Hewlett-packard Development Company, L.P.

Jack Lavier

Samuel Martin Babb

Kelly Jean Pracht

Peter Mardilovich

Ray Woodward

Electronic circuits and methods are provided for use in hot-swappable circuit board applications. Circuitry detects an electrical ground connection and signals operation of a hot-swap controller. Detection of stable operating power causes a hierarchical startup of plural voltage regulators. Sensing stable output power from the last of the voltage regulators triggers the configuration of one or more programmable devices. Circuitry and other resources of a hot-swappable circuit board are protected against electrical transient-related damage by virtue of the present teachings.

Circuitry for hot-swappable circuit boards

In an embodiment, a method of compensating for capacitance change in a piezoelectric element of a fluid ejection device includes sensing a current driving a piezoelectric element, determining from the current that capacitance of the piezoelectric element has changed, and altering a rise time of the current driving the piezoelectric element to compensate for the changed capacitance.

Compensating for capacitance changes in piezoelectric printhead elements

A control logic detects voltage regulator failure in a power supply. The control logic comprises first and second lines configured for respective connection to a controller node and a phase node of a voltage regulator, a delay element coupled to the first line configured to delay signals at the controller node into alignment with signals at the phase node, and a level detector coupled to the second line configured to convert the signals at the phase node into at least two digital representations indicative of respective signal thresholds. A logic compares timing of the delayed signals with the digital representations and detects occurrence of a voltage regulator fault based on the timing comparison.

Failure detection in a voltage regulator

Power supplies are disclosed herein. One embodiment of a power supply comprises a first input and a second input, wherein the first input and the second input are connectable to a pulse width modulation controller and wherein a pulse width modulation signal is outputable from the pulse width modulation controller. A power stage connected to the first input and the second input. A first comparator having a first comparator first input is connected to the first input and a first comparator second input connected to the output of the power stage. A change of voltage at the output of the first comparator constitutes a difference in phase between the first input and the output of the power stage.

Fault detection circuit

Systems and methods for providing redundant voltage regulation are provided. A representative method incorporates: providing a first voltage regulator and a second voltage regulator, the second voltage regulator having output rectifiers; electrically connecting the first voltage regulator to a load such that the first voltage regulator independently powers the load; disabling the output rectifiers of the second voltage regulator; detecting a fault of the first voltage regulator; responsive to the fault, enabling the output rectifiers of the second voltage regulator such that the second voltage regulator independently powers the load.

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Corvallis, OR, United States of America

Jack Lavier