Sony Corporation

Sony Trans Com Inc.

Printronix, Inc.

David M Stumfall

Kazutoyo Sekine

Bruce Robert Ferguson

David C Condon

An apparatus and method for reducing interference on a display screen in an in-flight entertainment system, where the interference results from power conversion by a power regulator that supplies voltage to the display screen, is disclosed. The apparatus comprises a clock generator that provides a video clock signal and a regulator clock signal having a frequency that is a multiple of a frequency of the video clock signal. The apparatus also comprises a video processing circuit coupled to the clock generator that provides video data to the display screen at a rate derived from the video clock signal. A regulator circuit that is coupled to the video processing circuit and to the clock generator, supplies voltage to the video processing circuit at a rate based on the regulator clock signal.

Apparatus and method of providing switching frequency synchronization

The present invention is a method and apparatus of providing EMI filtering through the implementation of a voltage sense circuit that is used in conjunction with a power correction circuit in an electromagnetic (EMI) filter system. The apparatus comprises a filter that receives an alternating current signal, where the filter has an input terminal and an output terminal. The apparatus also comprises a power correction circuit having a voltage reference input terminal and an output terminal. A voltage sense circuit having an input terminal is coupled to the input terminal of the filter. The voltage sense circuit has an output terminal that is coupled to the voltage input terminal.

Apparatus and method of providing EMI filtering

An apparatus and method for providing power control in an in-flight entertainment system is disclosed. The power control circuit comprises a first power supply that supplies a first voltage and a second power supply that supplies a second voltage. The circuit further comprises a detector circuit having an input terminal is coupled to the first power supply, and an output terminal that is coupled to the second power supply. The detector circuit generates a first signal upon detection of a valid first voltage level. A control circuit is coupled to the first power supply and the output terminal of the detector circuit. The control circuit is enabled upon receipt of the first signal. A processing circuit is coupled to the second power supply and the control circuit, wherein the second power supply provides the second voltage to the processing circuit upon receipt of the first signal, and the control circuit issues an enable signal to the processing circuit when the processing circuit has received the second voltage.

Apparatus and method for providing power to circuitry implementing two

An apparatus and method for extending the supply of reserved power during an interruption to power supplied by a primary power supply in an in-flight entertainment system is disclosed. The apparatus has a power supply that provides a first supply voltage and a capacitor coupled to the power supply that stores a second supply voltage. The apparatus further has a detector circuit that generates a first signal upon detection of an interruption in the first supply voltage. A control circuit coupled to the detector circuit, the capacitor and the power supply, generates a second signal in response to the first signal. A processing circuit coupled to the power supply, the capacitor and the control circuit, disables its operation in response to the second signal. The capacitor provides the second supply voltage to the control circuit in response to the interruption.

Apparatus and method for extending the supply of reserved power during a

In a printer in which drive transistors coupled to hammer drive coils control energization of the coils within each of a plurality of magnetic print hammer actuators to provide firing of hammer springs associated with the print hammer actuators, leakage of one or more of the drive transistors when they are switched off is detected by a testing circuit which flags a fault condition to turn off the driver circuits if the current at a junction common to all of the drive transistors exceeds a predetermined threshold value. This provides an early warning system in which faulty transistors are routinely detected well before they have a chance to fail and thereafter burn out the associated coil included within a hammerbank of the printer. The testing circuit which comprises a resistor and an operational amplifier coupled in parallel between the common junction and a power supply terminal is activated by a transistor switch which responds to a test control microprocessor to repeatedly close and thereby test for transistor leakage as well as possible shorted coils when the printer is not printing. The microprocessor also repeatedly sequences through the drive transistors to momentarily switch each of them on so that the testing circuit can determine that they and the associated hammer drive coils conduct properly by insuring that a current of predetermined minimum value is present at the common junction. A power transistor coupled to provide rapid current rise when the drive transistors are switched on is also tested for leakage using a second testing circuit, when the printer is not printing.

Magnetic print hammer actuator protection circuit

A printer having greatly reduced radio frequency interference from the system clock signal therein is provided by angle modulating the system clock signal in accordance with a desired modulation signal. The modulation signal is chosen so as to spread and thereby reduce the energy level of the system clock signal at the carrier and at the harmonics without interfering with proper detection of the system clock signal by the electronic circuits within the printer requiring the clock signal for proper timing. In a first embodiment the angle modulation is provided by an FM modulator responsive to a modulating signal which is either sinusoidal or randomly varying in nature. In a second embodiment the angle modulation is provided by an arrangement which combines a modulated subcarrier with the basic clock frequency in a phase locked loop.

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Santa Ana, CA, United States of America

David M Stumfall