Motorola Corporation

Ashok Ramakant Patil

Michael D Geren

Roland Sylvere Saint-Pierre

John Wendell Oglesbee

Marc B Riley

Macwien Krishnamurthi Annamalai

B Chester Hwang

Kee Eng Soo

This invention includes a circuit for the prevention of acoustic feedback between an electronic device and an audio accessory. In a preferred embodiment, the circuit prevents audio feedback between a cellular telephone and a speakerphone accessory. The circuit includes a current limiting device coupled serially in the receive (Rx) line. The current limiting device is actuated via a delay circuit coupled between the current limiting device and the transmit (Tx) line. When a bias current is presented to the Tx line, the bias propagates through the delay circuit, thereby actuating the current limiting device a predetermined time after the presentation of the bias. The circuit keeps the Rx line open long enough for the phone to deactivate its internal microphone.

Circuit to prevent acoustic feedback for a cellular speakerphone

An apparatus for indicating data transfer between a personal electronic device and a host device includes a common node that connects at least one data line to the personal electronic device and at least one data line to the host device. A high impedance amplifier has an input electrically coupled to the common node and generates an amplified signal corresponding to a signal value present on the common node. A monostable circuit is responsive to the amplified signal and generates a plurality of electrical pulses when the amplified signal exhibits changes in value corresponding to a data transfer through the common node. A lamp driver circuit, that is responsive to the plurality of electrical pulses, generates pulses of light correspond to the electrical pulses. Each of the plurality of electrical pulses is of sufficient duration so that each of the pulses of light is of sufficient duration to be perceived by a human eye.

Data transfer indicator circuit

A clamp circuit for limiting output voltage from a power supply secondary inductor to a ground when a first secondary node has a first secondary node voltage above a predetermined value relative to ground includes a silicone controlled rectifier and a control circuit. The silicone controlled rectifier has a first anode that is electrically coupled to the first secondary node of the secondary inductor, a first cathode that is electrically coupled to the secondary ground, and a first gate. The control circuit is electrically coupled to the first secondary node and to the gate of the silicon controlled rectifier. The control circuit senses the first secondary node voltage and applies a control voltage to the gate of the silicon controlled rectifier when the first secondary node voltage is above the predetermined value. The control voltage is sufficient to drive the silicon controlled rectifier into a substantially conductive state so that the silicon controlled rectifier clamps the first secondary node by sinking substantially all current received from the first secondary node to the ground.

Universal input flyback with secondary shunt voltage limiter

A series-resonant power converter (10) featuring a tap winding (106) on a transformer (100) that is coupled to a resonant capacitor (124) in a resonant tank circuit (122). An output voltage is taken at a secondary (104) of the transformer (100) via a rectifier (110). A control circuit (140) is coupled to the output voltage to monitor the output voltage with respect to a reference to determine load conditions and to generate a control signal representative thereof. An energy recirculation circuit (180) is coupled to the control circuit (140) and to the voltage source (12) and comprises a switch (186) coupled to the tap winding (106) of the transformer (100). The switch (186) is responsive to the control signal to clamp the voltage across the resonant capacitor (124) when the control circuit (140) detects light load conditions to couple energy extracted from the resonant tank circuit (124) via the tap winding (106) to the voltage source (12), and otherwise to maintain the voltage across the resonant capacitor (124) unaffected when the control circuit (140) determines heavy load conditions.

Circuit and method for reactive energy recirculation control in a

A series-resonant power converter (10) comprising a transformer (100), a resonant tank circuit (120) having a piezo-electric crystal (122) as the resonant element and a series-connected resonant capacitor (124). First and second switches (132 and 134) are connected to the transformer (100) and are driven by voltages at windings of the transformer so as to alternately turn on. The piezo-electric crystal (122) self-oscillates to store and release energy and thereby charge and discharge the capacitor (124). Moreover, as a result of the self-oscillation of the resonant circuit (120), the switches (132 and 134) are alternately driven in synchronism with the charging and discharging cycle of the capacitor (122) through windings of the transformer (100). No additional switching circuitry is needed to achieve proper oscillation of the resonant tank circuit (120).

Parallel-loaded series resonant converter having a piezo-electric

The power delivery of an energy source (10) is enhanced by a dual function circuit. The circuit utilizes a storage capacitor (32) to store a voltage higher than the source voltage by transferring charge from the energy source to the storage capacitor between current pulses (16), than transferring charge from the storage capacitor to the load during current pulses. This is achieved by the novel combination of a boost converter (40) operating in conjunction with a buck converter (45).

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Duluth, GA, United States of America

Ashok Ramakant Patil