at the phase and frequency of the controlled signal provided from the controlled signal generator means.

Dependencies are inferred from the claim text.

Method and apparatus for efficient phase and frequency coherence locking optimized for digital systems

Life of this patent

Method and apparatus for efficient phase and frequency coherence locking optimized for digital systems

Life of this patent

Abstract

Claims10