Ericsson Gmbh

Semtech Corporation

Thomas Joseph Karpus

Patrik Hans Lilja

Jason Donald Mareno

Karl Richard Volk

Russell Deans

Lee Daniel Griffin

David Paul Keesor

Michael E Nowak

Teresa Anne Muhlbauer

Paul Edward Hinson

Warren Richard Schroeder

Alan Burchfield

A system and method is provided for preventing a dropout of an LED current. In one embodiment of the present invention, the system includes a voltage source, a first circuit, a second circuit, a controller, and at least one LED. The first circuit receives a reference voltage from the voltage source, receives set-point current data from the controller, and uses the reference voltage and the set-point current data to produce a threshold voltage. The threshold voltage is then provided to the second circuit, where it is converted into an output current, which is drawn through the LED. The second circuit then compares the threshold voltage to an output voltage corresponding to the output current, and provides an output to the controller. The controller then uses the output to determine whether a dropout has occurred. If a dropout has occurred, then second set-point current data is provided to the first circuit.

Automatic dropout prevention in LED drivers

A battery charging circuit sets charging current according to either the capacity of the battery under charge or a constraint of the charging source, depending on the properties of the charging source. The battery charging circuit sets termination current, however, according to the capacity of the battery under charge, regardless of the properties of the charging source. For example, the termination current may be set as a fixed fraction of the recommended C rate of the battery even if the charging current supplied by the charging source is below this C rate. Always setting the termination current in proportion to the battery's capacity permits detection of the current at which charging should terminate even when the charging current is constrained by the charging source and no longer depends on the battery's capacity.

Method and apparatus for battery charging based on battery capacity and charging source constraints

A method is provided for controlling the quiescent current of a power amplifier in a wireless communication device, the amplifier configured to amplify an applied communication signal and employing biasing controlled by a reference voltage. In a preferred embodiment, the method includes: measuring the operating current of the communication device with no communication signal applied to the amplifier and with the reference voltage set to zero, increasing the reference voltage, while continuing to measure the operating current, until the difference between the operating current at a particular reference voltage and the operating current with the reference voltage set to zero reaches a pre-selected current value, and storing a digital value corresponding to the particular reference voltage. The pre-selected current value is preferably determined by characterizing a sufficient sample of amplifiers (e.g., based on model or production lot) to determine a minimum amplifier quiescent current adequate to meet desired performance characteristics for a particular system or application.

Methods and apparatus for controlling power amplifier quiescent current

A portable RF telephone for use in a vehicle may be coupled to an external antenna to overcome the shielding effects of the metallic enclosure of the automobile. While coupled to the external antenna, the portable RF telephone increases the amount of power used to transmit an RF signal. Preferably, the transmit power increases to a maximum level allowed within a defined power classification. Increasing the transmit power overcomes cabling and connector losses associated with using an external antenna and further increases the effective transmitting power without exceeding power levels defined by the telephones power classification.

RF gain enhancement for cellular telephone

An interface system for connecting various accessory devices to a radiotelephone and arbitrating between conflicting requests for access to the audio channel of the radio telephone by the accessory devices. Included is a controller for controlling operation of the interface system and a switch for connecting the audio channel of the selected accessory to the audio channel of the radiotelephone. A method is also provided for entering user selected operational settings for controlling operation of the interface system and prioritizing access to the radiotelephone.

Interface system for providing hands-free operation of a radiotelephone

A modular assembly for centrally locating electrical connections of cellular telephone accessories to a cellular telephone near a cellular telephone cradle. An adapter module containing electronics for effectuating the connections is located and mounted beneath the cellular telephone cradle. The adapter contains a plurality of connections for connecting to the cellular telephone accessories.

Modular assembly for centrally locating cellular telephone accessory

An apparatus for charging a battery has a power supply terminal, a controllable power control switch coupled to said power supply terminal, a charging circuit having a charging terminal for connection to a terminal of the battery, and means for opening and closing the power control switch if a battery is disconnected or connected to the charging terminal, respectively. The means for opening and closing the power control switch may include an analog circuit, a digital circuit, a hybrid analog/digital circuit or a mechanical switch. A method of controlling a power control switch of a battery charging system is disclosed, comprising the steps of generating a reference voltage level, sensing the voltage level at the charging terminal, comparing the voltage level at the charging terminal to the reference voltage, and controlling the power control switch in response to the comparison of the reference voltage level and the voltage level at the charging terminal.

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Apex, NC, United States of America

Thomas Joseph Karpus